Tuolumne Utilities District workers removed a storm-damaged spillway Wednesday at a small reservoir called Lakewood Park Lake north of Twain Harte as part of an emergency plan to reduce flooding dangers downstream on Sullivan Creek.
Growling excavator and bulldozer engines, trucks dumping loads of rock and the roar of auxiliary pumps created a cacophony of noise in a densely-wooded neighborhood of luxury homes off Middle Camp Sugarpine Road, where the tiny reservoir held less than a half acre-foot of water by Wednesday afternoon.
“We’re out of the immediate danger zone now,” Don Perkins, TUD operations manager, said at the reservoir. “The danger of any water getting dammed up and getting suddenly released, that danger is over.
“Now we need to protect the freshly excavated soil,” Perkins said. “We hope to be done by the end of the day Thursday. We’ll have staff on site monitoring this situation daily until further notice.”
Straw wattles and burlap rolls were in place along with truckloads of rock for use to stabilize muddy slopes churned up by heavy-duty excavators on tracks.
Lakewood Park Lake, which is used primarily for recreation in a subdivision, can normally hold about 6 acre-feet of water. An agreement with the Lakewood Park Homeowners Association allows TUD to use the reservoir for backup during ditch outages. Water in the reservoir is also available for fire protection when necessary.
Perkins described the water remaining in the reservoir Wednesday as “a puddle.”
At least one of the pumps had been running since Friday, when TUD workers inspected the dam and found the spillway
compromised by heavy runoff and erosion during last week’s storms. They increased releases from the lake and used multiple pumps to draw the water level down over the weekend.
More weather coming
The need for action was portrayed Tuesday by Tom Haglund, TUD general manager, as a public safety emergency in part because more rain and snow was forecast up and down the Central Sierra late Wednesday through today.
The storm system is expected to bring less precipitation than last week’s round of warm storms, but it could still cause problems, because slopes and soils across the Mother Lode region are still saturated and vulnerable to more runoff, flooding and erosion.
More runoff coming into the already-saturated Sullivan Creek watershed above Lakewood Park could create “the potential threat to human life, property and livestock in the areas below the dam,” “conditions of extreme peril,” and “imminent threat of disaster,” TUD staff said in an emergency declaration passed by the TUD board of directors 4-0 on Tuesday afternoon.
“District personnel believe that removal of the spillway is the safest and most prudent action to be taken to stabilize the remainder of the dam structure” at Lakewood Park Lake, TUD staff said in the declaration.
The emergency declaration was added to the TUD board agenda at the start of Tuesday’s meeting.
A sudden surge from the reservoir down Sullivan Creek could flood some outbuildings, Haglund said. There are about 15 homes downstream in the Shadybrook area, but they are not considered threatened.
Lakewood Park Lake is not subject to annual inspections by the state Division of Dams Safety, Haglund said. It is considered a non-jurisdictional dam, and there is no inundation map to illustrate the worst-case flooding scenario that could occur in the event of dam failure.