The suddenly unplugged culvert in Fryer Creek near MacArthur Street has opened more than a just a hole under the creek bed.
Neighbors, who awakened on the morning of July 24 to discover the creek level had drastically dropped behind their homes, continue to express dismay over the incident and to revisit long-held concerns about the Sonoma County Water Agency.
A few, including Greg Percival, who lives at Second Street West and MacArthur Street, have even suggested that the water agency may have caused the culvert to become unplugged a few months ago due to drill-work occurring near the hole – located just north of MacArthur Street where it crosses over the creek.
“I would bet that they loosened it,” Percival said.
Bruce Griggs, who lives on MacArthur next to the creek, recalled a moment earlier this year when two environmental engineers knocked on his door to talk about work planned by the water agency, which maintains the creek. They invited him to a community meeting, Griggs said, and spoke of plans for modifying the waterway in case of flood.
Soon after their visit, Griggs said, a machine was seen taking drill samples near where the hole is now. He said he did not know if the two events were related, or whether the workers drilled at the exact spot where the hole opened up.
But two water agency officials said there was no known connection, with Principal Engineer Kent Gylfe saying, “We don’t think that’s what has occurred out there at all.”
In his opinion, as well as that of Jon Niehaus, the agency’s stream maintenance coordinator, the “low-flow culvert” located there – an 18-inch pipe channeling water north-to-south underneath MacArthur – had become plugged by silt several years ago and stopped functioning as it was supposed to.
No one noticed, and during the summer the waters of Fryer Creek grew higher, warmer and more sluggish than engineers had intended. Then last week, late Wednesday night or early Thursday morning, for unknown reasons, the plugged culvert opened up.
“We’re still uncertain why it unclogged,” Gylfe said. “But it is the way that the system originally was designed.”
Gylfe acknowledged that drilling did occur there in late January or early February, as water agency contractors conducted “geotechnical boring” as part of the agency’s City Watersheds Project.
The $4 million proposal includes planned changes to the MacArthur overcrossing – which water agency officials call a “box culvert” – and “as part of that project, our consultants went out … and did one, maybe two drills,” Gylfe said.
At that time, the crew “Brought a drill rig out to drill a hole down” in the creek bed, he said, adding that no more than two drills were conducted, six inches wide and about 30 feet deep.
Gylfe said he could not immediately verify where the holes were drilled – but he emphasized that when it comes to water flow in Fryer Creek, “The way it’s been operating for the last many years is not the way it was designed to function.”
That function is at least partly ecological, according to Niehaus, who said the low-flow culvert “bypasses that box culvert and then comes in immediately below the box culvert” on the other side of MacArthur. The lower waters are cooler, he said, and therefore better for native species – and less habitable to the yellow-flowered ludvigia hexapetalia, or “water primrose,” an invasive plant species currently choking parts of the creek.
Niehaus said it “would take a little bit of investigation” to determine exactly where the creek’s summertime waters are coming from. However, “Typically, we find these things, sad to say, are urban runoff.”
Nonetheless, a chorus of neighbors remained unhappy with the newly lowered creek, which they worried would lead to increased flies, mosquitoes and a putrid smell due to the exposed mud.
“Have you taken a look at the creek???” wrote Lynne Joiner, another MacArthur Street resident, in an angry letter to Sonoma City Council members. “The fish and frogs are being swallowed down the drain, the ducklings are desperately vulnerable, the horrible ludvigia hexapetalia is growing worse and clogging the channel.”
“Why not re-plug the Fryer Creek bypass drain for now?” Joiner asked.
At present there are no plans to do so, said Dan Takasugi, Sonoma’s public works director and city engineer.
“Currently I’m in support of the Water Agency’s recommendations that would be to (keep it) as is, which eliminates the warm water pond which supported invasive growth of weeds, and also mosquito habitat,” Takasugi said.
“Unless some other information comes to light, we’re currently supporting that position,” he said.