Stretch of northbound East Chop Drive closed above fragile bluff
File photo by Ben Scott
The chairman of the Oak Bluffs selectmen issued an emergency order on Friday, November 2, closing the seaward traffic lane on East Chop Drive, because of significant erosion threatening the stability of the scenic road that wraps around East Chop Bluffs and overlooks Nantucket Sound.
East Chop Drive is now one-way traveling from the north (as if from Eastville) between Munroe Avenue and Brewster Avenue. Vehicles traveling from up the drive from the East Chop Beach Club must turn left at Brewster Avenue.
Kathy Burton, chairman of the Oak Bluffs selectmen, approved the emergency order after reviewing a report, prepared by CLE Engineering of Marion with town administrator Robert Whritenour and town emergency management director Peter Martell.
In an email to members of the board of selectmen and town officials, Mr. Whritenour said the state emergency declaration for hurricane Sandy gives the chairman the authority to take action without an official meeting of the five selectmen.
The lane closure could extend through the winter while town officials work with engineers to assess the situation and possible remedies.
Mr. Whritenour said that hurricane Sandy's storm surge exacerbated an existing problem. "Erosion in that area has really picked up, and immediately following the storm there was a lot of concern," he told The Times in a telephone call Friday afternoon.
He said the the town was already working to address bank stabilization issues and asked CLE engineers to inspect the bluffs. Based on the engineers' recommendations, the lane was closed.
Mr. Whritenour said CLE engineers and state engineers would arrive sometime next week to tour the site. "We are monitoring it on a daily basis," he said. "We are looking at some remedial measures that may be taken to stabilize the bluffs in some key areas where the erosion has been the worst."
Mr. Whritenour said the town would examine the cost and possible funding sources. He described the lane closure as a "precautionary measure."
He said the town would need to monitor the situation closely. "Long-term, we know that East Chop bluff is in serious need of bank stabilization along the entire part of it," he said. "And that is a big project that we are going to have to confront. That is one of the most scenic drives in all of Massachusetts. It's definitely a great resource."
Four areas of concern
Following an emergency inspection of the coastal bank beneath East Chop Drive, CLE engineers Carlos Pena and Susan Nilson furnished an assessment of the bank and recommendations for stabilizing it, in a report dated November 2, addressed to Mr. Whritenour.
The engineers said the coastal bank was damaged by storm waves generated by Hurricane Sandy on Sunday and Monday, and a micro burst of rain on Tuesday. The damage they said includes "erosion of coastal bank sediment along the base of the bank and near the roadway."
The report identified the four areas where the storm had the greatest impact:
1. The intersection of Arlington Park and East Chop Drive. "The previously eroded public access path to the jetty and beach and abutting the southerly private residence was severely scoured above the existing revetment," the report said. "The scoured section extends nearly to the roadway and the split rail fence on the northern section is undermined and should be closed off for public access."
2. A stretch approximately 140 feet north of the intersection of Brewster Avenue and East Chop Drive. "The vegetated coastal bank has failed and a large section has scoured from the top of the bank and slid in sections down the bank," the report said. "The first sign of failure along the top of the bank is approximately 10 feet from the edge of East Chop Drive."
3. A section between Brewster Avenue and Harrison Avenue along East Chop Drive. "The vegetated coastal bank has failed and a large section has scoured from the top of the bank," the report said.
4. Across from Harrison Avenue where erosion of the coastal bank, while not as severe as the previous three sections, "is noteworthy due to a gully [that] has scoured from the top of the bank where an existing drainage pipe outlets."
Based on its observations, CLE recommended Oak Bluffs "close the seaward lane along East Chop Drive at the above stated locations and monitor the remaining bank for weakened areas."
Earlier warning issued
A draft engineering report, prepared for the town conservation commission in October 2008 warned of the deteriorating conditions at East Chop bluffs. The report concluded that one of the Vineyard's most recognizable and popular scenic spots, from land and sea, displayed signs of distress and did 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.
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. The report said that the wave-breaking riprap at 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 recommended that if those conditions occurred, local traffic should be restricted to the southbound lane of East Chop Drive, and heavy trucks should not use the road at all.
The road 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).
The report suggested 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.