South Cedar ISGS Remediation

Project Overview

IET executed an In Situ Geochemical Stabilization (ISGS) remediation program at 3133 South Cedar in Tacoma, WA for Landau Associates. The six-day injection program utilized 23,112 lbs of ISGS amendment material with complete neutralization services, demonstrating our expertise in ISGS technology deployment on the West Coast.

Treatment Details

Technical Approach & ISGS Chemistry

In Situ Geochemical Stabilization (ISGS) is a patented remediation technology licensed exclusively to IET in North America by Evonik Corporation. ISGS uses a modified permanganate-based amendment that is injected into NAPL (non-aqueous phase liquid) source zones to chemically oxidize and polymerize organic contaminants in place — transforming mobile NAPL into a stabilized, low-solubility mass that dramatically reduces contaminant flux to groundwater. Unlike conventional ISCO which aims to fully destroy contaminants, ISGS focuses on source zone stabilization and flux reduction, making it ideal for sites with large NAPL masses where complete destruction would be cost-prohibitive.

For this Tacoma project, IET delivered 23,112 lbs of ISGS amendment over a 6-day injection program at 3133 South Cedar Street. The amendment was mixed and delivered using IET's proprietary injection trailer system, which maintains the permanganate-based reagent in suspension and delivers it under controlled pressure to achieve the designed radius of influence around each injection point. The 6-day field duration reflects the scale of the amendment delivery — approximately 3,852 lbs per day of ISGS amendment being mixed, pumped, and injected into the subsurface.

ISGS is particularly effective at sites with creosote, coal tar, or other heavy NAPL contamination — common at former manufactured gas plant (MGP) sites, wood treatment facilities, and industrial sites with historical solvent or tar use. The technology's stabilization mechanism physically coats NAPL globules with manganese oxide precipitate, reducing the NAPL's surface area available for dissolution and thereby reducing contaminant flux to groundwater by 80% or more in documented case studies.

Site Context & Pacific Northwest Geology

Tacoma, Washington is located in Pierce County within the Puget Sound Lowland physiographic province. The shallow geology consists of Quaternary-age glacial and interglacial deposits — predominantly Vashon Drift till (sand, gravel, and clay mixtures) overlying older glacial and non-glacial sediments. These deposits are highly variable, with interbedded sand, silt, clay, and gravel units that create complex hydrogeological conditions for in-situ remediation.

The project was managed for Landau Associates, Inc. (environmental consultant) with IET Sales Rep Mike Scalzi coordinating the engagement. The 3133 South Cedar Street site likely represents a former industrial or commercial property with historical NAPL contamination — common in Tacoma's industrial corridor along the Commencement Bay waterfront. The 6-day injection program was completed on June 9, 2025, under Project Number 2238001.010.015.051, with the ISGS amendment targeting the NAPL source zone for long-term flux reduction and site closure progress.