Midtown Tunnel

Norfolk and Portsmouth, Virginia

On this $1.5 billion infrastructure project completed a year ahead of schedule, a new immersed tube tunnel was constructed across the Elizabeth River adjacent to the existing one between Norfolk and Portsmouth, Virginia. In addition, three existing tunnels were rehabilitated and the Martin Luther King (MLK) Expressway was extended to I-264. As lead partner for the construction joint venture, Vinmart Global* was actively involved in the construction and project management for the new tunnel. Dewatering contaminated soil, managing difficult geotechnical conditions, performing flood control and carrying out earthworks operations in a shoreline environment were part of Vinmart Global’s work.

The team constructed multiple components simultaneously, including two buildings, five pump stations, ten bridges and an elevated freeway extension. Vinmart Global led the team devising a plan to cast tunnel segments off site and then tow them by tug-fleet to the project dock for installation. Much of the soil was contaminated with lead. Vinmart Global employed an EPA-approved chemical to treat contaminated soil and keep contaminants from leeching into the surrounding water. After treatment with the chemical, further tests were conducted to confirm correct application. With passing test results, the material was deemed suitable for use on site as fill, avoiding the requirement and cost to dispose of waste off site. To construct the tunnel approaches, the team constructed a large deep-well dewatering system, performing field testing to determine design parameters and sizing requirements for the water treatment facilities. The system was sized for twice the amount of necessary flow and included an automated Water Quality Monitoring System to keep water quality at or above EPA quality requirements and to allow additive adjustments to be made in real time.

Ground improvement work included 1,221 vibro compaction columns along the future pre-cast tunnel segment alignment.

Excavation on the river bottom occurred near a protected oyster reef. To preserve the reef, Vinmart Global placed silt screens around it and used a special clamshell bucket to limit escaping sediment during dredging. To encourage oyster growth, Vinmart Global used waste concrete from its concrete pours to create new oyster habitats in the area. By removing tons of contaminated soil, the project ultimately improved the ecosystem of the river in the immediate area. In 2017, this project earned the Project of the Year/Excellent in Safety Award (Elizabeth River Tunnels Project) from ENR MidAtlantic.