EVEREST June, 2013 - California Department of Boating and ...

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Orange County Coastal Regional Sediment Management Plan means (e.g., excavation/dredging with downstream placement) should be explored to move sediment through the watershed. These activities would help address sediment reductions associated with historical activities and, more importantly, help offset beach erosion and shoreline retreat associated with future rises in sea level. 4.16 High Fines Sediment Nourishment Pilot Study This activity would consist of monitoring the results of the high fine sediment beach nourishment pilot projects conducted in Santa Cruz and Imperial Beach, California and implementing a similar pilot study within Orange County. The pilot projects in Santa Cruz and Imperial Beach, California indicated that sands remained in the littoral zone while fines settled farther offshore, essentially mimicking the fate of storm discharges (SAIC, 2011). Energetic coastal processes facilitated the reworking of the sediments. Material significantly coarser, finer, or with a greater shell content than native beach sediments have the potential to adversely impact invertebrates, fish, or shorebirds. Therefore, project location, sediment volume, method of sediment placement, and timing are important considerations relative to the use of high fines sediments for beach nourishment. Generally, it is recommended that high fines sediments be discharged in the surf zone, scheduled during the fall and winter to mimic natural processes, and an adaptive process starting with small placement volumes and monitoring be used to determine appropriate limitations based on site specific conditions. The Imperial Beach pilot project is also known as the Tijuana River National Estuary Reserve Study, funded in part by the CSMW. While results from this project (California Ocean Protection Council, 2008; Buhbe et. al., 2011) are being digested into recommendations, it may be beneficial to initiate a high fines beach or nearshore nourishment pilot study within Orange County. The pilot study would provide quantitative data on impacts of high fines sediments on nearshore habitats for use in evaluating whether future placement of high fines sediments on the beach or nearshore is desirable. Potential pilot study locations could be East Beach, Seal Beach, Surfside-Sunset Beach, or Capistrano County Beach. Newport Beach is also a viable location for this study as it has a beach nourishment need and multiple sources of high fines sediment (e.g., Semeniuk Slough and Newport Harbor). These are all locations that have received nourishment in the past, are expected to require nourishment in the future, and could potentially benefit from opportunistic use of high fines sediment source material. If it were found that sediment sources with fine content higher than 20% had negligible habitat impacts, it could be argued that future sediment sources with similar physical and chemical characteristics may likewise have similar habitat impacts and should therefore be permitted. Conversely, if the high fine content sediment had significant habitat impacts, then future use of similar sediment would continue to be very difficult to permit. Everest International Consultants, Inc. 4.13
Orange County Coastal Regional Sediment Management Plan 4.17 Establish Funding Stream to Accommodate Incremental RSM Costs This activity would be to establish a permanent, county-wide, funding stream to accommodate the incremental costs associated with RSM construction. Typically dredging projects require the least cost disposal. If funds were available, the rather small incremental costs required to construct, transport, or dispose the dredged material the extra distance to achieve RSM would be accommodated. Thus RSM could be achieved within existing projects for only a small additional cost. Also, having a readily available funding source within Orange County would make the additional RSM required permitting and project planning more feasible. 4.18 Sea Level Rise Beach Sustainability Study This activity would entail performing an engineering and economics study to determine the nourishment requirements necessary to offset projected sea level rise impacts throughout the Orange County coastline and to find potential managed retreat options within Orange County. Th is study would have two foci: 1) to determine whether, where, and how much beach and nearshore nourishment would be necessary to offset sea level rise impacts on the Orange County coast; and 2) to find locations within Orange County where managed retreat is a viable economic adaptation option against sea level rise. The study would include a calculation of the recreational and flood damage costs of unmitigated shoreline erosion resulting from sea level rise. In addition, it would include development of conceptual solutions and associated costs to mitigate the sea level rise scenarios recommended by government agencies. Results from this study would be used in long-term planning for the Orange County coast. 4.19 Orange County Dredge Ownership Orange County recently completed a study of whether it would be financially beneficial for the county to purchase and operate a dredge (Moffatt & Nichol, 2009b). This study found that there is sufficient dredging demand to support the purchase and operation of a small dredge. Much of the dredging in Orange County is performed on low volume, shallow dredging projects with offshore disposal of fine grained sediments. This somewhat unusual project type requires a rare mix of small, shallow dredge equipment and ocean-classed disposal barges. The anticipated workload would range from 100,000 to 275,000 yd 3 /year. The routine maintenance projects identified and included in the study were: Dana Point Harbor, Newport Dunes Lagoon & Marina, Newport Harbor federal channel, miscellaneous private projects within Newport Harbor, Bolsa Chica Tidal Inlet, and Huntington Harbour. The study concluded that “the purchase of a small hydraulic dredge and ocean-ready disposal barges would be less expensive and better serve the dredging needs of the County as compared to the current system for contracting dredging on a project-by-project basis. However, there are complications that would have to be resolved, including aligning the various Everest International Consultants, Inc. 4.14
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