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<br />_UTi "18 <br />C L {, J '1 ' <br /> <br />alternatives for decreasing the operating costs and water <br />replacement obligations of the Desalting Plant. During the <br />meeting the treatment capacity needs of the city and the <br />potential of utilizing the Desalting Plant was revisited. <br /> <br />Recognizing that the city is currently diverting less than half <br />of their full Colorado River apportionment, an operational <br />concept was proposed that would allow .the Desalting Plant to meet <br />the provisions of Minute 242, save Wellton-Mohawk return flow, <br />while at the same time continuously provide potable water to the <br />city. The concept would require adding a water intake from a <br />Colorado River source, providing water transmission to <br />interconnect the Desalting Plant with the city's system, other <br />minor modifications, and the replacement for a minor increase in <br />operational bypass. <br /> <br />PROPOSED OPERATION <br />Under the proposal the method of operation, source of water and <br />specific process used by the Desalting Plant to treat the Yuma <br />supply will vary depending upon conditions of the Colorado River <br />system and Treaty requirements. During years that the Reverse <br />osmosis System is being used to full capacity, desalted Wellton- <br />Mohawk return flow water will be provided to the City in exchange <br />for a similar quantity of the city's Colorado River <br />apportionment. In those years that the Reverse Osmosis System <br />is not being used, Colorado River water will be treated in the <br />Pretreatment system and provided to the city. During years of <br />partial operation of the Reverse Osmosis System, desalted Wellton <br />Mohawk water, pretreated Colorado River water or a combination of <br />both would be provided to the city. <br /> <br />Years When Reverse osmosis Plant Being Used To Full capacity. <br />providing desalted water to the city does not significantly <br />impact the overall effectiveness of the Desalting Plant. The <br />city's effluent is a component of the local return flow. As <br />desalted water is provided to the city, the salinity of the local <br />return flow is in turn reduced. The potable water provided by <br />the Desalting plant is effectively made use of, while the <br />desalting benefits are kept intact. <br /> <br />During years of full desalting prOduction, a portion of the .. ~ <br />desalted Wellton-Mohawk return flow, normally available for 0Jl')..JJ' <br />blending with excess Well ton-Mohawk return and delivery to ~~~'~. <br />Mexico, would be provided to the city. In exchange for this ~.,- <br />supply the City would need to release a slightly greater quantity <br />of their Colorado River entitlement to the river to account for <br />both the product water delivered and any increase in Wellton- <br />Mohawk bypass directly related to providing the city desalted <br />water. Product water provided to Yuma would have a quality of <br />about 500 p/m, plus a small increase due to post-treatment with <br />lime. <br /> <br />12 <br />