| Subject | Potential
Impacts | Mitigation Measures |
| Aesthetics |
| Aesthetics | Significant and Unavoidable
The project would result in noticeable changes to the existing visual character of the project sites. | | Applicant must submit a Final Landscape Plan prepared by a licensed professional for review and approval by the Nevada County Planning department. Plan must include larger (24 gallon) tree plantings for screening purposes. |
| Light or Glare | Less than significant
Pole and building mounted exterior LED lighting at the Brunswick Industrial Site is fully shielded and "dark-sky approved". Photometric model shows no illumination from lighting beyond property boundary. | | None Required |
| Agricultural and Forestry Resources |
| Agriculture | No Impact | | None Required |
| Timberland | Less than significant | | None Required |
| Air Quality |
| Greenhouse Gas Emissions - Construction | Less than significant after mitigation
The project would exceed threshold of 1,100 tonnes CO2 during construction activities | | Applicant would maintain equipment in accordance with manufacturers specifications, employ the use of alterative fueled construction equipment where feasible, provide onsite utility electricity hookups, encourage use of carpools or other methods to reduce construction worker commutes, use locally sourced or recycled material with goal of 20% based on cost of building materials and volume for paving materials, minimize concrete use for paved surfaces or utilize low carbon concrete.
Purchase carbon offsets for CO2 emission of 2,664 tons above the threshold prior to issuance of grading permits. |
| Greenhouse Gas Emissions - Operations | Less than significant
The project would not exceed threshold of 10,000 tonnes CO2 per year during operations. | | None Required |
| Odors | Less than significant
The project would not result in odors that would adversely affect the public | | None Required |
| Air Emissions | Less than significant after mitigation
Estimated emissions of ROG, NOx, & PM10 are all below significance threshold level C of the local air quality district. | | Use of alternatives to open burning of vegetation, grid power shall be used where feasible, and temporary traffic control during construction to improve traffic flow. Activities scheduled to direct traffic to off-peak hours when practical. Diesel engines over 50 hp to be certified Tier 4F engines when commercially available. |
| Human Health | Less than significant after mitigation
Health risk assessment, using extremely conservative thresholds of the local air quality district, shows that the project effect on human health is less than significant. | | Asbestos dust mitigation plan required. Plan requires dust control measures on grinding mills, crushers, conveyors and transfer points. Dust mitigation plan required including removal of track-out material from vehicles, tire washing of earthwork vehicles exiting site, wetting or covering active storage piles, onsite speed limit of 15 mph on unpaved surfaces, watering as necessary to prevent visible dust emissions from leaving property boundary. |
| Biological Resources |
| Special Status Plants | Less than significant after mitigation
Pine Hill Flannelbush located on Centennial Industrial Site. | | Preservation of majority of Pine Hill Flannelbush plants and conservation easement over area of plant preservation.
Compensatory mitigation of disturbed plants to ensure no net loss. |
| Special Status Wildlife | Less than significant after mitigation
No Special-Status Wildlife observed in field studies. | | Pre-construction surveys for bat roosting, coast horned lizard, yellow and red-legged frog, western pond turtle, California black rail, and nesting raptors. |
| Wetlands | Less than significant after mitigation
~0.57 acres of wetlands to be filled by construction at Brunswick Site. | | Compensatory mitigation of permanent wetlands impact to ensure no net loss. |
| Stream & Riparian Zones | Less than significant after mitigation
~0.11 acres of permanent impacts for construction and installation of storm water system.
Temporary impacts to install discharge pipe and culverts.
No biological impact from discharge of treated water to South Fork Wolf Creek. | | Compensatory mitigation of permanent stream impact to ensure no net loss.
Management plans for work within 100 ft non-disturbance buffer zone. |
| Cultural Resources |
| Cultural Resources | Less than significant after mitigation
Underground mine workings are contributing elements of the Idaho-Maryland Mine Historic District. | | Rise to share historic documentation with the public. Sharing will consist of providing GIS output and copies of historic diagrams with California State Library, California Geology and Mining Library, or the Searls Library.
Following initial mine dewatering and prior to commencement of mining, a qualified historian will perform a historical study of accessible underground mine workings. The study would be provided to the library selected.
If archaeological resources are discovered during construction or mining, activities within 200 feet would be halted, the county will be notified, and an archaeologist will investigate and provide recommendations for further evaluation and treatment. Work would recommence after authorization of the Nevada County Planning Department. |
| Geology and Soils |
| Geotechnical | Less than significant after mitigation
Removal and replacement of sawdust in portion of berm of existing clay-lined pond at Brunswick site. Installation of geomembrane over existing clay liner.
Existing 48-inch culvert running underneath Brunswick site is near the end of its life and will be replaced.
Rock and sand tailings produced by mine will meet the geotechnical criteria for structural fill. Engineered fill to be composed of 100% sand tailings or up to 2-parts rock to 1-part sand tailings.
Risk of seismically induced hazards are remote (negligible). | | Submission of engineered final grading plans which incorporate recommendation from submitted geotechnical reports and best management practices from submitted management plans.
Closure of historic East Eureka and Idaho Shafts prior to mine dewatering.
Submission of a final onsite sewage disposal design report. |
| Hazards & Hazardous Materials |
| Use of Hazardous Materials | Less than significant after mitigation
All explosives will be stored and used underground. Explosive's storage, transport, and use are heavily regulated and have an extremely safe track record. | | The mine operator and its contractors and suppliers will comply with all applicable regulations governing the transport storage and use of explosives. A risk assessment and hazardous materials business plan will be prepared before the storage of explosives underground.
The mine operator will prepare a Hazardous Materials Business Plan which will be approved by the County prior to use or storage of hazardous materials onsite. |
| Release of Hazardous Materials | Less than significant after mitigation
Extensive mining and saw milling activities have taken place historically at the Brunswick Industrial Site. | | A portion of existing mine waste under paving shall not be removed from the site without approval from state agencies RWQCB or DTSC and specific handling procedures will be developed by a Certified Industrial Hygienist before excavation.
If unidentified contaminated soil is encountered during construction work shall stop and a qualified professional will investigate and prepare a report for remediation. Work shall not recommence in contaminated area until necessary remediation is complete and approved by the Nevada County Planning Department.
Prior to commencement of construction all existing wells onsite will be identified. Any identified wells will be properly closed prior to disturbance within 50 feet distance. |
| Hydrology and Water Quality |
| Geochemistry - Engineered Fill | Less than significant after mitigation
Use of barren rock and sand tailings produced by mine as engineered fill.
Sand tailings are environmentally benign.
Mineral process plant removes +93% of sulphide sulphur from sand tailings. Geochemical test work shows sand tailings have minimal metal content, similar to average crustal abundance. Leachate samples from waste extraction tests (WET-DI) show metal content less than all California regulatory thresholds.
Sand tailings are shown to be net-acid neutralizing with neutralizing potential ranging from 100-159 times acid potential.
Barren rock is environmentally benign.
Geochemical test work shows barren rock to have minimal metal content. Leachate samples from 96% of barren rock mined from waste extraction tests (WET-DI) show metal content less than all California regulatory thresholds.
Barren rock samples are shown to be net-acid neutralizing with neutralizing potential ranging from 7 -107 times acid potential. | | Approval of a Report of Waste Discharge prior to placement of engineered fill from the California State Water Resources Control Board. |
| Geochemistry - Cemented Paste Backfill | Less than significant after mitigation
Use of cemented sand tailings produced by mine as underground backfill.
The use of cemented paste backfill is an environmentally favorable disposal alternate for tailings as it significantly limits solute release, eliminates bleed water from placed backfill, and reduces the surface footprint of the mine. | | Approval of a Report of Waste Discharge prior to placement of backfill from the California State Water Resources Control Board. Strength, rheological, and geochemical testing of cemented paste backfill mixture to be completed. |
| Surface Water Quality | Less than significant after mitigation
Discharge of treated groundwater from underground mine to South Fork Wolf Creek.
Water treatment plant using conventional methods validated over years of application in facilities worldwide.
Treatment of mine water to standards of California Regional Water Quality Control Board Limited Threat General Order R5-2016-0076 (NPDES No. CAG995002). Water temperature, pH, and dissolved oxygen to be maintained within limits of General Permit.
Mineral process plant to run on a closed water circuit. | | Approval of Notice of Intent for coverage under Limited Threat General Order R5-2016-0076 (NPDES No. CAG995002) prior to discharge from the California State Water Resources Control Board.
Approval of a Report of Waste Discharge prior to discharge from the California State Water Resources Control Board for use of water treatment pond. An upgrade to the existing clay liner to a synthetic liner will be required.
Approval of Notice of Intent for coverage under the Industrial General Permit for the Brunswick Industrial Site prior to commencement of operations from the California State Water Resources Control Board. |
| Groundwater Drawdown | Less than significant after mitigation
Itasca Denver prepared a sophisticated groundwater model and simulation which was calibrated with historic groundwater inflows. EMKO Environmental prepared analytic solutions to confirm results and determine potential effects on domestic water wells.
One domestic water well located above the historic mine workings could be impacted, with an ~40% reduction in the well water column, due to the groundwater drawdown from dewatering of the mine. With the assumption of a 100% safety factor, an additional six domestic water wells could be impacted, with a reduction in the well's water column of ~7% - 12% . All potentially impacted wells are located in the E. Bennett Road area. Domestic water wells outside this area will not be impacted.
No significant effects to surface water flow in streams are anticipated. | | Monitoring wells will be constructed and well-level monitoring data will be collected for 12 months prior to commencement of dewatering.
Hydrologic data will be collected according to project stages. Prior to dewatering, monitoring wells and piezometers would be installed to measure water levels. The Itasca groundwater model would be updated periodically after dewatering commences to incorporate changes to the long-term mining plan, data from monitoring wells, and measured pumping rates.
Rise will construct an extension to the Nevada Irrigation District (NID) potable water line along East Bennett Rd. to connect 30 properties to the NID system prior to dewatering. Construction costs and NID capacity charges would be fully funded by Rise. Property owners would be allowed to continue using their domestic wells in addition to the NID potable water supply. NID water charges would be paid by Rise until the property is sold by the owner or annexed in the City of Grass Valley. |
| Storms & Flooding | Less than significant after mitigation
Storm water detention ponds will be constructed at both the Brunswick and Centennial sites.
Post project storm-water discharge from both the Centennial and Brunswick Sites, including, in the case of the Brunswick Site, the treated mine water discharge of 5.6 cfs will be equal to or less than the estimated pre-project storm-water discharge levels. Therefore, with the construction of the storm-water detention ponds, the project will have no impact or increase of flows in creeks during storm events.
No work is proposed within a floodplain but is within 100 feet of a floodplain at the Centennial site. | | A final drainage design and report will be completed by a qualified professional before approval of grading and building permits.
Grading and land disturbance within the 100-year floodplain shall be avoided and proposed designs for the Centennial site shall be followed. |
| Channel Geomorphology | Less than significant
Field sampling and calculations indicate that increasing the base flow of South Fork Wolf Creek by the discharge of treated mine water (maximum 5.6 cfs) will have no significant impact on erosion or sedimentation to the creek. | | None Required. |
| Land Use and Population and Housing |
| Nevada County General Plan | Less than significant
The project is consistent with the Nevada County General Plan goals, objectives, and policies. | | None Required. |
| Nevada County Zoning Code | Less than significant
Subsurface mining is allowed in all base districts, surface access to subsurface mining is allowed in the M1 base district (Sec. L-II 3.21) and surface mining is allowed in the M1 district (Sec. L-II 3.22).
The Brunswick Industrial Site will be rezoned from M1-SP to M1-ME.
A variance for buildings heights exceeding 45 ft will be required for the headframes and process plant building.
Boundary line adjustments will be required for three parcels of the Brunswick Industrial Site so that parcel lines do not cross proposed buildings. | | None Required. |
| Population and Housing | Less than significant | | None Required. |
| Noise and Vibration |
| Noise - Construction | Significant and Unavoidable
Construction noise is exempt from Nevada County noise regulations. However, noise from construction of the NID potable water line extension is considered significant and unavoidable under CEQA criteria.
All other construction noise is less than significant. | | Annotations will be added to improvement plans for the potable water line along E. Bennett Road requiring advance notification of construction dates to nearby residents, utilization of the quietest equipment capable of performing required construction, locating staging areas distant from residences, and shielding air compressors and portable generators. |
| Noise - Operations | Less than significant after mitigation
Consultant collected ambient noise and vibration levels at representative sensitive receptors and modelled noise from the project elements including machinery and truck traffic. | | Use of jake brakes by trucks will be prohibited.
All on-site mobile equipment will be fitted with broad-band "growler" type back-up warning devices rather than conventional "beeper" devices.
A noise monitoring program will be implemented to ensure compliance with regulations. |
| Blasting Vibrations | Less than significant after mitigation
The majority of planned mining is greater than 1000 feet from surface. The anticipated impact from drilling and blasting surrounding the proposed mine is negligible. | | A monitoring program will be implemented to establish background levels, record ground vibrations, and model ground vibration. |
| Drilling Vibrations | No Impact
The community will experience no ground vibration from the drilling activities at the mine. The drilling produces no longstanding ground vibration and has no effect a few feet from the hole being drilled. | | None Required. |
| Public Services and Utilities |
| Fire, Police, and other government services. | Less than significant
No new fire, police, parks, waste, or other government facilities are required. | | None Required. |
| Water Supply | Less than significant
There is sufficient water supply available to serve the project in normal, dry, and multiple dry years. | | None Required. |
| Electrical Supply | Less than significant
There is sufficient electricity supply available from PG&E to serve the project. | | None Required. |
| Transportation and Traffic |
| Traffic Intersections | Significant and Unavoidable
The majority of traffic from the project is scheduled during off peak hours.
One intersection at Brunswick Road and highway SR 174 is currently operating at a level of service E. The project would add 10 additional vehicles to this intersection during the 3:30 - 4:30 PM time period. This intersection is not currently identified in a traffic improvement program and therefore the impact to this intersection is considered significant and unavoidable despite the payment of a fair share for the installation of a traffic light.
Traffic delay shall not be considered a significant impact on the environment in recent changes to CEQA. However, the addition of additional vehicles to intersections currently operating at an unacceptable level of service is considered an impact due to the policies of Nevada County. | | Rise will enter into a Traffic Mitigation Agreement with Nevada county regarding the Brunswick Road / SR174 intersection which will require the payment of a fair share of 14.9% towards the improvement of this intersection. Rise estimates this fair share to be approximately $67,000.
Rise will pay a fair share payment of 8.5% to the City of Grass Valley for the future retiming of traffic lights at Brunswick Road and Sutton Way. Rise estimates this fair share payment to be negligible.
Rise will pay the Western Nevada County Regional Transportation Mitigation Fee, Nevada County Local Traffic Mitigation Fee, and Grass Valley Traffic Impact Fee, based on the square footage of buildings constructed. |
| Road Improvements | Less than significant after mitigation
Truck traffic will utilize Brunswick Road, a minor arterial road, to access State Highway 20/49. Engineered fill trucks would use Whispering Pines Drive from Brunswick Road to access the Centennial site.
Employees would enter and exit the site from the main gate on Brunswick Road.
Trucks would enter the site from the main gate on Brunswick Road and exit the site from the gate on E. Bennett Road. Exiting trucks would turn right on E. Bennett Road to the 4-way intersection at E. Bennett, Brunswick, and Greenhorn Roads. | | A construction signing and traffic control plan will be prepared and approved by Nevada County prior to the commencement of construction.
A road maintenance agreement will be negotiated between Rise and Nevada County and the City of Grass Valley to provide the project fair share of funding for maintenance of a portion of E. Bennett Road and Brunswick Road where truck traffic may impact pavement conditions.
The driveway at the E. Bennett Road gate from the Brunswick site will be widened to allow right hand turning of trucks exiting the property.
A left-hand turn lane will be constructed on Whispering Pines Lane for queuing of trucks turning into the Centennial site.
Two traffic signs will be installed on Brunswick Road.
Any landscaping or vegetation over 2 feet in height inside the sight line from the project driveway to Brunswick Road will be removed. |
| Vehicle Miles Travelled | Less than significant
The daily vehicle miles travelled per employee of 13.9 daily VMT per employee is less than the Nevada County threshold of 15.9 for the Grass Valley subarea. | | None required. |
| Wildfire |
| Emergency Evacuation | Less than significant
The project will not impair an adopted emergency response or evacuation plan. | | None required. |
| Wildfire Risk | Less than significant after mitigation | | A comprehensive Vegetation Management Plan will be submitted for review and approval by the Nevada County Fire Marshall Office before construction commences. |
