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h <br />April 18, 2003 <br />Mr. Paul Osborne <br />NATURAL S ODA, INC. E C E t V E D <br />3200 County Rd. 31 Ew Vii,, , } 2D03 <br />Rifle Colorado 81650 <br />Ground Water Program <br />US EPA Region VIII, Mail Code 8P-W-GW <br />999 18`~ Street, Suite 300 <br />Denver, CO 80202-2466 <br />Phone: (970) 878-3674 <br />i7ivisinn of Minerals and Geelagy Fax: (970) 8785866 <br />Mr. Cazl B. Mou~t~ <br />Senior Environ. Protection Specialist <br />Division of Minerals and Geology <br />1313 Sherman St., Room 215 <br />Denver, CO 80203 <br />Subject: Submittal Geotechnical Re ort§ from l~,an 2002 `'' <br />UIC Class III Pe}~it Number C03358- 69~ Rio Blanco ounty <br />DMG Permit Nd:1983-194; Natural Soda, Inc. ~ <br />Deaz Mr. Osbome and Mr. Mount: <br />Enclosed please find two Agapito Associates, Inc. geotechnical reports which evaluate <br />impacts of solution mining at Natural Soda, Inc. per your request. The enclosed reports <br />aze the basis for utilizing submersible pumps and "An Evaluation of Impacts of High- <br />Extraction Solution Mining on Overlying Aquifers". <br />The report dated November 22, 1995 provided an evaluation of impacts for the 1995 <br />Mine Plan "utilizing submersible pumps and balancing the in-cavern fluid pressures with <br />the surrounding groundwater pressures relieves the requirement of maintaining structural <br />integrity of the roof materials above the Boies Bed.......Solution mining of the nahcolite <br />above the Boies Bed would be possible if the permit constraints of the EIS were not <br />violated. This report addresses the potential impacts ofhigh-extraction solution mining <br />of the Boies Bed and overlying strata on the two controlling permit requirements:" 1. <br />Maintain mineability of oil shale in Mahogany Zone and 2. Protect the B-Groove <br />Aquifer. <br />The report dated April 8, 2002 was an "Evaluation of Geotechnical Impacts-Pane12 <br />Solution Mining". The report "evaluated the potential for adverse subsidence-related <br />impacts to 1. The integrity of overlying USDW aquifers (Perched, A Groove, B Groove <br />aquifers) and 2. The fixture mineability of the Mahogany Zone.... This letter presents our <br />estimate of ground response and assessment of geotechnical risk for Pane12 mining." <br />You will find these reports helpful in the prepazation of the UIC re-write and evaluation <br />of the forthcoming revised Mine Plan. If there aze any questions please contact me or <br />plant manager, Kyle Bazbot. <br />Six~~relyy ~ <br />Ed Baker, REM ' <br />EHS Manager <br />Cc: BLM-Meeker w/o reports <br />