Christine Perron
September 27, 2021
Ozone: The 1-hour 1979 and 8-hour 1997 ozone standards have since been revoked and the area was
recently reclassified as unclassifiable/attainment for ozone.
Particulate Matter: The study area is located in an EPA designated attainment area for particulate matter
(PMio and PM25s); therefore, PMio and PM25s Transportation Conformity requirements do not apply for
projects located in Hillsborough County.
CO Hot-Spot Analysis: The cities of Manchester and Nashua are designated a maintenance area by EPA
for CO, therefore, projects in these areas may require a CO hot spot analysis (i.e. microscale analysis
Phase Il-Level Il study) to ensure compliance with the National Ambient Air Quality Standards (NAAQS).
The hot-spot analysis typically examines worst-case ground-level CO impacts due to traffic flow in the
immediate vicinity of a project intersection/interchange. Since the project is located in an attainment
area for CO and projected traffic at the intersection could result in a drop below an LOS of C and another
intersection with an expected LOS of F; a quantitative CO hot spot analysis is proposed to demonstrate
that project level air quality impacts would not exceed the CO NAAQS.
Greenhouse Gases: Based on the President’s recent Executive Order? , the project impacts should be
documented in the Environmental Assessment (EA) consistent with the 2016 CEQ Final GHG NEPA
guidance. In order to meet the 2016 CEQ guidance, a qualitative GHG analysis is proposed for this
project to document GHG impacts unless NHDOT determines that a GHG is not required for this project.
Microscale CO Hot-Spot Analysis
As discussed above, assuming a Phase Il analysis is required for the signalized intersections, a microscale
hot-spot analysis will be conducted at the East Hollis Street and Bridge Street intersection using the latest
versions of the EPA Mobile Vehicle Emissions Simulator (MOVES) and CAL3QHC models to estimate
worst-case CO concentrations at individual receptor (i.e. receiver) locations for the Existing, and future
Build and No Build conditions. The future Build Alternative traffic, roadway geometry, signal timing data
and nearby roadway receptor locations will be included. The modeling results will be added to
appropriate CO background concentrations and compared to the NAAQS.
Mesoscale Analysis
A mesoscale analysis is typically performed to assess the total VOCs and NO, (i.e. ozone precursors),
carbon dioxide (CO2) if applicable, methane and nitrous oxide associated with motor vehicle emissions
for each condition and Alternative compared to the No-build condition. The mesoscale analysis evaluates
the regional impact of VOC, NO, and greenhouse gas (if required) emissions affiliated with the project.
HMMH assumes a regional impact analysis (i.e. mesoscale) will not be required for this project.
HMMH assumes the Build Alternative will not significantly affect air quality and/or cause a violation of
the NAAQS, therefore a Phase III analysis will not be required to evaluate abatement alternatives. HMMH
assumes a quantitative (Phase II) will be required to address CO impacts (see above microscale CO hot-
spot).
3. Task 3: Mobile Source Air Toxics (MSATs)
On October 18, 2016, the FHWA issued updated interim guidance regarding Mobile Source Air Toxics
(MSATs) in a NEPA analysis to include the EPA’s recent MOVES2014a emission model along with updated
research on air toxic emissions from mobile sources. The guidance includes three categories and criteria
! Executive Order on Protecting Public Health and the Environment and Restoring Science to Tackle the Climate
Crisis”. January 20, 2021.
* Memorandum for Heads of Federal Departments and Agencies from Christina Goldfuss, Council on Environmental
Quality. “Final guidance for Federal Departments and Agencies on Greenhouse Gas Emissions and the Effect of
Climate Change in the National Environmental and Policy Act Reviews”. August 1, 2016
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