Advantages of Using Horizontal Remediation Wells for ISCO Treatment

Horizontal Remediation Wells for In Situ Chemical Oxidation (ISCO) Treatment 

The key to successful ISCO treatment is contact with the contaminant. Horizontal Remediation Wells for ISCO treatment have huge advantages over vertical wells in delivering  the ISCO reagents.

• Most contaminant plumes are horizontal so that Horizontal Remediation Wells contact a greater amount of soil contamination.
• Horizontal wells have a greater amount of screen to deliver ISCO reagent. For example, a 1000-foot horizontal remediation well can have as much as 600 feet of screen to deliver ISCO reagents.
• The characteristics of Horizontal Remediation Wells result in a greater zone of influence (ZOI) in the soil and greater contact with the source material.
• With Horizontal wells, ISCO reagents contact source material at the concentrations intended. Because vertical wells use groundwater transport as its main form of delivery, oxidants are often diluted. Horizontal Remediation Wells deliver the oxidant at the required concentrations to optimally remediate the soil.

According to the EPA, ISCO is the most rapidly growing remedial technology applied at EPA hazardous waste sites. ISCO results in the transformation of a wide range of environmental contaminants for enhancing mass transfer and is used at both old and newly discovered hazardous waste sites. ISCO is specifically used to reduce contaminant mass and concentrations in soil and groundwater, contaminant mass flux from source areas to down gradient pump-and-treat systems, and to reduce anticipated cleanup times required for natural attenuation and other remedial options.

“Rebound” Reduction with Horizontal Remediation Wells

“Rebound” or the reappearance of a contaminant in groundwater after ISCO treatment using vertical wells is much reduced when ISCO oxidants are delivered using Horizontal Remediation Wells. By drilling through the source of the contamination, Horizontal Remediation Wells provide more contact between oxidant treatment and soil contaminant. And, because the oxidants are delivered undiluted by the Horizontal Remediation Well, the oxidation reaction is more complete and the chance of “rebound” is much less. Also, Horizontal Remediation Wells reduce the chance of clogging by manganese oxide precipitation when using permanganate as an oxidant.

ISCO Treatment with Horizontal Remediation Wells

With its partners, Directional Technologies used permanganate to remediate a dry cleaner site contaminated with chlorinated solvents. Soil concentrations were reduced to below regulatory standards, and no “rebound” was observed. An important lesson of this project was that because of the large area of the screen, Horizontal Remediation Wells greatly reduced the chance of manganese oxide clogging that is a common problem with vertical well delivery of permanganate.