2012-11-27_HYDROLOGY - M1979195 - Laserfiche WebLink

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Ryan Stitt Denver Water NRC SWSP November 27, 2012 Page 2 of 8 The Dunes Pit and Tanabe Pit have been fully reclaimed and no longer function as gravel pits. Their reservoirs have been lined and were approved as lined reservoirs by the State Engineers Office through letters dated January 22, 2007 and February 2, 2007, respectively. Since they are fully reclaimed, their DRMS permits were terminated on December 20, 2008 and September 22, 2010, respectively. Though a part of the NRC, these gravel pits are not covered under this SWSP, nor cause depletions that would require them to be covered. The Howe Pit was previously mined by Lafarge West (now Martin Marietta Materials) and was transferred to Denver Water once reclamation was completed. Lagged depletions accruing to the river from past mining operations is the responsibility of Martin Marietta Materials and is covered under their South Platte Combined SWSP (WDID 0202581). This pit is now a part of Denver Water's North Reservoir Complex and within the Howe Pit permit boundary is the Howe - Haller A and Howe - Haller B Reservoirs. These reservoirs have been lined and were approved as lined reservoirs by the State Engineers Office through letters dated August 1, 2006 and September 24, 2008, respectively. Also within the Howe Pit permit boundaries is an area of groundwater that was exposed to the atmosphere prior to 1981 ( "pre -81 ") due to gravel mining operation. Denver Water provided a 1979 aerial photograph to document that the surface area of the pre -81 ground water was approximately 28.0 acres. Of this area, the Applicant seeks to verify that the existing wetland area is eligible to claim the pre -81 status. In accordance with water court case 09CW49 and current administrative policy found in the State Engineer's General Guidelines for Substitute Water Supply Plans for Sand and Gravel Pits (updated April 2, 2011), the State Engineer will (1) not require replacement for evaporation on pre -81 areas regardless if mining continued at the site post 1980 and (2) the pre -81 area is limited to the location where it existed prior to 1981 unless the Applicant can show that the State Engineer previously recognized in writing a re- allocation of the pre -81 areas within the permit boundaries. Previous SWSPs approved for the Howe Pit recognized that 26.6 acres of ground water was exposed prior to 1981thus both conditions are met. The area to receive the pre -81 credit is shown on the attached "Addendum 2011 Road Edge and 5,033 -ft Elevation Contour" exhibit and is recognized as the pond and wetland area along the banks of the pond within the 5,033 -ft elevation contour. This pre -81 area is tied to this physical location and may not be applied to other areas of ground water exposure within the gravel pit permit boundaries, and is limited to 22.1 acres which is the area of the 5,033 -ft contour boundary. Any pre -81 area in excess of 22.1 acres is relinquished and no longer able to be claimed by any parties. The Road Runners Rest II Pit and the Reclamation Pit No. 1 are now commonly referred to as the Haze ine Reservoir. This boundary of this reservoir fully encompasses both gravel pits. The slurry wall liner has been installed but has not undergone the 90 -day leak test required by the State Engineer's Office. This test will commence after Denver Water removes more material from the site. Therefore all water exposed within the permit boundaries is assumed to be groundwater tributary to the South Platte River and will be replaced and accounted for pursuant to paragraph 11 of the Division of Water Resources' "General Guidelines for Substitute Water Supply Plans for Sand and Gravel Pits." This SWSP only covers depletions caused by the evaporation of groundwater within the Road Runnes Rest II and Reclamation Pit No.1 permit boundaries. Replacement for these depletions will come from water owned by Denver Water. Long term augmentation will not be required as all areas will either be lined with an approved liner, or will be backfilled so as to prevent any exposure of non pre -81 groundwater. As the operator of the gravel pit permit is a municipal entity, a bond for the cost of a liner or backfilling is not required by the Division of Reclamation Mining and Safety.