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Drinking Water Maximum Contaminant Levels • http://w~,v.dhs.ca.gov/ps/ddwem/chemicals/mcl/mclindex.htm California Drinking Wafer Standards, Action Levels, and Unregulated Chemicals Requiring Monitoring Last Update: June 4, 1999 Maximum Contaminant Levels (MCLS) are primary and secondary drinking water standards. They are enforceable regulatory levels under the Safe Drinking Water Act, and must be met by all public drinking water systems to which they apply. MCLS are part of California's drinking water regulations, which can be downloaded from the Division of Drinking Water and Environmental Management download oaee. Primary MCLS (Table I) are established for a number of chemical and radioactive contaminants. Primary MCLS can be found in Title 22 California Code of Regulations (CCR) for inorganic chemicals (§64431), trihalomethanes (§64439), radioactivity (§64441 and §64443) and organic chemicals (§64444). Lead and copper (Table 2) have specific regulations in 22 CCR, Chapter 17.5 §64670, et seq. The lead and copper regulations use the term "action level" for each substance, for purposes of regulatory compliance. These action levels should not be confused with the advisory action levels for other unregulated chemical contaminants, as described below. Secondary MCLS (Table 3) are established for a number of chemicals or chazacteristics. They are set for taste, odor, or appearance of drinking water, and are presented in 22 CCR §64449. Action Levels (ALs) (Table 4)~xcept for lead and copper, as described above-are health-based advisory levels for chemicals for which primary MCLS have not been established. They are not enforceable standards. DHS recommends [hat drinking water systems provide public notification if ALs are exceeded. If sources exceeding ALs are taken out of service, customer notification is not needed. Drinking water systems are required to notify local governing agencies (i. e., city council and/or county board of supervisors) whenever an AL is exceeded in a drinking water well, even if the well is taken out of service (Health & Safety Code § 116455). Unregulated chemicals requiring monitoring (Table 5). Some chemicals are "unregulated" but nonetheless have certain monitoring requirements, as set forth in 22 CCR §64450. There aze a number of unregulated chemicals that are or may be required [o be monitored, depending on [he vulnerability of drinking water systems. Detection of chemicals in drinking water supplies is defined by the detection levels for purposes of reporting Df LRs). I of 13 7/?1/993:32 PM