2016-04-20_REVISION - C1981019 - Laserfiche WebLink

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Rob Zuber Page 5 April 20, 2016 Please project the baseline potentiometric surface in the Trout Creek Sandstone over the Colowyo permit area, including the proposed Collom expansion, onto a map (possibly Map 1013). The map should identify the points that were used in the projection. Depending on seasonal variability, it may be appropriate to show a maximum and minimum projected surface. If CCC has already addressed this characterization through previous mapping or modeling work please direct DRMS to the appropriate documentation. CCC responded that Map 10B had been updated with the projected potentiometric surface of the Trout Creek Sandstone, and that the text had been inserted into Volume 15, Rule 2 to discuss the wells that were used to determine the surface. Contour lines at intervals of 100', from 6600' to 6800', were projected onto Map 10B. They indicate that the hydraulic gradient is such that groundwater would flow in in south-westerly direction. The text on proposed Page 23 indicates that 5 points were considered in the determination of this surface (C-05-33, DH -76-8, W-95-02, W-95-15 and UL -95-45). Of these, C- 05-33 and DH -76-8 were rightly discarded since they were dry and uncased respectively. Several issues are evident: (1) W-95-15 is not shown on Map 1013; (2) There is potential confusion over the location of W-95-02, since another point (also in the Wilson Creek drainage) is labeled MW -95-02; (3) considering just UL -95-45 and W-95-02, since the location of W-95-15 isn't shown, the potentiometric gradient is in the direction of W-95-02, (based on the data summarized in the proposed text), which is approximately opposite to what has been drawn on Map 10B. Please address these issues and update Map 10B accordingly. This item has not yet been adequately addressed. CCC responded that: (1) W-95-15 (and DH -76-8) had been added to Map 10B; (2) All wells were correctly labelled on the map; (3) The potentiometric contour intervals had been incorrectly labelled. In attempt to locate W-95-15, and verify the locations of UL -95-45 and W-95-02, the Division referenced data from Exhibit 7, Item 21: In the Collom Project Pre -Feasibility Hydrology Report prepared by Water Management Consultants in August 2005, Table 5.1 gives a summary of pre-existing wells. The three wells in question are all listed, together with an x,y coordinate in feet. Although the coordinate system is not known, the coordinates should allow all three points to be located relative to each other — unfortunately this was not found to be the case, casting doubt on the validity of data in the table. As an alternative, the permit numbers of the three wells were taken from Table 2.04.7-44 and used to identify the wells in the DWR database. Each well has a UTM coordinate in that database, which were used to verify the locations of UL -95-45 and W-95-02 and show that W- 95-15 is located at the point marked as a surface water monitoring location on Map 10B.