Skip to main content


The full text article is not available for purchase.

The publisher only permits individual articles to be downloaded by subscribers.

or click here to sign up for a free trial


Located in Ventura County California, the Calleguas Creek Watershed (CCW), though relatively small in area, suffers from more water quality impairments than most California watersheds, as defined by the USEPA's 303(d) list. Local stakeholders, along with the Los Angeles Regional Water Quality Control Board (LARWQCB), began a watershed planning process over eight years ago to develop a better understanding of the watershed and a strategy to address impairments.

The local stakeholders developed a comprehensive series of work plans designed to develop TMDLs to address groups of constituents in the 343 square mile watershed. TMDLs have been completed for three groups of constituents: (1) metals, (2) legacy pesticides, and (3) chlorpyrifos, diazinon and toxicity of unknown causes in water and sediment. The process followed in California appears to be unique in several respects. The purpose of the presentation is to present these unique aspects, with their advantages and disadvantages as experienced with CCW TMDL development, and to relate that experience to urban areas in general.

The general pollutant sources in the CCW watershed are agricultural, open space, community wastewater point discharges, and urban runoff. There are four incorporated communities within the watershed: Thousand Oaks, Simi Valley, Camarillo, and Moorpark. The total population in the watershed is approximately 334,000.

The first significant uniqueness was that the TMDLs were not prepared by a state or federal agency, as is common across the Nation. Rather the stakeholders themselves directed and provided the primary sources of funding for TMDL development. This approach provides many advantages, the first being an increase in funding to support the process. The Stakeholder groups included the cities, wastewater treatment facilities, agriculture interests, and environmental groups. Stakeholders chose to take direct responsibility because of the potential implications of TMDLs, and believed that substantial funding was necessary for a thorough technical analysis. Stakeholder involvement and participation was directly responsible for the development of the allocations and implementation plan. The authors will explain the process of stakeholder involvement, and the iterative interaction process with State agency and USEPA staff.

A second uniqueness relates to the Implementation Plan. Typically elsewhere the Implementation Plan identifies NPDES permit requirements including a mix of BMPs to be carried out to achieve the allocated loadings. This may not always be appropriate given the complexity of the beneficial use/water quality impairment and the lack of knowledge of the source(s) and spatial and temporal variation of the pollutant(s) causing the impairment. We therefore design the implementation plan as a stepwise process to carryout additional studies believed necessary to properly identify the effectiveness and costs of particular BMPs or strategies before prescribing BMPs.

Document Type: Research Article


Publication date: January 1, 2007

More about this publication?
  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

    WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access.
  • Subscribe to this Title
  • Membership Information
  • About WEF Proceedings
  • WEFTEC Conference Information
  • Ingenta Connect is not responsible for the content or availability of external websites

Access Key

Free Content
Free content
New Content
New content
Open Access Content
Open access content
Partial Open Access Content
Partial Open access content
Subscribed Content
Subscribed content
Free Trial Content
Free trial content
Cookie Policy
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more