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<br />2.6 ALTERNATIVE E: Ground Water from Infiltration Galleries <br /> <br />2,6.1 Location and General Description <br /> <br />2.6.1.1 Alternative E considers construction of an Infiltration <br />gallery (modified radial collector well) adjacent to and beneath the <br />White River near the existing water treatment plant for the town of <br />Rangely. The filtration plant Is located In the northwest quarter of <br />Section 6, Township 1 North, Range 101 West, Rio Blanco County. <br /> <br />2.6.1.2 Ground water quality In the White River flood plain alluvium <br />Is generally poor, with no prospect for significant Improvement. <br />Alternative E would enable the town of Rangely to develop a rel iable <br />water supply for future growth using Its existing water rights. <br />Figure 2 - 6 illustrates a typical geologic section near Rangely, The <br />water to be withdrawn under this alternative would be higher quality <br />river water Instead of water from the alluvium. <br /> <br />2.6.1.3 The Infiltration gallery concept Is essentially an Improved <br />surface-water diversion set below the streambed. It would consist of <br />two 12-inch (30.5 em) perforated collector pipes and aID-foot (3 m) <br />square wet well near the riverbank. Twin multi-stage vertical-turbine <br />pumps would be installed over the wet well to deliver up to 10 cubic <br />feet per second (0,28 m3/s) to the Rangely fll trat Ion pl ant, The <br />alternative would be able to supply water to only a small portion of <br />the district encompassed by Water Users Association No, 1. It also <br />lacks the flexibility for water exchanges provided by a reservoir. <br /> <br />2,6.1.4 A sand filter and pea-gravel backfill would surround the <br />collector pipe and extend upward to the original stream bottom, Water <br />would enter the filter either directly from the river or as subsurface <br />flow Inrnedlately below the river channel, Drought-year conditions <br />similar to those of 1977 should not present a serious problem to this <br />Installation, because subsurface flow would be utilized without <br />requiring any emergency channel modifications such as were required In <br />that year. However, this source could not provide a reliable <br /> <br />28 <br />