HomeMy WebLinkAboutDocuments & Plans - 1979-2001FlLt [ _, i
MEMORANDUM
Legal Files for Lots 8, 10, & 1 1, Bighom Subdivision, Second Addition
Gommunity Dwelopment Department
July 20, 2001
Results of Town Council Executive Session regarding the determination of
interest in purchasing or acquiring conseruation easements on Lols 8, 10, & 11,
Bighorn Subdivi$on, Second Addilion
TO:
FROM:
DATE:
SUBJECT:
suumaRv or REst LTs
Community Development Department slatf met with members of the Tovrrn Council on July 17, 2001, to
delermine the level of interest in purchasing or acquiring conservation easements on Parcel 40, noted in
the Comprehensive Open Lands Plan as being a high priority for acquisition. The Council had three
options:
OmoI A - PuRSUE A PURcHASE oF LoTs 8, 10 & 11
Parcel 40 is approximately 3.4 acres in size. The option to purchase the lots within Parcel 40 has
not been discussed with the present owners. The benefit to the Town in purchasing the lots is
that the Town would acquire all of the dwelopment rights. Hence, the Town would be able to
ensure that the lots would remain as open space in perpetuity. Though lhere may be limitations
due to geologic hazards, all of the lots may be developed at present.
Oprpl,t B - PuRsue coNsERvATtoN EAsEltEl{Ts upoN Lors 8, 10 & 11
The applicants' representative has informed statf that the owners of Lots 8, 10, & 1 1 may be
amenable to the Town of Vail acquiring a conservation or ervironmental easement across the red
hazard avalanche areas on these lots. This would not preclude derrelopmenl on the lots
altogether. Honve,/er, it could ensure that the geologically sensitMe areas and sleep lots would
not be det/eloped in the future. Also, the darrelopment rights for the easemenl areas could be
transfened to the Town of Vail and/or to the Eagle Valley Land Trust. This would significanfly
reduce the dwelopment potential ot Lots 8, 10 & 1 1 .
OPTION C _TAKE NO ACT]ON
The red hazard avalanche designation exists on a large portion ol Parcel 40 (Lots 8, 10, & 1 1).
The Town of Vail hazard regulations prohibit dwelopment in the red hazard avalanche area.
Hence, Council may decide not to take action on the subject lots. The dournside to this is that
although the red hazard area can not be built upon, the area is still included in calculating
dauelopment potential. Hence, the owners of Lots 8, 10 & 11 would retain all their existing
derrelopment dghts.
Town Council opted for Option C, to take no action on Parcel 40. The decision was rationalizd by the
faci that the Tom's existing hazard regulations and development standards will strictly regulate any
future dwelopment on this site. The Council noted that the owners should be encouraged to create
conseruation easements on their lots to ensure lhe preservalion of open space wfiile realizing a property
tax savings.
MEMORANDUM FIL E COPY
TO: Vail Town Council
FROM: Community Dwelopment Department
DATE: July 17,2ffi1
FORUM: Town Council Worksession, Executive Session
SUBJECT: Determination of Town Council interest in purchasing or acquiring conservation
easements on Lots 8, 10, & 'll, Bighorn Subdivision, Second Addition
SUiIMARY
Lots 8, 10, & 1 I , Bighorn Subdivision, Second Addition are referred to as Parcel 40 in the Gomprehensive
Open Lands Plan. Parcel 40 is idenlilied as a high priority for acquisition because it could proride access
lo a potential South Trail and is located in a geologically sensitive area.
The Community Ds/elopment Depanment has received a proposal to consolidate Lots 11 & 12. Another
proposal has been received to resubdivide Lots 8, 9, & 10. Both of these proposals were reviewed by the
Pfanning and Environmental Commission on June 25,2001. Since that time, it has been determined that
lhe minor subdivisions can nol occur withoul variances due to the lack of buildable area on Lots 9, 10, 1 1 .
& 12. Hence, a final rerriew ol bolh minor subdivisions and associaled variance requests is scheduled for
August 13, 2001. Prior to a final decision by the PEC, stafl would like to determine whether or not the
Town Council has an interest in purchasing or acquiring conseruation easements upon any of the subject
properties. There are three options:
Ornon A - Puasue A puRcHAsE oF Lors 8, 10 & 1 1
Parcel 40 is approximately 3.4 acres in size. The option to purchase the lots within Parcel 40 has
not been discussed with lhe present owners. The benelit to the Town in purchasing the lots is
that the Town would acquire all ol the de'velopment rights. Hence, the Town would be able to
ensure that the lots would remain as open space in pepetuity. Though there may be limilations
due to geologic hazards, all of the lots may be dweloped at presenl.
Oprtot{ B - Punsue coNsERvATroN EASEIENTS uFoN Lors 8, 10 & 11
The applicants' representative has informed statf that the owners of Lots 8, 10, & 11 may be
amenable lo the Town of Vail acquiring a conservalion or erwironmental easement across the red
hazard avalanche areas on these lots. This would not preclude dwelopment on the lots
allogether. Howgver, it could ensure that the geologically sensitive areas and sleep lots would
not be developed in lhe future. Also, the development rights for the easemenl areas could be
transferred to the Town of Vail and/or to the Eagle Valley Land Trust. This would signilicantly
reduce the development potential of Lots 8, 10 & 1 1 .
Oprtor G-Tme No AcloN
The red hazard avalanche designation exists on a large portion of Parcel 40 (Lots 8, 10, & 1 1).
The Town of Vail hazard regulations prohibit dwelopment in the red hazard avalanche area.
Hence, Council may decide not to take action on the subject lots. The dornside lo lhis is that
although the red hazard area can not be buih upon, the area is still included in calculating
ds/elopment potential. Hence, the owners ol Lols 8, 10 & 11 would retain all their existing
ds/elopment rights.
DEscRpnoN oFTHE MtxoR SueorvtsoN REouEsrs
The applicants, June Frazier and Jeff Dahl, represented by Steve Riden, have submitted an application to
the Town ol Vail Community Development Department for a minor subdivision ol Lots 8, 9, and 10,
Bighorn Subdivision, Second Addition. The request is for the reconfiguration ol the property lines shared
by these three lots. Currently, Lot 8 is 0.87 Acres in size, Lot 9 is 0.34 Acres in size, and Lot 10 is 0.30
Acres in size. With a resubdivision of these lots, Lot 8 would be 0.825 Acres in size, Lot 9 would be 0.372
Acres in size, and Lot 10 would be 0.357 Acres in size. The total area under consideration is 'l .56 Acres.
There are currenlly no dwelopment proposals for any of the lots. Howerrer, statf anticipates that these
would be lorthcoming if lhe minor subdivision is approred.
The applicant, Gary Weiss, represenled by Stwe Riden, has submitted an application to the Town of Vail
Community Dwelopment Departmenl for a minor subdivision of Lols 'l 1 and 12, Bighom SuMivision,
Second Addition. The request is for these two lots to be consolidated. Cunently, Lot 11 is 2.23 Acres in
size and Lot 12 is 0.71 Acres in size. The total area under consideration is 2.94 Acres. The creation of a
single lot would be accomplished by vacating the existing property line between Lots 11 and '12. In
conjunction with the minor suMivision request, the applicant is proposing to construct an addition to the
exisling singlefamily residence located on Lot 12.
BAcKGRoUND
The Bighom Subdivision, Second Addition was platted on July 22, 1963. The Board of County
Commissioners ol Eagle County apprwed the platting as the property was then under Eagle County
jurisdiction. Lots 8-12 have remained in the current configuration since being platted.
The Bighorn SuMivision, Second Addition was annexed into the Town of Vail pursuhnt to Ordinances 13
& 20, Series ol 1974. The annexalion became effective on November 5, 1974. Upon annexalion into the
Town of Vail, Lots 8-12 were zoned Two Family Primary/Secondary Residenlial. At the lime ol
annexation, residential structures existed on Lols g & 12, and Lots 8, '10, & 11 werevacanl.
In 1976, the Town of Vail contracted with Arthur l. Mears to complete a Geologically Sensitive Areas
Study. For purposes of the study, geologically sensitive areas were delined as snow avalanche, rock fall
and debris llow. In response to the findings of Mr. Mears' study, lhe Town of Vail adopted Geologic
Hazard Maps lor snow avalanche, rock fall and debris llow as components of the Town of Vail
Comprehensive Plan. The maps were adopted by the Town in 1977.
ln 1978, the Town of Vail adopted Hazard Regulations. The purpose of the regulations is to help protect
the inhabitants of the Town from dangers relating to development of flood plains, avalanche paths, steep
slopes, and geologically sensitive areas; to regulate the use of land areas wttich may be geologically
sensitive; and further lo regulate dwelopment on steep slopes; to protect the economic and property
values of the Town, to prolecl the aesthetic and recreational values and nalural resources of the Town,
which are sometimes associated with flood plains, avalanche areas and areas of geologic sensitivity and
slopes; to minimize damage to public facilities and utilities and minimize the need for relief in cleanup
operations; to give notice to the public of certain areas within the Town rvhere flood plains, avalanche
paths and areas of geologic sensitivity exisl; and lo promote the general public health, safety and weltare.
In 1986, the Vail Town Council adopted the Town ol Vail Land Use Plan. Like lhe Geologic Hazard
Maps, the Land Use Plan is a component of the Town ol Vail Comprehensive Plan. According to the
Land Use Plan, Lots 8-12 are designated 1or densily residential". The purpose of the low-density
residential designation is to provide sites tor single-lamily detached homes and twoJamily dwelling unils.
Density of dwelopment with in this category would typically not exceed 3 slructures per buildable acre.
Also within this area would be privale recreation facilities such as tennis courls, swimming pools, and club
houses for the use of residenls of the area. Institutional/public uses permitted would include churches,
lire slalions, and parks and open space related facilities.
ln 1994, the Vail Town Council adopted the Comprehensive Open Lands Plan. The objectives of the plan
are:
. To identify citizen ind visitor needs and preferences lor a comprehensive system of open space uses
such as parks, recreation, protection ol ervironmenlal resources, trails, and to reserve lands for
public use;
' To prioritize available open lands for acquisition or protection;. To identily crealive strategies to implement the acquisition and protection program;. To define a managemenl syslem to appropriately manage Town-owned open space lands, and;. To buffer neighborhoods with open space.
The Gomprehensive Open Lands Plan is an action-oriented plan that identifies specific parcels ol land
that require some kind of action either for protection ol sensitive lands, f or trail easements, or for public
use. In dweloping the plan, o'ver 350 parcels were s/aluated with 51 parcels on which aclions were
recommended. The recommendations were developed utilizing specitic criteria lo eraluale the areas of
highest priority. Generally, areas received the highest priority if they met the stated objectives of the
Town and its citizens and were an integral part of the open lands syslem. Within the 51 parcels, lhere are
five priority areas made up ol a number of recommended actions. These priorities are:
. Protect sensitive natural habitat areas, riparian areas, and hazard areas;. Extend the Vail Trail to East Vail and add several trailheads to access the trail:. Add a new trail on the north side and western half of Town to connect existing trailheads and
neighborhoods:. Add three'trailheads" in the core areas lo access Vail Mountain trails and inform visilors of trail
oppofiunities and prwide better access to Gore Creek;. Add bike lanes to the north and south frontage roads and add paved shoulders to Vail Valley Drive.
To date, the Town of Vail has taken action on at least 41 of the 5'l parcels identified for action in the Plan.
This most recently includes Lot 16 of Bighorn Subdivision, 2no Addition.
The Action Plan and Priority Plan of the Comprehensive Open Lands Plan identities Lots 8, 10, and 1 1 ,
Bighorn Subdivision, Second Addition as "Parcel 40" lor implementation purposes. Parcel 40 is classified
as a "High Priority". The high priority classification is based upon the Town's desire to acquire both the
dwelopment rights and trail easements tor the proposed Soulh Trail extension. However, in Seplember
ol 1999, Town slall worked wilh a former U.S. Forest Service trail construclion supervisor to determine
the feasibility of conslructing the South Trail from the East Vail water tank to Mill Creek and the Vail ski
area. As a result of this study, the following problematic issues were determined:
. Clitfbands and steep grades along the proposed route make acce$s to the trail from mosl East Vail
neighborhoods difficult and/or dangerous. Access points along the trail would be limited to the East
Vail waler tank and portions of the Vail Trail adjacent to Golden Peak.. The pending White River National Forest Management Plan r€visions change management direction
in the area from "Backcountry Recreation, Non-Motorized" to "Forest Carnivore." Therefore, the U.S.
Foresl Service may nol permit the construclion of a new recreation trail under this designation.
The plan also notes that Parcel 40 is located in a geologically sensitive area. Stralegies for protecting
Parcel 40 include purchasing the dwelopment rights, and/or acquiring an access easement through the
parcel.
As a high priority classification, Parcel 40 meels both Ls/el One and Lwel Two Evaluation criteria. Lsvel
One Evaluation locuses on meeting community needs relating to lhe natural resource system, lhe
recreation system, trails system, and reserving lands for future civic/public uses. Le/el Two Evaluation
focuses on the availability of the parcel ulilizing criteria such as the threat of dwelopment or irra,rersible
damage, opportunities to lwerage other funds, cost,uusual opportunity with a motivated seller,
J
opportunity for trade wilh the USFS, low managemenl requirements on the Torrrm of Vail and low liabitity
to the Town.
The Towtt of Vail Zoning Gode prescribes the land dwelopment regulations for dsrelopment within the
Town. The following code sections are particulady relevanl to the ervaluation of the applicants'proposals:
. Chapter6-Two-Family Primary/Secondary Residential . Chapler 21 -Hazard Regulations
The purpose slatement of Chapter 6 (Article D. Two-Family Primary/Secondary Residential (PS) District)
slates:
The Two-Family Primary/Smndary Besidential DistriA is intended to provide sites for
single-family residential uses or two-family residential uses in whidt one unit is a larger
primary residence and the second unit is a smaller caretaket apartment, t99ether with
suctt public facilities as may aproperiately be located in the same distrid. TheTwo
Family Primary/Seondary Residential District is intended to ensure adeguate light, air,
privacy and opn spacefor each dwelling, @mmqlsuratewith single-fanily and two-
family wupancy, and to maintain the desirable residential qualities of such sites by
establishing apropriate site development standards."
To dale, lhere are no slructures on Lots 8, 10, or 1 1 . This is due to the prwalence of geologic hazards
on these lots including avalanche and rockfall (see Figures 6 & 7 atlached). Dwelopment has been
proposed on Lot 1'l in the past. However, due to the dilliculties presented by geological hazards and
steep slopes, de4/elopment has ns/er occuned on the site. There are three geologic hazard analysis
reports in the legal lile for Lot 11. Each report identifies geologic hazards on the site including high
severity rock fall, debris flow, and snow avalanche. There are varying opinions as to whether Lot 'l 1 is
located in a moderate or high hazard avalanche area. Honrsyer, in a recent siudy ol Lots 8, 10, & 12,
Arthur Mears idenlifies an area of Red Hazard avalanche thal clearly impacts Lot 11. Figures 6 & 7 have
been attached for re{erence. All three of the reports suggest possible and potenlial hazard mitigation
measures; earlh-built struclures, locational siting of the structure, boulder barriers, a rear concrete
toundation wall protruding al least six feet abore linished grade and "splitting wedges". However, no
conslruction is permitted in a Red Hazard Avalanche area so these building techniques would not be
applicable.
According to the Hazard Regulations (Section 12-21-101:
No structure shall be built in any fld hazard zone or red avalandte hazard areas. No
structure shall be buift on a slope of fotty percent or greater except in Single-Family
Residential, Two-Family Residential, or Two-Family Primary/Swndary Residential Zone
Districts. The term "structure" as used in this Section does not include r&reational structures
that are intended for seasonal use, not including residential use.
Structures may be buift in blue avalanche hazard areas providd that proper mitigating
measures have been taken.
The Administrator may require any aflicant or person desiring to build in an avalandte
hazard zone of influence to submit a definitive study of the hazard area in which the appliant
proposes to build if the Tailn's master hazard plan does not @ntain sufficient information to
determine if the proposed location is in a rd hazard or blue hazard area. The requirement for
additional information and study shall be done in awrdance with Chapter 12 of this Title.
The Administrator may require any aplicant or person desiring to build in an identifid blue
avalandte hazard mne to submit a&itional information or reprts as to whether or not imryovements
are required to mitigate against the possible hazard. lf mitigation is required, said information and
reprt should specify the improvements proposd therefore. The required information and reprts
shall be done in awrdance with Chapta 12 of this Title.
4
B.
c.
D.
l-
il.ZONING ANALYSIS
Zoning
Existing Lot Size
LOT 8, BIGHORN SUBDIVISION, SECOND ADDITION
Two-family Primary/Secondary Residential (PS)
0.87 Acres (37,888 sf)
2DUs+,I EHU O 2DUs+{EHU
6,694 sf
7,187 6l
20ft.
15 ft.
1sft.
Proposed Lot Size 0.825 Acres (35,937 sf)
Standard Allowed Existinq Proposed
Density:
GRFA:6,889 sf 0sf
0sf Site Coverage: 7,578 sf
Setbacks:Front -20 ft. nla
Sides-1s ft. nla
Rear- 15ft. nla
Landscaping: 22,733 sf '
Building Height 33'max
undeveloped 21,562
undeveloped 33'max
o
LOT 9, BTGHORN SUBD|V|S|ON, SECOND ADDIT|ON
Zoning Two-Family Primary/Secondary Residential (PS)
Existing Lot Size 0.34 Acres (14,941 sf)
Proposed Lot Size 0.372 Acres (16,20a sf)
Cunently Proposed Standard Allowed Existino Allowed
.t
Density:
GRFA:
Site Coverage:
Setbacks:
1DU+1EHU
4,160 sf (+250)
2,968 sf
Front -20 ft.
Sides-15 ft.
Rear- 15ft.
8,956 sf
1DU 2DUe+lEHU
4,720 sf (+250)
3,211 sl
20ft
t5 fi
15ft
9,722 el
33'max
Landscaping:
BuildingHeight: 33'max
The existing development statistics for Lot 9 are not known.
a.
LOT IO, BIGHORN SUBDIVISION, SECOND ADDITION
Zoning Two-Family Primary/Secondary Residential (PS)
Existing Lot Size 0.30 Acres (12,898 sf)
Proposed Lot Size 0.367 Acres (15,986 sf)
Currently Proposed Standard Allowed Existino Allowed
Density: 1DU+1EHU
GRFA: 3,650 sf i
Site Coverage: 2,580 sf
Setbacks:Front -20 ft.
Sides-15 ft.. Rear- 15ft.
Landscaping: 7,739 sf
Building Height 33'max
*Lot 10 is an undevelop€d lot.
2DUs+lEHU
4,697 sf
3,197 sf
20ft
15ft
15ft
9,592 sf
33'max
LOT II, BIGHORN SUBDIVISION, SECOND ADDITION
Zoning Two-family Primary/Secondary Residential (PS)
Existing Lot Size 2.23 Acres (97,139 s0
Proposed Lot Size to be eliminated
Standard Allowed Existinq Prooosed
Density:
GRFA:
Site Coverage: 19,428 sf
2DUs+1EHU '
9,457 sf
Front -20 ft.
Sides-15 ft.
Rear-'15ft.
Setbacks:
nla
nla
nla
nla
nla
nla
nla
nla
Landscaping: 58,283 sf
Building Height 33'max
"Lot 'l 1 is an undeveloped lot.
Zoning
LOT 12, BIGHORN SUBDIVISION, SECOND ADDITION
Two-Family Primary/Secondary Residential (PS)
Existing Lot Size 0.71 Acres (30,928 sf)
Proposed Lot Size 2.94 Acres (128,066 sf)
Currently Proposed Proposed Standard Allowed Existinq Allowed construction
Density: 2DUs+1EHU 1DU 2DUs+lEHU 1DU
GRFA:6,146 sf (+250) 3,350 sf 'l1 ,003 sf
25,613 sf
20 tt
15ft
76,8,O sf
33'max
6,421 st
2,935 sf
22.5ft
17.5 ftt17.5 ft
16 ft'
124,385 sf'-
31'
Site Coverage: 6,185 sf
Setbacks:
1,378 sf
22.5ft
63 fU17.5 ft 15 ft
Front -20 ft.
Sides-15 ft.
Rear- 15ft. 16 ft'
Landscaping: '18,557 sf
Building Height 33'max
28,769 sf
31',
-The roof of the existing structure encroaches 1.5 ft more than is acceptable into a required
setback. This is a legally non-conforming situation.**lncludes natural areas not to be disturbed by construction.
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Nicholas Lampiris, Ph.D.
CONSULTING GEOLOGIST
0185 INGERSOLL LANE
stLT. coLoRADO 81652
(300) 8763()0 (?4 HOURS)
Ar-rgurst lCto 1??3
Robert Borne
5C,3?B $nowshoe Lane
Vai I CA 81657
ftHr l{arard Evaluahion, Lot 1. 1., Bighorn i*'nd Additinn
Dmar l'lr , Etonne r
It visited f"he above re{e.:re'nced lot in VaiL recently f clr purpose$
of a geologic haeard evaluation r especisl 1y as it pertains tf,r
r-oc[,: {aL l and debris avalanche potential " Ae you know t}Dth o+
t-trege lrarardg .are shown by the 'Iown of VaiI'5 naps as af fecting
yoLrr prop*rrty, with a "high severity' classif ication, l3now
av.rlarnche is also * poterrtial hatard at the site. Your have asJ,:ed
me to eval uerte thi s harard as wel 1 and ! el thoLtgh I do nclt
special ire in gnow avalanche studieEt I am involved i.n many and
o{ten am nsed as the expert in that tield" There{ore t have also
given my opinion as to this haenrd.
My general {indings are that the harards are indeed present and
that they al l shot-rld be mitigated as ef {ectively possitrle. The
titeep hillside above youtr home iii at least ,Sgr-t {eet high and is
hea.ri ly {orestecl . hjith re:ipect to the clehris avalanctre haaard, I
rjo not seter evi dence above ths home {r.rr any great thi ch:nnss of
mater i al hlecorni ng j, nv()I ved.The topography is a.[so Eomewhat
'f avorabl e in that there is a sw;\le on hhe slope which directs
material to the eas'L o{ the sub.ject lot n and also a ledqe o{ rock
about ?tXr {eet *rbove the tot which pre,ventg material frnm that
part of the slope {r-om easily reaching thig lot. There are a
nurmber o{ biE boulders near the curl-de*sac (indicatinE that there
has been signi{icant rock fall activity at the site).
The lot has a cut bench near the base which can be enhanced for
the home(s) and the rnitigation which wiII be proposed. I do not
believe that a large Enow avaLanche capable of geri oug
destruction is likely at this site. The main chLtte is well to
the east. The proposed rnitigation to ftll low should help to
protect the proposed home, which should be sited as +ar north cln
the lot ag; poseible'
Rtc'D OCL 2 LffiL
Becautse of the above cited {actors I believe it woutld be pos6iblt
to improve the situstion signi{icantly with sorne rnodifications tcl
the rear of the site. 'fhe very Large rocks on the site *hould tre
positioned as p€r a desiqn to be provided by me and an engineer
of your chcri cer t6 {orm a barrier acrclss the rear of the butilding
gite at or near the scrLrth boutndary o{ the proposed home. The
wall fi+ rocks Bhould be at least five feet high on the uphil. I
(soutth ) side and may contain dirt between the bourlders {or
cohesion,, added butlk, and for the potential +or veg*tation i{
that is desired. The rockE ghould be Flaced 6cr as to a{{ord
maximum protection. The pattern should be v-shaped burt should be
designed to stop or deflect alI threei o{ the potentiaI gravity
rel ated hazards.It wourl d be advanta6eoLts to i ncL ude a wel l
drai ned swal e on the sourth si de o{ the rock wal I to ai d i n
catching materi al wh j.ch may reach the site, incl urding e){cess Enclw
that could minimize tfre e{+ectivenegs o+ the wal. l.
The rear o{ the home shourl d be prow*shaped at the optimum angle
to receive only glancing blowt; {rom whatever gravity-derived
harard that mi Eht sti l I reach the strustLtre,Ag an added
precaurt i on the rear- of the home ghor-tl d be desi gned wi th a rear
{olrndati on walI protrudinq at least gix {eet above {inished qrade
and be capable o{ withstanding forces o'f up to 6(l{) pounds per
:sqlrare foot. There shoutl d be no windows in thig interval which
could break under presgure {rom dirt or snow which rnight still
reach the h ome.
Orainage around the home ghould be provided and the hnme should
be desi gned to prevent the accumulation o{ radorr gas as this is
becoming standard practice in the 9tate' Soils investigation +or
purpclse€ of proper f ourndati on degign shou.l. cl precede constrLlct j. on.
Becaurse of the ha:ard rac;utl ati ong of the Town n{ Va:i I o care rrLtrt
be taken to not increaseg the hazard tcJ a neighbor by vour
attempts at mi ti gati on,
The pr.operty doee lie in a qeoloqical 1y r;ensitive areaf bLtt
devel. opment wi 1 I not i. ncrease the h;rr ard to other property r otr
stnucturres, or to pr-rbt ic rights-of -wayo roadsr Btreetst
easementg n utilities or 'f acillties or other properties o{ any
hind, If there are {urther quegti onrir please contact me.
NicholaE Lampiris
Coneultirrg Geologiat
o o
FIGURE 1
a66l I e lc00'3iu
Robert Borne Constnrcdon, Inc.
P.O. Box /tzos
Vail, Colorado 81058 :!ttuoui i I t99z
A/ttt /Jk 6..r'4 /t{--J^^'</b=-
Town Of Vail / , /
Of f ice of Community Development U-h-u t"--^-- {Vail, Colorado 8155? t/ d
Att: Krlsten Pxltz, Director ,("Ul S"-,--ta /"J rL4
october 20r":-992
Dear Kristen, Pr-rr,fu *..--h---L-^._' /\ /f4.L.^..-'< tc/V\r-I have Just recelved the geologlcaI study'fb-r Lot 11, Bighorn
subdivision from Hydro-Triad, Ltd. As you know the lot is in an
area of possible avalanche influence which could require a site
specific study to see if a home can be built and occupied safely on
il. I therefore engaged the serviees of Hydro-Triad, Ltd., Nick
Lamper is and Intermountain Engineering to provide such a site
evaluation.
f am enclosing herewith two copies of the Hydro-Triad, Ltd'
report, two copies of a hazard evaluation made by Nicholas
Lamperis, ph.D. as well as three topographical studies made by
Intermountain Engineering. I also enclose a separate copy of a Snow
Avalanche Hazard Zone map prepared by Arthur I. Mears which clearly
shows Lot 11 to be west of the high avalanche zone and in an area
he identifies as MoDERATE I{AZARD. I also enclose a copy of a report
which was issued for lot 15 ( presently under construction and
which is East of lot 11 and obviously nuch closer to the chute
marked as number I on the maP.
I believe that both reports clearly show that a home could be
built and safely occupied on the lot with mitigation and that this
construction would noL have any adverse inplications on any
adjoining property or property owners.
I am pteparlng to start mltigatlon englneering and have t9
take tltle to the lot on November 15th and to that extent would
respectfully request an admlnistrative determination that I can
indeed secure a permit to bulld (wlth proper approved mltlgation),
prlor to my having to expend these further dollars.
I shall be more than glad to meet wlth you and your staff to
answer any further guestions that you may have.
once again I thank you for your courtesy and look forward to
hearing from you.
ct fu1
Bob Borne
29 May, J-992
Arthur I Mears, p.E
Krlstan pritz, Town
John M. Perkins, A.
xro,lutl 2 1992
of VaiL Department of Community Dev.I .A.
carroll Tyler
Sales Associ ate
Sitzmarl< Lodge
Vail, Colorado 81657
Dear Carroll:
Pursuant to conversations vith Arthur l4ears, natural
hazards engineer and author of the -?L October, 1990
engineering study of Lot 11, Bighorn ZnC ACCition,gast Vai1, Colorado, my architect and Kristan Pri+-z
of the Town of Vail Department of Community Develop-
ment , -w:e have concluded-. that the 1ot is in f act ur-
builCable. Mr. I.{ears bas stated to us that' the site
is i.n a "red zone" anC subject, therefore ' to the
restrictions of the relevant Tolsn oi Vail orCinances -
Further, it has been noted that another engineering
study might de+-errnine that the site is buiLdaSle. I\te
strongLy feel, hor-ever, tha'- based upon the hiEltly
reputed credentials, experience, integri!y and status
of NIr. Mears as consulting engineer for the Town of
VaiJ- regarding natural hazards that his analysis has
helped us to conclude that this location could not
be built upon both safely and economically. It has
been explained tc us that another englineer's hazard.
study might indicate that the property nas in fact
bui1Cable, We believe, however, that tbis would be
merely paying to "hear what we wj.sh to hear". rn
the event a future buyer should put |.he parcel under
contract and obtain another hazards evaluation favor-
able to construct j on , we rsouLd request that the To\"'n
of Vail seek a third opinicn to Cetermine the validi+'y
cf tlre conf licting report.
For these reasons $e are exercising our righ+- per
signeC real estate contract of 27 May, 1992, +-o
Ceclare said agreeroent nu11 and voiC a:C rquest re-
turn of all earnest nonies.
r-t-:
FIL T COF Y
7 J Soatb Frontagc Road
Vtil, Colorado 81657
t 0 t -47 9 -21 1 I / 47 9 -21 t9
D cpartment of Commanity Dclelopmcnt
June 2, 1992
Richard and Sheila Norris
38!|8 Bridge Road
Vail, CO 81657
Dear Richard and Sheila:
Thank you for your kind note of thanks conceming the research on hazards for Lot 11,
Bighorn Second Addition in East Vail. I wanted to add one more comment to your letter
concerning the issue of whether or not this site is buildable. When I discussed the issue with
Art Mears last week, he indicated that it may be possible to build on this site if the house was
completely underground. Of course, this would be quite an unusual structure. However, I felt
it was important to note that this was my impression from my discussion with Art Mears. In
addition, Art noted that there was a conflict with the Town of Vail ordinance in that people are
not allowed to build structures within the red avalanche zone. This study indicated that the lot
was in the red avalanche zone, however, a structure could be bullt if it was constructed
essentially below grade. ln addition, a second study may be submitted which may indicate
that the site is buildable. As you know, a similar situation occurred on a lot in Snowshoe
Lane.
lf you have any further questions, I will be happy to discuss this issue with you further. I will
be sure to put your letters in the permanent fils for this lot for future reference.
Sincerely,
t/ I nl
fvrslan [cf+
Kdstan Pdtr
Community Development Director
Arthur Mears, P.E,
John Perkins, A.l.A.
ARTHURI. MEARS, P.E", INC.
l.hnnrl tLan& Corulrar
Zl2 Eu Godt Ava Gdn, Cdc& st2xl nt-ut.tz%
I
S!t,r ftrro0ar.le.
Poct-{dl
lr-\tqhuv'
H'fluu
Por,th Nrol J,'{tto^t.I
l\[0. tD$lTL t:tff.
debris
Addition
Arthur I. Mears, p.E.
Avalanche-control engineer
Encr. )n# t\&,
llM "
\\"d0
fiblyd4'. A&cter . A&rhorrtn! eqncca
October 31, 1990
l{r. Bryan Hobbs Vail Associates Real Estate P.O. Box 7 Vail, CO 81658
Dear Mr. Hobbs:
The enclosed analysis of rockfall, snow avalanche, and avalanche affecting Lot 11, Bighorn Subdivision Second was cornpleted as we discussed 6arlier trris-no"Irrl-
PLease contact ne if you have any questions or desire additionar consultation.
"'friril{] \1tca*&' N'\- o'.wA^ /-.'\\ttt''\
Vt(x,,,.pn^.\ 6,',j 'f e( v'ri'u
il.r,e\l a- rrr{81.\'''itil-*d r
L\w$qr o- \ot!:t\-^q t,^^U
ikis \^"\d"I& 0
I
BOCtrFAr.L, SrOt lvll.lllcEE, ltiD DlBnrS rvl!'lxcEE lltll,rslE
&o!! 11, BTCEOnII SUEDrVISrOX, SBCOIID lDDrlIOr
Prcprr.d Por
t|l. Bt:rrtr lobb!
Prepared By
Arthur I. lleara, P.8., Inc.
Gunnison, Colorado
October, 1990
gUU}IANY IND RECOT,TITEITDAIION8
Lot 11 is exposed to rockfall, snow avalanches, and debri.s
avalanches over the entire area of the lot. Design-magnitude
events, which nust be considered in-planning and engineering,
have been considered in this analysis.
The design ROCKFALL event, based on field observations and a
conputer sinulation of rockfall, will consist of a 3-foot
diaileter rock which becones detached and begins rolling at the
limestone cliffE, more than 300 feet above the building site. At
the buitding site, this rock will have a velocity of roughly 7o
ftlsecond (48 nph) and will be bouncinS 3! least 13 feet above
the ground. Such conditions requi.re ranking the site as
poteitiatly Hiqh Hazard Rockf?Il. Mitigatign o! rockfall could
Le achieved only by construction of a catching fence innediately
above the building site. However, such construction would not be
practical because of the snow and debris avalanche exPosure
described below.
The design SNOW AVALANCHE event will begin approxinately 500 feet
vertically above the building site (north end of Lot 11), will
fall over the linestone cliffs and reach the bullding site at
approxinately 5o urph velocity.. stagnation- pressures of such an
eilnt will exceed 1,000 lbs/ftz. Such high pressures define the
building site as lying in a potentially Hiqh H?zard Snow
Avalanche area. In accordance with Town of Vail ordinance,
Uuitaing iE not pernitted in high-hazard areas.
The design DEBRIS AVALANCHE event will begin on the lleep slopes
below tfri }inestone cliff, will entrain wet snow, soil, rocks,
trees, and other vegetation, and nay deposit up to 15 feet deep
at thi: building site. Although veloclties and pressures are less
than those associated with snow avalanches, irnpact with a
structure will be conplicated by debris entrained into the flow.
MITIGATION of the rockfall, snow avalancbe, and debris avalanche
can be achieved only by avoidance. At this site avoidance could
be achieved by building underground, into the hillside and
forcing the slope Processes to pass over the building. some
residuil risk would be roaintained, however, because the persons
one wishes to protect nay not be inside the specially-designed
structure when the design event occurs.
l
a OB'IESIIYE8 IND LII|IEIIIOIIA OF 8l!!DI
Thisanalysisof|ldesign-maEnitude||rockfall,snowavalancheand iilii:-r'-."arinctre on Lof 11, was reguested PY uT- Bryan Hobbs of
illi-e"""ciates neif estate and hai the followinq objectives:
a. Analysis and computation of rssjgell hazard on the
lower Portion of Lot 11 i
b.Analysisandcomputationofsnowavalanchehazard
on the l6wer Portion of Lot tli and
c. Analysis and conputation of debris avalanche bazard
on the lower Portion of Lot 11'
The study is site specific,- therefore the results and conclusions
should not be .ppfiEa to oiher sites' Furthernore' although-the
analysis present=ee-i" tf,i" ieport does provide anal'tical and
cruantitative des;;ipii""= ot ine rockfall and avalanche
;;;;;;;;; ;e;is;-;iii'"t"r= ror structures have not been
;;il;;-l"I-"i3 u'.,y-na tne scope of the present study.
2 ROCXTIID llrllllgrs
2.1 PREVIOUS WORK
As indicated on aerial-photo mapping :9IP]t!:1 f-?I the Town of
VaiI in 1984, l,"i-ii-it-iocatea'in i ngigtr Severityr rockfall
area which was defined as follows:
rRock outcrops were thick or nunerous and uore than 1o0
feet abov" ;f,; ;iiri"iaa ritn =igtrlficant fracturins and
;;hd; a riitg lLii"t--ot rocks or boulders at the base
-oe a lteeP htllsid€"'rl
TheTownofVallstudystatesthatadditionalstudiesonrockfall phenomenanayaffir:n'negate,-or.reguiresubstantialrevisionsto iii:"ffi;rnir' oi-iil-'i"ttt'"t"iy, inciuaing revisions to the hazard
ii".= and ieveritY definitions'
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A field site insPection
1990. Observations made
sunmarized below-
of the site was cornpleted,on october 23'
during this site insPection are
a. the rockfalL sources consist of a rnassive llnestone
i"t"iJpping iocated south and approxLmately 320 to 360
feet above ttte =iit. Rockfall rniy also begil on-the
steep, aspen ""tt"""a coiruviaf sl6pe below thb cliff'
which has a row"r-iErtittot ut the irorth end of Lot 11'
I The rockfall process Itas sinulated tbrough application of the
rcolorado Roci<faii Sinutation Progran, rr (CRSP) , a computer
Drocrran tnat courputes rockfall veiocities, bounce treights, and
iun5ut distances-given input data about slope steepness,
i""gh"""", and haidness. The CR5P nodel treats rockfall as a
si"6n."tii process in which a large nunber of sinulated rockfalls
ffi.sizeacrrievevariousve1ocities,bouncehei9hts,ald i""o"[ distances, just as they do in nature. In nodeling rocks
"t iJt ii, " a-f6o€ dianeter iock was assuned' and 100 rocks of
ihis size vere rolled (by cRsP) down the slope to produc
=titi"ti"al range in rdci<tatl tehavior. This computer nodel has
been tested extensively and is used regularly in design of
rockfall ruitigation in Glenwood Canyon'
InapplicationtotherockfallaffectingLotll,-slopesteepness
wa= ii.rured, and estinates of slope lrardness and roughness were
;;r"il;e-Uy ifirUi.ng the steep colluvial slope to the linestone
"oor". arei. The piogram nas run and input paraneters were
iajustea so that t-ne 5Pservea distrlbution of rockfall stopping
noiitions along tne ariage Road cu]-de-sac etas duplicated' The
fi;;;;ii"ai Cnip nodel, therefore, was forced to simulate what
has actuallY occurred at the site.
Because rockfall behavior at the building site.located on the
north end of Lot 11 is of interest, an nanalysis-pointrr was
"no="n at this locatlon for generation of rockfall statistics by
the CRSp model . ,iExceedance probabilities'r of 5, 10, and 2Ot
were used to deternine the de3lgn rock behavior. This means
iila,-accoraing to CRSP, there ire 5, 10, and-2o* chances that
itre ioffowing ialues wiit be exceeded by a 3-foot diameter rock.
b. Rocks of various sizes, up to lO-feet in diameter
have rolled down the slope and over Lot Xl in the past,
however smaller rocks up to 3 feet in diaroeter are
tlpical of this rockfall area.
e. Roclcfall is not a annual event at this location,
however some fresh rockfall was observed on the steep
slope where rocks had been stopped by trees.
d. The slope supports a dispersed aspen forest and has
a rough sur?ace;-Loth factor! were considered in
cornpu€er sinulation of rockfall at the site'
TABLE 1. Design Rockfall Characteristics
Exceedance P velocitv Bounce Ht Kinetic Enercrv
225,994 ft-Ibs
2O9,L56 ft-lbs
L72,4oL ft-lbs
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I 5*10t 208
79 ftls 18 ft
76 ft-ls 16 ft
69 ttls 13 ft
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3 8IIO.r.IYIIJA}TCEE IITILYSIS
3.1 PREVIOUS WORK
Lot 11 ls located in an [avalanche influence zonerr on Town of
i.rr-r.p" produc-a in 1977. This designation neans that
i""f"""i,"=- or" in""ght to affect the site, but that the avalanctre
o=o"..t has not U."" quantified to determine the leve1 of -severitY or Potential hazard'
Inspection of Table 1 indicates that the snaller probabilities
;#;;;;e a; higher verocitv, hisher enerery, and hisher bouncins
i""ii.if events. - Hote.ter, even the least conservative (2ot)
;;;ffi;it has large velocity,. energy, .and bounce heights and nould
;;-ei;-i"urt to iesign for at this site'
Appendix A at the back of this report contains the detailed data
l:i"I"tlra-uv trre cRSp rockfall nodel and will enable alternate
ili;;-;; "i.""a"t.e probabillties to be used for design
purposes, lf desired.
As noted in Section 2.2, the slope tras clinbed on october 23'
-iggci . ouring this site inspection, clear evidence of snow
i.rai"tr"ne infact-irt"ai.t.t! Uetow' the lirnestone cliff indicates
in.I-i".f.r,c-h"r frave legin ibove the cliff and fallen on the
lower slope. ftr-iaai.ti5n, observations indicate a sufficiently
dispersed forest wnicn uiil also allow small avalanches to begin
within the trees n.ro" the linestone cliff. Danage to the trees,
i".i"ai"g broken 1G;4, be.t nain stens, and debris aligned down
;i6" suigest periodic' avaranche activity'
Thedesign-naEnitude("lOO-yearrr)avalanche,aneventusually
"or,ria.t6a in-prinnini ina Lnginlering of fixed facilities at
n;;i; was anal-yzed by the following 2-step procedure'
a. Avalanche runout distance, or stopping position,
wasdeterninea-tnrougilFPliEationof astatistical
ieg."ision equation basea- on 112 docunented rare
i"ipto*. tq[:year) avalanches studied in colorado'
b. Avalanche velocities along the path profile were
then conput;d EE;ugh-;pricafion oi a z-friction-
ainauics't"a"r-si"ei a -siar?ine p9?l!i:" ?!:1" th"
Iinestone cliff and a stopprng P-osition' deternined in
si-p "a," ai-irre intersection-or Lupine Drive and
Bridge Road.
| ..,.. .-.
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The conputed deslgn slow-aYalanche velocity and stagnatl-on
pi""rotl at the buitding Eite on Lot 11 are eumnarized in Table
2.
TABLE 2. Design Snolt Avalanche Characteristics
VelocitY: 22.6 als (50 nPb)
Stagnation Pressure: 51.1 Kia (1,068 lbs/ft2)
Appendix B at the end of this report contains the detailed
c-oiputations of the avalanche-dynamics analysis.
The pressure computed at the building site (1,058-tbs/ft2) is
subslantially in excess of the naxirnum pressure allowed in snow-
avalanche trB1uetr zones by Town of Vail ordinance, which al'low up
to 615 Lbslftz. This neans the building site, located at the
northern end of Lot 11 is in an avalanche nRedr zone, an area in
which residential construction is not pernitted by vail
ordinance.
. DEBRIS IVAIJII{CEE8
4.1 PREVIOUS I{ORK
As indicated in a 1984 report to the Town of Vail, Lot 11 lieE
within a high-hazard debris-avalanche area. Such areas are
defined in the Vail study as follows:
trlheise (high-hazard debris-avalanche) areas can
experience severe structural damage by inpact and
deposition of wet snou, soil, rock, and debris.r
Building within these areas is not reconmended by the Town of
Vail unless nitigation can block the flow, thereby reducing the
area of debris avalanche runout and preventing these events fron
reaching the proposed development.
4.2 CT'RRENT FIELD OBSERVATTONS
Field observations nade during the Octobet 23, 1990 site visit
indicate the steep slope above Lot 11 shows past evidence of
debris avalanches. Such evidence consists of undulating (lobe-
shaped) deposits and unsorted debris. The slope is sinilar in
teris of slope, soil, and vegetation, to several that produced
debris avalanching during the rapid thaw which occurred in the
Vail area during UaY, 1984.
4.3 POTENTIAL DEBRIS.AVAI,ANCHE CONDITIONS
Debris aval-anches will be much slower-noving that the snos
avalanches described in section 3, consequently they will not
travel as far into the runout zone- Nevertheless, Lot 11 is
steep and debris avalanches will cross the entire lot. Based on
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observations of nany sinilar avalanche events in the Vail area
during L984, debris avalanches will consist of wet snow' soil,
rocks, and entrained aspen and other vegetation, conseqluently
they would have a very high flow and deposit density. At the
Uuilding site, deposits of up to 15 feet thickness could occur
which would produce vertical pressures of 500 lbs/ftz. Dynamic
tlrrust for debris avalanches that stop in the cul-de-sac about 50 feet below Lot 11 could reach 25 KPa (520 lbs/ft'). Although
this ls less than the design snow avalariche pressure discussed in
Section 3, inpact nay be even nore danaglng than that associated
with snow avalanches because the flow will contain tree trunks
and rocks which can serve as battering rans on exposed
structures.
The present study, therefore, concurs with the rrHigh-hazar6n
rating for debris-avalanches defined in the Town of VaiI study.
Residential construction is not pernitted in high-hazard areas.
5 ilrrrcAtrof,
Details of nitigation design are beyond the scope of this study.
Honever, the following points should be considered lf nitlgation
ls to be considered at this site.
a. Surface buitdings (with exposed uphill walls) will
not be practical because of high inpact loads and would
be in violation of Vail ordinance.
b. surface aval.anche/rockfall defense structures,
intended to stop avalanches and rockfall above the
buildlng site, would not be practical because of hlgh
inpact loads.
c. Certain tlrpes of underground construction which
would avoid irnpact loading nay be feasible, but uay be ' undesirable fron the standpoint of building design
and/or appearance.
Rep4rt prepared by,
L\[1-^4 |(ll.ouo
Arthur I. l.tears, P.E.
Avalanche-control engineer
t,
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I FILE NAME \.rocksi te\hobbE. 1
COLORADO ROCII:FALL SIMULATIBN F'ROGRAM
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ROtrI{ STATI5TICs
If,f," LE gFHERICAL ROtrI.::
NUMEER OF CELLS
NUMBER OF ROCF:s
ANALYSIS FOSITIOI'J
INITIAL Y ZONE
INITIAL X VELOCITY
INIiIAL Y VELOCITY
1 .5 FT F{ADI U9
7
100
f,4(l
705 TO 715
1 FTISEC
-1 FTISEC
]NPUI DATA
EEG i NN INE
XrY
O , 7t-it-t
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155.56rj
nfrq qarr'r :r-.gtLrir-.
!90 . 4ht:,
36(l . 4OO
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CELL *
SURFACE
ROU6HNESS
TAI.J6ENT IAL
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APPffDIX A. Rockfall sinulatlon ushg mSP.
A-1
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o d o
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A d
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c9 e
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Y FEE' I ?1 FEET ?63f,1: FT
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V.E!-qEIIY
ieHu++,iEignil'""
"'
ANALYSIS PDiNT EOUNtrE HEIEHT DISTRIEUTION
106 exceed.a.nce probabillty (typ)
4(l 50
DISTRIBUTION
t
-r rrr r i ata s
clq teg
10% exceedance
probabilitY (tYP)
4 4-
4 4-
+4-1-
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HE- l LtFt I -?1
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ANALYSIS-FCIINT VELDE
L t' t'i,f ,r, r,
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'r rt EI t?t1i?r?rlririrTri J r rlrt,l
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ITY
t{it{tttt
FREGIUENEY 84.7+64 qd -4;3c a4 T +tt
Statlsticaltnfornatlonofrocktelocltyandbounceheightgenerated
at the "analysls point" (uu:'tarng slte) '
A-3
trrrff
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\rocr';=it"\EEEREit*rru*, GRAPH
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A-4
AVERAEE I.,IAX I PIUI,I EOUNEE EOUNCE HEIEHT (FT) HEIEHT iFT)
913 4L4 4 n-l
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( FT,/SEci
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RDCI{:S STEF.
STANDARD DEVIATIDN
VELEC I TY
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validate use of tlre CRSP nodel at this location.
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Enter r-l".e. oi f i 1e wi th Prof i I e \oroco\hobtts dFt---fi rst gue5s for mass/drag Calculation Frpcess lF. s-tartlnE.
i terat r on comp r eEe wl !,n FiLtn uuc
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HOEES AVALANCHE:East Vail, Colorsdo
Avalanche doe€ not stop.
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PLANNING AND ENVI RONTlENlAL COMl,lISS ION
May .l0, 1982
STAFF PRESENT
Jim Sayre
Peter Patten
Peter Jamar
Betsy Rosolack
CqUNCIL REP
Chuck Anderson
called the meeting to order and asked for a motion to
April 26. Duane Piper moved and Diana Donovan seconded
vote of 5-0 (Jim M. hadn't yet arrived).
PRESENT
Scott Edwards
t,lil I Trout
Diane Donovan
Duane Piper
Dan Corcoran
Jim Morgan
AqsSNl
Jim Viele
Dan Corcoran,. chairman,
approve the minutes of
to approve them wjth a
uest for a variance from section .l8,58,020 in order to build a l3 foot
e wall on
nnon va ures,
Peter Jamar reviewed the merno and Ron Frickel ,.engineer for the applicant, expla'ined
the criteria for the wall. He explained that the greater the angle of the wal 1, the
higher the wa'll must be.
Susan Kitler, owner of lots 8,9 and i0 voiced her objections to the wall and
sonre concerns. She asked about the landscaping of the wall, and also asked if
the wall would be diverting the avalanche to the adjoining lots, She asked that
there be an independent study rnde. Frickel answered that the Mears report did
not answer this question. He added that in the report the avalanche
appeared to follow a certain line, but that there was no way to predict this.
Jim Shannon,-applicant, answered landscaping questions, stating the intention
to plant 4" aspen on the exterior of the wal 'l , and 2-3" aspen on the interior.
He added that the terracing would be only visible from the back side of the building.
The walls of railroad ties would be 5' high, and the concrete wall on the ends
would be higher.
Peter Patten explained that one problem was that there was no comprehensive stndy
nnde of the entire ava.l.anche path, that it was uncertain how this lot fit into the
avalanche zone as a whole, The PEC members were concerned about the influence the
wal1 might have on the adjoining lots if there were an avalanche. Duane suggested that the build'ing might be shorter,.thus requiring a shorter wa1l. After more dis-
cussion.;the PEC members decided more study of the influence on the adjoining lots
was needed and required the applicant to submit a study showing where the runout
of the snow would go from this wall. The applicant asked to have the item tabled until the meeting of May 24. t.lill Trout moved and Edwards seconded to table the
re.quest until the meeting of May 24 as per the applicant's request. The vote was
ftO in favor of tabling.
PF.C 5/10/82 -2-
2, Igq-qe-qt ro-r 1!nq,r*oulou".-0r,,*!=,n oao=rlj1-slgl-L a gue .p-ql-o.t at fl![ NdrTh. rrqr'-er$.f"s{_:s._._i_'r_6;&;T-ga1lltil-blEfde{!_ft!]ElqEr e:.^_.'.-.-gn{_I[e_!!tlejovrgf-l!,gp_._ Appl'icant: Game City, Inc.
Jim Sayre expiained the sjtuation adding that the staff had three conditions
of approval . He added that he had called lease holders in the area and received
neutral comments. Gary Mitchel 1,. ovrner and appl jcant, added that he had vjsited
people jn the mall and received favorable comment. He stated that the arcade
would have a full time permanent manager and would allow no smoking, drinking
or food in the arcade.
Mrs, Al 1en',tr llest Vai'l resident voiced her objection to the arcade, stating
that it could have no possible benefit, and that she had considered asking
Safevray to remove their amusement machines. She added that her children were
constantly scrounging for quarters, she didn't see how the arcade could oe continu-
ously po1 iced. She felt that an arcade could be in the town core for the tourist
children, but should not be in West Vail where it would appeal to the local
chil dren,
Larry Kalusjn of The Great San Francjsco Seafood Company supported the arcade
as long as there would be full tjme supervision. He stated that the Avon arcade
was not supervised and objected to the lack of supervision.
Gary-Mitchel 1 , appl icant,.,answering l''lrs. A] 1en, stated that he had teen agers
and felt that their superv'ision vras his responiibility. He felt that the-environ-
ment of the arcade would be similar to the loca'l movie theater. Mrs. Allen
andwered that she had talked to the'local police chief and that he had stated that arcades do attract drugs and drug pushers. After more discussion, the
commission members were polled as to their feelings.
Piper pointed out that the arcade was in accordance w'ith the ordinance which
had gone through months of discussjon and public hearings, and unless the arcade didn't meet the criteriar-he was for it, and approved of the l year time period,
Trout was against the ordinance, but said that the appljcant's request was in order.
Donovan sajd that she had talked to Rags to Riches and that they were concerned about_the-noise,zthat they stated they-were sometimes bothered 6y the noise fronr The Great san Francisco seafood company, She added that sh-e wasn,t sure whether thjs was good for the neighborhood,-though she did feel it would be alright for tourists.
!|gryun's feelings were that there had already been enough study done, tirat the
PEC could not anticipate problems, but could deal with ihem wh-en they arose.
corcoran stated that exjsting ordinances dealt with drugs, liquor and nojse
and that the one year time period would allow the PEC to recorisider in one year.
Scott Edwards abstained from comment because he had an interest in the arcade.
Peter Patten reminded the citizens that the arcade ordinance had been under discussion sjnce last November and that the staff had concerns, too, The reason for the one year limitation is that the arcade is in an area not as'much oriented to tourists, but that it may prove to be a good ne.i ghbor,
PEC 5/10/82 -3-lo Diana asked about the hours, and Mitchel 1 respondeilthat they were thinking of ll to 11,.-but would fashion the hours to the dt-.nrand, Patten asked why the office space was so large and reminded Mitchel 1 that Lhe offjce could not be
used for any other use other than an offjce for thc arcade,
Duane Piper moved and Jim Morgan seconded to approve the request for conditional
use to instal 1 a major arcade in space #6 of the lllest Vail Mall as presented
in the staff memo dated May 5,.,1982 with the three conditions therein.
The vote was 3-2 in favor with Corcoran, Morgan and P'iper forn Donovan and
Trout against, and Edwards abstaining. Donovan and Trout felt that the arcade
was not in the best interest of Vail.
estate office out of
Bob Vol iter
and discussion cerrtered on the fact that there
Dan stressed that if, at a later date, there jcant would have to return with another request.
be tabled until May 24. Trout moved and
5-0 in favor of tabling. (Edwards out of rool
favor
+,
3.. Requast'.fo| conditjbnal use permit to operate a real Tfi-q-.!iTdT_,_q r@
Peter Patten reviewed the memo,
seemed to be no negative jmpacts.
may be a wish to expand, the appi
Trout moved and Donovan seconded to approve the request. The vote was 5-0 in
(Edwards had left the room.)
Peter Patten requested that this item
Piper seconded to table. The vote was
5.Proposed Aqteriai- 8ui;iness Zone
(Jim Morgan was one of the applicantso and therefore djd not participate as
a PEC member, )
Peter Patten reviewed the memo and went over the 6 major changes. Then the
members reviewed the changes proposed by the staff,
Patten suggested that .|8.27.070 Height be changed to read: ".l0% of the roof may
be flat to allow for a transitjon of roof lines," e1 iminating any reference to
the Design Review Board,zand setting a definite percentage of flat roof allowed.
Patten pointed out that the businesses that would be high traffic gerrerators were placed under Conditional Use. Al l.lilliams, one of the appljcants itatea that -
he wanted to see under Permitted Uses,.-those businesses that wouid augnent
business offices.., Bob Voliter, another app'l icant, stated that the setback require-rents listed were too stringent for his property, which was Iong and narrow.
Other concerns of Voljter were the fact that signs would not be allovred facing
toward Ir70, that the view corridors be addressed, wlry retail was not allowed
on the 2nd floor, and why the housing was limited to employees,
Patten stated that retail was limited to lst.floor to he1 p ensure its successo
and to make sure that there was not too much retail square footage whjch would
make the zone more of a shopping ma1 1. Corcoran ansrvered the sign question
by stating that this area was being treated jn the sanre t.lay the rest of Vail
was treated in the sign code, He added that varjous proceedings could be taken to get variances in signs and setbacks, Steve Isonr, architect for l,lilliams and
Morgan, stated that he wished Vail Associates and Ho'ly Cross had sent representative .to the meeting.
t"
-4-PEC 5/10/Bt
Will Trout stated that he supported h'igher F.A.R. than .75. He added that in
some of the original discussions, there was talk of having a high relatjve
density to support a lower rent area, and he did not understand the changes
nnde in the ordinance;'such as rernoving some uses first listed and lowering the density. He added that he still wanted to see interior pedestrian ways within
the property lines and ment'i oned some examples in other parts of the country.
He said that this would jncrease the value of the property and would increase
the commercial frontage. Patten reminded Trout that the ordinance required
the Plannning and Environmental Conrmission to adopt a general circulation and
access pian, Corcoran felt that the issue of pedestrian ways was addressed within the ordinance requirements. Piper felt that the ordinance could be gotq :tringent so that bike and pedestrian paths would be required rather than
f-rofosed. Morgan expressed the cbncern that the pl an not be tasTln cement, but
rather leave some flexibility as to r,rhere to place the buildings, Discussion
fo'l lowed concerning the location of a bike path.
Donovan suggested that the employee housing be required. Patten said that it
could be done, Much discussion on this topic foTlowe?l Patten added that a couple years.igo the issue of requiring a certain % of employee housing was considered,
and the Town Council decided to use the informal bargaining procedure instead.
Donovan a'l so felt that the traffic generators should be labeled as such for future
PEC members and p1 aced under Conditional Use, 't
Edwards felt that the G'len Lyon 0ffice Building should not be included in the districtZbecause the building could then be torn down and anothero larger
bui'lding put in its place. A'lso, this would be up zoning.
The cornmission then went through the lists of permitted, conditional and
accessory uses and made many changes,
The_question of requiring employee housing came up again, some feeling that'if
employee housing were required, other housing must be required, and oihers feeling that incentives could be g'iven to build enployee hous'ing. Donovan felt
employee housing should be requiredr-Piper felt that employee housing should not
be required, A vote was taken to see how each of the 5 members felt. It ended in a tie wjth Trout undecided, Duane and Scott against, and Corcoran and Donovan in favor, It was decided to include this in the report to Town Council,
scott Edwards moved and will Trout seconded to send to the Town council the
commission's recommendations on the proposed Arterial Business zone district
as amended by the staff and pointing out that the Commission was divjed
on the employee requirement issue,
The vote was 3'.2 in favor with Dan Corcoran that employee housing should be required in
and Diana voting against. They fe'lt this district. (Jim Morgan abstained.)
0, rngqll-elt*f,gr tgndgrqj!-i}In -c-olversio .]gg,e Wcs-t #I flppr'tcant: uenn'ls 5htmon
Peter Patten explained that the applicant requested to table to June .I4.
Donovan movedr;'Trout seconded to table as per applicant's request. The vote was 6.0 in favor of tabling to June .|4.
The meeting was adjourned at 6:45 p,m.
T/TLE INSURANCE Compa Qallas
Atachod to and forming a part ot
Policy r.r o 024789
lssusdbv vail-EagJ-e Titl-e company
USLIFE Title Insurance Company of Dallas
Schedule A, Date of Policy is hereby amended to read:
Aprii- 28, L982, at 8:00 A.M.
thereol.
^. May 7, L982
t
This endorsement is made a part of the policy or commitment and is subj€ct to all th€ t€rms and provisions
thereot and of any prior endorsements thereto. Except io the extent expressly stated, it neither modilies
any ot the terms and provisions ol the policy or commitment and prior endorsements, it any, nor does ii
extend the effective date of the policy or commitment and prior endorsomonts or incr€ase thc lace amount
Datad:
USLIFE Title Insurance Company of Dallas
fuiaU
P.esidant & Chief Executive Olficer
L^*g-e-
Attost Executiw Uce-Prdsiden. Sccrcttry end TrcasuQr
lssucd tt Vail-Eaqle Title
ffiyDAtlAS m[E AllO GIJAnANTy@ PAI{Y
Company
FORM S 10 40M SETS 378H
A.
B.
e.
D.
I
AGENT LD: NO.: .
PftOPERTY TYPE: . :
UNPD. BAL. PRIOR
POt. OR LIA.
5TAT. CODE:
FE.BRUARY E,
TITLE
1982
AT 8100 A.!1.
75,500.00
GF No. E-92-123
is covered by this policy is:
vested ln:
(a fee, a leasehotd, etc.)
LAilD owtrlER's POUCY, FORI. B . 1970 AXEilOEO tGlT-70 rdnu roororN zor,,r rsox
Gross Prem.
E' sPEcrAtDR/cRcoDE/s: codJk;"* .*-]# .""-E *"-
Date of Policy:
Amount ol Insurance $
1 . Name of Insured:
JACN T,.@{rPEl{s
2. The estate or inl€rest in the land described herein and which
FEB SIIIPI.E
3. The estate or interest reterred to herein. is at Date ot policy
JACK I,. COUPSNS
t. The land referred to in this policy is described as follows:
t"(It 11, BIcEonN $'BDMSION,
SE@ID N)DITION
OUATY OF EAGLE
STATS OF COI.ORADO
SCHEDULE
(
..; oLlcY No.
This Policy does not insure against loss or damage by reason of the following:
1. Rights or claims of pariies in possession not shown by the public records.
2. Easements, or claims of easements, not shown by the public records.
3. Discrepancies, conflicts in boundary lines, shortage in area, encroachments, and any facts which a correct survey and inspec-tion of the premises would disclose and which are not shown by the public records.
4. Any lien, or right to a lien, tor services, labor, or material heretotore or hereafter furnished, imposed by law and not shown
by the public records.
5. Taxes and asseaaments for 1981 and subsequent years.
6. Rlght of proPrLetor of a vein or lode to eetract and remove his ore there-from should the same be found, to ;renetrate or Lttersect the preniaes as grranted, recordd Aprll 28, 1900 Ln Book 48 at Paee 477.
7. Right of ray for dLtches and cdnals aa conatructed by the authority of the United States' all as reserved, ln Patent recorded April 28, 1900 in Book 48 at Page t77.
B. Ten percent non-particlpatlng royalty in and to proceeds derl.ved frorn the sale of any ninerals of whatsoever kLnd and nattre, produced and mine,il from sald premises, as.reserved to Gust Xiahtipes by l-nstrument reeorded tloveriber 2, L962 ln Book 166 at Page 40?, and any alstgnments thereof.
9. Restrictl-ons as contalned, Ln Lnstrunnat record.ed Decernber 2A, L962 Ln Book L74 at Page 403, and amended by Lnetrument, recorded, Septernber 19, 1962 in Book 175 at Page 257.
r0. Easements aa ghown on recorded plat 6al.d easements being along the Westerly and Northwesterly lot line.
AMERICAN LAND TITLE AssoclATloN owNER's PoLlcY, FoRM B l97o AMENoEO lGlz-zo
B'
o
FORM lM (CO) SCHEDULE E 35M 479F
o Project applicarit
Project lriame: fu Cr /"
S-.*n/oo'Projecl Description:
Contact Person and
,^r" ,(P.,'/ .{/ /?s=
t t^t
. btr.,qe S c)lzrtr.t ttat.<?"? s-?s7
owner, Address and phone: -'ihn ^ , " ( , / /eondufC, L' .n, kJ
ip Ji r"8d2r5:
Legal Description: Lot
i
Architect. Address and Phone:
lt Block rltine,/jr9/zorn E ,=on.
Commerlts:
Design Review Board
Date
Motionr by:
Seconded by:
APPROVAL DISAPPROVAL
Sum mary:
Dale:
Town Planner E statt Approval
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EAGLE VA ENEINEERIN t aURVEYING, fNc.
April 5, 1982
Mr. Peter Jamar
Town of Vail
75 South Frontage Road
Vail, Colorado 81557
Re: Lot 1I , Bighorn Subdivision Second Addition
Dear Peter'
+ ..
I have enclosed a copy of oui -draniing 1i7.9 for the above property. The:
draraing ls based on a field survey compieted in June 1979 and accurately-
depicts the topography at the time of survey.
If I can be of any further assistance please contact me.
Your tru1y.
Pr es id ent
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PLANNING AND ENVIRONMENTAL COTilISSION
ihy lOn 1982
2:15 'Site Inspection
3:00 p,m,
l. Request for a variance from section'18.58.020 in order to build a
13'foot high avalanche wall on lot 11, Bighorn 2nd Addition.
Applicant: James C, Shannon
2, Request for a condition use permit in order to install a game parlor
at 216'l North Frontage Road, space #6o West Vai1 'ltta'll.
App'licant: Gary Mitche'll/GarB Cityn Inc.
3, Request for a conditiona'l use pennit to operate a real estate office
in'a heavy service zone district at the Voliter Nursery, 1031 South
Frontage Road West.
Appl icant: Robert Vol iter
4. Request for an amendment to the Vail Municipal Codeo Section'18.52..|00
Parking Requirements to increase the required parking for professional
and business offices.
Applicant: Town of Vail
5, Request to amend the Town of Vaj'l zoning zode to add a new zone district
called Arteria'l Business for an area west of Vail Lionshead including
Vail Associates'west day parking lot' Vail Associates' shop and yard
arear.Eagle Va'l Iey Water and Sanitation site, old Town shop site, Chevron
siter,tls'ly Cross Electric's yard site, Texaco site, Voliter Nursery site
and the Glen Lyon office building site.
Applicant: Town of Vail
6. Request for condominium conversion on lot 42, Vail Village llest Fil'ing #l
f,or 3 units. Appl icant: Dennis Shimon
Pub1ished in the Vail Trail May 7, 1982
t.. t l-'IEIORANDUM
Planning and Environmental Corrnission
Department of Corununity Deve'lopment
May 6, 1982
review of Criteria and Findin Section'18.62.060 of
rtment of Cormunity Develo t recomnends approva
uDon tne o l 'l owi nq factors :
Consideration of Factors
The re]ati onshi of the uested variance to other exist
structures
Section'18.58.020 C. of the zoning code states that wal'ls shall not exceed three
ieit w.itnin any front setback or iix feet in height on.any other portion.of a site.
Thi applicant iequests a variance from this provision in order to allow the constructiot
oi-tfr!'avalanche'deflection wall which is netessary in order to construct a building
upon the lot.
CRITERIA AND FINDINGS
the MuniciPal code,
- ofTh-ie'Tequ es ted va ri a nce
L
TO:
FROM:
DATE:
SUBJECT: Application for a variance to construct an ava'lanche diversion wall on
lbt ii, gighorn Second Filing which exceeds the rnximum allowab'le height
of six-fee[ for any wa]ls constructed upon a site'
App'licant: Shannon Vail Ventures' Ltd'
DESCRIPTION OF VARIANCE REQUESTED
Lot ll, Bighorn Subdivision, Second Filing is subiect to snow avalanche hazard.
[-reiirt-.6nai,iteo uy nitnui Mears concludes that any-design ava'lanche (those which
have'been defined as-having a return period of 25 to 100 years) wil1 cross.lot.'11
ini-siop .i-the northern edge of the iroperlV. The ca'lculations of potential impact
piesiuibs indicate that the-pressure distribution can be classified within the
i'blue hazard,'or "moderate hizard" avalanche area. This means that avalanches in
the study area are eipected to produce a total pressure_l ess than six hundred pounds
p"i iquaie foot on a ilat surfate norma'l to the flow. The town has indicated that
in order to constrrct any structure within the moderate hazard zone' proper m-itigating
measures must be taken. Art Mears has recormended in his report that-any building
upon-toi tt stroutd be protected with a designed reinforced uphill.-wall such that
il-witi be ab'le to witirstand the design loads. A wa'll comesponding_to the recommen-
aition oi tne study has been designed-for 1ot'11 by a regjstered professional engineer
and at its highest po'int is 13 feet high.
ial uses
Lot'11 is situated at the end of a cu'l de sac. The lot to the east.of the.property
iiit t2) has a duplex constructed upon ii,-ind the lot to the west.('lot 19) ls currentll
iaiant,'but has the development potintial of a single family dwelling. The area
behind the'lot is Forest Service'property. Lot'll-is 84'847 square feet and is
liloweu a duplex. The constructibn bf the proposed wall is necessary-for any building
io be completed upon the lot. The propos-a'wail (see attached site plan)^has been
iiaced diiectly UbtrinO the proposeO'siiuiiure-and'extends to a distance of 30 feet
to.tt, Bighorn 2nd -z-
beyond the rear wal'l of the building. The interior portion of the wall is terraced
to allow landscaping, and the applicant proposes to landscape the area exterior
to the wal] as we] l. The site currently is very dense with aspen, as are the adjacent sites. The major impact of the wall is one of visual quafity, and the preservation
of existing trees durinq construction and the replanting of trees to screen the wall after constructionshould.lessen the visual impact.
The staff has received a letter from the owner of'lot'12 objecting to tlre variance.
ree to which re]ief from the strict or Iiteral inte retation and enforcement
a spec atlon 'ts necessa to ac ormi t
treatment amo sites in the vic or to attain ect ST tle
out grant o speclar pr]vr rege.
Two objectives of the zoning code are:
l. To secure safety from fjre, panic, fl ood, avalanche, accumulation of snow
and other dangerous cond'itions; and
2. To safeguard and enhance the appearance of the Town.
The staff feels that re'lief from the strict interpretation of the regulation specifying
a maximum wa'|1 height is necessary to secure the safety of the building which is to be constructed upon 1ot 11. The construction of the wal'l and the landscape
treatment of the site can be done in such a way as to minimize the'visual impact of the wa'l'1. In this case, safety of the future occupants of the building must
take first priority.
fhe effect of the.requested variance on'light and air, distrjbution of population,
transportation and traffic facilit'ies, public facilities and utilities and public
saTeE.
The wal'l is necessary for the safety of the occupants of the building.
Suc! other factors and criteria as the cormission deems applicable to the proposed
varlance.
FINDINGS:
The ?lanninq aTd Envirtnmental Conmission sha'l'l make the followinq findinqs before grantlnla varlance.
That the granting of the variance will not constitute a grant of special privilege
inconsistent with the Iimitations on other properties classified in the same district.
That the grantlng of the variance will not be detrimental to the public health,
Lot 11, stlrn zna -3-
!
safety, or we'lfare, or materially iniurious to properties or improvements in the
vi cinity.
That the variance is warranted for one or more of the following reasons:
The strict or literal interpretation and enforcement of the specified regulation
rnuld resu'lt in practica'l difficulty or unnecessary physical hardship inconsistent
wjth the objectives of this title.
There are exceptions or extraordinary circumstances or conditions applicable to
the site of thb variance that do not apply generally to other properties in the
sa[E zone.
The strict or literal interpretat'ion and enforcement of the specified regulation
rou'ld deprive the applicant of privil€ges enioyed by the owners of other properties
in the same district.
STAFF RECOIO4ENDATIONS :
The Department of Connunity Development recomnends approval o{ th9 requested variance.
At the'time the project is-reviewed by the Design Review Board, the visua'l impact
of the wal'l should be studied and proper screening with landscape materials shou'ld
be required. Jn order to reasonably attempt to minimize any visua'l impacts.
iof to
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o
Y ENEINEERING rNc _EAOLE VALLE
aURVEYING,
April 5,L982
Mr. Peter Jamar
Town of Vail
75 South Frontage Road
Vail, Colorado 81657
Re: Lot 11, Blghorn Subdivlsion Second Addition
Dear Peter,
I have enclosed a copy of our drawing ll79 tor
drawing ls based on a f i-e1d survey completed
depicts the topography at the time of survey.
If I can be of any further assistance please
Your truly.
Pres ident
Dc/dc
the above property. The
in June L979 ard accurately
contact me.
I
S.FBONT/ERAWE€T 5tJfe tC2, UNL, COL0RAOO Ol6r7 (3Or)176.4OT3
)
,.Iorrx J. McKsrrnex
Hoorx Pr-lxterrox
Colur.ralr, Lourstlrr zrare
April 23, 1982 il'"-'il
1"fu
2'ffi Shannon Equity Corporation
2201 Kipling Street
Suite G-7
Lakewood, CO 80215
RE: Lot *12
Bighorn #2
Dear Mr.. Shannon:
We acknowledge receiPt of Your in which you advise us you are
. fron the building code relative
*1I adjacent to mY lot there at
JJMcK/swr
cc: Si Frazier
Town of VaiI
Corununity Development DePartment
letter of ApriL l3th
applying for a variance to consbruction on Lot
Vail.
Please be advised that we oppose your application and
expect to be represented at the hearing in opposition
to same.
truly yours,
i.:"Application Dal 4- /Z-E z-
@>/J
I.
APPLICATION
This procedure is required
The application wil-l not be
FORM TOR A VARIAT.ICE
for any project reguesting a Variance.
accepted until all information is submitted.
' lLr L- VEuruee s
. 2o a,t Z 3 Y-oz/,/
?- KAzl,PIIONE
A.
B.
c.
D.
NA!,TE OF
ADDRESS
APPLICAI{T
Zzo/
NA!!E OF
ADDRESS
AUTITORIZATI
SIGNATT'RE
OFP PERTY
ADDRESS
LOCATION OF PROPOSAI
ADDRESS
LEGAI DESCRIPTIoN lot tl bl_ock ELIing Ft 6/lo€-a-t 7
{!,
il,"1'
E.
F.
FEE- $100.00 plus an amount equar to the then current first-cIass rate for each property ovrner to be notified hereunder.
A list of the names of owners of all property adjacent to subject property and their addresses.
Postage
the
<.+-
III.
fI . Four (4) copies of the foll_owing information:
A. A statement.of the_precise nature of the variance requested,the regulation involved, and the practical difficulty or'rrrrtr""essary Pflsicat hardship inconsistent with the objectives oi this title that woul-d result from strict or literal iiterpretation and enforce-ment of the specified regulation.
B- A site pran showing all existing and proposed features on the site, and on adjoining sites if nec6ssaryl p-ertinent a;-th.-;"riance requested, including site boundaries, requiied setbacks, buirding locations and heights, topography and phfsical features and similar data.
c. such additional material as the zoning administrator may pre-scribe or the appticant may submit pertin6nt to the app1i".iilrr.
application tornlr a variance page 2
Time requirements
Th-e Planning and Environmental commission meets on the 2nd and 4th Mondays of each month. - An appJ.icatiott ritr, it" r."""sary accom-Pqnying materiaL must be sr:brnittld four weeks. prior to the iate of 'che meetilg.
,. fll_tr ,/\/--?q' \4
siHANnloN Eourry eoBpoFrATroN H"li$rii"H h, '.= ,\y'* - -r\/< rrF \ >Y JIJ
April IO, I9B2
Town of Vail
Planning and Environmental Commission
Dear Sirs:
Please find enclosed the necessary signatures pursuant to a request
for variance for an avalanche wall for a proposed duplex improvement
situated on Lot 11 Block 2, Big Horn Subdivision, Vail , Colorado.
Pertaining to page 2 of the enclosed application please note the follow-
ing information:
A. The precise nature of the variance requested is that pertaining to
an avalanche wall. Said rva1l is to conform to specification de-
liniated by the Arthur Mears report dated Augutst L977. As shown
on page 11 of said described report, the height of the avalanche wall
should be approximately 13 ft. in height using a 45 degree deflection
angle. However, a 13 ft. height exceeds the Town of Vail zoning
statute. (See enclosed drawing.)
.ln conversations with Peter Jamar, it was determined that the Mears
report specifications should take precedence and a variance would
be required.
B. A site plan showing the proposed avalanche wall has been included.
C. Iitro other data is pertinent.
I hope this explanation will suffice for your records. Please feel free
to call should you have any further questions-
Sincerely yours,
- .^, f)-e)W C. lf. Shannon
General Partner, Shannon Vail Ventures Lt."..
SuiGe G-7 . ?2Cl1 l(ipling ScreeG o Lakewood, CCI BOa15 ' (3Cl31 234-Cl,?11
G
I,ot 8 Nelson, Susan K.
11218 Memorial Dr.
Houston, Texa! 77O24
Lot 10 Nelson
Lot 12 ltcKeithen, John J.
Box 648
columbial ,La. 71418
Lot 15 WibEon C.,Stanl-ey and Martha B.
5455 l{est Jewell
Denver' Colorado 50225
U. S. Forest Serwise
o
18.58.270
18.58.280
18.58.290
18.58.300
SUPPLEMENTAL REGULATIONS
Horsegrazing permit-Revocation or discon-
tinuance.
Horsegrazing permit-Appeal.
hoperty owner maintenance responsibility.
Setback from watercourse.
18.58.010 Applicability.
The provisions of this chapter shall be effective in all
districts og where specified, in particular districts, and shall be
in addition to the regulations prescribed for each district. (Ord.
8(1973) Art. t7 (part).)
18.58.020 Fences, hedges, walls and screening.
A. All accessory uses and structures except fences, hedges,
walls and landscaping, or ground level site development such
as walks, driveways, and terraces shall be located within the
required minimum required setback lines on each site.
Recreational amenities may be exempted by the design
review board if it determines that their location is not
detrimental environmentally and/or aesthetically.
B. To minimize traffic hazards at street intersections by
improving visibility for driven of converging vehicles in any
district where setbacks are required, no fence or stnrcture
over three feet in height shall be permitted within the
triangular portion of a corner lot measured from the point
of intersection of the lot lines abutting the streets a distance
of thirty feet along each lot line.
C. Fenccs, hedges, walls, and landscaping screens, whcrc. not
rcstricted by covenant or other legal instrument, shall not
exceed three feet in height within any required front
setback area and shall not exceed six feet in height on any
other portion of a site, provided that higher fences, hctlgcs,
walls, or landscaping screens may be authorized by thc
zoning administrator where necessary to screen public
utility equipment. No barbed wire or electrically chargc'd
fence shall be erected or maintained.
(ord" 8(1973) $ 17.100.)
463
Chapter t8.58
SUPPLEMENTAL REGULATIONS
Sections:
18.58.010 Applicability.
18.58.020 Fences, hedges, walls ard scrcening.
18.58.030 Permitted exceptions to development standards.
18.58.040 Architectural projections.
18.58.050 Porches, steps and decks.
18.58.060 Balconies, decks and stairways above ground.
18.58.070 Fireescapes.
18.58.080 Bay windows.
18.58.090 fuchitectural projections above height limit.
18.58.110 Application and interpretation of height
limits.
18.58.120 Application and interpretation of lot [nes.
18.58.130 Home occupations-Permit required.
18.58.140 Home occupations-Permit issuance and findings.
18.58.150 Home occupations-Permit time limit-Renewal.
18.58. 160 Home occupations-Requirements for permit.
18.58.170 Home occupations-Interpretation.
18.58.180 Home occupations-Permit revocation or
discontinuance.
t8.58.190 Home occupations-Permit-Appeal.
18.58.200 Regulations applicable to particular uses.
18.58.2t 0 Restaurants, bars or similar uses.
18.58.220 Sign regulations.
18.58.230 Horsegrazing permit-Required.
18.58.240 Horsegrazing pemrit-Issuance and findings.
18.58.250 Horsegrazing permit-Term-Renewal.
I 8.58.260 Horse-grazing permit-Requirements.
462-l (vuir 9-15-78)
.|'
LOT
AVALANCHE EVALUATION
AND
IIITIGATION HEASURES
11, BIGHORN SUBDIVISION,
zND ADDITION
VAIL, COLORAm
Preoared for:
Mr. Bob Borne
45032 Snowshoe Lane
Vai l, Colorado
october, 1992
Prepared by:
Hlonofnu\q uD
1310 Wadsworth Boulevard, Suite 100
Lakewood, Colorado 8021 5
Teleohone303/238-6022 FAX303/238-6382
I
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EXCUTIVE SUMMARY
I
vlr. MrrrcArroN
ReferencEs
I Appendix A
Appendix B
I
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TABLE OF CONTENTS
Paqe
t I. LocATIoN AND BAcKGRouND
I rr. cLrMATrc AsPEcrs
I
III. TERRAIN AND VEGETATION
I
rv. GENERAL oBSERVATIoNS
I
I
VI. AVALANCHE TYPES AND LOAOINGS
A. Dry Flowing Ava]ance B. Wet Spring Avalanche C. Ava'lanche Parameters
5
6
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EXEGLTTM SUMl'lAFtY
Lot 11 of the second addition, Bighorn Subdivision, VaiI, Colorado is
located within an area deslgnated as possib'le avalanche influence on the Town of
Vai l natura'l hazard-maps. The Lot is not within nor near any of the runout zones
or chutes of the major avalanche paths.
The resu.lts of this investigat'ion indicate that Lot 11 could be inf]uenced
bya dry snow ava'lanche or wet springavalanches originating below the cliff zone
that traverses the Lot on the southeast corner and extends to the west
immediately south of the property l.ine (See Figure 2). There are a significant
number of large (up to 24- inch diameter) conifers as we] 'l as mature aspen on the
property. A significant number of these trees are over 100 years of age. A
diligent search did not find any evidence of debri from a significant snow
movement from above the cliff band nor does the topography above the cliff
support this scenario.
The most Iikely scenario of a snow ava'lanche for this Lot is a wet spring
avalanche originating be'low the cliff band. Th'is avalanche would have velocities
ranging from 1t.4 meters/sec to 12.5 meters/sec at the cul-de-sac property 'l ine.
If a structure were constructed on the northwest extremity of the Lot (near the
cul-de-sac) with a wal'l perpendicular to the flon the'impact pressures wouid
range between 410 'lbs/ftl (2.0 tons,/ml) to 512 lbs/ft2 (2,5 ron/rl). If the
structure were constructed lrith a 45 degree angle (splitting wedge form) the
pressures would range from 290 tblftl (1.4 tons,/m2) to 362 lbs/rt2 (t.zz tons/m?).
The recurrence interval for this type of ava'lanche wou'ld exceed 30 years..
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A dry flow'ing avalanche originating below the cliff band would achieve
velocities ranging between 13.5 m/sec to 18.6 m/sec (30 mph to 41 mph) at the
cul-de-ac property Iine. The recurrence interval for this type of avalanche
exceeds 80 years due to the snow pack metamorphism in the va'l ley f'loor, i.e.
elevations between 8300 and 8750 feet above sea leve'l . Impact pressures on a
walI perpendicular to the flow would range from 470 1b/f* Q.2g l/nz) to 121
h/f{ Q.igT/nz). If a sptitting wedge of 45 degrees were utilized as part of
the building, the pressures upon the surface would 332 lbs/ftl (1.62 T/m2) to 512
'lbs/ft2 (2.50 1/nl). Shear forces would also have to be considered'in any
structural anal yses.
Lot 11 is unusua'l in that most of the release area is within the property
'l imits. This study has not examined the detai'ls or feasjbility of release area
control structures but this cou'ld be a possibility with this site.
A structure could be buj lt on this property that would withstand the impact
'loadjngs from either a wet spring or a dry flowing ava'lanche. The building could
be located and designed such that no significant additional hazard would develop
for adjacent propert'ies
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AVALANCHE EVALUATION AND
M:ITIGATION MEASIJFIES
LOT 1-t , BTGHOFTN SUBDTVTSION,2ND ADDITION vAr L , coLoFtADo
I. LOCATION AND E}ACKGFROIJND
Lot 11 of the second addition, Bighorn Subdivision, Vai1, Colorado is
located on a cul-de-sac immediate'ly south of the intersection of Lupine Drive and
Bridge Road on the south f'lank of the Gore Creek Valley (see Figure 1). fhe lot
abuts U.S. Forest property on the west and other 'lots of the second addition on
the northwest and northeast boundaries. Access to the property is v'ia the cul-
de-sac from Bridge Road. There are currently single family residences on lots
I and 12.
The orjentation of the general s'lope of the lot is northeast. The lot is
quite large with a diagonal distance from the cul-de-sac to the SW corner of 640
feet. The SW corner of the lot is actually above a signiflcant cliff (primari'ly
a Iimestone outcrop of the Minturn formation) that extends continually from well
east of the property to the "Terray" gully and avalanche path nearly 1800 feet
to the west, Reference 3. The topography of the lot and edge of the cliff is
shown on Figure 2.
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Previous avalanche investigations concerning this 'lot were summarized in
References 4 and 5, "Natural Hazards Reconnaissance Study to Lot 11, Bighorn
Subdivisjon, Second Addition, Vai'l Colorado," August '|.977 by Arthur Mears, P.E.
and "Rockfall, Snow Avalanche, and Debri Avalanche Analysis, Lot 11, Bighorn
Subdivision, Second Addition," October 1990 by Arthur llears, P.E.
The general area of the lot was identified in "Snow Ava'lanche Hazard of the
Vai'l Area, Eagle County, Colorado," 1975 by Arthur Mears for the Colorado
Geological Survey (Reference 3) as being subject to small ava'lanches but not
c'lassified as being subject to avalanches originating from above the cliff band.
rr -CLIMATIC ASPEGTS
The general cl'imatic conditions within the Upper Gore Creek basins are
typical of the west slope of the Colorado Rockies and since 1962 are fairly wel'l
documented by Vail Associates as part of their on-hilIavalanche control work.
The winter and ear'ly spring seasons c'l imatic condit'ions are an important aspect
of the avalanche hazard within the valley. The rather o1d adage that it takes
"bothsnow and a hil'l " to make an avalanche is a simplist'ic summary acknowledging
that a terrain analysis or a statistical analysis involving only terrain
general ly is not the only factor in the creation of an avalanche or avalanche
hazard. Snow conditions throughout the snow pack as well as storm snow falI
rates continue to be major factors in creating the potential for avalanche
hazard.
The part'icu'lar area of the Gore Valley in which the Bighorn Subdivision,
2nd Addition is 'located has a northeast exposure and thusly minima'l winter sun
upon the snow pack, The area is relatively sheltered from wind; thusly wind
deposit or wind s'lab formation wil'l be minimal. The maJor avalanche paths 1n the
Bighorn area all have release zones at or above 10,000 foot elevation. The area
surrounding or above lot 11 and below the cliff band ranges from 8400 foot
elevation to 8760 foot elevation. The snow pack critica'l to the avalanche
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potentia'l for'lot 11 will be subiected to climatic conditions of the maior
avalanche path release zones.
In recent history, Post Vail Inception (PVI , or thirty (30) years)' the
small ava'lanches a'long the southflank of the val1eyhave almost exclusively been
wet spring avalanches such as the May 1984 cycle.
Tn summary, the avalanche potentia'l must be considered on the basis of both I
I site specific c'l imatic conditions and terrain analysis. The wet spring avalanche
is the most Iikely design even at this site when both aspects are considered.
I III- TERRAIN AND VEGETATION
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The topography of the lot and the surrounding area 'is shown on Figure 2.
This topography and lot boundaries were surveyed by Inter-Mountain Engineering
'in late August and ear'ly September of 1992. The lower edge of the cliff bank is
also shown on the topographic map. The slope of the cliff varies between nearly
vertical to a ratio of 3 vertica] to t hori zontal (3:1). Fa] |ing snow wil'l not
adhere to this cliff except for freezing rime or graupel which is very unusual
for this valley.
Transverse sections from the base of the ]ot upward to the base of the
c'l iff were also developed by Inter-Mountain Engineering. Section A did not
extend the total d'istance to the c'l iff but Sections B and C extended the fu] 1
d i stance .
Section B is 'located c'lose to the center of the lot and was used primari ly
for the terrain analysis and avalanche dynamics analyses. Section C does
indicate somewhat flatter s'lopes on that segment of the lot.
The tree cover on the ]ot and the area west of the lot up to the base of
the cliff ismoderately thick withmany aspens but also a significant number of
conifers, some up to 24 inches in diameter, While a site specific
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dendrochronological or tree ring ana'lysis has not been performed on the trees in
this area, it 'ls obvious based upon other work in the Bighorn area that the 24
inch diameter conifers are on the order of 100 years old. The number of these
si zeable coni fers as we l I as the aspen and the profusion of 'low 'l imbs sti'l 1
attached to the trees do not indicate significant avalanche activity in the past.
A very deta'i led fie]d inspectjon of the area below the cliff band was
performed by R.L. Halley and Nicholas Lampirjs in August of 1992. While minor
amounts of debrj were found on the s'lope and at the base of the cljff; this debri
was not consistent with any sjgnificant avalanche activity originating above the
c] 1ff. It was the conclusion from this site inspection that any design snow
avalanche would originate from below the cliffs. This conclusion was reached
based upon the lack of typical debri, the consistent number of smal1, 1ow l'imbs
and branches on the older conifers (and aspens) in the area and the topography
above the cliffs.
The lot and surrounding area show ev'idence of past rockfal l and debri
activitybut those other natural hazards are dea'lt withby tlr. Nicholas Lampiris,
Ph.D. in a separate document.
IV-GENERAL OBSERVATIONS
This south f'lank of the Gore Val]ey between the Waterfall and Terray major
avalanche paths has been identified as being subject to smal'l avalanche hazard
(Reference 3 and other previous work). The terrain analysis certainly supports
this conclusion for the entire section between the two maior slide paths, not
just lot 11.
In recent history (PVI) snow ava'lanche activ'ity along this section has been
confined to wet spring avalanche or minor sluffs. The avalanche analyses as
described in Section V of this report however examines the velocities and
potential 'loadings from both dry f'lowing avalanches and wet spring avalanches.
4
V- AVALANCHE TYPES AND L()ADINGS
The snow ava'lanche anaiyses performed as part of this study utilizes both
a statistical approach, the Norwegian Geotechnical Institute (NGI) trith a
modification to reflect the frequency distribution skew for Colorado as
identifjed by Mears (1989) and the c'lassical dynamic mode'l developed by the Sw'iss
(A. Voel]my, Salm and Schaerer).
The avalanche considered were both the dry f]owing type and the Het spring
type. The details on the analyses are presented in Appendix A to this report.
A. Dry Flowinq Ava'lanche
The runout distance from the edge of the cul-de-sac (property |ine) was
calculated by themodified NCI method as 32 meters (105 feet). The dry flowing
avalanche velocities at the property line ranged between 13.5 meter,/sec to 18.6
meter/sec. The velocities would be essentially the same for a potentia'l building
site near the cul-de-sac.
The tota'l static and dynamic pressure created by the dry f'lowing avalanche
on a flat surface perpendicular to the f'low would range from e.es tons/# (azo
lbs/ft2) to 3.53 tons,/m2 (724 1bs/f*). If a splitting wedge of 45 degrees |,ere
utilized as a protection for a potentia] building the pressure upon the surfaces
woutd be 1.62 tons/m3 (ssz tbs/ft2) to 2.50 tons/m3 (512'lbs/ft2). shear forces
would a'lso have to be considered,
B. t{et Soring Avalanche
The wet spring avalanches would also originate from below the cliff band.
These avalanches wi'll be slower moving with fairly wet, and dense snow. The
course of the ava'lanche path will tend to run more perpendicular to the contours
on the site. Probable wet spring avalanche paths are shown on Figure 4.
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The ve'locities of the wet spring avalanches near the probable building site
(irnmediately SW of the cul-de-sac) will range from 11.4 n/sec to 12.5 m,/sec.
The tota'l static and dynamic pressure created by this range of wet spring
avalanches on a f'lat surface perpendicu'lar to the f'low would range from 2.0
tons,/ml (a10 |bs/ft|) to 2.5 tons,/m2 (512 lbs/ftl). The vet spring avalanches
often wil'l incorporate significant amounts of debrj and trees within the flow and
the design of any structure would need to consider relatively sma'l I point
loadings higher than the average pressures.
If a splitting wedge of 45 degrees rere utilized as a protectjon for a
potentjal bui'lding on the site the pressures upon the surfaces would range from
1.4 tons,/m2 (290 lbs/ft2) to t.77 tons/ml (362 tbs/ftz).
C. Avalanche Parameters
The snow avalanche and s'ite parameters considered in this analysis 'i nclude:
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Deta'i Ied fie'ld investigation
Detai'led topographic mapping
Terrajn and tree analysis
Both statist'ica] and dynamic modelling (NGI and C'lassica] Swiss
methods)
Climatic conditions typical of the Bighorn area of the Gore Val'ley
Consideration of known historical avalanche occurrences in the
Va11ey
The specific avalanche paraneters utilized in the analyses were derived
from loca] data and those identified in References 1,2,7,9, 10, 11 and 12.
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\/IT. MITIGATION
Th'is partjcular'lot as wel'l as adjacent properties, can be considered
subjected to snoy avalanche hazard. The Open File Report of the Colorado
Geological survey "Snow Avalanche Hazards of the Vail Area, Eagle County,
Colorado" by A. Mears c'lassifies this area as being subiected to small
avalanches. That document does not indicate ava'lanche potential involving the
area above the cliff band as it did for the south f'lank area between major s'l ide
paths, 7 and I (waterfal'l ) further up the Val'ley. Potentia'l mitigation measures
forthis'lot include sptittingwedges or roof extensions into the sloping ground.
Addit'ionalmitigation measures that may be viable for thjs particu'lar site, since
the property includes a significant part of the release zone, include defense
structures near the west property Iine. This particu'lar 'lot due to the size and
the relatively'l imited slide path length (less than 470 feet to the potential
building site) al lor{s the potential for mitigation measures that are not normally
avai labl e.
Some of this potent'ial mitigation measures are discussed in detail and
shown in sketch form inReference S "Avalanche andMudflow Defenses, Tenth Filing
at Katsos Range" by McDowell-Smith Associates with A. Mears. Some of the
sketches are presented in Appendix B.
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REFERENCES
1. 0n the Destructive Force of Avalanches, by Vo] lemy A., U.S. Department of
Agriculture, Forest Service, ALTA Avalanche Study Center, Wasatch National
Forest, 1955 (Second Translation, Harch 1964).
2. Martinell, Jr., M., Avalanche Protection in Switzerland, General Technical
Report RM-9, USDA Forest Service, Rocky Mountain Forest and Range
Experiment Station, March 1975.
3. Snow Ava'lanche Hazards of the Vail Area. Eaqle Countv. Co'lorado, Open Fi'le
Report, Co'lorado Geologica'l Survey, Department of Natural Resources, State
of Colorado, by Mears, Arthur L, 1975.
4, Natural Hazards Reconna'issance Studv For Lot 11. Bishorn Subdiv'ision.
Second Addition, Vail. Colorado, Prepared for Mr. L. Kelley and Mr. J.
Mason, August, by Mears, Arthur I., 1977.
5. Rockfa'l l Snow Avalanche. and Debris Avalanche Analvsis. Lot 11. Biqhorn
Subd'ivision. Second Add'ition, Prepared for Mr. Bryan Hobs, by Mears,
Arthur I., October, 1990.
6. Soi ls Exo loration and Foundation Recommendations for the Prooosed
Residence Lot 11. Biqhorn SuMivision Second Addition, Prepared for Gore
Range Propert'ies, by Richards Engineering, January 15, 1979.
7. Guide'l ines and ilethods for Detalled Snow Avalanche Hazard Investiqations
in Co'lorado, by Mears, Arthur I., Bul'letin 38, Colorado Geological Survey,
Department of l'latura'l Resources, State of Colorado, Denver, Co'lorado,
1976.
8. Avalanche And Mudf'low Defense, Prepared for Vai'l Associates, by l,lcDovell-
Smith and Mears, Arthur I., February 10, 1975.
9. Ava'lanche Dvnamics: EnEineering Aoolications for Land Use Planninq, by
Leaf , Char'les F. and Martinel I , Jr. , Research Paper Rl.l-183, USDA Forest
Service, February 1977.
10. Ca'lculation of Snow Ava'lanche Runout, by Bakkehoi, S. Domass, U., and
Lied, K., Annals of Glaciology, 4: 24-29.
11.
't2.
13.
14.
15.
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Ava'lanche Runout Distances and Dvnamics. Current Xethods and Llmitations,
by Art Mears, Nationa'l Ava'lanche Schoo'l Workbook, 1989.
Emo'i rical Calculat'ions of Snow-Avalanche Runout Distance, by Lied, K. and
Bakkehoi, S., Journal of Glaciology, Vol . 26(94), p. 165-177, 1980.
Tvo Parameter llodel of Snow-Avalanche Motion, by Perla, R., Cheng, T.T.
and ].{cClung, D.M., Journa'l of Glaciology, Vo1 26(94), p. 197-207, '1980.
Three Dimensiona'l Model of Turbulent Avalanche F'low, by Tesche, T.W.,
Proc. of the International Snow Science Workshop, Lake Tahoe, California,
1986.
Regional Comparisons of Avalanche-Profi'le and Runout Data, by Arthur I.
Mears, Arctic and Alpine Research, Vol. 21, No. 3, pp. 283-287, 1989.
o
1 F I GURE
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liill,l:.ia -i){rve L i',r- li Pioiror r, . r,i r,,1,'
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ll '': 'j t- :ir.:, l'!r--
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Ht ll: I jc ;,111rryir ii;t i j B igft, r,,
Snla l 'l I i ir,bs at 3- 4 f , rlt ab'c \.e
wllli
C I if f rIrove I
8l Jlti I lt :rr(j
A,l,J;1i,rtr, \l.t jl
t 11
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APPENDTX A
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APPENDIX A
CALCULA-f IONS SI-JM''rARY
Using NcI runout of analysis statisticai modifjed per Mears skew
B measured = 360
Xo = 135m
H' = 100m
Using ". : 0.96 B - 1.7o = 32.90
With modification to centroid of Colorado data - = 30.90
.'. Tan 30,9 = 0.598 and XB + X- = 100 : 167 m
0.598
.'. X* = 32 m approx. 105 feet
Matching runout with velocity segment calculations.
Dry flowing release below cliff.
Velocity range at property line cul-de-sac 13.5 m,/s to 18.6 m/s.
Wet spring avalanche velocity range at property Iine cul-de-sac
11.4 n/s to 12.5 m,/sec
stagnation pressures.
Dry f l ow j ng ava lanche 2.29 I /\ to 3. 53 T/tt1
Wet spring avalanche 2.0 l/n, to 2.5 l/n5
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APPENDIX B
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2:
i' t-SAannon Vnpk-p
SOT I,S E\P!,CPATION A}ID
l'OlJlt t)n't l(.)l.l Rll(lol.lt.tl:IJDAT I ONS
I.'OR T}IE
ITt()PC)S!JD RUS IDT'NCE
l,OT I l, Bl(;ilOltN -sirilt)IVISION SIICOND ADI)IT1()N
Prcpared For
Gorc Range ProPer:t.ir:s
Jar.uary 15, 1979
f'r ''D;r f ed lly :
ti l( )L l:'xl l.,tJ(; tli! l lililii
irox C- l 00
i\von, Co!"r'r(!o Plt fO
,'r Vcr lr I l19 '1012
l-/(jnver: fl93-l r' l'l
t.
" Sl'nops is
i-
.. I ntroduct ion
Author i za tion
Scope
Gc,nera 1
TABI,E OP CONTn't'fS
Fi cld Inv<:stirrations
Sc()pe
SanrPl ing P(oc( jdut'es
Ipc.r{ .ion of lir:pl oratory Test Pits
Grorrnd Sur f acc. E l evat i.ons
Ctol ogy
li.ltur,irl llazards
L.r)rola'tory Invcsti gat ion
!toisLu!:e Content
Conqiosit ion
ilt.terberg Lir:lits
Site
Sir!:surface Conditions
Gerrc.ral Soil Descr ipt ion
Grounti h'ater Observa t ions
Forrn6" a ' ott Di scussion and Recommendations
Pro.ioct Dcscr ipt ion
Foundat ion Rccoinmcnda tions
Cc.,nst ruct i on Considerations
Site Prcparation
Floor Slabs
r'iround Hat cr
Surface Dra i nagc
li>lcavat ions
(ir.t r, : r','tl Cr-rriilr.nl:!;
,:;'.r',.'rn I ll.Jl es
T, st Pit i,ur:at i on Di.rg r..:1, ligure I
T',.st Pi'. log
1
2
9
lo
I1
13
l6
SYTIOPSIS
A q!'ott'chnical exPloration and evaluation of the foundation conditions
has tr('.'n marle on tlre site of the proposed residence in Vail, colorado.
An ex1'lq\r'61.orv soil test pit has bcen excavated and the soil sarrpres
subie'cLed to labot'atory tests. The data has been carefully analyzed in the
liqht oi the project information provided by the client.
The r.r:;u1ts of orrr exploration and analysis indicate that conventional
s:rrr';rri fo.r: ings and./or continuous wall footings appear to be t}le most suita-
bl e ti'L,.: of forrnd,:tion for Lhe s.;upport of the proposed structure.
llt:t al lowatrl c' s;oi.l prr':;s'rcrs of 3500 psf rnay bc uscd at, dapths of I
1".rrrr Jlcr:t h,-..!ow tll{: f inal rlr:ade-
(i|r.,r:nd watt-'r conditions ;ire not cxp.rcted to c.-.rrse any di f f ictrlties,
lrut th<'s;o conditions wi 11 be discussed in roore detair in t-he report.
Tire uppor soils are suitable for the support of floor slabs. Recom-
mcndations for thc orcl.raration of the subgrade are also inclutled.
fti-'iailcd analys;es of strbsurfacc conditions, alternate foundation types
;rnrl p.-.r't inerrt dr. sign recommt'nilat j.ons are includeil \rithin thc tc.xt of this
1.1.1:o r.t.
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SIIBS(' }TFA(:F] I }W U SJ'T I GA'I I ON ---.'_.-.-.-
arle
FOUNDATI ON RECOI'lllF)'lDIrTI ()llS
INTRODUCTION
\r t i,C'r i 1.a t i\)n
'l.lris rt.1rcrr1 I)r.':,qnLs 1!1r' r-r,:irrl ts Of a !:oi ls cxPlorntion ;llld l'outlrl. t-ion
Jlrniysis for a ltrolroscd rcsidenc(.' condlrcted for Gore Rangr: Proy'ertlcs'
A,riiroriza't i r,n to lrt:rform l:his invr:stigation \'ras in the form of a verb.ll'
aorc,i.,r(:11t ()n Dec- rr-'ber 29, I9?8, betwoen Gore Range Propertics and Rich'.]rds
Enq ilri,'cr ing.
.19-!D9
.l,h(, r:co;r1l of t-lri s qcoL(.cltnical invcstiqlation jnclrrd[Jd a rcvi.cw of
ec(rl()(ri(,1 I 6"115 of tllc ,trca .)l)d a !-ovicvJ of gt.'olo(1ic a nc] rcllat-r'd lil:r''r''rtrtr-r''
a rc,,'on:l;ri:;sancL\ of tlle iruneilinte site, tha subsurface explor'ation' ficld
anrl I;,j,or.rtory t,(.s;tinq, and an cngineering anaf ysis and evaluation of the
folndat ion n.rLerials.
'ih" flrimar)' J,url)ose of +-his Preljrinary subsurface cxPloration r"tas to
deternr rre Lhc' vitrious soiL pr-ofile c:omPonents and the engineering charac-
I r'r-isti.cs of thc rn.it,.rl-ials encourtt-eretf . A secondary PurPosc was to provide
irrf. rrnar-i,:n to the tlcsign cnqinccrs and archit-ects which coltld be tl:;ed to
f,tr-:nulirt.c Jrrclitnin.)ry dc.sign criteria, and to.aid in t-he (ltlvelc)t-rnt':rtt of a
f i nal ,1,.:; j qn-
Ct,rr--'rd I
i
Th.-: reconi[,nda L j on s srrlrmitted are 6ased on the avai]able soil inforr'rtion
.rn(l :.hc !)r'climinary clc.sign details furnishetl by the clie-'nt for Lhe .!)ropcsed
.;tru -r ltre. nn-v revision in the plans for the proposed struct--ure slrr)rjl d be
l.,r r..rr..-llrt to thc itl.tcntion of the soils cngineer to di-'t,,:rmjrrc if charrt-tr-'s in
ti)., for:r(liltiorl r(,{jornjr(rndat lons ;rre !:equircil. AfLer the P'l ans and ug'.'cifications
(rre i'r',ro cOrrtr'! eter it is I'ocori;tt' 'rld r,'d that t))c soils and fortrlclation r nr'rr-ncer
::,, ir(.,..,icr]d t he ol)poriunity ro rivicw the f jnal design and specif ic'nr-ions,
-. :r (rr il r i.hat ( .)r i irr*ork and f ortndation r e colnnt':r n11'r t iorts rnay be f'Yai., YLy j nrer-
r:... 1r.ri. .,\L tlr.-rt trrrc, it Inay br n{,c{tssary Lo slr})mit su!)Pl( i:r"Iltaly recol !i'-I)da-
| | ()D3.
.tf rl,:viations from the Doted subsrrrface conditions are encountered during
ccnstnlction, they should also be brought to the attention of the soils engi-
neer.
The soils engj,neer $tarrants that tte findings, recornmendations, speei-
fications or professional advice containeil heretn, have been prepared in
accordarrce r.rith general Iy accc:pted professional engineering practice in the
fields of foundation cngineoring, soil mechanics and cnglitleerirrg geology-
lio otht r r,,.-rrrant i cs are i rnpl ied or exprcssed.
This r(rport has becn prepared for the exclusive use of the client
for the specific applicatjon to the Proposed residence, in accordance with
gt,nurally accePted soils and fountlation enqineering practices.
-3-
FIEI,D IWDSTIGATIONS
gcope
The fietd investigation to deterrnine the engineering characterj, sti cs
of the fcunCation rnaterials includecl a reconnaissance of the project site,
locating arrti oxcavating the exploratory test Pit, and the recovery of
9.I:lJr1f'S.
,llrc ;r1'parr.nt qrountl watcr Jev(,] was rccorded in the test Pit af t-er
cornp l c t ion.
A{ter cc,rn}rletion of the field testing Program, the test pit *'as back-
fiIlcd ivith excavated soit and rock material.
ggrr.o_li tS_ I r_o : c d_t I r e s
on6' cx])lor;troly lcst pit vltrs c>:cavated with a Case 5BOC backlrot'- to
a d( i)Lll of lO f ,'tlt, \ll(rr (| llackhoe rr'l-rr:;al \',rts ('Irc()lrnL( rcd'
SoiI i:,'nr'l rr,;neter ti'sts were not attained due to the larqe cluantities
of roc\ nai,'t'ials.
salnples of subsurface materials were taken of different subsurface
st'rata by hand s.impling techniques.
The depth of the sarnple, the tyPe of sample anil its identifying num-
ber, are slrown on the tcst pit Ioqs. continuous 1o9s of the consislency'
nloi sture, color arxl rlescri;rtion of the soils were kept during c'xcavating
.rnc :;alr1,l inrl i ot-lrer 1ri'rt i ncnt f i e ld nntes ar€r added vhrrro llrc'y are signi-
f i c.utt .
L,ocat ion of Exol.or atorv Test Pits
onc r'xpl()ratory soil tcst Pit bas been excavated in the location
det..rmi n.rrl by tJrc soils enginecr. The test pit location was partiall'y
dictatocl b1' 16^ :;tccPness of the slope and the depth of snov" this loca-
-.ion is chovn upon thc accompanying Test Pit Location Diagram, Figure l.
Gr ou:':_d-
-S-tr_r-
f .r_c-c- Jil'_cv-a-ij ( tr s
Tlr,-, r.:lt,v.ri irrn of thc aroun.l st.rfacel shown on the: Expi<-'ratory 'f1 'st
-4-
t,
f lt l.,oq uras
.rccuf ate to
the c r:nLer
I
tletcrrnltredrrslnghandllevellngtechnlquca'and
within + one foot. ' the edge of Paveheht on a
of the cul-de-sac to the :fest Plt r'tas usedl as a
is Presuirably
radllal lihe frodl
benchnarlt (El.- 100.or)
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' GEoloGy
Tlre Geologic Land Ose MaPs for Ea91e County' prepared by charles s'
Robinson and rssociatcs, Golden, cororado, in 1975, shorr the site of the
preliminary investigation to be part of the Minturn Forrnatlon' lfhis
formation consists of meil ium to very coarse grained' gray to reddish-brown
s.rndstone, conglomeratic sandstone' thin beds of reddish-brown siltstone
anil sandl' antl silty shale and proninent pinkish gray to gray limestone
becs. surficial deposits at this site are colluvium derived by the
\.r'cathering of this f ormation'
Nat ur:a I Jlaznrd|i
. As indicatcd in "Natural llazards Reconnaissancc study for Lot ll'
Bigrlrorn Sulxlivision, second Ad<lition' vailt colorado" prepared by Arthur I'
$c'ars in Augrrst 197?, there is a potential for snow avalanches' rockfall'
and debris sl idt.:s at this site' observations in the area of the exploratory
test Pit shovJ that no dcbris slides have occurred in that vicinity t"ithin
tile Fas-. several decadcs. Ilowever, slidles could be precipitated'by incorrect
construction practices; this topic will be addressed in the ttconstruction
Cons iclc r ati cns" section of thls report'
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I,AI]ORA'IORY TTIUEST1GATI ON
fn addition to the field investigation, a suppl enental l aboratory
investigation vtas conducted to ascertaln additional pertinent engineering
characteristics necessary in analyzing the behavior of the proposed struc-
ture. Thc laboratory testing program included visual cL.-rssif ication by
a soils rrngineer as rvell as the procedures listeil below. AII phases of
tlla la])or.rl.orry invr:stigation wcre conducted in accordarrce with applicable
ASTM splc j.f icat ions.
R(:Dr.'sentative samples of the soils were placed in sample jars, and
are riow stored in our laboratory for further analysis of desired. Unless
othcnvise notified, all samples will be disposed of after 50 days.
. 1l()', :il ur_c 9(]]1!_''f,S
A portion r>f c'.rr:h s..tnple is wcighed, oven-dried at I05"e, arrd rcrvcigh,'d
Lo obi,rrn tho r.,r:ight of waler. The nroisturc .ontott is the rat:io of the
weight of water tc, the weight of the dry soil. expressed as a f)ercentage.
qg'Lo_li_1_!9t1
'l'lrc corny:r"'s.i t i on of qr;rnular matr:rjals is o):taj.ned by passing a knowrr
nt:iglrt. of dri,:tl rrrnt,.,riol tlrrorrgh a sct of sicvcs, ranging from a 3/4 inch
sir:vc to a No. 2O0 tl .S. stand.rrd sir:ve. This Frocerlrrre is in accordance
r,'ith AsTlt D-422. i{here a knowledge of the distribution of particles
smal ler than a No. 2OO sicve is required, a Hydrorneter Analysis, described
in the second part of the ASTM D-422 procedure, is pcrfonned, frilfil ling
a c('mFl cte nrt,c),lnica1 analysis.
l_t:_r:rbql:,r-_LULI_-t:
..i - The waLr-'r contcnts corresponding to the transition from the liguid
. stJte to t.l.e plastic state and finally to a solid state usually differ
: for clays having differcnt physical properties in the rernolded state' and
. .3re approxirnatcly r.!u.r1 for clays having similar physical properties.
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,
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fherefore, these limiting hrater contefits, the Atterberg f,irntts, selve as
useful index propertieg fot the classificatlon of clays.
-8-
S]TE
The site of the proposed residence upon $thich this soils exploration
2\
:: has been naile is focated on Lot 11, Bighorn Subdivision, Second Addition'
. v"il, coloratlo. This location is sLown on the accompanyinq Test Pit
: Io;at-ion Diagram, Figure I.
. At the Lj.ne of the field investigatlon, aPProxinately 3.5 to 4.0
, ! f t.r:t of snon covcred the site. The site is located on a steep slope wlli ch
d(.scr.ncs from the southwest tc. Northeast portion of the site. surface
('(i1n.rge is facilitated by the sLeep slope and is tiirected to Gore creek
vi,r !lr-itl'.;c lload. Drainage pat.terns on the site an'l vegetative cover
.' '..,'rc rrot cliscernable <iue to thc large amounts of snow'
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-9-
SUBSURFACE CONDITIONS
j ' gencrfl__ro:!_!esc:-tg!lon
l-.l The soil proflle for the cxploratory test plt excavated ofri.thi s site t-
c<'nsists of an upper layer of topsoil approxirne,tely 10 inches in depth.
t ThPr€ rr'its no frost layer evirlent at the test plt location. Underlaylng
. this topsoil stratum are colluvial rnaterl-als consisting of large fragrnents
i of sandstone and shale. fndividual fragments were cobbl e and boulrler sized
- with some pieces as large as 48 jnches in one direction.
'i a cl ayey si It binder was int.t:rbedtled between rock f raqments. . Thcse
- coll uviall. mat-erial s oxtcnd the f il J. depth of the test pit. IJackhoo rcfusal
' \ias c"rcortntr:rL'd at IO.0 fe et.
r 'Ihe strati f i cation of the soils. as shown orrt thu accompanying I ogs,
r.'9rcsents the soil conditions in the actuar test pit location, and
" Vrlriations nay occur at other locations on the site. Lines of dcmar(l.ltion
1i rePrt)sent the approximate boundaries between'the soil types. but the t.rans-
itic,n may be g radrra 1.
, *arq-lr5ri!a{-o}:1ry9-tjgs.
Ground water uas not cncountered at the time the test pit r,ra s excavated.
-' ltowever' water may be present during the spring months, or after a prolonged
' period of rain. The perme,htlity of the solls, seasonal variati.ons, tempera-
: ture and recert rainf,all conditions, may influence the water levels at other
t i rnc s.
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I
I,.()IJNI)ATION DISCIJSSION AND RECOWDIIDATIONS
Project Description
It is unilerstood that the proposed structure will consist of a .single
fanily rb.sidence. It is further . a s surned that frame cons.truction will be
utilizr-,d.
No ,rst.imatcs t,('re available for w.-.ll loads at the time this report
was l)r|parcd. For the prlrl)oses of this report it bas been assumc'd that
tot.al wa l I loa:ls rvi I I be on the order of three kips per lineal foot. l*:en
Cesign data has been generated for this project, the soils engineer should
be inforrned if the actual loads are expected to substantially differ f rc/m
t.his est imate..
rgLn_t_":.-{-i_ql_I!,:._.IA:I_L,19 j_r,}l:
V.rrious f clund;rt ion typt-.s h.rve been consiclered for support of the pro-
i-'osed rr..siriLlnce; hcwever, considering the proposed structure and the in-situ
soil s, cc.'nvcntional spreail footings and/or continuous walI footin-qs or any
conbinat.ic)n of thr-se founclation types is recomrnended.
Tn tlre vic.inity of Test Pit TP-l , it is recommended that net allowable
soil i:car"i nq prcssllrcs of 350O lrsf be used for dlimensioning foundations
forurdcd at del)ths of forrr feet or more below the existing grade. Much
(rv0l'-(..x civ,r'" ir.n wi ll bt: cxj','r:i errccd on this site (luo to thc abundance of
l,:rr'9rc r;i.irctl r()c'ls. Voids cr.:atr.:d lty over-cxcavation may lle tracllf ilIed with
a s(:loct., clcan, gr.rnular soil placed in loose layers of not more than
I incl:es. Each lift should be compacted to a minimum density of 95 percent
of t.irc inaximrrm rlensity ach.ieved by folJ.owing ASTM Procedure D-I557. lf
tbis procr.<lrtre is fo1lowed, it is expected that this fill will be caPable
of supgor:tirrg l()ads up to 3500 psf. A gualified soils c.ngineer should be
c:rltagud to inspect Lhe Placcment of engineered fill if the above proce(lure
.i s .rdirl't r.d .
Ar; an alternate to the above dcscribed Procedure, lean concrete may
he irs..d to fill over-excavations.
In <>rder to avoid the effects of slight differential movements that
tnay oc-r\rr rlur: to v.lriat.ions in thc characrers of the supporting soils or
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variations in seasonal moisture contents, it iS re contnended that all continltoub
footings be suitably relrrforcel to make then as rigid as posslble.
The effects of seasonal variation in molsture content and the effects
of frost action would be alleviated if the foundations were founded at
ctepths of at least 48 inches below the finlsbett grade. Total and differential
settlement betlteen footings l'rould also be nininizetl.
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CONSTRUCTION CONSIDERATIONS
.s_l_!g__trSpa3!!"n
Excessively organic tcpsoi} generally undcrgoes high volune changes
rviren s,rbjected to Loads. This i6 detrimental to the behavior of Pavements,
floor slabs, structural filIs and shalloW foundations placed upon them.
Therefore, it is recor,inenried that cxcessively organic topsoiJ-s be st-riFpedl
f rcrm th',ses drcas to degths of approximately 12 inches and wasted or stock-
piled for L at-er use.
r1f tr-,r thc +:xisti.ng su\radc soils are excavated to design 9rade, nroPer
conlrol of :;uitgratle conlrilction' nnd t-hc pl accnrent and comPaction of new
f i lls slrorrld l)(t nrnint,ainr'd by a lcrprcsentative of the soils engincer. llelt
{ i I I n.1t-r.'r; al s;lrould conSist of a select, clean, qranular soil pJ aced in
loose I a1'ers of not more than I inches. Each lift should be cornpacted to
a ininirnum density achicved by following ASTT4 Procedure D-1557'
!t,.l_9. !f nU_t
Tlre on-site s;g1!Let:e s-t:rit.rblc t"- ,t-rj!:.j -:1ab-o,1--9:a9"
t9n.1!lttt]-t:Jt:
providud all vcget"rtion, d,:bris and topsoil are rcmoved from the buil<1ing
allea.Thesameproc-eduredescribeilfll'uagkfrrlingfounilationover-eT:w:t_ions
gl-rou1d be utilized if over-excavations g5.q---expe-r.ienced in the area of . any
floor slabs. Care should be taken to insure that alI excavations n'rde for
the ioundations are properly backfilled with suit.lble matr:rial comlrae teil
to 95 l-,or (:ent of the maximum tiensity achieved by a standard Proctor Test
(A!;')'t.t D-fr98). Bcft>rc tlrc Int-'kf i l1 is lrlaced' all watcr antl dcbris r;hortld
,111-r v q'1n1viti'11 f ront l-ht'9tl (:x(',rvaJti orl5.
,thefloorsl.rbshouldbesrritablyreinforccdtotnakeitasrigidas
possible, and ProPer joints should be provi<led at the junctions of the
slab and the foundation walls, so thaf the floor slab wilL act indepr:ndently
.rf structrlral portions of the bui 1ding.
A4-inchlayeroffreedraininggravelshouldbeprovirledbencath
t.he fIoor slab to distribrrtc floor loadings.
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CONSTRUCTION CONSIDERATIONS
Site Preparat ion
Excessively organic tcpsoil generally undcrgoes high volune changes
r,.?ren s,:bjected to loads. This is detrimental to the behavior of Pavefients'
floor s1abs, structural fills and shalloW foundations placed upon tbem.
The'iefore, it i s recor,,nended that excessively organic topsoils be st'ripped
frcrm tbr.ses drcas to depths of approximately 12 inches and wasted or stock-
piled for later use.
Af tr,.r 't-lrc t:xisting subgrarle soiLs are excavated to design grade, ProPer
r.cnt-rol of r;uirgrode conpaction, :rncl thc pJ accnront and comp.rction of new
'l lls slrorrl<l lre ntaint',ainocl by a roprcsentative of the soils engincer' llelt
fiJI rn..rt er j a1 should consist of a select, clean, granular soil p1 aced in
loose I a),ers of not more than I incbos. Each lift should be compacted to
a ininirnum tlensity achicveil by following ASTI{ Procedure D-1557.
F I cror _Sl abs
Tlre on-site soils are s.!4t-able t-o-suppoa tl":_"jl-9t-11" :9,1,t:t"9-tj"":
prov:irlt:d all vcaetation, clebris and topsoil are removed from the builtling
area. The saine proc_edure rlescribed fo1 ba3kfilling foundation ov er -excawlt ions
$]ould be util ized if over--excavat ions are .t:xperienced in the area of any
f loor slabs. Care should be taken to insUre that all excavations rnatle for
the ioundations are property backfilled with suitable material compacted
to 95 l',orcent of the maximum <lensity achievecl by a standard Proctor Test
(r'\5'i'11 D-(r3R). Rcft>rc Llrc lrar-'kf i l1 i5 1tl6g1'd, all wat:cr antl dcbris r:hortld
l1r, I r';r11r'.r1'11 f rt)nt t.ht'r|c-: (:x(',,v.tLiorl5.
,fhc floor slab should be suitably rr:inforced to make it as rigid as
possib)e, and Proper joints shoulcl be provided at the junctions of the
slab and the foundation walls, so that the floor slab will act indepcndently
of str:uctural portions of the bui lding'
A ,'t-inch layer of free draining gravel should be provicled boncath
rhe f l<:or slab to distributc floor loaclings.
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Ground llater
Because of the relatively low ground r^rater level, no difficulty during
excavation and construction of the proposed shalfow foundations is anticipated.
fiowever, since thcse foundation materials generally tend to soften when
exposed to free rdater, every effort should be made to keep the excavations
dry if water is encountered - A gravity drainage systen, sump prxnps, or
other conventional minor dewatering systems sbould be sufficient for this
i'.1):--OOSe.
ns stated in the previous subsectionl a granular mat should be placed
t'cneat-h any floor slabs. The wall excavations should be l-.'ackf ilIed wiLh a
frncly tlrainirrq material, with Froper rlrainage away from t-he subsurface struc-
trtro (r;,,c ncxt paragr-aph). Thesc Proce:durcs will help minimize the fonn.rtion
<'f t,xccssive lrydraulic uplift forces and hydrostatic lateral forccs on the
f loc,r slabs and foundation rv.'rl1s. respectively. This drainage systern should
not be oPen to surface water. Thus, the upper part of the exterior backfill
naterial slroulil consist of .relatively impermeable soils.
l{hile no ground vrater \^ras encountered at the time the field investi-
gaiion r;as conducted, it is possible that local perched water tables will
dcvolop drre to sprJng runoff, a prolonged period of rain or lanCscape
r'ater,ing- Tlr('refore, a subsurface perimeter ilrain shoultl be constructed
around thc ext.L'rior of tbe foundation system to carr), \"rater a\ray from the
bttilding. This drain should consist of a perforated discharge pipe, gravel
collcctor and sand filter. The discharge pipe shall be given free gravity
irccoss Lo the gro|rnd srtrface. Also, the gravel bencath the floor slab
slurtlrl r-r)nn(,ct. to Llrc strb:rur J';r r.:c <lr:aln oystcm.
rugg._e _!I's:"nE
Tlrc Around surface should be sloped away from the buildings on all
sidcs to control surface water runoff. Surface vrater running toward the
structure from upslope areas should be diverted around and away from the
building by mr:ans of drainage swales or other similar measures. The mj njmum
gr.rident within terr feet of the building will depend upon surface land-
s(:al)ing. Pare or paved areas should have a minimum gradient of 2 pr.lcan!,
r";hilc l.'rlrlscpaecl areas should have a rniprimum gradient of 7 perccnt-.
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Excavat ions
1t i:; imlrer-irllve that no opcraLlohs be porformed wlrlch would carrse
a slgnlfic.rnt rcdrrct,lon in slopo stabillty. DoeF cuts at the toe of the
slope slrorrld be avoided and cuts in general should be kept to a minimurn.
fn .order to avoid major cuts, lt uray be necepsary to terrace the proposed
residence to fit the contours of the slope.'
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Sirls-I jerg!ss.!,1-e n
The Unified Soil Classificatlon
(unieo= otherwise noted) as well as
particle size using the nonenclature
GENERAL N(yTES
Particl€ size
Systefi is useil to ldlentify the soil
a visual descriPtion of color and
dlefinedl below:
Bou ldle r s:
Cobbles:
Coarse Gravel:
Fine Gravel:
8 inch +
8 inch to
3 inch to
3,/4 inch
3 inch
3/4 inch
to 4 .76 ilr
Coarse Sand:
Mediurn Sancl:
Flne Sandl:
s ilr:
Clay:
4.?6 nrn to 2.0o rnin
2.O0 run to 0.42 nun
0.42 nun to 0.074 mn
o.0?4 nun to o.0o5 nm
Less than 0-005 mn
Dist ribution
usdi-f$rs-Je4.
Trace
Litt le
Some
"And" or "single Modifying
Termt'
Percentaqe
Less than lOX
l0 to 2Ot
2O to 35$
35 to 50t
N:
. So-lI ProDertI Svnbols
standard Pcrretration Value - Blows per foot of a 140 pouncl hanner
fa11in9 30 inches on a 2 lnch o'D' sPlit-spoon
Unconflned Compressive Strength' tsf
lland Pehetrometer Valuel tsf
t'loi sture Content, t
r,iqutdl Lirnit, t
P1.:stlc Limltr tl
Fl astici tY Tndex
Dry DensitY, Pcf
Apparctrt r.;round htater table at tfune noted after
Not apPl icable
au:
GP:
MC:
l_l_ r
PL:
PI:
D:
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cotnpl et i on of bor i n9
!Ja'
.v
Drll.llng antl Samqllnq SYnbols
SS: SPlit-spoon - 1-3,/8" l-D-, 2't O-D., except vhere noted
ST: Shelby tube - 3" O.D.' er(cePt where noted
DB: Diamondl Bit
CE: Carbicie Bit
l{S: llashed SamPle
Relatlve Density anil Cons+stencv \elnenclature
Term (non-cohesive soil s)N-VaLue
very Loose
Ir)ose
Fi rn
De nse
Very Dense
0-4
5-10
11- 30
31-50
Over 5O
ls:n_!:Th"t-i-"".-pj-E)- gg (rsF)
very Soft 0;0.25
soft o'25-o'50
Fledium o'5o-l'oo
stiff 1'oo-2'oo
Very Stiff 2.O0-4'OO
llard 4'oo +
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Gcre Fange Prope.rties
iTtIOJECT NAME ?roirs5gd F,'s i dcnce r Vail, Colo.
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I'ROJECT NO.
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NAME 1.er,osiir I tqu*r -t*:11:]PRO.IE CT
.LOCATTOil _v:!l-_c3!o1apo
DtscnrPltoi
Dark l:rrown organic clayey SILT (topscilj
--G. Ll-o-le?e- *
PROJFCT NO.
- -.-- SURFACE
eLorys
Pu. 6'
EL
ttGtt|o Rt rlRr€
I'r, rgnr,:nt:; of SnNlxjiloNE
(cobbLe and l'orrl<Jcr
large as 48'r in one
Clayey SfLT binder
and S,tAtt:
sized - gome as
d imension )
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END OF' BORTNG
in-
NF.MAFKS Trist Fii uas t*:rmi natad rlr:e to backhoe refusal.
T0: Planning and Environmenta'l Connnission
FR0M: Department of Conrnunity Development
DATE: May 6, 1982
SUBJECT: App'lication for a variance to construct an ava]anche diversion wall on
Lbt ti, Bighorn Second Filing which exceeds the maxjmum allowable height
of sfx-feei for any wal'l s constructed upon a site'
Applicant: Shannon Vail Ventures, Ltd.
DESCRIPTION OF VARIANCE REQUESTED
Lot 11, Bighorn Subdivision, Second Filing is subiect to snow avalanche hazard.
a-ieiiit-i6naulteo-uv Aiitrui Nears concludes that any design avalanche (those which
have'been defined as-having a return period of 25 to 100 years) will cross.lot.ll
ind-slop at the northern edge of the property. The ca'lculationg of potential impact
piesiuibs indicate that the-pressure distribution can be classified within the
i'blue hazard', or "noderate hizard" avalanche area. This means that avalanches in
the study area are expected to produce a total pressure_l ess than six hundred pounds
pei squai.e foot on a itat surfate norma'l to the flow. The town has indicated that
in order to construct any structure within the moderate hazard zone, proper m-itigating
measures must be taken. Art Mears has recorimended'in his report that any building
upon lot'll should be protected with a designed reinforced uphil'1.-t{all such that
it wil] be ab'le to witirstand the design loads. A wall corresponding to the recommen-
dation of the study has been designed-for lot ll by a registered professional eng'ineer
and at its highest point is l3 feet high.
Section'18.58.020 C. of the zoning code states that wa'lls shall not exceed three
ieet within any front setback or iix feet in height on any other portion of a site.
The applicant'requests a variance from th'is provision in order to allow the constructiot
oi tnb'avalanche'deflection wa]'l which is necessary in order to construct a building
upon the lot.
CRITERIA AND FINDINGS
MErcRANDUM
review of Criteria and Findi Section 18.62.060 of the Mun I code
rtnent of Corrnun Deve t recommends a variance
Consideration of Factors
The relationship of the requested variance to other existing or Potential uses
and structures in the vicinity.
Lot ll is situated at the end of a cu] de sac. The lot to the east-of the.property
iiJt t2) has a duplex constructed upon it, and the lot to the.west.(lot l0) is cumentl.1
vacant,'but has the development potbntia'l of a single family dwel'ling. The area
behind the lot is Forest Service'property. Lot ll is 84,847 square feet and is
allowed a duplex. The constructibn bf t-he oroposed wal'l is necessary for any building
to be completed upon the'tot. The proposea'wai'l (see attached site plan)-has been
iiaced diiectly Uinina the proposeA'st'r.uiiure and'extends to a distance of 30 feet
Lot ]iShorn Znd -2-
beyond the rear wall of the building. The interior portion of the wall is terraced
to allow landscaping, and the app'licant proposes to landscape the area exterior
to the wal'l as well. The site currently is very dense with aspen, as are the adjacent sites. The maJor impact of the wall is one of visua'l quality, and the preservation
of existing trees durinq construction and the replanting of trees to screen the vnll after construction shou'ld.lessen the visual impact.
The staff has received a letter from the owner of lot 12 objecting to the variance.
which rel ief from the strict or I iteral i nte retation and enforcement
aEr on s necessar,y Eo a eve +L un orm
ect
Two objectives of the zoning are:
l. To secure safety from fire, panic, flood, avalanche, accumulation of snow
and other dangerous conditions; and
2. To safeguard and enhance the appearance of the Town.
The staff feels that re1ief from the strict interpretation of the regulation specify.ing
a maximum wall height is necessary to secure the safety of the building which is
to be constructed upon 1ot 11. The constructjon of the wall and the landscape
treatment of the site can be done in such a way as to minimize the visual impact of the wa'll. In this case, safety of the future occupants of the bui'lding must
take first priority.
The effect of the ested variance on I i t and air distribution of I ati on
nsportation an acilit es and utilit
The wal1 is necessary for the safety of the occupants of the building.
Such other factors and criteria as the cormission deems applicable to the proposed
varrance.
FINDINGS:
The Planning ald Environmental Coflrnission sha]l make the fo]lowing findings before
granting a varjance.
That the granting of the variance will not constitute a grant of special privilege
inconsistent with the Iimitations on other properties classified in the same district.
That the grantlng of the variance will not be detrimental to the public health,
The
tle
code
Lot 11, Bishfnd -3-
'.' safety, or welfare, or materially iniurious to properties orimprovements in the
vicinity.
That the variance is warranted for one or more of the following reasons:
The strict or literal interpretation and enforcement of the_specified regulation .
uouta rdiutt in practical difficulty or unnecessary physical hardship inconsistent
with the objectives of this tit]e.
There are exceptions or extraordinary circumstances or conditions applicable to
the site of thb variance that do not apply generally to other properties in the
same zone.
The strict or literal interpretation and enforcement of the specified regulation-
rould deprive the applicant-of privileges enjoyed by the owners of other properties
in the same district.
STAFF RECOMMENDATIONS :
The Department of Conrmunity Development recornmends approva'l of the requested variance.
At the'time the project is-reviewed by the Design Review Board, the visual impact
of the wal'l shouid be studied and proper screening with landscape materials should
be required. in order to reasonably attempt to minimize any visual impacts.
IIATIJl?^'L II/\ZAI]DS
FOR
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SIIRIUVISIt|N
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PREPARED FOR
l1ll, [.. KELI.EY & lttp, .1,
nENVER, C0L0RAD0
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AUGU$I, T977
GUNN,I SQltr coLoRAIrO
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tlil r,,
t.'r ri.iit.\RY 0r.' Rr.:PoltT
sn.r"' rrrralanchns;, rockfall, and debtrs avaranches arr.occur on rot Lr,
Bigl r' srrt'dlviston' Sccon,:r A(rdltion, Va1r, coloi.ado. Although any of thcse
t'ree p.ocel;.ies may rcacrr Eo trre 10wcr or northcrn end of l.ot 1r. (Ftgure 1),
Ehc i:rree snor': av;rlattcltcs problbly occur nore ofcen than either rockfall or
debrtr: :rvalnnclres. Thercforet the snol.r avalanchc is cons{dcred to be the
ntost cr. i. Ic.rl untrrr,rl proccs:i af f ccttng poLenc{nl <lcvelopment of the properf y.
'l'lrrr r:lorilgrl nurgrrrtrr<rc snor.r avarnnche has n return perioct of 25 to 100
years. corrcsponrllng to an annrrfll probabilitv of 1to 4 Derccnc. rt eon_
sists oF . rlr;--f )-owin* avnlrncrrc which 'results from f ractrrrc an<r release of
:r <lry sc'f r. li.o.r st;rrr i. ,.rre tinrbcr near tlre rrppcr (sorrtlrern) reachcs of Ehe
pl ()prll t r''. 'r'rrr; 6'r'91',,1 of thr:; nvar.anche, ns dctcrm{nort by a ptcrimi.nary
tlyn.rmtc nn.rlyst:i or 'i.t:l f l<rrv, i:; srrown on Irgrrre l. Forces ;_rssoclated $rith
thc :r"';t [:tn'"he rvill pr:obably bc rnoderate nncl should not pr(,c1trd{l constt.etion
of a building on thc northern part of Lot 11.
i!u{lding srror:rd rrot t.kc plaee within thc indicated avnranche path
rrnlcss ;.orc detaired strrtlics .rc cnmplcced which trcf rne thc fror.r dapth and
[rreni:rrr e t! i s c r I b tr t i r-rns ruithin the movlng nvalanchc. soll stabilltv testE
slrotrlrl ll:;o bc t t,rrrlrrctr:rl to tlett.r.mlne (luantltatlvcly the sut
llope for excitvirtion an(l constrrrction.
II. IN1'NODUCTION
t
l)rcvlors rcports prep.rrc. for the Toqnr ot Vair (Royston, lr'namoto,
Rt:ck ' ;rrrrl '\ht'y' rg77) ir(tic.rt(. trl,rt loc ll, Bichorrr sub<rIvisl0n, scconrJ
Arldlt ir''n. ir l;uhi.r.t t(r sltor., ;lvil l.tncllL., dt.bris :rvtr l;lnt:lrr,, an<J rockfall
lrnzlrds. llowt:vct., clrcsc rePorts clo not
tl-all.r hlznr<lous l)ro(.cssos with a dcgrcc
specify the cxtont of the poCen-
of precision strfficicnt to plan
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brrt l'l lrr1', r.r';rIr'1'; 6a nr:rr:e r:r.common(r tions jrbout Iand .s;r, on tlle property.
'fltrt ,'lt lcct 1..'r':l of t |,' pt.(...i{.ltt. :;t_rr{y af c:
l. To rlelJrreatc tlxt c.xtent and typc of hazard from 4esign magnltude
snotr avll anches, itnd
2' To clcst:ribc the clrnracteristl.cs irn(l acrtcl oxtent of other rap16
ntass-wasting haz;tr<ls, incltrdlng rockfal l ;rna'dcbrts avalanches.
The rcstrlts of t'.is sttrtly are of n aetiri.r s'f f icient to mnke general
reconmcndaclons ah.'t !arr<r rrsc and to cvalrrate the feasibility of future
work.
I I I . :)r. ,;{:rlI t't.toll oF AnEA
'l'hc sorrth var rcy r+;r r 1 ;rbovc tot l I rs part of thc lflnturn Formation,
trhich is rr complr,.x ol sr:tlineut..rry rock rrnits consisIing of snn<]stones. con_
glomernt{e sanclst.ncs, s:rndy ;rnrr silty shares and lrmesconcs. A rrrominent
I tmt:st"nc rncmbcr of thc Irint.rn rrorm.tion cr(,ps out s a verrtcal cl.if f 20
to 50 Fu'et lrtl',h rrt nn erc'ation of appr.xlmately BB00 fect rrr.rcccly abo,ra
lot 11' Thts crrff an<t trra stccp sropes rrerow it wrll bc referred ro as
the 'rlc'r'rer slopes" in thts rcport. The lower sropes are the prlmary sources
of the potcnti:rlry ha::ardorrs nirtrrral processcs wrr{ch ;rf fcct loc 11.
The lower sl.opcs on an<t abovc lot 11 range in steepness from 20
to d5 degrces (36 to r00 pcrc.rr!) an<t are oriented tor.ra rd the northeasc
(Flgrrre I). l.lrcy consLst of collrrvlum (n hetero8cneous rnlxture of soll and
roek) <l.rtvr--rl f rrrm ,"'c"ch'c.tng ,rnd. ma*s'r^rastrnr;, of thc Minturn Forrnatron. The
cul-tlc-snc at thc norClrcrn c|rrl of lot ll is crrc into this colluvltrn and dls-
plays in cross sccrlon the chrrractt rJ.stlcs of tlre slopc m.rterial. It should
be rer':n11.1;:r'd th,rt tlrcsc sl.pcr.i nrc f orrnccr by sortrt mnterlar f a1.r.r.nJi, rolr-
lnJ;, ;rnrl sllrllrrll rloum$topc ov(!r it ,l.ong perlod rrf tl_nrc. It lg to |re {!xpected
t,lt;l t: i irc n;r(r,rAl
Cr'ri | 111'1. in thc
[) rocesse!;, oI r.reatherlngr rnass
f rrtrrrtr nnd cfln rerirrl t lrr the t'
transport ancl depos itlon w{11
na trrra I h.rzards" of rockfall,
debri s- slidtl;.;rurl <lcbris nvalrrnches if man bccones exposcd.
Ilccause the lor.rer slopc ls orlented Coward the northe
llttlc dlrecr sunlirht drrring thc r.rinter. Thcrcfore the slooc
t it rece tves
co 1l ec ts irnd
mli:rr;ri.n'; a <r.cp r.rillter .'rnrr spring snorupack. 1.rrls snoruprck is rrsuarly
anr.lt(rl'cil Lo tllc ground by vegetatlon, rocks, and othcr grourtrl surface lrregtr-
l.ari l'i.o:;. llo\,'cv(:r, rlrrri.lq eyf rcrne r.rcnther n'd snor*r r.:onrt itl.ns, a siinglc
ri r'ld 1;lx5 .f srrr*.r c;rrr fornr ;rcrol;r! the slope in trrc trccs, ,becomc parciar.ry
dt:tacir.'rl
.f
rom thc :;l.opc, an<r mo'e thtorrgh the trces as a f ror,rirrg sno,,
ava l :rrrclte.
In s trb.s equen t scctions of
tt:l:i f j ntl JrrocCSsC.i ;rrC dlSCtr:,r:ed ;lS
P l'of"-'r tY .
this report chc sno!, avalanche ancl mass_
they rclafe to thc dcvclopment of the
tv. Ro(;lil;All, ANl, DnBRIS AVAI,ANCIIES
...EslLttas occutred over the entlrc areo of lot 11 durlng the past
---sevcral thotrsan<l years. Large rocks seattered on the r.ower sropes conslst
prirtarllv of I lmcr;tone r.rhrcrr ts rtt'rtvr,d f r:om trrc l rmcstono cliff rocated
nt rit ('l'rvirt Ir'rr rrf npproxrrtirtor.y Bg00 feet. The lrmestone rn thts cllf f ls
Jolntcrl (lir'rctur.cr) rn such a r,ray as to produce large indlviduar hlocks.
Thcse ror:ks f ractrrrc and fa1l from the clrff continually over a long perrod
of t lme and tlrc potcnt iu't t'o. f utrrre rockf ar1 cxr sts. Fiet d inspection of
tltrr k:: r,rl r:lrlrr tlrc cli f f , :i,,rrrl wr, lJ,,lr irrli ns nrrclr nrr I ton,;. Frtrtltcrrnr)r(.,
irl)p(',.t r; to lr1' 1111d,,;1irrrr11 rl Lftcrcntinl wcntrrr:rrrrg nnd m.ss r,l;rsting
m.tssivc blocks .r.-c s()metlrnt,s erodccl from beIotr and gra<lually
the cllff
such/ L h,r t
1c:;c srrlPor!. llcir.'cver, tlrc clif f tn Bancral is quite stablc nnd shorrtd noc
@rt|trcilfrt,qrrellr(,rwldespren<lrockfalloverthcProPertynt
prcr;cllt.
\-------
Althotrgh rocltfnll nrust rrc consitrcred an ongoi.ng proccss at trrJ.s loca-
t1on, 1g doos not tt.".,ssnrll.y c.nr;!ittrcc ir signif leant haz.rrd to devel
'l'he rl,'qrcr,. of tlrr.' lr;ri:arrt rlt,pcrtrl:; on its f te;lrrcncy of occrrfrencc (oftcn
cxf rL':;scd arj rcturn pcriocl (lr annunl probahil.lty) as vclI as On tlre poten_
L.i illlY dcsErnct ivc 1.o111;1q114rrt:er; ol. lmpaC[. tJnfortrrnatcly, fhcrc ts no dlrect
nt'rrrs of dcrermlnl.l; how of ten;r large rock may rcaclr a givcn rocation, espec-
ially r'rlrcn thc rcttrrn pcrio<l of rockfdll is long r.rhen comparetl with the short
ol,'i{)!-!.'ntiorlJl T)r'r irrrl aE Vrri1.. A quaritative estirnatc of thc frcqrrency of rock-
f'rl t wltlrin thc .o.thcrn 100 feet of lot rr "ar mnde by observati.ns of soll
and li {:lrcrl covcr orr and atli:rr:cnt to larga borrlclets. I;rom this it is esC,imated
that tlrc algrjue-rcrurn-a ru od- for destrrrctir,c rockfall on the northcrn part
of lot ll is rotrghrv f!9jg-I9!-XgL. Appticarion of encounter prohabiliry
thcrrry :;lr.r,r;; g1.t"r, g, lven tlrr: ah.vc rerurn periods, Lhere is.nly an lB to
39 pcrcerrt cha.cc th.rt any ranrlomly selercted 100-year period wllr cxpertence
sc!.:crc errrl potcntlally cllrnnliing rockfall on rhc lower 1.00 fec! of 1of ll.
This assrrurcs th:lE rockfall cvcnts are randomly distrlbuted indeoenclent evenls
throuxh time. sucrr probabllitias (roughty one crrance in three that a
Dchr:js avalnnchcs m;ry occur on the L,esrern half of the property as
$tat('r-saturaccd colluvial rnaterinl slldes and flous rapl<[y rlownslope. such
processes, nltlroul;h probably rlre at ony glvcrl locatlon, havc oecurred on '
sloltcs of sirnll;rr orrcntxtrorrs, stcepncgsesr lnd corltrvial composltlon rn
V:ti I rlrrr In1; the p;rst Iec, yelrs. rror exrnple, nn rm'rc.+stvc rrcbrls avnrnnchc
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ffi"'-t
o(:crlrl','(l (rlr tl:o cilsr (rtrtl t'f tt'c K;ttsos Ranclr in Aprtl' 1975' 1t ls estLmatcdr
or1 tlro l'.'t:;ic oI t;oil rttttl l iclrr'rr ('ovtir (]n ;rnd nt"'t f borrldr:rs ' thilt largc debrls
av;rlllrrr-:ltt's t'lri.r'lt cottl <l lr;lvc t r'r:tclte<l glls lr')wcr 100 f t'ct of lot ll ltavc noc
(!ccurr!''l rlrrrinl; thc !;irme pcrio(l of tine nnd !h:rt [hc area hns been frce of
r.o<:k!..r.11(?00r<l!r0()ycarr;)',|'lttt:;<lelrril;ltv;tl;lnr.ltes<totr.'tr|F^nrEocr'n-
()cc uIr('llce ' Fur chcr-
t t'
f
T
:
:
rnof r:, i t r':as; .t 1::o olr:;ervr-'d tlta t
lnyerlr h;tt; ttot bccn Litkirtg nllct'
dccatl.:q.
llow,"vcr. ;rlthorrl'Jr slolrc:1 "tPpcar to bc rcl!;onably stnl)lc wlth respect
to (lchr is s lltlt's ltntl ccl.rris irvirl'anchcs, tli, nflturill con
tlpsct bv inc()rrocr c()nstrttction practiccsi'
canrlirsctrlrr.$].rrlcstnbilicvnndtriqgcrvnriorrstvpesof],ands1i<leswhich
c9-,1,l -1.'k.r tllc tl,.,l'. l!9IIil'1e to <t
sNor.l AvALANCIIF.S
nvir I lnches arc const(lcrcd ln rlris sLrrdy' These arc
vigorotrs crccp atrd slide of surfacc soLl
orr tlte lowcr slopcs witlrin the pnst feu
s s lirlci or 1!q!1gi s1 ava lanches '
l)t's i i,rr mng,rrl tu<lc
must bc cons idcred ln Planning the location and desiP'n
of a mnlqrri ttrde wltich
of f.i,:Llit con tlc f i ncd b the Tor^rn of V a ret
c:lrs. Dcsign avalanchcs at this locatlon nill cross
pertod o
1ot 11. nt1'.1 !itolr tn the ctrl-tle-sa(: nL tlrc northcrn cdgc of the propercy
00
(l'l grrrr' 1)It ls estirnatc(l' on the basls of the ages of standlng and dcad
,t""; nvalnncltc .leh,ils irr thc lowcr parc of the lotr thaE chc return
f'crio'l oI thcsc lrvnlatrchcs i:; 25 to 100 ycars (correspon<ling to an annual
probrbilitv of I to 4 Pcrcent) '
l)t:r;{1;n ;rv'rl:rncltcs llcliin aftcr fracturc ind rclcnsc of a dry' soft
!;rl(,w t;l;rh ltt l.ll(' t Inllrr'1' ht'lrtt'r tlt(' I ltrrt:::tone c1{f f ' 'l'h jl: s1;rb relcn:;es ln
t.
Lhc t ''(..1s (-\n ::l (rpes 0f 1r0 t-rr'45 (lcf,r(:cs;. llovcvcr, evcn rltrring thL' scvcre
de:; j:i:r .rr';tltrtclrc cotr<l ition:;. rr (:()nsld(!r.lble voltltlte of tlrc sl;rlr ',"'i l1 rcm;rin
ilnch(.,'c(l to tllc rpper c1ope.. As the relenscd nvatanehc falls through chc
trecs tlrc sl:rh wil.l tl ilrintcl,r;rtc irrto prrrgrcsr; ivcly smallcr particLcs wlllch
f I cr,r t lrrttugh tirc trecs n:.; a Iirrirl .Powtlcr ava lanclrcs r,t i I l. not dt-.ve!.orr
becnrrse of !lrc slrorr It'ngth rrf Lhe s1opc, thc moderntc avatnrrchc velocicy,
cnd tll(. nrrr(lcl'il tclv lrc;tv\' t it'rlrcr cov(-.r. Cnlt:trl irt.irrns ()[ r)r]LcnC ta1 inrnact
\J(.I'c rr()t nt:l (l (! f(rr sttrdv hrrL 1"y6s;l,l Plrrlr,tbly n,tt
Q Xrl t',,r I ;t I t'v1 c Tor.rrr of Vnll. Frrrther
strrdv i!i r)cc(r:s:iilry to .lef inc thc rrressrrre di to def lne peak
Dressr:Ies quanEitativcly.L
Bccause of the fact Elrat snow avalanchcs apparentl.y hatre a higher
probahility than tlrc otlrcr miss-wilsci.ng proccsses, thcy consritucc the most
erltlcal deslgn corrsirlcration on lot 11.
vI. nncol$rnNDATIoNs Ar'lD nlTt,RIi woRK
,\s disctrsscd, sncrr,r .lvnlilnches, rockf aJ.1., and dcbris aval.anchcs alI
occr:r r'ritlr vnriorrs nrob;rbl l.itics over most of lot 11.' Thc rcsults of this
prell,nlnrry sLu(lv sur',f,cst tll:rt srrow avalanchc.s probnbly prodtrct: only
]9,tor,_1 t_g-dyr.rn I c Fro:rsrrrcs ;rrrr{ that other nnss-r,rtrsCing nrocesscs are rela-
t.iv('l\' .[nf 1'rlrr,.rrt. llowcvcr, lot lt slrorrld not be dcvel opcd trnlcss the snow
F(rturc r.rorl,. r'roul.rl cstllbllsh thc deslrabil lty and f casibl11ty.of bulld-
lng r"ithin tlrc lowcr porEion of che hazard area indicatcd on Fig,ure 1. Such
study, lf dcsirerl shorrld int:l.udc tlre foll.owin8 steps: .
r 1. Dt tcrrninc vh:rt p()rrlons of thc hazard arca of F'igtrrc 1 is accept-
Irblc for brril.<liug .ln terms of tha impnct pressufc and freqtrcncy
ava I an,:he rro t c nt:ii
-l
, 1- t'-o
7
crrtc.ia prosentr.v 'cceptcd by the Town of \r..r'.. Thls step would
nlso pr:ovide desil,in critcrla for f111ll61nr!s .loc;rtcrl irr thtr hazartl
arca by spcci f .,ring
n. Avalanehe flow depths, ..rnd ,
Ir. Avr.llnrrclrc presstrrc dlgtrlbrrtiorr.
2' Fcsign spacific ,rvalanche mitigacrng acfcnscs for builaings.
. 1'rr is rresign srrorrL<r bcr hase<r on thc crtteria <rcveloped in step 1.
()no Inny d0c itlo Lo st()l) r.r()rl( Af tt'r oLther Stcp. At ttll.s tirnc I have
estJn;rto(l ;;r:olopical cnglrrecrlng costs for Stcp I to be $g00. Mrrch of the
.Li(:csq(rrr/ .r ir'r<l wo'k has bt.t. ,r.nc and tho necessnry datn colrectcd. lingl_
necrirrg cnr;ts of Srtp I trflve not bccn estlmnted but worrltl probably approxl_
nate the c(rsts of Stcn L.
In n<ldi tion 16 thc spccific recomnendations llste(! above,
recorn'lr'nd rhnt si tc'-spccif r.c-sorl-stabilrty tests bc co'ducted at
btrlltlin[ loc;rrions. Thesc tt'sts roul<r provtde qua'tttatrve data
I also
poss ib 1e
through whlch
site corrld
the s!opi-' stnbttiry irnrr poterrti.ar for land.s1ldes at thc brrr.1<ring
be ovsIuste(l.
Respectfully subrni. t t ed
Ctnlln* l.Ylltaru
Arthur l. Hcnrs, pli
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PANT II
DESIr:lt cnrtitRl^ n0tr ljt'nttgl1,fiAt, tTtolTc|tloN FROl.t AVALANCIIEtS ON IOUEIi POnTIOII
ot. l,ol. 11, DI(:llonN :iulll)Ivlst.oN gE(loNl, Al)ltl'rtoN, vATL' Col,otAtlo
. ProPrrod for
!|tr. J . ltlagon
Denver, Colorado
Arthur I. t'leiars
Cur|nfuiott, Colorarlo
Septonberl 1978
'ART
rT. nr'lrircN crt'milrrA li,'rt s,rtruc,rt,nAl rllo,r'c',roN
'r'M AVALANclrLrs oN l,(!l.,l,tti ir)tr,t,t r)N ol,, t,(;1, 1 1 , BTclt()ttN sunt)TvIsIOll sucoNu ADDITI.N,vAIL, apt,ollAt)0
A. General.*trformatlon qlr,l Llmitations.
'l'lre rreslgn crl beria devcl0pecr ln thls stud.y can be used. for protectl0n agalns+, deslBn _magnl tude avalanchos on the norther n ?5 feel of Lot 11, Blg_horn Suhilvlslon Seconcl Acldltlon, Vall , Colorado. ,l,hese crlterla can be app1lr:,:t only to c.lesign of structuros locato<l as dosr:rlbect above and would not rrocessaxlfy provt.o pr.toctton at ottrer 10c:rt10ns. Thts paru of the avaranchr: r;trrtry (Iar'r rr), ts lr,rs,rr r,rr Lho lrrf.r:rrrirLl'n obr,alnc<l 1n l,art r,a reconnalrt:;ant:o :;t,utly cortpl.etcd cluring August and. SepL:mbe t, L9??, ,lhero-fore dof lnltlons ancl ltrrltlrtlons of Prrr t I apply :rIso to l,:rrt II.As statcrj abovo 't tlre dcslg1 Jrirramot ;erc gl ve rt hcru 1.,r<rv[4c lrrt>toctlon a6ainsf "dcsl{.:n a v;r I;rtr.:t,u.. , ,, wlrlr:h artr <.1rrf in.ct .i, .*,.... , t,.
-_ro. It is lxtsslblc [lrat lar{jor (anrt ltr:;c
_,1^'.t:]::::l::,:rr,"
wirr .t:t:ur;rL Lhrs rt.rcarl<,', bur, ir ir; I..rr. r,h;LL r.r*y .ur.r, t,n;tL l,llt havo .r Jrob:tbl IIty cnurlJ. cnouglr to ba rllsre6arrlcrl Lrr ;rl;1n111 rtote<,t'i.n 'rsat'st othr--r n;rss-wastr"u n""""]."-. ...,,.,,''.::"::l:'*
-'t tlcslgn'
't,.hFt-,..'.#Sl|(:}l;lsr.(,(:l(fal1.rtld tlebrl s .virlc.nc6(_.$ ls
-
J s1r:r:ll,lcally lrrovltlcd l.-==-_ '*'rr |r.::q".:1i In <J,.lr;161y, bcr:;rrr;;s, ..,etatec"n@;;-
Procos'es appear to
-f.,,,",. ;;-.,. vr,trurit s appeaf to hzr.ve feturn perlods sub;;{.an11a.1 ly longer bhan thoso ,
!,cpa,"lr,.r | ', r - r
v _v..t:vr u.'du r'noso of enox avalanches and nlry be rllg_r.'cgande<l ln Jcsltin.
l)tr5l.61y for snow lrvitllrrrr;hes ars $J,ec lfi ed ! n cluile the nr:cc,s1;i!y for slope_stabl1lty analysts
Dec^rrse srn.lL i.lowin6
'varl.nchos <:.nsLltutc t'e rlr..1;i1;rr r:a:.i' rtL tho propoleil brrtldinll lor:itl'lons, it Is ru(:omnorrrlorr tlr;rL lrrri.rrtirrl;r.; tre Irr.oLccLod
-t-
v&e
-
thit; rtr1rorL clocs not prs_
prlor to constructlon.
B.
1-r.:!f Dcrtorl of
In thls particular o
case the nost rrlable
form of protectlon consists of deslgrred relnforce<I uptrlll wal_Ls such that
Lhe.v wl l.l lxr :r.l o t.o wi r:itlrrrrt l.llr; dosi6n lo;{t:;. ,[lre rllsllgn loarls on walIs
tlt'1x.:rt,l on avit:l.rrn{-.tro (,hirr.a(.:L()r.,llri.l.r:s and w;rl.l orlcntatlotuj. ,l,trc av;rl_anche
ctrarlcl.crls LI cs rrsod ln <l.c::l vln6 the dosl8rr crltorla ;rre 6glven 1n Table 1.
trelg-c-Ltr
sle -- lulr
920
TABI,E 1
I)eslgn Avalanche Characterlstics
'l)eniiity Fl.ow Holr<h!') -.-u.d!a_ - IU/l'l-, m __ t.r;
200 t?.t)1 .1 3,6
I Snow Helsht'
m--ft
o.5 L.6
ot' rlr:pth of
" U,rslgn r;rrowl);.l.ck trcllltrt, i.:; r:r1u;11 Lo one -trir1l.ttrrdlstuTtltrl l;nou.
whon.an avalanche rs stoppo. or defl0cted by an objoct ln lts path It,
wll..[ I'rrlrlrtr:tr Lht.trrl, IJr.r,lii..;ut,(.r:; lr11;r.l tr:;1, l,lro olt.!r1r:'|, l,o :totro lrr_r!.11lrL ott ir wit]..1 .
'l'|1r''1;rq r111ll l.r';':i irr:t' Irr l,rrt'r:r-: rnrrr,u;rr-ly rlr;rrrctrrll.t:rtr;r.t.rrlrr:cr,iorrl;: (1) norrurr
to tl'r'r ur'rrl, (2) vertic;rIly, ana (3) ln ahear. The area over l,hlch the forces
whlch iho aval-ancho ls cloflecbcd). Ftgures, Zr3r_mtf_+_@
ntttlon fol' rr]lq,gI_pa.se,LJo <losi611 aval;rnctres Locltctl on ttre lower part of
Lot 11.
C. Add-ltlonaL Deslqn Informatlon.
Archr t,ectr-rrar or structurar. engineorrng detarls are not given rn thrs
study ' h()weverr the folrowrrrg 60noral t'.rcomnenttrrt l0rrs str(ruf(r br: rncorporatetr
Into tlcs l.6rr r
@ H-our ovtrrhltrr8$ shorrl<l bo avolrlcd unlcss Lhey 'r.c above the deslgn tre16ht.
^$,,:f,j,
,;:.:::':: ;.::,;:,T;,..:1,:
r;rr'urr'| rx: rrcsis.ed " w1'ihs'i:rnrr
f - ii I4ZJ5 ::;t rrcslxrct.ri,'y ,;rrrrmrLr.r:rJ,qed[# e. tugu.*s*-
act dcpend on (t) the 1en5th of the exposetl wa11 (rlcl,r:rminnrl by archiLectur;rl
"" i nrxl by ther arr6lo through
I
A VAt,AN r ltl
(Pirrallel t.o
I
E rf,or{
lor:;tl
I
,l
(B)
t)lfiu(:'tt 0N
t';rl1 I l no
(r)
( r:)
[j!!l8!-?. Posst ble
rrr.r:r.ro' ;rre i::;":';ff :,t":':l"ns
w;rilr ril.h *,:;rx.:r.i to av;rran::he
r,rre lcrr:;r.r f;rr r. tir,,. ,,,. ,.-_--.,rriin
aroor.r.!. Ar.;rrrrrt.lrr: f.rcrx
(A, rr, ;rrxr 0) ,rl:'':,,j1;:'r.ttrl[<:trl'rt'
r', .lirrr.'r; t.r.r' r:,r';rL ,,r,,L.;:il:'"",,.J,L,]"
(A) Urrllr,l lrrg li.rrlcntcrt $uqrh [h;, 1.!l! .lc11r.r.rr.r3; lo llrc ;rvir[;rn(:lrc (l I
!r] ltll lrt irrt: I u orlqrr t.url :irrr:h l.1irl (r:) lrrrtl,lirrl4 is orltrrrLr:tl :.urulr l.hrl,1l.lltitlt; rJO ttcr.ljrjr:s;.
I'i6rrrcs lJ rrnrl /l l,l.ovl(lc tlclllBn ilrl l,oflrr ,rtul rr.111i1f l.l,r.r.,r;L ,u ,r,,r,rrl* _
'irr i;r'l l'ofrtl, lrt 1.r.11x,.' .l' rl.l;lfirr
t.l.r:,r.,, I (l,,rr.r. ,; .i ,,t""tt''.ttt l'r,r for' v;r'rl'us rx.i,..n t..q i,,,,.. ,'r.(rHr; l,(rl. 1l ||l t,lr r.lr$1,..,(: l, 1,6 l.lrrr r\,r l;r.rt,.l1l
I
t,
I
li ti
lr I
l
t
t,'t
tI
l'l orr
rlrrwtt
t jr l:;rj: i ,
tnrLh ulrtrlll [;t.l lgi ;tr.rr 1,. ;rtl ,rn13l.r.:. 0 , r,l.t1:r:liolt.
O, lrrl Ot rt i 1.1.,:r..
ttl,lrlll w;rl.l lli n(rl,ttrirl Lo t.lrr: l'l<rtr rrfr.l 0
rl;rl I hclgtr 1,, ll,
brrllrllng r;tllr:.
lt, '.!,h.
-10-
15.0
50 q 60ff'
$ . (,lr:grt;,:,;)
.u
IE
s \o
r{
2 \t
E)a
10.0
30
l)EI'Lll(llION
lllli!Lllri..J-:.'l'tre
If lBur s 2
tiPe c I1'l txl
rlcr;lgrt ltuLgtrt., llI 1s 6ivorl irl;;r fun(:l'i()!l ot the rlcl"le:r:i'ttrn arl6l (' t 0
l;hows S' Htth ro$poct to lval:rnclro flow rllrcrllort' 'Unlt' l'crr:€i;t al;
ln Fl6uro ll, uct 6vsr t.ho rteslgn hei6ht''
___ _ __r*.-
.b,.
it$P*hrr
'o?.,,,,,".,,..,u: ..-!,to tr -;F-i
plculg 4. ,!.rre nornrirr
i'Et'Lool'r0N AN.LE' 6- , 1,r,',rr',.,"i '- 'io t'o
l,, lLrt", t .
-r;;,,::1',:,,::,:1"1;,.,1;,' is r{iv{:r'| ;!:; 'r ri,.' r.j'rn cr r;h,.rre{'rt,.,i,,,r
. i,,i Othcr unlt l.orces an.r
"_],''
-'-
r{tLrr rc!;[x.:r I l.rr ir,:rl;rrr. lrr: t.l,.1s rl irer,.l.i.i,n.
"1.'i,lr. "" *"t*";,:[:":"i,."l,,.liu","trir'rirtri116 ',,rrr,,,,,',,.,;hr;;11-, p", ,nrr uprifr.,:"', rort:r:! acr on oxr'5s6r x.lrs urr,.",,il";;'l,T: ,:::",:,"::,,;,1,1 ,,,.;il1";1,
r7 '-L --.
\l
\
I
S
lri.lrrlt,_-1 . Lor,:rrtiorr of I_ot ll., ll{;:horn Subrlivision, Sccon<l l*l':":;:i'x:lil,'"l"l;::::u.''''n.',';rl' i'i i"",. o.'<rcsign
.,ir.r.ry,,r ii,i.".,,,i,:::li.ririlll_l'-.il"lui:ll.:*;;:l:;"
' ;tv;t l.r clrc:i lrf a1s() pol;slbl,_, ()n fhc rrr I c,;s r y1'q.,"n r ly rhan' ao= i'n -n,,,,, r;;;,[:"";:l',, :l':";]:;,'.tc.xt f1,p Inorc com'rctren.iuc ;;;;;;;r;; of che proee$ses a f l'sr.t .1 1,,, tlrc propercy.
l:s
[ ?"','"'"o
ARTHURT MEARS, P.8., INC
l.Ltrnl Flzrdr Coorul.qr
Zl2E G.dic Arr
Glaio, Cdd& gl2i0
nt-ut.t2%
I
[.\ic,, 9v' 0ntt' r lVo0a^..f r
tt,nl^.Sou RocLS,Ql
hrr;th Nlol J,{\"o^u
ruo. tNl{L rttf'l
October 31, 1990
!lr. Bryan Hobbs Vail Associates Rea] Estate P.O. Box 7 Vail, CO 81658
Dear l'!r. Hobbs:
The enclosed analy:i: :f-rockfall, snow aval.anche, and debris avalanche affecting Lot 11, aigrr-in sumivision--ilcono Addition was completed as we discussed 6arlie, Urf"-ronih:--
Please contact ne if consultation.
"'frii#u ntoa*
you hav6 any.questions or desire additional
?€' NA-a'.wJ.^ A\\o^\Arthurf. ltears, p.E.
Avalanche-control engineer
Encl .
Lb U/orlt4'o A&ttrl o A&d* crrtnt E {r,ralrlq-
'+
9:
,a
Boctrtlril., Srot tvlllreEE, llrD DEBrS lvll.llScEl lltlI.I8I8
LCX! 11, BTCEORtr SUBDIVISIOX, SECOIID lDDIIrOlf
Pr.pl8.C lor
f,r. Eayr! EoDbc
Prepared By
Artlrur I. llears, P.8., Inc.
Gunnison, Colorado
October, 1990
.:':'
'. ir* !:
8I'UI,TIRY ATD RECOTflEXDITIOXS
Lot 11 is exposed to rockfall, snow avalanches, and debris
avalanches over the entire area of the lot. Design-nagnitude
events, which nust be considered in planning and engineering,
have been considered in this analysis.
The design ROCKFALL event, based on field observations and a
computer siuulation of rockfall, will consist of a 3-foot
diaireter rock which becones detached and begins rolling at the
Linestone cliffs, nore than 300 feet above the building site. At
the building site, this rock sill have a velocity of roughly 70
ftlsecond (48 nph) and sill be bouncing at least 13 feet above
the ground. Such conditions require ranking the site as
potentiatty lticrh Hazard Rockf?Il. Mitigatign of rockfall could
Le achieved only by construction of a catching fence imediately
above the building site. However, such construction would not be practical because of the snow and debris avalanche exPosure
described below.
The design sNow AVALANCHE event will begin approxinately 500 feet
vertically above the building site (north end. of Lot 11), will
fall over the lirnestone cliffs and reach the building site at
approxinately 50 utph velocity.. Stagnation pressures of such an
evLnt wi]I exceed 1,000 lbs/ftz. such high Pressures define the
buildlng site as lying in a potentially Hiqh Hazard $now
Avalanche area. In accordance with Tolrn of Vail ordinance,
building is not pernitted in high-hazard areas.
The design DEBRIS AVALANCHE event will begin on the steep slopes
below th! lirnestone cliff, will entrain tret snow, soil, rocks,
trees, and other vegetation, and nay deposit up to 15 feet deep
at the building site. Although velocities and pressures are less
than those associated with snow avalanches, inpact with a
structure wiLl be conplicated by debris entrained into the flow.
MITIGATION of the rockfall , snow avalanche, and debris avalanche
can Ue achieved only by avoidance. At this site avoidance could
be achieved by buil.ding underground, into the hil'lside and
forcing the slope processes to pass over the building. Some
residual risk would be naintained, however, because the persons
one wishes to protect nay not be inside the specially-designed
structure when the design event occurs.
o o
1
This analYsis of
debris avalanche
vail. Associates
oBatEgllvE8 etrD r.rt(IlllrrottS 0F arnDl
trdesign-nagnitude'r rockfall, snow avalanche and
on Lot 11, was reguested by ltT. Bly?n ltobbs of
neif sstati and has ttre following objectives:
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a.Analysisandconputationofrockfal}hazard,onthe
Iower Portion of Lot 11 ,'
b, Analysis and couputation of snoJ avalanche hazard
on the l6wer Portion-of Lot 11; and
c.Analyslsandcomputationofdebrisavalanchehazard
on the lower Portion of Lot 11'
Thestudyissitespecific,thereforetheresultsandconclusions
should not be appriEa-io-oit"r sites. Furtherrnore, althouEh the
analysis p".="rrt"d-in trrir report does provide analltical and
cruantitative aesciip{i"ni oe tne rockfall and avalanche
ffi;;;;;;;';;i;;-F".'"t"" for structures have not been
;;;;i;;-l"a-"i6-lEiona the scope of tlre present studv'
2 BOCXlaI,t il[ALYgIS
2.1 PREVIOUS WORK
As lndicated on aerial-photo napping goTPleled f9I the Town of
Vail in 1984, r,ot-ii-is-iocatedin i "giifr Severityn rockfall
area which was defined as follows:
rRock outcrops were thick or numerous and uore than 100
feet abov" tt; trffi=ia" with signif,icant fracturing and
p"iftap" " faige rynler--of rocks'or boulders at the base
of a steeP hillside"'rl
The Town of vait study states that additl'onal studies on roclcfall
Dhenomenanayaffirn,negate,or.requiresubstantialrevisionsto "ril;;;eingr' "i-i;-"-iortt'"t,tiy, incfudinE revisions to the hazard
lines and severitY definitions'
A field site inspection of the site was co'lFleted.on octobet 23'
isi6l--ob".triti'""r-raae during this site inspection are
sunmarized beLow-
a. The rockfall sources conslst of a uassive-linestone
o"t"i"ppittg -io"it"d south and approxitot:1{.120 to 350
feet above tft"-rii". Rockfall ily also_begin. on the
steep, "=p"f iot"""a toff""ial stope below thb cliff'
which has a'rorrei-i"rninus at the north end of Lot 11.
I The rockfall process Iras sinulated through application of the
icolorado noc-kfatt Sinulation Program, r' (CRSP) , a cornputer
Drosra1 that computes rockfall velocities, bounce heights, and
iun6ut distances given lnput data about slope steePness'
ioughness, and haidness. The CRSP uodel treats rockfall as a
sioEnistil process in which a large number of siroulated rockfalls
ffi=C; lize acnieve vatious velocities, bounce heights, and
i""o"[ distances, just as they do in nature. In nodeling rocks
.i iot 11, a f-f6o€ dianeter iock was assuned, and 100 rocks of
tfri" siz" were rolled (by CRSP) donn the slope to produc
"i"iirii"al range in r6ctcfatl behavior. This computer model has
been tested extensively and is used regularly in design of
rockfall nitigation in Glenwood Canyon
In application to the rockfall affecting Lot 11, -slope steepness
n"r-i'""tt-,red, and estinates of slope trardness and rougltness uere
ol["i""a uy irinuing the steep colluvial slope to the limestone
source arei. The progran was run and input parameters Ifere
iajusteC so that tire 5Pservea distributlon of rockfall stoppilg
oo3itiotr- along tne Ariagre noad cul-de-sac was duplicated. The
[tt"oi"ti."i cnSp nodel, iherefore, was foreed to simulate what
has actuallY occurred at the site.
Because rockfall behavior at the building site-located on the
north end of Lot 11 is of interest, an nanalysis-pointrr was
"hor"n at this location for generaiion of rockfall statistics by
the cRSp nodel. rtExceedance probabilitiesn of 5' 10, and 20t
were used to determine the aelign rock behavior. This neans
ih;i, -iccording to CnSp, there ire 5, 10, and-20* chances that
ifre ioffowing ialues viit be exceeded Uy a 3-foot diameter rock.
b. Rocks of various sizes, up to lO-feet in dianeter
have rolled down the slope and over Lot 11 in the past,
however snaller rocks up to 3 feet in dlaneter are
tlpical of this rockfall area.
c. Rockfall is not a annual event at this location,
however sone fresh rockfall was observed on the steep
slope where rocks had been stopped by trees.
d. The slope supports a dispersed aspel forest and has
a rough suriacel-toth factori were considered in
cornpuler simulation of rockfall at the site.
TABLE 1. Design nockfall Characteristics
Exceedance P Velocitv Bounce Ht Kinetic Enercrv
18 ft 225,994 ft-lbs
16 ft 2O9,t56 ft-lbs
13 ft L72,4OL ft-Ibs
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I st 10t 20t
7e ttls
76 ft ls
69 ftls
'l ;.- - .:
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3 STIOT.AVALITCEE II[EIJ!8I8
3.1 PREVIOUS WORK
Lot 11 is located in an [avalanche l-nfluence zonerr on To\tn of
v"if t.p" produced Ln L977. This designation neans that
"rif"tt.it.s are thought to affect the site, but that the avalanche
oro""== has not beei quantified to determine the level of -severitY or Potential hazard
Inspection of Tab]e 1 indicates that the snaller probabilities
;#;;;;a to trigr,er vetocity, higher enerlty, and higher bounclng
i""iiiif events. HoltEver, even the least conservative (2Ot)
ilffi;ii has large velocity, elgTSy,.and bounce heights and would
;;-aiiii"ult to desisn for at thls site'
Appendix A at the back of this report contains the detailed data
a-e-nerated by the CRSP rockfall model and will enable alternate
i;i;;;-;i eiceedance probabilities to be used for desism
purposes, if desired.
Tbe design-rnagnitude (n1O0-yearn) avalanche, an event usually
!."=ia.i!a fn-pfannini ana Lnginlering 9f fixed facilities at
v;ii; wis anatlzed by-the following 2-step procedure'
a. Avalanche runout d!g!3f, or stopping position'
was deterrninea-tnrougf, appti-ation of a statistical
i-grJssion equation uased on 112 documented rare
iaiprox. tgfiyear) avalanches studied in colorado'
b. Avalanche velocities along the Path-profile were
then couputea EfruehE'Plication of a 2-friction-
ay".ti"=-toa"f-gi""" a ilarting position above the
linestone ciiit-ana a stopping-p6sition, determined in -tep "a,' ai-itre interseciion-oi Lupine Drlve and
Bridge Road.
Asnotedinsection2.2rtheslopewasclinbedonoctober23l
iggii. --Orii"g this site'inspection, clear evidence-of snow
l"ii""crre iniact -inneaiatery rctow the linestone cliff indicates
tfrii a""funcir"s have begin ibove the cliff and fallen on the
Iower slope. In additi5n, observations indicate a sufficiently
airplrsea forest rfti"tt wiil also allov snall avalanches to begin
within the trees l.fo, the linestone cliff. Dat0age to the trees'
i""i"ai"q broken ii"b;, bent nain sters, and debris aligned down -iop" suigest periodic avalanche activity'
'i)
The conputed desigm snow-avalanche velocity and stagnatlon
lressurl at the building site on I€t 11 atre sunnarized I'n Table
2.
TABLE 2. Design Snow Avalanche Characteristics
velocity: 22.6 n,ls (s0 npb)
Stagnat-ion Pressure: 51.1-KPa (1,068 lbs/ft2)
Appendix B at the end of this report contains the detailed
c-oiputations of the avalanche-dlmauics analysis.
the pressure computed at the building site (11068 lbs/ft2) is
substantially in excess of the uaximuo pressure allowed in snow-
avalanche nBlgen zones by Town of Val1 ordinance, which allow up
to 615 lbs/ftz. This neans the building site, located at the
northern end of Lot 11 ls in an avalanche nRedr zone, an area l-n
which residentlal constructlon is not pernitted by vail
ordinance.
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I DEERIS TVEIJATCEES
4.1 PREVIOUS WORK
As indicated in a 1984 report to the Town of Vait, Lot
within a high-hazard debris-avalanche area. Such areas
defined in the Vail study as follows:
11 lies
are
rrThdse (high-hazard debris-avalanche) areas can
experience severe etructural danage by inpact and
deposition of wet snor, soil, rock, and debrls.t
Building within these areas Ls not reconnended by the Town of
vail unless uitigation can block the flow, thereby reducing the
area of debris avalanche runout and preventing these events fron
reaching the proposed developnent.
4.2 CURREMT FIELD OBSERVATIONS
Field observations nade during the october 23, 1990 site visit
indicate the steep slope above Lot 11 shows past evidence of
debris avalanches. Such evidence consists of undulatlnE (Iobe-
shaped) deposits and unsorted debris. The slope is sinilar in
terrns of s1ope, soilr and vegetation, to several that produc-ed
debris avalanchlng during the rapid thaw which occurred in the
VaiI area during ljlay, 1984.
4,3 POTENTIAI DEBRIS-AVAI.AIICHE CONDITIONS
Debris avaLanches will be nuch slower-moving that the snow
avalanches described in Section 3, consequently they will not
travel as far into the runou! zone. Nevertheless, L,ot 11 is
steep and debris avalanches will cross the entire lot. Based on
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observations of nany sinilar avalanche events in the Vail area
durlng L984, debris avalanches will consist of wet snow, soil,
rocks, and entrained aspen and other vegetation, consequently
they would have a very high flow and deposit density. At the
Uuilding site, deposits of up to 15 feet thickness cguld occur
which would produce vertical pressures of 500 lbs/ftz. Dynanic thrust for debris avalanches that stop in the cul-de-sac about 50 feet below Lot 11 could reach 25 KPa (520 lbs/ft'). Although this is less tlran the design snow avalanche pressure discussed in
Section 3, irnpact nay be even Dore danaging than that associated sith snow avaLanches because the flow will contain tree trunks
and rocks which can serve as battering rans on e:cposed
structures.
the present study, therefore, concurs with the trHigh-hazardtr
ratlng for debris-aval.anches defined in the Town of Vail study.
Residential construction is not pernitted in high-hazard areas,._
5 ITIEIGEIION
Details of nitigation design are beyond the scope of this study.
However, the following points should be considered if nitigation
is to be considered at this site.
a. Surface buildings (vith exposed uphill walls) nill
not be practical .because of high inpact loads and would
be in violation of Vail ordinance.
b. Surface avalanche/rockfall defense structures,
intended to stop avalanches and rockfall above the
building site, would not be practical because of high
inpact loads.
c. Qertain tlpes of underground construction which
woul6 avoid inpact loading nay be feasible, but nay be ' undesirable from the standpoint of building design
and/or appearance.
Repprt prepared by,
L\lt-^l vlluao
Arthur I. Mears, P.E.
Avalanche-control engineer
sEr,tT.By: xER0x r0tscopier 7512- 4-92 ;10:20pil ;30U0382r t4?92100;s'l
}IYDrc.MABFD
3031479-2t66 .|310 tl,ld$aoilh Boula/erd, Sdb 100 ' tal€tr,oo4 Cobado802l5
T€tephom30il?38.6022 Fr$(303/238€384
FAX TR^ANqJ{Tr:rAL
TO:Town of Vail . . orrr, iSS
JO8:
ATTII:
381.002
ih. Grog Hal'1, P.E.
Tonn Englneer, Vail
DESCRI PTIOI,I/REI.IARKS
SubJect: Avalanch Investlgatlon, Lot 11, Blghorn 2ndAddltton, Vall, Colorado
Enclosgd are:
1. Coples of 2 pagea of the ca'lculatJons on the avalanchr lmpact prcssures
9!r our dlecuerlon thlc rmk.
2, Coffectad page 3 of Rrport. The typtng of thc 2nd draft of the report
dropped a v6ry lmportant llnr of trxt. I apologlzr for eny lnconvenlence.
If you have any gu.stlons pleaee contact me.
llrnbor of pagrc lncludlnl Covrr Elret:
Any problqm rucrlvlng, p
Roturn FA,l ilunbrr:
Ronald L. Hal]ey, P.
381.002 Presldent
gy3
SENT 8Yi XERoX Telecopier ?01?;tZ- 4-92 ;10:20pil ; O0lZ3E030Zr oo
HYDRO-TRIADTLTA
CALCULATIO,'V SHEEr
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SENT By: XEROX Tetecopierclilz- 4-s2 il0:!lp; ;
u00382..
14?S2100;# 3
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HyDRO-TRnO, LTD.
CALCULArIOIY SHETr
t. ey: ,2/./ Darc:-5ubpct:
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potentlal for lot 11 rlll be subJected to cllmrtlc condltJonr typlcrl of thc
valley floor' not tha higher zonss n.rr tlmbrr llnr cllmrtlc oondiHonr of thr
mrJor rvr'lrnchc path release zones.
In recent h'lstory, post vail IncGptlon (pvr, or thlrty (30) ymrr), thr
emrl'l avalanohes along the southflank of the valleyhave alnort exclurlvr'ly beon
vat sprlng avalancheg such ae thr l,lry lg6rl cyclr.
In sunnary, the avalanche potentlal must ba coneldffrd on thc barlr of both
slte speclflc cllmatlc condltlons and terruln rnrlyrlr. Thc rrt rprlng avalanohc
te the most llkely design €vsn at this sltr when both rspeott are consldered,
rII. TERRAIN A,ND VEGrETATION
The topography of thc lst and tho eurroundlng area 13 shown on Flgure 2.
This topography and lot boundrrlcs yore turvcyrd by ht€r-ilountrin EnglnoerlnE
1n late August and aarly september of leea. Thr lovrr €dg. of the cllff bank 1r
also shovn on the topographtc map. Ttn slope of the cllff vrlor between nearly
vertlcel to s rstloof 3 vertlcrl to I horl:onta'l (3:l). Falllngsnor rlll not
adhere to thls cl'lff excapt for frooztng rlme or grauprl whtch ,lr vrry unusual
for thlr vrlley.
Traneversa sectJonc from tha basr of thr lot upyard to thc buo of thr
cllff rcrc also developed by Int.r-Hountetn Engjnerrlng. gecilon A dld not
axtend thc total d{atance to thc cltff Dut Sectlonr 8 and C rxtrndcd thr full
dletancc.
Srctlon B 1s lecated cloar to ths centrr of the lot and wm urd prlmrrlly
for tho t.rraln analysls and rvalanchc dynmlcr enelyear. gcoHon c doa$
lndloate somsl,hat flattGr slopar on that s.Emnt of thc lot.
The tree cover on thc lot and the rrcr ucrt of thr lot up to iln base of
ths 0llff ls moderately thtck ulth msny rrp.ru but rlgo a rlgnlflcant numbrr of
conlfor:, sons up to 21 lnchas ln dlrmrtrr. Hhlle a slta spcclflc
ilATUl]AL IATAIIDS ptcoilil4tss^t,tct sTltDy
FOR L()T 1r
B I fiilr|Ri\| SIIRIIIVIS I(|N
stc0llD /\nntTI(|tl
v/\tL, c0lr)ttADg
,,,rl'
FNEPARED FOR
[i'lR, 1.. KELI.EY & llP, .1, l,,l/1S0ll
NENVER, COLORADO
:.
I
I
fi,wtlvrc o&-n,nsil
dkio4n, S@.."rt-
bv3
fuvq".
not-rr
n1 - \'i'i o
+o
I
^i^hn
'.t.a
L SI'i-iii.iR':' 0l: RliFOltT
snou \ralanches, rockfalt, and debrrs avalanches nlr.occur on rot 11,
Bigl rn srrtrdlvision, seconrt A<rdicion, Va11, cororcdo. Atthough any of thcse
three pToce:;lies m:ry rcach to the lowcr or northcrn end of loc 11. (Flgure 1),
thc J:rrgc s ncrr'; avnlatrches probably occur rnore of Een ttran either rockfalr or
debrts avalnnchcs. Thercfore, the snow avalancrrc is consrrtcred co rra the
nnst cri. lc;rl untur.rl proces:t af liccttrrg potcnttnl <lcvelopment of tho propcrfy.
'l'hr' rler:lgrr nurgrrrtrrdc snou avalnnche has .l rclrtrn pcriod of 25 to r00
qflto4 erccnt. It con-
si';ts cf ;r ,lrv-f .l.owin1; avnlnnctrc vhich 'results frorn fracturc and rcrease of
a <lrv so{ L r:.or,, s1:rb in tlre tinrber near thc rrppcr (sorrtlrern) reachcs of the
pr ()l)(rrr'.'. 'r'lr,: p*91'tt|' of tlrl:.| nvalanche, fls detcrmi.ncrl by a prelimi.nary
rlvn..rnic nn.rlystri of its f .l.r,,r, is shown orr I;igtrre 1. Forggl;issoclaced wich
thc l'.';r l:rrr,.hc rvill probably bo rnoderate and shotrld not frrcclude construction
of a bui Lding on the northcrn plrt of Lot Il.
ilullding shorrld rot rnkc place within thc rndicated avaranche path
rrnlcss ;rore dctaire<t strrtlics ;rre comprctet| whi.ch trcf lne thc flow dcpth and
Irecs:rrta t! istrlbrrtions r.rithin tho moving avnlnnchc. Sotl stabtlltv tests
!.,lrr'rrlrl ;llr;o bc t.r,u,1,,,.t..,1 to (lctct.minc .tunntltfltivclv the eulC
II. :NTNOI''IICTION
t
Itreviorrs reports prep.rrc, for the Tomr of Vail (Royston, trnamoto,
!lt'ck' 'rn'l .,\!rcy. r()?7) irrrtic;rrc th;rr lot rl, Bighorrr srrh<r ivislon, sccond
Arldl1i..11' jr :irrh j.r't trr srrov ;lv.r r,rncrrc, rlt'rlr is ;rv;rrnnt:rrr.. ;rnd rockfall
liaz:rrds ' !lor.r*vcr. tlrcsc rcp.rts (ro not spcci f y the extc,nt of the poten-
tLirll"r lr:rz;rr<l.trs !)ro.'c.scs with a dcg,rce of precision srrfficicnt to pl,.rn
slopc for excnvtrtion ancl constrrretion.
t
btrl l,llrrl; .l 'r';rt rrrrr:; or nr:rric r:ocomnon(l:r t I ons ahout rand rrr:r, on ttle pr.,perty.
'fhr: ,.tt'1r-at 1..,r':: of I ll,. lrl-(,n(,llt. :tlrrdy nrc:
l. To rlelJrreate tltc cxtcnt and type of hazard from dcsign rnagnltude
snow avnlanches, an<l
2' To dcscribc rhe cltarncteristles an<t aertal extcrrt oF other rapirl
nrnss-wilstin8 hnzirrds' incl.drng rockfarr nna'<rcbrrs nvalanches.
'l'he rc-strlts of trris sturry nre of a ,etai.r srfficiont to n'okc general
reconmcndacrons nbor!t raurt trse anct to evalu.te thc feasibility of future
work.
Itl. :rr",i(:riIPT[0N of. AnEA
'l'he sorrLlr vallcy r^ral r ;rbovc tot ll is part of thtr ltlnturn Formation,
rrhich is lr complr-,x ol scrlin<,rrt,.rry rock rrni ts consisting of sanctstones, con_
gl.omer.ri{c sandstoncs, san<ly antl sllty shales and limescones. A promlnent
'I tmest.ne mcmbcr 'f thc lri ntrrrrr rrorrn.tion crops orrt :rs fl vcrtlcal crif f 20
to 50 fcet lrtl'.tr at:rn clc'ntion of appr.xim.tely BB00 Fect rH.rectly abo.rc
loc 11' Thls ctrff rnd tlra s.ecp s)opes below rc wrl1 bc refcrre<t to a9
the "lr'r'rer slopest' in this report. The rower sropes are the prltnaty sources
of che
'otcntielly ha::ardorrs natrrral proccsscs whrch affect roc rr.
Thc lo'":er slopcs on an. above lot 11 range in steepness fron 20
to i5 dcgrdcs (36 to 100 pcreenr) and are oriented tor.rard the northeasc
(Flgrrre I). Tlrty co'srst of collrrvlrrm (n hcterogcneous rntxture of soll and
rock) dr'rtvr:rl Irt:m u'c,r t],'e r rng nnd ,nD=s'wnstlng of thc Minturn Format{on. The
cul-rlc-sac at the norEhcrn crrrl of lot 1l ts cut lnto thts colluvlum and dls-
plnys in cross scctron thc chxract('rJ.sties of trre sropc wrterial. rt should
be rotro;grr{r:r.d th.rt thesc slopcr; nre forncd by soltd miltcrlrl f;rll.infi, roll_ .
ln6' antl slrdrrrrr rr.r'rnrirorrc ov(rr ;l l.'ng pr:rr.od of tr.nc. Jt 1s to rrc cxpccted
It
[ll;rI i ir('] nntrtrflr []rocesses. of ueathcrrng, mass transport .rnd depositlon wirl
c()rt Inr:o in thc f lrtlrr(r ancl carr rc..irrl t irr the r'natural h;rztrrde,, of rockf all,
dehrJs slidt's, nnrl <lcbris nvnlanclrcs lf man becomcs exposed.
lJecattsethelowerslopelso"t"n.udffiTl."u{u."
llttlc direer strn! ight rtrrring thc wlnter. Thcreforc the slope collects and
m:riet;tins n deep r.rirrter and sprtng snor,rpack. This snoroprck is trsual!.y
nn('h'|rl'eil r'o thc grtrund by vcgetat 10n, rocks, and othcr ground surf ace trregu_
Lari';ior. lloucvur, drrrjs.111 cytt.eme rvcnthcr nnd snow eontt i.t lons. a slngle
rlilcl:;lab.f srrtrr'r c;rn form ;rcr.,1;s the sl0pe in trrc trces, become partiar.ry
dt--tac,r,..d
.f
ron thc slopc, lnd novc throrrgh the trces as a flor.riug sno,",
nval;rnclrc.
In s trlrs eq trctr t
tt:t!; ti nq Jtrorcs.--Li.i ..lre
p rof ,-'rty.
!;cc t ions of this report
<llscusr';etl ns thcy rclate
the sn or"r nvalanche anc! mass-
to the davclopment of the
tv. Ro(;KFALI, ANt, DtltiRIs AVAI,ANCI|ES
- -R*!&]-l-has occurred over Bhe enrrrc area of roc 11 durrng rhe past
scver.l thcrrsand )/ears. Large rocks seattercd on the l0wer slopes conslst
pr'lnrrlly of I imcr;tonc rvhlclr {s rlt,rtvccl f rom tlre I lmcntono elif f located
nt ":11 t'lf v;rt It'n .f ;rpproxlrr.toty 8800 feet. Thc llrnestone ln thts cIlf f is
Jolntetl (frncctrr*d) ln such a nay as to produce large indlvtdual blocks.
thcsc ror:ks frncturc and f:rlr frorn the crrff continu.rrly over a rong perrod
of time an<! thc potcnt t,r't fo. frrtrrre rockfarl cxrsts. Fie!d inspecEion of
,tr
l.r k:; uf thlrr t lr<r r:li lf , :r,,rrr. wr,lJ,,lr inli ns tnrrr;11 611 J ton:;. f rtr tltn rm!.rr(.,
:ll)p('ilt !i [' lr. rrrltlr:r1',' I rr11 tl if fer.ntJal uc;rthr:rlrrl ;r.d mrss qrir;ting
m'rssivu blc'rckn :lrc s()mccrmc-s crodcd f rorn bclor.r and gra<tuarry
rhe cl{ff
sullr/ L lr.t t
b 'lr.
I o:;e !rrrirl)nrt.ll(irr'cverr thc ctift tn
@lt|trccfrt.rlrtcllr('rl,1despticadrockfnllovcrthcproPertvat
prcr:cllt.
\.-----'
Altho*gh rocl([;rll nr.s! l)c consi(tcrcd fln ongoing process ar rhJ.s locil-
tlon' it doos n.g rrccr:ssnrrly constitrrEe . sr.gnif reant haz.rrd to devel nt
'l'he rl,'qp6q,' .I tlrr.. rr;r:::rrtl tlr,Fcnrlri on its f rcqtrcncy oI occrrrrcncc (oftcn
o*p.,-',,uo.l a:; rctul'lr pcrlocl r',r nnnrrnl probnhil.lty) as rucl I as on tlrc poten-
t.i ;rlly d(:structiv(: c(rn:ioqtcnccr; (.,11 lmpact. Unfortrrnatcly, thcrc ts no dtrcc!
no;r':s oF rlctermlnl.li rrow often a large rock rnay reaclr a Bivcn rocation, cspec-
lally r'r'hcn thc rctrrrn periorl of rockf:ill is long r.rhcn conpared wlch the short
ol'':r'!-r'ili iorul p0ri'tl at Viril.. A qrrnl{tative estimatc of thc frcqrrcncy of rock-
f'rl t r"ltlrin thr: .orthcrn 100 fcct of lot rr was marte by observations of soil
and l'ir:lrt:n covc'r on and arl.jlt:ent to largc borrlders. From this ic is estimated
that tlre avernxe r"r"rn Lrc for dcstrtrctJ'e rockfall on thc northcrn part
of lot ll is r.rrlglrly 200 to 500 years. Applicatlon of encounrer probabtrlty
thr.r)ry :;lrrrr*; tlt;l t, q I vcn t lrr: alrovc re turn perlods, Chcre is only nn lg to
39 pct'co.t ch;ruce rh t any ranrlomly sel..cted 100-year period wllr expertcnce
scr.'erc :rrr(l l,otcrrtlally rlarn;rliing roekfal I on t.hc lower 1.00 f ect of 1ot lI.
This nrrstrues that rockfall evcnts are randomly dlscrlbuted indepenclent evenc6
t'roulh time- s.ch probabrlitics (roughty one crrance rn three that a
lglu!:-nvalnnglsg nly occur on the rr'estern half of the properry as
wnc('r-siltrrrarod colluvial rnatcrlal slldes ond flows rapttny dor.rnslope. such
Proccsses, althotrlilr probably rlrc a! any givcn locatlon, havc occurred on
slopt':: of slrnllirr orl(,ntjtItolls. stccpnc8ses, anct collrrvial cornposltlon ln
V:ti I rltrr ln1; the 1r;tst fer.r yclrs. Itor ex.rnrple, nn ln'rcssivc dcbrls avatnnchc
gcncral is quite stablc and shorrtd noL
desrr
d cred
.:5
occrrrr.'(l (,tt tl:r' c;rst crr(l oI tltc Kilts()s Ranch in Apr{t' 1975' It ls estitnared'
on t lr(. l.:r:;lr ol :ioil :llr{l I i llrc.rr covcr on ;1r1(l nc;rr botrltlers. !hnt 1;rrgc debrls
;rvr'!rrr,:lr.'s r.'lt ir.'-lr corr'l tl lritve t t'ached tlre lowcr 100 f ect of lot 1I hnvc not
rrccrrrrt',| rhtrinl3 llrc samc pcriocl of tinre an<l thnE thc ;rrea has been frce of
lockf ,rl l (?00 to !r00 ye:rr:;) ' 'fhtr:; t!"ltr i* tt"tt
occrrrrcnce. Fur thcr-
rnorD, it r.ras 'tlso oh:;ervr:rl
layorr; llnri tlt)L bccn tllcing
docarl.:s.
ll()r,t''vCr'.
!o tlcbr in slltlt's
thot v lllorotrs crccP
o l;rce otl thc ltrucr
:rrr<t sli<te of strrfaca soll
slopcs wltlrin tbe P;rsc fcw
rlthorrt'Jr sLopgs 'tPpcdr to be rcasonably stnblc with respcct
nrrrl <!trl',r is irvalanches, tltis nacuril con
c()nstrrtction rrr:rctl.ccs' De4-cu!g-19!9 s!9
ccrul(l nt.lk.' the sl,t 'sccpt il)lc to
sli!)l, AVALANCIInS
l)csi i',rr nagni tudt:nv;rlirnchcs are consi<lt'rcd ln tlrit strtdy' These arc
s s li(le s o r--!le,!l!i 5 flli1l'anchcs '
mus! hc considcrcd ln Plnnning the locarion and des ign
of a r'rn 1:,rr i trrcle wltich
en rlef incd bY tlre 19I!-91 a ret
of l';iclliti
- P"tl",t "f ,;," 100 t
1ot I l. ntl,.l :itoI irr tltc cttl-tle-sn<: nt thc nortlrcrn cdgc of the propcrcy
(!'lnure 1). It is estinared'
Crecs lnd avalanchc dcbris in
pcri('t oI Elrcsc :rv:rlatrches ir;
prab:lbil.ity of 1 to 4 Perccnt) '
lrr:sl','n ar,ll:rtrcIrcs llcliirr rfter frlcture an<l rclc:rsc of a dry, sofc
lin(tw r;l;th ltt l.ll(t t lnrlr'\r hr''lot'r llrt' I ltnt::ttone cl{f f ' 'l'hll; sl;rh relca:;es ln
on
tlt
25
tlre basls of thc ages of standlng and doad
c lowcr parr of the lot, thaE thc reEurn
to 100 ycars (corrcspondirrg to an annual
ta .
thc t ''r'rts r'n s ltrptt:; r.f /r0 t,r'/'5 {trr:rces. llowc\tcr, evr'tr dttrinB C[t' sr:vcfe
de:.; j:::r .rr';tl lrrrclrc con<l ition:;, ;r (:()nstd(!rablc volunc. ol' tlrc sl;tlr '..ril1 remain
nnch("'c(l to tll(, rrl)[rer rilopes. As thc rclcasc(l avnlflnchc f :rlls through rhc
tr-ees I l o sl.rh uil I rl isintcfir;rtc jrrto pr(rflrcs!;ivcly smnllt:r particlcs $lrlch
f lcr,r t.hrorrgh tirc trccs n:; n Iluid. Powtlcr avalnnchcs will. not dr:vel.op
bec,irrsr: of thc slrort '! t ngth of Lho slopc, tl'rc modernte nva tanchc veloclty,
and tlrt, nlr)(tcrilf (r'l v ltL';tvv t ilrlrr.r covcr. (lnlt:rr.l;rt-.ions of prrt.ent tll inrtlact
pr,l:i'i!rt'e'; l,tcIr) rl.tt nrtt,lc f t'r_L!_Liji--!ls.ll-EL-!-Ilf atrrrlv hrrt wotrlrl Dr(llr.rbly not
stu(l\ i.; t)cc(:s:iilrv to .lcfjrrc thc rtrcssrrrc di to deflne peak
ilccause of the fect thirt snot, avalanchcs npparcntl.y harre a hi8her
probnl'ility than chc oEher mnss-r.rilsting proccsscs, thcy constitutc the most
ctltlcnl deslgn corrs irleratlon on lot 11.
It I nncoltltnNDAl'l0Ns Ar'tD nlTinti woRK
,\s rl iscrrsscd, snctr.r .rvnl;rnches, rockfnl.l, and dcbris aval.anclrcs aIl
occr:r r.rI th vrriorrs Irrobabl].itic!r over mosc of lot 11. The rcstrlcs of this
ngttr:lta .1yr,.""" Ft'
tivcl',' Ittf r,'rlrt,'trt. llorv<lver. lot l1 should not bc dcvel.opcd unless the snow
Ftrturc r.rork rvoul.(l esinbllsh tha des{rabit lty and f casibtltty of butld-
lnB r.'ithi n thc lolrcr portlon of the hnzard area indicatcd on Figure 1. Strch
studv, if dcsircd shorrld int:l.udc the f oll.or.ring sceps: .
r l. Irr.tr.,rrnirru uh;rL p()rt Jons of thc hnzard arca of F'igrrrc 1 is accepr-
:rlrlc for' brrilrliug 1n terms of the lmpar:t lressurc an<l freqtrcncy
a
cnr:r',.r1 ;r Ir'..r,rI rl<:fl]!t'Towrr <'f Va l1 . Frrr che r
Pressr:l:cs qunnti tat ivc ly.
JryLr,t"ll srrr',tcsr tlr,rt--
nvillr
I -.1
crltcriit Itrosent Ly ileccpted
nIso pt'ovidc dasifln crIterln
arca by spaci f .ring
1
by thc Town of tr.ril.. Thle step woul<l
for brrildlngs loc.rtcd in the lrazard
n. Avnlanehe f low depths, .,t ncl
!r. Ava.lanche pros.grtre dlstrlbtrtiorr.
Ft'si6n sp.ciFic ;rvalnnchc nitig,atrng aefenscs for burlrrngs.
Trri's rlesign shorrl<t b. hased on thc crtterrn acvcloperl rn step r.
().c rn.1y rr.rirrc to st.p wrrrk nfter elther stcp. At thrs time r trave
cst innlorl ;ir:rrl'r11icn t cnt:irnccrrnB costs for stc,p L to be $g00. urrch of the
rr(rceliq.rrr/ f ior<t r.ro'k lrns bct rr rl.nc antl thc neccssnry datn collccted. Engl_
rrecrlrrlg ..5[5 6f stcp 2 rurvc not bcen estimntccr but wotrltt probahly npproxt-
natc thc costs of Stcp 1..
In nddition to thc specific recommendations llste<! above,
recon:rr'nd rh.1t si tr.-spacif ic_soll_sCabif ilL!S$= bc con<lrrcted at
!rrrllrlinfl lncations. Tlres<r t<.r;tr; wouta provldc quantttnttve data
I also
posslble
through which
slte could
tlto s i o;"-'' srnbiliry irnrr porcnr i.al for rantrsrrdcs a! the burrdlng
be ovc I r:a t ed.
Respectfrrlty submj tted
Ct^tt^* 4.WUat+
Arthur I. Mcors, pE
b
PANT II
DESlr:il CnrflfiIA tnil Smumlrn^t, InmEclIIoN Flro|{
^vALAtlcllES
cN IOXER IfonTIoN
0b' l.or 11, DIGttonN ltUlll,IVlSlON SE(r)lll) AlrttIT t(tl' vArL' (ploll^to
Itoptrod ||or
ib. J. ltlason
Ilenvorl Colorado
Arllrur I. iloars
Cunnluon, Colorado
Septenberl 1978
PApT r t
(l
NF,'SIGN CIIIfi,]IIIA
I.oltl,:li irIt.t.t.(N 0,t..
vAIL, r:ol0lr^tx)
-
ton s'tnusllrnAl, Inol,Ecl,ION ttolt AvALAT{cl[)s ot{
1,0'l' .l1, DICttOfrN SUBt)IvIStOlt SUCONIT A|)DITION,
Tlre deslgn crlteria dovelopecl ln thls stud.y can bo used for parotectlon e,galns+- deslgn_magnttude avalanches on the northern ?5 feet,of Lot 11, Blg-horn suhrlvlslon seconcr A<Idltlon, va'1 , col0ra.o. Ttrese crlterla can be applle'l 0n1y to tcsl6n of structurss l0cated as dsscrr* abovo and woulrr not rlocessall]y provtdo protoctlon at ottrer locatlons. Thts par t of the avalanche rtrrrry (lbrt rr),
's l's,rl r,rr Lrr. 1nt,.r:'.t,1.n.utarned ln l,art r,a roconnatli:j.ulco sl,utly conrpletc,rl duclng August and Sr:ptenrbe t, Ig??, Thero_fore dof'rr'tl.ns and ltnrlt*tl0ns of pru,t r appry'lso to I,;*t rl .As statctJ ab.vo' tlre dusr6rt r).ramoterc glvutr .crtr rrr'vldc rrrotoctl0n a6ainst .
". It is pos:;lble Lhat larl;or (anrl 1o,,:;lt'rrtr'rhL:) :rvlllnchus wl rl ot:r:ur irL r,rrl$ Iocatlon, trur. it rr; l.cl r, r,h;r..1 r.ln..y
::: ".Srrohrblrrty cr'*lr cn'u6rr to be crlsregarrlcrl r' 1rl'6nf11g;rrrd rrcsrgn.Ilotect.ion a'at'st other m:rss_wasttrr' proceeses, srrr:^ .s .'r:kfa1l ;rnrl rlcbrls'virLanclx):i r-lj: . _rl"r_:li.l_.*r,otatcl on pa*es r+ and J of pa't r, ;;;;" n r".."." "ppu", ;" ;;;;;;_ r__vveee., 6pl^jar tO h:Ive fetUfn Perlods subct'antlally longer than thoss of enor avaranches ancl -nrlay be tlle_tegardcrl lrr Jesil:n"
-
Dr:s,16s1 for snow ;rvalorruhe{i as lilrccifl ed Lrr
clude the nccesr;lty for slope_stoblllty analysls
E. Structural Avalanche ltotectlon.
Decarrrse utni.rll l.lowing :rvllanchos r:orrrLltutc thc tlr;1;i1.11 r:a:;o aL tho
ProI'.r';c(t lrrrlrdlnll 10t::rtrons, it rs r.,r:'mlronrl'rr tturL rrrri. lrri1r1.3; rr: trro Lr:c r,nd
-tt -
thll: rrrporL docs not prg-
prlor Lo constructlon.
General Inforrnatlon an'tl Llmitatiens.
tt qEu"t *"t""tt""{G* rn this partrcurar i" ,n, nost vlab1e
fornr rf protect'l0n consists of deslgrred rclnforcecl uptrill walls such that
they ulll lro :tblo t.o wi r:itlrrrt l.lrrr tlusi(irr lo;nts. ,[,lrc rlcslgn loarls on vralle
dr'pt;rt,l on avirl;rnr:tro r.h; r ritr: Lr: r..1 :rt,lr:s arxl Hitl.l orlorrt;t Llotrg. J.he avalrrnche
cttarec l'*rrs Ll cs rrsod rn rlerrvrng the doslgrr crrterra are 6g1ven ln Table 1.
TAB],8 1
Desl6n Avalanche Characterlstlcs
.Le!g-c!tr t)enr;ity !.1ow Holrrtrt llg -- !ru,h \,il_ - rtltl--- 1.,9 20 2oo tz.t) 1.1 3.6 't
Drr:lgl, r;nolrlrirck trr:11;ht, ).r; r:r1u;t1 [o orrc_trirll.nrtdl strtr llr:rl l;n<.ru .
lJhcn an avalanche ls stop'orr or defl0cted by an objoct ln lts path 11,Hlll r'r.rIrt':rr rt11'11s1, rrl'(rl;:;rr'-:; ;r1i:rln:,;r, r,rr, 1rb.irr,:r, t.(r ::'rrrrr rrullllrL ott ir w;rl.l.
'l'lyr.r1;r I r;111L lor,:r::; irr:t, ttr l.lrtrrr: mrrl.u;rlJy |x;tllrcttrlI.rtl;r.r,rllr<:cl,i.r*;: (1) .orm;rl
to tl"r u;ilt, (2) verticr.rrly, and (3) 1n shear. The area over lrhich the forces
act dcpend cn (t) tre 1en6rh of the exposed walr (dctr:rmincd by archi Lectur.rrl
".rrt"t,tr,t^tt.r ht, H, (doterrnirtrxl by tho an6lo throu6h
"nt "n "_t:j""t.tr"l. t,i:!of r9. !4). _flguros 2 l J 1
-,antt- 4 pro.rilA;il;;_
1'*11..:l fo1 uarrq xposcrt..l-o,rlosl6n avalanctres loc.ttxl orr i,tre loxer part of
Lot 11.
Snow Helshtr
m--ft
o.5 t.6
o{' rlc1lth of
C. _Addltlcrnal Deslgn Infornatlon.
or structural. engineorlng detalls
folI ow I n13 6oncral r.ocommendlt lorr:;
are not 6iven ln thls
stroulrl br: lncorporatud
:,hould bg avolrled unlcss Lhcy ;rr.c abovs 16s
cloors on exJlouurJ w;r}1s ulroulrl bc rlcsigrred to
r;lrc(jII'lc(l irr i'i gure ll.
declgn trotght.
rll,hst:rnrl
llr:s1xrc 1.1\rl 1y l:ubnrl Ll,r:rJ,
W.[J',-\g'to/,-Art llur t. Muirrl.;. l liti
-9-
I
AVAt,ANTtilH
(l{trirrllcl to
I
F.T,OH
lor*rl
I
DlliU(]tI0N
l';rll IJne
(n)
(B)
( qr)
Elg!ru-e. Posstble
,*r''r,rror'rro i:It'|jt:ff :,t-::lt'* r;rils xit.h
'rj!;r,r.,r.i. r.o av;rlan::he r.lc,r l.lrr; l111;;11 t';rl.r rirr.. .,,".,.-'-.,rruw 'lool'u' Ar;tllrttt'lrt: f'l.or
!n: ,,, ;rrrrr o) ,r::":;,:;:''xirxtr(xrl.rr'
r', littr":;.J'r:rltt;rl ,,r',,l,:,';:il:-t;:",:',,:::::::,
(i ) lJrrl lrl I rrg I s or.l cn I trt such Lh;r t.rrJ.r,,111.g,.e3, rtr rlrc;rv;tlrrnr:rrs,,rr.,::,[i;:-rtrr r;r.il';trrr rr, rrrr;ur8rfrr 6 , t,t.(U) ltrri 1,1 ;rrti lt; rrr.lr.:lrl.r;rl liu.:h l.lr,rt O. ;rrrt O.rli l.li:r..((:) lrrrt].tt1r1g iu orlorrLr-.rl i:uch t,hrL
,.,,r,r,."lttr'^r:0
rt.r'{!t':r)$. 'tliltrrl w'tll i:; tt't'nirl trr Llrt: I'l'x ;rn,l {
.rrr{l ||(t!.nfuI tllr.u$l
g tlcol6rt clt l'61t"1. ltt l.s1'11.' ol' clr;;
1,.1.1111111 I (l'.tr.t. ,f
l''""",,'t'r l"r lir. v;r'rl'us (rr.lr.'nt.rr.irrr';l6rr
n'lrl hr:lgtrl', H,
) ril,.,r,; l.,rr. 1t rt.th trrgtx.,r:1. 1,. l.lrr: ,,.,rr;,:;;,n;:iil* r:rllr.
I I
I
I t
D
I i
I
d
!'-10-
15.0
G
T
;\0
ul :r
2
\1
vl rr o
l.'I(;tnt!: ,f. 'l'tre
1,'16111o ?
sPc (: l1'l (r(l
30 40 50 q t"o u'
. (tl.:grt.:r::;)l)EFLE(:tIoN AllGLu. 0
rlclilgrt lrutgtrt., ll , 1s glr'un irii ;r fttnr:l'iolt ol l'he rlct'ler:i'ton irflgl (., 0
:;hous $' Htth rospoct to aval;rnclro flox rll11;r'lt(r ' 'lJrltt' I'ort:c:;t alt
tn Fl6uro llr ;rct ovor l.hs rteslgrr height'' I
-lt -
I
--.- . ,L..tr* !'r{tt(.t!!tt#
,t'J,rr
i:tlti::n ].,t.;t,
il
5
{f 'll'
.tl 'tl
iF
ril
5.rt i't
t t.l
. i.'.1
3fi|
.1 :l irt:
o'., . '-
$w
f''l
t00 r-l s
o:,_l
a_r6a
(\
r\./A
.f ""'.\'
i>s 't
r I('
T I
I
I'
l i
t!t
I
n
tf
u a:
irl ti
!i,
H at
t,
t::
t1t
)di
$!'
I
I
s / r.[!'f-(-'._J.. [,or..ltiorr,i\tJtli([.rr, u"rr,,,,11^]:']: tl'-l!li:horn strbrlivision, sccon'
r;il,'r,, ;rv,'rlant:htr onttjlljl't.' Dotrnhll I linrlts ofl J"riii"""
:rrrrrl\, .f ;il;.";r;i, srrown r('!irrl L f ronr a reeonnlnssanee , u.,,, r
" u.tr,o; ";,.;: ";i:i]";l:,, l|,.;il t::.,,,1n,11,,, r, "",i
";;i;;;..
r t',;5 | r.c.rlucnr ly tlran <rcsi6in
"r,, r^"i,ii]u.;:l,,,fii";:;,,.
.:;i:,,1;;,..:;: ;:li::$"'i;; ;;:;;"ii'I. "',r," pi""".I.*
N
\')\.
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100
l-"
il
\',l
t *- ':"t 2:)o I'r.'rr l.
a
liIEI.IORANDUM f.r
T0: Planning and Environmental Cormission
FR0M: Department of Conrnunity Development
DATE: l4ay 6, 1982
SUBJECT: Application for a variance to construct an avalanche diversion wall on
Lbl tt, Bighorn Second Filing which exceeds the maximum allowab'le height
of slx feet for any walls constructed upon a site.
Applicant: Shannon Vail Ventures' Ltd.
DESCRTPTT0N 0F VARIANCE REQUESTED
Lot l'1, Bighorn Subdivision, Second Filing is subiect to snow avalanche hazard.
A-ieiiit-i6nairlteo by Arthui Mears conc'ludes that any-deslgn avalanche (those which
have'been defined as-having a return period of 25 to 100 years) will cross-lot.]l
and stop at the northern edge of the iroperty. The calculationl-of potential impact
pressurbs indicate that the pressure ilistribution can be classified within the hblui hazard" or "moderate hizard" avalanche area. This means that avalanches in
the study area are expected to produce a total Pqessure_less than six hundred pounds
per squaie foot on a ilat surfale nonnal to the flow. The town has indicated that
in oitier io construct any structure within the moderate hazard zonq, propeJ m-itigating
measures must be taken. Art l4ears has recormended in his report that any building
upon loi ll should be protected with a designed reinforced uphill.-wall such that
it will be ab'le to withstand the design loads. A wall corresponding to the recoffinen-
aition of the study has been designed-for lot l1 by a registered professional engineer
and at its highest point is l3 feet high.
Section 18.58.020 C. of the zoning code states that wa'l'ls sha'll not exceed three
feet within any front setback or six feet in height on any other portion of a site.
The applicant lequests a variance from this provision in order to allow the constructi
of thb'ava'lanche'deflection wa]'l which is necessary in order to construct a building
upon the 'lot.
CRITERIA AND FINDINGS
review of Criteria and Findin Section 18.62.050 of the l4unicipa] code
rtnent of Concnun ty Develo recommends aPprova e reques
Consideration of Factors
The re] ati onshi of the uested varianc r existinq or tentia'l uses
struclures n tne vlcln
lot ll ls situated at the end of a cul de sac. The lot to the east.of the.property
iiit t2) has a duplex constructed upon it, and the lot to the west-(lot !0) is current
riacant,-but has the development potlntia'l'of a single family dwelling. The area
behlnd the lot is Forest Service-property. Lot ll is 84,847 square feet and is
alloried a duplex. The constructibn bf t-he proposed wall is necessary-for any building
to be completed upon the lot. The pr-oposea'wait (see attached site plan)-has been
iiaced dii'ectly UltrinO the proposeO'sil.uituri-and'extends to a distance of 30 feet
t-otf Pishorn Znd -2-
beyond the rear wall of the building. The interior portion of the wall is terraced
to al'low landscaping, and the applicant proposes to landscape the area exterior to the wall as well. The site currently is very dense with aspen, as are the adjacent sites. The maior impact of the wall is one of visual quality, and the preservation
of existing trees durinq construction and the replanting of trees to screen the uall after constructionshould.lessen the visual impact.
The staff has received a letter from the owner of lot l2 objecting to the variance.
The ree to which re]ief from the strict or 'literal inte retat on and enforcement
s necessa toa
tes s title
grant
Two objectives of the zoning are:
To secure safety from fire, panic, flood, avalanche, accumulation of snow
and other dangerous conditions; and
2. To safeguard and enhance the appearance of the Town.
The staff feels that relief from the strict interpretation of the regulation specify.in
a maximum wall height is necessary to secure the safety of the building which is
to be constructed upon 1ot 11. The construction of the wal'l and the landscape
treatment of the site can be done in such a way as to minimize the visual impact of the wal'1. In this case, safety of the future occupants of the building must
take first priority.
The effect of the uested variance on I i tanda distribution of 'lati on
nsDortat acilit
The wa'll is necessary for the safety of the occupants of the building.
Such other factors and criteria as the connission deems applicab'le to the proposed
FINDINGS:
The ?lanninq alrd Environmental Comnission sha]l make the fo]lowing findinss before
gran[lng a varlance.
That the granting of the variance will not constitute a grant of special privilege
inconsistent with the limitations on other properties classified in the same district.
That the granting of the variance wi'l'l not be detrimental to the public health,
code
es and uti'l i t
t Lot ll, eisf ?na -3-
safety, or welfare,
vicinity.
That the variance is
or materially inJurious to pnoperties or improvements in the
ilarranted for one or more of the following reasons:
The strict or literal interpretation and enforcement
unuld result in practlcal dlfficulty or unnecessary
wlth the objectives of this title.
There are exceptions or extraordinary circumstances
the site of the varlance that do not apply genera'lly
sanE zone.
The strict or literal interpretation and enforcement
muld deprive the applicant of privileges enjoyed by
in the same district,
STAFF RECOMMENDATIONS :
The Department of Cornmunity Development recomnends-approval o{ thg requested variance.
At the'time the project is'reviewed by the Design Review Board, the visual impact
of the wal'l shouid be studied and proper screening with landscape materia'ls shou'ld
be required. in order to reasonably attempt to minimize any visual impacts.
of the specified regu'lation
physical hardship inconsistent
or conditions applicable to
to other properties in the
of the specified regulation
the ovners of other ProPerties
lt
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LO'T.tO
APPENDIX B
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Descript'ion: tot // aloct,
Zonc District
Lot Area
Setbacll ron'u-Requi red 20
Rcar -Rcctu j rcci l5 ' Prol)osecl ,8(t\
hlater.cour.se-requ.irerl L]-fi propcsed _
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Alloned t A4</Z 4 Propo: ed
Prirnarj, A'llor+ecl A48 # -a Prirnery Proposed lA/Z/
Sr:conclary Allor+ed 2ll,l / Secondary Proposecl
Requi red
-Required
slope Permitted €ta, slope tictJal
A]l oired 7O/r - Proposed
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GRFA:
Archi tect
Proposed Use
Hei ght Al I oired 30' Propo
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Proposcd __!_2aUil_, IL
Proposcd -&*1-
Site Coverage:
Land sc.iping :
Parking: .
Drive:
Envi ronnental /l-laza
Corintents :
Proposcd
Fi1in9
s: .Ava'l a
Flood Plai
Zonins'@ i sapproved
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Datc:
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Lesal Description: L"t /f Block
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Filins 6tathp{ 2e'
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owner }#tNMoxL nrchitecr .' '4 / (ar/Sutf -'DeNue^'
Zone District T Proposed Use .bU?LEL I
Lot Area 4Sl1l-I11flffinht Ar|owed
/T
Setbacks: Front-Required 20' Proposed
Sides-Required 15' Proposed
Rear -Required '15' Proposed
llaterccu rse-requ i red Proposed
30' Proposed
GRFA:
GRFA:
A'floued i : "/ { .Proposed 1L' (:-
Primary Attorved 5 378 6 Primary Proposed 97 OB d
ZO oZ-
SecondaryProp.osed : 7 A:
/ -- r-Required (t O "/ 0 Proposcd
' I , t,Required Z /t'4'u^f
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Environmental/Hazards: Avt:lanche /.,u*
Fl ood P'lain
Sl ope
Zcrn'irrq : hppl'ovci!/D i s.: 1t;lro,.'cti D.:i.': :
Secondary
Site Coverage:
Landscaping:
Parking:
A'l'lor,red
Al I oived
Propc: ed
Actual I
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Project Name:
Proiect Oescription:
Owner Address and Phone:
Project Application ?
Date
27F- 7d3 4
b't l",|to 6.-z
Architect Address and Phone:
Legaf Descriptio n: tot / ,/ , elocX
Zoning Approved:
Design Review Board
Date
./- J- 6'0'"
Motion by:
Seconded by:
APPROVAL DISAPPROVAL
Administrator Chief Building Official
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Owner Address and Phone:
Architect Address and Phone:
Legal Description: Lot il , Block
Zone:
Zoning Approved:
Design Review Board
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Motion by:
Seconded by:
APPROVAL DISAPPROVAL
Chief Building Official