2022-04-05_PERMIT FILE - M2021059

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TELEST � S O L U T 1 O N 5• I N c CJ ft PO R n t E D March 24, 2022 Via Electronic Mail Mr. Peter Hays Colorado Division of Reclamation, Mining and Safety 1313 Sherman Street, Room 215 Denver, Colorado 80203 Subject: Dunn Pit,File No. 3rd Adequacy Review Dunn Pit New Permit Application,Exhibits F,G and Appendix D Review Memo,File No. M2021-059 Dear Mr. Hays: We appreciate the Division's third adequacy review of Loveland Ready-Mix Concrete, Inc.'s (LRM's) hydrology section of the 112c Permit Application for the Dunn Pit. This letter summarizes our response, and commitment regarding the Division's comments. We list the Division's comment in italics, followed by our response. Appendix D Comment 16 DRMS Follow-up:In SOP #S Groundwater Sampling, the Division could not find where it is stated that a well may be purged for volume only. Specifically in Section 4.2 it states "To demonstrate that you have collected a representative ground water sample, measure field parameters during purging and purge the well until these parameters stabilize. ". Please commit to collecting field parameters during purging per the Groundwater Sampling SOP and recording those measurements on the field sheet. The completed field sheets are to be submitted with the other sampling data. Response 16 We appreciate the Division's comments and helped us realize that over time, the SOP has morphed into too much of a discussion/tutorial and does not make the steps clear as could otherwise be. Based on experience, and the construction of these wells, three well purge volumes is more than enough for the wells to stabilize. However, it is good practice to verify this. Thus,on LRM's behalf,Telesto commits to monitoring field parameters during well purging. We will compare the purged samples to one another as described in the SOP for consistency, and report that information on the completed field sampling sheets,which we will submit with the laboratory results.