BISMARCK — The families of two people who were killed and two others who were severely injured when heavy rains caused a massive washout of a highway culvert in July 2019 have filed claims against the Bureau of Indian Affairs and the federal government seeking unspecified monetary damages.

If the BIA does not resolve demands made in the administrative filings within six months, a lawsuit will be filed in federal court, according to Tim Purdon, a Bismarck attorney with the law firm Robins Kaplan LLP, which is representing the families of the two injured and the two killed in the washout.

The administrative claims filed by the law firm on Wednesday, Sept. 9, allege that the BIA had known since 2010 that the culvert was unsafe and needed replacing, according to a statement from Robins Kaplan.

The claims also state the BIA allowed the culvert beneath BIA Road 3 in the Standing Rock Indian Reservation to deteriorate for years prior to July 9, 2019, when flash flooding washed out the culvert and created a chasm 70 feet deep.

Four drivers, two from Mobridge, S.D., and two from the Standing Rock Indian Reservation, drove vehicles into the chasm, with two of the drivers ultimately dying and two others suffering serious injury, according to Purdon.

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The claims made this week against the BIA and the federal government were filed under the Federal Tort Claims Act, which gives the government six months to respond, according to Purdon, who said the government could deny or agree to the claims, negotiate a settlement, or not respond at all.

If the BIA denies the claims, or if the claims aren't resolved in six months, a suit will be filed in federal court, Purdon said.

A message left with the BIA seeking comment Thursday was not returned in time for publication.