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City of Santa Ana Environmental Checklist elimination or reduction of non-stormwater discharge off site into storm drainage systems or other water bodies, and the implementation of BMPs (Mitigation Measure HYD-1). The SWPPP requires a description of the project site, identification of sources of sediment and other pollutants that may affect the quality of storm water discharges, a list of BMPs to provide sediment and erosion control, waste handling measures, and non-stormwater management. The SWPPP would be required to meet or exceed measures required by the Construction General Permit. As a result, construction of the proposed project would result in less-than-significant impacts related to water quality standards after implementation of Mitigation Measure HYD-1. Historical high groundwater elevations below the project site are as shallow as four feet bgs as identified in the Soil Report (Appendix B). As described in Chapter 2, "Project Description," the proposed project would require excavation of soils to a depth of 5 feet below the existing grade to complete the building foundation, parking structure, and installation of underground utilities. As a result, it is anticipated that groundwater would be encountered during construction. Upon exposure of groundwater, construction-related contaminants would have a direct path to the groundwater table. However, implementation of the SWPPP (as described above) would prevent runoff, contaminated soils, or construction contaminants from entering excavated areas and impacts with implementation of the SWPPP would be less than significant. Because groundwater would be encountered during construction, dewatering may be required to lower the existing water level to allow construction without excessive water. Dewatered groundwater may contain high levels of total dissolved solids (TDS), salinity, high nitrates, or other contaminants that could be introduced to surface waters during construction. Groundwater and any other non-stormwater dewatering activities could potentially result in a significant impact. The implementation of Mitigation Measure HYD-2 to comply with the Waste Discharge Requirements (WDRs) issued by the RWQCB is required to reduce potential impacts to a less-than-significant level. Therefore, impacts related to water quality that would occur from implementation of the proposed project would be less than significant with incorporation of Mitigation Measures HYD-1 and HYD-2. Mitigation Measure HYD-1: Prior to issuance of grading and building permits, the applicant will prepare and have approved by the City an SWPPP to be implemented during construction, which will include BMPs to prevent discharges of polluted stormwater from construction sites from entering the storm drains or the existing retarding basin. The SWPPP will be prepared as directed in the City's stormwater protection requirements, and may include, but not be limited to, the following measures: • Diversion of offsite runoff away from the construction site. • Revegetation of exposed soil surfaces as soon as feasible following grading activities. • Installation of perimeter straw wattles to prevent offsite transport of sediment, • Protection of drop inlets (filters and sand bags or straw wattles) with sandbag check dams in paved roadways. • Provision of specifications for construction waste handling and disposal. • Training of subcontractors on general site housekeeping. Mitigation Measure HYD-2: Three months prior to any dewatering activities, the applicant will submit a Notice of intent to the RWQCB and obtain the Santa Ana RWQCB De Minimus Permit for General Waste Discharge Requirements for Discharges to Surface Waters that Pose an Insignificant The Bat Nha Buddhist Meditation Center 3-53 June 2013 Initial Study/Mitigated Negative Declaration ICP 00215.12 31 C-106