Air Quality Analysis

South and East Beltways Study

Lincoln, Nebraska

Prepared for

Federal Highway Administration

Nebraska Department of Roads

Lancaster County

City of Lincoln

October 2000

(Revised 2/01)

AIR QUALITY ANALYSIS

for

South and East Beltways Study

Lincoln, Nebraska

Page

1.0 PURPOSE B.3

2.0 PROJECT DESCRIPTION B.3

3.0 ANALYSIS FRAMEWORK B.4

4.0 AIR QUALITY MODELS B.4

5.0 STUDY AREAS B.4

6.0 AIR QUALITY IMPACTS B.5

6.1 Traffic B.5

6.2 Construction B.5

7.0 REFERENCES B.6

Appendix B-A Model Inputs and Assumptions B.7

Appendix B-B CAL3QHC Air Dispersion Model Output B.23

Table B.1 Highest 1-Hour and 8-Hour Carbon Monoxide Concentrations B.5

AIR QUALITY ANALYSIS

for

South and East Beltways Study

Lincoln, Nebraska

1.0 PURPOSE

The Clean Air Act (CAA) and the National Environmental Policy Act (NEPA) require that air quality impacts be assessed for proposed roadway projects. The CAA also requires that the roadway project conform with the State Implementation Plan (SIP) with respect to maintaining compliance with the National Ambient Air Quality Standards (NAAQS).

The Clean Air Act of 1970, as amended in 1977, 1990 and 1997, establishes NAAQS for seven criteria pollutants- PM_10, PM_2.5, Ozone, Sulfur Dioxide, Lead, Nitrogen Oxides and Carbon Monoxide. To determine the significance of the air quality impact of the proposed project, those impacts, together with the existing background air quality levels, must be compared to the national ambient air quality standards (NAAQS) on a regional and project-level basis.

The objective of a regional analysis is to determine the impact the project will have on regional air quality and if the project is in conformance with the State Implementation Plan (SIP). Based upon the most currently published data (Nebraska Air Quality, 1998), the entire State is in compliance with the NAAQS, therefore, a regional analysis is not necessary.

The objective of the project-level analysis is to predict the criteria pollutant concentration proximal to the worst-case (high traffic volume) portions of the project and compare the predicted concentration to the NAAQS. Although there are several criteria pollutants associated with mobile source emissions, the Federal Highway Administration (FHWA) considers carbon monoxide to be the most significant criteria pollutant of concern for a project-level analysis (FHWA Memorandum, 1986). The NAAQS for carbon monoxide are:

• 35 parts per million as a maximum 1-hour concentration not to be exceeded more than once per year.
• 9.0 parts per million as a maximum 8-hour concentration not to be exceeded more than once per year.

2.0 PROJECT DESCRIPTION

The purpose of the South and East Beltways Study has been to conduct a feasibility study and alternatives evaluation for preferred beltway alignments on the south and east fringes of the City of Lincoln to complete a circumferential transportation system. The south beltway would connect US 77 with N-2, while the east beltway would connect N-2 with I-80.

The study area for the south beltway is bounded on the north by Yankee Hill Road, on the south by the half-section line 0.5-mi south of Bennett Road, on the east by the half-section line 0.8 km (0.5-mi) east of 148^th Street, and on the west by US 77. The study area for the east beltway is bounded on the west by 98^th Street, on the east by the half-section line 0.8 km (0.5-mi) east of 148^th Street, on the north by I-80, and on the south by N-2.

The Nebraska Department of Roads Standard Section for a Rural Expressway was used for all beltway alignments. A rural expressway typical section has the following features:

• Approximately 76.2 to 91 m (250 to 300 ft) right-of-way; right-of-way needs vary with topography
• Two 3.7 m (12 ft) driving lanes in each direction
• 2.4 m (8 ft) paved outside shoulders
• 0.9 m (3 ft) paved inside shoulders
• 12 m (40 ft) unpaved depressed median (includes inside shoulders)

3.0 ANALYSIS FRAMEWORK

To determine the significance of the air quality impact of the proposed project, a screening level analysis has been completed. In this analysis, a relatively large degree of "conservatism" is incorporated to provide reasonable assurance that maximum concentrations will not be underestimated.

If the predicted carbon monoxide concentration at receptors located near the worst-case roadways and intersections, when added to the background carbon monoxide concentration, do not exceed the NAAQS, none of the roadway segments should. The background carbon monoxide concentration used in the analysis was 3.9 parts per million for the 1-hour average. This concentration was recorded at the NDEQ's Arlington Street ambient air quality monitoring station located in Lincoln, Nebraska during the1998 monitoring period which is the most recent monitoring period available.

4.0 AIR QUALITY MODELS

The project-level analysis utilized the CAL3QHC (Version 2) and the MOBILE 5A models. The CAL3QHC model is listed in the Guideline on Air Quality Models as an appropriate model. The CAL3QHC model can predict carbon monoxide or other inert pollutant concentrations from both moving and idling vehicles. The model is based upon the Gaussian diffusion equation and employs a mixing zone concept to characterize pollutant dispersion over the roadway. MOBILE 5A is used to generate traffic source emission factors for input into the CAL3QHC model. Model inputs and assumptions are described in Appendix B-A.

5.0 STUDY AREAS

Two roadway segments and two interchanges; representing worst-case conditions, were selected for analysis based upon predicted Average Daily Traffic (ADT) volumes. A description of these roadways and interchanges follow:

• The SM-4 alternative between South 27^th Street and South 68^th Street (20,711 ADT) and the EC-1 alternative between Adams Street and "O" Street (29,837 ADT). All traffic is under free-flow conditions and travel speeds are estimated to be 105 km/h (65 mph).
• The US 77 and SM-4 interchange (35,539 ADT), and the Interstate 80 and EM-1 interchange (83,600 ADT) . To maintain free-flow traffic conditions, these intersections are a cloverleaf design and incorporate several grade separations. Driving lane widths will vary from two lanes to single lane. Average travel speeds are estimated to be 97 km/h (60 mph) with slower speeds (56 km/h (35 mph)) along tight curves.

6.0 AIR QUALITY IMPACTS

6.1 Traffic

The maximum carbon monoxide concentrations are summarized in Table B.1 below. Based upon this study, the carbon monoxide contribution together with the background carbon monoxide concentration is within the 1-hour and 8-hour concentration limits established in the NAAQS at all receptors. Since these roadway segments and interchanges are in compliance, it is reasonable to assume that all the interchanges and roadway segments for any of the alternatives will be in compliance with the NAAQS.

6.2 Construction

Construction equipment emissions generated from internal combustion engines and fugitive dust generated during excavation, grading and site preparation will cause a short term impact on ambient air quality. Of these emissions, fugitive dust will be the most predominant. Dust generated from these activities is predominantly large particles which are redeposited in close proximity to the source. However, a fraction of the dust is composed of small particles referred to as PM₁₀ which remain airborne for an indefinite period of time. Application of water to construction areas to reduce airborne dust and abatement devices on construction equipment are mitigative measures which will be implemented if necessary.

Table B.1

HIGHEST 1-HOUR AND 8-HOUR

CARBON MONOXIDE CONCENTRATIONS

7.0 REFERENCES

• Nebraska Air Quality 1998, Nebraska Department of Environmental Quality
• Appropriate Level of Highway Air Quality Analysis for a CE, EA/FONSI, and EIS, March 1986.
• Guideline on Air Quality Models, EPA-450/2-78-027R. EPA Office of Air Quality Planning and Standards, Research Triangle Park, NC.
• Breeze Roads, Version 2.0, Trinity Consultants Inc., 1999
• User's Guide to MOBILE 5, EPA, Ann Arbor, MI., 1992.

Appendix B-A

Model Inputs and Assumptions

Mobile 5A Model

The Mobile 5A program is used to determine vehicle exhaust emission factors. Because more newer cars with better pollution control devices are replacing the older cars, the vehicle mean exhaust emission factors usually decrease faster than the traffic volumes increase each year. Consequently, the projected first year of traffic activity (Year 2020) was used to simulate a worse case situation for the design life span of the project.

Mobile 5A Inputs

Mobile 5A default values for the operating mode (percent of cold starts) and percent of diesel vehicles were used, and a Reid vapor pressure (RVP) of 10 psi was input. Since vehicle exhaust emissions are higher during the colder months, an ambient temperature of -1^o C (30^o F) (an average temperature for December through February) was input for worst-case conditions. The year 2020 was input into the model for calculation of the exhaust emission factors at various travel speeds (refer to Attachment B-A-1, Mobile 5 Output).

Emission Factors

Emission factors for traffic are determined using the Mobile 5A emission output combined with the predicted vehicle mix percentages provided by HWS Consulting Group, Inc. (Table B-A.1). Vehicles are grouped into three categories; Light Duty Vehicles (LDV), Light Duty Trucks (LDT) and Heavy Duty Trucks (HDT). Light Duty Trucks include all vehicles having two axles and six wheels, generally having a gross weight greater than 44 000 newton (10,000 pounds) but less than 116 000 newton (26,000 pounds). Heavy Duty Trucks include all vehicles having three or more axles, generally having a gross vehicular weight greater than 116 000 newton (26,000 pounds). Each category includes gasoline and diesel fueled vehicles.

VEHICLE MIX PERCENTAGE

¹ Provided by HWS Consulting Group, Inc.

² Provided by Nebraska Department of Roads

Free Flow Traffic

The free flow emission factors for the roadway segments analyzed are summarized in Table B-A.2. An example calculation is provided below.

Assume vehicle mix on roadway is 96% LDV, 1.07% LDT and 8.3% HDT and travel speed is 105 km/h (65 mph).

Calculate CO emission for each vehicle class. Use Mobile 5A output for CO emissions at 105 km/h (65 mph) and the vehicle-class kilometers (miles) traveled-percentage.

• (LDG vmt % x Exhaust CO ) + (LDD vmt % x Exhaust CO) = LDV exhaust g/km (grams/mi)

(99.7 % x 19.31) + (0 .3 % x .87) = 11.96 g/km (19.25 g/mi)

• (LDGT vmt % x Exhaust CO ) + (LDDT vmt % x Exhaust CO) = LDT exhaust g/km (g/mi)

(98.3 % x 26.55) + (1.6 % x 0.98) = 16.22 g/km (26.11 g/mi)

• (HDGT vmt % x Exhaust CO ) + (HDDT vmt % x Exhaust CO) = HDT exhaust g/km (g/mi)

(28.8 % x 21.89) + (71.2 % x 6.77) = 6.91 g/km (11.12 g/mi)

Calculate composite emission factor based upon vehicle mix % from traffic study.

• 97% LDV x 11.96 g/km (19.25 g/mi) = 11.60 (18.67)
• 1.3 % MDT x 16.22 g/km (26.11 g/mi) = 0.21 (0.34)
• 1.8% HDT x 6.91 g/km (11.12 g/mi) = 0.12 (0.20)

Total............= 11.93 g/km (19.2 g/mi)

Table B-A.2

COMPOSITE EMISSION FACTORS

FREE FLOW SEGMENTS

CAL3QHC Air Dispersion Model

Model Inputs. The following model inputs were used:

1. Meteorology

The regulatory default values for the following inputs were used:

Wind Speed: 1 meter/second

Stability Class: E (stable conditions, rural areas)

Wind Direction: "Worst Case" wind direction angle (determined using ten degree increments.

Mixing Height: 1000 meters

2. Emission Factors

The composite emission factors derived from the MOBILE 5A program were input.

3. Roadway, Intersection and Receptor Parameters

The geometrics of the roadways and interchanges were derived from the South and East Beltways Study, Interim Report No. 3, June 1997 (revised March 1999). Source heights were input at 0 feet above ground level with the exception of the elevated portions of the interchanges which were input at 7.6 meters (25 feet) above ground. All receptors were input at 1.8 meters (6 feet) above ground level and are located along the roadway at the edge of the mixing zone.

4. Other Site Variables

A surface roughness factors (Z_o) of 4.0 was input based upon the surrounding land use which is predominantly grassland.

The settling velocity (V_s) and the deposition velocity (V_d) were set at zero because carbon monoxide is a gaseous emission. All predicted carbon monoxide concentrations are based upon an averaging time of 60 minutes.

5. Traffic Parameters

Traffic volume was obtained from the Lincoln-Lancaster Planning Department (Lincoln-Lancaster Beltway Alternatives Study Data, memo from Mike Brienzo to Mike Gorman, January 12, 2000) (refer to Attachment B-A-2). The traffic volume used in this study is based upon 2030 projections. Typically, roadway projects are modeled using 20 year traffic projections, however, the 2030 data was developed to correspond to the Build Out Scenario (BOS2) Land Use Plan adopted by the City of Lincoln. This plan assumes a population of 374,630. The peak hour traffic used in the model was assumed to be 10% of the ADT.

ATTACHMENT B-A-1

MOBILE 5A EMISSIONS OUTPUT

ATTACHMENT B-A-2

TRAFFIC VOLUME

Appendix B-B

CAL3QHC Air Dispersion Model Output

Attachments to this portion or in Adobe Acrobat (315KB)