With Lake Shasta practically full this spring, extra water has begun to seep out of the face of Shasta Dam, on the aspect reverse the lake.
Water has been trickling down the downstream face of the dam in a number of spots, with vegetation rising in locations the place the water leaks out.
Regardless that the large concrete construction is 602-feet tall and 543-feet vast on the base, there are nonetheless methods for the water to get by means of from the lake aspect to the other aspect, mentioned Don Bader, space supervisor for the U.S. Bureau of Reclamation.
The 6.2 million yards of building materials could look from the skin like it’s composed solely of huge blocks of concrete. However the dam isn’t stable during. There are passageways, walkways, pipes and tunnels inside, Bader mentioned. As a result of the lake is sort of full this 12 months, the seepage is bigger, he mentioned.
The water coming by means of is because of leaky seals on the drum gates that management how a lot water flows down the spillway close to the middle of the construction, Bader mentioned. The gates are the identical ones initially put in on the dam within the early Forties, he mentioned.
“I do not need to be quoted saying it is nothing to be involved about, however it’s it’s regular seepage,” Bader mentioned. “We do have a upkeep program to rehab it as we go, however they’re (the gate seals) not our prime precedence. That leakage is minimal within the huge scheme of issues.”
The seepage was not as noticeable throughout the previous two years, when the drought dropped the extent of Lake Shasta to near-record-low ranges. However this 12 months, with the elevation of the lake to close capability, the water stress pushing on the drum gates has brought about extra leakage, Bader mentioned.
The seepage seems to be oozing from the grouted seams between the concrete on the face of the construction. On earthen-fill dams, leakage is extra of a priority, however not with concrete dams like Shasta, he mentioned.
There was concern about potential seepage on the earthen-fill Oroville Dam following a failure on that dam’s spillway in 2017. In February of that 12 months, giant chunks of the concrete spillway gave out, forcing a precautionary evacuation of about 188,000 residents residing downstream.
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Vegetation grows alongside an space the place water is seeps out alongside the downstream face of Shasta Dam on Monday, Might 15, 2023.
No harm was brought about past the spillway collapse, however residents and officers, already cautious of the situation of the dam, had been involved a few inexperienced space they seen on the face of the dam, with vegetation progress probably attributable to seepage.
The California Division of Water Assets had the dam inspected, and a workforce of investigators decided the vegetation progress was seasonal. The company report concluded there was not elevated seepage by means of the dam.
As a substitute, vegetation had for a few years grown on the face of the dam, the report mentioned. An space of the dam greened up throughout the wet season after which dried out and turned yellow and brown in the summertime.
There’s a patch of vegetation rising on the face of Shasta Dam in an space the place water seeps out from the seams within the concrete.
Bushes and different vegetation have lengthy grown on the aspect of the dam. Bader mentioned that about 12 years in the past, climbers rappelled down the face of the dam on ropes and minimize down a tree, which was about 10 toes tall.
There are screens inside Shasta Dam that hold observe of the quantity of water stepping into the construction. Bader mentioned the quantity of seepage recorded isn’t uncommon or a priority.
Reporter Damon Arthur welcomes story ideas at 530-338-8834, by electronic mail at [email protected] and on Twitter at @damonarthur_RS. Assist native journalism thrive by subscribing at the moment!
This text initially appeared on Redding File Searchlight: With a fuller Lake Shasta, extra water seeping from entrance of Shasta Dam