Opportunity
The Woodrow Wilson Service Area on the New Jersey Turnpike offers a gas station and fast food restaurants. Leaks from the gas station’s underground fuel tanks, discovered in 1988, had contaminated soil and groundwater.
Removal of light non-aqueous phase liquid (LNAPL) was challenging because its limits were not well defined, and it was trapped in the underlying soil matrix. Conventional methods were ineffective, expensive, or disruptive to the rest area’s operations.
Solution
Mott MacDonald decided to use surfactants to mobilize the LNAPL and make it easier to remove. If the LNAPL could be turned into a Winsor Type III microemulsion, it could be easily dislodged by moving the groundwater, and could be pumped out together with it.
Mott MacDonald created a carefully proportioned mix of polysorbate 80, sodium lauryl sulfate, and N-butanol. The mixture was poured into existing monitoring wells using traffic cones as funnels — an effective and inexpensive method. The mixture was left to “cook” for three or four weeks, then pumped out with conventional centrifugal pumps and taken away in 55-gallon (208-liter) drums.
Outcome
After about 1,500 gallons (5,678 liters) of LNAPL was removed, concentrations of groundwater contamination fell by about 50%. The removal technique looks promising for sites like airports, military bases, power plants, and rail yards where it is important to avoid interfering with mission-critical infrastructure. Christopher Rossi, Senior Environmental Manager for the New Jersey Turnpike Authority, said, “This is why we hire Mott MacDonald.”