Overview

The Los Angeles County Structural BMP Prioritization Methodology (Methodology) is a new, systematic tool to prioritize structural BMP projects within Los Angeles County watersheds. This GIS-based method is designed to help watershed planners, managers, and stakeholders throughout LA County in strategic, conceptual planning of structural BMP placement. The method helps users identify and rank both large-scale regional and small-scale distributed BMP projects. The strength of the Methodology is its ability to systematically process multiple factors that affect BMP placement and effectiveness, and to process multiple data sources in a semi-automated and reproducible manner. The Methodology is flexible and transparent so the user can tailor results to specific goals by adjusting the weights associated with various watershed and BMP factors.

A free, comprehensive User's Guidance Manual has been developed and is available for download. To further aid users in applying the Methodology, the results of a demonstration application of the tool to the Ballona Creek Watershed are provided.

Motivation For Developing The Methodology
Runoff from Los Angeles County’s urban landscape carries many pollutants into local creeks, rivers, Santa Monica Bay and the Pacific Ocean. Among the contaminants are gasoline, oil, metals, pesticides, fertilizers, detergents, bacteria, viruses and fecal matter. Curbing runoff pollution is a countywide priority driven not only by state and federal water quality regulations, but also by local and regional pollution prevention plans and environmental objectives.

The primary tools for reducing runoff pollution are usually referred to as best management practices (BMPs). BMPs are often categorized as either structural or nonstructural. Structural BMPs are those that improve water quality through some treatment mechanism. The mechanism can be regional, like a constructed wetland, or highly localized, like a parking lot bioretention swale.

To date, the implementation of structural BMPs in developed areas of the Los Angeles region has been largely opportunistic and site-specific. Projects are completed in response to a specific local funding opportunity or regulatory requirement, and often focus on only one or two pollutants (or sources). Project locations are often chosen based on land availability and public ownership, so sites such as school yards and parks are favored. Implementation planning has not emphasized the strategic location of BMPs that have been chosen to achieve specific water quality goals within a watershed or other targeted geographic area.

The Methodology was developed to provide the LA County region with a tool that allows the users to systematically prioritize BMP projects for a watershed. Importantly, the Methodology is flexible and transparent. It requires the users to explicitly weight the relative importance of multiple factors that affect the overall effectiveness of BMP implementation. This allows the user to tailor the method to water quality goals specific to their watershed, and provides the user with a systematic, semi-automated process for investigating multiply objectives and implementation scenarios.

Project Team
A technical Project Team led by GeoSyntec Consultants developed the Methodology. The team also included representatives from Heal the Bay, the County of Los Angeles Department of Public Works, and the City of Los Angeles Bureau of Sanitation. The development process was unique in that it was informed by the expertise of a small, yet integral subset of stakeholders with considerable interest in the project’s outcome. This made it possible for the project team to receive constructive technical input from the beginning of the project and at all levels of detail – from data collection feasibility to implementation and potential regulatory implications.

Funding
Funding for development of the Methodology was provided in part through an agreement with the State Water Resources Control Board (SWRCB) pursuant to the Costa-Machado Water Act of 2000 (Proposition 13) and any amendments thereto for the implementation of California’s Nonpoint Source Pollution Control Program. The contents of this web page and associated project documents do not necessarily reflect the view and policies of the SWRC, nor does mention of trade names or commercial products constitute endorsement of recommendation for use.

In-kind services for the project were provided by the County of Los Angeles Department of Public Works and the City of Los Angeles.