1136 GRAND AVE A&B 2016-01-01 MF Import

C � April 23, 2007 Mc Scott Andcrson LScA Job No. 6A 126 Page 11 Drainage Contrul Building Footprint Excavation Excavation of building footprint, if cncountering groundwater, should have the bottom of excavation sloped and ditches excavated along the bases of cut banks to direct groundwater seepage to ilow into a sump pit Gom which water can be pumped out of the pit into a neazby storm inlet. A laycr of 2-inch crushed rocks should be placed over firm subgrade soils under footings, as required, to protect the soils from disturbance by construction equipment and foot traflic. This crushed rock base should be built lo a few inches above groundwater Icvel, but not less than 4 inches thick. The crush rock basc should be compacted in 12-inch lifts to a non- yielding state with a vibratory mechanical compactor. Runotf over Impervious Surfaces Storm runoff over impervious surf:ucs, such as roofs and pavcd areas, should be collected by underground drain line systems connected to downspouts and by catch basins installed in paved areas. StormwAter thus collccted should bc tightlined to discharge inu�a nearby stomi sewcr. Building Footing Drains A subdrain should bc installed around thc perimetcr footings of the duple� building to minimize accumulation of groundwater under the building. The subdrain should consist of a 4-inch- minimum-diameter, perforated, rigid, drain pipe, laid a few inchcs belo�v the bottom of pernneter footings. The [rench and the drain linc should have a sufticient gradient (0.5 percent minimum) to gencrate tlow by gnvity. Thc drain linc should bc embedded in washed gravel completely wrappcd in non-woven filter fabric to within about 12 inches of finish grade. The remaining trcnch may bc backfillcd with on-sitc impervious soils. Watcr collectcd by thc footing drain LIU & ASSOCIATES, INC.