Engineers brainstorm to lower cost of North County Corridor

Slimming the North County Corridor from six lanes to four east of Riverbank could shave $10 million off the future freeway’s estimated $400 million cost, a team of road construction experts will tell transportation leaders Wednesday in a public meeting.

That’s just one of 10 big ideas in a “value analysis” generated for the expressway envisioned between Modesto and Riverbank with a tie into Highway 108 east of Oakdale. The ideas, including using rubberized asphalt and pavement with synthetic fibers, could save up to $90 million all told, the study says.

“This just forces everyone to sit and think about the best, most cost-effective way to build this,” said Matt Machado, Stanislaus County’s director of public works.

Plans have stirred controversy as engineers study options for the route, which will be selected in a couple of years, with construction possibly starting in 2019. Proponents look forward to smoother-flowing traffic toward Highway 99, while critics fear loss of farmland, some homes and quiet country living.

The partners – Modesto, Riverbank, Oakdale and the county – quietly have finished 13 technical and environmental studies and submitted them for approval to the California Department of Transportation. The documents are expected to become public in May, followed by a public hearing in June before state transportation leaders weigh them in 2016.

The Federal Highway Administration requires value analyses for projects worth more than $50 million. They’re usually done later in the game, but Caltrans wants a preliminary analysis now because of the North County Corridor’s unique nature, Machado said.

Some ideas would save money by reducing the amount of land officials would have to buy from neighbors.

For example, shrinking the freeway from six lanes to four east of Riverbank’s Claus Road could save $2 million to $10 million, the study says. Crews also could streamline the road by partially tunneling crossroads underneath and by employing new technology in sheer walls where the freeway would jump over a railroad track near Riverbank.

Previous drawings showed standard freeway interchanges at four spots between Modesto and Riverbank, with McHenry Avenue, Coffee and Oakdale roads and Roselle Avenue passing beneath the North County Corridor, which would be a raised freeway in that stretch. The new study suggests that the crossroads could dip into partial tunnels, meaning the freeway would not have to be raised so high and would require less land, perhaps saving $21 million.

Superstrong mechanically stabilized earth walls also would use less space, saving about $2 million on the cost of shooting the freeway over Burlington Northern Santa Fe tracks between Roselle and Claus, the team says. Also, rock trenches running along the freeway could drain rainwater as efficiently as wide ditches and retention basins, shaving $8 million, the team says.

A similar trench in the median could save more than $18 million, and a narrower median with a steeper slope than usual could save $2.8 million. But that’s more aggressive than Caltrans’ standard and would require special permission, a report says.

Reducing to four lanes east of Riverbank might not meet Caltrans’ standard, either, and might not be justified if fewer lanes result in more accidents, the report says.

Caltrans has not approved the use of asphalt fortified with some synthetic fiber in freeways, but if tested and approved by the time construction starts, such additives could save more than $15 million because the surface wouldn’t have to be as thick, Machado said.

Caltrans has given a green light for a rubberized surface, which provides a quieter ride than regular asphalt and should save nearly $4 million, the report says.

The partners will review a presentation on the value analysis at a meeting of the North County Corridor Authority starting at 4:30 p.m. Wednesday in the basement chamber at Tenth Street Place, 1010 10th St., Modesto. For more information, go to www.stancounty.com/publicworks/pdf/ncc/2014/november/agenda-11-05-2014.pdf.

This story was originally published November 3, 2014 at 5:17 PM with the headline "Engineers brainstorm to lower cost of North County Corridor."