Abstract
A natural cover system with gravel used as a capillary barrier was designed and evaluated as a method to hydrologically isolate buried water soluble oil and gas wastes. Simulated cover systems were installed in 200 liter barrels and tested in a greenhouse. The treatments contained gravel barrier thicknesses of 0, 8, 15, 23, and 30 cm. Gravel was placed over a salt contaminated soil and was covered with 30 cm of a sandy clay topsoil. Drains were installed in the bottom of the barrels to collect drainage from the gravel layer and below the buried saline waste. Treatments were tested for effectiveness in both a wet and dry moisture regime using simulated monthly rainfall applications. Upward migration of soluble salts was monitored by measuring the electrical resistance of the soil by means of salinity sensors at the base of the topsoil. Electrical conductivity (EC) measurements of the leachate were used to determine the downward movement of soluble salts. Total volume of leachate from each drain was also monitored for each simulated month. Core samples were taken to determine the EC of the topsoil at the conclusion of the experiment. Electrical resistance values indicated that upward soluble salt migration occurred immediately on treatments which did not include a capillary barrier. EC values for all gravel barrier treatments indicated no upward migration of the buried saline waste. Values for EC at the base of the topsoil ranged from 10 to 20 dS M-1 in the treatments with no capillary barrier to 0.1 to 1.0 dS M-1 in treatments containing a capillary barrier. Effluent EC was significantly higher (29-56 dS M-1 ) from below the saline soil than from the gravel drain (2-9 dS M-1 ). In addition, 93 % of the leachate from both moisture regimes that permeated the cover system was collected from the gravel drain. These results indicate that a cover system which includes a capillary barrier would protect groundwater by greatly decreasing downward movement of water soluble constituents. Upward migration of buried water soluble wastes would also be prevented which would in turn protect the topsoil and surface waters.
Rooney, Daniel James (1995). A method to hydrologically isolate water soluble wastes. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1995 -THESIS -R66.