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i <br /> i' <br /> t. <br /> t > <br /> I <br /> t <br /> 1. BMP T7.30—Bioretention: Bioretention cells will be constructed within the low spots of <br /> the parking lot area. The bioretention cells will contain the following elements: <br />� � t <br /> • 6-inch ponding depth <br /> • 6-inch freeboard <br />( ; x • 3:1 side slopes <br /> 18 inches of bioretention soil mix <br /> • Underdrain system (Some will be constructed with the drain pipe at the top of the <br /> crushed rock material because of site elevation constraints.) <br /> i <br /> • Overflow Structure <br /> t <br /> g g <br /> The cells will be constructed with minimal curbing surrounding the cells to allow <br /> maximum stormwater flow into the facility. <br /> S . <br /> 2. BMP T5.12— Sheet Flow Dispersion: Stormwater from the proposed pedestrian <br /> walkways within the open landscape area will disperse into the adjacent vegetation. <br /> 3. BMP T5.13 —Post-Construction Soil Quality and Depth: All proposed landscape areas <br /> will use imported topsoil mix to meet the requirements of this BMP. <br /> e CONVEYANCE <br /> i <br /> The storm conveyance system for the project is sized to convey the 25-year recurrence interval <br /> peak flow from the site. The Rational Method was used to develop runoff flows from the site. <br /> Manning's equation was used for preliminary pipe sizing. Appendix B provides pipe sizing <br /> calculations. <br /> E OPERATIONS AND MAINTENANCE <br /> i <br /> The proposed project will construct a new LRC building. The site improvements include paved <br /> parking lots and driveways and pedestrian hardscapes. Additional improvements include <br /> landscaping, underground utilities, and a stormwater conveyance system. <br /> The project owner will be responsible for maintaining and operating the on-site stor nwater <br /> drainage facilities, as explained below and in the maintenance guidelines in Appendix C. <br /> I <br /> Stormwater Facility Responsible Party for Maintenance/Operations <br /> Bioretention Cell Everett Community College Staff <br /> Catch Basin Everett Community College Staff <br /> I „ <br /> The project owner will comply with the maintenance guidelines, which include relevant sections <br /> of maintenance guidelines from the Stormwater Manual. In addition, the following operation <br /> and maintenance plan is proposed: <br /> Stormwater Site Plan 10 <br /> Learning Resource Center <br /> i <br />