ADVENTUS GROUP

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ISGS Pilot Study Report

Field Performance Assessment

Cabot Carbon/Koppers Superfund Site in Gainesville, Florida

EXECUTIVE SUMMARY:

In situ geochemical stabilization (ISGS) entails the use of a modified solution of sodium permanganate (NaMnO₄) designed for in situ management of non-aqueous phase liquids (NAPL). When added to an impacted aquifer, the technology is designed to rapidly react with organic (and certain inorganic) constituents of interest (COI) present as soil residuals (e.g., NAPL or ganglia).  Various reactions associated with ISGS processes serve to rapidly reduce aquifer permeability and stabilize the NAPL residuals thereby leading to enhanced passive remediation or accelerated remediation by natural attenuation. 

Using subsurface soils from the Cabot Carbon / Koppers wood-treating site in Gainesville, Florida (Site), bench-scale engineering optimization tests previously demonstrated that such stabilization of creosote/penta NAPL residuals at the Site was technically feasible, and that this combination of reagents could potentially yield effective long-term NAPL stabilization and flux reduction of all monitored COI (Adventus Americas, Inc., 2004). Field testing of the ISGS approach was subsequently undertaken in January 2008 to yield site-specific field data necessary to validate full-scale technology efficacy. Implementation of the ISBS field test was completed in the surficial aquifer at the former North Lagoon Area of the Site during the period January 22-26, 2008 (Adventus Americas, Inc. - March 31, 2008).  Post-treatment soil cores were collected approximately 60 days after the Remox EC reagents were injected (Appendix E).

This report describes the initial performance monitoring activities conducted for pilot-scale field validation of the ISBS technology.  Specifically, the report summarizes field observations, analytical results for soil cores and "crust" analyses on soil cores collected approximately 60 days after treatment.  In addition, it presents the data associated with the Variance requirements associated with the use of the material.

As described herein, multiple units of measure were used to define the effectiveness of the ISGS technology, and to assess the long-term permanence of the stabilization process.  After only 60 days post-treatment, the ISBS technology was shown to provide safe, rapid, effective and predicted long-term treatment as follows:

Field NAPL Measurement: There was no measurable free-phase NAPL in any of the monitoring wells.

Reduced Soil COI Concentrations. Using data from all samples, the concentrations of total soil polycyclic aromatic hydrocarbons (PAHs) were reduced by an average of 11% (for the DIP area) to 98% (for the TIP area). Considering data from the best paired cores (as described below), a 50% reduction of total PAHs in soil was observed, with the average soil PAH concentration being reduced from of 7,250 mg/kg soil to 3,600 mg/kg soil.

Reduced COI Concentrations in Soil Leachate: Using data from all leachate samples, the average concentrations of COIs in the soil leachates post ISGS treatment were reduced by 71% (for the DIP area) to 98% (for the TIP area).  Using data from the best paired cores, the amount of site-specific COIs present in soil leachate was reduced by 95%, with an average total of 11,700 mg/L total PAHs present in the leachates prior to Remox EC treatment and an average of 560 mg/L of total PAHs being present in the leachates from the soil cores collected 60 days after treatment.

Rapid, Uniform and Environmentally Stable Encrustation of NAPL residuals:  Using optical microscopy, electron probe microscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), independent expert studies by Dr. Tom Al (University of New Brunswick; UNB) showed that the ISBS precipitates formed coatings around aquifer grains and NAPL droplets.  The coatings were composed of crystalline aluminum silicate hydroxides that were not representative of conventional manganese oxyhydroxides that would typically form with the use of standard permanganate.  Unlike the manganese oxyhydroxide coatings, the ISGS coatings are not expected to be affected by changes in the redox potential of the aquifer and are therefore considered to be stable and persistent with time.

Reduced Permeability: Adventus' lab tests showed a qualitative decrease in "leachability" post-ISGS treatment.  Independent studies by UNB indicated that 27 to 81% of the pre-injection pore space was filled in lightly coated to heavily coated areas, respectively. It was noted that field aquifer permeability reductions were likely even greater than 81%. This is consistent with the bench-scale column testing work conducted previously, which showed >90% reduction in permeability / transmissivity within 8 days of ISGS treatment.

Minor Exceedance of Variance Secondary Analytes: There was an apparent increase in Aluminum (Al) in some wells, but there was no clear pattern identified with the distribution. There was a slight increase in pH noted in two wells (HG-10D and UHG-HG-16S), both of which have had a history of containing small amounts of basic NAPL.

No Significant Exceedance of Variance Primary Analytes: Groundwater monitoring showed that the ISGS treatment did not induce any significant exceedance of primary analytes, and there were no impacts observed at either the newly installed zone of discharge monitoring well (ZOD-1) nor in any of the other six Variance monitoring wells. In particular, no Chromium (Cr) exceedance was noted at any well location. There was a minor exceedance in Arsenic (As) noted in one well (supplemental Variance monitoring well UHG-HG-16S) that is located far down gradient of the treated area. 

Beazer East, Inc.

Prepared by:

Adventus Americas Inc.

Freeport, IL

8153/235-3503

In cooperation with:

GeoTrans, Inc.