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Home My WebLink About1.14 Geotechnical ReportH-R�XUMAR 5020 County Road 154 Glenwood Springs, CO 81601 Geotechnical Engineering I Engineering Geology Phone: (970) 945-7988 Materials Testing I Environmental Fax: (970) 945-8454 Email: hpkglenwood@kumarusa.com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado June 20, 2018 David Jones 6809 County Road 214 New Castle, Colorado 81647 drichmondjones @ gmail.com Project No. 18-7-415 Subject: Observation of Excavation, Proposed Residence, 6809 County Road 214 (Peach Valley Road), Garfield County, Colorado Dear David: As requested, a representative of H-P/Kumar observed the excavation at the subject site on June 19, 2018 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 June 19, 2018. The proposed residence will be a one story wood frame structure with a slab -on -grade floor. Foundations were designed based on an assumed allowable soil bearing pressure of 1,500 psf. At the time of our visit to the site, the foundation excavation had been cut in one level from 3 to 5 feet below the adjacent ground surface. The soils exposed in the bottom of the excavation consisted of clayey sand and gravel with cobbles. The natural soils had been mostly covered with 3/a inch screened rock in the excavation area. The results of a gradation analysis performed on a sample of the clayey sand and gravel (minus 3 inch fraction) obtained from the site are presented on Figure 1. Free water was observed in the excavation and the soils were moist to very moist. The source of the water appears to be the nearby irrigation ditch located uphill of the house site. We understand that it is planned to line this ditch later in the summer. 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 1,500 psf 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. Groundwater seepage should be diverted and collected outside of footing areas. Loose disturbed soils and mud in footing areas should then 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 David Jones June 20, 2018 Page 2 at least 10 feet. Foundation walls acting as retaining structures (if any) 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. An underdrain can be provided around the foundation to prevent temporary buildup of hydrostatic pressure. Structural fill placed within floor slab areas should consist of compacted 3/4 inch screened rock or other suitable gravel soils (such as road base) compacted to at least 95% of standard Proctor density at a moisture content near optimum. Backfill placed around the structure should be compacted and the surface graded to prevent ponding within at least 10 feet of the building. We recommend below slab vapor retarders conform to at least the minimum requirements of ASTM E1745 Class C material. Certain floor types are more sensitive to water vapor transmission than others. For floor slabs bearing on angular gravel or where flooring system sensitive to water vapor transmission are utilized, we recommend a vapor barrier be utilized conforming to the minimum requirements of ASTM E1745 Class A material. The vapor retarder should be installed in accordance with the manufacturers' recommendations and ASTM E1643. 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:-,' KUMAR Daniel E. Hardin, P Rev. by: SLP DEH/kac P p /CF� 9� ;Q 24443 Z• €\�0NAL attachment Figure 1— Gradation Test Results cc: Brad Jordan (brad jordanarchitect@gmail.com) H-P45KUMAR Project No. 18-7-415 HYDROMETER ANALYSIS SIEVE ANALYSIS TIME READINGS U.S. STANDARD SERIES CLEAR SQUARE OPENINGS 100 24 NRS 45 MIN 7 NRS 15 MIN 60MIN 19MIN 4MIN 1MIN alloo aloo &5D A40 930 & 6 AID as 44 3 S' 3/0 1 1/2* 3..a t0 10 6020 70 30 60 40 SO 7 G SO 40 60 30 70 20 s0 10 90 I O .. L _ _ _ _ _. _ . _.. __ _ 111 1 100 .001 .002 .005 .009 .019 .037 .075 .150 .300 1 .600 1.16 2.36 4.75 9.5 19 36.1 76.2 127 425 2.0 152 DIAMETER OF PARTICLES IN MILLIMETERS 200 CLAY TO SILT SAND I GRAVEL COBBLES FINE I MEDIUM 1COARSE1 FINE COARSE GRAVEL 44 X SAND 39 X SILT AND CLAY 17 X LIQUID LIMIT PLASTICITY INDEX SAMPLE OF: Clayey Sand and Gravel FROM: South Side Footing Grade These test results apply only to the samples which were tested. The testing report shall not be reproduced, except in full, without the written approval of Kumar 3 Associates, Inc. Sieve analysis testing is performed In accordance with ASTM D422, ASTM C136 and/or ASTM DII40. 18-7-415 H -R KUMAR GRADATION TEST RESULTS Fig. 1