The following story was written and reported by Talli Nauman, Native Sun News Health & Environment Editor. All content © Native Sun News.

POPLAR, MONTANA –– Pink and yellow patches formed by squiggly lines on a map show pollution plumes extending from oil rigs toward the headquarters of the Fort Peck Assiniboine and Sioux Tribes in northeast Montana.

The pollution has reached the city limits of the tribal government seat, located in Poplar. The plumes have been advancing on the town through underground water channels ever since oil and gas drilling began back in the 1950s in the Bakken and surrounding formations of Montana’s east side.

On March 26, the U.S. Environmental Protection Agency announced that the oil companies responsible for the pollution have accepted an administrative order to pay $320,000 to the Fort Peck Tribe Water Resource as reimbursement for costs related to water infrastructure and relocating water wells.

The polluters also agreed to EPA’s request that they carry on monitoring of the tribe’s public water system, serving a population of approximately 3,000, which is 75 percent American Indian.

The court-ordered agreement “ensures safe drinking water for Poplar,” the EPA said in a news release. The signatories are Murphy Exploration & Production Co., Pioneer Natural Resources USA Inc., and Samson Hydrocarbons Co.

“These requirements will remain in effect until a new and safe source of drinking water is secured by the city of Poplar,” the EPA said.

The agreement tasks the companies with “monthly monitoring and a contingency plan to provide an alternate water source if water quality degrades to a degree posing a public health concern.”

When the pollution plumes reached Poplar in 2010, the EPA issued an emergency order under the Safe Drinking Water Act for the polluters to pay for fixing the water system and to conduct monitoring.

The companies appealed the order in December of that year. A federal judge mandated mediation, resulting in the agreement to comply with the new administrative order.

Ruination of the underground and surface water quality on the Fort Peck Reservation to date has been mapped, monitored and mitigated by a tax-supported effort of the EPA, the tribe and the U.S. Geological Survey’s Montana Water Science Center. It detected low levels of oil production contaminants, called brine, chlorides or salts, in the water supply of public and private wells around the reservation and in the Poplar River.

A team of Geological Survey scientists and partners garnered the Interior Department’s 2008 Environmental Achievement Award for tracking the pollution plumes, plugging leaking wells and disposing of brine more than a mile underground to stave off health problems.

“The remediation system has and will continue to remove contaminated groundwater from the aquifer, which is currently the only source of drinking water for Poplar residents,” noted Joanna Thamke, hydrologist for the Montana Water Science Center.

However, the EPA noted, “While treated water from the city’s system is currently safe to drink, EPA expects the quality of the groundwater used by the system’s wells to degrade over time.”

According to the EPA order, the companies’ requirements will remain in effect “until a new and safe source of drinking water is secured” by the city of Poplar. Some private drinking water wells already have been rendered useless by the plumes.

The source of the contamination is billions of barrels of highly saline wastewater containing trace metals, inorganic salt concentrations and volatile organic compounds. The EPA estimates that more than 40 million gallons of this brine, seven times saltier than ocean water, entered the drinking water over the span of five decades. The direction of the brine plumes’ movement is generally toward the town of Poplar.

“The companies will continue to monitor water quality and will take all actions necessary to maintain an uninterrupted supply of safe water to residents,” EPA’s Denver Regional Administer Jim Martin said.

Monthly samples already collected by the oil companies indicate an upward trend in total dissolved solids, chloride and sodium. Under the order, EPA and the companies have identified trigger values that will initiate action before the public water supply presents health risks.

“If these values are met, the companies will take immediate steps to secure additional treatment or provide alternative water to ensure contamination levels are below human health thresholds,” the EPA said.

A long-term alternative water source for Poplar is being developed through construction of a pipeline from the Missouri River. The city also has plans to relocate its water wells to secure a back-up supply. These efforts are expected to be completed as early as this year. Fort Peck Assiniboine and ---Sioux Tribes have taken a hands-on approach to exploit the petroleum bonanza in their 2-million-acre northeast Montana jurisdiction.

Today, more than a half-million acres within tribal boundaries are being leased to facilitate seven active drilling programs. Tribal and allottee mineral ownership encompasses over 1 million oilfield acres.

The tribes formed the Fort Peck Energy Co. to watch over permitting, leasing, drilling, production and seismic activity.

In June of last year, the tribal enterprise signed onto a joint venture with Samson Oil and Gas USA Montana Inc. for exploration and development on 90,000 acres. The contract has resulted in the drilling of two test wells to date.

The drilling is part of an oil boom that resulted in a total of 69 new wells in 2011 in Montana’s share of the Bakken-Three Forks oil formation. North Dakota witnessed the opening of 1,299 wells, and Saskatchewan 597.

To take further economic advantage of the boom, the tribes are negotiating a joint venture for a feasibility study and other first steps aimed at building a small, simple oil refinery, known as a topping plant.

(Contact Talli Nauman at talli.nauman@gmail.com)