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FAQ: Idaho-Maryland Mine

By Community Environmental Advocates Foundation

Updated: December 3, 2022

Idaho-Maryland Mine Frequently-Asked Questions

What is the mine reopening proposal?

Rise Gold, a junior mining company with questionable experience, submitted an application to restart mining operations at the old Idaho-Maryland Mine in Grass Valley. Initially, the mine will be dewatered and some operational structure will be built on the surface. Then, underground development will begin. The permit application describes a drill and blast regime to remove 1,500 tons of rock per day. Operations will take place 24 hours a day, 7 days a week for the 80-year life of the project. The main processing facilities will be on the corner of Brunswick Rd and E. Bennett. Mine operations would create approximately 2.4 million cubic yards of mining tailings and rock waste deposited at two locations. An additional site will be located closer to downtown Grass Valley at the old Idaho-Maryland Mine location along Idaho Maryland Rd.

What are the potential impacts of the mine?

Even using the most current mining technologies and techniques, gold mining is an inherently high-risk venture with potentially negative impacts. Chief among them are concerns about water quality and quantity due to mine dewatering, significantly higher levels of noise and vibration impacting local residents, truck traffic, and increased levels of dust and industrial emissions that impact air quality locally and contribute to greenhouse gases. The prospect of replacing open forested areas with two huge mining waste piles threatens local wildlife and quality of life for neighbors. Neighbors also may have impacts to wells and lowered property values.

Read more about the top 8 reasons to stop the Idaho-Maryland Mine.

Where is the mine? Do the mineral rights extend beyond the borders of the site?

The mine would be located at two sites; the Brunswick Industrial Site is 119 acres, at the junction of East Bennett Street and Brunswick Road and along Brunswick Rd. This is where the ore processing facilities and mine access shafts are planned. The second, 56-acre Centennial site, which was the site of the old Idaho-Maryland Mine and processing facilities, is along Idaho-Maryland Rd, east of Centennial Drive.

Map of mining site locations

As shown in the map below, the underground mineral rights cover a huge area, about 2585 acres. These mineral rights extend west under Highway 49 and completely under Sierra Nevada Memorial Hospital, east of Brunswick Road under the Nevada County Airpark, north as far as Plaza Drive in Glenbrook Basin, and to Highway 174 and much of Cedar Ridge. The subterranean mining operations can potentially include all of this area and to within 200 feet of the surface.

Map showing mining site boundaries (red) and mineral rights boundaries (orange)

Who is the lead agency in the government?

Nevada County Planning Department is the lead agency preparing the EIR (Environmental Impact Report) pursuant to CEQA (California Environmental Quality Act) guidelines. Raney Planning & Management, Inc. is the consulting firm selected by Nevada County Supervisors to provide expert analysis and draft the EIR. Multiple Nevada County and City of Grass Valley departments will review the work in progress and draft EIR submittals including Planning, Engineering, Transportation, Environmental Health, Fire Departments, and County Sheriff, and outside agencies such as Fish and Wildlife.

How does the decision process work?

The decision will be made by the five members of Nevada County Board of County Supervisors. A majority vote of 3 is needed to approve or reject the project. The County Planning department is preparing two reports to inform the Supervisors' decisions: 1) an Environmental Impact Report (EIR), which is required and regulated by the California Environmental Quality Act (CEQA), and 2) an Economic Impact Report that isn't required by regulation, but was commissioned by the Nevada County Board of Supervisors to help with decision-making. Both reports rely on independent consultants to review information provided by the applicant (Rise Gold) and assess the impacts.

How far along are we in the decision process?

A Draft Environmental Impact Report was released in early 2022 and the community submitted over 1,100 applicable comments. Experts found massive flaws in the DEIR. We are currently waiting for the County to release a revised version. Learn more about the community's response here.

An Economic Impact Report was released in November 2022. Learn more here.

A decision is currently anticipated in 2023, but because this is a complex process, we can't predict with certainty. See the County's current schedule.

How will the mine impact our local creeks and rivers?

At the Brunswick site, the first sixth months of mining operations would include “dewatering” the abandoned mine shafts by pumping 3.6 million gallons of water daily into South Fork Wolf Creek. Once the mine is dewatered, 1.2 to 3.6 million gallons per day (1.9 to 5.6 cfs) will be pumped from the underground workings to maintain the dewatered state.

Before discharging into the creek, the water would need to be treated to remove the metal contaminants. This water treatment facility will have to operate in perpetuity to prevent the discharge of contaminated water, even after the mine closes in 80 years. These high, artificial water discharges into the creek will disrupt the natural flow regime in the creek, disturbing the life cycles of the organisms that sustain the ecology of this riparian corridor.

It should be noted that it is not possible to predict the full effect that dewatering will have on the underground hydrology in the vicinity with absolute certainty. This includes nearby wells, the creek, riparian zones, and subterranean groundwater.

How will the mine impact air quality?

Nevada County already gets and "F" for air quality today. Mining operations would produce additional exhaust emissions from trucks and equipment, and dust from ore processing operations, trucking, grading, and compacting of the “engineered fill” as mine waste rock and tailings are deposited at the two planned locations. Air pollution from the chemical discharges associated with mining activities are anticipated. There will be impacts from the use of ammonium nitrate, the explosive used to blast new shafts and tunnels through the bedrock to develop the mine workings. Significant greenhouse gas emissions will be generated by the mine because tremendous amounts of energy are used to extract tons of rock from depths up to 5000 feet below surface level and pulverize them to extract the ore.

Asbestos is a naturally occurring mineral of the subterranean rock of this area. Mine tailings and waste rock brought to the surface for processing and disposal will result in asbestos being released into the air as fine dust particles. The most common exposure pathways for humans are through water and air. Other contaminant emissions from the prior contaminated soils on the site are also of concern.

Many people in the area live on wells. How will the mine impact water quality and quantity?

Since the closure of the Idaho-Maryland Mine in 1956, residential neighborhoods have developed around the site. There are approximately 300 homes within a 1000-foot radius of the mineral rights boundary area that rely on wells to supply their water. And over 500 within a 1/2 mile. The geology of this area contains networks of fractures and faults in the rock that fill with water and provide water to local wells. The recent experience of the local San Juan Mine demonstrated that mining can have unpredictable consequences for wells near its operations. Should wells fail or become contaminated as a result of mining activity, affected households would have to connect to another water supplier, most likely NID. The impacts and scope of this problem are unknown. Rise Gold’s own hydrology study identifies about 200 wells that are predicted to have a drop in ground water levels, and this study has a number of shortcomings.

Alarmingly, well owners and agencies like the Nevada Irrigation District (NID) found the protections described in the Draft Environmental Impact Report (DEIR) to be woefully inadequate. Read The Union newspaper's coverage: ‘Hung out to dry’: Well owners contend with Idaho-Maryland Mine report’s findings.

How will the mine impact noise and vibration in the area?

Construction of the above ground facilities will last for 18 months. Unregulated construction noise may occur 7 days a week for the duration of the construction.

Once mining operations commence, underground blasting and mining operations will continue 24 hours a day for 80 years. Vibration from heavy equipment operations, blasting and other mining activities, will transmit through the ground to nearby residences. Haul trucks will transport rock between the New Brunswick mine access shaft and processing site on East Bennet to the Centennial site. This will increase traffic and noise along Brunswick Rd and Whispering Pines Blvd. Grading and compacting with heavy equipment will occur on both sites.

How will the mine affect traffic?

Waste rock and tailings haul trucks will make up to 100 roundtrips a day, 7 days a week, from 6:00 AM to 10:00 PM which equates to about one heavy truck passing every 10 minutes all day, every day. The trucks will use Brunswick Rd to reach Whispering Pines lane and to access Hwy 49. Additional truck trips will transport fuel oil, diesel fuel, explosives, large amounts of cement for backfill, and other supplies, as well as gold mining concentrate transported out of the area for further processing.

Mine operations would entail two shifts a day for 300 workers travelling from and to the Brunswick site. The safety hazards from heavy haul truck traffic during winter conditions and destruction of local roads from the heavy haul truck traffic are of concern.

How will the mine affect real estate/ property values?

“Projects with unknowns like mining projects hurt values. Perception becomes reality.” (Local real estate agent, 8/3/2020) The projected impacts associated with the Rise Gold Idaho-Maryland Mine (IMM) and the Centennial Mine Cleanup projects include noise, dust, and dewatering of the mine into Wolf Creek. This could impact water tables and well performance. In addition, the project description notes up to 100 dump truck loads daily from the IMM to the Centennial site. Questions regarding impacts to homeowners and their property could lead to weakness in property values. When another mining company proposed to reopen IMM between 2005 and 2012, new homes near the proposed site saw a dramatic value decline.

How can the public be involved?

These are ways residents can be involved.

  1. Get informed and keep updated about the proposed mine.

  2. Visit

  3. Subscribe to our eNewsletter

  4. Follow us on Facebook, Instagram, or NextDoor groups

  5. Browse articles, videos, and meeting recordings in the MineWatchNC Library.

  6. View information on the County Website.

  7. Share what you’re learning about the mine with others. The more public attention this proposal receives, the more the application process will reflect the interests and concerns of the people who must live with the decision the County makes about the mine. A good way to get shareable news is to follow us on our public Facebook page (per Facebook rules, the private group listed above doesn't allow sharing),

  8. Influence the decision-making process. Read the guide about how to submit public comments to the Nevada County Board of Supervisors.

How do changes in zoning to allow mining impact the nature of the surrounding community?

The current zoning at the Brunswick Industrial Site is M1-SE, Light Industrial. Rise Gold has requested a zoning change to M1-ME Light Industrial with Mineral Extraction to allow for surface mining facilities related to the underground mining operations. Numerous buildings are planned, covering 122,000 feet. Many of the structures planned are large, including a 6-story tall 425’ long mineral processing facility along Brunswick Rd, and a headframe structure reaching 16 stories tall.

Properties surrounding the Brunswick Industrial Site are zoned RA-1 to RA-5 and are primarily residential. Many parcels overlook the proposed site and may be significantly impacted by noise and dust generated at the site. Since the mine will operate 24/7, 365 days/year, this could have consequences for livability and property values in the area.

Properties surrounding the Centennial Site are Commercial/Industrial, Business Park, and undeveloped Medium Density Residential designation. Anticipated heavy truck traffic of up to 100 roundtrips per day to the Brunswick Industrial Site would significantly impact this area.

The City of Grass Valley has the Centennial Site in its near-term annexation plan. The County’s Industrial zoning classification for the Centennial Site on Idaho-Maryland Rd, is inconsistent with the Grass Valley Zoning designation of Business Park and Medium Density housing. The mine project’s level of cleanup for planned mine waste deposits will alter future possible land use of this site unless the city reaffirms its zoning in advance of the project.

Have other companies tried to re-open mines in the area? What were the results?

Canadian junior mining company Emgold Mining attempted to open the Idaho-Maryland Mine in the 2005-2012 timeframe, submitted a Draft EIR which was not adequate, and failed to complete a second Draft Environmental Impact Report due to environmental concerns and financial problems.

The San Juan Mine (Siskon) opened and was forced to shut down in 1995 after a disastrous draining of local wells due to mining. The impacts of this failure are still felt amongst the residents. Wells were permanently damaged.

A mine in nearby Sutter Creek opened in 2013, but after only a brief period of operation the mineshaft flooded and the operation shut back down in 2014.

What is the Centennial site, and how is it related to the Rise Gold proposal?

The Centennial property covers 56 acres and is located at 10344 Centennial Drive in Grass Valley, along Idaho Maryland Road. It is currently County land, but the City of Grass Valley has included it in their near-term annexation plans. Up until its closure in 1956, the site was the primary processing and access site for the Idaho Maryland Mine. The site now contains over 270,000 cubic yards of legacy tailings material.

A significant portion of these tailings have excessive contamination. Reports from the DTSC determined that lead, arsenic, nickel, and mercury are present at hazardous levels and must be removed regardless of whether the mine project is approved or not.

An agreement between Rise Gold and the California Department of Toxic Substances (DTSC) mandates that the contaminated tailings be cleaned up, and a work plan is being prepared. This cleanup project permit is a separate project from the mine permit. After the cleanup is done, the mine proposal includes dumping more mine waste on this site.

Note that if the mine is approved, even the tailings that are not hazardous must be removed and then later mixed into the new mine waste, as they are not structurally suitable for a base layer for the “engineered fill” of the proposed mine waste pile.

Who is Rise Gold?

Rise Gold Corp is a 15 year old company that has never opened a mine and never made a profit. They are publicly traded corporation incorporated in Nevada, but their headquarters have always been in Vancouver, British Columbia, Canada. They've gone through multiple name changes. They originally purchased the mine under the name Rise Resources, Inc., then the name was changed to Rise Gold Corp in April 2017. Rise Gold Corp is an exploration stage mining company whose principal asset is the historic past producing Idaho-Maryland Gold Mine located in California, USA, which it purchased in January of 2017. The CEO for Rise Gold Corp is Benjamin Mossman, a Canadian mining engineer based in Vancouver, Canada. Rise Grass Valley is a wholly owned subsidiary of Rise Gold Corp, also incorporated in Nevada. It was formed in 2017 and is the named applicant for the permit application.

Read more about why Rise Gold shouldn't be trusted.

Where will the tailings piles be located? Will they be visible?

One of the piles of waste rock and tailings will be close to downtown, covering most of the former 56-acre Idaho-Maryland Mine site along Idaho-Maryland Road and west of Centennial Way. This former mine site is now called the Centennial Site. The pile will be up to 7 stories high covering 44 acres and would likely be visible from the Centennial Business Park area and residential units off of Sutton Way. The hospital should have a pretty good view of it, and also drivers along the Hwy 49/20 Freeway. It would be visible from the proposed Dorsey Marketplace apartments looking across the Wolf Creek valley. Bicyclists and walkers along the proposed Wolf Creek trail on I-M Road will find it looming to the south, right across the creek.

The second tailing pile will be located at the southern portion of the main processing area on Brunswick Road. It will cover 31 acres and be up to 9 stories high (90 feet), so it will be plainly visible from quite a few of the rural/residential homes and empty lots surrounding neighborhoods, including the new subdivision currently under construction diagonally across the intersection. It will be also visible by anyone driving along Brunswick Road.

How does the Environmental Impact Report (EIR) process work?

Once Nevada County Planning determined an EIR was required, the County needed to prepare a scope of work based on the applicant’s (Rise Gold’s) project description and submittals. A consulting firm was selected to complete the EIR. In July 2021, County Planning prepared a NOP (Notice of Preparation) to inform the community about the project. Included in the NOP was information about the location, project description, an issues list and brief description of each, and details about the project’s operational profile. The NOP gave the community a minimum of 30 days to review the project and identify issues and concerns that needed to be addressed by the consultant during the EIR process and in the final document. Our community submitted over 750 comments.

These comments were reviewed by the lead agency and handed off to the consultant. The ADEIR (Administrative Draft EIR) was prepared for review by the lead agency (review is typically 90 days), their comments and requests lead to a Draft EIR. The DEIR was published on January 4, 2022 and made available for public comments. A public hearing was held by the Planning Commission on March 24, 2022. An extended comment deadline was given and the community submitted comments by April 4, 2022. Learn about the community response here. Our community submitted over 1,100 legitimate comments and subsequently submitted over 5,500 opposition petition signatures to the County Supervisors.

The County is still reviewing comments on the DEIR. All of the comments from the public have to be addressed and all the questions answered. Typically, changes based on comments are then made to the DEIR by the consultant to produce the Final EIR. However, agency, city, community, and legal reviewers found the significant flaws in the report and are calling for a recirculation of the report before moving to the final draft. The community is currently waiting for the County's final decision on what form the next version of the EIR will take.

When completed, the Final EIR again undergoes County Departments review, Planning Department review, and Planning Commission Hearings, and Board of Supervisor Hearings. The Board of Supervisors ultimately vote on whether to approve the project. The County's current schedule can be found here. Watch a video to learn more about how the environmental report process works.

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