Review of Soils Design, Construction and Performance Observations Overbank Structure, Old River Control Appendix B: Pumping Tests and Well Cleaning Operations, 1969-1970.

摘要

This appendix is the second in a series presenting the results of tests performed at intervals of several years on the relief wells at the overbank structure, Old River Control, near Natchez, Miss. The tests reported herein were performed in 1969 and 1970 by the U.S. Army Engineer Waterways Experiment Station (WES) and included well pumping tests, analysis of well water samples, inspection of well screens with a borehole TV camera, and well sounding and cleaning operations. These tests were conducted to determine the decrease in efficiency of the relief wells since the latest pumping tests were conducted (1966) and since installation of the wells in 1957. Renovation attempts on four of the wells using chemical treatments and surging were not effective. A borehole TV camera was used to inspect several of the well screens prior to and after pumping and cleaning operations. Generally, the well screens appeared to be in excellent condition before pumping and cleaning. Very little sand or gravel was found in the slots of the screens except in well 11, where the screen was about 50 percent clogged with filter material. There were no noticeable chemical or biological deposits on the interiors of the screens. Chemical analyses of the water samples indicated that conditions are favorable for the buildup of incrustation in the wells. Initial 1969-70 pumping tests on the wells indicated an average specific yield of 33 percent of the original yield. After cleaning by surging, the specific yield increased to an average of 50 percent of the original yield.