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STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Depart mem of Natural Resources <br />I } 13 Sherman 51.. Room 215 <br /> <br />Denver, Colorado 80203 ~~~~~ <br />Phone: 13031 B66~ 3567 <br />FAX 13071 8128106 <br /> DEPARTMENT OI <br /> NATURAL <br /> RESOURCE` <br /> Roy Rumrr <br />Memo Governor <br /> Ken Salazar <br /> E.ecw lve Dueao~ <br />Date: February 24, 1994 Michael B long; <br />To: Marr Strip, 1992 and 1993 Mnual Hydrologic Report Review, File No. C-80-006 Dlv~sion Dirrcmr <br />From: Randall Price <br />RE: 1992 & 1993 Mnual Hydrologic Reports <br />The following is a review of the Marr Strip, 1992 and 1993 annual hydrologic reports (AI-IR), <br />submitted by the Kerr Coal Company. These reports were submitted in fulfillment of the <br />requirements of Rule 4.05.13(4)(c) and with the commitments in the permit application. They <br />contain the results with analysis of hydrology monitoring for water years 1992 and 1993 and are <br />compared with the previous four years. <br />The water quality sampling performed by Kerr Coal, and analysis performed by Terra Matrix, on the <br />water samples and as compared with the previous 4 years, did not show any degradation of water <br />quality from mining.. However, the mine has had pond discharges that have exceeded NPDES <br />discharge limitations in total suspended solids and iron during snowmelt. <br />The following are comments that I have concerning the AHRs, and [conclude with a summary list of <br />concerns that should be addressed. <br />Well Construction <br />The wells are constructed of PVC pipe that is slotted for the entire length. The problem with long <br />screen intervals is that they do not isolate aquifers, and allow several water bearing zones to mix. <br />This causes dilution ofthe water in an aquifer and hinders detection of water quality changes caused <br />by mining. Ideally the screened interval should be placed in a water barring zone that represents the <br />aquifer to be monitored and the annulus sealed above the screened interval. Sealing the annulus will <br />prevent surface water or perched aquifer water from flowing down the annulus or down the well <br />screen and diluting the aquifer that is of concern. The Marr Strip monitoring wells result providing a <br />composite sample that may lack sensitivity to changing water quality conditions. However, these <br />wells have been used to gather baseline water quality information and have been monitored for the <br />past 10 years, although not ideally constructed, monitoring should continue on these wells. <br />Well 79-1 <br />During my inspection in June of 1992, I noted that well 79-1, had an open annulus of about I.5 feet <br />in diameter. This was probably caused by surface water washing the backfilled cuttings into the <br />