Saratoga resident Robert Karlak heard the noise from his home. "It was really loud," he said. "But it was only one night. The thing is, it moves along."

The racket is part of the Valley Transportation Authority's Route 85 Noise Mitigation Project. "What we're doing is grinding the highway to reduce the impact of freeway noise," VTA community outreach supervisor Miriam Ayllon said. "Generally our construction hours are from 8 p.m. to 5 or 6 a.m., depending on the stretch of highway. On Saturday it might go to 8 a.m."

Bill Grimes, who lives on Saratoga Avenue near the highway, was awakened by the noise. Grimes, Karlak and their neighbors can expect to hear these loud noises intermittently until spring, when the project is scheduled for completion. "Got to make noise to reduce noise," Grimes said.

Work crews move northbound and southbound using machines with parallel saw-wheels that grind away surface bumps and rough spots. The machines give the pavement a corduroy-like surface with narrow, longitudinal grooves in a process called texture-grinding. Texture-grinding generates noise levels approximately 10 percent higher than freeway traffic but, once finished, makes for a quieter highway.

Ayllon said that the grinding is now taking place on two lanes between Highway 17 and Saratoga-Sunnyvale Road. "We do not want to close the highway so we are doing the grinding on lanes one and two." The noise level will drop off for Saratogans as work crews move down the highway, but will return when they come back to grind lanes three and four, she said.

Work is being done at night to increase safety for motorists and construction workers and to minimize the impact to commuters. Motorists can expect partial lane closures on weekdays between 8 p.m. and 5 a.m. Partial lane closures on Saturdays may end at 8 a.m. Full freeway closures, if necessary, will be scheduled for 11 p.m. to 5 a.m.

Residents along the corridor between Almaden Expressway and I-280 have complained about traffic noise since the section of highway was completed in October 1994. Tests conducted by the VTA in 2003 indicated that texture-grinding the pavement could reduce overall noise, but less than the three decibel threshold perceptible to the human ear. The VTA tests determined texture-grinding caused a downward shift in the tonal characteristics of sound and decibel reductions at frequencies that are easily heard by humans.

Karlak, a retired physicist, made an effort to get Highway 85 paved with asphalt but was unable to get county officials to agree. Asphalt would provide a smoother ride and is quieter for motorists and nearby residents alike, he explained. "The asphalt is far superior," he said. "We're throwing away good taxpayer dollars for marginal benefit."

The Route 85 Noise Mitigation Project is being paid for with $9 million from 1996 Measure B funding.

"Work is expected to be completed we think mid-2006," Ayllon said. "It all depends on the weather and how this winter is going to be."