2019-09-09_PERMIT FILE - M2018063

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Environment,Inc. Page 7 Ellicott Sand& Gravel LLC -M-2017-063 Adequacy response 01 excavated area would be shallower then 3:1 slopes since when the sediment laden water enters the mined area it will slow down and begin to deposit that material until the flooding ends. The proposed armoring and widened setbacks are designed to keep the normal storm event flow in the original channel and prevent a 100 year flood from relocating the channel into the excavated areas.. 6.4.6 EXHIBIT F—Reclamation Plan Map 14. Proposed topography: There are no adequacy issues with Exhibit F other than the concerns the proposed final topography has on potential groundwater exposure and stream capture discussed in comments under Exhibits C, D, E and G in this letter. Please make appropriate changes to Exhibit F based on responses to these other comments. I revised Map Exhibit F to show the new setbacks and bank armoring proposed. 6.4.6 EXHIBIT G—Water Information 15. Division of Water Resources (DWR): Given the unique situation related to the proposed deep excavations (70 feet) and large area adjacent to and in the floodplain of both Black Squirrel Creek and Big Springs Creek, the DRMS consulted with the DWR on potential impacts to the hydrologic balance. DWR responded stating the proposed mine is within the Upper Black Squirrel Creek Designated Basin and the Colorado Ground Water Commission (GWC)will require any captured runoff to be released within 72 hours of capture or the mine will need a GWC approved replacement plan to offset the evaporative losses. Furthermore, with a proposed depth of 70 feet, the excavation would intercept groundwater in that area. If that occurs, they would need a well permit and replacement plan. Please address the following: The intent is not to intercept ground water in this mine. The commitment originally made was to stay 2 feet above the water table and to immediately place a 2 foot cover over it if encountered. Per the request from the Upper Black Squirrel Creek Groundwater Commission ESG will stay 10 feet above the ground water table so no Well Permit or replacement plan is needed. This may change if stormwater is retained on the mine for more then 72 hours. Details on how ESG will handle this is discussed below. a. How is any captured stormwater(this includes flood flows) to be released in 72 hours; both during operations and post reclamation (Note: the DRMS believes there is a significant chance during a 100-year flood or greater, that the full build out of the proposed pits could capture more than 30,000 acre-feet of water). As suggested by the Board of the Upper Black Squirrel Creek Designated Basin and the Colorado Ground Water Commission pumping would not be practical due to the high absorption rate of Black Squirrel Creek. In that case, it would be better to let the water be absorbed into the ground and any left after the initial 72 hours would be best be offset by not pumping one of the basin wells owned by the Schubert Ranch.