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Home My WebLink About2008 Geotechnical Engineering RecommendationsCprreçpnd ehæ ås. tT- l-vLr' KC Hamilton Engineering, Inc. June 8, 2008 Atür: Richad Neiley ttleiley & Alder' ÀttomeYs 6800 HighwaY 82, Sulte I Glenwood SPrings, CO 81601 8.ç*u, bv¡tuEirnerofRer Subjectl Geoüec{rnlcal EngineeÉng Recommsndaüons Proposed Triplex, 4{24 County Road 154 Garfield County, Colorado Xob Ho. O8-1O5 Mr. Neiley, As requested, KC Hamilton Englneering, Inc. (Hamllton) obseryed subsurfuce conditions at the iù¡lã* s¡te and prepared this Geotecùnical Engineerlng report for the subJect projed. srrE cof{DmoNs At the time of the site vislt, the slte was vacant with a sparse cover of trees. The slte slopes ¿ã*"-tó tt" southwest at moderate slopes of about 15% to 20%' The slte is bound by resìãential lots to the northwest and southeast, and by Highway 82 to the no¡theast and by County Road 154 to the southwest. PROPOSED CONSTRUCTION It is proposed þ construct a triplex.at the subJect slte. The triplex will be one to two stories ¡n Ë¡éñi. ñ" basement is planned, The maxlmum excavation depths planned. for tte basement triñáat¡ons will be on th'e order of 6 to I fieet. The proposed structure wlll be of concrete and wood frame constructlon. The structurat loading will be generally light consistent with the p.p*ø type of construct¡on. Accæs to the slte ls from the southwest from County Road 154. it is ptannäd to construct the foundation at three different levels down the hillslde. The munOåtion for each portlon of the triploc wlll step do¡rn the hlllside. If the proposed construcdon varies frcm that descrlbed above or hercin, Hamilton should be noun"åto'*-evaluate the recommendatlons provlded in this reporÇ lf necessary' su Bsu RFACE I]{VESTTGATTO il Subsufface condiüons were observed ln two test pits excavated fur an ISDS design. The tæt ıltr-*ur. ¿¡,*vated on July Z$7.and in the vicinlty of the propgsed.structurc. The pits iålealeã a thtn layer of top iotl underlatn by clayey and.gravelly sand wlth some cobbles and ¡ãulAers. The pitd were excavated down to depths of about 6 to I feet. Free water was not ;;p"rù¿ ¡n tne test ptts; however, seasonai runoff may result in perched groundwater conditions below üre buildlng. 250 Pearl Street, Unlt 206, Denver, Colorado 80203 Phone: 303-733-4742 KC Hamilton Englneerlng, Inc. Job t',|o.08-105,June 8, 20(E Page 2 SITI IXCAVATIOilS AND ORADII{O The solls at the site dassiff as Type C solls per the OSHA Excavatlon Guide. All excavatlon slopes are to be lald back pø as per the OSHA Excavatlon Gulde fur Type C soils. The basement excaratlon should be peÉormed under the supervision of the contractors'Cornpetent PeFon' per the OSHA Excavation Gulde. Un-retained cut and flll slopes less than 10 fee in helghÇ should be constructed wlll a maxlmum slope of 2:f (H:V) provlded good dnlnage is incorporated lnto the grading plan b divett water away ftom the slope. If sheet dralnage ls planned actCIss the site and down the slope faces, the maximum fill slopes should be consbucted at 3:1 (H:V). The topsoil, vegetatlon and other deleÞrious mateñals ln planned flll areas should be removed and the underlylng subgrade materials scadfied a mlnlmum of I indtæ, mols'h¡re conditloned and properly compacted, Fill materfals should be placed in maximum 8-ln$ thick loose lifrs. The maximum slze of cpbbles ard boulders placed in the fill should not exæed 6 lnches. Nesting of cobbles and boulders ln fllls should be avoided. All fills should be compacted to at least 950¡6 of the standard proctor maxlmum dry density (ASf¡q D 698) and near the optimum molsture content (OMC). Considerlng the slze of some of the cobbles, a thln layer of CDOT dass 6 aggregate road base may be used to provide a smoother suface on which to pave. Good surface drainage should be provided for all cut and fill slopes, and the slopes should be re-vegetated wlth natlve grasses. FOUN DATION RECOM }I EilDATTONS The subsuface materials observed in the test pib are suitable to support conventlonal sprcad footing foundatlons, The footings should be designed based on a maximum allowable soll bearlng pressure of 21000 psf. The foundations should bear on undistuÖed natural solls. The fioundations should be deslgn so that unlform foundatlon pressures are applled to the subgrade across the footprint of the sbucture, to a degree that ls pracffcal in older to minimize the poþntlal fur differential settlement. Additional Spread Footing Foundaüon Qpslon Con¡lderatlons: 1. Spread fiootings should have a mlnimum width of 16 inches for continuous footings placed on reworked material as described abwe, and Z4lnches for isolaH pads also placed on reworked materlal. 2, Fooüngs placed beneath unheated areas should have at least 36 inches of covering soils to protect from frost heave, and per local building code' 3. Lateral resistance to of the spread footlngs ls bäsed on both ftlcüon between the footlng and its subsoils and passlve eañfr pressures of the soils on the side of the footing. A coefficient of ftlcüon of 0.4 and a passlve prêssune based on an equivalent fluid weight of 2O0 pcf are recommended for the onsite solls. These valuæ should be considered working values. 250 Pearl Street, Ste 206, Denver, Colorado 80203 Phone: 303-733'47A2 KC Hamllton Englneedng, Inc. Job No. 08-105, June 8, 2008 Page 3 4. Continuous fuotings should be reinforced to and bottom to span an unsupported length of 10 feet, S. Any loæe or soft materials when obserued in the foundation excavat¡on by thg- eeôtectrnlæl Engineer (Engineer) prior to flll placement should be removed and replaced, as recomrnended by the Engineer' 6, A'r€prúGnÞtlve of the Englneer sho¡rld obserue the foundation excavation priorto flll Placement Z. fhe foundatli¡n o(ca!/ation should be protected from runoff. FLOORSLABS I Çubgrade: The onsite soils are sultable to suppoft slab-on-ground construction. In order to ffi"-fu potenüal fur settlement of new slabs. any loose subgrade soils obscrved in the slab area should' be scarified and be properly compacted. Sub-floor soils (and fill rnaterials where i"ıuri.ol should be compacted to qt least 95 percent of th9 standard proctor maximum dry tú;',b/ í¡srm D 699) w¡tir¡n ZVob the optimum molsh¡re content (oMc)' Slãb Dêslgnt To rcduce the effiects of dlfürential movement, floor slabs should be separated ñilñãi-b.ãri.gs walls and columns with expanslon j_ ne.t¡.u¡ allow for unrestralned vertlcal movement. Jolñt spaclng should be determlned on floor thlckness, nomlnal aggregate size, ,Urp, àn¿ be consisËnt with the recognlzed guidelines such as the Portland Cement Assobaüon and the Amerlcan Concrete Instih¡te' Sub-Floor Gfavel: A 4-lnch layer of gravel should be placed beneath the floor slab to reduce ihäî"rãñäffi-.tr of moisture if the suþgrade soils w-ere.to become wetted. The gravelshould ¡. ¡,ru. a nomlnal slze of s/¿" , with at least 609o to 1000é retalned on the No. 4 sleve and less tñ 3 percent passing the No. 200 sieve. The subfloor gravel layer is- prssentpd^ in Figures 1.o ;nd i,i, ifrá iuU-noór gravel layer should be connected to the perimeter drainage system at locatlons where the foundation steps down the hillslde' Garage Slab: A 6-lnch layer of grave! placed beneath the garage slabìs_suggested to improve ñããË;ffinom the slab to the subgrade, and reduce the potential for cracklng. sub-floor ,o¡¡, rn¿ flll materials should be compacted to at least 95 percent of the standard proctor maximum dry density within z:ys tÐ the optimum moisture content. FOUNDATION WATLS Wall Design¡ Foundation walls which are laterally supported ard expected to undergo a ffiimal to moderate amount of movement should be designed with based on an at'rest lateml earth pressure computed based on an equlvalent fluid weight 9f 60 pcf. Lateral resistanæ to of ùt " ipr.ua footings supporting foundation walls is based on both ftictlon between the footlng -ãit ãäu*¡tr año palilve eãrth pressures of the soils on the slde of the footing. A coefficient of n¡ction of o.d and a pasive piessure based on an equivalent fluld welght of 200 pcf are iecórnmenaed. Tîese vaiues should be considered worklng values. Th*g pressures assume ddn;¡ conu¡tions behind the foundatlon walls. The buildup of free water behlnd a foundation wall wlll increase the lateral pressures on the wall' 250 Pearl StreeÇ Ste 206, Denver, Colorado 80203 Phone: 303-733-4702 KC Hamllton Eng¡neerlng, Inc. Job No,08-105, June 8, ?008 Page ¡t All foundation walls should be designed for appropriate hydrostatlc and surcharge pro.esul€s such as: adjacent buildlng fuundatlons and slabs, traffic, constuction materlals and equipment. Foundatlon Well Eeddil.l: In landscape aneasr fourdaüon wall backflll should be æmpaded to at least 90% percent of the standard proctor ma¡dmum dry density (AS[M D 698) within 20'6 to the optlmum molsture eontënt (OMC). In areas or e)dernål flatwork (1.e, sldewalls) or pavements, areas beneath adJacent foundations and interior slabs, wall backflll should be compacted to at least 950/o percent of the standard proctor maximum dry denslty wlthln 27o to the optimurn moisture content. SUBSURFACE DRAINAGE It li reæmmended that the new basement be protected from lnfiltntion with a psimeter drain system, and a sub-floor layer of gravel. A drain should be lnstalþd at the belov grale perimeter o-F all foundations to reduce tfie risk for water migratlng beneath floor slabs and reduce the development of hydrostaüc pressures behlnd the foundatlon wall. The drain should lead to a day-light polnt down slope from the stucture, or to a sump where water can be removed by pumplng, Notc þ Chc Foandafun Dæigner and Confiactu: The sub-floor gravel layer should be connected to the exüerlor perimeter dmin to alloru water to flow from beneath the floor' This can occur wlth an interior draln pipe located behind lnterlor stem or foundatlon walls and connected to the perimeter piplng, or with an interior drain on the inside of the foundatlon wall at the down hill slde of the structure, or at ottrer appropriate locaüons. Foundation drain details are presented on Figures 1.0 and 1.1. SURFACE DRAINAGE The following drainage precautions should be obsewed and maintained at all times durlng and afrer mnstruction: 1, Excessive wetting of the foundation excavation and sub-floor sc¡ils should be avolded. 2. ÐÊerior backfill should be placed as recommended herein. 3. The gruund should be sloped away from the buildlng. A minimum slope of 6 inches in the first 10 feet. 4. Roof down spouB should dlsclrarge beyond backfill zones. 5. Plastic membranes should not be placed adjacent to the fuundatlon walls, A pervlous textlle should be used to control weed growth' 6. Any settllng of foundatlon or foundatlon wall backfill should be rearaded to maintain the slopes noted above. TIMTTATIONS This sfudy has been conducted ln accordance wlth generally accepted geotechn¡cal engineerlng practlces in thls area and for use by the client for design putposes. The ændusions and ieømmendations presented in this report are based on the date obtâlned from the test pits and the prçosed constructbn. If during construction, soil, bedrock or water conditions appear to be different than that presented ln thls report, Hamllton should be cuntacted to reevaluate 250 Pearl Street, $te 206, Denver, Colorado 90203 Phone: 303-733'4702 KC Hamilton Engineering, Inc. rob No, 08-10s, t"* ?jJ"ol the recommendations presented herein, if necessary. A representative of the Engineer should ı¡rur" foundation .iárvrtionr and foundatlon bearing strata. It should be noted that l'{amilton ñ; ;;i piou¡¿. .omþ*ion tesüng services, a third party must be contacted for thæe seruices, r you have any queslons regardtng this report, pleaæ call (303'733'4702 ar 720'261'9358). Prepared bY: Kenneth C, Hamilton, P'E. ProJect Engineer Attachments - Flgures 1.0 and 1.1 3 Coples Sent KCH/kch 3grìr t/8tøs 250 Pearl Street, Ste 206, Denver, colorado 80203 Phonel 303'733-47Q2 BACKFILL MIRAFI ll+ON OR ó"-8" MlN, CLEAN WASHED GMVEL GEOTEXTILE rc 12' MIN /.-INCH DIAMETER PERFORAÏED PVC PIPE MINIMUM SLOPE OF I/8'PER FOOT FOR RICID PIPË MINIMUM SLOPE QF llt4' PER FO0T FOR FLEXIBLE PIPE I INSTALL DRAIN ABOVE LINE NOTES: I, DRAIN PIPH SHOIII D I EÀD TO SUMP OR POSITIVE GRAVITY DISCHARGE. 2. COVbR GRAVEL Cüf'{PLtIÈLY WI'IH GEOTËXIILb IN SANI]Y OR 5ILI'Y SUILS. 5. BOTTOM OF DRAIN SHOULD BE A MINIMUM OF 12 INCHES BELCIW TOP OF SLAB AT HIGH POINT. 4. GRAVEL SPËC|F|CAT|ONS: CLEAN WASHED GRAVEL, 100% PASSING 1.5", ó0-1007o RETAINED #/n, <5% PASSING #2OO SLÄB WALL Ð ç 6o oôêÉ' o o K.C. HAMILTON Engineoring, lnc. 25O Pearl Etregt, Urdt 2Oe, Denv€r, OO 8O2Og Phons/Fa* 3O3-7SS-47O2 Tlplcal Perlmeter Draln Detail JOB NO. O8-105 FIGUFIE 1.O SUBSURFACE DRAINAGE DETAIL FORINTERIOR OR LOWER FOUNDATION WALLSFIGURE 1.1JOB NO. O8-105K.C. HAMILTON Eng¡nêering, lnc-250 Pearl Süeet, Unit206, Derwer, CO 80203PhonerFa¡<: 303-733-4702TIIRAFI I¿ON OR EOUIVÀLENTGEOTEXTILE FILTÊR FABRICNOTES:I. DRAIN PIPË $IOULD LEAD TO SLIMF OR POGITIVE ËRAVITY DISCIIARGE.2. BOTTOT'1 OF DRAIN SHOI.JIJ BE A ÈîINIMUH OF 12 INCHES SEI.OìÂ/ TOP OF SI AB ÂT HIGII POINT,5, GRAVEL SFEçIF|CAT|0NS: CLEAI-I WA$IED GRAT;EL, 10096 PASSING 1.5', ó0{00% RETAINED *4AND LESS THAN 5% PASSING +2OO SIEVE,5, THE SIJB-FLOOR GRAVEL MTJST BE CONNECTED TO THE EXTERIOR PERIHETER DRAIN ATII{TERIOR STEF1 AND/OR FOUNDATION WALLS, OR AT TTIE FOU\DATION WALL OI.I THEDOW¡IHILL SIDE OF THE STRUCTI.RE,DA}IP-PROOFING FOR INTERIOR WALLNEXT TO HÄBITABLÊ SPACEINTERIOR WALL OR LOWER (DOW\-SLOPE) FOThIDATION WALL.GGooo6aINTERIOR SLAB OR EXTERIOR CRADE(\GD(0oQ.'aös..6åo,s!GqCLEAN GRAVELqSLÁBôå4q.,s,.Àoôt?"MINs4t'llN,DCLEA! WAS1IED GRAVEL (SEE NOTES AND REFORT)ô-INCH DI,ÄMETER PERTORÀTEDFVC PIPE Î'4INIM|'.F4 SLOFÊ OFI/8'PËR FOOT FOR R¡GID PIPEMlNlMuH SLOPE OF l//*'PER FOOTFOR FLEXIBLE PIPÊIIISIALL DRATN ÂBOVE LINESL¡S KC Hamilton Englneerlng, Inc, October 1, 2008 Attr: Richard Nellèy Neiley & Alder, Atþrneys 6800 Hlghway 82, Sulte I Glenwood Springs, CO 81601 Subject:G€oüeclrnical Englncedng Reoommendations - Supdemental #l Proposed Triplex,4{24 County Road 154 Garfleld County, C¡lorado Job No. O8-tO5' Mr. Nelley, KC Hamilton Érglneering, Inc. (Hamilton) prepared this letter regarding supplemental Geotechnical Engineering recommendations fur the subject prqect, FOUNDATION AND RFTAINING WALIS Wall Deslgdl Foundatlon walls whlch are laterally supported and ocpected to underyo a minimal to moderate amount of movement should be designed with based on an aþrest lateral earth pressufe computed based on an equlvalent fiuld welght of 6O pcf. Latelal reststance to of the spread footings suppofting foundation walls is based on both fictlon betwæn the footÍng and lb subsolls and passive eafth pressures of the soils on the slde of the footing. A coefficlent of frlctlon of 0.4, and a passlve pressure based on an equivalent fluid weight of 2ül pcf are recommended. Slte Retalnlng Walls: Slte retainlng walls that are allowed to a moderate amount of movement can be deslgned based on an active lateral earth pressure computed based on an equivalent ffuld weight of 45 pcf. These values should be censidercd workinE values. These pr€ssutes assunrc dralned currdl[lorts behlnd the foundation walls. The bulldup of free water behind a foundation wall will lncrease the lateral pressures on the wall. All foundation walls should be designed for appropriate hydrcstatic and surcharge pressures such as: sloping backfill, adþcent bulldlng foundations and slabs, taffic, constructlon matertals and equlpment. 250 Pearl Street, Unlt 206, Denver, Colorado 80203 Phone: 303-7334702 KC Hamllton Englneerlng, Inc, Job No. 08-101 October 1, 2008 Page 2 If you have any questíons regarding this report, please call (303-733-4702 or 72Q-26L-9358). Prepared by: Kenneth C. Hamilton, P'E' Project Engineer 2 copies Sent via USP$ and 1 copy via electronic fnail' KcH/kch 397!ı t0 r43 250 Pearl Street, Ste 206, Denver, Colorado 80203 Phone: 3O3'733'47t2