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U.S. DEPARTMENT OF AGRICULTURE 1 PAGE 2 OF 3 N?"~UR.-lL RESOURCES CONSERVATIGN $SRVICE 08/9/DO SANITARY FACILITIES Endnote -- SANITARY FACILITIES This report shows the degree and kind of soil limitations that affect septic tank absorption fields, sewage lagoons, and sanitary landfills. The limitations are Considered "Slight" if soil properties and site features generally are favorable far the indicated use and limitativris are minor and easily overcome; "MVderate" if soil properties or site features are not favorable for the indicated use and special planning, design, or maintenance is needed to overcome or minimize the limitations; and "Severe" if soil properties or site features are so unfavorable or so difficult to overcome that special deaj.gn, significant increases in construction casts, and possibly increased maintenance are required. This report also shows the suitability of Che soils for .use as daily cover for landfills. A rating oP "Good" indicates that soil properties and site features are favorable Ear the use and good performance and low maintenance can be expected; "Fair" indicates that soil properties and site features are moderately favorable for the use and one or more soil properCies or site features make the soil less desirable than the soils rated "Good"; and "Poor" indicates that one or more soil properties or site features are unfavorable for the use and overcoming the unfavorable properties requires special design, extra maintenance, or costly alteration. SEPTIC TANK ABSORFTIDN FIELDS are areas in which effluent from a septic tank iB distributed iriC4 Che soil through subsurface tiles or perforated pipe. Only that part of the soil between depths of 24 to 72 inches is evaluated. The ratings are base on soil properties, site features, and observed performance of the Boils. Permeability, a high water table, depth to bedrock or to a cemented pan, and flooding affect absorption of the effluent. Large stones and bedrock or a cemented pan interfere with installation. Unsatisfactory performance of septic tank absorption fields, including excessively slow absorption of effluent, surfacing of effluent, and hillside seepage, can affect public health. Groundwater can be polluted if highly permeable sand and gravel or fractured bedrock is less than 4 feeC below the base of the absorption field, if slope is excessive, or if the water table is near the surface. There must be unsaturated soil material beneath the absorption field to filter the effluent effectively. Nany local ordinances require that this material be of a certain thickness. SEWAGE LAGOONS are shallow ponds constructed to hold sewage while aerobic bacteria decompose Che solid and liquid wastes. Lagoons should have a nearly level floor surrounded by cut slopes or embankments of compacted soil. Lagoons generally are designed to hold the sewage within a depth of 2 to 5 feet. Nearly impervious soil maCeri.al for the lagoon floor and sides is required to minimize seepage and contamination of ground water. This report gives ratings for the natural soil that makes up the lagoon floor. The surface layer and, generally, 1 or 2 feet of soil material below the surface layer are excavated to provide material for the embanlonents. The ratings are based on soil properties, site features, and observed performance of the soils. Considered in the ratings are slope, permeability, a high water table, depth to bedrock or to a cemented pan, flooding, large stones, and content of organic matter. Excessive seepage due to rapid permeability of the soil qr a water table that is high enough to raise the level of sewage in the lagoon causes a lagoon to function unsatisfactorily. Pollution results if seepage is excessive qr if floodwater overtops the lagoon. A high content of organic matter is detrimental to proper functioning of the lagoon because it inhibits aerobic activity. Slope, bedrock, and cemented pans can cause construction problems, and large stones can hinder compaction of the lagoon floor. SANITARY LANDFILLS are areas where solid waste is disposed of by burying it in soil. There are Cwo types oP landfill, trench and area. In a trench landfill, the waste is placed in a trench. It is spread, compacted, and Covered daily with a thin layer of soil excavated at the ai,te. In an area landfill, the waste is placed in successive layers on the surface of the soil. The waste is spread, compacted, and towered daily with a thin layer of soil form a source away from the site. Both types of landfill must be able to bear heavy vehicular traffic. Both types involve a risk of groundwater pollution. Ease of excavation and revegetation need Co be considered. The ratings in this report are based