Horizontal Wells Access Contamination

Background and Setting

An environmental consultant had been treating multiple source areas of chlorinated solvent contamination at a manufacturing facility for over a decade. Previous remediation efforts using traditional vertical wells had been effective in remediating portions of the project site. One of the last remaining source areas was associated with a building that held a laboratory facility as well as industrial equipment. During the process of evaluating how to address the contaminants beneath the building, the consultant faced several challenges.

 

Problem

The remaining contaminant plume was located beneath a building that was integral to the day to day operations at the facility. A shallow horizontal SVE system had previously been installed directly beneath the foundation of the building to manage vapor intrusion; however, additional remediation efforts were required to address the contaminants beneath the building. The consultant was faced with three main problems:

• The building in question was both filled with industrial equipment and had low hanging ceilings, making access inside the building with a drill rig virtually impossible
• Due to these factors, the client had not been able to collect soil samples using vertical drilling techniques to accurately characterize the extents of the plume beneath the building.
• Their client had indicated that interruptions to the operations within the building were unacceptable. If they had to shut down the building for two to three days to install remediation wells, the client’s company stood to lose significant revenue.
  
  

Solution

Having worked successfully with Directional Technologies on various other projects in the past, the client began an evaluation of horizontal remediation wells with input from Directional Technologies. Due to the site conditions, the consultant had been unable to gather subsurface data beneath the building. However, the consultant wanted to be able to characterize the extent of the plume beneath the building without incurring significant additional costs. Directional Technologies proposed using their proprietary horizontal soil sampling techniques which allow for samples to be collected during the horizontal well installation process without the need for additional borings.

Using horizontal wells and horizontal soil sampling, the consultant found they could:

•  Prevent interruptions to facility operations
• Place the wellheads out of the way of the building, avoiding future interruptions to the facility during O&M events
• More accurately characterize the contaminant plume beneath the building so that the remediation wells could be screened accordingly
• Provide more precise targeting of hot zones, and,
• Allow significantly more screen to be placed within the plume allowing for more efficient groundwater extraction.
  
  

Results

Two horizontal wells were installed beneath the facility with the wellheads located in a nearby landscaped area. Soils beneath the facility were primarily glacial till overlain by sandy silt. A specialized horizontal soil sampling tool was used to penetrate the glacial till and collect viable samples. While drilling the horizontal borings for well installation, soil samples were collected at 5-foot intervals along the bore path and evaluated in the field for VOCs. Based on the data previously collected from monitor wells around the exterior of the facility and the soil data collected during horizontal drilling, the horizontal wells were installed to depths of 40 and 60 feet below ground surface with screen intervals approximately 45 feet long.

Using horizontal remediation wells and horizontal sampling techniques developed by Directional Technologies, the consultant was able to:

 

Do your clients have remediation projects that demand a solution despite challenging site conditions?
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