U.S. Water News Online
DES MOINES, Iowa -- Leaky hog-manure lagoons are threatening Iowa's water supply, according to a study made by Iowa State University researchers.
The recently-released report is one of the most comprehensive looks at geological factors that make pollution from livestock lagoons in the state to have a worse impact. There are 750 livestock waste lagoons in Iowa.
Iowa State University hydrology professor William Simpkins and hydrologist Michael Burkart of the ISU-based National Soil Tilth Laboratory found that many older lagoons were built in areas where groundwater sometimes surrounded the structures.
That means manure seeped through the lagoons and contaminated groundwater, the report shows.
Research by Simpkins and Burkart also shows that in other cases water pressure weakened the lagoon walls while in still other cases floods threatened the lagoons.
``There are places in north-central Iowa that just shouldn't have these things,'' Simpkins said.
He said there are some places in north-central Iowa where lagoons sit atop leaky soil and fractured rock, and in some cases near farm-field drainage wells that could funnel manure into the groundwater.
Simpkins said state regulations require private engineers to certify that lagoon bottoms are built at a depth that groundwater won't rise above. The problem, he said, is that the method used to determine that depth is often crude and inaccurate.
Simpkins also was critical of the state for not doing a better job of monitoring groundwater around lagoon sites.
The Iowa Department of Natural Resources inspects the lagoons once a year.
``DNR oversight has been nonexistent in this area,'' Simpkins said of the agency's monitoring of groundwater near lagoons. ``I don't blame the DNR for doing a poor job. If they had the staff and the stick to look at these things, we'd be a lot better off.''
He said the DNR's hands are tied because of a tight budget and weak laws.
Wayne Gieselman, who supervises DNR lagoon inspectors, said that six months ago the state began requiring that each new earthen lagoon have monitoring wells.
Most new lagoons are concrete and those offer more protection than clay, he said.
The study recommends that the state ban lagoon construction in areas with leaky soil, near streams and in flood plains. Other recommendations include the timing of manure applications to cut leaching into groundwater and banning the spread of manure on ground that is often flooded.
The study also suggests the state use information on landscape, soils, hydrology and other natural factors to decide where lagoons should be built. It also recommends that the state require scientifically controlled monitoring of the water table to make sure lagoons are built where they will be surrounded by groundwater.
The study was released as state lawmakers are preparing to debate whether to impose new environmental restrictions on Iowa's hog industry, which is the largest in the nation.
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