By Tomas Will, Sr. Environmental Scientist

Background and Setting:

A large jet fuel leak had been discovered at a military facility. Following the discovery of the release, approximately 3,600 tons of contaminated soil were removed and multiple vertical air sparge and soil vapor extraction wells were installed. Site characterization activities indicated that the contaminant plume extended to depths of greater than 100 feet below ground surface. Lithology at the site consisted primarily of fine-grained quartz sands with a high degree of hydraulic conductivity.

Problem:

The remediation system had been operating for 9 years and required maintenance. During an extended period of downtime while the blower mechanism for the air sparge system was being replaced, the dissolved-phase plume migrated outside of the zone of influence of the current vertical remediation well system. Furthermore, the plume had migrated beneath several aircraft hangar buildings that were integral to the operations at the facility. Installing additional vertical wells to address the migrating plume would be impractical in this portion of the facility.

Solution

The consultant needed to act quickly, as the petroleum hydrocarbon plume that had previously been under control was now migrating further and further away from the existing remediation system. Having successfully worked with Directional Technologies on previous projects, they reached out and shared their plan to use horizontal remediation wells to address their time-sensitive problem. However, they were initially unsure if horizontal wells could be installed deep enough to implement their plans as they had hoped. Using their 28 years of expertise, Directional Technologies designed a plan incorporating the use of a wireline locating system and specialized drilling equipment to implement the consultant’s approach.

Using horizontal wells, the consultant found they could:

  • Avoid impacting the critical base infrastructure in the hangars above the plume
  • Prevent interruptions to facility operations during well installation and subsequent O&M
  • Significantly improve on the zone of influence produced by the existing vertical wells
  • Provide more precise targeting of hot zones, and,
  • Allow significantly more screen to be placed within the plume allowing for more efficient air sparging.

Results

One deep horizontal air sparge well was installed underneath the aircraft hangars to target the contaminant plume. The horizontal well contained 325 feet of screen interval placed within the target zone at a depth of approximately 90 feet below ground surface. A wireline system was used to provide highly accurate tracking of the bore path even at deeper depths. Utilizing their proprietary horizontal well screen design software, Directional Technologies produced a site-specific screen design to deliver an internal airflow rate of 1 cfm per foot. Well material consisted of 3’’ diameter HDPE. The newly installed horizontal air sparge well was able to control the migration of the contaminant plume and greatly expand the zone of influence as well as the effectiveness of the existing remediation system. Without the use of horizontal remediation wells, the consultant would not have had a viable solution to achieve site closure.

Conclusions

Horizontal wells are an effective solution to bring regulatory site closure to challenging sites, no matter the site conditions. With the proper equipment, techniques, and experience, horizontal remediation wells can be successfully installed to depths of greater than 100 feet.

Do your projects have contaminant plumes that are difficult to access?  Call our horizontal remediation well experts at 1-877-788-4479 to discuss your current project needs.