Traffic Noise Technical Report. November 2008

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1 Traffic Noise Technical Report November 2008

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3 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report Table of Contents 1.0 INTRODUCTION RESOURCE DEFINITION APPLICABLE LAWS, REGULATIONS, AND GUIDANCE FOR TRAFFIC NOISE ANALYSIS EXISTING CONDITIONS METHODOLOGY Identification of Noise Sensitive Sites Noise Monitoring STAMINA Model Validation Existing Conditions 66 dba Noise Contours FINDINGS Noise Sensitive Sites Noise Monitoring STAMINA Model Validation Existing Conditions 66 dba Noise Contours DESCRIPTION OF ALTERNATIVES EFFECTS ANALYSIS METHODOLOGY ALTERNATIVE EFFECTS Section 1 I-25 to Brighton Boulevard Section 2 Brighton Boulevard to Colorado Boulevard Section 3 Colorado Boulevard to I Section 4 I-270 to I Section 5 I-225 to Tower Road MITIGATION MITIGATION STRATEGIES PROPOSED MITIGATION CONCLUSIONS AND RECOMMENDATIONS CONSTRUCTION NOISE LOCAL AGENCY COORDINATION REFERENCES List of Figures Figure 1 Project Area...1 Figure 2 Noise Sensitive Sites...7 Figure 3 Alternative Figure 4 Alternative Figure 5 Alternative Figure 6 Alternative Figure 7 Lane Representations in STAMINA...12 Figure 8 Section 1 Receiver Locations and Noise Contours...16 Figure 9 Section 2 Existing Alignment Receiver Locations and Noise Contours...20 Figure 10 Section 2 Realignment Receiver Locations and Noise Contours...21 Figure 11 Section 3 Receiver Locations and Noise Contours...23 Figure 12 Section 4 Receiver Locations and Noise Contours...25 Figure 13 Section 5 Receiver Locations and Noise Contours...26 Figure 14 Section 2 Barriers Realignment Alternatives 4 and 6 West...30 Figure 15 Section 2 Barriers Existing Alignment Alternatives 4 and 6 East...31 Figure 16 Section 2 Barriers Existing Alignment Alternatives 1 and 3 North...31 November 2008 i

4 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement Figure 17 Section 2 Barriers Existing Alignment Alternatives 1 and 3 South...32 Figure 18 Section 3 Barriers Existing Alignment Alternative 4 West and East...33 Figure 19 Section 3 Barriers Existing Alignment Alternative 6 West and East...33 List of Tables Table 1 CDOT Noise Abatement Criteria...4 Table 2 LOS D Traffic Modeling Assumptions...5 Table 3 Section 1 General Contours...14 Table 4 Section 1 Noise Model Results...15 Table 5 Section 2 General Contours...17 Table 6 Section 2 Noise Model Results...17 Table 7 Section 3 General Contours...21 Table 8 Section 3 Model Results...22 Table 9 Section 4 General Contours...23 Table 10 Section 4 Noise Model Results...24 Table 11 Section 5 General Contours...25 Table 12 Section 5 Noise Model Results...26 List of Appendices Appendix A Appendix B Monitoring Results Colorado Department of Transportation Noise Abatement Determination Forms ii November 2008

5 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report List of Acronyms A B C CDOT Colorado Department of Transportation D db decibels dba A-weighted levels DEIS Draft Environmental Impact Statement Denver City and County of Denver E EIS Environmental Impact Statement M mph N NAC NEPA O P Q R RTD S miles per hour Noise Abatement Criteria National Environmental Policy Act Regional Transportation District F FEIS FHWA FTA G H I J K L Leq LOS Final Environmental Impact Statement Federal Highway Administration Federal Transit Administration equivalent sound level level of service T U V W X Y Z November 2008 iii

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7 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report 1.0 INTRODUCTION The I-70 East Environmental Impact Statement (EIS) is a joint effort between the Federal Highway Administration (FHWA) and the Colorado Department of Transportation (CDOT). The intent of the EIS is to identify potential highway improvements along I-70 in the Denver metropolitan area between I-25 and Tower Road and to assess their potential effects on the human and natural environment. Analysis of I-70 through this area began in June 2003 as part of the I-70 East Corridor EIS, a joint effort conducted by CDOT, FHWA, the Regional Transportation District (RTD), the Federal Transit Administration (FTA), and the City and County of Denver (Denver). In June 2006, the highway and transit elements of the I-70 East Corridor EIS were divided into two separate projects because they serve different travel markets, are located in different corridors, and have different funding sources. The I-70 East EIS focuses on potential I-70 improvements and the transit improvements are now being evaluated under the East Corridor EIS, conducted by RTD and FTA. Figure 1 Project Area The project area, shown in Figure 1, includes portions of Denver, Commerce City, Aurora, and Adams County. The area covers established neighborhoods on the west end of the corridor including Globeville, Elyria, Swansea, Cole, Clayton, and Northeast Park Hill. The emerging residential and commercial areas on the east include Stapleton (former Stapleton Airport), Montbello, Green Valley Ranch, and Gateway. These communities are diverse in their character November

8 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement and history, providing a wide variety of residential, commercial, public facility, and institutional land uses. Adding to the complexity of the project area is the presence of the National Western Complex as a major travel destination and redevelopment. This report discusses traffic noise as it relates to the I-70 East EIS, including existing conditions in the corridor, resource effect analysis, and mitigation measures. 2.0 RESOURCE DEFINITION Noise is generally defined as unwanted or undesirable sound. Noise typically affects humans in three different ways, noise intensity or level, noise frequency, and noise variation with time Noise intensity is determined by how sound pressure fluctuates and is expressed in decibels (db). The range of noise normally encountered can be expressed by values between 0 and 120 db on the db scale. A three-db change in sound level generally represents a barely-noticeable change in noise level, whereas a ten-db change would typically be perceived as a doubling of loudness. The frequency of noise is related to the tone or pitch of the sound and is expressed in terms of cycles per second or Hertz. The human ear can detect a wide range of frequencies from about 20 Hertz to 17,000 Hertz. The A-weighting system is commonly used when measuring noise to provide a value that represents human response because human sensitivity to sound varies from person to person. Noise levels measured using this system are called A-weighted levels, and are expressed as dba. Because noise fluctuates during the course of a day, it is common practice to condense all of this information into a single number, known as an equivalent sound level (Leq). Leq represents a steady sound level over a specified time period (typically 15 minutes). 3.0 APPLICABLE LAWS, REGULATIONS, AND GUIDANCE FOR TRAFFIC NOISE ANALYSIS This section discusses applicable laws, regulations, and guidance as they pertain to the analysis of traffic noise in this EIS. National Environmental Policy Act The National Environmental Policy Act (NEPA) of 1969, as amended, (42 United States Code 4321 et seq., Public Law , 83 Stat. 852), mandates that transportation decisions involving federal funds and approvals consider social, economic, and environmental factors in the decision-making process. NEPA also requires that agencies making such decisions consult with other agencies, involve the public, disclose information, investigate the environmental effects of a reasonable range of alternatives, and prepare a detailed statement of the environmental effects of the alternatives. Council on Environmental Quality Regulations Council on Environmental Quality Regulations Part 1502, Environmental Impact Statement, (40 Code of Federal Regulations ), requires that an EIS be prepared when a proposed action is projected to have a significant impact on the quality of the human environment. Under the Council on Environmental Quality regulations EIS documents must provide full and fair discussion of significant environmental impacts and inform decision makers and the public about project alternatives. 2 November 2008

9 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report Procedures for Abatement of Highway Traffic Noise and Construction Noise Title 23 Code of Federal Regulations Part 772 codifies procedures for considering noise studies in NEPA federal-aid processes and establishes requirements for transferring traffic noise information to local planning agencies to assist in their land use planning activities. FHWA Highway Traffic Noise Analysis and Abatement: Policy and Guidance FHWA s Highway Traffic Noise Analysis and Abatement Policy and Guidance defines FHWA procedures for abatement of highway traffic noise and construction noise and establishes standards for mitigating highway traffic noise. The document provides FHWA policies and guidance for the analysis and abatement of highway traffic noise based on 23 Code of Federal Regulations 772. FHWA Measurement of Highway-Related Noise FHWA s Measurement of Highway-Related Noise Policy is intended to provide a uniform guidance reference for highway noise practitioners and researchers, addressing measurement and analysis instrumentation, site selection, measurement procedures, data reduction, and analysis techniques. CDOT Noise Analysis and Abatement Guidelines The CDOT Noise Analysis and Abatement Guidelines (2002a) implements the FHWA noise regulation for CDOT projects. It provides guidance on conducting traffic noise studies, analyzing abatement options, investigating construction noise levels, and coordinating noise levels with local land use planning officials. 4.0 EXISTING CONDITIONS The project area is almost entirely urbanized with varied land uses. At the west end of the project area, a mix of residential and commercial properties gradually changes to primarily commercial/industrial uses near Colorado Boulevard. Continuing east, residential and commercial development begin to appear east of I-225. Major new developments are planned or on-going within the project area in the Stapleton Redevelopment Area between Quebec Street and Havana Street and in the Gateway area north of I-70 and east of Peña Boulevard. 4.1 METHODOLOGY The existing conditions noise analysis was performed in accordance with the requirements of Title 23 Code of Federal Regulations Part 772, Procedures for Abatement of Highway Traffic Noise and Construction Noise, using methodology established by CDOT in their Noise Analysis and Abatement Guidelines. Predicted noise levels were produced using the FHWA traffic noise model STAMINA 2.0 with Colorado vehicle noise emissions (1994). All measured and predicted noise levels are expressed in db using a dba weighting. The dba weighting of the db scale most closely approximates the response characteristics of the human ear. All noise levels are reported as hourly equivalent noise levels. The hourly equivalent noise levels are defined as the equivalent steady-state sound level that, in a given hourly period, contains the same acoustic energy as the time-varying sound for the same hourly period. Noise from traffic emanates from four primary sources: tire/road interface, engines, aerodynamics, and exhaust stacks. The dba weighted numbers are used to determine the effect upon potential noise sensitive sites. Each of these is considered in the STAMINA 2.0 model. November

10 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement Identification of Noise Sensitive Sites Noise sensitive sites are defined as any property (owner-occupied, rented, or leased) where frequent exterior human use occurs and where a lowered noise level would be of benefit. CDOT has established noise levels at which noise abatement must be considered for various types of noise sensitive sites. These noise levels are referred to as the Noise Abatement Criteria (NAC). As presented in Table 1, the NAC vary according to the land use activity category. Noise abatement measures must be considered when either of the following is true: Predicted traffic noise levels meet or exceed the NAC. A substantial noise increase of 10 dba over existing conditions is predicted. Table 1 CDOT Noise Abatement Criteria Activity Category A B C L eq (h) 56 (Exterior) 66 (Exterior) 71 (Exterior) D -- Undeveloped lands. E 51 (Interior) Description of Land Use Activity Category Lands on which serenity and quiet are of extraordinary significance and serve an important public need and where the preservation of those qualities is essential if the area is to continue to serve its intended purpose. Picnic areas, recreation areas, playgrounds, active sports areas, parks, residences, motels, hotels, schools, churches, libraries, and hospitals. Developed lands, properties, or activities not included in Categories A or B. Residences, motels, hotels, public meeting rooms, schools, churches, libraries, hospitals, and auditoriums. Source: CDOT Noise Analysis and Abatement Guidelines (2002a) Noise Monitoring To validate the computer noise model (see Section 4.1.3, STAMINA Model Validation), field measurements were taken within the project area following procedures documented in FHWA s Measurement of Highway-Related Noise Policy. Field measurements were obtained using Larson Davis 812 and Larson Davis 712 Sound Level Meters. Meters, microphones, and calibrators are calibrated to factory settings at Larson Davis s Utah lab annually. Monitoring events generally lasted 15 minutes, but 1-hour and 24-hour measurements were also taken. Noise monitors were calibrated using a Larson Davis sound level calibrator before each measurement STAMINA Model Validation Site selections for the field validation measurements were conducted in the vicinity of noise sensitive sites, where safe access to monitoring sites existed, where a representative sampling of free-flow traffic could be obtained, and where roadway geometry remained relatively constant. Measurements may be taken at anytime; however, standard practice states it is best to measure when traffic is moving at or near the posted speed limit. At least two measurements were taken at each validation location and averaged to avoid skewed results. Traffic volumes and vehicle classifications (car, truck, heavy truck) were recorded with hand counters during noise readings. Volumes and classifications for each validation are included in Appendix A. Traffic speeds were 4 November 2008

11 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report estimated by driving in mainstream traffic during the measurement. Speeds were typically at posted speed limits. A STAMINA noise model was built to simulate traffic and roadway conditions for each validation site. Modeled noise levels were compared to measured noise levels. Validation of the STAMINA model occurred when measured and modeled values are within 3 dba. Validation of the model was necessary before STAMINA can be used to predict noise levels for existing, no-action, and build project scenarios. At the start of the validation process, validation sites were selected throughout the corridor by reviewing project aerials. Multiple sites were chosen to represent the entire project area. Successful validation of sites in different neighborhoods with different roadway geometry, traffic conditions, terrain lines, and shielding (buildings and other impediments to the propagation of noise) provided high confidence in the STAMINA model results and subsequent decisions made in the remaining portions of the noise study Existing Conditions 66 dba Noise Contours Based on CDOT s Noise Analysis and Abatement Guidelines, 66 dba was used as the approach noise level in the analysis of the existing conditions in the study area (see Table 1). The distance from the edge of pavement to the 66 dba noise contour under existing conditions was estimated using the STAMINA computer model, traffic volumes from the loudest hour existing conditions (based upon existing traffic studies and Highway Capacity Manual), and posted speed limits. Noise studies typically use worst-case noise conditions in determining the dba. Generally, worst-case level of service (LOS) C conditions are considered in noise analysis because the greatest volume is traveling at the highest speeds. Given the operations along I-70 in this area, the Highway Capacity Manual LOS curves were used to demonstrate that LOS D conditions result in the worst-case noise conditions in the project area. Data for a typical freeway segment having characteristics similar to I-70 were used as input to determine the maximum number of vehicles (per hour) traveling at five miles per hour (mph) above the posted speed limit. These traffic volumes were used in developing the 66 dba noise contours. Traffic volumes on relatively low volume ramps and side streets were not considered in the model because the ramps speeds were below the program threshold of 30 mph or the volumes were minimal. However, ramps carrying significant volumes of traffic were considered as these ramps impacted noise levels. These included the I-70 to I-25 ramps near the Globeville area and the ramps at I-225 and at I-270. Traffic volumes and vehicle mixes that were used in developing the 66 dba contours are presented in Table 2. It should be noted that all segments of I-70 within the project area exceed optimal traffic conditions (LOS A, B, or C) at some time during a 24- hour period, thus LOS D was used for all segments of I-70 at the loudest hours. Table 2 LOS D Traffic Modeling Assumptions Roadway Type Volume* Speed (mph) Truck Percentage (total - medium/heavy) Highway (I-70) 1, (10-40/60) Ramps 1, (18-50/50) Frontage roads (20-50/50) Cross streets (interchanges) (20-65/35) *Passenger cars per hour per lane November

12 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement 4.2 FINDINGS The existing conditions analysis identified potential noise sensitive sites in the project area and described the noise monitoring process, modeling process, and existing conditions results Noise Sensitive Sites The existing land uses adjacent to I-70 consist of residential, commercial, and light industrial uses. Existing residences, hotels, historic structures, multi-use recreational trails, parks, schools, and planned Land Use Category B sites in the Stapleton redevelopment and Tower Road areas were identified as noise sensitive sites within the project area. Category B sites were identified by reviewing land use maps and project aerials, and verified through field surveys. Noise sensitive areas and noise monitoring locations are shown in Figure Noise Monitoring The 2005 noise monitoring included 15-minute, 1-hour, and 24-hour measurements. Most measurements were taken in Land Use Category B areas. Detail regarding each measurement is included in Appendix A (Table A-1) along with field notes for each measurement. The 15-minute measurements were used to validate the STAMINA model, develop baseline ambient (surrounding environment) noise levels, and gain a better understanding of how multiple noise sources may be affecting a noise sensitive site. The 24-hour noise measurements provided insight on the noise peaks and valleys during a 24-hour period and helped determine the worst-case traffic conditions for noise. Time history graphs for the 24-hour noise measurements have been included in Appendix A. Two observations can be made: Existing noise levels at these 24-hour locations exceed 66 dba for most of the 24-hour period Early morning rush hour noise levels are higher, but their duration is shorter than evening rush hour 6 November 2008

13 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report Figure 2 Noise Sensitive Sites STAMINA Model Validation Data collected in the field, including noise readings, atmospheric information, noise sources, and other site specific information were used along with existing roadway configurations, traffic volumes, speeds, and vehicle mix to calibrate and validate the model at the locations identified as Land Use Category B areas. For the most part, the averages of the measured and modeled values were within the acceptable range of plus or minus 3 dba. There were certain individual instances where a trial was outside of this range, such as reading 13 at Swansea Elementary. At this location the modeled Leq value was 4.0 dba higher than the field measurement during one reading. This is due in part to the unique noise environment that occurs in close proximity to the viaduct section. Because the measured and modeled variances over 3 dba were rare and occurred in unique noise environments the model was considered acceptable for use Existing Conditions 66 dba Noise Contours The existing conditions 66 dba contour is a line, roughly parallel with I-70, where a 66 dba noise level is expected. This distance is generally between 300 and 350 feet from the edge of pavement. Noise levels may be higher for points closer to I-70. The contour considers hard and soft propagation surfaces, terrain, existing noise barriers, and limited shielding effects from other buildings. Hard and soft propagation surfaces refer to land cover types such as grass (soft surface) or pavement (hard surface). Noise waves reflect or bounce easier over hard surfaces allowing noise waves to travel farther. Soft surfaces diffract or break-up noise waves making the wave dissipate sooner and not travel as far. These features may cause the contour to deviate. November

14 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement Examples of this can be seen near existing noise barriers in the Globeville neighborhood (west end of the project) and existing noise barriers west of Chambers Road (north side of I-70). Contours at these points rest on top of the noise barriers because the barriers are effective at reducing noise levels behind the wall to less than 66 dba. The noise contour does not account for other noises sources (e.g., Nestlé Purina Petcare Company). Limited intersecting or adjacent streets were used in the noise model. Figure 8 through Figure 13 in Section 6.0 show maps of the modeled receiver locations and 66 dba noise contours for Sections 1 through DESCRIPTION OF ALTERNATIVES The I-70 East EIS is examining potential social, environmental, and economic resources effects of possible improvements to I-70. Consistent with federal regulation, the EIS evaluates potential effects that might result from a No-Action Alternative and a set of highway build alternatives. For this EIS, the No-Action Alternative is defined as replacement of the existing viaduct between Brighton Boulevard and Colorado Boulevard with no additional lanes or other capacity improvements. The four build alternatives are evaluated in the Draft EIS (DEIS) are shown in Figure 3 through Figure 6 and include: Alternative 1. Adding new general purpose lanes on the existing I-70 alignment along the length of the corridor with interchange improvements throughout the corridor and consideration of a new interchange at Central Park Boulevard. Alternative 3. Adding a combination of general purpose lanes and tolled express lanes on the existing I-70 alignment, with tolled express lanes added from Colorado Boulevard to Chambers Road, and general purpose lanes added west of Colorado Boulevard and east of Chambers Road. Interchange improvements would be made per Alternative 1. Alternative 4. Placing I-70 on new alignment beginning at Brighton Boulevard and extending northeast toward a new interchange with I-270 near Colorado Boulevard, then following I-270 southeast to its existing interchange with I-70. New general purpose lanes would be added to I-70 along its entire length within the study area. New interchanges would be provided along the realignment at Brighton Boulevard, Colorado Boulevard/Vasquez Boulevard with interchange improvements at the remaining interchanges along the corridor and consideration of a new interchange at Central Park Boulevard. The existing viaduct east of Brighton Boulevard would be removed and 46th Avenue would serve as a four- to six-lane roadway along the existing I-70 alignment between Brighton Boulevard and Quebec Street. Alternative 6. As with Alternative 4, placing I-70 on new alignment beginning at Brighton Boulevard and along a portion of I-270. General purpose lanes would be added from I-25 to west of Brighton Boulevard on the realignment and from Chambers Road to Tower Road on the existing alignment. Tolled express lanes would be developed between Brighton Boulevard and Chambers Road. Access improvements would be made per Alternative 4. The existing viaduct east of Brighton Boulevard would be removed and 46th Avenue would serve as a four- to six-lane roadway along the existing I-70 alignment between Brighton Boulevard and Quebec Street. Different options are being evaluated within the alternatives. These options include shifting to the north or south between Brighton Boulevard and Quebec Street on Alternatives 1 and 3, and two options for connecting the realignment to existing I-70 near Brighton Boulevard. For more detail on alternatives, see the I-70 East EIS Alternative Analysis and Screening Process Report (2008). 8 November 2008

15 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report Figure 3 Alternative 1 Figure 4 Alternative 3 November

16 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement Figure 5 Alternative 4 Figure 6 Alternative 6 10 November 2008

17 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report 6.0 EFFECTS ANALYSIS The effect analysis presents the results of traffic noise effects that would result from implementation of project alternatives and discusses mitigation measures to minimize adverse effects. The effect assessment for the I-70 East EIS compares the build alternatives to a No- Action Alternative. 6.1 METHODOLOGY The assessment of noise effects from traffic operations is based on a comparison of existing and projected future noise exposure for noise sensitive land use categories. At the start of the traffic noise study several methodologies were proposed. The methodologies were approved by the project management team with an understanding that some flexibility should be built in for special issues that surfaced. The following describes the methodologies followed for the noise effects analysis. Noise Prediction Model STAMINA 2.0 (Colorado emissions) was used for all traffic noise modeling. Colorado emissions refer to modifications made to the initial STAMINA model during development, to account for Colorado s specific conditions (e.g., thinner air at higher elevations). Shielding No shielding was assigned to second and third row receivers. This guidance was provided by CDOT. Placement of Receivers Receiver locations were placed in the middle of the property closest to the noise source, unless there was another apparent area of frequent outdoor human use. Traffic and Speed As discussed previously, monitoring was conducted during time periods having the worst-case noise conditions. The same is true for modeling. Worst-case conditions on the I-70 mainline were at volumes determined using the Highway Capacity Manual to be at a free flow speed of 55 mph and LOS D. Table 2 in Section 4.1.4, Existing Conditions 66 dba Noise Contours provides the volume, speed, and truck percentage assumptions for the traffic noise modeling. Input Data Vertical and horizontal data for roadways, receivers, and walls was gained from project area mapping and was used for noise modeling. Microstation design files, field reviews, and Geographic Information System were used to provide accurate vertical/horizontal data. Representative lane configurations and receiver locations were created in Geographic Information System prior to STAMINA input. Number of Lanes in STAMINA Model (Existing and Future Scenarios) The STAMINA model limits the number of roadways that may be used in a specific model. Roadways are typically consolidated to facilitate the modeling of complex roadway systems. Figure 7 shows the configurations that were used for the modeling efforts. A single modeled travel lane was used to represent two- or three-directional lanes in the STAMINA model runs November

18 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement and two modeled travel lanes were used to represent four-lane configurations. Two modeled travel lanes were also used to represent the five-lane and six-lane configurations. Figure 7 highlights the number and placement of representative lanes in the STAMINA noise model. The red arrow in the figure represents the location of the modeled lane in the STAMINA model. Figure 7 Lane Representations in STAMINA Three Lane Four Lane Five Lane Six Lane 12 November 2008

19 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report Two-lane ramps and collector-distributors required one modeled lane in STAMINA. The lane was modeled down the center of both lanes. Three-lane frontage roads and ramps also required one modeled lane in STAMINA, but the lane was modeled down the center of the middle lane. One modeled lane of traffic was used to represent cross streets unless the proposed cross streets had four or more lanes in each direction. Interchange Modeling Because it is difficult to model complex interchanges in STAMINA, only high volume ramps adjacent to noise sensitive areas were included. Analysis of other ramps demonstrated that they had little effect on noise sensitive areas. Apartments/Hotels/Condos Noise sensitive structures with multiple floors having areas of frequent human outdoor use were analyzed/modeled. The noise analysis included one floor above existing grade of the adjacent roadway and all floors below it. For example, if the second floor of an apartment building is at the same elevation as the adjacent roadway, the first, second, and third floors were included in the existing conditions noise analysis (this assumes the first, second, and third floors have different tenants). Pool areas and playgrounds associated with these land uses were also included in the noise analysis. Arterial Streets/Alternate Corridors The traffic noise modeling included noise sensitive areas along major arterial streets within 500 feet of I-70. Additional traffic corridors were added to the existing conditions noise study as they were identified in the DEIS process. Viaducts Since STAMINA does not model viaducts effectively, a noise model was constructed replicating I-70 traffic variables (speed, volume, and mix) and a separate noise model was constructed to represent the viaduct noise input variables. The results of these two models were combined through db addition to get an overall noise level. Severe Traffic Noise Severe traffic noise conditions (75 dba or greater) are present in the corridor. Additional monitoring and modeling for severe traffic noise may be required for areas receiving traffic noise at or above 75 dba in the Final EIS (FEIS). Abatement Goals The project team analyzed barriers to achieve at least 5 dba of insertion loss, which is the amount of noise reduction from proposed abatement, with a goal of 10 dba insertion loss. In many cases, analyses of barriers that provide a 10 dba insertion loss goal were considered to be infeasible due to extraordinarily high wall heights required. Rounding Noise values were not rounded or truncated. Values are reported to the tenth of a dba. November

20 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement 6.2 ALTERNATIVE EFFECTS The evaluation of alternative effects is organized by project area sections and focuses on specific locales or communities of sensitive NAC B receivers shown previously in Figure 2. To aid in the comparison of alternatives for these NAC B sensitive receiver areas or communities, tables were developed comparing the existing noise levels and predicted 2030 noise levels for the various alternatives. In addition to these tables, aerial photographs of each area are shown with the receiver locations and the approximate 66 dba contour line for each alternative is provided for general information and is not to determine impacts. The location shown for the 66 dba contour line does not assume any potential mitigation strategies. Efforts were made to include all representative receivers in the analysis of each alternative. However, some receivers evaluated in one alternative were directly impacted by another alternative. These receivers are still presented in the tables to allow for comparison of the alternative to which they are valid. Graphic depictions of contours were not developed for NAC C areas, commercial or industrial type developed lands. As NAC B areas are more sensitive to noise impacts, the focus of the analysis was on those areas and a further detailed analysis of commercial areas was not performed as part of this study Section 1 I-25 to Brighton Boulevard Section 1 includes the Globeville neighborhood, which has existing noise barriers along I-70. No construction is proposed in Section 1 for any of the alternatives. The existing pavement is proposed to be restriped for an additional lane eastbound. Residential properties are the primary land use from I-25 to Washington Street, with a stretch from Washington Street to Brighton Boulevard primarily NAC C (e.g., the Denver Coliseum and National Western Complex). The general NAC B and NAC C contour distances from edge of pavement are presented in Table 3. The modeled receiver locations and 66 dba (NAC B) noise contours for each alternative are shown in Figure 8. Because difference between existing and no-action will only involve the restriping of one lane, which does not affect the overall noise environment, the contour lines for these two alternatives are the same. The specific noise model results for each receiver and alternative are presented in Table 4. Table 3 Section 1 General Contours Alternative Contour line distance from edge of pavement (feet) 1 66 dba (NAC B) 71 dba (NAC C) Existing Primarily on existing barrier except for a small area on the north and south where it is 125 On existing barrier No-Action Primarily on existing barrier except for a small area on the north and south where it is 180 On existing barrier 1 Distances shown are for general comparison purposes and represent an average location of a contour line. 14 November 2008

21 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report Receiver Globeville Existing Table 4 Section 1 Noise Model Results 2030 No-Action 2030 Build Alternatives Build Change * Note: All noise readings are shown as dba. Bold indicates impacted receivers at 66 dba or above for any of the build alternatives. *Change in db compared to existing conditions November

22 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement Figure 8 Section 1 Receiver Locations and Noise Contours Section 2 Brighton Boulevard to Colorado Boulevard Section 2 includes the Elyria, Swansea, Cole, Clayton, and Northeast Park Hill neighborhoods. All build alternatives affect the noise environment for these communities. The general NAC B and NAC C contour distances from edge of pavement are shown in Table 5. The modeled receiver locations and 66 dba (NAC B) noise contours for each alternative are shown in Figure 9. The specific noise model results for each receiver and alternative are shown in Table November 2008

23 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report Table 5 Section 2 General Contours Contour line distance from edge of pavement Alternative (feet) 1 66 dba (NAC B) 71 dba (NAC C) Existing No-Action and 3 (shifts north and south) and 6 (western and eastern connections) th Avenue 75 N/A 1 Distances shown are for general comparison purposes and represent an average location of a contour line. Table 6 Section 2 Noise Model Results Receiver Existing No-Action Alternative North South Elyria and Swansea North of I Build Alternatives Alternative 1 or 3 Alternative 4 or 6 North South West East Build Change * Build Change * Build Change * Build Change * N X X N X N N N N N X 72.1 X N X N X N N N N N N X N N N N N Note: All noise readings are shown as dba. Bold indicates impacted receivers at 66 dba or above for any of the build or No- Action Alternatives. *Change in db compared to existing conditions 1. The existing dba level for receiver N12 was used as a surrogate for receiver N2 due to their equivalent distance from I The existing dba level for receiver N22 was used as a surrogate ambient noise level for receivers RA41 through RA51. November

24 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement Table 6 Section 2 Noise Model Results Receiver Existing No-Action Alternative North South 2030 Build Alternatives Alternative 1 or 3 Alternative 4 or 6 North South West East Build Change * Build Change * Build Change * Build Change * N N X 70.3 X N N X N N N X 72.0 X N X X N X 73.4 X N X N X N N N N X N X N N X Elyria and Swansea South of I-70 S X X X X S X X S X X S X S S S S S S S S X S X X X X S X X X S X S X S S S Note: All noise readings are shown as dba. Bold indicates impacted receivers at 66 dba or above for any of the build or No- Action Alternatives. *Change in db compared to existing conditions 1. The existing dba level for receiver N12 was used as a surrogate for receiver N2 due to their equivalent distance from I The existing dba level for receiver N22 was used as a surrogate ambient noise level for receivers RA41 through RA November 2008

25 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report Table 6 Section 2 Noise Model Results Receiver Existing No-Action Alternative North South 2030 Build Alternatives Alternative 1 or 3 Alternative 4 or 6 North South West East Build Change * Build Change * Build Change * Build Change * S S S S S X S S S S S S S X I-70 Realignment RA RA RA RA RA RA RA RA RA RA RA Note: All noise readings are shown as dba. Bold indicates impacted receivers at 66 dba or above for any of the build or No- Action Alternatives. * Change in db compared to existing conditions 1. The existing dba level for receiver N12 was used as a surrogate for receiver N2 due to their equivalent distance from I The existing dba level for receiver N22 was used as a surrogate ambient noise level for receivers RA41 through RA51. November

26 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement Figure 9 Section 2 Existing Alignment Receiver Locations and Noise Contours 20 November 2008

27 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report Figure 10 Section 2 Realignment Receiver Locations and Noise Contours Section 3 Colorado Boulevard to I-270 There are very few NAC B sites in Section 3 along the existing I-70 alignment as most of the sites in this section fall under the NAC C category. However, the realignment along I-270 does include the Commerce City neighborhood between Quebec Street and 56th Avenue. The general NAC B and NAC C contour distances from edge of pavement are presented in Table 7. The modeled receiver locations and 66 dba (NAC B) noise contours for each alternative are shown in Figure 11 and the specific noise model results for each receiver and alternative are presented in Table 8. Alternative Table 7 Section 3 General Contours Contour line distance from edge of pavement (feet) 1 66 dba (NAC B) 71 dba (NAC C) Existing No-Action and 3 (shifts north and south) (western and eastern connections) (western and eastern connections) Distances are shown for general comparison purposes and represent an average location of a contour line. November

28 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement Table 8 Section 3 Model Results Receiver Existing 2030 No- Action 2030 Build Alternatives Alternative 1 Alternative 3 Alternative 4 Alternative 6 Build Change * Build Change * Build Change * Build Change * Northeast Park Hill N N N S S S Commerce City Note: All noise readings are shown as dba. Bold indicates impacted receivers at 66 dba or above for any of the build alternatives. * Change in db compared to existing conditions 22 November 2008

29 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report Figure 11 Section 3 Receiver Locations and Noise Contours Section 4 I-270 to I-225 Section 4 includes the noise sensitive areas of the west portion of the Montbello neighborhood north of I-70/I-225 and the Sand Creek Trail adjacent to the Stapleton redevelopment site which does not have NAC B sensitive receivers proposed to be located adjacent to I-70. The majority of the receivers in Section 4 are commercial (NAC C) category. Existing Alternative No-Action 1 and 4 (all options) Table 9 Section 4 General Contours Contour line distance from edge of pavement (feet) 1 66 dba (NAC B) 71 dba (NAC C) and on existing barrier in the Montbello area and on existing barrier in the Montbello area and Approximately beyond the existing barrier in the Montbello area and on existing barrier in the Montbello area and on the existing barrier in the Montbello area and on the existing barrier in the Montbello area and beyond the and on beyond the existing 3 and 6 (all options) existing barrier in the Montbello area barrier in the Montbello area 1 Distances shown are for general comparison purposes and represent an average location of a contour line. November

30 Traffic Noise Technical Report I-70 East Draft Environmental Impact Statement Table 10 Section 4 Noise Model Results Receiver Existing 2030 No- Action 2030 Build Alternatives Alternative 1 or 4 Alternative 3 or 6 Build Change * Build Change * Montbello Note: All noise readings are shown as dba. Bold indicates impacted receivers at 66 dba or above for any of the build alternatives. * Change in db compared to existing conditions 24 November 2008

31 I-70 East Draft Environmental Impact Statement Traffic Noise Technical Report Figure 12 Section 4 Receiver Locations and Noise Contours Section 5 I-225 to Tower Road Section 5 includes the noise sensitive areas of the east portion of the Montbello neighborhood and large lot residences south of I-70 and east of I-225. The general NAC B and NAC C contour distances from edge of pavement are presented in Table 11. The modeled receiver locations and 66 dba (NAC B) noise contours for each alternative are shown in Figure 13 and the specific noise model results for each receiver and alternative are presented in Table 12. Alternative Table 11 Section 5 General Contours Contour line distance from edge of pavement (feet) 1 66 dba (NAC B) 71 dba (NAC C) Existing No-Action All Action Alternatives Distances shown are for general comparison purposes and represent an average location of a contour line November