3800 RIVERFRONT BLVD 2025-07-23 - Laserfiche WebLink

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