HomeMy WebLinkAboutLIONS RIDGE FILING 1 BLOCK C LOT 1 TO 5 TIMBER RIDGE WALL MITIGATION LEGALoa
MONTGOMERY LIT,TLE YOUNG CAMPBELL & McGREW I
ROY E. MONTGOMERY
ROBERT R. MONFGOMERY
DAI'ID C. LITTI-E
i,. BAYARD YOUNG
RICHARD O. CAMPRNLL
DAN McCREw
H. WAYNf, LEISEN
JAMES J. SONAN III
RICHARD L MURRAY, JR.
MICHAEL D. Ktr,I,IN
PATRTCX F. GARTI-AND
WILLIAM H. ReMINE III
KXVIN J. KUHN
THOMAS J. HELMS
BRIAN IL STTITHEIT
PNOT.'ESSIONAL CORPORATION
ATTORNEYS AT LAW
89OO E. BDLI.EVIEW
ENCLEWOOD, COLORADO 801rr ITI.EPHONE
(303t 770-4:J,r4
MAILING ADDRESS:
P.O. BOX 22796
DEI{VE& COLORADO E0222
September 21, 1982
Mr. Steve Patterson
Department of Cornmunity Services Vail l{unicipal BuiLding Vai1, CO 81657
Dear l4r. Patterson:
Thank you very much for taking the time to confer with
me yesterd.ay about the wall behind the Valley Hi Apartments.I very much appreciate your candor in analyzing the work of the design engineer and the effect of the design on the distress in the wall .
Since it is necessary that T evaluate the case, I have taken the liberty of trying to surunarize our conversation for my files. I have enc1osed a draft of the summary which t would very much appreciate your revie\^/ing to see if there
are any glaring errors. If so, I would appreciate your
giving me a call and letting me know where I have been
mistaken.
You might be interested to know that I have checked further with people involved in the construction of the wall to find out a little something more about the backfilling process. From what I have been told, it appears that the backfilling was done in a very haphazard fashion with almost
no concern for the requirements of the design. As a matter rtf fA..|- - i f annc,ars that the area behind the wal1 became a
dumping area for trash and debri-s cleaned up from the constructj-on site. This certainly supports your observation that the
composition of the backfill material had such a large effect
on the cause of the distress in the walI.
o
MONTGOMER
Septenber 2L, L982
Page Two
Again, thank you very
anaLysis.
Y LITTLE YOUNG CAMPBELL &
PROFESSIONAL CORFOI,ATION
t
McGREW
rnuch f,or your tlme and your
Ikf
Encl-osure
Conversation with Steve Patterson
Snf emhrcr 2O, 1982
Mr. Patterson is involved ln the Buil_ding Department for the Town of Vail. He was notified by someone, apparently from the Va1-Ley Hi Apartments, that the retaining waLL behind the apartment buil-dings was beginning to tip away from the hillside and toward the buiLdings. He observed the situation and became concerned, about the apparent Lack of discharge through the weep hol-es in the wal1. The purpose of.the weep holes was to relieve hydrostatic pressure whj-ch would normally build up behind. a walL of this type. The pressure wculd be relieveo by making provision for water to flow from the hillside and gather behind the wall in the gravel backfill rnaterial and thence be discharged through the hol-es.
Because of the lack of discharge, Mr. Patterson directed that the materiaL behind the wal-l- be exposed to determine whether or not the gravel material- had been placed behind the wall_ and to see whether or not it was working properly. The reverse side of the wal-l was exposed and two problems were noted. Initially the specified backfill material was not in p1ace. Instead there were large quantities of debris and trash mixed with dirt. Since this material ls not the type which encourages water flow, it
hras Likely the !'/ater was being trapped in the material and simply incresaing the pressure against the reverse side of the wall.
Secondly, the {{r*ttiry bf "or,"r"te, especially in the bultresses or counterforts, was very poor. There were considerable areas of honeycomb and indications that either the method of pJ-acing the concrete or the concrete itself was not quite proper for this particular use. The indications were that water may have been added to the concrete in order to increase the flow int.o difficult areas or that perhaps the vibrating of the concrete had not accompl_ished a good distribur_ion of t!:e aggregate through the structure. In any event, the concrete was simply not of the type and quality necessary for this type of instaLLation. As a resu1t the strength of the concrete at the time of probable backflLl was simply not sufflcient to withstanil the Loadl-ng to which it was immediatel_y exposed and this, coupl-ed with the increase loading from hydiostatic pressure,
was the principal cause of the wal-l failure.
Mr. Patterson aLso noted that at certain locations in the wall- surface there appear to be diagonaL cord Joint.s.These are ind.icatlve of the teehnique of piaeing concrete which titight not have been the most appropriate ior this instal_l_at,lon. .i since the wall itself did not fail-, these coJ.d Joints may not be a factor Ln analyzinE the cause of the firiluie. Nonelheress,they night be indicative of the quality of construction work generally.
It was also noted that the wal1 did not sLip nor was there a monoLithic overturn or rotation of the entire structure.The mechanLcs of the falLure appeared to be the separation of the buttresses from the foundation slab ancl in nany cases the faiLure of buttresses themserves"at locations where there was probabJ-y_lapplng of the reinforcing steel. rn al-l cases, however,the foundation itself remained. stable and in pl_ace.
Mr. Patterson noted. that. imrnediateJ-y upon relieving the back tr)ressure frorn behind the wall_ during-thl excavation process the wal-L virtual-ly righted itself to within ipproxirnately an inch of its original. position. rt became obvibus that the design of the waLl was deficient in terms of the amount of reinforclng steel- in the counterforts. This d.eficiency, however,
I-"s lo!.a.maJor contributing factor to this particul-ar-failure.
The. deficiency obviously prevented the warl from being able to withstand, to any extent, the added ]_oading created, Uf tfre hydrostatic Pressure and the problerns caus6d by the concrete treatment. At some future ti-me it is possibre-that the rebar deficiency might have resurted in some sort of failure in the wall. That did not appear to be the situation with this failure. Mr. Patterson a]-Located the contribution to the fail-ure to be perhaps 40? to the backfill_ content, 308 to the concret,e deficiencies, ZOZ to design deflciency with respect to the rel-nforcing steel- and perhaps the bllance of l-0? allocated between various secondaiy cairses,
Enrrurvn II. Dna.erR, JR.
ATIIOITNF]Y AND COUNSI'LOR
P.O. I]OX lAaO
\/AIL, COL()I.ADO ara57
PIIoNE (3og) {76-1314
November 30, 1981
SECOND IILOOR
VAIL NAITIONAL
BANK }IT,DG.
Mr. Steve Patterson
Town of Vail
Box 100 Vai1, Colo. 81658
HAND DELIVERED
Re: Valli-Hi Apartments
Dear Steve:
This letter is written pursuant to our conversation of November 30, 1981 , wherein you r-equested clarification of my November
20 , 1981 letter in a couple of particulars.
First of all, Mr. Hopkins will not request a refund of any of the
$S4,000.00 which he posted with the Town relative ro compieti-on of recreational amenities until the landscaping of Va1li-Hi Apart-
ments is in compliance with the landscaping plan approved by the
Design Review Board, on or before July 1, L982.
I regret that my letter of November 20, 1981 was not clear in that respect, but I want to make sure that everyone understands that Mr. Hopkins was not simply giving the Town his money which it was holding.
As I previously explained to you, Mr. Hopkins will do whatever is necessary to see that the landscaping of Va1li-Hi Apartments will be in compliance with the landscaping p1an. At this point in time, we do not know whether the planting done most recently will survive the weather or not, and we are willing for the Town to retain that money until both Mr. Hopkins and the Town are satisfied that the planting will survive, particularly on the slope above the retaining wall which was most reeently replaced.
Again, 1et me express my thanks for your cooperation.
Very !
Smith and H. Drager, Jr.
DES/mc
cc: Doyle Hopkins
truly yours,/
-,ll / S.n-Ztt
BoswelL AND Snrrx. P, A.
ATTOFN EYS AT LAW
BRYANT CENTER
B RYANT, ARKANSAS 72 O22
TED Bosw ELL
Davto E. SMlrH
FLoYo CLARDY
RoBERI P, PLUMM ER
TELEPHONE
LIiTLE ROCK ANO BRYANf
{5C) 0 647 - 3o3 |
B E NTON
77 6-2573
November 30, 1981
Mr. Steve Patterson Building official-
Municipal Building Vail, Colorado 81657
Re: Valli-Hi Apartments
Dear Steve:
This letter is written pursuant to our conversation
of November 30, 1981, wherein you requested clarification
of my November 20, 1981, l-etter in a couple of particulars.
First of all, Mr. Hopkins will not request a refund of
any of the $54,000.00 which he posted with the town relative to construction of recreational amenities until
the Landscaping of Vall-i-Hi Apartments is in compliance
with the landscaping plan approved by the Design Review
Board, on or before JuIy 1, !982.
I regret that my letter of November 20 ' 198f' was not
cl-ear in that respecg. but I wanted uo make sure that
everyone understood that Mr. Hopkins was not simply giving the town his money whlch it was holding.
As I previously explained to you. Mr. Hopkins will do
whatever is necessary to see that the landscaping of
Val"Li-Hi Apartments wil-l be in compLiance with the
landscaping pLan. At this point in time, we do not
know whether the p1-anting done most recently will
survive the winter or not, and we are willing for the
City to retain that money until both Mr. Hopkins and
the City are satisfied. that that planting wilL survive,particuJ-arly on the s1ope above the retaining wal1 which
was most recently repS-aced.
l'!r. Steve
November
Page 2
Patterson 30, 1981
Again, let me exPresa ny thanks for your cooperation.
Yoqps very fiuly,
l//
avid E.\Smith
DES/dh
cc: l!r. Doyle Hopkins
Boswelu auo SvrrH, P, A.
ATTORNEYS AT LAW
BRYANT CENTER
BRYANT. ARKANSAS 72022
TEo BoswELr-
Davrp E. SMrrH
FLoYD CLAFoY
RoB ERr e PLUMM ER
TELEFHONE
LIfTLE ROCK ANO BFIYANT
(5Ot) 847 - 3O3r
BENION
77 A-?573
November 20, l-98I
Mr. Steve Patterson
Building OfficiaL
Municipal Building
Vail, Colorado 81657
Re: Val-li-Hi Apartments
Dear Steve:
Tbis tetter will confirm our agreement reached by telephone
on November 19, 1981.
Although all planting and seeding has been accomplished as
required by the landscaping plan approved by the Design Re-
view Board, you are fearful that the seeding and planting
done since September may not survive the winter. Mr. Doyle
Itopkins undertakes and agrees that the landscaping of Val-l-i-
Hi Apartments wil-l be in compliance with the landscaping plan
approved by the Design Review Board, on or before ilu1y 1,
1982.
To secure this undertaking, the town of Vail may retain, as
security, the approximate sum of $54r000.00 which Mr.
Hopkins posted with the town relative to construction of
the recreational arnenities at Val-Ii-Hi, and for which he has
not, as yet, requested a refund. (It is understood that the
money is not being forfeited to the town, but is being re-
tained as security on1y, and Mr. Hopkins is not waiving his
right Lo request a refund.) As r understand i-t, you are pri-
maril-y concerned that those 30, plus or minus, trees planted
recently, and the seeding of the slope above the retaining
wal-l recentty repaired, take root and survive.
In return for this undertaking and promise by Mr. Hopkins,
you have agreed to forthwith issue a Certificate of Occu-
pancy for Valli-Ili Apartments, in accordance with S15.04.070'
VaiL Municipal Code, and to provide me with a letter stating
that al-1 the buildings and structures have passed final in-
spection and comply with the Uniform Buil-ding Code and ordinances.
I
Mr. Steve Patterson
November 20, 1981
Paqe Two
f have enjoyed dealing with
luck.
DES/mc
Mr. Doy1e Hopkins
you and wish
Yours very
you the best
L.r u.!J ,
of
David E.
o
NAAR.
16 0ctober 81
Mr. Chris Dittmar
1280 North Frontage Road
Vai I , Col orado 81657
Subject: Slope Inspection
Retaining t,lall Excavation, Valley
Hi gh Apratnients , Vai I , Col orado
Project No. 81767
Dear l4r. Di ttmar:
0n October 15, 1981, at 11:30 am, I visited the Val1ey High Apartments
in Vail, Colorado to observe the construction excavation behind the retain-
ing wall modifications. A visual inspection of the cut slope was made
to determjne if any obvious signs of instability existed.
At the time of the inspection the steel braces from counterforts 1 to 15
had been placed and concrete had been placed from counterforts 8 to 15.
Based on my visual inspection, I found
There did not appear to be any effects
and snow.
\A PHC\E 303 759 4100 2rao s rvaNHoE SurrE 5
SOIL Af{D F OU\DAr'O\ CO\5U-lA|\TS
DENVER C OLORA OO 4O222
WASSE I NC.
no apparent signs of instability.
on the slope due to the recent rain
lnle recommend the construction crew maintain their daily surveilance of the
slope and continue scaling loose rnaterial as necessary. l,le encourage
construction and backfil ling to proceed as soon as possible,
If you have any questions regarding this, please call me.
Si ncerely,
ACAFA
JAC/ sen
Enclosures (2)
cc: Steve Patterson, Cjty of Vail
Mr. Kenneth Cockram
Statement of Services
NA
o
WASSENAAR 1NC.
^v
sOIL ANO FOUNOATION CONSUITANT9
DENVER. COLORADO 80222 PHONE 303 759-8100 ?l80 5 lvaNHOE 9urTE 3
7 0ctober 81
Mr. Chni s Dittmar
i2B0 North Frontage Road
Vai I , Col orado 81657
Subject: Slope Inspection
Retaining tdall Excavation, Valley
High Apartments, Vail, Colorado
Project No. 81767
Dear Mr. Dittmar:
0n 0ctober 6, 1981, at 11:00 am, I visited the Valley H'igh Apartments in
Vail, Colorado to observe the construction excavation behind the retaining
wall modifjcations. A visual inspection of the cut slope was made to
determine if any obvjous signs of instabi1ity ex'i sted.
Based on my visual inspection, I found no apparent signs of instability.It is my understanding that it rained at the site on 0ctober 3 and 4, 1981.
The rain caused several minor erosion gullies but did not appear to effect
the stab'i1i ty of the cut s'lope.
!,Je recommend the construction crew maintain thejr daily surveilance of the
slope and continue scaling loose material as necessary. f.Je also encourage
construction to proceed so backfillinq can be done as soon as possible.
If you have any questions regarding this, please call me.
n I'
JAC/sen
Enclosures (2)
cc: Steve Patterson, City
Mr, Kenneth Cockram
Sj ncerely,
ffi*:ru
e''.'..#
of Va iI
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CONSULTING GEOLOGICAL ENGINEER
EDWARD O. CHURCH, P,E.
925 E. tTrh AVENUE
DENVER, COLORAOO E0218
a?
NA SOIL AND FOUNOATIOITI CONSULTANTS
PHONE 3C3 759.8 r OO OENVER COLOF ADO 8O222 LL
iB September 81
Mr. Chri s Dittmar
1280 North Frontage Road
Vai I , Col orado 81657
Subject: Slope Stabi l ity Assessment at
Exist'ing Retainjng lnlall Excavation
Val1ey High Apartments, VajI, C0
Project llo. 81767
Dear I1r, Dittmar:
I NTRODUCT I ON
TF TolIowmg letter presents our findings and opinions regarding the
stability of the cut slope behind the existinq retajninq wall at the
Va11ey High Apartments in Vail, Colorado. The purpose of our study was
to determine whether shoring is needed to prevent failure of the slope
during repairs of the retaining walls. Repairs are expected to take
approximately one month.
i NVEST I GATI ON
On-SeFTember 17, 1981, we visited the site. During that visit the exca-
vation was inspected as well as excavations in similar materials in the
Vail area. Also, a previous geoloeic study by Willard 0wens Associates
(November 1981) was reviewed and intervjews with Mr. Kenneth Cockrairn,
project architect and Mr. Chris Dittmar, construction superintendent vlere
conducted. "In-situ" shear strength measurements were conducted and sam-
ples were obtained for laboratory unconfined cornpressive strength tests.
CONCLUS I ONS
Tne open e.xcavation behind the retaininq wall was made through road fill
and "in-situ" soiis comprised of glacial debris. The material was variable
and consisted of a mjxture of cobbles, boulders, sand, gravel, silts and
c1ays. The excavation basically was vertical for lC to 15 feet then was
sloped back at the top.
It js our opinion based on our visit, testinS, literature review and exper-
ience, that there are no signs of incipient slope failure or past'i nsta-
bility of the cut s1ope. This 'is based on the following:
1) "In-sjtu" testing and laboratory results indicate shear
strengths (cohesion) of the silty clay matrjx to be approx-
imately 500 to 1400 pounds per square foot. This data and 'resonable estimates of unit weights of soiI and soil fric-
tion angles of 130 pounds per cubic foot and 34 degrees,
respectively, yield factors of safety for slope failures in
the range of 1.3. This is reasonable for short term con-
structi on cases.
A. G. WASSENAAR. INC,
Mr. Chris Dittmar
18 Sept. 81
page rwo
2) Case hjstories in the Vail area for excavations in similar material have shown reasonable short
term stability. Specifical ly, the excavation for
the retainjng wa11 under repair was originally
made in 1979 and stood open for approximately one
year before the wal l was placed. l^Je were told
no failures occured during that tjme.
3) During the failure of the wall jtself, no cracks
0r scarps were noticed jn the original ground
which would indicate no movement except in the
backfi I I .
4) The existing road above the retaining wall and the utilities in the area have shown no damaqe due to
movement.
l'Je, therefore, feel that construction should be allowed to proceed wjthout
shoring of the excavation providing the following recommendations are
followed.
RECOMMENDAT IONS
IE-is our unierstanding that construction will take approximately one
month to complete jncludjng backfilling of the retaining wa11. Also,
punping of concrete and crane work for lifting of steel will be conducted
from the road above the retaining wa'l l. I'Je, therefore, recommend the
fol I owi nq:
1) Construction should be conducted as soon as possible
to mjnjmize the time the cut slope is exposed. Back-fill should be placed as soon as possible. The con-
clusions of this report should not be consjdered
valid beyond the proposed one month construction time
(assumed to begin upon date of this report) unless
the site is re-evaluated at the end of the one month
period.
2) Before construction begins the slopes should be
cleared of all loose soil, slabs, boulders, cobbles
and overhangs. This poIicing of the slopes should
continue throughout construction on a regular basis.
l4ire mesh could be used to retain small rock falls.
3) An impervious ljner such as PVC, visqueen, etc.,
should be draped over the slopes to maintain moisture
contents of the soil and reduce surface ravelling.
4) Construction equipment should be kept on the paved
road above and as far from the edge of the slope as
possible.
Mr. Chris Dittmar
18 Sept. 81
na ara + hY.ao
5) A series of survey points should be placed at
the top of the slope (nominal 50 feet on center)
and measured dai'ly to determine if any movement is occuri ng.
6) A daily vjsual inspection of the head of the slope
should be made to determine if any cracks are
formi ng.
7) The soi1s enEineer should be notified once con-
struction begins so he can conduct periodic inspec-
tions to see if visual signs of instability are
developing.
L II,Ii TAT I ONS
Thls-reporE has been prepared to assjst in the completion of this pro-ject. l^le cannot guarantee the performance of the s1ope, only that pro-
fessjonal judgements used jn preparing this report meet wjth current
standards of the geotechnical profession. There is always a risk in
any engineering project. It is our opinion, however, that jf the reco-
mmendatjons of this report are followed that the risk is reasonable for
construction of this nature,
l,Je have enjoyed the opportunity to assist you with this project. Please call if you have any quest'ions.
JAC/ s en
Encl osures
cc: [4r. Kenneth Cockram
I'lr. Eric H. M. Rami rez,
l4r. Steve Patterson
S i ncerel y
US Dept of Labor
i. i,
I KENNETH F" COCKRA},I
- 5600 Euper Lane Fort Smlth, Arkansas 72903 (50L). 452-2255
September L7, 1981
Mr. Bill Andrews City Engineer
TOWN OF VAIL P. 0. Box 100 Vail, Colorado 81658
RIFERENCE: Retaining Wall Failure Valli-Hi Apartments
1380 North Frontage Road Vail, Colorado
Dear Sir:
I have reviewed the original design of the counterforted reEaining wall for the subject project, as prepared by Boyle EngineerinB, Inc., Vail ,
Colorado and have reached the following conclusions:
1. The toe of the footing is overstressed and should have
extended farther out from the wall.
2. The wall that spans between the counterforts is over-
stressed in its lower section and should have been made
thicker andlot additional sLeel used,
3. The counEerfort connection to the footing is totally
oversEressed and laeks the required area of steel and
the required inbedment depth.
The wa1l that spans between counterforts has reflected out\^rard and requires
additional bracing to maintain its suructural integrity.
Almost all of the counterfort show signs of total failure due to the vertical dowels pull-ing loose from Lherconcrete footing or counterfort.Also, some counterforts have sheared completety through at the approxi-
mate top of the vertical dowels. Thus, I can only assume total failure of aLL counterfort -- footing connectioas..
I have reviewed the above conclusions with }lr. E. Thouas Punshon, Consult-
ing Structural- Engineer, and he was in general agreement on all items.
Mr. E. Thom4s Punshon and the undersigned net at.the project site on the
afternoon of September 15, 19_81 . At this peetinBr w€ reviewed each
others remedial'designs for the repair and rehabilitation of the retain-
ing wall. My design and Mr." Punshon's design were very similar in
concept. We agteed to use my design drlb Eo the fact that I had taken
a more conservative approach .vftich uELl{"zed larger steel sections and
larger amount, of concrete. ':
-'
:
I am, therefore, submitting and data, prepared by the
i:
dfawings .'\
Mr. BilL Andrews
Ol.ty Eigineer
TOI^IN OF VAIL
September 17, 1981
Page Two
undersigned, for your approval.
Sincerely,
Colorado License No. 599
KFC/j ac
enc/Drawings
Data
fILe/
Renheth F. Cockram Architect
Enuuwo H. DneeER, JR.
ATTORNTIY AND
P.O. BOX 100e
\/AIL, COLOEADO a1667
PIToNE (3o3) 47a-1314 SECOND FI,o()R
I/AIL NATIONAL
BANI< BLDG.
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August 26, 1981
Mr. Steve Patterson
Chief Bui'lding Official
Town of Vai'l Bui'lding Dept.
Box 100
Vail, Colo. 81658
Re: Va'l I i l-li Employee Housi ng
Certificate of 0ccupancy
Dear Steve:
This letter is being written to confirm the understanding we reached during
the meeting of Tuesday, August 25, 1981 attended by Chris Ditmar, Ken Cochram,
David Smith and myself on behalf of Doyle Hopkins and you and Larry Rider
and Bi'l 'l Andrews on behalf of the Town of Vail . At that meetingn we dis-
cussed the repairs to the retaining wal'l and permits for and inspections of the remedia'l work required and the fina'l certifr'cate of occupancy for
the entire proJect.
The repairs on the retaining wal'l are to be considered'in two phases, the first covering theeaster'lyone-half of the wa'l I from the defective joint all the way to the east end of the wall. That entire area of the wal1 will
be complete'ly excavated, at which time Ken Cochram, Doyle,s project archi-tect wil l set up a meeting with an engineer of his choosing and yourse'l f .1- /""
to inspect the areas of failure or problem areas in the wall. At that time, Cochram and his engineer will present you with a plan to restore the
structua'l integrity of the waIl, to include correction of the concave exterior surface of that wal'l . }|e understand that as a result of your
inspection and their suggested plan of correct'ion, provided it covers all
problem areas,you will approve the ptans for corrective work and cause
a permit to be'issued for that work in an expeditious manner.
Phase II, that area of the retaining wall to the west of the joint, will
be handled in the same manner, but will be delayed due to time constraints.
tl|e need to work out our procedures for approvals due to the rather sub-stantial amount of work to be done and the fal'l and winter season which is fast approaching.
At the time of your meeting with lr1r. Cochram and his engineer, you should
be prepared to set up the necessary inspect.ions you will need of the
severa'l phases of the work so the work can progress without delay, yet
give you adequate oppor.tunity to inspect the various stages of the work
you deem appropriate.
\
August 26, 1981
Page 2
The balance of our discussion concerned the permanent Certificate of
Occupancy for the entire project. It's our understanding that the major
areas of concern from your point of view are:
a) Comp'l etion of landscaping substantia"l 1y as shown on the approved
landscape plans and replacement of dead trees.
Insta'l 'l ation of guard rails on the gabion wa1 ls.
Completion of and repair of the asphalt drives and parking areas
according to approved plans.
d) Repair of the retaining wa'l ls to be accomplished as outlined above.
e) A variety of sma'l I correction items sn individual buildings to
bring them up to code.
It is our intention that these all be accomplished as quickly as possible
so as to bri ng the build'ing totally into compliance with the Town of Vail
codes so permanent Certificate of Occupany can be issued. lite shall 'l ook
forward to working with you and your staff to accomplish this end.
After you have had a chance to review this letter, please advise if this
does not set forth our aqreements of the 25th.
EHD/mc
cc: Chris Ditmar
Ken Cochram
David Smith, Esq.
Di ck Ryan
Larry Rider, Esq.
b)
c)
yours,
t
boyle engineering, inc
'143 e meodow dr, suite n-10
crossroods shopping cenler
voil, colorodo 81657
3O3/476-217O
August 5, 1981
Mr. Cri s D'ittmar
Doyle*Hopkins Construction Company
c/o Valley-Hi Apartments 0fftlce
1280 North Frontage Road
Vail, Colorado 8i657
Subject: Concrete Retaining l'|al'l
Va1'ley-Hi Apartments
Vail, Colorado
Dear Mr.Dittmar:
As you know, we are quite familiar wjth the above-ment'ioned wall. We
are the designers of the original wall and also have been invo'l ved in
the remed'ia1 process since the boulder damaged sa'id wall.
In May, 1981, we made a site inspection to determine the extent of
damage to the wall as a result of the impact of the 3,000 pound
boulder trave'l ing approximately 400 vertical feet. At this point in
t'ime, the wall was approx'imately 9 inches out of plumb, and shear
cracks were observed at the points where the counterforts joined the
main wall. There was also a marked differential movement at the con-
struction joint between the east wall hit by the boulder and the west
section of the same wa] 'l . l.le observed, at this time' that this con-
struction joint had not been constructed as per standard practice for
a counterfort retainjng wa1 1.
Based upon the observations of this site visit, we furnished you w'i th
a detail for constructing "deadmen" upslope from the wall and thereby
stabilizing the system. This "deadman" system was premised upon the
assumption that the integrity of the counterforts was 85 percent intact
and des'igned basical'ly to restore the factor of safety against overturn.
Between the time this detail was prepared and the time the system was
actua'l ly installed, the wa1 1 crept another 12 inches. This 'l eads us
to question the assumption that the 'integrity of the counterforts was
85 percent intact. The impact of the bou'lder could have overstressed
the reinforcing steel in these counterforts to the extent that their
capacity 'is appreciably reduced. If, jn fact, this is the case, then
the capacity of the "deadmen" needs to be reconsidered to see how much
additiona'l ho'l ding power they have provided.
Mr. Cris Dittmar
August 5, 1981
Page 2
Now we understand that the wa] 'l has stabi'l ized since the addition of
the "deadman" system. In reviewing the calculations for this sytem, we
find that the resisting capac'ity of the "deadmen" is approximately
double of the available rod capacity. Therefore, we would recormend'
as an inrnediate measure, that the rods be doubled to utilize the fu] I
value of the "deadmen." The connection of rods to the wall and "dead-
men" should also be changed, adding shims to eliminate the eccentricity
in the connections.
|lje feel reasonably confjdent that this wall will remain stable through
next wjnter, if you take this measure. However, it has been noted that
the gravel backfill spec'i fied on the original_plan was.not installed.
This could'lead to a hydrostatic pressure bu'i1d-up behind the wall that
it was not designed foi during wet periods (i.e. spring runoff). For.
this reason, we-wou1d reconmend a monitorjng program tO be implemented
immediately to be sure no further creep occurs. It seems this would be
the most prudent solution at this point in time, since the system seems
to h'ave stabilized and any fa1lure of the wall would be a slow, steady
type of creep and not a catastrophic failure- If, in fact, the wall
dilbs begin to move again at some point in time, then the entire system
would hive to be reviewed and a more conservative and costly approach
be taken. It seems fair, at th'is point in t'ime, to simply monitor the
wall for a full year's cycle and see if this would be iustifiable.
As inmediate measures, we would a'l so recommend installing "deadmen" on
both sides of the constructjon iojnt mentioned above, as it has been
placed at an'improper locat'i on and greatly weakens the wal 1. through this
region. Also, the French drain below the toe of the wall decreases the
faitor of safety against sliding and should be rep'laced'irmediately w'ith
properly compacted structural fill.
shou'l d you have any questions of further need for our serv'ices regard-
ing this matter, please feel free to call us.
TMB: cdb
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DENVER, COLORADO 80227
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E. THOMAS PUNSHON
CONSULYING ENGINEER
3t20 SO. WADSWORTH BLVD.. SUITE fs
DENVER. COLORADO AO227
TELE. (3031 948-0444
August 1, 1981
Chris Dittmar
Doyle Hopklns Const. Co.
1380 North Frontage Road
Vail, Colorado
Dear Chris:
0n July 29, at your request, I made a structura'l 'inspection of
of the reinforced concrete canti'lever counterforted retaining wall at the
rear of the property at 1380 North Frontage Road, Vall, colorado. I was
accompan'ied by Leo Keller' P.E., and we iointly made the inspection.
Subsequent calculations and concluslons were made separately.
DESCRIPTION OF THE WALL.
The wall is 18 feet high on a 9 foot wide footing. ilall and footing
are 12" thick. A vertical joint, diagonal in Plan, separatei the two portions
into approximately 200 feet long at the east end and 75 feet at the west end.
The earth slopes upward to the north at an angle of 25 degrees. A roadway
parallels the wall 55 feet (horizonta'l distance) north of the wall.
The 1on9 segment of the wa'll tilts south at the top a maximum of
22". The west segment also leans south from 9 to 10N".
. A Swiss hammer test of the concrete indicates a strength of
4500 psi.
At the east end of the east wa] 1 there are numerous cracks in the
south face, running down to the left at about 45 degrees'
A large boulder has impacted the wall near the toP, at about the
center of the east portion. The boulder did not penetrate the wall, but
it knocked out a large piece of concrete from the exposed face'
The toe of the foot'ing is accessible for the full length of the wall
by removing a th'i n cover of earth. This footing was level at a'll of the points
where jt was checked, including the area where the wal 'l has a maximum tilt.
The wal't is stiffened by counterforts 20 feet on center. Adjacent to
most of the counterforts in the east portion heavy galvanized threaded rods
have been run from the wall to heavy concrete "deadmen" about 40 feet up the
slope. The concrete anchors are below ground, but relatively near the surface.
I have been informed that the wall was moving out until these ties were
installed, but they have stopped the movement.
il,
81-47
E. THOMAS PUNSHON
CONSULTING ENGTNEER
3t20 SO. WADSWORTH ELVD., SUTTE
'3 DENVER. COLORADO 8O227
TELE. 1303, 9AA-O484
CONCLUSIONS:
As a result of the field observations and later calculations, I have
formed the following opinions.
1) Both portions of the wall had actually failed before being hit by the
boulder. The west port'ion was not hit by the rock, but it has moved
outward si gni ficantly.
2) The impact of the rock moved the east portion further out than lf it
had not been disturbed.
3) The addition of the steel ties probably saved the wal'l from complete
col 1apse.
4) These "deadmen" should not be counted on as a permanent sol ution as they
lie within a posslble failure area. (See enclosed drawing.)
5) The reinforcing ln the north face of the counterforts calculates to be
overstressed past ultimate capacity and has probably been completely
fractured. This condition can be verified by excavating a pit at a
typical counterfort.
6) ttre horizontal wall reinforcing ln the south face of the wall ls over-
s tres sed .
7) The horizonta'l wall reinforcing'ln the north face of the wa1l, at the
counterforts, is also overstressed; and it is too short to be effective-
it does not extend far enough to reach the area of zero noment.
8) Bearing pressures at the toe of the footing are guite high. Footings
for a wal'l this high are usually made wider.
9) The footing thickness is not sufficient to span between counterforts.
The steel reinforcing area is adequate, but the concrete is overstressed.
81-47
E. THOMAS PUNSHON
CONSULTING ENGINEER
3t2O 50. WADSWORaH ELVD.. SU'TE fs
DENVER. COLORADO f,0227
TELE. (303' 9Aa-Oa84
RECOMI'|ENDATIONS:
In my opinion this wa] I can be repaired in a structurally sound manner
as outlined in the enclosed drawing and as described following. This work
is expensive, and nay approach the cost of reroving and replacing the wa] 1
with a revised design. It is possible that a slightly less expensive
design might be worked out using tie rods and visible walers. I feel that
to install reliable ties through this cobb]y soil may be very difficu'lt.
I recommend the following repair procedure:
l) Rernove a'll of the backfill to provide working space. Leave all deadman
ties in P1 ace.
2) Fl ame cut all broken reinforcing at the counterfort, flush with the
bottom surface of the concrete.
3)A11ow the wall to return to its origina'l position. (or force it back
with the steel tierods). r
4) Thru bo'lt the 7x4 angle assembly to the far edge of the counte?ort.
This will tie the counterfort to the footing.
5) tnstal'l new 24'x30" concrete beam along the far edge of the footing.
This will reinforce the footing and also will reduce toe pressures
by widening the footing.
6) Install two 14" beams on the inside face of the wall in each bay'.
This reinforces the overstressed wa'l 'l steel .
7 ) Ti ghten al I exi sti ng Deadman ti es .
8) Remove the gravel drain in front of the footings, and replace with
compacted claY (imPervious ).
9) Replace the backfil'l . Ensure that pervious material is placed at the
wa1 I face to conduct water to the weep hol es.
Note: a'l I of the above listed work should be done for both the
east and west portions. Protectmen against rolling stone hazards.
If this procedure is selected to repair the wall, additional detail
design and dravlings must prepared. F'i eld observation by a Registered
Si ncerel y
Y ,.Fo
D.
Engineer should be Provided.
yours,
a I ':.
I
RETAINING WALL INVESTIGATION
AT VA]I,I HI APARIUENTS
Vall, Colorado
For Doyle llopkins Constructl-on t
1380 North Frontage Road'
Vai1, Colorailo. 81657
By: Leo M. Keller'
1550 Dover Street'
Lakewood, Colorado. 80215
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JuIy 31, 1981
Doyle HopkLns Construction
1380 North Frontage Road
Vail, Colorado 81657
Attn: tlr. ChriE Dittmar:
::'i:lit' Jtl.lH:s tis ation
Dear Mr. DLttmar:
I have completed the investigation and analysig of the re-
taining wail ana have includtd sorne pos-sible renedies to the
Eit"ati"" in the rePort. I feel thal the suggested repair
ie feasible but no -effort has been made to arrive at final
design or details at this tlne.
Very truly yourE'
LEO !,T. KELI.ER E ASSOCI.ATES
Leo M. KeUer
LMK: jh
Enclosure
I
I
REPORT OF FIEI.D INSPECTION OT
RETAINING IIALL FOR DOYLE BOPKINS CONSERUCTION
1380 FRONTAGE ROAD, VAII., COIORADO 81657 (VAI,LI gI APARTI,TENTS)
fhe Problem:
A retaining waII 18' high above the footing and approxi.nately
180 feet long was conatructed in 1980 at the sl-te. At the
present tirne the top of the wall has d,efLected outward over
much of its lengtlr by as rnuch as 24' from a vertical plane.
The east end remains vertical because of a wall running
perpendicular to the wall in question. DurLng March of L981
a dislodged boulder of undetemined eize struck the-back
of the wall approxirnately 2'-6o below its top. Thl.s fractured
concrete from the front face of the rall in an area approxi-
mately four feet horizontally and three feet vertically to
a maximun depth of about eight inches.
Corrective measures completed to this date include the in-
stallation of ln / threaded galvanized rods inserted through
plates on the front of the wall and anchored approxirnately
40 feet up the slope in a concrete 'dead-mann rneasuring
8r x 3r x 2'-6o.
The Investiqation:
on July 29' I98I I inspected the retaining wall and found
that a sfunilar wallr separated by an open construction joint,
I
3
.a
E I
t
r
lq
-1-
adjoins the wall in guestion.
found to lean outward at the
up to 15" at the end near the
wall leans out approxinately
of 5' at the top of the wall)
The adjacent waII aleo was
top in varying amourts ranging
wall in question. The subject
20i at that point (a difference
The fooling for the wall was found to be level and the tilt
of the wall fron vertical starts at the top of the footing.
Several modetate cracks (approxinately I/8" wide) near the
west end of the wall run diagonally fron the top right to ttre
bottom left between the counterforts. Sirnilar visable crackg
occutr along the rest of the lrall but measure }ess than L/32'
wide. One crack near the east end of the wall and one crack
at the first counterfort from the east are visible from the
back face. the cracks extend part way through the wall
thickness and from the top of the wall donnward. Fill naterial
prevented detemination of the extent of the vertical crack.
?he earth slope above and behind the wall was determined to
stand on a 2 (horizontal) to I (vertical) slope. Uany heavy
cobbles are included in the fill material .
the remedial anchor rods with dead-men are in place at
approxinately 20' intervals and are installed adjacent
t
l|
.l
-2-
to the exlsting counterforts. Several of the 8' x 8' x 3/8"
anchor plates at the front face of the wall through which
the anchor rods are threaded show evidence of 'dishing'
which would indicate falrly high strain on the rodE.
Conclusions:
It is ny opinion (since the footing of the wall was found
to be level and the wall slopes outwarcl beginning at the
top of the footing) that the footing remains intact and
the counterforts have separated fron the footing due to the
pressure of the earth. This theory is substantiated by the
fact that the adjacent eection of wall (to the west) also
I leans outward but by a different arnount. This wall was
constructed on a footing eonmon to the wall in question and
the footing shows no evidence of failure.
I believe that the falling boulder contributed very little to
the deflection of the waII since the acljacent waII leans
outward by as much as 15o without the effect of a blow from a
falling boulder.
It is ury opinion that the reinforcing steel provided at the
heel of the counterfort was insufficient to resist the
-3-
force on the wall resulting fron
surctrarge behind the wall. (see
the earth pressure and
calculatione)
:
l
Recommendations:Possible repair measures inslude:
1. Renove entire wall and footing (including the portion
of the wall west of the wall construction joint) and
replace with a cantilever or counterforted retaining
waII designed to withstand the pressures subjected
to it.
2. Renove the fill for 10' t behind the walI for the
entire length of the waII and pull the wall back to verti-
cal by meanE of the anchor rods and dead-men in place'
supplemental reinforcenent of the counterfort could then
be added to the faces of the counterforts and anchored
to the footing. Additional anchor rods and dead-men
ptaced horizontally and tested to the required capacity
could be used in addition to the supplemental reinforcenent
of the counterforts. (see Sheet ll0)
This solution assunes that the *8 dowels from the footing
to the wall have not been damaged by stresses that exceed
the yield point of the reinforcing bars. It also assumes
-4-
3.
that the wall can be reinforced by the addition of
vertical whalers on the outside of the wal} and anchora
into the fil-l . This will reduce the stresses to the
point nhere the existing reinforcing steel is adequate.
(see calculations)
Leave the wall aE it now stands and add sufficient
horizontal rods with dead-meu at each counterfort to
resist the horizontal forces applied to the wall . The
wall must be reinforced with vertical whalers and appro-
priate anchor rods as outlined in alternate 2 above.
The rods should be field tested in place to assure that
they will wLthstand the assigned force. The entire
length and height of the wall should then be faced with a
material on a vertical plane that would canroflage the
sloping waII , the exposed ende of the anchor rods and
the whalers between counterforts. (see Sheet *II)
I believe that alternate 2 Ls the better solution because
it would relieve the very high concentration of stregs
in the concrete at the front face of the wall at the
top of the footing, it restores the integrity of the wall
from a visual standpoint and alsor if properly cornpleted'
from a structural standpoint.
-5-
Any repair measures should be inspected at appropriate
intervals by a registered engineer to insure conplianee
with the plans and specifications.
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REPORT
ON
RETAINING l.lALL INSPECTION
VALLI HI APART},IENTS
vAIL, C0L0RAD0
JULY, 'I981
PREPARED FOR: DOYLE HOPKINS
I28O NORTH FRONTAGE ROAD
VAIL, C0 81657
PREPARED BY: R0BILLARD & ASS0CIATES, INC
CONSULTING ENGINEERS
SUITE 3 - DILLON BUILDING
P.0. Box 2lt7
DILLoN, C0 80435
a:,"
REPORT
RETAIiIING I.IALL Ii{SPECTION
VALLI HI APARTI"IENTS
VAIL, C0L0RAD0
INTRODUCTION
This report will cover the findings of a visua'l inspection of the
subject retaining wall plus a brief review of the Structural ca'lcu'lations
that have been done by another firm. Additjonally, reconrnendations for
further action wil'l be nnde and possible alternatives presented.
BACKGR0UND - The subject retaining wall lies a'long the north edge of the
Valli Hi Apartmetn project in Vail. Total length of the wall is approxi-
mately 600 feet. Height varies but the majority is 18 feet from the top
of the foot'i ng to top of the wall. The wall serves to retain the steep
hillside rising to the north above the north edge of the project. There
is a gap of approximately l0 to 15 feet between the face of the retain-
ing wall and nearest buildings. (See Photo 1)
The wall was designed by Boyle Engineering, Inc. of Vail in 1980 and
constructed for the owner by a subcontractor during the summer and fall
of 1980. No problems or structural defects were noted in the wall prior
to the date of impact.
In late March, l98l an excavating contractor dislodged a large bou'l der
(estimated at somewhere around 3,000 lbs.) while landscap'i ng for a home
some 200 to 300 vertical feet above the Valli Hi retaining wal1. The
boulder rolled essentially unobstructed down a slope varying anywhere
from 40 to 60% and struck the wall at a point approximately 3 feet down
from the top of the wa'll at approximately the mid-point of Build.ing J.
Impact of the boulder was absorbed by the retain'ing wal1 thereby pre-
venting major damage to the building and possible loss of life or
injury to several occupants of the building.
The manager of the project noticed in early April that a segment of the
wal1 (approximately 200 feet long) had tilted slighily. The motion or
creep of the wall continued into May while negotiations between the
project owner and the excavat'ing contractor's insurance company con-
tinued. In mid-May, l98l Boy'le Engineering was retained by Doyle
Hopkins to design remedial measures to stop the continued creep of the
wall. Boyle Engineering designed a "dead man" system which was insta'l led
near the end of May.
Since installation of the remedial system and initial strain "take up"
in the "dead man" system movement of the wall has stopped. The wall is
monitored every 4th day and no movement has been noted for the past
three to four weeks.
The Town of vail has asked for severa'l additiona] professional opinions
as to the adequacy of the retaining wall and the renedial measures
recently instal'led. This report will attempt to comply with the Town of
Vai'l 's requirement.
FINDINqS 0F ylsuAL IMEIIIII - A visual inspection of the wat't was made
on July 20,1981 with lilr. Chris Ditmar, project manager for Doyle
Hopkins. Although no measurements were taken by this firm, the approxi-
ment values noted below can be confirmed.
The wall has bowed overits entire 200 foot length. At the top of the
wall the bowing reaches a maximum of approximately 1 foot near the point
of impact and decreases to essentially zero at the east end. At the
west end of Building J there is a construction joint at which point the
top of the wall has moved approximately 5 inches wjth respect to the
remaining wall west of the construction joint. The wall west of the
construction joint has also tilted slightly. (See photos Z & 3.)
The source of impact has knocked some concrete off of the exposed
face of the retaining wal1 opposite the point of impact. This material
was driven with such force that small part'ic'les of concrete are em-
bedded in the siding of Building J, approximately 10 t0 l5 feet away.
(SeePhotos4&5.)
The entire 200 foot length of the wall has tilted toward the buitding.
Max'imum measured eccentricity was approximately 14 inches at the time of
the inspection as reported by Mr. Ditmar. (See photo 6.)
some cracks runn'ing diagonally along the front face of the wall were
noted. (See Photo 7.)
One or two of the "all thread,,rods connecting the ',dead men,'to the
face of the wall were visible, The boulder that had struck the wall was
comp'letely buried by the remedial construction work excavat.ion and the
entire area behind the walI had been disturEed by the remedia] con_
struction. (See Photo 8. )
The method of connecting the a1'l thread rod to the wa]l was visible and
photographed. More will be said about this later in the report. (see
Photo 9. )
tl
4
A drainage swale along the toe of the retaining wall between the wall
and the buildings has been constructed to camy roof drainage and snow
melt from the west end of the project to the east end of the project.
(seePhotosl&6.)
The clean gravel backfi'l'l called for in Boyle's original design was
never instal 1ed.
REVIEW 0F..S:IRUCTURAL CALCULATI0NS - BoyIe Engineering, Inc. has sub-
mitted their original design calculations and drawings to this firm as
well as the design sketch and calculations for the remedial work that
they designed and was recently constructed. l,,le have briefly reviewed
the original design calculations but have not checked them in great
detail as this has been done already by severa'l other engineering firms
as wel'l as engineers on the staff of Doyle Hopkins. The renr,edjal work
was also reviewed by the writer and several more comments will be made
on these later in this report.
lr_
CQNCLUSI=ONS - Based on our inspection and a review of the calcu1ations
and p'lan for the project it is our opinion that;
1. The remedial repairs to the wall have stabilized it under
present load conditions and the wall is in no inmediate danger
of failure.
2. Any additional movement should also be very gradual and any
failure should not be catastrophic.
3. Some additional work is probably required to improve the
factor of safety against overturni.,ng for the wall and to
monitor the wall for a period of time to assure its stability.
4. Some of the remedial work was not done exactly in accordance
with the p1 ans prepared by Boyle Engineering, Inc. and some
additional work is needed to correct and/or modify this work.
t
h
REC0III'IENDATIONS - Based on the findings and conclusions above we
recomnend that the following action be taken:
1. Tapered washers shou'ld be installed between the meta] plates
and the nuts at the exposed surface of the retain.ing wa.l I to
reduce or eliminate any eccentric loading on the nut and
threads. In Iieu of this a more detailed analysis of the
existing connection should be nnde to check its structural
soundness.
2. At least one "dead man,, was left out during the origina.l
installation of the remedial work. This should be installed.
3. An additional tendon or uall threadx rod should be installed
at each "dead manu location to take advantage of the full
capabilitles of the "dead man" and to provide an additiona'l
margin of safety.
4, check the area above the site to rake sure that another mis-
hap cannot occur.
!
Once the aforementioned items are completed, i.t is the t,lfiter's opinion
that the wa'll wi'll have been permanently stabilized and no additional
construction will be required. This assumption is based mainly on the
fact that the movement of the wall has stopped and conditions at the
site appear to have stabilized. 0bviously, conditions are subject
to change and this assumption cannot be completely guaranteed with-
out major additional expenditures.
In our review of the structural calcu'lations for the remedial work done
'in 198'l it is noted that these calcu'lations assume that the structural
integrity of the wal] is maintained and that there is rerely sone
additional load'ing due to eccentricity. lle are not certain that this is
true' It is entirely possible, in our opin'ion, to assume that one or
more of the counterforts was loaded beyond the yield point of the struct-
ural steel and that its load carrying capabilities have been severely
reduced, If this has occurred additional load has been placed on other
counterforts along the wall and the "dead man, system needs to camy
more than just the additional load caused by eccentrjcity, 0bviously,
the most conservative approach is to design the ',dead man,' to carry the
entire load that the counterfort originally was assumed to camy.
I
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Additiona'l'ly, some other severe structural
t0 other parts of the wall covered by earth
damage could have been done
at the present time.
Since the wal'l has apparently
prudent to excavate to expose
check this theory. Therefore
sented for consideration:
stabjl'ized at this time it does not appear
the wall or counterfort system in order to
the following two alternatives are pre-
5a. A monitoring and 'inspect'ion program should be established to
carefully check the status of the wall. Exact details of this
program are not within the scope of this report. A suggested
program might 'i nvolve a week'ly inspection from now until
approximat'le1y Thanksgiving with less frequent inspections
during the winter and weekly inspections resuming next spring
and continuing until next fall.
Th'is inspection program and initial monumentation should be
established by a registered professiona'l engineer and 'l and
surveyor. 0nce the program is established and the owner's
personnel have been trained they can do the monitoring. A
quarterly report by the professional eng'ineer might be advis-
ab1e.
d_
0bviously, if additional movement is noted jt should be reported
to the professional engineerimmediately for hi s consideratf on
and possible additional repair work. If, at the end of the
monitoring period, no movement has occurred, it could then be
assumed that the wall has completely stabilized and no additiona'l
work or monitoring would be needed.
5b.If neither the Town of Vail
with the claim for damages
the program recorffnended in
to take a more conservative
posing all or a portion of
of tilting, soils testing,
repairs to the wal].
nor the insurance company involved
on the project is willing to consider
5a, it wjll obviously be necessary
approach. This might include ex-
the counterfort system in the area
and/or additonal dead men or other
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7-20- 1981
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. ',{KBNA
Lrorpoaatad
Co|r&li|nd Engldaa.a
7456 wb.t Fittrl Aveouo
Ocnver Color.do 80226
3dl u2 @50
T€Lr {H3rc INO€V@ ovF
Mi:|lasl H. gaar€tt PrlnctFla
Oonavon O. Nct(el
Davu E. Ausbn Don I Pvlt
Donaid C. Webat
A. J. Byan Leroy E. Tobl€r
0s0&1s€4
John K. Sright AasocLL PrlrtclpaL
Chadas D, Kgyes
Wllhem 8. O N€d Jam63 B. DaviS
Noil E Ounba. G. James Eickson
Rob€n D. Scarrow
Howard B. Bro*ning
Founabl'
Milo S. Ketchlrn
gp€ctal corBultant
E. \bmon KonkC
(19231970)
July 21, 1981
l.Ir. Chrls Detnar
Doyle Eopklos Couatructlon Co.
1280 North Froutage Vail, CO 81657
RE: Valll fll Apartneots - Retainlng Wall
Dear Chrls:
As requested by you and Mr. DoyLe ltopkios, the owaer of the valli Ht Apartlleot complex, r lnspected the concrete retaining wall north of the west portlon of the aparLment complex orr July ll, 1981. Subsequently Irve analyzed the wall and the deadnen whlch were lnstalled above the wall recently, to determin6 the stabLllty of the wall systen. Ttris letter wlll reflect the results of that revlew_
The-exlsting coocrete retainlng nall lra s designed by Ttmothy M.*{}", of Boyle Englneering, Inc. in.Vail, and the destgn is reflected in hls drawlng dated June 4, 1940. Ttrts 12- Ifrtek retainlng wall ls l8r high fron top oi wall to top of foorLng,lrlth a continuous 12' thlck by 9r-0 wlde footlng. Ttre wall extends for a length of soroething over 200r. Backftll above the wall slopes at a very steep angle up the mountaLu, wtLle the grade level below the nall is approrlnately 12- above the top of the footlng. you indlcai"d tfrat the wall rras bullt ln August of 1980. ,Lo lare Aprll or early ltay of .
1981 a boulder rolled down the mountaln, and stiuck-the top ofthewallapprox1nately70rto80|fromtheeastend.11re
inpactofthisrockbrokeas00allpleceofthereta1nl'ngwal1
out and after that event the eastern l20r (approxtnatelt) of the wall length was found to be 20" out of prtub. Ttre ilstero half of the retatuing wall ls currently measured to be ap-proxinately 6" out of phub.
After the rock rolled down the nountaln and struck the wall, 6 .
deadnen were installed up the bank fron the retalnlng wall at approxiuately 20r on ceater. you indicated these deadnen are about_8t long, about 2t-6- wlde aad about 3r htgh, and that the top of the deadroen are about 6t below grade. Itreee dead,Ereo are located 35r to 40t away fron the wall, and each dead_oan ls connected to the top of the wall by a l'. round steel
Igd. Each rod pasaesrrhrough a hole drilled ln the rop of the-wall, with a nut and raiher on the dosnhlrl r"ce oi the I4tall.
i
-,...
l,tr. Chrls Detnar
July 21, I98l
Page 2
Ttre first portl.on of our review consl.sted of a check m the
lnltial deelgn, as preeented in l'tr. Boyler s drawlng of June
4, 1980. That drawlng lndlcated that the design was based
on an assuned lateral Preasure of 45 pcf. Ttre horlzontal
pressure that earth appliee to a retalning wall varlesr de-
pending on the naEure of the sol1 and the slope of the top
surface. Lt Ls our experlence that when the backftll elope
ls,very-steep, as,ls the case on thls wallr the lateral
pressure:-ntrl.ch-should be applied ln deslgn ls probably note
ln the range of 55 to 65 pcf.
Design of a retainlng wall is governed by 2 posslble fallute
modes.. FLrst, the wall must be proportioned so that lt
. wtll not overturo due to the horizontal Pressure app lled
from the backftll. this tendency to overtura ls resisted
by the weJ.ght of the soll on the uphlll portion of the
footing, as well as by the welght of the wall and footlog
tteelf. It i6 normally accepted design practlce to proportlon
the wall and foottng system to provlde a safety factor of
at least 2.0 against overturoing. In thls wall our caleulaLions
show the safety factor against overturning to be substatrtially
less than 2.0, even ustng the lower deslgn Pressute. l&e feel
the safety factor against overturnLng too low to assure the
stabllity of the walI.
Tbe second failure node Ls horizontal sllding due to the
horizontal preasure of the backfill. The resistence to
sliding ls provided by frlctlon between the soil below the
footing and the bottom of the footing. the frLctioo forces
are a functlon of the welght of the footlng and wall aseenbly
as well aa the weLght of the sol.l above the footlng. It ls
normal practlce to proporcioo the wall so that the safety
factor againet sltdlng is at least 1.5. Our calculatlone
show the safety factor agalnst sllding to be substantl'ally
less than.1.5, even using the lower destgn pressure.' Ile
feel the safety factor l-s too low to assure stabillty of the
wal l.
Next we revlewed lhe reLnforclng described ln the conslructlotr
drawlng to check its adequacy. Ttre deslgn lncorporates
buttresses at 20r otr cenler on the uphlll slde of the wall to
connect the heel of the footing wlth the top of the wall. The
relnforclng ln the wall and footlng ls defined ln such a manner
that both wall and footing nust spaa horlzontally the 20r be-
tneen the buttresses. The dowels fron the footlng Lnto the
wall are placed at the center of the wall, ao linlted re-
slstance to bendlng 6tresses is provlded betlteen the footing
and the irall betoeen the buttresses. Ttrls requLres relnforcing
to be placed ln the back (uphill) slde of the buttresaes
adequate to carfy 20r of horlzontal loading betl4teen the wall
and the heel of the footlng. Our calculatLons indicate t
l{r. Chrls Detmar
July 21, 1981
Page 3
based on 45 pcf equtvalent fluld pressure, a relnforcl.ng re-
qulrement of over 4 times the reinforclng provlded.
Slnce the hlghest pressures occur when the soil above the
wall ls wet, we suspecc (but have no way to verlfy) thaE
durtng the sprlng snorroelt, whlle water was passing through
the backfi.ll and out the weep holes through the wall, the
soil pressure -whlch was rnobj.ll.zed behlnrl thls wall caused
the najor portlon, and perhaps all, of the 20" of horlzoatal
deflectloo presently vlsible. Ttrere is a strong posslblllty
that the fuopact of the rock hltting the top of the wall had
L:Lttle or no affect on the actual posltioo of the wall.
Since no ooe lras behind the apartment buildings duri.ng the
winter and sprlng, we feel thls moveoent could have occurred
wlthout being notlced.
We next attenpted 8o evaluate the capacity of the deadmea
whlch were installed thls sr.rnmer above the retainlng wall.
This is dlfficult to do accurately, because of the uncertalnty
of the actual locatlon of the deadoen, Ehe slope of the ground
above the wal1, and the nature of the sol.l ln whlch the deadnen
were constructed, Ttle capaclty of the deadneu is controlled
by both the capaclty of the tierods and by the capaclty of
the soil below lhe deadneo to resis! horlzontal loading. A
l- round threaded standard steel (436) rod has a rension
capacity of 12100 pounds. Based on passive earth pressure
of 300 pcf ln front of the deadmen, with a depth of 3r ard a
length of 8r, assr.-rlling thete ls no resistaDce at the top of the
deadman due Eo its relatlonshlp to the slopiag ground gurface,
we flnd the reslstance of the deadnan to be about 10800 pouads.
Ihese figures are reasonably conpatible with each other, but
nelther the reslstance of the deadnen or the capacity of the
steel todg appears adequate to restore the stablllty of the
wall, ln our oplnlon
In sunmary, our conc luslong are as follows:
l. ftre retainlng wall stabiltty appears to ua to be ta-
adequate for boEh sllding ald overturnl.ng, nith safety
factors substaatially below what ls corrnonly accepted
deslgn prectice.
2. Ihe relnforclug in the retalnlng wall seema to be ln-
adequate to resist the expected loading fron the back-fll l.
3. The capaclty of the deadnen seems lnadequate to resCore
stabillty to this retainlng wall systero
4. The total stab.ility of the mountain ls unknown, and
should be nore adequately establlshed by a soils engineer.5. We feel that the enllre wall ls questionable, not Just the eastem portLon where the greatest horlzontal nove-
ment has occurred.
l,fr. Chrls Detmar
July 21, 1981
Page 4
' lle have consLdered possible methods of repalr of thls wall
system. One ue thod would requlre renoval of the backflll,
and LnstallatLon of a larger footlng above the existlog
fooE,lng, lrlth either an adequate co[nection bet\reen a but-
tress syster0 on top of the new footlng aod the existlng
wall, or poseibly construction of an entirely new wall north
. of the exlsting wallr.- properly rsl n felqgd to reslst the
an.tlcipated-Loacling from the backflll. A second method,
whlch roay be posslble, ls to lnstall a systen of permanenc
hor1zontaltlebacksthroughthefaceoftsheex1et1ngwal1
into the soil behind the wall. I talked to Mr. Rob Sargent
of the Schnabel Foundatlon Company on July 20th an<l l earned . that his flru has done thls type of work Ln other sinilar
Lnstances prevlously. Whlle lt riould be difficult to
install such a systeo wlth the lfuoited space between the
exlstlog wall and the buildtng, h, Sargent indicated that
it night be posslble. I{e sald if deslred, his firn woukl
be williog to look at the problen and give an estLmate of
the cost of such a repal.r. If it were <lecided to go ln
that, dlrection, the Schnabe 1 Foundation Conpany would do
thelr own deslgn and develop whatever soll lnfornatLon was
necessary to support that deslgn. In case you wish to pursue
that method to establish comparatlve costs, you mlght call
Mr. Sargent at the Denver office of Schnabe I Foundatlon Conpany
at 696-7268, or you could talk Eo !G. Ron Chapan, Vice
?resident of Schnabe I Foundatlon Cornpany, at their main offlce
Ln Stone Mountain, Georgia at (404)-938-0940.
' Neither of these suggested repaLr methods would allow restorlng I
the urall Eo its orlglnal vertlcal position. It might be possible
aftet Ehe wall ls properly seablllzed to lnstall some sort of
wood coverlng, or by sone other means re-establish a vertlcal
surface so that it would be visually more acceptable.
I hope these coments wlll be helpful to you ln the resolution
of thls problen. Please let me know Lf you have questions, or
It I may be of further service to you ln thls matter.
' Sincerely yours,
Davld E. Auscin, CCE
Princlpal
DEVgb
box 100
vail, colorado 81657
(303) 476-5613
department of community development
DATE:
TO:
FROM:
REGARD:
August 14, 1981
Chris Ditnar, Valli-Hi Superintendent
Steve Patterson, Chief Building Official
Vacation of 48 units adjacent to concrete retaining walls
(Buildings JrL, N, P) Valli-Hi.
Due to nutnerous problems with above nentioned" retaining walls, the
Town of Vail Building Departnent is notifying you to vacate all
above nentioned units irrnediately. We are further stating that
these units are to be vacated prior to any work being done to
problenatic walls. In addition, we feel that these units can
all be vacated by August 19, 1981 inclusive, as it is our under-
standing that there is adequate housing elsewhere in the project.
to facilitate the vacar^!ies.
Acknowledging Receipt
.--.'
box 100
vail. colorado 81657
(303) 476-s613
department of community development
DATE:
TO:
FROM:
REGARD:
August 14, 1981
Chris Ditnar, Valli-Hi Superintendent
Steve Patterson, Chief Building Official
Vacation of 48 units adjacent to concrete retaining walls
(Buildings J,L, N, P) Valli-Hi.
Due to nunerous problens with above nentioned retaining walls, the
Town of Vail Building Departnent is notifying you to vacate all
above nentioned units innediately. We are further stating that
these units are to be vacated prior to any work being done to
ploblematic walls. In addition, we feel that these units can all be vacated by August 19, 1981 inclusive, as it is our rmder-
standing that there is adequate housing elsewhere in the project
to facilitate the iacancies.
Acknowledging Receipt
for Town of Vail
box 1(X)
vail, colorado 81657
(303) 476-5613
department of community development
DATE:
TO:
FROM:
8-14-81
Chris Ditnar, Superintendent of Valli-Hi
Steve Patterson, Chief Building Official, Town of Vail
p
REGARD: First step in deterrnination of problen retaining rePair progr;uu
and guard rail installation.
The Town of Vail Building Departnent asks that you start rectifying the
retai.ni.ng wal1 problen (north side of project) as soon as possible by
uncovering the backfill of said wall donn to footers in possibly 6 areas
as pointed out by the Town of Vail Staff. This is only the first step
in finding out what the condition of the wall is at this tine and what
future steps should be taken. In addition, please rope off this entire
area to the public. l
There shall also be permanent guard rails installed along the entire
length of gabian retaining walls, that necessitate such, in accordance
with building codes,
j , ,. t I
hun o
box 100
vail, colorado 81657
(3031 476-5613
department of community development
t
DATE:
TO:
FROM:
REGARD:
8,14-8r
Chris Ditnar, Superintendent of Valli-Hi
Steve Patterson, Chief Building Official, Town of Vail
First step in deterrnination of problen retaining repair progran
and guard rail installation.
The Town of Vail Building Departrnent asks that you start rectifying the
retaining wall problen (north side of project) as soon as possible by
uncovering the backfill of said wall down to footers in possibly 6 areas
as pointed out by the Tonn of Vail Staff. This is only the first step
in finding out what the condition of the wall is at this tine and what
future steps should be taken. In addition, please rope off this entire
area to the publ ic.
There shall also be permanent guard rails installed along the entire
length of gabian retaining walls, that necessitate such, in accordance
with building codes.
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81"-47
I U
E. THOMAS PUNSHON
CONSULTING ENGINEER
- 3rao so. waoswoRTll ELVD-. SUITE tS
DENVER. COLORADO AO227
TELE. 13031 9aa-o484
August 1, 1981
Chr:ls Dittmar
Doyle HoPkins Const. Co.
13-80 North Frontage Road
Yail, Colorado
Oear Chris:
0n July 29, at your request, I made a structural inspection of
of the reinforced concrete cantilever counterforted retaining wall at the
rear of the property at 1380 North Frontage Road, vail, colorado. I was
accompanied by Leo Keller, P.E., and we joint'ly made the inspection.
subsequent calculations and conclusions were made separately.
gEscRIPTI0N 0[ THE I,IALL.
The wal] js 18 feet high on a 9 foot wide footing. Il'al'l and footing
are 12,'thick. A vertical joint, diagonal in Plan, separates'the two portibns
into approximately 200 feet long at the east end and 75 feet at the west end'
The earth slopes upward to the north at an angle of 25 degrees. A roadway
parallels the wall 55 feet (horizontal distance) north of the wall.
The.|ongsegmentofthewalltiltssouthatt,hetopamaximumof
22". The west segment also leans.south from 9 to 10%"'
A Swiss hanmer test of the concrete indicates a strength of
4500 psi.
At the east end of the east wa'l'l there are numerous cracks in the
south face, running down to the left at about 45 degrees'
Alargeboulderhasimpactedthewa.l.lnearthetop,atabout
center of the east portion. The boulder did not penetrate the wa'll'
it knocked out a'large piece of concrete from the exposed face.
The toe of the footing is accessible for the ful 1 length of the walI
by removing a thin cover of earth. This footing was leve] at all of the points
where it was checked, including the area where the waI1 has a maximum tilt'
Thewa]lisstiffenedbycounterforts20feetonc-enter.Adjacentto
most of the counterforts in the east portion heavy galvanized threaded rods
have been run frOm the wa]l to heavy concrete "deadmen" about 40 feet Up the
slooe. The concrete anchors are belovr ground, but relatively near the surface'
I have been inforrned that the wa] I vas moving ou*r unti'l these ties urere
insta't'led, but they have stopDed tne movenen"'
the
but
//t/' .t
6L-C T
-E. THOMAS PUNSHON
CONSULTING ENGINEER
3t20 so. waDswoRTH gLvD-. sutrE r:'
DENVER. COLORADO AO227
TELE. 13031 946-0444
CONCIUSIONS:
As a result of the field observations and'later calcu]ations' I have
formed the fol'lowing oPinions.
1) Both portions of the wall had actually fa_iled before being hit by the
boulder. The west portion was not hit by the rock, but it has moved
outward si gni ficantlY.
2) The impact of the rock rnoved the east portion further out than if it
had not been disturbed.
3) The addition of the steel t'ies probably saved the wal'l from complete
col'l apse.
4) These,,deadmen" should not be counted on as a permanent solution as they
. lie wjthin a posslble failure area. (See enclosed drawing.)
S) The reinforcing in the north face of the counterforts calculates to be
overstressed past ultimate capacity and has probably been completely
fractured. This condition can be verified by excavating a pit at a
typical counterfort.
6) The horizontal wall r,einforcing in the south face of the wall ls over-
stressed.
7) The horizonta'l wa] 'l reinforcing in the north fice of the wall, at the
counterforts, is also overstressedi and it is too short to be effective-
it does not extend far enough to reach the area of zero moment.
8) Bearing pressures at the toe of the footing are quite hi9h. Footings
for a walI this high are usually made wider.
9) The footing thickness is not sufficient to span between counterforts.
The steel reinforcing area is adequate, but the concrete is overstressed,
I
{.
81-47
U
E. THOMAS PUNSHON
CONSULTING ENGINEER
3l2O SO. WAOSWOFIH BLVO.. sulT€ f3
OENVER. COLORADO AO227
TELE. l303l.9aa-o444
o
RECOMMENDATIONS:
Inmyopinionthiswallcanberepairedinastructurallysoundmanner
as out'l ined !n the enclosed drawing and as described following' This work
isexpensive,and|IEyaPProachthecostofremovingandrep.lac.ingthewall
uith a revised design. It is possible that a slightly'l ess expensive
design might be worked out using tie rods and visib] e walers' I feel that
to install re]iable ties through this cobbly soil may be very difficult'
I recommend the following rePair procedure:
l) Remove al'l of the backfil]
ties in Place.
to provide working sPace. Leave all deadman
Z) Flame cut a'l I broken reinforcing at the counterfort, f'l ush with the
bottom surface of the concrete'
3)A]]ow the wall to return to its original position. (or force it back
with the steel tierods). ?
4) Thru bolt the 7x4 angle assembly to the far edge of the counte'fort'
, This will tie the counterfort to the footing'
5) InstalI new 24'x30" concrete beam a'long the far edge of the footing'
This will re.inforce the footing and also will reduce toe pressures
by w'idening the footing'
6) Insta'l'l two 14', beams on the inside face of the wa] I in each bay.
This reinforces the overstressed wall stee'l '
7) Tighten al'l existing Deadman t'ies'
8)Removethegraveldraininfrontofthefootings,andreplacewith
compacted claY (imPervious)'
g) Replace the backfill. Ensure that pervious material is pl aced at the
wa1 'l face to conduct water to the weep holes'
Note: all of the above listed work should be done for both the
east and vrest portions. Protect men against rolling stone hazards '
,ou-gL--+1 /
- (aiJ-Edt
..'tr THOMAS PUNSHON
Consulting Engine-er '
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E. THOMAS,PUNSHONO
Consulting Engineer
3120 S Wadsworth Blvd.
DENVER, COLORADO 80227
Phone 988-O484
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Consulting Engineer tfl
3120 S Wadsworth Blvd. -
DENVER COLORADO 80227
Phone 988'O484
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' DENVER, coLoRADo &227
Phone 988'O484
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RETAINING WALL INVESTICATION
AT VN,LI HI APARTIIENTS
Vail, Colorailo
For Doyle HoPklns Constructlon '1380 North Frontage Road,
Vat1, Colorado. 81657
By: Leo M. Keller'
1550 Dover Screet 'Lakewood, Colorado. 80215
f.-
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JuIy 31' I98l
ooyle ltopklns Construction
1380 North Frontage Roacl
Vailr Colorado 81657
Attn: l4r. Chris Dittmar:
Re: Retaining Wall Investigation
- at Vatli Ei APartments
Dear !lr. Dittnar:
I have conpleted the investigation an! analysis of the re-
["i"i"g-roait ana bave includid sorne pos_sible remedies to the
"fi""ii"" in the report. I feel that the suggested repair
is-teastUle but no iffort has been made to arrive at final
desi.gn or details at this time.
Very truly Yoursr
LEO U. KELLER S ASSOCI.ATES
=j-- -.-.-- ,,. 1). ...' \ . '*'*')/'-- ),-a /'i
Leo lil. KeIIer
Ll{K: jh
Enclosure
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REPORT OF FIELD INSPECTION OF
RETAINING WALL FOR DOYLE tsOPKINS CONSTRUCTION 1380 TRoNTAGE ROAD, VAIL, COLORADO 31657 (VALLI EI APA,RAMENTS}
The Problen:
A retaining waII 18' high above the footing and approxirnately
180 feet long was constructed in 1980 at the site. At the
present time ttre top of the rrall has deflected outward over
rnuch of its lengttr by as much as 24" from a vertical plane.
The east end remains vertical because of a wall running
perpendicular to the wall in guestlon. During March of 1981
a dislodged boulder of undetermined size struck the-back
of the wa1l approximately 2t-6" beLow its top. This fractured
concrete from the front face of the walI in an area approxi-
rnately four feet horizontal.ly and three feet vertically to
:a maximum depth of about eight inches.
Corrective measures
stallation of L" I
plates on the front
cornpleted to this date include the in-
threaded galvanized rods inserted through
40 feet up the slope
8r x 3r x 2r-6o.
of the waI1 and anchored approxirnately
in a concrete " dead-rnErn n rneasuring
The Investiqation:
on July 29, l98l I inspected the retaining wall and found
that a similar '*-ali, separateo by an open construc+_ion joint,
adljoins the wall in guestion.
found to lean outward at the
up to 15" at the end near the
saIl leans out aPProxi-natelY
of 5' at'the top of the wall)
the adjacent wall also was
top in varying a:nounts'ranging
waII in question. The subject
20' at that point (a difference
The footing for the wall was found to be level and the tilt
of the waII from vertical starts at the top of the footing.
Several moderate cracks (approximately 1,/8' wide) near the
sest end of the walI run diagonally from the top right to tlre
bottom left between the counterforts. Similar vlsable cracks
occur along the rest of the wall but measure less than L/32'
wide. One crack near the east end of the wal1 and one crack
at the first counterfort from the east are visible frorn the
back face. The cracks extend Part way through the wall
thickness and fron the top of the wall downward. Fill naterial
prevented determination of the extent of the vertical crack.
lhe earth slope above and behind the wall rpas determined to
stand on a 2 (horizontal) to I (vertical) slope. Many heavy
cobbles are included in the fill material .
The remedial anchor rods with dead'men are in place at
approximately 20t intervals and are installed ad3acen:
to tbe exiBting counterforts. Several of the 8" x 8' x 3,/8"
anchor plates at the front face of the wall through which
the anchor rods are threaded show evldence of 'dishing'
rybich sould indicate fairly high strain on ttre rods'
Conclusions:
It iE ny opinion (since tlre footLng of the wall was found
to be level and ttre wall slopes outward beginning at the
top of the footing) ttrat the footing remains intact and
the counterforts have separated from the footing due to the
pressure of the earth. This theory is substantiated by the
fact that the adjacent section of wall (to the west) also
leans outward but by a different amount. This wall was
constructed on a footing corrmon to the waIl in question
the footing shows no evidence of failure'
''
and
I believe that the falling
the deflection of the wall
outward bY as much as 15"
f alling bould'er.
boulder contributed very litttre to
since the adjacent wall leans
without the effect of a blow from a
Itisrryopinionthatthereinforcingsteelprovidedatthe
heel of the counterfort was insufficient to resist the
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force on the wall resulting from the earth pressure and
surcharge behind the wall. (see calculations)
RecounendalieBs3 Possible repair measures include:
1. Re$ove entire waII and footing (including the portion
ofthewallwestofthewallconstructionjoint)and
replace with a cantilever or counterforted retaining
wall designed to withstand the pressures subjected
to it.
2. Renove the fill for 10' t behind the wall for the
entirelengthofthewallandpullthewallbacktoverti-
cal by means of the anchor rods and dead-men in place'
Supplenental reinforcement of the counterfort could then
be added to the faces of the counterforts and anchored
to the footing. Additional anchor rods and dead-men
placed horizontally and tested to the reguired capacity
couldbeusedinadditiontothesupplementalreinforcenent
of the counterforts. (see Sheet *10)
Thissolutionassumesthatthe|sdowelsfromthefooting
to the wall have not been damaged by stresses that exceed
the yield, point of the reinforcing bars' It also assumes
3.
that the wall can be reinforced by the addition of
vertical whalers on the outside of the waLl and anchors
into ttre fill. ?his will reduce the stresses to the
point where the existing reinforcing steel is adequate'
(see calculationsl
Leave the wall as it now stands and add sufficient
horizontal rods with dead-men at each counterfort to
resist the horizontal forces applied to the waII ' The
wall must be reinforced wittr vertical whalers and appro-
priate anchor rods as outllned in alternate 2 above'
The rocls should be field tested in place to assure that
they will withstand the assigned foree' The entire
Iength and height of the wall should then be facedl with a
material on a vertical plane that would calroflage the
sloping wallr the eriposed ends of the anchor rods and
the whalers between counterforts. (see Sheet i11)
I believe that alternate 2 is the better solution because
itwouldre}ievetheveryhighconcentrationofstress
concrete at the front face of, tlre ctall at the
the footing, it restores the inteqrity of the wall
visual standpoint and also, if properly completed'
structural standPoint.
in the
top of
from a
from a
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Any repair measures should, be inspected at appropriate
intervals by a registered engineer to insure compliance
with tbe plans and specifications.
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REPORT
ON
RETAINING }IALL INSPECTION
VALLI HI APARII4ENTS
VAIL, COLORADO
PREPARED FOR:
PREPARED BY:
JULY, t98t
DOYLE HOPKINS
I28O NORTII FRONTAGE ROAD
VAIL, C0 81657
ROBILLARB & ASSOCIATES, INC
CONSULTIIS ENGINEERS
SUITE 3 . DILLON BUILDING
P.0. Box zil7
DILLoN, C0 80435
o
REPORT
RETAIiIING b|ALL II.ISPECTION
VALLI HI APARTI'IENTS
VAIL, C0L0RAD0
INTRODUCTION
This report will cover the findings of a visuaf inspection of the
subject retaining wa'|1 plus a brief review of the Structural calculations
that have been done by another firm. Additiona'l ly, recomnendations for
further action will be made and possible alternatives presented.
BACKGROUND - The subject netaining wall lies along the north edge of the
Valli Hi Apartmetn project in Vail. Total length of the wa1l is approxi-
mate'ly 600 feet. Height varies but the majority is '18 feet from the top
of the foot'ing to top of the wall, The wal 1 serves to retain the steep
hillside rising to the north above the north edge of the project. There
is a gap of approximately 10 to 15 feet between the face of the retajn-
'ing wall and nearest buildings. (See Photo 1)
The wall was designed by Boyle Engineering, Inc. of Vai'l in1980 and
constructed for the owner by a subcontractor during the summer and fall
of 1980. No problems or structural defects were noted in the wal1 prior
to the date of impact.
In 'late March, 'l 981 an excavating contractor dislodged a large boulder
(estimated at somewhere around 3,000 lbs.) while landscaping for a home
sore 200 to 300 vertical feet above the Valli Hi retaining wa1 1; The
boulder rolled essent'ially unobstructed down a slope varying anywhere
from 40 to 60% and struck the wall at a point approximately 3 feet down
from the top of the wall at approx'imately the mid-point of Building J.
Impact of the boulder was absorbed by the retaining wa'|1 thereby pre-
venting major damage to the building and possible loss of life or
injury to several occupants of the building.
The manager of the project notjced in early April that a segment of the
wall (approximately 200 feet long) had tilted s1ightly. The rrotion or
creep of the wall continued into May wh'i1e negotiatjons betureen the
project owner and the excavating contractor's insurance company con-
tinued. in mid-May, I981 Boyle Engineering was retained by Doyle
Hopk'i ns to design remed'ia'l fiEasures to stop the continued creep of the
wa'll. Boyle Eng'ineering designed a "dead man" system which was installed
near the end of May.
Since installation of the remedial system and initial strain "take up"
in the "dead man" system movement of the wall has stopped. The wall is
monitored every 4th day and no rovement has been noted for the past
three to four weeks.
o
The Town of Vail has asked for several additional professional opinions
as to the adequacy of the reta'ining wa1 I and the renedial npasures
recently installed. This report will attempt to comply with the Town of
Vail 's requirement.
IINDINGS 0F vIsuAL INSPECTI0N - A visual 'inspection of the wa]l was made
on July 20, l98l with Mr. Chris Ditmar, project manager for Doyle
Hopkins, A1 though no measurements were taken by this firm, the approxi-
ment values noted below can be confirmed.
The wa'll has bowed over its entire 200 foot length. At the top of the
wall the bowing reaches a maximum of approx'imately I foot near the po.int
of impact and decreases to essentially zero at the east end. At the
west end of Building J there is a construction joint at whjch point the
top of the wall has moved approximately 5 inches w.ith respect to the
rema'ining wall west of the construction joint. The wall west of the
construction joint has also tilted s'lighily. (See Photos 2 & 3.)
I o
The source of impact has knocked some concrete off of the exposed
face of the retaining watl opposite the point of impact. Thls material
was driven with such force that smalI particles of concrete are em-
bedded in the siding of Building J, approximately l0 t0 l5 feet away.
(SeePhotos4&5.)
The entire 200 foot length of the wall has tilted toward the building.
Maximum measured eccentricity was apprcximately 14 inches at the time of
the inspection as reported by Mr. Ditmar. (See photo 6.)
Some cracks running diagonally along the front face of the walI qrere
noted. (See Photo 7. )
One or two of the "all thread,'rods connecting the ,,dead men,'to the
face of the wall were vis'ibl e. The boulder that had stfuck the wall was
completely buried by the remedial construction work excavation and the
entire area behind the wall had been disturbed by the remedial con-
struction. (See Photo 8.)
The method of connecting the all thread rod to the wall was visible and
photographed. More will be said about this later in the yeport. {See
Photo 9. )
I
A drainage swale along the toe of the retaining wall
and the buildings has been constructed to carry roof
mel t from the west end of the project to the east end
(SeePhotosl&6.)
between
dra i nage
of the
the wal I
and snow
proj ect .
The clean gravel backfill ca] led for in Boy'le's original design was
never installed.
BEVIEW 0F STRUCTURAL CALCULATIONS - Boyle Engineering, Inc. has sub-
mitted their original design calculatjons and drawings to this firm as
well as the desfgn sketch and calculations for the remedial work that
they designed and was recently constructed. l.le have briefly reviewed
the original design calculations but haye not checked them in great
detaiI as this has been done already by severa'l other engineering firms
as wel'l as engineers on the staff of Doyle Hopkins. The renedia'l work
was also reviewed by the writer and several more comments will be made
on these laterin this report.
o
C0NCLUSI0NS - Based on our inspectjon and a review of the ca]culations
and plan for the project it is our opinion that:
l. The remedial repairs to the wall have stabi'lized it under
present load conditions and the wal'l is in no irrnediate danger
of faflure.
2. Any additiona'l movement should also be very gradua'l and any
failure should not be catastroph'ic.
3. Some additional work is probab'ly required to 'improve the
factor of safety against overturni.ng for the wall and to
monitor the wall for a period of time to assure its stability.
4. Some of the remedial work was not done exactly in accordance
with the p'l ans prepared by Boyle Engineering, Inc. and some
additional work is needed to comect and,/or modify this work.
b
o
RECOMMENDATIONS - Based on the findings and conclusions above we
recormend that the follow'ing action be taken:
l. Tapered washers should be installed between the metal plates
and the nuts at the exposed surface of the retaining walt to
reduce or eliminate any eccentric 'l oading on the nut and
threads. In lieu of this a more detailed analysis of the
existing connectjon should be rnde to check its structural
soundness.
2. At least one "dead man" was left out during the original
installation of the remedia'l work. This should be installed.
3. An additional tendon or "all thread,, r"od should be instal.l ed
at each "dead man" location to take advantage of the full
capabilities of the "dead man" and to provide an additional
margin of safety.
4. Check the area above the site to make sure that another mis-
hap cannot occur.
7
0nce the aforementioned items are completed, i.t is the wf.i ter's opinion
that the wall wil'l have been permanently stabilized and no additional
construction will be required. This assumption is based nninly on the
fact that the movement of the wa]l has stopped and conditions at the
site appear to have stabilized. Obviously, conditlons are subject
to change and this assumption cannot be completely guaranteed with-
out major additional expenditures.
In our review of the structural calculations for the remedia'l work done
in 198] it is noted that these calculations assume that the structura'l
integrity of the wall is maintained and that there is merely sore
additional loading due to eccentricity. l.|e are not certajn that this is
true. It is entirely possible, in our op'inion, to assume that one or
more of the counterforts was loaded beyond the yield point of the struct-
ural steel and that'its 'load carrying capab'ilities have been severely
reduced. If this has occurred additional load has been placed on other
counterforts along the wall and the "dead man" system needs to carry
more than just the additional load caused by eccentricity. 0bviously,
the most conservative approach is to design the "dead man,' to carry the
entire load that the counterfort originally was assumed to cany.
IL
Add'itjonal'ly, some other severe structural
to other parts of the wall covered by earth
damage could have been done
at the present t'ime.
Since the wa]'l has apparently
prudent to excavate to expose
check this theory. Therefore
sented for consideration:
stabilized at this time it does not appear
the wall or counterfort system in order to
the following two a1 ternatives are pre-
5a. A monitoring and inspection program should be established to
carefully check the status of the wa'll. Exact details of this
program are not within the scope of this report. A suggested
program might involve a weekly inspection from now unt'il
approximatle'ly Thanksgiving with less frequent inspections
during the winter and weekly inspect'ions resuming next spring
and continuing until next fall.
This inspection program and initial monumentation should be
established by a registered professional engineer and land
surveyor. 0nce the program is established and the owner's
personnel have been trained they can do the monitori ng. A
quarterly report by the professional engineer might be advis-
abl e.
l o
Obviously, if additional movement is noted it should be reported
to the professional engineer irmediately for his consideration
and possible additional repair work. If, at the end of the
monitoring period, no movement has occuned, it could then be
assumed that the wall has completely stabilized and no additiona'l
work or mon'itoring would be needed.
5b. If neither the Town of Vail nor the insurance company involved
with the claim for damages on the project is willing to consider
the program recorunended in 5a, it wil'l obviously be necessary
to take a more conservative approach. Th'is might include ex-
posing all or a portion of the counterfort system in the area
of tilting, soils testing, and,/or additonal dead men or other
repairs to the wall.
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KKB}IA
l|lcorDorriad
Cmaulllne Engkrara
7,156 Wesl Fitth Avenle
O€nver Colorado 80226
303 232 @50
T€l€t 45-4370 INDEVCO oVF
Founabl'
E Vemon Konkel
{1923-1970)
Michae H. Earfett
Donavon D Nrckel
Davd E Austin
0908-1967)
Prlnclpala
Oon T Pyle
Leroy E Tobl€r
At ocfr P.lnolp.l.
Jarnes R. Davis
C James Erickson
John K Eright
Charles D Keyes
William 8. O Neal
Nerl F Dunbar
Rob€rt O Scarrow
Howard B. Erowning
July 21, l98l
l,lr. Chris Detmar
Doyle Hopkins Conatructlon Co.
1280 North Frontage
VaiI, CO 8L657
RE: Vallt Ht Apartments - Re talaing Wall
Dear Chrls:
As requested by you and Mr. Doyle Hopkins, the owaer of the valli Hi Apartment conp lex, r lnspected the concrete retalnlng wall north of the rrest portion of the apartment complex on July ll, 198 1. Subsequently Ifve analyzed the wall and the
deadmen whlch were installed above the wall receotly, to deternine the stabiliry of the wall systeu. This leiter wlll reflect the results of that revlew.
The exlstlng concrete retainLng lrall was deslgned by Tlnothy M.Boyle, of Boyle Engineering, Inc. in Vail, and the deslgn ii reflected ln hls drawlng dated June 4, 1990. This 12" ;hlck retainlng wall ls l8f htgh from top of wall to top of footlng,with a continuous 12" thick by 9r-0 wide footlng. The wall extends for a length of sonethlng over 200r. Backfill above the wall elopes at a very steep angle up the nountaln, whlle the grade level below the wall is approxlmately l2'. above the top of the footing. you tndicated that the wall was bullt ln August of 1980. In late Aprll or early May of l98l a boulder rolled down the nountaln, and stiuck the top of the wall approxlnately 70t to 80t from the east end. Ttre lmpact of thls rock broke a small plece of the retalnlng wall out and after that event the eastern l20r (approxlnately) of the wall length was found to be 20" out of plunb. Ttre western half of the retaining wall ls currently measured to be ap-proxlnately 6" out of plunb.
After the rock rolled down the nountai.n and struck the wall, 6 deadmen were installed up the bank fron the retalnlng wall at approxinately 20t on center. you indlcated these deadmen are about 8r long, about 2t-6' wlde and about 3r hlgh, and that the top of the deadmen are about 6t below grade. Ttrese dead-
men are located 35t to 40r away frorn the wall, and each dead_nan ls connected to the top of the wall by a l', round ateel t9d. Each rod passes Ehrough a hole drllled ln the top of the-wall, nlth a nut and waiher on the downhill face oi the wall.
l,tr. Chrls Detmar
July 21, l98l
Page 2
The first portion of our revLew conslsted of a check on the
initial desLgn, as presented in I'lr. Boyler s drawing of June
4, 1980. Ttrat drawlng lndlcated that the desigo waa baaed
oo an assuned lateral pressure of 45 pcf. the horlzontal
pressure that earth applles to a letaLnlng wall varles, de-
pendlng on the nature of the soil and the slope of the top
surface. It is our experLence that when the backflll slope
is very steep, as ls the case on thle wall, the lateral
pressure whlch should be applled in deelgn ls probably nore
in the range of 55 to 65 pcf.
Destgn of a retainlng wall ls governed by 2 possible failure
modes. First, the wall rnust be proportloned 5o that it
wlll not overturn due to the horizontal pressure applled
from the backflll. Ttris tendency to overturn 16 resisted
by the welght of the soll on the uphlll portLon of the
footing, as well as by the weLght of the wall and footlng
ltself. It ie nornally accepted design Practlce to Proportlon
the wall aad footlng systen to provtde a safety factor of
at leaat 2.0 against overturning. In this wall our calculatlons
shon the safety factor agalnst overturnlng to be substantially
less than 2.0, even uslng the lower deslgn Pressufe. I'le feel
the safety factor agalnet overturnLng too low to aseure the
stabiltty of the wall.
The second failure mode is horizontal slidlog due to the
hotlzontal preasure of the backftll. Ihe resLstence to
slldlng ls provided by frlctlon between the soll belos the
footing and the bottom of the footing. ltre frictlon forces
are a functlon of the weight of the footlng and wall assernbly
as well aB the welght of the soll above the footlng. It ls
normal practice to proportlon the wall so that the safety
factor agaLnst slldlng ls at least 1.5. Our calculatlons
show the safety factor agalnst sllding to be substantlally
less than 1.5, even using the lower design presaure. We
feel the safety factor Ls too low to assure stabillty of the
wall.
Next rre revlewed the reinforcing described in the construction
drawing to check lts adequacy. The design lncorporates
buttresses at 20f on center on the uphtll side of the wall to
connect the heel of the footLng wlth the top of the rtall. The
reinforclng ln the wall and footing ls deflned ln such a manner
that both wall and footlng must span horLzontally the 20r be-
tween the buttresses. Ttre dowels fron the footing lnto the
wall are placed at the center of the wallt so llnlted re-
ststance to bending atteeees ls provlded between the footing
and the wall between the buttresses. Thls requires relnforclng
to be placed in the back (uphlll) side of the buttreases
adequate to carry 2Ot of horizontal loadlng between the wall
and the heel of the footing. Our calculatLons lndicate'
l{r. Chris Detnar
July 21, 1981
Page 3
based on 45 pcf equlvalent fluid pressure, a reinforcing re-
quirement of over 4 tlmes the reinforclng provlded.
Since Ehe highest preasures occur when the soil above the
wall ls rtet, we Buspect (but have no way to verlfy) that
durlng the sprlng snor*me I t, whlle water was passing through
the backfill. and out the weep holes through the wall, the
soLl pressure which was nobllized behind thls wall caused
the najor portl.on, and perhaps all, of the 20" of horlzontal
deflectLon presently visible. Ttrere Ls a strong posslbllity
that the irnpact of the rock hlttinq the top of the wall ha-d
lltf 1" ,^. rr- af fect on t
Slnce no one waa behind the apartment bulldtngs durlng the
wlnter and sprlng, we feel thLs rnovenent could have occurred
without being notlced.
We next attempted to evaluate the capacLty of the deadmen
vhLch were lnstalled thls sunner above the retalnlng rrall.
This ls difficult to do accurately, becauee of the uDcertalnty
of the actual locatioo of the deadmen, the slope of the ground
above the wall, and the nature of the soLl l-n whlch the deadmen
lrere constructed. Ihe capaclty of the deadnen is controlled
by both the capacity of the tierods and by the capacity of
the soll below the deadnen to reslst horlzontal loading. A
l" round threaded standard steel (A36) rod has a tenslon
capaclty of 12100 pounds. Based on passive earth preeaure
of 300 pcf 1n front of the deadrnen, with a depth of 3r and a
length of 8r, assuming there is no resLatance at the top of the
deadman due to lts relationshlp to the sloping ground surface,
we find the resl8tance of the deadman to be about 10800 pounds.
These flgures are reasonably conpatible wlth each other, but
nelther the resistance of the deadmen or the capaclty of the
steel rods appears adequate to restore the stability of the
wall, ln our opinion.
In summary, our concluslons are as followe:
l. The retaining wall stablllty appears to us to be l-n-
adequate for both slldlng and overturnlng, with safety
factora substantially below what ls cormonly accepted
deslga practl.ce.
2. The reinforcLng in the retaining wall seems to be in-
adequate to resist the expected loadlng fron the back-
flll.
3. The capactty of the deadnen seems Lnadequate to restore
stabllity to thle retalnLng wall systen.
4. The total etabllity of the mountain ls unknown, and
should be more adequately establlshed by a solle engLneer.
5. We feel that the entire nall ls questionable, not Just
the eastern portlon where the greatest horlzontal move-
metrt has occurred.
ltr. Chrls Detnar
July 21, 1981
Page 4
We have considered possible nethods of repair of this wall
system. One method would require remova I of the backflllt
and installatlon of a larger footlng above the exlsrlng
footlng, wlth either an adequat.e connection between a but-
tress system on top of the new footlng and the exlstlng
wall, or posslbly construction of an entirely new rtall north
of the existing wall, properly reinforced to reslst the
antlclpated loading fron the backfill. A second method,
which nay be poselble, ls to install a system of permanent
horlzontal tlebacks through the face of the exlsting wall
lnto the soil behlnd the wall. I talked to Mr. Rob Sargent
of the Schnabel Foundatl.on Conpany on July 20th and learned
that his flrm has done thls type of work in other eimllar
instances previously. Whtle lt would be dlfflcult to
lnstall such a system with the llnited space betrteen the
existl.ng wall and the buildlng, Mr. Sargent indicated that
it nlght be possible. Ile said lf desired, his flrm woultl
be willing to look at the prob lern and give an estLmate of
the cost of such a repalr. If it were declded to go ln
that directlon, the Schnabel Fouodatlon Company would do
their own deslgn and develop whatever soil lnfomatLon waa
necesaary to support that deslgn. In case you wlsh to pursue
that method to establlsh comparative costs, you night call
I'lr. Sargent at the Denver office of Schnabel Foundatlon Company
at 696-7268, or you could talk co Mr. Ron Chapman r Vlce
President of Schnabe I FoundatLon Conpany, at their maln offlce
in Stone llountain, Georgia at (404)-938-0940.
Neither of these suggested repair nethods would allow restoring
the wall to Lta orlgLnal vertlcal positLon. It night be poselble
after the wall is properly stablllzed to lnstall some sort of
wood covering, or by some other means re-establlsh a vertical
surface so that lt would be visually nore acceptable.
I hope these coments nlll be helpful to you in the resolution
of thls problen. Please let me know lf you have queatLona' or
if I nay be of further servlce to you ln this matter.
Sincerely yours ,
/l
/rl^r( t
Davld E. Austln,
Principal
DEA/gb
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boyle engineering, inc.
143 e meodow dr. suite n-10
crossroods shopping center
voil. colorodo 81657
3O3/476-2170
July 1, 1980
iq#
Doyle -Hopkins Constructi on
P. 0. Box 1313
Vail, Colorado 8t657
Att: Richard Glover
Sub ject: Valley-Hi APartments
Vail, Colorado
Richard:
This is to confirm that I have reviewed the gabion retaining
waLl design that you are presently using for the 12 foot high
and 1J foot high retaining situations at the above referenced
project. Based upon sope conservative assunptions that f na$e
for the soil-s conditions, I have found the designs adequate
to resist the maximuro anticipated lateral pressures. This
is based upon an analysis that checked the walls for overturning
noment, sliding and bearing pressure on the soil be1ow. Should
you need any further analysis, feel free to call me-
Sincerely yours '
?imothy
ffi}I
: 14965 :
to''^ee U pE
o t o
l V
department of community dwelopment
lmn
box 100
vail, colorado 81657
(3031 47ffi613
,lune 2, 1980
arry
own o
oodley, Chief Building Inspector
Vai'l
Val'lj-Hi Employee Housing Project
Vaj'l , Co]orado 81657
Attn: DoyIe Hopkins Construction
Gentl emen :
Upon revievl of your project the fo1lowing 'list of Bui'lding
Code vio'lations have been noted:
1. Inadequate handrails have been installed in a1l build'ings
except building "F" and recreation building. Sec. 3305-J 2. Proper handrail to be installed on exterior steps in front of buildings A,C,& D. Sec. 3305-J, Sec. 1716.3. 6 X 6 porch supports are not acceptable on building numbers
D & B. Sec. 2517, C-4.4. Attic access are to be installed in all buildings excluding
building "F" and recreation building. These have not been instal1 ed,
the size to be 22" X 30". Access to be located in hallway of bui'ld'ings
3 stories or more. Sec. 3205-4.5. Draft stops to be jnsta'l'led in all attics. Attics must be
separated into maximum areas not to exceed 3000 sq.ft. These partitions are to be not'less than !" gypsum wal'lboard, type X.
These part'itions are to be installed'in all existlng buildings as
well as future units. Sec. 3205-8.
Compl i to the above mentioned violat'ions must be expedited and
compl 120/80.
I
f
Ll^l: df
cc: Steve Patterson
Job File
Doyle engrneenng, Inc.
143 e. meodorru dr suite n-l0
crossroocls shopping center
voil. colorodo 81657
303/476-2170
May 21, 1980
\/ai1 Building Department Att: Larry Woodley
P.O. Box 100 VaiI, Colorado 81657
Re: Employee Housing Project North Frontage Road Vail, Colorado 81657
Larry:
Enclosed find detail-s of the Slab-to-wall condi-tion for the above noted project. These are consistent with our discussion on May 19 and pertain to buildings I, J,K, L, M, N. and O and P. Buildings N and O hrere done as per alternate while the remainder will be d.one as per the basic detail.
Doyl
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Timothy
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Richard Glover,z
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