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runoff. Increased runoff can increase soil erosion, transport of pollutants, and the potential flooding of he Stockton Metropolitan streams. In conjunction with t p Airport Master Plan, Reinard Brandley, the Airport Consulting Engineer, prepared an 'Overall Drainage Studies Report," which identifies improvements to the airport property that would consist of redirecting the majority of the drainage from j the property to detention basins, with metered discharge to the Mansville Ditch. The Mansville Ditch, F however, has limited capacity and flows through private property. Weber Slough also has limited capacity from south of Farmington Fresh to French Camp Slough. Although the proposed drainage is expected to avoid drainage impacts, actual land uses could differ from those assumed in the Master Plan, and due to the limited capacities of Weber Slough and the Mansville Ditch, the potential impacts from development could be significant. Therefore, to mitigate this impact, a comprehensive drainage plan will be prepared as part of a Special Purpose Plan for the airport property, prior to development. Construction of storm drainage detention basins could pose a flight safety hazard as an attraction to water fowl. Water will only be in basins for a short period of time before being discharged to a water course, and the noise associated with an airport facility is expected to deter most birds from entering the area. In order to ensure that this impact is reduced to a less than significant level, the Department of ' Aviation shall evaluate the degree to which water fowl are attracted to the drainage basins. If the Department determines there is a hazard, measures shall be incorporated into the design-and operation of the basins to minimize the bird attraction, including such things as cables, netting, and automated noise generators. Construction activities could cause discharge of eroded soil, petroleum products, and other construction wastes into water courses. Operation of airport, industrial, commercial, and recreational facilities may result in increased discharge of pollutants in storm water associated with vehicle traffic, industrial waste water, and runoff from paved parking areas. For construction related activities, an erosion control plan and grading permit will be required to mitigate impacts. A National Pollution Discharge Elimination System (NPDES) permit will also be required to address storm water pollution issues associated with construction and operational activities. Vegetation and Wildlife A freshwater marsh is located in the channel bottom of Weber Slough. The freshwater marsh vegetation consists mostly of cattails. The freshwater marsh is considered a wetland subject to Corps of Engineers jurisdiction under Section 404 of the Clean Water Act (CWA). In order to mitigate this impact, the fDepartment of Aviation shall replace the lost wetland in accordance with the Biological Resources Mitigation Monitoring Plan prepared by Simpson Moore. The wetland shall be relocated to the realigned Weber Slough. i Two seasonal pools occupy approximately 1.2 acres adjacent to the abandoned runway in the northern portion of the project site. Vernal pool fairy shrimp were observed in the two seasonal pools by a Jones & Stokes Associate staff biologist in the winter of 1995. In order to mitigate the impact of the loss of these seasonal pools, the Department of Aviation shall create seasonal pool replacement habitat on the project site in accordance with the Biological Resources Mitigation Monitoring Plan. A Section 404 permit from the Corps and consultation with the U. S. Fish and Wildlife Service are required prior to any action being taken on the pools. The giant garter snake is state and federally listed as threatened. No giant garter snakes were observed during field surveys, and no records exist of this species occurring near the project site. However, Weber Slough and the drainage ditch are suitable habitat for the giant garter snake.. Replacing the wetland will mitigate this impact to a less than significant level. San Joaquin County . ER-96-1, et al\Stockton Airport Community Development Page 15