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|Site Type: Non-NPL
ZIP Code: 80424
EPA ID: CO0001093392
Congressional District: 2
Updated March 2014
The U.S. Environmental Protection Agency is conducting the first five-year review of cleanup actions performed at the French Gulch site near Breckenridge, Colorado. The purpose of the review is to make sure the selected cleanup actions effectively protect human health and the environment. The review is scheduled to be completed by summer 2014.
The French Gulch site, which includes the former Wellington-Oro mine, is located about two miles upstream or east of the confluence of French Creek with the Blue River near the town of Breckenridge, Colorado. Extensive underground mining occurred in the valley from the late 1850s to the 1960s. Lode mining recovered lead-zinc-silver sulfide and gold ores from an extensive network of tunnels and adits originating on the steep valley sides. Large floating dredge boats were used to placer-mine the valley floor for gold. The placer dredging disrupted French Creek and its associated alluvial valley material. This resulted in large dredge piles covering the French Gulch valley floor and extending upstream approximately one mile east of the former Wellington-Oro mine.
Ore veins targeted by the underground mines are commonly associated with faults and fractures that serve as a conduit for groundwater flow. In 1934 the mine workings were reported to consist of more than 12 miles of tunnels. In the 1940s, the present owner, B&B Mines, acquired the Wellington-Oro properties.
Sporadic mining and milling operations occurred at the mine from the late 1940s to the early 1970s. Since this area contains a large quantity of sulfide-bearing minerals, these conditions promote the formation of acid mine drainage. This is caused by the oxidation of sulfur in the presence of water, forming sulfuric acid in the mine pool water which makes the water acidic. Metals such as cadmium and zinc are soluble in acidic water. As a result, acid mine water flowing through the mine workings becomes highly contaminated with dissolved metals, exits the mine in the form of seeps, and enters French Creek.
Elevated zinc concentrations in the seep water are primarily responsible for the absence of fish populations in the downstream portion of French Creek and a segment of the Blue River. EPA investigations in the late 1980s determined that the Wellington-Oro Mine pool was the major contributor of zinc and cadmium load from French Creek into the Blue River
In 1998 mine wastes including roaster fines, tailings, and waste rock were removed from the mine site to an area with reduced potential for human contact. The materials were capped with impermeable clay and clean gravel. Drainage ditches were installed to reduce infiltration of rain and snow melt into the mining wastes. This material provides little or no contribution to the contamination of French Creek and the Blue River.
|Media Affected||Contaminants||Source of Contamination|
|water, aquatic species and habitat||zinc and cadmium||acid mine drainage from Wellington-Oro mine pool|
Beginning in 1989, EPA conducted numerous investigations into surface wastes, groundwater, surface water, geology, ecology, and precipitation. Surface water and groundwater sampling was initiated in an attempt to determine the source(s) and magnitude of metal contamination present in the water and migration pathways leading to French Creek and the Blue River. Based on data collected from 15 sample locations, the Wellington-Oro mine pool was found to be the major contributor of zinc and cadmium load from French Creek into the Blue River.
A natural seep identified as FG-6C is the primary conduit of mine pool water into French Creek. Additional unidentified seeps may also be present. The seep flows year round at an average rate of approximately 100 gpm (gallons per minute) except during spring runoff when flows have been measured as an average high of 500 gpm. The high metal concentrations of zinc and cadmium in the FG-6C seep water have the greatest effect on aquatic species.
The average cadmium and zinc concentrations at FG-6C are 59 µg/l (micrograms per liter) and 123,000 µg/l, respectively, and are much higher than brown trout can tolerate. The pH of the seep water is 6.4, which is slightly acid (neutral water has a pH of 7). The presence of limestone formations in close proximity to the mine workings adds alkalinity to the groundwater after it has dissolved high levels of metals, thereby neutralizing the high pH in the seep.
In October, 2002, EPA signed an Action Memorandum selecting semi-passive water treatment with settling ponds as the preferred cleanup remedy. The remedy was to treat 300 gpm of water contaminated with zinc and cadmium. The cleanup goal was toeduce metals loading from French Creek into the Blue River to support a sustainable brown trout fishery in the Blue River directly downstream of the confluence with French Creek by:
Reduce metals loading from French Creek into the Blue River in order to support a sustainable brown trout fishery in the Blue River directly downstream of the confluence with French Creek.
- Improving the water quality in French Creek.
- Limiting the concentration of dissolved cadmium and zinc in the Blue River to 4.0 µg/l and 225 µg/l, respectively.
EPA amended the 2002 Action Memorandum based on the adoption of site-specific water quality standards in French Creek and the Blue River and to allow for alternative water treatment technologies. The new proposed alternative while similar to the original would reduce the treatment of contaminated water to150 gpm.
In May 2003 the Summit Water Quality Committee submitted a Use-Attainability Analysis, Lower French Gulch and the Blue River Downstream from French Gulch near Breckenridge, Summit County, Colorado report to the Colorado Water Quality Control Commission. It provided documentation for site-specific water quality standards in the Blue River. This study concluded that aquatic habitat in the Blue River was severely impacted by historic dredge mining. Although sections of the Blue River have been restored, habitat is limited to supporting adult brown trout.
Revisions to the water quality standards were approved by the Colorado Water Quality Control Commission and are summarized below:
- In French Creek, below the Wellington-Oro mine to the confluence with the Blue River, are existing water quality conditions since water quality impacts from historic mining could not be reversed.
- In the Blue River, for approximately 3 miles downstream from the confluence with French Creek, the standard was revised to 4.0 µg/l for cadmium. The zinc standard is based on mineral hardness with a range between 500 to 800 µg/l.
As part of the Town of Breckenridge and Summit County's Golden Horseshoe Open Space Purchase, a settlement was reached that provided for the construction of a water treatment plant at the Wellington-Oro mine. The Wellington-Oro mine was included as part of the 1,800 acres purchased from B&B Mines.
Based on the settlement agreement and changes to the water quality standards, water treatment was proposedand implemented based on the following components:
- A water treatment facility was designed and constructed, and is operated by the town of Breckenridge and Summit County. EPA oversaw the design and construction, and oversees operations.
- Water discharging from the Wellington-Oro mine at seep FG-6C would be collected and pumped to the water treatment facility at the Wellington-Oro mine.
- The maximum pumping rate is150 gpm. During spring runoff, flows are expected to exceed this pumping rate. It is expected that flows exceeding 150 gpm will bypass the treatment process and flow into the Blue River.
- A physical/chemical process is used to remove contaminants from the water. The treatment process is based on cost, performance, reliability, sludge disposal, and operator preferences.
- The effluent water quality discharged is to have a cadmium concentration of less than 4 µg/l and a zinc concentration of less than 225 µg/l. Solids generated from the treatment process will be separated from the water prior to discharge. The metal sludge generated is disposed of into the abandoned mine workings, sold as a metal concentrate, or disposed of into a solid waste landfill.
- Treated water is discharged into the French Creek watershed.
- A physical barrier constructed in French Creek prevents non-native trout from migrating from the Blue River into upper French Creek.
- The water treatment system is operated 24 hours per day, 7 days per week until water discharges from FG-6C no longer pose a risk to the environment.
The cleanup remedy is to be considered successful if five years after treatment water quality in Segment 2a of the Blue River meets the standards for zinc and cadmium.
Since the mid 1990s a citizen's advisory group called the French Gulch Remediation Opportunities Group (FROG) has met to discuss cleanup actions for the Wellington-Oro mine. Over the years the group has been actively involved with EPA and the State of Colorado in identifying cleanup options for French Gulch. Most recently, the group organized an effort to conduct a use attainability analysis in order to modify the standards for French Creek and the Blue River. In addition, the FROG facilitated the acquisition of the property once owned by B&B Mines. The land has been purchased by Summit County and the Town of Breckenridge to be set aside as open space. The FROG is no longer meeting since the conclusion of this purchase has resulted in a consent agreement which embodies the cleanup goals identified in the amended Action Memorandum. Both the Town of Breckenridge and Summit County will assume responsibility for implementing the cleanup of contaminated water from the Wellington-Oro mine Site.
Remedial Project Manager
U.S. Environmental Protection Agency, Region 8
1595 Wynkoop Street (8EPR-SR)
Denver, Colorado 80202-1129
800-227-8917 ext. 312-6095 (toll free Region 8 only)
State Project Manager
Colorado Department of Public Health and Environment
Hazardous Materials and Waste Management Division
4300 Cherry Creek Drive South
Denver, CO 80246-1530
888-569-1831, ext. 3413 (toll free)