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<br />ExxonMobil <br />Global Services Company <br />Colony Shale Oil Project <br />P.O. Box 2567 <br />Houston, Texas 77252-2567 <br />October 27, 2010 <br />Colorado Division of Reclamation Mining & Safety ? <br />Grand Junction Office <br />101 South 3rd Street, Suite 301 <br />Grand Junction, Colorado 81501 <br />Attention: Travis Marshall <br />? <br />E,-zzonMOP" <br />f` ??r 3 2010 <br />d S 31 -; <br />EEIVEEocT 2 s 200 ,/ <br /> <br />GRAND ;=i'--'LC OFFICE <br />M WETY <br />Re: ExxonMobil, Colony Oil Shale Project, Permit No. M-1980-047, <br />Preliminary Adequacy Review, Technical Revision, TR-13. <br />Dear Mr. Marshall: <br />This letter is to respond to DRMS letter of October 12, 2010 requesting more information before <br />the TR-13 can be approved. <br />1. Please provide an estimate of the volume of water that will be captured and discharged <br />from the four (4) to eight (8) proposed A-Groove drainage holes. <br />Response : Based on extrapolation of water drainage observed in the inclined tunnel at Colony, <br />we estimate a total water rate from this group of wells to be 100 to 1000 gallons per day. This <br />value is uncertain because the upper portion of the Mahogany and the A-Groove in the <br />experiment area are within the vadose zone and are not consistently saturated with water. We <br />expect that flow rates will be highest in the spring and early summer during snow melt season <br />and lowest in the late summer, fall and winter. <br />2. Monitoring of the A-Groove aquifer immediately above the Mahogany zone is not <br />included in the monitoring program. The operator must protect and monitor aquifers above and <br />below the mining/experiment interval. Therefore, an A-Groove monitoring well(s) shall be <br />included in the monitoring program. <br />Response : At the location of the experiment and down-gradient from it, the A-Groove is above <br />the potentiometric groundwater surface, so the zone is not saturated and would not produce water <br />for monitoring. If DRMS requires such a well, ExxonMobil could drill it and sample water if <br />any is found. An up-gradient well where the A-Groove is water-saturated 1500-2000 ft up- <br />gradient from the experiment would not be informative. This was explained onsite to T. <br />Marshall when he visited the location on 10/22/2010. <br />An ExxonMobil Subsidiary