Wednesday, November 15, 2006
239-15
Developing State Specific Interpretations for Conventional and Alternative Onsite Wastewater Systems.
Vicki M. Meyers, Robert R. Dobos, and Paul R. Finnell. USDA NRCS, MLRA 148 Soil Survey Project Office, 1238 County Welfare Road, Suite 230, Leesport, PA 19533
Current NRCS national interpretations for onsite wastewater systems in the National Soil Information System (NASIS) database are limited to two types: septic tank absorption fields and sewage lagoons. However, states can tailor interpretations using state developed criteria. NRCS in Pennsylvania (PA) has developed interpretations for several onsite wastewater disposal systems based on criteria supplied by the Pennsylvania Department of Environmental Protection (DEP). A variety of conventional (i.e. in ground bed, sand mound bed, spray irrigation) and alternate onsite wastewater disposal systems are permitted at the discretion of the DEP. New interpretations were developed for these PA wastewater systems to provide soil survey users additional guidance related to soil limitations. Additional state specific interpretations are needed as technology improves our ability to provide interpretive soil information to the public. Using the NASIS interpretations generator, interpretations for seven conventional and 16 alternate wastewater systems were developed using criteria in the PADEP regulations for site selection and specific soil limitations for each wastewater system. The soil properties used to develop these interpretations are percolation rate (Ks), slope, depth to bedrock, seasonal high water table and amount of rock fragments in the soil. The allowable domain of each pertinent soil property was evaluated based on the regulatory requirements and given a fuzzy membership value. The individual evaluations are compiled into an interpretive rule where an overall rating is assigned for each system.Tailored interpretations, like the PA wastewater systems mentioned above, provide soil survey customers more accurate guidance for the type of wastewater system that might be permitted on a specific soil type. These interpretations are specific to PA DEP regulations; however, the criteria can be tailored to any location having similar regulations or guidance. This information will be available to individual homeowners and representatives of regulatory agencies through the Web Soil Survey (http://websoilsurvey.nrcs.usda.gov).
Handout (.pdf format, 1606.0 kb)