State and federal agencies are responding to a 23,000-gallon gasoline spill on the Southern Ute Indian Reservation near Durango that the tribe called “the largest gasoline pipeline spill in Colorado history.”

The pipeline at the center of the spill belongs to energy operator Enterprise Products, and failed on Dec. 5, 2024, near La Plata County Road 219 and Riverview Ranch Road. The area sits on Florida Mesa, hundreds of feet above the Animas River, and contains a patchwork of Tribal and private land.

Since the spill, benzene has seeped away from the spill site and has been detected 0.3 miles away from the Animas River, according to the Southern Ute Indian Tribe. Benzene is a carcinogenic and cancer-causing chemical found in gasoline.

The Colorado Department of Public Health & Environment is overseeing Enterprise’s response to the spill, and the U.S. Environmental Protection Agency is monitoring the situation due to the proximity to the Animas River.

Last week, the tribe criticized Enterprise and CDPHE for not working with enough urgency to address the spill.

“We will not stand by while our ground and surface water, tribal resources, and the health of our tribal members are put at risk,” said Tribe Chairman Melvin J. Baker. “Enterprise must treat this with the seriousness and urgency it deserves — not just from a regulatory standpoint, but from a moral and environmental one. Failure to move now will impact our water rights, wildlife, cultural sites, and properties for years to come. It is our duty as leaders and original stewards to protect the land that has been home to our ancestors since time immemorial and will be home for our future generations to come.”

According to a release, CDPHE did not visit the spill site until May 1, more than 5 months after the spill occurred.

The Tribe said that Enterprise has installed 12 cistern systems for homes in the area with contaminated wells and 15 “Point of Entry Treatment” systems, but “Enterprise still does not have a site-specific contingency plan in place to protect the Animas River.”

For its part, CDPHE has set up a webpage for the incident, and is requiring Enterprise to catalogue its progress in monthly community bulletins that are to be published on the 7th of each month. The agency is also requiring the company to submit quarterly reports going forward.

If the spill were to reach the nearby Animas River in elevated concentrations, the danger to plant, animal, and human life in the local area and potentially downstream along the river could be widespread, tribal officials said.

Throughout the process, the CDPHE has promised that “any identified threat to human health and the environment will be mitigated and immediately addressed.”

According to the May bulletin from Enterprise, the company said it will begin drone flights May 12 to detect potential spring and seep locations in the area.

“The type of cleanup technology used will depend on several site-specific factors, including the density and moisture content of the soil, as well as the concentration of constituents of concern present in soil, water, and/or soil vapor samples,” the bulletin said.

Enterprise has not commented on the spill other than directing press requests to the monthly bulletins. The company is publicly traded on the New York Stock Exchange and operates energy infrastructure throughout the country.

The pipeline that released the gas spill near Durango begins in New Mexico, passes through La Plata County, and travels through Eastern Utah north to Wyoming.

At least one family has been displaced because of the spill, according to The Durango Herald.

This is not the first time the Animas River has been threatened by a spill. In 2015, an EPA crew accidentally released 3 million gallons of acid mine drainage into a tributary of the Animas, turning it a vivid orange. The mine is still part of a Superfund cleanup site.