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. 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. <br />• Shape basin to fit site with longest dimension oriented toward the longest inflow <br />area. <br />. Install provisions for draining to prevent standing water problems. <br />. Clear the area of all debris. <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 II-4.2.8 Block and Gravel Filter (p.360). <br />. Provide a height of 1 to 2 feet above inlet. <br />. Recess the first row 2-inches into the ground for stability. <br />. Support subsequent courses by placing a 2x4 through the block opening. <br />• Do not use mortar. <br />. Lay some blocks in the bottom row on their side for dewatering the pool. <br />. Place hardware cloth or comparable wire mesh with 1/2-inch openings over all <br />block openings. <br />. Place gravel just below the top of blocks on slopes of 2H:1 V 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. <br />. Provide al -foot wide level stone area between the structure and the inlet. <br />. Use inlet slope stones 3 inches in diameter or larger. <br />. Use gravel % to 3/-inch at a minimum thickness of 1-foot for the outlet slope. <br />2014 Stormwater Management Manual for Westem Washington <br />Volume 11 - Chapter 4 - Page 359 <br />