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Home My WebLink AboutSD-23-10 - Supplemental - 0255 Kennedy Drive (40)Vermont Operational Stormwater Permit ‐ Standards Compliance Workbook The name above will appear on all the discharge point tabs Site Summary Total SN1 SN2 SN3 SN4 SN5 SN6 SN7 SN8 SN9 New 7.46 0.00 0.00 0.00 7.46 0.00 0.00 0.00 0.00 0.00 Redeveloped 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Existing 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Previously Authorized 6.22 0.00 0.00 0.00 6.22 0.00 0.00 0.00 0.00 0.00 Total 13.68 0.00 0.00 0.00 13.68 0.00 0.00 0.00 0.00 0.00 Site Area 19.20 0.00 0.00 0.00 19.20 0.00 0.00 0.00 0.00 0.00 0.00000 0.00000 0.00000 44.46039 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 ‐73.07617 0.00000 0.00000 0.00000 0.00000 0.00000 Receiving Water Potash Brook Recharge Total SN1 SN2 SN3 SN4 SN5 SN6 SN7 SN8 SN9 Required 0.2953 0.0000 0.0000 0.0000 0.2953 0.0000 0.0000 0.0000 0.0000 0.0000 Provided 1.4440 0.0000 0.0000 0.0000 1.4440 0.0000 0.0000 0.0000 0.0000 0.0000 Standard met?Yes n/a n/a n/a Yes n/a n/a n/a n/a n/a Notes: Water Quality Total SN1 SN2 SN3 SN4 SN5 SN6 SN7 SN8 SN9 Required 0.6136 0.0000 0.0000 0.0000 0.6136 0.0000 0.0000 0.0000 0.0000 0.0000 Provided 1.9057 0.0000 0.0000 0.0000 1.9057 0.0000 0.0000 0.0000 0.0000 0.0000 Standard met?Yes n/a n/a n/a Yes n/a n/a n/a n/a n/a Notes: Channel ProtectionImperviousProject Name Do not fill this tab out, apart from the project name and notes. It will auto‐populated based on the values on the discharge point tabs. Discharge points (SN) will only show on the summary if an area has been entered on that tab. Areas listed below are those seeking permit coverage. Hillside @ O'Brien Farm Latitude Longitude A minimum WQ V of 0.2" (P*R V ) is required for sites with low impervious (<16.67%). This calculation has not been incorporated into this workbook. Designers should check that the minimum WQ V has been met for their site. Last Updated 8/28/2018 Summary: Page 3 of 9 Vermont Operational Stormwater Permit ‐ Standards Compliance Workbook Total SN1 SN2 SN3 SN4 SN5 SN6 SN7 SN8 SN9 Standard Applies?000Yes 00000 Waiver n/a Method n/a n/a n/a Hydrologic Condition Method n/a n/a n/a n/a n/a HCV 1.0375 0.0000 0.0000 0.0000 1.0375 0.0000 0.0000 0.0000 0.0000 0.0000 TV Provided 1.4440 0.0000 0.0000 0.0000 1.4440 0.0000 0.0000 0.0000 0.0000 0.0000 Notes: Overbank Flood Protection SN1 SN2 SN3 SN4 SN5 SN6 SN7 SN8 SN9 Standard Applies?000Yes 00000 Pre‐Dev Q (cfs) 3.46 Routed, Post‐Dev Q (cfs) 1.23 Waiver n/a Notes: Extreme Flood Protection SN1 SN2 SN3 SN4 SN5 SN6 SN7 SN8 SN9 Standard Applies?Yes Pre‐Dev Q (cfs) 18.09 Routed, Post‐Dev Q (cfs) 14.54 Waiver n/a Notes: General Notes Last Updated 8/28/2018 Summary: Page 4 of 9 Vermont Operational Stormwater Permit ‐ Standards Compliance Workbook Last Updated 8/28/2018 Summary: Page 5 of 9 Vermont Operational Stormwater Permit ‐ Standards Compliance Workbook General Discharge Point Information Project name Discharge point serial number (e.g. S/N 001) Name of receiving water Latitude (decimal degrees to five decimal places) Longitude (decimal degrees to five decimal places) Precipitation Data NOAA Atlas 14 Storm WQ Storm 1 yr, 24 hr 10 yr, 24 hr 100 yr, 24 hr Precipitation (inches) 1.00 1.90 3.25 4.85 Drainage Area Information Landuse A B C D Total Grass 0.190 0.190 3.300 0.000 3.680 Meadow 0.000 0.000 0.000 0.000 0.000 Woods 4.500 4.500 0.300 0.000 9.300 Existing Impervious 0.000 0.000 0.000 0.000 0.000 Impervious previously authorized under 2002 VSMM (not included in calculations)6.220 Total Pre Site Area 19.200 % Landuse A B C D Total Grass 1.110 1.110 3.300 0.000 5.520 Meadow 0.000 0.000 0.000 0.000 0.000 Woods 0.000 0.000 0.000 0.000 0.000 New Impervious 3.730 3.730 0.000 0.000 7.460 57.5% Existing for Permit Coverage (Treated to New Standards) 0.000 0.000 0.000 0.000 0.000 0.0% Existing Impervious Not for Permit Coverage 0.000 0.0% Redeveloped Impervious 0.000 0.0% 6.220 Total Site Area 19.200 Total Impervious for Permit Coverage 13.680 Net Reduced Impervious 0.000 0.0% Reduced Existing Impervious (for redevelopment)0.000 0.0% Average Catchment Slope, Y (%) Hydraulic Length, l (ft) Pre Development 9.1 1275.00 Post Development 9.1 1275.00 Information for Calculating TC by the Watershed Lag Method Hillside @ O'Brien Farm 4 Potash Brook 44.46039 ‐73.07617 * Preciptation values shall be obtained from Pre Development Land Use (acres) Post Development Land Use (acres) Impervious previously authorized under 2002 VSMM Last Updated 8/28/2018 SN4: Page 6 of 9 Vermont Operational Stormwater Permit ‐ Standards Compliance Workbook Runoff Calculations 1 yr, 24‐hr 10 yr, 24‐hr 100 yr, 24‐hr 0.0927 0.4243 1.0375 1.1302 2.2215 3.6694 Tier 1/Runoff Reduction Practices Practice TV (ac‐ft) TV (ac‐ft) Infiltration Basin 1.444 Runoff Reduction Calculations Standard Re WQ CP QP10 QP100 TV Required (ac‐ft)0.2953 0.6136 1.0375 1.7972 2.6320 TV Provided (ac‐ft)1.4440 1.4440 1.4440 1.4440 1.4440 TV Remaining (ac‐ft)0.0000 0.0000 0.0000 0.3532 1.1880 Standard met with HCM?Yes Yes Yes No No Post‐Development CN n/a 95 91 88 87 CNadj n/a n/a n/a 67 72 Pre‐Development CN n/a n/a 63 59 56 Groundwater Recharge Standard (Re)1 Standard Applicable? ReV 0.2953 Standard met with Tier 1 Practices? Yes Recharge Notes: Recharge is met via existing Infiltration Basin A Predevelopment runoff volume (ac‐ft) Pre‐routed, post development runoff volume (ac‐ft) List all Tier 1 practices below with the associated treatment volume (TV ). The T V will be applied to all treatment standards, except for Green Roofs, which do not receive recharge or water quality credit. Please include the appropriate STP worksheet(s) with the application. Practice Yes No Last Updated 8/28/2018 SN4: Page 7 of 9 Vermont Operational Stormwater Permit ‐ Standards Compliance Workbook Water Quality Treatment Standard (WQ)11 (ac‐ft) Apply Reduction? WQV ‐ New & Existing 0.6136 0.0% WQV ‐ Redevelopment 0.0000 0.0% Total WQV 0.6136 WQV met with Tier 1 practices 0.6136 1 WQV to be met with Tier 2 and/or Tier 3 practices 0.0000 WQV Provided (ac‐ft)Tier 0.1068 Tier 2 0.3549 Tier 2 Total WQV Provided (ac‐ft)0.4617 ac‐ft Is the WQV Standard met?Yes Water Quality Notes: Channel Protection Standard (CP)21 Standard Applicable? Standard Met with HCM?Yes Provide Extended Detention for:n/a ac‐ft Warm or Cold Water Fishery?→Provide: FALSE Extended Detention STP: CNAdj n/a 7.2 (Watershed Lag Method) Channel Protection Notes: The channel protection standard has been fully met with hydrologic condition method. Additional treatment of the 1 year storm is not required. 24 hours of extended detention See the Vermont Water Quality Standards for warm and cold water designations OR The Alternative Extended Detention Method (§2.2.5.4) is being used. Gravel Wetlands #1 and #2 Modeling Info: When demonstrating CP compliance with extended detention in a hydrologic model, use the CN and TC below if the practice being modelled is not a Tier 1 practice. The CN Adj takes into account the reduction in runoff volume achieved through Tier 1 practices. The T C is calculated by the watershed lag method using CNAdj as CN'. Post Development TC (min) Gravel Wetlands #1 and #2 provide minimum 1" orifices for stormwater draining to each practice. % Net Reduction % Removed Existing Impervious (Redevelopment) Is all impervious treated by disconnection? NOTE: Please include a copy of the appropriate STP worksheet(s) with the application. Tier 2 & 3 Water Quality Practice Gravel Wetland Gravel Wetland Yes No Cold Warm No Yes (WQv met) No Yes No Yes Last Updated 8/28/2018 SN4: Page 8 of 9 Vermont Operational Stormwater Permit ‐ Standards Compliance Workbook Overbank Flood Protection (QP10)1 Standard Applicable? Standard Met with HCM?No STP used: Pre‐development peak discharge rate (cfs) 3.46 Pre‐routed, post‐development peak discharge rate (cfs) Routed, post‐development peak discharge rate (cfs) 1.23 Pre‐Development CN (Flow‐ weighted composite)59 22.7 CNAdj 67 18.4 Overbank Flood Notes: Extreme Flood Protection (QP100)1 Standard Applicable? Standard Met with HCM?No STP used: Pre‐development peak discharge rate (cfs) 18.09 Pre‐routed, post‐development peak discharge rate (cfs) Routed, post‐development peak discharge rate (cfs) 14.54 Pre‐Development CN (Flow‐ weighted composite)56 24.6 CNAdj 72 16.3 Extreme Flood Notes: Pre Development TC (min)(Watershed Lag Method)Post Development TC (min) The extreme standard has not been fully met. Provide additional STPs to ensure post development peak runoff does not exceed pre development peak runoff for the 100 yr, 24 hour storm event. Wet Pond, Infiltration Basin, Gravel Wetlands Modeling Info: When demonstrating Q P100 compliance in a hydrologic model, use the following CN and T C below, if the practice used to meet QP100 is not a Tier 1 practice. The CN Adj takes into account the reduction in runoff volume achieved through runoff reduction practices. The T C is calculated by the watershed lag method using CN Adj as CN'. The QP10 standard has not been fully met. Provide additional STPs to ensure post development peak runoff does not exceed pre development peak runoff for the 10 yr, 24 hour storm event. Wet Pond, Infiltration Basin, Gravel Wetlands Modeling Info: When demonstrating Q P10 compliance in a hydrologic model, use the following CN and T C below, if the practice used to meet QP10 is not itself a Tier 1 practice. The CN Adj takes into account the reduction in runoff volume achieved through Tier 1 practices. The T C is calculated by the watershed lag method using CNAdj as CN'. Pre Development TC (min)(Watershed Lag Method)Post Development TC (min) Yes No Yes No Last Updated 8/28/2018 SN4: Page 9 of 9 STP Selection Matrix Project Name: Version 5/8/2017 Discharge Point: Step 1: Is the Water Quality Treatment Standard entirely managed with one or more of the following Tier 1 practices? Infiltration Basins/ Trenches/ Chambers Simple Disconnection Drywells Disconnection to Filter Strips and Vegetated Buffers Bioretention (designed to infiltrate) Dry Swales (designed to infiltrate) Filters (designed to infiltrate)Permeable Pavement1 Reforestation1 2 1. These practices do not require specific justification due to feasibility limitations Step 2: Assess the feasibility of using Tier 1 Practices Infiltration Basin/ Trench/ ChamberDrywellBioretention (infiltrating)Simple DisconnectionDisconnection to Filter Strips or Vegetated BufferDry Swales (infiltrating)Filters (infiltrating)Practice Availability for Water Quality Treatment?Not Feasible Not Feasible Yes Yes Yes Yes Yes Response Available Available Available n/a n/a Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available Available n/a n/a n/a Available Available n/a n/a n/a n/a n/a Available n/a n/a n/a n/a n/a n/a n/a Available n/a n/a Available n/a Available n/a n/a Available Available Available Available Available n/a n/a Available Available Not Feasible Not Feasible n/a n/a n/a n/a n/a Not Feasible n/a n/a n/a n/a n/a n/a Tier 1 Practices are available to meet the Water Quality Treatment Standard. If using one of these practices, stop here. If additional site constraints exist other than those listed here, proceed to Step 3. Hillside @ O'Brien Farm S/N 004 Complete the matrix below in its entirety for each drainage area. Proceed to Step 2 Seasonal high water table or bedrock would be less than 3 feet from the bottom of the practice. Is the slope of the filter strip greater than 15% Is the slope of the vegetated buffer greater than 8% Are natural slopes where an infiltration trench or basin could be sited greater than 15% Bottom of practice would be below seasonal high water table Seasonal high water table or bedrock would be less than 1 foot from the bottom of the practice. Practice Availability Based on RestrictionsFeasibility Restriction Do underlying soils have an infiltration rate of less than 0.2 inches per hour, as confirmed by field geotechnical tests or are classified as Hydrologic Soil Group D according to the NRCS Soil survey? Will runoff to the practice include discharge from a hotspot landuse or activity? Is the site a brownfield or contaminated site where infiltration is restricted or where infiltration would increase the threat of pollution migration, as confirmed in writing by the Department’s Waste Management and Prevention Division? Is the slope of the vegetated buffer greater than 15% Yes No Yes No Yes No Yes No Yes No Yes Yes No No Yes No No Yes No Yes No Yes STP Selection Matrix ‐ SN1 Page 1 of 2 Available Available Available n/a n/a Available Available Available Available Available n/a n/a Available Available Available Available Available n/a n/a Available Available Available Available Available n/a n/a Available Available Available Available Available n/a n/a Available Available Available Available Available Available Available Available Available Step 3: Other feasibility constraints for remaining Tier 1 and Tier 2 practices 1 Provide written feasibilty justification below or list attachments Will the practice be located within 200 feet of non‐ transient non‐community groundwater source? Will the practice be located within 75 feet down‐ gradient of a wastewater disposal area system, within 35 feet up‐gradient or 75 feet down‐ gradient of a wastewater disposal system? Will the practice be located within 150 feet of a drinking water source located in an unconfined aquifer? Will the practice be located within 100 feet of a drinking water source located in bedrock or a confined unconsolidated aquifer? Will the practice be located within Zone 1 or Zone 2 of a public community groundwater source protection area? Stop. No further justification is needed. If the the use of a Tier 1 or Tier 2 Practice is infeasible for reasons beyond those listed in Step 2 of the STP Selection Matrix, a designer may submit site specific detailed feasibility justification that such practices are not feasible following the guidance in Section 2.2.4.1 of the 2017 VSMM. Only after completion of the STP Selection Matrix and determination that Tier and Tier 2 Practices are infeasible shall a designer consider Tier 3 Practices or existing stormwater infrastructure for meeting the Water Quality Treatment Standard (WQTS) on the project site. Is the Water Quality Treatment Standard entirely managed with Tier 2 Practices? If, following completion of Step 2 of the STP Selection Tool there are no Tier 1 Practices available for use on the project site, designers shall consider the use of Tier 2 practices for treatment of the Water Quality Treatment Standard. Will the practice violate any restrictions of the Vermont Wastewater and Potable Water Supply Rules, or their replacement? Yes Yes Yes No Yes No Yes No Yes Yes No No No No STP Selection Matrix ‐ SN1 Page 2 of 2