Submitted to: Effects of Animal Feeding Operations on the Environment US Geological Survey
Publication Type: Abstract Only
Publication Acceptance Date: 9/2/1999
Publication Date: N/A
Technical Abstract: The hydrogeologic settings of 34 Earthen Waste Storage Structures (EWSS) in Iowa were investigated. Sites represented all aquifer vulnerability regions. Analysis included digital soils and topographic data and oblique aerial photographs. EWSS expose water resources to substantial contamination risk. Nearly 18% were constructed over alluvial aquifers, potentially affecting many water supplies, and in flood plains with risk of stream contamination from manure application and structure failure. Large areas around most sites have soils with a saturated permeability of greater than or equal to 1 in/hr and well or moderately to well drained soils. The dominance of EWSS depths greater than 10 ft and areas with water tables less than 5 ft deep, suggests that most sites are below the water table. Ephemeral streams were within 500 ft at 21% of the sites and perennial streams were within 500 ft at 12% of the sites. Many sites had unmapped drainages that led to ephemeral or perennial streams. Further reduction of risks to water resources may be attained by using siting criteria that incorporate geologic, hydrogeologic, and soils data as outlined in this paper. EWSS sites built on alluvial aquifers should not be permitted unless measures are taken to ensure that the aquifer is not being contaminated. Control of the timing of manure application and avoiding application on frequently flooded soils may reduce the risk of water-resource contamination. Application of well established, scientifically defensible groundwater monitoring techniques should be used to locate measure the hydraulic separation between the EWSS and the water table. Uniform setback distances may not be appropriate for all topographic, hydrogeologic, and ecologic settings.