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Home My WebLink AboutObservation of Excavation 08.08.08E4 lJri ..rr¡ii-irlni.;1.. t '¡.rq,..ii¡1¡. ¡i l¡,, _)\ ._\ ( tJi r' l.Li., ¡ i.:Ì tiltrr ,¡,,i 11 r'r;tr'. ( ,,1,'r rrl, \lr Jl iìlt 'i¡' 'r;,1 tl.¡; 1i;ti. FIEPWORTH . FAWLAX GEÕTECIi NICAL August 8,2008 Dave Cardiff Construction 506 Mesa Verde Carbondale, CO 81623 APR I I 20tr Job No. 108 4594 Subject:observation of Excavation, Proposed Residence, 2.9 miles up cattle creek Road, Garfield County, Colorado Dear Mr. Cardiff: As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. observed the excavation at the subject site on August 5, 2008 to evaluate the soils exposed for foundation support. The findings of our observations and recom¡nendations for the foundation design are presented in this report. The services were perfonned in accordance rvith our agreement for professional engineering services to Dave Cardiff Construction, dated August 5,2008. The proposed residence will be a one story wood frame structure over fl walkout basement. The floors of the attached garage and basement âre proposed to be slab-on- grade. Foundations were designed based on an assumed soil bearing pressure of 4,000 psf. At tltc time of our visit to the site, the foundation excavation lrad been cut in three levels from I to 6 feet below tlre adjacent ground surfaee. Thc soils exposed in tlre bottorn of the excavation consisted primarily of natural slightly sihy to clayey ¡noist gravelly sand to silty sandy gravels and cobbles. Tlre subgrade soils in the fiost walt trend on the south side of the house tvere moist and had sand and silt lenses within the silty sandy gravel. Results of swell-consolidation testing performed on a sample of sand and silt taken from the sitq shown on Figure 1, indicate the soils have low to rnoderate compressibility under conditions of loading and wetting. The results of a gradation analysis performed on a sarnple of silty. sandy gravels (minus 3 inch fraction) obtained liom the site are presented on Figure 2. No free water was encountered in the excavation. Dave Cardiff Construction August 8,2008 Page 2 Considering the conditions exposed in the excavation and the nature of the proposed constructioq spread footings placed on thc undisturbed natural soil designed for an allowable soil bearing pressure of 1,500 psf should be adequate for support ofthe proposed residence. The exposed soils tend to compress when wetted and there could be some post-construction settlement of the foundation if the bearing soils become wet. The amount of settlement would be related to the depth and extent ofthe settlement. Footings should be a minimum width of I 6 inches for continuous walls and 2 feet for columns. Loose and disturbed soils in footing areas should be removed and the bearing level extended down to the undisturbed naturalsoils. Exterior footings should be provided with adequate soil sover above their bea¡ing elevations for frost protection. This site should be considered Class D ((IBC 2003) for seismic design. 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 also be designed to resist a lateral earth pressure based on an equivalent fluíd unit weight of at least 50 pcf for on-site soil as backfill. A perimeter foundation drain should be provided to prevent temporary buildup ofhydrostatic pressure behind the basement walls and prevent wetting oftbe lower level. An impervious membrang such as 20 mit PVC should be provided below the drain gravel in a trough shape and attached to the foundation wall with mastic to prevent wetting ofthe bearing soils. Structural fillplaced within floor slab areas can consist of the on-site soils compacted to at least 95.orå of standard Proctor density at a moisture content near optimum. Backfill placed around the structure should be compacted and the surface graded to prevent ponding within at least l0 feet of the building. Landscape that requires regular heavy irrígation, such as sod, and sprinkler heads should not be located within l0 feet ofthe foundation. The recommendations submitted in this letter are based on our observation of the soils exposed within the foundation excavation and do not include subsurface exploration to evaluate the subsurface conditions within the loaded depth of foundation influence. This study is based on the assumption that soils beneath the footings have equal or better support than those exposed. The risk of foundation movement may be greater than indicated in this report because of possible va¡iations in the subsurface conditions. In order to reveal the nature and extent of variations in the subsurface conditions below the excavation, drilling would be required. lt is possible the data obtained by subsurface exploration could change the recommendations contained in this letter. Our services do Job No. 1084594 effiecfr Dave Cardiff Construction August 8,2008 Page 3 not include determining the presence, prevention or possibility of mold orother biological contaminants (MOBC) developing ln the future. If the client is concerned about MOBC, then a professional in this special field ofpractice should be consulted. If you have any questions or need further assistance, please call our office. Sincerely HEPWORTH * PAWLAK GEOTCHNICAL, TNC. Scott W. Richards Roviewed by: Ðaniel E. Hardin, P.E. SWR/ksw attachments Figure I * Swell * Consolidation Test Results Figure 2 * Gradation Test Results cc:Chris Krabacher, Architect @ JobNo.108459Â cåStecrr 0 1 2 3 òQ .ottt an o)o Eo CJ 4 5 6 7 I .0 10 APPLIED PRESSURE - ksf Moisture Content * 19.0 percent Dry Density * 110.1 pcf Sample of: Q¡¿yelly Silty Sand From: Frost Walf Footing Grade, South Side {t-t+; 7 Compres ¡þn il uPun wetting il \) il 0.1 100 108 459A SWELL.CONSOLIDATION TEST HESULTS Figure 1 7HF 15 MrN. TIME RÊADINGS U S. STANDARD SEFIES #100 #50 #30 #16 #8 CTEAR SOTJAREOPENINGS 24045 4 1 #4 E8' U4' 111? 3' 5'6' 8.100 s0 80 ?o 't0 20 30 c¡ 240 l¡Ju l- 50zl¡JC' Ë, t¡Jo-60 602 ñ UI o- ı0 l-z l¡J(Jül¡l40 o- 70 80 90 100 30 20 10 0 0ol .002 .005 ,009 .019 ,037 .A74 .150 ,300 .600 1.18 2.36 DIAMETER OF PARTCI..ES IN MII.I.IMEÌERS 4,7â 9.5 19.0 37,6 125 762 1S2 203 127 fltY fe $r,f cosstEs GRAVEL 47 O/"SAND 26 0/"SILTAND CIAY 27 % LICIUID LIMIT %PLASTIGnY INDEX OA FROM:Footing Grade, West Side + -EE -- -- E- -------E ---------------- ---- ------ EE ----- ---- E¡- -tI Ë -E -- - E --- SAMPLE OF: Silty Sandy Gravet 108 459A GHADATION TEST BESULTS Figure 2 GARFIELD COU T.ITY ENVIRONITIENTAL H EALTH ÐEPA RTMENT Percolatlon Teet and Soils Data Form - TABLE f - PROJECT {532 PROFILE PIT 0-1', 1'- 8.0' Date of Test: Sandy Root Zone Sand, Clayey, Oense, Moist, Brown / Grey Scattered Rocks up to 8-inches in diameter No Groundwateror Bedrock was Hole No. Hole Deplh {in.) lnterval {min.} Measurement at Start of lnterval (in.) Measurement at End of lnterval {in.) Change {in.} Percolation Rate {min.lîn.}MPl 133 20 2A 20 20 2t 20 20 29 2A 2A 2A 20 20 20 20 20 2A 2û 2.50 4.oCI 5.00 6.00 3,50 4.50 4,00 5.00 6.r)0 7.25 4,50 5.50 r.50 1-00 1.00 1.25 1.00 1.00 fiü 2A 237 1.75 3.25 4,00 5.00 5.75 6.50 3.25 4.00 5.00 5.75 6.50 7-25 1.50 0"75 1_00 0.75 0.75 o75 27 339 2.50 4.00 s.26 6.00 7.00 7.75 4.00 5.25 6.00 7.00 7.75 dry 1.50 1.25 0.75 1.00 0.75 27 AVG = 25 lUlPl EXHIBIT A LAND SURVEYING@CTvlLENGINEERING ENGINEERS ESTIMATE OF PROBABLE PUBLIC COSTS Date: l1-10-16 RE: Velasquez Water System Estimated improvements include: Well pump and well pipe - $3000 Purecore piping from well house and tank 140' $30/ft. - $4200 Electrical work from house to well pump - $500 Pressure tank and switch in house - $1500 Total Estimated Cost of improvements: $9,200 Prepared by Roger Neal, PE I5I7 BUKE AVÊNUE, SUllE IOI GLÉNwooD SPRTNGS, cO 8l 6()l 9709458676. PHoNE 97O9¿1F2555. Fff www,HcENG.coM