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How CAN THIS PROBLEM BE SOLVED? A survey of wells in the Metropolitan Water District of Southern California (MWD) service area revealed the pervasiveness of groundwater contamination. The 1994 study concluded that 46 percent of the wells were contaminated with some constituents to the point that the wells exceeded maximum contami- nant levels at least once in a 14-year period. Nitro- gen, vacs, minerais and total dissolved solids, mostly salts, were the most common problems. In general, MWD found the problem to be increasing as pollutants from decades past move into ground- water, and that trend undermines the region's plans to make better use of its groundwater to meet grow- ing demands. In a portion ot MWD's service area, the San Gabriel Valley, water agencies are cooperating in a compre- hensive approach to solving the problem. Prior to extensive urban development, the basin was home to orchards and dairies. Beginning in World War II, the valley's rural lifestyle and agricultural economy were replaced with defense-related industries, and later, suburbs. Intense demands on the valley's groundwater led to a court adjudication. In the 1 970s, water managers detected nitrate in the groundwater. Today an estimated one-third of the basin's groundwater has nitrate concentrations exceeding drinking water standards. Much of the nitrate is still migrating from the soil into the ground- water. In 1979, water managers detected vacs in the groundwater. By 1980, 89 out of 300 wells were shut down because of vacs. The San Gabriel Basin Water Quality Authority was formed in 1993 to coordinate the clean-up efforts of a variety of agencies involved in the basin. Nearly $40 million has been spent by EPA to monitor and detect problems and plan the clean up of the groundwater basin. In 1994, EPA issued a plan tor treating groundwater beneath a major portion of the valley, in which the local authority formed a project to clean-up the groundwater and deliver it to MWD customers, using revenue from the water sales to pay for part of the treatment costs. In addition to EPA's efforts. 19 different treatment programs have been started to treat vacs, nitrates and salts. The treatment programs have cost from less than $60 an acre-foot to as much as $820 an acre-foot depending on the pollutant and the treatment process. Authorities believe they have made substantial progress toward controlling the migration ot pollutants and have designed the infrastructure that will help to reslore the aquifer over the next century. In some ways, groundwater remediation is a frontier science. Decisions have to be made with incomplete intormation about the hydrology of a basin, the health threats of certain contaminants, and the natural decomposition or path of pollutants in the soil and water. The extraordinarily high costs of clean up technologies have convinced many officials of the economies associated with better wellhead protec- tion efforts and proper demolition of abandoned wells. The SDWA amendments of 1996 require states to develop wellhead protection programs, and EPA officials are among those who believe California needs to do a better job ot keeping pOllutants away from wells and destroying abandoned wells. The state DHS has taken the lead in developing a wellhead protection program. The potential for urban landscape designs to either assist or prevent nonpoint source pollution from reaching streams and bays, as well as groundwater, is getting more attention. Extensive paved areas concentrate runoff and pollutants, compromising the ability of soils to filter, decompose or capture poten- tial pollutants. More greenbelts, stream buffer zones, and artificial wetlands are among the designs being explored to slow runoff and control pollution. The improper disposal (~r chemicals in il/exal dump site... sllch as this one contrihute 10 groun(hmter cOJ/laminatioll. UO""_ _ ...........< - 17