Lower Duwamish Waterway Pre-Design Studies

Lower Duwamish Waterway
Pre-Design Studies

On behalf of the Lower Duwamish Waterway Group (LDWG), Windward is currently conducting the pre-design studies for the Lower Duwamish Waterway (LDW) Superfund site in Seattle, Washington, with oversight provided by the US Environmental Protection Agency (EPA). We have assembled and effectively managed the consultant team to gather and analyze samples from a variety of media in order to establish baseline conditions for surface water, sediment, porewater, and fish, crab, and clam tissues. Surface water sampling has included discrete samples as well as those collected with passive samplers; porewater evaluations for polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) have been conducted using passive samplers in ex situ exposures. In addition, source control sampling, a survey of waterway users, an assessment of physical structures, and a design implementation strategy have been conducted. Clearly identified objectives have guided the process of data collection and allowed us to meet the project’s aggressive schedule.

Windward has designed and implemented sampling plans for all aspects of the pre-design studies. Our staff has statistically evaluated these plans to ensure that the baseline datasets will be sufficiently robust for the evaluation of long-term trends.

The remedial investigation for the LDW, also conducted by Windward, was finalized in 2010 and the feasibility study was completed in 2012. Since that time, a great deal of data have become available. To support the pre-design studies analyses as well as upcoming design, Windward data managers have compiled a project database with more than 150,000 records that combines the RI/FS database with all more recent data. This database will be critical in creating the comprehensive data evaluation report, which will provide an evaluation of the pre-design dataset relative to the cleanup levels and remedial action levels provided in the EPA Record of Decision.