By MARY ANN GREIER
SALEM - The question of whether to repair or demolish the Highland Avenue water tank remains unanswered for now.
The city Utilities Commission heard a presentation Thursday on the value of completing a water study using calibrated computer modeling to help them answer the question about the still-in-use water tank which needs sandblasted and repainted.
A calibrated water model would be based on actual numbers for the Salem water system's flow, pressure and chemical readings for chloride, PH, temperature, and anything connected to the water quality. The computer model could run a scenario to show how the water system would be affected if the Highland Avenue water tank shut down.
Burgess & Niple project manager Zach Held gave a presentation to the commission to show the value of a calibrated water model, not just for this question, but for everything associated with the water system now and in the future.
"I think it's a valuable tool for making decisions," he said.
Held previously gave a presentation in February on his evaluation of the Highland water tank, explaining how different scenarios were plugged into a computer model of the water system both with and without the Highland water tank. The scenarios showed what would happen if there was a fire, what happened during peak demand or how the supply would be affected during a power outage.
At the time he said he preferred a calibrated model be considered using actual flow and pressure at hydrants throughout the system before making a final recommendation on the Highland water tank. He said that would be more accurate.
The commission had agreed to do the calibrated testing at a cost of $12,500, but assistant Utilities Superintendent Matt Hoopes advised the commission that he and Utilities Superintendent Don Weingart wanted more information on what a calibrated model could do for the department before going forward with the cost.
Held told the commission the computer modeling needs calibrated due to some discrepancies they were seeing with estimates in the model and actual water pressures. He said calibrating gives a better picture of existing pressures and flows.
He said calibrated water modeling "serves as a tool for problem identification and risk management."
Held identified several ways the calibrated water modeling can help the city, including where to best complete loops of the water system which can help keep the water on for customers when there's a break.
A main water line break on Allen Road this week left some residences and businesses without water, but a loop in the system could have prevented that.
Areas can be identified where there's low flow that needs improving and spots in the system where water age is a factor for quality.
The city could see the impact on the system from a new large water customer or proposed new housing development. The city could use the model to evaluate selling water to other municipalities or find out what would happen if a certain pipe failed.
"You can analyze the system to death," Held said.
He also explained that the water modeling would give the department a tool for managing assets and assess the condition of pipe and equipment through the information available.
When asked how long it would take to complete the calibrated computer modeling, Jeff Marnicio, also from Burgess & Niple, said it would depend on what happens after everything is entered. He said it could take anywhere from a week to a month or longer.
The commission agreed to have Burgess & Niple go forward with the calibrated computer modeling, with assistance from the utilities department in gathering some of the information needed.