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City of Santa Ana <br />Environmental Checklist <br />will treat stormwater. The treated stormwater will be discharged at four locations along North <br />Fairview Street and join the existing drainage pattern of the street that will transport flows into the <br />existing storm drain system in 17th Street. Stormwater from the remainder of the site will infiltrate <br />into permeable pavers, with any overflow going to the existing curb and gutter on North Fairview <br />Street. The project does not include changes to the existing offsite drainage patterns as a result of <br />the proposed project. The project would not alter the course of a stream or river and would not <br />result in substantial erosion or siltation offsite. <br />As discussed above under IX.a, a required NPDES General Construction permit and a SWPPP would <br />be required to address sediment control and flooding during construction activities. As a result of <br />compliance with existing regional and local regulations, impacts are related to changes in the <br />drainage pattern or erosion /siltation from the site and are less than significant. <br />d. Substantially alter the existing drainage pattern of the site orarea, including through the <br />alteration of the course ofastreamorilver, orsubstantia llyincreasetherateorarnountof <br />surface runoff in a manner that would result in flooding on site or offsite? <br />Less - than - Significant Impact. Refer to IX.c. Although construction of the proposed project would <br />take place within 500 feet of the concrete -lined portion of the Santa Ana River, development of the <br />proposed project would not impact its course or flow patterns. Existing flows from the project site <br />enter the river through existing stormwater facilities, as described in IX.c. The overall drainage <br />pattern of the site would not be substantially altered, and the project would construct onsite <br />stormwater infrastructure to connect to the existing offsite facilities. <br />The planned operational stormwater drainage for the center portion of the project site will direct <br />surface flow to drain into a bioretention system that will treat stormwater. The treated stormwater <br />will be discharged at four locations along North Fairview Street and join the existing drainage <br />pattern of the street that will transport flows into the existing storm drain system in 17th Street. <br />Stormwater from the remainder of the site will infiltrate into permeable pavers, with any overflow <br />going to the existing curb and gutter on North Fairview Street. The project does not include changes <br />to the existing offsite drainage patterns. Offsite stormwater flows from the proposed project would <br />be conveyed in the same manner as existing conditions, and the project would not substantially alter <br />the existing drainage pattern of the site. In addition, as described previously, the project site will <br />include a 2% increase in pervious area, which is approximately 6,000 sf greater than the pre - project <br />condition. As a result, stormwater flows from the project site would not increase with development <br />of the project and flooding on or off site will not result. <br />As discussed in Ma, the project would be required to obtain a General Construction Permit and <br />implement a SWPPP containing BMPs and a WQMP, which would address flooding issues for <br />construction and post - construction phases. As a result, the proposed project would not alter the <br />existing drainage pattern or increase runoff in a manner that would result in flooding. Therefore, <br />impacts are less than significant after mitigation. <br />e. Create or contribute runoff water that would exceed the capacity of existing or planned <br />stormwater drainage systems or provide substantial additional sources of polhuted runoff? <br />Less - titan- Significant Impact. Refer to IX.a and IX.c. As described above, the proposed project <br />would not alter the existing drainage pattern or substantially change the amount of impervious <br />surfaces on the project site. Because the project site has been long developed with approximately <br />74% impervious surfaces, redevelopment of the site with 72% impervious surfaces would not <br />The Academy Charter High School 12 <br />3 58 June 20 <br />Initial Study /Mitigated Negative Declaration ICF 0092011 <br />31 B -134 <br />