SITE INFORMATION AND CORRESPONDENCE_1993-2003

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INFORMATION SHEET 11 WASTE DISCHARGE REQUIRMENTS ORDER NO.R5-2002-XXXX U.S.DEPARTMENT OF DEFENSE DEFENSE LOGISTICS AGENCY DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN SHARPE GROUNDWATER REMEDIATION SYSTEM SAN JOAQUIN COUNTY Data Adjustments In most situations, EPA's NPDES regulations require that limits for metals in permit's be stated as total recoverable. Since most water quality criteria are expressed in the dissolved form, it is necessary to translate between dissolved metal in ambient waters and total recoverable metal in effluent. EPA guidance on the use of translators provides three options including, (1) assuming the translator equivalent to the criteria guidance conversion factor, (2) developing a translator directly as the ratio of dissolved to total recoverable metal, and/or, (3) developing a translator through the use of a partioning coefficient. Reasonable potential analysis for this permit was conducted using the first option, applying criteria guidance conversion factors. To assure that metals criteria are appropriate for the chemical conditions under which they are applied, EPA also provides for adjustment of the criteria through application of the water-effect ratio (WER). The WER approach compares bioavailability and toxicity of a specific pollutant in receiving waters and in laboratory waters. For this permit, reasonable potential analysis was conducted using a WER default value of 1. As described in the CTR, freshwater aquatic life criteria for certain metals are expressed as a function of hardness, since hardness, and/or water quality characteristics that are usually correlated with hardness can reduce or increase the toxicities of some metals. Hardness is used as a surrogate for a number of water quality characteristics which affect the toxicity of metals in a variety of ways. To ensure the level of protection intended by the EPA's 1985 Guidelines for hardness is maintained or exceeded, the minimum observed hardness of the upstream water that does not contain effluent was used to adjust the applicable criterion. The minimum observed hardness of the SSJID Canal, upstream of the point of effluent discharge, was reported as 28 mg/L (ppm) as CaCO3 (on 7/1/97 and 10/11/01). The minimum observed hardness of the SSJID Canal downstream of the point of effluent discharge was also reported as 28 mg/L (ppm) as CaCO3 (10/11/01). For purposes of the reasonable potential analysis, hardness dependent criterion were adjusted using these lowest observed hardness levels of the SSJID Canal. Determination of Priority Pollutants Requiring Water Quality Based Effluent Limitations Section 1.3 of the SIP requires that the Regional Board to conduct an analysis for each priority pollutant with an applicable criterion or objective to determine if a water quality based effluent limitation is required. Attachment C summarizes final effluent inorganic priority pollutant data collected from the three GWTPs during the most recent periods of discharge to the SSJID Canal. Attachment C also includes a summary of aquatic life and human health criteria for each inorganic priority pollutant. The Criteria Maximum Concentration (CMC) is defined by USEPA as the water quality criteria to protect against acute effects in aquatic life and is the highest in stream concentration of a priority toxic pollutant consisting of a short-term average not to be exceeded more than once every three years on the average. The Continuous Criteria Concentration (CCC) is the water quality criteria to protect against chronic effects in aquatic life and is the highest in stream concentration of a priority toxic pollutant consisting of a 4-day average not to be exceeded more than once every three years on the average.