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I <br /> . Provide a depth of 1-2 ft as measured from the crest of the inlet structure. ' <br /> • Slope sides of excavation no steeper than 2H:1 V. <br /> . Minimum volume of excavation 35 cubic yards. 1 <br /> . Shape basin to fit site with longest dimension oriented toward the longest inflow <br /> area. 1 <br /> . Install provisions for draining to prevent standing water problems. <br /> . Clear the area of all debris. I <br /> . Grade the approach to the inlet uniformly. <br /> . Drill weep holes into the side of the inlet. <br /> . Protect weep holes with screen wire and washed aggregate. <br /> . Seal weep holes when removing structure and stabilizing area. <br /> . Build a temporary dike, if necessary, to the down slope side of the structure to pre- <br /> vent bypass flow. <br /> Block and Gravel Filter-A barrier formed around the storm drain inlet with standard con- <br /> crete blocks and gravel. See Figure 11-4.2.8 Block and Gravel Filter(p.360). 1 <br /> . Provide a height of 1 to 2 feet above inlet. <br /> • Recess the first row 2-inches into the ground for stability. I <br /> . Support subsequent courses by placing a 2x4 through the block opening. <br /> . Do not use mortar. 111 <br /> • Lay some blocks in the bottom row on their side for dewatering the pool. <br /> . Place hardware cloth or comparable wire mesh with'/2-inch openings over all <br /> block openings. <br /> . Place gravel just below the top of blocks on slopes of 2H:1V or flatter. <br /> . An alternative design is a gravel donut. <br /> . Provide an inlet slope of 3H:1 V. <br /> . Provide an outlet slope of 2H:1 V. I <br /> . Provide a1-foot wide level stone area between the structure and the inlet. <br /> . Use inlet slope stones 3 inches in diameter or larger. I <br /> . Use gravel '/2-to 3/-inch at a minimum thickness of 1-foot for the outlet slope. <br /> I <br /> 2014 Stormwater Management Manual for Western Washington <br /> Volume II- Chapter 4 -Page 359 1 <br />