1710 W MARINE VIEW DR 2024-01-03

condition. OR o Continuous Simulation Method: The 10-year peak flow rate, as determined by an approved continuous runoff model with a 15-minute time step for the worst -case land cover condition. Worst -case land cover conditions (i.e., producing the most runoff) should be used for analysis (in most cases, this would be the land cover conditions just prior to final landscaping). Consult local drainage requirements for sizing permanent pipe slope drains. • Use care in clearing vegetated slopes for installation. • Re-establish cover immediately on areas disturbed by installation. • Use temporary drains on new cut or fill slopes. • Use BMP C200: Interceptor Dike and Swale to collect water at the top of the slope. • Ensure that the entrance area is stable and large enough to direct flow into the pipe. • Piping of water through the berm at the entrance area is a common failure mode. • The entrance shall consist of a standard flared end section for culverts 12 inches and larger with a minimum 6-inch metal toe plate to prevent runoff from undercutting the pipe inlet. The slope of the entrance shall be at least 3 percent. Sand bags may also be used at pipe entrances as a temporary measure. • The soil around and under the pipe and entrance section shall be thoroughly compacted to pre- vent undercutting. • The flared inlet section shall be securely connected to the slope drain and have watertight con- necting bands. • Slope drain sections shall be securely fastened together, fused or have gasketed watertight fit- tings, and shall be securely anchored into the soil. • Thrust blocks should be installed anytime 90 degree bends are utilized. Depending on size of pipe and flow, these can be constructed with sand bags, straw bales staked in place, "t" posts and wire, or ecology blocks. • Pipe needs to be secured along its full length to prevent movement. This can be done with steel "t" posts and wire. Install a post on each side of the pipe and wire the pipe to them. This should be done every 10-20 feet of pipe length or so, depending on the size of the pipe and quantity of water to divert. • BMP C200: Interceptor Dike and Swale shall be used to direct runoff into a pipe slope drain. The height of the dike shall be at least 1 foot higher at all points than the top of the inlet pipe. . The area below the outlet must be stabilized. See BMP C209: Outlet Protection. If the pipe slope drain is conveying sediment -laden water, direct all flows into a sediment trap- 2019 Stormwater Management Manual for Western Washington Volume 11 - Chapter 3 - Page 342