2011-06-23_HYDROLOGY - M1980149 - Laserfiche WebLink

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Ms. Michelle L. Hatcher Page 2 of 7 June 22, 2011 If the information you are providing to DRMS is pursuant to approach no. 4, you will need to provide additional documentation to this office that specifies what water rights or other permanent water source will be dedicated to the SWSP to assure that all permanent depletions from either an unforeseen abandonment of the site by the Applicant or as a result of long term ground water exposure after completion of mining and reclamation will be replaced so as to prevent injury to other water rights. To date, this Information has not been provided to this office. No additional ground water will be allowed to be exposed by this mining operation, beyond that _ specified in this SWSP, until the required information is received. Depletions The County has completed mining in all pits, except the 9.9 -acre and 20.9 -acre cells located in the center of the gravel pit site (Figure 1). Mining in these cells is not anticipated to occur during this plan period. According to the information provided by the applicant, the County will continue to dewater the 35.0 -acre cell during this plan period. The County intends to line this cell, but lining has been delayed and the cell will continue to be dewatered until lining is complete. The surface area of the dewatering trench and collection pond for this cell total 0.37 acres. The 9.9- acre cell has a stable exposed surface area of one acre and will not be dewatered during this plan period. The remaining cells have been reclaimed. Currently 71.47 acres of surface area is exposed at the Hokestra Pit site. According to the submitted information, a total of 15.0 acres of ground water surface was exposed to the atmosphere within the reclamation permit boundary prior to January 1, 1981. Based on the Division 1 Water Court decision in case no. 2009CW49, the replacement of evaporative depletions is not required for ground water exposed to the atmosphere prior to January 1, 1981 through open mining of sand and gravel, regardless of whether open mining operations continued or were reactivated on or after that date. The Water Court effectively held that Senate Bill 120 of 1989, as amended in Senate Bill 93 -260, exempted all pre -1981 exposed ground water regardless of whether open mining operations continued or were reactivated on or after January 1, 1981. Of the 15.0 pre -81 acres, 10.0 are located within the 35.0 -acre cell which is currently being dewatered, and 1.4 acres have been backfilled, leaving 3.6 qualifying pre -81 acres. If the Applicant wishes to claim that the State Engineer approved in writing a re- allocation of the pre -81 area, please refer to item 12 of the General Guide lines for Substitute Water Supply Plans for Sand and Gravel Pits (Updated April 1, 2011). Based on the above, for the 71.47 acres of ground water currently exposed at the Hokestra Pit, replacement of evaporative depletions is only'required for the 67.87 acres exposed after December 31, 1980. The area exposed prior to January 1, 1981 is shown on the attached Figure 2. The exemption from augmentation requirements for the pre -1981 area is tied to the physical location identified on Figure 2 and may not be applied to other areas of ground water exposure within the gravel pit permit boundaries. Net evaporative depletions were calculated using a gross annual evaporation of 40 inches from the exposed water surface, with a credit of 9.38 inches for effective precipitation. No phreatophyte credit has been applied to this plan. The net depletion of ground water due to evaporation from the 67.87 acres of ground water exposed at the site after December 31, 1980 was calculated to be 173.3 acre -feet.