Cal. Code Regs. tit. 23 § 3939.2

Current through Register 2024 Notice Reg. No. 43, October 25, 2024

Section 3939.2 - A Total Maximum Daily Load for Nitrogen Compounds and Related Effects in Calleguas Creek, Its Tributaries, and Mugu Lagoon

Los Angeles Regional Water Quality Control Board (Regional Board) Resolution No. 02-017, adopted on October 24, 2002 by the Regional Board, modified the regulatory provisions of the Water Quality Control Plan for the Los Angeles Region by establishing a Total Maximum Daily Load (TMDL) for nitrogen compounds in Calleguas Creek, its tributaries, and Mugu Lagoon. The TMDL specifies concentration-based targets for ammonia, nitrate, nitrite, and combined nitrate and nitrite, which must be fully attained seven years after the effective date of the TMDL. The TMDL includes a margin of safety with both implicit and explicit components. The TMDL establishes a four-year plan for reducing nitrogen loading from five wastewater treatment plants in the watershed. To allow time to meet the targets, interim limits will be allowed. The final wasteload allocations (WLAs) for ammonia assigned to the wastewater treatment plants must be met no later than October 24, 2004, and the final wasteload allocations for nitrate and nitrite must be met four years after the effective date of the TMDL. Load allocations for agriculture and other nonpoint source discharges are implemented through various management practices. One year after the effective date of the TMDL, monitoring plans to evaluate the effectiveness of the TMDL must be submitted to the Regional Board by Calleguas Creek Watershed Management Plan Water Resources/Water Quality Subcommittee (CCWMP). CCWMP is responsible for the watershed monitoring and special studies required by this TMDL. The special studies must be completed five years after the effective date of the TMDL.

In preparing the NPDES permit renewals, Regional Board staff identified a typographical error in the mass based daily WLAs for ammonia in the Calleguas Creek Nitrogen Compounds and Related Effects TMDL. Translating concentration based limit into a mass based daily limit requires multiplying the concentration-based limit by the flow rate. The mass based daily WLAs for ammonia, however, were incorrectly calculated as the product of the daily flow rate and the average monthly effluent limits (AMEL), rather than the daily flow rate and the maximum daily effluent limits (MDEL).

The TMDL was revised and then adopted by the Regional Board under Resolution No. R4-2008-009 to correct the mass based daily WLAs for ammonia to be based upon the MDEL, and updates the WLAs to be consistent with the current practice of recognizing that flow is variable. The mass based WLAs for ammonia are corrected to be based on the maximum daily effluent limit, MDEL, and the actual discharger effluent flow rate at the time the monitoring is conducted.

Cal. Code Regs. Tit. 23, § 3939.2

1. New section summarizing amendments to Water Quality Control Plan filed 6-5-2003; amendments adopted by the Los Angeles Regional Water Quality Control Board 10-24-2002 per Resolution No. 2002-017. Approved by State Water Resources Control Board 4-10-2003; approved by OAL and effective 6-5-2003 pursuant to Government Code section 11353 (Register 2003, No. 23).
2. Amendment of first paragraph and new second and third paragraphs summarizing changes to Basin Plan filed 9-30-2009; amendments adopted by the Los Angeles Regional Water Quality Control Board 9-11-2008 by Resolution No. R4-2008-009. Approved by State Water Resources Control Board 6-16-2009 by Resolution No. 2009-0052; amendment approved by OAL 9-30-2009 pursuant to Government Code section 11353 (Register 2009, No. 40).