Custom Solutions for Successful Remediation

By Tomas Will, Sr. Environmental Scientist

Background and Setting:
The site was a former metalworking facility about to undergo rapid redevelopment, with one large warehouse building undergoing construction and additional structures planned for the future. Previous remediation efforts included injection events that had managed to treat a significant portion of the chlorinated solvent contaminant plume. However, soon before the scheduled start of construction for the new warehouse, a large zone of additional groundwater contamination was discovered directly beneath the footprint of the proposed building. With concerns mounting over the newly discovered contamination and tensions growing between the developer and former metalworking facility owner, the environmental consultant was given the difficult task to try and find a solution.

Problem:
The consultant was told to avoid delaying the construction schedule at all costs and was asked to try and avoid installing any vertical wells inside the new building once construction was complete if possible. One initially proposed solution was to install several groundwater extraction vertical wells that could be operated for approximately 2 months prior to needing to be abandoned when construction began on the building. Depending on the performance of the initial vertical wells, a separate set of vertical extraction wells would likely be needed so they could operate for longer periods of time to continue addressing the large zone of additional groundwater contamination. However, the second set of vertical wells would only be able to access the outside edges of the plume since the developer did not want to have to install extraction wells in the interior of the bustling warehouse that would be completed in the near future.

Solution
The client called Directional Technologies to explore other options, and it was determined that horizontal extraction wells could help them deal with the many restrictions they were facing.

Using horizontal wells:

• Prevented delays to the construction schedule
• Avoided the need to spend additional money on short term wells that would be abandoned once the building was constructed,
• Placed the wellheads out of the way of the building,
• Provided more precise targeting of hot zones, and,
• Allowed significantly more screen to be placed within the plume, allowing for more efficient groundwater extraction.

Results
Once the grading was completed and the site was brought to its final elevation, Directional Technologies mobilized to begin work within the short window of time that would allow them to avoid slowing down the ongoing construction activities. Over the course of one week, Directional Technologies was able to install three horizontal DNAPL extraction wells totaling over 850 feet and containing 280 feet of well screen in the target zones. The horizontal wells were installed to depths ranging from 35 to 40 feet below ground surface. Due to the limited available work area, the horizontal wells were installed from the same entry point via blind (single-entry) method. Proprietary drilling techniques were used to curve the paths of the horizontal wells so that the screens could fan out from the entry point and cover a large area of the plume with the screens of the three wells being set more than 70 feet apart from one another.

In summary, not only was the consultant’s client able to avoid the various complications posed by the project but they were also able to save money on overall project costs.

Do you face projects where you are asked to work around site-specific restrictions that make remediation challenging? Call our horizontal remediation well experts at 1-877-788-4479 to discuss your current project needs.