Cleanup of radioactive well equipment is set to be underway March 13 in North Dakota following the discovery of filter socks illegally dumped within the city limits of Williston, N.D.

Green Diamond Environmental Trucking Services LLC contracted Absorbent & Safety Solutions LLC, a licensed radioactive materials transporter, to remove roughly 100 new and used filter socks in North Williston, state officials said.

Filter socks are essentially large strainers used primarily during saltwater disposal operations. The netting can become radioactive when it contacts drill cuttings of naturally occurring radioactive material.

Green Diamond Trucking is renting the location where the filter socks were found and has agreed to cover the costs of clean-up unless other responsible parties are identified. The company has told state officials a subcontractor likely dumped the filter socks there and that the company has since been out of contact, said Alison Ritter, a spokeswoman for the North Dakota Oil and Gas Division (OGD).

The socks were found in a grassy area next to a large shop Green Diamond occupies. The company had allowed its subcontractor to use the area for equipment storage.

The owner “has not seen subcontract in months. Green Diamond is doing the responsible thing and cleaning up the filter socks,” Ritter said.

Ritter said it isn’t clear if any penalties will be levied. Improper disposal of the filters can result in fines of up to $12,500 per day.

Ritter said investigation into the subcontractor and the well operator is underway.

A resident contacted the state March 9 about possible filter socks left in Williston. An ODG investigator confirmed the filter socks were present and contacted Williston city officials and representatives from the North Dakota Department of Health to assist in locating a responsible party and beginning proper clean-up and disposal operations.

Field tests indicate the level of radioactivity of the socks is slightly above the background radioactivity level at the site. They do not pose a threat to the public unless they are improperly handled or material from the socks is ingested.

The incident is the first reported improper disposal since the OGD began requiring covered, leak-proof, labeled containers at well sites beginning June 1. Permit requirements were tightened to prevent illegal dumping of the filters after incidents of illegal dumping of filter socks. In April, the OGD had to pay to remediate filter socks abandoned at a gas station in Noonan, N.D. Those items were eventually sent to Idaho for disposal.

Permits now require companies to have covered, leak-proof containers designated for filter sock disposal onsite at saltwater disposal wells during the drilling, completion and flowback phases of all new spud oil and gas wells.

Disposal containers must then be collected by a licensed waste hauler and disposed of at an authorized facility.