DOON, Iowa -- Cleanup efforts began Friday at the site of a derailed BNSF Railway train that spilled thousands of gallons of crude oil into a swollen river in southern Lyon County near its border with Sioux County.
The derailment forced the evacuation of residents from several neighboring farms, and sent oil downstream to Rock Valley, where hundreds of workers and volunteers spent much of Friday morning sandbagging and constructing berms to protect homes on the city's west side from the flooded Rock River.
Though investigators have not yet identified the cause of the accident, local authorities believe floodwaters from the nearby Little Rock River caused the ground to weaken beneath the tracks. Standing water was visible on both sides of the tracks Friday morning.
State officials notified other downtown communities -- including Hawarden, Akron and Sioux City -- that oil could flow further south into other rivers and possibly water supplies. Humans and animals should avoid contact with the water, the Iowa Department of Natural Resources advised.
The Little Rock River is a tributary of the Rock River, which feeds into the Big Sioux River and eventually the Missouri River.
The 33-car train was heading southbound from Alberta, Canada, when it derailed around 4:30 a.m. Friday morning. No injuries were reported, said Amy McBeth, a spokesperson for BNSF.
HAZMAT teams, environmental experts and other BNSF teams arrived Friday to using containment booms and skimmers to try and prevent the oil slick from spreading further downstream.
"We're working to contain oil that spilled as close to the site as we can," McBeth said.
McBeth said she could not say how much oil the cars were carrying or how much had spilled into the water. As of Friday afternoon, the cars remained sunk in the water. Not all of the tankers were leaking, but a substantial number were, according to observers.
Depending on the size, a rail tanker car can hold about 700 barrels of crude, or nearly 30,000 gallons, according to industry figures.
Four nearby residences were evacuated as a result of the derailment and oil spill. A firefighter serving the Doon Volunteer Fire Department said he was paged at 5:46 a.m. and asked to respond to a BNSF derailment some 1.5 miles west of the intersection of 270th Street and Goldfinch Avenue.
Firefighters arriving at the scene were greeted with a strong odor coming from the train.
"I can smell it, we're a mile and a half away, and I can smell it in the air," Lyon County Sheriff Stewart Vander Stoep said.
Access to the derailment site, close to the Darwin Vink farmstead, remained open only to law enforcement personnel, firefighters and those with the BNSF. The engines pulling the train were removed from the derailment site and sat more than a mile southeast of the wreckage.
The Doon Fire Department as well as crews from the Lyon, Osceola, O'Brien and Sioux County Sheriff's Offices were all on scene, as well as the BNSF crew. The Iowa Department of Natural Resources also sent a team to monitor the situation.
In Northwest Iowa, BNSF lines run through Lyon, Sioux, Plymouth and Woodbury counties.
Rail companies are required to notify state emergency management agencies of the number of trains carrying 1 million gallons or more of crude oil through the state. Iowa Homeland Security and Emergency Management Department records show that a high of 20-30 trains per week transported crude oil on BNSF tracks through Sioux City in March 2015. That number had dropped to four or fewer trains per week by last July.
The decrease in rail transported by crude has been driven primarily by lower U.S. oil production and the use of pipelines, such as the Dakota Access Pipeline, which began carrying crude through parts of Northwest Iowa and Southeast South Dakota last year.