Landscape Architect Articles

LASN July 2016 Hardscapes: New Bedford Harborwalk07-08-16 | Department

New Bedford Harborwalk
by Kimberly Drake, RLA, CDM Smith

The New Bedford – Fairhaven Hurricane Barrier was completed in 1966 by the US Army Corps of Engineers to protect New Bedford Harbor and the neighboring cities from hurricanes. In 2015, the city of New Bedford, Mass., built a concrete walkway, which was designed by landscape architects CDM Smith, on top of the 22' tall barrier. Phase one covers 3,500 linear feet and was completed in the fall of 2015; phase two will cover 4,800 linear feet and will be completed in the fall of 2016. The walkway will have 1.5 miles of elevated paths accessible via ramps.

The city of New Bedford, Mass., has created a walkway atop their portion of the New Bedford - Fairhaven Hurricane Barrier. The first phase (3,500 linear feet) was completed autumn of 2015. The second phase (4,800 linear feet) is currently under construction, scheduled for completion autumn of 2016, and will provide over 1.5 miles of elevated walkway. The project includes a 10-foot wide concrete walkway atop the existing stone barrier. There are railings on each side, lit with bollard-style light fixtures, and access ramps, meeting the requirements of the Architectural Barriers Act (ABA). Mosaic images of the hurricane symbol and names and dates of notable local hurricanes will be embedded into the walkway surface over time. In addition to providing a safe work environment for maintenance activities that must occur atop the barrier, the new walkway allows visual access to New Bedford Harbor and Buzzards Bay for the first time since the barrier's original construction 50 years ago. The path, now accessible to residents and visitors of all ages and abilities, will ultimately provide a connection to trails throughout New England.

Before the construction of the walkway, access was limited to only those brave souls who would climb the rocks. Now, with dedicated parking and access ramps, everyone can view the harbor from a safe environment, and workers have safe access. The project owes its success in part to community involvement and support, collaboration between city departments, and meeting safety requirements while providing a public amenity.

History
The barrier was designed in 1962 to protect New Bedford Harbor and the cities of New Bedford and Fairhaven from hurricanes up to Category 3 and storms of up to 500-year frequency. In 1966, the United States Army Corps of Engineers (USACE) completed the 18,000-foot long barrier as a federal flood control structure. It is comprised of a 22-foot tall earthen berm capped with 4.5-ton armor stone. The New Bedford portion includes three gates, five access ramps, a pump station protecting low areas landward, and three gated conduits, all of which are owned, operated and maintained by the city. The gates are closed multiple times a year for storms and high tide surges.

Maintenance has historically been a challenge. Although the access ramps and top of the barrier are relatively flat, the stones become slippery when wet or icy, and vegetative growth must be controlled within the large gaps that occur between stones and along the side slopes. Valves and conduits required for operation of the gates are located on unprotected, steep (2:1) side slopes. The height of the barrier restricts views of harbor conditions, which limits visibility during inclement weather – when access to the barrier is critical.

The Army Corps permitted the walkway, provided that improvements could not penetrate the barrier. To accommodate this, two layers of choke stone, which is a thin aggregate designed to prevent overall aggregate loss, were prepared as part of the base. On top of that, two layers of epoxy-coated reinforcing steel finished the base for the 14" thick concrete. Haunches on either side allow electrical conduit to pass through the walkway, and provide a space for custom railings to be mounted.

Renovation – Making it Happen
The project to create a pathway on top of the barrier was funded by a Commonwealth of Massachusetts PARC grant, MASSDOT, and city funds. The Harborwalk, designed by CDM Smith and constructed by city forces, was the joint vision of Mayor Jonathan Mitchell, who wanted to make the harbor more accessible to residents, and the Department of Public Infrastructure, headed by Commissioner Ronald Labelle, whose primary concern was the safety of the workers who must regularly access it.

Permitting required close coordination with the USACE New England District and included a submittal for modifications to the barrier to provide necessary improvements requested by the city. This included the requirement for notifications to the National Marine Fisheries Service, US Fish and Wildlife Service, the Massachusetts Natural Heritage and Endangered Species Program, Massachusetts Coastal Zone Management, Massachusetts Historical Commission, the Wampanoag Tribe of Gay Head, and the Mashpee Wampanoag Tribe. Representatives from the city and USACE met representatives from Massachusetts Department of Environmental Protection (MADEP) to discuss impacts and requirements for a project modification in accordance with the Massachusetts Waterfront Act. The city was required to file a Request for Determination of Applicability with the New Bedford Conservation Commission, which is responsible for upholding the Massachusetts Wetlands Protection Act locally on behalf of MADEP.

The 10' wide walkway has railings on either side, lit with bollard-style lighting fixtures. The fixtures are only located on the land side of the path in order to be less of a distraction for seafaring visitors. The fence has removable panels that allow crews to access valves and the side slopes for maintenance, as vegetation sometimes grows through the 4.5-ton armor stone that makes up the bulk of the wall.

Although the structure is owned and operated by the city, the designation as a Federal Flood Control Structure required input and review by USACE, who stipulated that the improvements could not penetrate the barrier structure. To meet this requirement, two layers of choke stone were used to prepare a base for the concrete. Choke stone is a fine aggregate that makes a more dense mix when embedded, with the goal of preventing aggregate loss. Two layers of epoxy coated reinforcing steel were installed atop the choke stone.

The 14-inch thick surface has haunches on either side to allow electrical conduit to pass within the walkway, and to provide a means to mount the custom railings. Bollard-style lighting is mounted to the railings on the landward side only, minimizing the distraction to mariners. Electrical conduit is provided toward the midpoint of the barrier from each ramp location, as the electrical cabinets had to be installed at the street level. The width of the existing barrier dictated mounting the lights on the railing posts to maximize the travel area, and photometrics, the measurement of light and its perceived brightness, dictated the post spacing. The fence has removable panels that allow access to valves and the side slopes for maintenance. Access ramps meet ABA standards for trails on federally built, owned, or operated facilities, and include bollards to prevent unauthorized vehicle access.

As a nod to the history and purpose of the wall, mosaics depicting the hurricane symbol and notable hurricanes in the region have been embedded into the walkway. This portion represents hurricanes Gloria (Sept. 1985) and Bob (Aug. 1991). Over time, additional significant hurricanes will be depicted along the wall, which is rated to withstand a Category 3 storm.

In addition to providing a safer environment for those responsible for maintaining the structure, there is now dedicated parking and a community connection that includes harbor views previously only available to a few brave souls.

Keys to the success of this complicated project included community involvement and support early on; collaboration between multiple city departments; successful navigation and understanding of the permitting; candid communication between the city, USACE, and DEP; the ability of the city to effectively write grants and have shovel-ready funded projects; developing a program that meets the safety needs of the city, while providing a public amenity.

As seen in LASN magazine, July 2016 Hardscapes.