REVISION - 3/31/2009, 2:53:54 PM-JWD

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Letter to Richard Blubaugh 2 March 31, 2009 Centennial Project Receipt of Modification MD-02 File No. P-2008-043 the two mile zone. For water quality data generated from samples collected by Powertech, provide the field notes from each sample collection event. State affirmatively for all wells installed or rehabilitated by Powertech in the two mile zone that the Standard Operating Procedure (SOP) for monitoring well installation approved by DRMS was followed, or if there have been variations from the SOP describe the variations, the reasons for the variations, and their potential affects on the usefulness of the wells. For the water quality data from the two mile zone generated from samples collected by Powertech, state affirmatively that the following SOPs were followed, or if there have been variations from the SOPs describe the variations, the reasons for the variations, and their potential affects on the data collected: i. Decontamination of Sampling Equipment ii. Purging and Sampling Monitoring Wells iii. Field Parameter Measurements (Including Instrument Calibration) iv. Note Taking and Log Book Entries v. Analytical Data Validation The water quality data from wells IS-003T and IS-003Ta is the most representative of water quality at the proposed pump test wells and disposal pit available at this time. Further characterization of water quality at the proposed pump test location is discussed in item no. four below. Other than the data from the IS- 003T and IS-003Ta samples collected June 23, 2008, is there any other data from these wells? If so, provide the data in accordance with the discussion above. d. Powertech stated in MD-02 that it has done preliminary hydrogeologic modeling and water production calculations for the strata to be investigated by the proposed pump test. Please provide these for DRMS review. Provide data and analysis of all aquifer and aquitard properties from the Centennial Project area developed from pump tests previously conducted by Powertech, and from documents in Powertech possession from testing done by Rocky Mountain Energy. This information will be useful in completing a more rigorous ground water chemical mixing analysis as discussed in item no. four below. 4. The ground water chemical mixing analysis provided in MD-02 must be redone and tailored using the information available on stratigraphy, aquifer and aquitard properties, ground water hydrology, and ground water quality required for submittal under item three above. The mixing analysis provided in MD-02 assumes column permeation from the base of the proposed disposal pit to the water table, and uniform columnar mixing from the water table to the base of the Laramie Formation. Since the stratigraphy of the Laramie Formation in the project area is characterized by vertical permeability much lower than horizontal permeability, it is more likely that water infiltration through the base of the proposed disposal pit will pool on low permeability strata and flow laterally away from the pit location. Using the information required for submittal under item no. three above, Powertech must construct and submit an analysis of the flow path of the water from the pit, and if that analysis indicates that pit water will reach the water table, provide a mixing analysis and map boundaries where all metals and radionuclides that exceed ground water standards in the A2 sand ground water will be diluted to levels below standards. The DRMS will also require that radon be included in the mixing analysis. Depending on the degree of certainty that can be assigned to the analytical results, the location of the predicted boundaries where standards will be met, and the current and potential future use of Laramie Formation ground water in the project area, the DRMS will determine if the impacts to the prevailing hydrologic balance will be sufficiently minimized to allow the disposal pit to be constructed and used.