1987-12-01_PERMIT FILE - C1981017 (94)

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�I i The depth to the water table was between 13. 0 to 19. 0 feet below the ground surface during the field investigation in summer 1983. The water level measurement data , obtained during summer 1983, were used to develop a water table map of the study area. The water table in the outwash deposits, as indicated on Plate 1, follows the topographic surface of the area. Ground water flows southward and discharges into Coal Creek. The hydraulic gradient was approximately 0. 1 ft/ft during the time of the field investigation. The interpretation of the water table map is shown on Plate 1. Mid-Continent has been performing systematic ground water level measurements in the monitoring wells E-1 and W-1. These measurements cover the time period between July, 1983 until March , 1984. They are presented in Table 1. It is evident that the ground water fluctuations are considerable. Generally, ground water levels are much higher during this time (March, 1984) than during the time of the ground water investigation. 5. 3 Horizontal Extent of Ground Water The horizontal extent of ground water in the outwash deposits has been interpreted on Plate 1 as coinciding with the width of both east and west valleys. No attempt has been made to interpret the width of ground water farther north of the proposed site , but it can be reasonably assumed that it will coincide with the width of the valley. 5. 4 Permeability The hydraulic conductivity of the outwash deposits was measured directly in the field. Field permeability tests were performed in both types of the outwash deposits, in silty clays and underlying clayey gravel. Results of field testing indicated that both types of the material have a low per- meability in the range between 2.4 x 10-6 and 4.1 x 10-5 cm/sec. Due to the almost identical permeability of both layers, the silty clay stratum is not considered to be a con- fining bed, and the water bearing layer is under water table, or unconfined conditions. Results of field permeability test- ing are supported by three laboratory testin�q results whic gave permeabilities ranging from 1.3 x 10- to 2.5 x 10- cm/sec. It was not considered to be practical to perform a pumping test in materials with such low permeability. We cal- culated that a four inch well would yield only ?pproximately 0. 16 gpm. Results of pumping tests with such a low yield are 17 GEO-HYDRO CONSULTING.INC.