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Home My WebLink AboutSP-23-11 - Supplemental - 0113 Garden Street (12)STORMWATER MANAGEMENT SUMMARY City Center March 17, 2023 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)UNDER CONSTRUCTION 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) not constructed Catamount Run – Block A (Lot N)PROPOSED 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 UNDER CONSTRUCTION Bio-retention area #1 (BR#1)UNDER CONSTRUCTION Bio-retention area #2 (BR#2)PROPOSED 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 Future development 0.56 acre 0.60 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 1.98 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 Future development 0.90 acre 1.23 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 Future development 0.52 acres 0.52 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. 302.5302.5 302.5302.5 302.5 LLLL L LL FM FMFMFMFM3103093093103113113103053123123143153143123 1 1 3113113113103103123123 1 2 31 2 298308 308305305308305300 300 300305308298 299305310 3 1 0 31031 0 309311310308309307309312314314DDDRDRDRDRDRD FM 305307UUUUUU312311311311310310 3 1 0 3 10 311312MARKET STLOT M410' WIDE SHARED USE PAVED PATH6' WIDE CONCRETE SIDEWALKEX. SIDEWALKEXISTING BOXSEE PLANS BY WAGNERHODGSON FOR LAYOUT ANDLANDSCAPING IN MINI PARKGARDEN STREETLOT M5110.2' 1 0 0 .0 '209.1'NEW CONCRETE SIDEWALK6' C ON CR E TE S I D EW A LKPROPOSED 61 UNITRESIDENTIAL BUILDINGBIKE RACKS(4 HOOPS)5' CONCRE T E S I D EW A L K20' R.30' R.10' R.20' R.22'20'20' R.CONCRETE CURBCONC R E T E CU R B RAMPTRASH & RECYCLING CONTAINERSTO BE LOCATED IN PARKING GARAGEBLDG B1MARKET STREETCI T Y H A L L / SCHOO L DR I V EWAY FU TURE PUB L IC S TREE T 3 2 4 'LOT B-B2LOT B-B1TRANSECT T-4TRANSECT T-5TRANSECT T-4TRANSECT T-5BUILDING A2BUILDING A1BUILDING A3FU TUR E PUB L IC S TREE TBIOERETENTION AREAPOCKET PLAZAEXISTING PAVED DRIVECLASS 2 WETLANDEXISTING PAVED PARKINGEXISTINGPAVEDPARKINGEL E CELEC ELECSOUTH BURLINGTON CITY CENTERCATAMOUNT RUN - PH.IIMARKET ST. & GARDEN ST. SOUTH BURLINGTONDateSheet numberScaleCheckedDrawnSurvey DateRevisionByThese plans shall only be used for the purpose shown below:Sketch/ConceptFinal Local ReviewConstructionRecord Drawing01-25-23KBABRB&GTHE SNYDER GROUP, INC.4076 SHELBURNE ROAD, SUITE 6SHELBURNE, VERMONT 05482802-985-5722WWW.SNYDERHOMESVT.COMAS SHOWNSTORM POND 1STLOT N (BLOCK A)STORMWATER EXHIBITGRAPHIC SCALE3003060120(IN FEET)1" = 30 ft.#155 MARKET STREETMIXED USE BUILDINGLOT BBUILDING B2LOT BBUILDING B1#112 GARDEN STREET#303 MARKETSTREETBIO-RETENTION AREAOVERFLOWS TO STORM PONDTO GW#5 TO INFILTRATIONSYSTEM (OVERFLOWTO GW#1)FROM CITY HALL / SCHOOLDRIVEWAY & BLOCK B (TOSTORM POND)FROM OFFSITETO STORM PONDTO GW#5 PORTION BUILDING A1ROOFTOP TO GW#5PORTION BUILDING A1 ROOFTOPTO INFILTRATION SYSTEMBUILDING A1 ROOFTOPTO BIORETENTION AREARAMP TOBIORETENTION AREA(VIA PUMP STATION)LOT N DRAINAGE AREATO STORM PONDPRETREATMENT UNITFOR OFFSITE RUNOFFPRETREATMENT UNITFOR SITE DEVELOPMENTRUNOFF03-17-23MAINTENANCE PLANGENERALINSPECT SYSTEM ANNUALLY IN ACCORDANCE WITH DEC PERMIT REQUIREMENTS. SUBMITCOMPLETED ANNUAL INSPECTION FORM TO DEC STORMWATER MANAGEMENT PROGRAM BYJULY 1 5TH OF EACH YEAR.BIORETENTION-INSPECT SEASONALLY TO ENSURE THAT VEGETATION IS WELL ESTABLISHED AND REMOVEWEEDS AND INVASIVE SPECIES. ENSURE THAT NO VEGETATION IS RESTRICTING ORCONCENTRATING THE FLOW PATH THROUGH THE SYSTEM.-ANNUALLY INSPECT FOREBAY SEDIMENT DEPTH AND REMOVE AND PROPERLY DISPOSEWHEN SEDIMENT ACCUMULATION EXCEEDS 12" AS MEASURED ON THE FIXED VERTICALSEDIMENT MARKER.-IF STANDING WATER REMAINS FOR GREATER THAN 72 HOURS AFTER A PERIOD OF HEAVYRAINFALL INSPECT RISERS AND CLEANOUTS FOR BLOCKAGES, AND REMOVE ANYBLOCKAGE DISCOVERED.-ANNUALLY INSPECT INLETS, OUTLETS, AND SURFACE AREA TO ENSURE THAT NOVEGETATION IS RESTRICTING OR CONCENTRATING THE FLOW PATH THROUGH THESYSTEM.-DURING WINTER MONTHS SNOW SHALL NOT BE PUSHED INTO THE BIORETENTION SYSTEM.GRAVEL WETLAND-INSPECT SEASONALLY TO ENSURE THAT VEGETATION IS WELL ESTABLISHED AND REMOVEWEEDS, INVASIVE SPECIES, DECAYING VEGETATION, LITTER AND DEBRY. ENSURE THAT NOVEGETATION IS RESTRICTING OR CONCENTRATING THE FLOW PATH THROUGH THESYSTEM.-IF STANDING WATER REMAINS FOR GREATER THAN 72 HOURS AFTER A PERIOD OF HEAVYRAINFALL INSPECT RISERS AND CLEANOUTS FOR BLOCKAGES, AND REMOVE ANYBLOCKAGE DISCOVERED.-DURING WINTER MONTHS SNOW SHALL NOT BE PUSHED INTO THE BIORETENTION SYSTEM.WET POND-ANNUALLY INSPECT INLETS AND OUTLET FOR VEGETATION THAT IS RESTRICTING ORCONCENTRATING FLOW PATH THROUGH THE SYSTEM. REMOVE ANY VEGETATIONOBSTRUCTING FLOW.CATCHBASINS/MANHOLES /SWIRL SEPARATORS-INSPECT ANNUALLY. REMOVE SEDIMENT WHEN SEDIMENT ACCUMULATION REACHES 50%OF STORAGE CAPACITY OF THE SUMP.-ANNUALLY INSPECT FRAME, GRATE, AND RISERS FOR DETERIORATION.