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HomeMy WebLinkAboutB15-0020_Geotech Foundation letter_1432650720.pdf Hepwurrh-P;twlak.Georechnical, Inc. a� e tunty r 154 GlerllULI Springs, CLII UI:U u 516h1 Pllt?ne: LW-9-15,79M HEPWORTH—PAWLAK GEOTECHNICAL Fax:970 ) 5-515 4 email: hj' t1)Q:pgeorech.cum May 21, 2015 DW Dantas Construction Attn: Dave Dantas P. O. Box 2322 dave(&,dwdantas.corn Job No. 115 218A Subject: Observation of Excavation, Proposed Duplex Residence - Eastern Portion, Lot 10, Block 9, Intermountain Subdivision, 2755 Snowberry Drive, Vail, Colorado Dear Dave: As requested, a representative of Hepworth-Pawlak Geotechnical observed the excavation at the subject site on May 18, 2015 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 as part of our agreement for professional services to DW Dantas Construction dated May 13, 2015. The duplex will be a one and wood frame story structure over a walkout basement level. Ground floors will be slab-on-grade. The building has been designed to be supported on spread footings using an allowable soil bearing pressure of 2,000 psf based on a previous subsoil study report we performed for the site dated June 30, 1999, Job No. 109 404. Only the eastern half of the duplex will be constructed at this time. At the time of our site visit, the foundation excavation for the eastern half of the duplex was essentially complete and had been cut in multiple levels up to about 10 feet below the adjacent ground surface and daylighting to the northeast. The soils exposed in the bottom of the excavation consisted of medium dense, clayey to very clayey sand and gravel with bedrock fragments to small cobble size. Results of swell-consolidation testing performed on samples taken from the site, shown on Figure 1, indicate the soils are moderately compressible under conditions of loading and wetting under a low hydro-compression potential. The sample may have been partly disturbed due to the rock content. The laboratory testing is summarized in Table 1. No free water was encountered in the excavation and the soils were slightly moist to moist. The soil conditions exposed in the excavation are generally consistent with those previously encountered on the site and suitable for support of spread footings designed for the recommended allowable bearing pressure of 2,000 psf. Loose and disturbed soils should be removed in the footing areas to expose the undisturbed natural soils and the subgrade compacted. Other recommendations presented in our previous report which are Parker 303-841-7119 • Colorado Springs 719-633-5562 • Silverthorne 970-468-1989 DW Dantas Construction May 21, 2015 Page 2 applicable including those relating to perimeter foundation and basement under slab drainage systems should also be observed. The recommendations submitted in this letter are based on our observation of the soils exposed within the foundation excavation and the previous limited subsurface exploration at the site. Variations in the subsurface conditions below the excavation could increase the risk of foundation movement.. We should be advised of any variations encountered in the excavation conditions for possible changes to 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. We should observe the foundation excavation for the western half of the duplex when complete. If you have any questions or need further assistance, please call our office. Sincerely, HEPWORTH—P e .AK U 1 ICAL, INC. .•.� sR 'c �o G3 I David A. Young, P.E, 2.216 ,��. , .''; DAY/ksw047:7 ,6 i ZIP attachments Figure 1, Swell-Consolidation Test Results Table 1, Summary of Laboratory Test Results Job No. 115 218A Gtech Moisture Content = 17.7 percent Dry Density = 106 pcf Sample of: Very Clayey Sand with Shale Fragments From: North-Central Portion of Excavation C 0 w C RS xQ W 0 Compression Nupon m wetting a U 2 • 1.1 3 4 5 6 7 0.1 1.0 10 100 APPLIED PRESSURE-ksf 115 218A IGec�H tech I SWELL-CONSOLIDATION TEST RESULTS I Figure 1 HEPWORTH-PAWLAK GEOTECHNICAL a LO ) ci g 0 §§ 3 / /a @ g o 7 > • 0 m �Cd .laa / / P en LI &» 00 &± O « o LU )§$ e co Z CD CC uj k Dk� / CO ( \/ * $ § ° � cc § \ la care 0 C - Z -uj \ \ 03 � /C�- �I- \< ± 0 I— \ § \ Z ƒ 5 k LU D k ) { CD / / j§§( <5In 0 -C CC Z ,—I - E ` 2 §) k g \ ] © ; 2 = # 2 ;`0 \Z'