At a glance
Location: Massachusetts
Geology: Silty sand
Contaminant(s): Heavy petroleum, LNAPL
ETEC Solution(s): CBN, PetroBac, PetroSolv
Unique challenge(s): Difficult Contaminate, Residential Area
Site Summary
No. 4 fuel oil was released from a leaking underground storage tank that fed oil-fired boilers within a housing complex. ETEC worked with the environmental site consultant to apply surfactants and bioremediation products in conjunction with our automated recirculation equipment to oxygenate, biologically-treat, and recycle groundwater within the subsurface to support in-situ biodegradation during product removal. Massachusetts GW-1 standards were met, and the system was decommissioned.
Site conditions and remedial goal
At project start-up, a 10-foot-thick impacted vadose soil zone and a free product layer (up to 7 feet in some wells) was present in the subsurface. This fuel oil plume measured 120 feet x 100 feet, requiring an innovative remediation strategy to capture, remove, and degrade the significant fuel oil volume.
ETEC Solution
ETEC worked with the environmental site consultant to apply surfactants and biological products in conjunction with our automated recirculation equipment to oxygenate, biologically-treat, and recycle groundwater within the subsurface to support in-situ biodegradation during product removal. Our specialized surfactant product (PetroSolv™) was chosen to maximize removal of free product in the subsurface, followed by our bioremediation products (Petrobac™) to stimulate subsequent in-situ biological degradation.
A series of horizontal injection trenches were installed at 5 feet bgs on 15-foot centers across the plume area, and extraction wells are placed along the plume edge as well as within the plume. This layout promoted the creation of a series of “recirculation cells” within the subsurface which minimized travel time for the injected treatment water and maximized contact with the heating oil in these zones. The overall treatment train consists of a coalescing grid oil-water separator, the ETEC DO-IT™ system, which included an integrated bioreactor system which pre-treated dissolved and emulsified heating oil in the extracted groundwater, and an oxygenation system which generated >40 ppm dissolved oxygen levels in the water stream and injected it into the trenches.
Remedial outcome
Over 500 gallons of free oil was removed from the subsurface, and detectable product was eliminated across the site. After removal of the free product, the system continued to operate using dissolved oxygen and bioremediation product recirculation to focus on the treatment and degradation of the residual adsorbed and dissolved-phase constituents. Site goals were achieved, and the system was decommissioned and removed from the site after 36-months of total system operation.
