Screening Evaluations for Upland Confined Disposal Facility Surface Runoff Quality

Abstract : Section 404 of the Clean Water Act requires evaluation of the potential impacts of dredged material discharges from confined disposal facilities (CDFs). A joint U.S. Army Corps of Engineers (USACE) and U.S. Environmental Protection Agency (EPA) Technical Framework (USEPA/USACE 2004) provides guidance for evaluation of potential contaminant pathways to determine if controls or management actions are required. Guidance for implementation of the Technical Framework is provided in the USACE Upland Testing Manual (UTM) (USACE 2003). The UTM provides a tiered approach for performing pathway evaluations. Tier II of the UTM contains a screening methodology to determine the need for pathway testing. The screens compare screening criteria, such as water quality standards, with predictions based on bulk sediment chemistry and partitioning/bioavailability relationships. One potential pathway of contaminant release from CDFs is surface runoff water discharged after CDF filling operations have been completed. The simplified laboratory runoff procedure (SLRP) and runoff simulator/lysimeter system (RSLS) tests are available to predict chemical releases in surface runoff for comparison to water quality criteria, and water column bioassays are available to determine potential toxicity of surface runoff (USACE 2003). This technical note provides procedures for evaluating CDF surface runoff quality at the screening level of a multi-tiered approach. The screening evaluation is based on equilibrium partitioning principles (Hill et al. 1988) and conservative application of design and operating principles for CDFs.