1710 W MARINE VIEW DR 2024-01-03

BMP C204: Pipe Slope Drains Purpose The purpose of pipe slope drains is to prevent gullies, channel erosion, and saturation of slide -prone soils by using a pipe to convey stormwater away from or over bare soil. Conditions of Use Pipe slope drains should be used when a temporary or permanent stormwater conveyance is needed to move water down a steep slope to avoid erosion. Pipe slope drains should be used at bridge ends to collect runoff and convey it to the base of the fill slopes along the bridge approaches. Another use on road projects is to collect runoff from pavement in a pipe slope drain and convey it away from side slopes. Temporary installations of pipe slope drains can be useful because there is generally a time lag between having the first lift of asphalt installed and the curbs, gutters, and permanent drainage installed. Used in conjunction with sand bags, or other temporary diversion devices, these will pre- vent massive amounts of sediment from leaving a project. Pipe slope drains can serve the following purposes: . Connection to new catch basins and temporarily use until permanent piping is installed. . Drainage of water collected from aquifers exposed on cut slopes and conveyance of water to the base of the slope. . Collection of dean runoff from plastic sheeting and routing the runoff away from exposed soil. . Installation in conjunction with silt fence to drain collected water to a controlled area. . Diversion of small seasonal streams away from construction. They have been used suc- cessfully on culvert replacement and extension jobs. Large flex pipe can be used on larger streams during culvert removal, repair, or replacement. . Connection to existing downspouts and roof drains and diversion of water away from work areas during building renovation, demolition, and construction projects. There are several commercially available collectors that attach to the pipe inlet and help prevent erosion at the inlet. Design and Installation Specifications See Figure II-3.13: Pipe Slope Drain. Size the pipe to convey the projected flow. The capacity for temporary drains shall be sufficient to handle flows calculated by one of the following methods: o Single Event Hydrograph Method: The peak volumetric flow rate calculated using a 10-minute time step from a Type 1 A,10-year, 24-hour frequency storm for the worst -case land cover 2019 Stormwater Management Manual for Western Washington Volume 11 - Chapter 3 - Page 341