An old underground storage tank is buried on your property. It’s leaking and contaminants are seeping into the soil and groundwater. You are invested in this location. Picking up and moving is not an option. What do you do?
To solve groundwater contamination, you need to do what’s called a groundwater investigation and remediation. Using traditional and specialized tools, a qualified environmental service professional can investigate, determine the level of contamination, and create a cleanup plan. This is exactly the type of work LAN Associates’ environmental team routinely performs. Below is a case study that will walk you through what is involved in the process.
LAN was retained by a northern New Jersey Board of Education client to assist with a 20-year-old lingering New Jersey Department of Environmental Protection (NJDEP) groundwater gasoline spill case related to an underground storage tank removal performed by another firm. For over two decades, various consulting firms worked on the site, performing traditional investigation, sampling, and monitoring, but they failed to address NJDEP comments or meet reporting requirements.
Upon taking on the job, LAN reviewed all the work up until that point. Despite the efforts of previous firms, their results did not provide a well-defined understanding of the subsurface environment by way of a conceptual site model or delineation of contamination. A conceptual site model or CSM is required by NJDEP, and it is needed to fully understand the underground conditions of the site.
Soil and groundwater contamination are traditionally measured by collecting samples and submitting them for laboratory analyses. However, in this case, LAN worked with S2C2, Inc. of Raritan, New Jersey to use specialized direct sensing tools to acquire real-time, continuous data profiling of the subsurface contamination.
Data collected from the direct sensing investigation provided more information than the past 20 years of investigations combined, including an extensive background, and understanding of the subsurface conditions. The data analysis and three-dimensional (3D) data visualization were used to develop a visual updated conceptual site model. This information lowered cost estimates by 30% by pinpointing areas requiring remediation, thus avoiding over-estimates about the required scope of the job.
For this project, groundwater and soil were impacted by a gasoline spill. The remedial design included a two-phase injection program consisting of in-situ chemical oxidation (ISCO) followed by injection of oxygen releasing compounds into the subsurface between depths of 4 to 11 feet below ground surface.
In-situ means you treat the contamination in place by applying remedial amendments to the subsurface soil and groundwater by drilling and injection methods. In layman’s terms, basically, you drill down and release chemical agents into the soil that break down the contaminates. You then continue to sample and monitor the spill until the problem is solved.
The project is still ongoing. Typical remediations like the approach used here may take a few years to achieve cleanup. In this case, there is a very high standard to meet with regards to one of our contaminants, and therefore it takes a little longer to reach the project’s goal. The goal is to remediate contaminants in groundwater so that they no longer exceed applicable NJDEP groundwater quality standards, or to demonstrate that contaminant concentrations were decreasing over time.
LAN evaluated the two years of groundwater data and determined that while contaminant concentrations were initially reduced by greater than 90%, contaminants were desorbing from soil back to groundwater and contaminant concentrations started to increase again.
An additional remedial injection event was designed to address the desorbing of contaminants from soil to groundwater and was completed during the last week of June 2022. Initial post-injection groundwater results indicate that contaminant concentrations have been reduced compared to baseline groundwater sampling results.
Cleaning up groundwater contamination is a long, laborious, and complicated process. It is not easy or even sometimes possible to completely reverse the damage done by a spill. Prevention is vital, but it’s not realistic to assume spills can be eliminated completely. If a spill leads to contaminated groundwater and soil, it is important to engage an environmental team with the tools and experience to help undo the damage.
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