The dramatic water main break on Washington Street last Tuesday was likely the result of a result of a large increase in water pressure the night before that weakened some of the older pipes in the system, according to Lexington Director of Public Works Patrick Madigan.
The pressure increase came about due to the city’s water tank on Houston Street, which feeds into the system of Maury Service Authority pipes known as The Loop, being taken offline so that the MSA could replace portions of the asbestos pipe in The Loop between Pizza Hut and Houston Street. The replacement of that water line is one of several ongoing projects to update their water treatment plant and distribution system.
Madigan told The News-Gazette that The Loop is normally fed by both the Houston Street tank and the MSA’s Enfield storage tank and that, when both tanks are online, the pressure in the system is balanced.
When one of the tanks is taken offline – as the Houston Street tank was on March 20 – the system needs to rebalance itself, which can lead to increased pressure in the system.
The city has a system of “new and calibrated” pressure reducing valves that they use to control the water pressure in those situations, and with the age of the pipes in the water system, Madigan says, “It’s kind of a balancing act.”
Overnight, from Monday into Tuesday, there was an increase in water pressure in the system of about 15 psi (pounds per square inch). Madigan said that higher water pressure levels during overnight hours is not unusual due to people not using the water, but that the increase is usually around 5 psi in that part of the city. The extra pressure, he said, likely weakened part of the older pipe, and when water usage increased the next morning, the pipe failed and water burst through the street and into the air.
The Washington Street break wasn’t the only one to occur following the increase in water pressure in the system that night. Around 1 a.m. Tuesday, a water main on Myers Street also failed and needed to be repaired. The Houston Street tank was brought back online around 9 Tuesday morning, before the break on Washington Street.
Madigan also said that part of the city’s capital improvements plan is to bring in a company to do a survey of the water system that would help identify potentially weakened sections of pipe in order to repair or replace them before they fail. The contract is still in the early stages, so it will likely be “six months to a year” before the city is able to get the data from it, but these surveys are something that will be conducted every year, along with regular valve testing and hydrant testing.
“The idea is, once we can get that in place, some of that will be using a combination of inspection technologies to try to find any potential weaknesses in our distribution system that we can observe,” he said. “It’s not going to capture everything, but the idea would be that you try to at least go out there and … kind of get an analysis of the whole system and some potential hot spots, and … a priority list of those hot spots, and then we [can] go out and investigate, which may mean we need to dig up sections and look at sections and try to repair them. That’s kind of the long-term strategy with our system. We have plans to do active monitoring so we can identify weak spots early and repair them.”
Madigan also told The News-Gazette that the MSA is looking into some additional work that may be needed for the section of The Loop by the Houston Street tank, which would require the tank to be taken offline again. There is not currently a date set for when the tank will be taken offline, but it may happen in the near future.
