In January of 2018, a major snow storm labeled a “Bomb Cyclone” traveled up the entire East Coast and brought over 12 continuous hours of blizzard conditions, intense winds, and over 17 inches of snow onto the Cape and Nantucket. Winds of up to 76mph and extreme high tides compounded the impact of the storm causing flooding in much of downtown Nantucket.
Following the retreat of storm surge and coastal floodwaters caused by the Bomb Cyclone, the Town experienced a major sewer force main failure in the downtown area on South Beach Street, adjacent to the Nantucket Yacht Club. Utilizing an existing on-call contract, the Town called Environmental Partners (EP) to support recovery efforts including to provide emergency engineering services and to conduct a forensic investigation into the cause of the break.
The immediate repairs implemented by the Town temporarily diverted sewage flows from the broken sewer main and into Nantucket Harbor to prevent backups and further damage to properties. An emergency pipe connection was made over the next two days and nights into a redundant forcemain as an important but temporary measure, thereby ending the discharge to Harbor.
The original forcemain was a 20” cast iron pipe installed in 1930 and lined with a 16” polyethylene PE liner in 1982.Within one week, EP personnel visited the damaged area, reviewed background documents and developed an aggressive schedule with town manager, DPW, Sewer Department, and emergency response personnel. A comprehensive pipe assessment scope of work, and prepared bidding plans and specifications within 2 weeks so that a contractor could be hired under an expedited procurement approach.
In the first 20 days, EP developed emergency bid packages using GIS maps and field verified record drawings, solicited quotes from 5 contractors under a DCAMM waiver for expedited procurement, and engaged a contractor for the $2.9M assessment and repairs to the 3.5 mile long forcemain. Emergency funding through the Massachusetts Department of Environmental Protection State Revolving Fund (SRF) program was also successfully obtained.
The design includes the strategic positioning of air relief valves, isolation plug valves, and blow off valves and manholes at some of the access pits. Services included construction administration and resident engineering services, which included access pit dewatering, support of excavation, access for cleaning and television inspection using CCTV crews, followed by pipeline repairs. Construction work was completed with multiple crews working extended hours, 6 days per week with EP providing end-of-day progress updates to town management personnel and presenting to the Board of Selectmen throughout the project.
Using closed circuit television inspection and two camera crews, access pits were excavated, the pipe was cut and cameras were placed into the damaged forcemain. The location of the damaged pipe on South Beach Street was precisely located, as were five other locations of compromised pipe. Additional access pits were required at the damaged pipe locations to facilitate repairs.
Pipe repairs were carried out using electrofusion welding of new HDPE pipe to the existing pipe, and additional valves and air relief valves and structures were installed as part of the repair work. Environmental Partners also provided alternative cost estimates for roadway and sidewalk restoration work along the downtown corridor on South Beach Street and Oak Street. Damaged section of the existing pipe were carefully removed and sent out to a specialty laboratory for forensic analysis. EP provided a detailed report on the damaged pipeline segments and recommendations for diligent operation and maintenance procedures.
All pipe repair work was completed and in service by the end of March, with roadway and sidewalk repairs commencing in mid-April so as to not impact the annual Spring tourist season.