DANVILLE -- Contractors have begun a $32 million project to build new merge lanes along two miles of Interstate 680 between Danville and San Ramon.
The lanes are meant to speed up traffic and make travel safer on the busy commute route.
Before the new 12-foot-wide lanes are finished, however, I-680 motorists will have to deal with the inconvenience of nighttime lane closures and slowing traffic at times for perhaps a year or more.
It's a case of the pain before the gain.
Begun in the last 10 days, the project will add an extra lane in each direction on the freeway between Sycamore Valley Road in Danville and Crow Canyon Road in San Ramon.
The extra lanes give motorists more time and space to merge onto and off the freeway, easing congestion on a heavily used route between the East Bay and Silicon Valley.
"We're addressing the weaving problem that disrupts traffic flows," said Randy Iwasaki, executive director of the Contra Costa Transportation Authority. "This will make traffic flow better, faster and reduce accident risks."
Northbound I-680 has an above-average collision rate — something traffic engineers hope to reduce.
The construction contract permits the project to be finished in mid-2014. The contractors -- a joint venture of Bay Cities Paving & Grading and Inc/Myers J.V. — are pushing for an earlier completion if dry weather allows, officials said.
Once the work is done, motorists will save up to two minutes during the rush hour drive time because of the combined effect of the new lanes, and other merging lanes finished in 2006 and 2007 just to the north and south, engineers said.
In the earlier projects, the Contra Costa Transportation Authority and Caltrans added merge lanes from Crow Canyon to Bollinger Canyon roads and from Sycamore Valley to Diablo roads.
The added lanes also are also expected to ease traffic on local roads.
With less rush hour congestion on I-680, fewer motorists will be tempted to cut onto local roads such as San Ramon Valley Boulevard to bypass the freeway, said Tai Williams, Danville's community development director.
"This project is not only about helping freeway commuters," she said.
She sees the project as a way of making freeway sections operate more efficiently in an era without big state or federal dollars available to widen entire freeways.
Caltrans and the county Transportation Authority are jointly managing and financing construction of the lanes, also called auxiliary lanes.
Half or $16 million of the cost is paid for with funds from Contra Costa County's voter-approved half cent sales tax for transportation. Another $9.2 million comes from developer fees collected in the Tri-Valley region. Another $4.2 million comes from state and federal grants.
Preparation for the construction began this winter when crews chopped down some 300 trees along the freeway — including eucalyptus, which are non-native — that were in the way. Some people denounced the logging.
Iwasaki said that to make up for the tree loss, some trees or shrubs already have been planted, and another 1,600 trees and shrubs will be planted later.
Unlike many of the trees that were removed, the new plants and trees will be native plants, including valley oaks, California pepper trees, primrose jasmine and rosemary.
"They will try to create a scenic freeway with landscaping that has minimal water needs," Iwasaki said.
He cautioned motorists to slow down during the evening lane closures and restriping of lanes.
"Things are going to be different with the lanes," he said, "so people need to pay attention."
Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff.