Submitted to: Report to Iowa State Legislature
Publication Type: Other
Publication Acceptance Date: January 29, 1999
Publication Date: N/A
Thirty-four of the 639 Earthen Waste Storage Systems (EWSS) permitted between 1987 and 1994 were investigated to characterize their hydrogeologic settings. Sites represent five groundwater vulnerability regions. Data included soil maps and attributes, topographic maps, and oblique aerial photographs. More than 10% of the sites were located on alluvial aquifers and flood plains, the most vulnerable setting for contamination of groundwater and streams. More than 80% of the soils within 2 miles of the majority of sites (70%) were found to have permeability of > 1 in/hr. Similarly, 80% of the soils in more than 1/4th of the site areas were well or moderately-well drained. More site areas had soils with seasonally high water tables above 5 feet than with deeper water tables. The frequency of sites with a combination of two or more of these chemical-leaching indicators means that groundwater is exposed to substantial potential for contamination. A substantial number of site areas are vulnerable to contamination resulting from application of EWSS manure. The median excavated depth of the EWSS was 15 ft and more than 30% exceeded 20 ft. Excavations to these depths in Iowa are likely to intercept the water table. Surface water bodies also appear to be exposed to potential contamination by seepage and failure of EWSS. Ephemeral streams were found within 500 ft at 21% of the sites and perennial streams were found within 500 ft at 12% of the sites. All of the investigated sites appear to have been constructed to permit requirements except for the distance to the water table. Reduction of risks to water resources by EWSS may be possible with permit standards that include measures of vulnerable hydrogeologic settings.