Los Osos retention basin bursts, 20 homes damaged

January 11, 2023

Los Osos retention basin burst


Heavy rains destroyed a retention basin in Los Osos on Monday, leading to hundreds of thousands of gallons of water and mud crashing into Vista de Oro Estates. The force of the rushing water and mud filled homes with up to three feet of debris.

More than a half-century ago, developers built the Cabrillo Estate subdivision on a hillside on the way to Montana de Oro. The retention basin was constructed at the base of the Cabrillo Estates to protect neighboring, lower-elevation properties.

For years, San Luis Obispo County managed the retention basin. Then in 1998, Los Osos residents voted to create a community service district, which several years later became responsible for upkeep of the retention basin.

Runoff from Los Osos retention basin into homes on Vista Court

During Monday’s atmospheric river, the rubber liner tore and the berm on one side of the basin burst. A raging river of water and mud then slammed into homes on Vista Court.

Water rushed through the back of the closest homes. The force was so great, water and mud pushed cars from garages and moved yard furniture and barbecues up to a half mile away.

An aerial shot of the damage on Vista Court

The raging water and mud damaged 20 homes, though it is not currently known if the homeowners are eligible financial assistance.

Los Osos Community Services District staff said they checked the basin on Monday, and it was not full. It is unknown at this time if the district was providing proper upkeep of the basin.

With a new atmospheric river headed towards California, district staff is attempting to temporarily remedy the Cabrillo Estates’ drainage issue.

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The problem could be attributed to ground sqirrels, when the water levels have been down for so long, they burrow right on through dams, levees, dikes etc. Water goes right on through, creating a breach, highly errosive soil like that in Los Osos would be very susceptible to that kind of failure!

I’ve seen it happen to many Ranch dams and ponds, they used to use highly effective poison to keep the squirrels at bay but those methods are basically outlawed or chemicals available now are ineffective.

A hard-earned and expensive lesson for LOCSD. They had at least 4 years of drought, during which the retention basin was empty, to reinforce the bottom and sides by adding another synthetic lining or clay layer, inspect the berms, and engineer a system for controlled runoff via a spillway, siphon, or active pumping. Live and learn.

What can you expect when the CSD continuously hires reject leaders. If I recall the CSD leader was intimately involved in oversight of the County Integrated Waste Management Authority and low and behold embezzlement went on for years under his watchful oversight.

Is it me or do these “Services Districts” really help a community? I see high salary’s and excessive overreach in my local one. Too much control by people with no clue.

The community of lawyers?

Fun thing to do, look at different nearby districts and see what names keep showing up.

Should have left it in the hands of the county…

As is the case with every CSD. They’re all dumpster fires managed by corrupt cronies. 7 cities and ONE County government that we can keep an eye on. These not-so-little CSD fiefdoms are ridiculous.