decim
28-07-2009, 08:53 PM
Test result triggers safety inspection of Warm Springs Dam
http://www.pressdemocrat.com/apps/pbcsi.dll/bilde?Site=SR&Date=20090728&Category=ARTICLES&ArtNo=907289979&Ref=AR
Warm Springs Dam
By BOB NORBERG
THE PRESS DEMOCRAT
Published: Tuesday, July 28, 2009 at 9:53 a.m.
Last Modified: Tuesday, July 28, 2009 at 9:53 a.m.
A team of experts called in by the U.S. Army Corps of Engineers began inspecting Warm Springs Dam Tuesday after a monitoring well showed an unusual amount of water in the dam’s earthen interior.
The water level in a “piezometer,” one of five monitoring wells that are on top of the earthen dam and drilled into its interior, rose 14 feet in a week, then dropped down slightly, the Corps said Tuesday.
Corps officials stressed that no other monitoring device showed anything unusual, and they are undertaking the investigation as a precaution.
Dam operators routinely monitor interior water levels and core pressures for signs of seepage and erosion, which in some cases could indicate weakness.
“We are looking at dozens of other instruments and they are reading as they have,” said Mike Dillabough, the corps division chief of operations. “We are setting up sloped stakes and checking it to make sure there are no other changes to the dam face. There has been no change.”
Dillabough said that there was no public safety risk at this time.
“Right now we are going through the process of elimination, our dam safety officers are read in on it, we have a dozen dam safety engineers working on it trying to figure out what it means. But there is no indication it is a danger,” Dillabough said. “We want to make sure it does not lead to that.”
The monitoring well that showed the increase on July 21 is a one-inch diameter pipe that goes 60 feet into the dam. It was just installed in January, Dillabough said.
“Any dam leaks somewhat, that is the nature of dams,” Dillabough said. “When you find a different source you were not expecting, that is a concern, but not a high concern. We need to start taking more measurements, more review from geo-technical sciences to see what is causing it, if there is an issue.”
The Sonoma County Water Agency on Tuesday alerted the county’s Office of Emergency Services, other emergency service providers, property owners’ groups along Dry Creek, and local, state and federal official, said spokesman Brad Sherwood.
“At this point we just want more information and find out what the research will tell us,” Sherwood said. “Public safety is our priority and we want to make sure the dam is functioning and operating as it should.”
Sherwood said the agency will have daily updates on its Internet site.
The dam’s last annual inspection was in September, and no problems were reported except for some minor rust on some control valves and minor rodent damage and erosion on the dam face, officials said at that time.
Warm Springs Dam was completed 25 years ago at a cost of $330 million, creating Lake Sonoma as a source of water and recreation and as a flood-control project, taking 5 to 8 feet off flood levels as measured on the Russian River at Guerneville.
The water from Lake Sonoma is released into Dry Creek, which flows into Russian River near Healdsburg.
The compacted earthen dam, made with 30 million yards of dirt and rock scraped from surrounding hillsides, is 3,000 feet wide and 319 feet tall.
The dam created a lake that when filled covers 3,600 acres and has a 73-mile shoreline. Its Dry Creek arm is nine miles long and its Warm Springs arm four miles.
It holds a water supply of 212,000 acre-feet and a flood pool of 130,000 acre-feet.
http://www.pressdemocrat.com/article/20090728/ARTICLES/907289979?Title=Safety-inspection-of-Warm-Springs-Dam-#
http://maps.google.com/maps?q=warm%20springs%20dam&um=1&hl=en&ie=UTF-8&sa=N&tab=wl
http://www.pressdemocrat.com/apps/pbcsi.dll/bilde?Site=SR&Date=20090728&Category=ARTICLES&ArtNo=907289979&Ref=AR
Warm Springs Dam
By BOB NORBERG
THE PRESS DEMOCRAT
Published: Tuesday, July 28, 2009 at 9:53 a.m.
Last Modified: Tuesday, July 28, 2009 at 9:53 a.m.
A team of experts called in by the U.S. Army Corps of Engineers began inspecting Warm Springs Dam Tuesday after a monitoring well showed an unusual amount of water in the dam’s earthen interior.
The water level in a “piezometer,” one of five monitoring wells that are on top of the earthen dam and drilled into its interior, rose 14 feet in a week, then dropped down slightly, the Corps said Tuesday.
Corps officials stressed that no other monitoring device showed anything unusual, and they are undertaking the investigation as a precaution.
Dam operators routinely monitor interior water levels and core pressures for signs of seepage and erosion, which in some cases could indicate weakness.
“We are looking at dozens of other instruments and they are reading as they have,” said Mike Dillabough, the corps division chief of operations. “We are setting up sloped stakes and checking it to make sure there are no other changes to the dam face. There has been no change.”
Dillabough said that there was no public safety risk at this time.
“Right now we are going through the process of elimination, our dam safety officers are read in on it, we have a dozen dam safety engineers working on it trying to figure out what it means. But there is no indication it is a danger,” Dillabough said. “We want to make sure it does not lead to that.”
The monitoring well that showed the increase on July 21 is a one-inch diameter pipe that goes 60 feet into the dam. It was just installed in January, Dillabough said.
“Any dam leaks somewhat, that is the nature of dams,” Dillabough said. “When you find a different source you were not expecting, that is a concern, but not a high concern. We need to start taking more measurements, more review from geo-technical sciences to see what is causing it, if there is an issue.”
The Sonoma County Water Agency on Tuesday alerted the county’s Office of Emergency Services, other emergency service providers, property owners’ groups along Dry Creek, and local, state and federal official, said spokesman Brad Sherwood.
“At this point we just want more information and find out what the research will tell us,” Sherwood said. “Public safety is our priority and we want to make sure the dam is functioning and operating as it should.”
Sherwood said the agency will have daily updates on its Internet site.
The dam’s last annual inspection was in September, and no problems were reported except for some minor rust on some control valves and minor rodent damage and erosion on the dam face, officials said at that time.
Warm Springs Dam was completed 25 years ago at a cost of $330 million, creating Lake Sonoma as a source of water and recreation and as a flood-control project, taking 5 to 8 feet off flood levels as measured on the Russian River at Guerneville.
The water from Lake Sonoma is released into Dry Creek, which flows into Russian River near Healdsburg.
The compacted earthen dam, made with 30 million yards of dirt and rock scraped from surrounding hillsides, is 3,000 feet wide and 319 feet tall.
The dam created a lake that when filled covers 3,600 acres and has a 73-mile shoreline. Its Dry Creek arm is nine miles long and its Warm Springs arm four miles.
It holds a water supply of 212,000 acre-feet and a flood pool of 130,000 acre-feet.
http://www.pressdemocrat.com/article/20090728/ARTICLES/907289979?Title=Safety-inspection-of-Warm-Springs-Dam-#
http://maps.google.com/maps?q=warm%20springs%20dam&um=1&hl=en&ie=UTF-8&sa=N&tab=wl