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Catch Basin Insert
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See also Catch Basin Screens

Low Flow Diversions | Catch Basin Screens | Netting Systems | End-of-Line Systems |
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Catch Basin Inserts in the City of Los Angeles consist of a 5 millimeter (mm) screen installed inside the catch basin just in front of the catch basin outlet pipe. The function of the CB insert is to retain all trash greater than 5 mm while maintaining adequate drainage capacity of the CB and storm drain system. These vertical inserts maximize the catch basin’s trash capture volume by extending vertically to just below the bottom lip of the curb opening, while providing both a flow through and bypass system to ensure proper catch basin operation. The entire insert and its components are made from stainless steel. During a typical rain event, trash accumulating in street gutters is washed into the catch basin, where it is retained by the insert. Routine catch basin maintenance ensures that the insert is performing as a * "Full Capture Device" year-round.

A white paper analysis of the hydraulic capacity of the CB inserts utilized by the City and a pilot study to determine their effectiveness was completed by WPD. The white paper concluded that the CB inserts used by the City, meet the Trash TMDL definition of a full capture system. The results from the pilot study indicated that the inserts retained all trash from the 1 year-one hour storm.

In October of 2006, the City formally requested the Regional Board to certify that the inserts used by the City are Full Capture Devices. In April of 2007, the Los Angeles Regional Water Quality Control Board (LARWQCB) completed its evaluation of the City’s request and issued the City a certification letter.

Catch basin inserts have been installed in City-owned catch basins in areas identified to be problematic.

* "A full capture system is any single device or series of devices that traps all particles retained by a 5mm mesh screen and has a design treatment capacity of not less than the peak flow rate (Q) resulting from a one-year, one-hour, storm in the subdrainage area. Rational equation is used to compute the peak flow rate: Q=C x I x A, where Q = design flow rate (cubic feet per second, cfs); C = runoff coefficient (dimensionless); I = design rainfall intensity (inches per hour, as determined per the rainfall isohyetal map), and A = subdrainage area (acres)."