RAPID CITY, S.D. (AP) — State regulators say Rapid City Regional Airport did not cause contamination when it dumped sewage on its property last month.

The South Dakota Department of Environment and Natural Resources says tests of the airport’s septic lagoon found that its contents would have been safe to spread on land had airport officials sought permission to do so.

A department spokesman tells the Rapid City Journal that regulators also determined there was “no evidence of runoff or impacts to surface water bodies” in places where wastewater was dumped. Those results were corroborated by a private firm that also conducted tests.

The airport dumped about 74,000 gallons of sewage on its property without a permit.

The airport’s executive director said the open-air lagoon was at risk of overflowing following weeks of heavy rainfall.