Posted on April 24, 2018
By Debra Herrick, CoastalView.com
Santa Barbara County Flood Control continues its emergency response to the January debris flows with hydraulic dredging of the Carpinteria Salt Marsh Reserve. The dredging is an effort to relieve 20,000 cubic yards of sediment from the Salt Marsh deposited either naturally via the Franklin and Santa Monica Creeks during the heavy rains, or by truckload afterwards during the initial emergency response. The dredging began on March 19 and will continue through April 30 when the emergency permit expires. Schock Contracting Corporation was awarded the project through a competitive bid process, and the cost is set at an estimated $1.3 million. Funding will be drawn from the South Coast Flood Zone reserves and is expected to be reimbursed by FEMA.
It will be several years before Carpinteria Valley watersheds fully recover, according to Maureen Spencer, operations and environmental manager of the Santa Barbara County Flood Control District. At present, there is a strong potential for increased amounts of debris and sediment to go through the area’s system of channels. For that reason, the sediment must be quickly moved towards the ocean, where it would naturally flow anyway, but at a much slower pace, according to Spencer. “If we don’t de-silt the marsh then the marsh is going to fill in and will impact marsh habitat and nearby residences.”
“There is absolutely no indication that what we are putting out there is toxic,” Spencer said regarding toxicity near the dredge pipe’s mouth. “I think people get alarmed because of how it looks—it’s a dark slurry, but this is natural… because of the size of the storm and the risk of additional sediment coming down and causing a flood risk, we’re quickening this process.”
Flood Control did sediment tests every three days during the initial emergency response, as crews used cranes and trucks to clear Santa Monica and Franklin Creeks and dumped sediment at Ash Avenue. Samples were taken by spoon from trucks, then mixed to make a composite sample that was sent to a lab for testing. All tests came back within acceptable limits for ocean disposal.
Before moving forward with the hydraulic desilting, Flood Control dug five different pits along the length of the dredging footprint and took samples from each one of those pits, which were tested by regulatory agencies—the Army Core of Engineers, Regional Water Quality Control Board, California Department of Fish and Wildlife and the California Coastal Commission—and approved for ocean disposal.
Flood Control is taking ocean water samples two days a week from three locations during the dredging process—one about 300 feet up-coast from the Salt Marsh mouth, one near the discharge pipe and a third about 300 feet downcoast from the discharge pipe. The samples are sent to the regulatory agencies to be tested for total coliform, fecal coliform and enterococcus. “As very much expected we had some readings that were right around the discharge pipe that were over, which is completely normal,” Spencer stated. “These are naturally occurring. It’s usually not human. There’s no reason to think that it is. In general they have been remarkably clean. There have been a couple overruns of enterococcus right at the discharge pipe, but this is similar to the routine de-silting we do. Every time it rains these bacteria always go up as sediment is flushed out. Then, sunlight hits it, it gets diluted, ocean water kills it, ocean organisms eat it, and levels go down, it’s not a persistent level.” “No Swimming” signs have been posted near the discharge pipe.
While dredging is fairly common, according to Ben Pitterle, watershed and marine program director of Santa Barbara Channelkeeper, when fecal levels are high it is important for beach goers to adhere to warnings. There are also a number of other environmental issues associated with dredging that Channelkeeper, a grassroots non-profit organization focused on watershed conservation, is monitoring closely and working with the County on, including the impact of dredging, which sucks up bottom animals like mussels and clams. Additionally, the mud that was dumped had ammonia, which can be highly toxic to animals, Pitterle said.
Source: CoastalView.com
