3121 8TH ST AB 2016-01-01 MF Import

.lunc l. 2008 Duplex [3uilding L&A Job No. 8A055 Pagc 15 12unoff ovcr Itnpervious Surfaces Storm runol�Covcr impervious surfaces, such as roofs and paved drivc«ay, sh�uld bc collectcd by underground drain line systems connected to downspouts and by catch basins installed in pavcd �Iriveway. Stormwater thus collcctcd shoul�l bc tighUined to dischargc into a storm se�ver. Duilding Footing Uruin A subdrain should bc installcd, aruund thc perimctcr Ibotings uf thc piuposcd �luplcx building. The subdrain should consist of a 4-inch-minin.um-diameter, perforated, rigid, drain pipe, laid a fe��• inches below bottom of the perimeter footings of the building. The trench and the drain line should have a sufficient gradicnt (0.5% minimum) tc generate llow by gravity. The drain line should bc fitted with a non-woven filtcr fabric sock and completely enclosed in clean ��ashed gravel. "I'he remaining trench may be backfilled widi clean on-site soils. Water collected by thc perimeter footing subdrain systeni should bc � ohtlincd, ceparutcly I�om thc rooC and surl��cc stomr.vatcr tJrain lines, to dischargc into a stami sewer. SurEacc Drainagc Water should not be allowed to stnnd in any areas where (ootings, on-grade-slabs, or pavement is to be constructed. �inish ground surface should be gradcd to direct surface runoff away from the proposcd duplex building. We recommend the finish ground be sloped at a gradient of 3 perecnt ntinimum for a distancc of at Icast 10 fcet away lrom thc building, escept i❑ the areas to be paved. Clcanouts SuCficient number of cleanauts at strategic locations should be provided lor underground drain lines. Thc underground drain lincs should be cleaned and maintained periodically to prevent clogging. LIU & ASSOCIATES, INC.