In-Situ, Inc.

Multiparameter sonde used in Combined remedy approach and saves $200,000 in potential costs - Case study


Courtesy of In-Situ, Inc.

A former dry-cleaning site in the Pacific Northwest Ultra Custom Care Cleaners, was found to be contaminated with PCE (perchloroethylene). According to the U.S. Geological Survey (USGS), PCE was widely used in the dry cleaning of fabrics since the 1940s. PCE is one of the most frequently detected VOCs (volatile organic carbons) in groundwater at a national scale (Moran 2004). PCE is highly mobile, dense, and largely immiscible in water, causing it to sink below the water table, and making deanup extremely challenging.

Multiparameter sonde used in combined remedy approach at former dry cleaning site
ln-Situ lnc. multiparameter water quality sonde helps resolve treatment challenges and saves $200,000 in drilling, reagents, and consulting at site contaminated with PCE.

Site Summary:
The Ultra Custom Care Cleaners site was acquired by the City of Bothell as a part of the city's downtown redevelopment plan. As a part of the Toxics Cleanup Program, the Washington State Department of Ecology and the City entered into an agreement for the cleanup. Groundwater contamination above cleanup standards had migrated downgradient into City rights-of-way. The cleanup actions agreed upon, including a Remedial Investigation and Feasibility Study (RI/FS) and Cleanup Action Plan (CAP), were designed to protect human health and the environment from soil and groundwater exposure to PCE (Fact Sheet 2013 and TCP Site Cleanup).

Cleanup History:
Characterization of the source area site geology indicated a surficial layer of clean, relatively homogenous, glacial outwash sand, which initially appeared favorable for in-situ chemical oxidation (ISCO), due to high permeability and low organic carbon. ISCO was attempted using a theoretically calculated injection design (i.e., not verified via real-time monitoring during treatment), but did not achieve significant removal of contaminants.

Design Approach:
A second cleanup effort was then designed, which included a combined remedy approach using in situ chemical reduction (ISCR) and enhanced bioremediation. Arnie Sugar of HWA GeoSciences Inc. led the restoration effort. HWA contracted Leo Lehmicke, Ph.D., to help design the cleanup, which included'flipping'the aquifer chemistry to a reducing environment (by adding zero-valent iron), adding electron donor (emulsified vegetable oil), substrate (lactic acid), and chlorinated solvent-degrading bacteria. This approach was designed to address PCE and daughter products in the upper geologic unit at the site.

The design included real-time groundwater monitoring durinc initial treatment to establish injection spacings and volumes. During initial pilot/tracer testing, data from an In-Situ TROLL® 9500 Multiparameter Sonde was used to help develop the pore volume replacement and dilution factor necessary to achieve targeted distribution of injected materials.

A combination of Z-Loyw (zero-valent iron), Newman Zone (emulsified vegetable oil and lactic acid), SiREM KB1 (microbial consortia), and reduced water was chosen for the source area. Several down gradient subsurface barriers were treated with Newman Zone, SiREM KBl microbes, and reduced water.

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