Grand Calumet River Remediation: Monte Carlo Analysis of Projected Post-Capping Pore Water Concentrations

摘要

Reaches 1 and 2 of the West Branch of the Grand Calumet River were remediatedby removal of 2.5 feet of contaminated sediment and capping with sand/organoclay active cap covered with gravel. To support development of a monitoring plan,a one-sided, bootstrapping Monte Carlo procedure was used to assess the likely range ofcap performance. The USACE RECOVERY model was used to predict transport ofPAHs through the cap for a total of 200 randomly selected parameter combinations. Resultsfor pore water concentration evaluated for the first 5 years after capping werestrongly a function of the contaminant partitioning. Preliminary evaluation of the concentrationsafter 5 years at 1 cm and 5 cm below the bioturbation layer suggests thatvariability within the results is largely controlled by the active layer thickness (consideringinterfacial mixing and mass of amendment), and to some extent by enhanceddiffusion/groundwater advection and deposition characteristics. Analysis of core samplesfrom the capped site allowed refinement of the input parameters for a second modelingeffort. Results show that phenanthrene should be a suitable tracer compound to monitorcap performance in the first five years.