The Ohio EPA is now working with the U.S. EPA, the Army Corps of Engineers and private contractors to finish the cleanup, which began with an anonymous tip on Jan. 31.

EPA spokesman Abbruzzese says the biggest challenge is coming from the weather and from the process needed to clean up sediment.

“The big thing that we notice is when there are big weather events of rain events or even snow events,  that’ll obviously stir up the sediments. ... But that’s why they’re out there and that’s why they’re going to through the tributary very meticulously.”

Even after the cleanup is finished, Abbruzzese says crews will need to monitor and maintain the site with special collection and containment areas.

He also confirmed that a criminal investigation is continuing.

So far, Ben Lupo, the owner of more than a dozen oil-and-gas companies in the Youngstown area,  faces a single count of violating the federal Clean Water Act. He’s pleaded not guilty to ordering his employees to dump brine, oily residue and chemicals down the storm sewer . Investigators are trying to figure out if he did it as many as 20 times in the past year.