“Pipelines in the collection system on the west side are more than 50 years old,” said Laurie McCollum, senior engineer with the Redding-based firm. “They are constructed primarily of clay pipe and are in poor condition.”
The Williams City Council last week adopted its Wastewater Master Plan, a study of the collection and discharge system, which was funded by a $500,000 grant, officials said.
McCollum said if the council sets aside $200,000 a year, they could probably replace about 40 percent of the old pipes in 20 years, or $477,000 a year over the next 20 years to replaced them all.
The wastewater collection system was analyzed using the Innovyze InfoSewer, a computer program for wastewater flow determination and pipeline sizing.
The city’s existing wastewater collection system currently consists of about 85,000 feet of 6-to-10-inch sewer mains, 7,200 feet of 12-to-20-inch interceptor sewers, and 3,700 feet of force mains.
McCollum said the old pipes on the west side of town have cracks that allows infiltration of rain water during wet years, which greatly adds to the amount of sewage that needs to be treated.
“This high infiltration and inflow indicates deficient sewers in need of replacement,” she said.
McCollum said the collection system east of Interstate 5 appears to be in good condition and has adequate capacity for existing conditions and projected 20-year future flows, although several sewer segments on the east side (D and G streets) show they have the potential for blockage and possible overflow due to apparent deficiencies in sewer grade and construction.
McCollum said if growth exceeds 2 percent, then the city will reach sewer capacity sooner than anticipated, so improvements would also have to be shifted in time.
City officials said the population projection for the wastewater treatment plant is lower than what the city could potentially realize, given the growth in the local economy. The city’s General Plan projected an annual growth rate of 4.4 percent to 9,822 residents by 2030, but city officials said that figure is not realistic for wastewater treatment planning.
Although City Administrator Frank Kennedy said the city would likely have to raise rates for customers to cover some of its capital improvements on the wastewater system, the city would likely have financial assistance from the state because Williams is an economically disadvantaged city.
“There is no way our citizens would be able to afford it,” Kennedy said. ■