HomeMy WebLinkAboutObservation of Excavation 06.30.2022 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email: kaglenwood@kumarusa.com www.kumarusa.com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado June 30, 2022 SCIB, LLC Attn: Luke Gosda 0115 Boomerang Road, Ste 5201B Aspen, Colorado 81611 luke.gosda@sunriseco.com Project No. 21-7-657.A Subject: Observation of Excavation, Proposed Residence, Lot 59, Ironbridge Phase 3, 63 Blue Heron Drive, Garfield County, Colorado Gentlemen: As requested, a representative of Kumar & Associates, Inc. observed the excavation at the subject site on June 29, 2022 to evaluate the soils exposed for foundation support. The findings of our observations and recommendations for the foundation design are presented in this report. We previously conducted a subsoil study for design of foundations at the site and presented our findings in a report dated September 29, 2021, Project No. 21-7-657. The proposed residence is similar to that described in our previous report and will be above crawlspace in the residence and slab-on-grade in the garage. At the time of our visit to the site, the foundation excavation had been cut in one level from 2½ to 3½ feet below the adjacent ground surface. The soils exposed in the bottom of the excavation consisted of sandy silt. Results of in-place moisture and density tests on the soils, presented in Table 1, indicate low density, compressible soils. No free water was encountered in the excavation and the soils were slightly moist below the moist surface from recent precipitation. The soils exposed in the excavation are generally consistent with those previously encountered and compressible under loading and wetting conditions which could result in foundation settlement. We recommend the footing grade be sub-excavated 3 feet to 1½ feet beyond footing edges and replaced compacted to at least 98% of standard Proctor density at near optimum moisture content. Other recommendations presented in our previous report which are applicable 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 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 TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No. 21-7-657.A SAMPLE LOCATION NATURAL MOISTURE CONTENT NATURAL DRY DENSITY GRADATION PERCENT PASSING NO. 200 SIEVE ATTERBERG LIMITS UNCONFINED COMPRESSIVE STRENGTH SOIL OR BEDROCK TYPE BOTTOM OF DESIGN FOOTING GRADE GRAVEL SAND LIQUID LIMIT PLASTIC INDEX (%) (%) (%) (pcf) (%) (%) (PSF) Southeast Corner 8.9 87 Sandy Silt Northwest Corner 7.1 88 Sandy Silt