Toward Site‐Specific Design Standards for Animal‐Waste Lagoons: Protecting Ground Water Quality

Seepage losses from animal‐waste lagoons can affect ground water quality, if facilities are not properly sited, designed, and constructed. Most states in the Great Plains stipulate that earthen lagoons cannot seep more than some specified rate (mm d −1 ). These criteria often apply to the entire state and all livestock species, although ground water vulnerability and waste characteristics are highly variable from site to site. Because of this variability, statewide “blanket” regulations may overregulate some producers and underregulate others. Furthermore, wide disparity exists in seepage allowances among neighboring states, and regulations often are influenced by public opinion rather than scientific findings. This paper argues that lagoon design should be site specific and presents a logical framework to determine the maximum allowable seepage rate for a given location and type of operation (e.g., dairy, swine, cattle feedlot). Site‐specific factors, such as soil properties, depth to water table, and chemistry of the waste, are used to arrive at lagoon performance standards that minimize long‐term risk. The decision process within the framework is presented as a conceptual model for lagoon permitting and may need to be customized to meet the requirements of each state. Nevertheless, use of site‐specific design criteria will ensure that manure storages are adequate (e.g., plastic‐lined lagoons) in regions with vulnerable ground water, while providing reduced lagoon construction costs (lower cost of soil‐lined lagoons) for producers who site their operations in areas of low risk. To complement the site‐specific approach, the whole‐lagoon seepage rate should be measured after construction to verify that the prescribed performance criteria have been met.