The 57.5-million-gallon reservoir has only one 48-inch diameter concrete pipe, which was built more than 60 years ago. At peak demand, more than 10,000 gallons of water flows through the pipeline per minute.
In the event of a massive pipe failure, about half of the city's homes could be left without water, officials said.
While the council ultimately approved the contract, some council members — fresh off a vote to increase water rates — questioned the increased cost.
"The only issue I have is that the winning bidder is 18% above the engineer's estimate," said Mayor Ara Najarian. "And typically we have been seeing these bids coming in the other end of the estimate, below the engineer's estimate."
Glendale Water & Power officials attributed the increased contract cost to a variety of factors that will make the construction more difficult than originally expected, including the need for a 30-foot deep trench.
"All of these things came into effect as we started to look at the project during the bidders process," said Glendale Water & Power General Manager Glenn Steiger. "It turns out it was a bit more complex than was originally expected."
The project comes at a time when most scheduled capital improvements — including maintenance of the city's aging pipelines — have been postponed for at least five years as officials grapple with tight budgets.
While many postponed projects are classified as critical, utility officials have said the reservoir project is simply too pressing to put off.
"Should we have a major earthquake, or even experience some kind of fault in the existing line, we would lose service to about 50% of the city right now," Steiger said. "So this will back that up and provide much more reliability."
Construction is slated to start in January and take about eight months.