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Automated downhole monitoring at Southwest Harbor (WHS 2005)

Pilot testing of a permanganate injection system (WHS 2005)

Evaluating ASR using Columbia River water (WHS 2005)

Anatomy of a Sinking Chlorinated Solvent Plume (WHS 2003)

Comparison of Actual Evapotranspiration Estimates to a Soil Moisture Budget and Plant Growth (WHS 2003)

Hydrogeologic Characteristics of the Columbia River Basalts near Goldendale, Washington (WHS 2003)

Geology of the Brightwater Tunnel corridor (NGS 2004 / GSA 2003)

Abstract

Automated Downhole Groundwater Monitoring to Characterize Post-Redevelopment Conditions in a Tidally Influenced Aquifer System, Port of Seattle Southwest Harbor Project

Presented at the 5th Annual Washington Hydrogeology Sympoisum, April 12–14, 2005, by Peter Bannister, William Goodhue, Kathy Bahnick1

The Port of Seattle’s Southwest Harbor Redevelopment Project (SWHP) site was historically used for landfilling, wood treatment, steel processing, and ship building. The SWHP site underwent coordinated remediation and redevelopment in the late 1990s, and is currently a state-of-the-art shipping terminal. The primary objective for remedial actions completed concurrent with the SWHP redevelopment was future protection of surface water quality in Elliott Bay. Automated, downhole, groundwater-monitoring systems were installed at the SWHP site to collect sufficient water level and water quality data to confirm predicted post-redevelopment conditions in the tidally influenced Fill and Estuarine Aquifers.

The post-redevelopment SWHP monitoring program includes an initial 2-year, post-redevelopment hydrologic characterization phase, followed up by a water quality compliance monitoring phase. Specific goals of hydrologic characterization phase included:

  • Documenting reduced recharge to Fill and Estuarine Aquifers
  • Confirming reduction in downward vertical gradient
  • Confirming reduced discharge to Elliott Bay and the Duwamish River
  • Confirming reduced reduction in leachate production from a capped landfill
  • Documenting the effect of tight-lining the Longfellow Creek Overflow Line (LFOL) on the Fill Aquifer groundwater flow system

To meet the hydrologic characterization phase goals, downhole water level / water quality monitoring systems were deployed in 21 wells, and 2 years of continuous water level, conductivity, temperature, and pH data were collected. The downhole automated systems proved to be a very cost-effective approach to collecting the high-resolution data necessary to characterize the tidally influenced aquifer systems at the SWHP site. Major post-redevelopment changes in Fill Aquifer behavior were documented, particularly in the areas of the capped landfill and tight-lined LFOL stormwater line. Goals for the hydrologic characterization phase were met, and evaluation of site groundwater quality in relation to surface water standards is currently underway.

1 Port of Seattle; PO Box 1209, Seattle, WA 98111