Loading...
HomeMy WebLinkAboutSubsoil Studyffi CTL ITHOMPSON W SOILS AND FOUNDATION INVESTIGATION SINGLE.FAMILY RESIDENCE LOT 41, FOUR MILE RANGH GARFIELD COUNTY, COLORADO Prepared For: HAGEMANN BUILDERS P.O. Box 1692 Glenwood Springs, CO 81602 Attention: Mr. Frank Hagemann Project No. GS04451 -B-120 March 18,2005 234 Center Drive IGlenwood Springs, Colorado 81601 Telenhone: 97ñ-9,4F'-2F'00 Fev' Q7ñ-q^c-7 ^11 ffi TABLE OF CONTENTS SCOPE SUMMARY OF CONCLUSIONS SITE CONDITIONS PROPOSED CONSTRUCTION SUBSURFACE CONDITIONS EARTHWORK FOUNDATION FLOOR SYSTEM AND SLABS.ON-GRADE BELOW-GRADE CONSTRUCT¡ON SURFACE DRAINAGE LIMITATIONS FIGURE 1 -APPROXIMATE LOCATIONS OF EXPLORATORY BORINGS FIGURE 2 - SUMMARY LOGS OF EXPLORATORY BORINGS FIGURES 3 AND 4 - EXTERIOR FOUNDATION WALL DRAINS TABLE I _ SUMMARY OF LABORATORY TEST RESULTS HAGEMANN BUILDERS LOl 41, FOUR M|LE RANCH CTLIT PROJECT NO. GS0¿1451-B-120 1 1 2 2 2 3 4 5 6 7 I ffi SCOPE This report presents the results of our soils and foundation investigation for the single-family residence proposed on Lot41, Four Mile Ranch in Garfield County, Golorado. We conducted this investigation to evaluate subsurface conditions at the site and provide foundation recommendations for the proposed construction. Our report was prepared from data developed from exploratory borings, laboratory testing, englneering analysis and our experience with similar conditions and construction. This report includes a description of the subsurface conditions at the site, and presents recommendations for design and construction of foundations, floor systems, and criteria for details influenced by the subsoils. Construction plans were not developed at the time of our investigation. lf actual building plans differ significantly from the descriptions contained in the report, we should be informed so that we can check that our recommendations and design criteria are appropriate. SUMMARY OF CONCLUSIONS Subsurface conditions encountered in our exploratory borings consisted of about 0.5 feet of clay "topsoil" and nil to 4.5 feet of silty clay underlain by clayey silty gravel with cobbles and lenses of sand and clay. Practical auger refusal occurred on cobbles at a depth of 14 feet in TH-1. Free ground water was not observed in the exploratory borings at the time of drilling. 2.we recommend constructing the residence on footing foundations that are supported by the undisturbed, natural soils. care should be taken to prevent significant wetting of the soils below the building. Design and construction criteria for footings are presented in the report. we judge the potential for differential movement will be tow for slabs- on-grade supported by the undisturbed, natural soils. Additional discussion is in the report. surface drainage should be designed to provide for rapid removal of surface water away from the residence. A foundation drain should be installed around below-grade areas in the building. HAGEMANN BUILDERS LOT 4f, FOUR MILE RANCH cTLIT PROJECT NO. cS0445l-8.120 1 3. 4 1 ffi SITE CONDITIONS Four Mile Ranch is located east of County Road 117 (Four Mile Road) in Garfield County, Colorado. Lot 4l is southwest of the terminus of Maroon Drive. An emergency access road is present along the north property boundary. Ground surface on the lot generally slopes gently down to the west at grades of about 5 percent. Some grading was performed in the east part of the lot Vegetation in the east part of the lot consists of grass. Sage and native grasses are in the west part of the lot. PROPOSED CONSTRUCTION Building plans for the residence were not developed at the time of our investigation. lf construction will differ significantly from the descriptions below, we should be informed so that we can adjust our recommendations and design criteria as necessary. We expect the proposed residence will be a two-story, wood-frame building with an attached garage. A basement and/or crawl space may be constructed below the building. Similar residences in the area are typically constructed with slab-on-grade floors in basement and garage areas. Maximum foundation excavation depths will likely be on the order of 7 to g feet if a basement is constructed. Foundation loads are expected to vary between 1,000 and 3,000 pounds per lineal foot of foundation wall with maximum interior column loads of 30 kips. Completed wall backfill depth may be slightly more than excavation depth as final grades are adjusted for drainage. SUBSURFACE CONDITIONS Subsurface conditions at the site were investigated by drilling two exploratory borings (TH-1 and TH-2) in the building envelope. The approximate locations of the exploratory borings are shown on Figure 1. Exploratory drilling operations were directed by our staff engineer who logged subsurface conditions encountered in the HAGEMANN BUILDERS LOT 41, FOUR MILE RANCH CTLIT PROJECT NO. c50¿1451-B-120 2 ---ïrITf*lffi borings and obtained samples of the soils. Graphic logs of the soils encountered in our exploratory borings are shown on Figure 2. Subsurface conditions encountered in our exploratory borings consisted of about 0.5 feet of clay "topsoil" and nil to 4.5 feet of silty clay underlain by clayey silty gravelwith cobbles and lenses of sand and clay. Practicalauger refusal occurred on cobbles at a depth of 14 feet in TH-1. Observations during drilling operations and results of field penetration resistance tests indicated the clay was stiff and the gravel was dense. Free ground water was not observed in the exploratory borings at the time of drilling. Exploratory borings were backfilled immediately after our field investigation was completed. Samples of the soils obtained from our exploratory borings were selected for laboratory testing. Laboratory test results are summarized on Table l. EARTHWORK We anticipate excavations for the building foundation and utilities can be accomplished using conventional, heavy-duty excavation equipment. Excavation sides will need to be sloped or braced to meet local, state and federal safety regulations. We believe the soil at this site will generally elassiff as Type B orType C soils based on OSHA standards governing excavations. Temporary slopes deeper than 5 feetshould be no steeperthan I to I (horizontalto vertical) in Type B soils and 1.5 to 1 in Type C soils. Contractors should identify the soils encountered in the excavations and refer to osHA standards to determine appropriate slopes. We do not anticipate excavations for foundations or utilities will encounter significant amounts of ground water. However, excavations should be sloped to a gravity discharge or to a temporary sump where water can be removed by pumping. The ground surrounding the excavations should be sloped as much as practicat to direct runoff away from the excavations. HAGEMANN BUILDERS LOT 41, FOUR MILE RANCH CTLIT PROJECT NO. GS0¡l4sl-8.120 3 ffi Fill may be required to obtain subgrade elevations for the garage floor and exterior concrete flatwork. Areas which will receive fill should be stripped of vegetation, organic soils and debris. The on-site soils free of rocks larger than 6 inches in diameter, organic matter, and debris are suitable for use as fill. Fill should be placed in loose lifts of l0 inches thick or less, moisture conditioned to within 2 percent of optimum moisture content, and compacted to at least g5 percent of standard Proctor (ASTM D 698) maximum dry density. Moisture content and density of fill should be checked by a representative of our firm during placement. Properly placed backfill adjacent to foundation wall exteriors is impoÉant to reduce infiltration of surface water and subsequent consotidation. Backfill placed adjacent to foundation wall exteriors should be free of organic matter, debris and rocks larger than 6 inches in diameter. Backfill should be moisture conditioned to within 2 percent of optimum moisture content and compacted to at least gS percent of standard Proctor (ASTM D 698)maximum dry density. FOUNDATION We recommend constructing the residence on footing foundations supported by the undisturbed, naturalsoils. Care should be taken to prevent significantwetting of the soils below the building. Our representative should be called to observe conditions exposed in the completed foundation excavation to check that the exposed soils are suitable for support of the designed footings. Recommended design and construction criteria for footings are presented below. 1 Footings supported by the natural soils should be designed for a maximum allowable soil bearing pressure of 3,000 psf. soils toosened during excavation or the forming process for the footings should be removed or re-compacted prior to placing concrete. 2. HAGEMANN BUILDERS LOT 41, FOUR M|LE RANCH CTLIT PROJECT NO. GS0¡1451.8-120 continuous wall footings should have a minimum width of at least 16inches. Foundations for isolated columns should have minimum dimensions of 24 inches by 24 inches. Larger sizes may be required, depending upon foundation loads. 4 ffi Grade beams and foundation walls should be well reinforced, top andbottom, to span undisclosed loose or soft soil pockets. We recommend reinforcement sufficientto span an unsupported distance of at f east 12feet. Reinforcement should be designed by the structural engineer. 4 The soils beneath exterior footings should be protected from freezing. we recommend the bottom of footings be constructed at a depth of ãt least 36 inches below finished exterior grades for frost protection. FLOOR SYSTEM AND SLABS.ON.GRADE Similar residences in the area are typically constructed with slab-on-grade floors in garage and basement areas. Based on our laboratory test data and experience, we judge slab-on-grade construction can be supported by the undisturbed, natural soils with low risk of differential movement and associated damage. Some fill may be required below the garage floor slab and exterior concrete flatwork. Fill should be in accordance with the recommendations ouilined in the EARTHWORK section. We recommend the following precautions for slab-on-grade construction at this site. we recommend against placing a gravel or sand tayer below slabs because it increases the potential for wetting of the soits below the slabs. slabs should be separated from exterior walls and interior bearing members with slip joints which allow free vertical movement of the slabs. underslab plumbing should be pressure tested for leaks before the slabs are constructed. Plumbing and utilities which pass through slabs should be isolated from the slabs with sleeves and provided with flexible couplings b slab supported appliances. Exterior patio and porch slabs should be isolated from the residence. These slabs should be well-reinforced to function as independent units. Frequent control joints should be províded, in accordance with American concrete lnstitute (Acl) recommendations, to reduce problems associated with shrinkage and curling. our experience HAGEMANN BUILDERS LOT41, FOUR MILE RANCH cTLIT PROJECI NO. cS01145,t.B-120 3 1 2. 3 4. 5. 5 ffi indicates panels which are approximately square generally performbetter than rectangular areas. BELOW.GRADE CONSTRUCTION Foundation walls which extend below-grade should be designed for lateral earth pressures where backfill is not present to about the same extent on both sides of the wall. Many factors affect the values of the design tateral earth pressure. These factors include, but are not limited to, the type, compaction, slope and drainage of the backfill, and the rigidity of the wall against rotation and deflection. For a very rigid wall where negligible or very little deflection will occur, an ,,at-rest', lateral earth pressure should be used in design. For walts which can deflect or rotate 0.5 to I percent of wall height (depending upon the backfilltypes), lower,,active', lateral earth pressures are appropriate. Our experience indicates that typical basement walls can deflect or rotate slightly under normal design loads, and that this deflection results in satisfactory wall performance. Thus, the earth pressures on the walls will likely be between the "active" and ,,at-rest" conditions. lf the on-site soils are used as backfitl, we recommend design of below-grade walls using an equivalent fluid density of at least 45 pcf for this site. This equivalent density does not include allowances for sloping backfill, surcharges or hydrostatic pressures. The recommended equivalent density assumes deflection; some minor cracking of walls may occur. lf very little walldeflection is desired, a higherequivalent fluid density may be appropriate for design. our recent experience indicates most basement and below-grade walls designed with 45 pcf to 50 pcf equivalent fluid density have performed satisfactorily. Backfillshould be placed and compacted in accordance with the recommendations outlined in the EARTHWORK section Water from rain, snow melt and surface irrigation of lawns and landscaping frequently flows through relatively permeable backfill placed adjacent to a residence and collects on the surface of relatively impermeable soils occurring at the bottom of the excavation, This can cause wetting of the soils below the building and wet or moist conditions in basement and crawl space areas after construction. We HAGEMANN BUILDERS LOT 41, FOUR MILE RANCH cTLIT PROJECT NO. cS04451-B-120 6 ffi recommend provision of a foundation drain around below-grade areas in the building. The drain should consist of a 4-inch diameter, slotted PVC pipe encased in free draining gravel. The drain should lead to a positive gravity outfall, or to a sump pit where water can be removed by pumping. Typical foundation drain details are presented on Figures 3 and 4. Ventilation is importantto maintain acceptable humidity levels in crawlspaces. The mechanical systems designer should consider the humidity and temperature of air, and air flow volumes, during design of crawl space ventilation systems. lt may be appropriate to install a ventilation system that is controlled by a humidistat. SURFACE DRAINAGE Surface drainage is critical to the performance of foundations, floor slabs and concrete flatwork. We recommend the following precautions be observed during construction and maintained at all times after the residence is completed: The ground surface surrounding the exterior of the residence shourd be sloped to drain away from the residence in all directions. We recommend providing a slope of at least 12 inches in the first 10 feet around the residence, where possible. ln no case should the slope be Iess than 6 inches in the first 5 feet. Backfill around the exterior of foundation walls should be placed in maximum 10 inch thick loose lifts, moisture conditioned to within 2 percent of optimum moisture content and compacted to at least gS percent of standard Proctor (ASTM D 698) maximum dry density. 3.The residence should be provided with roof gutters and downspouts. Roof downspouts and drains should discharge well beyond the limits of all backfill. Splash blocks and downspout extensions should be provided at all discharye points. 4. Landscaping should be carefully designed to minimize irrigation. Plants used near foundation walls should be limited to those with low moisture requirements; irrigated grass should not be located within 5 feet of the foundation. Sprinklers should not discharge within 5 feet of the foundation and should be dirccted away from the building. 5. lmpervious plastic membranes should not be used to coverthe ground surface immediately surrounding the residence. These membranes HAGEMANN BUILDERS a LOT41, FOUR MILE RANCH I cTLIT PROJECT NO. G504451-B-120 1 2. ffi tend to trap moisture and prevent normalevaporation from occurring. Geotextilefabrics can be used to controlweed growth and aUowsome evaporation to occur. LIMITATIONS The exploratory borings drilled at the site provide a reasonably accurate picture of subsurface conditions. Variations in the subsurface conditions not indicated by the borings will occur. A representative of our firm shoutd be called to observe subsoils exposed in the completed foundation excavation to check that the soil are as anticipated and suitable for support of the footings as designed. This investigation was conducted in a manner consistent with that level of care and skill ordinarily exercised by engineering geologists and geotechnical engineers currently practicing under similar conditions in the locality of this project. No other warrant¡r, express or implied, is made. lf we can be of further service in discussing the contents of this report or in the analysis of the influence of the subsoit conditions on the design of the structure, please call. cTL ITHOMPSON, tNC.Reviewed by Edward R. White, E.l Staff Engineer ERW:JDK:cd (5 copies sent) HAGÊMANN BUILDERS LOT 41, FOUR MILE RANCH CTLIT PROJECT NO. cS0¡1451.8-120 James D. Kellogg, P.E. Project Engineer I tr Scale f '=1OO \ tcrffll"lt- ã.rîr¡ -l -u{rt T TT JÊ \ \ tc ûFdt 2flÞ.lgg¡* ¿lÊf H 54',å!'fi.rs t l€' tt\ I ,2.äBã ¡ rt \ .Ë.ItI \ ,1\ \ \\\ I t t¡ll47rn'59'!..ür¿rl {qt Lor {Í J I o Hegomann Bullder€ tot41, FoúMf,6Fânctt Project No. GS04451-B-12O Approximate Locations of Exploratory Borings \\ I\ \I 1I \ \,n I I tII \ \ ,l-üI t/.tÊsrf,ol Aèl' +l€Et Fls. f BELOW GRADE WALL ENCASE PIPE IN WASHED coNcRrrf AGGREGATE (ASTM c33, NO. 57 0R NO. 67) EXTËND GRAVEL TO AT LEAST 1/2 HETGHT OF FOOT|NG. NOTE: DRAIN SHOULD BT AT LEAST 2 INCHES BELOW BOTTOM OF FOOTING AT THT HIGHEST POINT AND SLOPE DOWNWARD rO A POSITIVI GRAVITY OUTLF| OR TO A SUMP WHERE WATER CAN BE REMOVED BY PUMPING. REINFORCING STEET PER STRUCTURAL DRAWINGS PROVIDE POSITIVT SLIP JOINT BETWEEN SLAB AND WALL, FLOOR SLAB FOOTING OR PAD PROVIDE PVC SHETflNG GLUED TO FOUNDATION WALL TCI REDUCE MOISTURE PENTTRATION E¡derlor Foundation Wall Drain SLOPE PER REPORT \\ aecxnLt---.. (coMPosmoN Ar.rD \ coMPAcTIoN PER REPoKf) \ SLOPE PER OSHA I I !Iô COVER GRAVEL WITH FILTER FABRIC- 2,' MINIMUM 8'' MINIMUM OR BEYOND 1:1 SLOPE FROM BOTTOM OF FOOTING. (WHTCHEVER tS GRIATER) 4_INCH DAMTTER PERFORATED DRAIN PIPE. THE PIPE SHOULD BE LAID ¡N A TRENCH WITH A MINIMUM SLOPË OF 0.5 PERCENT. fo tnÂü{ F,roject No. GSO¿I451 -B-1 20 Flg.O SLOPË REPORT BELOW GRADE WALL SLOPE PER OSHA ENCASE PIPE IN WASHED coNcRrrE AGGREGATI (ASTM c33, NO. 57 0R NO. 67) EXTEND GRAVE TO AT LEAST 1/2 HEtcHT OF FOOTING. INIM 8,, MINIMUM OR BEYOND 1:1 SLOPE FROM BOTTOM OF FOCITING. (wHrcHEVtR ts GREATER) PROVIDE PVC SHEIIING GLUED TO FOUNDATION WALL TO REDUCI MOISTURE PENTTRATION. REINFORCED STEEL PER STRUCTURAL DRAWINGS CRAWL S FCIOTING OR PAD BOTTOM OF EXCAVAÏON NOTE: DRAIN SHOULD BE AT LtrEST 2 INCHES BELOW BOTTOM OF FOOTINC AT THE HIGHEST POINT AND SLOPE DOWNWARD TO A POSITIVE GRAVTTI OUTLfl' OR TO A SUMP WHERE WATER CAN BE RÊMOVED BY PUMPING. Exterior Foundation Wall Drain \\gRcxnLL ---- (COMPOSMON AND \ òovpncno¡¡ pen nrponr)t COVER GRAVEL WITH FILTER FABRIC 4-INCH DIAME'TER PERFORATED DRAIN PIPE. THE PIPE SHOULD BE PLACED IN A TRENCH WITH A sLoPE RANGE BETWEEN 1/8 |NCH AND 1/4 rÑCH DROp PER FOOT OF DRAIN. ãJ:! c SUPPORTED SLOPE IÔ DRÀN Prcject No. GSO4451 -B-1 20 Flg.4 TABLE ISUMMARY OF LABORATORY TEST RESULTSPROJECT NO. cs0445t_B-120SOIL CLASSIFICATIONPASSINGNO.200SIEVE(o/o\13SOLUBLESULFATES(%)UNCONFINEDCOMPRESSIVESTRENGTH(PSF)ATTÊRBERG LIMITSPLASTICITYINDEX(Y'\LIOUIDLIMIT(o/"115SWELL*('/')NATURALDRYDENSITY(PCF)97NATURAL16.2.5DEPTH(FEEÐBORINGTH-1TH-2nNote: swell due to wetting under an applied load of 1,000 psf. Negative values ind¡cete consolidation.Page 1 of 1 lt æ n TH-f TH-2 Drive somple. The symbol 22/12 lndlcofes thql 22 blows of o 140 pound hommer folling 50 lnchss wsre requlred lo drlve o 2.5 inch O.D. Collfornio sompler 12 inches. I Drive somple. The symbol 5O/7 indicotes thot S0 h blows of o 140 pound hqmmer folllng 50 inches wers F required lo drivs o 2.O inch O.D. stqndqrd splif-spoon | "ompler 7 inches. LEGEND: þ lndlcoles bulk somple token from ouger cuttlngs. î lndicotes procllcol solid-stem oug6r refusol. Explorotory borlngs wore drlllod on Februory 22, 2005 with 4-lnch dlomsfer, solld-slcm ouger ond q trock-mounled drlll rlg. Explorolory borlngs were bsckfllled lmmedlolely ofler drllllng operollons were completed. Locoflons of explorolory borlngs orô opproxlmote. No free ground wqler wos found in our explorolory borings ol lhe llms of drllling. ffi 00 5 tr Sondy cloy otopsollo, orgonics, molst, brown. n Cloy, silty, sond, scottered grovel, sllff, sllghtly molst,lU brown. (Ct, C¡-UL, ML) ffi Grovel, cloyey, sllty, cobbles, lansas of sond ond cloy, dense, slightly moist lo moisl, brown, rust. (GC-GM, GM, SC-SM, SM, CL-ML) 22/t2 42/12 50/7 5 10 Iort:r 3 Tloo ool¡- c to 15 20 25 30 50/s 20 25 NOTES: t. 30 4. These explorolory borings ore subfecf to lhe explonotions, llmilotlons ond concluslons os conlolnedin lhfs report 2. 5. ProJecl No. GS0445|-B-120 SUMMARY LOGS OF EXPLORATORY BORINGS Fïg, 2