I-95/I-695 Preliminary and Final Design

JMT was responsible for Stage I and II Project Planning engineering, environmental documentation, and preparation of the FONSI for the entire Section 100 project, refining all I-95 electronic toll lanes (ETL) Section 100 alternatives. Subsequently, JMT was selected to provide preliminary and final design for the $450 million I-95/I-695 interchange, which was advertised in multiple contracts. Final design included 11 lane-miles of I-95, 12 lane-miles of I-695, one lane-mile of local roads, and 16 lane-miles of ramps. JMT coordinated the design with adjacent developers to minimize negative impacts.

Highway Design: The preliminary design included developing and analyzing multiple concepts for general purpose and managed lanes for I-95’s mainline. In addition, JMT refined multiple line and grade options for the I-95/I-695 interchange and prepared the final design and geometrics of this complex interstate interchange. The preliminary design encompassed an array of design elements, which included horizontal and vertical alignment, typical sections, developing and reviewing design standards, and minimizing negative impacts to the existing ROW and utilities.

One unique challenge was the re-design of the existing “double-braided” directional I-95/I-695 interchange to a fully directional multilevel design with no ingress or egress ramps from left lanes of the two mainlines. Complex maintenance of traffic (MOT) plans were prepared to stage this interchange without disrupting the existing traffic of nearly 200,000 ADT.

Traffic Forecasting and Engineering: JMT performed travel demand forecasts for the various alternatives, conducted travel time runs, and performed traffic counts. In addition, JMT performed capacity and operational analyses, studied MOT options, and evaluated constructability issues and evaluated impacts to signing, lighting, and ITS systems.

Structural Engineering: JMT prepared preliminary layouts of bridge structures in a complex network of multilevel interchange design at the I-95/I-695 interchange involving many elevated structures for the directional ramps. The preliminary structural design work included superstructure types, span arrangements, pier locations and sizes, and phased construction. JMT prepared final design for 22 bridges, 30 retaining walls, six noise barriers, and five culverts at the I-95/I-695 interchange.

Geotechnical Engineering: More than 290 borings were required to satisfy the project requirements. Our geotechnical investigations and evaluations culminated in the development of a geotechnical report of findings and recommendations for bridge foundations, retaining walls, noise walls, pavement design, slope stability, stormwater management ponds, and utility directional drilling.

Additional Services: Preliminary and final design included wetland and forest delineation, coordination with environmental agencies, permitting requirements, drainage and stormwater management, utility coordination and relocations, hydrologic/hydraulic analyses, and extensive public involvement and interagency coordination. JMT utilized focus group meetings with agencies and communities to establish the purpose and deed, ARDS document, and FONSI. Brochures, displays, and materials for the I-95 Section 100 website were prepared.