Lake Merritt flood control station tour

By Constance Taylor

So… why doesn’t this happen in Oakland anymore?

Downtown Oakland, 1962 flood


It’s because after the millions-of-dollars worth of damage that the 1962 flood did to downtown Oakland, the forward-thinking overlords of our fair city installed this in 1970…

Outside the 7th street flood control station

Inside the flood control station

The flood control station at Lake Merritt!

If you’re wondering why the outside of the station looks so much smaller compared to the inside, it’s because the main pump room floor (pictured above) is mostly below water level, beneath the 7th Street bridge right by Laney College.

Gene Mazza, the Flood Control Station (FCS) Supervisor, was the leader for the walk.  And a fine leader he was, having 30 years of experience working with the East Bay flood control stations.

Mazza explains how the pump engines work

These massive pumps are capable of pumping up to 400,000 gallons per minute when all four are working at full tilt, something that only needs to happen in extreme weather events like 100-year storms or king tides.

“The winter 2012 king tides alone would have flooded Lake Merritt without the FCS, let alone any other rain we had on top of that,” explains Mazza.

“The last time the pumps were all going full-tilt was in 1997 during a 100-year storm.  Shifts were a full 17 hours- when the tides went out, we went home to sleep, and woke up to get back to the station before the tides came back in.”

This particular FCS is only one of 24 stations around the East Bay.  There are eleven in Hayward, five in San Leandro, four in Union City, and four in Oakland.  All can be controlled remotely except for the station at Lake Merritt “mostly because they ran out of money before they got to it,” laughs Mazza.

There are three water level sensors around the lake that keep record of tidal activity.  When the water gets to a certain point, the sensor sends a radio signal to a cell phone tower, which then shoots a message to the FCS staff’s cell phones to alert them to take action.

Water level being recorded from sensor information

The FCS uses Mean Sea Level as their elevation standard, and they try to keep the water level rise in the lake below three feet as a general rule.  Here’s why:

At a one-foot increase of water level, one pump comes on.  At a two-foot increase, the second pump comes on.  A 3-foot increase is the red-line mark- Oakland won’t be flooded at this point, but for peace of mind it’s best to keep it below that level.

A 4.8-foot increase is a bad thing, since a 5-foot or more increase means the streets of Oakland will flood.

Control panel inside the station (apologies from the author for the blurry shot)

80-90% of the year the floodgates are open, but between October and April a close eye needs to be kept on the lake level to make sure there aren’t weather events that will cause it to flood.

Every six months, divers are hired to do underwater maintenance.  They clean the trash grates of barnacles, mussels, and tubeworms, swim up into the huge blue pipes to check for rust and structural problems, and generally do a check of all the underwater FCS components that can’t normally be seen.

Trash grate on the lake side of the FCS

Divers literally swim into the blue pipes when they're doing their six-month maintenance checks!

There are two floodgates on either side of the pump station.  They’re 28 feet tall, 14 feet wide, weigh about 8.5 tons each, and open by pivoting 90 degrees.

An open flood gate at the FCS

Measure DD will be knocking out the second culvert at 14th street, which will further increase tidal activity at the lake.  Channels will be built around the FCS to allow small crafts to float by, but floodgates will be built in to regulate tidal flow in case of extreme weather events.  The planned year for completion is 2015, which is coming up fast!

A big thanks to Gene Mazza for leading us into the FCS and giving us a tidal history lesson of Oakland and Lake Merritt.

Isn’t infrastructure great?!

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