9205 4TH AVE W 2025-12-03 - Laserfiche WebLink

July 2, 2008 Duplex Buildings L&A Job No. 8A067 Page 16 inch perforated PVC pipe through which stormwater is discharged into the trench should be laid level in the gravel or crushed rock filled trench at about 12 inches below the top of the trench. The top of the gravel or crushed rock fill should also be covered with the filter fabric liner. The remaining trench should then be filled additional gravel. Building Footprint Excavation Building footprint excavation for the proposed duplex buildings, if encountering groundwater seepage, should have the bottom of excavation sloped and ditches excavated along bases of the cut banks to direct collected groundwater into sump pits from which water can be pumped out. A layer of 2-inch crushed rock should be placed over footing bearing subgrade soils, as required, to protect the soils from disturbance by construction traffic. This crushed rock base should be built to a few inches above groundwater level, but not less than 6 inches thick. The crush rock base should be compacted in 12-inch lifts to a non -yielding state with a vibratory mechanical compactor. Runoff over Impervious Surfaces Storm runoff over impervious surfaces, such as roofs and paved driveway and parking areas, should be collected by underground drain line systems connected to downspouts and by catch basins installed in paved driveway and parking areas. Stormwater thus collected should be tightlined to discharge into a storm sewer or suitable stormwater facilities, such as rain gardens or distribution trenches with vegetated flowpaths as described above. Building Footing Drain A subdrain should be installed, around the perimeter footings of each of the proposed duplex buildings. The subdrains should consist of a 4-inch-minimum-diameter, perforated, rigid, drain pipe, laid a few inches below bottom of the perimeter footings of the buildings. The trenches and LIU & ASSOCIATES, INC.