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Mine Waste and the Water Pollution Problem

The Final EIR for Rise Gold’s Idaho-Maryland Mine is inadequate because it fails to address the potentially significant impact of mine waste disposal.


January 10, 2023

The Mine project plans to export 1000 tons of tailings and waste rock per day. This mine waste will be dumped into 2 Engineered fill piles over the course of the first 11 years. After that, the mine waste will be disposed of through off-site sales. There are significant issues with the disposal of mine waste due to the potential to pollute groundwater and surface waters by leaching hazardous chemicals. This falls under the jurisdiction of the Regional Water Quality Control Board. The Water Board classifies mine waste by Groups A, B, and C. Only Group C, which has relatively low levels of contaminants, is clean enough to be used for off-site sales. Groups A and B require more stringent controls. The Water board requires mine waste testing to determine classification. In response to the Draft EIR, the Water Board stated: “The applicant shall not sell or utilize waste rock and tailings from the Project for construction aggregate or fill purposes offsite unless such material has been tested and confirmed to qualify as Group C mining waste...” [1] In the EIR, the Water Board and numerous other parties identified that there was insufficient testing to determine whether the mine waste would be Group C, suitable for off-site sales. Per the Water Board comments:

“...the alternative scenario that the mining waste is not suitable for off-site use should be examined.” The Water Board goes on to state that Rise should assess any constraints or challenges associated with waste disposal in case they can’t do off-site sales for construction aggregate. They conclude with: “The Draft EIR should be revised to address this comment.”[3]

Rise Gold acquired a collection of drill cores and samples from Emgold Mining when they purchased the mine. In addition, they did over 67,500 linear feet of exploratory drilling. Yet, from all those samples, they chose to test only 11 feet to characterize what will be over 25 million tons of waste rock that will be produced over the life of the mine. [2] Disposal of mine waste is a critical element of the project with the potential for causing significant long term impacts. Yet no further testing was produced for the Final EIR. This is inexplicable. CEQA requires that the EIR “…give the public and decision makers the most accurate and understandable picture practically possible of the project’s likely near-term and long-term impacts.”[4] This Final EIR fails to do that.

--- You are being asked to approve a project without knowing if any portion of the mine waste will qualify as Group C. Currently, there is no realistic plan for continued mine operations if you can’t sell the mine waste.

The Final EIR response uses speculative, unproven assumptions stating that the mine rock “...would not be mined until mine waste characterization has been performed to ensure the rock will be suitable for off-site sale. Rock types that are not suitable for off-site sale would likely not be mined, and if mined, the waste rock would be placed underground” [5].

Mine waste classified as Group A and B requires specific management that must be determined by the Water Board, and cannot automatically be placed underground.

Backfilling with waste rock and tailings is the exact scenario which has led to polluted ground water discharges in so many mines in our area. This new element, the placement of Group A or B mine waste underground, was not included in the Draft EIR.

Even disposal of mine waste on the project sites for Engineered fill (Centennial for 5 years, Brunswick for 6 years) requires testing and will have to meet the Water Board’s approval. Quoting the Final EIR:

“The barren rock and sand tailings would undergo testing as part of obtaining [Water Discharge Requirements] WDRs for use in the Engineered fill pads, and compliance with water quality objectives will need to be demonstrated to the [Water Board ] prior to that placement .” [6]

The project description fails to provide an adequate means of interim storage for mine waste.

The viability of the entire project is dependent upon the safe disposal of mine waste under Group C. There were numerous core samples available that could have undergone static and long-term dynamic testing, yet, subsequent to the release of the Draft EIR, no additional testing was done.

Even if the mine waste is all Group C, it is hard to believe there will be no need to stockpile any of it for shipping off site.1,000 tons/day will be coming out of the shaft. That’s about 50 truck loads/day. Construction aggregate is seasonal. Most construction shuts down in the winter.

The Final EIR is inadequate because if fails to address the potentially significant impact of mine waste disposal. Again, critical testing after project approval does not provide an “…accurate and understandable picture…of the projects likely…impacts”.



[1] FEIR Page 2-61 (p134)

[2] 1000 Metric tons per day x 365 days per year x 75 years = 27,375,000 tons.

[3] FEIR Page 2-233, 234

[5] FEIR Page 2-60

[6] FEIR Page 2-59, 2-60 Master Response 11


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