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Callahan Mine Superfund Site Community Update July 2018

Calahan Mine EPA Superfund Site Update

The United States Environmental Protection Agency (EPA) and Maine Department of Environmental Protection (MEDEP) continue their efforts to implement the cleanup of the Callahan Mine Superfund Site.

The major accomplishment to date in 2018 has been the award of a contract for the performance of the cleanup work. The United States Army Corps of Engineers (USACE), working for EPA, awarded a contract to Environmental Quality Management, Inc. The EQM team has substantial expertise in mine closure design and remediation. The initial phase of the work includes activities to stabilize and grade the tailings impoundment in preparation for the installation of the cover system. Other activities that will be performed include periodic maintenance of the horizontal drain installed in 2015 to drain water from the tailing pile, flow measurements, water level measurements, and water quality sampling of the horizontal drain, bioreactor, and groundwater.

EQM will be developing detailed plans for the work to be performed over the next several months. As part of the development of the plans, there will also be an evaluation to determine how much of the existing rock at the Site that was left behind after mining activities could be used in place to reduce or eliminate the need for blasting to produce the needed rock. In addition, the following activities will take place in 2018:

  • Periodic inspections of the completed work along with performance sampling of the
    passive bioreactor and measurement of flow and water levels in the Tailings
    Impoundment;
  • Sampling of residential wells;
  • Groundwater sampling; and
  • Continued progress on the design of the sediment cleanup and overall site restoration;

2019 Plan: Looking ahead to 2019, EPA anticipates the following activities:

  • Continued periodic inspections of the completed work along with performance sampling
    of the passive bioreactor and measurement of flow and water levels in the Tailings
    Impoundment;
  • Sampling of residential wells;
  • Groundwater sampling;
  • The initiation of the cleanup work for the Tailings Impoundment, including the
    stabilization of the outer wall by lowering the wall; installing wick drains; and shaping
    the tailings to create a platform for the final cover system;
  • Rock crushing activities could begin in winter 2018/2019; and
  • Completion of the design for the sediment cleanup and site restoration.

Background

The Callahan Mine Superfund Site is located in the Town of Brooksville, Hancock County, Maine. The Site is the former location of a zinc/copper open-pit mine. The mining operations were conducted adjacent to and beneath Goose Pond, a tidal estuary.

The major mining operations occurred from 1968-1972, although there were some limited mining activities from 1881 to 1887. For the open-pit mining operation, two dams were constructed at the saltwater inlet and freshwater inlet of Goose Pond. Fresh water that normally flowed into Goose Pond was diverted south to Weir Cove via a drainage ditch. Goose Pond was subsequently drained to allow for the excavation of the mine. After the mining operations ended in 1972, the dam at Goose Falls was opened, flooding the mine site. The ore contained zinc, copper, lead, and trace silver along with cadmium and arsenic. Figure 1 shows the operational areas for the Callahan Mine during operation. The Site includes the following areas:

  • A 21-acre tailings impoundment containing the process waste from the floatation mill.
    Three waste rock piles covering about 27 acres and containing overburden rock and low
    grade ore: Waste Rock Pile 1 (19 acres); Waste Rock Pile 2 (6 acres); and Waste Rock
    Pile 3 (2 acres).
  • The former processing facility (Mine Operations Area).
  • The ore storage area (Ore Pad).
  • Goose Pond estuary and associated wetlands.
  • A mine pit and associated shafts and adits, which are all under Goose Pond. The pit was
    600 feet wide and 320 feet deep at the end of the mining activities.Callahan Mine Superfund Site USEPA

The Site was listed on the National Priorities List (“NPL”) on September 5, 2002. EPA began the Remedial Investigation and Feasibility (“RI/FS”) for the Site in 2004, although some preliminary RI/FS activities began in 2003. In June 2005, the Maine Department of Transportation (“MaineDOT”) took over the RI/FS pursuant to an Administrative Order on Consent (“AOC”) between EPA and the State.

Based on the September 2009 EPA Record of Decision for Operable Unit 1 (“OU1”) and September 2013 Explanation of Significant Differences (“2013 ESD”), EPA is implementing the cleanup for the Callahan Mine in three distinct phases.

Phase 1 (Operable Unit 1)

Cleanup of the arsenic, lead, and thallium contamination in several residential properties along with the cleanup of the PCB contamination in the former Mine Operations Area. As part of the Phase 1 actions, the waste rock and remnant ore at the Ore Pad was removed and placed on the Tailings Impoundment. The Phase 1 (Operable Unit 1) cleanup actions were completed in 2013.

Phase 2 (Operable Unit 2)

Study of the groundwater contamination and waste rock outside the major waste areas. This component of the cleanup is still in the investigation phase.

Phase 3 (Operable Unit 3)

Stabilization of the Tailings Impoundment and removal of sediments and soils from the salt marsh and southern portion of Goose Pond and placement of the excavated sediments and soils into an on-site Confined Aquatic Disposal Cell (former Mine Open Pit). The Phase 3 cleanup is being implemented in two components. The first is the stabilization of the Tailings Impoundment. The design for this work was completed in 2015 and the cleanup began in 2015 with the installation of a horizontal drain to facilitate drainage of the Tailings Impoundment. The work to stabilize the Tailings Impoundment will continue through 2018. The design for the sediment cleanup is ongoing and should be complete in 2018. Figure 2 shows the areas that have been identified for cleanup actions.

More information about the Callahan Mine Superfund Site can be found at the EPA website: www.epa.gov/superfund/callahan.