Mystery flooding stumps agencies
Homeowners man the pumps as water wells up; dam releases, storm saturation among suspects
Residents in Claremont are experiencing mysterious flooding, raising concerns about infrastructure and home safety.
The cause of the flooding is unknown, according to the city. There could be multiple reasons water is percolating and collecting in yards, the city said, including saturated ground from recent storms and the release of water from the local dam.
The city said the San Antonio Dam, located at the foot of the San Gabriel Mountains in San Bernardino County, reported releasing 23 feet of water over 15 days as of Thursday. The dam’s operational plan requires the release of water when it reaches capacity to keep from overflowing.
The water was released into basins on either side of the San Antonio Creek channel, according to Bevin Handel, public information officer for Claremont. This, paired with melting snowpack and the already saturated ground from recent rainfall, could be the cause of the flooding, Handel said.
Since the city can’t point to one specific cause for the flooding, Handel said, officials are working with local water agencies to try to pinpoint the problem.
The Army Corps of Engineers, which operates the dam, confirmed it is in communication with the city to determine the cause of the flooding.
“We are considering possible options; however, at this time, we do not know how much of the high groundwater condition — if any — is due to the operation of San Antonio Dam,” the corps’ chief of public affairs, Dena M. O’dell, said in an email.
O’dell said the dam’s primary role is to reduce the risk of flooding, and water is diverted into detention basins for groundwater recharge.
Releases from the dam have been routine and have not exceeded 300 cubic feet per second, O’dell said. Concrete channels that convey the released water can hold up to 8,000 cubic feet per second, she noted.
The city said that on April 6, reports came into the engineering department from residents saying water was welling up in yards in the Stone Canyon neighborhood off Mt. Baldy Road.
“The groundwater and geologic conditions in the Stone Canyon neighborhood are complex,” O’dell wrote in her email. “Due to the complexity and inter-relationships, there are likely multiple sources of water contributing to the conditions currently being experienced.”
Kenny Larson said he noticed flooding in his yard Sunday.
He and his wife, Anet, live two streets away from Stone Canyon in Chantclair Estates. Larson said water seemed to well up from the ground, seeping into his pool and creating large puddles that submerged grass in his yard.
Larson said he’s been stuck at home and unable to go to work as he tries to mitigate the effects of the flooding. He’s using five industrial pumps to control the water in his yard, he said.
Larson said a city building inspector recommended he and his neighbors place sandbags to stop water from seeping under the foundations of their homes.
“We are responding by providing sand and sandbags,” Handel confirmed. “We have our inspectors up there making sure that the structures, the foundation, the homes are safe. We also have provided the homeowners with a list of contract referrals that can do the pumping of water out there and assist with getting the water off their property.”
The city urges affected residents to watch for retaining wall cracks, cracks inside the home, water leakage inside the home, and damage to foundations.
If any such problems are found, Handel said, residents should alert the city immediately so it can send an inspector to assess damage and the safety of structures.