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<br />w <br />(0 <br />CJ1 <br />C,;;) <br /> <br /> <br />CHAPTER 3 - WATER QUALITY STANDARDS FOR SALINITY <br /> <br /> <br />OVERVIEW OF STANDARDS <br /> <br />On December 18, 1974, the EPA promulgated a regulation (40 CFR 120; see <br />Appendix A) which set forth a basin-wide salinity control policy for the Colorado River Basin. <br />This regulation also established a standards procedure, and required the Colorado River Basin <br />states to adopt and submit to the EPA water quality standards for salinity, including numeric <br />criteria and a plan of implementation, consistent with the policy stated in the regulation. The <br />Basin states, acting through the Forum, initially responded to this regulation by developing and <br />submitting to the EPA a report entitled Water Oll~lity Standards for Salinity Includini Numeric <br />Criteria and Plan of Iml'lementation for Salinity Control - Colorado River System dated June <br />1975. Since the states' initial adoption, the water quality standards have been reviewed every <br />three years (1978, 1981, 1984, 1987 and 1990) as required by Section 303(c)(1) of the Clean <br />Water Act. This document was prepared in conjunction with the sixth triennial review <br />conducted by the Forum as required by that law. <br /> <br />In 1975 the Forum proposed, the states adopted and the EPA approved water quality <br />standards, including numeric criteria and a plan of implementation to control salinity increases. <br />The Forum selected three lower Colorado River main stem stations as being appropriate points <br />in the Colorado River system at which numeric criteria should be established as required by the <br />1974 regulation; these stations are below Hoover Dam, below Parker Dam and at Imperial <br />Dam. The plan of implementation, developed in 1975 by the Forum and participating federal <br />agencies, was designed to ensure compliance with the water quality standards for salinity. <br />During each triennial review, the plan of implementation has been updated to ensure continuing <br />compliance. <br /> <br />The standards require that a plan be developed that will maintain the flow-weighted <br />average annual salinity at or below the 1972 levels while the Basin states continue to develop <br />their compact-apportioned water supply. The plan of implementation was not established to <br />reduce the salinity of the river below levels that were caused by natural variations in river flows <br />or human activities prior to 1972, but to offset the effects of water resource development in the <br />Colorado River Basin after 1972. <br /> <br />The Colorado River water quality standards for salinity and the approach taken by the <br />Basin states in complying are unique. During the course of each triennial review, the Forum <br />projects the Basin states' use of compact-apportioned waters and the resulting changes in salinity. <br />The salinity projections are based on the use of the long-term mean water supply of 15 maf/yr. <br />The plan of implementation is revised as necessary to ensure that the numeric criteria will be <br />maintained. <br /> <br />The regulation specifically stated that salinity control was to be implemented while the <br />Basin states continue to develop their compact-apportioned water. Historically, the Forum <br />designed the plan of implementation to maintain the numeric criteria for a period of 15-20 years <br />(e.g., the 1990 Review contained a plan of implementation through the year 2010). In this <br />triennial review, the Forum not only looked at the amount of salt that needs to be removed by <br /> <br />3-1 <br />