Supplemental Draft Environmental Impact Statement (SDEIS)

Introduction

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.