Among their key findings is that the location, design and maintenance of the lagoon are critical factors in protecting groundwater from such nutrients as nitrogen and chloride.

"Compared to four years ago, we know a lot more about lagoons – how they work, how much they seep, and more," said Jay Ham, the project leader and an agronomist with K-State Research and Extension. "Until four years ago, seepage rates from lagoons had never been measured in Kansas. We now have a lot more science-based information that can help people make decisions."

Ham presented the research team’s report to members of the Kansas House of Representatives Environmental Committee March 8. The first and fourth years of the study were funded by the Kansas Department of Health and Environment (KDHE); the middle two years were funded by the Kansas Water Office.

State officials initially sought more information on seepage rates of animal waste lagoons as a result of some people’s concern that the nutrients contained in those lagoons were threatening public water supplies. Agencies like KDHE hope to use the research results to develop guidelines for granting permits to landowners who are building waste lagoons.

Lagoons are commonly found in confined animal feeding operations (CAFO) in Kansas. In 2000, KDHE reported 3,000 active permits for CAFOs in Kansas.

Ham said that K-State’s study shows clearly that lagoons seep at rates much lower than the previous state standard of one-fourth inch per day. On average, the 20 lagoons tested seeped less than 1/20 inch per day. He added that most of the nitrogen that does seep through the bottom of the lagoon stays close to the lagoon while it’s being used.

But there is a risk that the "reservoir" of nitrogen that accumulates under lagoons could convert to nitrate and migrate toward groundwater after the lagoon is closed. "This is our biggest concern," Ham said.

"There is a lot of variation in Kansas soils, especially in the central and eastern parts of the state, and that makes a difference," Ham said. For example, the best lagoons in Kansas are built in clay soils, because they hold waste and adsorb (gather) nitrogen much better than lagoons built in sandy soils.

In addition to soil type, important factors in deciding where to build a lagoon include the land’s depth to the water table; the chemistry of the waste the lagoon will handle; and how long it will be open, according to the K-State researchers.

To illustrate the point, Ham cited his team’s work this year on the area in central Kansas known as the Equus Beds. The region contains the wells that supply drinking water to numerous towns, including the cities of Wichita, Hutchinson and McPherson.

Last year, the K-State researchers measured seepage rates of four lagoons in the Equus Beds region; the average seepage from those lagoons was 1/28 inch per day. Ham said the findings indicate that, like other areas of Kansas, there are good and bad places to build lagoons in that region.

"We found that the Equus Beds region was just like anywhere else in Kansas; there were places in the Equus Beds that had clay soils and a water table 30 to 40 feet from the surface. That’s a pretty safe place to build a lagoon," Ham said. "But then we found places in the Equus Beds that had shallow groundwater and very sandy soils.

"So, the science says that even in the Equus Beds region, you should still take a site-specific approach to building a waste lagoon. Even on an individual farm, there are areas where there may be some danger [to groundwater], and there are areas where there isn’t."

K-State’s research also suggests that, prior to building a lagoon, landowners must take into account the chemistry of waste that it will handle. For example, swine waste contains up to seven times more ammonium (the main form of nitrogen in lagoons) compared to cattle waste. Cattle lagoons, though, contain higher concentrations of chloride.

K-State’s four-year study introduced the concept of a "Lagoon Design Tool", which Ham said is a "logical framework" for site-specific lagoon design.

"So, for example, using a short list of inputs about a site (for example, soil type, depth to groundwater, and type of operation), the tool customizes the lagoon design so that the lagoon can be used safely," Ham said. "This could mean using plastic-lined lagoons at locations with vulnerable groundwater."

In December, 2000, K-State’s work on the proposed "logical framework" was published in the Journal of Environmental Quality, a peer-reviewed publication.

Other states also are interested in K-State’s methods of measuring lagoon seepage, Ham said. The U.S. Environmental Protection Agency recently awarded a $110,000 grant to K-State to develop a standardized method for measuring seepage.

Even though the university’s study on seepage rates has ended, Ham said K-State researchers still are involved in other waste management projects, including studies on lagoon closures; applying waste to land; nutrient management; and air quality for feedlots and production sites.