By: Tomas Will, Sr. Environmental Technical Scientist
Being prepared to deal with challenges can often make or break a project. When our clients approach us for help with a project, one of the first topics we are likely to discuss are the subsurface conditions. Every so often we speak to a client who is concerned that they may not be able to utilize horizontal wells for their project because of difficult lithology. Here’s how one of our clients recently teamed up with Directional Technologies to implement a time-sensitive remedial solution at a site with a number of challenges waiting just below the surface.
Challenge
A large oil tanker rollover incident in the northeastern United States had resulted in significant impacts to soil and groundwater. The road where the incident occurred was adjacent to a large reservoir that was a popular spot for sport fishing and recreation. Boring logs and cross-sections for the project area indicated shallow bedrock beginning at depths ranging from 16 to 18 feet. Our client coordinated with us to develop a remedial action plan that included two horizontal air sparge wells with 260 total feet of screen to be installed underneath the road at a depth of approximately 17 feet.
Solution
Our experience with similar projects led us to mobilize equipment that is suited to dealing with subsurface obstructions and competent rocky material. Shortly after beginning drilling activities, our field crew encountered large cobbles within the matrix of medium-to-fine sands. The presence of cobbles persisted for large portions of the bore path. Utilizing proprietary techniques developed to overcome the difficult conditions and specialized equipment that was already on site, our well-prepared field crew continued to advance the original bore. After advancing towards the target depth, the directional drilling crew encountered what appeared to be structural fill material that contained large chunks of concrete. Using the appropriate equipment, the master directional driller on site was able to carefully continue the bore path through the various obstructions without significant deviation from the designs. The presence of shallow bedrock posed the final challenge, with depth to groundwater measured approximately 6 to 7 feet above the layer of bedrock. To achieve the best air sparging performance, the horizontal wells were designed to be set as deep as possible without fully becoming bedrock wells.
Despite encountering these multiple challenges, Directional Technologies was able to successfully install the horizontal wells according to the original designs and was able to do so without having to introduce costly delays from repositioning the boring locations or waiting on the delivery of specialized equipment. In addition, both horizontal wells were installed beneath the road without any road closures or interruptions to traffic. Our client was able to stay on schedule to begin implementing the remedial action plan and is now equipped with the best tools available to see their site to closure.
Horizontal remediation wells have been utilized for over three decades and both the technology and techniques have evolved tremendously over that time. Difficult lithology that may have been impractical or cost-prohibitive for a horizontal well projects 10 years ago presents a more manageable challenge using present day methods implemented by an expert remediation well driller.
What are your biggest concerns when dealing with tough lithology? Call our horizontal remediation well experts at 1-877-788-4479 to discuss your current project needs.