4620 SEAHURST AVE 2020-05-20 - Laserfiche WebLink

March 7, 2011 Mr. Paul ThompsonlKolbear, Inc. L&A Job No. 11-001 • Page 16 paved driveways. Stormwater thus collected should be tightlined to discharge into a nearby storm sewer or a suitable stormwater disposal facility system, such as rain gardens. Building Footing Drains A subdrain system should be installed, around the perimeter footings of each of the new residences. The subdrains should consist of a 4-inch-minimum-diameter, perforated, rigid, drain pipes, laid a few inches below bottom of the perimeter footings of the buildings. The trenches and the drain lines should have a sufficient gradient(0.5%minimum)to generate flow by gravity. The drain lines should be wrapped in non-woven filter fabric socks and completely enclosed in clean washed gravel. The remaining trenches may be backfilled with clean onsite soils. Water collected by the perimeter footing subdrain systems should be tightlined, separately from the roof and surface stormwater drain lines, to discharge into a storm sewer or a suitable stormwater disposal facility, such as rain gardens. Surface Drainage Water should not be allowed to stand in any areas where footings, on-grade-slabs, or pavement is to be constructed. Finish ground surfaces should be graded to direct surface runoff away from the proposed residences. We recommend the finished 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 underground drain lines. The underground drain lines should be cleaned and maintained periodically to prevent clogging. LIU & ASSOCIATES, INC.