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Home My WebLink AboutPRJ07-0233 B09-0071 Soil ReportHEPWOR7H - PAUULAK GE4iECNNICAL I-3eptiti��t��-�e��(ak C`ieutech�uca�, €ne. �=`?tlCoutatv �`ci�ac 3?� Ciler�u<<oci �E,;i lr C;uf�ra�o Sii��?t i`hr>�Rc 9ri`-�?�� r`?�5 Fa�:: �>7�-9'�5-`�� e�.tai!: Iz��;e� �E�[3 ;e:>tec.li.c«a�t SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED A,DDITIONS TO RA,MSHORN LODGE LOT A, BLOCK 3, VAIL VILLAGE STH FILING 416 VAIL VALLEY DRIVE VAIL, COLORADO JOB NO. 108 041A FEBRUARY 24, 2009 PREPARED FOR: RAMSHORN CONDOMINIUM ASSOCIATION ATTN: JOHN AND DIANE MILLIGAN 416 VAIL VALLEY DRIVE VAIL, COLORADO 81657 > 1� , . ��-, s r.-; ar �c r 3� ,�..`;� � - i 119 • C1c;lr>r��c3�:� `;��-�gs f ; �1-�> � � � �C��_ * `ii Ivert�i��rne "� f i�'..�c7�- l 9�9 � � � TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY ........................................................................ - 1- FROPOSED C4NSTRUCTION ................................................................................. - 1 - SITECONDITIONS .........................................•-........................................................ - 2 - FIELDEXPLOR.ATION ............................................................................................ - 2 - SUBSURFACE CONDITIONS .................................................................................. - 3 - FOUNDATION BEARING CONDITIONS ............................................................... - 3 - DESIGN RECONIIvIENDATIONS ............................................................................. - 4 - FOUNDATIONS.................................................................................................... - 4 - FOUNDATION AND RETAINING WALLS ......................................................... - 5- FLOORSLABS ...................................................................................................... - 6 - LINDERDRAINSYSTEM ...................................................................................... - 7 - SITEGR.ADING .................................................................................................... - 8 - SURFACEDRAINAGE ......................................................................................... - 8 - LIMITATIONS.......................................................................................................... - 9 - FIGURE 1- LOCATION OF EXPLORATORY BORINGS FIGURE 2- LOGS OF EXPLORATORI' BORINGS FIGURE 3- LEGEND AND NOTES FIGURE 4- GRADATION TEST RESULTS TABLE 1- SLTMMARY OF LABORATORY TEST RESULTS � � PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for proposed additions and remodel ta the Ramshom Lodge located on Lot A, Block 3, Vail Village 5`� Filing, 416 Vail Valley Drive, Vaii, Calorado. The project site is shown on Figure 1. The purpose of the study was ta develop recommendations far the foundation design. The study was conducted in accordance with our agreement far geotechnical engineering services to the Ramshorn Candominium Association dated February 7, 2008 and revised January 20, 2009. }" � A fieId exploration program consisting of exploratory borings was conducted to obtain information on the subsurface conditions. Samples of the subsoils abtained during the � field exploration were tested in the laboratory to determine their classification and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recc�mrnendations for foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained during this study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION The proposed construction will include partial building demolition and new building additions increasing the current 3 story building to 4 stories in height and also expanding the building footprint. The lower Ievel will be a partial basement and typically retain earth. Ground floors will be slab-on-grade. Grading for the additions is assumed to be relatively minor with cut depths between about 3 to 8 feet. There will probably be some additional loading to the existing building foundation, as well as new foundations. We assume generally moderate foundation loadir�gs, typical of the proposed type of construction. � 3ob No. ] OS 04 f A � C�teCh C � � _2_ �" When addition locations, grading and loading information have been developed, we �' should be notified to re-evaluate the recommendations presented in this report. SITE CONDITIONS The site is located at the intersection of Vail Valley Drive and Hanson Ranch Road in the �, southeastern partion of downtown Vail. The ground surface is strongly sloping down to ,� the north at grades from about 7 to 10%. The existing lodge building is cut into the slope '� and daylights to the north. Elevation difference across the site is about 14 feet ranging � from elevation 8190 to 8180 feet. Gore Creek is located about 200 yards to the north of � the site and 30 feet or more lower in elevation. Vegetation consists of evergreen and � aspen trees, and other landscape. Up to about 3 feet of snow covered the site at the time � of our fieId exploration. There are scattered cobbles and boulders on the ground surface. � The existing building is a three story wood frame structure with the lower level a walkout basement. Ground fioor is slab-on-grade. The building was apparently constructed in the r � 196Q's with the third story added in the late 1980's. The building is reportedly founded on shallow spread footings. � FIELD EXPLORATION � The field exploration for the project was conducted on February 3, 2009. Three � exploratory borings were drilied at the locations shown on Figure 1 to evaluate the � subsurface conditions. The borings were advanced with 4 inch diameter continuous flight � augers powered by a truck-mounted CME-45B drili rig and located in areas that had been � cleared of snow. The borings were logged by a representative of Hepworth-Pawlak Geotechnical, Inc. "� Samples of the subsoils were taken with a 1'/s inch and 2 inch I.D. spoon samplers. The � samplers were driven into the subsoils at various depths with blows from a 140 pound '" hamxner falling 30 inches. This test is similar to the standard penetration test described `' by ASTM Method D-1586. The penetration resistance values are an indication of the r� �' Job No. i 418 fl4l A �� C� � -3- �` relative density or consistency of the subsoils. Depths at which the samples were taken �' and the penetration resistance values are shown Qn the Logs of Exploratory Borings, �' Figure 2. The samples were returned to our laboratory for review by the project engineer �'" and testing. SUBSURFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The subsoils, beiow about 1%z to 5 feet of man-placed fill, consisted of relatively dense, silty sand and gravel with cobbles and boulders. The dense coarse granular soiLs extended down to the drilled depths of 17 and 11 feet in Borings 2 and 3, and down to a depth of about 28 feet in Boring 1 where medium dense, silty sand with gravel and � scattered cobbles was encountered to the drilled depth of 36 feet. Drilling in the dense � coarse granular soils with auger equipment was di�cult due to the cobbles and boulders and drilling refusal was encountered in the deposit. The fill was sandy silty clay with � gravel and cobble material that was mixed with some topsoil and ofvariable density. �. Laboratory testing performed on samples obtained from the borings included natural � moisture content and gradation analyses. Results af gradation analyses performed on � sma11 diameter drive samples (minus 1%z inch fraction) of the coarse granular subsoils are shown on Fi g u re 4. The laborato ry t e s t i n g i s s u m m a r i z e d i n T a b l e 1. ,� Free water was encountered in Boring 1 at the time of drilling and when checked 1 and 2 days later at a depth of about 27%z feet. No free water was encountered in Borings 2 and � 3. The subsoils were slightly moist to moist becoming wet near and below the free water leveL � � FOUNDATION BEARING CONDITIONS The natural caarse granular soils possess maderate bearing capacity and relatively low settlernent potential. Spread footings bearing on these soils should be suitable for � J�b�o. �osoal� V ` rf � L� ,� -4- � foundation support of the a.dditions. It should be feasible to appty some additional load to � the existing spread footing foundatian of the building. There could be some dif�'erential �� settlement between new and exista,ng foundations depending on the loadings. We should � perform a settlement analysis of the proposed ct�nstruction when the foundation has been � designed and loadings provided. ,� FOUNDATIONS DESIGN RECC?MMENDATIONS +. Considering the subsurface conditions encountered in the exploratory borings and the �. nature of the proposed ct�nstruction, we recommend the building be founded with spread �, footings bearing on the natural coarse granular soils. ,� The design and construction criteria presented below should be observed for a spread r footing foundation system �,, 1) I�'ew footings placed on the undisturbed natural granular soils should be �„" designed for an allowable bearing pressure of 4,000 psf. It should be � feasible to increase foundation loading an existing faotings to 6,000 psf � depending on the footing sizes and settlement analysis. Based on � experience and the assumed moderate foundation loadings, we expect � settlement of footings designed and constructed as discussed in this section w could range up to about I to 1%2 inches. The settlements should essentially occur during consiruction but cauld be differential with respect ta the w existing structure which should be considered 'uz the design. 2} The footings should have a minimum width of 18 inches for continuous walls and 2 feet for isolated pads. 3) Exterior footings and footings beneath unheated areas should be provided � i with adequate soil cover above their bearing elevation for frost protection. � Placement of foundations at least 48 inches below exterior grade is � typieally used in this area_ � � I � 3csb �io. I�8 041 A ' GE'.ic�tE:Ch � � � -5- � 4) Continuous foundation walls should be wetl reinforced top and bottom to �" span local anomalies such as by assuming an unsupported length of at least �' 12 feet. Foundation walls acting as retaining siructures should also be �'° designed to resist lateral earth pressures as discussed in the "Foundation � and Retaining Vt�alls" section of this report. 5} All existing fill, topsoil and any loose or disturbed soils should be removed �� and the footing bearing level extended down to the relativel dense natural Y �~ coarse granular soils. The exposed soils in footing area should then be � moistened and compactett. If water seepage is encountereri, the footing � areas should be dewatered before cancrete placement. v- 6) A representative of the geotechnical engineer should abserve all footing r excavatians prior to concrete placement to evaluate bearing conditions. � r L' FOUNDATION AND RETAINING WALLS Foundation walls and retaining structures which are Iaterally supported and can be expected to undergo only a slight amount of deflection should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 50 pcf for backfill consisting of the on-site granutar soils. Cantilevered retaining structures which are separate from the building and can be expected to deflect sufficiently to mobilize the full active earth pressure condition should be designed for a Iateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 45 pcf for backfill consisting of the on-site granular soils. The wall backfill should not oontain debris, tapsoil or oversized rocks. All faundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, traffc, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will increase the lateral pressure imposed on a faundation wall or � �" 3ob No. 108 04I A �?..fpt�Ch L.:�C:O I� � � � -6- retaining structure. An underdrain should be provided to prevent hydrostatic pressure buildup behind walls. Backfill shontd be placed in uniform lifts and compacted to at least 90% ofthe maximum standard Proctor density at a moisture content near optimum. Backfill in pavement and walkway areas should be compacted to at least 95% of the maximum standard Proctor density. Care should be taken not to overcompact the backfill or use large equipment near the wall, since this could cause excessive lateral pressure on the wall. Some settlement of deep foundation wall backfill should be expected, even if the material is placed conectly, and could result in distress to facilities constructed on the backfill. Use of a select granular material, such as base course, and increasing compaction to at least 9$% standard Proctor density could be done to help mitigate the settlement potential. The lateral resistance of foundation or retainirig wall footings will be a combination of the sliding resistance of the faoting on the foundation materials and passive earth pressure against the side ofthe footing. Resistance to sliding at the bottoms ofthe footings can be caiculated based on a coefficient of friction of O.SQ. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalent fluid unit weight of 375 pcf. The coefficient of friction and passive pressure values recommended above assume uhimate soil strength. Suitable factars of safety should be included in the design to limit the strain which will occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads should be a well graded granular material compacted to at least 95% of the maxixnum standard Proctor density at a moisture content near optimum. FLOOR SLABS The naturat on-site soils, exclusive oftopsoil, are suitable ta support lightly loadeti slab- on-grade construetion. To reduce the effects of some differential movement, floor slabs should be separatec3 from all bearing walls and colurnns with expansion joints which allow unrestrained vertical movement. Floor siab contral joints should be Used to reduce �'. �° Jab iVo. 1 os 041 A � G�C�it�Ch � � -7- �' damage due to shrinkage cracking. The requirements for joint spacing and slab +� reinfarcement should be established by the designer based on experience and the intended '' slab use. A minimum 4 inch layer of free-draining gravel should be placed beneath � basement level slabs to facilitate drainage. This material should consist of minus 2 inch a aggregate with at least 50% retained on fhe No. 4 sieve and less than 2% passing the No. +� ZOQ sieve. � � All fill materiais for support of floor slabs should be compacted to at least 95% of *� maximum standard Proctor density at a moisture content near aptimum. Required fill can ,� consist of the on-site granular soils devaid of debris, topsoil and oversized rocks. .� UNDERDRAIN SYSTEM �, �, Althqugh free water was not encountered within probable excavation depth during our ,� exploration, it has been our experience in the area that local perched groundwater can A develop during times of heavy precipitation or seasonal runoff. Frozen ground during w spring runaffcan also create a perched condition. We recommend below-grade � construction, such as retaining walls, crawlspace and basement areas, be protected from � wetting and hydrostatic pressure buildup by an underdrain system The drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert leveI with free-draining granutar material. The drain should be placed at each level of excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum 1% to a suitable gravity outlet or a sump where the water can be callected and pumped. Free-draining granular material used in the underdrain system should contain less than 2% passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size af 2 inches. The drain gravel backfill should be at least 1 % feet deep. I , � Job Na. 108 041A _L��.±±��s� i' �� _�_ SITE GRADING We assume the cut depths for the basement level will not exceed one level, about 10 feet. Shoring of the excavations may be needed to prevent undermining of existing structures and utilities. Providing a 1 horizontal to 1 vertical or flatter slope of natural soils below and beyond the edge of existing footings, uti�ities or other structwres should limit the need � for shoring. We should review the grading and foundation plans prior to construction to � deternune areas that may need excavation cut sIopes shored. � All fills should be properly placed and compacted to limit settlements and distress to structures canstructed on fill. In general, all fi11s supporting pavernent or slabs should be � compacted to at least 95% of the maximum standard Proctor density near optimum moisture content. Fills deeper than about S feet may require a higher degree of � compaction to Iimit settIements. Prior to fill placement, the subgrade should be carefully prepared by removing all existing fill and topsoil, and compacting to at least 95% of the � maximum standard Proctor density. Permanent unretained cut and fill slopes should be graded at 2 horizontal to 1 verticat or � flatter and protected against erosion by revegetation or other means. Ff seepage is encountered in permaneni cuts, an investigation should be conducted to determine if the seepage will adversely affect the cut stability. SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the additions have been completed: 1) Inundation ofthe foundation excavations and underslab areas should be avoided during construction. 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95% of the maximum standard Proctor density in � J4b :��fl. t oa aa i� ^u -M � I� �� `' �) Y. � pavement and slab areas and to at least 90% of the maximum standazd Proctor density in Iandscape areas. The ground surface surrounding the exterior of the building should be sloped to drain away from the foundatzan in alI directions. We recommend a minimum slope af b inches in the first 10 feet in unpaved r areas and a minimum slope of 2'/z inches in the first 10 feet in paved areas. � Free-draining wall backfill should be capped with a ieast 2 feet of the on- r site finer graded soiIs to reduce surface water infiltration. s 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. W LIMITATIUNS �. This study has been conducted in accordance with generally accepted geotecluiical , engineering principles and practices in this area at this time. We make no warranty either r express or implied. The conclusions and recommendations submitted in this report are i based upon the data obtained from the exploratory borings drilled at the locatians � indicated on Figure I, the pmposed type of canstruction and our experience in the area. y Our services do not include determining the presence, prevention or possibility of mald or r other biological contaminants (MOBC} developing in the future. Ifthe client is � concerned about MOBC, then a professional in this special field of practiee shauld be consulted. Our findings include interpolation and extrapolation of the subsurface � � conditions identified at the exploratory borings and variatians in the subsurface conditions may not become evident until excavation is performed. If conditions � � encountered during construction appear different from those described in this report, we ., should be notified so that r�evaluation of the recommendations may be made. This report has been prepared for the exclusive use by our client for design purposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should provide continued cansultation and field services during construction ta review and rnonitor the implementation of our recommendations, and to � Job No. I08 041A - -- E„i _— �#eCh � � - 10- verify that the recommendations have been appropriately irrterpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We recommend on-site observation of excavations and foundation bearing strata and testing of structural fill by a representative of the geotechnical engineer. Respectfully Submitted, HEPWORTH - PAWLA David A. Young, P Reviewed by: �'��ttN�liti`��' ��-��°�"�,` �' �"� Steven L. Pawlak, P.E. DAY/ksw INC. cc: Friztlen — Pierce Architects -- Attn: Bill Pierce Job No. 1 d8 041 A Ge�teC"t APPROXIMATE SCALE 1" = 3d' 8180' - -.._ 108 041A 1 � ♦ � � � � � � � � � PAVED PARKING � � l �-'� � BORlNG 2 � • _ � i v EXISTING RAMSHORN LODGE 416 VAIL VALLEY DRNE � \ 80RING 3 , . � �� \ C \ \ \ \ \ �� BENCH MARK: SEWER MIANHOLE 022 � RIM; ELEVATION = 8192.1', AS PROVIbED. � \` \ \ � � \ � � ALL SEASONS LODGE 185' TRACT F-1 � i i ,,,,_ ,,,. ...._ LOCATION OF EXPLORATORY BORINGS I Ffgure 1 �"' � � 8190 B�RING 1 �, ELEV.=8183.3' � 8185 n � " � 81 I P e. w b 81; . M $1� � a> � � �� c 0 .� i� � w 81f ,, y< r Wm 81 � � 1 r- — 81 �- h. � 81, p. Y• ,_ y 8145 1� 108 D41A ,� � 52112 WC = 4.4 -200 = 17 23J9 36/12 2616,10lQ WC — 5J +4=35 -200 = 17 56/10 ss/� z BCIRING 2 ELEV.=8181.1" 441t2 44/12 45/12 WC = 4.4 +4 = 39 -200 = 15 90/10 BORING 3 8190 ELEV. =8187.7` 51y2 8185 24/12 WC = 6.8 -2d0 — 15 81$0 37/8 BASEMENT FINISH FLOOR ELEV. = 8177.T 8175 8170 a� ti � 0 .� a�i 8165 w 8160 8155 815Q 32/12 Note: F�cplanation of symbois is shown on Figure 3. 8145 H ,_ _ LOGS OF EXPLORATORY BORINGS Figure 2 i� � � �� ° �., � � M �: p � I ". y, � IEGEND: �Fill; manplaced sandy siity clay with gravel and cobbles, medium stiff to soft, moist to very moist, dark brawn, mixed with topsoil. � Sand (SM); silty, graveily, with eobbfes, medium dense, wet, brown. • Sand and Grave! (SM-GM}; with cobbles and boulders, silty, dense, slightly moist to moist, brawn. � Relatively undisturbed drive sample; 2-inch I.D. Califarnia liner sample. � Drive sample; standard penetratian test (SPT), 1 3/8 inch I.D. spfit spoan sampfe, ASTM D-1586. 52/i2 Drive sample blow count; indicates that 52 blows of a 14Q pound hammer talling 30 inches were required to drive the California or SP7 sampler 12 inches. �'2 Free water level in boring and number of days foilowing drifling measurement was taken. � Depth boring caved when measured on February 3, 20d9. � Practical drilling refusaf. NOTES: 1. Exploratory borings were drilled on February 3, 2009 with 4-inch diameter continuous flight power auger. 2. Locations of exploratory borings were measured appraximately by pacing from features shown on the site pian provided. 3. Elevations of exploratory barings were measured by instrument levef and refer to the Bench Mark shown on Figure 1. 4. The exploratory boring locations and elevations should be considered accurate only to the degree implied by the method used. 5. The lines between materials shown on the exploratory boring logs represent the approximate boundaries between material types and transitions may be gradual. 6. Water level readings shown on the logs were made at the time and under the conditions indicated. No free water was encountered in Borings 2 and 3. Fluctuations in water level may occur with time. 7. La�ratory Testing Results: WC = Water Content (%) +4 = Percent retained on the No. 4 sieve -200 = Percent passing No. 200 sieve 10$ 041 A LEGEND AND NOTES j Figure 3 � � �� HEPW(7R7H-PAWIAK GEOTECNNICAL, INC. TABLE 1 SUMMARY OF LA64RATORY TEST RESUlT5 1ob Na. 108 041A SAMPLE LqCATION NATURAL GRADATION ATTERBERG L1MIT5 UNC4NFINED � NATURAL .......� ' MOISTURE PERCENT BORING DEPTH DRY DEN5ITY GRAVEI SANp pA551NG NO. LIQUID LIMIT P�STIC COMPRE551VE SOIIOR CONTEN7 (%j {%) 200SIEVE �NDEX STRENGTH 6EDRqCKTYPE �ft� ��0) �P�fl (%) {%) jPSF) 1 -- � �''�' �� Silty sand with gravel 15 5.7 35 4$ 17 Silty sand with gravel _ _ _ 2 10 4.4 39 46 IS Silry sand w.ith gravel - _ — 3 5 6.8 15 Silty sand with gravel _...� ...... _ � _... ...... �