Specific Capacities of Wells in Crystalline Rocks

摘要: In the Rothschild area, Wisconsin, most water wells are completed in glacial deposits. When deposits unsaturated or thin, fractured crystalline rocks of Pre-Cambrian age. Specific capacity data from 56 tapping these reveal: 1 Yields and specific generally small, with a median log 0.17 gpm/ft mean value 0.10 gpm/ft. 2 Wells which close together may have substantially different capacities. 3 The occurrence saturated sand gravel above has no obvious influence on yield capacity. 4 Specific capacities seem to be inversely proportional (a) thickness penetrated below table, (b) depth (c) land surface. Assuming that related number contributing fractures diminishes linearly depth, following relation is derived: where Sc= capacity, Q = discharge, s drawdown, B constant, b fracture frequency at surface, z E maximum fracturing. 100 feet. In exploring for ground rock, problem find area b. If sound scientific methods not available, then exploration will consist drilling random until satisfactory well completed. However, because achieve 60 80 percent their first 20 feet test should pump tested when they reached about table. Unsuccessful need drilled completion.