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 implementedfor a non-time-critical removal action (NTCRA) under the ComprehensiveEnvironmental Response, Compensation, and Liability Act (CERCLA) clashed with therequirements 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, undertakena series of interim remedial actions, and is under a State order to complete afeasibility study. As a part of the Superfund process, Arkema is concurrently completingan engineering evaluation/cost analysis for a NTCRA of the sediments adjacent to thesite. Even though stormwater discharges were previously permitted under the NationalPollutant Discharge Elimination System (NPDES), Oregon Department of EnvironmentalQuality (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 Mutualand Agreed Order with the State of Oregon to implement the stormwater SCM underthe jurisdiction of both programs. The lower Willamette River is 303d limited under theCWA for a number of water quality parameters including DDT, which complicated theNPDES permit process. DEQ has not identified a total maximum daily load (TMDL) orconducted any analysis of the load or waste load allocation for DDT, including a verylarge upstream load of DDT from the agricultural Willamette Valley. Because load allocationshave not been assigned through the TMDL process, DEQ assumed for thestormwater permit renewal that Arkema was a “new source” with respect to DDT andsubsequently set the DDT stormwater “goals” at Oregon’s new, much lower, ambient waterquality standards. A thorough search of national databases of stormwater remediationtechnologies did not identify any viable stormwater treatment options that could reliablytreat 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 issuesthat became stumbling blocks to achieving consensus on the stormwater SCM forthe site. Compromise was necessary on both sides of the table; however, DEQ requiredthe final design to incorporate many “more conservative” design features in an attempt to