The existing concrete pipes under the road to Dowse's Beach in Barnstable, Mass., were too small, leading to degraded water quality in Phinney's Bay. The restoration project called for installation of a 4x10-foot precast concrete box culvert under the beach road to restore tidal flow to the area. Photos: Horsley Witten Group
The WRP also publishes a Coastal Tidal Restriction Atlas to help towns determine where problems exist in their region. The group can be a resource for public works departments in other ways as well, said Durey, by providing technical guidance and helping towns secure the right kinds of permits for their projects—particularly if the towns are not initially aware that in addition to the infrastructure replacement, their project also has environmental implications.
“We strongly encourage DPWs and other town officers to contact our program when they have a question about whether a culvert is tidally restrictive,” said Durey. “If they don't know, it can cause permit problems. They may be required to go back and include the restoration.”FIXING THE BAY
The Phinney's Bay project in Barnstable is one of several recent projects of this type in the region. (The WRP has been involved in other projects in Barnstable but was not directly involved in the Phinney's Bay initiative, said Durey.) According to Jacobsen, the projected cost of the project was $260,000 and it was funded by a variety of sources, including federal grants.
In Phinney's Bay, the public works department replaced two concrete pipes under the beach access road with a 32-foot-long, 4x10-foot precast concrete box culvert. That size was decided on based on a cost/benefit analysis to determine what would produce balanced flushing and optimum salinity levels in the bay, said Rich Claytor, principal with Horsley Witten Group, the Sandwich, Mass.-based environmental engineering firm contracted for Phinney's Bay and several other culvert replacement projects.
“We try to come up with an optimum size and geometry based on cost,” said Claytor. “We put pressure transducers in the water to measure the elevation for a month to record the average tides—to get a range of what the tide is doing upstream and downstream. Then we model the existing opening using a variety of different culvert capacity software.”
Horsley Witten helped the Barnstable public works department conduct the feasibility study for the effort, determine the culvert size and design, and helped secure local, state, and federal permits for the project, Claytor said.
“We also had to build a temporary culvert adjacent to the permanent structure to allow tidal exchange during construction,” said Claytor. “That adds cost, but if you have critters living in the embayment, they need tidal exchange to survive.”
Other important considerations for Phinney's Bay were location and timing, particularly given the time of year. “This road goes out to a coastal beach access, so it's very popular,” said Claytor. “We have to get the road back open for beach season.”CONSERVATION COLLABORATION
Durey of the WRP is familiar with the challenges faced at the local level, having worked as a local conservation agent prior to joining the state. He knows that local level infrastructure improvement and state and federal conservation efforts don't always gel, and his aim is to make sure that through proper planning, those groups connect on projects like these.
“Historically, there has been a disconnect between those efforts,” said Durey. “The opportunity really lies in advance planning—for the transportation and the restoration people to work enough in advance to plan these projects in collaboration.”