Achieving Stormwater Source Control for an Engineering Evaluation/Cost Analysis on the 303d Water Quality Limited Willamette River

摘要

Background. When embarking on the design of a stormwater source control measure (SCM) for the Arkema site, part of the larger Portland Harbor Superfund site in Portland, Oregon, it quickly became evident that the requirements for a stormwater SCM being implemented for a non-time-critical removal action (NTCRA) under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) clashed with the requirements for a stormwater permit renewal under the Clean Water Act (CWA). Approach/Activities. DDT manufacturing occurred at the Arkema site for about 7 years (from the late 1940s to early 1950s). Arkema has completed a remedial investigation, undertaken a series of interim remedial actions, and is under a State order to complete a feasibility study. As a part of the Superfund process, Arkema is concurrently completing an engineering evaluation/cost analysis for a NTCRA of the sediments adjacent to the site. Even though stormwater discharges were previously permitted under the National Pollutant Discharge Elimination System (NPDES), Oregon Department of Environmental Quality (DEQ) required an update of the NPDES permit as part of the stormwater SCM. This negotiation led to years of project delay and numerous meetings over a separate Mutual and Agreed Order with the State of Oregon to implement the stormwater SCM under the jurisdiction of both programs. The lower Willamette River is 303d limited under the CWA for a number of water quality parameters including DDT, which complicated the NPDES permit process. DEQ has not identified a total maximum daily load (TMDL) or conducted any analysis of the load or waste load allocation for DDT, including a very large upstream load of DDT from the agricultural Willamette Valley. Because load allocations have not been assigned through the TMDL process, DEQ assumed for the stormwater permit renewal that Arkema was a “new source” with respect to DDT and subsequently set the DDT stormwater “goals” at Oregon’s new, much lower, ambient water quality standards. A thorough search of national databases of stormwater remediation technologies did not identify any viable stormwater treatment options that could reliably treat stormwater flows ranging from 0 to 30 cubic feet per second to sub-part-per-trillion (PPT) concentrations (i.e., below the practical quantification limit). Results/Lessons Learned. This paper provides a case-study of the process and key issues that became stumbling blocks to achieving consensus on the stormwater SCM for the site. Compromise was necessary on both sides of the table; however, DEQ required the final design to incorporate many “more conservative” design features in an attempt to