- SCOTT WISHER, PG
Every day we are bombarded with choices, and many of us elect to simplify our lives where we can: we buy a cup of coffee while grocery shopping instead of making a second stop; we write emails while listening to a conference call; we get our tires changed while stocking up on bulk household items at the warehouse store. Environmental consultants can (and sometimes) do the same thing—they select one contractor to complete multiple scopes of work. This approach can create immense savings of time, cost and confusion, as well as provide better coordination around health and safety, scheduling, accountability and reporting.
In a recent project in Ft. Thompson, South Dakota, Bristol Environmental Remediation Services (BERS) and the Environmental Protection Agency (EPA) made that choice, bringing Cascade in to provide drilling and remediation services. Because we served in several capacities, BERS and the EPA realized cost and time savings. In this blog post, we’ll first briefly discuss the site requirements, then cover the ways in which a single vendor approach benefited BERS and the EPA—and could benefit your clients, too.
The site, a former fueling station with previously removed underground storage tanks (USTs), had groundwater contaminated with petroleum hydrocarbons above State cleanup objectives. Previous remediation efforts at the site, including excavation and disposal, had effectively addressed vadose zone and source zone impacts. The remaining contamination was bound in a lithology consisting of poorly graded sands with elevated dissolved oxygen and low natural demand, which provided ideal conditions for remediation injection through wells.
Cascade’s drilling team started by advancing hollow stem augers to 30 feet below ground surface (bgs) for the installation of two-inch diameter injection wells. Using continuous sampling through the augers, they facilitated the lithology review and assisted with determining the length of the screened zone within the saturated interval. Each well was completed with 10 feet of 10-slot screen, silica sand, and grouted with a concrete slurry.
As the drilling team progressed to advance more wells, Cascade’s technical services team stepped in to begin injections within the newly-cured wells. Specifically, the technical services team began an in situ chemical oxidation (ISCO) event to address the dissolved-phase petroleum hydrocarbons remaining in the groundwater. At each ISCO location, 1,950 gallons of 10% caustic-activated persulfate solution was injected at flow rates ranging from 4 to 10 gallons per minute.
Cascade manifolded a custom-built injection system in order to allow for simultaneous injection at five locations, utilizing air diaphragm pumps to effectively distribute the persulfate. Injecting at multiple locations simultaneously saved time and associated costs for the client.
Multiple contractors and crews on a single site can invite opportunities for miscommunication (or a lack of communication altogether), which can unintentionally contribute to safety risks and hazards. Because Cascade was the sole contractor at the Ft. Thompson site, it meant that identification of, communication about and action on any safety issues could be streamlined. There was one safety process and protocol to follow, and no other contractor to loop in.
As mentioned before, as the drilling team advanced injection wells, the technical services team began injections concurrently. Because there was a single contractor, there were less logistics in making sure timelines for well advancement and completion were understood and aligned with scheduling of equipment and personnel for the actual injections—even planning for multiple simultaneous injections to prevent delays and adhere to project benchmarks.
During field work, BERS was able to maintain communication with one on-site Cascade project manager, which increased accountability and minimized reaction time. This supported less field labor costs for BERS and Cascade, ultimately providing a more cost-effective program to EPA.
Logistical efficiencies relating to health and safety, scheduling, accounting and reporting are all affected by the number of contractors involved with a project. Partnering with a company that can offer drilling, investigation and environmental remediation at a single project location provides clients with greater control over site operations, simplifies communications related to logistics, and reduces overall overhead. Take advantage of a single contractor approach by beginning the planning process early in a project’s lifecycle.