Whitney Bailey Cox & Magnani, LLC

MD 200 – Intercounty Connector (ICC) Contract C

MD 200 – Intercounty Connector (ICC) Contract C

MD 200/US 29 InterchangeWBCM played a significant role in the design of the State of Maryland’s Intercounty Connector (ICC) Project. The ICC, also known as MD 200, is a state-of-the-art, toll-operated, multi-modal roadway that covers approximately 18.8 miles and links existing and proposed development between the I-270 and I-95/US 1 corridors within Montgomery County and Prince George’s County. The ICC was completed through the use of phased design/build contracts.

Under Contract C, WBCM was responsible for the design of the MD 200/US 29 interchange, which included the I-95 and US 29 interchanges and the associated connecting roadway. WBCM’s design efforts included highway plans, erosion and sediment control, drainage, stormwater management, bridges, retaining walls, noise walls, traffic control, signing, signalization, and pavement markings. WBCM personnel served as the Lead Highway and Traffic Engineers and the Design Quality Control Manager for the entire Contract C project.

During the proposal stage, WBCM developed significant modifications to the MD 200/US 29 interchange layout that saved millions of dollars in construction cost. Once the contract was awarded, WBCM refined the interchange lay-out to achieve an acceptable line of sight at all of the ramp merges and ensure that the geometric layout met AASHTO criteria. WBCM also developed significant modifications to the bridge layouts and types that resulted in significant savings in both time and construction cost. A rolling design was used to expedite the review and approval process, which allowed the contractor to start work while design was still proceeding. WBCM completed the design process in a little over a year.

The MD 200/US 29 interchange is a three-level interchange that provides full movements to and from MD 200 and US 29. WBCM designed six bridges, numerous retaining walls and noise walls, a pedestrian underpass, and drainage structures. Bridges included multiple span steel plate girder and prestressed concrete bulb-T bridges and the majority of the retaining walls weremechanically stabilized earth.

WBCM had to ensure that the design complied with very strict environmental requirements due to the environmentally sensitive nature of the area. Requirements included avoidance of sensitive wetlands and streams within the corridor and extensive use of silt fences, sediment basins, sediment traps, diversion dikes, and stream diversions to prevent sediment from entering the wetlands and streams. WBCM’s plans sequenced erosion and sediment control throughout every step of construction to ensure that no phase of construction was occurring without appropriate sediment control measures.

As part of the stormwater management efforts, WBCM designed the diversion of runoff from a deteriorated pond with a high-hazard dam to ponds located along the MD 200/US 29 interchange. WBCM coordinated with Montgomery County, SHA, MDTA, and MDE to develop a design acceptable to the all parties. The final design resulted in the deteriorated pond bring reclassified as a low-hazard dam by the MDE Dam Safety Division.

WBCM was responsible for overseeing the development of the Contract C traffic signal plans, traffic signal interconnect plans, signing and marking plans, and maintenance of traffic (MOT) plans. WBCM developed signalized corridor and freeway interchange traffic models using SYNCHRO and CORSIM, reviewed CLV, queuing, crash data, traffic data, traffic signal timing, geometrics, field conditions, and construction sequencing in the development of the Maintenance of Traffic Alternative Analyses (MOTAA) and preparation of the project-wide Transportation Management Plan (TMP).