This project involves the addition of an office building over an existing freeway tunnel. The existing tunnel carries Interstate 395 below several local streets and existing structures. An electrical room, which houses lighting and ventilation equipment for the tunnel, is located below ground adjacent to the tunnel. A local developer has proposed an eight-story office building to be constructed atop the electrical room and portions of the tunnel. The tunnel and electric room were originally designed to accommodate the load requirements of such future construction. This project involves the testing of existing materials in the tunnel and electric room to assure they were constructed according to specifications and are capable of carrying the additional load.

The tunnel is actually comprised of a series of two-span steel girder bridges oriented perpendicular to the flow of traffic, such that the abutment walls comprise the exterior walls of the tunnel and the center pier wall comprises the interior tunnel wall. The electric room is approximately 152 feet by 58 feet and is supported by 18 reinforced concrete columns supported on pile footings. The columns were constructed with top bearing plates and anchor bolts to accommodate future above-ground construction.

Modjeski and Masters, Inc. is providing supervision of destructive and non-destructive materials testing for this project, including field observation. A security evaluation of the project site was also performed as part of this project, at the request of the FHWA. The AASHTO Guide to Highway Vulnerability Assessment for Critical Asset Identification and Protection was used as a basis for the study. The methodology outlined in the guide was used to evaluate potential vulnerabilities for pre- and post-construction conditions. The before and after “scores” were then compared to determine whether the proposed structure had a net positive or negative impact on the security of the I-395 tunnel. As part of this study, Modjeski and Masters provided the services of a field crew to collect data on the existing conditions a the site. Project drawings and interviews with the developer were used to assess the condition of the site upon completion of the office building. The final security report contained recommendations for improving the security of the electrical room and the adjacent I-395 tunnel. To assess security during the construction phase of the project, a National Institute of Standards and Technology (NIST) document entitled Best Practices for Project Security (July 2004) was utilized.