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CREST
Cleaner Rivers through Effective Stakeholder-led TMDLs
crestmdl.org

The Trash Total Maximum Daily Load (TMDL) for the Los Angeles River and Ballona Creek watersheds requires the City of Los Angeles to reduce its trash contribution to these water bodies by 10% each year for a period of ten years. The first compliance milestone was on September 30, 2006, where the City of Los Angeles was required to reduce its trash contribution by 20%. TheCity of Los Angeles has met and exceeded that established milestone and as of September 2006, has achieved a 26% reduction of its trash contribution to those water bodies.

The Watershed Protection Division (WPD) of the Bureau of Sanitation is the lead office in charge of the city-wide Trash TMDL Implementation. In its undertaking of the Trash TMDL, WPD completed a study entitled High Trash Generation Areas and Control Measures, which identified the spatial distribution of trash in the City for both the Los Angeles River and Ballona Creek watersheds.

The City of Los Angeles' strategy for compliance is based on using the following two-prong approach:

implementing institutional measures such as, public outreach, street sweeping, catch basin cleaning, enforcement, etc., with a special focus on the high trash generation areas, and
installing structural trash control devices in the storm drain system.

The Bureau of Sanitation/ WPD has used this strategy to implement various measures such as, online structures (i.e., netting systems and CDS systems) and catch basin (CB) trash capture/deflection systems (i.e., CB inserts and opening covers). Following evaluation of the existing city storm drain system and assessment of the different structural trash control devices deployed within the city, the City of Los Angeles concluded that implementation of either CB inserts and/or CB opening screen covers at all catch basins within the city is the most feasible, practical and cost effective approach for compliance with the TMDL. City-conducted pilot studies have indicated that the CB inserts used by the City of Los Angeles meet the definition of Full Capture Devices *. As for the CB opening screen covers, pilot studies conducted by the City concluded that they are very effective in preventing trash greater than _ inch from entering the catch basins and from being discharged to the receiving waters.

The passage of Proposition O in the Fall of 2004 has provided much needed funding to push forward the City’s aggressive implementation program to ensure compliance with the Trash TMDLs. At the inception of the program, the implementation of the trash TMDL in the City was projected to cost well over $1 billion in capital costs to achieve compliance.

Through the City’s leadership and use of its strategic two-prong approach, paralleled with a commitment to invest in piloting new products and BMPs, the capital costs are now projected to cost approximately $70 million to achieve compliance. In addition, the City will achieve compliance several years ahead of the actual mandated compliance deadlines. The City’s program has proven to be so practical and effective, that other cities within the County of Los Angeles have modeled their implementation strategy after the City's program.

* “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).”