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SCEA Training
Training Modules / Interactive Presentation

Introduction :: Presentation Format & SCEA Overview
Module 1 :: How to Determine Which Resources Should be Considered in a SCEA
Module 2 :: How to Establish the SCEA Geographical Boundary
Module 3 :: How to Determine SCEA Time Frames
Module 4 :: How to Develop SCEA Land Use Information
Module 5 :: How to Prepare the Analysis & Reach SCEA Conclusions
Module 6 :: Presentation of SCEA in the Environmental Documentation

Module 3

Slide 1 How to Determine Time Frames

Slide 2 Overview

  • Past Time Frames?
  • Future Time Frames?

Slide 3 Determining Time Frames

Factors to Consider in the Past Time Frame

  • Major events in the historic context of the SCEA geographical boundary
  • Dates when major roads were built within the SCEA geographical boundary
  • Land use changes
  • Availability of data
  • Agency input

Slide 4 Past Time Frames

Major Events in the Historic Context of the Area

  • Include both private and public actions that had a major effect on population growth, land use, and consequently on environmental resources.
  • These changes may, of themselves, result in noticeable effects to the environment, or may stimulate development, which in turn, results in noticeable environmental effects.
    • Opening of a military base or employment center → noteworthy direct impacts → increases population of the area → stimulates residential development → service industries result as "spin off".
    • Large Residential Subdivision → noteworthy direct impacts → service industries result as "spin off".
    • Landfill → noteworthy degradation of water quality.
  • Census tract data can verify population and employment increases/decreases associated with a major event.

Slide 5 Past Time Frames (continued)


  • It is important to consider only major events that had a noteworthy effect on population, land use, employment, and consequently environmental resources.
  • Individual home construction and/or small subdivisions are not considered major events, but may be the result of such events.

Slide 6 Time Frames (continued)

Dates when Major Roads were constructed within the SCEA Geographical Boundary

  • Major events include roads, bridges, and other transportation projects which resulted in changes to employment, population, and consequently on environmental resources.
  • Census tract data can verify population and employment increases/decreases associated with a major event.

Slide 7 Time Frames (continued)


  • Care must be taken to identify the major event that resulted in changes. (i.e. Was it development of the Interstate highway, or expansion of a military base, or construction of a new airport.)
  • Population trends data (US Census) can often be used to substantiate a major historical event. Land use planning professionals can also shed some light on this.

Slide 8 Past Time Frames (continued)

  • Often the direct effects of a major event, such as a road, bridge, employment center, etc.
  • May occur regardless of zoning and/or land use planning proposals.
  • Land use changes may also include government initiatives which had an effect on land use, population and employment.
  • Examples include:
    • lifting of building moratoriums
    • establishment of comprehensive zoning

Slide 9 Past Time Frames (continued)

  • An important factor, but not the only factor, in determining past time frames. All of the factors should be considered collectively in determining the past time frame for a SCEA .
  • Much of the readily available data we have today (both mapped, and numerical data) became available in the 1970's due in part of enhanced environmental awareness following NEPA. Be careful not to focus on this fact as the only factor in making this decision.

Slide 10 Past Time Frames (continued)

Rationale and Description for arriving at Decision on Past Time Frames

Be careful not to establish all SCEA past time frames based upon data availability and the passage of NEPA in the 1970s. Consider all factors in conjunction with data availability.

Slide 11 Past Time Frames (continued)

Agency Input

  • Agency comments on time frames provided during the scoping process should be considered.
  • Be sure to document these comments in the environmental document appendices and summarize in the SCEA narrative.

Slide 12 Factors to consider in Defining Past Time Frames

D-link table summary




Major events in the historic context of the area


Dates when major roads were built within the SCEA boundary


Changes in land use


Population changes


Employment changes


Data Availability


Agency Input


Slide 13 Past Time Frames (Data Sources)

State Road Commission Archives used to determine when major transportation projects were opened

Consultation with county planners used to determine when major events occurred (openings of employment centers, military bases, etc.)

U.S. Census data used to determine when population and/or employment changes (increases or decreases) occurred

Historic aerial photography from counties and USDA used to determine major land use changes

Slide 14 Future Time Frames

  • The project's design year should be used for the future time frame, as design year traffic is normally based on the land use planning agency's future land use assumptions.


Exercise 1


Slide 15 MRECAS Time Frame Notes

Secondary Effects Analysis The time frame used for the secondary effects analysis was the present (1999) to the year (2020). 1999 was selected because it is the time that planned development within the MREC would start. 2020 was selected because it represents the project design year. In addition, projections beyond year 2020 are not readily available for some environmental resources.

Cumulative Effects Analysis 1963 was selected as the initial year because I95 was opened in Baltimore County that year. The year 2020 was chosen because it is the design year for the project and also because projections beyond 2020 are not readily available for some environmental resources.

Do not use two or more different timeframes in your analysis. Under current SHA Guidelines, there should be only one SCEA timeframe.

Slide 16 US Route 1 Bel Air Bypass


Slide 17 US Route 1 Bel Air Bypass

See Location MapD-link

Slide 18 US Route 1 By Pass

Time Frame Notes

  • The time frame for the SCEA was established between 1980 and the year 2020.
  • The decision to begin in 1980 was made based on a number of different reasons. These include the lifting of the building moratorium in Harford County in 1976, the establishment of the Development Envelope in 1977, the initiation of comprehensive zoning in 1982, and the opening of MD 24 in 1986. These were all factors in the general "building boom" which occurred in the County during the 1980's.
  • The year 2020 was chosen because it is the design year for the US 1 Bel Air Bypass project. The year 2020 was also appropriate because traffic data and travel demand forecasts were developed for this year.

Slide 19 US 113 Planning Study


Slide 20 US 113 Planning Study

See Location Map Southern SectionD-link

Slide 21 US 113 Planning Study

Time Frame Notes

  • The time frame covered by the cumulative effects analysis for US 113 was determined to be from the early 1970's through the design year, 2020.
  • The time frame was based on growth trends, the initiation of environmental protection policies; the implementation of other area transportation improvement projects; available data; and, the project's design year.
  • The 1970's were chosen because of: (1) a large population increase (26.4%); (2) the opening of the parallel bridge of the Chesapeake Bay Bridge in 1973; (3) increased environmental awareness, The National Environmental Policy Act (NEPA), passed in 1969; (4) development of an extensive database of Worcester County by the county and the Maryland Office of Planning in the 1970s and; (5) additional highway projects constructed in the 1970's, including the Snow Hill Bypass, MD 90, and the dualization of US 113 around Berlin.

Slide 22 MD Route 4: East of I95/I495 Interchange to West of MD 223


Slide 23 MD Route 4: East of I95/I495 Interchange to West of MD 223

See Location MapD-link

Slide 24 MD Route 4: East of I95/I495 Interchange to West of MD 223

Time Frame Notes

  • The time frame for this study is 19632020.
  • Data used in this study dates back to 196364. This date is used because it was the year the Capital Beltway was completed.
  • The Beltway is an important factor in determining effects since it runs directly through the center of the established SCEA boundary.

Slide 25 MD 5 Hughesville Transportation Improvement Project

Time Frame Notes

  • The study time frame was established as 1972 to the year 2020.
  • In the early 1970s, MD 5 was dualized north and south of Hughesville. For the purpose of the study, the start of the time frame was set at 1972. Historic aerial photos were available in this time frame.
  • The year 2020 is the design year for the project and was considered the time frame within which project direct effects, combined with effect of other actions could reasonably be projected based upon the land use assumptions used in generating design year traffic.

Exercise 2 | Back to top

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