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AUGUSTIN BERNAL MOUNTAIN BIKE TRAIL PROJECT DRAFT INITIAL STUDY Less Than Significant Potentially Impact With Less Than Significant Mitigation Significant Impact Incorporated Impact No Impact iii) 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;or iv) impede or redirect flood flows? ❑ ❑ ❑ d) In flood hazard,tsunami,or seiche zones, risk release of pollutants due to ❑ ❑ ❑ project inundation? e) Conflict with or obstruct implementation of a water quality control plan or ❑ ❑ ❑ sustainable groundwater management plan? Setting The project would construct a mountain bike trail descending the easterly slope of the Pleasanton Ridge. There are no streams or natural drainage courses within or adjacent to the project site.As shown in Figure 1, there is one primary drainage slightly north of the project site, within the Augustin Bernal Community Park.This drainage flows eastward as a tributary to Arroyo de la Laguna,east of Foothill Boulevard.Arroyo de la Laguna continues south and then west into the City of Fremont,generally along the same alignment as State Route 84, until it enters Alameda Creek and ultimately the San Francisco Bay. Impact Discussion a) Would the project violate any water quality standards or waste discharge requirements or otherwise substantially degrade surface or ground water quality? Soil disturbance during grading and construction could potentially result in erosion and sedimentation of downstream water bodies. Erosion and sedimentation affect water quality and interfere with photosynthesis; oxygen exchange; and the respiration, growth, and reproduction of aquatic species. In addition to sediment, other pollutants associated with construction activity could include heavy metals,oil/grease,fuels,debris/trash from construction-related materials,and concrete curing compounds.Sediment can also be a carrier for these pollutants if such pollutants impact on-site soils and are subsequently transported off site. Because the area of ground disturbance would be less than 1 acre,grading and construction would not be subject to the State Construction General Permit and would not require completion and implementation of a Stormwater Pollution Prevention Plan. However, the City would implement typical BMPs to minimize soil erosion and associated adverse effects to water quality, including measures to stabilize work areas including fiber wattles, silt fencing, concrete washout areas,soil 12956 DUDEK 65 April 2022