1710 W MARINE VIEW DR 2024-01-03

BMP C241: Sediment Pond (Temporary) Purpose Sediment ponds are temporary ponds used during construction to remove sediment from runoff ori- ginating from disturbed areas of the project site. Sediment ponds are typically designed to remove sediment no smaller than medium silt (0.02 mm). Consequently, they usually reduce turbidity only slightly. Conditions of Use . Use a sediment pond where the contributing drainage area to the pond is 3 acres or more. Ponds must be used in conjunction with other Construction Stormwater BMPs to reduce the amount of sediment flowing into the pond. . Do not install sediment ponds on sites where failure of the BMP would result in loss of life, damage to homes or buildings, or interruption of use or service of public roads or utilities. Also, sediment ponds are attractive to children and can be dangerous. Compliance with local ordin- ances regarding health and safety must be addressed. If fencing of the pond is required, show the type of fence and its location on the drawings in the Construction SWPPP. . Sediment ponds that can impound 10 acre-ft (435,600 cu-ft, or 3.26 million gallons) or more, or have an embankment of more than 6 feet, are subject to the Washington Dam Safety Regu- lations (Chapter 173-175 WAC). See BMP D.1: Detention Ponds for more information regard- ing dam safety considerations for detention ponds. . Projects that are constructing permanent Flow Control BMPs or Runoff Treatment BMPs that use ponding for treatment may use the rough -graded or final -graded permanent BMP foot- print for the temporary sediment pond. When permanent BMP footprints are used as tem- porary sediment ponds, the surface area requirement of the temporary sediment pond must be met. If the surface area requirement of the sediment pond is larger than the surface area of the permanent BMP, then the sediment pond shall be enlarged beyond the permanent BMP footprint to comply with the surface area requirement. The permanent control structure must be temporarily replaced with a control structure that only allows water to leave the temporary sediment pond from the surface or by pumping. Alternatively, the permanent control structure may used if it is temporarily modified by plug- ging any outlet holes below the riser. The permanent control structure must be installed as part of the permanent BMP after the site is fully stabilized. Design and Installation Specifications General See Figure II-3.28: Sediment Pond Plan View, Figure II-3.29: Sediment Pond Cross Section, and Figure II-3.30: Sediment Pond Riser Detail for details. . Use of permanent infiltration BMP footprints for temporary sediment ponds during 2019 Stormwater Management Manual for Western Washington Volume 11- Chapter 3 - Page 388