San Juan Creek Ocean Outfall Junction Structure Rehabilitation Project

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SOCWA’s San Juan Creek Ocean Outfall discharges treated wastewater, known as effluent, from four upstream water reclamation plants:

  • City of San Clemente Water Reclamation Plant
  • SOCWA J.B. Latham Treatment Plant
  • SMWD/MNWD Plant 3A
  • Santa Margarita Water District Chiquita Water Reclamation Plant

The land and marine sections of the outfall were constructed in 1979. Both outfall sections were constructed with 57-inch reinforced concrete pipe (RCP). The outfall extends approximately 10,550 feet into the Pacific Ocean. The Junction Structure is located in Doheny State Beach near the outlet of the San Juan Creek to the Pacific Ocean. Typically, the structure is buried beneath the sand at the State Beach, though sometimes it is uncovered and visible to beachgoers. The Junction Structure is a 10 foot diameter reinforced concrete structure that forms the interface between the land and marine sections of the outfall. The original construction included a reinforced concrete top with a four-foot square, bolted steel access hatch to allowed access into the outfall. In the early 1990’s, the top was modified to increase the maximum internal hydrostatic pressure. This modification project also eliminated the hatch, rendering the Junction Structure inaccessible for internal inspections of the outfall. The Junction Structure currently serves no functional purpose.

In 2006, SOCWA retained Carollo Engineers to evaluate the hydraulic capacity of the San Juan Creek Ocean Outfall. Part of this evaluation included an analysis of the pressure rating of the system. The analysis found structural weakness that could compromise the Junction Structure and possibly result in the spill or unregulated discharge of treated effluent within the San Juan Creek land and ocean outfall. A subsequent finite element analysis of the Junction Structure confirmed the weakness of the structure at the connection points for the 57-inch diameter pipe.

To eliminate the need for excavation outside of the Junction Structure and minimize the impact on Doheny State Beach activities, SOCWA retained the engineering firm Black and Veatch to develop and evaluate alternatives for rehabilitating the San Juan Creek Outfall Junction Structure. Black and Veatch recommended installing an internal stainless steel (SS) pipe liner through the Junction Structure with external pipe seals on both ends.

Important aspects of the project included maximizing construction safety and minimizing disruption to the State Beach.

Black and Veatch retained Dudek to complete Environmental Services for the project. These Environmental Services include obtaining the necessary permits and approval to conduct the project as well as completing a Biological Resources Letter Report and a Cultural Resources Inventory Study to support the project’s CEQA Mitigated Negative Declaration (MND). The draft CEQA MND was distributed for public review in September 2015.

 

DOCUMENTS

Initial Study and Mitigated Negative Declaration (w/o Appendices) September 2015

Initial Study and Mitigated Negative Declaration (w/ Appendices) September 2015

San Juan Creek Outfall Junction Structure Rehabilitation Technical Memorandum April 2014