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Home My WebLink AboutDurham Tech Facilities Building - 2018.07.24 SNAP Version 4.0 DRAFT FINALProject Information Project Name:Durham Tech Facilities Building Submission Date: Project Area (ft2):1,093,052 ft2 Disturbed Area (ft2):1,093,052 ft2 Development Land Use Type:Institutional Development Activity Type:Development ‐ New Designated Downtown Area?no Project Location/Address: County: Local Jurisdiction:Durham Project Latitude Coordinates:N Project Longitude Coordinates:W Precipitation Station:Durham Physiographic Region: Nutrient Management Watershed:Jordan Lake Subwatershed:Jordan ‐ Upper New Hope Phosphorus Delivery Zone:Jordan Zone 9 Nitrogen Delivery Zone:Jordan Zone 10 Project Designer and Contact Phone Number / Email: Part of Common Development Plan?no Project Owner Type:State non‐NCDOT Project Description: Project Area Land Cover Characteristics Roof 1.18 0.11 13,241 Roadway 1.64 0.34 Parking/Driveway/Sidewalk 1.42 0.18 55,937 50,508 Protected Forest 0.97 0.03 225,372 225,372 Other Pervious/Landscaping 2.48 1.07 811,743 803,931 CUSTOM LAND COVER 1 CUSTOM LAND COVER 2 CUSTOM LAND COVER 3 LAND TAKEN UP BY SCM 1.18 0.11 SIMPLE METHOD Stormwater Runoff Volume Generated, V Runoff Coefficient, R v V =Pj * Rv * (P/12) * A Rv = 0.05 + (0.009 *I) where A = drainage area (ft2) where I = percent impervious (%) Pj = Average Annual Pollutant Load, L P = L = where C = Pre‐Project: Post‐Project: A = 25.0930 ac A =25.0930 ac P = 47.81 in. P =47.81 in. V = 376489 ft3 V =401700 ft3 I = 5%I = 6% Rv = 0.10 Rv = 0.10 Pj = 0.9 Pj = 0.9 CTN = 1.78 mg/L CTN = 1.73 mg/L CTP = 0.51 mg/L CTP = 0.48 mg/L LTN = 41.88 lb/yr LTN = 43.35 lb/yr LTP = 11.94 lb/yr LTP = 11.95 lb/yr Net Change of Land Covers (ft2):13,241 Total Pre‐Project Calculated Area (ft2): Total Post‐Project Calculated Area (ft2): Total Project Area Entered (ft2):1,093,052 1,093,052 1,093,052 LAND COVER AREA CHECK PROJECT AREA LAND COVERS TN EMC (mg/L) TP EMC (mg/L) Post‐ Project Area (ft2) Pre‐ Project Area (ft2) event mean concentration (mg/L) Equations Used and Project Area Calculations fraction of rain events with runoff average annual rainfall depth (in) (Pj * Rv * (P/12 )) * (C * A * 2.72) 3. SCM Characteristics Catchment ID 1 1 1 SCM ID 101 102 103 Type of SCM Sand Filter per MDC ‐ Closed Predominant hydrologic soil group at SCM location B SCM Description Design Storm Size (inches/24hrs) 1.00 Percent of Full Size 100% Hydrologic Value ‐ Percent Annual Effluent 90% Hydrologic Value ‐ Percent Annual Overflow 10% Hydrologic Value ‐ Percent Annual ET/Infiltrated 0% SCM Effluent TP EMC (mg/L)0.12 SCM Effluent TN EMC (mg/L)1.33 SCM Land Cover TP EMC (mg/L)0.11 SCM Land Cover TN EMC (mg/L)1.18 Drains to SCM ID 0 SCM Characteristics 3. SCM Characteristics Catchment Routing (Source Catchment)Catchments Draining to SCM 101 Catchments Draining to SCM 102 Catchments Draining to SCM 103 Catchment 1 Catchment 2 Catchment 3 Catchment 4 Catchment 5 Catchment 6 SCM ID:101 102 103 SCM Drainage Area Land Covers Area Draining Directly to SCM 101 (ft2) Area Draining Directly to SCM 102 (ft2) Area Draining Directly to SCM 103 (ft2) Roof 13,241 Roadway Parking/Driveway/Sidewalk Protected Forest Other Pervious/Landscaping CUSTOM LAND COVER 1 CUSTOM LAND COVER 2 CUSTOM LAND COVER 3 LAND TAKEN UP BY SCM TOTAL AREA DRAINING TO SCM (ft2):13,241 0 0 CATCHMENT AREA (ft2):13,241 3. SCM Characteristics Catchment ID SCM ID Type of SCM Predominant hydrologic soil group at SCM location SCM Description Design Storm Size (inches/24hrs) Percent of Full Size Hydrologic Value ‐ Percent Annual Effluent Hydrologic Value ‐ Percent Annual Overflow Hydrologic Value ‐ Percent Annual ET/Infiltrated SCM Effluent TP EMC (mg/L) SCM Effluent TN EMC (mg/L) SCM Land Cover TP EMC (mg/L) SCM Land Cover TN EMC (mg/L) Drains to SCM ID SCM Characteristics 3. SCM Characteristics Catchment Routing (Source Catchment) Catchment 1 Catchment 2 Catchment 3 Catchment 4 Catchment 5 Catchment 6 SCM ID: SCM Drainage Area Land Covers Roof Roadway Parking/Driveway/Sidewalk Protected Forest Other Pervious/Landscaping CUSTOM LAND COVER 1 CUSTOM LAND COVER 2 CUSTOM LAND COVER 3 LAND TAKEN UP BY SCM TOTAL AREA DRAINING TO SCM (ft2): CATCHMENT AREA (ft2): Total Land Use Area Treated By All SCMs (ft2) Allowable Total Land Use Area to be Treated Based on Post‐Project Areas (ft2) Post‐Project Untreated Land Area (ft2) 13,241 13,241 0 000 0 50,508 50,508 0 225,372 225,372 0 803,931 803,931 000 000 000 000 13,241 1,093,052 1,079,811 Project Summary1,093,052ft225.0930acres1,093,052ft225.0930acres89% 97%0.82 2.2020.58 55.2011.97 43.718.00‐8.63 ‐11.86‐8.61 ‐11.50‐7.66 ‐11.15 Nutrient Export SummaryPre‐Project Whole Site ConditionsPost‐Project Whole Site without SCMsPost‐Project Whole Site with SCMsPost‐Project SCM‐Treated AreaPost‐Project Untreated Area5.1% 5.8% 5.8% 100.0% 4.7%5.1% 5.8% 5.8% 100.0% 4.7%376,489 401,700 401,700 45,105 356,5950% 7% 7%1.78 1.73 1.74 1.31 1.8041.88 43.35 43.713.69 40.011.67 1.73 1.74 12.15 1.610% 4% 4%0.51 0.48 0.48 0.12 0.5211.94 11.95 11.970.33 11.640.48 0.48 0.48 1.10 0.470% 0% 0%Local Jurisdiction:DurhamTotal Phosphorus % Change (relative to pre‐D)Total P Load Reduction Needed (lb/yr):Nitrogen Loading Rate Target (lb/ac/yr):Nitrogen Load Target at Site (lb/yr):Nitrogen Load Leaving Site w/SCMs (lb/yr):N Offsite Buy‐Down Threshold Load (lb/ac/yr):Total N Load Reduction Needed (lb/yr):State non‐NCDOTSubmission Date:Total Phosphorus Load Leaving Site (lb/yr)Total Phosphorus Loading Rate (lb/ac/yr)Percent Built‐Upon Area (BUA) (%)Annual Runoff Volume (ft3)Annual Runoff % Change (relative to pre‐D)Total Nitrogen EMC (mg/L)Total Nitrogen Load Leaving Site (lb/yr)Development Activity Type:Percent Impervious (for runoff calculation) (%)Total Phosphorus EMC (mg/L)Phosphorus Loading Rate Target (lb/ac/yr):Phosphorus Load Target at Site (lb/yr):Phosphorus Load Leaving Site w/SCMs (lb/yr):P Offsite Buy‐Down Threshold Load (lb/ac/yr):Durham Tech Facilities BuildingTotal Nitrogen Loading Rate (lb/ac/yr)Total Nitrogen % Change (relative to pre‐D)Project Name: Project Area (ft2):Disturbed Area (ft2):County:Development Land Use Type:P Load Treatment Balance at Lake (lb/yr): N Load Treatment Balance at Lake (lb/yr):Nutrient Management Watershed:Phosphorus Delivery Zone:N Load Treatment Balance at Site (lb/yr):Phosphorus Delivery Factor (%):P Load Treatment Balance at Site (lb/yr):Nitrogen Delivery Factor (%):Owner Type:Designated Downtown Area?Subwatershed:Nitrogen Delivery Zone:InstitutionalnoJordan ‐ Upper New HopeJordan Zone 10Jordan LakeJordan Zone 9Development ‐ New SCM/Catchment SummaryVolume Reduction (%)TN Out (mg/L) TP Out (mg/L)TN Out (lbs/ac/yr)TP Out (lbs/ac/yr)TN Reduction (%)TP Reduction (%)0.00% 1.31 0.1212.15 1.10‐11.15% ‐7.91%0.00% 1.31 0.1212.15 1.10‐11.15% ‐7.91%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%0.00% 0.00 0.000.00 0.000.00% 0.00%602: NA603: NA501: NA502: NACatchment 6503: NA601: NACatchment 3Catchment 4Catchment 5202: NA203: NA301: NA302: NA303: NA401: NA402: NA403: NA102: NA101: Sand Filter per MDC ‐ ClosedSCM ID and Type103: NA201: NACatchment 1Catchment 2SCM rows in red have a data entry error for the SCM that makes an error in the calculation. Type of SCM:Sand Filter per MDC ‐ ClosedArea Treated by SCM (ft2):13,241Percent Impervious of Contributing Watershed (%): 100%Runoff Coefficient, Rv: 0.95Inflow Volume (ft3):45,105Incoming Total Nitrogen Concentration (mg/L): 1.18Annual Incoming Total Nitrogen Load (lbs): 3.32Incoming Total Phosphorus Concentration (mg/L): 0.11Annual Incoming Total Phosphorus Load (lbs): 0.31Total Volume Leaving SCM (ft3):45,105Outgoing Total Nitrogen Concentration (mg/L): 1.31Annual Outgoing Total Nitrogen Load (lbs): 3.69Outgoing Total Phosphorus Concentration (mg/L): 0.12Annual Outgoing Total Phosphorus Load (lbs): 0.33Annual Volume Reduction by SCM (ft3):0Annual Volume Reduction by SCM (%): 0%Annual Total Nitrogen Reduction by SCM (%): ‐11.15%Annual Total Nitrogen Reduction by SCM (lb): ‐0.37Annual Total Phosphorus Reduction by SCM (%): ‐7.91%Annual Total Phosphorus Reduction by SCM (lb): ‐0.02Rv = 0.05 + (0.009 *I), where I = percent impervious (%)Supporting CalculationsV = Pj * Rv * A * (P/12), where A = area of catchment (ft2) P = average annual rainfall depth (in)CATCHMENT 1, SCM 101L = ((P * Pj * Rv) ÷ (12 )) * (C * A * 2.72) where L = annual pollutant loading (lbs) Pj = fraction of rain events that produce runoff (dec) C = event mean concentration of pollutant (mg/L)Lout = Vout * EMCout * 6.243ᴇ‐5 where Vout = outflow volume (ft3), EMCout = effluent median concentration (mg/L)Vout = Vin * (1 ‐ Red) where Vin = inflow volume (ft3) Red = volume reduction by SCM (%)