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4. NATURE OF INJECTION FLUID The nature of the injection fluid is made up of three combined waste streams: 1) process waste water, 2) miscellaneous brines, and 3) recovered groundwater. The Report of Waste Discharge (RWD) submitted to the RWQCB described the charac- teristics of each of these waste streams. The injection fluid is described in Table One. 5. WELL CLASSIFICATION The proposed injection well is a Class V well, according to 40 CFR 144.6, because the disposal well will inject fluids into or above an Underground Source of Drink- ing Water (USDW). The injection fluid is not classified as a Resource Conservation and Recovery Act (RCRA) hazardous waste. 6. AQUIFER EXEMPTION No aquifer exemption is necessary for this activity. 7. VARIANCES No variances are necessary for this activity. 8. AREA OF REVIEW The radius of endangering influence is calculated to determine possible effects of pressure build-up on wells within the area. The distance at which the pressures in the injection zone may cause migration of the injection or formation fluid into the USDW is considered the radius of review. Three methods are commonly used to calculate the area of review when applying for a UIC permit. These are the fixed radius method, the volumetric method, and the pressure build-up method. The fixed radius method involves the selection of a fixed distance as the radius around the well. The volumetric method uses a simple equa- tion relating the total volume of fluid to be injected during the life of the well and the radius. The pressure build-up method is more involved and can be solved several different ways. A fourth method, which is optional, involves numerical modeling. The applicant has calculated the area of influence using the first three methods. EPA has reviewed the submitted calculations and concludes that a three mile radius is a conservative estimate for the radius of influence. The draft permit requires the 4