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Title: SEALING POND BOTTOMS WITH MUDDY WATER

Author
item Bouwer, Herman
item LUDKE, JAMIE - PHYS SCI TECH, USWCL(TEMP
item RICE, ROBERT - RETIRED

Submitted to: Journal Hydrologic Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Leakage from water impoundments often needs to be controlled to minimize water losses or contamination of groundwater. Plastic, clay, and other artificial linings can be expensive. In time, bottom sediment can build up, which naturally reduces leakage rates. This process can be hastened by applying soil slurries to the water. Since coarse soil particles sink faster to the bottom than fine particles, the liner thus formed is layered with the coarsest particles on the bottom and the finest on top. To see how effective such liners can be for seepage control, laboratory studies were performed on soil columns. Results showed that layered linings, which also formed naturally with muddy inflows, effectively reduce seepage from impoundments. These results should be of interest to water resources managers, consultants, regulatory agencies, farmers, and environmentalists.

Technical Abstract: Column studies were performed in the laboratory to see how earth linings for seepage control in ponds, lakes, lagoons, wetlands or other surface impoundments should be placed for maximum seepage reduction per unit of earth used. The soil for the lining can be placed on the bottom of a dry pond and mechanically compacted, or it can be added as a soil slurry to the ewater in the impoundment. Different settling velocities of the soil particles in the water then create a lining with the coarsest particles at the bottom and the finest particles at the top. To study these effects on seepage control, four plexiglass columns 183 cm long with a diameter of 11 cm were filled with an 11 cm silica sand layer at the bottom that gave an initial average seepage rate of 950 cm/day at a water depth of 160 cm. A loam soil was placed in a dry column and mechanically compacted to form a lining layer of 16.5 cm on the silica sand. The same amount of soil was then applied as a slurry to the top of the other three columns in various applications. Equilibrium seepage rates were 2.7 cm/day for the compacted lining, 1.2 cm/day for the lining formed by the full amount of soil in one slurry application, 1.0 cm/day for the lining formed by 5 split slurry applications, and 0.85 cm/day for the lining formed by 15 split slurry applications. Additional seepage reductions to about 0.2 cm/day were obtained by adding 17 grams of sodium carbonate in 500 ml water to the water in the columns three weeks after the soil lining and slurries had been applied. Thus, layered linings which also formed naturally with muddy inflows, effectively reduce seepage from impoundments.