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HomeMy WebLinkAboutSubsoil Study for Foundation Design 07.31.07) ~tech HEPWORTH-PAWLAK GEOTECHNICAL July 31, 2007 Gary Setnes ~ ( l P.O. Box 1270 .JO c. To Carbondale, Colorado 81623 Hepworth-Pawlak Geotechnlcal, Inc. 5020 County Road 154 Glenwood Springs, Colorado 81601 Phone:970-945·7988 Fa."(: 970-945-8454 email: hpgeo@hpgcocech .com Job No.I 07 0440 Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot 2, Overview Subdivision, Garfield County, CoJorado . · Dear Mr. Setnas: . ' As requested, Hepworth-Pawlak Geotecbnical, Inc . performed a subsoil study for design of foundations at the subject site. The study was conducted in accordance with our agreement for geotechnical engineering services to you dated June 6, 2007. The data .. obtained and our recommendations based on the proposed construction and subsllr:face " conditions encountered are presented in this report. Evaluation of potential geologic hazard reports to the site is beyond the scope of our study. Proposed Constru~tion: The proposed residence will be a single story wood frame structure over a walkout basement level located in the area of the pits shown on Figure 1. The attached garage and basement floors will be slab-on-grade. Cut depths are expected to range between about 3 to 6 feet. Foundation loadings for this type of construction are assumed to be reiatively light and typical of the proposed type of construction. ' . If building location, conditions or foundation loadings are.significantly different from those described above, we should be notified to re-evaluate the recoz:nmendations presented in this report. · . ' Site Conditions: The site was vacant at the time of our field exploration. There is a . . rough graded diiveway into the building area and the vegetation has been stripped. The ground surface slopes gently to moderately down to the south. Vegetation consists of sagebrush, grass and weeds with s~ds of scruboak surrounding the building area. Scattered pasalt cobbles and boulders were exposed on the ~ound surface . . , Subsurface Conditions: The subsurface conditions at the site were evaluated by . I-' observing three exploratory pits at the approximate locations sho~,pn Figure i. The pits bad been excavated prior to our arrival on-site. We understand that the pits had been · · excavated to planned footing grade. 'The Jogs of the pits are presented on Figure 2. :rb:e subsoils encountered, below about 1 to 2 feet of topsoil, generally consist of rel,atively dense,.~~~Y -~l~yey g:r~v_el VJith cobbles and boulders to the pit depths of 2~ to 5 feet. · The soils were mote' clayey and less rocky in Pit 2. Results of swell-consolidation testing · performe9 on relatively undisturbed samples of clay soils and clay matrix, presented on Parker 303-841-7119 • Colorado Springs 719-633 -5562 • Silverthorne 970-468-1989 •' (" :, .~ l •. :~ _) .) Figure 3, indicate low compressibility under existing moisture conditions and light loading and a low expansion potent ial when wetted. Results of a gradation ana lysis performed on a sample of clayey sand and gravel (minus 3 inch fraction) ob tained from Pit I are presented on Figure 4. The laboratory testing is swnrn arized on Table I. No free water was observed in the pits and the soils were slightly moist to moist. Foundation Recommendations: Considering the subsoil cond itions encountered in the exploratory p its and the nature of the proposed construct ion, we recommend spread footings p laced on the undisturbed natural soil designed for an allowable soil bearing pressure of 1,500 psffor support of the proposed residence . The clay soils appear to be expansive when wetted and compressible under increased loading after wetting. The movement would tend to be differential between footings bearing on the more granular soils and footings bearing on the clays. The clay soils could be removed to reduce the differential movement potential and should be further evaluated at the time of construction. Footings should be a min imum width of 18 inches for continuous walls and 2 feet for columns. Loose and disturbed soils encountered at the foundation bearing level withi n the excavation should be removed and the footing bearing level extended down to the undisturbed natural soils. Exterior footings should be provided with adequate cover above their bearing elevations for frost protection. PJacement of footings at least 36 inches below the exterior grade is typically used in this area. Continuous foundation walls should be 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 structures should be des igned to resist a lateral earth pressure based on an equivalent fluid unit we ight of at least 50 pcf for the on-site soil, excluding vegetation, topsoil or oversized rock, as backfill. Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade construction. The clay soils appear expansive when wetted which could result in some slab movement and distress if they become wet. To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and colwnn s with expansion joints which allow unrestrained vertical movement. Floor slab control joints should be used to reduce damage due to shrinkage cracking. The requirements for joint spacing and slab reinforcement 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 aggregate with less than 50% passing the No. 4 sieve and less than 2% passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95% of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on-site predominantly granular soils or imported granular fill devoid of vegetation, topsoil and oversized rock. Underdrain System: Although free water was not encountered during our exploration, it bas been our experience in the area and where clay soils are present that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen Job No.107 0440 .. -3- ground during spring runoff can 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 level with free-draining granular 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. 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 of2 inches. The drain gravel backfill should be at least 1 Yl feet deep. An impervious membrane such as 20 mil PVC should be placed beneath the drain gravel in a trough shape and attached to the foundation wall with mastic to prevent wetting of the bearing soils. Surface Drainage: The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: I) 2) 3) 4) Inundation of the foundation excavations and underslab areas should be avoided during construction. Drying could increase the expansion potential of the clay soils. Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95% of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximum standard Proctor density in landscape areas. Free-draining wall backfill should be capped with about 2 feet of the on-site, finer graded soils to reduce surface water infiltration. The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. We recommend a minimum slope of 12 inches in the first 10 feet in unpaved areas and a minimum slope of3 inches in the first 10 feet in pavement and walkway areas. Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Irrigation sprinkler heads and landscaping which requires regular heavy irrigation, such as sod, should be located at least 5 feet from foundation walls. Limitations: This study has been conducted in accordance with generally accepted geotecbnical engineering principles and practices in this area at this time. We make no warranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory pits excavated at the locations indicated on Figure I and to the depths shown on Figure 2, the proposed type of construction, and our experience in the area. Our services do not include determining the presence, prevention or possibility of mold or other biological contaminants (MOBC) developing in the future. If the client is concerned about MOBC, then a professional in this special field of practice should be consulted. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory pits and variations Job No.107 0440 .. _) -4- 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 at once so re-evaluation of the recommendations may be made. This report has been prepared for the exclusive use by our client for design pwposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should provide continued consultation and fie ld services during construction to review and monitor the implementation of our recommendations, and to verify that the recommendations have been appropriately interpreted. 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. If you have any questions od f we may be of furth er assistance; please let us know . Respectfully Submitted, HEPWORTH · PAWLAK GEOTECHNICAL, INC. Jordy Z. Adamson, Jr., P.E. Reviewed by: Steven L. Pawlak, P.E. JZA/cay attachments Figure 1 -Location of Exploratory Pits Figure 2 -Logs of Exploratory Pits Job No.107 0440 Figure 3 -Swell-Consolidation Test Results Figure 4 -Gradation Test Results Table 1 -Summary of Laboratory Test Results i~) _) .. LOT1 H-PGEOTECH JOB NO . 1070439 --- 7525 -_.,,,, ~ ~ -------....... -... -----~ -------.,....,....----.,,,------ .,,,-_____ ..... _ ..... LOT2 OVEAVIF)N SUBDIVISION -- ------~ ---' --....... EXISTING ..aWELL ------....... -----• PIT2 ............ --' ...-" ..... ' .,... ,,.. / PIT 1 • • PIT 3 '\ ~-~ \ -\ ---... ---......... --' ,,..---\ .,,,., .,,,.,./' \ ------' -' --'\ APPROXIMATE SCALE 1" == 60' \ \ \ 7525 1070440 o&5tech LOCATION OF EXPLORATORY PITS Figure 1 Hll"WOR'TH·PAWLAI( GEOTECHNICAL -{ ., . i u.. ' .J:: a. Q) 0 0 5 10 LEGEND: PIT 1 PIT2 PIT3 WC=19.5 00=101 WC=20.4 no .. 100 ·200:80 TOPSOIL: sandy silty clay, organics , roots, firm, slightly moist, dark brown to black. 0 5 10 CLAY AND GRAVEL (CL-GC); sandy, scattered cobbles, medium dense, moist, reddish brown, subangular fragments of siltstone/sandstone. NOTES: GRAVEL (GC); clayey, sandy, with cobbles and boulders, dense, moist, reddish brown, subangular fragments of siltstone/sandstone. 2" Diameter hand driven liner sample . Disturbed bulk sample . 1 . Exploratory pits were obseNed on June 12, 2007 , and had been excavated with a trackhoe prior to our visit. 2. Locat ions of exploratory pits were measu red approximately by pacing from featu res shown on the site plan provided. 3. Elevatio ns of exploratory pits were not measured and the logs of exploratory pits are drawn to depth. 4. The exploratory pit locations should be considered accurate only to the deg ree implied by the method used. 5 . The lines between materials shown on the exploratory pit logs represent the approximate boundaries between material types and transitions may be gradual. 6. No free water was obseNed in the pits. Fluctuation in wate r level may occur with time. 7 . laboratory Testing Results: WC = Waler Content (%) DD = Dry Density (pcf) -+4 =Percent retained on the No. 4 sieve -200 = Percent passing No. 200 sieve cu Q) u. • .£:. a. Ql 0 107 0440 LOGS OF EXPLORATORY PITS Figure 2 .. . . .-Moisture Content = 19.5 percent , -Dry Density = 101 pcf Sample of: Sandy Silty Cfay Matrix From: Pit 1 at 2.5 Feet '#-0 5 -r-'(ii i-c ,.... '"'"" -~~ CG tiD a. 1 ~ Expansion ~ • ~t> c upon 0 wettina "Iii 2 Cl) f!! a. E 0 (.) 3 0 .1 1.0 APPLIED PRESSURE • ksf 10 100 _) Moisture Content I:> 20.4 percent Ory Density= 100 pcf Sample of: Sandy Silty Clay From : Pit 2 at 4 Feet '#-0 c 0 -r--( ~ 1n i-c ~ i---... CG ~"" I'..... a. 1 ~ Expansion l~ I c upon I\ ·~ 2 wettina ~ IJ 0. E 0 3 (.) ) 0 .1 1.0 10 100 APPLIED PRESSURE -ksf 107 0440 ~~ HEPWORTH-PAWLAK GEOTECHHICAL SWELL-CONSOLIDATION TEST RESULTS Figure 3 . . . c IJJ z ~ w a:: 1-z w 0 a:: IJJ ) a. ) . . I HYDAOMETERANALYSIS I SIEVEANALYSIS I ~ H TIME READINGS U.S. STANDARD SERIES I Cl.EAR SQUARE OPENINGS O ~rn~.15Ml~.60MIN19MIN.4MIN.1 MIN. #200· #100 #50 #30 #16 #8 #4 318' 3/4' 11/2' 3' 5"6' fr 100 10 20 30 40 50 60 70 80 90 100 .001 .037 .074 .150 .300 .600 1.18 2.36 4.75 9.5 19.0 37.5 76 .2 152 203 12.5 127 .002 .oos .009 .019 DIAMETER OF PARTICLES IN MIWMETERS QAY'R>s:t.T I =.... !CXlARS£ I FU T ?'S I coeeLES GRAVa 29 % SAND 28 % SILT AND CLAY 43 % LIQUID LIMIT % PLASTICITY INDEX % SAMPLE OF: Clayey Sand and Gravel FROM: Pit 1 at 3 to 3.5 Feet 90 so 70 50 40 30 20 10 0 1070440 G~ GRADATION TEST RESULTS Figure 4 Hu>WORTH·PAWLAK Gl:OTECHNICAl. lJ SAMPLE LOCATION NATURAL NATURAL MOISTURE DRY PIT DEPTH CONTENT DENSITY (I\\ (%\ (ocf\ 1 21h 19.5 101 3 to 31h. 2 4 20.4 100 ;--· .. HEPWORTH-PAWLAk-dEOTECHNICAL, INC. TABLE 1 SUMMARY OF LABORATORY TEST RESULTS GRADATION PERCENT ATTERBERG LIMITS GRAVEL SANO PASSING UQUID PLASTIC NO. ZOO UMIT INDEX (%) (%) STEVE (%) (%\ 29 28 43 80 UNCONANED COMPRESSIVE STRENGTH (P5F) ·0 Job No. 107 0440 SOJLOR BEDROCK TYPE Sandy Silty Clay Matrix Clayey Sand and Gravel Sandy Silty Clay . . wa~ne Shelton 970-927-3801 p.2 -· ! I WELL CONSTRUCTION AND TEST REPORT FOR OFFICE USE ONLY I ST A.Tl?. OJ:' COT ,ORA n0. nFFTCF. OF THE c;TATE. ENG1NEEP .--~ -· t. I WELL PERMIT NUMBER 2~?~64. -· ---I ·:~ ! 2. Owner Name(s): Rudd Constr1:.1ction Mailing Address: 0132 Park Ave. City, State, Zip : Basalt, Co. 8 t 621 Phone # . 970-927-9119 APPROVAL# GWSJ 1-91.0l I . ' ~~El L J.!:lC8IIQIS ~S 12B.IJ,LEQ NW 1/4 SW 1/4 Sec: 36 3. DISTANCES FROM SEC. LINES Twp: 6 s Range: 88 w ' 1600 fl . from South Sec. line and 1050 ft. from West Sec. line OR Northing: Easting: SUBDIVISION : LOT: BLOCK: FILING (UNIT): STREET ADDRESS AT LOCATION I GROUND SURFACE ELEVATION ft. DRILLlNG METHOD Air Rotary 4. DATE COMPLETED: 6/4/2003 TOT AL DEPTH: 215 DEPTH COMPLETION: 215 s. GEOLOGIC LOG 6 . HOLE OlAMETER (ill) FROM (ft) TO (fl) Deoth Tvoe of Material (Size. Color. and TVJ>e) 9.0 0 40 000-012 Dirt. Rocks 6.S 40 ns ..... _ 012-215 Maroon Formation = 7. PLAIN CASING OD (in) Kind Wall Size From (ft) To {fl) 7.0 Steel 0.240 _, 40 s.s PVC 0.250 35 170 PERF. CASING: Screen Slot Size s.s PVC 0 .250 170 115 I I i 8. Filter Pack 9. Packer Placement I Water Located : 170 + Material : Type : Size : Deprh : Remarks : Interval : 10 . GROUTING RECORD Mata'ial Amount Densicy -, 1111~""''' J J l'l>a:mcn1 Cement 5 sks 6 ual/sk I 10-40 ~ · oourcd I I I I I I I. DISINFECTION : Type : HTH Amt. Used: 3 oz. I 12. WELL TEST DAT A : () Check Box If Test Data Is Submitted On Supplemental TESTING METHOD : Air Compressor I ' Static Level : 162 ft. Date/Time Measured 6/4/2003 Producrion Rare 20 gpm I Pumping Level : Total ft. Date/Time Measured 6/4/2003 Test Length : :?. hours I Test Remarks: I 13. l h:vc rc >J lhc .:otcmcn .. n :odc herein and know lh• CllDICnll lhcrcDf. 21\d lh:ll lllcy atC llVC lo my ....... led~·· (i>•mon110 Seaton 24-4-1-4 ( 13)(:1> CKS.1h: •n:ll:in~ or false Jl.-.!Clncl\I< conu1101c: P:I]•,,_ 1n 111: ~tccnd dci;Jcc 111d •• purnslt:l>lc &S •class I mts.1cmunor) • CONTRACTOR : Shelton Drilling Corp. Phone: (970) 927~4 I &2 l Mailing Address : P.O. Box I 059 Basalt, Co. 81621 L..ic . Xo. 1095 Name I Title (Please Type or Print) Signature Date Wnync Shelton I President 6/26/2003 ! . -. .•. . . ·~. ~ . ,,. ~i,. -,,,, • .. ' OFFICE OF THE STA TE ENGINEER COLORADO DIVISION OF WATER RESOURCES ---·---~·f..Ji~f ~ ;.i .. :-· ... 'Form No. GWS-25 818 Centennial Bldg., 1313 Shennan SL, Denver, Colorado 80203 (JC'll~ !!5€-3!''3~ APPLICANT RUDD CONSTRUCTION 0132 PARK AVE BASALT, CO 81621- Lot WEi..L PEi<Fl.IT i~LJrt.SER -----'2::;5::.:-'::.:5'-"6'-'4'-------- DIV. 5 . WO 38 DES. BASIN MD C Block: Ftllng: Subdiv: 29 PEAKS APPROVED WELL LOCATION GARFIELD COUNTY NW 1/4 SW 1/4 Section 36 Township 6 S Range 88 W Sixth P.M. DISTANCES FROM SECTION LINES 1600 Ft. from South 1050 Fl from West UTM COORDINATES Section Line Section line (970) 927-9119 PERMIT TO USE AN EXISTING WELL Northing: Easting: ISSUANCE OF THIS PERMIT DOES NOT CONFER A WATER RIGHT CONDITIONS OF APPROVAL 1) This well shall be used In such a way as to cause no material injury to existing water rights. The issuance of this permit does not assure the applicant that no injury will occur to another vested water right or preclude another owner of a vested water right from seeking relief In a civil court action. 2) The construction of this well shall be in compliance with the Water Well Construction Rules 2 CCR 402-2, unless approval of a variance has been granted by the State Board of Examiners of Water Well Construction and Pump Installation Contractors in accordance with Rule 18. 3) Approved pursuant to CRS 37-92-602(3)(b){ll)(A) as the only well on a tract of land of 35.3 acres described as that portion of the NW 1/4 of the SW 1/4, Sec. 36, Twp. 6 South, Rng. 88 West, Sixth P.M.,(aka Lot C, 29 Peaks subdivision), Garfield County, more particularly described on the attached exhibit A. - 4) Approved for an amended legal description and use of an existing well constructed on June 4 2003, to a depth of 215 feet, under permit no. 250693 (canceled). Issuance of this permit hereby cancels permit no. 250693. 5) The use of ground water from this well is limited to fire protection, ordinary household purposes inside not more than three (3) single family dwellings,·the irrigation of not more than one (1) acre of home gardens and lawns, and the watering of domestic animals. 6) The maximum pumping rate of this well shall not exceed 15 GPM. 7) The return flow from the use of this well must be through an Individual waste water disposal system of the non-evaporative type where the water Is returned to the same stream system in which the well is located. 8) This well shall be located not more than 200 feel from the location specified on this permit. NOTE: Parcel Identification Number (PIN): 23-2187-363-00-146 (subject to change with amended survey 07/02/03} NOTE: Assessor Tax Schedule Number: R007348 ~ gp 'f 8 APPROVED MSC State Engineer Recei t No. 9501584C DATE ISSUED 08-26-2003 ' S~p fl 04 10:3Sa R EPORT DATE 09/21/04 RECEIPT APP DATE 9501584B 07/17/03 DIV CO FILE NUMBER 5 23 252563 ADDRESS 0132 PARK AVE ZIP -EXT PHONE Wa~ne Shelton 970-927-3801 COLORADO WELL APPLICATIONS AND PERMITS COLORADO DIVISION OF WATER RESOURCES p.2 PAGE STAT DATE NP DATE WELL-X-REFER I I os/26/03 2so297 TRANS ACTIV STAT CD PI CD NP CD WD BAS 38 00 MD 00 ADDRESS2 NAME RUDD CONSTRUCTION CITY BASALT QlO Q40 Q160 ST co l 81621 (9709)279-119 NE SE SEC TWNSHP 35 6 s RANGE 88 w PM s CASE NUM USES 8 L SUBDIVISION 29 PEAKS DRLR EXST PUMP INST -----COORDINATES 1196 N/S 1530 S E/W 325 E LOT B BLK FLG REPT ~-WELL --COMP REPT PUMP --COMP 07/17/03 DATE 05/21/03 06/24/04 DATE 06/0l/04 COMMENTS ENG USER To use existing well & change legal description of well permit #250 MBC AOT NWC RECD NBU RECD --DATE----DATE-- I I I I AC RE-FT TOP/PERF/BOT 120 1.60 EXPIRE DATE STATUTE I I I ( 6023} SBU RECD BENEF USE --DATE----DATE-- I I I I DEPTH YIELD LEVEL 163 15.00 107 ID ACRE IR QUAL 00000 1.00 N AMENDED --DATE-- / I ELEV RECD -ABAND --COMP --DATE ----DATE I I I I METER LOG AB~.ND REQD N N N AQUIFER (S) OWNER DESIGNEE ( l) GW ( 2} ~ep ~l u~ lU:3Sa REPORT DATE 09/21/04 RECEIPT APP DATE 9501584C 07/i7/03 DIV CO FILE NUMBER 5 23 252564 ADDRESS 0132 PARK AVE ZIP EXT PHONE W~~ne Shelton 970-927-3801 COLORADO WELL APPLICATIONS AND PERMITS COLORADO DIVISION OF WATER RESOURCES p.3 PAGE STAT DATE NP DATE WELL -X -REFER I I oa/26/03 250693 TRANS ACTIV STAT CD NP CD NP CD WD BAS 38 00 MD 00 ADDRESS2 NAME RUDD CONSTRUCTION CITY BASALT Q10 Q40 Q160 ST co 1 81621 (9709)279-119 NW SW SEC TWNSHP 36 6 s RANGE 89 w PM s CASE NUM USES 8 L DRLR PUMP INST -----COORDINATES ----- EXST N/S 1600 S E/W 1050 W LOT BLK FLG c SUBDIVISION 29 PEAKS REPT --WELL --COMP REPT PUMP --COMP 07/17/03 DATE 06/04/03 I I DATE I I COMMENTS ENG USER To use existing well & change legal description of well permit #250 MBC MBC NWC RECD NBU RECD SBU RECD BENEF USE AMENDED RECD -ABAND--COMP --DATE----DATE----DATE-- --DATE----DATE----DATE----DATE I I I I I I I I I I I I I I ACRE-FT TOP/PERF/BOT DEPTH YIELD LEVEL ELEV METER LOG .u.EAND REQD 170 215 215 20.00 162 N N N EXPIRE DATE STATUTE ID ACRE IR QUAL AQUIFER {S) OWNER DESIGNEE I I (6023) 00000 1.00 N (1) GW (2)