Hutchinson leak pathway. Quaternary alluvions are composed of sands and gravels, 50-ft thick. Elevations are in feet. Below are the Permian Ninnescah Shale, the Upper Wellington Shale and the Hutchinson Salt member. The gas-bearing interval ranges from 270-ft deep in the east side of the city to 400-ft deep several miles northwest of the city; the dip is 20 ft per mile. Gas migrated through fractured dolomite layers (G-G). (Kansas Geological Survey Web Site, 2001).