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Home My WebLink AboutSW5210202_SIA 05-10-2021_20210510 SITE Zpv!dsfbufe!uijt!QEG!gspn!bo!bqqmjdbujpo!uibu!jt!opu!mjdfotfe!up!qsjou!up!opwbQEG!qsjoufs!)iuuq;00xxx/opwbqeg/dpn* Zpv!dsfbufe!uijt!QEG!gspn!bo!bqqmjdbujpo!uibu!jt!opu!mjdfotfe!up!qsjou!up!opwbQEG!qsjoufs!)iuuq;00xxx/opwbqeg/dpn* Zpv!dsfbufe!uijt!QEG!gspn!bo!bqqmjdbujpo!uibu!jt!opu!mjdfotfe!up!qsjou!up!opwbQEG!qsjoufs!)iuuq;00xxx/opwbqeg/dpn* ZJ!4 DC!3 EJ!3 QJQF!5 QJQF!4 QJQF!3 FY/!QJQF QJQF!2 SFQMBDFNFOU ZJ!5 QJQF!6 QJQF!7 QJQF!9 QJQF!8 QJQF!21 QJQF!: Last Modified 5/23/03 Tar-Pamlico Stormwater Rule 15A NCAC 2B .0258 Piedmont of the Tar-Pamlico River Basin: Includes Oxford, Henderson, Rocky Mount and Tarboro as well as Franklin, Nash and Edgecome Counties BMP Removal Calculation Worksheet (Automated) Project Name:Franklin Co. 911 Center Date: 3/23/2021 By:MMGChecked By: Directions: > It may be advantageous to split the development into separate catchments to be handled by separate BMPs. The tables below allow the development to be split into as many as three catchments, and can be copied for greater than three. NOTE: Unless runoff flowing onto the development from offsite is routed separately around or through the site, the offsite catchment area draining in must be included in the acreage values of the appropriate land use(s) and treated. > Above each table: Enter the catchment acreage in the top green blank. Based on a comparison of the post-development TN and TP export coefficients you calculated above to the rule requirements of 4.0 lb/ac/yr TN and 0.4 lb/ac/yr TP, select BMP(s) from the list for treating the catchment runoff. Enter the chosen BMP(s) nutrient removal rates in the green blanks. If more than one BMP is to be used in series, the combined removal rates will be calculated automatically in the blue blanks. > Catchment Tables: Enter the acres of each type of land cover in the green boxes. The spreadsheet will calculate all of the light blue boxes. NOTE: Compare the Total Catchment Acreage for the Development (final table) to the value you established in the pre-BMP worksheet tables, and also to the site plans, for consistency. All of these values need to be the same TNTPDesign Standard Wet Detention Pond NC BMP Manual 2540 BMP Stormwater Wetland NC BMP Manual 4035 Nutrient Sand Filter NC BMP Manual 3545 Removal Bioretention NC BMP Manual 3545 Rates Grass Swale NC BMP Manual 2020 Vegetated Filter Strip w/ NC BMP Manual 2035 Level Spreader Dry Detention NC BMP Manual 1010 Catchment 1: Total acreage of catchment 1 =ac 14.32 First BMP's TN removal rate =%First BMP's TP removal rate =% 2540 Second BMP's TN removal rate =%Second BMP's TP removal rate =% Third BMP's TN removal rate =%Third BMP's TP removal rate =% TOTAL TN REMOVAL RATE =%TOTAL TP REMOVAL RATE =% 2540 (1)(2)(3)(4)(5)(6)(7) Type of Land CoverCatchment S.M. Formula Average EMC of Column Average EMC of Column Acreage(0.46 + 8.3I)TN (mg/L)(2) * (3) * (4)TP (mg/L)(2) * (3) * (6) Transportation impervious 1.381.422.605.090.190.37 Roof impervious 0.271.421.950.750.110.04 Managed pervious 10.941.421.4222.020.284.34 Wooded pervious 1.621.420.942.160.140.32 Area taken up by BMP 0.111.421.950.300.110.02 Pre-BMP TN Pre-BMP TP Fraction Impervious (I) = 0.1230.325.09 Load (lb/yr) =Load (lb/yr) = Pre-BMP TN Pre-BMP TP Total Area of Development = 14.322.120.36 Export (lb/ac/yr) =Export (lb/ac/yr) = Post-BMP TN Post-BMP TP 22.743.06 Load (lb/yr) =Load (lb/yr) = Post-BMP TN Post-BMP TP 1.590.21 Export (lb/ac/yr) =Export (lb/ac/yr) = Last Modified 5/23/03 Tar-Pamlico Stormwater Rule 15A NCAC 2B .0258 Catchment 2: Total acreage of catchment 2 =ac 13.47 First BMP's TN removal rate =%First BMP's TP removal rate =% Second BMP's TN removal rate =%Second BMP's TP removal rate =% Third BMP's TN removal rate =%Third BMP's TP removal rate =% TOTAL TN REMOVAL RATE =%TOTAL TP REMOVAL RATE =% 00 (1)(2)(3)(4)(5)(6)(7) Type of Land CoverCatchment S.M. Formula Average EMC of Column Average EMC of Column Acreage(0.46 + 8.3I)TN (mg/L)(2) * (3) * (4)TP (mg/L)(2) * (3) * (6) Transportation impervious 1.702.512.6011.110.190.81 Roof impervious 1.632.511.957.990.110.45 Managed pervious 9.252.511.4233.030.286.51 Wooded pervious 0.892.510.942.100.140.31 Area taken up by BMP 0.002.511.950.000.110.00 Pre-BMP TN Pre-BMP TP Fraction Impervious (I) = 0.2554.248.09 Load (lb/yr) =Load (lb/yr) = Pre-BMP TN Export Pre-BMP TP Export Total Area of Development = 13.474.030.60 (lb/ac/yr) =(lb/ac/yr) = Post-BMP TN Post-BMP TP 54.248.09 Load (lb/yr) =Load (lb/yr) = Post-BMP TN Post-BMP TP Export 4.030.60 Export (lb/ac/yr) =(lb/ac/yr) = Catchment 3: Total acreage of catchment 3 =0.37ac First BMP's TN removal rate =%First BMP's TP removal rate =% Second BMP's TN removal rate =%Second BMP's TP removal rate =% Third BMP's TN removal rate =%Third BMP's TP removal rate =% TOTAL TN REMOVAL RATE =0%TOTAL TP REMOVAL RATE =0% (1)(2)(3)(4)(5)(6)(7) Type of Land CoverCatchment S.M. Formula Average EMC of Column Average EMC of Column Acreage(0.46 + 8.3I)TN (mg/L)(2) * (3) * (4)TP (mg/L)(2) * (3) * (6) Transportation impervious 0.000.462.600.000.190.00 Roof impervious 0.000.461.950.000.110.00 Managed pervious 0.370.461.420.240.280.05 Wooded pervious 0.000.460.940.000.140.00 Area taken up by BMP 0.000.461.950.000.110.00 Pre-BMP TN Pre-BMP TP Fraction Impervious (I) = 0.000.240.05 Load (lb/yr) =Load (lb/yr) = Pre-BMP TN Export Pre-BMP TP Export Total Area of Development = 0.370.650.13 (lb/ac/yr) =(lb/ac/yr) = Post-BMP TN Post-BMP TP 0.240.05 Load (lb/yr) =Load (lb/yr) = Post-BMP TN Post-BMP TP Export 0.650.13 Export (lb/ac/yr) =(lb/ac/yr) = Last Modified 5/23/03 Tar-Pamlico Stormwater Rule 15A NCAC 2B .0258 Weighted Average of Nutrient Loadings from the Catchments: Post-BMP Post-BMP Catchment AcreageTN Loading TP Loading (lb/ac/yr)(lb/ac/yr) Catchment 1 14.321.590.21 Catchment 2 13.474.030.60 Catchment 3 0.370.650.13 TOTAL FOR DEVELOPMENT 28.162.740.40 Note: The nutrient loading goals are 4.0 lb/ac/yr for TN and 0.4 lb/ac/yr for TP. If the post-development nutrient loading is below these levels, then the BMPs planned are adequate. Otherwise, additional BMPs and/or modifications in development plans are required.