In Situ Chemical Oxidation (ISCO) Case Study for VOC Contamination Remediation

• The text discusses a case study of in situ chemical oxidation (ISCO) for the remediation of a contaminated site with volatile organic compounds (VOCs), specifically chlorinated VOCs, in the US Marine Corps Recruit Depot in South Carolina.
• The site includes perchloro ethylene (PCE) or tetra chloroethylene (TCE) contamination, and the contamination occurred due to the spillage of an unknown amount of PCE from an overfilled holding tank into a concrete catch basin.
• The contaminated water from the spill flowed into the surrounding soil and storm water drains.
• ISCO using permanganate as an oxidant was used to remediate the site.
• The study focused on the remediation of both the gaseous and adsorbed phases of the VOCs in the soil.
• The organic matter or soil fraction played a significant role in the adsorption of the VOCs.
• The site served as a reception and recruit training facility for the US armed forces, with recruits from states east of the Mississippi river.
• The chlorinated VOCs were used previously as industrial solvents, particularly in a large dry cleaning unit, which contributed to the soil contamination.
• The study monitored the remediation process for both the target contaminant (PCE/TCE) and its decomposition products (DCE, TCE, vinyl chloride).
• The drain system transported the contaminated water, potentially contaminating other areas.
• The study involved the use of nested micro-wells and conventional wells for monitoring the remediation process.
• The total CVOCs were monitored due to their toxicity, especially vinyl chloride, which is known to be highly toxic.
• The Indian context is mentioned as having a large number of dry cleaning units with inadequate treatment or enforcement for toxic solvent disposal, potentially leading to similar contamination scenarios.- Soil at the facility is contaminated with hydrophobic compounds, making it difficult to remove through pump and treat methods as the compound adsorbs to the soil and acts as a reservoir.
• Tanks were overfilled and spilled, leading to contamination during operation.
• Minor spills during operation also contributed to the contamination by entering the sewer.
• The facility is located near an old dry cleaning facility where a PCE leak from a sewer pipe contaminated soil and groundwater, leading to the formation of two plumes.
• One plume was due to contamination from the sewer line, while the other was due to storm water drains.
• The dry cleaning building and related structures were demolished in 2001 after the contamination was discovered.
• Contaminated soil at the original spill location was excavated and treated, but some contamination still remains in the subsurface and groundwater.
• The storm and sanitary sewers at the site are shown on the map, with the sanitary sewer in red and the storm water drains in green.
• The flow of the storm water and sanitary sewers is important to understand as leaks in these directions can lead to contamination at specific locations.
• Temporary wells were drilled at the site to monitor the extent of contamination in groundwater.
• The facility is located in an ecologically sensitive area, making remediation more challenging due to the potential impact on thriving ecosystems.
• The site has a shallow surficial aquifer that extends to 15 feet below the surface.
• The aquifer has high permeability and hydraulic conductivity, allowing for the transport of contaminants to greater depths.
• The site also has some localised silty and clayey layers, but they are not expected to act as confining units for the aquifer or NAPL.
• A peat and silty clay layer occurs from 17 to 27 feet below the ground surface, serving as a confining layer for the water and NAPL.
• The groundwater table is just 3 feet below the surface, making it susceptible to tidal influence.
• The contamination is typically limited to the shallow regions, reducing the requirement for injection pressure.
• The hydraulic conductivity is remarkably high at a depth of 6-10 meters, allowing for the transport of contaminants over a wider area.
• The site is classified into two aquifer zones: shallow and deep, with the shallow zone having almost 4 times higher hydraulic conductivity and hydraulic gradient.
• Groundwater levels are important to understand to determine the direction of groundwater flow and identify potential contamination sources.
• The major source of contamination is not just from the one-time spill, but from daily spills that leak into the sanitary sewer.
• The groundwater is assumed to be flowing in a particular direction based on the groundwater levels and the location of the contaminant plume.
• Control wells, soil core transects, and background course data were collected to understand the initial soil characteristics before contamination.
• Permanent wells were drilled into the aquifer to obtain a more complete picture of the contamination and its transport.

This quiz covers a case study of in situ chemical oxidation (ISCO) used for the remediation of a contaminated site with volatile organic compounds (VOCs) such as chlorinated VOCs, specifically perchloro ethylene (PCE) or tetra chloroethylene (TCE) contamination. The study discusses the use of permanganate as an oxidant, the role of organic matter in adsorption, monitoring processes, and the challenges and considerations in remediating the site. It also touches on the impact of daily spills and the potential influence on groundwater flow due to the site's location.