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HomeMy WebLinkAboutPermit Field Test & Inspection Report 2005-1-6 lo03La Orchid- \xJ ; -a engineering K & A Engineering, Inc. P.o. Box 23624, Eugene, OR 97402 521 Market St., Suite 0, Eugene, OR 97402 (541) 684-9399 Voice (541) 684.9358 FAX January 6, 2005 Project: 74.04 Hayden Homes 2464 SW Glacier Place, Suite 110 Redmond, OR 97756 Subject: General Foundation Drainage Recommendations Jasper Meadows Subdivision - 2nd Addition Springfield, Oregon PURPOSE AND SCOPE , This letter provides additional recommendations for drainage for the construction of single-family residences at the subject new subdivision. These are intended to supplement recommendations provided in the original geotechnical report provided by Boire Associates, which included general construction criteria for development of the project site. SITE CONDITIONS As documented in our summary report of September 20, 2004, the gently sloping site had from 1 to 3-feet of gray plastic silts over weathered yellow/tan tuffaceous sandstone. Excavation for the foundation pads consisted of benches cut into the slope with cuts as high as 4-feet. K & A Engineering, Inc. witnessed excavation and provided on-site recommendations so that all foundation cuts were made to suitable sUbgrade soils or bedrock. After excavation and grading of subgrade to undisturbed soils/rock, 10 to 24-inches of granular fills were placed on the foundation subgrade and compacted. Groundwater was not encountered in any of the excavations except at the lower elevation of the project in the road subgrade. FOUNDATION DRAINAGE RECOMMENDATIONS Since a significant amount of low permeability, dense granular fill will support foundation loads on the underlying native soils and rock, if groundwater were present above the excavation grade it is likely that the granular fill could trap and isolate water in the foundation excavation. Conventional footing drains would not remove this water because it would be below the footing grade. K & A Engineering, Inc. As a precaution to avoid the possibility of trapping water below the foundation, we recommend that low point drains be installed in the crawlspaces with the inlet at subgrade level. This will effectively drain the entire foundation. This low point drain can replace the recommended conventional footing drains. The low point drain should be constructed at the base of a small well excavated in the granular fill. The sides of the well should be uniform with a slope not exceeding 2 horizontal to 1 vertical. The inlet pipe should be covered with some sort of grate or galvanized screen to prevent fines from entering into the drain system. The low point drain should be located in the crawlspace as close to the downhill side of the foundation as possible. Additionally. we recommend that the fmal grading at the surface between houses slope to a gentle swale that routes surface runoff away from the foundation to the street or to an approved storm drain collector. The swale should have a total drop of at least 1-foot. Thank you for the opportu,nity to be of service. Please call if you have any questions. Sincerely, EXPIRES {vj~ ~ Michael Remboldt, P.E. K & A Engineering. Inc. Project: 74.04 Jasper Meadows Subdivision Phase II, Springfield. OR Client: Hayden Homes Page 2 of 2 January 6. 2005