Slide One


I-495 & I-270 Managed Lanes Study

Supplemental Draft Environmental Impact Statement (SDEIS)

In compliance with the National Environmental Policy Act (NEPA), the Maryland Department of Transportation State Highway Administration (MDOT SHA) and Federal Highway Administration (FHWA) published the Supplemental Draft Environmental Impact Statement (SDEIS), which provides new information related to Preferred Alternative, Alternative 9 – Phase 1 South, for the I-495 & I-270 Managed Lanes Study.

The SDEIS public comment period will run from Friday, October 1, through 11:59 PM on Monday, November 15, 2021. The comment period includes two virtual public hearing sessions, scheduled for Monday, November 1, as well as opportunities for email, written and recorded comments. Following the 45-day public comment period, SHA and FHWA will consider comments received and will respond to substantive comments on both the SDEIS and DEIS in the Final Environmental Impact Statement (FEIS.)


This SDEIS has been prepared to consider new information developed after the DEIS was published in July 2020, and presents results relevant to Alternative 9 – Phase 1 South: American Legion Bridge I-270 to I-370, which was identified in May 2021 by FHWA and MDOT SHA as the Preferred Alternative. While the Managed Lanes Study considers ways to relieve congestion and improve trip reliability, mobility and connectivity for modes of travel, including transit, in the National Capital Region, this alternative focuses on replacing the 60-year-old American Legion Bridge and delivering two high occupancy toll (HOT) managed lanes in each direction within Phase 1 South: American Legion Bridge I-270 to I-370. The scope of the SDEIS builds upon the analysis and information that remains valid in the existing DEIS but is limited to new information about the Preferred Alternative.

On I-495, the Preferred Alternative consists of adding two new HOT managed lanes in each direction from the George Washington Memorial Parkway in Fairfax County, Virginia to east of MD 187, Old Georgetown Road. On I-270, the Preferred Alternative consists of converting the one existing HOV lane in each direction to a HOT managed lane and adding one new HOT managed lane in each direction on I-270 from I-495 to north of I-370 and on the I-270 east and west spurs. There is no action, or no improvements, included at this time on I-495 east of the I-270 east spur. Transit buses and HOV 3+ vehicles would be permitted to use the managed lanes toll-free. Transit buses, motorcycles and HOV 3+ vehicles – those carrying three or more people – would be permitted to use the managed lanes toll free. There is no action, or no improvements, included at this time on I-495 east of the I-270 east spur.

The Preferred Alternative is designed to provide a new American Legion Bridge, address existing traffic and long-term traffic growth, enhance trip reliability, support regional transit improvements, foster new opportunities for increased carpool/vanpool/ridesharing and improve the movement of goods and services within Phase 1 South. In addition, the alternative would provide pedestrian and bicycle improvements to enhance the connectivity of area sidewalks and trails, including the addition of a shared use path on the new American Legion Bridge across the Potomac River.

MDOT SHA and FHWA continue to consider the nearly 3,000 comments received as part of the DEIS and public hearings held last fall. Responding to public input, the SDEIS reflects successful efforts by MDOT SHA to reduce community and environmental impacts, including complete avoidance of Morningstar Cemetery in the Cabin John area. On Plummers Island, a research site for the Washington Biologists Field Club, the team collaborated with regulatory agencies and interested stakeholders to reduce the impact by 90% to 0.2 acre, consisting of one pier piling for the American Legion Bridge replacement.

View the SDEIS Documents

MDOT SHA and FHWA have completed the Supplemental Draft Environmental Impact Statement (SDEIS) for the Managed Lanes Study, with the Notice of Availability published in the Federal Register on October 1, 2021. The Supplemental Draft Environmental Impact Statement or SDEIS provides a summary of the 11 technical reports and contains 10 chapters.

Executive Summary also available in Amharic, Chinese, French, Korean, and Spanish.

SDEIS Document by Chapter

Cover, Signature Page, Title Page, and Table of Contents

Executive Summary

Chapter 1 presents the Study’s Purpose and Need.

Chapter 2 presents the Preferred Alternative and elements of the alternative.

Chapter 3 presents results from the traffic operational analyses conducted for the 2045 No Build Alternative and Preferred Alternative.

Chapter 4 presents the permanent and temporary impacts associated with the Preferred Alternative.  It also provides an update on the measures to avoid, minimize, and mitigate potential environmental effects, where applicable. Final mitigation will be included in the FEIS.

Chapter 5 presents the Updated Draft Section 4(f) Evaluation, which updates the potential Section 4(f) uses and mitigation associated with the Preferred Alternative to significant public parks, recreational areas, and historic properties in compliance with Section 4(f) of the US Department of Transportation (USDOT) Act of 1966.

Chapter 6 acknowledges that on January 20, 2021, Executive Order 13807: Establishing Discipline and Accountability in the Environmental Review and Permitting Process for Infrastructure Projects, was revoked in the Executive Order 13990: Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis.

Chapter 7 presents a summary of the public outreach and agency coordination that has occurred for the Study from the time the DEIS was published in July 2020 through summer 2021.

Chapter 8 presents the List of Preparers of the SDEIS.

Chapter 9 presents the Distribution List of agencies, organizations, and persons to whom the SDEIS was made available for review and comment as well as information on public availability of the SDEIS.

Chapter 10 presents the references for the SDEIS.

SDEIS Technical Reports

To review the 11 supporting SDEIS Technical Reports click on the report titles below.  Due to the large file size, Appendices C and H have each been broken up into smaller file sizes for viewing.

APPENDIX A Traffic Evaluation Memorandum: Alternative 9 - Phase 1 South
APPENDIX B COVID-19 Travel Analysis and Monitoring Plan

Compensatory Stormwater Mitigation Plan (5 files)

Part 1: Comp SWM Report

Part 2: Comp SWM Report

Part 3: Comp SWM Report

Part 4: Comp SWM Report Impact Maps (1 of 2)

Part 5: Comp SWM Report Impact Maps (2 of 2)

APPENDIX D Environmental Resource Mapping
APPENDIX E Noise Technical Report Addendum
APPENDIX F Natural Resources Impact Tables
APPENDIX G National Park Service, Wetland and Floodplain Statement of Findings

Rare, Threatened and Endangered Species Reports (5 files)

Part 1: Bat Survey Reports

Part 2: RTE Plant Survey Reports

Part 3: Bald Eagle & Peregrine Falcon Comments and Wood Turtle Report

Part 4: National Park Service Tree Inventory including Clara Barton Parkway and George Washington Memorial Parkway

Part 5: National Park Service Tree Inventory including National Parks East

APPENDIX I Hazardous Materials Report: Limited Phase 1 Environmental Site Assessment Phase 1 South
APPENDIX J MLS Visual Impact Assessment Scoping Questionnaire
APPENDIX K EJSCREEN Data & Mapping Supporting the Environmental Justice Analysis

SDEIS Document Availability

Hard copies of the SDEIS and its supporting information are available for review starting on Friday, October 1 through November 15, at the following locations:

Document Availability

Gaithersburg 18330 Montgomery Village Avenue, Gaithersburg, MD 20879

Mon, Wed, Fri & Sat: 10 AM - 6 PM

Tue & Thu: 12 - 8 PM

Quince Orchard 15831 Quince Orchard Road, Gaithersburg, MD 20878
Rockville Memorial* 21 Maryland Avenue, Rockville, MD 20850
Potomac 10101 Glenolden Drive, Potomac, MD 20854
Davis 6400 Democracy Boulevard, Bethesda, MD 20817
Kensington Park 4201 Knowles Avenue, Kensington, MD 20895
Chevy Chase 8005 Connecticut Avenue, Chevy Chase, MD 20815
Silver Spring 900 Wayne Avenue, Silver Spring, MD 20910
White Oak 11701 New Hampshire Avenue, Silver Spring, MD 20904
Beltsville 4319 Sellman Road, Beltsville, MD 20705

Mon, Tue, Thu, & Fri: 10 AM - 6 PM

Wed: 12 - 8 PM

Sat: 10 AM - 5 PM

Greenbelt* 11 Crescent Road, Greenbelt, MD 20770
New Carrollton 7414 Riverdale Road, New Carrollton, MD 20784
Glenarden 8724 Glenarden Parkway, Glenarden, MD 20706
Largo-Kettering 9601 Capital Lane, Upper Marlboro, MD 20772
Spauldings 5811 Old Silver Hill Road, District Heights, MD 20747
Oxon Hill 6200 Oxon Hill Road, Oxon Hill, MD 20745
Dolly Madison 1244 Oak Ridge Avenue, McLean, VA 22101

Mon & Tue: 10 AM – 9 PM

Wed, Thu, Fri & Sat: 10 AM – 6 PM

Juanita E. Thornton/Shepherd Park 7420 Georgia Avenue NW, Washington, DC 20012

Mon, Tue, Wed, Fri & Sat: 10 AM - 6 PM

Thu: 12 - 8 PM

* The Rockville and Greenbelt libraries will have hard copies of the SDEIS and Technical Reports available. All other libraries will have the technical reports on USB flash drives.

In the event of changes with COVID-19, please visit the library website for hours of operation.

Ways to Comment on the SDEIS Documents

Written comments and call-in testimony will be accepted for the official record through 11:59 PM November 15, 2021. Those interested may:

Jeffrey T. Folden, P.E., DBIA
Deputy Director, I-495 & I-270 P3 Office Maryland Department of Transportation State Highway Administration
707 North Calvert Street
Mail Stop P-601, Baltimore, MD 21202

All comments received, regardless of method of submission, will be given equal consideration.  All substantive comments received or postmarked by the end of the comment period will be responded to in preparation of the FEIS. Comments received or postmarked after the close of the comment period will be reviewed and considered to the extent practicable.

SDEIS Virtual Public Hearing

MDOT SHA and FHWA will conduct one virtual public hearing with two sessions.  Members of the public will be allotted three minutes and elected officials will be allotted five minutes, per person, for verbal testimony. Responses to questions will not be given at the hearing. After the hearing, a transcript of public comments will be available on the website.  MDOT SHA and FHWA will consider and respond to substantive comments in the FEIS.  In addition to the virtual public hearing sessions, written comments and call-in testimony through voicemail will be accepted for the official record through 11:59 PM November 15, 2021. Visit Provide Feedback for other methods of submission.

Hearing Materials

Prior to attending a public hearing session, the public is encouraged to review the online presentation that includes the informational display boards.

The informational flyer includes ways to comment on the SDEIS and how to register and provide verbal testimony at the hearing.

Also available in Amharic, Chinese, French, Korean, and Spanish.

Virtual Public Hearing



Session 1  •  2:00–4:00 PM

Session 2  •  6:00–8:00 PM


  • Click the link above to register for one of the sessions or by calling 833-858-5960
  • Advance registration is required to be admitted to the phone queue for comment—register through November 1
  • Approved session time and instructions will be emailed to registrants prior to November 1


  • Provide verbal testimony by calling 855-432-1483 and leaving a single voicemail message limited to three minutes
  • Advance registration is not required—voicemail testimony will be accepted throughout the 45-day public comment period


  • On November 1, 2021, click the link above to watch the virtual public hearing (closed captioning available)
  • On November 1, 2021, call 855-432-1483 and listen live to the virtual public hearing


The Maryland Relay Service can assist teletype users at 7-1-1. Individuals requiring assistance to participate, such as an interpreter for hearing/speech difficulties or assistance with the English language, should contact the Op Lanes Maryland toll-free number at 833-858-5960 by October 22, 2021.