August 29, 2006 -- Nevada County road officials are determined to keep Allison Ranch Road open through the upcoming rainy season, and will monitor the landslide area that split and closed it last spring.
The county will build a detour around the slide just outside of Grass Valley, just in case the main road goes out again.
"We're anticipating a report that hopefully will tell us the road is stable enough to just pave over for the winter," Michael Hill-Weld said Monday. The director of the county's Transportation and Sanitation Department said the county has been letting the slide area dry out before doing any more temporary or permanent repairs.
Heavy rains caused the road on a steep incline above Wolf Creek to collapse last April 7, closing about 500 feet of pavement. The slide area is about one mile south of the North Star Museum where Mill Street turns into Allison Ranch Road.
Officials feared the slide might grow large enough to back the creek up to the nearby Grass Valley Wastewater Treatment Plant, but it never happened as rains subsided. The county fixed the problem temporarily in May by putting down two gravel road stretches through the slide area.
Not much visible work has occurred since then as drying took place, and that alarmed area resident Steve Tintle, who uses the road frequently to see his mother.
"Maybe they should blacktop it before it becomes a mess," Tintle said. "It's going to start raining here pretty quick."
County road officials are aware of area weather patterns, which is why the detour plan was unveiled. According to Doug Farrell, a civil engineer for the county, the detour will run parallel to the slide area for about one-quarter mile.
Both Hill-Weld and Farrell said a landslide monitoring system was put in at the site this summer. Tom Holdrege of Holdrege and Kull Consulting Engineers and Geologists of Nevada City said inclinometers were installed to track movement.
"They're in a well casing and you run equipment down a hole and it's sensitive to changes in internal position," Holdrege said. "Through time, you can see where the movement happens and when it happens."
Farrell said the monitoring will continue through the rainy season this year to gather more data for a permanent fix for the road. The county hopes to start those repairs next summer.
Since this past summer when the devices were installed, "there's been no movement," Hill-Weld said.
"It's been very stable, it may be the water was held back in an old mine shaft that was released," Hill-Weld said. "It may be the slide has shifted all that it will."
