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									                       Exelon Medway Station (ORIS #1592)
                         9 Summer Street, Medway, MA

      CO2 Budget Program (310 CMR 7.70) – Hardcopy CO2 Monitoring Plan


The Exelon Medway electric generating station (ORIS #1592), located at 9 Summer
Street in Medway, MA, consists of six Rolls-Royce AVON simple-cycle peaking
turbines, designated: J1T1, J1T2, J2T1, J2T2, J3T1 and J3T2. Diesel oil is the primary
fuel. The units are permitted to burn natural gas as well; however, the site does not
presently contain any infrastructure to enable natural gas combustion.

The six turbines are arranged as three pairs (“twins”), with each pair serving a single
electric generator. These twins may run together or separately. The rated nameplate
capacity of each electric generator is 45MW. The six units have been subject to the
existing NOx Budget Trading Program (310 CMR 7.28) and will be subject to the
upcoming ozone season CAIR program (310 CMR 7.32) and CO2 Budget Trading
Program (310 CMR 7.70). They are classified as Low Mass Emissions (LME) Units, as
defined in 40 CFR 75.19 and have been reporting emissions as such under the NOx
Budget Program.

A NOx Budget monitoring plan was previously submitted under Transmittal W024227,
and all enclosed information (including the units’ LME designation, and electric output
monitoring plan) is remaining unchanged. This document comprises the CO2 monitoring
plan required under 310 CMR 7.70(8)(e)(2). These LME units do not utilize any CEMS
or DAHS; therefore, a DAHS verification test is not applicable to this submittal.
The EDR generation software will be updated prior to January 1, 2009 and will include
the CO2 calculation formula detailed below. If applicable, a CO2 formula verification
will be forwarded to MassDEP at that time.

Monitoring of CO2 Mass Emissions:

In accordance with 310 CMR 7.70(8)(a)(3)(c), the hourly CO2 mass emissions for the six
low mass emissions (LME) units at Medway Station shall be determined using Equation
LM-11 from 40 CFR 75.19:

                        WCO 2  EFCO 2  HI hr
                                      (Eq. LM-11)

       WCO2           = the hourly CO2 mass emissions (tons)

       EFCO2          = the fuel-based CO2 emission factor as specified by 40 CFR
                      75.19, Table LM-3 (0.081 tons/mmBTU for oil combustion; 0.059
                      tons/mmBTU for natural gas combustion)

                      Oil is the only fuel combusted by Medway Station. As long as
                      there is no natural gas combustion capability at Medway, the oil
                      emission factor will be used for all unit operating hours.

                      If natural gas combustion capability is added to Medway Station at
                      a later date, then: if more than one fuel is combusted in the hour,
                      the oil emission factor will conservatively be used. If records are
                      missing as to which fuel was combusted in the hour, the oil
                      emission factor will conservatively be used.

       HIhr           = the unit’s maximum rated hourly heat input (i.e., 392.3
                      mmBTU/hr for each unit, consistent with that reported under the
                      NOx Budget Program), multiplied by the operating time of the unit
                      for each hour.

The quarterly CO2 mass emissions (tons) for the low mass emissions unit shall be the
sum of all of the hourly CO2 mass emissions in the quarter. The year-to-date cumulative
CO2 mass emissions (tons) for each low mass emissions unit shall be the sum of all of the
quarterly CO2 mass emissions, for all of the calendar quarters in the year to date.

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