RWQCB approves recycling permit for Camp Pendleton plant

The Regional Water Quality Control Board approved a master recycling permit for Camp Pendleton’s Southern Regional Tertiary Treatment Plant.

The RWQCB board voted 5-0, May 9 with one board member absent, to allow Camp Pendleton to inject recycled water into the lower aquifer of the Lower Ysidora groundwater basin and to create a hydrologic seawater intrusion barrier.

The seawater intrusion barrier is intended to protect the base’s groundwater resources within the Santa Margarita River watershed. The Marine Corps proposes to use up to 870 acre-feet of recycled water annually to create the seawater intrusion barrier. The project consists of pumping recycled water into two reservoirs and 16 injection wells in the Ysidora Flats area.

The interbedded fine-grained strata in the area creates a protective semi-confining aquitard system which separates the lower aquifer from the shallow aquifer. A technical demonstration showed that vertical migration of the recycled water into surface water will not occur.

The tentative order includes discharge specifications with a daily maximum of 45 milligrams per liter for biological oxygen demand and for total suspended solid and a monthly average of 30 mg/L for biological oxygen demand and total suspended solid.

The sodium content has a daily maximum of 60 percent. The discharge order includes annual averages of 750 mg/L for total dissolved solids, 300 mg/L for chloride and sulfate and 10 mg/L for total nitrogen. The pH level must be between 6.5 and 9.0 at all times.

Excess recycled water will be pumped into existing injection wells at Red Beach which are currently used to dispose of treated wastewater from Sewage Treatment Plant Number 9. The Marine Corps’ long-term plan is to transfer the wastewater stream from that sewage treatment plant to the Southern Regional Tertiary Treatment Plant to increase the quantity of wastewater available for recycled water.