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Drilling the test holes. Caltrans photo

GRASS VALLEY, Calif. January 25, 2017 – Caltrans crews were busy on Hwy 49 today near the sinkhole on Freeman Lane in Grass Valley. Early this morning, CHP reported “As of last night, the depression in the roadway has increased into the fast lane. Caltrans engineers and CHP personnel were on-site overnight to investigate. This morning, additional construction crews will be brought in for emergency drilling and further investigation underground to determine the extent of the damage under the freeway.”

Caltrans brought emergency contractors in to drill three 20-ft deep holes near the culvert carrying a large portion of runoff water for the City of Grass Valley.

Good news for Hwy 49

Caltrans spokeswoman Liza Whitmore told YubaNet: “Caltrans noticed the dip on southbound 49 and that was concerning to us, because it is just on top of the culvert that Grass Valley feels is responsible for the big sinkhole. The drilling contractor went down 20 ft and did not find any voids. Therefore, we fell pretty confident that there is no damage to Hwy 49.”

A Caltrans contractor, NorCal Pipeline Services, examined the length of the 7-ft tall culvert by sending highly-trained videographers through the culvert. After rappelling down into the culvert, they videoed a 222-ft section under the freeway and further on to the sinkhole.

The last portion of the video, near the 13-minute mark, shows the proverbial light at the end of the tunnel – where the giant sinkhole is. The steep decline prevented the crew from going all the way through.

“The culvert looks in fabulous shape, ” Whitmore said. “At this point in time, we’re going to pull all our equipment off the roadway and keep a really close eye on it.”

CHP PIO Greg Tassone was on scene and he expects the lane closure to be lifted once all equipment has been removed and the lane cleaned up, by later this afternoon.

Meanwhile, the City of Grass Valley’s contractor is working on the sinkhole and placing stabilizers to prevent further erosion.

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January 25, 2017 at 6:03 PM Update from CHP:  After extensive testing by Caltrans engineers and private contractors, there are no imminent or catastrophic problems occurring with the freeway. The roadway depression was determined to be a settling of the soil caused by excess groundwater from the recent heavy storms. Other than settling, the soil is all intact and safe. This means the freeway is currently being opened back up and is safe for continued use.

Here are some examples of the testing performed during this process:

– An underground, confined-space team physically entered and examined the inside of the culvert under the entire freeway, continuing through underneath much of Freeman Ln. It is completely intact with no detected problems.
– Several monitoring holes were drilled from the surface to test the soil and check for void spaces. No voids or other problems were found.
– The soil was examined and water levels in certain areas were determined to be high. This is not unusual given recent storm activity, and it should abate over time.

At this point, Caltrans will be monitoring this location periodically to check the settling levels. They will also formulate a long-term plan to reinforce the soil and/or replace a portion of the roadway, as needed.

Thanks for your patience while we ensured the roadway was still safe for travel!