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1 <br />BMP C204: Pipe Slope Drains <br />Purpose <br />To use a pipe to convey stormwater anytime water needs to be diverted away from or <br />over bare soil to prevent gullies, channel erosion, and saturation of slide -prone soils. <br />Conditions of Use <br />Pipe slope drains should be used when a temporary or permanent stormwater con- <br />veyance is needed to move the water down a steep slope to avoid erosion (Figure II- <br />4.2.4 Pipe Slope Drain (p.345)). <br />On highway projects, pipe slope drains should be used at bridge ends to collect runoff <br />and pipe it to the base of the fill slopes along bridge approaches. These can be <br />designed into a project and included as bid items. Another use on road projects is to col- <br />lect runoff from pavement and pipe it away from side slopes. These are useful because <br />there is generally a time lag between having the first lift of asphalt installed and the <br />curbs, gutters, and permanent drainage installed. Used in conjunction with sand bags, or <br />other temporary diversion devices, these will prevent massive amounts of sediment from <br />leaving a project. <br />Water can be collected, channeled with sand bags, Triangular Silt Dikes, berms, or other <br />material, and piped to temporary sediment ponds. <br />Pipe slope drains can be: <br />• Connected to new catch basins and used temporarily until all permanent piping is <br />installed; <br />Used to drain water collected from aquifers exposed on cut slopes and take it to <br />the base of the slope; <br />• Used to collect clean runoff from plastic sheeting and direct it away from exposed <br />soil; <br />o Installed in conjunction with silt fence to drain collected water to a controlled area; <br />• Used to divert small seasonal streams away from construction. They have been <br />used successfully on culvert replacement and extension jobs. Large flex pipe can <br />be used on larger streams during culvert removal, repair, or replacement; and, <br />• Connected to existing downspouts and roof drains and used to divert water away <br />from work areas during building renovation, demolition, and construction projects. <br />There are now several commercially available collectors that are attached to the pipe <br />inlet and help prevent erosion at the inlet. <br />2014 Stormwater Management Manual for Western Washington <br />1 <br />1 <br />1 <br />1 <br />1 <br />�1 <br />1 <br />1 <br />1 <br />1 <br />f] <br />1 <br />1 <br />1 <br />1 <br />1 <br />Volume 11 - Chapter 4 - Page 342 <br />1 <br />