Description
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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.
Organizations Involved:
Beazer East, Inc.
Prepared by:
Adventus Americas, Inc.
In cooperation with:
GeoTrans, Inc.
Companies On This Project
ADVENTUS GROUP
