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Home My WebLink AboutSP-24-23 - Supplemental - 0200 Garden Street (13)STORMWATER MANAGEMENT SUMMARY City Center May 15, 2024 PERMIT STATUS: An individual stormwater discharge permit (7736-INDS.A) was obtained for the lands owned by South Burlington City Center, LLC. The Permit approved a comprehensive approach to the stormwater management system for the future site development along Market Street, as well as the future construction of Garden Street and the associated site development. The stormwater collection system along Market Street is subject to a separate permit associated with the City’s reconstruction of the street and utilities. The proposed permitted stormwater treatment practices for City Center consist of a wet pond, five constructed wetlands, two bioretention areas, an infiltration trench/chamber system, and simple disconnection. Note that the simple disconnection applies to the path leading to Dumont Park. The Permit approved a total impervious surface of 18.5 acres. The stormwater management system provides water quality treatment for 9.65 acres of offsite impervious surface (included in the 18.5 acres total). CONSTRUCTION STATUS: Site Development 146 Market Street (Allard Square)CONSTRUCTED 180 Market Street (City Hall)CONSTRUCTED 310 Market Street (Garden Apartments) CONSTRUCTED 303 Market Street (Union Place)CONSTRUCTED 112 Garden Street (Prospect Place)CONSTRUCTED 324 Garden Street (Dover Place)CONSTRUCTED 224 Market St (Catamount Run-Block B) UNDER CONSTRUCTION 268 Market St (Catamount Run-Block B) UNDER CONSTRUCTION 339 Garden St (Catamount Run-Block B) UNDER CONSTRUCTION 225 Market St (Catamount Run Block A) UNDER CONSTRUCTION 267 Market St (Catamount Run Block A) UNDER CONSTRUCTION 113 Garden St (Catamount Run Block A) not constructed Market Street Commons (Black Bay)CONSTRUCTED Garden Street – north & south segments PARTIALLY CONSTRUCTED Stormwater Practices Gravel wetland #1 (GW#1)CONSTRUCTED Gravel wetland #2 (GW#2)CONSTRUCTED Gravel wetland #3 (GW#3)CONSTRUCTED Gravel wetland #4 (GW#4)not constructed Gravel wetland #5 (GW#5)CONSTRUCTED Storm pond #1 (pond #1)CONSTRUCTED Infiltration system CONSTRUCTED Bio-retention area #1 (BR#1)UNDER CONSTRUCTION Bio-retention area #2 (BR#2)not constructed Note that not all of the site development areas listed contribute fully to the listed stormwater practices. Gravel Wetland 1 Drainage Data Subwatershed description Drainage area Impervious surface 303 Market Street (Union Place) 0.96 acre 0.70 acre Block A (portion Bldg A1 rooftop) 0.34 acre 0.34 acre 112 Garden St (portion rooftop)0.32 acre 0.32 acre Lot M4 / Building 7 0.38 acre 0.30 acre Future development 0.18 acre 0.30 acre Approved TOTAL 2.18 acres 1.96 acres * Note that the impervious surface exceeds the drainage area Gravel Wetland 2 Drainage Data Subwatershed description Drainage area Impervious surface 310 Market Street (Garden Apts) 1.07 acres 0.87 acre 324 Garden Street (Dover Place) 0.63 acre 0.53 acre Garden Street (north of Market St) 0.66 acres 0.55 acre Partial Lot B **1.99 acres 1.67 acres Future development 0.23 acres 0.84 acres* Approved TOTAL 4.58 acres 4.46 acres * Note that the impervious surface exceeds the drainage area ** Lot B includes bioretention area #1 Gravel Wetland 3 Drainage Data Subwatershed description Drainage area Impervious surface Market St. Commons (Black Bay) 0.62 acres 0.60 acres Approved TOTAL 0.62 acres 0.60 acres Gravel Wetland 4 Drainage Data Subwatershed description Drainage area Impervious surface Future development 0.43 acres 0.41 acres Approved TOTAL 0.43 acres 0.41 acres Gravel Wetland 5 Drainage Data Subwatershed description Drainage area Impervious surface 112 Garden St (Prospect Place)2.08 acres 1.99 acres 303 Market St (Union Place)0.37 acre 0.37 acre Garden Street ROW (south of Market St)1.35 acres 1.11 acres Block A (portion Bldg A1 rooftop) 0.52 acre 0.41 acre Lot M4 / Building 7 0.10 acre 0.01 acre Future development 0.80 acre 1.21 acres* Approved TOTAL 5.22 acres 5.10 acres * Note that the impervious surface exceeds the drainage area Storm Pond #1 Drainage Data Subwatershed description Drainage area Impervious surface Offsite 13.95 acres 9.65 acres 146 Market St. (Allard Sq. rooftop) 0.21 acres 0.21 acres City Hall/School driveway 0.43 acres 0.27 acres Partial Lot B 1.02 acres 0.90 acre Block A (partial Lot N)4.26 acres 2.38 acres Future development 0.43 acres 1.13 acres Approved TOTAL 20.30 acres 14.54 acres Notes: -Allard Sq. rooftop area taken from Permit 7736-INDS application -City Hall/School driveway taken from Operational Stormwater Permit Application prepared by Engineering Ventures, PC -Lot N includes bioretention area #2 -Note that the impervious surface exceeds the drainage area Rooftop Infiltration System Drainage Data Subwatershed description Drainage area Impervious surface 112 Garden St (portion rooftop)0.32 acres 0.32 acres Block A (portion Bldg A1 rooftop) 0.34 acre 0.34 acre Lot M4 / Building 7 rooftop 0.29 acre 0.29 acre Future development 0.23 acres 0.23 acres Approved TOTAL 1.18 acres 1.18 acres Bioretention Area #1 Drainage Data Subwatershed description Drainage area Impervious surface Partial Lot B 0.60 acres 0.45 acres Future development 0.38 acres 0.50 acres Approved TOTAL 0.98 acres 0.95 acres -Bioretention area #1 flows to gravel wetland #2 for storm events > WQv Bioretention Area #2 Drainage Data Subwatershed description Drainage area Impervious surface Block A (partial Lot N -Bldg A3 rooftop & garage ramp)0.55 acre 0.42 acre Future development 0.37 acre 0.46 acre Approved TOTAL 0.92 acre 0.88 acre -Bioretention area #2 flows to Storm Pond #1 for storm events > WQv Note that some stormwater practices are in series. For larger storm events, the rooftop infiltration system discharges to GW#1, bioretention area #1 discharges to GW#2, and bioretention area #2 discharges to storm pond #1.