Midnite Mine Superfund Site Cleanup on the Spokane Indian Reservation Continues to Progress

Details
Published: Monday, 17 January 2022 18:16

Background

The Midnite Mine Superfund site is a 350-acre, inactive uranium mine located on the Spokane Indian Reservation. A legacy of the Cold War, uranium mining from 1954 to 1981 left more than 33 million tons of waste rock, unprocessed ore and low-grade ore (also known as protore) laced with contaminants. Contaminants include radionuclides and heavy metals resulting from mining, transport activities and related operations.

Human health issues such as cancer effected tribal members that worked on the mine or were exposed to radioactive dust brought into homes, lands and other facilities due to poor safety protocols and equipment.  Tribal members are currently warned against eating fish from Blue Creek, using creek water in sweat lodge ceremonies, or eating wildlife such as elk and deer.

After mine closure, legacy issues included two large open pits partially filled with water and several pits backfilled with waste rock. In addition, contaminated surface water and groundwater from the pits entered Blue Creek, which flows 3.5 miles to the Spokane River (also known as the Spokane Arm of Lake Roosevelt and the Upper Columbia River).

After years of litigation and regulatory activity, the mine was added to the superfund list in 2000, EPA selected a cleanup plan in 2006, Newmont and Dawn mining companies were found liable in 2008, and cleanup of the site began in 2016.

Cleanup Activities to Date

This is a snapshot of cleanup activities. A tremendous amount of engineering and complex construction is occurring to achieve these results.

  • Strategically, mine waste is primarily being consolidated into the two largest open pits (called Pit 3 and Pit 4).
  • Pit 4 has been lined at the bottom with drain rock and vertical wells installed. The wells are needed to assure contaminated water from on-going seepage and groundwater can be transferred to a water treatment plant. Currently, contaminated water from the pit is being moved to the south pond. In addition, the pit has been backfilled to about 85%. In 2022, backfilling will be completed and the capping and revegetation process will begin.
  • Pit 3, the largest open pit at the mine, will begin to be backfilled in 2022 by placing drain rock, a liner and starting to build the vertical wells.
  • The water treatment plant built in 1988 will continue to operate until 2023. This plant will be torn down and placed into the pits along with the waste rock under the water treatment site. Treated water from the plant is currently discharged directly into a tributary to Blue Creek.    
  • In 2022, a new water treatment plant will begin construction and is expected to be operational in 2023. In addition to operational improvements, the new plant is designed to treat less contaminated water because the need for ongoing treatment will decline as cleanup in Pits 3 and 4 are complete. Newmont Mining will be responsible for operating the water treatment plant in perpetuity.
  • In 2021, construction began on a closed pipeline that will move effluent from the new water treatment plant to the Spokane River via a route that hugs Blue Creek. Once discharged into the river, the water quality in “the mixing zone” will meet tribal water quality standards as dilution takes place. Completion of the pipeline is expected in 2022.

Completion of the cleanup activities is scheduled for 2027. After that, on-going monitoring will be used to determine if additional cleanup is needed.

Technical Assistance Needs Assessment

In 2021, EPA also conducted a Technical Assistance Needs Assessment (TANA) for the community near the Mindite Mine site. The goal is to identify additional community outreach and support that EPA can offer.

Tribal members cited overcoming mistrust of the U.S. government, concerns of racial bias, and receiving mixed messages as among their concerns. Providing more robust and regularly updated outreach materials, regularly scheduling in-person meetings, and using “plain language” with graphics to explain information more clearly were among the recommendations. There were also calls for a health study to address ongoing health concerns of tribal members.

The TANA was released in November and available at https://semspub.epa.gov/work/10/100369943.pdf

EPA 2021 MIDNITE MINE CLEANUP STATS

CONSTRUCTION

  • Crushed 500K CYDs of material
  • Place 1.5 million CYDs of mine waste into Pit #4 WCA
  • South Pond and pump station commissioned
  • Pumped 22.5 million gallons of water from Pit #3 to South Pond
  • Installed 10,500 ft of HDPE pipe
  • Paved 2,400 ft of two-lane road
  • Awarded $20 million contract for the construction of the new water treatment plant
  • Treated 66 million gallons of water as of Nov. 3, 2021. Discharged 45 million gallons under NPDES permit

WORKFORCE

Employed 112 people

Employed ~ 55 tribal members

71 construction workers

Operated:

  • 12 x CAT 745 haul trucks
  • 6 x CAT excavators
  • 2 x fuel trucks
  • 4 x bull dozers
  • 2 x water trucks

Maintained our equipment at overall operational readiness rate over 90%

126,000 hours worked without a lost time accident or fatality