2013-03-01_HYDROLOGY - P2010026 - Laserfiche WebLink

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Proposed Injection Zone An injection zone is a geological formation, group of formations, or part of a formation that receives fluids through a well The proposed injection zone is listed in TABLE 2.2. Injection will occur Into an injection zone that is separated from USDWs by confining zone(s) which - is free of known open faults or fractures within the Area of Review. The proposed injection zone is within the R4 Seal hydrostratigraphic unit from 2,100 to 2,300 feet, • rounded depths of the open interval. The Dissolution Surface (approximately located at 2,013 feet) marks the extent of groundwater infiltration and top of the saline mineral deposits, or Saline Zone. The proposed injection zone is located below the Dissolution Surface, within the Saline Zone,.where groundwater is not present, remains dry, and the units are not considered USDWs. In general the Injection zone is comprised of very tight, very low permeability nahcolitic oil shale. TABLE 2.2 INJECTION ZONE Fracture Hydrostratigraphic Unit Top (ft)* Base (ft)* TDS (ma/1) Gradient (psifft) • Green River - R4 Seal 2,100 2,300 NA 0.68 Injection zone top and base correspond to the open hole where the dissolution will occur, plus an additional The proposed injection zone is a complex array of bedded and non - bedded nahcolite. The nahcolite occurs as finely disseminated crystals, nodules, crystalline aggregates, and several thin continuous beds. The dominant continuous beds within the injection zone are the "upper" and "lower Greeno and TI beds, with a greatest thickness of approximately twelve feet. On a layer by layer basis, the grade of nahcolite in the injection zone ranges from less than 1% to about - 80 %, and the average grade is 26 weight %. Approximately 1000 tons of nahcolite is expected to be leached resulting in a maximum 20 feet leaching radius, mainly in these continuous beds. Confining Zones A confining zone is a geological formation, part of a formation, or a group of formations that limits fluid movement above and below the injection zone. The confining zone or zones are listed in TABLE 2.3. - ----- - - - - -- - -- Hydrostratigraphic rich zone R5 appears to operate regionally as a highly confining unit and this is reflected in the tendency for a large hydraulic head difference between water - bearing intervals (WBIs) or aquifers above and below the R5 in the region that is northwest of the RDD. The United States Geological Survey (USGS) Produced Water Database was reviewed for regional water quality data below the injection zone. Based on the TDS values contained in the database, the Wasatch and Mesa Verde may be USDWs, near the East RDD Project Site. A lower confining layer has also been Identified below the injection zone. TABLE 2.3 CONFINING ZONES Hydrostratlarabhic Unit Top (ft)* Base (ft)* Formation Lithoiogv upper confining units Green River - R8 - 944 1,004 oil shale Permit CO32210 -00000 8 FINAL PERMIT Statement of Basis