State Water Resources Research Institute Program


Project ID: 2007DE100B
Title: Modeling Hydrologic and Geochemical Effects of Land-Based Wastewater Disposal
Project Type: Research
Start Date: 3/01/2007
End Date: 2/28/2008
Congressional District: At Large
Focus Categories: Wastewater, Hydrogeochemistry, Groundwater
Keywords: Land based wastewater disposal, rapid infiltration systems, groundwater contamination
Principal Investigators: Andres, Alan; Imhoff, Paul
Federal Funds: $ 20,720
Non-Federal Matching Funds: $ 41,440
Abstract: As a result of a Clean Water Act lawsuit related to establishment of total maximum daily loads for water quality impaired water bodies, efforts are underway to reduce pollutant discharges to surface and ground water. Because of limited public funds to build or upgrade public sewage treatment facilities, though, wastewater disposal in DE and other states in the mid-Atlantic is now being directed to privately funded and operated land based wastewater disposal (LBWD) systems. Originally spray irrigation and large community septic systems were most common, but now with increasing land costs rapid infiltration basin systems (RIBS) have become the most popular permit application for new discharges in DE (John Barndt, DNREC, personal communication). Unfortunately, the effects of significant increases in discharges from LBWD to ground water and surface water quality are unknown and comprise a large-scale "experiment" on regional water quality that may have deleterious consequences. Research is needed to evaluate existing guidance for siting RIBS (e.g., appropriate set back distances between RIBS and surface water bodies) and monitoring and modeling requirements for both design and on-going maintenance of these systems. With these issues in mind we propose the following research objectives:

  1. Characterize the effects of RIBS and spray irrigation systems on hydrology and geochemistry at selected test sites (two to four) by application of linked ground and surface water flow and contaminant transport modelsk;
  2. Assess the probability of ground and surface water contamination by nitrogen and phosphorus at the selected test sites;
  3. Based on the results from objectives 1 and 2 and additional analyses using "typical" hydrogeologic settings anticipated for future spray irrigation and RIBS systems, develop recommendations for flow and transport modeling that might guide future assessment of proposed RIBS and spray irrigation systems;
  4. Develop recommendations for the design of RIBS and spray irrigation systems and monitoring of the vadose zone and ground water that will protect human health and the environment.

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