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Broadway Everett Expansion Storm Drainage Report <br /> November 16, 2022 <br /> 4.0 — PERMANENT STORMWATER CONTROL <br /> 4.1 - On-Site Stormwater Management <br /> List#2 was used to evaluate the feasibility of Low Impact Development (Stormwater BMPs). All BMPs for <br /> roofs and hard surfaces were deemed unfeasible due to soil type and low infiltration. See Appendix D— <br /> Geotechnical Report. <br /> Landscaped Areas: <br /> All proposed landscaped areas will utilize amended soils per BMP T5.13: Post Construction Soil Quality <br /> and Depth. <br /> Roof: <br /> 1. Full Dispersion is infeasible due to the lack of a dispersion area containing forest or native <br /> vegetation. <br /> 2. Downspout Full Infiltration is infeasible due to lack of space for an infiltration trench. 190 LF of <br /> trench is required per 1,000 SF of roof and the site does not have the available space to <br /> accommodate for the trenches and to meet the appropriate steep slope and property line setback. <br /> 3. Bioretention is infeasible due to the lack of space on-site for a vegetated area. <br /> 4. Downspout Dispersion Systems are infeasible due to the lack of space on-site to implement <br /> appropriately sized vegetated flow paths. <br /> 5. Perforated Stub-Out Connections are infeasible due to the lack of space on-site to implement <br /> appropriately sized trenches backfilled with washed drain rock. <br /> Walkways: <br /> 1. Full Dispersion is infeasible due to the lack of a dispersion area containing forest or native <br /> vegetation. <br /> 2. Permeable Pavement is feasible and proposed on-site. <br /> 4.2 - Conveyance System Analysis and Design <br /> A Conveyance System Analysis and Design can be provided upon request. <br /> Page 7 <br />