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Home My WebLink AboutORIGINAL Observation of Excavation & Perc Testing 06.30.2006HEPWORTH -PAWLAK GEOTECHNICAL June 30, 2006 Character Builders Attn: Steve Maznio P.O. Box 680 New Castle, Colorado 81647 Hepworth-Pawlak Georechnical, Inc. 5020 Canty Road 154 Glenwood Springs. Colorado 81601 Phone: 970=945-7988 - Fax 970-945-8454 hpw:(Qhrigeotech.com Job No. 106 0593 Subject: Observation of Excavation and Percolation Testing, Proposed Residence, _got "A, Mayfly mid, Garfield ounty,k-olorado Dear Mr. Maznio: As requested, a representative of Hepworth-Pawlak Geotechnical, Inc. obserfred the excavation at the subject site on June 22, 2006 to evaluate the soils exposed for foundation support. Percolation testing was conducted on June 23, 2006. 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 Character Builders, dated June 22, 2006: Hepworth-Pawlak Geotechnical, Inc. previously performed a -preliminary geotechnical study for the Mayfly Bend Subdivision and reported our findings June 16, 2000, Job No:100 412. The proposed residence will be one and two story structural panel construction above a shallow crawlspace with an attached slab -on -grade garage. The septic system is proposed in the northeast corner of the propeaty.. Observation of Excavation: At the time of our visit to the site, the foundation excavation had been cut in one level from one to two feet below the adjacent ground surface. The soils exposed in the bottom of the excavation consisted of silty sandy gravel with cobbles and small boulders. Silty sand layers were observed in the northeast and SoutbweSt-corners and the excavation base was loose. No free water was encountered in the -excavation and the soils were slightly moist -to moist. We recommend the -excavation base be moistened and compacted prior to placing concrete. Foundation Recommendations: Considering the conditions exposed in the excavation and the nature of the proposed construction, spread footings placed on the undisturbed natant soil designed for an allowable soil beating pressure of 1,000 psf should be Parker 303-841-7119 • Colorado Springs 719-633-5562 • Silverthorne 970-468-1989 Character Builders June 30, 2006 Page 2 adequate for support of the proposed residence. Footings should be a minimum width of 16 inches for continuous -walls and 2 -feet for columns. 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 10 feet Foundation walls -acting -as. retaining structures should alsobe designed to resist a -lateral- earth pressure based on an equivalent fluid unit weight of at least 45 pcf for on-site gravel soil as backfill Structural fill placed within floor slab areas can consist of - the :on-site gravel soils, devoid of topsoil and oversize rock, 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. Percolation Testing: Percolation tests were conducted on June 23, 2006 to evaluate the feasibility of an infiltration septic disposal system at the site. One profile pit and three percolation holes were dug at the locations shown ' Fig . 1. The test holes (nominal 12 inch diameter by 12 inch deep) were hand dug at the bottom of shallow backhoe pits and were soaked with water one day prior to testing. The soils exposed in the percolation holes are similar to those exposed in the Profile Pit and below one foot of topsoil consist of 2 feet of silty sand overlyin sandy gravel with cobbles and small boulders to the maximum depth excavated of 51/2 feet. Free water was encountered in the Profile Pit at a depth of 51 feet below the ground surface. The percolation test results are presented in Table I and indicate a percolation rate of 1 to 2 minutes per inch. Eine to the relatively fast percolation rates and elevated" groundwater, we recommend the iniiitration area be designed by a civil engineer. Limitations: 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 subsurfaceconditions 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 couldchangethe recommendations Job No. 106 0593 Character Builders June 30, 2006 Page 3 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, HEPWORTH - PAWLAK GEOTCHNICAL, INC. Louis E. Eller Reviewed by: ZpO Rf�1s t�' Ay I: Daniel E. Hardin, P.3 I LEE/ksw 4..fi0!!Al E; irn n °' attachments Figure 1 - Location of Percolation Test Holes Table 1 - Summary of Percolation Test Results ce : Timberline Engineering - Attn: Dave Powell lob No. 106 0593 1 106 0593 IRRIGATION DITCH .APPROXIMATE Sa_AE = So / 7-7 O WELL -Y, I I BUILDING 1 ENVELOPE PONDEROSA PINES WAY 1.4 HEPWORTI.PAWLAK G OTECHNI CAL PROPOSED RESIDENCE i P2L AP3 PROFILE PIT LOCATION OF PERCOLATION TEST HOLES Figure 1