East Chop bluff needs costly fix
A draft engineering report concludes that the East Chop bluffs, among the Vineyard's most recognizable and popular scenic spots, from land and sea, display signs of distress and do not meet minimum stability standards.
The report's recommended solutions to stabilize the bluffs and protect them from catastrophic storms could cost as much as $10 million.
Public and private stakeholders are at work to resolve legal issues that now prevent the town from seeking state and federal funds to repair the coastal bank.
"If we have a storm, it's going to cost us millions of dollars to fix it, means we don't have," said Craig Dripps, president of the East Chop Association. The private property owners association owns the bluffs.
Unstable and vulnerable
The engineering report, prepared by Deere & Ault Consultants, working with CLE Engineering, analyzed the coastal bank using drill borings, historical records, and visual observations to determine the stability of the bluff. Funding for the engineering was approved in the form of a $40,000 appropriation approved by voters at a 2006 special town meeting. The report says the wave breaking riprap constructed around the base of the bluff, is in fair condition, but that the upper slope is in poor condition, with numerous eroded gullies and areas bare of stabilizing vegetation.
"Rapid deterioration with significant erosion may occur if waves start to overtop the heavy riprap wave break and contact the bottom of the upper slope," said the engineers in their report. "Periods of heavy rain (i.e. a 25-year storm) may also destabilize local areas of the slope." The report recommends that if those conditions occur, local traffic should be restricted to the westbound lane of East Chop Drive, and heavy trucks should not use the roadway.
The roadway was closed for more than a year following Hurricane Bob, in the fall of 1991. That storm caused significant erosion, which was repaired by building the wave break around the base of the bluff, funded by the Federal Emergency Management Agency (FEMA). But that repair has failed to stop long-term deterioration of the coastal bank, and left it vulnerable to a hurricane force storm, according to Mr. Dripps.
"Unfortunately, it went to the lowest bidder, and we got what we paid for," Mr. Dripps said.
The report suggests four basic engineering solutions for the eroding bluff. One option would be to "armor" the slope with heavy riprap or pre-cast concrete blocks. Another would be to add rock fill to the top of the wave break, and fill behind it to reduce the angle of the slope. A third option would be to construct a stabilizing wall of pre-cast concrete blocks at the bottom of the slope. A fourth option is called sheet piling. In this solution, sheets of reinforced steel would be driven vertically into the top of the slope, and anchored into the more stable soil at the top of the coastal bank. The slope could then be reshaped and stabilized with plants. Joan Hughes, chairman of the Oak Bluffs conservation commission (CONCOM) , said this option might be the most affordable, with the least negative impact.