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CV-SALTS - Agricultural Dominated Water Bodies Evaluation

Agriculturally Dominated Water Bodies Evaluation

Municipal and Domestic Supply (MUN) Beneficial Use Project

Background
Via the Sources of Drinking Water Policy (88-63), the Central Valley Regional Water Quality Control Board Basin Plans (Basin Plans) designate MUN beneficial use to all water bodies unless they are specifically listed as water bodies that are not designated with MUN. The Basin Plans state that waters designated for MUN must not exceed Maximum Contaminant Levels (MCLs) for chemical constituents, pesticides, and radionuclides. While 88-63 does contain exceptions for the MUN designation, to utilize the exception, the Basin Plans require “. . . a formal Basin Plan amendment and public hearing, followed by approval of such an amendment by the State Water Board and the Office of Administrative Law.”

During permit adoptions for the National Pollutant Discharge Elimination System (NPDES) program, there have been challenges to protecting the MUN beneficial use designation in agricultural drains due to the stated exception in 88-63. The cost for POTWs to comply with protecting the MUN beneficial use has been estimated at $3 - $7 million (City of Willows, case example).  The POTWs have been provided the option of pursuing a basin plan amendment as part of their permit compliance.

Concurrently, the CV-SALTS initiative has identified the need to evaluate the protection of MUN beneficial uses in agriculturally dominated water bodies. CV-SALTS identified receiving waters of four Publically Owned Treatment Works (POTWs - Cities of Willows, Colusa, Biggs and Live Oak) as potential archetypes (case studies) for evaluating appropriateness of a MUN designation. These same potential archetypes have challenged the MUN designation during NPDES permit renewals.

In May 2011, a draft Central Valley Water Board staff report evaluated the appropriateness of the MUN beneficial use in a water body (agricultural drain) receiving effluent. The report found that more data needs to be collected before determining if a basin plan amendment is needed. The data needs noted included: characterization of the receiving waters, water quality data for the effluent and all receiving waters, flow data for all of the receiving waters, an antidegradation analysis, and an environmental analysis.

This MUN beneficial use project is the first phase of the agriculturally dominated water bodies evaluation effort. Sponsored by the Central Valley Water Board in conjunction with the CV-SALTS initiative, the project attempts to combine and leverage the work desired by four POTWs (the cities of Willows, Colusa, Live Oak, and Biggs) and the archetypes identified by CV-SALTS. The second phase of the evaluation will be focused on determining the appropriate beneficial uses for all agricultural dominated water bodies.

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