August 19, 2015

Beach lagoon breached to alleviate flooding

By Jessica York

Santa Cruz Sentinel

SANTA CRUZ >> About a quarter of Main Beach was fenced off from sunbathers Monday as workers bulldozed a massive diagonal trench from the San Lorenzo River’s mouth to the Monterey Bay.

To alleviate flooding in the area, the city of Santa Cruz is stepping in to help nature along, while remaining careful not to damage the local habitat, said Scott Collins, assistant to the city manager. The 7-foot-deep river has been seeping below the levies that are meant to contain a river up to 5 feet deep, sending water into low-lying properties nearby, Collins said.

“It’s been particularly bad because of the drought. You have low flows from the river, so the sandbar gets bigger, with more wave overtopping and filling the lagoon with salt water,” Collins said. “It’s counterintuitive that you have flooding in a drought year.”

Although the San Lorenzo River is the city’s primary source of drinking water, the lagoon’s proximity to the ocean makes it unsuitable for drinking.

The emergency permit from state and federal regulatory agencies, including the California Coastal Commission, for Monday’s major undertaking allowed the city to lower the water level to about 4 1/2 feet deep, a stopgap measure the city is hoping will evolve into a three-year management plan from the same agencies. Collins estimated the day’s work to cost between $20,000 and $40,000, as city public works, parks and recreation trash pickers, lifeguards and biologists worked side-by-side with contractors from Watsonville-based Graniterock Co. Inc. to manage the temporary breach.

Keeping environmental concerns in mind, the beach digging was carefully overseen by an contracted geomorphologist who was working to prevent an unstoppable headlong gush into the ocean, Collins said. Nets were stretched across the river mouth to snag any steelhead trout or the tiny endangered tidewater goby, and biologists surveyed the lagoon for increasing temperature, bacteria and salinity levels, Collins said.

By noon, the crews had been working steadily since before dawn and the water only dropped about 1 1/2 feet. City Watershed Manager Chris Berry said monitors had rescued one tidewater goby, releasing it further upstream, where most of its peers were seeking shade on the hot afternoon.

“We got a few topsmelt, which aren’t protected,” Berry said. “Fish aren’t migrating this time of year. It’s really a nonissue this time of the year. It’s mostly we don’t want to strand fish and end up in the ocean inadvertently.”

Flooding has affected everyone from Beach Flats cellars to the waterlogged intersection at Ocean Street and San Lorenzo Boulevard, while beach and emergency vehicle access has been restricted near the river, Collins said. The nearby Santa Cruz Beach Boardwalk regularly has been pumping water from its basement, Collins said. Besides damaging private property, the water overflows have caused potholes to form on city streets and traffic lights to short out, he said.

Monday’s effort was a short-term solution to a long-standing problem, as the city investigates more permanent alternatives. Collins said it is unclear if the pending three-year management plan, which calls for two years of surface dredging costing about $150,000 a year, and a third-year installation of a $500,000 underground piping system, will solve the city’s flooding problem in the long term. The gravity pipe system will be designed to be triggered when water level exceeds 5 feet deep in the lagoon, and cost the city about $100,000 a year in maintenance costs, Collins said.

“We’re hopeful we’ll get this permit, we’ll get funding and within a couple years we’ll have a pipe system that we can experiment with,” Collins said.

Historically, such efforts have been led by Santa Cruz Beach Boardwalk parent, Seaside Co. In September, the company took a similar effort to reduce the lagoon’s size. Again, in March 2012, the lagoon was dredged by the entertainment company as the river’s course shifted too near the park.