Arizona Water Resource Mar-Apr 2005

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March -April 2005 Arizona Water Resource 5 Water Quality Concerns Along the Colorado River ADEQ Checks if Plume is Risk to AZ Water The Arizona Department of Environmental Quality will con- duct a study to determine whether groundwater in Arizona has been contaminated by a plume of hexavalent chromium coming from the Pacific Gas & Electric Topock natural gas compressor near Needles, California. PG &E has agreed to pay for the study that is expected to cost more than $350,000. The intent of the study is to examine the groundwater flow on the Arizona side of the Colo- rado River to determine if the hexavalent chromium plume, also called chro- mium 6, is migrating under the riverbed and contami- nating water supplies in Colorado River Arizona. Although none Photo: Bureau of Reclamation has been found in the river itself, the polluted water could have flowed beneath the river. Also, drinking water wells in the communities of Topock and Golden Shores, Arizona, will be sampled as part of the study. Recent test results have raised concerns: California regula- tors announced on Feb. 22 that high levels of chronium 6 have been detected in a monitoring well just 60 feet from the Colorado River. The sample detected 354 parts per billion of total chromi- um; California's limit is 50 ppb in drinking water. The Colorado River provides drinking water for more than 18 million Southern Californians and 4 million Arizonans. In response to the test results ADEQ Director Owens wrote a letter to the California Regional Water Quality Control Board on March 14 stating, "The plume of hexavalent chromium may have already moved beneath the Colorado River and may now be contaminating Arizona's groundwater." Owens wrote that heavy levels of chromium 6 occurring at a depth of 90 to 100 ft. below the surface demonstrates that "the potential threat to Arizona's groundwater and surface water re- sources from the plume has increased significantly." Arizona is not alone in its concern about the pollution. Also worried about the plume are Metropolitan Water District of tablish an AMA in the area. He said that not only was there sufficient groundwater in the area to meet future needs, but groundwater pumping was not resulting in land subsid- ence or fissuring nor was it degrading water quality in the basin; thus the legal criteria for establishing an AMA were not met. Studies determined that the basin stores between 20 million to 26 million acre -feet of groundwater, with pumping in Southern California and local water agencies. Also, five Indian tribes residing along the Colorado River fear the utility's clean -up plans will dishonor tribal sacred sites. DOE May Move Toxic Pile From Colorado River The U.S. Department of Energy announced that its "preferred alternative" for solving the problem of a 12- million -ton pile of radioactive waste located along Colorado River is to move it away from the river banks. DOE had considered other options includ- ing leaving the pile on -site, 750 feet from the river, near Moab, Utah, capped with a layer of impermeable clay. DOE's consideration of an on -site option attracted strong opposition, with western governors, bipartisan members of Con- gress, various water agencies including the Metropolitan Water District of Southern California, and a number of Lower Colo- rado River state agencies, including the Arizona Department of Environmental Quality, voicing vigorous objections. The U.S. En- vironmental Protection Agency also joined the chorus, informing DOE that leaving the waste pile by the river is "environmentally unsatisfactory" and possibly poses a public health hazard. The toxic pile's proximity to the river raised fears that toxic chemicals will leak into the river, a source of water for about 25 million people including residents of Phoenix, Tucson, Los An- geles and Las Vegas. According to DOE present leakage does not pose a hazard; the agency reports that the 15,000 gallons of toxic chemicals in- cluding ammonia, selenium and chromium now leaking into the river each day are diluted in the drift and flow of the river. Of concern to many is not just the daily discharge, which could continue for centuries if the pile remains in place, but the potential of a flood scouring the area and washing the toxic pile into the river, with catastrophic results. If removal does in fact become DOE's final decision, the agency would be taking the more costly option. Energy officials say leaving the pile on -site would cost about $166 million where- as moving it would cost between $329 million and $464 million. Work is not expected to begin until 2007, with an expected com- pletion date of 2012. Getting Congress to approve funding for the project may be a hurdle to overcome. DOE intends to review all public comment before issuing a final decision, expected early summer. the area drawing out more than 9,500 acre feet than is naturally recharged. Although a cone of depression is deepening around Sierra Vista and Fort Huachuca, the state found that not much change has occurred in groundwater levels adjacent to the river. Some officials say that the request to establish an AMA in the San Pedro basin to help preserve the flow of San Pedro River is asking the GMA do something it was not intended to do; i.e., provide for sustainable use without adverse environmental conse- quences. The AMA goal of safe yield — a condition in which the amount of ground- water pumped does not exceed the amount recharged — would not necessarily preserve the flow of the San Pedro. It is possible that the river could diminish in flow even though pumping is equal or less than recharge; therefore the GMA would not be violated.