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Environmental Impacts of the Proposed Changes to the Original Project Addendum to the City of Pleasanton Downtown Specific Plan Final Environmental Impact Report 47 type and locations of stormwater treatment measures to be installed (numbered sequentially for identification purposes), and sizing calculations. The Stormwater Management Plan shall be subject to review and acceptance by the City Engineer, prior to the issuance of an engineering or building permit, whichever occurs first.  Stormwater Pollution Prevention Plan: The applicant shall submit one hard copy and one PDF copy of the Stormwater Pollution Prevention Plan (SWPPP) for review and acceptance by the City Engineer prior to issuance of a building or engineering permit, whichever occurs first. A hard copy of the City-accepted SWPPP shall be available at the project site until all work is complete and engineering and building permits have been finalized. A site specific SWPPP shall be combined with proper and timely installation of the Best Management Practices, thorough and frequent inspections, maintenance, and documentation. Failure to comply with the reviewed construction SWPPP may result in issuance of correction notices, citations, or a stop work order.  Excess Soil And Soil Stockpiling: All excess soil from the site shall be off-hauled from the site and disposed of in a lawful manner. No temporary stockpiling of dirt on this site shall occur without specific review and approval by the Director of Community Development. The DSP also includes policies, listed in Section 4.3, Biological Resources, which would minimize the impacts of construction on Arroyo del Valle. Compliance with existing DSP policies and state and local regulations would avoid or minimize erosion and contamination to the extent feasible by requiring erosion and sediment controls and runoff water quality monitoring. With compliance with these existing policies and regulations, the proposed project would not result in violations to water quality standards or waste discharge requirements, and would not otherwise substantially degrade surface or groundwater quality. Impacts would be less than significant. The Final EIR includes an analysis of groundwater supply and estimated water demand for projects associated with envisioned land uses in the DSP area. The project site is currently designated for Downtown Commercial use, and the project would involve changing the site’s land use to allow for residential use. Although the project would involve different land uses than what originally envisioned in the DSP, the project would facilitate the development of residential and commercial uses, which is consistent with development envisioned by the DSP and accounted for in its water supply analysis. Therefore, the water demand associated with the proposed project has been accounted for in water supply estimates in the Final EIR. Additionally, the project would result in a net decrease in impervious surface area within the project site, and stormwater and irrigation runoff generated by the project would be collected and directed to onsite bioretention areas and modular suspended pavement systems (often referred to as “Silva cells”). Stormwater would be managed pursuant to Chapter 9.14, Stormwater Management and Discharge Control, of the PMC, and no water would be directly released into Arroyo del Valle. Therefore, the project would not substantially alter the drainage pattern of the project site. Impacts would be less than significant. According to flood maps prepared by the Federal Emergency Management Agency, the portion of the project site that borders Arroyo del Valle is within a Zone AE flood hazard zone, which includes areas subject to a one percent annual chance of a flood (Federal Emergency Management Agency 2023). Arroyo del Valle is also designated as a regulatory floodway, which means that the channel of the arroyo must be maintained so that flood waters may flow through the arroyo without increasing the water surface elevation more than a designated height. The project would not involve construction within the flood hazard zone and residences would be set back 20 feet from the top of the existing bank. Therefore, the proposed project would not impede or redirect flood flows. Additionally, as a primarily residential development, the project would not involve storage of