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Site Report: Treadwell Mine Complex

Site Name: Treadwell Mine Complex
Address: Douglas Island along Gastineau Channel; S of Douglas, Douglas, AK 99824
File Number: 1538.38.007
Hazard ID: 25594
Status: Active
Staff: Nick Waldo, 9074655270 nick.waldo@alaska.gov
Latitude: 58.269813
Longitude: -134.378573
Horizontal Datum:WGS84

We make every effort to ensure the data presented here is accurate based on the best available information currently on file with DEC. It is therefore subject to change as new information becomes available. We recommend contacting the assigned project staff prior to making decisions based on this information.

Problems/Comments

From 1891 until 1922 the Alaska Treadwell Gold Mining Company managed the mine complex, which was operated by three financially-separate mining companies. Ready Bullion Mine and 700 Foot Mine were operated by the Alaska United Gold Mining Company; Mexican Mine, operated by the Alaska Mexican mining Company; and Treadwell Mine of the Treadwell Gold Mining Company. The four mines produced a total of 20.7 million tons of gold-bearing ore during their operations years. Pit mining was utilized at first, although by 1906 all mining activities were being conducted in underground tunnels. Mined ore was brought to the surface by a central hoist and distributed to the separate mills on the shore of Gastineau Channel. The Mill Sites of concern for this contaminated site record include: the 300 Treadwell Stamp Mill Site adjacent to Sandy Beach and the former Concentrating House; the 240 Treadwell Stamp Mill Site located next to the powerhouse site and below the Glory Hole (Fed by Paris Creek); the 700-Foot Mine Mill Site located below the foot trail and above Gastineau Channel and the The Ready Bullion Mill located south and east along Gastineau Channel beyond the Mexican Mine, away from Douglas. Milling operations included both mercury and cyanide ore processing and if present in the tailings may present an exposure risk. Addendum to Site Assessment Report - Savikko Park by Nortech Environmental Engineering Inc. submitted for the CBJ as an assessment of the western portion of the course sandy mine tailings on the shoreline of Savikko Park. Laboratory results confirmed that levels of RCRA 8 Metals are below DEC Method Two cleanup levels, with the exception of Arsenic. Arsenic was detected in samples at levels ranging between 3.59 and 6.79 mg/kg. As noted in the previously submitted Site Assessment Report (January 2013) by Nortech for the CBJ, the level of arsenic detected is within historical background levels for the Juneau area. Based on information in the Report, in 2013 DEC requested that CBJ continue the site assessment of coarse, sandy mine tailings at the Treadwell Mine Complex site using the same sampling methodology and analysis plan for the remaining shoreline of Sandy Beach in Savikko Park eastward to the cave-in site. The shoreline is extensively used by the residents of Juneau and Douglas and deserves the same level of attention. Hazard ID 25594 (file no. 1538.38.007) was created on 12/16/2010 to track information on all portions of the Treadwell Mine Complex, except the Mexican Mine Mill Tailings site. For all work recorded for the Mexican Mine Mill Tailings portion of the complex, refer to Hazard ID 405 (file no. 1538.38.001). Environmental Protection Agency (EPA) ID AKD981767387; EPA site name Treadwell Mines.

Action Information

Action Date Action Description DEC Staff
8/26/1993 Update or Other Action Treadwell Mine Complex was entered on the CS Database as a result of a DEC investigation by E&E that documented the presence of elevated levels of lead, zinc, arsenic and mercury in soil and surface water. Bruce Wanstall
11/10/1994 Update or Other Action Ranked with the Alaska Hazard Ranking Module (AHRM) resulting in high priority site. Bruce Wanstall
11/1/1999 Update or Other Action Re-ranked. Changed Air Exposure index from 0.2 to 1.0; Release Information Value from 0.2 to 1.0; and Quantity Value to 2.1. The unknown quantity value is based on the elevated arsenic levels at the cyanide tailings area. Volume or areal extent unknown. Bill Janes
11/12/1999 Update or Other Action Re-ranked. Changed the Value for Environmental/Recreation Area from 0 to 3 based on the fact that the entire complex is probably about a mile long. At one end is the Sandy Beach recreation area, a City park. Sandy Beach is comprised of old Treadwell mine tailings. At the other end is the cyanide mill tailings area. Obvious stress to vegetation because no vegetation is growing there. Bruce Wanstall
1/18/2001 Update or Other Action CERCLIS ID # AKD981767387. History: state-lead Discovery 3/1/87, PA 6/23/89, SI 6/30/91. Site Reassessment federal lead 6/30/99 thru 9/18/00. Bruce Wanstall
2/15/2002 Update or Other Action Project tickler update - Reviewed SI data. Conferred with department risk assessor regarding potential health risks. Sent email to Program Manager recommending that we move on further investigation and probable cleanup. Bill Janes
12/15/2003 Update or Other Action GW values changed to minimals. GW not used in the area. Bill Janes
12/17/2010 Site Added to Database A new site has been added to the database for the 240, 300 and 700 mill processing sites in the Treadwell Mine historical mine district site. The former database record for the Treadwell Mine Complex is the record for the Mexican Mine cyanide tailings site. Mitzi Read
7/1/2011 Site Visit DEC Juneau staff conducted a site visit to the intertidal lands offshore from the Treadwell Mine 240 and 300 mill sites where ore processing waste tailings are located. The tide was slack to minus four feet below mean low tide. DEC was accompanied by members of the Douglas Indian Assn Tribal Response Program to collect samples of buried sediment and interstitial (pore) water from discrete locations in Gastineau Channel. The clams and worms observed at sample collection sites appeared to be healthy. Samples will be laboratory analyzed for mercury and arsenic that were identified as contaminants of concern in previous site investigations. Bruce Wanstall
11/9/2011 Exposure Tracking Model Ranking Initial ranking with ETM completed for source area id: 79095 name: 240 and 300 Ore Processing Stamp Mills Bruce Wanstall
11/21/2011 Meeting or Teleconference Held A meeting was held at City Hall in Juneau with deputy City Manager Kim Keifer and staff, Douglas Indian Assoc Tribal Response Program manager Eric Morrison and DEC/CS Manager Schlichting and staff to discuss the results of pre-Phase I environmental sampling conducted in July 2011, the scope of recommended additional sampling, and funding opportunities in the Brownfield competitive grant program. Bruce Wanstall
11/22/2011 Update or Other Action DEC is requesting assessment of waste rock (tailings) on the Treadwell Mine Complex property for water, sediment and soil contamination stemming from historical processing of hard rock mining ore to extract precious metals. The targets of the assessment are the mineral processing chemicals mercury and cyanide and naturally occurring arsenic. If these chemicals are mixed with the waste rock tailings in sufficient concentration and are exposed by erosion or by excavation they may present an exposure risk to human health and ecological life at each trophic level. Bruce Wanstall
9/18/2013 Document, Report, or Work plan Review - other DEC reviewed and approved by letter sent today Addendum to Site Assessment Report - Savikko Park by Nortech Environmental Engineering Inc submitted for the CBJ as an assessment of the western portion of the course sandy mine tailings on the shoreline of Savikko Park. Laboratory results confirmed that levels of RCRA 8 Metals are below DEC Method Two cleanup levels, with the exception of Arsenic. Arsenic was detected in samples at levels ranging between 3.59 and 6.79 mg/kg. As noted in the previously submitted Site Assessment Report (January 2013) by Nortech for the CBJ, the level of arsenic detected is within historical background levels for the Juneau area. Based on information in the Report, DEC requested that CBJ continue the site assessment of course sandy mine tailings at the Treadwell Mine Complex site using the same sampling methodology and analysis plan for the remaining shoreline of Sandy Beach in Savikko Park eastward to the cave-in site. The shoreline is extensively used by the residents of Juneau and Douglas and deserves the same level of attention. Bruce Wanstall
11/18/2013 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 79095 Milled Ore Tailings. Source Area includes the Gastineau Channel Sandy Beach shoreline between the Savikko Park parking lot and the cave-in site next to the Mexican Mine. Extends into the channel as far as the pump house on the intertidal mud flats. Bruce Wanstall
7/16/2014 Site Characterization Report Approved Douglas Indian Association Tribal Response Program "Sandy Beach Sampling Data Report" by Ridolfi Environmental approved by B. Wanstall. Sampling took place from April 29 to April 30, 2014. Julie Fix
9/1/2016 Site Characterization Report Approved Douglas Indian Association Tribal Response Program "Sandy Beach Sampling Data Report" by Ridolfi Environmental approved by B. Wanstall. This sampling event was performed on behalf of the Douglas Indian Association. Sampling took place from June 7-8, 2016. Julie Fix
2/15/2017 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 79095 Milled Ore Tailings . Bruce Wanstall
3/21/2022 Update or Other Action ADNR places Leaseholder Location Order (LLO) on state tide and submerged lands including this site. LLO #45 applies to this site; contact information for the affected mining claim has been added to the affiliates tab. Julie Fix

Contaminant Information

Name Level Description Media Comments

Control Type

Type Details

Requirements

Description Details
Hazard ID Site Name File Number
405 Mexican Mine Mill Tailings 1538.38.001

Missing Location Data

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State of Alaska Department of Environmental Conservation

P.O. Box 111800
Juneau, AK 99811-1800
Phone: 907-465-5066
Fax: 907-465-5245
TDD: 800-770-8973
Physical Location: 410 Willoughby