Napa Sanitation District plans to go on a sewer line rehabilitating, street repaving tear in the residential neighborhood near east Imola Avenue.
This area north of Napa State Hospital has some sections within the city of Napa and others in unincorporated Napa County. It has such streets as Parrish Road, Mayfair Drive and London Way and on the city of Napa website is called the Shurtleff neighborhood.
Napa San plans to rehabilitate 5.9 miles of sewer lines. Napa County is piggybacking on the bid to pave 1.6 miles of residential streets within the unincorporated pockets.
“We’re trying to stay ahead of both the city and county paving schedules,” Napa San General Manager Tim Healy said on Monday. “Nothing worse than digging up a brand-new street.”
The Napa San Board of Directors on Dec. 19 approved a $7 million contract with Cratus Inc.—$5.3 million for sewer rehabilitation and $1.7 million for the county’s road repaving. Work is to be done from March to October.
Typically, Healy said, Napa San renovates sewer lines one summer and the city or county does repaving the next summer.
“In this case, we’ll do it at the same time so there’s less disruption to the neighborhood,” he said.
Sewer line rehabilitation is an annual exercise for Napa San. Last year, it rehabilitated 6.1 miles of lines. In 2017, it rehabilitated 5.7 miles.
The goal is to keep groundwater from leaking into cracked, aging sewer lines during big storms. Water-swamped sewer lines can overflow, as happened in February 2017 when sewage-tainted water bubbled up at an intersection and drained into Napa’s Lake Park.
Napa San tries to rehabilitate 2 percent of its system every year, Healy said. This year’s Imola-area project hits that target at 2.2 percent.
The district in 2016 approved raising sewer rate by 53 percent over five years. Officials said at the time that one reason for the hikes is to double the amount of aging sewer lines rehabilitated annually, something that is happening.
Sewer rehabilitation projects don’t necessarily involve digging trenches into the streets and tearing up the pavement. When possible, Napa San uses trenchless methods.
One approach is to snake a metal cone through the sections of the system to break clay pipe and pull a new, polyethylene pipe into place behind it. The only excavation needed is where the laterals hook to the line.
Healy said that in places with good street conditions Napa San might use cast-in-place pipe. This involves pulling a liner into the existing sewer pipe and doesn’t require trenching at the laterals.
Napa San serves about 20 square miles in the city of Napa, Silverado Country Club, the Napa County airport area and several adjacent, unincorporated areas. It has 270 miles of sewer lines.
People can learn more about the Imola-area project by attending a meeting hosted by Napa County and Napa San at 5:30 p.m. Jan. 14 at Skyline Park Social Hall, 2201 Imola Ave.