title: Field demonstration of the combined effects of absorption and evapotranspiration on septic system drainfield capacity.
abstract: Drainfields for disposal of septic tank effluents are typically designed by considering the loss of water by either upward evapotranspiration into the atmosphere or lateral and downward absorption into the adjacent soil. While this approach is appropriate for evapotranspiration systems, absorption systems allow water loss by both mechanisms. It was proposed that, in areas where high evapotranspiration rates coincide with permeable soils, drainfield sizes could be substantially reduced by accounting for both mechanisms. A two-year field demonstration was conducted to determine appropriate design criteria for areas typical of the Texas High Plains. The study consisted of evaluating the long-term acceptance rates for three different drainfield configurations: evapotranspiration only, absorption only, and combined conditions. A second field demonstration repeated the experiments for additional observation of the combined evapotranspiration and absorption and achieved similar results as the first study. The field tests indicated that the current design loading criteria may be increased by at least a factor of two for the Texas High Plains region and other Texas areas with similar soil composition and evapotranspiration rates, while still retaining a factor of safety of two.
authors.affiliation: Water Resources Center, Texas Tech University, Lubbock 79409-1022, USA. ken.rainwater@ttu.edu
authors.forename: Ken
authors.initials: K
authors.lastname: Rainwater
authors.forename: Andrew
authors.initials: A
authors.lastname: Jackson
authors.forename: Wesley
authors.initials: W
authors.lastname: Ingram
authors.forename: Chang Yong
authors.initials: CY
authors.lastname: Lee
authors.forename: David
authors.initials: D
authors.lastname: Thompson
authors.forename: Tony
authors.initials: T
authors.lastname: Mollhagen
authors.forename: Heyward
authors.initials: H
authors.lastname: Ramsey
authors.forename: Lloyd
authors.initials: L
authors.lastname: Urban
mesh_terms: D000042:Absorption; D003247:Conservation of Natural Resources; D012621:Seasons; D012987:Soil; D013781:Texas; D014835:Volatilization; D014865:Waste Disposal, Fluid / Q000379:methods*; D014867:Water / Q000737:chemistry*
chemical_list: D012987:Soil; D014867:Water