In November 1990, the Clean Air Act Amendments (CAAA) were passed by Congress and signed into law by the President. Title I of the CAAA requires development of emission inventories for designated areas that failed to meet the National Ambient Air Quality Standards (NAAQS) for Ozone and Carbon Monoxide (CO). These inventories are to be prepared as a part of the State's revision to its State Implementation Plan (SIP) to formulate a strategy to attain the NAAQS for Ozone and CO.

The Massachusetts Department of Environmental Protection (MassDEP) is the agency responsible for developing the required draft emissions inventory submitted May 1, 1992. This November 1993 Emissions Inventory for Base Year 1990 incorporates revisions arising from comments on the July 1993 Public Hearings on the Draft version.

MassDEP has followed as closely as feasible, the four core U.S. Environmental Protection Agency (EPA) procedural guidance documents for the development of this Base Year Emissions Inventory. These documents include:

  1. Procedures for the Preparation of Emission Inventories for Carbon Monoxide and Precursors of Ozone, Volume 1: General Guidance for Stationary Sources, known as the Procedures Document or Volume 1, (EPA 450/4-91-016).
  2. Procedures for Emission Inventory Preparation, Volume IV: Mobile Sources, (EPA-450/4-91-026), together with the revised Interim Guidance, February 1992.
  3. Emission Inventory Requirements for Ozone State Implementation Plans (EPA-4504091-010) known as the Ozone Requirements Document.
  4. Emission Inventory Requirements for Carbon Monoxide State Implementation Plans (EPA-450/4-91-011), known as the CO Requirements Document.

Massachusetts is in non-attainment of the Ozone (O3) and Carbon Monoxide (CO) Standards and is required by Title I of the 1990 Clean Air Act Amendments (CAAA) to prepare a revision to the State Implementation Plan (SIP) by developing strategies and programs to attain these Standards. The initial requirements of the CAAA and the SIP revision is to develop a 1990 base year emission inventory for the precursors of these pollutants. For the Ozone SIP, emission inventories are required for a typical summer day for the three precursors of Ozone: Volatile Organic Compounds (VOC), Nitrogen Oxides (NOx) and Carbon Monoxide (CO). For the CO SIP, an emissions inventory is required for typical winter day for CO. In Massachusetts, exceedances of the federal ozone standard occur during the summer whereas elevated CO levels occur during the winter.

Inventory Preparation Plan & Quality Assurance

As part of the emissions inventory effort, an Inventory Preparation Plan (IPP) was submitted to EPA in February 1992. The IPP specified how the inventories are to be developed, documented and presented for Massachusetts. The IPP included a Quality Assurance (QA) Plan which an EPA Level of Effort (LOE) contractor implemented for the Draft Inventory. The QA process ensures that  Massachusetts Department of Environmental Protection (MassDEP) utilized approaches to develop the most accurate emission estimates that are of the highest quality and are consistent with EPA's CAAA requirements and emission guidance documents. The result of the QA review are presented in Appendix F.

The LOE Contractor QA review comments were incorporated into this inventory. The definition of VOC was revised and is presented in Section A covering the Stationary Point Sources. Emissions from Asphalt Roofing Kettles and Tankers are included in this report in Section B under Stationary Area Sources, Solvent Section. The input of the emissions into the EPA National Aerometric Information Retrieval System, Area and Mobile Subsystem (AIRS-AMS) serves as another level of QA/QC.

EPA's review comments on the 1st and 2nd Inventory submittals provided further quality assurance. EPA's comments were followed as closely as feasible and incorporated into this inventory submittal. Comments from EPA Office of Mobile Sources on the Mobile Section of the May 1992 Draft Inventory were finally received in August 1993 as part of EPA's public hearing comments.

Non-Attainment Status

Some inventory requirements are based on the non-attainment classification of the area of study. In early 1991, EPA recommended designation classification of serious for ozone non-attainment for the Western and Eastern Regions of Massachusetts and moderate ozone non-attainment for the Central Region. Massachusetts requested that the Central Region be reclassified as serious which was granted, thus making the whole state serious non-attainment for ozone. The federal Register 56 FR 56693 11/6/91 established two serious ozone non-attainment areas covering the whole state: the Boston and Springfield non-attainment areas. The Boston ozone non-attainment area covers the following counties: Worcester, Middlesex, Essex Suffolk, Norfolk, Bristol, Plymouth, Barnstable, Dukes and Nantucket. The Springfield ozone non-attainment area includes Berkshire, Franklin, Hampshire, and Hampden counties. Figure I-1 shows the location of these counties.

For Carbon Monoxide, areas were either designated non-attainment by operation of law with passage of the 1990 CAAA if they were considered non-attainment prior to November 1990 or were designated non-attainment based on 1988 or 1989 air monitoring data. For Massachusetts, the cities/towns of Worcester, Lowell, Springfield, Boston, Cambridge, Quincy, Waltham and Medford were designated non-attainment by operation of law. In addition, EPA originally recommended that the entire Boston CMSA be designated non-attainment and classified moderate.

Massachusetts requested that the new non-attainment area around Boston be reduced from CMSA-wide to a select and limited number of cities and towns around Boston. The result, as published in the Federal Register (56 FR 215) on November 6, 1991 was a much reduced moderate non-attainment area comprised of the cities/towns of Boston, Cambridge, Medford, Quincy, Everett, Malden, Somerville, Chelsea and Revere. The remaining pre-existing non-attainment communities of Waltham, Worcester, Springfield, and Lowell remained unclassified non-attainment.

These CO non-attainment areas are presented in Tables I-1 and Figures I-2 and I-3. CO emission inventories for the winter were estimated at the statewide, county and CO non-attainment city/town levels.

Inventory Components

The 1990 Emission Inventories were developed in a similar format as that of 1987 which was the last complete emissions inventory developed for Massachusetts. This 1990 Base Year emissions inventory is presented as a single document comprising the three precursors of ozone: VOC, NOx, and CO for a typical summer day (TPSD). As described in EPA's Emission Requirements Document for Ozone, a typical summer day or, a typical peak ozone season weekday or typical ozone season day, refers to emissions activities and weather conditions that occur during the three month period in which the ten highest ozone exceedances occur (June-August) averaged on a daily basis. EPA's Procedural Documents (Volume IV) were followed for determining a typical ozone or summer day based on Ozone data for the days with the ten highest ozone levels for the last three years (1988 to 1990) and are described in Section C of this document for On-Road Mobile Sources. Emissions were estimated or adjusted for a typical ozone or summer day which is generally from June to August in Massachusetts.

This document also includes CO emissions for a typical winter day. The peak CO season comprises the contiguous months when the ten highest CO NAAQS exceedance episodes occur during the coldest months of the year, generally from November to January for Massachusetts. This determination is based on ambient CO data for the last three years, 1988 to 1990 as described in Section C of this document. Emissions were estimated for a typical CO or winter day at the statewide, county and CO non-attainment city/town levels.

The VOC emission inventory is subdivided into two basic categories: anthropogenic and biogenic. The anthropogenic emission inventories for VOC, Nox and CO are developed and subdivided into four broad source categories: Stationary Point, Stationary Area, On-Road Mobile and Non-Road Mobile Sources. The Stationary Point Source category (Section A) includes stationary facilities which emit actual emissions over 10 tons per year (TPY) of VOC, over 50 TPY of NOx and 100 TPY of CO. Stationary Area sources are smaller. usually more widespread emitting activities that are too small and numerous to be inventoried as point sources. The Stationary Area source emission categories (Section B) define various activities or processes which can be estimated as a group and include gasoline distribution, solvent use, waste management practices and combustion processes. The On-Road Mobile source inventories (Section C) comprise Mobile5a emission estimates for on-road mobile sources for eight vehicle classes which include cars, trucks and buses. Non-Road Mobile sources include emissions from Aircraft, Railroads, Commercial/Military Vessels and Off-Highway Vehicle emissions, including Recreational Marine vessels, were obtained from EPA's Non-Road Engine Emission Inventories for CO and Ozone Non-Attainment Boundaries, EPA, Office of Mobile Sources, Ann Arbor, Michigan, December, 1992.

Inventory Pollutants

A volatile Organic Compound (VOC) as defined in 310 CMR 7.00 is any compound of carbon which either participates in atmospheric reactions or which is measured by the applicable reference methods under 40 CFR 60. The excluded non-reactive VOC compounds are outlined in the Stationary Point Source Section A.

VOC's are generally emitted from industrial, commercial and residential solvent and fuel combustion processes, on-road, non-road mobile sources and biogenic sources. VOC, NOx and CO react photochemically at high temperatures in the presence of sunlight to form ozone. Ozone is a respiratory irritant and can result in adverse health effects as well as damage to materials and vegetation. The federal ozone one-hour standard is set at 0.12 parts per million.

One of the major components of NOx is nitrogen dioxide (NO2. NOx is generally emitted through fuel combustion by on-road mobile sources, non-road mobile sources and stationary industrial, commercial and residential sources. Even though Massachusetts is in attainment of the annual NO2 federal standard of 100 ug/m3, an inventory of NOx is required because they are precursors to ozone.

CO is an asphyxiant gas with a federal one hour standard of 35 ppm and an 8-hour standard of 9ppm. CO is produced by the same combustion process as described for NOx. Massachusetts is in non-attainment of the 8-hour standard which generally occurs during the winter period. CO is also a precursor to ozone formation in the summer.

Inventory Methodology

The general methodology used in developing the emission inventories for Stationary Point, Stationary Area, On-Road Mobile, Non-Road Mobile and Biogenic sources involves the application of activity factors or default values to appropriate emission factors and estimated or adjusted seasonally. Several recent EPA guidance documents provide procedures for estimation of emissions. These EPA documents are referenced for each methodology and source category throughout this report.

The Stationary Point Source (Section A) emissions are originally estimated from a mail survey source registration (Appendix A.2) and DEP field data verification inspections. The activity factor is the quantity and type of material of fuel used. The table of emission factors is based on source classification codes related to the source process type. If control equipment is used at any source, its effectiveness is factored into the equation. Field staff also supplemented data based on plant inspections and manually calculated plant emissions. Stationary point source emissions are initially stored in DAQC SSEIS data base. The SSEIS Point Sources above 10 TPY VOC, 50 TPY NOx and 100 TPY were then downloaded into the SAMS 4.1 software system for uploading into the EPA National Aerometric Information Retrieval System (AIRS) Facility Subsystem (AFS).

The Stationary Area Source emissions category (Section B) represent point sources which are too small and numerous to be recorded in the point source inventory. The activity factors include material sales records, State registration records, fuel/material usage, and default employment and per capita data. Emission factors were obtained from EPA guidance documents and some categories were estimated based on State employment and population data. The rule effectiveness formula was applied to those categories which are subject to state regulations in which the control efficiency and rule effectiveness were quantified. In some categories which overlapped with those of the point source inventory, eg. degreasing, the point source employment or fuel/material usage were subtracted from the corresponding area source inventory to avoid double counting. Emissions were apportioned to counties based on available fuel/material used, employment, State registration and population data.

The On-Road Mobile source category (Section C) emissions represent roadway and highway vehicles. The activity factor is daily vehicle miles traveled (DVMT) obtained from the Massachusetts Department of Transportation (MassDOT). DVMT data was seasonally adjusted for typical summer and winter days for the entire state. Emission factors were developed from EPA's December 1992 MOBILE5a emissions model which required a wide range of input parameters such as vehicle type mix, age distribution, mileage accumulation, temperature, and I/M data such as anti-tampering rates, hot/cold start mix and emission failure rates, Emission factors were calculated for the eight vehicle types for different speeds up to 65 mph. Emission factors were calculated for a worst case scenario for ozone and CO in which the temperatures were based on the 10 days with the highest ozone and CO levels over the last three years. These temperatures are presented in Section C. Emission factors were applied to DVMT based on MHD's speed estimates for each roadway type in each county. Emissions were calculated for the summer for VOC, NOx and CO, and for the winter for CO. Because emissions are not required for the winter for VOC and NOx, mobile source emissions are not required for the winter for VOC and NOx, mobile source emissions are calculated in tons per summer day and not in tons per year.

EPA's comments on the On-Road Mobile Section were incorporated into MOBILE5a. The mobile source inputs or criteria sets were entered into the EPA AIRS Area and Mobile Source Subsystem (AMS) System, together with the VMT and Speed data with the assistance of an EPA contractor.

The Non-Road Mobile Source (Section D) includes emissions estimation from different types of engines used by Aircraft, Locomotives, Commercial/Military Vessels, and other Off-Highway vehicles. The basic activity level is the estimation of the amount and type of fuel used for each activity and applied to appropriate emission factors. Resultant emission estimates were apportioned to counties based on state registration data employment and demographic data. The Off-Highway Non-Road Mobile source emissions including Recreational Marine Vessels were taken from EPA Office of Mobile Sources (OMS) Non-Road Engine Study and is presented in Section D.4

The Biogenic hydrocarbon emissions category is being inventoried for the first time and is presented in Section E. The EPA PC-BEIS model was utilized to estimate biogenic emissions. The model incorporates default land use, crop acreage and forest type by county, and assigns emission rates to different land use types. The model estimates emissions based on calculations using crop acreage and leaf biomass for the summer growing season. The model utilizes inputs such as meteorological data which includes temperature and insolation for the typical summer day.

Emissions Summary

The 1990 Base Year emissions were calculated in tons per summer day (TPSD) for VOC, NOx and CO. Emissions were also calculated in tons per winter day (TPWD) for CO.

Emissions were developed and presented for anthropogenic emissions comprising the following four broad categories: Stationary Point, Stationary Area, On-Road MOBILE5a and Non-Road Mobile Sources. Biogenic emissions were developed and presented by county in Tables I-4 to I-22 and Figures I-9 to I-13. CO winter emissions by CO non-attainment cities and towns are presented in Table I-19 and Figure I-14.

In the statewide anthropogenic VOC inventory for a typical summer day, the source categories account for the following contributions: Stationary Point 5.9%, Stationary Area 40.9%, On-Road MOBILE5a 31.6% and Non-Road Mobile 21.6%. The inclusion of Biogenic emissions changes to the following proportions: Stationary Point 3.5%, Stationary Area 24.4%, On-Road MOBILEa 18.8%, Non-Road Mobile 12.9% and Biogenics 40.5%. These proportions are presented in Table I-2 and Figures I-4 and I-5.

The following are the proportions of the source categories statewide for a typical summer day for NOx: Stationary Point 37.7%, Stationary Area 3.4%, On-Road MOBILE5a 40.5% and Non-Road Mobile 18.4%. NOx emissions for these categories are presented in Table I-2 and Figure I-6.

The following are the proportions of the source categories statewide for the CO inventory for a typical summer day: Stationary Point 0.9%, Stationary Area 1.4%, On-Road MOBILE5a 61.2% and Non-Road Mobile 36.5%. The contributions of the Co summer source categories are presented in Table I-2 and Figure I-7.

The proportions of the CO winter day inventory are as follows: Stationary Point 0.8%, Stationary Area 16.8%, On-Road MOBILE5a 79.9% and Non-Road Mobile 2.6%. The contributions of the source categories are presented in Table I-2 and Figure I-8. CO winter emissions by counties were apportioned by population to CO non-attainment cities and towns in Table I-18 and presented in Figure I-14.

Table I-3 presents a breakdown of the summer day emissions for the two Ozone Non-attainment areas: Boston and Springfield. The counties comprising these Ozone Non-attainment and their emissions ate presented in Table I-20 to I-22. Table I-3 shows that the Boston Non-attainment area accounts for 85 to 88 percent of the anthropogenic emissions for VOC, NOx and CO.

Last Updated: January 12, 1998