CEA Comments on Centennial Cleanup Plan


We all want the Centennial Site cleaned up, but the proposed plan only prepares the site for dumping more mine waste and wants to destroy habitat over sensitive areas. We can do better.


The following comments were submitted to the Department of Toxic Substances Control by Community Environmental Advocates Foundation. These comments are the result of a coalition effort that included the Wolf Creek Community Alliance and the Redbud chapter of the California Native Plant Society. In addition, CEA Foundation's law firm, Shute, Mihaly, and Weinberger, provided extensive legal comments. Learn more about the entire project here.

September 24, 2021


Dean Wright Project Manager 800 Cal Center Drive Sacramento,CA95826 (916) 255-3591 dean.wright@dtsc.ca.gov Reg: Comments regarding the Centennial M-1 RAP and MND, Project ID 60000716


Dear Mr. Wright,


Community Environmental Advocates Foundation (CEA Foundation) has been looking forward to the opportunity to fully support the cleanup of the Centennial site. This 56 acre site is only a short distance from town, and with good planning it has the potential to be developed to support smart growth within a walkable community. The central and southern portions of the property would be ideal for mixed use and medium density housing, providing a rare opportunity to meet some of Grass Valley’s housing needs as well as business and light industrial development within convenient live/work settings. It could ultimately tie in to residential development along East Bennett Rd with easy walking/cycling opportunities along East Bennett Rd and along Wolf Creek. Unfortunately, Rise Gold (dba Rise Grass Valley) has seemingly sought to use this cleanup project as a means of incorporating many of the impacts of the proposed mine. In addition to the required cleanup activities, the Remedial Action Plan (RAP) and Mitigated Negative Declaration (MND) include preparation of the site for the dumping of mine waste. Thus, rather than minimizing the destruction of valuable wetlands and riparian habitat, the RAP proposes to destroy all habitat over extensive areas.

This constitutes impacts far and above what would be necessary to simply complete the cleanup. Therefore, we cannot support the project as currently proposed. Impacts caused by the mine project should be borne by the mine project, not the cleanup project. 1. An Environmental Impact Report should be prepared for this project As presented in the RAP, all living things over a 37 acre site will be annihilated, and all surface soils will be reworked, mixed with crushed rock and compacted. The project will cause the destruction of all of the 4.35 acres of wetlands, 0.6 acres of seasonal streams and surrounding riparian habitat, woodlands, chaparral, grasslands, plus potentially cause long term impacts to local surface and ground waters, air pollution from equipment operations and fugitive dust. noise, traffic, and aesthetic degradation. On this basis alone there is a fair argument that the project may have a significant effect on the environment and an Environmental Impact Report is required.

2. None of the proposed Remedial Action Alternatives provide for preservation of ANY of the viable wetland habitat. As shown on the project “Site Map” (RAP Sheet 1, pg 131),most of the wetlands are located within the areas designated as “Borrow Areas” (RAP Sheet E2, pg 539). The soils within these areas are considered clean enough to be used as clean cover soil for the Encapsulated Mine Waste Area and areas C1-C15 and is indicated on the grading maps (RAP pgs 537-540). In other words, the reason for removing most of the wetlands and surrounding habitat appears to be simply to provide clean cover soil over the areas of treatment. None of the proposed remedial actions provide for preservation of any of the viable wetland habitat. The following Remedial Actions Alternatives should, at the very least, be evaluated:


A. Sourcing the clean cover soil entirely from off site to eliminate the need to excavate on site soil from Borrow Areas and other non-contaminated areas.

B. Identify and assess preservation of regions of the wetland habitat where feasible, such as the WTP Remainder area, and source a portion of the clean cover soil from off site to make up the difference.

C. In all Remedial Action Alternatives, minimize the impact by removal of surface vegetation in incremental steps until cover soil needs are met, concentrating on deeper soil areas and minimizing biological impacts. Since not all of the designated areas may be needed, this would reduce the impact. Finish grading can be modified to accommodate this approach. 3. No evaluations of the impacts based upon the City of Grass Valley’s Land Use Designations, Zoning, Development Code, or Public Works plans were provided. The site is within the Sphere of Influence of the City of Grass Valley, slated for “Near Term Annexation”, and adjacent to the City on three sides. The DTSC should evaluate the project with respect to the following City issues:

a. City of Grass Valley and LAFCo have the property designated as Business Park (BMP) and Urban Medium Density (UMD). Some analysis of this impact should be provided. In particular, some effort to not artificially constrain the potential best uses of the land should be made. For example, according to the RAP, a large portion of the 56 acre site is currently suitable for "unrestricted use". With the exception of a few hot spots, this includes much of the southern and western portions of the 56 acres.

The RAP should aim to delineate between the areas which are suitable for unrestricted use, and those that are not, and it should plan to designate those areas in a such a way as to avoid unnecessarily limiting the potential uses of the entire parcel. For example, the southern portion of the Encapsulated Mine Waste falls within an area designated for UMD land use. Why not modify the encapsulated area slightly to avoid limiting that future intended use? A justification for not doing this should be provided.

b. The analysis of “Aesthetics” for the project did not consider the City’s standards. However, it is the City that is surrounding much of the property and being directly impacted. The Aesthetics should consider the impacts to the City by City standards in addition to County standards.

c. Similarly, analysis of noise standards should be based on the City’s standards in addition to County standards.

d. Impacts on City infrastructure should be evaluated. For example:

  1. Does the proposed location of the Encapsulated Mine Waste impact potential Centennial Drive realignment plans, utility service line plans, and drainage plans?

  2. Will the plans for encapsulation fully allow for the City to realign the Springhill/Centennial intersection?

  3. The City may wish to evaluate the grade and location of the capped materials, recognizing possible conflicts of the encapsulated materials with the need for road development, utility trenches, pole placement, etc. in the future.

e. How does the proposed plan impact the Wolf Creek trail project?


4. The RAP is apparently based upon the presumption that the parcel will ultimately be used entirely for dumping mine waste, followed by Industrial development. The current owner, Rise Gold clearly plans to use the site for dumping mine waste. However, there is no assurance that the mine will be approved, or that the plans for dumping on the Centennial site will be a part of the mine project if it is approved.

If the RAP is intended to prepare the site for dumping of mine waste rock and tailings from the proposed Idaho-Maryland Mine, then this RAP should be incorporated in the Mine project application and Environmental Impact Report rather than treated separately. Otherwise, the cumulative impacts of the Mine project will not be adequately evaluated. But in any case, alternatives for cleaning up the site in the event that the mine is not approved must be provided.

5. The location of the encapsulated material creates potential problems for long term stability a. There exists a culvert under the built up gravel road berm on the east boundary that drains from the legacy pond to the East. The plan is to extend that culvert under the encapsulated material. It includes a transition from the existing box culvert to a round culvert, and a sharp bend in the planned culvert. This seems like a bad approach that is prone to failure in the future. b. The hydrological transmissivity of the built-up gravel road berm along the east boundary needs to be assessed. Horizontal water migration from the pond that is to the east may compromise the encapsulation, cause leaching of the encapsulated materials. Was the berm tested for transmissivity?

6. Impacts to a seasonal creek flowing from North-West property corner are not evaluated. The “Existing Drainage Culvert” system shown on RAP Figures 5, 6, and Sheets E1, E2, E3 is discontinuous and has not functioned correctly for many years.


Currently, most of the Centennial site drains from the Northwest corner of the site into the Historical Drain Towers and through a culvert. But it then discharges to the surface at the North side of the paved Di Martini access road. A portion of the original drainage system, an old, damaged 4 ft. culvert, lies across a gap, about 4 feet away from the outlet. As a result, from this point, the creek runs on the surface approximately 75 feet to Wolf Creek. This seasonal creek also appears to support two small wetlands.


During high water, a small fraction of the flow does enter the 4 ft. culvert and discharge to the point designated as the “Surface Water Discharge Point” on the plans, but it functions only as a partial discharge point during high flows.


The proposed uniform grading would dry up this creek and wetlands, and impact riparian habitat. This needs to be evaluated. 7. Further assessment needed at the Hap Warnke site Mercury was listed as a Constituent of Potential Ecological Concern (COPEC) at the Hap Warnke Lumber Mill (HWLM) site. Considering that the site will be ideal for future development, existing degraded paved surfaces should not be considered as sufficient long term protection from exposure or mobilization. 8. Public Records were not made available Despite a Public Records Request submitted by CEA Foundation for access to all public documents relating to the Centennial project, many documents were not made available for review. These include supporting technical studies such as the Asbestos Dust Mitigation Plan, technical comments that were submitted regarding the Preliminary Environmental Assessment (PEA), and relevant facts that were provided regarding City of Grass Valley Land Use designations.


9. Avoid wetland mitigations by off site wetland creation or restoration

Wetland mitigations by off site wetland creation or restoration is a poor substitute for preserving wetlands on site and avoiding the elimination of valuable habitat. If off site mitigations are utilized, they should be fully evaluated and should be at least a 2:1 replacement.


A map that shows the areas of disturbance should include the biological features. In particular, protection areas for wetlands and special species habitat such as the Pine Hill Flannelbush should be clearly delineated on the map which shows disturbance areas.


10. Additional information for inclusion in the RAP

  • Rise Grass Valley is a wholly owned subsidiary of Rise Gold Corporation, a Canadian based corporation with main offices in Vancouver, BC, but registered in Nevada.

  • Provide a clear delineation of which portions of the 56 acre site will be protected from disturbances

  • Cement used in Encapsulation Areas for stabilization should be certified as free of hexavalent chromium.

  • The statement “Nevada Irrigation District (NID) uses Wolf Creek downstream of the site as a waterway to transfer water between its canals and water distribution system.” is not correct.” (RAP pg 9) The NID canal water enters Wolf Creek above the site, near Sutton Rd, and increases the flow along the site during the periods of conveyance. This information was provided previously in PEA comments.


Thank you for your consideration of these points,


On behalf of the CEA Foundation Board of Directors

Ralph Silberstein, President

CEA Foundation

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