Skip to content U.S. Department of Transportation/Federal Highway AdministrationU.S. Department of Transportation/Federal Highway Administration

Office of Planning, Environment, & Realty (HEP)
PlanningEnvironmentReal Estate

HEP Events Guidance Publications Awards Contacts

WOODROW WILSON BRIDGE PM2.5 CONFORMITY ANALYSIS

PM2.5 Hot Spot Analysis

Project of Air Quality Concern

As noted previously, EPA's final rule on PM2.5 hot-spot analyses requires localized assessment for projects of air quality concern. The final rule defines the projects of air quality concern that require a PM2.5 or PM10 hot-spot analysis in 40 CFR 93.123(b)(1) as:

  1. New or expanded highway projects that have a significant number of or significant increase in diesel vehicles;
  2. Projects affecting intersections that are Level-of-Service D, E, or F with a significant number of diesel vehicles, or those that will change to Level-of-Service D, E, or F because of increased traffic volumes from a significant number of diesel vehicles related to the project;
  3. New bus and rail terminals and transfer points that have a significant number of diesel vehicles congregating at a single location;
  4. Expanded bus and rail terminals and transfer points that significantly increase the number of diesel vehicles congregating at a single location; and
  5. Projects in or affecting locations, areas, or categories of sites which are identified in the PM2.5 or PM10 applicable implementation plan or implementation plan submission, as appropriate, as sites of violation or possible violation.

Examples of projects of air quality concern that would be covered by 40 CFR 93.123(b)(1)(i) and (ii) include:

Examples of projects of air quality concern that would be covered by 40 CFR 93.123(b)(1)(iii) and (iv) include:

Based on traffic projections at major locations within the study area, as shown in Table 2, it has been determined that the Woodrow Wilson Bridge project meets the criteria set forth in 40 CFR 93.123(b)(1) as a project of air quality concern as it is estimated that the project will have a significant increase in the number of diesel vehicles. Therefore a hot-spot analysis must be performed for the project.

Table 2
Predicted Vehicular Volume and Associated Truck Percentages
Area 2008 AADT Truck Percentage
MA-5: I-295 HOV Ramp Area 244,275 8.0%
MB-5: MD210 HOV Ramp Area 179,356 7.5%
VA-10: US 1 HOV Ramp Area 221,315 6.6%
VB-2/3/6: Telegraph Road Interchange 200,234 6.5%


Year of Peak Emission Burden

As clarified in the preamble to the July 1, 2004 revision to the transportation conformity rule (64 FR 40056), the conformity rule requires that project-level analyses consider the year of expected peak emissions from the project. For PM2.5, this is expected to be a near-term year, such as the first year of operation of the project, because emission rates from diesel vehicles are predicted to substantially decline between the opening year (2008) and the design year (2020) and these decreases would more than offset any increase in projected traffic volumes. The decline in emissions in future years are due in part to improvements in tailpipe emissions, national vehicle emissions control programs and the mandated use of ultra-low sulfur diesel-fuel. As shown in Figure 4, the regional PM2.5 emissions are much higher in current years than in future years. Since regional emissions are a good indicator of the overall emissions trends in the region, it is therefore expected that 2008 would be the year of peak emissions from the project and other emissions sources that affect the project area. This is true even though several minor phases of the project will not be operational until after 2008 because the affects on traffic from these phases will be minimal.

Bar graph showing estimates of NOx and Direct PM2.5 emissions.  Direct PM2.5 values are reported in tons/year and NOx values are reported in 1000 tons/year.  The 2002 values are 1651 and 92 for Direct PM2.5 and NOx, respectively.  The 2010 values are 933 and 44 for Direct PM2.5 and NOx, respectively.  The 2020 values are 766 and 15 for Direct PM2.5 and NOx, respectively.  The 2030 values are 800 and 12 for Direct PM2.5 and NOx, respectively.  The source of the data is the Metropolitan Washington Council of Governments, Standards Air Quality Conformity Assessent, December 21, 2005.

Traffic Data

Overall traffic and truck data have been analyzed to assess the location associated with the remaining project phases that are most likely to have the highest emissions burden.

2008 AADT for the Build scenario for the roadways near the remaining project phases, were derived from the Woodrow Wilson Bridge FEIS and from information provided by the Maryland State Highway Administration. Truck percentages for these roadways were taken from the VDOT report "2005 Daily Traffic Volume Estimates Including Vehicle Classifications Estimates - Jurisdiction Report 29". Since the project is not changing the overall character of the area, it is not expected that the project will change in the current vehicle mix within the area. As such, the truck percentages present in 2005 are applied to 2008 vehicular volume estimates to obtain 2008 truck volumes. A description of the traffic characteristics for the project area of each remaining phase of the project is given below.

MA-5: I-295 HOV Ramp Project Phase
The 2008 Build AADT volumes for the roadways in the project area are approximately:

For I-95, truck percentages from the portion of I-95 between US1 and the Potomac River were used. Truck percentages for I-295 were assumed to be similar to those for I-95. The overall truck percentage for the area is 8.0%, with an AADT of 244,275.

MB-5: MD210 HOV Ramp Project
The 2008 AADT volumes for the roadways in the project area are approximately:

For I-95, truck percentages from the portion of I-95 between US1 and the Potomac River were used. Truck percentages for MD210 were assumed to be similar to those for Telegraph Road. Taking a weighted average based on volume, the overall truck percentage for this area is 7.5% with an AADT of 179,356.

MM-6: Anacostia East Wetland Mitigation Project
This project phase is not predicted to increase AADT as compared to the No Build Scenario. The project is not expected to increase the overall diesel truck percentages on nearby roadways.

VA-8: Jones Point Park Redevelopment
This project phase is not predicted to increase AADT as compared to the No Build Scenario. The project is not expected to increase the overall diesel truck percentages on nearby roadways.

VA-10: US 1 HOV Ramps

The 2008 AADT volumes for the roadways in the project area are approximately:

Taking a weighted average based on volume, the overall truck percentage for the area is 6.6% with an AADT of 221,315.

VB-2/3/6: Telegraph Road Interchange
The 2008 AADT volumes for the roadways in the project area are approximately:
Taking a weighted average based on volume, the overall truck percentage for the area is 6.5% with an AADT of 200,234.

VM-5: Jones Point Park Reforestation Construction
The project phase is not predicted to increase AADT as compared to the No Build Scenario. The project is not expected to increase the overall diesel truck percentages on nearby roadways.

VM-6: Elmwood Drive Stormwater Management Project
The project phase is not predicted to increase AADT as compared to the No Build Scenario. The project is not expected to increase the overall diesel truck percentages on nearby roadways.

Witter Drive Recreational Facility
This phase is the construction of a recreational facility for the City of Alexandria.
The operation of this facility is not expected to increase the overall diesel truck percentages on nearby roadways.

Freedman's Cemetery
This project phase includes fencing, landscaping, and possibly interpretive signage/panels and other memorializing features. These actions are not expected to increase the overall diesel truck percentages on nearby roadways.

Streetscape Improvements
These improvements are not expected to increase the overall diesel truck percentages on nearby roadways.

Local Neighborhood Traffic Improvements
These improvements are not expected to increase the overall diesel truck percentages on nearby roadways.

Equipment Purchase Projects
The equipment to be purchased is not expected to increase the overall diesel truck percentages on nearby roadways.

Local Neighborhood Community Enhancement Program
These programs are not expected to increase the overall diesel truck percentages on nearby roadways.

In summation, the traffic data indicate that the remaining project phases that do not affect diesel traffic are:

As shown earlier in Table 2, the project areas of the remaining phases that are affected by diesel traffic are:

PM2.5 Qualitative Methodology

According to 40 CFR 93.123(b)(2) and (4), a quantitative analysis for applicable projects is not required until the EPA releases modeling guidance in the Federal Register. However, a qualitative hot-spot analysis is still required. For this project, a qualitative project-level hot-spot assessment was therefore conducted following the joint EPA and FHWA March 29, 2006 guidance Transportation Conformity Guidance for Qualitative Hot-Spot Analyses in PM2.5 and PM10 Nonattainment and Maintenance Areas (EPA420-B-06-902) in order to assess whether the project will cause or contribute to any new localized PM2.5 violations, or increase the frequency or severity of any existing violations, or delay timely attainment of the PM2.5 NAAQS.

Following the methodologies provided in the March 2006 guidance, a comparison approach of monitored PM2.5 levels within the study area, roadway volumes, future emission projects, and future AADT estimates was used to determine whether the remaining phases of the project have the potential to cause or exacerbate a violation of the PM2.5 NAAQS. Table 2 summarizes the traffic and truck characteristics of the project area for the four remaining project phases that have the potential to impact PM2.5 levels. The project area of Phase MA-5: I-295 HOV Ramp Project has the highest overall vehicular volume and the highest truck percentages of all the phases analyzed. For this analysis therefore, it was determined that the project area of phase MA-5 would be analyzed as the worst case site of the remaining project phases. Thus the conditions for this phase would be used in the qualitative comparison approach to determine if the remaining phases of the project have the potential to cause or exacerbate a violation of the PM2.5 NAAQS.

Existing Conditions - PM2.5 Monitored Levels near the Study Area

The Virginia Department of Environmental Quality (DEQ) and the Maryland Department of the Environment (DOE) are required to conduct air quality monitoring by both federal and state regulations. Regional operators routinely service the monitoring instrumentation, perform the quality assurance checks necessary to ensure that the analyzers are operating properly, and perform various types of preventive maintenance. The current PM2.5 monitoring network for Virginia and Maryland has been developed following the requirements of 40 CFR Part 58 and applying the EPA's "Guidance for Network Design and Optimum Site Exposure for PM2.5 and PM10".

Following the March 2006 guidance, monitoring data collected at a monitor located in an area similar to the area affected by the proposed project should be used to represent the air quality in the study area.

Eleven PM2.5 monitors are located in the Washington DC-MD-VA PM2.5 nonattainment area: three in the District of Columbia, five in the Commonwealth of Virginia, and three in the State of Maryland. The traffic levels near these monitors, which are a summary of 2004 AADTs on nearby roadways, and are based on the latest available traffic information, were analyzed in May of 2006 as part of the recently approved "Project-level Conformity Determination for the Intercounty Connector Project in Maryland", and are shown in Table 3.

Table 3
Monitor Number and Name Traffic Impact Volumes Weighted Truck Percentage Trucks per day
240330030 Muirkirk, MD 303,600 7.9% 24,288
240313001 Rockville, MD 74,375 ** ---
240338003 Upper Marlboro, MD*** 93,650 ** ---
110010041 RFK Stadium (34th & Dix), DC*** 235,600 5.4% 12,722
110010043 near Howard University, DC 130,900 ** ---
110010042 near Tidal Basin, DC 223,652 5.04 11,272
510130020 near Pentagon City, VA 346,000 2.17 7,508
510595001 McLean, VA 301,000 3.4 10,234
511071005 Ashburn, VA 124,000 ** ---
510590030 Franconia, VA 216,500 6.2 13,423
510591005 Annandale, VA 282,000 2.7 7,614
(Source: Project-level Conformity Determination for the Intercounty Connector Project in Maryland, Appendix C)
* Based on major roads within approximately two miles of the monitor
** Where traffic impact volumes were less than ½ of the worst case traffic volumes, weighted truck percentages were not calculated.
***There are two monitors at this location.


Representative Monitor

While the Franconia monitor (also referred to as the Lee Park monitor) is the closest monitor to the project area (see Figure 5), the AADT and the truck percentages near the Muirkirk monitor are most representative of (and more conservative than) those near the worst case analysis site (i.e., near the phase MA-5: I-295 HOV Ramp project). The Muirkirk monitor, which is located approximately 20 miles from the study area (see Figure 5), has the highest AADT (303,600) and truck percentages (7.9%) of all the monitors listed in Table 3 while the AADT and truck percentages near the Franconia monitor are lower than those near the analysis. The Muirkirk monitor, therefore, was used as the representative monitor for the study area. However, as the Franconia monitor is closer to the study area, values recorded at this monitor were also considered.

Detailed road map showing the location of the Muirkirk and Franconioa air quality monitors relative to the study area

Monitored PM2.5 Levels

As shown in Figures 6 and 7, the latest two full years (2004 and 2005) of monitored values (note: the Muirkirk monitor was not operational prior to 2004) as well as monitored values for 2006 (January 1 through September 5, 2006) at the Muirkirk monitor are below the applicable NAAQS. Based on these data, the highest 98th percentile 24 hour monitored value is 38 μg/m3, which occurred in 2004. This is 58% of the applicable standard of 65 μg/m3. The highest annual monitored value is 13.4 μg/m3, which occurred in 2005. This is 89% of the annual standard. No violation of the PM2.5 NAAQS has been reported at this monitor.

The highest values recorded at the Franconia monitor, as shown in Figures 8 and 9, are 36 ug/m3 over 24 hours (98th percentile) and 13.9 ug/m3 annually. No violation of the PM2.5 NAAQS has been reported at this monitor.

Updated: 07/06/2011
HEP Home Planning Environment Real Estate
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000