City investigating cause of four water main breaks

posted on 9/29/2021; updated 9/30/2021

The City of Dover experienced four water main breaks on Wednesday, Sept. 29. Three of the breaks occurred during the early morning hours, and one occurred in the evening. All have since been repaired, and water service has been restored. The cause of the breaks remains under investigation.

Community Service crews responded to a water main break near 121 Broadway around 1:30 a.m. Sept, 29. There were other breaks reported soon after near 24-26 Atkinson Street and 39 Hough Street. All pipes were 1880s vintage cast iron pipes. Some water users from different areas of the city reported low-water pressure resulting from the breaks. The last break was reported at about 6 p.m. in the area of 10 Oak Street. This was a six-inch cast iron pipe dating to 1900. 

Community Services Director John Storer, Deputy Director Bill Boulanger, and other department personnel are looking at possible issues for why these breaks occurred on the same day. Storer believes that a "water hammer" played a role in one or all of the breaks. A water hammer is when there is a surge of water in pipes that reverberates through the system. This pressure surge may have found weak spots in the system, Storer said.

Overnight hydrant flushing suspended

Overnight hydrant flushing has the potential to create a hammer effect. Until it is understood why the breaks occurred, Storer has temporarily suspended the seasonal hydrant flushing program. However, Storer and Boulanger are now doubtful it was the cause, as flushing last night took place in the city's high-pressure zone serviced by the Long Hill water tank. The three breaks occurred in the low-pressure system serviced by the Garrison Hill water tank. The two systems are only connected by a pump and isolation valve that was closed.

Community Service crews began seasonal hydrant flushing Sunday night, Sept. 26. While there has been a report of property damage from the hydrants' water flow, there have not been any water main issues reported. Last night, crews began hydrant flushing on Sixth Street, Liberty Way and Members Way. They stopped once the breaks were reported and began working on the repairs.

The type of hydrant flushing utilized this fall is called "directional" flushing. Water is flushed in only one direction by selectively closing specific isolation valves within the water distribution system, concentrating water flow through a single point in the piping system. This maximizes the scouring effect of pushing high flow through the water pipes. This process flushes old or stagnant water out of the piping network and pulls any potential residual sand or silt that may pass through one of the water well screens.

Rose Street water main break potential culprit

Last week on Sept. 22, a private contractor damaged a water main on Rose Street, located off Broadway and near where the water main break occurred this morning. It is possible that during the process of repairing the Rose Street water main that a water surge found a weak spot on the water main on Broadway. The leak may have started as a trickle and remained undetected until it created a larger hole in the pipe.

It is also a possibility that the process to shut the water off at Broadway this morning resulted in a surge through the water system and found weak spots in water mains on Atkinson and Hough streets, though crews take time and care when closing and opening valves to avoid surges. Staff is analyzing operational SCADA data to help pinpoint when the events occurred and if they are connected. SCADA stands for supervisory control and data acquisition, which provides computerized monitoring and remote adjustment of water system infrastructure.

Brief period of low water pressure at Wentworth-Douglass Hospital

For a brief time during the early morning hours of Sept. 29, Wentworth-Douglass Hospital experienced low water pressure. Contractors have been working by the hospital to replace two water mains in a project known as the Central Avenue North Water Improvements. On Sept. 28, Community Services turned off water to a 14-inch water main between Abbey Sawyer Memorial Drive to Old Rollinsford Road in preparation for pipe replacement due to begin Sept. 29. However, the water main was turned back on this morning after the report of low pressure came in, which corrected the issue. It is unclear why this occurred and may be an issue at the Lowell Avenue Water Treatment Plant. The contractor is now installing a temporary water line from a hydrant on Abbey Sawyer Memorial Drive to a hydrant on Old Rollinsford Road, adding redundancy to the hospital water system. The 14-inch water main will remain open and operational until the temporary pipe is online.

Potentially some, all or none of the issues played a role in the water main breaks. More information will be published as Storer, Boulanger and other city staff better understand what happened.