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ARROYO LAGO RESIDENTIAL PROJECT ADDENDUM FCS 185 Https://adecinnovations.sharepoint.com/sites/PublicationsSite/Shared Documents/Publications/Client (PN-JN)/2148/21480036/Addendum/21480036 Arroyo Lago Residential Project Addendum.docx Stormwater Stormwater generated by the proposed project would be collected via storm gutters along the proposed internal streets and conveyed through an on-site network of 18-inch underground storm drainpipes. Under normal operating conditions, stormwater would be conveyed east from the project site using an approximately 45-inch diameter pipe that would be constructed east of Street F. The stormwater would be conveyed to a proposed primary bioretention area located approximately 0.45 mile east of the project site, adjacent to El Charro Road (Exhibit 9b). The proposed project would include a primary bioretention area, which would include a treatment area of approximately 40,000 square feet. The bioretention area would contain two layers: an approximately 18-inch layer of bioretention soil mix and an approximately 12-inch layer of Class II permeable rock. After being treated, the stormwater would be pumped out of the bioretention basin into a storm drain force main that would be located in El Charro Road that would flow south until turning west and following Busch Road to a connection to an existing City storm drainpipe in Busch Road. In larger storm events, stormwater would be temporarily stored in a detention basin just northeast of the bioretention area. The detention basin has been sized to hold back-to-back 100-year storm events before providing metered outflow into the City’s storm drain system to ensure that the capacity of the City’s system is not exceeded. In addition to the normal stormwater system, the proposed project is also designed with overland release, which includes a path for surface floodwater to flow through a development in a manner that protects structures should the underground storm drain system be blocked or overwhelmed. In order to protect structures from flooding at the project site, the overland release would direct most of the surface flow south to Busch Road, but a portion of the project site starting from approximately Lot 118 and proceeding north has been designed to be captured in a secondary overland release inlet which would convey the stormwater into an approximately 24-inch diameter pipe that would connect with an existing storm drain line in Mohr Avenue. All stormwater infrastructure improvements would be designed and constructed in accordance with the City of Pleasanton’s Standard Specifications and Details and implemented through the City’s COAs for the proposed project. Based on the foregoing, the proposed project would not require relocation or construction of new or expanded stormwater facilities beyond what is proposed under the proposed project, and the proposed bioretention area, stormwater detention basin, and other City stormwater facilities would have adequate capacity to serve the proposed project. The proposed project would also be subject to the San Francisco Bay MRP, which includes LID standards and post-construction monitoring to encourage stormwater infiltration and retention. Electricity, Natural Gas, and Telecommunications Electric and gas services for the proposed project would be provided by PG&E, while AT&T would provide phone services, and Comcast would provide phone and high-speed internet services. The