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WPO201600012 Other 2016-02-23
STORMWATER MANAGEMENT REPORT Landmark Aviation Hangar I)AIAD AND ASSOCIATES IIl1C REFLECTING TOMORROW 1561 Commerce Road, Suite 401 Verona, VA 24482 540-248-3220 Prepared by: Kent O'Donohue, Jr. Balzer & Associates Project No: 34150043 February 16, 2016 D. KENT O'DONOHUE, JR. Lic, No. 0406001683 Table of Contents: INTRODUCTION.......................................................................................................................... 1 HYDROLOGIC & HYDRAULIC ANALYSIS............................................................................. 1 ExistingConditions................................................................................................................. 1 Pre-Development.................................................................................................................... 1 Table 1: Pre -developed Storm Rates.............................................................................. 1 Post-Development................................................................................................................... 2 Table 2: Post -developed Storm Rates before Detention ................................................ 2 Stormwater Quantity Management......................................................................................... 2 Table 3: Pre- to Post -Developed Storm Rates after Detention ...................................... 3 StormwaterQuality................................................................................................................. 3 AdequateChannel................................................................................................................... 3 Stormwater Conveyance Calculations.................................................................................... 3 OutletProtection..................................................................................................................... 4 Stormwater Maintenance........................................................................................................ 4 Attachments: Pre -development Calculations Page 5 Post -development Calculations Page 21 Stormwater Conveyance Calculations Page 43 Outlet Protection Sizing Worksheets Page 53 Water Quality Calculations Page 56 1 STORMWATER MANAGEMENT REPORT Landmark Aviation Hangar INTRODUCTION This project consists of the construction of a new hangar at the Charlottesville -Albemarle Airport. The leased project site area encompasses approximately 0.62 acres located in the County of Albemarle, Virginia. The existing site is characterized as vacant with lawns and the existing airport development adjacent. Slopes are gentle to steep. A total of approximately 1.97 acres will be disturbed during construction. Stormwater compliance for this project is in accordance with current state regulations for a "Re -development" project. (County code 17-302 and State Code 9VAC25-870- 62 thru 9VAC25-870-66). This report documents the storm water design recommended by Balzer & Associates, Inc. After analysis of the site under pre and post -development conditions, a determination of the appropriate stormwater management design was made. HYDROLOGIC & HYDRAULIC ANALYSIS Existing Conditions The existing site conditions comprise of un -developed, open land with grasses adjacent to the existing airport development. Stormwater run-off from the existing site is conveyed from sheet flow and existing on-site channelized flow within broad natural swales to existing detention facilities and manmade conveyance systems under Dickerson Road. Pre -Development Existing topography slopes generally from northwest to southeast in a large natural swale. Ground cover consists of open lawn. The enclosed Drainage Map (Sheet DA -1) illustrates the drainage area for the site and the path of the pre -developed time of concentration. Based upon a hydrologic analysis of the site (see attached Pre -Development Calculations), the pre -development run- off rates for the identified drainage areas are as follows: Table 1: Pre -developed Storm Rates Storm Event DA -A Flowrate cfs DA -B DA -C Q 1 = 0.14 -- -- Q2 = -- 0.52 0.98 Q10 = 1.04 0.96 2.16 TOC = 16.1 min. 5.5 min. 5.0 min. 2 Stormwater Management Report Landmark Aviation Hangar These values were achieved using existing site contours, averaging slopes across the time of concentration lengths, and using appropriate Curve Numbers. The analysis of the pre -development run-off rates for the drainage areas was performed using Hydro-CADO v. 10 computer software. All calculations were performed in general accordance with the TR -55 Method outlined in the Virginia Stormwater Management Handbook. Post -Development For post -development analysis, we have determined the amount of additional impervious area within the drainage areas for the currently proposed site development as well as additional drainage that will be diverted into the bioretention basin from adjacent structures (see DA -2, Post Development Drainage Map). Based upon a hydrologic analysis of the site (see attached Post -Development Calculations), the post -development run-off rates are as follows: Table 2: Post -developed Storm Rates before Detention Storm Event DA -A Flowrate cfs) DA -B DA -C Q 1 = 1.12 -- -- Q2 = -- 0.40 0.79 Q10 = 3.75 0.62 1.49 TOC = 16.1 min. 5.0 min. 5.0 min. Due to the reduction in drainage area and impervious area within DA -B and DA -C, there is reduced runoff for the 2 -yr and 10 -yr events and further downstream analysis is not required. DA -A which encompasses the proposed development will be analyzed further to meet Energy Balance and Flood Protection requirements below. Stormwater Ouantity Management A Level 2 Bioretention basin with 0.5' of surface storage is proposed for stormwater quantity management. This basin will treat runoff from the proposed hangar, as well as capturing some of the runoff from the adjacent hangar that currently flows undetained. As depicted on the Water Quality drainage map, DA B and DA C both shrank considerably in size and runoff was reduced in both drainage areas due to re-routing of runoff into the DA -A post condition and overdetention of pre- existing impervious areas. An analysis of the proposed basin was performed using Hydro-CADO v. 10 computer software. The following table illustrates the reduction in run-off rates when comparing pre -development flowrates and required Energy Balance flowrates to detained post -development flowrates. 3 Stormwater Management Report Landmark Aviation Hangar Table 3: Pre- to Post -Developed Storm Rates after Detention Storm Event Flowrate (cfs) Pre Ener Balance Max Post Q1 = 0.14 0.05 0.03 Q10 = 1.04 -- 0.78 By providing detention, the post -development stormwater flowrates are below pre -developed flowrates when comparing 1 -year pre -developed Energy Balance Runoff to the 1 -year post -developed and pre -developed 10 -year to the post -developed 10 -year stormwater flowrates. Stormwater Quality For water quality analysis, the project site area of 1.97 acres was used to calculate phosphorus loading rates. The existing conditions comprise 0.27 acres (14%) of impervious area. The proposed development will result in total impervious area of 1.01 acres (51%). Based on the proposed development, a total Phosphorous load reduction of 1.50 lbs P/yr is needed. To treat the stormwater quality, the proposed development includes the construction of a level 2 Bioretention Basin Based on the existing and proposed land use of the area draining to the BMP, the basin obtains a total removal rate of 1.74 lbs P/yr, exceeding the required P removal. We have provided calculations for the water quality measures proposed for the site development (see attached Water Quality Calculations). Adequate Channel Since the Energy Balance method was used and the 10 -yr post development discharge rates into the existing conveyance channel are lower than the pre developed condition the existing storm conveyance system is adequate for DA A. DA B and DA C were both reduced in size and impervious area and thus do not require further analysis. Stormwater Conveyance Calculations An analysis of the existing and proposed stormwater structure inlets was performed to verify adequate pipe sizing (see attached Storm Sewer calculations) and headwater elevations (see attached Culvert Calculations). The analyses revealed that stormwater run-off produced from a 10 -year storm event is contained within the storm sewer system. 4 Stormwater Management Report Landmark Aviation Hangar Outlet Protection An analysis of the outlet of all stormwater structures was performed to provide adequate amounts of stone rip -rap for outlet protection (see attached Outlet Protection Calculations). All calculations were performed in conformance with the Virginia Erosion and Sediment Control Handbook, Third Edition. Stormwater Maintenance Maintenance of stormwater pipes within the subject property will be the responsibility of the leaser. Maintenance of the Bioretention Basin will be the responsibility of the property leaser. PRE DEVELOPMENT CALCULATIONS \ \ \ \ ,-6U 0 60 120 180 --_ ----_ II�IIIIIII� •� l / I+ I -------- \\ / II---------- I-----——--——— \-------- ' 11 --- \_ Tit' — I I j l I l l 1 1 I I I II I PRE DA B \ I I III I I I I I I I I II �/I/ I\� — I ' ' I I I I I 1 111 I I I I I /tel/�� c� 0.29 ACS 613, I I I I I I II111 \ J \ 0.11 ACS IMP. ,� �/ J--- -- ------ 611 — - — — — \ \ \\ \ \ \ \ II ,— L' \\\\ RE DA C II I / \ / .82 ACS `\ PRE DA A I .16 ACS IMP. 0.87 ACS II / 0.00 ACS IMP.waft 10. snow moo / / / ' l �= \ / \ \ \ f / IIIIIIIIIIIIIIIII� IIIIIIIIIIIIIIIII� \ \ `\ `\ `\ (' \� ,' 1 11 ti /---- 612--------_ — – – --- –_--- ___--_ --/--- ---1– –I �_� _ ----- –– ----------- NEWEL-:1600 — - _-_=_610 = - __ ________- \\\ _`-----------------_---------------------------------- `� � ���—�-�-� -- _ - � =_ __—=-605-=--- -________________---------- now_ , ------ - - _ — �' � - - _ _______-= ==_- — — — — — — _===_= \ 1 \ _ -- --- - - - — — '\ =__=600:�� = =---- _= __ ______- '� ' \ _=595-= -_---- ---- - - '===_ ---------------------______________----- — _ -590-7 _ _ 580 ' 3 \ \ \ \ \\ \\ \ \ \\ / / / / / / , / —T— 1 I \ \ I 77 / 1 I I I\ � II 1 \. \ \ \ \ \ \ \ —600 // ,/ / /'/ / //,' //,�/,//,'/ l/�'/ /� // / , _T_ ^ % � \ I -1 1 a 1 � I I I I 1 \ \ III ' \ \ 1 I \\ \\ \ \\ \\ \\ \ \ \ \\ \\ -- 4 1 -00 \ \ \ \ \ / / , / / / / , / � / /�, F . / / / f \, h I • � I � I 1 1 I 1 1 \ \ I / I I IIII' \ \ \ 1 31 4 1 5 I R 7 1 R Q i(1 11 17 ii 14 15 ifi 17 iR iQ 7D 71 w .balzer.cc st—t.. New River Valley Roanoke Richmond Harrisonburg Balzer and Associates, Inc 1561 Commerce Road Suite 401 Verona, VA 24482 540-248-3220 FAX 540-248-3221 W (D Z W Q Q Q Z � Z U9� O w> w HZ 0 z Q° ZJ O a W Q C) Q� a W L� Y O x a W w w Ina a 0 Z W Q a J ONO DRAWN BY DESIGNED BY ONO CHECKED BY ONO DATE 01-20-2016 SCALE 1"=60' REVISIONS - 02 -16-2016 SHEET NO. DA -1 JOB NO. 34150042 T A A 1 �- n 1 1 1Jt1-ti 1-V1 dIIU 1V -Vi %�dI(-UIdLIk)11J DA-Ap Pre DA A Subcat Reach on Link Routing Diagram for 2016-01-20 SWM Calcs Prepared by Microsoft, Printed 1/22/2016 HydroCAD® 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC 8 2016-01-20 SWM Calcs Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 2 Ground Covers (selected nodes) HSG -A HSG -B HSG -C HSG -D Other Total Ground Subcatchment (acres) (acres) (acres) (acres) (acres) (acres) Cover Numbers 0.000 0.870 0.000 0.000 0.000 0.870 >75% Grass cover, Good DA-Ap 0.000 0.870 0.000 0.000 0.000 0.870 TOTAL AREA 2016-01-20 SWM Calcs Landmark A viation 24 -hr S1 1 -yr Rainfall=2.98" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 3 Time span=0.10-90.00 hrs, dt=0.01 hrs, 8991 points Runoff by SCS TR -20 method, UH=SCS, Weighted -CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment DA-Ap: Pre DA A Runoff Area=0.870 ac 0.00% Impervious Runoff Depth=0.36" Flow Length=273' Tc=16.1 min CN=61 Runoff=0.14 cfs 0.026 of Total Runoff Area = 0.870 ac Runoff Volume = 0.026 of Average Runoff Depth = 0.36" 100.00% Pervious = 0.870 ac 0.00% Impervious = 0.000 ac UO 2016-01-20 SWM Calcs Landmark A viation 24 -hr S1 1 -yr Rainfall=2.98" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment DA-Ap: Pre DA A Runoff = 0.14 cfs @ 12.28 hrs, Volume= 0.026 af, Depth= 0.36" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs Landmark Aviation 24 -hr S1 1 -yr Rainfall=2.98" Area (ac) CN Description 0.870 61 >75% Grass cover, Good, HSG B 0.870 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 15.0 150 0.0133 0.17 Sheet Flow, Grass: Short n= 0.150 P2= 3.60" 1.1 123 0.0730 1.89 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fDs 16.1 273 Total Subcatchment DA-Ap: Pre DA A Hydrograph 0.15- 0.14 cfs 0.14-- 0.13-- 0.12 .140.130.12 - - - 0.11 0.1-- 009- 0 .10093 0.08-- -2 0.07 - - 0.06 - - 0.05 0.04-- - - - 0.03 - 0.02 - 0.01 - - Lantlmai�kAvia�n�-hLS17 yr _ - -1 -I Rainfall=2.98" Runoff Area=0.870 ac Il2unb"olur%e=0.026 of �u"offPept�l =0.36" _ Flow_LenRth=273' _ _1 _ tc=16.1 min - - CCN=61 --1 A -t 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 Time (hours) -Runoff is 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 5 Time span=0.10-90.00 hrs, dt=0.01 hrs, 8991 points Runoff by SCS TR -20 method, UH=SCS, Weighted -CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment DA-Ap: Pre DA A Runoff Area=0.870 ac 0.00% Impervious Runoff Depth=1.63" Flow Length=273' Tc=16.1 min CN=61 Runoff=1.04 cfs 0.118 of Total Runoff Area = 0.870 ac Runoff Volume = 0.118 of Average Runoff Depth = 1.63" 100.00% Pervious = 0.870 ac 0.00% Impervious = 0.000 ac fi" 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment DA-Ap: Pre DA A Runoff = 1.04 cfs @ 12.20 hrs, Volume= 0.118 af, Depth= 1.63" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Area (ac) CN Description 0.870 61 >75% Grass cover, Good, HSG B 0.870 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 15.0 150 0.0133 0.17 Sheet Flow, Grass: Short n= 0.150 P2= 3.60" 1.1 123 0.0730 1.89 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fas 16.1 273 Total Subcatchment DA-Ap: Pre DA A Hydrograph — Runoff Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Runoff Area=0.870 ac Runoff Volume=0.118 of Runoff Depth=1.63" Flow Length=273' Tc=16.1 min CN=61 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 Time (hours) 13 T A T 1 T A /l n 1 !1 1 7 Ilii -D dilu lJt1-l. G -VI d1lu IU -VI 1.'d1GU1dL1Ui1J DA -Bp Pre DA B DA-Cp Pre DA C Subcat Reach on Link Routing Diagram for 2016-01-20 SWM Calcs Prepared by Microsoft, Printed 1/22/2016 HydroCAD® 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC 14 2016-01-20 SWM Calcs Prepared by Microsoft HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Printed 1/22/2016 Page 2 Ground Covers (selected nodes) HSG -A HSG -B HSG -C HSG -D Other Total Ground Subcatchment (acres) (acres) (acres) (acres) (acres) (acres) Cover Numbers 0.000 0.840 0.000 0.000 0.000 0.840 >75% Grass cover, Good DA -Bp, DA-Cp 0.000 0.270 0.000 0.000 0.000 0.270 Paved parking DA -Bp, DA-Cp 0.000 1.110 0.000 0.000 0.000 1.110 TOTAL AREA W61 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 2 -yr Rainfall=3.60" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 3 Time span=0.10-90.00 hrs, dt=0.01 hrs, 8991 points Runoff by SCS TR -20 method, UH=SCS, Weighted -CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method SubcatchmentDA-Bp: Pre DA B Runoff Area=0.290 ac 37.93% Impervious Runoff Depth=1.38" Flow Length=255' Slope=0.0120 '/' Tc=5.5 min CN=75 Runoff=0.52 cfs 0.033 of SubcatchmentDA-Cp: Pre DA C Runoff Area=0.820 ac 19.51% Impervious Runoff Depth=0.97" Flow Length=288' Tc=5.0 min CN=68 Runoff=0.98 cfs 0.066 of Total Runoff Area= 1.110 ac Runoff Volume= 0.100 of Average Runoff Depth= 1.08" 75.68% Pervious = 0.840 ac 24.32% Impervious = 0.270 ac My 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 2 -yr Rainfall=3.60" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment DA -Bp: Pre DA B Runoff = 0.52 cfs @ 12.04 hrs, Volume= 0.033 af, Depth= 1.38" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs Landmark Aviation 24 -hr S1 2 -yr Rainfall=3.60" Area (ac) CN Description 0.110 98 Paved parking, HSG B 0.180 61 >75% Grass cover, Good, HSG B 0.290 75 Weighted Average 0.180 62.07% Pervious Area 0.110 37.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.5 255 0.0120 0.77 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps Subcatchment DA -Bp: Pre DA B Hydrograph 0.55 - 0.52 cfs 0.5 JLandmai k7�via`ibn 24 -hr S1 yr 0.45 Rainfall=3.-60" Runoff Area=0.290 ac o.aRuni #- ollurrhe=0.033 of f -� 0.35 °_" llpep#i�=' -38„ 0.3- Flow Length=255' 2 1 �lop�e=0J0120 '/' LL 0.25 Tc _ Tin - 0.2 0 2 C75 W 0.15 0.1 — — - — 0.05 — — 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 Time (hours) — Runoff 17 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 2 -yr Rainfall=3.60" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment DA-Cp: Pre DA C Runoff = 0.98 cfs @ 12.03 hrs, Volume= 0.066 af, Depth= 0.97" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs Landmark Aviation 24 -hr S1 2 -yr Rainfall=3.60" Area (ac) CN Description 0.160 98 Paved parking, HSG B 0.660 61 >75% Grass cover, Good, HSG B 0.820 68 Weighted Average 0.660 1.11 80.49% Pervious Area 0.160 19.51 % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.5 100 0.0100 1.11 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.60" 1.3 129 0.0100 1.61 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.1 59 0.5000 11.38 Shallow Concentrated Flow, Unaaved Kv= 16.1 fas 3 0 LL 2.9 288 Total, Increased to minimum Tc = 5.0 min 0 Subcatchment DA-Cp: Pre DA C Hydrograph 0.98 cfs Landman Aviation 24 -hr s1 2 -yr Rainfall=3.60" Runoff) Area=0.820 ac Runoff Vblume=0.066 of Runoff Depth=0.97" Flow Length=288' Tc=5.0 min CCN=68 5 10 15 20 25 30 35 40 45 50 55 60 65 70 Time (hours) — Runoff 18 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 6 Time span=0.10-90.00 hrs, dt=0.01 hrs, 8991 points Runoff by SCS TR -20 method, UH=SCS, Weighted -CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method SubcatchmentDA-Bp: Pre DA B Runoff Area=0.290 ac 37.93% Impervious Runoff Depth=2.81" Flow Length=255' Slope=0.0120 '/' Tc=5.5 min CN=75 Runoff=0.96 cfs 0.068 of SubcatchmentDA-Cp: Pre DA C Runoff Area=0.820 ac 19.51% Impervious Runoff Depth=2.21" Flow Length=288' Tc=5.0 min CN=68 Runoff=2.16 cfs 0.151 of Total Runoff Area= 1.110 ac Runoff Volume= 0.219 of Average Runoff Depth =2.37" 75.68% Pervious = 0.840 ac 24.32% Impervious = 0.270 ac 19 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment DA -Bp: Pre DA B Runoff = 0.96 cfs @ 12.03 hrs, Volume= 0.068 af, Depth= 2.81" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Area (ac) CN Description 0.110 98 Paved parking, HSG B 0.180 61 >75% Grass cover, Good, HSG B 0.290 75 Weighted Average 0.180 62.07% Pervious Area 0.110 37.93% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.5 255 0.0120 0.77 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps Subcatchment DA -Bp: Pre DA B Hydrograph — Runoff Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Runoff Area=0.290 ac Runoff Volume=0.068 of Runoff Depth=2.81" Flow Length=255' Slope=0.0120 '/' Tc=5.5 min CN=75 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 Time (hours) 20 2016-01-20 SWM Calcs Landmark A viation 24 -hr S1 10 -yr Rainfall=5.43" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 8 Summary for Subcatchment DA-Cp: Pre DA C Runoff = 2.16 cfs @ 12.03 hrs, Volume= 0.151 af, Depth= 2.21" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Area (ac) CN Description 0.160 98 Paved parking, HSG B 0.660 61 >75% Grass cover, Good, HSG B 0.820 68 Weighted Average 0.660 1.11 80.49% Pervious Area 0.160 19.51 % Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 1.5 100 0.0100 1.11 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.60" 1.3 129 0.0100 1.61 Shallow Concentrated Flow, Unpaved Kv= 16.1 fps 0.1 59 0.5000 11.38 Shallow Concentrated Flow, Unaaved Kv= 16.1 fas 2.9 288 Total, Increased to minimum Tc = 5.0 min 2 3 0 LL 1 0 Subcatchment DA-Cp: Pre DA C Hydrograph 2.16 cfs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Runoff Area=0.820 ac IRunoff �olume=0.151 of Runoff Depth=2.21" Flow Length=288' I Tc=5.0 min CN -68 - 5 10 15 20 25 30 35 40 45 50 55 60 Time (hours) — Runoff 21 POST DEVELOPMENT CALCULATIONS oe- 0 0 ,-6U 0 60 120 180 —�_ ----_ II�IIIIIII� •� l / --__ I � I I+ I � -------- \\ /1 II---------- I - - - - - - - - - - -- \-------- / IN / I I - - - - - - - - - - - - - - 1 - - \ \ \ N -F --- \ _ Tit' 1 M I I It 1\\III ''tll'II111III I I I I I I i' i //// \ L 1111111\'111111IIIlilllll�////' I I II II 11I 111 II IIII K K I I I I l I IIIIIIIIIIIII////II� / \ DA B I I I I I I I I I I 111 11 I I 0.13 ACS 613, I I I I 11111111 \ \ 0.09 ACS IMP. / 611,E — \\A I I I I I \\\\\\\\\\\\\ \ \ I �7-- '' POST I DA A DET.- I II �/ \ 6-, ,,�\ 1.39 MACS I p,\ \\\\ �o 0.76CN IACS IMP. 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DA -2 JOB NO. 34150042 T A A T T LrI.-IA rust. 1 -yr r.ii 23 Balance Compliance DA-JA1—V /fB MP Post DAA 1 -yr BioRetention Subcat Reach on Link Routing Diagram for 2016-01-20 SWM Calcs Prepared by Microsoft, Printed 1/22/2016 HydroCAD® 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC 24 2016-01-20 SWM Calcs Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 2 Ground Covers (selected nodes) HSG -A HSG -B HSG -C HSG -D Other Total Ground Subcatchi (acres) (acres) (acres) (acres) (acres) (acres) Cover Numbers 0.000 0.000 0.000 0.000 1.390 1.390 Adjusted CN from VRRM Spreadsheet 0.000 0.000 0.000 0.000 1.390 1.390 TOTAL AREA 107 2016-01-20 SWM Calcs Landmark A viation 24 -hr S1 1 -yr Rainfall=2.98" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 3 Time span=0.10-90.00 hrs, dt=0.01 hrs, 8991 points Runoff by SCS TR -20 method, UH=SCS, Weighted -CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method SubcatchmentDA-A1: Post DA A 1 -yr Runoff Area=1.390 ac 0.00% Impervious Runoff Depth=0.85" Flow Length=179' Tc=10.3 min CN=73 Runoff=1.12 cfs 0.098 of Pond BMP: BioRetention Peak Elev=600.60' Storage=3,948 cf Inflow=1.12 cfs 0.098 of Outflow=0.03 cfs 0.012 of Total Runoff Area = 1.390 ac Runoff Volume = 0.098 of Average Runoff Depth = 0.85" 100.00% Pervious = 1.390 ac 0.00% Impervious = 0.000 ac 2016-01-20 SWM Calcs Landmark A viation 24 -hr S1 1 -yr Rainfall=2.98" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment DA -A1: Post DA A 1 -yr Runoff = 1.12 cfs @ 12.10 hrs, Volume= 0.098 af, Depth= 0.85" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs Landmark Aviation 24 -hr S1 1 -yr Rainfall=2.98" Area (ac) CN Description 1.390 73 Adjusted CN from VRRM Spreadsheet 1.390 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.3 92 0.0130 0.15 Sheet Flow, Grass: Short n= 0.150 P2= 3.60" 0.1 87 0.1150 20.88 25.06 Channel Flow, Area= 1.2 sf Perim= 3.9' r= 0.31' n= 0.011 PVC, smooth interior 10.3 179 Total Subcatchment DA -A1: Post DA A 1 -yr Hydrograph — Runoff Landmark Aviation 24 -hr S1 1 -yr Rainfall=2.98" Runoff Area=1.390 ac Runoff Volume=0.098 of Runoff Depth=0.85" Flow Length=179' Tc=10.3 min CN=73 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 Time (hours) 27 2016-01-20 SWM Calcs Landmark A viation 24 -hr S1 1 -yr Rainfall=2.98" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 5 Summary for Pond BMP: BioRetention Inflow Area = 1.390 ac, 0.00% Impervious, Inflow Depth = 0.85" for 1 -yr event Inflow = 1.12 cfs @ 12.10 hrs, Volume= 0.098 of Outflow = 0.03 cfs @ 24.03 hrs, Volume= 0.012 af, Atten= 97%, Lag= 715.7 min Primary = 0.03 cfs @ 24.03 hrs, Volume= 0.012 of Routing by Stor-Ind method, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 600.60' @ 24.03 hrs Surf.Area= 2,409 sf Storage= 3,948 cf Plug -Flow detention time= 740.9 min calculated for 0.012 of (13% of inflow) Center -of -Mass det. time= 566.5 min ( 1,457.4 - 890.8 ) Volume Invert Avail.Storage Storage Description #1 594.17' 10,412 cf Custom Stage Data (Irregular)Listed below (Recalc) Elevation Surf.Area Perim. Voids Inc.Store Cum.Store Wet.Area (feet) (sq -ft) (feet) (%) (cubic -feet) (cubic -feet) (sq -ft) 594.17 1,415 164.0 0.0 0 0 1,415 596.17 1,415 164.0 40.0 1,132 1,132 1,743 597.00 1,415 164.0 40.0 470 1,602 1,879 598.50 1,415 164.0 25.0 531 2,132 2,125 600.00 1,724 230.0 25.0 588 2,720 4,215 601.00 2,936 252.0 100.0 2,303 5,023 5,093 601.50 3,321 261.0 100.0 1,563 6,587 5,482 602.00 3,720 271.0 100.0 1,759 8,346 5,926 602.50 4,560 290.0 100.0 2,066 10,412 6,786 Device Routina Invert Outlet Devices #1 Primary 596.00' 15.0" Round Culvert L= 100.0' CPP, projecting, no headwall, Ke= 0.900 Inlet/ Outlet Invert= 596.00'/ 595.00' S=0.0100'/' Cc= 0.900 n= 0.011, Flow Area= 1.23 sf #2 Device 1 601.50' 24.0" Horiz. Riser C= 0.600 Limited to weir flow at low heads #3 Device 1 600.50' 6.0" Vert. Orifice C= 0.600 Primary OutFlow Max=0.03 cfs @ 24.03 hrs HW=600.60' (Free Discharge) L1=Culvert (Passes 0.03 cfs of 9.30 cfs potential flow) �2=Riser ( Controls 0.00 cfs) 3=Orifice (Orifice Controls 0.03 cfs @ 1.06 fps) 28 2016-01-20 SWM Calcs Landmark A viation 24 -hr S1 1 -yr Rainfall=2.98" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 6 1.12 cfs 3 0 LL Pond BMP: BioRetention Hydrograph InflowlArea= 1.1390 a1c Beak �lev6� =�0�.' (Storage=31,948 cf Time (hours) F--1 -If I --11 — Primary DA -Al 0 Post DAA 1 Subcat Reach on Link 29 DA -A Post 10 -yr Calculations BioRetention Kit] 2016-01-20 SWM Calcs Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 2 Ground Covers (selected nodes) HSG -A HSG -B HSG -C HSG -D Other Total Ground Subcatchi (acres) (acres) (acres) (acres) (acres) (acres) Cover Numbers 0.000 0.000 0.000 0.000 1.390 1.390 Adjusted CN from VRRM Spreadsheet 0.000 0.000 0.000 0.000 1.390 1.390 TOTAL AREA 1911 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 3 Time span=0.10-90.00 hrs, dt=0.01 hrs, 8991 points Runoff by SCS TR -20 method, UH=SCS, Weighted -CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment DA -A10: Post DA A 10 -yr Runoff Area=1.390 ac 0.00% Impervious Runoff Depth=2.80" Flow Length=179' Tc=10.3 min CN=75 Runoff=3.75 cfs 0.325 of Pond BMP: BioRetention Peak Elev=601.43' Storage=6,350 cf Inflow=3.75 cfs 0.325 of Outflow=0.78 cfs 0.239 of Total Runoff Area = 1.390 ac Runoff Volume = 0.325 of Average Runoff Depth = 2.80" 100.00% Pervious = 1.390 ac 0.00% Impervious = 0.000 ac Kia 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment DA -A10: Post DA A 10 -yr Runoff = 3.75 cfs @ 12.09 hrs, Volume= 0.325 af, Depth= 2.80" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Area (ac) CN Description 1.390 75 Adjusted CN from VRRM Spreadsheet 1.390 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.3 92 0.0130 0.15 Sheet Flow, Grass: Short n= 0.150 P2= 3.60" 0.1 87 0.1150 20.88 25.06 Channel Flow, Area= 1.2 sf Perim= 3.9' r= 0.31' n= 0.011 PVC, smooth interior 10.3 179 Total Subcatchment DA -A10: Post DA A 10 -yr Hydrograph — Runoff Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" 3 Runoff Area=1.390 ac Runoff Volume=0.325 of Runoff Depth=2.80" Flow Length=179' Tc=10.3 min CN=75 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 Time (hours) 33 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 5 Summary for Pond BMP: BioRetention Inflow Area = 1.390 ac, 0.00% Impervious, Inflow Depth = 2.80" for 10 -yr event Inflow = 3.75 cfs @ 12.09 hrs, Volume= 0.325 of Outflow = 0.78 cfs @ 12.68 hrs, Volume= 0.239 af, Atten= 79%, Lag= 35.2 min Primary = 0.78 cfs @ 12.68 hrs, Volume= 0.239 of Routing by Stor-Ind method, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs / 2 Peak Elev= 601.43' @ 12.68 hrs Surf.Area= 3,264 sf Storage= 6,350 cf Plug -Flow detention time= 220.6 min calculated for 0.239 of (74% of inflow) Center -of -Mass det. time= 116.1 min ( 965.7 - 849.6 ) Volume Invert Avail.Storage Storage Description #1 594.17' 10,412 cf Custom Stage Data (Irregular)Listed below (Recalc) Elevation Surf.Area Perim. Voids Inc.Store Cum.Store Wet.Area (feet) (sq -ft) (feet) (%) (cubic -feet) (cubic -feet) (sq -ft) 594.17 1,415 164.0 0.0 0 0 1,415 596.17 1,415 164.0 40.0 1,132 1,132 1,743 597.00 1,415 164.0 40.0 470 1,602 1,879 598.50 1,415 164.0 25.0 531 2,132 2,125 600.00 1,724 230.0 25.0 588 2,720 4,215 601.00 2,936 252.0 100.0 2,303 5,023 5,093 601.50 3,321 261.0 100.0 1,563 6,587 5,482 602.00 3,720 271.0 100.0 1,759 8,346 5,926 602.50 4,560 290.0 100.0 2,066 10,412 6,786 Device Routina Invert Outlet Devices #1 Primary 596.00' 15.0" Round Culvert L= 100.0' CPP, projecting, no headwall, Ke= 0.900 Inlet/ Outlet Invert= 596.00'/ 595.00' S=0.0100'/' Cc= 0.900 n= 0.011, Flow Area= 1.23 sf #2 Device 1 601.50' 24.0" Horiz. Riser C= 0.600 Limited to weir flow at low heads #3 Device 1 600.50' 6.0" Vert. Orifice C= 0.600 Primary OutFlow Max=0.78 cfs @ 12.68 hrs HW=601.43' (Free Discharge) L1=Culvert (Passes 0.78 cfs of 10.22 cfs potential flow) �2=Riser ( Controls 0.00 cfs) 3=Orifice (Orifice Controls 0.78 cfs @ 3.97 fps) 34 2016-01-20 SWM Calcs Landmark A viation 24 -hr S1 10 -yr Rainfall=5.43" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 6 Pond BMP: BioRetention Hydrograph 4 3.75 cfs 3 3 2 0 LL 0.78 d 0 5 10 1 i _1 I Inflow lArea=1.1390 a I C -Peel k -E l ev -iQ1. �' Storage=6l390 If - ' I I I I --4 Time (hours) F--1 -If I --11 — Primary 35 T A T i T% A e 1 T /1 1-11-1-13 aiiu ruby /,-yi aiiu 10 -yr Residual Calculations 1I7_d: POST DA B DA -C POST DA C Subcat Reach on Link Routing Diagram for 2016-01-20 SWM Calcs Prepared by Microsoft, Printed 1/22/2016 HydroCAD® 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC KIy 2016-01-20 SWM Calcs Prepared by Microsoft HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Printed 1/22/2016 Page 2 Ground Covers (selected nodes) HSG -A HSG -B HSG -C HSG -D Other Total Ground Subcatchment (acres) (acres) (acres) (acres) (acres) (acres) Cover Numbers 0.000 0.330 0.000 0.000 0.000 0.330 >75% Grass cover, Good DA -B, DA -C 0.000 0.250 0.000 0.000 0.000 0.250 Paved parking DA -B, DA -C 0.000 0.580 0.000 0.000 0.000 0.580 TOTAL AREA RYA 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 2 -yr Rainfall=3.60" Prepared by Microsoft Printed 1/22/2016 HvdroCAD® 10.00-12 s/n 07714 © 2014 HvdroCAD Software Solutions LLC Paae 3 Time span=0.10-90.00 hrs, dt=0.01 hrs, 8991 points Runoff by SCS TR -20 method, UH=SCS, Weighted -CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment DA -B: POST DA B Runoff Area=0.130 ac 69.23% Impervious Runoff Depth=2.24" Tc=5.0 min CN=87 Runoff=0.40 cfs 0.024 of Subcatchment DA -C: POST DA C Runoff Area=0.450 ac 35.56% Impervious Runoff Depth=1.32" Tc=5.0 min CN=74 Runoff=0.79 cfs 0.049 of Total Runoff Area = 0.580 ac Runoff Volume = 0.074 of Average Runoff Depth = 1.53" 56.90% Pervious = 0.330 ac 43.10% Impervious = 0.250 ac 2016-01-20 SWM Caics Landmark Aviation 24 -hr S1 2 -yr Rainfall=3.60" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment DA -B: POST DA B Runoff = 0.40 cfs @ 12.03 hrs, Volume= 0.024 af, Depth= 2.24" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs Landmark Aviation 24 -hr S1 2 -yr Rainfall=3.60" Area (ac) CN Description 0.090 98 Paved parking, HSG B 0.040 61 >75% Grass cover, Good, HSG B 0.130 87 Weighted Average 0.040 30.77% Pervious Area 0.090 69.23% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment DA -B: POST DA B Hydrograph 0.44 0.42 0.40 cfs — —Runoff 0.4 0.38 — — — Lan mk-�4vi n -1yr 0.36 - i-infa�i=3o' 0.34 0.3zRunoff RunoffArea A13Qac 0.3 a w 0.26 1 1 1 1 �u�oiep=24' 0.24 — — — Tc- .O -mi 0 0.22 — 1 — --iCN4 LL 0.2 — — — 0.18 1 1 1 —I-1-1 0.16 0.14 1 1 1 11--1 A A—t 0.12 0.1 0.08 1 I I I 1 1 —I —I A 4 0.06 — — — 0.04 n n� — 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 Time (hours) 01 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 2 -yr Rainfall=3.60" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment DA -C: POST DA C Runoff = 0.79 cfs @ 12.03 hrs, Volume= 0.049 af, Depth= 1.32" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs Landmark Aviation 24 -hr S1 2 -yr Rainfall=3.60" Area (ac) CN Description 0.160 98 Paved parking, HSG B 0.290 61 >75% Grass cover, Good, HSG B 0.450 74 Weighted Average 0.290 64.44% Pervious Area 0.160 35.56% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment DA -C: POST DA C Hydrograph 0.85 0.79 cfs -Runoff 0.8-- — 0.75 — —I —I — I Lat�dmaik�ia#tbn 24-hrIS1 yr 0.7 Rainfall="0' 0.65 -Runoff A -r -ea=- .4Wac 0.6 —I — ——kun%ffl oluur e-=�.046 a 0.55 �unoff�ept =1�2" w 0.5 U Tc= .0 min 0.45 3 I C N 474 LL 0.35 0.3 0.25—————III —I 0.2 0.15 0.1 n nG 5 10 15 20 25 30 35 40 45 50 Time (hours) Cfol 2016-01-20 SWM Calcs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Prepared by Microsoft Printed 1/22/2016 HvdroCAD® 10.00-12 s/n 07714 © 2014 HvdroCAD Software Solutions LLC Paae 6 Time span=0.10-90.00 hrs, dt=0.01 hrs, 8991 points Runoff by SCS TR -20 method, UH=SCS, Weighted -CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment DA -B: POST DA B Runoff Area=0.130 ac 69.23% Impervious Runoff Depth=3.93" Tc=5.0 min CN=87 Runoff=0.62 cfs 0.043 of Subcatchment DA -C: POST DA C Runoff Area=0.450 ac 35.56% Impervious Runoff Depth=2.73" Tc=5.0 min CN=74 Runoff=1.49 cfs 0.102 of Total Runoff Area = 0.580 ac Runoff Volume = 0.145 of Average Runoff Depth = 3.00" 56.90% Pervious = 0.330 ac 43.10% Impervious = 0.250 ac 41 2016-01-20 SWM Calcs Landmark A viation 24 -hr S1 10 -yr Rainfall=5.43" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment DA -B: POST DA B Runoff = 0.62 cfs @ 12.03 hrs, Volume= 0.043 af, Depth= 3.93" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Area (ac) CN Description 0.090 98 Paved parking, HSG B 0.040 61 >75% Grass cover, Good, HSG B 0.130 87 Weighted Average 0.040 30.77% Pervious Area 0.090 69.23% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment DA -B: POST DA B Hydrograph 0.65 0.62 cfs 0.6 — Land mar Av atio 24 -hr S1 14- Y r0.55 — Rainfall=5.43" 0.5 -Runoff Area=O-. 130 ac Kun6ff-�olume-=�.043 of 0.45 w 0.4 �unoff Peptt =3.93„ V Tc=5.0_min 3 0.35 - _ _ _ _ _ _ _ —1 7 17 -1 7CN=87 0 LL 0.3 A 0.25 --1 0.2-- 0.15-- 0.05 5 10 15 20 25 30 35 40 45 50 Time (hours) — Runoff 42 2016-01-20 SWM Calcs Landmark A viation 24 -hr S1 10 -yr Rainfall=5.43" Prepared by Microsoft Printed 1/22/2016 HydroCADO 10.00-12 s/n 07714 © 2014 HydroCAD Software Solutions LLC Page 8 Summary for Subcatchment DA -C: POST DA C Runoff = 1.49 cfs @ 12.03 hrs, Volume= 0.102 af, Depth= 2.73" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.10-90.00 hrs, dt= 0.01 hrs Landmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Area (ac) CN Description 0.160 98 Paved parking, HSG B 0.290 61 >75% Grass cover, Good, HSG B 0.450 74 Weighted Average 0.290 64.44% Pervious Area 0.160 35.56% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, w 3 0 LL M 0 Subcatchment DA -C: POST DA C Hydrograph andmark Aviation 24 -hr S1 10 -yr Rainfall=5.43" Runoff Area=0.450 ac Runoff �olume=6.102 of Rano ept -� 3" Tc=5.0 min CN474 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 Time (hours) — Runoff 43 STORMWATER CONVEYANCE CALCULATIONS oe- 0 0 ,-6U 0 60 120 180 —�_ ----_ II�IIIIIII� •� l / ---_ I � I I+ I � -------- \\ /1 II ----------I------------ \-------- / N / I I - 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CULVERTto _ II III `II 11111'1 1 \ \11\ `-----'ll ` '♦ �, 0.27 ACS 1 \\ I 0.24 ACS IMP. 1 \+ / • 1 ____ /-\ /T/ - \ \ \\J \\ \\\\ \\\\\\\\ \ Cp / -WN _ III I I \\\\\\\\\ \\\ \\ \ .6J,1/,J-- N, ,,J / I; ; III 11\\�\\�� \\ I \\ , �\ I'� I II \\ % � � L I I IIII 11` N\�\� \\\ \ 11 \\ ---' 3 STR7 STR #6 1 '1 H/ ���� I \Y /' \ , \ \ 6 0.37 AGS 0.58 ACS tOP H 0.21 ACS\ IMP. 0.42 ACS IMP. I CN X CN � \ /' _, � I � 613... 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DA -3 JOB NO. 34150042 OTHER INLET WORKSHEET PROJECT NAME: LANDMARK AVIATION HANGAR PROJECT #: 34150042 DATE: 1/25/2016 BY: WSK inlet DATA CALCULATIONS 45 IDF CURVE REFERENCE: ALBEMARLE CO. OLF-Seelye from VDOT Drainage manual App 6D-1 Total Adj AREA C Time of Concentration Area = C 0.10 ac = 41.667 %@ 0.90 C = 0.38 ft OLF@ % = 0.00 min SCC # I SLOT: N 0.14 ac = 58.333 %@ 0.35 C = 0.20 ft CF 4H = 0.00 min - "Type ac = 0 %@ C= 0.00 ft CF AH = 0.00 min Com ac = 0 %@ C= 0.00 Tc = 5.00 min ac = 0 %@ C= 0.00 ADJ. F= 0.579 IC factor for OLF= Total Adj AREA C Time of Concentration Area = C 0.76 ac = 54.676 %@ 0.90 C = 0.49 ft OLF@ % = 0.00 min 9 1.39 ac 0.65 SLOT: N 0.63 ac = 45.324 %@ 0.35 C = 0.16 ft CF AH = 0.00 min Twe_ RISER ac = 0 %@ C= 0.00 ft CF AH = 0.00 min Comments: 24" NYLOPLAST RISER W/ ac = 0 %@_ _ C = 0.00 Tc = 5.00 min TRASH RACK ac = 0 %@ C= 0.00 ADJ. C' = 0.651 C factor for OLF= Total Adj AREA C Time of Concentration Area = C 0.21 ac = 56.757 %@ 0.90 C = 0.51 ft OLF@ % = 0.00 min IN 0.37 ac 0.66 SLOT: N 0.16 ac = 43.243 %@ 0.35 C = 0.15 ft CF 4H = 0.00 min Tvoe- ES -1 ac = 0 %@ _ C= 0.00 ft CF AH = 0.00 min Comments: ac = 0 %@ C= 0.00 Tc = 5.00 min ac = 0 %@ C= 0.00 ADJ. C'= 0.662 IC factor for OLF= Total Adj AREA C Time of Concentration Area = C 0.42 ac = 72.414 %@ 0.90 C = 0.65 ft OLF@ % = 0.00 min 60.58 ac 0.75 SLOT: N 0.16 ac = 27.586 %@ 0.35 C = 0.10 ft CF AH = 0.00 min Twe_ DI ac = 0 %@ C= 0.00 ft CF AH = 0.00 min Comments: 30" NYLOPLAST W/ DOME ac = 0 %@ _ = 0.00 Tc = 5.00 min YARD INLET GRATE ac = 0 %@ _C C= 0.00 ADJ. C'= 0.748 IC factor for OLF= Total Adj AREA C Time of Concentration Area = C ac = ###### %@ _C = #DIV/0! ft OLF@ %= 0.00 min 4 0.00 ac 0.00 SLOT: N ac = ###### %@ _ C= #DIV/0! ft CF AH = 0.00 min Twe- MH ac = ###### %@ _ C = #DIV/0! ft CF AH = 0.00 min ( omments: 30" NYLOPLAST W/ SOLID ac = ###### %@ C= #DIV/0! Tc = 5.00 min FLAT TOP ac = ###### %@ C = #DIV/0! ADJ. C'= 0.000 C factor for OLF= Total Adj AREA C Time of Concentration Area = C ac = ###### %@ C= #DIV/0! ft OLF@ % 0.00 min 7 0.00 ac 0.00 SLOT: N ac = ###### %@ _ C = #DIV/0! ft CF AH = 0.00 min Twe- MH ac = ###### %@ C- #DIV/0! ft CF AH = 0.00 min Comments: 30" NYLOPLAST W/ SOLID ac = ###### %@ _ C = #DIV/0! Tc = 5.00 min FLAT TOP ac = ###### %@ _ C= #DIV/0! ADJ. C' = 0.000 IC factor for OLF= LU-Zby Rev. 3-83 Project : LANDMAR Structure: HYDROLOGICAL DATA: D.A.= 0.37 ac #7 feet No. Rev. Date DISCHARGES USED 2 yr = 1.27 CFS 10 yr = 1.63 CFS Rational Method 2.01 CFS 100 yr = Total Area = CA Total= Cw = Tc = 5.00 12 = 5.18 I10= 6.67 125 = 7.48 I100 = 8.76 0.37 0.25 0.66 min in/hr in/hr in/hr in/hr Q2 = Q10= Q25 = Q100= 1.27 1.63 2.01 2.68 cfs cfs cfs cfs A (ac) C O O Time of Concentration Overland Flow: 0.5 0.21 0.90 CA= 0.19 0.16 0.35 CA= 0.06 ft Slope= % = Overland C = 0.00 min CA= 0.00 CA= 0.00 Channel Flow: loyr CL elev. 611.50 CA= 0.00 ft H = ft = 0.00 min CA= 0.00 Tc = 5.00 min CA= 0.00 DISCHARGES USED 2 yr = 1.27 CFS 10 yr = 1.63 CFS 25 yr = 2.01 CFS 100 yr = 2.68 CFS CFS RISK ASSESSMENT Detours Available Overtopping Stage Flood Plain Management Criteria and Significant Impact ADT ,Length W. uesigner: vvz:irc SIZE s c .L c m -- O � °� O/B CULVERT TYPE (in) L_ 100 yr. Flood plain elev. (cfs) m (cfs) Structures elev. freq. TW (feet) O O tR .L 0.5 4t 0.85 25 yr = Shoulder U W rn 609.04 loyr CL elev. 611.50 Freeboard HDPEP 15 0 15.00 1.27 1 1.27 HDPEP 15 0 15.00 1.63 1 1.63 HDPEP 15 0 15.00 2.01 1 2.01 HDPEP 15 0 15.00 2.68 1 2.68 ADT ,Length W. uesigner: vvz:irc OUTLET CONTROL sneer or _ Date: 1/25/2016 Treat. HW/D STATION: AHW Controls do 100 yr. Flood plain elev. ho Design AHW depth elev. LSo Structures elev. freq. TW (feet) 0.43 2yr= 0.5 10 yr= 0.85 25 yr = Shoulder 1 00yr = elev. 611.50 609.04 loyr CL elev. 611.50 Freeboard EC -1 C.L. 1 2.37' 0.63 Skew ° Cover ft. Inv. In EI. 608.50 So = 0.128 Inv. Out EI. 601.50 Orig. Gr. Elev. L= 54.8 Orig. Gr. Elev. n = 0.011 10.71 CONT. OUTLET End 0.73 0.5 0.57 HW. VELOCITY 0.10 COMMENTS INLET CONT. OUTLET CONTROL ELEV. Treat. HW/D HW Ke do (dc+D)/2 ho H LSo HW #REF! 0.43 0.54 0.5 0.46 0.85 0.85 0.04 7.00 -6.11 609.04 9.93 Y EC -1 C.L. 1 0.51 0.63 0.5 0.52 0.88 0.88 0.07 7.00 -6.05 609.13 10.71 Y EC -1 C.L. I 0.58 0.73 0.5 0.57 0.91 0.91 0.10 7.00 -5.99 609.23 11.41 Y EC -1 C.L. 1 0.77 0.96 0.5 0.66 0.96 0.96 0.18 7.00 -5.86 609.46 11.41 Y EC -1 C.L. I (SUMMARY & RECOMMENDATIONS: Endwall TVpe: Design Flood Exceed. Prob. _Elev.� Overtop Flood Exceed. Prob. Elev. A Base Flood 1% Exceed. Prob. Elev. LU-Zby Rev. 3-83 Project : LANDMAR Structure: HYDROLOGICAL DATA: D.A.= 0.27 ac # 34150042 EX CULVERT feet No. Rev. Date DISCHARGES USED 2 yr = 1.17 CFS 10 yr = 1.51 CFS Rational Method 1.86 CFS Total Area = CA Total= Cw = Tc = 5.00 12 = 5.18 I10= 6.67 125 = 7.48 I100 = 8.76 0.27 0.23 0.84 min in/hr in/hr in/hr in/hr Q2 = Q10= Q25 = Q100= 1.17 1.51 1.86 2.48 cfs cfs cfs cfs A (ac) C #REF! Time of Concentration Overland Flow: 0.24 0.90 CA= 0.22 0.03 0.35 CA= 0.01 ft Slope= % = 0.00 min Overland C = CA= 0.00 CA= 0.00 Channel Flow: CA= 0.00 ft H = ft = 0.00 min CA= 0.00 Tc = 5.00 min CA= 0.00 DISCHARGES USED 2 yr = 1.17 CFS 10 yr = 1.51 CFS 25 yr = 1.86 CFS 100 yr = 2.48 CFS CFS RISK ASSESSMENT Detours Available Overtopping Stage Flood Plain Management Criteria and Significant Impact ADT ,Length uesigner: vv,5K Date: 1/25/2016 AHW Controls 100 yr. Flood plain elev. Design AHW depth elev. Structures elev. a'A STATION: freq. TW (feet) 2yr= 10 yr= 25 yr = Shoulder 100 yr = elev. 611.45 loyr CL elev. Freeboard 1.20' Skew ° Cover ft. Inv. In EI. 609.50 So = 0.027 Inv. Out EI. 608.00 Orig. Gr. Elev. L= 55.2 Orig. Gr. Elev. n = 0.013 OUTLET End CONT. HW. VELOCITY COMMENTS INLET CONT. SIZE s c .L c m -- O � °� O/B CULVERT TYPE (in) L_ (dc+D)/2 (cfs) m (cfs) HW #REF! O O tR .L 0.5 4t 0.73 0.73 0.11 U W cn 610.14 5.81 N RCP -CLASS III 12 0 12.00 1.17 1 1.17 RCP -CLASS III 12 0 12.00 1.51 1 1.51 RCP -CLASS III 12 0 12.00 1.86 1 1.86 RCP -CLASS III 12 0 12.00 2.48 1 2.48 ADT ,Length uesigner: vv,5K Date: 1/25/2016 AHW Controls 100 yr. Flood plain elev. Design AHW depth elev. Structures elev. a'A STATION: freq. TW (feet) 2yr= 10 yr= 25 yr = Shoulder 100 yr = elev. 611.45 loyr CL elev. Freeboard 1.20' Skew ° Cover ft. Inv. In EI. 609.50 So = 0.027 Inv. Out EI. 608.00 Orig. Gr. Elev. L= 55.2 Orig. Gr. Elev. n = 0.013 OUTLET End CONT. HW. VELOCITY COMMENTS INLET CONT. OUTLET CONTROL ELEV. Treat. HW/D HW Ke do (dc+D)/2 ho H LSo HW #REF! 0.64 0.64 0.5 0.46 0.73 0.73 0.11 1.50 -0.66 610.14 5.81 N No outlet protection reqd. 0.75 0.75 0.5 0.53 0.76 0.76 0.18 1.50 -0.55 610.25 6.27 Y EC -1 C.L. I 0.86 0.86 0.5 0.59 0.79 0.79 0.28 1.50 -0.43 610.36 6.68 Y EC -1 C.L. 1 1.06 1.06 0.5 0.68 0.84 0.84 0.50 1.50 -0.16 610.56 6.68 Y EC -1 C.L. I (SUMMARY & RECOMMENDATIONS: Endwall TVpe: Design Flood Exceed. Prob. _Elev.� Overtop Flood Exceed. Prob. Elev. A Base Flood 1% Exceed. Prob. Elev. R-1 STORM SEWER DESIGN 10 YEAR FREQUENCY =ptecrii� T9Mors Rpw • N1MtS - teCo•LI.. yppoEx[x. Project: Job# : Date: By: LANDMARK AVIATION HANGAR 34150042 1/25/2016 WSK IDF CURVE REFERENCE: ALBEMARLE CO. FROM POINT TO POINT DA (ACRES) CA C INCR. ACCUM. TC (MINUTES) RAINFALL RUN-OFF (IN/HR) (CFS) LINE INVERT UPPER INVERT LOWER LENGTH (FEET) SLOPE DIAM. (INCHES) MANNING'S N COEFF. CAPACITY (CFS) VELOCITY (F.P.S.) FLOW TIME (MINUTES) PERCENT CAPACITY 6 4 0.58 0.75 0.43 0.43 5.00 6.67 2.89 5 605.35 604.32 47.39 2.17% 15 0.011 11.25 7.69 0.10 0.26 4 2 0.00 0.00 0.00 0.43 5.00 6.67 2.89 3 604.32 601.50 209.44 1.35% 15 0.011 8.86 6.51 0.54 0.33 2 1 OUT 0.00 0.00 0.00 0.43 5.00 6.67 2.89 1 601.50 600.00 23.19 6.47% 15 0.011 19.41 11.26 0.03 0.15 71N 2 0.37 0.66 0.25 0.25 5.00 6.67 1.63 7 608.50 601.50 54.76 12.78% 15 0.011 27.29 12.04 0.08 0.06 9 8 OUT 1.39 0.65 0.90 0.90 5.00 6.67 0.78 8 596.00 595.00 33.20 3.01% 15 0.011 13.24 5.81 0.10 0.06 FROM HydroCAD 49 f l PROJECT: LANDMARK AVIATION HANGAR FAM - PROJECT NO: 34150042 CREATED BY: WSK f DATE: January 25, 2016 10 YEAR RETURN FREQUENCY t=_ HYDRAULIC GRADE LINE CALCULATIONS INLET STATION OUTLET WATER SURFACEJUNCTION ELEV. FINAL H INLET WATER SURFACE ELEV. RIM ELEV. Do Qo Lo Sfo Hf LOSS Vo Ho Qi Vi QiVi Vi"2/2g Hi ANGLE Ho Ht 1.31 -It 0.51 -It 2 4 1 601.00 15" 2.89 23.19 0.20 0.05 11.26 0.49 2.89 6.51 18.82 0.66 0.23 12 0.05 0.78 1.01 0.001 1.05 604.57 1 • 607.83 4 6 604.57 15" 2.89 209.441 0.20 0.42 1 6.51 0.16 2.89 7.69 22.25 0.92 0.32 90 0.64 1.13 1.47 0.00 1.89 606.46 1 611.65 6 606.46 15" 2.89 47.39 0.20 0.09 7.69 0.23 0.23 0.30 0.00 0.39 606.85 609.68 2 71N 601.00 15" 2.89 23.19 0.20 0.05 11.26 0.49 1.63 12.04 19.66 2.25 0.79 78 1.45 2.73 3.55 0.00 3.60 604.60 607.83 7 1 N 604.60 15" 1.63 54.76 0.06 0.03 12.04 0.56 0.56 0.73 0.00 0.77 605.37 609.27 0.00 9 596.00 15" 0.78 33.20 0.01 0.00 5.81 0.13 0.13 0.17 0.00 0.18 596.18 600.83 0.00 0.5 Ht = INLET SHAPING SFo = FRICTION SLOPE (OO-Qi)/Qo = X 1.3 Ht - DROP INLET Hf = FRICTION LOSS DROP INLET X = >20 % H" =BEND LOSS Ho = CONTRACTION LOSS MANHOLE X,20% Ht = TOTAL HEAD LOSS Hi = EXPANSION LOSS 50 STIR # TYPE NOSE TOP ELEV. HEIGHT LENGTH DIAMETER MATERIAL SLOPE INV.IN INV.OUT COMMENTS 1 23.19 15" 15" TYPE S HDPE 6.47% 601.50 600.00 ES -1 30" NYLOPLAST W/ 2 MH 608.50 7.00 SOLID FLAT TOP 3 209.44 15" 15" TYPE S HDPE 1.35% 604.32 601.50 30" NYLOPLAST W/ 4 MH 612.32 8.00 SOLID FLAT TOP 5 47.39 15" 15" TYPE S HDPE 2.17% 605.35 604.32 30" NYLOPLAST W/ 6 DI 610.35 5.00 DOME YARD INLET GRATE 7 54.76 15" 15" TYPE S HDP 12.78 % 608.50 601.50 ES -1 8 33.20 15" 15" TYPE S HDP 3.01 % 596.00 595.00 ES -1 24" NYLOPLAST RISER 9 RISER 601.50 5.50 W/TRASH RACK Project Summary Report Project Description Worksheet SCC #1 2 -yr Flow Element Triangular Char Method Manning's Forn Solve For Channel Depth Input Data Mannings Coeffic 0.030 Channel Slope 170000 ft/ft Left Side Slope 3.00 H : V Right Side Slope 3.00 H : V Discharge 0.72 cfs Results Depth 0.23 ft Flow Area 0.2 ft2 Wetted Perim 1.44 ft Top Width 1.37 ft Critical Depth 0.32 ft Critical Slope 0.025879 ft/ft Velocity 4.63 ft/s Velocity Head 0.33 ft Specific Ener( 0.56 ft Froude Numb 2.42 Flow Type supercritical 62 Project Engineer: Balzer j:\...\civil\calcs\storm\scc #1.fm2 Balzer and Associates, Inc. FlowMaster v7.0 [7.0005] 02/15/16 09:14:40 AM © Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Page 2 of 2 Project Summary Report Project Description Worksheet SCC #1 10 -yr Flow Element Triangular Char Method Manning's Forn Solve For Channel Depth Input Data Mannings Coeffic 0.030 Channel Slope 010000 ft/ft Left Side Slope 3.00 H : V Right Side Slope 3.00 H : V Discharge 0.93 cfs Results Depth 0.43 ft Flow Area 0.5 ft2 Wetted Perim 2.70 ft Top Width 2.56 ft Critical Depth 0.36 ft Critical Slope 0.024939 ft/ft Velocity 1.71 ft/s Velocity Head 0.05 ft Specific Ener( 0.47 ft Froude Numb 0.65 Flow Type 3ubcritical 52 Project Engineer: Balzer j:\...\civil\calcs\storm\scc #1.fm2 Balzer and Associates, Inc. FlowMaster v7.0 [7.0005] 02/15/16 09:14:40 AM © Haestad Methods, Inc. 37 Brookside Road Waterbury, CT 06708 USA +1-203-755-1666 Page 1 of 2 53 OUTLET PROTECTION SIZING WORKSHEETS 1992 OIRLE-a�xg-- Source: USDA -SCS 40B.4 '@ZLS dpadpj 05p m W. 111- 164 WN. WMAN lm� m 0 54 3.18 C) Lo Ln -V *7 CY) 0 ID C) 11Gl. f+-rh�: Ix LLI LLJ F Cr� LLI -44-4 M C) CD Ln w + C3 V in v s - 'MO WM- F- LU M F- 7M Cli m -j C> C) ad U Cl- LLJ i L Li CO C) CO < C) 41 41 a) CO q 4- M U) CD m C1 LLJ C) f Source: USDA -SCS 40B.4 '@ZLS dpadpj 05p m W. 111- 164 WN. WMAN lm� m 0 54 3.18 C) Lo Plate 3.18-3 Ln -V *7 CY) 0 ID C) 11Gl. Plate 3.18-3 1992 Source: USDA -SCS 4aaj `DZLS de.adLU 05P It m N III - 164 0 0 o N 55 3.18 0 0 C3 0 0 LO 0 0 N O O r U d) N 4-- N O Plate 3.18-3 61.1 WATER QUALITY CALCULATIONS oe- 0 0 ,-6U 0 60 120 180 —�_ ----_ II�IIIIIII� •� l / --__ I � I I+ I � -------- \\ /1 II ----------I------------ \-------- ' N / I l - - - - - - - - - - - - - - I - - \ \ \ N --- \ _ Tit' 1 7 M L 111 11 11 \'IIII II I l I l 7711 K I I I I I I I I I I I I I I , C DA B (UNTREATED) �� II K 0.13 ACS ' I j1 I I I II111 ` ` 0.09 ACS IMP. I \\d 1 \ \ 1 \ \ \ \\\ \ \ \ \/T/ 11 I I I I > \\\\ \ \\\\\\\\\\\ \ I ----------- I - /---- 611,E x� y==--/ I I I I 1 \\\\\\\\\\\\\ \ \ I '7 DA A TREATED) 1 II rx H, \1.39 ASS I j/ /' H I /0.76 PCS IMP. CNCN _ I -'r \\ I 613 / I ' ME millilli �` \ \ r\ / \ I I ----------- -- - --------------- -----_ -_ -- _— _610�� - — —_--=—---------------=�=-- -'� - - ---- -- _-- _ - --- - - --- --- -------------- E__--_- _ — --- ____ _-_ _5= ---\ — ! 60 _-�-� � _605 _ ---- -= = --- _ -SEA=---- - — --= —_ _ E ' 605 - %=kf - ---600:�_ _ __ = ------------- ----------_ —_—_ _ —_ \ 600_ _ _ _ _5_95_-___=__-- _-- — — — — —— — — =' I ' -�==590__ ----- — i // \\ — — — — \ \ \ \ \\ \\ \ \ \\ \ \ \ \ \ \ -600-- B B \\ \\ \ \\ l l \ 1 Il A ",4Of / / f \ h •� 111 111\ \ I / I 111111 \ \ \ \ w .balzer.cc Staunton New River Valley Roanoke Richmond Harrisonburg Balzer and Associates, Inc 1561 Commerce Road Suite 401 Verona, VA 24482 540-248-3220 FAX 540-248-3221 X LU a Z a Q W Q U O g �' w > 0 HZ o o z QZ > J J O H = C) J Qe Q H K 2 W a Q J DRAWN BY ONO DESIGNED BY ONO CHECKED BY ONO DATE 01-20-2016 SCALE REVISIONS - 02 -16-2016 SHEET NO. DA -4 JOB NO. 34150042 Virginia Runoff Reduction Method Worksheet Virginia Runoff Reduction Method ReDevelopment Worksheet - v2.8 - June 2014 Site Data Summary Total Rainfall = 43 inches Site Land Cover Summary Site Rv A Soils I B Soils I C Soils D Soils Total % of Total orest (acres) 0.001 0.001 0.00 0.00 0.00 0.0 urf (acres) 0.001 0.961 0.00 0.00 0.96 48.7. npervious (acres) 0.001 1.011 0.00 0.00 1.01 51.2 1.97 100.0 Site Rv 0.58 Post Development Treatment Volume (ft) 4180 Post Development TP Load (Ib/yr) 2.63 Post Development TN Load (Ib/yr) 18.79 Total TP Load Reduction Required (Ib/yr) 1.50 Total Runoff Volume Reduction (ft) 2463 Total TP Load Reduction Achieved (Ib/yr) 2 Total TN Load Reduction Achieved (Ib/yr) 12.71 Adjusted Post Development TP Load (Ib/yr) 0.89 Remaining Phosphorous Load Reduction (Lb/yr) Required 0.00 Drainage Area Summary Drainage Area Compliance Summary D.A. A I D.A. B I D.A. C I D.A. D I D.A. E I Total P Load Red.(lb/yr) 1 1.741 0.001 0.001 0.001 0.001 1.74 N Load Red. (Ib/yr) 1 12.711 0.001 0.001 0.001 0.001 12.71 Summary Print 58 D.A. A D.A. B D.A. C D.A. D D.A. E Total Forest (acres) 0.00 0.00 0.00 0.00 0.00 0.00 Turf (acres) 0.63 0.00 0.00 0.001 0.00 0.63 Impervious (acres) 0.76 0.00 0.00 0.001 0.00 0.76 1.39 Drainage Area Compliance Summary D.A. A I D.A. B I D.A. C I D.A. D I D.A. E I Total P Load Red.(lb/yr) 1 1.741 0.001 0.001 0.001 0.001 1.74 N Load Red. (Ib/yr) 1 12.711 0.001 0.001 0.001 0.001 12.71 Summary Print 58 Virginia Runoff Reduction Method Worksheet Drainage Area A Summary Land Cover Summary BMP Selections 1.39 Practice A Soils I B Soils I C Soils I D Soils I Total I % of Total Forest (acres) 0.001 0.001 0.001 0.001 0.001 0.00 Turf (acres) 0.001 0.631 0.001 0.001 0.631 45.32 Impervious (acres) 0.001 0.761 0.001 0.001 0.761 54.68 BMP Selections 1.39 Practice Credit Area (acres) Downstream Practice 6.b. Bioretention #2 (Spec #9) Impervious: 0.76 Turf (Pervious): 0.63 Total Impervious Cover Treated (acres) 0.76 Total Turf Area Treated (acres) 0.63 Total TP Load Reduction Achieved in D.A. A (Ib/yr) 1.74 Total TN Load Reduction Achieved in D.A. A (Ib/yr) 12.71 Summary Print 59 Virginia Runoff Reduction Method Worksheet Channel and Flood Protection Summary Print 60 Weighted CN 1 -year storm Adjusted CN 2 -year storm Adjusted CN 10 -year storm Adjusted CN Target Rainfall Event (in) 2.98 3.60 5.43 D.A. A CN 81 72 74 76 D.A.B CN 0 #N/A #N/A #N/A D.A. C CN 0 #N/A #N/A #N/A D.A. D CN 0 #N/A #N/A #N/A D.A.E CN 0 #N/A #N/A #N/A Summary Print 60 SPECIFICATION #9 - BIORETENTION BASIN A WORKSHEET Design Level Level #2 BMP Sizing PROJECT NAME: PROJECT #: DATE: BY: Landmark Aviation 34150042 1/20/2016 DKO 61 Data Transcribed Runoff Reduction Worksheet Inflow Area (Al Treatment Volume (Tv) Level #2 Impervious 2,097 (cf) Impervious 0.76 (ac) Level #2 Turf 366 (cf) Turf 0.63 (ac) Treatment Level Treatment Volume Total Coefficient (Tv) TvBMP 1.25 * 2,463 (cf) = 3,078 (cf) Storage Equivalent Storage Depth Void Ratios Equiv. Surface Storage 0.50 (ft) 1 0.50 (ft) Bioretention Soil Media & Mulch 3.00 (ft) 0.25 0.75 (ft) Choker Stone 0.33 (ft) 0.4 0.13 (ft) Additional Gravel 1.00 (ft) 0.4 0.40 (ft) Required Gravel Below Underdrain 1.00 (ft) 0.4 0.40 (ft) Total Depth 5.83 (ft) 2.18 (ft) Required Surface Area Treatment Volume 3,078 =1411 (sf) Equivalent Storage Depth 2.18 Pond Design Elevations (ft Top of Bioretention Berm Top of Riser 6" Orifice P.T. Cell Low Flow Weir Top of Media Bottom of Media / Geotextile Fabric Bottom of Choker Stone 6" Underdrain Invert Bottom of Gravel Flow Path Pre -Treatment Measures Length of shortest flow path w/ >20% contributing DA Overall length Ratio Measure 1 Measure 2 Pre -Treatment Cell Grass Filter Strip 602.50 601.50 600.50 600.25 600.00 597.00 596.67 596.17 594.67 37 (ft) 45 (ft) 0.82 No Baffle Required Pre -Treatment Cell Desi¢n Design Cell Surface Area 334 (sf) Design Cell Depth 1.50 (ft) Provided Storage 501 (cf) Required Storage (TVBMP*0.15) 462 (cf) Suggested Plant Material 6 (ea.) Trees, 1" Caliper Minimum (and) 1 per 250 (sf)