2013-04-29_REPORT - C1981014 - Laserfiche WebLink

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EFCI Southfield Mine — 2012 Annual Hydrology Report April 18, 2013 assure ongoing access control and to prevent contamination from entering the wells. Monitor wells MW -16, MW23, and MW -65 were performing as designed for obtaining representative water samples through the period of this report. It was determined during 2012 that conditions of monitoring well MW -NW had changed. This well consists of a 6 inch steel casing running from the surface to the roof of the mine opening in the 1 North mine section of the Southfield mine. The casing is part of what was a dewatering well system (North Well) designed to dewater the mine, but its use was discontinued in 1994. In 2003, with approval of Technical Revision No.35 (TR35) the dewatering well casing with pump removed was converted to a groundwater monitoring well designated as Monitor Well -North Well (MW -NW). During 2012, the landowner adjacent to Well MW -NW, The Corley Company (Corley), filed concerns with the DRMS and EFCI that he felt the MW -NW casing might be caved or plugged at some point above the bottom of the casing. In response to the concerns, on March 22, 2012, EFCI, using a wooden block as a weight, measured 356 feet from the top of the casing to an unknown obstruction in the casing. The obstruction is estimated to be approximately 20 feet above the roof of the mine workings. At that point, the probe became lodged and could not be retrieved. Efforts to retrieve the probe broke the 1/16 inch diameter cable that was attached to the probe. The cable broke near the top of the casing, dropped and coiled above the obstruction in the casing. On April 17, 2012, to determine if the casing was open to water flow, EFCI truck hauled 1,500 gallons of water and gravity fed the water into the top of NW -MW. It was estimated that the 1,500 gallons volume was enough to fill the well casing three times if the well was completely plugged at the bottom of the well. The DRMS inspector /hydrologist Kent Gorham was present and monitored and reported the water test procedure of the monitor well. The water was fed from the water truck through a 3 inch diameter rigid hose providing an estimated minimum flow rate of 140 gallons per minute (GPM). There was no build -up of the fed water visible in the well casing indicating that the water flowed down through the well at a high rate of flow. After the water valve was closed, the sounds of the gushing water flowing through the casing ceased within one minute from the time the water valve was closed. EFCI estimated that the flow rate of the fed water flowing down through the lower portion of the casing was at a range of 50 to 100 GPM. Inspector Gorham concluded in his report dated April 17, 2012, based on the results of the 1,500 gallon water test, that MW -NW was functional for monitoring groundwater and collecting samples in the flooded (if /when flooded) Southfield mine workings. Pursuant to the above, two DRMS inspectors, Kent Gorham and Janet Binns with George Patterson attending, lowered a remote camera into the casing on May 15, 2012 to view the partial obstruction in the well. The camera encountered the coils of broken 1/16 inch diameter cable at 346 feet below the top of the casing, the cable being attached to the wooden probe. Following this procedure, DRMS directed EFCI to remove the coiled cable and probe. On August 27, 2012, contractor Bellino and George Patterson removed 350 feet of the cable from the casing using a borehole fishing tool. It is believed that 3 or 4 feet of the cable and approximately 12 inches of 3/8 inch diameter bridle rope remain attached to the wooden probe. 2012 AHR text doc Page 7