PB Network | Issue 52 | Intermodal Corridor: The South Boston Haul Road

The Central Artery/Tunnel (CA/T) project in Boston, Massachusetts is certainly one of the largest infrastructure investments in the U.S. Mirroring PB's early history--William Barclay Parson's career began with railroad work--the CA/T project's design and construction contracts began with railroad work. The South Boston Haul Road (SBHR), now renamed the South Boston Bypass Road, transformed an old, over-grown, under-used, four-track urban railroad corridor into one rebuilt railroad track with an adjacent two-lane commercial vehicle roadway.

The concept of the SBHR was to use an existing transportation corridor for both railroad freight and commercial highway vehicles. The positive benefits projected for various stakeholders included:

PB, in joint venture with Bechtel, performed the concept development and preliminary design, wrote a stand-alone environmental impact statement, assisted with final designer procurement, managed technical and commercial issues during final design, assisted with contractor bid/award and acted as owner's representative during construction. The unique challenges we resolved during planning/permitting, design and construction of this multimodal shared-access corridor are the focus of this article.

History of the South Boston Haul Road

In the 1850s, the SBHR route began to be used for railroad access to Boston from south of the growing city. Before 1900, it was made a two-track, depressed route with 12 overhead bridges. Extensive freight yards and maintenance facilities were constructed near the South Boston waterfront. The present MBTA Red Line subway tunnel, constructed in 1913 along Dorchester Avenue, crosses the cut on a diagonal under a bridge. The top of the tunnel is about 0.6 m (2 feet) below the railroad track on a three-level multimodal structure: passenger subway below freight railroad below highway. The depressed railroad route was widened from two tracks to four by 1920.

After the 1940s, passenger service was discontinued and freight service levels declined. The result was that two tracks in the depressed track area and seven yard tracks remained in various levels of deferred maintenance. The other two tracks remained in service for the (usually) daily local freight until the mid-1980s. The route was suggested as a possible multimodal shared-access corridor early in the CA/T project; community reaction was favorable, and a study of feasibility was authorized in 1987.

Preliminary Engineering

Field Survey and Mapping. The first effort was an old fashioned field survey. Much of the SBHR area was outside of the aerial mapping prepared for the CA/T project although, ultimately, aerial photographs were taken and mapping prepared for final design. Interestingly, the aerial photographs were enlarged and used as wall displays at community hearings, where they generated numerous positive comments. Initially, however, Mylar base map roll plans were prepared manually from the field surveys (CAD systems were not in place at the time).

Highway and Railway Layouts. Highway and railroad layouts were plotted manually on the Mylar base map roll plans. These layouts were found to be unusually straightforward. The highway alignment was straight (tangent) for 1.6 km (1 mile)! This was surprising in Boston, the largest city in New England, long noted for its "unusual" street grid patterns. It was especially surprising considering that one end of the SBHR is only 1.6 km (1 mile) from downtown locations such as Boston City Hall and the Massachusetts State House.

It was no surprise, however, that the existing grade (profile) was not a problem for highway traffic because railroads are flatter than highways. Vertical clearances under the existing overhead bridges were not a problem for highway vehicles because railroad equipment is higher than trucks.

Highway Traffic Analyses. Traffic analyses showed that one lane in each direction was adequate for the expected commercial traffic, and that a single through railroad track plus a runaround track and a two track yard was acceptable for railroad service. The wall-to-wall width of the four-track railroad cut was just wide enough for the two-lane highway and single railroad track; therefore, favorable horizontal and vertical alignments probably already existed-a major benefit of multimodal shared access routes: No homes or businesses were taken or even disrupted-another major benefit in a city.

The Environmental Impact Study

After we determined that the SBHR was technically feasible, the approvals process started. We decided that a stand-alone environmental impact statement would be prepared to allow the SBHR to be constructed before and serve as mitigation for the extensive CA/T project work that was to follow. The project would result in the many positive benefits listed above; however, some specific considerations were also identified. These were:

Nevertheless, public hearings resulted in positive responses from the community. The lack of negative comments was considered unusual in our increasingly litigious society. In hindsight, we have a better understanding of why the public probably reacted favorably. The route had long been accepted as a transportation corridor through the community so its existence was not an issue and this project would only improve it. Approval to proceed was given in due course.

Design Issues

The actual final design of the SBHR consisted of three main parts: highway, railroad and drainage.

Highway. The highway design itself consisted of three main parts:

Tie-in at the North End. The existing railroad line crossed a designated truck route street at grade so the SBHR simply tied into this street. Traffic modeling indicated that only a stop sign was needed for traffic control, but that traffic control signals would be warranted after a few years if traffic volume increased as expected. Provisions were made for tie-ins to a future CA/T Interstate Route 90 Interchange.

Main Highway Route. The northern half of the SBHR alignment was in flat, open area of the former railroad freight car storage yard. The area, built on land filled by dredging, had less that 0.3 m (1 foot) of elevation change in 0.8 km (0.5 mile) and no occupied buildings within hundreds of feet. The southern half of the SBHR alignment was in the formerly four-track railroad cut. There were 12 overhead bridges.

In the open area, full-width standard highway shoulders were provided, but in the cut area narrower shoulders filled the distance between concrete "Jersey" barriers on the railroad and wall sides of the highway. There was sufficient highway width to allow two-way traffic around a disabled truck in the shoulder except at the Dorchester Avenue bridge center pier (with subway underneath). Interestingly, because of high axle loads from the high percentage of trucks, the owner decided to construct four test pavement sections using different combinations of varying thickness and type of material for sub-base, gravel base, and bituminous concrete. The granite and concrete walls of the railroad cut, which also served as bridge abutments in most cases, were rehabilitated where needed.

Three of four one-lane wooden bridges (one of which was closed due to fire damage) were removed and not replaced. The fourth was repaired to serve as access/egress to a new police station constructed concurrently with SBHR work. Bridge protective screening was added at sidewalks on the remaining bridges to protect highway and railroad traffic below. Other bridge repairs were performed at each bridge as needed, with needs varying greatly. A noise barrier at the adjacent park playground, general brush/vegetation clearing, fire protection, fire truck access, water lines, fencing, signs, lighting, duct banks, slope improvements plus many other miscellaneous needs along both sides of the cut were included.

Tie-in at the South End. The existing railroad line ran under Dorchester Avenue, a major city thoroughfare and a designated truck route. A loop ramp at a 5 percent grade was constructed partly through a bus storage yard to a traffic control signal at Dorchester Avenue. Provisions were made for direct access from the bus garage access to the SBHR. The design included elements to allow easy extension of the SBHR via a future CA/T connecting viaduct to an interchange with Interstate Route 93.

Railroad. Railroad design was routine, as expected on an existing railroad line. The former yard area was reconfigured with a single through track to the waterfront, a runaround track and two storage tracks. The old yard was then removed along with several abandoned railroad structures, such as freight car scales, scale pit, team track loading dock, light towers, etc. A single new track on the east side of the railroad cut provided access to the yard. Turnouts at the south end of the cut were relocated to match the new track location and new turnouts to two freight sidings were installed. There are no railroad signal systems on these tracks. No railroad/highway grade crossings were added.

All work was done without disrupting railroad operations. The CA/T construction contractor built the tracks and railroad personnel installed the track tie-ins. Freight trains were re-scheduled to avoid operation during day-shift construction.

Drainage. Highways always require drainage, but SBHR's drainage needs were a surprise. An early field survey revealed that portions of the railroad cut were more than 1.5 m (5 feet) below mean sea level. As one might expect, the expression, "You have got to be joking," was heard many times. Gravity drains to the nearby ocean were physically impossible.

Additional investigation revealed that there was a railroad pump station near the south end of the railroad cut. It became clear that a pump station with force main to a properly approved outfall would be required. The drainage collection system for the SBHR was of conventional design. The total distance from the pump station to outfall is over 0.8 km (0.5 mile). Numerous utilities and obstructions were encountered, so close coordination with the operations of the various entities along the outfall route was necessary.

Several Surprises and Lessons Learned

Several surprising, unexpected, and "lessons learned" items emerged on the SBHR.

Property Acquisition. One big surprise was the amount of effort required for property acquisition. Much of the railroad right-of-way was owned by Conrail, but other portions were owned by Amtrak and Massachusetts Bay Transportation Authority (MBTA). Portions of the railroad yard were owned by a local businessman, including the air rights over land owned by Conrail. Some of the bridges were owned by three parties, with the City of Boston owning and maintaining the roadway and sidewalks, the Commonwealth of Massachusetts owning and maintaining the bridge structures, and Conrail owning and maintaining the bridge abutments and walls.

When the railroad cut was physically widened from two tracks to four, the railroad did not officially widen the property in all cases. The City of Boston and several abutters owned some of the land where trains operated. Some land was owned by the U.S. Postal Service and by the U.S. Army, so special federal procurement procedures were activated. Land owned by MBTA, the Massachusetts Port Authority and the City of Boston activated special Massachusetts procurement procedures. These property items had to be handled properly and legally to allow clear title for the highway to pass to the Massachusetts Highway Department.

Hazardous Materials. Railroads are at locations with high potential for finding hazardous material, so careful assessment for hazardous material is always prudent if railroad right-of-ways are to be reused/rebuilt. The SBHR was no exception. A large site with polychlorinated biphenyls (PCBs) in the ground was found at a former junk yard that specialized in cutting-up and scrapping electrical transformers. Locations with high concentrations of other hydrocarbon products were also identified. Substantial investments of time and money were required to determine the extent of pollution and mitigate the sites. Interestingly, the regulations for site mitigation changed greatly during program development, but the impacts to final remediation were slight. Two buried railroad tank cars, probably used for fuel storage, were found and removed during construction.

Nearly a Decade of Service

After more than one year of construction the SBHR opened in 1993. It has served emergency and commercial vehicles continually since then. The SBHR was extended to the south to tie into a recently constructed frontage road system at Interstate Route 93. The north end was modified to provide direct commercial vehicle access to the new Third Harbor Tunnel to Boston's Logan Airport while retaining access to the local street system in Boston's growing waterfront area. Railroad freight volumes actually increased due in part to delivery of bulk and over-size materials to the CA/T Project.

The SBHR is essentially an urban two-lane limited access highway more than 1-mile long. As such, the SBHR has future potential for use as a very long ramp for all highway vehicles to and from Interstate 93 and Interstate 90.

Additionally, a large convention center complex is under construction adjacent to the SBHR. The potential exists for the SBHR to provide substantial traffic relief before and after convention center events.

In Summary

The highly successful transformation of a little used railroad corridor into a busy multimodal route was both routine and challenging. With its combination of the easy and the difficult, however, the SBHR was an extremely satisfying project to work on. PB should always be proud to transform an underused transportation route into a highly useful piece of infrastructure. When it is possible to add another transportation mode to an existing route, all planners and engineers should seriously consider doing so.

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