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WPO201800012 Stormwater Management Maintenance Agree. Stormwater Management Plan 2018-01-31
I1 /LPPROJECT.MANAGEMENT CIVIL ENGINEERING LAND PLANNING . : ENGINEERING January 31,_20,18 County of Albemarle Department of Community Development :: 401 McIntire Road Charlottesville,VA22902 Regarding: Greenmont Hopworks :Stormwater Management Plan : Dear:Reviewer, The purpose of this project is to construct an agricultural processing facility with associated stormwater management.TMP121-92 is currently a 5.75acre vacant lot zoned rural area. The total area of disturbance is 1.57 acres: The stormwater_management for this:site will be addressed through the use of a detention pond to decrease the peak-flow"of concentrated runoff, a biofilter to reduce the volume of runoff, and-conserved open.space to satisfy:the remaining nutrient reduction requirements.;The energy balance:equation is : satisfied; and'a:summary of pre and post development flowrates is in the table below. Greenmont Hopworks Energy Balance Equation 24 Hr 1 year Storm: Qdeveloped- I•F• (Qpre-developed RVPre-Developed)/RVdeveloped Qdeveloped(Qforested*RVforested)/RVdeveloped I. Drainage Area:: .- Qpre-developed, loped — kt0 . . . RVPre-Developed. = 0059 e MaXQdev loped = 0.39 cfs RV Developed = i.,Q,096 Qdeveloped" = 0.39 .cfs PreDevelopment: ;. : PostDevelopment 10 yr 3.29 1.97 According to the VRRM spreadsheet included in this packet;the target phosphorus load reduction { exceeded by 0.08:lbs/ r • —1 Contents: Pre-Development Stormwater Management Calculations: Pre-Development SWM Map Pre-Development HydroCAD Analysis Post-Development Stormwater Management Calculations: Post-Development SWM Map Post-Development HydroCAD Analysis LD-268 Roadside&Ditch Design Time of Concentration Calculations: Pre-Development Time of Concentration Calculations Post-Development Time of Concentration Calculations Nomographs Stormwater Quality Calculations: VRRM New Development Spreadsheet Independent Reports: Excerpt from NRCS Soils Report NOAA Precipitation Report Pre-Development Stormwater Management Calculations Pre-Development SWM Map Pre-Development HydroCAD Analysis rr I ' it i r \\* ire Deve oDment \�� SWV VcD Green m on t - o3worKs P \`\�/1 --- s Ropy l ank Rood \ -\ \, _565` v — H\ d f ^ ' _____ \ \ ,,J, .......,• ......... . • . . .,....-)„..‘.-0-E- , ........„, v. \\\`\\ \ \\\`• \\\\ \_ \u'_ W�� W '�' may._ .. y v, W v, _y'-'�v. /v's. / / /' / VP / / /W i �O �, W\_ W Y t / / o \ • � v v � = *.W y'' i/ /\`\ \ \ Z .\\ v_ _ // '/ /// /� iP.g . ` ` - - \w W ySGJo W - \ \\W .-\ r,\ �\\ v�may.\� `r\\W \ .' „ ,r / // ��� /- W `S3p ` \ \\ '\ \ \ v\\.. N v. \.' !�v. k\\ \�, W ,. W_ - /' //'/' //' -, v. ..,*". ,--,11101111111;1'tPDr------ - si 1 1 1 I L .a a\ \Jr ��3,5 � / // i G ' �.. \ '1 , / r--:. l ( L „ ....... ,..\ .......... /' ./' r Oli: )7\ // z...... \I. j?,.t\i'..-.41 / -\ \ \ HSG �D� '' )�Q7� ... _____.__._... 110. 1.2 '.., 7 ,.. ,0.---- . •.., '.... \O \ ..221,.1 ? \,, ...7...:.... * *\/-' ..---. 0 - .....,........-- et ,?\"1.... _2:: ._._n.): ?___ 4,t,:?,.. * 0 0 0\ °0°0.%00°0°00°00° °2; , It 0 0 P 0 r \s ., 2. ?,1 .?...... 0. -./\I , 0 0 * 0 0 - 51C 62B I( 0 0 0 0°°0 0 P Do,0 r n HSGD HSGB * 0 0,� ,-0 0 0 0 0 .4\/-C 0 0 ---\/---.1 ��,- 0 OPEN SPACEe44 00 ‘---I\-,°00 . 000.. 00 Total 0.03 acres `)./---C 0 0 s, 0 0 0 0 0 ‘ -\ (+1.15 ac Outside 0 0 ,,,°0 0 n Limits of Disturbance) P 0 `�, Pre Development ,0 _\/-" 0Drainage Area for MANAGED TURF0 0Water Quantity Analysis: Total 1.53 acres * 0°CZ 0 .---,/,\ 1.15 acres i/ ---------- Limits of Disturbance: % --4 1.57 acres TOC: 14.3 min. IMPERVIOUS ' Total 0,01 acres 50 0 50 100 150 ■ ■ ■ ■ ■ iimms ■ ■ ■ ■ ■ Scale: 1"=50' PreDev Type 1124-ht lyr Rainfal1=2.97" Prepared by Shimp Engineering Printed 1/31/2018 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 1 Summary for Subcatchment 1S: Existing Drainage Area Runoff = ' 0.79 cfs @ 12.09 hrs, Volume= 0.059 af, Depth> 0.61" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 1 yr Rainfall=2.97" Area (sf) CN Description 32,328 61 >75% Grass cover, Good, HSG B 16,896 80 >75%Grass cover, Good, HSG D 689 79 Woods/grass comb., Good, HSG D 393 98 Paved parking, HSG B 50,306 68 Weighted Average 49,913 99.22% Pervious Area 393 0.78% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.3 Direct Entry, PreDev Type 1124-hr 10yr Rainfall=5.43" Prepared by Shimp Engineering Printed 1/31/2018 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment 1S: Existing Drainage Area Runoff = 3.29 cfs @ 12.07 hrs, Volume= 0.210 af, Depth> 2.18" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr Rainfall=5.43" Area (sf) CN Description 32,328 61 >75% Grass cover, Good, HSG B 16,896 80 >75% Grass cover, Good, HSG D 689 79 Woods/grass comb., Good, HSG D 393 98 Paved parking, HSG B 50,306 68 Weighted Average 49,913 99.22% Pervious Area 393 0.78% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.3 Direct Entry, Post-Development Stormwater Management Calculations Post-Development SWM Map Post-Development HydroCAD Analysis LD-268 Roadside & Ditch Design \ Dost Deve op nent \ swv Vc �;'\ Green m on t - o9worKs .,\ \ �� - - \ �'l -- -_ _ ` ` � __�140� Ado k\ 1 ` SS pti� R�\ \ -565 Od� _ � `\ \`���'L ����010-...�— — — �`\ ...v..... _Alt�2 Acres Undetained Area fi$ ts — �♦ ... .... -_,,,,, ......s...„ v, ts,.... ''\/\...A ,---___ ,:-/r/ ---- .11;1177,1,,=,,,,,„..... EllElljiliPjP-'1-1 :11:-..11.;!---::,-,;:s.------:'''-fi,_-;,_.,----J -"---;:.- - ------ ,„Ts -- -- , --, ----__. --•- -#:vv. vaiiiik -. , ` , !.♦.4.ice♦.�♦ov♦�♦���'..�. �-AL Ai�_ / 350 I00♦♦♦♦�♦4.41,♦44',�♦♦♦•♦+414 i♦•_•♦♦*♦:`4♦•♦*♦♦♦♦4.• , - O`k 0 ; ► 1 - ♦♦♦♦ 4.;c+♦:4.44, ♦♦4�i,:iO4 W ---- // , , .r �_ '\ ,� i•♦♦`♦♦♦a+tii!♦i+♦i♦♦+♦,♦+•°♦:e♦♦+♦_.!V•♦, - / - / 6-.-0-4.40,..-..........,....4.40.4.,♦ iC4 ♦ ♦♦ ♦ ii♦♦ii�♦!i0to• /u •;, --'---/ /// ---- - ----- --- - w --- -- _ , , ,- /,/ A , i ♦ .!♦ ♦ ♦t / ,�' ' _ - ..�. • •.,. . `D ♦ i � ♦♦ / 54 ....... \ ♦ ♦ 4♦ ? ♦♦i♦ ♦ , I . a ♦ o .♦ /014 ♦♦• ♦ ♦ '4.0.♦♦• . + ♦ ♦ + ♦ '-\ 1� � ,: ♦♦♦♦ ♦♦♦♦ ♦♦♦+ ♦♦♦ smo _ \'/ I � tea• eAs ♦♦i*•♦c ♦ ♦ +♦'o ♦♦ 1`1 i ''''N\ '. ;.*** 14007tV...AVVIV.41- . . *ZZ- 4 0*-0.4 4.11.0.4 g i ,..."--- ...--. ."*"." ....../ ....-- '-'...---- ---' ..s.--/ /1[ I . \ . .....'..".;,,,' .' ,,' -..,...''''' ---',!.......:44,10010 41.4114:y . / ,-- ......./ ,,, .---- W illkI\*, S30 --,_:,..t \\\ \ v N- .\..:4":"\ --k.'1‘,Iii...,...,,'......**".\ -,. ......_"%••.— -------____ ___--::,,--::„-'::„- -, --- --- __ _ ....----- Pto a�/ / / L11 ‘ --- ----.."N\\\\.";.,,,\ -..\\- 7:-","'"'"k>s,,,,,_ "."1". _...* ,....•,_ --- Th540 „, __„..- ....,...„. ..,..- \\ \ 1,...\ ., . . -e_____ . ....--- t , r \\''`,. -<,. •' . is , .--• „.---- ----, 1 i 1 1 I 1 ` W\\W W\�W 1 r ,11111le* fr ./' // .� /-'" \ ` - - ,,. ....-aor iip-__ ..- I 1 1 ; i. ,1 N' ,..:\ - // '‘ ---. , - 410-- _1-1 .0 ,' / 1 I 7.•-•, . c 1 1 , ..... .._, ,i,.# -_--. --. • --__—_-.......- ............-'-.-.-- .. . A0' // / /,/ / \ \:.-_\ \ \ \`__ — N-.\,.•0,\ �\ \ \```_ /// // // 7 E.4-0'_-'rl 2,',-,\---3\..-_-v-.-..,40-7x:1\ \ '/ 7.-._.- ,.. -----,-'-_,,_1- ../- / /'////'---- \\\l N\\\\\_- \\\ \\\\`, HSG �D�- / /// / , '/ .,7 --� -- '` \` N` S� -_/' / `�� \‘ IA /'° ‘ Ti‘-Pr '7(‘41 \ --____ / V-' \ -,� - ' , -___ --------- - Zv , .*7 '<1' - eit F\,1?-- , -",A7 0,----rA__'1/- e- `lA \ 410t '- 0 5.-A? y/\:i, `--\/--A i/V? ---2\ -Cry\_.,40 0 --A. „AO -,.-\/__ '4 2-a r'\-7 ..--/C-V6 YA., v....A -V-1 4\/--C \/1 0 Af 41r 0 TA;AAt_ V2--\/ 5 \';-\72\r'?0)/\- t/V_ 0 1/ 0 / 51C 62B I� �'�,0 r/\, P �. ' /Y//\ ('°O' 174\/ 07 15.A.7/ r HSG D HSG B * 0 V ` 0 -•/Vi �`' ,0 d 0 1 y_? , 0 0 i„,4,-c /y/;._,,\ ,,z 0`\/-'t\r -c 0 0 . ,,n 0 OPEN SPACE ' - Total 0.00 acres ,0 0 V -- - "`.�,- 1 (+1.15 ac Outside A 4-v-1 0 A Limits of Disturbance) ' L 0 ✓—.---._.._ Limits of Disturbance: v. * 1�' j C 1.57 acres MANAGED TURF _ 5-A s _____-__ � � - Pond DA: 1.37 acres v, Total 0.94 acres 0 0 �.. . TOC1: 7.0 min. - 4 4, , r- - Not Drawn] Untreated DA: 0.18 Acres Not Drawn] IMPERVIOUS TOC2: 5.0 min. Total 0.63 acres 50 0 50 100 150 ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Scale: 1"=50' 15 2S Pond Drain e Area Untreatel) Drainage Area 4P Detention and /61\ Bioretentio 3L Point of Analysis SubCat Reach 'on. MI Drainage Diagram for PostDev Prepared by Shimp Engineering, Printed 1/31/2018 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC I PostDev Type 1124-hr lyr Rainfall=2.97" Prepared by Shimp Engineering Printed 1/31/2018 HydroCADO 9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment 1 S: Pond Drainage Area Runoff = 2.86 cfs @ 11.99 hrs, Volume= 0.140 af, Depth> 1.23" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type 1124-hr 1yr Rainfall=2.97" Area (sf) CN Description 23,945 61 >75% Grass cover, Good, HSG B 25,863 98 Paved parking, HSG B 9,089 80 >75% Grass cover, Good, HSG D 940 98 Paved parking, HSG D 59,837 80 Weighted Average 33,034 55.21% Pervious Area 26,803 44.79% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.0 Direct Entry, Summary for Subcatchment 2S: Untreated Drainage Area Runoff = 0.39 cfs @ 11.96 hrs, Volume= 0.018 af, Depth> 1.23" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 1yr Rainfall=2.97" Area (sf) CN Description 71 61 >75% Grass cover, Good, HSG B 7,556 80 >75%Grass cover, Good, HSG D 7,627 80 Weighted Average 7,627 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 4P: Detention Pond Inflow Area= 1.374 ac, 44.79% Impervious, Inflow Depth > 1.23" for 1yr event Inflow = 2.86 cfs @ 11.99 hrs, Volume= 0.140 af Outflow = 0.26 cfs @ 12.56 hrs, Volume= 0.135 af, Atten= 91%, Lag= 34.0 min Primary = 0.26 cfs @ 12.56 hrs, Volume= 0.135 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 539.37' @ 12.56 hrs Surf.Area= 2,379 sf Storage= 2,646 cf Plug-Flow detention time= 123.3 min calculated for 0.135 af (96%of inflow) Center-of-Mass det. time= 103.4 min ( 946.7 - 843.3 ) PostDev Type 1124-hr 1 yr Rainfall=2.97" Prepared by Shimp Engineering Printed 1/31/2018 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 3 Volume Invert Avail.Storage Storage Description #1 538.00' 11,400 cf Custom Stage Data(Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 538.00 1,510 0 0 539.00 2,130 1,820 1,820 540.00 2,810 2,470 4,290 541.00 3,540 3,175 7,465 542.00 4,330 3,935 11,400 Device Routing Invert Outlet Devices #1 Primary 538.00' 15.0" Round Culvert L= 33.0' Ke= 0.600 Inlet/Outlet Invert= 538.00'/536.00' S= 0.0606 '/' Cc= 0.900 n= 0.010 #2 Device 1 538.00' 3.0"Vert. Orifice/Grate C= 0.600 #3 Device 1 539.78' 10.0"Vert. Orifice/Grate C= 0.600 #4 Device 1 541.40' Custom Weir/Orifice, Cv=2.62 (C=3.28) Head (feet) 0.00 0.60 Width (feet) 6.25 6.25 Primary OutFlow Max=0.26 cfs @ 12.56 hrs HW=539.37' (Free Discharge) =Culvert (Passes 0.26 cfs of 4.77 cfs potential flow) -2=Orifice/Grate (Orifice Controls 0.26 cfs @ 5.36 fps) -3=Orifice/Grate ( Controls 0.00 cfs) -4=Custom Weir/Orifice ( Controls 0.00 cfs) Summary for Pond 6P: Bioretention Inflow Area= 1.374 ac, 44.79% Impervious, Inflow Depth > 1.18" for 1 yr event Inflow = 0.26 cfs @ 12.56 hrs, Volume= 0.135 of Outflow = 0.21 cfs @ 15.04 hrs, Volume= 0.078 af, Atten= 19%, Lag= 148.9 min Primary = 0.21 cfs @ 15.04 hrs, Volume= 0.078 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 535.44' @ 15.04 hrs Surf.Area= 2,258 sf Storage= 2,566 cf Plug-Flow detention time= 243.4 min calculated for 0.078 af (58% of inflow) Center-of-Mass det. time= 119.4 min ( 1,066.1 - 946.7) Volume Invert Avail.Storage Storage Description #1 531.50' 3,820 cf Custom Stage Data(Prismatic) Listed below (Recalc) PostDev Type 1124-hr 1 yr Rainfall=2.97" Prepared by Shimp Engineering Printed 1/31/2018 HydroCAD©9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 4 Elevation Surf.Area Voids Inc.Store Cum.Store (feet) (sq-ft) (%) (cubic-feet) (cubic-feet) 531.50 1,704 0.0 0 0 531.51 1,704 40.0 7 7 532.92 1,704 25.0 601 607 533.92 1,704 25.0 426 1,033 534.92 1,704 25.0 426 1,459 534.93 1,704 30.0 5 1,465 535.15 2,258 100.0 436 1,900 536.00 2,258 100.0 1,919 3,820 Device Routing Invert Outlet Devices #1 Primary 531.50' 15.0" Round Culvert L= 61.0' Ke= 0.600 Inlet/Outlet Invert= 531.50'/529.00' S= 0.0410 '/' Cc= 0.900 n= 0.010 #2 Device 1 535.40' Custom Weir/Orifice, Cv=2.62 (C=3.28) Head (feet) 0.00 0.60 Width (feet) 6.25 6.25 Primary OutFlow Max=0.19 cfs @ 15.04 hrs HW=535.44' (Free Discharge) 4-1=Culvert (Passes 0.19 cfs of 10.09 cfs potential flow) L2=Custom Weir/Orifice (Weir Controls 0.19 cfs @ 0.69 fps) Summary for Link 3L: Point of Analysis Inflow Area = 1.549 ac, 39.73% Impervious, Inflow Depth > 0.74" for 1 yr event Inflow = 0.39 cfs @ 11.96 hrs, Volume= 0.096 af Primary = '0.39 cfs @ 11.96 hrs, Volume= 0.096 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs PostDev Type 1124-hr 10yr Rainfall=5.43" Prepared by Shimp Engineering Printed 1/31/2018 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment 1 S: Pond Drainage Area Runoff = 7.49 cfs @ 11.98 hrs, Volume= 0.374 af, Depth> 3.27" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr Rainfall=5.43" Area (sf) CN Description 23,945 61 >75%Grass cover, Good, HSG B 25,863 98 Paved parking, HSG B 9,089 80 >75% Grass cover, Good, HSG D 940 98 Paved parking, HSG D 59,837 80 Weighted Average 33,034 55.21% Pervious Area 26,803 44.79% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.0 Direct Entry, Summary for Subcatchment 2S: Untreated Drainage Area Runoff = 1.02 cfs @ 11.96 hrs, Volume= 0.048 af, Depth> 3.27" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 10yr Rainfall=5.43" Area (sf) CN Description 71 61 >75% Grass cover, Good, HSG B 7,556 80 >75% Grass cover, Good, HSG D 7,627 80 Weighted Average 7,627 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 4P: Detention Pond Inflow Area= Inflow 1.374 ac, 44.79% Impervious, Inflow Depth > 3.27" for 10yr event 7.49 cfs @ 11.98 hrs, Volume= 0.374 af Outflow = 2.26 cfs @ 12.13 hrs, Volume= 0.363 af, Atten= 70%, Lag= 8.9 min Primary = 2.26 cfs @ 12.13 hrs, Volume= 0.363 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 540.71' @ 12.13 hrs Surf.Area= 3,329 sf Storage= 6,474 cf Plug-Flow detention time= 117.1 min calculated for 0.362 af (97%of inflow) Center-of-Mass det. time= 99.3 min ( 914.6 - 815.3 ) PostDev Type 1124-hr 10yr Rainfall=5.43" Prepared by Shimp Engineering Printed 1/31/2018 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 6 Volume Invert Avail.Storage Storage Description #1 538.00' 11,400 cf Custom Stage Data(Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 538.00 1,510 0 0 539.00 2,130 1,820 1,820 540.00 2,810 2,470 4,290 541.00 3,540 3,175 7,465 542.00 4,330 3,935 11,400 Device Routing Invert Outlet Devices #1 Primary 538.00' 15.0" Round Culvert L= 33.0' Ke= 0.600 Inlet/Outlet Invert= 538.00'/536.00' S= 0.0606 '/' Cc= 0.900 n= 0.010 #2 Device 1 538.00' 3.0"Vert. Orifice/Grate C= 0.600 #3 Device 1 539.78' 10.0"Vert. Orifice/Grate C= 0.600 #4 Device 1 541.40' Custom Weir/Orifice, Cv=2.62(C=3.28) Head (feet) 0.00 0.60 Width (feet) 6.25 6.25 Primary OutFlow Max=2.25 cfs @ 12.13 hrs HW=540.71' (Free Discharge) L1=Culvert (Passes 2.25 cfs of 7.99 cfs potential flow) -2=Orifice/Grate (Orifice Controls 0.38 cfs @ 7.74 fps) -3=Orifice/Grate (Orifice Controls 1.87 cfs @ 3.44 fps) -4=Custom Weir/Orifice ( Controls 0.00 cfs) Summary for Pond 6P: Bioretention Inflow Area= 1.374 ac, 44.79% Impervious, Inflow Depth > 3.17" for 10yr event Inflow = 2.26 cfs @ 12.13 hrs, Volume= 0.363 of Outflow = 1.87 cfs @ 12.35 hrs, Volume= 0.305 af, Atten= 18%, Lag= 13.4 min Primary = 1.87 cfs @ 12.35 hrs, Volume= 0.305 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 535.60' @ 12.35 hrs Surf.Area= 2,258 sf Storage= 2,922 cf Plug-Flow detention time= 113.9 min calculated for 0.304 af (84% of inflow) Center-of-Mass det. time=44.0 min ( 958.5 - 914.6 ) Volume Invert Avail.Storage Storage Description #1 531.50' 3,820 cf Custom Stage Data(Prismatic) Listed below (Recalc) PostDev Type 1124-hr 10yr Rainfall=5.43" Prepared by Shimp Engineering Printed 1/31/2018 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 7 Elevation Surf.Area Voids Inc.Store Cum.Store (feet) (sq-ft) (%) (cubic-feet) (cubic-feet) 531.50 1,704 0.0 0 0 531.51 1,704 40.0 7 7 532.92 1,704 25.0 601 607 533.92 1,704 25.0 426 1,033 534.92 1,704 25.0 426 1,459 534.93 1,704 30.0 5 1,465 535.15 2,258 100.0 436 1,900 536.00 2,258 100.0 1,919 3,820 Device Routing Invert Outlet Devices #1 Primary 531.50' 15.0" Round Culvert L= 61.0' Ke= 0.600 Inlet/Outlet Invert= 531.50'/529.00' S= 0.0410 '/' Cc= 0.900 n= 0.010 #2 Device 1 535.40' Custom Weir/Orifice, Cv=2.62(C= 3.28) Head (feet) 0.00 0.60 Width (feet) 6.25 6.25 Primary OutFlow Max=1.85 cfs @ 12.35 hrs HW=535.60' (Free Discharge) L1=Culvert (Passes 1.85 cfs of 10.33 cfs potential flow) L2=Custom Weir/Orifice (Weir Controls 1.85 cfs @ 1.47 fps) Summary for Link 3L: Point of Analysis Inflow Area = 1.549 ac, 39.73% Impervious, Inflow Depth > 2.73" for 10yr event Inflow = 1.97 cfs @ 12.35 hrs, Volume= 0.352 af Primary = 1.97 cfs @ 12.35 hrs, Volume= 0.352 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs PostDev Type 1124-hr 100yr Rainfall=8.91" Prepared by Shimp Engineering Printed 1/31/2018 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 8 Summary for Subcatchment 1S: Pond Drainage Area Runoff = 14.34 cfs @ 11.98 hrs, Volume= 0.741 af, Depth> 6.48" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr Rainfall=8.91" Area (sf) CN Description 23,945 61 >75% Grass cover, Good, HSG B 25,863 98 Paved parking, HSG B 9,089 80 >75% Grass cover, Good, HSG D 940 98 Paved parking, HSG D 59,837 80 Weighted Average 33,034 55.21% Pervious Area 26,803 44.79% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.0 Direct Entry, Summary for Subcatchment 2S: Untreated Drainage Area Runoff = 1.94 cfs @ 11.95 hrs, Volume= 0.095 af, Depth> 6.48" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type II 24-hr 100yr Rainfall=8.91" Area (sf) CN Description 71 61 >75% Grass cover, Good, HSG B 7,556 80 >75%Grass cover, Good, HSG D 7,627 80 Weighted Average 7,627 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 4P: Detention Pond Inflow Area = 1.374 ac, 44.79% Impervious, Inflow Depth > 6.48" for 100yr event Inflow = 14.34 cfs @ 11.98 hrs, Volume= 0.741 of Outflow = 9.91 cfs @ 12.06 hrs, Volume= 0.709 af, Atten= 31%, Lag= 4.9 min Primary = 9.91 cfs @ 12.06 hrs, Volume= 0.709 of Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 541.85' @ 12.06 hrs Surf.Area= 4,210 sf Storage= 10,749 cf Plug-Flow detention time= 89.1 min calculated for 0.709 af,(96% of inflow) Center-of-Mass det. time= 63.7 min ( 859.6 - 795.9 ) PostDev Type II 24-hr 100yr Rainfall=8.91" Prepared by Shimp Engineering Printed 1/31/2018 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 9 Volume Invert Avail.Storage Storage Description #1 538.00' 11,400 cf Custom Stage Data(Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 538.00 1,510 0 0 539.00 2,130 1,820 1,820 540.00 2,810 2,470 4,290 541.00 3,540 3,175 7,465 542.00 4,330 3,935 11,400 Device Routing Invert Outlet Devices #1 Primary 538.00' 15.0" Round Culvert L= 33.0' Ke= 0.600 Inlet/Outlet Invert= 538.00'/536.00' S= 0.0606 '/' Cc= 0.900 n= 0.010 #2 Device 1 538.00' 3.0"Vert. Orifice/Grate C= 0.600 #3 Device 1 539.78' 10.0" Vert. Orifice/Grate C= 0.600 #4 Device 1 541.40' Custom Weir/Orifice, Cv= 2.62 (C=3.28) Head (feet) 0.00 0.60 Width (feet) 6.25 6.25 Primary OutFlow Max=9.56 cfs @ 12.06 hrs HW=541.83' (Free Discharge) t=Culvert (Passes 9.56 cfs of 9.92 cfs potential flow) -2=Orifice/Grate (Orifice Controls 0.45 cfs @ 9.27 fps) -3=Orifice/Grate (Orifice Controls 3.35 cfs @ 6.15 fps) -4=Custom Weir/Orifice (Weir Controls 5.75 cfs @ 2.14 fps) Summary for Pond 6P: Bioretention Inflow Area = 1.374 ac, 44.79% Impervious, Inflow Depth > 6.19" for 100yr event Inflow = 9.91 cfs @ 12.06 hrs, Volume= 0.709 af Outflow = 9.12 cfs @ 12.10 hrs, Volume= 0.650 af, Atten= 8%, Lag= 2.2 min Primary = 9.12 cfs @ 12.10 hrs, Volume= 0.650 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 535.98' @ 12.10 hrs Surf.Area= 2,258 sf Storage= 3,782 cf Plug-Flow detention time= 67.0 min calculated for 0.649 af (92% of inflow) Center-of-Mass det. time= 24.1 min ( 883.7 - 859.6 ) Volume Invert Avail.Storage Storage Description #1 531.50' 3,820 cf Custom Stage Data(Prismatic) Listed below (Recalc) PostDev Type 1124-hr 100yr Rainfall=8.91" Prepared by Shimp Engineering Printed 1/31/2018 HydroCAD®9.10 s/n 07054 ©2011 HydroCAD Software Solutions LLC Page 10 Elevation Surf.Area Voids Inc.Store Cum.Store (feet) (sq-ft) (%) (cubic-feet) (cubic-feet) 531.50 1,704 0.0 0 0 531.51 1,704 40.0 7 7 532.92 1,704 25.0 601 607 533.92 1,704 25.0 426 1,033 534.92 1,704 25.0 426 1,459 534.93 1,704 30.0 5 1,465 535.15 2,258 100.0 436 1,900 536.00 2,258 100.0 1,919 3,820 Device Routing Invert Outlet Devices #1 Primary 531.50' 15.0" Round Culvert L= 61.0' Ke= 0.600 Inlet/Outlet Invert= 531.50'/529.00' S= 0.0410 '/' Cc= 0.900 n= 0.010 #2 Device 1 535.40' Custom Weir/Orifice, Cv=2.62 (C=3.28) Head (feet) 0.00 0.60 Width (feet) 6.25 6.25 Primary OutFlow Max=9.02 cfs @ 12.10 hrs HW=535.98' (Free Discharge) 4-1=Culvert (Passes 9.02 cfs of 10.88 cfs potential flow) 1-2=Custom Weir/Orifice (Weir Controls 9.02 cfs @ 2.49 fps) Summary for Link 3L: Point of Analysis Inflow Area= 1.549 ac, 39.73% Impervious, Inflow Depth > 5.77" for 100yr event Inflow = 9.59 cfs @ 12.09 hrs, Volume= 0.745 of Primary = 9.59 cfs @ 12.09 hrs, Volume= 0.745 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Greenmont Hopworks Modified LD-268 Roadside and Median Ditch Design Form MIN MAX Earth Protective Lining DITCH A (ac) Tc(min) 110 (in/hr) 010 _:1 L _:1 R SLOPE SLOPE ALLOW. n=.03 EC-2: n=.05 n=.015 C Ft/Ft Ft/Ft VEL. VEL.* On VEL* DEPTH On DEPTH 1 0.54 0.73 5.0 7.01 2.79 2 2 0.02 0.14 6 0.14 3.37 0.56 2 0.54 0.73 5.0 7.01 2.79 2 2 0.02 0.07 6 0.14 2.71 0.64 *Velocity calculations performed using average slope for this application Time of Concentration Calculations Pre-Development Time of Concentration Calculations Post-Development Time of Concentration Calculations Nomographs Hunter's Branch Pre-Development Time of Concentration Calculations LOD (Blue) 100 ft overland flow-turf 10.0% slope 0.35 C-value 9.5 min Seelye Chart 288 ft s. c.flow-turf 10.0% slope 1.0 fps velocity 4.8 min. NEH Figure 15-4 14.3 min. Hunter's Branch Post-Development Time of Concentration Calculations Pond DA(Green) 100 ft overland flow-impery 10.0% slope 0.9 C-value 5.0 min Seelye Chart 140 ft s.c.flow-impervious 5.0% slope 4.5 fps velocity 0.5 min. NEH Figure 15-4 90 ft s.c.flow-turf 10.0% slope 1.0 fps velocity 1.5 min. NEH Figure 15-4 7.0 min. Untreated DA 5.0 min. v G LENGTH " L" OF STRIP IN FEET nr 1 1 I 1 I I l I l I I I III ! Hipp I I I I 1 7 J , l l I —�• d / IQ) W N i 01 O 00(0 . O 0 O 0 0 0 0 0 0 00 4 / 0 0 :1:1n- : vDctri co co �cD �� _, - o Tj oN NW fD N N -i CCD O I CHARAGTER OF I GROUND If�T "C'✓ALGAE N /W A 6 J Oo -o "C'✓ALUL ., r /cD / v)ri, nv / • r c PIVO LINE O \ N — N — O 2 0 0 0 O O cn I i Illl 11 1 l 111111 rn P 'CENT SLOPE \ b \ Iv u \— N N W (A cn Q1 -4 CO cD • (r 0 cn O Cn ~' I 1 I i I I I l 1 1 1 \I 1 1 1 _1 1 . 1 1 1 1 1 1 1 1 f l l l INLET CONCENTRATION TIME IN. MINUTES N Slope(ft/ft) 0 0 0 0 0 0 0 © © 0 0 0 0 0 ppp- 0.15 2 a P 8 �wCOo 0 0 0 8 8 o0e8 0.2 i . 0.3 Fore — 'Yt 0.4 41thhea a dt0.6 ere, /tte rvk0.7 kalio a 4 0.8 e e 0.9 ° tov /4 el, 1.0 ! • 8 ` earfyb Gv/ovate, SSA-01.4. o a `� tb e -14 0._ ilk/ko 2 Pa`e�t Gt„ 1 (1er4, '� 44(s 47 ent 7 orate I I c) t 3 ati Sys d q, . 4 u lid -Wf4ir w 7 8 • 10 lb 20 . Stormwater Quality Calculations VRRM New Development Spreadsheet Project Name'. Date' "$ ..... eslNMaeRiRea T.._..__ UMar DevelopmentPeoJBct? - illiliall Site Information Post-Development Project(Treatment Volume and Loads) Enter Total Disturbed Area(acres) 4 11=1111111Check:. aMP Design Specifications List:'.2013 Draft Stds&Specs Maximum reduction required.' 20% Linear project? No The site's net increase in impervious cover(acres)is:IMICIMI Land cover areas entered correctly? V Past-Development TP Load Reduction for Site(lb/yr): W Total disturbed area entered?) v, --_ - ---- Pre-ReDevelopment Land Cover(acres) a sods esail, csanz Dsad: Tatas • s. Finast/Open Space(acres)-undisturbed. protected forest/open space or reforested land 0 02 1.16 1.18 • {. Managed Turf(acres)-disturbed,graded for yards or other turf to be mowed/managed 1.10 039 1.53 impervious cover(acres) 0 OI 0 0: 27: Post-Development land Cover(acres) A Soils a Soils c Soils D Soils Totals forest/Open Space(acres)-undisturbed, • e pro tected forest/open space or reforested land 1.15 1.15 Manaaad Turf(acres)-disturbed,graded for ..............................._._____....____.._....._...._...._..__._.._..___. .. .yards or other turf to be mowed/managed 0.56 0.30 0.90 Impervious Cover(acres) 0 61 0.02 0.63 - Area Check OK. OK. OK. OK. 2,72 •forett/Open Spare areas must be otereed:n orrordanrrwtn the Vrgnic Runoff F roan MCMed1 Constants Runoff Coefficients(M) Annual Rainfall(inches) 03 ASepe BSoh [Sops DSoas ---�__-- - --_ --- Target Rainfall Event(inAa) 1.00 _ m est/Open Space 0.02 0.03 0.04 0.05 Total Phosphorus UP)Ent‘OVA) 0.26Managed Turf 0.15 0.20 0.22 0.25 Total Nitrogen(Tel)EMC(nWL) 1.36 nrpero0u0Cover 0.95 0.95 0.95 095 Target TO Load Ob/acreM) 0A1 _ 1 pl(unness correction factor) 0.90 LAND COVER SUMMARY--PRE-REDEVELOPMENT LAND COVER SUMMARY--POST DEVELOPMENT Land Cover SvmmnI r l'._..._.._...__..._.. ._..__..._. .. y-Pre Land[over Summary-POft(F/no9 Landfowr SumlrNrrylest Land[avelSvnvnary-Pose Pre4laDerNapment listed Adjusted' Pat WOev.a New Impervious PmtA.O.atlapnwm PeatievdapewM New Supervene Forest/Open Space Cover(acres) 1.18 1.15 Forest/Open Space 1.15 Forest/Open Space Cover(acres) Cover(acres) Weighted Rv)fcresq 0.05 0.05 Weighted IN(forest) 0.0.5 Weighted Rv(tOred) %Forest 03ri. 55% %Forest 42% %Forest Managed Turf Cover(acres) 1.53 0.90 Managed Turf Cover 0.90 Managed Turf Cover (acres) Mows) Weighted Rv(tur0 0.21 0.22 _-_ Weighted M(turf) 0.22 Weighted es(turf) ....._......... %Managed Turf 56% 45% %Maluged Turf 35% %Managed Turf Impervious[weer(acres) 0.01 0.01 Impetuous Cover(acres) 0.63 tlOev.Impertoos New Impervious Cover Cover(acres) (acre) Rv(impervbus) 0.95 095 Rv(impercoue) 0.95 Rv(impemous) M(Impervious) %Impervious 0% 0% %Impervious 23% %Impervious Total Site Area(arrest 2.72 2.10 Final see Area(acres) 2.71 Total Rellev.SateRnas III (acres) Sae no 0.14 0.13 final Pose Ow SkeM 0.32 Were Sate M .1111 Treatment Volume and Nutrient Load Treatment Volume and Nutrient Load Pre-ReDevelopment Treatment Volume Final Post-Devalopment I Poe-a 0.uelopment I Post Oevelopment r...., _.._.. (acre el 0.0328 0,0228 Treatment Volume 0.0719 Treatment Volume 0.0228 Treatment Volume 00492 C. (aaett) (acre-n) (acr n) i. -...._ .t-e.am Vaknw N • - Rnal eMtvetpre-eeDeveopment Treatment Volume pert«emVd�me kabk 3,1381A29 995 Treatment Vo 3.133(eWefwt) (cubic feet) (tulle Mat( tee) Pre-ReDevelopment TP Load anal Post- IatyDevebprleM :. Iro/nl 0.90 0.62 • Develo(pment)TP Load 1.97 a RMI• 8 T }a,, Pare.oevellppme)nt rp 1.34 w he-Peoewmomer.mived perm 0.33 030 . Fin o:!n0010 en tr P Rene ekpmemn ablweMl Lv a per acre 0.71 Laid n,star • Ib/arreMl • 16/«/y.l bareiine Tr Load(IbMl Ma Reduction eeeuired (eel Be/emM apdied to prs.edewMw pnd arc... dos vs 0.86 Ieelew Pre- 20% land paed br mot Rrw.e o'a coral n neoeeelnplem Lead) r Adlusted LOnd CnvrtSummory, TP Load Reduction TP Load Reduction Pre veoevelnpment Iona cove,minus pervious land cover(foresVopen space an e Required for -0.24 Required for New 1.09 managed NIB ocmoge proposed for new impetuous rover. Redeveloped AreaImpervious Area lib/Yr) (lb/WL Adjusted total ucreoge's cvnslstent mai,Post-ReDevelopment acreage(minus ocrcope . aJ new OnpeMws raver) a Reduction below new development load • limitation nor required Column I slaws hind reammon requement/an new impervious rover(Lased on on new development Mod limit Os11hs/ocre/yeoa,, Post-Development Requirement for Site Area TP Load Reduction Required(Ib/yr) OAS Drainage Area A Land Cover (acres) A Soils B Soils C Soils D Soils Totals Land Cover Rv Forest/Open Space 0.00 0.00 (acres) Managed Turf 0.55 0.21 0.76 0.21 (acres) Impervious Cover 0.59 0.02 0.62 0.95 (acres) Total 1.37 Total Phosphorus Available for Removal in D.A. A (Ib/yr) 1.70 Post Development Treatment Volume in D.A.A (cf) 2,710 Stormwater Best Management Practices (RR = Runoff Reduction) Volume Runoff Managed Impervious from Runoff Remaining Total BMP Phosphorus Untreated Phosphorus Remaining Downstream Practice Reduction Turf Credit Cover Credit Upstream Reduction Runoff Volume Treatment Phosphorus Removal Load from Phosphorus Removed By Phosphorus Practice to be Credit (%) Area (acres) Area (acres) Practice 3 3 3 Efficiency (%) Upstream Load to (ft3) (ft3) Volume (ft3) Practice (Ib) Load (Ib) Employed (ft3) Practices (Ib) Practice (Ib) 6. Bioretention (RR) •... :lore en ion or Micro- 80 0.76 0.62 0 1,084 1,626 2,710 25 0.00 1.70 0.94 0.77 Bioretention #2 (cnar tfQl TOTAL IMPERVIOUS COVER TREATED (ac) 0.62 AREA CHECK: OK. TOTAL MANAGED TURF AREA TREATED (ac) 0.76 AREA CHECK: OK. TOTAL RUNOFF REDUCTION IN D.A.A(ft3) 1,084 TOTAL PHOSPHORUS AVAILABLE FOR REMOVAL IN D.A. A(Ib/yr) 1.70 TOTAL PHOSPHORUS REMOVED WITH RUNOFF REDUCTION PRACTICES IN D.A. A(Ib/yr) 0.94 TOTAL PHOSPHORUS REMAINING AFTER APPLYING RUNOFF REDUCTION PRACTICES IN D.A. A(Ib/yr) 0.77 SEE WATER QUALITY COMPLIANCE TAB FOR SITE COMPLIANCE CALCULATIONS Site Results(Water Quality Compliance) Area Checks O.A.A D.A.B D.A.C D.A.D D.A.E AREA CHECK FOREST/OPEN SPACE(ac) 0.00 0.00 0.00 0.00 0.00 I OK. I IMPERVIOUS COVER lac) 0.62 0.00 0.00 0.00 0.00 I OK. IMPERVIOUS COVER TREATED lac),' 0.62 0.00 0.00 _ 0.00 0.00 MANAGED TURF AREA(ac) 0.76 0.00 0.00 _ 0.00 0.00 MANAGED TURF AREA TREATED(ac) 0.76 0.0C 0.00 0.00 0.00 I OK. AREA CHECK I OK. OK. I OK. OK. I OK. Site Treatment Volume(ft3) 3,133 Runoff Reduction Volume and TP By Drainage Area D.A.A II D.A.B lI D.A.C II D.A.D II D.A.E TOTAL RUNOFF REDUCTION VOLUME ACHIEVED(h) 1,084 0 0 0 0 1,084 TP LOAD AVAILABLE FOR REMOVAL(Ib/yr) 1.70 0.0C 0.00 0.00 0.00 1.70 _ TP LOAD REDUCTION ACHIEVED(Ib/yr) 0.9.1 0.0C 0 00 0.00 0.00 0.94 TP LOAD REMAINING(Ib/yr)I 0 77 II 0.00 D 0.00 II 0.00 II 0.00 II 0.77 NITROGEN LOAD REDUCTION ACHIEVED(Ib/yr)II 7.79 II 0,00 II__0.00_� 0.00 II 0.00 II_ 7.79 Total Phosphorus FINAL POST-DEVELOPMENT TP LOAD(Ib/yr) 1.97 TP LOAD REDUCTION REQUIRED(Ib/yr) 0.85 TP LOAD REDUCTION ACHIEVED(Ib/yr) 0.94 TP LOAD REMAINING(Ib/yr).1 1.03 REMAINING TP LOAD REDUCTION REQUIRED(Ib/yr): 0.00 " "TARGET TP REDUCTION EXCEEDED BY 0.08 LB/YEAR" Total Nitrogen(For Information Purposes) POST-DEVELOPMENT LOAD(Ib/yr) 14 08 NITROGEN LOAD REDUCTION ACHIEVED(Ib/yr) 7.79 REMAINING POST-DEVELOPMENT NITROGEN LOAD(Ib/yr) 6.29 Virginia Runoff Reduction Method W orvsheet DEQ Virginia Runoff Reduction Method ReDevelopment Compliance Spreadsheet-Version 3.0 BMP Design Specifications List.2013 Draft Stds&Specs Site Summary Total Rainfall(in): 43 Total Disturbed Acreage: 1.57 Site Land Cover Summary Pre-ReDevelopment Land Cover)acres) A soils B Sells C Solis DSolb Totals %of Total Forest/Open(acres) 0.00 0.02 0.00 1.16 1.18 43 Managed Turf(acres) 0.00 1.14 0.00 0.39 1.53 56 Impervious Cover(acres) 0.00 0.01 0.00 0.00 0.01 0 2.72 100 Post-ReDevelopment Land Cover(acres) A soils B Soils C Soils D Soils Totals %of Total Forest/Open(acres) 0.00 0.00 0.00 1.15 1.15 42 • Managed Turf(acres) 0.00 0.56 0.00 0.38 0.94 35 Impervious Cover(acres) 0.00 0.61 0.00 0.02 0.63 23 •Forest/Open space areas must be protected In ucordence with the Virginia Aunoft Reduction Method 2.72 100 Site Tv and Land Cover Nutrient Loads Final Post-Development Post- Pre Final Post-Development Post-ReDevelopment TP PestReDevelo Post- Adjusted Pre- ReDevelopment TP ( pment fleDevelopment Development peDevelopment Load per acre TP Load per acre load per acre i New Impervious) (New lmpeMous) (Ib/acre/yr) (Ib/acre/yr) (lb/acre/Tr) Site Rv 0.32 0.13 0.95 0.13 0.30 0.72 0.30 Treatment Volume(fts) 3,133 995 2,138 995 TP Load(Ib/yr) 1.97 0.62 1.34 0.62 Baseline TP Load pS/p): 0.861• 'Aeduaron baba new A..Aa,.nt bad lbniturbn,orimuled Total TP Load Reduction Required)lb/yr) O.BS -0.24 1.09 C--"'k"&q d`%^-��E,' ' .rt: Final Post Development Load '- *ird.0 � V:. Post.ReDevelo Impervious) Pre-ReDevelopment y 1c ( pmenti New TN Load(Ib/n) 14.08 6 42 Site Compliance Summary Maximum%Reduction Required Below 20% •Note:%Reduction will reduce pesn-deeelapmenn OP load to less than or equal to baseline load of 0.86 lb/yr(0.4116/oc/yr) Pre.ReDevelopment Load (Required reduction for Post.Re0ev.•Post-Re0ev TP load-baseline Budd of 0.11611b/yrl bowline load-site area r get lb/oc/y, Total Runoff Volume Reduction(fe) 1,084 Total TP Load Reduction Achieved(lb/n) 0.94 Total TN Load Reduction Achieved(Ib/yr) 7.79 Remaining Post Development TP Load(Ib/yr) 1.03 Remaining TP Load Reduction pb/yr) 0.00 ••TARGET TP REDUCTION EXCEEDED BY 0.08 LB/YEAR•• Required 'Reduction below new development load limitation not required Drainage Area Summary DA.A DAB DA C D.A.D D.A.E Total Forest/Open(acres) 0.00 0.00 0.00 0.00 0.00 0.00 Managed Turf(acres) 0.76 0.00 0.00 0.00 0.00 0.76 Impervious Cover(acres) 0.62 0.00 0.00 0.00 0.00 0.62 Total Area(acres) 137 0.00 0.00 0.00 0.00 L37 Drainage Area Compliance Summary 0.A.A D.A.B D.A DAD DA.E Total TP Load Reduced llh/yrl 094 0.00 000 0.00 0.00 ..i TN Load Reduced(lbfort /.79 000 0 n0 0.00 0.00 Ai Drainage Area A Summary Land Cover Summary - - ASelh BSoils CSalb 0UN Total %al Total Forest/Open(acres) 0.00 0.00 0.00 0.00 0.00 0 Managed Turf(apes) 0.00 0.55 0.00 0.21 0.76 55 Impervious Cover(acres) 0.00 0.59 0.00 0.02 0.62 OS 1.37 BMP Selections Managed Turf Impervious Cover BMP Treatment TP Load from Untreated TP Load TP Removed TP Remaining Downstream Treatment Practice Credit Area Credit Area Upstream (acres) (acres) Volume(le) practices(I,,) to Practice)Ibs) Ills/Tr) )Ib/yr) to be Employed Total impervious Cover Treated Dues) 0.62 Total Turf Area Treated(acres) 0.76 Total TP load Reduction Achieved In DA (lb/Yr) 0.90 Total TN Load Reduction Achieved in DA (lb/yr) 7.79 Summary Print Independent Reports Excerpt from NRCS Soils Report NOAA Precipitation Report Custom Soil Resource Report m Soil Map 714EE0 7147E0 714740 714780 714820 7148E0 7149E0 714940 714990 715020 37°51'57'N 1 37°51'57 N le I 1 may sr., .,: B . a w 1.4,,, 51G tt 1 J i 46B MB H&c)1hnau woe 1)G4 W DBd&. CAB@ Ao° 1 37°51'49"N 37°51'49"N 7146E0 714700 714740 714780 714820 714EE0 714920 714940 714980 715220 3 3 n Map Scale:1:1,790 if printed on A landscape(11"x 8.5")sheet A Meters N 0 25 50 100 150 Feet 0 so 100 200 300 Map projection:Web Mercator Corner coordinates:WGS84 Edge tics:UTM Zone 17N WGS84 9 Custom Soil Resource Report MAP LEGEND MAP INFORMATION Area of Interest(A01) Spoil Area The soil surveys that comprise your AOI were mapped at n Area of Interest(AOI) Stony Spot 1:15,800. P Soilsezi Very Stony Spot ul Soil Map Unit Polygons Warning:Soil Map may not be valid at this scale. 7 Wet Spot Soil Map Unit Lines Enlargement of maps beyond the scale of mapping can cause Other misunderstandingof the detail of mapping and accuracyof soil • Soil Map Unit Points PP 9 .- Special Line Features line placement.The maps do not show the small areas of Special Point Features contrasting soils that could have been shown at a more detailed to Blowout Water Features scale. Streams and Canals " Borrow Pit Transportation Please rely on the bar scale on each map sheet for map Clay Spot Rails measurements. 0 Closed Depression 0%0 Interstate Highways Source of Map: Natural Resources Conservation Service Gravel Pitow US Routes Web Soil Survey URL: Gravelly Spot Major Roads Coordinate System: Web Mercator(EPSG:3857) 0 Landfill Local Roads Maps from the Web Soil Survey are based on the Web Mercator A. Lava Flow Background projection,which preserves direction and shape but distorts distance and area.A projection that preserves area,such as the 41, Marsh or swamp . Aerial Photography Albers equal-area conic projection,should be used if more it, Mine or Quarry accurate calculations of distance or area are required. • Miscellaneous Water This product is generated from the USDA-NRCS certified data as • Perennial Water of the version date(s)listed below. -,. Rock Outcrop Soil Survey Area: Albemarle County,Virginia + Saline Spot Survey Area Data: Version 11,Oct 11,2017 Sandy Spot Soil map units are labeled(as space allows)for map scales Severely Eroded Spot 1:50,000 or larger. • Sinkhole Date(s)aerial images were photographed: Apr 22,2015—Mar Slide or Slip 10,2017 • Sodic Spot The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps.As a result,some minor shifting of map unit boundaries may be evident. 10 Custom Soil Resource Report Map Unit Legend Map Unit Symbol Map Unit Name Acres in AO1 Percent of AOI 46B Lignum silt loam,2 to 7 percent 0.0 0.0% slopes 51C Manteo channery silt loam,7 to 5.4 59.1% 15 percent slopes 62B Nason silt loam,2 to 7 percent 3.7 40.9% slopes Totals for Area of Interest 9.1 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas.A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each.A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or 11 Custom Soil Resource Report Albemarle County, Virginia 46B—Lignum silt loam, 2 to 7 percent slopes Map Unit Setting National map unit symbol: kbbr Mean annual precipitation: 25 to 65 inches Mean annual air temperature: 54 to 59 degrees F Frost-free period: 195 to 231 days Farmland classification: Farmland of statewide importance Map Unit Composition Lignum and similar soils: 85 percent Minor components: 3 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Lignum Setting Landform: Hillslopes Landform position (two-dimensional): Summit Landform position (three-dimensional): Interfluve Down-slope shape: Convex Across-slope shape: Convex Parent material: Residuum weathered from serecite schist Typical profile H1 -0 to 9 inches: silt loam H2-9 to 38 inches: silty clay loam H3-38 to 58 inches: channery silt loam H4-58 to 79 inches: bedrock Properties and qualities Slope: 2 to 7 percent Depth to restrictive feature: 40 to 60 inches to paralithic bedrock Natural drainage class: Moderately well drained Runoff class: High Capacity of the most limiting layer to transmit water(Ksat): Very low to moderately low (0.00 to 0.06 in/hr) Depth to water table: About 12 to 30 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Moderate (about 8.4 inches) Interpretive groups Land capability classification(irrigated): None specified Land capability classification(nonirrigated): 2e Hydrologic Soil Group: D Hydric soil rating: No Minor Components Worsham Percent of map unit: 3 percent Landform: Drainageways Landform position (two-dimensional): Footslope 13 Custom Soil Resource Report Landform position (three-dimensional): Head slope, tread Down-slope shape: Concave Across-slope shape: Convex Hydric soil rating: Yes 51C—Manteo channery silt loam, 7 to 15 percent slopes Map Unit Setting National map unit symbol: kbc6 Mean annual precipitation: 25 to 65 inches Mean annual air temperature: 54 to 59 degrees F Frost-free period: 195 to 231 days Farmland classification: Not prime farmland Map Unit Composition Manteo and similar soils: 80 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Manteo Setting Landform: Interfluves Landform position (two-dimensional): Backslope Landform position (three-dimensional): Interfluve Down-slope shape: Convex Across-slope shape: Convex Parent material: Residuum weathered from serecite schist Typical profile H1 -0 to 6 inches: channery silt loam H2- 6 to 18 inches: very channery silt loam H3- 18 to 79 inches: bedrock Properties and qualities Slope: 7 to 15 percent Depth to restrictive feature: 10 to 20 inches to lithic bedrock Natural drainage class: Somewhat excessively drained Runoff class: Low Capacity of the most limiting layer to transmit water(Ksat): Very low to high (0.00 to 5.95 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Very low(about 2.1 inches) Interpretive groups Land capability classification(irrigated): None specified Land capability classification(nonirrigated): 6e Hydrologic Soil Group: D Hydric soil rating: No 14 Custom Soil Resource Report 62B—Nason silt loam, 2 to 7 percent slopes Map Unit Setting National map unit symbol: kbd2 Mean annual precipitation: 25 to 65 inches Mean annual air temperature: 54 to 59 degrees F Frost-free period: 195 to 231 days Farmland classification: All areas are prime farmland Map Unit Composition Nason and similar soils: 80 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Nason Setting Landform: lnterfluves Landform position (two-dimensional): Summit Landform position (three-dimensional): Interfluve Down-slope shape: Convex Across-slope shape: Convex Parent material: Residuum weathered from serecite schist Typical profile H1 -0 to 8 inches: silt loam H2-8 to 39 inches: silty clay loam H3-39 to 50 inches: channery silt loam H4-50 to 79 inches: bedrock Properties and qualities Slope: 2 to 7 percent Depth to restrictive feature: 40 to 60 inches to paralithic bedrock Natural drainage class: Well drained Runoff class: Medium Capacity of the most limiting layer to transmit water(Ksat): Very low to high (0.00 to 1.98 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Moderate (about 8.3 inches) Interpretive groups Land capability classification(irrigated): None specified Land capability classification(nonirrigated): 2e Hydrologic Soil Group: B Hydric soil rating: No 15 1/15/2018 Precipitation Frequency Data Server NOAA Atlas 14,Volume 2,Version 3 4�-„f o` a'4q Location name: Esmont,Virginia,USA* ' ✓ ''°" ' 4, Latitude:37.8656°,Longitude:-78.5579° noes ; k i Elevation:570.07 ft** i e 4-s,„,0,. •source:ESRI Maps Na. M1 **source:USGS POINT PRECIPITATION FREQUENCY ESTIMATES G.M.Bonnin,D.Martin,B.Lin,T.Parzybok,M.Yekta,and D.Riley NOAA,National Weather Service,Silver Spring,Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)1 Duration Average recurrence interval(years) 1 2 5 10 25 50 100 200 500 1000 5-min 0.343 0.405 0.473 0.537 0.604 0.657 0.706 0.751 0.802 0.846 (0.310-0.381) (0.366-0.450) (0.426-0.524) (0.483-0.594) (0.541-0.667) (0.586-0.725) (0.626-0.779) (0.662-0.829) (0.700-0.889) (0.731-0.939) 10-min 0.548 0.648 0.757 0.858 0.962 1.05 1.12 1.19 1.27 1.33 (0.495-0.609) (0.585-0.719) (0.682-0.838) (0.772-0.949) (0.862-1.06) (0.933-1.16) (0.995-1.24) (1.05-1.32) (1.11-1.41) (1.15-1.48) 0.686 0.814 0.957 1.09 1.22 1.33 1.42 1.50 1.60 1.67 15-min (0.618-0.761) (0.735-0.904) (0.863-1.06) (0.976-1.20) (1.09-1.35) (1.18-1.46) (1.26-1.57) (1.32-1.66) (1.39-1.77) (1.45-1.86) 30-min 0.940 1.13 1.36 1.57 1.81 2.00 2.17 2.34 2.54 2.71 (0.848-1.04) (1.01-1.25) (1.23-1.51) (1.42-1.74) (1.62-2.00) (1.78-2.20) (1.93-2.40) (2.06-2.58) (2.22-2.82) (2.34-3.01) 1.17 1.41 1.74 2.05 2.41 2.71 2.99 3.28 3.65 3.95 60-min (1.06-1.30) (1.27-1.57) (1.57-1.93) (1.84-2.27) (2.15-2.66) (2.41-2.98) (2.65-3.30) (2.89-3.62) (3.18-4.04) (3.42-4.39) 2-hr 1.40 1.69 2.10 2.48 2.95 3.35 3.75 4.16 4.71 5.17 (1.25-1.59) (1.50-1.90) (1.86-2.36) (2.20-2.79) (2.60-3.31) (2.94-3.76) (3.27-4.20) (3.60-4.66) (4.03-5.28) (4.38-5.82) 3-hr 1.54 1.85 2.29 2.71 3.22 3.66 4.10 4.55 5.15 5.67 (1.36-1.75) (1.63-2.09) (2.02-2.60) (2.39-3.06) (2.83-3.64) (3.19-4.13) (3.56-4.63) (3.91-5.14) (4.38-5.82) (4.76-6.42) 6-hr 1.97 2.36 2.91 3.45 4.14 4.75 5.38 6.06 6.99 7.82 (1.75-2.23) (2.09-2.67) (2.57-3.29) (3.04-3.90) (3.62-4.67) (4.13-5.36) (4.64-6.07) (5.16-6.83) (5.86-7.89) (6.47-8.84) 12-hr 2.47 2.97 3.67 4.38 5.31 6.17 7.08 8.07 9.49 10.8 (2.20-2.83) (2.63-3.38) (3.25-4.18) (3.86-4.98) (4.64-6.03) (5.34-6.98) (6.04-8.00) (6.80-9.11) (7.84-10.7) (8.77-12.3) 24-hr 4heror 4.59 r 5.43 6.67 7.74 i 8.>Iae 10.2 12.1 13.8 (2.66-3.34) (3.23-4.04) (4.11-5.16) (4.84-6.09) (5.91-7.47) (6.81-8.64) (7.78-9.94) (8.82-11.4) (10.3-13.5) (11.6-15.3) 3.49 4.23 5.37 6.32 7.69 8.84 10.1 11.4 13.4 15.0 2-day (3.14-3.90) (3.81-4.72) (4.83-6.00) (5.66-7.04) (6.85-8.55) (7.82-9.81) (8.85-11.2) (9.96-12.7) (11.5-14.9) (12.8-16.8) 3-day 3.71 4.50 5.71 6.71 8.15 9.37 10.7 12.1 14.1 15.9 (3.36-4.13) (4.07-5.00) (5.17-6.34) (6.05-7.44) (7.32-9.02) (8.35-10.4) (9.45-11.8) (10.6-13.4) (12.3-15.7) (13.6-17.6) 4-day 3.94 4.77 6.05 7.10 8.62 9.90 11.3 12.7 14.9 16.7 (3.59-4.36) (4.34-5.27) (5.50-6.69) (6.44-7.84) (7.78-9.50) (8.88-10.9) (10.0-12.4) (11.3-14.1) (13.0-16.5) (14.5-18.5) 4.56 5.49 6.86 7.98 9.59 10.9 12.3 13.9 16.1 17.9 7-day (4.18-4.99) (5.04-6.00) (6.28-7.50) (7.29-8.72) (8.71-10.5) (9.87-11.9) (11.1-13.5) (12.4-15.2) (14.1-17.6) (15.6-19.6) 10-day 5.17 6.20 7.65 8.83 10.5 11.8 13.2 14.7 16.8 18.6 (4.76-5.61) (5.72-6.73) (7.05-8.30) (8.11-9.57) (9.58-11.4) (10.8-12.8) (12.0-14.4) (13.2-16.0) (15.0-18.3) (16.4-20.3) 20-day 6.81 8.12 9.81 11.1 12.9 14.3 15.8 17.2 19.2 20.8 (6.35-7.32) (7.58-8.73) (9.14-10.5) (10.4-12.0) (12.0-13.9) (13.2-15.4) (14.5-16.9) (15.8-18.6) (17.5-20.7) (18.8-22.5) 30-day 8.37 9.92 11.7 13.1 14.9 16.2 17.6 18.9 20.6 21.9 (7.85-8.94) (9.31-10.6) (11.0-12.5) (12.3-14.0) (13.9-15.9) (15.1-17.4) (16.3-18.8) (17.5-20.2) (19.0-22.1) (20.1-23.5) 45-day 10.5 12.4 14.4 16.0 18.0 19.4 20.9 22.2 24.0 25.3 (9.85-11.1) (11.6-13.1) (13.6-15.3) (15.0-17.0) (16.9-19.1) (18.2-20.6) (19.5-22.2) (20.7-23.7) (22.3-25.6) (23.4-27.0) 60-day 12.3 14.5 16.7 18.4 20.5 22.0 23.5 24.9 26.7 27.9 (11.6-13.0) (13.7-15.3) (15.8-17.6) (17.3-19.4) (19.3-21.6) (20.7-23.3) (22.1-24.8) (23.3-26.4) (24.9-28.3) (26.0-29.7) 1 Precipitation frequency(PF)estimates in this table are based on frequency analysis of partial duration series(PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90%confidence interval.The probability that precipitation frequency estimates(for a given duration and average recurrence interval)will be greater than the upper bound(or less than the lower bound)is 5%.Estimates at upper bounds are not checked against probable maximum precipitation(PMP)estimates and may be higher than currently valid PMP values. Please refer to NOAA Atlas 14 document for more information. Back to Too ' https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=37.8656&Ion=-78.5579&data=depth&units=english&series=pds 1/4