Mayor Daniel M. Knapik has submitted a $2.9 million bond request to fund the replacement of the water line connecting the city’s water supply to the largest surface water source in the city.
The council referred the $2,893,000 bond request for the Granville Raw Water Pipeline Replacement project to its Finance and Legislative & Ordinance committees for review.
The Water Commission has been developing the project, which includes a green energy component, for more than a year because of the engineering challenge of replacing a major pipeline snaking along the north side of the steep Granville Gorge. Options included abandoning the existing pipeline and constructing a new line along a more accessible route.
The present pipeline limits the flow of water and is leaking, while the proposed pipeline is projected to increase flow from the reservoir to the treatment plant, located in Southwick, by 1 to 1.5 million gallons a day, a cost avoidance measure by substantially reducing the demand for well water.
Dave Edson of Hoyle, Tanner & Associates, Inc., of Westborough, the Water Commission’s engineering consultant for the pipeline replacement project, said at the February board meeting, that the Granville Reservoir is the city’s most cost-effective drinking water option because the system is based on gravity flow. Water pumped from wells requires a substantial amount of electrical power.
The consultant has assessed the function of the pipe for more than a decade and observed a drop in the volume of water reaching the treatment facility.
“The (existing) pipeline is losing capacity, which has a real economic impact on the department because this is the least expensive water to produce, because the system is almost entirely gravity fed,” Edson said at the February meeting. “When you have pipe that is over 100 years old, catastrophic failure is a concern. The treatment plant has a (treatment) capacity of 2,800 gallons per minute, while the pipeline has a capacity of (delivering) 1,900 to 2,000 gallons per minute.”
The commission has opted to replace the existing pipeline which carries water from the city’s Granville reservoir to the treatment plan in Southwick, using a mix of technology and traditional construction methods.
The Granville pipeline replacement project will employ the use of trenchless technology.
Edson said at the Water Commission’s March 6 meeting that pipe bursting technology will be used in the upper half of Granville Gorge, while traditional trenching method, which are more cost-effective, approach will be used for the more accessible lower half of the project.
The purpose of the project is to replace a 14-inch pipe, originally installed in 1890, with a 16-inch high-density plastic pipe. Charles Darling said this morning that an expanding slug is pushed through the existing line, bursting the walls of the cast iron pipe. The slug pulls the larger replacement line behind it as it moves through the existing line, resulting in a larger diameter line being put into place.
The project would be financed through a federal low-interest loan, part of which may be forgiven over time, administered through a state revolving fund program. The state has approved $2,357,000 for the project.
However, the Water Department will have to fund the engineering and design work. The state program established a short timetable which requires the city to begin the design process, appropriate funding by June 30, and submit the loan application, with engineering, design and permitting documents in place, by Oct. 15, 2012, with a construction contract awarded by April 2013.
The project is also required to have a “green” energy element. The proposed option to meet that requirement is to install turbines inside the pipeline to take advantage of the “head” of water rushing down through the pipe from the reservoir. The power generated would be sufficient to operate the treatment plant, furthering reducing the cost of producing the city’s drinking water.
Edson said the project will still include a “green energy” generation component, but that the turbines would be placed inside the basement of the treatment plant at the end of the transmission line.
“You have a high-flow, low-head rate that would require two turbines in parallel,” Edson said. “The electric generation would be sufficient to operate the treatment plant.”
Edson said the project would take a summer construction season to complete, meaning that the department would have to draw water from is aquifers. “The wells can provide seven to eight million gallons a day,” he said.
Charles L. Darling of the city’s Water Department said the city is attempting to secure participation in the state’s low-interest water improvement loan program, but that the state has established strict requirements and a timeline for qualification in the program which would provide funding with a 2 percent interest rate, lower than the bond interest rate available to the city.
“The city also is an environmental justice community, which may qualify it for forgiveness of some of the principal,” Darling said.”There is also funding available for energy recovery projects.”
“The next phase is the final design of the work,” Darling said. “We have to submit the project, with the permits, to the state by Oct. 15, 2012 and have the project out to bid before April 2013.”
The city will have to obtain orders of conditions from the Granville, and possibly the Southwick, Conservation Commissions because the line is located in the resource buffer of Munn Brook.
