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Site Report: Grant Mine Site

Site Name: Grant Mine Site
Address: 1.2 Mi. St. Patricks Road, Ester Dome, Fairbanks, AK 99708
File Number: 100.38.182
Hazard ID: 731
Status: Cleanup Complete - Institutional Controls
Staff: Laura Jacobs, 9074512911 laura.jacobs@alaska.gov
Latitude: 64.880147
Longitude: -147.960172
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

Cyanide contamination of groundwater from a silt lined tailings pond used to contain waste generated by an ore processing mill. Contamination first detected in 1988. Human health hazard and extent of contamination are currently unknown. The ore processing mill has been inactive since February 1989. CERCLIS # AKD983067513. One of three (water) wells on site (thought to be a conduit for contamination to aquifer) was sealed in 5/1989. One sample of 1.26 parts per million (ppm) cyanide from monitor well "A" on 5/3/1989. Drinking water standard for cyanide is 0.2 milligrams per liter (mg/l). Site has also been subject of Notice of Violations (NOVs) for wastewater (septic) disposal. National Pollutant Discharge Elimination System (NPDES) permit AK-004348-6. Silverado entered joint venture agreement with American Copper and Nickel Co. (ACNC) in 6/1990. Also permit 8130-DB001. Cross reference file numbers 175.62.001 and 175.62.104; FKA 100.23.031.

Action Information

Action Date Action Description DEC Staff
2/13/1981 Update or Other Action (Old R:Base Action Code = PER - Permit Action at Site). Application for wastewater permit for discharge into Happy Creek. Waste disposal permit #8130-DB001 issued. Former Staff
1/9/1985 Update or Other Action (Old R:Base Action Code = PER - Permit Action at Site). NPDES permit AK-004348-6 issued. Former Staff
3/20/1985 Update or Other Action (Old R:Base Action Code = PER - Permit Action at Site). Application for solid waste disposal permit - were advised that disposal covered in NPDES permit. Former Staff
3/29/1985 Update or Other Action (Old R:Base Action Code = PER - Permit Action at Site). Application for air quality control permit. Former Staff
1/15/1986 Notice of Violation NOV issued regarding failed septic systems and advising of potential hazardous waste disposal violations. Former Staff
10/31/1986 Update or Other Action (Old R:Base Action Code = PER - Permit Action at Site). Expiration of waste disposal permit #8130-DB001. Former Staff
1/14/1988 Update or Other Action (Old R:Base Action Code = FI - Field Inspection (General)). Sampled water at site from 1/14/88 to 12/17/89. Up to 1.26 ppm cyanide (5/3/89) and 0.96 ppm arsenic detected in these samples. Discharge water from operation to pit showed up to 180 ppm cyanide (2/17/88). Former Staff
3/6/1989 Notice of Violation Issued an NOV for cyanide leakage from tailings disposal pit. Ron McCallister
3/8/1989 Update or Other Action (Old R:Base Action Code = FI - Field Inspection (General)). ADEC sampled water at site every month/two months from 3/8/89 to 9/20/89. Up to 0.03 ppm cyanide detected in these samples. Former Staff
5/15/1989 Interim Removal Action Approved (Old R:Base Action Code = SC - Site Control (Emergency Response)). Well "R" (near disposal pit dike) was sealed this date because Tri-Con concluded it to be a conduit for contamination to the aquifer. Former Staff
6/7/1989 Update or Other Action (Old R:Base Action Code = PER - Permit Action at Site). NPDES permit AK-004348-6 to expire 8/7/89. Former Staff
10/5/1989 Update or Other Action (Old R:Base Action Code = FI - Field Inspection (General)). One monitoring well installed by Aurora Drilling. Former Staff
12/1/1989 Preliminary Assessment Approved Performed by Ecology and Environment, Inc. Former Staff
6/26/1990 Update or Other Action (Old R:Base Action Code = FI - Field Inspection (General)). Water samples obtained from monitoring well, A well, and tailings pond. Results showed 0.06 ppm cyanide in pond, no detected cyanide in monitoring well and 0.13 ppm in A well. A well concentration down from 1.26 ppm (prior to sealing R well). Former Staff
7/30/1990 Update or Other Action (Old R:Base Action Code = FI - Field Inspection (General)). Monitoring well M2 installed by Aurora Drilling. Former Staff
11/28/1990 Update or Other Action (Old R:Base Action Code = FI - Field Inspection (General)). Cyanide in A well above 0.2 ppm. Former Staff
12/13/1990 Site Ranked Using the AHRM Initial ranking. Former Staff
7/26/1991 Update or Other Action (Old R:Base Action Code = FI - Field Inspection (General)). Armstrong visited site to view S02 Air process reduce cyanide solution to prescribed levels. Armstrong noted that the facility was clean and devoid of any cyanide solutions, solids, and any other toxic chemicals or hazardous waste. Ed Armstrong
7/28/1991 Update or Other Action (Old R:Base Action Code = MS - Monitoring/Sampling). RP treated 37,000 gallons of cyanide solution by S02/Air Process and discharged to tailings pond. Dissolved CN (WAD) reduced to less than 1 ppm. Dissolved CN in filtered discharge <1ppm. Unfiltered solution showed 15 ppm due to partial decomposition of ferro-cyanide complex. Former Staff
12/17/1991 Update or Other Action (Old R:Base Action Code = MS - Monitoring/Sampling). Analytical results (total CN) of water samples: Monitoring Well# A = 0.03mg/l, Well# M1 = <MDL, Well# M2 = 0.19mg/l. EPA drinking quality = 0.20 mg/l. EPA Method 335.2. Former Staff
9/30/1993 Site Added to Database Cyanide contamination. Former Staff
5/31/1994 Site Ranked Using the AHRM Reranked. Former Staff
5/31/1994 Update or Other Action (Old R:Base Action Code = RPL2 - Site Information Request Letter). Sent PRP-CS Database Notification Letter to RP requesting update and more environmental information concerning the contaminated site. RP called and then responded with updated and completed information form. Jeff Peterson
5/4/2001 Site Ranked Using the AHRM Changed Toxicity Value from 2 to 3 to reflect metals contamination. Former Staff
7/10/2002 GIS Position Updated Plotted latitude and longitude coordinates and found them to be acceptable for associated property or address. Heather Goldman
11/29/2004 Update or Other Action Reviewed file, GW monitoring results for Cyaninde below Drinking Water standards from 1990 to present with the exception of one 1992 sample result of 0.23 mg/l. Kim DeRuyter
11/30/2004 Update or Other Action Merged this file with the Tri Con file Grant Mine Site, file # 100.23.031. Also refrence file # 175.62.001 &.104. Kim DeRuyter
12/1/2004 Update or Other Action Personal Correspondence with Ed Armstrong, they hope to move this site toward closure possibly as soon as the summer of 2005. Will send soil boring reports from tailings pond. Kim DeRuyter
10/17/2006 Update or Other Action Received calls from DNR, and Ed Armstrong regarding the tailings pond at the site. Ed plans to meet later this winter to discuss a plan for capping the tailings pond. This work is expected to take place next summer. DNR is working with ADOT to approve use of some clean gravel from the site for roadwork in the Ester area. Kim DeRuyter
5/27/2008 Update or Other Action Mailed letter to RP requesting current status of the site. Tamara Cardona-Marek
5/29/2008 Exposure Tracking Model Ranking Initial ranking with ETM completed. Tamara Cardona-Marek
6/11/2008 Update or Other Action Received call from Dan Basketfield. Sampling has taken place quarterly or semiannually at the tailings pond. Tri-con will be meeting with Shannon and Wilson to submit a plan for cleanup and closure. Tamara Cardona-Marek
6/16/2008 Meeting or Teleconference Held Met with Dan Basketfield and Shannon and Wilson onsite. Discussed the plan that will be proposed for site cleanup. Plan will include a one time permit for disposal. Contaminated soil will be excavated and site capped and revegetated. Tricon will send previous monitoring reports and will present proposal to FNSB and DEC for approval (expected in 2009). Tamara Cardona-Marek
6/27/2008 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed. Tamara Cardona-Marek
7/8/2013 Update or Other Action Site symbol visually adjusted using ArcGIS and documents from file. 64.880147, -147.960172. 7/8/13; MLB. Michelle Barnes
4/28/2017 Update or Other Action Sent letter to Ed Armstrong with Tri-Con Mining inquiring about cleanup plan. Requested response by May 31st. Janice Wiegers
5/15/2017 Update or Other Action Letter to Ed Armstrong returned undelivered. Sent another letter to Roger Burggraff, listed as the registered agent in the state corporations database. According to this database, Tri-Con Mining has been involuntarily dissolved. Letter requested response by June 30th. Janice Wiegers
6/23/2017 Update or Other Action Mr. Burrgraf called in response to the letter sent by DEC staff. A meeting is planned for the week of June 26th. Laura Jacobs
1/16/2018 Meeting or Teleconference Held ADEC staff met with RP's agent to discuss current status of mine site and tailings pond. Monitoring wells -1,-2, and -3 have been sampled through time after cyanide-laden tailings effluent was mistakenly routed near a drinking water well. That well has been grouted closed and monitoring well sample results have been consistently clean. Agent plans to work with consulting company Shannon & Wilson to finalize a closure plan for the tailings pond. Laura Jacobs
4/20/2018 Meeting or Teleconference Held DEC staff met with the RP and their Qualified Environmental Professional to plan approach to cap the tailings impoundment and then how to complete site characterization of released tailings to groundwater. Laura Jacobs
5/15/2018 Potentially Responsible Party/State Interest Letter PRP letter sent to BLM. Laura Jacobs
5/16/2018 Meeting or Teleconference Held Meeting to discuss closure options with agent for Silverado and TriCon Mining, consultant Shannon & Wilson, DNR Mining, Land and Water staff, and DEC Solid Waste staff. Laura Jacobs
5/17/2018 Potentially Responsible Party/State Interest Letter PRP letters sent to DNR Lands, Silverado Gold Mines Inc. and Tri-Con Mining Inc. Laura Jacobs
6/21/2018 Update or Other Action DEC staff received an update on whether the tailings are considered qualifying for the Bevill Amendment by EPA staff. Shannon & Wilson, consultant to the RP, received a decision that the mine tailings are solid wastes from the extraction, beneficiation, and processing of ores and minerals. The tailings are not considered hazardous wastes based upon the exclusion outlined in 40 CFR 261.4 (b) (7), and the cyanide present would not be a characteristic waste based upon the reactivity characteristics (40 CFR 261.23). Laura Jacobs
8/2/2018 Document, Report, or Work plan Review - other ADEC staff reviewed "Work Plan Grant Mine Tailings Impoundment Closure, Ester Dome, Alaska, July 2018" from Shannon & Wilson. Work objectives include confirming drainage ditch competency, ground trothing 1996 topographic survey, measuring moisture content of tailings, re-developing monitoring well M-1, collecting soil samples around the perimeter of the primary tailings impoundment and within the secondary tailings impoundment, and collecting groundwater samples from monitoring wells M-1 and M-2 to determine current cyanide levels in the groundwater. Laura Jacobs
8/10/2018 Document, Report, or Work plan Review - other ADEC staff received a revised work plan from Shannon & Wilson, for the proposed site characterization work to be conducted at the Grant Mine in Ester. Laura Jacobs
11/15/2018 Meeting or Teleconference Held ADEC met with Shannon & Wilson, R Burggraf, ADNR Lands Section staff P Burns and T Meares to discuss sample results from monitoring well sample event in 2018 and other work at the site. Plans are to have Shannon & Wilson complete a report and make a case for what happens to move forward towards eventual closure. Laura Jacobs
5/3/2019 Document, Report, or Work plan Review - other ADEC staff reviewed the Site Characterization Report, Grant Mine Tailings Impoundment, Fairbanks, Alaska, April 2019. The updated Conceptual Site Model describes the remaining mine tailings in the primary tailings impoundment as the main exposure medium of concern. Exposure pathways include direct contact with tailings or groundwater leading to potential incidental ingestion and dermal absorption of contaminants. Shannon & Wilson recommends capping be considered as the appropriate corrective action for the site. Laura Jacobs
9/19/2019 Document, Report, or Work plan Review - other After coordination with the Alaska Department of Natural Resources, and the Solid Waste Program of ADEC, Contaminated Sites Program staff issued a letter approving of the revised site characterization report and proposal to design an engineered cap for the primary tailings impoundment after tailings from the secondary impoundment have been transferred to the primary tailings impoundment. Laura Jacobs
10/17/2019 Site Visit Arranged to visit the Grant Mine site to view the current tailings removal from the secondary tailings impoundment. DNR Mining, and Lands staff met ADEC staff, RP and RP's consultant. Site is almost ready for confirmation testing. ADEC and Shannon & Wilson have decided that Incremental Sample Method is appropriate for three decision units within excavation area. Three discrete soil sample near the southern portion of impoundment, and six discrete samples from the side walls outside of excavation for confirmation samples. Laura Jacobs
4/20/2020 Document, Report, or Work plan Review - other Staff from ADEC Solid Waste Program, Contaminated Sites Program, and Alaska Department of Natural Resources - SAIL consolidated comments for the Closure and Capping Plan (conceptual at this time), and the Secondary Tailings Impoundment Excavation report. Agency staff have agreed that the remaining levels of metals in the secondary tailings impoundment excavation area are below background levels for arsenic and cleanup levels for all other metals. Agency staff have agreed that the closure and capping plan can be approved as a conceptual design until final engineered design plans are available. Laura Jacobs
5/13/2020 Document, Report, or Work plan Review - other ADEC staff completed comments for the report "Groundwater-Quality Assessment Summary, Grant Mine" and issued an approval of the report with one comment to be addressed in the final capping and closure plan. Laura Jacobs
1/14/2021 Document, Report, or Work plan Review - other A request to consider decommissioning the groundwater monitoring wells resulted in a technical review of the groundwater data for free cyanide at the Grant Mine site. Because one of three sample events returned a sample with free cyanide above the ADEC groundwater cleanup value, additional sample events will be required before closure can be considered. Laura Jacobs
5/11/2021 Document, Report, or Work plan Review - other ADEC received six documents from the RP's consultant for Dam Stability, Mine Closure Memo, Closure Detailed Design Report, Opinion of Probable Construction Costs, Mine Closure and Capping Plan, and Grading Plan. When final and approved, these documents will be included in the record. Laura Jacobs
6/11/2021 Document, Report, or Work plan Review - other ADEC staff from Solid Waste Program and the Contaminated Sites Program reviewed the version R2 of the Grant Mine Primary Mine Tailings Impoundment Final R2 Capping and Abandonment Plan submitted to our office June 10, 2021. The capping plan is the culmination of regulatory guidance and requirements of ADNR and ADEC programs for the approved abandonment of the primary tailings impoundment at Grant Mine. This approval is the first step in moving the site towards a Best Interest Finding. Groundwater monitoring will continue for two more times: June and September to document three consecutive sample results for Free Cyanide below the ADEC Groundwater cleanup level. Laura Jacobs
6/14/2021 Document, Report, or Work plan Review - other ADEC issued a CORRECTION letter to revise some language that was not entirely correct in the first approval letter. Laura Jacobs
9/16/2022 Document, Report, or Work plan Review - other The Monitoring Well Decommissioning Work Plan was reviewed and approved for decommissioning of the two monitoring wells installed to monitor groundwater contamination downgradient of the Grant Mine tailings release to an upgradient groundwater supply well. Laura Jacobs
10/7/2022 Site Visit A site visit was made to view the final capping contours of the primary tailings impoundment and the secondary tailings impoundment. Erosion control channels were constructed to redirect potential high runoff events around the capped facility. Laura Jacobs
11/10/2022 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 71710 tailings pond. Laura Jacobs
11/15/2022 Meeting or Teleconference Held Discussions with the consultant regarding the closure report submitted 11/4/22 occurred remotely. Additional comments were sent by email on this date. Laura Jacobs
11/16/2022 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 71710 tailings pond. Laura Jacobs
5/16/2023 Meeting or Teleconference Held Attended Public Meeting for the Public Notice of Preliminary Decision for Restricted Use Authorization for ADL 421226 - RP's name - Grant Mine Primary Mine Tailings Impoundment Closure Restricted Use Authorization was held in the evening of May 15, 2023. Staff representing ADNR Mining, Land and Water were present, as well as the RP's consultant. No members of the public attended. Laura Jacobs
6/14/2023 Meeting or Teleconference Held A request was made by the public to hold another informational session by DNR SAIL, and an extension of the comment period to June 20th. DEC staff attended the second information session hosted by DNR on June 13th. Five members of the public attended. A presentation was made by DNR SAIL, followed by discussion and questions. Laura Jacobs
7/31/2023 Workplan Requested A letter requesting additional work at the site was sent. Based upon a review of the administrative files, DEC is requesting some additional monitoring to demonstrate that contaminated groundwater is not spreading from the now-closed supply well known as the Burggraf Well or the capped impoundment. Laura Jacobs
9/12/2023 Update or Other Action DEC staff received DNR's Final Finding and Decision document for the Grant Mine Restricted Use Authorization ADL 421226 and a copy of the signed Environmental Covenant for the capped tailings impoundment on the site. Laura Jacobs
3/29/2024 Document, Report, or Work plan Review - other DEC approved the Revised 2023 Groundwater Sampling Report as submitted. Groundwater samples were collected from wells M-1, M-2 and M-3 on September 22, 2023. Depth to water measurements were collected to further define the groundwater gradient. The resulting calculations indicated groundwater-flow direction to be to the east. Completion of a conceptual site model for the geology in the area underlaying the tailings impoundment was requested. Arsenic was the only analyte to be above the DEC groundwater cleanup levels during this sample event. Background concentrations of arsenic in groundwater in the Ester Dome area have been documented as elevated. The levels of arsenic in groundwater surrounding the tailings impoundment were considered to be within the range of background arsenic levels for the area. Free cyanide was not present in detectable concentrations in groundwater samples. Laura Jacobs
5/24/2024 Institutional Control Record Established Institutional Controls established and entered into the database. Laura Jacobs
9/18/2024 Document, Report, or Work plan Review - other DEC reviewed the 2024 Monitoring Well Decommissioning Report which describes the decommissioning of monitoring wells (M-1, M-2, M-3, ADNR-1, and the Trailer Housing Well) in accordance with the June 2016 Alaska Best Management Practices – Maintaining or Decommissioning Water Wells and Boreholes prepared by the Groundwater Protection Stakeholder Workgroup and the approved May 16, 2024 Monitoring Well Decommissioning Work Plan. Wells were decommissioned July 25, 2024. Included in the report were the Alaska Department of Natural Resources Well Record of Decommissioning Forms and photographs of the completed activities. DEC approved the report as submitted. Laura Jacobs
9/19/2024 Cleanup Complete Determination Issued DEC has completed a review of the environmental records associated with the Grant Mine Site. Based on the information provided to date, it has been determined that the contaminant concentrations remaining on site do not pose an unacceptable risk to human health or the environment and no further remedial action will be required as long as the institutional controls are maintained and effective, and no information becomes available that indicates residual contamination poses an unacceptable risk. Laura Jacobs
9/19/2024 Exposure Tracking Model Ranking A new updated ranking with ETM has been completed for source area 71710 tailings pond. Laura Jacobs

Contaminant Information

Name Level Description Media Comments
Antimony - Total > Human Health/Ingestion/Inhalation Soil
Arsenic - Total > Human Health/Ingestion/Inhalation Soil
Cyanide > Human Health/Ingestion/Inhalation Soil
Manganese Between Method 2 Migration to Groundwater and Human Health/Ingestion/Inhalation Soil
Mercury - Total Between Method 2 Migration to Groundwater and Human Health/Ingestion/Inhalation Soil
Silver - Total Between Method 2 Migration to Groundwater and Human Health/Ingestion/Inhalation Soil

Control Type

Type Details
Environmental Covenant Environmental covenant for capped tailings pond signed 9/11/2023.

Requirements

Description Details
Other Grantor, its successors and assigns, all present and subsequent owners, and current and future occupants, lessees or other persons holding or acquiring an interest in the Property shall not take any of the following actions without prior written approval from DEC: 1)Any action that may negatively impact or interfere with either the response action or any operation, maintenance, inspection or monitoring of that response action (18 AAC 75.395). "Response action" shall mean "any action taken to respond to a release or threatened release of a contaminant, including mitigation, cleanup, or removal."
Other Grantor, its successors and assigns, all present and subsequent owners, and current and future occupants, lessees or other persons holding or acquiring an interest in the Property shall not take any of the following actions without prior written approval from DEC: Any action that may increase the risks to human health, safety, welfare, or to the environment at the Property. This includes, but is not limited to, any activity that results in the release of residual contamination that was contained as part of the remedial action or that creates a new exposure pathway for residual contamination remaining on the Property.
New Construction Restrictions Grantor, its successors and assigns, all present and subsequent owners, and current and future occupants, lessees or other persons holding or acquiring an interest in the Property shall not take any of the following actions without prior written approval from DEC: Construct, modify, or use buildings on the contaminated area of the Property.
Excavation / Soil Movement Restrictions Grantor, its successors and assigns, all present and subsequent owners, and current and future occupants, lessees or other persons holding or acquiring an interest in the Property shall not take any of the following actions without prior written approval from DEC: Grade, excavate, dig, till, or otherwise disturb the contaminated area of the Property.
Restricted to Industrial / Commercial Land Use Grantor, its successors and assigns, all present and subsequent owners, and current and future occupants, lessees or other persons holding or acquiring an interest in the Property shall not take any of the following actions without prior written approval from DEC: Use the Property for residential purposes including child day care, educational facilities, playgrounds, hospitals, or similar facilities.
Subdivision Restriction Grantor, its successors and assigns, all present and subsequent owners, and current and future occupants, lessees or other persons holding or acquiring an interest in the Property shall not take any of the following actions without prior written approval from DEC: Subdivide or replat of the Property.
Maintenance / Inspection Of Engineering Controls Grantor, its successors and assigns, all present and subsequent owners, and current and future occupants, lessees or other persons holding or acquiring an interest in the Property shall: Ensure the engineered feature is inspected every month for five years between the months of April through October following closure and maintained as needed to prevent contact by humans or animals with subsurface contaminated soil, and to prevent the infiltration of water and potential leaching of contaminants. Following the first five years, the engineered feature will be inspected once every five years. Grantor shall report any damage to the engineered feature to DEC using the contact info below within ten (10) days after discovery. Gran tor shall ensure the engineered feature is repaired as quickly as possible. Documentation of the repairs shall be submitted to DEC within 30 days after discovery.
When Contaminated Soil is Accessible, Remediation Should Occur Grantor, its successors and assigns, all present and subsequent owners, and current and future occupants, lessees or other persons holding or acquiring an interest in the Property shall: Notify DEC if contaminated soil on the Property becomes accessible in the future, characterize the contamination, and, if determined necessary by DEC, cleanup the soil pursuant to DEC's Site Cleanup Rules
Advance approval required to transport soil or groundwater off-site. DEC approval is required prior to moving soil where contamination remains above applicable cleanup levels. If DEC approval for movement is granted, any moved soil must still be characterized and managed following regulations applicable at that time.
Movement or use of contaminated material (including on site) in a manner that results in a violation of the water quality standards is prohibited (18 AAC 70) Movement or use of contaminated material in a manner that results in a violation of 18 AAC 70 Water Quality Standards is prohibited.

No associated sites were found.

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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
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