SITE INFORMATION AND CORRESPONDENCE_2005-CURRENT

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measures could further reduce the EC of its effluent,to an average of 725 to 926.7 µmhos/cm, although it questions the extent to which source control measures will be effective in view of statutory protections for use of water softeners.18 The City contends that the only way it could assure compliance with the 700 µmhos/cm EC effluent limitation in its permit would be through construction and operation of a reverse osmosis water treatment facility. The City estimates that the capital cost of reverse osmosis facilities would be $75 million and that annual operation and maintenance costs would be $13.7 million. The City estimates that compliance with the effluent limitations on EC would result in increasing City sewer rates from approximately$28 per month up to $85 per month. There is insufficient evidence in the record for this Board to fully evaluate the cost of compliance with the EC effluent limitations in the City's permit. However, the existing record supports the conclusions that: (1) assuring compliance with the 700 µmhos/cm EC limitation in the City's permit for April through August would probably require construction and operation of a reverse osmosis treatment plant for at least a portion of the City's effluent at a very large cost; and (2)because of the relatively high salinity of the receiving water and the relatively small portion of flow provided by the City's discharge, the City's use of reverse osmosis would have relatively little effect on the EC of water in the river. In addition, the State Board takes official notice"of the fact that operation of a large-scale reverse osmosis treatment plant would result in production of highly saline brine for which an acceptable method of disposal would have to be developed. Consequently, any decision that would require use of reverse osmosis to treat the City's municipal wastewater effluent on a large scale should involve thorough consideration of the expected environmental effects. Although the conditions in waste discharge permits are established to implement relevant water quality control plans, the effluent limitations in permits may differ from the s Health and Safety Code section 116786 establishes requirements governing local regulation of water softeners and provides that local ordinances may not require removal of water softeners installed before the effective date of the ordinance. However,the statute does not prevent cities or other local agencies from providing financial incentives for removal of water softeners. " Cal. Code Regs,tit. 23, § 648.2. 12.