Because earthen manure and process generated wastewater storage structures are generally less expensive to build than above-ground metal or concrete tanks or below-ground concrete tanks, most operators choose earthen storage construction (ponds) where possible. To minimize potential for surface and ground water contamination, storage structures are located at least 150 feet from any uphill well, 500 feet from other wells, and 50 feet from the manure production/collection area (typically, animal housing). Check state and/or local regulations for specific setback distances for manure collection and storage structures in your area.
For gravity transfer of collected manure wastes to storage pond and possible settling basin use, sewer lines are generally installed on 1% slopes and sized for flow velocities greater than 2 feet per second. A waste storage pond should not be located in a flood plain nor should the bottom of the pond be constructed to a depth below the underground water table unless curtain drains or interception drains are installed around the perimeter of the pond at least 1 foot below the pond bottom.
Properly designed, installed and operated according to accepted engineering standards defined by USDA-NRCS and ASABE publications listed below under "Recommended Reading on Earthen Manure Containment Structures", earthen manure structures should pose little risk to water quality.
Geologic conditions and treatments are determined from county soil surveys and performance of other waste storage ponds in the area and an on-site inspection. A backhoe under the direction of an experienced engineer, geologist, or soil scientist is one of the best subsurface soil investigation tools available.
An on-site subsurface soils investigation determines if the planned manure storage site has shallow soil over coarse sand and gravel, creviced limestone, or permeable bedrock. If any of these conditions exist, construction procedures and materials to prevent seepage to ground water, such as clay liners, geotextile or fabric liners, or concrete, are used.
As part of the animal waste management technical assistance program, Natural Resources Conservation Service (NRCS) currently offers on-site soils and geologic investigation assistance for animal waste management structures. NRCS should be contacted for assistance. Corrective treatments at some locations could be so costly that aboveground storage may be required or a waste management system at the site may be totally impractical. This could force moving an existing animal facility to a more suitable location and should definitely be a significant part of the site investigation process for new animal facility installations.
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