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Gary M. Carlton Page 2 November 23, 1999 sufficiently characterize the range of removal rates provided by the treatment plant, especially given the critical nature of this parameter in the health risk assessment. 3. How does the risk of infection vary with proximity of recreation activities to the outfall plume? The study does not differentiate between various zones (nodes) on the receiving area in terms of exposure to pathogens from the treatment plant effluent. These differences should be examined, as they might be significant. 4. How does the risk of infection vary with the immunological status of the recreating public? The risk assessment assumes that "the population is homogeneous with respect to susceptibility to disease' (bullet 3, page 4-5), and provides no information on the potential risks to illness to the following types of individuals should they recreate near the wastewater treatment facility outfall: • young, or very young, children • immuno-compromised adults • the elderly The entire recreating public does not need to be assumed to be members of these susceptible populations, but to not discuss them at all is inappropriate. 5. Are there other significant routes of exposure to effluent-bome pathogens in addition to body-contact recreation that need to be analyzed? This report focuses on recreational watercraft use, and does not address a number of other potential exposure pathways that the RWQCB needs to consider. These include the following uses of water in and from the San Joaquin River: • as a source of irrigation water, particularly as sprayed upon leafy vegetables which may be harvested for immediate consumption, and • as a source of freshwater shellfish harvested for food use. (We understand that this occurs, particularly among immigrants from Southeast Asia.) Based upon the information that is now available, we recommend that the Regional Water Quality Control Board require the City of Stockton to modify its wastewater treatment plant to enhance pathogen reduction in the plant effluent. Such modifications should include filtration and enhanced disinfection sufficient to comply with the following criteria: