Cal. Code Regs. tit. 23 § 3978
This Basin Plan amendment establishes revised boundaries for groundwater management zones (formerly termed groundwater "subbasins") throughout the Santa Ana Regional Water Quality Control Board. For each of the new management zones, this amendment identifies existing and potential beneficial use designations, and total dissolved solids (TDS) and nitrate-nitrogen water quality objectives based on historical water quality ("antidegradation" objectives). For certain management zones, this amendment establishes a second set of TDS and nitrate-nitrogen objectives. This second, less stringent set of objectives is based on the finding that water quality consistent with "maximum benefit to the people of the State" will be maintained (the "maximum benefit" objectives), provided that specific water and wastewater projects and programs are implemented. These project and program commitments are delineated in the revised Implementation Plan in the Basin Plan amendment (see below). The "maximum benefit" objectives apply unless the Regional Board finds that the maximum benefit project and program commitments are not being implemented and that the finding of maximum benefit cannot continue to be made. In that case, the "antidegradation" objectives would apply. To address this situation, the amendment specifies that mitigation for TDS and nitrate-nitrogen discharges in excess of discharge limitations based on the antidegradation objectives will be required. The amendment also revises the narrative water quality objectives for chloride, TDS, hardness, sodium, and sulfate applicable to groundwater.
The Basin Plan amendment establishes revised reach boundaries and revised numeric TDS and nitrate-nitrogen water quality objectives for the following surface water bodies: San Timoteo Creek, Chino Creek and Temescal Creek. For San Timoteo Creek, Reach 1A, the groundwater recharge designated use is deleted. No other changes to the beneficial use designations for these surface waters are included in the amendment.
The amendment establishes the Prado Basin Management Zone as a surface water feature. Beneficial uses and surface water quality objectives already established for the major tributary streams in the Prado Basin Management Zone apply for regulatory purposes.
This Basin Plan amendment incorporates revisions to the TDS and Nitrogen Implementation Plan, including the following provisions: revised wasteload allocations for Publicly Owned Treatment Works discharges of nitrogen and TDS to the Santa Ana River and tributaries; revised findings regarding nitrogen and TDS assimilative capacity in the new groundwater management zones; findings regarding nitrogen loss coefficients and their implementation in waste discharge requirements; special considerations for salt management of subsurface disposal system discharges; and monitoring program requirements.
For the agencies and dischargers that are implementing the "maximum benefit" TDS and nitrate-nitrogen objectives, the amendment specifies compliance dates for the implementation of certain projects and programs. The amendment also includes requirements for implementing salt reduction programs when management zone TDS and/or nitrate-nitrogen reach specified concentration trigger points. Finally, with regard to the implementation of the "maximum benefit" objectives, the amendment specifies that if the Regional Board determines that the agencies/dischargers have not complied with the specified requirements for implementation of projects/programs, the Regional Board, at a duly noticed public meeting, would make the determination that the lowering of water quality is not of "maximum benefit" to the people of the State and by default, the TDS and nitrate-nitrogen historical "antidegradation" objectives would apply. The Basin Plan amendment specifies that in this situation, the Regional Board will require mitigation for TDS and nitrate-nitrogen discharges in excess of waste discharge limitations based on the antidegradation objectives.
Cal. Code Regs. Tit. 23, § 3978