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Home My WebLink AboutOpen Soils Report.pdf H- Ku mAR5020 County Road 154 Glenwood Springs,CO 81601 Geotechnical Engineering I Engineering Geology Phone:(970)945-7988 Materials Tesirng I Environmental Fax:(970)945-8454 Email: hpkglenwood@kumarusa.com Office Locations: Parker, Glenwood Springs,and Silverthome,Colorado November 22, 2016 Shaeffer Hyde Construction Attn: Rob Fawcett P. O. Box 373 Vail, Colorado 81658 robf@shaefferhyde.com Project No. 16-7-591 Subject: Observation of Excavation, Proposed Exterior EIevator Addition to Johnson Residence, Lot 14, Block 6, Vail Valley 76 Addition, 1195 Hornsilver, Vail, Colorado Dear Rob: As requested, a representative of H-P/Kumar observed the excavations at the subject site on November 16, 2016 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 Shaeffer Hyde Construction, dated November 15, 2016. The addition will be two stories in height and attached to the south side of the existing residence at the garage. The ground floor will be slab-on-grade. The addition has been designed to be supported on spread footings assuming an allowable soil bearing pressure of 2,000 psf. The existing residence is apparently founded on shallow spread footings with no signs of excessive settlement and distress reported. At the time of our site visit, the foundation excavation which was essentially complete had been cut in one level from about 51/2 to 6 feet below the adjacent ground surface. The soils exposed in the bottom of the excavation consisted of stiff, sandy silty clay. The existing spread footing foundation for the residence had been exposed at excavation subgrade. Results of swell- consolidation testing performed on a sample taken from the site, shown on Figure 1, indicate the silty clay soils are moderately compressible under conditions of loading and wetting. No free water was encountered in the excavation and the soils were moist. It was planned to place and compact 12 to 18 inches of CDOT Class 2 base course in the bottom of the excavation to achieve proposed design footing bearing elevation. Considering the conditions exposed in the excavation and the nature of the proposed construction, spread footings placed on the compacted road base placed on the undisturbed silty clay soil designed for an allowable bearing pressure of 2,000 psf can be used for support of the proposed addition. There could be some long term settlement of the addition due to the clay Shaeffer Hyde Construction November 22, 2016 Page 2 nature of the soils which should be considered in the design. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns. Loose and disturbed soils in footing areas should be removed or re-compacted prior to the footing construction. The bearing soils should 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 well 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 fluid unit weight of at least 50 pcf for on-site soil as backfill. A perimeter foundation drain should be provided around any below grade construction as needed. Structural fill placed within floor slab areas can consist of the on-site soils compacted to at least 95% of standard Proctor density (SPD) at a moisture content near optimum. Backfill placed around the structure should be compacted to at least 90% SPD (95% in pavement areas) and the surface graded to prevent ponding within at least 10 feet of the building. Landscape that requires regular heavy irrigation, such as sod, and sprinkler heads should not be located within 10 feet of the 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 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, H-P t KU MI fl 00411,, ��t, '4 100 .#,. -'1� i r • W-P" Ii ;- .o'er taliir Zit CA David A. Young, P.Ei \ •216 if , DAY/ksw ri ;j . .w. �� ♦diff � attachment Figure 1, Swd t �pedation Test Results cc: Shaeffer Hyde Construction—Bob Batten (bobb@shaefferhyde.com) H-Plz KUMAR Project No. 16-7-591 Moisture Content = 19.8 percent Dry Density = 103 pcf -200 = 89 percent Sample of: Sandy Silty Clay From: Bottom of Excavaion 0 a2 1 c No movement 0 upon 2 • wetting 0. E 0 U 3 4 • 5 6 • 0.1 1.0 10 100 APPLIED PRESSURE-ksf 16-7-591 H-PKUMAR SWELL-CONSOLIDATION TEST RESULTS Figure 1