Guille said that BP — Amoco’s successor company — and the DEQ are working together to find the source of the sheens. BP is also putting together a plan to to find the contamination source. According to the release, that plan may include:

checking a barrier wall between the refinery site and the river for leaks

increasing the pumping rates for wells inside the barrier wall that pump oil from the surface of the groundwater

installing similar pumping wells outside the barrier wall

using ground-penetrating radar to find piping and other structures that could be the source

excavating along the barrier wall to find possible leaks.

A ruling by a U.S. district judge in January 1998 ordered Amoco to build a barrier wall around the old refinery property. Soon after, the company entered into an agreement with the city and Natrona County in which it set aside $60 million for redevelopment of the property and got a guarantee that the former refinery site would not be used for residential development. If it had been, Amoco would have had to clean up the site to a higher standard.

Over the course of 80 years, about 30 million gallons of crude oil and refined hydrocarbons — or three times what the Exxon Valdez spilled off the Alaskan coast in 1989 — spilled onto the refinery’s grounds, according to a previous Star-Tribune report.

No sheens were visible to a reporter who walked a length of the river Thursday afternoon. A pair of people strolling along the river also said they had not noticed any oil in the water.

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