Formatted Title
From LNAPL to Beyond: Elimination of Significant LNAPL and BTEX Resulting from a Leaking Aboveground Storage Tank while Overcoming Refusal Using BOS 200+™
Background/Objectives
A leaking aboveground storage tank (AST) created a large LNAPL and dissolved plume at an active pipeline and petroleum storage site in the Gulf Coast Region. The impact area was 93,000 ft2. Site lithology consisted mainly of silty clay to clay over weathered shale with some sand and gravel. Depth to water varied from 5 to 25 ft bgs. Using direct push and high flow high volume injection, BOS 200+® was applied during a six-month period. Shallow refusal occurred at some injection locations. A pre-drill technique was used in these locations to overcome refusal and accommodate direct push. The site objective was LNAP elimination.
Approach/Activities
One thousand one hundred ten (1,100) soil samples were collected over the impact area. The soil samples were processed and analyzed for petroleum constituents by GC/MS. The results were used in remedial design to optimize loading for carbon, electron acceptors, and neutrients. 361,000 lbs of BOS 200+ was installed in over 1,000 injection points using top-down emplacement. Areas of refusal were drilled and backfilled with bentonite, after which they were penetrated by direct push and injected consistent with the other injection points on the site.
Results/Lessons Learned
A total of 15 monitoring wells had measurable LNAPL before remediation. The average dissolved TPH concentration in the monitoring wells before remediation was 20.9 mg/L. The post-treatment reduction was 60% for benzene and 93% for TVPH at day 250. At the last sampling, day 1803, the drop was 99.9% for benzene and 96.8% for TVPHs. There is no measurable LNAPL. A regulatory NFA is in progress.