Winter weather didn't impede progress on the current stage of the East Sonora Bypass, which is still slated to wrap up in July 2014, Caltrans said.
Agency spokeswoman Angela DaPrato said construction crews were able to continue structural work, which is 85 percent completed.
However, crews ceased earth-moving operations in November to comply with the U.S. Environmental Protection Agency's Stormwater Pollution Prevention Plan, DaPrato said. Caltrans expects to resume the work within the next two to three weeks.
Also during winter months, contractor Teichert Construction conducted stormwater maintenance.
The Central Valley Regional Water Quality Control Board cited both Caltrans and Teichert in December, alleging that inadequate erosion protections at the project site led to unlawful amounts of sediment discharged into local waterways.
Water board spokeswoman Wendy Wyels said the project site has been brought up to code, and workers have been measuring and reporting pollutant levels after storms.
Wyels said Caltrans and its contractor have not yet been fined because the water board is still reviewing extensive documents it subpoenaed regarding the project.
The maximum they could be fined is $10 per gallon of stormwater leaked and $10,000 for each day the alleged violation occurred, she said.
"Caltrans is committed to following the best practice for stormwater prevention and takes it very seriously," DaPrato said in response to the citations.
The current stage will extend the bypass from Peaceful Oak Road to Via Este Road.
It will include a partial interchange at Peaceful Oak Road, a grade separation to connect Mono Way with the bypass and a frontage road.
Crews broke ground on the second stage April 19, 2012.
The state announced in 2006 that the $53 million stage was fully funded and set for construction to run from 2010 through 2012. However, state funding issues stalled the project until project officials were able to find available funds from multiple sources.
It received almost $15 million from Proposition 1B, a transportation bond passed by California voters in 2006. Other funding comes from the Transportation Improvement Program, the state's main road-funding mechanism.
However, a few cutbacks led to a redesign, with the updated plan excluding two entrance and exit ramps.
Caltrans is still planning to implement a third stage of the project to extend the bypass even further, but no timeline has been set and or funding secured.
The most recent plan for Stage 3 was to extend the bypass to Sunshine Road in Mono Vista but DaPrato said it could change.
She said the state is working with the Tuolumne County Transportation Council to find funding sources.
The stretch passing through East Sonora is the heaviest traveled section of Highway 108 outside of the busiest part in Modesto, according to state traffic statistics from 2011.
According to the data, an average of 22,300 vehicles pass along Highway 108 on the existing bypass every day. During peak summer months, that average is closer to 24,600 people.