|Simpkins, William - IOWA STATE UNIVERSITY|
|Helmke, Martin - IOWA STATE UNIVERSITY|
|Twedt, Trenton - IOWA STATE UNIVERSITY|
Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2002
Publication Date: June 26, 2002
Citation: SIMPKINS, W.W., BURKART, M.R., HELMKE, M.F., TWEDT, T.N., JAMES, D.E., JAQUIS, R.J., COLE, K.J. POTENTIAL IMPACT OF EARTHEN WASTE STORAGE STRUCTURES ON WATER RESOURCES IN IOWA. JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION. 2002. V. 38(3). P. 759-771. Interpretive Summary: The risk to water resources from Earthen Waste Storage Structures (EWSS) used with animal feeding operations was studied in Iowa. The geology, soils, hydrology, and topography surrounding 34 EWSS were examined to define the potential effects each may have on surface- and ground-water resources. The selected sites represent 439 recently permitted lagoons and dbasins but not the many more unpermitted facilities in Iowa. Analyses indicate that the hydrogeologic setting received little consideration in siting of EWSS. Nearly 18 percent of the sites are constructed over alluvial aquifers, the most vulnerable type of aquifer in Iowa and the most common source of water for private and small municipal supplies. Most sites in alluvial aquifers also lie in flood plains where contaminants can enter flood water from manure application and failure of the storage structure. A majority of the EWSS sites are surrounded by soils that are well drained with the potential to allow contaminants in manure to enter shallow aquifers. The majority of EWSS are also excavated deeper than 10 feet, which means they are constructed below the water table. This condition puts the stored manure in direct contact with ground water. At least 50 percent of the sites leak at rates greater than the allowable limit of 1/16 inch per day. The results of this study may impact individual attempts to locate an EWSS and develop environmentally sound manure management plans. The results may also be used by the Iowa Department of Natural Resources to reconsider the criteria for permitting future earthen storage systems and manure management plans.
Technical Abstract: The hydrogeologic settings of 34 Earthen Waste Storage Structures (EWSS) used with Confined Animal Feeding Operations (CAFOs) were evaluated for their risk to water resources. The selected sites represented 439 lagoons and basins and were classified into 5 Aquifer Vulnerability Classes (AVCs) of alluvial, drift, and confined aquifers overlain by thin drift, moderate drift thickness, and shale. Sites were also classified by surficial material consisting of sand and gravel, loess, till, and colluvium. Analyses indicate that the hydrogeologic setting received little consideration in siting of EWSS during the period. Nearly 18 percent of the sites are constructed over alluvial aquifers, the most vulnerable type of aquifer in Iowa and the most common source of water for private and municipal supplies. Most sites in alluvial aquifers also lie in flood plains where contaminants can enter flooding surface water from manure application and berm failure. A majority of the EWSS sites are surrounded by soils with vertical permeability greater than 25.4 mm/hr that are well and moderately to well drained. The dominance of EWSS deeper than 3.3 m suggests that a majority of the sites are constructed below the water table. Leakage rates were not significantly different among surficial materials or AVCs. However, at least 50 percent of the sites studied leak at rates greater than the allowable limit of 1.6 mm/day. The unpermitted sites must also be considered when assessing the overall impact of EWSS and CAFOs on water resources.