and/or presence of contaminants will dictate 

 their ultimate disposal. Off-shore deposition 

 in an authorized deep-sea dump site is an 

 additional option. 



• Experimental berm. The feasibility of 

 using dredge spoils for upland habitat creation 

 will be determined in a major field 

 experiment. A small berm will be constructed 

 from the spoils from the Model Project. 

 Experiments to vegetate the berm will test 

 different plant species and different soil 

 amendments. A primary concern is how 

 rapidly the salty substrate will leach so that 

 non-halophytic species can establish and 

 grow. Should leaching prove to be rapid, the 

 spoils could then be used for slope restoration 

 at a nearby abandoned gravel pit and for 

 capping and vegetating the proposed river 

 training structure. 



• Salvage efforts. Dredging to restore 

 channels will disrupt small areas of benthic 

 animal communities and creek-side vegetation 

 and infauna. Tiger beetles have not been 

 transplanted previously, but a relocation 

 program will be attempted on an experimental 

 basis before critical habitat is allowed to be 

 damaged. To the extent possible, areas of 

 native vegetation will be avoided; where 

 unavoidable, a salvage and revegetation 

 program will be undertaken. Experiments 

 will focus on the size and depth of soil cores 

 needed to retain native vegetation and soils, 

 including root zones and seed banks. Other 

 studies will compare species establishment 

 rates with and without revegetation. The new 

 channel adjacent to the Visitor Center will 

 house these experiments and allow public 

 interpretation, thus making Tijuana Estuary a 

 major demonstration site for state-of-the- 

 art restoration methods. 



6.5 MITIGATION CONCERNS 



Throughout California, continuing 

 development projects in coastal wetland 

 habitats (e.g., highway widening, dock and 

 marina construction, port expansion) have led 

 to several mitigation projects. Their success 

 or failure is rarely assessed, and quantitative 

 documentation is rarely achieved (although 



see Langis et al. 1991, Zedler and Langis 

 1991, and Zedler 1991). Few mitigation 

 projects increase habitat area; most simply 

 change one type of wetland habitat into 

 another. Yet changes in habitat quality do not 

 compensate for reduced wetland area. More 

 likely, they cause a loss in wetland 

 functioning. Nor does the exchange of quality 

 for quantity fulfill President Bush's "no net 

 loss" policy, which not only calls for acreage 

 and function to be sustained, but also proposes 

 a net gain in wetlands through the restoration 

 process (Conservation Foundation 1988). 



6.5.1 Projects at Tijuana Estuary 



Small habitat restoration projects have 

 been undertaken at Tijuana Estuary, and each 

 has failed in one or more respects. Two were 

 mitigation projects that were to offset habitat 

 losses in San Diego Bay. In 1983, two dikes 

 across the tidal lagoons were breached to 

 improve tidal flushing. A segment of one dike 

 was made into an island, with sand placed on 

 top to create least tern nesting habitat. The 

 proposed enhancement was supposed to 

 mitigate a non-permitted fill operation in San 

 Diego Bay. The project was poorly designed 

 and had to be modified by the Fish and Wildlife 

 Service prior to implementation. 

 Unfortunately, specific goals were not 

 enumerated, and the success of the 

 "enhancement" was not assessed. After dike 

 breaching, the northernmost tidal lagoon did 

 show increased tidal flushing, but canine and 

 human intruders were not deterred by the 

 narrow breaches. And, rather than attracting 

 terns, the sand added to the dike island 

 stimulated weed invasions. 



The second mitigation project further 

 widened one of the dike breaches to reduce 

 human access. In addition, a deep "loop 

 channel" was constructed around a patch of 

 upper salt marsh. This project eliminated 

 about 0.2 acres of urban fill (disturbed salt 

 flat). It also made possible the eventual 

 construction of the PERL tidal mesocosms, 

 which now connect to the subtidal loop. No 

 assessment or monitoring of the mitigation 

 project was required or conducted. 



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