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086 Oo Temporary culverts, ditches, catch basins, dams, and settling ponds will be installed in the street construction areas to maintain existing drainage flows and to collect excess water and sediments flowing out of the construction sites. Sediments collected will be disposed of at a Class II or Class III disposal site. If reconstruction of the Santiago Creek Bridge supports is determined to be necessary, construction activities will be limited to dry months. Bridge design and construction activities will be coordinated with the Orange County Environmental Management Agency, the California Department of Fish and Game, and the U.S. Army Corps of Engineers, and will comply with all of their requirements. Temporary drainage and erosion controls such as sandbags, ditches, dams, culverts, catch basins, and settling ponds will be used, as needed. Collected sediments will be properly disposed of at a Class II or Class III disposal facility. Rationale Covering of exposed ground surfaces will effectively minimize the amount of ground surface area which can be directly disturbed by strong winds. Installation of temporary culverts, ditches, catch basins, dams, and settling ponds within the construction zones, will provide ongoing drainage controls, should a rainstorm interrupt the construction process. The collection of run- off from the construction zones in culverts, catch basins, dams, and settling ponds will prevent this run-off from flowing onto the paved street and into the street drainage system, enabling proper disposal of the sediment in a suitable landfill facility, rather than contributing to potential downstream water pollution. By limiting construction of the bridge widening to typically dry months, the potential for erosion and increased sedimentation within the streambed is significantly diminished. With installation of the various temporary drainage and sediment collection controls, additional sedimentation due to bridge construction will be effectively minimized. Floodplain/Floodway Encroachment Significant Effects A small portion of the project area, in the vicinity of the Warner Avenue/Bristol Street intersection is within a floodplain, subject to potential overflow with a one-foot flooding depth from a 100-year flood event along the Santa Ana River. In addition, the Santiago Creek Channel has the potential for overtopping its banks and the existing Bristol Street Bridge, during a 100- year storm event. This channel has been identified as a floodway, by the Federal Emergency Management Agency. Construction of street and bridge improvements could affect flooding conditions in these areas.