NCI prepared a report recommending an enhancement plan for the improvement of the San Onofre Lagoon, which is located on the U.S. Marine Corp’s Camp Pendleton base. Work consisted of site visits, data collection, engineering analysis and evaluation of the site’s hydrology/oceanography conditions to identify erosion characteristics, and proposing a range of feasible alternatives including structural and non-structural measures to enhance the San Onofre Lagoon. A detailed hydrodynamic analysis under small or moderate flood conditions was performed using the modules of RMA2 and SED2D of the Surface-Water Modeling System (SMS) that was developed by the Corps of Engineers to simulate the flow field within the lagoon boundary and to estimate the potential sediment scouring and re-deposition in the proposed excavation areas for various lagoon habitat improvement options.

The RMA2 modeled results indicate that flow pattern in San Onofre Lagoon will be altered under each proposed enhancement option, particularly during a flood event, as the direct consequence of the changed lagoon configuration. Based upon the SED2D modeled results, sediment deposition occurs throughout most of the lagoon region, particularly in the proposed expansion areas. It was estimated that 20 percent of the storage capacity would be refilled under a 5-year flood event. Therefore, the estimated re-excavation cycle is approximately from 5 to 10 years.

The effectiveness of each lagoon enhancement alternative in improving the lagoon marine habitat and preventing bank erosion was then assessed for the selection of an optimal alternative. In addition, construction costs for the proposed alternatives were also presented in the analysis, based upon each itemized estimate of mobilization/demobilization, construction material, required construction equipment and manpower.