The Remediation Technology Summit

February 26-28, 2019

Colorado Convention Center
Denver, CO

rockwellCathy Rockwell
Principal / Technical Manager, Environment & Remediation
Woodard & Curran

Cathy is a professional engineer with a focus in environmental and hydrogeological investigations, feasibility evaluations of remedial alternatives, design and implementation of remedies at both state-led and federally driven sites. She is currently responsible for the overall management of several multi-phase investigation and remedial programs with combined remedies. She received B.S. in civil engineering from Rensselaer Polytechnic Institute (RPI) and a master of science (M.S.) in civil/ environmental engineering from the Massachusetts Institute of Technology (MIT).

PLATFORM PRESENTER - Thermal Treatment: It's Cookout Time

Assessing Changes in Groundwater Chemistry in an LNAPL Source Zone during and following In Situ Thermal Remediation: Implications for Closure Demonstration and Post Thermal Management Requirements

In-situ thermal remediation via steam enhanced extraction (SEE) was recently implemented to address aromatic and chlorinated VOCs in a mixed waste oil source zone. While SEE was effective in removing over 25,000 gallons of LNAPL and meeting the stringent site-specific soil cleanup goals (including naphthalene), there was a sharp increase in the groundwater concentrations for certain target contaminants and naturally occurring constituents in groundwater within the treatment zone as a result of the heating. This presentation examines the changes in groundwater chemistry in and around the LNAPL source zone as a result of heating both during and after. Post thermal groundwater temperature and chemical data are being evaluated to assess the relationship between concentration and temperature as groundwater cools both with additional extraction post-thermal and without, with an emphasis on the target contaminant naphthalene, and naturally occurring arsenic and bromide. The benefits and results of the post-thermal extraction are currently being used to address lessons learned in the design and operation for the second phase of thermal treatment at the site, as well as what, if any, post-thermal enhancements may provide benefit to achieving groundwater cleanup standards down the road.

FLASH POSTER PRESENTER – Biological Treatment: Strength in Small Packages

Accelerated Biodegradation of Chlorinated Contaminants Facilitated Using an In-Situ Liquid Activated Carbon: A Pilot Study and Full-Scale Application in South Carolina

A pilot study was conducted in two areas near the leading edge of a long, narrow chlorinated volatile organic compound (cVOC) plume located in south-central South Carolina. The pilot study included the application of an in-situ, liquid activated carbon (LAC) solution (known as PlumeStop™) that purports to accelerate biodegradation and shorten timeframes for achieving remedial objectives. The cVOC plume extends over 1,700 feet beyond its identified source. Approximately 80 percent of the contaminant mass is found in a Coastal Plain sediment aquifer that is comprised of a relatively low-permeability silt and very fine-grained sand. The impacted zone is present approximately 20 to 40 feet below ground surface. Both overlying and underlying zones are impacted to a lesser degree in the source area but unimpacted near the leading edge of the plume. A residential area is located less than 1,000 feet from the leading edge of the plume.

Enhanced biodegradation and monitored natural attenuation (MNA) are effective, widely-used remediation tools but the timeframe for treatment by these methods can be on the order of months to years. The results of a remedial alternatives evaluation recommended accelerated biodegradation using this innovative, in situ LAC solution. The remediation agent consists of highly sorptive, micron scale (1-2 micron) activated carbon particles stabilized to transport widely through an aquifer upon injection. The stabilized colloids deposit on soil surfaces, forming a biomatrix that retains contaminants and accelerates their degradation. The reagent formulation is also effective in subsurface environments consisting of low-permeability porous deposits where back-diffusion may be a concern.

Prior to implementing a full-scale remedial effort, two pilot studies were conducted to evaluate the effectiveness of the approach near monitoring wells with higher (~12 milligrams per liter) and lower (20 micrograms per liter) total cVOC concentrations. The pilot-scale tests consisted of a remedy that coupled the LAC with a controlled release electron donor and bioaugmentation culture to promote enhanced reductive dechlorination. The performance monitoring phase indicated that total cVOC concentrations decreased by 91 percent at the high concentration well and by 100 percent in the lower concentration well.

Based on the positive results of the pilot tests, the technology was implemented as the long-term remedial solution for the site at the downgradient portion of the contaminant plume. The full-scale application involved injecting the LAC solution in three passive-diffusion barriers that transect the downgradient plume. Combined with ongoing source-reduction activities, this remedial alternative should effectively prevent the plume from migrating further downgradient, which has been a concern of both the state and federal regulatory agencies. The protective effects of the remedial approach theorized to last many years will be evaluated through ongoing performance and long term groundwater monitoring. Results from the first year of performance monitoring will be available prior to the conference and will be presented.