ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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(3)Where high quality waters constitute an outstanding National resource, such as waters of National and States parks and wildlife refuges and waters of exceptional recreational or ecological significance,that water quality shall be maintained and protected. Safe Drinking Water Act The Safe Drinking Water Act(SDWA)was passed in 1974(Public Law 93-523)to regulate the Nation's drinking water supply. The law was amended in 1986 and 1996 and requires many actions to protect drinking water and its sources—rivers, lakes,reservoirs, springs, and groundwater. The SDWA authorizes EPA to set national health-based standards for drinking water to protect against both naturally occurring and human-made contaminants of concern that may be found in drinking water. Contaminants of concern relevant to domestic water supplies are defined as those that pose a public health threat or that alter the aesthetic acceptability of the water. Drinking water contaminant levels are reported as MCLS. MCLS are legally enforceable standards based on health risk or nonhealth concerns such as odor or taste.National Primary Drinking Water Regulations(NPDWRs or primary standards) are legally enforceable standards that apply to public water systems. Primary standards protect public health by limiting the levels of contaminants in drinking water. National Secondary Drinking Water Regulations(NSDWRs or secondary standards)are nonenforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color)in drinking water. EPA sets national standards for drinking water based on science to protect against health risks, considering available technology and costs. These National Primary Drinking Water Regulations set enforceable primary and secondary MCLS for particular contaminants in drinking water or require ways to treat water to remove contaminants. MCLS and the process for setting these standards are reviewed triennially. Amendments to the SDWA enacted in 1986 established an accelerated schedule for setting drinking water MCLs. Stage 1 Disinfectants and Disinfection Byproducts Rule Amendments to the SDWA in 1996 require EPA to develop rules to balance the risks between microbial pathogens and disinfection byproducts(DBPs). The Stage 1 Disinfectants and Disinfection Byproducts Rule(40 CFR Parts 9, 141, and 142), announced in December 1998, is the first of a set of rules under the 1996 SDWA amendments. The Stage 1 Disinfectants and Disinfection Byproducts Rule applies to all community and nontransient,noncommunity water systems that treat their water with a chemical disinfectant for either primary or residual treatment. The rule establishes maximum residual disinfectant level goals and maximum residual disinfectant levels for three chemical disinfectants—chlorine, chloramine, and chlorine dioxide. It also establishes maximum contaminant level goals and MCLs for total trihalomethanes,haloacetic acids, chlorite, and bromate. Interim Enhanced Surface Water Treatment Rule The Interim Enhanced Surface Water Treatment Rule (40 CFR Parts 9, 141, and 142),was also announced in December 1998, as another rule developed to balance the risks between microbial pathogens and DBPs under the 1996 SDWA amendments. The Interim Enhanced Surface Water Treatment Rule applies to public water systems that use surface water or groundwater under the direct influence of surface water(GWUDI) and serve at least 10,000 people. In addition, States are required to conduct sanitary surveys for all surface water and GWUDI systems, including those that serve fewer than 10,000 people. The final rule includes treatment requirements for waterborne pathogens, e.g., Cryptosporidium. In addition, systems must continue to meet existing requirements for Giardia lamblia and viruses. Specifically,the rule includes: ► Maximum contaminant level goal(MCLG) of zero for Cryptosporidium, ► 2-log Cryptosporidium removal requirements for systems that filter, EDAW DER Hydrology and Water Quality 4.9-16 City of Manteca