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Home My WebLink AboutExcavation ReportHEPWORTH-PAWLAK GEOTECHNICAL March 27, 2014 Sherry Rubin P. O. Box 747 Carbondale, Colorado 8I623 srubin@masorunorse.com Subject: Dear Sherry: Hcpworth-Pawlak Geotechnlcal, Inc 5020 County Road 154 Glenwood Springs, Colorado 81601 Phone. 970-945-1988 Fax: 970-945-8454 Email: hpgeo@hpgeotech,com Job No. 114 085A Observation of Excavation, Proposed Residence, 5326 County Road 243 (Main Elk Creek Road), Garfield County, Colorado As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. observed the excavation at the subject site on March 23, 2014 to evaluate the soils exposed for foundation support. The findings of our observations and recommendations for the foundation design are presented in this report. The services were performed in accordance with our agreement for professional engineering services to you, dated March 24, 2014. The residence will be a single story wood frame structure with an attached garage. The floors will be over crawlspace and slab -on -grade in the garage. The uphill (western) side of the garage will retain up to about 9 feet of soil. The building has been designed to be supported on spread footings assuming an allowable soil bearing pressure of 2,000 psf. The site has a strong slope down to the east. There is a steep slope down to (about 20 feet) Main Elk Creek about 10 to 15 feet to the east of the proposed residence. At the time of our site visit, the foundation excavation, which was essentially complete, had been cut in generally three levels from about 1 to 8 feet below the adjacent ground surface. The soils exposed in the bottom of the excavation consisted of relatively dense, silty sandy gravel and cobbles with scattered boulders up to about 3%2 feet in diameter. The excavation subgrade had been compacted. No free water was encountered in the excavation and the soils were slightly moist. Considering the conditions exposed in the excavation and the nature of the proposed construction, spread footings placed on the undisturbed natural soil designed for an allowable bearing pressure of 2,000 psf should be adequate can be used for support of the proposed residence. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns. Loose disturbed and any muddied soils in footing areas should be removed and the subgrade re -compacted as needed. The bearing soils should Sherry Rubin March 27, 2014 Page 2 be protected against frost and concrete should not be placed on frozen soils. Exterior footings should be provided with adequate soil cover above their bearing elevations for frost protection. Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 10 feet. Foundation walls acting as retaining structures should also be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 45 pcf for on-site granular soil, excluding topsoil and oversized rocks, as backfill. A perimeter foundation drain should be provided to prevent temporary buildup of hydrostatic pressure behind the foundation retaining wall areas and prevent wetting of the building interior areas. The underdrain system should include at least 4 inches of free draining gravel below the floor slabs. Structural fill placed within floor slab areas can consist of the on-site sand and gravel soils compacted to at least 95% of standard Proctor density 9SPD) at a moisture content near optimum. Backfill placed around the structure should be compacted to at least 90% SPD and the surface graded to prevent ponding within at least 10 feet of the building 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 variations 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. It is possible the data obtained by subsurface exploration could change the recommendations contained in this letter. 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. If you have any questions or need further assistance, please call our office. Sincerely, HEPWORTH — W]lICAL, INC. 4 E u n David A. Young, P.E. S i r DAY/kdi� sw `.,,om attachment Figure 1, Gradation Best Results Job No. 114 085A HYDROMETERANALYSLS 24I4I. 7141 45 Int 13 MUt 0 10 80 80 40 so so 70 so go 100 ID1 TLVE (REAd0006 OOMSI.lOAK INK www 11 1 1101. 4741 21E0 U.S. STANDARD SERIES 450 400 410 15 Sem ANALYSIS 14 CLEAR SoUAFE OPENNGS atr 11Q 3' 15 ME, www— w • Irwmwwl.. w—wwww,FM,C�� MIIMMA www— AM_ww1.111 —�—�——w—wwww/wwwMww —wwYr WIMEMw — —w— wwwrwr— —��///. •rw� rr �� •111•11r 1.�— IMM — �_ www —w w� •—,tr � MI s wwr 11 Mr 1111 MI MIdml www—wwwwtr— www-,nMN www --.—w ,111M11 IN II imol wwwww.�lir., MI 1111 III --- --- ME 11111111 -w,1 /.ww. wwr. —wIdad- I1 il.I rt 111 ,M1 NA 11, INIMME11 11,,I 11111 1111d P111, AE PI 1111E1 11. 11111 —N .SIMM — wwwt �— liMml 11M wwwRM— —w ww114 V• A 1111 •AM ww•wwww—w_ —�� ww�111 11111r�1 .11MM 1[11 1111.1 +wa wwiwww— ww.ww—www�t� 1111111.1111111111— 111 —w—� .11 11 PMP www—�� --i—� 111111111 wiy— -- OMiwr♦� wwwwRww•wi— —� —_Mi 11111 PREft 111111111111— _ --- -rOF — 11111 111.41 .1302 1111111 � 11— �w 205 CLAY TO SILT 141 100 w 80 ill so2 tc 40 30 io 10 0 2174 .150 ,700 d00 1.10 205 4.70 !id 173 1521 32.3 755 rv107 203 DIAMETER OF PARTICLES IN MIWMErERS 171E cum MEOW 1 CONSE 13151521. FIE I COMO Gravel 50 % Liquid Limit Sample of: Silty Sand with Gravel 114 085A Gtech HEPWORT14PAWLAFC GEOTECHNICAL Sand 25 % Slit and Clay 25 % Plasticity Index % From: Bottom of Southern Portion of Excavation GRADATION TEST RESULTS FIGURE 1