AgdaPkt 2017-09-11 Closed and Joint SA PFA

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7.A. - Page 88 LSA ASSOCIATES, INC. ROCKETSHIP REDWOOD CITY ELEMENTARY SCHOOL PROJECT SEPTEMBER 2016 INITIAL STUDY/MITIGATED NEGATIVE DECLARATION be contaminated by off-site historic chemical releases). Therefore,potential impacts related to the depletion of groundwater supplies are less than significant. c) Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, in a manner which would result in substantial erosion or siltation on-or off-site?(Less-Than-Significant Impact) The proposed project would not alter the course of a stream or a river. The proposed project would temporarily alter the existing drainage pattern of the project site during construction,which would involve ground disturbing activities such as excavation and grading. Compliance with the Erosion and Sediment Control Plan(Mitigation Measure HYD-1)would ensure that construction activities would not result in substantial erosion or siltation on-or off-site. Upon completion of construction,the project site would again be covered with structures,pavement,and landscaping,and runoff from the site would continue to drain into a stormwater drainage system consisting of underground culverts. Consequently,the potential of the proposed project to alter the drainage pattern on the project site in a manner that would result in substantial erosion or siltation on-or off- site is less than significant. d) Substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river, or substantially increase the rate or amount of surface runoff in a manner which would result in flooding on-or off-site? (Less-Than- Significant Impact) The proposed project would not alter the course of a stream or a river. Although redevelopment would alter the existing drainage pattern of the project site,implementation of the proposed project would decrease the impervious surface area of the project site. The project would increase the infiltration of rainfall into the ground,thereby decreasing the rate of stormwater runoff from the project site and decreasing the potential for flooding. Consequently,the potential of the proposed project to substantially alter the drainage patterns on the project site such that on-or off-site flooding would occur is less than significant. e) Create or contribute runoff water which would exceed the capacity of existing or planned stormwater drainage systems or provide substantial additional sources of polluted runoff? (Less-Than-Significant Impact) As discussed in Section IX.a above,implementation of the proposed project would decrease impervious surfaces on the project site; this in turn would decrease the rate of stormwater runoff from the project site and would reduce the potential for stormwater runoff to exceed the capacity of the public storm drain system. Therefore,the potential of the proposed project to result in stormwater runoff rates that exceed the capacity of the existing storm drainage infrastructure is less than significant. Adherence to the Erosion and Sediment Control Plan and Stormwater Control Plan (Mitigation Measures HYD-1 and HYD-2)would reduce potential of construction and operation of the proposed project to provide substantial additional sources of polluted runoff to a less-than- significant level. P:1RWC1401B Rocketship Sch-I\PRODUCrSUS-MND1Public\Ra ketship Public Review 09-29-16.docx(09/29/16)PUBLIC REVIEW DRAFT 64 ATTY/RESO.0084/CC RESO ADOPTING CEQA-ROCKETSHIP CHARTER SCHOOL APPEAL REV:09-05-17 VR Page 72 of 124