2015-02-23_REVISION - M1977526 - Laserfiche WebLink

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Mr. Dick Wolfe, P.E., October 8, 2014 Page 2 NARRATIVE DESCRIPTION A. PROJECT DESCRIPTION The Worthing Pit is located in Section 26, Township 1 South, Range 67 West in Adams County, Colorado as shown on Figure 1. The Worthing Pit began operation in 1977 and is currently permitted under Division of Reclamation and Mining Safety Permit M- 1977 -526. Active mining activities at the pit are complete. The original permit area was 111 acres. In November 28, 2000, a Technical Revision to the permit (TR -2) authorized dewatering and dry mining of the pit lakes at the Worthing Pit. In 2005, Permit M- 1977 -526 was amended to add 50.3 acres to the mine boundary of the Worthing Pit. The exposed water surface area prior to January 1, 1981 is shown on Photograph 1 (dated June 4, 1980). Figure 2 shows the exposed water surface as of February 21, 2012. A typical cross section is provided in Figure 3. The final reclamation map is Figure 4. Based on a February, 21, 2012 aerial photograph of the Worthing site, there was 32.11 acres of exposed groundwater remaining after active mining activity ceased. As part of the approval process of previous Worthing Pit SWSPs, and pursuant to §37- 90- 137(11)(b), C.R.S., it was determined that 28 acres of the 32.11 acres was to be considered pre -81 acreage and therefore exempt from evaporative replacement requirements. In the previous SWSPs, AFS replaced the evaporative depletions associated with the 4.11 acres (32.11 — 28 = 4.11) of post -80 groundwater exposure. However, as part of the ongoing reclamation work in 2014, AFS backfilled 3.38 acres of the post -80 water surface area. The post -80 area that was backfilled to eliminate the exposure of ground water was surveyed and is shown in Figure 5. Need and Use of Water AFS expects to backfill the remaining 0.73 acres (4.11 — 3.38 acres) of post -80 water surface in late 2014 and early 2015. It is AFS's intention to have completed the backfilling operation prior to June 2015. Therefore, the estimated 2015 plan year water requirements for the Worthing Pit are those associated with the evaporative losses from the 0.73 acres of post -80 exposed ground water and the water needed for dust suppression during processing of Stagecoach Stop Pit material at Worthing Pit for January through May of 2015. Estimates of the 2015 depletions and replacement requirements are summarized in the following subsections and tables. Evaporative Loss Gross evaporation at this site is estimated to be 45 inches (3.75 feet) per year with an effective precipitation amount of 0.83 feet. This equates to a total evaporative loss of 0.64 acre -feet for 0.73 acres of post -80 water surface area for the first five months of 2015 (see Table 1). AFS will continue to replace groundwater depletions at Worthing Pit associated with evaporation until backfilling of all post -80 groundwater is completed and AFS submits proof that no more than 28.0 acres of exposed groundwater exists. As previously mentioned, AFS fully expects to have all post -80 exposed groundwater backfilled by no later than May 2015.