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+ LSA ASSOCIATES,INC. INAL.STUDY/ENVIRONMENTAL DOCUMENTATION JULY 2oao ITISTOCKTON METROPOLITAN AIRPORT fOtherwise substantially degrade water quality? SPECIAL PURPOSE PLAN No impact. The proposed project will not affect water quality other than as described above. It should be noted that with the implementation of the Special Purpose Plan,the previous agricultural production activities will be terminated. As �- such,there will be a decline in the use of chemicals to enhance crop production and a concurrent reduction in chemicals that are flushed into the adjacent slough resources. Also,the increase in paved surfaces should reduce erosion, sediment production,and siltation of New Weber Slough. By eliminating agricultural production, surface soil I stability should improve,thus reducing the amount of sediments-discharged into New Weber Slough. r g) Place housing within a 100-year flood hazard area as mapped on a federal Flood Hazard Boundary or Flood Insurance Rate Map or other flood hazard delineation map? No impact. The proposed project does not include housing. h) Place within a 100-year flood hazard area structures which would impede or redirect flows? Potentially significant unless mitigated. The 1988 FEMA flood insurance rate maps E . for the airport property indicated that all of the major drainage channels and large portions of the airport property lie within a FEMA-designated I00-year floodplain, subject to flooding of I to 3 feet deep during a 100-year flood event. Old Weber Slough,which was designated as being within the floodplain,will be filled, and therefore, removed as a drainage channel. Most of the airport area north of the runway is outside of the 100-year floodplain. This includes the Airport East Development Area where most of the future airport development is proposed. A Master Plan of Storm Drains will be implemented in conjunction with the Special Purpose Plan to assist in mitigating the drainage concerns to less than significant levels(see"c"above). Mitigation Measure H-1 In conjunction with developing the uses proposed in the Airport SSP, construct the infrastructure specified in the Master Plan of Storm Drains. Airport Master Plan Mitigation: Mitigation Measure DW-1: Evaluate the effect of new construction on the 100-year floodplain elevation and implement measures to ensure that no substantial floodplain elevation increase occurs. i) Expose people or structures to a significant risk of loss,injury or death F. involving flooding,including flooding as a result of the failure of a levee or dam? Potentially significant unless mitigated. Portions of the proposed Special Purpose Plan are located in areas where flooding or flood hazards expose people or structures 7/24100(P:1SIC0301Environmentallinitial studympd) 38 ff