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Low Flow Diversions | Catch Basin Screens | Continuous Deflection Separators | Pollution Abatement Main Page

During December 2001, trash capture screens were installed at the outlets of five storm drains into the Los Angeles River. The total design and installation cost of the units was $40,000. These five trash capture screens were originally conceived to be part of the Los Angeles River Trash TMDL Baseline Monitoring Plan. As part of the plan, the amount of trash was to be quantified for the purpose of developing trash generation rates at four different landuse areas.

The performance of these screens was assessed by visual inspections to determine if these screens overflow during intense rainstorms. WPD staff made the observations during two rain events, and documented their observations on performance. However, the screens were evaluated based on the ability to function as full capture systems and if there were any other constraints such as safety, vectors (mosquitos), and upstream flooding.

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Land Use
Drainage Area
100% Residential
Elysian Park
Duvall & Blake
42" CMP
0.055 sq. mi.
Primarily Residential
Silver Lake
Fletcher Bridge
66" drain
0.390 sq.mi.
100% Recreational
Griffith Park
Crystal Springs Grounds
0.896 sq.mi.
100% Commercial
Studio City
Ventura Blvd & Laurel Canyon
18" CP
0.026 sq.mi.
Primarily Industrial
Owensmouth & Osborne St
60" RCP
0.310 sq.mi.
The observations from December 20-21, 2001 show that two of the four screens overflowed and that in all four screens, the 5-mm opening mesh became easily clogged by debris and trash. Other key observations included that, at sites 1 and 2, the screens allowed water, trash and debris to escape from underneath the bottom of the screen.

At Site location 4 (installed on December 31, 2001) observations made on February 26, 2002 show that the screens successfully trapped trash and debris. Additionally, catch basin inserts were installed upstream from this outlet screen and this monitoring site was removed from the pilot study.


The evaluation of outlet screens/baskets as a potential BMP was one of the seven pilot studies conducted during the first half of 2002. A summary report for this pilot study was made which describes the methodology used in evaluating the performance of the newly installed screens/baskets, assesses its flooding potential and finally makes recommendations with respect to optimum design and widespread implementation.

Summary Report 608k [download]

Trash Containment BMPs map