Creative Teamwork Makes the Dreamwork

Contributed by Lance Loken, President, Western Plains Consulting

Assessing and remediating a large petroleum product release is always a fun challenge.

In the case before us, the release occurred near the largest shopping mall and busiest commercial street in North Dakota (Fargo), making the project even more complex. Petroleum had leaked from petroleum delivery lines prior to 1994, which were replaced in 1994.  This was in the northern portion of the Site. Under the southern building on-site, five underground hydraulic hoist reservoirs and an oil-water separator located inside the building had leaked. Once the Phase II Subsurface and Groundwater Assessment was completed, several things were evident:

  • The vast majority of the site soils and groundwater were impacted.
  • The release threatened a buried glacio-alluvial stream bed buried about 11-12 feet below ground surface. Even with fat clays from the surface down to that depth, the underlying material was over 90% sand, which was water bearing and free product (gasoline) was floating on the water in the northern portion of the Site.
  • Initial estimates pointed to a need to remove between 16,000-18,000 cubic yards of impacted soil, plus impacted groundwater.
  • To remove the impacted soils and backfill, the area would have required over 1,800 loaded heavy haul trucks to transport across the highest traffic zone in the state of North Dakota. The tipping fee alone at the nearest landfill (roughly 100 miles away) was estimated at around $700,000.
  • Initial estimates for the total cost for a traditional dig-and-backfill project would have exceeded $1,000,000.

Sticker shock from that initial estimate inspired the Western Plains Consulting team to get creative.

Reflecting on a similar project conducted in 2009 with friends at Geo-Tactical Remediation (of Calgary, Alberta, Canada), I reached out to GTR and shared initial data from the Fargo site. We suspected they had a technology that could solve most of our high dollar challenges, and we were right! GTR agreed that their technology would work at the Fargo Site.

With approval in hand from the state & local authorities, remediation work commenced in January 2020, with a single round of soil fracturing and injection. We used GTR’s down-hole tooling and mixing/pumping unit along with WPC’s drill rig to perform 68 shallow soil fracture injections of sodium persulfate solution (to depths of around 12 feet). WPC placed 18 injection wells across the Site and GTR injected a solution of hydrogen peroxide into the groundwater. Essentially, the combined sodium persulfate and the hydrogen peroxide solutions caused a geochemical reaction that converted the petroleum into carbon dioxide and water. A scaled back second round of hydrogen peroxide injection was performed later in the year. 

Next, 38 confirmatory borings were completed to document the success of the process, and these borings confirmed that near-surface impacts would need to be dealt with separately. By July 2020, spot excavations and backfill were completed and reported, and by August 2020 the North Dakota DEQ issued a letter stating no further remediation was required. The DEQ did require two years of groundwater monitoring and documentation at the site.

To date, WPC and GTR’s combined effort has cost about $650,000, a huge savings over the earlier cost estimate for a traditional dig-and-backfill. The final amount of soil excavated and disposed of was less than 3,500 cubic yards (instead of 16,000-18,000!), and a single-use disposal location within 15 miles of the Site mitigated landfill fees, contributing major cost savings. This technique precluded more traditional groundwater response efforts, such as air sparging/soil vapor extraction, or pump and treat, and resulted in a much faster remediation compared to 2+ years by any other methods. Groundwater monitoring and documentation for the next two years will be a minimal cost.

This project taught us that we can fracture impacted soils and inject a remedy directly into the site to remediate both soil and impacted groundwater without requiring excavation and disposal. By combining forces, GTR and WPC conducted the fastest, most efficient cleanup of a major petroleum release in the history of North Dakota. Also, we generated a beneficial side effect: the petroleum was converted to carbon dioxide and water, making this a successful carbon sequestration effort. As environmental professionals, we see that as a fantastic bonus!

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