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Home My WebLink AboutMIN23-0001_Power House Full ApplicationDepartment of Development Services Paula M. Daneluk, AICP, Director Curtis Johnson, Assistant Director 7 County Center Drive Oroville, California 95965 T: 530.552.3700 F: 530.538.7785 buttecounty.net/dds MEMORANDUM DATE: TO: FROM: July 10, 2024 Surface Mining Aggregate Operations Committee Austin Forde, Assistant Planner Butte County Department of Development Services RE: Request for Recommendation – Granite Construction Company (MIN23-0001) _ The Butte County Planning Division requests that the Surface Mining Aggregate Operations Committee review and provide a recommendation regarding a new mining permit application. The full application and final Transportation Impact Study are linked within the Agenda which may be accessed from the webpage below: https://www.buttecounty.net/526/Surface-Mining-Aggregate-Operations-Comm PROJECT DESCRIPTION: The applicant proposes an amendment to approved Mining Permit MIN09-0001 for the Power House Mine, a request to allow the off-site transport of mined materials from the mine site, totaling ±495 acres in size, to Granite Construction’s separately permitted aggregate processing facility on Pacific Heights Road (“Pacific Heights Facility”) via Highway 70. MIN 09-0001 currently allows for the off-site transport of mined materials via a haul road through the Oroville Wildlife Area (OWA). The operation’s previously approved transportation route is outlined on page 5 of this packet, with the new transportation route located on page 6. As the new transportation route will entail use of a portion of Pacific Heights Road within the City of Oroville’s SOI, the project was distributed to the City of Oroville’s Planning and Engineering Divisions, who returned no comments, noting that they do not plan to annex the area in the near term, and deferring to CalTrans to designate the road standard along SR-70 and to the County for the standard along Pacific Heights Road. After review of the applicant’s final TIS (Transportation Impact Study), CalTrans indicated no required roadway improvements. Final conditions of project approval were then applied by the Butte County Public Works Department, indicating the proper road standard along Pacific Heights Road. PROJECT LOCATION: The project site is located at 2859 HWY 70, PALERMO CA 95965, south of the City of Oroville via HWY 70, APNs: 025-160-046 and 025-160-066. ZONING: AG-80 (Agriculture, 80-acre minimum) GENERAL PLAN DESIGNATION: AG (Agriculture) I• ss / r• 1 M,/tel;...',..•• aove: '' 1r } { 1 t may' ..c. ; td 1 i.-?, r•C.•r.r• j ,,;:.'`' .c.,•••••'. I45V7. ;1 .`.'• • e•,y.G Irl t W'r-e%•.'?:.. ( ; 1, '14/ t .-22'30'• •.•n _ (,'.. I ( r y l._1• rli• vwF•*. I- 1. i. rcfi-••, l'•" ':'•iil, ylP--{ „ - 1._ • _ ;•'=•'!`-• .- :•,. 1..19 A.v S, .J_.-. ., /• ` .•<•t'r•J--''''t.'''''!4.-44•, t /1,7a.:.-:.#4. .':''';'"i= 7 '•••. T,a N-L `Z'<nU. •t; ! `1 ns ••_._' ' 11µs-,yf•.; Disclaimer: The data was mapped for planning purposes only. No liability isassumed for accuracy of the data shown. ´0 2,100 4,200 Feet ^_ Power HouseHillRdHwy 70Lone Tree RdPalermo RdPacificHeightsRd Ophir Rd Power House Hill RdWelsh Rd Aerial Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community Site and Vicinity Map Power House Mine Use Permit Amendment Butte County, California Legend:Figure 1 Projects\002 - Granite Valley\Powerhouse\Site Map for Traffic Study\Site Map.mxd6/5/2023 Power House Mine Site Pacific Heights Processing Site Haul Route Along Hwy 70 F e a t h e r R i v e r PacificHeightsRdProposed Haul Route Power House Mine Site ^_Pacific Heights Processing Site 4235 Forcum Avenue SUITE 100 MCCLELLAN, CA 95652 TEL: 408.640.6553 WWW.COMPASSLAND.NET Via: Electronic Mail Delivery October 24, 2023 Mr. Dan Breedon Planning Division Manager Butte County Department of Development Services 7 County Center Drive Oroville, California 95965 Subject: Use Permit Amendment – Transport of Mined Materials Via Highway 70 Power House Mine (Mine ID #91-04-0034) Dear Dan: On behalf of Granite Construction Company, we are pleased to submit the enclosed application for an amendment to the Power House Mine Use Permit (MIN 09-0001) to allow for off-site transport of mined materials utilizing Highway 70 from the Mine site to the Pacific Heights Facility (“Project”). The following documents are enclosed in support this request: 1.Attachment 1. Project Information Form (DPL-1). 2.Attachment 2. Agent Authorization Form (DPL-2). 3.Attachment 3. Project Setting Description Form (DPL-4). 4.Attachment 4. Project description and application supplement with appended technical studies. 5.Attachment 5. Check for fees in the amount of $25,400.88. *** We look forward to working with you on this Project. Please contact me at 408-640-6553 if you have any questions or need additional information. Sincerely, Candice Longnecker Compass Land Group clongnecker@compassland.net Mr. Dan Breedon October 24, 2023 Page 2 Encl. cc: Carter Rohrbough, Granite Construction Company Jason Jarvis, Granite Construction Company Jake Hinchey, Granite Construction Company ATTACHMENT 1 PROJECT INFORMATION FORM ATTACHMENT 2 AGENT AUTHORIZATION FORM ATTACHMENT 3 PROJECT SETTING DESCRIPTION FORM 1 of 2 PROJECT SETTING DESCRIPTION INSTRUCTIONS Applicant Name: _________________________Project Number: __________________ Please address the following in the space provided. Attach a separate sheet of paper, if needed: 1. Identify any applicable proposed development schedule, including anticipated, incremental, or phased development and all associate projects. 2. List and describe any other related permits and other public approvals required for this project, including those required by city, regional, state and federal agencies. 3. Describe the site as it exists before the project, including information on topography, soil stability, plants, animals, and any cultural, historical, or scenic aspects. Describe any existing structures on the site and the use of the structures. Butte County Department of Development Services PLANNING DIVISION 7 County Center Drive, Oroville, CA 95965 Planning Center Phone 530.552.3701 Fax 530.538.7785 dsplanning@buttecounty.net FORM NO DPL-04 2 of 2 4. Describe the surrounding properties, including information on plants, animals and any cultural, historical, or scenic aspects. Indicate the type of land use (residential, commercial, etc.), intensity of land use (one-family, apartment houses, shops, department stores, etc.), and scale of development (height, frontage, setback, rear yard, etc.). 5. Include any special studies prepared for the project site including, but not limited to traffic, biology, wetlands delineation, archaeology, etc. Please contact Planning Division Staff with any questions. ATTACHMENT 4 PROJECT NARRATIVE AND APPLICATION SUPPLEMENT PROJECT NARRATIVE AND APPLICATION SUPPLEMENT AMENDMENT TO USE PERMIT (MIN 91-0001) TO TRANSPORT MINED MATERIALS VIA HIGHWAY 70 GRANITE CONSTRUCTION COMPANY POWER HOUSE MINE (CA MINE ID #91-04-0034) BUTTE COUNTY, CALIFORNIA Applicant: Granite Construction Company 4001 Bradshaw Road Sacramento, CA 95827 Prepared by: Compass Land Group 4235 Forcum Avenue, Suite 100 McClellan, CA 95652 October 2023 Power House Use Permit Amendment i October 2023 TABLE OF CONTENTS 1.0 INTRODUCTION ................................................................................................ 1 1.1 General Ownership/Operator Information ............................................................ 1 2.0 Project Description ........................................................................................... 1 2.1 Air and Greenhouse Gas Emissions Study .............................................................. 2 2.2 Environmental Noise and Vibration Assessment ................................................... 2 2.3 Transportation Impact Study (Draft) ..................................................................... 2 3.0 Mining Operation and Reclamation Summary .................................................. 3 Power House Use Permit Amendment ii October 2023 FIGURES Figure 1 Site and Vicinity Map APPENDICES Appendix A Air and Greenhouse Gas Emissions Study Appendix B Environmental Noise & Vibration Assessment Appendix C Transportation Impact Study (Draft) Power House Use Permit Amendment 1 October 2023 1.0 INTRODUCTION This Project Narrative and Application Supplement is intended to summarize the Project and address the submittal items required by Butte County’s Mining Permit & Reclamation Plan Application Packet (PLG-08), where applicable to the Project. 1.1 General Ownership/Operator Information Mine Name: Power House Mine CA Mine ID: 91-04-0034 Location of Mine: 2869 Highway 70, Butte County, CA 95965 The Mine is located south of the City of Oroville on the west side of Highway 70 adjacent to the Feather River. See Figure 1, Site and Vicinity Map. Section/Township/Range: Section 15, Township 18 North, Range 3 East, Mount Diablo Base and Meridian Assessor’s Parcel Numbers: 025-160-046 and 025-160-066 Applicant/Mine Operator/Property and Mineral Rights Owner: Attn: Carter Rohrbough Granite Construction Company 4001 Bradshaw Road Sacramento, CA 95827 2.0 PROJECT DESCRIPTION The Mining Permit, Use Permit and Reclamation Plan for the Granite Construction Company (“Granite”) Power House Aggregate Project (“Power House Mine”) was originally approved by Butte County in 2012 (MIN 09-0001). The entitlements allow for mining on two parcels totaling ±495 acres. After mining ceases and reclamation is complete, the land will be returned to agriculture and open water lake and habitat. Mining has not yet commenced and an extension to the commencement date was approved in 2021 pursuant to Butte County Code Section 13-111(c). Additionally, a minor modification to amend MIN 09-0001 was approved by Butte County in April 2023 to reflect changes to the approved entitlements due to the removal of approximately five acres of property by Caltrans associated with the widening of Highway 70. MIN 09-0001 currently allows for off-site transport of mined materials to Granite’s separately- permitted aggregate processing facility on Pacific Heights Road (“Pacific Heights Facility”) utilizing a haul road through the Oroville Wildlife Area (“OWA”), subject to Condition #8, which reads: One month prior to the start of any earth-moving activities for this project, the applicant shall provide the Department of Development Services with a copy of a memorandum of agreement between the Department of Water Resources, the Department of Fish and Game and Granite Construction. The memorandum of agreement shall allow for project material to be transported through the Oroville Wildlife Area as provided in the Power House Aggregate Project Draft EIR Project Description and Traffic and Transportation sections. Power House Use Permit Amendment 2 October 2023 The Department of Water Resources (“DWR”) and Department of Fish and Game (known as the Department of Fish and Wildlife; “CDFW”) have not yet granted a memorandum of agreement to Granite to allow for the transport of mined materials through the OWA to the Pacific Heights Facility. The proposed project (“Project”) involves amending MIN 09-0001 to allow, as an alternative, off-site transport of mined materials to the Pacific Heights Facility utilizing Highway 70 from an existing encroachment at the Power House Mine site. With the exception of the alternative haul route, the Project does not propose changes to the mining footprint, production levels, operating hours, or any other fundamental element of the approved operation. Appropriate technical studies have been prepared in support of the Project and are summarized below. 2.1 Air and Greenhouse Gas Emissions Study Compass Land Group prepared an air and greenhouse gas emissions study for material transport to evaluate air quality and greenhouse gas emissions associated with the Project. The study compared the emissions from on-road haul trucks (proposed project) to the emissions from off-road haul trucks evaluated under the 2012 EIR for the Power House Mine (“baseline”). The modeling results show that the Project would have fewer criteria pollutant emissions and greenhouse emissions than the existing permitted baseline. See Appendix A, Air and Greenhouse Gas Emissions Study. 2.2 Environmental Noise and Vibration Assessment Bollard Acoustical Consultants conducted a noise and vibration assessment to evaluate potential impacts to nearby receptors related to the Project. The assessment indicates that the proposed Project would result in a negligible (less than one decibel) increase during peak and average day conditions at existing residences along Highway 70 and result in no discernable vibrations associated with the Project vehicles. See Appendix B, Environmental Noise and Vibration Assessment. 2.3 Transportation Impact Study (Draft) W-Trans prepared a draft transportation impact study to evaluate potential transportation impacts and operational effects associated with the Project. The study concludes that the Project is expected to add an average of 790 daily truck trips to public roadways along the haul route, and would not conflict with any relevant Butte County policies or plans or have a significant impact on emergency response vehicle response times. Additionally, the Level of Service (“LOS”) at the studied intersections of the proposed haul route would be expected to continue to operate at an acceptable LOS with the addition of Project-related traffic. Based on the results of the study, the Project will implement a right-turn lane from Highway 70 into the site using the existing encroachment. See Appendix C, Transportation Impact Study (Draft). The Transportation Impact Study will be finalized following review by Butte County and Caltrans. Power House Use Permit Amendment 3 October 2023 3.0 MINING OPERATION AND RECLAMATION SUMMARY Characteristics MIN 91-0001 Changes Under Proposed Project Operational Activities Excavation to a maximum depth of 40 feet in Phase 1 and 50 feet in Phase 2 using mobile equipment (e.g., scrapers, dozers, excavators) and loading to haul trucks. No change. Acreages Project Boundary 495 acres. No change. Surface Disturbance 449 acres. No change. Reclamation to Agriculture 262 acres. No change. Reclamation to Open Water/Lake Habitat 187 acres. No change. Volume (Annual) Annual: 1 million tons (maximum) No change. Transport Off-site transport approximately 3 miles via the OWA, pending agreement with DWR and CDFW. Off-site transport approximately 3 miles via the OWA, pending agreement with DWR and CDFW. OR Off-site transport approximately 4 miles via Highway 70. Typical Operating Hours Monday – Saturday, 5:00 a.m. – 9:00 p.m. (with potential for 24- hour operations to service emergency or traffic sensitive projects). No change. Operating Period 50 years, depending upon market. No change. FIGURE 1 SITE AND VICINITY MAP Disclaimer: The data was mapped for planning purposes only. No liability isassumed for accuracy of the data shown. ´0 2,100 4,200 Feet ^_ Power HouseHillRdHwy 70Lone Tree RdPalermo RdPacificHeightsRd Ophir Rd Power House Hill RdWelsh Rd Aerial Source: Esri, Maxar, Earthstar Geographics, and the GIS User Community Site and Vicinity Map Power House Mine Use Permit Amendment Butte County, California Legend:Figure 1 Projects\002 - Granite Valley\Powerhouse\Site Map for Traffic Study\Site Map.mxd6/5/2023 Power House Mine Site Pacific Heights Processing Site Haul Route Along Hwy 70 F e a t h e r R i v e r PacificHeightsRdProposed Haul Route Power House Mine Site ^_Pacific Heights Processing Site APPENDIX A AIR AND GREENHOUSE GAS EMISSIONS STUDY GRANITE CONSTRUCTION COMPANY POWER HOUSE USE PERMIT AMENDMENT AIR AND GREENHOUSE GAS EMISSIONS STUDY FOR MATERIAL TRANSPORT PREPARED FOR: Granite Construction Company 4001 Bradshaw Road Sacramento, CA 95827 FOR SUBMITTAL TO: Butte County Development Services Department 7 County Center Drive Oroville, CA 95965 OCTOBER 2023 Air and Greenhouse Gas Emissions Study i October 2023 Power House Use Permit Amendment TABLE OF CONTENTS 1.0 PURPOSE AND SCOPE ................................................................................................... 1 2.0 PROJECT DESCRIPTION ................................................................................................. 1 3.0 METHODS AND ASSUMPTIONS .................................................................................... 1 4.0 RESULTS ....................................................................................................................... 1 4.1 Criteria Pollutant Emissions of ROG, NOx, PM10, and PM2.5 ..................................... 1 4.2 Greenhouse Gas Emissions ......................................................................................... 2 TABLES Table 1 Daily Criteria Air Pollutants and Precursor Emissions Analysis (lb/day) ........... 2 Table 2 Annual Criteria Air Pollutants and Precursor Emissions Analysis (tons/year) .. 2 Table 3 Greenhouse Gas Emissions Analysis (MT/year) ............................................... 3 APPENDICES Appendix A Proposed Project Models and Inputs Appendix B Approved Project Models and Inputs Air and Greenhouse Gas Emissions Study 1 October 2023 Power House Use Permit Amendment 1.0 PURPOSE AND SCOPE Compass Land Group (“Compass”) has prepared this Air and Greenhouse Gas Emissions Study for Material Transport (“Study”) in support of the Granite Construction Company (“Granite”) Power House Use Permit Amendment in Butte County, California (“Project”). This Study evaluates the air quality and greenhouse gas (“GHG”) emissions associated with mined material transport for the proposed Project and compares those emissions to the approved 2012 project. The sections that follow provide a brief description of the Project, methods for air quality and GHG emissions evaluation, and emissions estimates. 2.0 PROJECT DESCRIPTION The Project proposes to modify the Power House Conditional Use Permit (“Permit”) to allow for the transport of mined materials to the Pacific Heights aggregate plant using on‐road trucks on Highway 70. The Permit currently allows for mined materials to be transported using off‐road trucks through the Oroville Wildlife Area (“OWA”). 3.0 METHODS AND ASSUMPTIONS Given that the Permit already allows for off‐road transport of mined material through the OWA (permitted baseline), this Study compares the emissions from on‐road haul trucks to the permitted baseline. Compass used the CARB 2021 EMFAC model to calculate on‐road mobile source emissions for Project haul trucks transporting mined materials to the existing Pacific Heights aggregate plant. Mobile source emissions are evaluated using estimates of vehicle miles traveled (“VMT”) based on the maximum annual and daily production. An average one‐way trip distance of four (4) miles was used to be consistent with the Project traffic analysis. On‐road mobile source emissions were then estimated by multiplying the VMT estimates for haul trucks by the applicable EMFAC emissions factor. To estimate emissions for off‐road trucks (permitted baseline), Compass used the latest off‐road emissions factors available from the California Emissions Estimator Model (“CalEEMod”) version 2022.1, which are based on the CARB OFFROAD2017 model. Granite no longer has 65‐ton haul trucks, which have been retired due to modern fleet emissions regulations. Per Granite, their largest off‐road trucks are 45‐ton Caterpillar 745 model articulating haul trucks with 2018 engines. Detailed estimating methods and assumptions are provided in this Study’s appendices. 4.0 RESULTS 4.1 Criteria Pollutant Emissions of ROG, NOx, PM10, and PM2.5 The modeling results indicate that the Project’s daily and annual criteria pollutant emissions associated with material transport would be less than the approved project (see Tables 1 and 2 Air and Greenhouse Gas Emissions Study 2 October 2023 Power House Use Permit Amendment below). Based on these results, the Project’s potential criteria pollutant impacts would be less‐ than‐significant. A complete report of modeling inputs and emissions is included in Appendix A (Proposed Project Models and Inputs) and Appendix B (Approved Project Models and Inputs). TABLE 1 DAILY CRITERIA AIR POLLUTANTS AND PRECURSOR EMISSIONS ANALYSIS (LB/DAY) Emissions Category ROG NOx PM10 PM2.5 Proposed Project On‐Road Mobile Source Emissions 0.08 10.5 0.04 0.04 Approved Project Off‐Road Mobile Source Emissions 5.50 61.74 2.12 1.96 NET CHANGE ‐5.42 ‐51.24 ‐2.08 ‐1.92 TABLE 2 ANNUAL CRITERIA AIR POLLUTANTS AND PRECURSOR EMISSIONS ANALYSIS (TONS/YEAR) Emissions Category ROG NOx PM10 PM2.5 Proposed Project On‐Road Mobile Source Emissions 0.00 0.58 0.00 0.00 Approved Project Off‐Road Mobile Source Emissions 0.31 3.43 0.12 0.11 NET CHANGE ‐0.31 ‐2.85 ‐0.12 ‐0.11 4.2 Greenhouse Gas Emissions The modeling results indicate that the Project GHG emissions associated with material transport would be less than the approved project (see Table 3 below). Based on these results, the Project’s potential GHG impacts would be less‐than‐significant. A complete report of modeling inputs and emissions is included in Appendix A and Appendix B. Air and Greenhouse Gas Emissions Study 3 October 2023 Power House Use Permit Amendment TABLE 3 GREENHOUSE GAS EMISSIONS ANALYSIS (MT/YEAR) Emissions Category CO2e Proposed Project Emissions 522.3 Approved Project Emissions 727.2 Net Change ‐204.9 Notes: 1. Emissions reported for Caterpillar 745 articulated haul truck. See Appendix B for detail. 2. MT= metric tons. CO2e = carbon dioxide equivalent. APPENDIX A PROPOSED PROJECT MODELS AND INPUTS Granite Construction CompanyPower House Mine ProjectAir and Greenhouse Gas Emissions StudyAPPENDIX A: PROPOSED PROJECT MODELS AND INPUTS1. ON‐ROAD MOBILE SOURCE EMISSIONSDescription:EMFAC2021 (v1.0.2) Emission Rates (Butte County):Calendar Year: 2023Season: AnnualVehicle Classification: EMFAC202x CategoriesUnits: g/mile for emission rates; miles for trip distanceSpeed Selections: Average speed of 35 mph for truck trips (diesel).RegionCalendar YearVehicle Category Model Year Speed FuelTrip Distance (one‐way) ROG CO NOx SOx CO2 CH4 PM10 PM2.5 N20Butte 2023 T7 Tractor Aggregated 35 DSL 4 0.013 0.1361.654 0.015 1559.149 0.001 0.007 0.007 0.246Notes:T7 Tractor = Heavy‐Heavy Duty Diesel Tractor TruckTrip distance based on EMFAC reported VMT divided by trips, except for T7 Tractor trip distances based on actual project trip distance. On‐road vehicle emissions associated with haul truck travel to and from the Pacific Heights aggregate plant. Emission factors from EMFAC 2021. Production assumptions from Granite. 1 APPENDIX A: PROPOSED PROJECT MODELS AND INPUTSProduction Assumptions:Annual Production: 1,000,000 tonsTons per truck ‐ haul trucks:25tonsDaily Max Production: 9,000 tonsConversion factors: Global warming potential (to calculate CO2e):grams/lb: 453.592CO2:1grams/ton: 907,184 CH4:34MT/ton: 0.907N20:298CO2e = 1 * CO2 + 34 * CH4 + 298 * N20* Per Table 3‐1 of the Final 2017 Clean Air Plan (BAAQMD April 19, 2017). GWP values in Table 3‐1 are based on IPCC climate carbon feedback values from the IPCC 5th Assessment Report (AR5).Daily Emissions Calculation:On‐road Mobile SourceEMFAC Source T7 TractorVMT/TripEmployees VMT/dayROG (lb/day)NOX (lb/day)CO(lb/day)PM10 (lb/day)PM2.5 (lb/day)Haul trucks T7 Tractor4 2,880 0.08 10.50 0.86 0.04 0.04 TOTALS: 2,880 0.08 10.50 0.86 0.04 0.04 Notes:N/A.Annual Emissions Calculation:On‐road Mobile SourceEMFAC Source T7 TractorVMT/TripVMT/yrROG (tons/yr)NOX (tons/yr)CO(tons/yr)PM10 (tons/yr)PM2.5 (tons/yr)CO2 (MT/yr)CH4 (MT/yr)N20 (MT/yr)C02e (MT/yr)Haul trucks T7 Tractor4 320,000 0.00 0.58 0.05 0.00 0.00 498.83 0.00 0.08 522.29 TOTALS: 320,000 0.00 0.58 0.05 0.00 0.00 498.83 0.00 0.08 522.29 Notes:N/A.Greenhouse Gases2 APPENDIX B APPROVED PROJECT MODELS AND INPUTS Granite Construction CompanyPower House Mine ProjectAir and Greenhouse Gas Emissions StudyAPPENDIX B: APPROVED PROJECT MODELS AND INPUTS1. OFF‐ROAD MOBILE SOURCE EMISSIONSDescription:Production Assumptions:Annual Production: 1,000,000 tonsTons per truck ‐ haul trucks:45tonsDaily Max Production: 9,000 tonsHaul truck max trips per year: 22223 one‐way tripsAnnual Operating Days at Daily Max Production: 111 daysHaul truck max trips per day: 200 one‐way tripsHaul Time and Hours Assumptions:Trip distance (one way):3.3milesHaul truck max hours per year: 7334hoursAvg. travel speed (off road):20mphHaul truck max hours per day: 66hoursTravel time (one way):0.165hours Max # of haul trucks:8trucks (based on 8 hr work day)Travel time (round trip):0.33hoursEquipmentQtyModel Year HPLoad Factor Hrs/DayOff‐Highway Truck 8 2018 511 0.38 8Notes:1. Load factors per CalEEMod Appendix G, Table G‐12, based on the weighted average horsepower (by equipment population) and load factors for the mode of the engine groupings in OFFROAD2017.EquipmentROG NOx PM10 PM2.5 CO SO2 CO2 CH4Off‐Highway Truck 0.29 3.12 0.11 0.11 1.58 0.01 527.16 0.02Notes:1. Emissions factors per CalEEMod Appendix G, Table G‐11, Statewide Average Annual Offroad Equipment Emission Factors.Conversion Factors:1 g = 0.0022 lbMT / ton = 0.907Global warming potential (to calculate CO2e):CO2:1CH4:34N20:298CO2e = 1 * CO2 + 34 * CH4 + 298 * N20* Per Table 3‐1 of the Final 2017 Clean Air Plan (BAAQMD April 19, 2017). GWP values in Table 3‐1 are based on IPCC climate carbon feedback values from the IPCC 5th Assessment Report (AR5).Off‐road vehicle emissions associated with haul truck travel to and from the Pacific Heights aggregate plant. Emission factors and load factors per CalEEMod User Guide Appendix G, Table G‐11 (2022). Production assumptions from Granite. Emissions calculated for articulating haul trucks, assuming 45 ton max carrying capacity each.ModelCat 745Emissions Factors (g/bhp‐hr)1 APPENDIX B: APPROVED PROJECT MODELS AND INPUTSDaily Emissions Calculation:EquipmentROG(lb/day)NOx(lb/day)PM10(lb/day)PM2.5(lb/day)CO(lb/day)SO2(lb/day)CO2(lb/day)CH4(lb/day)Off‐Highway Truck 7.87 85.19 3.12 2.87 43.17 0.14 14412.90 0.57Annual Emissions Calculation:EquipmentROG(tons/yr)NOx(tons/yr)PM10(tons/yr)PM2.5(tons/yr)CO(tons/yr)SO2(tons/yr)CO2(MT/yr)CH4(MT/yr)CO2e(MT/yr)Off‐Highway Truck 0.44 4.73 0.17 0.16 2.40 0.01 726.25 0.03 727.23Greenhouse Gases2 APPENDIX B ENVIRONMENTAL NOISE & VIBRATION ASSESSMENT Environmental Noise & Vibration Assessment Granite Construction Company Power House Aggregates Haul Route Modification Project Butte County, California BAC Job # 2022-140 Prepared For: Compass Land Group Sage Thurmond 3140 Peacekeeper Way, Ste. 102 McClellan, CA 95652 Prepared By: Bollard Acoustical Consultants, Inc. Paul Bollard, President October 19, 2022 Bollard Acoustical Consultants, Inc. (BAC) P.O. Box 7968  Auburn, CA 95604 (530) 537-2328 BACNOISE.COM Bollard Acoustical Consultants, Inc. (BAC) Noise & Vibration Assessment Granite Construction Company Power House Aggregates Haul Route Modification Project Butte County, California Page 1 Introduction The Granite Construction Company Power House Aggregates Haul Route Modification project (project) proposes to utilize public roads (Highway 70 and Ophir Road), to haul materials from the mine site to the processing facility as an alternative to the currently permitted private road (Pacific Heights). Both the mine site and processing facility are located in Butte County, California, with the processing area approximately 3 miles north of the mine site. Figure 1 shows the locations of the mine site, the processing area, the currently permitted haul route and the proposed haul route. No other changes are proposed to the existing Use Permit including mining activities, hauling levels, or processing operations. This assessment therefore focuses on the evaluation of potential noise and vibration impacts related to the proposed change in haul routes between the mine site and processing area only. Noise and Vibration Fundamentals Noise Noise is often described as unwanted sound. Sound is defined as any pressure variation in air that the human ear can detect. If the pressure variations occur frequently enough (at least 20 times per second), they can be heard and are designated as sound. The number of pressure variations per second is called the frequency of sound and is expressed as cycles per second, or Hertz (Hz). Definitions of acoustical terminology are provided in Appendix A. Measuring sound directly in terms of pressure would require a very large and awkward range of numbers. To avoid this, the decibel scale was devised. The decibel scale uses the hearing threshold (20 micropascals of pressure) as a point of reference, defined as 0 dB. Other sound pressures are then compared to the reference pressure, and the logarithm is taken to keep the numbers in a practical range. The decibel scale allows a million-fold increase in pressure to be expressed as 120 dB. Another useful aspect of the decibel scale is that changes in decibel levels correspond closely to human perception of relative loudness. Noise levels associated with common noise sources are provided in Figure 2. The perceived loudness of sounds is dependent upon many factors, including sound pressure level and frequency content. However, within the usual range of environmental noise levels, perception of loudness is relatively predictable and can be approximated by filtering the frequency response of a sound level meter by means of the standardized A-weighting network. There is a strong correlation between A-weighted sound levels (expressed as dBA) and community response to noise. For this reason, the A-weighted sound level has become the standard tool of environmental noise assessment. All noise levels reported in this section are in terms of A-weighted levels. 0 1,000 2,000 Scale (Feet) Figure 1 Legend Permitted Haul Route Power House Aggregate Haul Route Modification Project Butte County, CaliforniaProposed Haul Route Mine Site Processing Site Bollard Acoustical Consultants, Inc. (BAC) Noise & Vibration Assessment Granite Construction Company Power House Aggregates Haul Route Modification Project Butte County, California Page 3 Figure 2 Noise Levels Associated with Common Noise Sources Community noise is commonly described in terms of the ambient noise level, which is defined as the all-encompassing noise level associated with a given noise environment. A common statistical tool to measure the ambient noise level is the average, or equivalent, sound level (Leq). The Leq is the foundation of the day-night average and day-evening-night average noise descriptors, DNL and CNEL, and show very good correlation with community response to noise. DNL and CNEL are based on the average noise level over a 24-hour day, with a +5-decibel weighting applied to noise occurring during evening hours (CNEL only), and a 10-decibel weighting applied to noise occurring during nighttime hours (both DNL and CNEL). Because DNL and CNEL represent a 24-hour average, it tends to disguise short-term variations in the noise environment. Bollard Acoustical Consultants, Inc. (BAC) Noise & Vibration Assessment Granite Construction Company Power House Aggregates Haul Route Modification Project Butte County, California Page 4 Vibration Vibration is like noise in that it involves a source, a transmission path, and a receiver. While vibration is related to noise, it differs in that noise is generally considered to be pressure waves transmitted through air, while vibration is usually associated with transmission through the ground or structures. A person’s response to vibration will depend on their individual sensitivity as well as the amplitude and frequency of the source. Vibration can be described in terms of acceleration, velocity, or displacement. A common practice is to express vibration in terms of peak particle velocity in inches-per-second or (PPV, ips) or root- mean-square velocity in decibels (VdB, RMS). Standards pertaining to perception as well as damage to structures have been developed for vibration in terms of peak particle velocity as well as RMS velocities. As vibrations travel outward from the source, they excite the particles of rock and soil through which they pass and cause them to oscillate. Differences in subsurface geologic conditions and distance from the source of vibration will result in different vibration levels characterized by different frequencies and intensities. In all cases, vibration amplitudes will decrease with increasing distance. Human response to vibration is difficult to quantify. Vibration can be felt or heard well below the levels that produce any damage to structures. The duration of the event has an effect on human response, as does frequency. Generally, as the duration and vibration frequency increase, the potential for adverse human response increases. According to the Transportation and Construction-Induced Vibration Guidance Manual (Caltrans, April 2020), operation of construction equipment and construction techniques generate ground vibration. Traffic traveling on roadways can also be a source of such vibration but traffic rarely generates sufficient vibration amplitudes to cause damage to structures or annoyance to persons in the vicinity of roadways. At high enough amplitudes, however, ground vibration has the potential to damage structures and/or cause cosmetic damage, and be a source of annoyance to individuals who live or work close to vibration-generating activities. Bollard Acoustical Consultants, Inc. (BAC) Noise & Vibration Assessment Granite Construction Company Power House Aggregates Haul Route Modification Project Butte County, California Page 5 Existing Sensitive Receptors in the Project Vicinity Noise-sensitive land uses are generally defined as locations where people reside or where the presence of unwanted sound could adversely affect the primary intended use of the land. Noise-sensitive receptors located along the currently permitted Pacific Heights Haul Route consist of the Golden Oaks Mobile Home Park (GOMHP), and residences further north on Bob Way, Gold Run Court, Pacific Heights Road, and Sun Cloud Circle. The GOMHP is located approximately 1,200 feet to the east of the currently permitted haul route, and the various residences to the north range from 250 to over 1,100 feet from the currently permitted haul route. Noise-sensitive receptors located along the proposed haul route consist of the GOMHP, the Dingerville MHP, and various residences located near Highway 70. The distance between these sensitive receptors and the proposed Highway 70 haul route varies, with the nearest residences generally located approximately 100 feet from the Highway 70 centerline. Criteria for Acceptable Noise and Vibration Exposure Standards for acceptable noise exposure in Butte County are contained within the Butte County General Plan and County Code of Ordinances. However, those documents do not currently contain policies for assessing vibration impacts or noise impacts related to changes/increases in noise levels due to a project. As a result, federal criteria and recommendations were applied to the project in addition to the locally-adopted Butte County criteria. Federal Criteria Federal Interagency Commission on Noise (FICON) The Federal Interagency Commission on Noise (FICON) has conducted research into criteria for use in assessing project-related noise level increases. The results of the FICON research, which are shown in Table 1, have been used extensively in recent years in the preparation of the noise sections of Environmental Impact Reports that have been certified in California cities and counties. Based on the FICON research, as shown in Table 1, a 5 dB increase in noise levels due to a project would be required for a finding of significant noise impact where ambient noise levels without the project are less than 60 dB DNL. Where pre-project ambient conditions are between 60 and 65 dB DNL, a 3 dB increase is applied as the standard of significance. Extrapolation of the FICON research to areas already exposed to higher noise levels, specifically pre-project noise levels in excess of 65 dB DNL, a 1.5 dB increase is frequently used as the threshold of significance. Bollard Acoustical Consultants, Inc. (BAC) Noise & Vibration Assessment Granite Construction Company Power House Aggregates Haul Route Modification Project Butte County, California Page 6 The use of the FICON standards is considered conservative relative to thresholds used by other agencies in the State of California. For example, the California Department of Transportation (Caltrans) requires a project-related traffic noise level increase of 12 dB for a finding of significance, and the California Energy Commission (CEC) considers project-related noise level increases between 5 to 10 dB significant, depending on local factors. Therefore, the use of the FICON research, which set the threshold for finding of significant noise impacts as low as 1.5 dB, provides a very conservative approach to impact assessment for this project. Table 1 Significance of Changes in Cumulative Noise Exposure Ambient Noise Level Without Project (DNL) Change in Ambient Noise Level Due to Project <60 dB +5.0 dB or more 60 to 65 dB +3.0 dB or more >65 dB +1.5 dB or more Source: Federal Interagency Committee on Noise (FICON) State of California California Environmental Quality Act (CEQA) The State of California has established regulatory guidelines that would be applicable to this assessment. Specifically, Appendix G of the State of California Environmental Quality Act (CEQA) Guidelines are used to assess the potential significance of impacts pursuant to local General Plan policies, Municipal Code standards, or the applicable standards of other agencies. According to Appendix G of the CEQA guidelines, a potentially significant noise or vibration impact would be identified if the following were to occur as a result of a project: A. Generation of a substantial temporary or permanent increase in ambient noise levels in the vicinity of the project in excess of standards established in the local general plan or noise ordinance, or other applicable standards of other agencies. B. Generation of excessive groundborne vibration or groundborne noise levels. C. For a project located within the vicinity of a private airstrip or an airport land use plan or, where such a plan has not been adopted, within two miles of a public airport or public use airport, would the project expose people residing or working in the project area to excessive noise levels. It should be noted that audibility is not a test of significance according to CEQA. If this were the case, any project which added any audible amount of noise to the environment would be considered significant according to CEQA. Because every physical process creates noise, the use of audibility alone as significance criteria would be unworkable. CEQA requires a substantial increase in noise levels before noise impacts are identified, not simply an audible change. The FICON research described above (as presented in Table 1), are used in this evaluation for assessment of the significance of project-related noise increases. Bollard Acoustical Consultants, Inc. (BAC) Noise & Vibration Assessment Granite Construction Company Power House Aggregates Haul Route Modification Project Butte County, California Page 7 California Department of Transportation (Caltrans) Vibration Criteria Butte County does not currently have adopted standards for groundborne vibration that would be applicable to this specific project. As a result, the vibration impact criteria developed by the California Department of Transportation (Caltrans) was applied to the project. The Caltrans guidance criteria for building structure and vibration annoyance are presented in Tables 2 and 3, respectively. Table 2 Caltrans Guidance for Building Structure Vibration Criteria Structure and Condition Limiting PPV (in/sec) Historic and some old buildings 0.5 Residential structures 0.5 New residential structures 1.0 Industrial buildings 2.0 Bridges 2.0 PPV = Peak Particle Velocity Source: 2020 Caltrans Transportation and Construction Vibration Guidance Manual, Table 14. Table 3 Caltrans Guidance for Vibration Annoyance Potential Criteria Human Response Maximum PPV (in/sec) Transient Sources Continuous/Frequent Intermittent Sources Severe/very disturbing 2.0 0.4 to 3.6 Strongly perceptible 0.9 0.1 Distinctly perceptible 0.24 0.035 Barely/slightly perceptible 0.035 0.012 Note: Transient sources create a single isolated vibration event, such as blasting or drop balls. Continuous/frequent sources include pile drivers, pogo-stick compactors, crack-and-seat equipment, vibratory pile drivers and vibratory compaction equipment. PPV = Peak Particle Velocity Source: 2020 Caltrans Transportation and Construction Vibration Guidance Manual, Tables 4 & 6. Bollard Acoustical Consultants, Inc. (BAC) Noise & Vibration Assessment Granite Construction Company Power House Aggregates Haul Route Modification Project Butte County, California Page 8 Local Butte County Criteria Butte County General Plan The Health and Safety Element of the Butte County General Plan contains the County’s noise- related policies. The specific policies which are generally applicable to this project are reproduced below: Policies HS-P1.1 New development projects proposed in areas that exceed the land use compatibility standards in Tables 4 and 5 (General Plan Tables HS-2 and HS-3) shall require mitigation of noise impacts. HS-P1.2 Noise from transportation sources shall not exceed land use compatibility standards in Table 4 (General Plan Table HS-2). Table 4 Maximum Allowable Noise Exposure to Transportation Noise Sources Land Use Exterior Noise Level Standard for Outdoor Activity Areas (dBA)1 Interior Noise Level Standard (dBA) DNL Leq DNL Leq (dB)2 Residential 603 -- 45 -- Transient Lodging 603 -- 45 -- Hospitals, Nursing Homes 603 -- 45 -- Theaters, Auditoriums, Music Halls -- -- -- 35 Churches 603 -- -- 40 Office Buildings -- -- -- 45 Schools, Libraries, Museums -- 70 -- 45 Playgrounds, Neighborhood Parks -- 70 -- -- 1 Where the location of outdoor activity areas is unknown, the exterior noise level standard shall be applied to the property line of the receiving land use. 2 As determined for a typical worst-case hour during period of use. 3 An exterior noise level of up to 65 dB DNL may be allowed provided that available exterior noise level reduction measures have been implemented and interior noise levels are in compliance with this table. Source: Butte County General Plan, Health and Safety Element, Table HS-2. Bollard Acoustical Consultants, Inc. (BAC) Noise & Vibration Assessment Granite Construction Company Power House Aggregates Haul Route Modification Project Butte County, California Page 9 Table 5 Maximum Allowable Noise Exposure to Non-Transportation Sources Noise Descriptor Day (7am – 7pm) Evening (7pm – 10 pm) Night (10 pm – 7 am) Designation Urban Non- Urban Urban Non- Urban Urban Non- Urban Hourly Average (Leq) 55 50 50 45 45 40 Maximum (Lmax) 70 60 60 55 55 50 Notes: 1 “Non-Urban designations” are Agriculture, Timber Mountain, Resource Conservation, Foothill Residential and Rural Residential. All other designations are considered “urban designations” for the purposes of regulating noise exposure. 2 Each of the noise levels specified above shall be lowered by 5 dB for simple tone noises, noises consisting primarily of speech or music, or for recurring impulsive noises. These noise level standards do not apply to residential units established in conjunction with industrial or commercial uses (e.g., caretaker dwellings). 3 The County can impose noise level standards which are up to 5 dB less than those specified above based upon determination of existing low ambient noise levels in the vicinity of the project site. 4 In urban areas, the exterior noise level standard shall be applied to the property line of the receiving property. In rural areas, the exterior noise level standard shall be applied at a point 100 feet away from the residence. The above standards shall be measured only on property containing a noise sensitive land use. This measurement standard may be amended to provide for measurement at the boundary of a recorded noise easement between all affected property owners and approved by the County. Source: Butte County General Plan, Health and Safety Element, Table HS-3. HS-P1.6 Applicants proposing a new noise-producing development project near existing or planned noise-sensitive uses shall provide a noise analysis prepared by an acoustical specialist with recommendations for design mitigation. Butte County Code of Ordinances The Butte County Code of Ordinances exterior noise level standard applicable to non- transportation noise sources are identical to the County General Plan standards shown in Table 5. As a result, compliance with the County’s exterior General Plan standards would also result in compliance with the County Code of Ordinances exterior noise standards. In addition, due to the noise attenuation provided by residential dwellings, compliance with the County’s exterior noise standards would also ensure compliance with the County’s interior noise standards. Therefore, this analysis focuses on compliance with the County’s General Plan exterior noise level standards. Bollard Acoustical Consultants, Inc. (BAC) Noise & Vibration Assessment Granite Construction Company Power House Aggregates Haul Route Modification Project Butte County, California Page 10 Noise Impact Assessment Methodology As noted above, Table 4 provides noise criteria applicable at various land uses affected by transportation noise sources. Transportation noise sources include traffic on public roadways, railroad operations, and aircraft. Conversely, the Table 5 standards are applicable to non- transportation noise sources. Non-transportation noise sources include and noise generated on private property, including traffic on private roads. The evaluation of potential noise impacts for this project is somewhat complicated in that project heavy truck traffic on the currently permitted private haul route is subject to the non-transportation noise standards shown in Table 5, whereas the alternative haul route which utilizes a public roadway (Highway 70), is subject to the transportation noise standards contained in Table 4. However, because both routes could be utilized for heavy truck traffic, any utilization of the alternative Highway 70 haul route would result in a reduction in heavy truck usage and corresponding heavy truck noise levels at existing noise-sensitive receptors located along the currently permitted haul route. As a result, no adverse noise impacts would be identified at the existing receptors along the currently permitted haul route as a result of the project. Therefore, the focus of this evaluation is on the change in traffic noise exposure which would occur at the receptors located along the proposed Highway 70 alternative haul route. Noise Impacts of the Proposed Project According to published Caltrans Traffic Counts, the existing average daily traffic (ADT) volume on the segment of Highway 70 which will be utilized by project traffic is approximately 17,000 vehicles. Approximately 6% of those vehicles are reported as being medium duty trucks (2 axles), and approximately 9% of those vehicles are reported as being heavy duty trucks (3 or more axles). The observed speed on Highway 70 varies but was generally in the range of 60 mph. Existing traffic distribution on Highway 70 is approximately 80% daytime and 20% nighttime. The FHWA Traffic Noise Model (FHWA-RD-77-108) with the traffic data cited above to predicted existing Highway 70 traffic noise levels in terms of DNL at a representative distance of 100 feet from the roadway centerline. The predicted traffic noise level at 100 feet from the roadway centerline was computed to be 71.4 dB DNL. According to the project transportation consultant, W-Trans, the project is expected to generate approximately 720 trips on a peak day, with fewer trips on a typical day. On peak days, project heavy truck trips would occur on Highway 70 between the hours of 5 am and 9 pm, a period of 2 nighttime and 14 daytime hours (87.5 daytime / 12.5% nighttime). During typical conditions, the project would reportedly generate half as many daily trips, or 360 one-way heavy truck trips. The FHWA Traffic Noise Model (FHWA-RD-77-108) was again used with the project traffic data cited above to predicted project-only heavy truck noise levels on Highway 70 in terms of DNL at a representative distance of 100 feet from the roadway centerline. The predicted project-only traffic noise level at 100 feet from the roadway centerline was computed to be 63.6 dB DNL during peak day conditions, and 60.6 dBA during typical day conditions. Bollard Acoustical Consultants, Inc. (BAC) Noise & Vibration Assessment Granite Construction Company Power House Aggregates Haul Route Modification Project Butte County, California Page 11 Adding project traffic noise levels to existing Highway 70 traffic noise levels yields a sum of 72.1 dB DNL and 71.8 dB DNL at the reference distance of 100 feet from the roadway centerline during peak and typical conditions, respectively. At receptors located farther than 100 feet from the centerline the traffic noise levels would be lower, decreasing at a rate of approximately 4.5 dB DNL per each doubling of distance from the roadway centerline. The difference between existing-plus-project and existing-no-project traffic noise levels is 0.7 dB and 0.3 dB DNL during peak and average day conditions, respectively. In other words, the project would result in traffic noise level increases of 0.7 and 0.3 dB DNL during peak and average day conditions, respectively, at existing residences located along the segment of Highway 70 which will be utilized by peak day project heavy truck traffic. Table 6 summarizes the existing and existing+project traffic noise levels at a representative distance of 100 feet from the centerline of Highway 70. Table 6 Highway Traffic Noise Levels and Project-Related Traffic Noise Level Increases Existing vs. Existing Plus Project Conditions Roadway Condition Distance Traffic Noise Level at 100 feet, DNL (dB) Substantial Increase? E E+P Increase Highway 70 Typical day 100 71.4 71.8 0.3 No Peak Day 100 71.4 72.1 0.7 No Source: FHWA-RD-77-108 with inputs from Fehr & Peers. Appendix B contains FHWA model inputs. Although existing Highway 70 traffic noise levels currently exceed the 60-65 dB DNL exterior noise level standard considered acceptable for outdoor activity areas of new residential uses at residences located approximately 100 feet from the roadway centerline, the noise generation of the project by itself is predicted to be within that conditionally acceptable range. In addition, the 0.3 to 0.7 dB DNL traffic noise increase resulting from the project during typical and peak day conditions is below the 1.5 dB threshold required for finding of a significant noise impact. As a result, noise impacts of the project at existing noise-sensitive receptors located along Highway 70 during both typical and peak day operating conditions are predicted to be less-than-significant. Vibration Impacts of the Proposed Project BAC staff observations in conducted in the immediate project vicinity indicates that there was no discernible vibration associated with heavy truck passbys at a distance of 100 feet from the Highway 70 centerline. According to published Caltrans truck classification counts, this segment of Highway 70 currently carries approximately 1,500 heavy trucks per day. Because the project would not result in heavy truck passages closer to residences than current conditions, and because heavy truck passby vibration was imperceptible at distances representative of the nearest residences to the roadway, vibration impacts of the project are predicted to be less- than-significant. Bollard Acoustical Consultants, Inc. (BAC) Noise & Vibration Assessment Granite Construction Company Power House Aggregates Haul Route Modification Project Butte County, California Page 12 Conclusions This evaluation concludes that the proposed project would not result in adverse noise or vibration impacts at existing sensitive land uses (residences) located in the immediate project vicinity. This conclusion applies to both peak day and typical day conditions. These conclusions are based on traffic data provided by the project transportation consultant and information contained within the March 2012 Draft Environmental Impact Report prepared by Benchmark Resources for the Power House Aggregate Project (SC#2009092088). This concludes BAC’s noise and vibration assessment for the Power House Aggregates Haul Route Modification Project in Butte County, California. Please contact BAC at (530) 537-2328 or info@bacnoise.com if you have any comments or questions regarding this report. Appendix A Acoustical Terminology Acoustics The science of sound. Ambient Noise The distinctive acoustical characteristics of a given space consisting of all noise sources audible at that location. In many cases, the term ambient is used to describe an existing or pre-project condition such as the setting in an environmental noise study. Attenuation The reduction of an acoustic signal. A-Weighting A frequency-response adjustment of a sound level meter that conditions the output signal to approximate human response. Decibel or dB Fundamental unit of sound. A Bell is defined as the logarithm of the ratio of the sound pressure squared over the reference pressure squared. A Decibel is one-tenth of a Bell. CNEL Community Noise Equivalent Level. Defined as the 24-hour average noise level with noise occurring during evening hours (7 - 10 p.m.) weighted by a factor of three and nighttime hours weighted by a factor of 10 prior to averaging. Frequency The measure of the rapidity of alterations of a periodic signal, expressed in cycles per second or hertz. IIC Impact Insulation Class (IIC): A single-number representation of a floor/ceiling partition’s impact generated noise insulation performance. The field-measured version of this number is the FIIC. Ldn Day/Night Average Sound Level. Similar to CNEL but with no evening weighting. Leq Equivalent or energy-averaged sound level. Lmax The highest root-mean-square (RMS) sound level measured over a given period of time. Loudness A subjective term for the sensation of the magnitude of sound. Masking The amount (or the process) by which the threshold of audibility is for one sound is raised by the presence of another (masking) sound. Noise Unwanted sound. Peak Noise The level corresponding to the highest (not RMS) sound pressure measured over a given period of time. This term is often confused with the “Maximum” level, which is the highest RMS level. RT60 The time it takes reverberant sound to decay by 60 dB once the source has been removed. STC Sound Transmission Class (STC): A single-number representation of a partition’s noise insulation performance. This number is based on laboratory-measured, 16-band (1/3- octave) transmission loss (TL) data of the subject partition. The field-measured version of this number is the FSTC.