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City of San Leandro Housing Element Update (2015-2023) Project Initial Studv and Environmental Checklist d) Would the project 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 flooding on- or off-site? The housing sites are generally located on sites where drainage impacts can be fully mitigated by connecting to the city's storm drain system. In addition, the Housing Element supports green roofs, rain gardens, and other forms of low impact development which would retain a greater quantity of stormwater on-site. These policies may be applied to existing development as well as proposed development, resulting in net environ- mental benefits. Accordingly, impacts would be less than significant. Also see Section IX.c above. e) Would the project create or contribute runoff water which would exceed the capacity of existing orplanned stormwater drain- age systems? Adoption of the Housing Element alone would not result in the development of residential units; however, development as a result of implementation of the Housing Element could result in physical changes that could occur which could increase impervious surfaces that could create or contribute to runoff water that would exceed the city's stormwater drainage systems. However, the type of anticipated development associat- ed with the Housing Element would primarily be restricted to the existing urbanized environment in areas where residential uses are currently allowed. The impacts related to stormwater drainage runoff would be less than significant. Also see Section IX.c and IX.d above. fi Would the project provide otherwise substantially degrade water quality? A principal source of water pollutants is stormwater runoff containing petrochemicals and heavy metals from parking lots and roadways. Given that the proposed Project would not create such surfaces or directly in- crease vehicular use of existing parking lots and roadways, implementation of the proposed Project would not contribute to these types of water pollutants. As discussed under Section IX.c and IX.d, where excessive con- struction related grading or excavation is required, pursuant to the SWQCB Construction General Permit, a SWPPP would be required to be prepared and implemented for the qualifying projects under the proposed Project, which would reduce polluted runoff to the maximum extent practicable during construction phases. Furthermore, implementation of the proposed Project would be subject to the oversight and review processes and standards outlined in Section IX.a. As such, compliance with these existing regulations would result in less -than -significant water quality impacts. g) Would the project place housing within a I00year flood ha.Zard area as mapped on a federal Flood Ha.Zard Boundary or Flood Insurance Date Map or other flood ha.Zard delineation map? According to the 2002 General Plan, flood hazards in San Leandro are associated with overbank flooding of creeks and drainage canals, dam failure, tsunamis, and rising sea level.27 The Federal Emergency Management Agency (FEMA) identifies areas within San Leandro that lie within a 100 -year floodplain generally located along the San Leandro Shoreline at the western city limit stretching east into the city generally to the Union Pacific Railroad.28 FEMA is currently conducting a new coastal study called the California Coastal Analysis and Mapping Program (CLAMP) that will revise and update flood and wave data for San Francisco Bay and its estuaries. The analyses rely on a combination of hydrodynamic models and wave models to calculate ele- vated still water levels (SWELs), wave heights, and overland wave propagation that will be used to produce 27 City of San Leandro General Plan, 2002, Chapter 6, Environmental Hazards, page 6-7. 28 ArcGIS, FEMA Preliminary Flood Map, http://www.arcgis.com/home/webmap/viewer.html?webmap=b0061 a5a0b07470d8c72381772fl2f6b&extent=- 122.4681%2c37.4427%2c-121.5816%2c37.9155, accessed on November 11, 2014. Page 135