8525 EVERGREEN WAY BURGER KING 2021-05-10

threshold to for water quality. See Section 3 for hard surface replacement, PGHS, and effective impervious totals. The total disturbed area for Basin B will be 0.61 acres. The total new hard surface quantity is 0.01 acres (200 SF) and the total replaced hard surface will be 0.07 acres (3,078 SF) of new impervious is proposed. The total effective impervious area for the Basin B is 3,280 SF Minimum requirements 1-9 apply to Basin B as the proposed improvements will exceed 50% of the existing site's value. Refer to the Flowchart for Determining Requirements for Redevelopment attached in the next page. Basin B is exempt from flow control as there will be less than a 0.15 CFS increase in offsite runoff and the effective impervious are is 3,280 SF which is less than the 5,000 SF threshold requiring flow control. See Section 8D of this report for the hydraulic calculations. Water quality is also exempt as the proposed PGHS is 596 SF which is less than the 5,000 SF threshold to for water quality. See Section 3 for hard surface replacement, PGHS, and effective impervious totals. For onsite stormwater management (MR#5) list # 2 was used for both basins per Vol 1 section 2.5.5 of the SWMMWW. Full dispersion was considered first however it was deemed infeasible due to the lack of native vegetation. Downspout full infiltration was deemed infeasible as the site lacks the necessary area to accommodate full infiltration facilities within the required setbacks. Bioretention was deemed feasible. Onsite stormwater management for roof areas will be provided by two bioretention facilities, one for each basin, per BMP T5.14B. The overflow from the bioretention will be connected to the existing drainage system onsite that drains to Evergreen Way for Basin A and South to Holly Drive for Basin B within a closed pipe system. For other new and replaced hard surfaces, full dispersion was considered infeasible due to the lack of vegetation, permeable pavement was deemed feasible and will be used. Most of the parking lot will receive a 2" overlay and follow the existing grade to sheet flow to onsite catch basins. BMP T5.13 Post Construction Soil Quality will be used for all pervious areas. Insight Engineering Co. -Stormwater Site Plan 12/20/2018 - 15 -