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ARCOSA the top of the pit within the unlined quarry excavation - which at this time contains a significant amount of exposed water. The operator will need to provide sufficient information to demonstrate that they are in compliance with Colorado Department of Public Health and Environment, Water Quality Control Commission 5 C.C.R. 1002-41, Regulation No. 41 - The Basic Standards for Groundwater (WQCC Rule 41). This will likely require (at least) an in- depth characterization of: local geology and quarry pit, process waste and waste placement (existing and future), background/up-gradient groundwater conditions, pit water, current surrounding/downgradient groundwater conditions, and a comparison of existing groundwater to the Table Value Standards contained in Rule 41. The operator should also include a monitoring plan with proposed points of compliance to monitor downgradient groundwater for possible impacts due to the disposal of process waste in the pit. The predictions for long term quality of water in the post reclamation pond within the pit should also be discussed, especially if this water will be available to livestock and wildlife. Due to the on-site waste disposal at this site, and apparent lack of historical data, this is potentially a complex issue to address. Therefore, DRMS would be willing to meet with the operator and/or their consultant to discuss the requirements of this exhibit. Arcosa's Response: 1. As discussed above, Exhibit G has been updated to include a revised narrative, Exhibits G-1, G-2-a, G-2-b, and G-3. These maps show surface water features within 2 miles of the facility, regional groundwater geology and hydrologic features, a cross section of those regional groundwater features, and site stormwater features, respectively. Updated Exhibit G is provided in Attachment 5. 2. Water rights were investigated by a third-party consultant. A summary from the third- party consultant is included in Attachment 5. The summary presents a table of existing water rights including case number, decreed amount, date of agreement and the intended use. The report provides additional recommendations with respect to water augmentation. Exhibit G has been updated to reflect the findings of the water rights investigation and to clarify the conveyance of surface and groundwater at the site, the use of water during processing and mining activities, and the post-reclamation surface and groundwater conditions anticipated at the Site. The existing water bodies within the quarry are identified on Exhibit G-3. The Hogan Pond (also known as the Hogan Reservoir) is used to store water from surface water run-on. The decreed amount for the Hogan Pond is 204 acre-feet. Two temporary ponds within the quarry area store excess water captured in previous years. Based on historical investigation and design informations, there is no groundwater contribution to these ponds, except where intermittent water seeps from the overburden materials into the Pond. Exhibit D and Exhibit G have been updated to describe how Arcosa will manage the intermittent seeps. The majority of the water in the temporary storage ponds and the Hogan pond remains from the 2013 flood event in Colorado. Water from that event Reference the Colorado Department of Health-approved report, Engineering Design and Operations Report, prepared by Sergent, Hauskins & Beckwith in 1992 for the Western Aggregates, Inc (former owner) proposed Shale Mine Ash Backfill Project