If you’ve ever backed a boat trailer down a ramp anywhere in the Midwest, you’ve seen the sign. Clean, drain, dry. It’s there because of the zebra mussel, a shellfish the size of a thumbnail that rode over from Eurasia in ship ballast decades ago and has been gluing itself to American pipes, docks and dam gates ever since. Most of us read the sign and go fishing anyway.<\/p>\n
Well, California has its own version of that bug now, and it’s apparently a tougher one. It’s called the golden mussel, it turned up in the Port of Stockton two years ago, and last month it did something that got my attention. It stopped a $96 million flood gate from closing.<\/p>\n
On September 25, divers went into Stockton’s Smith Canal to scrape golden mussels off the 50-foot gate that’s supposed to seal the canal off from the San Joaquin River when the water comes up. State and county officials stood on the bank and watched, and the assemblymember who represents the area, Rhodesia Ransom, summed up the situation for CBS Sacramento<\/a>: “Knowing now they can’t close the flood gate until they scrape the golden mussels, so it’s very concerning for me.”<\/p>\n That’s a pretty wild sentence when you sit with it. A brand-new piece of flood control, finished at the end of 2024, that has to be cleaned before it can do the one job it was built for.<\/p>\n The Smith Canal Gate is what engineers call a miter gate, which is the same basic design as the doors on the Panama Canal locks, just a lot smaller. You get two steel leaves hinged into the walls on either side of a 50-foot opening. When you need to close it, the leaves swing in and meet in the middle at an angle, like a V pointing into the current, and the water pressing on them is what jams them shut and seals the joint. When they’re open, boats go in and out of Atherton Cove and the canal like nothing’s there.<\/p>\n Basically, it’s a door that needs its edges to meet cleanly to work. If you’ve got a crust of shellfish growing on anything that has to touch, or on anything that has to move, you’ve got a problem, and from the looks of things that’s exactly what Stockton has.<\/p>\n The gate was designed by HDR and built by Shimmick for the San Joaquin Area Flood Control Agency, or SJAFCA, which owns and runs it. Shimmick says<\/a> it’s still installing variable-frequency drives so the gate can be run remotely, because right now somebody has to hand-crank the leaves through the last bit of travel at the fully open and fully closed positions. So the newest flood gate in the Delta still has a manual step at the end, and now it also has a scraping step at the beginning.<\/p>\n Why does any of this matter to people who don’t own a boat? Because of who lives behind it. FEMA pulled the accreditation on the old Smith Canal levees years ago, which put about 5,000 properties and 15,000 residents in central Stockton into a high-risk flood zone and forced most of them to carry flood insurance. The gate was the fix. It closed for real for the first time on January 5, when the river came up, and on February 9 FEMA’s revised flood map took effect and the mandatory insurance requirement went away<\/a>.<\/p>\n Which is, frankly, what I’d be nervous about if I lived there. The paperwork that says you don’t need flood insurance anymore assumes a gate that closes.<\/p>\n The golden mussel was first found in North America in October 2024, stuck to a float near the Port of Stockton. State water workers spotted it during routine operations and reported it to the Department of Fish and Wildlife, and the working theory is it came over in ballast water from Asia, the same way the zebra mussel got into the Great Lakes.<\/p>\n Since then it has spread more than 500 miles through California’s connected waterways, as far south as San Diego and, as of June 25, as far north as West Sacramento. In Stockton itself, the city’s deputy director of water resources, Travis Small, told the council that the screens on the intake pipes feeding the city’s drinking water were 30 to 40 percent covered. The usual treatments, copper and ultraviolet light, weren’t practical on that infrastructure, so there too the answer was divers with scrapers.<\/p>\n Martha Volkoff, who runs the invasive species program at the Department of Fish and Wildlife, put it this way to KALW<\/a>: they may only be the size of a fingernail, but they cluster into hard-shelled masses that “essentially can act like cement and can block small diameter pipe.”<\/p>\n So why can’t you just scrape the gate once and be done with it? Because the thing breeds like it’s getting paid to. KALW reported back in the spring that a single mussel can produce a million offspring in a year, and the larvae are microscopic and drift with the current until they find something hard to sit on. A freshly cleaned gate sitting in that water is, as far as I can tell, just a clean surface waiting for the next batch.<\/p>\n And cleaning isn’t free. San Joaquin County Supervisor Paul Canepa told KALW in April that the last time the floodgate needed it, the job took ten hours and $10,000, and that was before anyone was talking about a historic storm season.<\/p>\n Timing, mostly. Governor Gavin Newsom proclaimed a statewide emergency on September 21 to get ahead of what forecasters are calling a potentially record El Ni\u00f1o. Four days later, divers were in the canal chipping shellfish off the gate that’s supposed to handle the water that El Ni\u00f1o sends down the San Joaquin. You don’t need to be an engineer to see why the county supervisors wanted cameras there.<\/p>\n Three counties, San Joaquin, Sacramento and Kern, had already declared their own emergencies over the mussel earlier this year. The city of Stockton declared one too, over the intake screens. So the local people have been loud about this for a while.<\/p>\n I’ll admit the limits of what I can tell you. Nobody involved has published how many pounds of mussels came off the Smith Canal Gate on September 25, how many divers went down, or whether the gate has been test-closed since. If it has, SJAFCA hasn’t said so, and that’s a slightly odd thing to leave out of a story whose entire point is whether the door shuts. I’d want to know before the first atmospheric river shows up, and I suspect the people in Smith Tract would too.<\/p>\n It’s also fair to say this isn’t just a Stockton thing. We covered a Missouri River dam this summer where an intake gate came out of the water 25,000 pounds heavier<\/a> than it went in, all of it zebra mussel. Same story, bigger door, older infestation. The only place I’ve seen the arrangement run the other way is Poland and Minneapolis, where mussels with magnets glued to their shells<\/a> are on the payroll as water-quality sensors. Stockton’s mussels aren’t on the payroll.<\/p>\nSo what is this gate, exactly?<\/h2>\n
The mussel that got here two years ago and hasn’t stopped moving<\/h2>\n
So why does this winter matter?<\/h2>\n
The state did move, for what it’s worth<\/h2>\n