San Elijo Lagoon Inlet Excavation Underway

We Are Breaching Accumulated Sands From The Mouth Of The Lagoon Now, And Overnight, To Restore Oxygen Levels For Aquatic Species.

It is that time of year when the lagoon’s connection to the ocean—the inlet—closes when blocked by accumulated sand and sediment. The blockage causes low dissolved oxygen levels in the lagoon’s tidal channels.

Image: The inlet to San Elijo Lagoon is located at Cardiff State Beach. You can see how sand has accumulated under the Coast Highway 101 bridge. It is now being excavated.

During the winter storm cycles the inlet often becomes blocked by an accumulation of sand in the tidal channel. As temperatures rise in the spring, the demand for oxygen increases. Without the circulation provided by the ebb and flow of tides, the lagoon can become stagnant. The lagoon inlet, rarely, if ever, opens naturally. Each spring, and when needed, we mechanically breach a re-opening.

Today we began working to re-open the mouth of the lagoon at Cardiff State Beach by excavating the sands to allow ocean water back in. Constant water flow is vital not only to the plants and animals that live in lagoon waters (without oxygen fish begin to die), but also the Reviving Your Wetlands restoration underway.

This inlet excavation is more urgent than in recent years. Crews will be excavating overnight to restore water flow. We were able to begin excavating efficiently by diverting equipment from San Elijo Lagoon Restoration over to the inlet re-opening—thereby speeding our response.

The casualties of fishes in several pockets of water are not related to the construction projects occurring with Build NCC. This urgent excavation is why we are Reviving Your Wetlands, so that water flows will reach consistently and farther into the lagoon. We will still need to annually excavate the inlet, just not in urgency.

A Modified Lagoon
When early settlers arrived, only beach and dunes separated the lagoon from the ocean. The inlet was open most of the year, sometimes closing during the late summer, but opening again with the combined force of winter rains and surf. The inlet migrated between north and south according to the prevailing forces of the season. 

It has been decades since San Elijo Lagoon was naturally connected to the Pacific Ocean. Coastal development occurred at a rapid pace after the 1880s. The first bridge and berm crossing the lagoon was constructed by the railroad in 1881, followed by Pacific Coast Highway in 1891 and, in 1965, Interstate 5, which divided the wetland in half.

This partitioning of the lagoon created altered flows for both fresh water and salt water. leading to accelerated sediment deposition and reduced water quality.

One of the goals of Reviving Your Wetlands restoration is to improve tidal circulation in the lagoon by removing sediment and making the channels deeper and wider. Water will flow more easily into and out of the lagoon.

Learn more about water quality monitoring and annual inlet excavation online at SanElijo.org/inlet

We will continue monitoring water quality and guiding the actions underway to restore optimal oxygen levels for aquatic species. Here in Lagoon Connections, we will provide updates of this inlet re-opening as we make progress during the next few days.