SITE INFORMATION AND CORRESPONDENCE_CASE 2

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REGIONAL WATER BOARD RESPONSE (SWRCB/OCC File A-1846(a) and 4-1846(b)) -17- PETITIONS FOR REVIEW OF '4.., TE DISCHARGE REQUIREMENTS 1,0 ORDER NO. R5-2007-0036 (NPDES NO. CA0079154)AND TIME SCHEDULE ORDER NO R5-2007-0037 CITY OF TRACY, WASTEWATER TREATMENT PLANT Facility, the Discharger has proposed mitigation measures to ensure that any thermal impacts will be less than significant. The Discharger proposes to conduct four years of intensive monitoring of thermal impacts in the vicinity of the outfall and develop an appropriate range of mitigation measures, if necessary. Furthermore, as required by other regulations, the Discharger is required to conduct consultations with the United States Fish and Wildlife Services, National Marine Fisheries Service, and California Department of Fish and Game to develop mitigation measures for the protection of aquatic species, including rare, threatened, and endangered species protected under the Endangered Species Act. Before increasing the discharge, the Order requires the Discharger to demonstrate compliance with the temperature effluent and receiving water limitations, or the Discharger must have obtained an exception from the Thermal Plan. CSPA — CONTENTION H: The Order allows degradation of groundwater. CSPA contends that the use of asphaltic concrete paved sludge drying beds does not meet best practicable treatment or control.(BPTC), because the liners are not completely impermeable and would allow groundwater degradation. Order R5-2007-0036, the subject of this petition, only regulates the surface water discharge to Old River. Separate waste discharge requirements (Order R5-2007-0038) were adopted by the Regional Water Board in May 2007 that regulates discharges to groundwater, including discharges from the sludge drying beds. CSPA did not petition that Order, which requires the following to protect groundwater quality and limit degradation: 1. Includes groundwater limitations requiring that the, "Release of waste constituents from any storage, treatment, or disposal component associated with the Facility shall not cause underlying groundwater to contain waste constituents in concentrations statistically greater than background water quality.' 2. The Discharger must evaluate its groundwater monitoring network so compliance with the groundwater limitations can be determined, and must add new groundwater monitoring wells, as needed; 3. The Discharger must characterize groundwater quality, both upgradient and downgradient of the Facility; 4. If groundwater monitoring results show that the discharge of waste is threatening to cause or has caused groundwater to contain waste constituents in concentrations statistically greater than background water quality the Discharger shall submit a BPTC Evaluation Workplan that sets forth a scope and schedule for a systematic and comprehensive technical evaluation of each component of the facilities' waste management system, including the sludge drying beds, to determine BPTC for each waste constituents of concern.