1228 GRAND AVE Geotech Report 2022-10-25

April 7,2008 Mr.Don Levin L&A Job No.8A037 Page 15 Building Footing Drains A subdrain should be installed around the perimeter footings of the new residence to minimize accumulation of groundwater under the building. The subdrains should consist of a 4-inch- minimum-diameter,perforated,rigid,drain pipe, laid a few inches below the bottom of perimeter footings. The trenches and the drain lines should have a sufficient gradient (0.5 percent minimum)to generate flow by gravity. The drain lines should be enclosed in washed gravel and completely wrapped in non-woven filter fabric to within about 12 inches of finish grade. The remaining trenches may be backfilled with on-site impervious soils. Water collected by the footing drain systems should be tightlined, separately from the roof and surface stormwater drain systems,to discharge into a nearby storm sewer. Surface Drainage Water should not be allowed to stand in any areas where footings, slabs, or pavement is to be constructed. Finish ground surface should be graded to flow away from the new residence. We recommend the finish ground be sloped at a gradient of 3 percent minimum for a distance of at least 10 feet away from the buildings,except in the areas to be paved. Cleanouts Sufficient number of cleanouts at strategic locations should be provided for the underground drain line systems. The underground drain line systems should be maintained periodically to prevent clogging. RISK EVALUATION STATEMENT The site is underlain at shallow depth by dense silty sand and hard fine sandy silt soils. These soils are of high shear strength in their native undisturbed state and have excellent resistance LIU & ASSOCIATES, INC.