Multicomponent Floating Spatial Domain Averaging in Surface Soil Remediation

Cleanup objectives for contaminated surface soil are frequently developed with the goal of meeting regulatory risk exposure criteria. Currently, some plans for Superfund sites are based upon the premise that a concentration equal to the average goal is not to be exceeded (NTE). However, in cases of wide-spread low-level contamination at multicomponent sites, the NTE constraint may result in lowering risk well below the regulatory criteria and concomitantly increasing remediation costs. A floating domain spatial averaging (FSDA) technique developed by Brakewood and Grasso (2000) is extended to include multiple risk factors, maximum contaminant level (MCL) constraints, spatial domain or lot size variations, and sampling limitations. The model and selected resultant linear programming solutions are compared to the NTE approach and presented in this paper. Multicomponent FSDA is a multiobjective, multicriteria decision making tool in which concentrations or risk factors are averaged over domains that represent possible human exposure areas. The averaging domain floats over the surface in increments representative of a field sample size (cells). The multicomponent FSDA model portraying a hypothetical site with low-level, wide-spread surface soil contamination and MCL constraints resulted in the determination of several remediation alternatives. Many of these alternatives allow for a marked reduction in the extent of required remediation, while complying with the predetermined cleanup goals and considering flexibility in future land use decisions. The reduction was particularly evident in cases where the number of cells within each exposure area was limited by sampling data constraints.