2018-03-09_PERMIT FILE - M2017049 (29)

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o41— 'b o Transit Mix Concrete Co. 5) The Applicant should clarify how and how often groundwater level monitoring will be conducted during the life of the mine. Given the concerns for impacts to surrounding wells, and the usefulness of the data for the groundwater model calibration/verification, the Applicant should commit to monthly groundwater level monitoring for the life of the permit. Response: Transit Mix will submit the surface water and groundwater monitoring results to the Division as a Technical Revision following the completion of the 15-month monitoring period. Operational groundwater monitoring will depend on the baseline monitoring results and will be proposed in the Technical Revision. The operational monitoring plan will likely include groundwater level monitoring on a monthly or more frequent basis. Several monitoring locations are instrumented with transducers and data loggers that record water level at approximately 15-minute intervals, and Transit Mix intends to continue the water level monitoring. 6) Exhibit G should include a proposed mitigation plan for the event that nearby domestic wells show adverse impacts due to mining activities. If this plan is included in another exhibit in the application, it should be referenced in Exhibit G. Response: The proposed mitigation plan is included in the Pre-Blast Survey Plan included in Exhibit D. A reference to the mitigation plan has been included in the Exhibit G text. 7) The Applicant should commit to updating the groundwater model with all available monitoring data annually, and submitting the results and monitoring data with the Annual Report. Response: Transit Mix commits to updating the model as new data are collected from ongoing monitoring, observations of seepage into the pit, pre-blast surveys, and communication with surrounding landowners. Each annual report will include a discussion on new data and potential impacts to the conceptual groundwater model; however, there likely will not be sufficiently new data every year that warrants updating the groundwater model. Groundwater Quality: 8) The Applicant should confirm the total phosphorus level in Table G-2A for the 6/16/15 samples. The result shown is 110 and the applicable standard is shown as 0.11. Response: The total phosphorus level in Table G-2A for the 6/16/15 samples has been revised to show 0.11mg/L. Phosphorus was not included as part of the groundwater analysis suite. 9) Table G-10 does not provide total phosphorus data, and compares groundwater data to surface water standards. Groundwater data should be compared to the CDPHE, Water Quality Control Commission's Interim Narrative Standards established in Regulation No. 41 — The Basic Standards for Groundwater, as appropriate throughout the application. Same comment for Table 3-3 standards. Hitch Rack Ranch Quarry(M-2017-049) Response to Comments—March 9,2018