HomeMy WebLinkAboutGOLDEN PEAK SKI BASE AND RECREATION DISTRICT PARCEL 1995\ Lll\l N%t\5f""JF letr^P'*k DRB $q5
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=ALPINE ENGINEERING, INC.
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- :. development plan for this project was submitted and approved in 1984; the current submittal': constitutes an amendment to the 1984 plan. The redevilopment plan includes: l) replacing. . the-existing Golden Peak building rvith an improved ski portal; 2) improving skier access and
rraffic flow to the facility; 3) modifuing the base area with improved lifts, aicess and outdoor
space. Modifications to the lifts and planned increase in skier use of the base area will
' . require moving the existing stormseu'er inlet out of the planned skier maze located near rhe
bottom of Lift 6' .The stormsewer inlet is fed by the East Branch of Mill Creek, an artificial
i'ectangular charurel which carries u'ater diverted fro. Mill Creek for rhe p,rrpot" of flood
protection. VAI proposes to convert 378 feet of the open channel of the East Branch to
buried stormsewer, extending the existing stormseu,er, and constructing a new inlet structure
further up the ski slope out of the way of converging ski traffic n"* tf," base area-.
Edwards Business Center. P0. Box 97 . Edwards,Colorado 81632 . (970) 926-3373. Fax (9i0) 926-33yJ
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Mr. Bill Andree
. ftme I, 1995
Daoc )
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NEERING,INC.
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ALPINE ENGI
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May 3l; 1995
. Mr. Mike Claffey
, 'U. S. Army Corps of Engineers
402 Rood Avenue, # .A2: . Grand functiop, qO 815.01
' Dear lv1r. Claffey:
Request for Review and comment, Golden peak Redevelgpment, Vail, co
' development plan for this prpject u'as submitted and approved in 1984; the current submittal' constitutes an amendment to the 1984 plan. The redevelopment plan includes: l) reptacing
the-existing Golden Peak building with an improved ski porral; 2) improving skier access 2[d' traffic flow to the facility; 3) modifuing the base area rviih improved'lifts, a'ccess and outdoor:- space- Modifications to the lifts and planned increase in skier use of the base area will. require mgving the existing stormsewer inlet out of the planned skier maze located near the
bottom of Lift 6. The stormserter inlet is fed by the East Branch of Mill Creek, an artificial
rectangular chanael which carries water diverted from Mill Creek for tt "'porpotl "f n""J--protection. VAl proposes to convert 378 feet ofthe open channel of.the East Branch to, : buried stornsewer, extending the existing stornsewer, and constructing a new inlet structure
further up the ski slope out of the u'ay of converging ski.traffic near the base area.
fdwards Business center ' P0. Box 9z . Edwards, colorado 8163) 1 070) 926-3373. Fax (970) 926-3390
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AU0 2 1 1gg5
prepared by Hydro-Triad, Ltd., dated January,
1985, titled "Design Report Improvements to East Branch of Mill Creek", provide peak flows for Mill: -. r ' Creek which are significanrly higher than peak flows provided per the Flood Insurance Study, dated
TOV . CO|Vl[/l. DEV. DbT I
FEMA
serves to provide an opinion of the 100 year runoff
l. Both Hydro-Triad (per Gore Creek Flood Plain Information, Vail, Colorado, dated June, 1975)
and the FEMA study note that except for small basins, less than l0 square miles, the snowfall
events yielded higher discharge peaks than rainfall events.
Since Mill,Creek Basin is 7.5 miles2 and is approaching the l0 square mile area, it would
seem that snowmelt derived runoff would be similar in magnitude to the rainfall derived
quantity.
2. We checked Hydro-Triad's basin area, curve number, length of channel, etc. used for
calculating runoff quantities, per their June 1975 report. Specific basin data is not provided
per their January 1985 report. Basin criteria per the 1975 report appears to be consistent with
our study:
Mill Creek Basin
Area = 7.56 miles2
Basin length = 27,000 ft
9l% Basin = Timber, CN = 60
9% Basin = Grass\Tundra CN = 69
The 1975 report did not specifically calculate the Mill Creek runoff events.
3. The FEMA Report notes that "The analysis was completed for both snowmelt events and
rainfall events", thus, FEMA's runoff event, whether snowmelt or rainfall derived, (or both)
was estimated to be 300 cfs for the 100 year event.
4. We estimate the Mill Creek 100 year rainfall event to be from 400 cfs to 463 cfs. The range
is based upon an estimate of the travel time and the time of concentration: The stream
channel characteristics have an impact on channel velocities, and travel time. FEMA indicates
that a Manning's "n" of .04 to .06 was used for flows within the channel, and .05 to .08 for
overbank "n" values. Without a detailed study of the channel, channel velocities were
estimated using a 2:l sideslope channel with "n" values ranging from .03 to.05, with gg
' increase in the friction factor for overbank conditions. Since the basin is fairly long (23,000
ft), a slight change in channel velocities (12.5 fps to l4 &s) changes the time of concentration
by 0.a0 hr, and hence has a significant affect on peak discharge quantities.
To be consenvativg a value of 463 cfs should be used, unless a detailed study of channel
characteristics is desired.
5. Hydro-Triad's 1975 report derives their own precipitation amounts from data obtained from
precipitation records. Their 1985 report does not note which design criteria was used (Soil
Conservation Service, or their previous report).
Thunderstorm Rainfall Values
Hydro Triad (1975) 24 hr l0 yr = 1.07 in 100 yr = 1.85 in
Soil Conservation
Service 24hr l0 vr: 1.6 in 100 vr = 2.4 in
GENERAL STORM
The Hydro-Triad Repoft also studied a qeneral rainstorm, which occurs primarily in September and
last several to 48 hours, which was also developed from Dillon rainfall records.
T\e24 hr cumulative precipitation for the 100 yr general storm was noted as 1.89 inches, then, based
upon the recommendations of "Design of Small Dams", they arrive at 0.44 inches of precipitation in
the most intense hour. The report then states, 'fte oeat< intensiw au
ereater than the 0.8 inch per hour infiltration rate". Thus, the 100 year general storm is not expected
to generate runoff in excess of the snowmelt or thunderstorm events.
SUMMARY AND RECOMMENDATIONS
We feel that the peak flows for Mill Creek per the FEMA study should be accepted. but desien the
improvements for the Golden Peak project using runoffvalues per 1985 Hydro-Triad report, with the
exception of their 100 year thunderstorm event which should be disregarded. Hydro-Triad's values are
always more conservative then FEMA's values, so the design will also be conservative.
*The Alpine Engineering, Inc. Mill Creek runoff amounts are higher than Hydro Triad's numbers
because we assumed a 50/50 split at the diversion structure, while Hydro Triad assumed a 60/40 split
We also recommend that flows are assumed to be split 50% at the diversion structure durine the major
runoff evenl which it appears, FEMA also assumed.
Based upon stream profiles per the FEMA study, existing culverts on both east and west branches are
generally at capacity during the 100 year runoffevent, assuming a 50% split at the diversion structure.
The culvert on the south side of Mill Creek circle, west branch Mill Creek, does p! contain the 100
year flood. The profile indicates that the 100 year flood overtops the culvert by less then halfa foot.
Any change to tle split at the diversion structure during major runoff events would have a negative
impact on existing downstream culvert capacities.
Mill Creek East Mill
Creek
Return Period
(years)
AEI Hydro-
Triad
FEMA AEI Hydro-
Triad
FEMA
2 r90 190 50/50*80
10 290 290 210 t45 120 105
25 340 340 t70 140
50 400 400 260 200 160 r30
100 480 480 300 240 r90 r50
500 700 700 3s0 280 230
100 Year
Thunderstorm
480 800 240 320
The Army Corps asked us to consider directing mor€ runoff at the diversion structure to the west Mill
Creek branch, to improve the scouring and cleansing of tbe west Mill Creek branch. Wi feel that this
can best be accomplished by constructing a small diversion berm upstream ofthe divenion structure,
to direct a majority of low flows to the west branch, but as tbe west culvert reaches capacity, pgg!
flows would be split equally at the diversion structure.
The existing diversion structure appears to function as desircd, and is simple and requires low
maintenance. Minor modifications could be made to the structure to include the desires of rhe Armv
Corps, and still retain the desirable functions of the existing structure.
The inlet capacity of the diversion structure should be increased to the 100 year (design) runoff event
of 480 cfs, or 240 per side.
This can easily be accomplished by increasing the headwater depth (or adding fill above the pipes) by
1.0 feet.
HWD = 1.4 (for 240 cfs)
HW = 7.7 feet
Existing = 6.9 feet (add I foot)
PROPOSED IIEADWALL AT CTTLVERT EXTENSION
The 6' x 7.5' arch culvert at the existing culvert entrance has a HWD of I .65. Using a 40% clogging
factor for the trash rack, the design flow used is 400 cfs (-4Q%o = 240 cfs). The existing inlet has a
capacity of 380 cfs, or 5olo overflow = 12 cfs over flow.
A 5' round culvert is proposed at the new inlet, which requires HWD of 1.9 or headwater depth of
I ln, using a 4QYo clogging factor.
Overflow of500 year event = ll2 (700\ -240 = ll0 cfs
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5OO YEAR RUNOFF EVENT
During the 500 year runoff event:
A. The diversion structure will overtop. It is unknown which direction the overflow will take
after it ovenops the structure.
B. The existing channel dounstream of the diversion structure (per area topo'd) is approximately
2'deep, 12'wide, with 2:l side stopes, andT.lYo average slope. The capacity of the channel
,is approximately 400 cfs.
The channel will contain the 100 year design event of 240 cfs(l/2 of 480 cfs), but could
overtoP should the 500 year event have ocJuned or should it occur, (Q500 = ll2(7OO) = 350
cfs), due to ditch irregularities.
Sincerely,
"60rt EA
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l99,,lL
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CRITERH
Prcedurcs for dctcrmining pcalc flows in Colorado,
$oil Conscrvarive Service, USDA
lvlarch 1980
P,, = 2.4 inches
P,o = 1.6 inches
MILL CRDEK Area = 7.56 mi2
CN - 69 mcadow 9o/o = 6.21
CN * 60 forest 9l% = 54.60
CNw = 6l
TIME OT CONCENTR.{TION
Ir = 23,(X0 llVo waage slopg 400 cfs V = 14 fps t = .45 hr
I.o = 4000 27o1o V=3frs t=.37hr
Tc = .E2 hr
Tc = 0.82 tr, q = 360 csrn/in
Pr.= 2.4 in Qroo = 0.l7in
Qroo - QA9 - (0.17[7.56mi2)(360 csm/in1= !Q! cfs
TIME OF CONCENTRATION
l* -23,030 ll% slope, 400 cfs n =.035 V= 13.5 frs t =.47 hrL4=4fi)0ft V=2frs t=.55hr
Tc = 1.02 hr
q - 320 csm/in
Prr-2.4 in Q,, = 0.17
Qm = QAq = (0.17X320 csm/in)(7.56 mi2) = 4l I r*
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Creu*\3.0 EI.IGINEERING
" jt. ;Por the flooding Sources studied in detail in the community, standard
hydrologic and hy6j"u1ic study methods were used to determine the flood
hazard data required for this study. Flood events of a magnitude which
are expected to be equalted or exceeded once on the average during anyl0-, 50-, 100-, ef-.5g-0-vear period (recurrence interval) have been selected
as having special ,ligniiicance for flood plain management and for flood
insurance prernirto raie6. These events, conmonly termed the 10-, 50-,
100-, and 500-year floodsr have a J-o. 2, 1, and 0.2 percenE chance,
respectivelYr of being equalled or exceeded during any year. Although
the recurrence interval represents the long tern average period between
floods of a sPeci_fic nagnitude, rare floods csuld occur at short intervalsor even within thd sarns-year. The risk of experiencing a rare flood
increases when periods greater than I year are considered. For exampLe,
the risk of having a flood which equals or exceeds the 100-year flood
(1 Perceng chanie of annual occurrence) in any 50-year period is approxi-
mately'40 percent,"(4 in 10), and, for any 90-year period, the risk in-
creases to approxinately 60 percent (6 in 10). The analyses reported
here reflect flooitlng potentials based on conditions existing in the
comnunity at. the time of conpletion of this study. Maps and flood eleva-
tions sill be amendled'periodicalty to reflect future changes.
. .. '1.:
ttydrologic Analyses
Hydrologic, analyses were carried ouC to establish the peak discharge-
frequency relationships for floods of the selected recurrenceintervals f6r each flooding source studied in detail affecting
the conmunity.' -
The hydrologic analysis for
a Flood Insurance Study for
this study is covered
Eagle County, Colorado
in detail in
(Reference 5).
alvsis was for both snowmeLt even
= constant x (dr a inage . 0.7area)
then nodified to
drainage areas
usrng
include
using a
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Flood discharges for the I0-, SO-, LOO-, and SOO-year floods onall the streams except Gore Creek t ere calculated using the regressionequations direcely. The l0- and 100-year discharges for Gorecreek were taken from a Flood plain rnformation report (Reference 4).The 50- and 500-year discharges were extrapolatecl from freguency-
. _^ discharge relationships in that report
- Peak discharge-dlrainage area relationships for each strean studledin detail are shown in Table l.
3,2 Hydraulic Analyses
Analyses of the hydraulic characteristics of the flooding sourcesstudied in the cornrnunity were carried out to provide estimatesof the elevations of floods of the selected recurrence intervarsalong each of these flooding sources.
cross sections for the backwater analyses of arl the streams inthis study were obtained either by field survey or from topographicnaps at a scale of I:2400, with contour intervals of 2, 10, and20 feet (Reference 6), obtained fron the Town of VaiI.
A11 bridges and curverts h'ere field checked to gather elevationdata and structural geometry. rn the case of the spraddle creekculverts running under Interstate Highway 20, no iniormation couldbe rocated showing the actual profile. Therefore. sropes weredesigned by assuning a 2-foot rninimun of cover over the pipes.However' actual analyses showed that even with a rarge variationof'slope, culvert capacity to handle flows varied slightly. Itwas determined that the culverts could not handle 500-year fLoo6flows.
Locations of serected cross sections used in the hydraulic analysesare shown on the Flood profiLes (Exhibit I). For strean segrnentsfor which a floodway is cornpu ted (Section 4,2), selected crosssection locations are arso shown on tbe Flood Boundary and FloodwayMap (Exhibit 2).
Roughness factors (Manningrs "n',) used in the hydrauric computationswere chosen by engineering judgrnent and were based on field observationrof the streams and floocl plain areas. For all the.streams inthis study, roughness values for the channel ranged from 0. O4O -to q:9!9. 3he overbank "n,, values varied fron 0.0S0 to O.OgO.
water-surface elevations of floods of the selected recurrenceintervals were compu ted through use of the U.S. Army Corps ofEngineers HEC-2 stefbackwater computer program (Reference 7).
Flood profiles were drawn showing conputed water-surface erevations' to an accuracy of 0.5 foot, for floods of the selected recurEenceintervals (Exhibit l) . .. . .:.1
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ALPINE ENGINEERING, INC. PAGE_-!-OF PAGES
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Figure 3-1.--Average velocities for estimating travel tine for
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Storn sewer or road gutter fLow
Travel tine through tbe storm sewer or road gutter system to the roain
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ENYIROIYMENTAL IMPACT REPORT
GOLDEN PEAK REDEVELOPMENT
kcparcd for:Vail Associates, Inc.
P.O. Box 959
Avon, CO 81620
Alpine Engineering, Inc.
P.O. Box 97
Edwards, CO 81632
(970) 926-3373
Prepared by:
o
TABLE OF CONTENTS
I.O INTRODUCTION ..... Il.lscoPE ........1
I.2PROJECTDESCRIPTION. .....I
2.OMILLCREEKCULVERTEXTENSION .......I
2.1 CULVERTDESIGN ....2
2.2 FLOODPLAINALTERATION .........3
3.0 CONSTRUCTIONIMPACTS .........3
3.1 AIRQUALITY ........3
3.2 EROSIONANDSEDIMENTATION ....,4
3.3 CONSTRUCTIONDEWATERING... ..,......4
3.4 STREAMDIVERSION ........4
4.0 EXTERIORDRAINAGEPLAN .......5
5.0 NON-POINTSOURCESTORMWATERDISCHARGES .. ...... 5
5.I PARKINGSTRUCTURE.. .....5
5.2 SNOWSTORAGE ......6
6.0 MILLCREEKDIVERSIONSTRUCTURE ......6
7.0 MUDANDDEBRISFLOWHAZARD ........6
s.OREFERENCES. ......8
o
GOLDEN PEAK REDEVELOPMENT
ENVIRONMENTAL IMPACT REPORT
1.0 INTRODUCTION
1.1 SCOPE
Alpine Engineering, Inc. was retained by Vail Associates, Inc. (VAI) to prepare an
Environmental Impact Report to be submitted to the Town of Vail with an application for
Development Plan approval for the Golden Peak Base Area Redevelopment. The scope of
this report was defined through discussion between Alpine, VAI and Mr. Russell Forrest,
Environmental Planner for the Town of Vail. Environmental issues identified include:
l. Impacts of the Mill Creek culvert extension;
2. Definition of an exterior drainage plan;
3. Mitigation of non-point source stormwater discharges;
4. Determination of the adequacy of the existing diversion structure; and
5. Mud and debris flow mitigation plan.
I.2 PROJECT DESCRIPTION
VAI is proposing to redevelop the Golden Peak Base Area. A development plan for this
project was submitted and approved in 1984; the current submittal constitutes an amendment
to the 1984 plan. The redevelopment plan includes: l) replacing the existing Golden Peak
building with an improved ski portal; 2) improving skier access and traffic flow to the
facility; and 3) modiffing the base area with improved lifts, access and outdoor space.
Modifications to the lifts and planned increase in skier use of the base area will require
moving the existing stormsewer inlet out of the planned skier maze located near the bottom of
Lift 6. The stormsewer inlet is fed by the East Branch of Mill Creek, an artificial rectangular
channel which carries water diverted from Mill Creek for the purpose of flood protection.
VAI proposes to conved 378 feet ofthe open channel ofthe East Branch to buried
stormsewer and constructing a new inlet structure further up the ski slope out of the way of
converging ski traffic near the base area.
2.0 MILL CREEK CULVERT EXTENSION
The East Branch of Mill Creek is an artificial stream created to abate flood levels dwing the
spring runoff and summer stormflows along the West Branch of Mill Creek as it runs through
the center of the Town of Vail to Gore Creek. From the point of diversion, located above the
Golden Peak Base Area (see Site Plan, Exhibit 1), the East Branch of Mill Creek flows
through the base area between Lifts 6 and 12 and enters the existing stormsewer near the
Environmental lmpact Report Golden Peak Redevelopment
o
bottom oflift 6. Cunently, the East Branch consists ofa rip-rap-lined rectangular channel
with drop structures for energy dissipation near the entrance to the stormsewer.
The East Branch of Mill Creek is aligned across the Golden Peak base area at an angle to the
general flow of skier traffic. In order to allow skier and snowcat traffic across the open
channel, VAI places half culvert sections over the channel bed during the ski season and
plows snow over the culverts to provide a passable surface. This temporary piping of the
East Branch flow is problematic for several reasons: l) frequent maintenance is required to
allow safe skier passage through this area of high traffic and skier convergence; 2) snow is
packed into the channel, decreasing the flow capacity; and 3) the half culverts cause
significant disturbance to the stream bed.
VAI is proposing reconstruction and regrading of the Golden Peak base area. As part of this
redevelopment, the lifts will be realigned and the existing stormsewer inlet will be located in
the area of a planned skier maze. In order to accommodate these changes, and to eliminate
maintenance and traffic problems related to the artificial channel, VAI proposes to extend the
stormsewer culvert up the course of the East Branch of Mill Creek approximately 378 feet
from the existing stormsewer entrance (see Proposed Stormsewer Extension Plan, Exhibit 2).
This extension will be sized at a minimum to accommodate the 100-year snowmelt event
which was determined in a previous hydrologic study (Hydro-Triad, Ltd., 1983). The existing
stormwater culverts which carry flows from the East Branch of Mill Creek to Gore Creek are
oversized for the 100-year snowmelt event (95 cfs) and the 100-year thunderstorm event (160
cfs); the proposed extension will be designed commensurate with the existing system.
One alternative to the stormsewer extension was considered: replacing the existing
rectangular channel with a broad swale. This alternative would have many of the same
disadvantages as the existing artifrcial channel including: l) frequent maintenance required to
allow safe skier passage through this area of high traffic and skier convergence; 2) snow
packed into the channel, decreasing the flow capacity; and 3) potential overflow or escape of
flow from the artificial channel would result in damage to property. Extension of the
stormsewer with regrading to eliminate the channel cutting across the hill slope would allow
greater skier safety in the area of traffic convergence and greater control of the flood waters.
This alternative is more expensive, but is balanced by decreased maintenance costs over time.
2.T CULVERT DESIGN
The proposed stormsewer extension will consist of a headwall with a 66-inch comrgated metal
pipe (CMP), which then reduces to a 54" CMP aligned approximately along the existing
stream course. The existing stormsewer inlet located near the boffom of Lift 6 will be
removed along with the concrete bulkhead. Stormsewer manholes will be located for change
in alignment or grade of the pipe. A new stormsewer headwall and inlet will be located at
the top of the extension with a series of drop structures for energy dissipation and to provide
Environmental lmpact Report Golden Peak Redevelopment
o
some sediment removal. With the exception of the stormsewer inlet, the extension will be
located entirely at or below grade.
The proposed extension will be capable of transmitting 210 cfs, slightly in excess of the 100-
year snowmelt event and commensurate with the existing stormsewer capacity. Hydraulic
velocities within the stormsewer extension have been calculated to exceed current velocities in
the East Branch of Mill Creek. The use of conugated metal pipe is recommended over
smoo*r pipe as its increased roughness will partially abate velocity increases within the
stormsewer extension. Energy dissipating structures have been included within the design of
the stormsewer extension to mitigate increased velocities due to the replacement of rip-rap-
lined channel with culvert (see details, Culvert Extension Plan, Exhibit 2).
The capacity of a stormsewer is related to its cross-sectional area which may be affected by
debris and sediment accumulation within the pipe. To maintain the full capacity of the
proposed sewer extension, a sedimentation structure and trash screen will be provided at the
stormsewer inlet. In addition, VAI will clean and maintain the system as needed.
2.2 FLOODPLAIN ALTERATION
The East Branch of Mill Creek is not mapped on Federal Emergency Management Agency
Flood Insurance Rate Maps. The proposed construction is therefore not located within a
jurisdictional floodplain. The East Branch of Mill Creek is an artificial sheam originally
created by the Mill Creek Diversion Structure for the purpose of abating flooding on the West
Branch of Mill Creek. The existing stormsewer at the Golden Peak site has suffrcient
capacity to carry the 100-year flood event. In keeping with its intended use, the design of the
stormsewer extension will accommodate the same event as the existing system.
The East Branch of Mill Creek is classified as a "navigable waters of the United States" and
is within the jurisdiction of the U.S. Army Corps of Engineers (ACE) as mandated under the
Clean Water Act. Conversion of a portion of the East Branch of Mill Creek to below-grade
stormsewer requires notification of the ACE. As part of this environmental impact report,
Alpine prepared a letter of notification including a project description and site plan for review
by the ACE. The ACE will provide review and comment on the project and will make a
determination whether a 404 permit application is required. A copy of this notification is
presented in Attachment B. No response was received prior to submittal of this report.
3.0 CONSTRUCTION IMPACTS
3.1 AIR QUALTTY
An increase in diesel emissions and fugitive dust will result in air quality impacts dwing
construction activities. The proposed area of disturbance for the Golden Peak redevelopment
is less than 25 acres and therefore is exempt from fugitive dust permitting requirements.
Environmental Impact Report Colden Peak Redevelopment
o
Fugitive dust and diesel emissions will be controlled in accordance with standard construction
practices. Construction roadways used by heavy machinery will be watered three times per
day or as needed to control dust. The redevelopment ofthe Golden Peak base area will cause
no permanent degradation of air quality.
3.2 EROSION AND SEDIMENTATION
Areas disturbed by construction activities are subject to erosion and subsequent sedimentation
impacts downstream during storm events. Prior to the commencement of construction
activities, VAI will apply for a Colorado Department of Health, Water Quality Control
Division Stormwater Discharge Permit. The permit application will include current Best
Management Practices for erosion control and stormwater detention as required during the
proposed construction. Following issuance of the permit, construction activities at the site
will conform to all requirements of the permitting authority.
3.3 CONSTRUCTION DEWATERING
A geotechnical investigation (CTl/Thompson, Inc., 1983) of the Golden Peak site identified
the groundwater table to be as shallow as l0 feet below ground surface. It is anticipated that
free groundwater may be encountered during excavation activities during the proposed
redevelopment. Prior to commencement of excavation activities at the site, VAI will apply
for a Construction Dewatering Permit under the Colorado Wastewater Discharge Permit
System. The permit application will include current Best Management Practices for
groundwater discharge and sediment control. Following issuance of the permit, construction
activities at the site will conform to all requirements of the permitting authority.
3.4 STREAM DIVERSION
During construction of the stormsewer extension, discharge to the East Branch of Mill Creek
will be diverted at the Mill Creek Diversion Structure to the West Branch of Mill Creek. In
keeping with the purpose of the East Branch diversion as flood abatement, diversion of flow
will not occur during spring run-off or during the summer thunderstorm season. Construction
of the extension will be scheduled for the late summer or early fall when the likelihood of a
flood event is remote.
Diversion of East Branch flow may potentially impact wildlife and fish habitat along the
course of the stream. The Colorado Department of Wildlife (DOW) has been notified of the
proposed Golden Peak redevelopment construction activities in a letter requesting DOW
revierv and comment. A copy of this letter of request is presented in Attachment B. No
response was received prior to submittal of this report. VAI will coordinate all changes in
streamflow in the East Branch of Mill Creek due to construction activities with the DOW
thLroughout the life of the redevelopment project. VAI will conform to all requirements of the
DOW.
Environmental Impact Report Golden Peak Redevelopment
o
4.0 EXTERIOR DRAINAGE PLAN
An exterior drainage plan for the proposed redevelopment of the site is provided on the
Proposed Drainage Plan, Exhibit 3. In general, surface run-off generated from impervious
surfaces, including roadways, plazaand roof areas, will be directed to the stormsewer system
via drains, swales or gutters, as appropriate. The proposed parking structure is situated
below-grade with a landscaped surface. Subsurface drains will convey soil water from the
landscaped surface to surrounding native soils. Stormwater run-off from the landscaped
parking structure surface will be directed to the stormsewer system via drains, swales or
gutters. A detailed drainage plan will be submitted for approval by the Town of Vail as
required for the issuance of a building permit. In general, stormwater run-off following
redevelopment of the site will not increase over current levels. The existing stormsewer has
been determined to be adequate at this time.
A potential altemative to the below-grade parking structure, dependant upon market conditions
at the time of construction, is a 30-space surface parking lot (see Altemative Surface Parking
Lot, Exhibit 4). The detailed drainage plan for this alternative will address the mitigation of
the increase in stormwater water run-off due to the impervious parking lot area.
5.0 NON.POINT SOURCE STORMWATER DISCHARGES
5.I PARIilNG STRUCTURE
A recent study conducted by the Northwest Colorado Council of Governments and the Town
of Vail (Draft, March 1995) indicates that levels of pollutants, including sediment, dissolved
solids and oil, are found in stormwater run-off from parking surfaces and roadways in the
Town of Vail in similar proportions found in highly urbanized areas. The proposed
redevelopment of the Golden Peak base area will not significantly increase the area of
roadways associated with the site. In addition, traffic management to the site is anticipated to
result in no significant increase in vehicular use or trips to the site. The proposed below-
grade parking structure will have a landscaped surface, contiguous with the surrounding land
surface. Amounts of pollutants from vehicles will accumulate in the below-grade parking
areas at the same rate as in a surface parking area. However, a great advantage to a covered
parking area is that the removal and disposal ofaccumulated pollutants can occur under
controlled conditions as opposed to occurring with unpredictable storm events. Drainage
within the structure will capture run-off from all parking areas. The parking structure will be
provided with a &ain system with integrated sediment and oil traps for the removal of
accumulated pollutants. A periodic inspection, cleaning and maintenance program will be
implemented by VAI to ensure that the traps are working properly.
The alternative 3O-space surface parking lot will not have the advantage of being covered, but
will accommodate far fewer vehicles resulting in a decrease in total pollutant accumulation on
impervious surfaces. Mitigation of non-point source pollutants from this parking surface will
Environmental Impact Report Golden Peak Redevelopment
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be provided. Potential mitigation measures may include drainage to a subsurface sediment
and oil trap, or a grassed swale filter strip. VAI will conduct a periodic inspection, cleaning
and maintenance program to ensure that the mitigation measures are working properly.
5.2 SNOW STORAGE
Snow removed from roadways and parking areas also contain sediment, dissolved solids, and
oil. It is expected that snow removed from roofareas and plazas will contain significantly
lesser amounts of pollutants than areas subject to vehicular traffic. In general, snow removed
from roof areas and plazas will be stored where eventual melt water can either infiltrate into
soil or be diverted to the stormsewers. Snow removed from roadways and parking areas will
be placed in a designated snow storage area. Mitigation of non-point source pollutants from
this storage area will be provided. Potential mitigation measures may include drainage to a
subsurface sediment and oil trap, or a grassed swale filter strip. VAI will conduct a periodic
inspection, cleaning and maintenance program to ensure that the mitigation measures are
working properly.
6.0 MILL CREEK DIVERSION STRUCTURE
The Mill Creek Diversion Structure, located approximately 1,000 feet south of the existing
Golden Peak base area w€rs designed to split the flow of Mill Creek approximately 40% to the
East Branch and 600/o to the West Branch. Upon inspection of the diversion structure by
Alpine on May 22, 1995, it was observed that these gates are now absent. Discussion with
Mr. Paul Tesr*uide, VAI revealed that the structure has removable gates and that they have
been removed for the spring run-off to allow maximum flow through the structure. In the
absence ofthe gates, flow is controlled by an approximately two-tenths-of-a-foot difference in
invert elevations. At the time of inspection, flow to the two branches was split approximately
60-40 as intended. Both culverts branching from the diversion structure headwall were free of
sediment and debris, and appeared to be properly maintained.
The adequacy of the Mill Creek Diversion Structure is addressed in an engineering analysis
and schematic design prepared by Alpine as part of this Environmental Impact Report, and is
presented in Attachment C. The diversion structure appears to be adequate to accommodate
the 10O-year flood.
7.0 MUD AND DEBRIS FLOW HAZARI)
Mud and debris flow hazard areas are mapped on Town of Vail Hazard Maps. A portion of
the Golden Peak base area is located within an area designated "moderate debris flow hazard".
This delineated hazard area has been overlaid on the Golden Peak redevelopment site plan
(see Debris Flow Hazard Map, Exhibit 5). A debris flow within the delineated hazard area
could cause the blockage of the Mill Creek Diversion Structure or blockage of the proposed
stormsewer inlet, potentially causing diversion of flood waters towards homes or to the
Environmental Impact Report Golden Peak Redevelooment
Golden Peak base area. A debris flow is a catastophic and highly unpredictable ev€nt both
in time and space- Engineering mitigation is generally very expensive with no guamntee tbat
the mitigation structure has been placed in the path of the next major deb,ris flow.
VAI will be responsible, in the case of a debris flow causing blockage to the Mill Crcck
Diversion Stucture or the proposed stormsewer inlet point, for removing the blockAge and
restoring flow to the East and West Branches of Mill Creek.
o
Environmenta I Impact Report Golden Peak Redcvclopncnt
8.0 REFERENCES
nDesign Report Improvements to East Branch of Mill Creek, Golden Peak Development Vail
Colorado," Jan. 1985, Hydro-Triad, Ltd.
"Soils and Fowtdation Investigation, Proposed Golden Peak Building, Vail, Colorado",
November 22, 1983, CTl\Thompson.
"Vail Non-point Source Water Quality Management Plan", Draft, March 1995, Northwest
Colorado Council of Governrnents.
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Environmental Impact Report Golden Peak Redevelopment
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.''. . '. , ,. .June l; 1995 -..'
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,. .Mr. Bill Andree : . . . '- :,
P.O. Box 633
Minturn, CO 81645
C-omment, Golden Peak Redevelopmentl Vait, CO
. -'. . . JAI.is proposing to redevelop rhe Golden Peak Base Area of the Vail Ski Resort., A " .l. .F.- ----.r !.rv vvrsr.rr r, edJ\ r;r4)s flJ sa1 ul utc vall Jr(l lleson.; A
.:". .development plan fo5 this project was submitted and approvea in f 9S+; thelr11.", ,uU*in"t'i, . :iolltl.]l:jgfl:"d:.lt i".jl." le84-plan. rhe reaeverop**t pi* ilft;'ltr.jr.ing
. traffic florv to the facility; 3) modiging rhe base area *ith irpto.'.aiin",-;-".;;;;;"ia"",
spac!.: Modifications t" tr,"iin, -iE;;ffi,]*li,, ;ir;il;ffLi,?'"ili,ir;' require r^o-ui1e
-tt
=xisting
oot t.*lilnet out of the pranned skier mat ' .' . require moving rhe existing stormsewlr inlet out of the planned skier maze located n.", th. I l
9:-1"- of Lift 9. 'P: .srgtm9e1=t inlet is fed by the iit e;.h or rrrll ciee(-* *in.i"t'. :-'.'Y"^:'"'l'\" ..rus )rtrgr)E\t'er uuel lS IeO Oy tne.EaSt Branch Of lvllll Cfeek, an aftifiCiigctangl]lar chaiurgl u'hich carrjes rvater diverted fto- Mill Creek for the p"r"";;f;;;J'protection. VAI proposes to conl'ert 378 feet of the open channel of the East Branch to\,r trt\, tJct)t JJf<lllLlI Lt,
r ::l"d ttoTttY:T'..xtendingrhe existing stormsewer, ar:d constructing a new intet structure,. ,, fi'tter up tr,, ,riirroft;;;';f ,t";;;? il;;;il'#;;il;:'Jii",base
lroposes diverting the flow to tlie East Branch of Mill.Creek to'the Wesi Branch of Millat the existing diversion structure located approximately 1,000 r."t ,o*l-oi,i" ;;ld;;south of the Golden;tn;ilil;il;de east';
Creeh the prproposed construction will be scheduled fibr the fall when floods ',r\tJ_
fdwards Busiries Cenrer . P0- Box 97 . tdwards, Colo rado g1632 . (970) 926-3373 . Fax (9701 g2il33g0
May 3l; 1995 ..:. :-
:.. ' Mr, Mike Claffey '
..'....'U.S.li'rmyCorpsofEngineers.
402 Rciod Avenue, # A2
:
. Grand Junction, CO 815.01 r
.
r ' {Y*} review and comment on the pioposJ conversion of a portion of the East Branch of,, , .. Yitlcr::k to buried.srormsewer. Bhcrosed you u,ilr.find u riopfr.i b-ri;ilil;
.-lAl,rs proposrng ro redevelop rhe Golden peak Base Area of the Vail Ski Resort. A' development plan for this project was submitted and approved in 1984: th" "rr.r"r,r ",,r,r.;r,approved in 1984; the current iubmittal
io.ihe re84 pran. rhe red#;il;,;;il iil;;'lj';0"#,[| '
', .,,. l"fn" {p.t.lo the facliry; :l *"iiryi"}]il f;; ;;id d#iliil;:.J,.ffiHifi:. . r. uaruc. uow to ue ractllfy; J) modirying the:. space.. Modifications to the lifts and pt]-an ,.planned increase in skier use'of the base.area u,ill' :' .' . require m^o_ving the existing stormsewlr inlet out of the planned iki;; ;; il; n.* tt , '
bottom,of Lil u. In:,ioi",* ini; ;;;;j;;il;ffi;ffi il,tr ;J,*;ilffi,rectangular channel *'hich carries uater divertea rro- Mill creek fibr the'
up the ski sl ope out o f the way bf conrierging ski traffic n"* th" base area.
gned across area
p
over the channel bed during the ski season and
:1o.y lu.r ge c!1eng to p-rovide
" p^r"ui, ,*a;;. a;#o"rrry-pipi"g of the
rr'!r<u'rBur'1r G;lasurEl \\rucn calTles \rcter dlverted fiom Mill Creek for the purpose of flood, flol.:tign''.vAI proposes to convert 37g feet of the opin "r,-u*"r "f rh" i;L;;f ,;- ,; burled stormsewer,.exte4dingrhe existing stormsewer, and constructing a new inlet structure
of ltlill Creek ir
. '. .'.East Branbh flow i
: ' , allnrp cqfa "l,io. -'
yrs Lut\Er.s ro p-rovtoe.a passable surlace. This temporary piping of the
.tl lloo_,..**rc tor several-reasons:-. l) frequent maintenance is requirid.io' allow safe skier passage through this area of high trurn" ,"i *i.,
"o,.']. '' ,, ;.^L^J i-r^ rL^ ^L^,--t'skier convergence; 2) snow is,
e.ac\1d into rhe channel, decreasing,the flow capacity; and 3) the half culverrs cause.
tt. rs .arrgne<r across rne Uolden peak base area at an angle to the
In order to allow skier and'snowcat traffic aciosb the olen
-
Edwards Eusiness center. p.0. Boxgt . Edwards,colorado il6i2. o7o) 926-3313 , Fax (9701g26-3jgo
' .:
reclangufar channel with a broad swalej This alternative would havg il-v "i,r," same- disadvantages as the existing artificial r..t"ngutr, .1,;.1 ili"Gl 'iiii;q"*
,ainrenance
. .l
- required to allow safe skier-passase- rhrough it;, "r." oitigh traffii ana sUrr convergence; 2) .:' '' ' sngw packed.into the channbl, aeJtlasingitg flow."p*,ty; and 3) potential overllow or .
-'' '' ."
:': , esc..ape of flow fiom rhb artificial channel would result in iamage to property. Exension of' ' :. rhe'stormse*'er. wjth r-egrading ro eriminare ;;;;;r;;iing i=,,orr',r,Jiiri ,ro]" *oura| .,:..,':atloy gr3igr skiei *frthil;.;;..;fn;.;ilrr."." -o srearer conrro! of flbodt'' '" ' ""waters'": J[is altemative js mole expensive, but is balinced by decreased maintenance costs: : over timi.
. ll:::::1S me of vour determination of rhe need for' a 4l4permit for rhis project. If youha}€anyquestionsconcerningthisrequest,donothesitatetocaIlme.
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Jim Curnutte - Off-Site Improvenents *10
ORIGINAL
AGREEIqElilll TO TERMINATE ITEASES
THIS AGREEMEIIT TO TERMfNATE IJEASES (the "AgreemenL"), made
ef fect,i.ve E,he ?o ry day of //At/ 1995, is by and betrween VAIL
AssocIATEs, ffi t corEEE"o5Go-rporaEion ("vAr"), and vArIJ
RECREATIoN DISTRICT, a guasi-municipal corporaE,ion (nvRD") .
RECITAI.,S
WHEREAS, vAf and VRD, formerly known as Vail MetroPoliEan
Recreation DisErict or U{RD, entered ingo a Ground Lease, daEed
effect.ive tlay 27 , L965, whereby VAI leased Eo VRD and lrRD ]eased
from VAI a porE,ion of Tract. F, Vail Village, FifEh Filing, Eagle
County, Colorado, in the area commonly referred to as Golden Peak,
for VRD'S uge as E,ennis courtrs. The Ground Lease was amended on
November 11, 1969 by a First Amen&nent co Ehe Ground lrease, on
April 30, 1988 by an ArnendmenE, to Ground L,ease Relating Eo IJease of
f6nnis Courts/Golden Peak Base Facility, on April 30, 1988 by an
Anendnent Eo Ground Irease ReIaC j-ng go l,ease of Tennis
Courts/Children's Cent,er, and on December 2L' 1988 by a Second
AmendnenE go Ground lJease. The Ground Lrease, as amended, is
atEached hereEo as ExhibiE A and shall hereinafter be collectively
referred Eo as the "Ground lrease. r
!{IIEREAS, VAI and VRD enEered inEo a L,,ease, daEed effecCive l4ay
L, 1988, whereby VAI leased to l/RD and VRD leased from vAI
approximatsely 1,200 square feeL of conmercial space in the GoldenpElf luifding and pubfic parking spaces in the Golden Peak parking
1oE, both locaued aE 458 vail Va1ley Drive, Town of Vail , Eagle
CounLy, Colorado for VRD'g use as adminiscration offices and a
tennii pro shop. Such Lease is aEtached hereg,o as Exhibit, B and
shall hereinafter be referred Eo as Ehe "Pro Shop Lease-'l
WIIEREASi, vAf desires Eo redewelop Golden Peak, including,
without limiEation, Ehe Golden Peak building and VRD desires Eo
consolidat,e its tennis progrErms in the area commonly known as Ford
Park, Vail, Colorado.
WHERE"AS, relocating VRD's E,ennis courEs, adminisEratriwe
offices and Eennis pro shop will faciliEage an improved site plan
and yield beEt,er pedesC,rian and skier circulat,ion at Golden Peak
and iesurfacing VRD's Eennis courgs from hard courEs to clay court,s
will improve Ehe character and qualiEy of Ehe Eennis courts aE Ford
Park.
AGREEMETiI'T
NOW, THEREFOR, VAI and VRD respectively desire t,o tel:ninaEe
Ehe Ground Lease, Ehe Pro Shop Lease and any and alL ocher
leasehold inEeresus aE Golden peak which VRD may hold or claim Eo
hold whatsoever (collectively, Ehe 'rl-,easesu). In considerat,ion of
Ehe benefiLs and obligaEion! seE forth herein, Ehe receipE and
sufficiency of which is hereby acknowledged, Ehe parties hereEo
agree as f ollows:
1. TERMINATION OF AI{D RELEASE REGARDING LEASEHOLDS. (A)
VRD and VAI hereby E,erminate Ehe Leases and, further, VRD hereby
relinguishes any right what,soever Eo possess or claim Eo possess
any property under the auspices of the Leases.
(b) VRD hereby forever releases and discharges VAI from
all liabiliEy, claims, liens, demands. causes of action, danages,
costs and ecpenses whatsoever arising from or relat,ing in any way
Eo Ehe Ireases. The parEies int,end EhaE this release be interpreEed
aE broadly aE possible Eo release all claims relaE,ing to Ehe
Leases, including wichouE limitation, claims for breach of contracE
and clajlrs which are undiscovered, unaccrued and,/or unknown as of
2. CONSIDERATION.
so long as such clains relage in any way
In consideraEion for Ehe termination of
the dat,e of this Agreement,gO t,he IJeaSes.
Ehe Leases and \IRD'g release set fortrh in Section t hereof, VAI'
agrees t,o pay Three Hundred Ten Thousand Dollars ($Sf0,000) (Ehe
nResurfacing Fundsn) to VRD, which Resurfacing Funds shall be used
by t/RD for resurfacing and/or reconsirucEing Ehe exiscing Eennis
court,s at Ford Park to clay teruris courts as well as for any and
all landscaping or other recreat,ional ameniEies, whether at Ford
Park or elsewhere, as deemed needed by t/RD for improvement of IIRD's
tennis program. The Resurfacingr Funds are payable by vAf uo VRD on
the earlier of: (a) !!ay 30, 1995, or (b) Ehe daEe of execution and
recordat,ion of Ehis Agreemeng.
3. LICENSE FOR SIIMMER 1995. (a) Subject to SecEion 3(b)
below, VAI hereby grants ltRD a limit.ed license to use the Golden
Peak E,ennis court! and Eennis pro shop formerly leased E,o VRD under
the Leases (Ehe rlicensed Premises") during Ehe Period of !!ay 1,
1995 Ehrough Septernber 30, 1995 excepting Eherefrom the period ilune
5, 1995 thiough Jutre 12, L995 during which time bike races' sEaging
and ewenEs wilt be held by vAr or iEs licensees on or adjacenc Eo
Ehe r.,icenged premises, (Cne nr.ricense Periodi) for use. by vRD in
connect,ion with iEs sumer E.ennis progr€rm. Upon execuE,ion of Ehis
Agreementr, 1IRD agrees Eo Pay VAI a fee in Ehe amount of $300.00 for
the five month period of Ehe license (the nlicense Feen).
(b) 't RD agrees Eo uE e tshe Licensed Fremises in a
careful , safe and proper manner. VRD agrees Eo maintain Ehe
Licensed Premises iaa sightly, clean and sanitary condition at all
times during Ehe License Period. vRD shalf not use or permit Ehe
Licensed Premises Eo be used in any manner thaE may inEerfere with
or disturb the use and enjoyment of any owner, occupanE or oEher
person of or on property locaE,ed near Ehe l-,icensed Premises,
including, withoug-limieation, VAf. vAI, in its sole and absoluEe
discrecion, with or wichout cause, has Ehe right Eo terminate the
license granted VRD herein upon fourEeen days' writtren noEice Eo
\fRD. Upon such E,erminaE,ion, VAI shal1 refund to VRD a pro raEa
VNDTERM.AON
Ir/docr/lcrrcr
-2-Mry 25, 1995
portion of Che License Fee for any porEion of Ehe License Period
unoq)ired as of the date of trenninaEion.
(c) AE aLI Eimes during Lhe L,j-cense Period, vRD shall
carry and maintain, aE ifs sols cosE and elqpense, cormnercial
geneial liability insurance in an occurrence format in an amounE of
St,OOO,OOO per bccurrence; VAI shal1 be named as additional
insured as igs int,eresEs nay appear on such policy. .In addiEion,
vRD agrees Eo carry (i) - workers' compensation insurance in
accordance with Ehe provisions of Ehe Colorado l{orkers'
Compensatrj-on AcE for all VRD employees engaged aE Ehe Licensed
Premises and (ii) property insurance, in an anounts noE less Ehan
the full replacement cost of aI1 VRD'S personal properEy on or
abouE the Licensed Premises. VRD agrees to submit lo VAI
cerEificates of insurance evidencing such policies upon execution
of this Agreement.
(d) (i) Subject to vAls indennity under Section 3 (d) (ii)
below, \IRD agrees Uo indemnify, defend and hold harmless vAI , iEs
subsidiariesl affiliages, agents, officers, directors and enployees
from and against any and aI1 liabiliEy, claims, liens, demands and
causeE of Ection whatsoever arising out of any lose, costE, damage
or injury, including deaEh, of any person or damage to property. of
any tcind arising in- connection wieh the lJicensed Premises during
the lJicense Period.
(ii) vAf agrees to indemnify, defend and hold
harmless '\IRD, its agent,s, officers, directors and enployees from
and against any and aLl liabiliEy, claians, J-iens, demandle and
causes of act,ioir what,soever arising out of any loss, cos!, damage
or injury, including d.eath, of any person or dama-ge to propertsy.of
any kind'arising iri'connection with Ehe L,icensed Premises during
Eha License per:iod which is caused by Ehe gross negligence or
willful misconduct of vAI .
(e) AE Ehe end of Ehe License Period, VRD shalL prompEly
guiE and surrender Ehe Licensed Premises Eo VAI and VAI shall
iccept Ehe lricensed Premises in nas iso condition;. any equipment,
impr6vements or materj-als not removed by -VRD prior to surrender
shiff conclusively be deemed abandoned and may be disposed of- by
VAf withouE noEi;e or accountring therefor to VRD or any oUher
person.
4. MISCELIJAMOUS. (a) This AgreemenE contains the ent'ire
agreemenE and undersEanding of the parties wiEh respecE to Ehe
sifiect magtrer hereof. Ttreie are no rePresentationE, inducernenEs,
proirises or agreements, oral or oEherwise, not embodied herein.
iny ana all prior discussions, agreemengs, proposals,,negoEiations
and representagions relacing t'hereEo are merged herein.
(b) If any clause or prowision of this AgreemenE shal1
- 3 - MrY 25' 1995VRD'TERM.AOR
ntldc,.lla,r|
be held to be invalid in whole or in part, Ehen Ehe remaining
clauses and provisions, or portions Ehereof, sha1l neverEheless be
and remain in fu1l force and effect.
(c) No amendment, alEerat,ion, modificacion or addieion
Eo Ehis Agreement shall be valid or binding unless ocpressed inwriting and sigmed by the part,ies to be bound Ehereby.
(d) Any and all- warranties, provisions, righLs andobligations of the parEies herein described and agreed Eo be
performed subseguent to the terminat,ion of Ehis .A'greement shall
sunrive the terminaEion of this Agreement.
IN wfTt{ESS I{HEREOF, the parties hereto have executed Ehis
AgreemenE to become effective as of the dat,e set forth abowe.
VAIL RECREATION DTSTRICT VAII.,INC.
Ti l- 'l e .Tir,le:f-t+r.'ttc'J /ftalr/-
VRD.TERM.AGN
dtuc|/lr!|sr
-4-!t!y 25, 1995
EXHTBTT A
(AcEached Eo and forming part of
Agreenent, to Ternrinate lJeaaes
between VaiL Aeaociates, Inc.
and vail Recreational DisErict,dated ?c" *aV , 1995. )
GROUIID ITEiASE
(Attached)
A-1