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HomeMy WebLinkAboutObservation of Excavation 06.22.2022 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 22, 2022 Tyler Miles 16425 County Road 309 Parachute, Colorado 81635 tymiles2010@gmail.com Project No. 22-7-427 Subject: Observation of Excavation, Proposed Residence, 188 Eagle Ridge Drive, Battlement Mesa, Garfield County, Colorado Dear Tyler: As requested, a representative of Kumar & Associates observed the excavation at the subject site on June 15, 2022 to evaluate the soils exposed for foundation support. The findings of our observations and recommendations for the foundation support are presented in this report. The services were performed in accordance with our agreement for professional engineering services to you dated June 14, 2022. The proposed residence will be a one and two story wood frame structure with a slab-on-grade ground floor. Foundations were designed for a maximum soil bearing pressure of 2,000 psf. At the time of our visit to the site, the foundation excavation had been cut in one level from ½ to 4 feet below the adjacent ground surface. The soils exposed in the bottom of the excavation consisted of whitish, sandy clayey silt to clayey silty sand with gravel. Results of percent finer than sand size gradation analysis and moisture density testing indicate the soils are potentially settlement prone under conditions of loading and wetting. No free water was encountered in the excavation and the soils were slightly moist to 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 soil bearing pressure of 1,200 psf are recommended for support of the 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. Footings should be a minimum width of 20 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 natural 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 12 feet. Foundation walls acting as retaining structures (if any) should 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 not be installed for the proposed slab on grade main floor. Structural fill placed within floor slab areas can consist of the on-site soils compacted to at least TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No. 22-7-427 SAMPLE LOCATION NATURAL MOISTURE CONTENT NATURAL DRY DENSITY GRADATION PERCENT PASSING NO. 200 SIEVE ATTERBERG LIMITS UNCONFINED COMPRESSIVE STRENGTH SOIL TYPE BUILDING AREA DEPTH GRAVEL SAND LIQUID LIMIT PLASTIC INDEX (%) (%) (ft) (%) (pcf) (%) (%) (psf) Southwest Corner Footing grade 15.4 75 79 Sandy Clayey Silt Northeast Corner Footing grade 11.1 77 45 Clayey Silty Sand