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Risky waste
New Iowa State study says common sense necessary to operating livestock
facilities.
- A recent study on waste lagoons and basins, by researchers at Iowa State
University and the National Soil Tilth Laboratory, has found that the structures
pose potential risks to Iowa's water resources and that "common sense"
guidelines could be enacted to ensure that future structures pose less risk.
The findings are from a study by William Simpkins, associate professor of
geological and atmospheric sciences, and Mike Burkart, a hydrologist at
the National Soil Tilth Laboratory, located at Iowa State.
Simpkins and Burkart's work summarizes the results of their 1998 hydrogeologic
study of earthen waste storage structures in Iowa. The research was funded
by the Iowa legislature, which is soliciting information on revised regulations
for hog confinement facilities.
Simpkins and Burkart found that earthen waste storage structures (EWSS)
associated with concentrated animal feeding operations and permitted between
1987 and 1994 pose potential risks to water resources in Iowa.
Potential for water contamination from these structures is greater than
previously thought, with more than 90 percent of the structure liners in
Iowa built below the water table, Simpkins said.
"Topographic, hydrologic and geologic settings were not major factors
in EWSS siting during this period, but they should be major factors in future
sitings," Simpkins said.
Other findings of the study include:
* Eighteen percent of the earthen waste storage structures are located on
flood plains and in alluvial aquifers. Floods could affect EWSS structural
integrity and increase the potential for direct stream contamination. Alluvial
aquifers are the most widely used in Iowa for domestic and municipal water
supplies. They also are the most vulnerable to contamination derived from
surface activities.
* Manure is being applied on permeable and frequently flooded soils. Application
to permeable soils increases the potential for groundwater contamination.
Manure applied to soils that are frequently flooded increases the potential
for direct stream contamination.
* Although most earthen waste storage structures are built in accordance
with mandated setback distances from water bodies, such setbacks ignore
the local topographic, geologic, and hydrologic settings.
* Misinterpretation of the depth of the waste storage structures in relation
to the water table and its seasonal variability during
construction has resulted in a high percentage (as much as 94 percent) of
the EWSS with liners below the water table at some time of the year. This
is at odds with the current EWSS construction standards.
Based on these findings, the researchers recommend:
* Discontinue construction of new waste storage structures on alluvial
aquifers and flood plains.
* The timing of manure application from waste storage structures should
be controlled to minimize leaching to groundwater. Application on frequently
flooded soils (such as flood plains overlying alluvial aquifers) should
be discontinued.
* More site-specific information should be utilized and regulations should
incorporate topographic, geologic, hydrologic, soil, and ecologic data
in assessing site suitability. Site-specific information could be used
to deny permits or require additional groundwater or surface-water-quality
monitoring at the sites.
* More thorough groundwater monitoring techniques should be used to locate
the position of the water table during construction. Continued water table
monitoring should be used to confirm that the state-mandated separation
between the liner and the water table is maintained during the life of
the structure.
"We make fairly specific recommendations directed toward the Iowa
state legislature and to the Department of Natural Resources," Simpkins
said. "We addressed this briefly in our first report in 1999, but
the results were not complete and we could support fewer recommendations
at that time.
"The 'common sense' recommendations will provide guidance to the
state and help it take a proactive role in safeguarding the quality of
our water resources," he added.
--ISU News Services
Around LAS
February 11-24, 2002
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