As is fitting for a site this large and complex, BP is using a broad array of both time-tested and state-of-the-art technologies to clean up residual petroleum left over from nearly 75 years of refining operations in Wood River.
BP uses a system of wells to contain on site a plume of petroleum products from the old refinery and removes up to 70,000 gallons of petroleum products per month. Four large, industrial-size wells create what's called a cone of depression. A cone of depression is an area where groundwater is pulled down by pumping, creating a downward gradient that contains or traps a plume of petroleum in place. Then, a system of 21 more wells skims the petroleum off the top of the water table. The petroleum is collected and sold to a recycler for industrial uses.
BP recently has successfully used a simple process that injects sulfate, a product like common Epson salts, into the groundwater on our site. The salts have been very successful in helping to break down the petroleum products, causing them to degrade more quickly so they will no longer negatively impact the environment.
BP has recently upgraded the soil vapor extraction (SVE) system on the Wood River site and is considering a further expansion. Petroleum products, especially lighter end ones like gasoline, easily change from liquid to vapor. Petroleum trapped underground changes to vapor over time. The SVE system uses a series of vacuum wells connected by pipes to a main unit. The wells create a vacuum that pulls the vapors into the piping system and back to the main unit where they are burned off. BP also uses a process called air sparging. The system injects air into the ground. The air causes the petroleum to change to vapor faster, pushing more vapors into the SVE system. The air sparging system also introduces oxygen to subsurface water and soils. Oxygen helps feed microbes that break down petroleum products and speed up their elimination. More oxygen means more microbes, and more microbes mean faster deterioration of petroleum.
In a number of locations, petroleum products occur in the surface and near surface soils. BP has excavated the contaminated soil in these areas and has disposed of it at landfills permitted to accept such material.
While attracting new development to the site has been slower than anticipated and sometimes things have looked quiet on the surface of the site, environmental remediation has continued on a steady pace, cleaning up acres of soils and removing hundreds of thousands of gallons of petroleum products from the groundwater per year.
Wells and pumps