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.  

At present, the inlet is open under 1 bay of the Pacific Coast Highway bridge. Tidal circulation is significantly muted as a result of sand buildup under the other 3 bays and the main channel. Timing of the excavation is 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.

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:

  • increased diversity and abundance of fishes
  • improved water quality
  • reduced numbers of mosquitos and midges
  • expanded nesting areas for California Least Terns, Belding's Savannah Sparrows, and Western Snowy Plovers
  • increased foraging by birds







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.

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.

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.



June 2-6, 2014
(Construction equipment arrives May 29)

Improved Tidal Circulation is Funded By:

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