**EPA New England**![](media/image1.wmf){width="1.0381944444444444in"
height="0.9798611111111111in"}

**[MEMORANDUM]{.underline}**

**DATE:** August 14, 2006

**SUBJ:** Technical Support Document for Massachusetts' Request to Amend
Certification of

> Roadway Tunnel Ventilation Systems in the Metropolitan Boston Air
> Pollution Control District.

**FROM:** Donald O. Cooke, Environmental Scientist

> Air Quality Unit, Office of Ecosystem Protection

**TO:** Files

I have completed my review of Massachusetts\' July 12, 2006, submission
to revise the certification of roadway tunnel ventilation systems in the
Metropolitan Boston Air Pollution Control District approved into the
Massachusetts State Implementation Plan on October 8, 1992, (57 FR
46310).

Technical Support Document

*Background and Purpose.*

On July 12, 2006, the State of Massachusetts submitted a formal revision
to its State Implementation Plan (SIP). The SIP revision consists of
technical revisions to 310 CMR 7.38, entitled "Certification of Tunnel
Ventilation Systems in the Metropolitan Boston Air Pollution Control
District". The technical revisions apply to the emissions monitoring
section of the regulation at 310 CMR 7.38(8)(a) and are a result of
improved emissions monitoring techniques developed during early
operating phases of the Central Artery/Tunnel Project (CA/T Project) and
of the availability of more cost effective, longitudinal tunnel
ventilation technology. A new subsection 310 CMR 7.38 (1)(b) requires
the tunnel ventilation systems subject to federal New Source Performance
Standard or National Emission Standard for Hazardous Air Pollutants to
operate in compliance these regulations. A new section 310 CMR 7.38 (10)
"Removal of Air Pollution Control and Monitoring Equipment" has been
added to protect air pollution control equipment, and equipment used to
monitor emissions or operations required in accordance with 310 CMR
7.38. In addition to the technical revisions, typographical errors are
also being corrected in the existing regulation.

The Certification of Tunnel Ventilation Systems in the Metropolitan Air
Pollution Control District regulation, 310 CMR 7.38, was promulgated on
January 18, 1991 and applies to the construction and operation of any
tunnel ventilation system for highway projects constructed after January
1, 1991. On October 8, 1992, EPA approved 310 CMR 7.38 as a revision to
the Massachusetts SIP (57 FR 46310). In the final rule, EPA agreed with
Massachusetts Department of Environmental Protection (MA DEP) that
tunnel ventilation systems are not stationary sources subject to
Prevention of Significant Deterioration (PSD) or to New Source Review
(NSR) permitting requirements of the Clean Air Act (CAA), nor to MA DEP
Plan Approval and Emissions Limitations Regulation for stationary
sources, 310 CMR 7.02.

The purpose of the regulation is to require certification that tunnel
ventilation systems for highway projects in the Metropolitan Boston Air
Pollution Control District[^1] including the CA/T Project, meet
applicable air quality requirements, thereby protecting public health
and the environment. The regulation requires an initial,
"preconstruction" certification, an operation certification (required
12-15 months after a project becomes fully operational), and
re-certification every five years. In accordance with 310 CMR 7.38(2)(a)
through (c), the proponent must certify that the project will not: (a)
cause or exacerbate a violation of any National Ambient Air Quality
Standard as set forth at 40 CFR 50, or a Massachusetts Ambient Air
Quality Standard as set forth at 310 CMR 6.00; or (b) cause or
exacerbate a violation of the MA DEP's one hour ambient NO~2~ guideline
of 320 ug/m^3^; or (c) result in an actual or projected increase in the
total amount of non-methane hydrocarbons measured within the project
area when compared with the no-build alternative.

This action will improve emission monitoring techniques for roadway
tunnel ventilation systems in the Boston Metropolitan Air Control
District. Under the air emission monitoring protocol established by this
process as a SIP element, MA DEP will be able to amend the monitoring
requirements to ensure that the most appropriate monitoring techniques
are implemented, and that ambient air quality does not exceed Federal
National Ambient Air Quality Standards (NAAQS) in the tunnel portal
areas, or downwind of the roadway ventilation stacks. Air emission
monitoring protocols, subsequent modifications, (preconstruction,
operating, and 5-year renewal operating certificates), and all
mitigation plans or conditions imposed by the state under this SIP
revision, will be subject to Federal enforcement under the SIP. While
the certification process is established as a SIP element; approval of
individual certifications or conditions which require written approval
by MA DEP, will not require SIP revisions. This concept is included in
the existing SIP-approved rule and the recent revisions do not change
this previously established process. Finally, statistical and modeling
elements were addressed under subsection (8)(a) to be used where actual
emission monitoring is not feasible.

*Addition of Longitudinal Ventilation.*

During the late 1980s when the CA/T Project was initially planning and
designing the ventilation system, the only Federal Highway
Administration (FHWA) authorized tunnel ventilation system was the
traditional "full transverse ventilation." Therefore, when 310 CMR 7.38
was promulgated in 1991, the emissions monitoring requirements were
based on full transverse ventilation technology. In 1995, FHWA issued a
memorandum titled "Mechanical Ventilation in Road Tunnels using Jet
Fans" authorizing applicable projects, including the CA/T Project, to
use longitudinal ventilation with jet fan technology. The availability
of this additional ventilation technology was neither anticipated nor
provided for in 310 CMR 7.38 (8).

Following the FHWA authorization memo, the CA/T Project studied the
supplementary use of longitudinal ventilation at several exit ramps as a
cost saving measure. The CA/T Project subsequently filed a Notice of
Project Change, and implemented longitudinal ventilation at eight exit
ramps. Although longitudinal ventilation was approved for use on the
CA/T Project, the resulting emission impacts at the eight exit ramp
portals cannot be monitored using CFR Part 60 Continuous Emissions
Monitoring (CEM) methods because Part 60 is designed to measure
emissions from stacks, not exit ramp portals. The revised subsection
7.38(8)(a) specifically requires the development of an "Air Emissions
Monitoring Protocol" to install and operate emissions monitoring and
recording equipment in tunnel roadway exit portals that utilize
longitudinal ventilation.

The revisions to the Certification of Tunnel Ventilation Systems in the
Metropolitan Air Boston Control District, contain a revised set of
allowable techniques and emissions monitoring approaches that
incorporate elements of 40 CFR 58 -- Ambient Air Quality Surveillance,
40 CFR 60 -- Standards of Performance for New Stationary Sources, 40 CFR
75 -- Continuous Emission Monitoring, as well as statistical analysis,
computer modeling, and innovative technologies. This proposed "hybrid"
approach to emission monitoring, (which includes elements of ambient air
quality monitoring and continuous emission monitoring), will provide
more accurate monitoring of ambient emissions within the portal area
environment which could not be conducted with the original stack
monitoring approach under 40 CFR 60 Appendix B --Performance
Specifications. Additional monitoring flexibility is proposed by
allowing the MA DEP approved "Air Emissions Monitoring Protocol" to be
modified, but any modification would require written approval by MA DEP.

*Ted Williams Tunnel Emission Monitoring Program.*

The years of experience gained from the monitoring program developed
since the early opening phase of the TWT, as well as the need to meet
the unique monitoring requirements of longitudinal ventilation, has
afforded DEP and the CA/T Project the opportunity to develop and assess
more appropriate monitoring methods than those allowed by the
traditional 40 CFR Part 60 CEM methods as required by 310 CMR 7.38.
These proposed monitoring approaches will apply to the CA/T Project as
well as apply to future highway projects with tunnel ventilation
systems.

On December 15, 1995, the Ted Williams Tunnel (TWT) opened to commercial
and authorized traffic only. MA DEP notified the CA/T Project that the
emissions monitoring requirements of the regulation applied to this
restricted-use tunnel operation and required the CA/T Project to develop
and begin an air monitoring program to measure the emissions from
ventilation buildings six and seven, which service the TWT. The CA/T
Project then developed an emissions monitoring and data collection and
reporting program, which was subsequently approved by MA DEP. In 1996,
the CA/T Project began the emissions monitoring program, which was
originally planned for five quarters (15 months). The monitoring program
was extended to nine quarters (27 months) at the request of MA DEP, and
was refined and enhanced during this period. The monitoring program
approved for this "early opening phase" lasted through December 1998.
Data gathered during this monitoring program served two purposes. First
it provided an indication of the emission levels from the two
ventilation buildings during the "early opening phase." Second, as
required by 310 CMR 7.38 (8), it would be used to determine the
appropriate scope of the required compliance monitoring program (CMP)
for the CA/T Project's eventual full operation. It should be noted that
monitoring has continued since the specific "early opening phase" as
required by 310 CMR 7.38 (8) and is being used to gather supplemental
data to further refine the CMP.

Vent building six in South Boston serves a section of TWT including east
and west-bound lanes and has six exhaust stacks linked to two
ventilation zones. Vent building seven in East Boston serves a section
of TWT including east and westbound lanes, Ramp T-AD, and has fourteen
exhaust stacks linked to five ventilation zones. Of the seven
ventilation zones, six cover both the east and westbound lane
directions. MA DEP determined that monitoring at the exhaust plenums of
these six ventilation zones instead of the twenty associated exhaust
stacks housed in ventilation buildings six and seven would enable a more
efficient and cost effective capture of [all]{.underline} ventilation
building emissions for TWT without compromising the results.

Based on the monitoring program completed in 1998, MA DEP and the CA/T
Project determined that there were more practical alternatives to
monitoring in strict accordance with 40 CFR Part 60. For example, while
310 CMR 7.38(2)(c) requires a tunnel ventilation system, project roadway
or roadway network (including the CA/T) to "not result in an actual or
projected increase in the total amount of" NMHC, no monitor actually
exists to measure NMHC; instead, THC emissions are the chemical
substances typically measured. In attempting to measure THC, the
monitored concentrations of THC were found to be low, leading to
"operational difficulties regarding system calibration and maintenance
due to low concentration measurements" (see page 33 in "Ted Williams
Tunnel Emissions Monitoring Data Collection Program and Proposed
Project-Wide Compliance Monitoring Program - Final Report - Revision 1,"
April 2000). Based on these issues, MA DEP has devised an innovative
approach of using continuously monitored traffic data as a surrogate for
NMHC.

Similarly, based on the results of continuous CO, NO and NOx monitoring
in the TWT, the CA/T Project proposed a statistical approach to explore
the possibility of using continuously monitored CO emission levels as a
surrogate to predict NO and NOx concentrations. The results of a
correlation analysis indicate a moderate to strong correlation between
CO and NO and CO and NOx. This correlation analysis was based on data
sets representing different seasons, ventilation zones, and direction of
traffic. Pollutant monitoring data collected since this "early opening
phase" continues to support the CO/NOX relationship and a statistical
approach to determining NOx emissions based on measured CO
concentrations.

The "Air Emissions Monitoring Protocol" to be required under the
proposed SIP revision provides flexibility in monitoring at the exhaust
stacks or exhaust plenums of roadway tunnel ventilation buildings. In
addition, the "Air Emission Monitoring Protocol" can provide alternative
methods to cost-effectively and accurately measure emissions. MA DEP has
devised innovative approaches of using continuously monitored traffic
data as a surrogate for NMHC; as well as using continuously monitored
carbon monoxide (CO) emission levels as a surrogate to predict nitrous
oxide (NO) and nitrogen oxides (NOx) concentrations.

*Future Monitoring Improvements*

MA DEP has also proposed a revision to the emissions monitoring
requirements at 310 CMR 7.38 (8)(a) to allow flexibility so that as
technological advances occur in contaminant and emissions monitoring, MA
DEP will be able to modify monitoring procedures without necessarily
having to complete a regulatory revision process. Therefore, the
proposed regulation would allow affected projects to periodically modify
or update their air emission monitoring protocol with written approval
of MA DEP.

*Administrative Processing*

A Public Hearing on the State\'s proposed amendments to 310 C.M.R. 7.38
was held on July 19, 2005, after proper advertisement and legal notice.
Following the public comment period Massachusetts Department of
Environmental Protection -- Bureau of Waste Prevention, Division of
Consumer and Transportation Programs, prepared a summary and
satisfactory responded to comments raised. The regulation was filed with
the Massachusetts Secretary of State on December 13, 2005 and became
effective upon publication in the Massachusetts Register on December 30,
2005.

EPA is now proceeding with the publishing of a direct final rulemaking
notice, at the same time as we are publishing the notice of proposed
rulemaking associated with a direct final rule in the
[Federal]{.underline} [Register]{.underline}. The EPA is publishing this
action without prior proposal because the Agency views this as a
noncontroversial amendment and anticipates no adverse comments. However,
in the proposed rules section of this [Federal]{.underline}
[Register]{.underline} publication, EPA is publishing a separate
document that will serve as the proposal to approve the SIP revision
should relevant adverse comments be filed. If the EPA receives relevant
adverse comments, then EPA will publish a notice withdrawing the final
rule and informing the public that the rule will not take effect. All
public comments received will then be addressed in a subsequent final
rule based on the proposed rule. The EPA will not institute a second
comment period on the proposed rule. If EPA receives adverse comment on
an amendment, paragraph, or section of this rule and if that provision
may be severed from the remainder of the rule, EPA may adopt as final
those provisions of the rule that are not the subject of an adverse
comment.

[^1]: Boston Metropolitan Air Control District is defined at 310 CMR
    7.00 ­­­\-- Air Pollution Control Districts; as well as at 40 CFR 81.19
    \-- Metropolitan Boston Intrastate Air Quality Control Region.