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<br />United States Department of the Interior
<br />y GEOLOGIUL SURVEY
<br />~ pFS TON, vA ]1091
<br />In Reply Refer To:
<br />YGS-Mall Stop 923
<br />CFP ~ 7 ItYIF
<br />Memorandum
<br />To: Dureau o1 Land Management, Yhite River Resource Rrea,
<br />Meeker, Colorado
<br />From: Assistant Director for Engineering Geology
<br />Subject: Review of draft environmental statement for Yolf Ridge Corporation,
<br />mine plan (or a na he of lte solution mine, Rio 81a ncO COUM1ty,
<br />N Colprd do
<br />~ Ye have reriered the statement as requested in a letter inc lu0e0 in the
<br />drag document.
<br />Page 3-I2 states. 'The two bedrock aquifers are generally confined or
<br />ar[esia n, This means Coat the water level Of a well In the rater-bearing
<br />zones rill be higher Loan the rater [able.' Tnis points t0 a need for a
<br />better ex plans [ion of the hydrologic system Of the project site. DO water-
<br />table contlitio ns tntleed exist beneath the upland site? Tne zonation of [he
<br />upper aquifer should then be discussed. If, however, the meaning of [he
<br />statene nt in question is [hat the water level in a tell penetrating one of
<br />the con (shed aquifers rill be higher Loan [he base of [he uDPer confining
<br />layer, the statement should De reworded. If indeed the piezametric surface
<br />In both the upper aquifer and the lover aquifer is above the water table in
<br />an unconfined shallarer aquifer, this should be significant in evaluating [ne
<br />potential for an0 the direction of quality-Of-rater impacts.
<br />60
<br />The basis for the cant lu sian Coat In the project it te, hydraulic head
<br />Oif fe rencei be [weer the upper and lower aquifers range from 1 LO ]0 feet
<br />(p. 3-12) should be ex pia lned. This factor may be especially Important In
<br />considering the posslbillty of impacts from the Proposed mining on both
<br />ground-rater quality end on the Integrity of the Mahogany Zone. Unpublished
<br />data from U.S. Geological Surrey (USGS) tests on both aquifer 1n four wells 60,
<br />located a few miles from [he site indicated differences in head of 4, 7. 9 J5
<br />and 12 feet (Yon Lier, Y1l llam P„ Oral common lcatlan, September 19, 1986).
<br />The evaluation of the sign if lea nee of the head differences between the upper
<br />and lower aquifers should include consideration of the slmila rity in elevations
<br />of recharge for the fro aqulfe rs and the location of the mining site an [he
<br />flank of the basin with respect [o the recharge areas. the eralua[/on should
<br />also incorporate conside ra Cio~ of the sign if is ante of di (ferenc es in water
<br />12
<br />Bureau of Land Ib nagenent -2-
<br />quality Of the up Der and lower aquifers. For example, the floors de cOncen-
<br />[rations measured by the USGS a few miles from the proposed solution mine
<br />site were 0.9 mg/1 in the upper aquifer an0 22 my/1 in the lower aquifer. 60,
<br />a very significant difference suggesting very little mixing of waters of J$
<br />the two aquifers under prevailing conditions (Van Liew, 4111iam P., Oral
<br /><aaanunication, September 19, 1986; TO bin, Robert L., Oral communication,
<br />3 eyt 0Mber 1%, 1986 ).
<br />Yna[ ml tlga [ion, If anY. would De passible if effects of fracturing and roof
<br />collapse should--contrary to expectations--extend upwa ra into Cne Ma hp9d ny
<br />Zone? The pa ray raphs on ground-water monitoring (p. 2-B, 2-I7) Outline yro-
<br />posed monitoring oT pi ezometric head and quality o! wafer in the lower 27,
<br />aquifer. However, adequate mOn~toring should also include both piezometric 56,
<br />head and quality of water in at least the tower part of the upper aquifer. 80,
<br />USGS analyses indicate that CAC Dresent ground-water quality in [he upper 8t
<br />aquifer will satisfy U. S. Envirorxv en[al Protection Ag¢ncy, 1976 and U. S.
<br />Public Health Service, 1962 drinking water criteria (Van Lier, 4illiam P.,
<br />Oral communication. Seytember 19, 1996; Tobin, Robert L., Oral communication,
<br />SeDtOnber 17, 1986). Th0 statement should as ss potential ultimo [e effects
<br />on the hydrologic system 'from project-relate ges in the quail ty o/ water
<br />in the lower aquifer, if [he head In the ayuif 'pc teased as a result of
<br />mining acts vl ti es. If there is a[ Dresent an a ~ d0 degree of hydraulic
<br />continuity between the upper and lower aquifers a te, or if permedDility 56,
<br />of the Mahogany Zone shoul0 De increased by mining _ ies or subsidence 6~
<br />stresses, the potential for upward m~9ration of poor water into the
<br />` J6
<br />i0c laded in the
<br />upper aquifer would be increased. This Dossibili ty shoo
<br />assessment. Planned sur (ace injection pressures and anticipdted discharge
<br />pressures should De discussed to aid in this assessment. Calculated suS-
<br />sidence at the level of the Ha soya ny Zone should be included. Page 7-12
<br />states that the flaw of ground water in the lower aquifer is [award a s{nk
<br />located in the northwestern portion of [he lease area, the alt Tina [e fate
<br />of Cols flow should be considered. Figure 3.2 and work by Previous invests- 56,
<br />gatoril indicate that the movement of ground water fron Che lover aquifer i5 60
<br />ultimately upward to Piceance Creek an0 tributaries. The long-tens effects
<br />of mining on the lower aquifer sn0ultl be assessed In to nos of Cne ultimate
<br />des tlna tlon of the flaw of [he aquifer.
<br />z . _•_~.
<br />Ames F. Devine
<br />1/ (a) Yan Ller, 41111am P., Oral common station, September l9, 1986
<br />(b) Yeeks. John 0., 1979, Oigi[al Model of ground-water flaw in the
<br />Picea nee Basin, Rio Blenco and Gerfield Counties, Colorado:
<br />U. S. Geol oyic al Survey 4ate r-Resources Investigations Report
<br />79-90.
<br />(c) fleets, John 8., 1971, Simu la tea effects of oil shale development:
<br />U. S. Geological Surrey Professlanal Paper 908.
<br />Copy to: 015trlct Chief, YpD, Lakeraod, Colorado
<br />
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