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Robert A. Hubbard: Rise Gold emphasizes ‘best possible outcome’ for Noise

Local resident Robert Hubbard concludes that the Noise section of the Draft EIR is only as good as its data and is based on best-possible conditions, not real life.

This opinion piece was originally published in the Union.


The recently published draft environmental impact report for the proposed reopening of the old Idaho Maryland Mine needs careful scrutiny.

Taken at face value, it concludes that the project would have no impact on the community that could not be mitigated. The report is based on language and measurement values provided to it by Rise Gold, and is correct in its conclusions only to the degree that that language and those measurement values are correct.

The real-life conditions could be quite different from the conclusions in the report. Evaluating the level of impact should be based on worst-case conditions, not best-possible conditions.

The ambient noise levels used in the study are currently four to five years old. The operations at issue will not start occurring for several years in the future, so these noise levels will likely not reflect the actual ambient noise at the time operations actually start. The conclusions are questionable.

The Nevada County General Plan, Table 4.10-4, notes:

“(The noise) standards shall be measured only on property containing a noise sensitive land use as defined in Policy 9.8 and may be measured anywhere on the property containing said land use. However, this measurement standard may be amended to provide for measurement at the boundary of a recorded noise easement.”

Rise Gold has chosen to measure and compute noise levels at what they call “the nearest receptor,” which in the case of the multi-acre parcels surrounding the mine operations is the residence on the property located at the greatest distance from the mine operations. To provide a realistic level of the impact on the property, those measurements and computations should be made at the property boundary, rather than the far end of those properties.

The draft environmental impact report also says: “Assuming a bulldozer, grader, excavator, front-end loader and compactor were operating concurrently at the Brunswick and Centennial industrial sites, … it was assumed that all of this equipment could be operating concurrently, but that the equipment would be spread out over the sites during the site clearing/construction operations. As a result, average noise levels were predicted for the Brunswick and Centennial industrial sites … assuming the noise sources were distributed throughout the sites, … based on the closest proximity of the equipment to the sensitive receptor locations.”

This seems to be a false assumption, since these machines work jointly to accomplish their task, and would sometimes be operating in close proximity. The impact report is full of statements that use “is assumed” and “is projected to be” as given fact in arriving at its conclusions.

Sound level calculations for the the report’s tables are based on values for construction noise from The FHWA Roadway Construction Noise Model, and shown in Table 4.10-10. These values differ substantially from sound levels shown in the Noise Navigator Sound Level Database, published by the University of Michigan Department of Environmental Health Science.

For example, where the noise model shows compactor and front end loader sound levels at 80dBa, the Noise Navigator chart lists them as 92 and 93dBa. An earth scraper in Table 4.10-10 is listed at 85dBa. In the Noise Navigator chart, it is 107 to 111 dBa. The noise level values on the Noise Navigator chart are twice and four to five times those on the chart used in the impact report.

The actual machines to be used, the true sound levels of those machines, the real numbers of those machines in use at any given time, and their locations around the working locations at any given time are not actually known.

The impact report describes a sound monitoring plan that says: “If the results indicate that the county noise standards are being exceeded either by individual equipment or processes, or cumulative noise generation of the entire facility, operations shall cease until additional engineering controls can be implemented as needed.”

At this point, Rise will have sunk several million dollars into construction and development costs prior to starting operations. Are we to believe that they will just shut down until they can solve the problem, or will they continue to operate and pay fines levied as “the cost of doing business?”

These issues must be resolved before any permit is issued.


Robert A. Hubbard is retired symphony musician who lives in Grass Valley. This letter is based on comments prepared for the Nevada County Planning Commission about the Draft Environmental Impact Report.


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