North Boeing Field Stormwater Treatment Design

(Seattle, WA)  Landau Associates assisted The Boeing Company with investigation of the nature and extent of soil, groundwater, and sediment contamination and evaluation of potential sources of storm drain system contaminants at the North Boeing Field facility in Seattle, WA. We also designed and implemented short- and long-term stormwater treatment systems.

Landau Associates assisted Boeing with negotiating the terms of the Agreed Order with U.S. EPA for stormwater treatment. We selected the stormwater treatment technology, prepared the design of the new 500 gpm stormwater capture and conveyance system, managed installation of the short-term stormwater treatment system, and worked with our subcontractor partner Clean Water Services to have the system fully operational within a three-month period.

Both the short- and long-term stormwater treatment systems operated to consistently meet the applicable marine water quality criteria for PCBs.  The concentrations of PCBs in treated stormwater from the current long-term stormwater treatment system have consistently been below the laboratory reporting limit.

Stormwater from the facility discharges to the Lower Duwamish Waterway. Activities have included evaluation of soil and storm drain data from numerous previous investigations; collection of additional samples to fill data gaps, including sampling a network of passive sediment traps and implementing stormwater filtration sampling to quantify contaminant mass flux at various locations in the storm drain network; providing recommendations for areas to target for storm drain system cleaning and repair; implementation and oversight of cure-in-place pipe (CIPP) lining to prevent contaminated soil from infiltrating portions of the storm drain system and oversight of contractors performing source removal jet cleaning of storm drain pipes; CAD and GIS mapping of storm drain sampling results; identification of likely historical sources of contamination; and support for regulatory agency interactions.

For the full duration of operation (September 15, 2010 through October 28, 2011), the short-term stormwater treatment system treated and discharged approximately 35 million gallons of stormwater.  Influent concentrations of TSS ranged from 3.0 to 63.2 mg/L with a mean of approximately 11.3 mg/L, and effluent concentrations of TSS were not detected above 1.5 mg/L, representing an order of magnitude improvement in stormwater quality. 

This project was awarded an Engineering Excellence Gold Award (Originality-Innovation) from the American Council of Engineering Companies (ACEC)–Washington.