Protecting ground water from pollution is of prime concern. In Ohio, the Natural Resource Conservation Service, USDA, requires exploration of subsurface conditions on livestock farms before siting and designing facilities that will store manure.

A minimum of four trackhoe test pits are dug at the corners of a proposed facility, with additional pits dependent upon its size and subsurface conditions. Pits extend to a depth of five feet below the planned bottom. Subsurface geology, including soil type and its structure, depth to perched water surface, and description of any bedrock is logged. Soils are classified visually using the ASTM Unified Soil Classification System D 2488.

A minimum thickness of three feet of low permeability in situ soil or in situ soil plus a 2-foot compacted low permeability blanket of soil is required where storage facilities are located over a perched ground water zone. A minimum thickness of 15 to 25 feet feet of low permeability in situ soil, or in situ soil plus blanket, is required where facilities are located over aquifers.

Laboratory testing of soil samples is required for facilities that require an Ohio EPA permit to operate. Tests are made on the in situ soil below the facility and on soil that will be used for blanketing.

("in situ" should be in italics.)