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Gary M. Carlton Page 4 November 23, 1999 5. The RWQCB should inquire whether the receiving waters are used for irrigating fresh market crops, or the extent to which the impacted area is used for non- commercial shellfish harvesting. If these uses are found to be prevalent, the City should examine the risk the discharge poses to the public via these pathways. 6. The data should be reanalyzed to determine the frequency with which the discharge will result in an annual risk of infection that exceeds one in 10,000 (10-4). This is the level of acceptable risk used by the U.S. EPA for the Surface Water Treatment Rule, and has been used as a goal in a risk assessment for exposure to treated wastewater2. 7. The determination of whether the current situation is adequately protective of public health should be based upon a 95% "confidence level"; i.e., the computed annual risk posed by the treatment plant discharge should not exceed one in 10,000 (10'4) in 95% of the computer simulations. In addition, it should not exceed 10-3 in 99% of the simulations. Other Remarks and Observations It should be noted that California's growing population in the Central Valley will likely result in more wastewater entering the San Joaquin River, as well as more people recreating in the San Joaquin River. Therefore, we believe the RWQCB should consider applying more stringent water quality discharge requirements for all dischargers along its length. Further, the dramatic reduction of flow in the San Joaquin River at Stockton to near-stagnant conditions in recent years suggests to us that the RWQCB should treat the River as more of a lacustrine water body than a stream environment, and enhance the quality requirements of permitted discharges commensurately. In addition, we encourage the RWQCB to change its determination of the beneficial uses of the lower San Joaquin River. If the prevailing view is that the river below Vernalis is primarily an agricultural drain there will be little incentive to set discharge requirements that will improve the quality of the River. We do not concur with this view; rather, we consider this stretch of the San Joaquin River to be a severely stressed water body that is a source of drinking water. It is also important as a source of fish and 1 U.S. EPA, 1989. -Final Surface Water Treatment Rule" (Federal Register 54, 124, 27486) 2 Tanaka, et al., 1998. "Estimating the Safety of Wastewater Reclamation and Reuse Using Enteric Monitoring Data"