III. Results of Y-Spectral and Sr Analyses of C-Series Water Samples A. LASL Results B. LLL Results 90 IV. Results of Y-Spectral and Sr Analyses of D-Series Water Samples 76 A. LASL Results 76 B. LLL Results 90 V. Results of Y-Spectral and Sr Analyses of E-and F-Series Water Samples , 79 A. LASL Results 79 B. LLL Results 80 VI. Results of Y-Spectral Analysis of Sidewall Core Samples. 81 VII. Tritium Analyses of Pumped Water Samples 82 A. Comparison of LASL and LLL Results of T and Li Analyses of Filtered and Unfiltered B-Series Water Samples • • • • 82 B. B-Series Water Samples ..... 84 C. C-Series Water Samples 85 D. D-Series Water Samples 87 E. E-Series Water Samples 88 F. F-Series Water Samples 89 PREFACE The site of the Cambric underground nuclear test was re-entered nearly ten years after its detonation at the USERDA Nevada Test Site. The experimental results obtained from radiochemical analysis of sidewall cores and water taken during the re-entry drillback and sampling operations are summarized and discussed in this repcvt. The investigation was part of the Radionuclide Migration Project sponsored by the Nevada Operations Office of ERDA. The entire report was reviewed and modified by all three of the authors, but primary responsibility for the compilation and interpretation of the data and for writing given sections was divided among the authors as follows:

The anisotropic, areal hydraulic conductivity of the Felix No. 2 coal (Eocene, Wasatch Formation) has been defined in a four‐well pump test at a site in the Powder River Basin of northeastern Wyoming. The direction of maximum hydraulic conductivity of the subbituminous coal bed bears N59°E and is associated with a horizontal hydraulic conductivity of 0.27 m/day. The direction of minimum hydraulic conductivity bears N31°W and is associated with a horizontal hydraulic conductivity of 0.15 m/day. The direction of maximum hydraulic conductivity approximately corresponds to the trend of the prominent face cleat in the coal, while the direction of minimum hydraulic conductivity corresponds to the trend of the butt cleat. The cleat orientation appears related to the alignment of major structural features of the region. Prediction of the direction of both maximum and minimum horizontal hydraulic conductivity in near‐horizontal coal beds appears possible. However, either the cleat orientation of the bed or the alignment of the controlling fold structure must be known or obtainable.

No abstract

An investigation was conducted to evaluate the effects of aquifer interconnection caused by the collapse of cavities formed in coal seams by two small underground coal gasification experiments in the Powder River Basin, Wyoming. The main objective of the work was to assess the magnitude and extent of changes in the ground‐water flow patterns near the sites of the two experiments. Hydraulic head measurements in the three affected aquifers were used to calibrate a steady‐state ground‐water flow model of the interconnection zone at each site. Flow modeling and field measurements show that water from one or both of the upper aquifers enters the collapse rubble and flows down to the lowest aquifer (the gasified coal seam) where it flows away from the collapse zones. The hydraulic conductivity of the collapse rubble is less than that of the aquifers and provides only a very moderately permeable interconnection between them. A marked reduction in the hydraulic conductivity of the gasified coal seam near the collapse zones causes restriction of flow in the seam, away from them. Changes in hydraulic head and flow patterns caused by aquifer interconnection extend generally only 200–300 ft (60–90 m) away from the experiment sites. Flow in the uppermost aquifer at one of the sites may be influenced as far as 400 ft (122 m) away. At both experiment sites, aquifer interconnection allows water from the uppermost (sand) aquifer, which contains the poorest quality water of the three aquifers, to enter one or both of the underlying coal aquifers.

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