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<br />(0 . . <br />M <br />0 <br />0 <br />C <br />~, <br />-' <br /> <br />The Grand Valley Unit <br /> <br />The Grand Valley Unit is a component of the Colorado River Basin <br />Salinity Control Project and was authorized for construction by the <br />Colorado River Basin Salinity Control Act of 1974, Public Law 93-320. <br />Development of the unit is planned in two stages. <br /> <br />Stage One <br /> <br />Construction is ongoing in a portion of the unit area where plans <br />and designs are complete, where data can be gathered to assess effects <br />of initial development and where environmental impacts are not considered <br />significant. As part of the development, 6.8 miles of the Government <br />Highline Canal have been concrete lined and cross drainage facilities <br />have been completed. The Grand Valley field station was constructed to <br />serve as headquarters for construction of the overall unit, and after <br />construction will be used for operation and maintenance or for other <br />project uses. Work is underway to consolidate 13 open channel laterals <br />serving the area under the newly lined portion of the Government Highline <br />Canal into 12 pipe laterals. Installation of an automated debris collection <br />device is also planned. <br /> <br />Under a monitoring program for Stage One, water level measurements <br />and samfles are taken bimonthly from observation wells to provide base <br />data for evaluating the effects on the ground-water flows and quality of <br />Stage One improvements. In addition to ground-water monitoring, the <br />program includes weekly measurements of water quantity and quality in <br />tributary drains. Samples are also taken from canals at certain points <br />in the Stage One area. Results from the water quality testing are used <br />to assess the effectiveness of Stage One development in reducing salt <br />loading to the Colorado River. <br /> <br />Wildlife resources are also being monitored in the Stage One area <br />to determine the unit's effect on wildlife. <br /> <br />Stage Two <br /> <br />The Stage Two area generally consists of the remainder of the Grand <br />Valley outside of the Stage One area. Planning activities on Stage Two <br />began in November 1981 and include various hydrologic, engineering and <br />environmental studies as well as formulation and evaluation of alter- <br />native plans. <br /> <br />Out of the many salinity control measures originally considered, <br />the structural alternatives described on the following page were the <br />most viable. The nondevelopment alternative is included for purposes <br />of evaluating and comparing plans. <br /> <br />4 <br />