Proposal for Pilot Evaporation Pond

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Paradox Valley Unit Proposal for Evaporation Pond level of less than$30 million per year. Additional salt control is needed through 2030 to offset what would otherwise be increases in salinity levels. Paradox Valley Salinity The Paradox Valley in Montrose County, southwest Colorado, has long been identified as a major contributor of salt loading into the Colorado River. The valley overlies a fractured gypsum cap that covers a formation of salt and salt rich shale that extends from approximately 800 feet to 14,000 feet below ground surface. The 1978 Definite Plan Report for the Paradox Valley Unit identified an annual salt loading to the Dolores River of approximately 205,000 tons of salt. Observations since the Definite Plan Report show that annual salt loading to the river is quite variable, and that presently what would be the annual salt loading to the river has been reduced by approximately 110,000 tons per year due to the project. The salt comes primarily from the surfacing of natural brine groundwater. The Bureau of Reclamation first began studying salinity in the Paradox Valley in 1971. By 1979, a plan was approved to remove brine groundwater from a series of shallow extraction wells at a collective rate of 5 cubic feet per second(cfs),and dispose of it by evaporation in a 3,630 acre pond. This plan was projected to prevent approximately 90%of the natural brine (185,000 tons of salt per year) from entering the Dolores River. Deep well injection was also considered for brine disposal,but an injection rate of 5 cfs was considered too much for the geologic formations to absorb. The Environmental Protection Agency (EPA) believed deep well injection to be the environmentally preferred disposal method and recommended that it be seriously considered. This recommendation prompted further testing and investigations of the brine well field,which indicated that the desired 90%reduction of brine flow into the river could be achieved by intercepting approximately 2 cfs of brine in lieu of the 5 cfs rate outlined in the initial plan. The reduced removal rate and other research indicated that the deep well disposal method was feasible. Paradox Valley Unit Salt Disposal Challenges Construction of initial features at the Paradox Valley Unit(Unit)was completed in January 1990, as part of the Colorado River Basin Salinity Control Project. The Unit included a series of nine shallow brine extraction wells near the Dolores River, 3.5 miles of pipeline, and a well for brine injection into a 14,000 foot deep reservoir. Testing and data collected over the first five years of operation indicated that long-term brine injection would be feasible. The facilities were re- fitted for permanent operation and long-term operations were initiated in August 1996. The Unit currently consists of the 16,000 foot deep injection well,brine injection facilities building, 9 brine production wells, approximately 36 observation wells, numerous piezometer stations, at least 5 drill (core)holes,4 electroconductivity stations, a surface treatment facility for gathering and filtering,brine and fresh 2