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THE ARIZONA REPUBLIC CAP ISpeclal Report 7 o -. :"\l M a :.::> I rl Mingling waters Imported CAP flow could affect quality of pure state sources Water-quality problems will flow into central Arizona along with the imported Colorado River water. The problem is that the poorer-quality imported water likely will become mixed with ground water and with Salt and Verde river water, both much purer. Mixing will occur if the Salt River Project agrees to transport Colorado River water in its canals to some Valley cities. The Colorado River water, delivered through the Central Arizona Project, would mingle with the Salt and VeIde water behind the SRP's Granite Reef Diversion Dam before entering the canal. Pumped water would be introduced along the canals. Tucson officials say CAP water will be mixed with that city's ground water when deliveries begin. Colorado River water contains high levels of calcium, magnesium, sulfates, suspended matter, dissolved solids, organics, salts and bacteria, all difficult and costly to remove. Because California has been treating Colorado River water to meet drinking standards since at least 1941, the technology is available to Arizona, but treatment of the mixed waters will be more costly. Colorado River water is harder ~ more calcium and magnesium ~ than that currently used in central Arizona. Many water companies in the West deliver Colorado River water, but few soften it for customers. Most likely, central Arizona customers who want 80ft water will have to pay to have it treated. A high amount of sulfates can act as a laxative, but usually the body can adjust to the change and symptoms disappear within a few days. The mixed water also will have a higher potential for ~ J , 'I , 1 ~ algae growth and the production of trihalomethane -; THM - according to preliminary federal studies. Although algae does not present health problems, it can cause water to taste and smell musty. It also can grow to be so thick that it stops the flow of water in canals And clogs reservoir outlets. Most taste and odor problems can be dealt with by adding powdered activated carbon or other chemicals. Canals and outlets will need additional maintanence. THM, known to cause cancer in humans, is produced from organic compounds when chlorine is added during the standard water-treatment process. The Environmental Protection Agency limit for THM in treated water is 100 parts per billion. The Colorado River water, when mixed with Salt and Verde river water, potentially could result in 300 parts per billion. The Salt River Valley 80 far has not had a THM problem. The THM prohlem can be solved by modifying the current water-treatment process. Salt and Verde river water and ground water now are chlorinated as one of the last steps in the treatment process. By adding chlorine at the beginning of the treatment, THM can be reduced significantly because the first dose. of chlorine kills the organics that contribute to THM production. More-expensive chemicals, instead of chlorine, also Can be used to disinfect the water. Existing Valley treatment plants must be modified to treat Colorado River water at an additional cost to be passed along to the consumer. About 30 people employed by the Metropolitan Water District of Southern California keep a constant check on water quality because about 42 percent of the users get water above the allowable THM limit. Water here also will be monitored. As Upper Colorado River Basin water users develop the delivery systems to take their full river entitlement.s, the reduced flow to the CAP is expected to have higher and higher concentrations of salts. Preliminary studies by the SRP say the increased salts will not affect farmlands. More water may be needed, however, for leaching out the salts. , , Tempe tempest Officials may sue to stop mixing with Salt, Verde Officials in Tempe do not. like the idea of mixing salty Colo- rado River water with purer water from the Salt. and Verde rivers. One reason is that treating Colo- rado River water to reduce the salt and heavy mineral content is more costly. Anot.her reason is that the higher salt levels cause corrosion to pipes and mechanical equipment. Tempe has raised the possibility of going to court to prevent the mixing. As a result, the proposed federal contracts for Central Arizona Project municipal and industrial water con- tain a provision that would prevent users from suing other cities because of the poorer-quality Colorado River \'fater. Tempe has rights to and a plenti- fUl supply of Salt and Verde river water. Because of this, the city has little need for its CAP water alloca- tion of 4,315 acre-feet. annually. The city is undecided about taking its allocation, which could be used to serve a small area near its southern limits outside the Salt River Project service area. Ground water is used now for serving this area. IC the city signs a contract in its proposed form to accept CAP water, it will lose its right to sue; on the other hand, because Tempe's Salt (dnd Verde river water apparently will : be mixed with Colorado River water, 'Tempe must modify its treatment plants whether it accept.s its CAP allocation or not. "We aren't sure if CAP Water is worth enough to us to give up our right to sue," Mayor Harry Mitchell said. "The water will be mixed no matter what we do. We will have to modify our treatment plants, and this will cost us." Mitchell said the City Council has been careful not to annex Jands without adequate water supplies. "That's why we did not annex Ahwatukee," he said. "If you look around, however, you will see other cities taking in lands whether they have water or not." The Salt River Project., which manages water-storage reservoirs on the Salt and Verde rivers, has been asked to deliver CAP water to some users through its canals. Wesley Steiner, director of the Arizona Department of Water Re- sources, supported the contract clause against suing on the basis of water quality, arguing, "What's good for one part of the Valley should be good for all parts of the Valley." The final municipal and industrial contract must be approved by the Department of the Interior. Mayor Harry Mitchell "We aren't sure if CAP water is worth enough to us to' give up our right to sue. "The waler will be mixed no 'mafler what we do. We will have to modify our treatment plants, and this will cost us. "