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Selecting Numerical Limits • - 5 - 20 August 2002 An Algorithm for Inland and Estuarine Surface Waters Different numerical limits apply to surface waters. Additional beneficial uses—for example, those that protect aquatic life—normally apply. There are additional standards that apply to surface waters. The California Toxics Rule (CTR) and National Toxics Rule (NTR) contain promulgated numerical criteria for pollutants in California inland and estuarine surface waters. CTR and NTR criteria to protect human health or aquatic life have stronger legal standing than the use of an advisory limit to.interpret the narrative Toxicity objective also to protect human health or aquatic life. For example, if the CTR contains a human health protective criterion for the chemical of concern, it has precedence over the use of the Public Health Goal to interpret the narrative Toxicity objective to protect human health. Similarly, if the CTR includes an aquatic life protective criterion, it would supersede use of a USEPA recommended aquatic life criterion for the same chemical, even if the latter is newer or more stringent. This CTR/NTR constraint does not apply to groundwater. In addition, the CTR, NTR and USEPA Recommended Ambient Water Quality Criteria for human health protection apply only to surface water, because they are derived assuming exposure through consumption of fish and shellfish from the water. ❖ California Toxics Rule and National Toxics Rule (NTR criteria are listed in Water Quality Goals under "California Toxics Rule Criteria"and footnoted accordingly.) ➢ Criteria for human health protection (Use criteria for drinking water sources, consumption of water plus aquatic organisms, unless the MUN beneficial use has specifically been de-listed for the water body.) _ _ ➢ Criteria for aquatic life protection [Both the Criteria Continuous Concentration (CCC, 4-day average) and Criteria Maximum Concentration (CMC, 1-hour average) criteria apply. Sampling frequency should allow determination that both types of criteria are satisfied] ❖ Chemical Constituents Objective (Each of the following three items apply separately) Drinking Water MCLS; select the lowest of the following • California Primary MCL ■ California Secondary MCL ➢ Numerical water quality objective from the Basin Plan (may supercede CTR or NTR criteria if approved by USEPA) ➢ Concentrations that indicate impairment of any designated beneficial use; select the lowest of the following ■ Agricultural use protective limits ■ Federal Primary MCL, if lower than California Primary MCL 13 ❖ Toxicity Objective Human health-risk based limits for drinking water use, normally in the following hierarchy (applies only if there are no CTR or NTR criteria for human health protection) 13 See footnote 10,above.