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HomeMy WebLinkAboutcoa.lu.sp.Little Nell.A34870 ASPEN/PITKIN PLANNING OFFICE 130 South Galena Street Aspen, Colorado 81611/��)_ p� (303) 925-2020 LAND USE APPLICATION FEES City 00113 - 63721 - 47331 GMP/CONCEPTUAL - 63722 - 47332 GMP/PRELIMINARY - 63723 - 47333 GMP/FINAL - 63724 - 47341 SUB/CONCEPTUAL - 63725 - 47342 SUB/PRELIMINARY 63726 - 47343 SUB/FINAL 63727 - 47350 ALL 2-STEP APPLICATIONS - 63728 - 47360 ALL 1-STEP APPLICATIONS/ %OO OO CONSENT AGENDA ITEMS REFERRAL FEES: 00125 -63730 - 47380 ENVIRONMENTAL HEALTH 00123 -63730 - 47380 HOUSING 00115 - 63730 - 47380 ENGINEERING SUB -TOTAL County 00113 - 63711 - 47431 GMP/GENERAL - 63712 - 47432 GMP/DETAILED - 63713 - 47433 GMP/FINAL - 63714 - 47441 SUB/GENERAL - 63715 - 47442 SUB/DETAILED - 63716 - 47443 SUB/FINAL - 63717 - 47450 ALL 2-STEP APPLICATIONS - 63718 - 47460 ALL 1-STEP APPLICATIONS/ CONSENT AGENDA ITEMS REFERRAL FEES. 00125 -63730 47480 ENVIRONMENTAL HEALTH 00123 - 63730 47480 HOUSING 00113 - 63731 -47480 ENVIRONMENTAL COORD. 00113 - 63732 - 47480 ENGINEERING SUB -TOTAL PLANNING OFFICE SALES 00113 - 63061 - 09000 COUNTY CODE - 63062 - 09000 COMP. PLAN - 63066 - 09000 COPY FEES - 63069 - 09000 OTHER SUB -TOTAL Name: �" +���L �� `� ALL Phone: TOTAL Address: Project: — Check # 1 Additional Billing: — Date: # of Hours: V 0 CASELOAD SUMMARY _SHEET City of Aspen DATE RECEIVED: 15 $ / DATE COMPLETE: PROJECT NAME: (i Project Address: APPLICANT: Applicant. Address: REPRESENTATIVE: Representative Address/Phone: TYPE OF APPLICATION: PAID: OYES NO AMOUNT: 1 STEP APPLICATION: P&Z MEETING DATE: DATE REFERRED: 2 STEP APPLICATION: CC MEETING DATE: DATE REFERRED: REFERRALS: City Attorney City Engineer Housing Dir. Aspen Water City Electric Envir. Hlth. Aspen Consol. S.D. PARCEL ID AND CASE NO. 3illl-,?l STAFF MEMBER: VL1 M6p l r Mtn. Bell Parks Dept. Holy Cross Fire Marshall Fire Chief Roaring Fork Transit PUBLIC HEARING: YES NO INITIALS: PUBLIC HEARING: YES NO INITIALS: School District Rocky Mtn Nat Gas State Hwy Dept(GW) State Hwy Dept(GJ) B1dg:Zon/Inspect Roaring Fork Energy Center Other FINAL ROUTING: DATE ROUTED: INITIAL: City Atty City Engineer Bldg. Dept. Other: FILE STATUS AND LOCATION: r TABLE OF CONTENTS CONCLUSIONS 1 1.0 PLRPOSE AND SCOPE OF STUDY 2 Fig. 1. 0 -1 - Location Map 3 2.0 PROPOSED DEVELOPMENT 5 3.0 SITE CONDITIONS 7 4.0 SUBSURFACE ODNDITIONS 8 4.1 Subsoils 8 4.2 Groundwater 10 5.0 BUILDING FOUNDATION CONSIDERATIONS 11 6.0 SITE GRADING 12 6.1 Proposed Grading 12 6.2 Stability Considerations 12 6.3 On -Site Surface Drainage 14 6.4 Off -Site Surface Drainage 14 7.0 GROi) TWATER 16 7.1 Groundwater Regime 16 7.2 Potential Lnpacts 17 7.3 Mitigation Concepts 17 8.0 SOIL CORROSI VI TY 19 9.0 ADDITIONAL STUDIES 20 10.0 LIMITATIONS 21 APPENDIX A - FIELD F�LORATION AND LABORATORY TESTING FIGS. A-1 AND A-2 - LAGS OF EXPLORATORY BORINGS FIG. A-3 - LEGEND AND NDTES FIGS. A-4 THROUGH A-9 - GRADATION TEST RESULTS TABLE A -I - SUMMARY OF LABORATORY TEST RESULTS PLATE 1 - SITE PLAN AND PROFILE SHOL,TING LOCATIONS OF EXPLORATORY BORINGS AND PROPOSED GRADING Chen& Associates CONCLUSIONS 1. Subsoils: The subsoils encountered in Soles 1 through 3 on the slope consist of the earthflow, deposits which are comprised of unstratified, angular to subangular cobbles, gravels and occasional boulders in a clayey sand to sandy clay matrix. The subsoils in Holes 4 through 6 on the north portion of the site consist of existing fill and/or natural sandy clay to depths between 10 and 15 feet overlying relatively clean granular glaciofluvial deposits. Numerous cobbles and boulders were encountered to a depth of about 30 feet. 2. Foundation Considerations: The dense to very dense granular soils under- lying the proposed hotel location are suitable for support of spread footing foundations at relatively high allowable bearing pressures. We anticipate an allowable soil bearing pressure on the order of 6,000 psf. 3. Site Grading: The major factors which will influence slope stability with respect to the proposed grading are potential shallow groundwater and fill placement on the slopes. The extent and depth of the fill placed on the slope should be limited. Additional slope stability analysis will be conducted after further field data are gathered in the Spring of 1986. 4. Groundwater: Groundwater mitigation measures consisting of subsurface drains in the slope and underdrain systems for the building may be re- quired. These relatively shallow mitigation measures should not affect performance of the existing well near the north side of the site. Chen & Associates - 2 - 1.0 PURPOSE AND SCOPE OF STUDY This report presents interim results of Phase II of a preliminary geo- technical study for the Little Nell Base Development, Aspen, Colorado. The site vicinity is shown on Fig. 1.0-1 and the project site is shown on Plate I. The study was conducted for the purpose of developing preliminary foundation recoc endations, evaluating impacts associated with proposed site grading and evaluating potential impacts of site development on gxisting groundwater con- ditions. The study is being conducted in general accordance with our proposal to Aspen Skiing Company, dated October 22, 1985. Wee have completed Phase I of the study, a preliminary engineering geologic investigation based on site re- connaissance, as reported under our Job No. 1 990 85 on November 4, 1985. The Phase II field exploration program, consisting of exploratory borings completed as groundwater monitoring wells, was conducted to -obtain information on subsurface conditions. Material samples obtained during the field explora- tion program were tested in the laboratory to determine the classification and index properties of the on -site soil. 'three of the borings were located on the upper portion of the site in the area of proposed slope excavation to evaluate soil and groundwater conditions as they will relate to excavation. The remaining three borings were located on the low lying north portion of the site to explore subsurface conditions at the location of the proposed hotel and to explore groundwater conditions in the area of the existing well and the area of a suspected spring near the west site boundary. The results of the Chen & Associates ,t, GOLF COURSE ' << j /` / • / J U spefi r 04 �'�� • •T" a .o ' J i SITES 1� LITTLE NELL,,,, BASE DEVELOPMENT 8 G i Pits 0 SCALE: 1'. 200 ill 00' 1 1122 85 Chen & E-SSOCIate; LOCATION MAP 1.0-1 - 4 - field exploration and laboratory testing were evaluated to develop preliminary recommendations for building foundations, site grading and groundwater mitiga- tion. 9his preliminary study will not be complete until groundwater monitor- ing is completed in the spring of 1986. At that time, the analysis and report will be completed. The results of the field exploration and laboratory testing are presented in Appendix A. This report has been prepared to sunnarize the data obtained during this study and to present preliminary conclusions and recommendations based on the proposed construction and the subsurface conditions encountered. A discussion of geotechnical engineering considerations related to developrrrent of the pro- posed project are included in this report. Chen & Associates • • - 5 - Conceptual plans indicate the proposed 'rase development will include a 96-unit hotel near the northeast corner of the property. A pedestrian/ commercial area is planned at approximately the existing grade of Durant Avenue. Much of the proposed commercial area will be earth sheltered, con- structed below grade into the toe of the slope. New ski base facilities, including a higher capacity lift or gondola, are planned just upslope of the hotel and commercial facilities. We understand the proposed hotel will have three levels above grade and two parking levels below grade. Since the development is in the conceptual stage, the proposed type of construction and anticipated structural loadings are unknown at this time. assume the structures will be of reinforced concrete or reinforced concrete and steel frame construction. Based on our understanding of the proposed structure, we anticipate maximum column loads on the order of 500 to 700 kips. `Ib accommodate the planned base facilities and improve the grade of the ski slope, extensive site grading of the lower mountain slope is planned. ahe generally convex portion of the slope on the project site will be excavated to provide a more uniform slope as shown on Plate I. Excavation depths on the slope range to about 25 feet. Subsequent to our field investigation, we were provided with a revised grading plan which indicated large quantities of fill will be placed upslope of the project site. Fill depths up to about 25 feet are now proposed in that area. Chen & Associates • • - 6 - If the design varies from the project description presented above, the recommendation presented in this report should be reevaluated. Men a speci- fic project configuration is developed, a geotechnical review of the proposed project should be conducted and additional exploration and analysis as re- quired performed. Chen & Associates • • - 7 - 3.0 SITE CONDITIONS The site is located south of Durant Avenue between Spring Street and Galena Street near the base of Aspen Mountain. 'ihe site boundary is indicated on Plate I. there are several existing structures on the northern part of the site including the Aspen Mountain Ski Company offices, maintenance shop, lift ticket office, and the Little Nell Restaurant and associated businesses. An existing ski lift is located on the eastern portion of the site. The North of Nell commercial and condominium building is located near the northwest corner of the site. An existing well and pump house are located just north of the northern property boundary. Existing condominium and residential structures are located near the east and west boundaries of the site. The ski trails on Aspen Mountain are located south and upslope of the site. Approximately the northern one -quarter of the site is relatively flat. The southern three-quarters of the site on the lower slopes of Aspen Mountain slope down from south to north. The existing slope on the project site ranges from about 25% to 33%. Slopes less than 20% are present immediately south of the site with much steeper slopes further south up the mountain. The center porton of the site is the toe of a large lobate earthflow. The surficial geo- logy on -site and upslope of the site is discussed in our Phase I (prelhninary engineering geologic investigation) report. Chen & Associate~ ' 4.0 SUBSURFACE CONDITIONS 4.1 Subsoils Subsurface exploration was conducted as described in Appendix A. Holes 1 through 3 were drilled on the upper portion of the site in the large lobate earthflow deposit. Holes 4, 5 and 6, drilled in the relatively flat northern one -quarter of the site, penetrated a layer of existing fill and colluvium overlying granular glaciofluvial deposits. Zhe earthflow deposit encountered in the borings consists of unstrati- fied, angular to subangular cobbles, gravels and occasional boulders in a clayey sand to sandy clay matrix. Layers of sandy clay and clayey to very clayey sand were encountered in Holes 2 and 3. Penetration resistance values indicate the granular materials are generally medium dense to very dense. However, the clayey sand at the bottom of Hole 2 was loose. Very stiff sandy clay was encountered in the lower 7 1/2 feet of Hole 3. We have conducted previous exploration in the vicinity and upslope of the site which indicates that most of the gravel, cobbles and boulders are aplite porphyry with minor amounts of shale and limestone which were probably derived from the Beldon Formation, and minor amounts of sandstone. The subsoils encountered in Holes 4, 5 and 6 consist of 11 to 15 feet of existing fill and/or natural sandy clay colluviun overlying granular glacio- fluvial deposits. She existing fill materials consist of varying mixtures of sand and clay with cinders. Our observations and the penetration resistance values indicate the existing fill materials are erratic in ccinposition and degree of compaction. VL- did not determine the vertical and lateral extent of Chen & Associates - 9 - fill on the site as a result of this study. However, fill was encountered in two of the three borings drilled in the level area of the site. Sandy clay colluviun was encountered just above the granular subsoils in Holes 4 and 6. Based on penetration resistance values, the clay is soft to medium consistency. Granular subsoils were encountered in Holes 4, 5 and 6 at depths between 11 and 15 feet. Those materials generally consist of slightly silty to silty, sandy gravel with cobbles and boulders. Lenses of slightly silty to silty sand were encountered at depth. Extremely difficult drilling conditions in- dicating relatively large quantities of cobbles and boulders are present at about 15 to 30 feet in depth. Granular materials with smaller grain sizes and less difficult drilling conditions were generally encountered below that depth. The granular materials in Holes 4, 5 and 6 were derived principally from relatively hard granitic rock away from the immediate vicinity of the site. The rock fragments are generally subrounded as opposed to the angular to subarg ular rock fragments in the earthflow deposit. Penetration resistance values indicate most of the glaciofluvial deposits are very dense. However, samples of medium dense to dense sand were obtained from Holes 4 and S at a depth of about 40 feet. The results of grain size analyses conducted on samples of the granular subsoils from the borings are presented on Figs. A-4 through A-9 in Appendix A. Chen & Associates • • - 10 - 4.2 Groundwater Groundwater monitoring walls were installed in all of the exploratory borings, as described in Appendix A. The water levels imasured in the borings are shown the lags of Exploratory Borings, Figs. A-1 and A-2 in Appendix A. The water levels imasured in Holes 2 and 3 range from 29 1/2 to 32 1/2 feet. Water was not encountered in Hole 1 to a depth of 26 feet. Water was not encountered in Holes 4 and 6 to depths of about 50 feet and 26 feet, respectively. Observation wells were installed in those two holes to depths 46.5 feet and 24 feet, respectively. The crater level in Hole 5 stabi- lized at a depth of about 40 feet. A water level of about 34 feet has been reported in the cell just north of Hole 5. The corresponding elevation of that water level is within 2 to 3 feet of the water level elevation measured in Hole 5. A water level profile was estimated based on the water level readings in the borings as shown on Plate I. Chen & Associates 5.0 BUILDING FOUNDATION CONSIDERATIONS The dense to very dense granular subsoils underlying the proposed hotel site are suitable for support of spread footing foundations at relatively high allowable bearing pressures. As previously noted, we assure the maximum anti- cipated column loads will be in the range of 500 to 700 kips or less. Based on our understanding of the proposed construction and the preliminary explora- tion, wo anticipate spread footings placed on the natural undisturbed granular soils may be designed for an allowable soil bearing pressure on the order of 6,000 psf. Those materials were encountered at a depth of about 11 feet in Hole 4. Existing fill materials and clay will have to be removed before placement of foundations. However, the proposed two -level basement would indicate excavation beyond the expected depth of fill and clay. Once specific structural types and locations have been determined, a design level soil and foundation study should be conducted to determine foundation design criteria. Chen & Associates - 12 - 6.0 SITE GRADING 6.1 Proposed Grading The grading proposed on and above the site is summarized by the contours and profile shown on Plate I. At the time of our field exploration, �%;e under- stood the planned grading would consist only of excavation. Wb now understand it is proposed to place the excavated material upslope above the excavated area in the shaded area shown on Plate I. The intent of the fill placement is to dispose of the excavated material and to improve the configuration of the ski slope. the preliminary grading plan indicates cut depths up to about 25 feet and fill depths up to about 25 feet. 6.2 Stability Considerations The stability of a slope depends on the engineering properties of the subsurface materials, the geometry of and interaction between the various sub- surface units, and the groundwater conditions. A limit equilibrium stability analysis calculates a factor of safety, which is the ratio of forces resisting slope movement to the forces tending to cause slope movement along an assumed failure surface. To conduct a stability analysis, it is necessary to realistically model all of the above factors. For the proposed grading, it is necessary to con- sider the effects of changing all of those factors both above and below the graded area. In general terms, excavation into the toe of a slope can reduce the forces resisting slope movement and placement of material on the top of Chen & Associates - 13 - the slope can increase the forces tending to cause slope movement. 'Therefore, both grading actions are destabilizing influences. A destabilizing influence is one which reduces the factor of safety, but not necessarily to an unac- ceptable level. A detailed stability analysis was not proposed or conducted as a part of this preliminary study. The grading proposed at the time we initiated our study would have essentially resulted in unloading the existing slope by re- moval of the lower bulged portion of the slope. `That grading would not be a major destabilizing influence; the major concern was to identify potential shallow groundwater levels or seepage conditions. As previously noted, we now understand fill placement on the slope above the excavation is planned. Sur- charging the excavated slope will have a destabilizing influence. Holes 1 through 3 were primarily intended to explore the materials which will be excavated and determine groundwater levels. water levels 32 1/2 and 29 1/2 feet below the proposed grade were encountered Holes 2 and 3, respec- tively. Nb expect a rise in those water levels during the spring and early summer period. The water levels in the exploratory borings will be checked during that period. A groundwater level near the final ground surface planned and seepage through the cut face .will have destabilizing influences on the slope. After the data have been gathered, the influence of the higher ground- water levels will be studied. Additional study including detailed stability analyses will be required to evaluate the impact of the proposed fill on the slope. Although we expect some fill placement will be possible, we do not have enough information at this time to comment on the degree of destabilization which will. be induced by the proposed fill. Some of the proposed grades are significantly steeper than Chen &Associates - 14 - the existing grades near the east side of the proposed fill. Fbr planning purposes, we suggest the extent and depth of the fill be limited. Prior to further evaluation of the impacts the planned grading will have on slope stability, water level information must be obtained during spring runoff. Pdditional field exploration required to analyze the effects of the proposed fill placement should be done at that time. The present water level in Hole 3 indicates groundwater could impact the toe of the slope. Groundwater mitigation concepts are discussed in Sec- tion 7.3 of this report. 6.3 On -Site Surface Drainage Good surface drainage should be provided to protect slope faces fram sur- face runoff. All slope faces should be protected against erosion by revegeta- tion or other methods. In addition, positive surface drainage should be provided away from buildings to prevent surface water infiltration into backf ill. 6.4 Off -Site Surface Drainage As stated in our previous preliminary engineering geologic investigation report, potential off -site impacts to the proposed development include the potential for flood and debris flow events entering the site. The existing Copper/Spar Gulch and Vallejo Gulch drainages discharge near the top of the Little Nell earthflow. As previously recarxriended, the potential flood/debris flow risk should be studied by a surface water hydrologist and evaluated in a Chen &Associates • • - 15 - comprehensive eater/flood routing study. pacts associated with the proposed grading. Tie study should consider the im- Chen & Associates tWIM 7.0 GROUNDWATER 7.1 Groundwater Regime A projection of the groundwater levels in the holes along a longitudinal section through the site is shown on Plate I. Our experience in the area indicates water levels on Aspen Mountain can be quite shallow and with sig- nificant fluctuation due to seasonal runoff. The lower portion of the site and the well near the north site boundary are underlain by relatively clean glaciofluvial deposits. The well taps an aquifer of relatively high perme- ability and large areal extent. The'earthflow deposit upslope has consider- able fines content and the soils are probably much less permeable than the glaciofluvial deposits. The groundwater system in the earthflow deposit probably contributes little recharge to the glaciofluvial aquifer compared with total available recharge. Seasonal fluctuations in water levels within the earthflow deposit should have little impact on the water levels in the aquifer tapped by the well. We understand seepage has been reported in the vicinity of Hole 6 on the northwest portion of the site. We also understand that seepage may have resulted from a broken waterline upslope. Based on the groundwater levels in Holes 4 and 5 and the absence of water in Hole 6, we do not believe the reported seepage resulted from a high groundwater level. It is possible surface runoff or water from a broken waterline could manifest itselE as seepage at that location due to the relatively low permeability expected of the shallow clay soils. Chen & Associates :7 - 17 - 7.2 Potential Impacts Me primary impact groundwater will have on the proposed project is the potential effect on stability of the regraded hill slope above the building sites. Based on the present water levels, there appears to be a potential for shallow crater conditions or seepage to occur near the toe of the proposed cut. water levels will be measured in the monitoring wells throughout the spring and early summer of 1986 to better evaluate the potential groundwater impact on grading. Another potential impact is the groundwater mitigation measures on the slope to effect the performance of the existing well. In our opinion, the relatively shallow mitigation crnasures which may be required on the slope will not significantly impact the well production. 7.3 Mitigation Concepts It is likely subsurface drainage measures will be required to prevent high water levels and seepage in the proposed cut. Although subsurface drain- age recam-endations will depend on additional exploration, monitoring and analysis, we suspect transverse trench drains on the order of 10 to 15 feet deep on the lower portions of the cut may be necessary. Chen &Associates Below ground construction on the site should be protected by underdrain systems. Although the present water level in Hole 4 is well below the proposed lower floor level, our experience in mountain areas indicates wet basement conditions can result from snow melt infiltrating the subsoils around structures. Chen & Associates - 19 - 8.0 SOIL CORROSIVITY We understand there have been problems in the area with corrosion of buried metal pipes. Wt treasured water soluble sulfate contents and pH of four samples of the materials Erom the earthflow deposit to determine whether those factors would contribute to corrosion of buried metal. The water soluble sulfate contents range from 0.001 to 0.007 and pH ranges from 7.0 to 7.4 as shown in Table A-1. The cater soluble sulfate contents are low and the pH's are neutral to slightly basic. Therefore, those factors will not contribute to corrosion of buried metal. The electrical resistivity of a soil will indicate it's corrosivity to buried metal. Some of the clayey materials in the earthflow deposits are likely to have relatively low resistivities, especially at high moisture contents. Wb do not expect the granular glaciofluvial soils at the north end of the site to have resistivities low enough to be of concern. If buried metal pipes are to be embedded in the earthflow deposits, or in the existing clay or fill materials near the north end of the site, soil resistivity sur- veys should be conducted in the field at the locations of the proposed pipes. Chen & Associates • - 20 - 9.0 ADDITIONAL STUDIES The recotmwndations presented in this report are preliminary in nature. Additional studies will be required to address building foundations and site grading. A design level foundation study should be conducted in the proposed hotel area once plans are more definite. A thorough study of the conditions effecting the stability of the slope should be conducted if any fill placement is proposed on the slope. Tie studies cannot be completed without high groundwater level information obtained during spring runoff. Additional studies are also warranted to define the surface water hydrology of the site and evaluate the flood and debris flow'risk. Chen & Associates 0 0, - 21 - 10.0 LIMITATIONS This report has been prepared in accordance with generally accepted geotechnical engineering practices in this area for use by the client for preliminary design and planning purposes. The conclusions and recommendations submitted in this report are based on the data obtained from the widely spaced exploratory borings drilled at the locations shown on Plate I. Additional studies have been recaTunended to further evaluate site geotechnical condi- tions. If you have any questions or if we can be of further assistance, please contact us. CHEN & ASSOCIATES, INC. °` 1. R Alan Claybourn, E. • I `Y • ' - ;Ur/'3 and "sneering Geologist Reviewed By Harold Holling rth, Jr., P.E. AC/eac cc: sign 4%brkshop, Inc. Attention: Mr. Bill Kane Chen R Associates APPENDIX A FIELD EXPLORATICN AND LABORATORY TESTING PROGRAMS Chen & Associates Field Exploration Progran The field exploration program was conducted from November 5 through 8 and 11, 1985. Six exploratory borings were drilled at the locations shown on Plate I. Locations and elevations of the borings were surveyed by the client's surveyor subsequent to drilling and given to us prior to preparing this report. The borings were advanced through the overburden soils with 4-inch dia- meter continuous flight augers. The borings were logged by a representative of Chen & Associates, Inc. Samples of the subsurface materials were taken with a 2-inch and a 1 3/8-inch I.D. spoon sampler. The samplers were driven into the various strata with blows from a 140-pound hammer falling 30 inches. This test is the standard. penetration test described by ASTM Method D-1586 when the 1 3/8-inch I.D. sampler is used. Penetration resistance values, when properly evaluated, indicate the relative density or consistency of the soils. Depths at which the samples were taken and the penetration resistance values are shown on the Lags of Fxploratory Borings, Figs. A-1 and A-2. Groundwater monitoring wells were installed in all of the borings by placing slotted plastic casing wrapped in filter fabric to near the bottoms of the holes. Granular backfill was placed around the casings. Steel surface casings with locking caps w-�re embedded in concrete at the tops of the wells for protection. 'lhe tops of the casings were placed flush with the ground surface. Measurements of the water level were made in the borings by lowering a weighted plumbline into the monitoring wells twn days to seventeen days Chen & Associates - 2 - subsequent to drilling. The depths of the water levels measured and the number of days subsequent to drilling are shown on the Logs of Exploratory Borings. Laboratory fisting Progran Samples obtained fron the exploratory borings were examined and visually classified in the laboratory by the project engineer and project geologist. The laboratory testing conducted included standard property tests, such as natural moisture content (ASTM D-2216), dry unit weight, grain size analysis (ASTM D-422) and liquid and plastic limits (ASTM D-4318). The percentage of water soluble sulfates in general accordance with "Standard Methods for the Examination of Water and Wastewater, 15th ed.," and the pH were determined for selected samples. Results of the laboratory testing program are shown on rigs. A-4 through A-9 and in the attached Summary of Laboratory Test Results, Table A- I. The laboratory testing was conducted in general accordance with applicable ASTM standards. Chen & Associates r Hole 1 Hole 2 Hole 3 E1.=8041.1' E1.=8012.6' E1.=7973.6' Proposed Grade (Typical) 0 :b 0 5 32/ 12o•' •o- 0 E 10 0': 24/12 22/12 ° 107 WC=13.9 00=98.7 19/12 +4=10 WC=9.3 -2oo=46 15 +4=78 -2oo=6 LL=34 PI=16 32/12 IS LL=27 WSS=0.007 °o- PI=7 pH=7.2 WSS=0.00I-- t 6/ t 2 u, P H=7.0 u' u WC=12.0 u 20 28/12 24/12 +4=45 20 = WC=5.8 0. -200=21 r +4=65 LL=28 CL o O -200=10 PI=11 0 ° WSS=0.003 -a 'a �a. pH=7.4 25 36/t2 10", 28/60 6 •o 25 '. 17 30 25/12 —� 40/12 30 6 2.17 35 38/12 25/12 35 8/12 WC=16.3 WC=10.9 +4=5 +4=28 -200=31 -200=73 LL=29 LL=35 40 PI=12 --� F i=i 6 12 40 WC=20.0 -2oo=68 LL=29 PI=8 1 1122 35 Chen & Associates LOGS Of EXPLORATORY BORINGS Fig. A -I Hole 4 Hole 5 Hole 6 E1.=7940.0' E1.=7938.4' E1.=7938.0' 7940 7935 7930 52/12 4/12 13/t2 15/12 e 0 q 7925 53/12 V,br. o. 40/6 . 7920 :o 00: 0, —56/6: 0 o. WC=1.4 Estimated +4=54 age 40/3 Lower Flnor '.' -200=8 Level 7915 °• 50/6 a r m o 120/8 o: o WC=4.3 ° +4=4o 200=13 7910 53/12 a' O°. m —1 75/12 wC=4 3 +4=16 7905 ;i -200=8 7940 7935 7930 7/12 WC=21.2 -200=78 LL=34 PI=11 7925 Wss=0.003 pH=7.4 75/8 7920 7915 --j m r m C D —1 J Z 7910 j m --J{ m m 7905 7900 42/12 :o o; WC=8.0 50/6 13'i6 +4=8 — -200=26 3 NP 19/12 wC=8.6 +4=1 -200=7 7900 7895 �. , 7895 r a p.o N o :po 7890 68/6 7890 r b• 110/8 D 0 7885 7885 Z M D N rJ N 00 Vl LEGEND: n ® ravellnd a l i so To , s, p gravelly, silty, clayey, moist, dark brown. C Pizol Crushed rock fill. O n ®Fill, varing percentages of sand and gravel, clayey to silty, occasional sandy clay, generally not compact, moist, brown to black, cinders. Clay (CL), low to medium plasticity, sandy, silty, medium to very stiff, moist to very moist, yellowish brown to brown, lenses of clayey to silty sand, scattered gravel and, cobble. Sand (SP-SM), fine to coarse grained with gravel, slightly silty, medium dense to very dense, light moist to wet, light brown. 17771 Sand (SC), fine to coarse grained with gravel, clayey to very clayey, loose to very dense, light moist n. to wet, mixed browns. Sand (SM), fine to coarse grained with gravel, silty, dense to very dense, light moist, light brown. Gravel (GP-GC),fine to coarse grained with cobbles and boulders, slightly clayey sand matrix, medium ° dense to very dense, moist to wet, mixed browns. aGravel (GC), fine to coarse grained with cobbles and boulders, clayey sand to sandy clay matrix, medium dense to very dense, moist to wet, mixed browns. Gravel (GP -GM), fine to coarse grained with cobbles and boulders, sandy, slightly silty to clean, very dense, light moist to wet, light brown. Drive sample, 2-inch I.D. California liner sample. Drive sample, Standard Penetration Test, 1 3/8-inch I.D. split spoon sample. 24/12 Drive sample blow count. Indicates that 24 blows of a 140-pound hammer falling 30 inches were required to drive the California or SPT sampler 12 inches. 19 Indicates PVC pipe installed in hole to depth shown. 6 Depth to water level and number of days after drilling measurement was made. —0-- Depth at which test hole caved. fPractical rig refusal. NOTES: 1. Exploratory borings were drilled on November 5 through 8 and 11, 1985 with a 4-inch diameter continuous flight auger. 2. Locations of borings were surveyed by the client's surveyor. 3. Elevations of borings were, surveyed by the client's surveyor. 4. The lines between materials shown on the boring logs represent the approximate boundaries between material types and the transitions may be gradual. 5. Water level readiny5 shown urr Lhe iugs were made at the time and under conditions indicated. Fluctuations in the water level may occur with time. 6. Laboratory Test Results: WC=Water Content CO., r DD=Dry Density (pcf); c +4=Percentage retained on No. 4 Sieve; z -200=Percentage passing No. 200 Sieve; LL=Liquid Limit (); z P1=Plasticity Index (�); NP=Non-plastic; o WSS=Water Soluble Sulfates M m pH=Soil Acidity. cn , F-- W Q l.L O LU J CD d < C� f- O m d J LL O c coF � F N T I'l c co Y T (D Q) T " Q1 > 41 > N > > N U > N U > ru C T In > _0 Cn -D u o� m >-rD I-N m m rD C C > `^ a >T L- r0 >• L V) > L > m >T Co rD .— ,n >` U) b >T _0 _0 -0 cr •— C f0 L Q) C N •— C c m m •— C — m •— — IN Vl : Ln �D .--. U U V) V1 V) Ln Vl V1 •— V) •— V) Q) �p V7 v O N V• n n p M p O C. (D O o C) r rK N �D o0 J J r u 0 �r co u. m N M N N M N e Y=8� � C) �„� •— M co co w N �D N N co O cV S M N �D S J > co p U- in v� -1 co O c ^ N S U\ S J y � r a y C ro= 00 J � r co Ol O M O S (D M rt p p = J cy-\ M U\ p N �o O co -T Z Z F r Ln C) Ul U U 111 U1 p U\ 0 i y O N Lj-\ M O N U\ M O -zr Ol -T i J O I S L"1 W Q U O co V) 4 0 z z W Z U) J U) w CC 7 U) LIJ 0 • v c Ln T T O a T T - L (V L T cy) > CT _ rD - C L. (D N (X Ln Ln M O r N 7 J Y V O •I O � O r J -J r r Z Z 8 u •"'u co co O r J v � Y K � J y < r r u = Y _ Z ] 1l � co N Z r U1 U-\ O � O J ` y o J O M Q1 M i J O Z lI\ Lf\ MEMORANDUM TO: Aspen City Council THRU: Robert S. Anderson, Jr., City Manager fv FROM: Alan Richman, Planning and Development Director kK RE: Little Nell Hotel Parking Plan Increase DATE: October 7, 1987 SUMMARY: The staff recommends that you grant the applicant's request to place an additional 26 parking spaces below the Little Nell Hotel, in partial fulfillment of ASC's obligation with respect to the Aspen Mountain Master Plan. PREVIOUS COUNCIL ACTION: Council approved the Little Nell Precise Plan on April 14, 1986. Included in the Plan was a requirement for the applicant to provide 118 parking spaces subgrade, plus 13 spaces in the drop-off area and 2 service delivery spaces. This number of parking spaces was in excess of the number originally proposed by the applicant, and appears to adequately handle the needs of hotel guests, users of the commercial space and certain employees of the ski area. BACKGROUND: On May 6, 1985, the Board of County Commissioners approved the Aspen Mountain Ski Area Master Plan. One condition of their approval, based on a referral of the Plan to the City, was that the applicant provide 46 off-street parking spaces to mitigate the impacts of the ski capacity increase on the mountain from 3,000 to 4,300 skiers at one time. The condition gave ASC the option to provide these spaces in a number of ways, including at the base area, via cash -in -lieu or via construction off -site, subject to approval by the City of Aspen. PROBLEM DISCUSSION: Section 24-7.9 of the Municipal Code provides the Planning Director with the authority to authorize minor changes to adopted precise plans, if required by engin- eering standards or other technical design needs not anticipated during review of the project. The applicant states that due to detailed soil borings, foundation design and construction drawings for the hotel, additional parking on -site has become feasible. We believe this situation meets the test for an amendment which can be approved by the staff. A drawing of the proposed new parking plan has been submitted to me, showing 144, rather than 153 subgrade spaces. Therefore, the maximum number of new spaces we can approve at this time is 26, not the 35 cited in the attached letter. If additional spaces are able to be accommodated on the site in later drawings, I will 1: handle such changes at that time. I am prepared to issue a formal order amending the Precise Plan to include the 26 spaces below the hotel, unless City Council removes this item from the consent agenda and directs me to put this amendment through the public review process. Please be aware that if this cannot be approved by the Planning Director, Section 24-7.9 requires all other amendments to go through the full conceptual and precise plan review, a four step process. Requiring this type of review will effectively kill the proposal, as it will not be possible to design the hotel for construction in 1988 to include these spaces. The reasons that I believe this minor amendment should be approved are as follows: 1. There is nothing in the approved SPA agreement pre- cluding provision of these spaces on -site. The agreement includes a condition that 46 spaces be provided, as per the County approval, but places no limits on their location. 2. The 46 spaces were required to offset additional ski area impacts. Since we know that many skiers drive right to the base area in search of parking, provision of the spaces by ASC will help to mitigate the effects of the ski area on surrounding streets and on circulation in the neighborhood. 3. Provision of these spaces in the hotel guarantees that they will be provided in the most timely manner for the commun- ity. While the community may be moving towards development of a parking facility on its own, there is presently no guarantee that such a facility will be built. I would suggest, however, that if the public facility moves forward and the hotel is delayed, we retain our ability to request cash from ASC for all 46 spaces, and not just the 20 which are not yet designated for development. 4. Since the spaces are all to be subgrade, there will be no visible change to the hotel as approved by Council. There are several issues which are raised by the applicant's letter. First, there is a statement about rental of the spaces. From comments received from both Jay Hammond and Tom Baker, I believe long term rental of the spaces should be precluded. Our studies demonstrate that rented spaces are occupied far less frequently than are spaces open to the general public. Further, these spaces are intended to mitigate the impacts of ski area expansion, and should therefore be open, at least during the ski season. We will require these spaces to be available on this basis as a condition of our approval. The second issue is that of fees. Jay questions the appropriate- ness of charging a fee for public parking. I feel that the SPA Plan gives me no guidance in this regard. Further, it is unclear whether or not we will be charging fees if a public structure is built. Council could choose to add a condition requiring the applicant to keep the fees for these spaces in line with any fees which we charge in a public structure, if one is built. ALTERNATIVES: The alternatives available to Council are: 1. Leave this item on the consent agenda, in which case it will be approved subject to the conditions listed below. 2. Remove this item from the consent agenda and place it on the regular agenda, to provide direction to staff as to revised or additional conditions. 3. Remove this item from the consent agenda and place it on the regular agenda, to direct staff not to approve this applic- ation, but instead to have it processed as a substantial amend- ment to an approved SPA. RECOMMENDATION: Staff recommends that you leave this item on the consent agenda, allowing the addition of 26 public spaces to the Little Nell Hotel parking garage, in partial fulfillment of ASC's 46 space obligation, subject to the following conditions: 1. If construction of a public facility precedes con- struction of the Little Nell Hotel, then the City reserves the right to request cash payment for all 46 spaces. 2. There shall be no long-term rental of the public parking spaces during the traditional Thanksgiving to Easter ski season. parknell 1 �CS o b P� s,c r✓ �,✓� — it c N- P.X,N 9.�L �o r �,�9 %'r ,tee fRc SPprers Wlc,� /r w� y -�+ �aLt•+�.��� �P`C Gt SE_n �Afx V'9'-' i • 1 N�7 r ASPEN SKIING COMPANY Post Office Box 1248 } SP 15 197 i 117 Aspen Airport Business Center Aspen, Colorado 81612 (303) 925-1220 + - 11 September 1987 Mr. Alan Richman, Director Aspen/Pitkin Planning Office 130 South Galena Aspen, CO 81611 Dear Alan: I am writing to formally request a minor, technical amendment to our SPA precise plan approval for the Little Nell Hotel. Specifically, we are requesting a plan amendment to permit the addition of 35 structured parking spaces under the hotel. In addition, subject to the conditions outlined below, we are seeking agreement with the City and County to allow the construction of these spaces to meet, in part, our commitment to public parking from the Aspen Mountain Ski Area Master Plan approval. As you may recall, our final Little Nell SPA approval called for the construction of 118 spaces in levels -10, and -20 of the Hotel. For structural and cost reasons, we felt that 118 was the maximum physical plan achievable on the site. With the benefit of more detailed soil borings, foundation design and construction drawings for the Hotel, we now feel it is feasible and appropriate to add parking to the site. A lower level parking plan is attached which depicts our original parking plan and the proposed addition. We plan to manage these spaces as follows: Ifloolluall Hotel Guest 67 spaces* Retail (Employees, public) 17 spaces* Restaurant/Bar 5 spaces* Employees 5 spaces* SKI AREA ADMINISTRATION 7 spaces* GENERAL PUBLIC PARKING (fee) 17 spaces* TOTAL 118 spaces GENERAL PUBLIC PARKING (fee) 35 spaces NEW TOTAL 153 spaces *Provided for SPA approval. ASPEN MOUNTAIN • BRECKENRIDGE• BUTTERMILK MOUNTAIN •SNOWMASS Mr. Alan Richman, Director • 11 September 1987 Page Two The general public parking spaces will be available on a rental basis or a first come, first served basis. Also, we anticipate some trading of spaces between those reserved for rental and ski area operations. The parking analysis conducted by TDA (appendix 3 of our SPA submission) outlines a recommen- dation to use 17 spaces in summer for retail and 7 for ski operations. It goes on to recommend that this arrangement reverses in the winter. This is a feature of our parking plan which we would like to test and evaluate. As noted above, we are also requesting credit for 35 spaces against our total commitment of 46 spaces from our previous AMSAMP approval. We believe that there is sound public policy rationale to support this request as follows: 1. These new spaces will fulfill the same parking demand supplied by a public parking structure regardless of its location and, therefore, alleviate public parking demand. 2. This plan will locate parking at the skiers' destination and it is, therefore, an optimum location. 3. These spaces will relocate 35 cars from on -street parking and, therefore, will reduce congestion on Ute Avenue. 4. There will be no above ground modification in the Little Nell Hotel Plan. 5. The location of these spaces within the Hotel structure is consistent the AMSAMP which Pitkin County approved. 6. To the best of our knowledge, the parking spaces, as designed and depicted on the attached drawings, conform to existing City of Aspen Parking Standards. We appreciate your review of this request and look forward to a response at your earliest convenience. Sincerely, Fred Smith PI,anning Director /fS:gw Enclosure • 0 MEMORANDUM TO: Alan Richman, Planning Director FROM: Jay Hammond, City Engineering__ - DATE: October 2, 1987 RE: Nell Hotel Parking Amendment -------------------------------------------------------------- -------------------------------------------------------------- Having reviewed the above application from the Aspen Skiing Company to amend the Little Nell Hotel plan to provide 35 additional on -site parking spaces for public use, the Engineering Department would offer the following comments: 1. The plan submitted to our office shows 144 total spaces for an increase of 26 spaces over the SPA precise plan, not 35 as indicated in the correspondence. 2. I would question the appropriateness of charging a fee for public parking. The conditions of approval under the Aspen Mountain Ski Area Master Plan obligate the Ski Company to provide 46 public parking spaces with no reference to fees for their use. Charging for parking may discourage use and minimize the benefit on adjacent streets. 3. I am somewhat confused by the reference in Fred's letter of September 11 regarding provision of parking on a "rental" basis. I would suggest that providing reserved "rental" spaces again does not meet the need for public parking by tying up spaces that may or may not be used. Further, the reference to trading spaces between "rental" and ski area operations seems inappropriate in that any agreement to credit the Skiing Company toward its commitment for 46 spaces, should be based on spaces strictly reserved for public use. 4. Finally, I would note our support for providing at least some amount of public skier parking on -site to minimize the shuttling of private cars to and from Little Nell. JH/co/NellPkingAmend cc: Chuck Roth ASPEN SKIING COMPANY r • Post Office Box 1248 117 Aspen Airport Business Center Aspen. Colorado 81612 (303)925-1220 20 August 1987 Mr. Alan Richman Planning Director Aspen Pitkin County Planning Office 506 East Main Street Aspen, CO 81611 Dear Alan: Aw. AM 2 51987 As part of the 1985 Aspen Mountain Ski Area Master Plan process, which was approved on May 6th of that year by the Pitkin County Commissioners, certain requirements were imposed on the Aspen Skiing Company to provide 46 off-street skier automobile parking spaces. In Exhibit A "Conditions" of the Board of County Commissioners; Section 1, Paragraph E, it was discussed that this requirement could be met by providing on -site automobile parking, off -site automobile parking, or a cash contribution to the City of Aspen, or a combination of each method. Further, the conditions suggested that Aspen Skiing Company, at its discretion, could provide the off-street automobile parking on site at the base of Little Nell and this would be subject to appropriate land use approval by the City of Aspen. The Aspen Skiing Company is now investigating the opportunities to construct such parking spaces underground within the Little Nell Hotel complex. Although we have not done sufficient technical analysis to confirm that this is a possibility, we would like to assure ourselves that the requirement and the commitment that we made to Pitkin County, would be satisfied with the construction of at least a portion of these spaces at this location. I would, therefore, request that we be allowed a discussion with the appropriate City staff or officials to determine the conformity of this request. As we are currently planning to begin construction of our Little Nell Hotel facility in the Spring of 1988, it is imperative that we begin our final planning and construction documentation work immediately. I would, therefore, suggest that we arrange for these meetings as soon as it is possible. ASPEN MOUNTAIN • BRECKENRIDGE • BUTTERMILK MOUNTAIN • SNOW MASS • • Mr. Alan Richman 20 August 1987 Page Two It does not appear that all of the 46 spaces can be constructed within the Little Nell Hotel and it will still be necessary to provide either additional parking or cash in lieu of, for the remaining spaces. However, the Aspen Skiing Company is prepared to meet its commitments and would request only that we proceed as quickly as possible to help mitigate what we believe to be an increasingly serious problem within the downtown area of Aspen. If you have any questions in this to contact my office at 925-1220. from you in the very near future. Sinc ly / ; red?mith Plan ing Director FS.gw cc: Jerry Blann Paula Crown Jeff Rhodes regard, please do not hesitate I look forward to hearing u w z w > z Q cr I � • • • SOUTH SPRING STREET ASTINSIBUILDING \ (TYPICAL) EXISTING PROPOSED L ,—__--I SKI LIFT ^� - LITTLE NELL / HOTEL I i 19�0� �— — _ _ 7/� _.L/ - �, t I HOLE 4 L / o I I A O w O r O 0 0 \ 1 UT o �\ a 0/ I HOLE 3 w • o 0 ON ^ • \ r r OL 10 r HOLE 5 I I I I (HOLE I21 \\ �I • i A J CITY OF ASPEN 'ATER SUPPLY WE L AND PUMP HOUSE PROPOSED 1 EARTH -COVERED PEDESTRIAN/ COMMERCIAL I \ AREA I � I A 8150 8100 8050 8000 HOLE 5 7960 7900 7850 PF JOPO ED N W L T TE MINA I l ` r i r O jj © 0 f d /71 A" 77 I /. I e % a O O i 4 \ ae e e } J. • • PROPERTY LINE A' also 8100 8000 7950 7900 7850 Z,I so _ o so 100 SCALE IN FEET EXPLANATION: SITE PROPERTY BOUNDARY EXISTING CONTOUR PROPOSED CONTOUR LIMITS OF PROPOSED FILL • HOLE 1 EXPLORATORY BORING AND GROUNDWATER MONITORING WELL v _ WATER LEVEL ESTIMATED BETWEEN BORINGS •I •I • •I •I Match Sheet U]IIIIIIIIIIIIIII c C7 • I, I Little NT Hotel West Wing I I I ; I I I I I I ' I I I I I I I I I I I ' I I I I I I I I I I I I I I I I I I o �- o o S -4 � I LT/L. /T / G EAM zon�E z ��b Shr A � A r a 1 ^� ,gN t• /N MJG iS c t F 1 + it ��I►� s NONE • • • • 1. • • . -��� North of Nell • • / c P� • - x + Y w I � _ G I 1L-0 ' II ET Acrt r✓JF fir=. Y'•. °I I ALLDrn/ FoKG Of�V/N/o I !1►" _.w w 6"vw iN Uoo,a G Uri--- i � C P o �i of G off —/t-Uw //• SG W DH// Durant Street