Demonstrating Trash TMDL Compliance using a Combination of Structural and Institutional Measures
As many agencies are grappling with the upcoming 2015 Statewide Trash Amendments, the City of Los Angeles (City) has been proactive in taking steps to demonstrate compliance. The City, in collaboration with the Regional Water Quality Control Board (RWQCB), developed a two-pronged approach for demonstrating compliance with the Trash Total Maximum Daily Load (TMDL) through the implementation of institutional measures and structural measures.
Shortly after the Trash TMDL was approved by the RWQCB in September 2001, the City conducted a study to identify baseline trash accumulation rates and characterize all areas as high, medium, or low trash generating areas of the City. The study examined the amount of trash accumulating in the City’s catch basins and was completed in an effort to assist with the selection and placement of best management practices (BMPs). Then, in 2004, the City performed pilot studies to assess the performance of two trash capture measures: a catch basin insert with 5 millimeter (mm) openings, and a catch basin opening retractable screen cover. Study results indicated that the 5 mm inserts were 100 percent effective in preventing the trash generated from a one-year, one-hour storm event from entering the storm drain. The RWQCB subsequently approved the inserts as “full capture systems.” Based on study results, the RWQCB rated the effectiveness of the catch basin opening retractable screen covers as 86 percent effective in preventing trash from entering the storm drain system, and acknowledges them as “partial capture systems.”
To demonstrate compliance with the Trash TMDL and future Statewide Trash Amendments, the City implemented structural measures throughout its entire jurisdiction. Full capture systems were installed in the high trash generating areas of the City; and, partial capture systems were installed in the low and medium trash generating areas of the City. Due to the effectiveness of the trash capture devices, it is estimated that the installation of the structural measures alone will allow the City to demonstrate a trash reduction of approximately 90 percent.
The City has also implemented institutional measures throughout its jurisdiction to supplement the effectiveness of the installed structural measures. Examples of institutional measures implemented by the City include anti-littering statutes, street sweeping, catch basin cleaning, public outreach, and community clean-up programs.
The Quantification Study of Institutional Measures for Trash TMDL Compliance (Study) was completed to assess the effectiveness of the City’s implemented institutional measures in preventing trash from entering the City’s stormwater system and ultimately reaching its waterways. The Study was conducted at ten sites throughout the City over two eight-week periods in the summers of 2012 and 2013. Land use categories and baseline trash accumulation rates were considered as part of the Study.
Two factors that contributed to the success of this project are the development of a detailed workplan by the City and weekly field monitoring which provided quality control and led to improvements and refinement of the Study protocol. In addition, while not required by the Trash TMDL, the City decided to take this Study a step further by characterizing the type of trash collected at each project site. The City aims to utilize the characterization data to target high trash-generating behaviors and develop future institutional measures that will be most effective in preventing trash from reaching its waterways.
This presentation will share Study methods, results, and lessons learned. The presentation will also touch on the Study’s repeatability and how other stormwater agencies can apply the City’s methods to demonstrate compliance with upcoming trash regulations like the 2015 Statewide Trash Amendments.