Annual Inlet Excavation



Reconnecting San Elijo Lagoon with the Pacific Ocean 

The small opening, just south of San Elijo State Beach Campground, is the lagoon's only access to the Pacific Ocean. Keeping the inlet open to the ocean is critical to maintaining the health of San Elijo Lagoon. Left unattended, it could remain closed much of the year from buildup of sand transported by high incoming tides, surf, and storm surges.  

Before dredging to re-open the inlet was conducted June 2-6, the inlet was 80% blocked. Tidal circulation was significantly muted as a result of sand buildup in 3 of 4 bays beneath the Pacific Coast Highway bridge and in the main channel. Timing of the excavation was conducted outside the closed grunion season.

The conservancy’s efforts to keep the inlet open to tidal flushing have substantially improved habitat quality relative to the stagnant conditions that previously developed when the inlet was closed for prolonged periods.

WHY WE DREDGE
In 2001, a long-term financial endowment was established to actively fund maintenance of tidal flushing. Efforts to keep the lagoon open to tidal circulation have shown that significant ecological benefits result from increased tidal flushing, as evidenced by:



 

 

 

 

 

 

The inlet becomes intermittently blocked by an accumulation of sand in the tidal channel during the winter storm cycles. The cool weather helps keep oxygen levels in the lagoon in the safe zone. As temperatures rise in the spring and the demand for oxygen increases, an inlet operation is conducted before problems arise.

SPRINGTIME DREDGING
Typically, the sand berm that forms west of Pacific Coast Highway 101 is breached by excavation equipment. Larger dredging operations remove sand accumulations east of Highway 101 and under the bridge. Clean sand removed from the tidal channel is deposited south onto Cardiff State Beach. Conservancy staff manage these operations.

A major dredging operation to remove accumulated sand and cobbles can cost nearly $100,000. Timing this procedure in the spring after the winter storm cycle greatly increases the chances of continued inlet circulation throughout the warmer summer months.

A MODIFIED LAGOON
It has been decades since San Elijo Lagoon was naturally connected to the Pacific Ocean. Human modifications to hydrology occurred at a rapid pace after the 1880s. The first bridge and berm crossing the lagoon was constructed in 1887 for Santa Fe Railroad, followed by Pacific Coast Highway 101 (1891) and the completion of Interstate 5 in 1965, which divided the wetland in half. This "partitioning" of the lagoon created altered flows for both fresh and saltwater, leading to accelerated sediment deposition, dramatically-reduced water quality, and a reduction in native estuarine habitats due to increased runoff from development upstream.

 

 

INLET EXCAVATION
June 2-6, 2014

Inlet Photomonitoring Slideshow

 

 

 

 

 


View Slideshow

See daily photomonitoring of San Elijo Lagoon's only channel to the Pacific Ocean. The inlet is restricted by a railroad and highways. Watch the slow accumulation of sand and cobble that becomes trapped in this passage, thereby restricting water flow.

Improved Tidal Circulation is Funded By:

CONTACT
Doug Gibson, Executive Director / Principal Scientist
San Elijo Lagoon Conservancy
(760) 436-3944 x 707
doug [at] sanelijo [dot] org