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Home My WebLink AboutWPO201400087 Plan - As-built 2023-01-13Channel Report Hydrallow Express Extension for AutadeeF4 AutoCAM Civil 3M by Autodeck. lm. Thursday. Feb 19 2015 Downstream Section A -A User -defined Highlighted Invert Elev (ft) = 412.24 Depth (ft) = 0.79 Slope (%) = 11.08 Q (cfs) = 5.350 N-Value = 0.050 Area (sqft) = 1.14 Velocity (ft/s) 4.71 Calculations Wetted Perim (ft) = 3.30 Compute by: Known Q Crit Depth, Yc (ft) = 0.89 Known Q (cfs) = 5.35 Top Width (ft) = 2.88 EGL (ft) = 1.13 Elev (ft) 422.00 420.00 418.00 416.00 414.00 412.00 Section Depth (ft) 9.76 7.76 5.76 3.76 1.76 -0.24 410.00 -2.24 -5 0 5 10 15 20 25 30 35 40 45 Sta (ft) Channel Report Hydmllow Express Extension far Au odesk& AutoC/ Downstream Section B-B User -defined Invert Elev (ft) = 408.34 Slope (%) = 6.40 N-Value = 0.050 Calculations Compute by: Known Q Known 0 (cfs) = 5.35 3M by Attached, Inc. Thursday, Feb 19 MI5 Highlighted Depth (ft) = 0.50 Q (cfs) = 5.350 Area (sgft) = 1.76 Velocity (ft/s) = 3.05 Wetted Perim (ft) = 6.46 Crit Depth, Yc (ft) = 0.51 Top Width (ft) = 6.37 EGL (ft) = 0.64 ra .- .�� Itl� I, -T a� tt t I r 1 1 0,050) Channel Report Hydrallow Express Extension for AUWdesF® AutoGAM Civil 3M by Aubdeck. lm. Downstream Section C-C User -defined Invert Elev (ft) = 406.70 Slope (%) = 3.30 N-Value = 0.050 Calculations Compute by: Known Q Known Q (cfs) = 5.35 Thursday. Feb 19 2015 Highlighted Depth (ft) = 0.60 Q (cfs) = 5.350 Area (sqft) = 2.31 Velocity (ft1s) = 2.31 Wetted Perim (ft) = 7.85 Crit Depth, Yc (ft) = 0.54 Top Width (ft) = 7.75 EGL (ft) = 0.68 Elev (ft) Section Depth (ft) 413.00 412.00 411.00 410.00 409.00 408.00 407.00 406.00 405.00 6.30 5.30 4.30 3.30 2.30 1.30 0.30 -0.70 -1 70 0 5 10 15 20 25 30 35 40 45 Sta (ft) MS-19 Analyis Summary Segment ID Q2 (cfs) Slope (ft/ft) Liner Material n Allowable Velocity Q10 (cam) 10-Year Depth (ft) Maximum Channel Remarks A -A 2.51 0.111 Existing Vegetation 0.050 5.00 5.35 0.79 1.50 Velocity OK Depth OK B-B 2.51 0.064 Existing Vegetation 0.050 5.00 fl24 5.35 0.50 1.50 Velocity OK Depth OK C-C 2.51 0.033 Existing Vegetation 0.050 5.00 5.35 0.60 1.50 Velocity OK Depth OK * COMPOSITE n NOT WARRANTED AS CHANNEL SIDE SLOPE MATERIAL HOMOGENEOUS MS-19 CHANNEL ADEQUACY CALCULATIONS BIORETENTION FILTER CONSTRUCTION SPECIFICATIONS BIORETENTION BASIN SHOULD BE CONSTRUCTED AFTER ALL SITEWORK IS COMPLETE AND STABILIZATION MEASURES HAVE BEEN IMPLEMENTED. BIORETENTION FILTERS MUST BE PROTECTED FROM ALL SEDIMENT LOADS TO PREVENT MALFUNCTION. ALL BIORETENTION AREAS WILL REMAIN "OFF-LINE" FROM STORMWATER INFLOW UNTIL THEIR RESPECTIVE DRAINAGE AREAS ARE FREE FROM LOOSE SEDIMENTS WHICH COULD WASH INTO THE FACILITY. IN ADDITION, ALL CONSTRUCTION ACTIVITIES IN THESE AREAS MUST BE MINIMIZED TO REDUCE COMPACTION OF IN -SITU SOILS, WHICH SHALL BE CORDONED OFF TO PREVENT ACCIDENTAL COMPACTION BY EQUIPMENT DURING THE REMAINDER OF THE CONSTRUCTION PHASE IN THAT AREA. EMBANKMENT, IMPERVIOUS CORE AND CUTOFF TRENCH TO BE IMPERVIOUS MATERIAL AVAILABLE ON -SITE, EMBANKMENT FILL TO BE BENCHED 1:1 INTO EXISTING GROUND, EMBANKMENT TO BE COMPACTED TO 95% DRY WEIGHT DENSITY t2% PER ASTM D-698, CONSTRUCTION OF EMBANKMENT TO BE SUPERVISED BY A GEOTECHNICAL ENGINEER LICENSED TO PRACTICE IN THE COMMONWEALTH OF VIRGINIA. BIORETENTION FILTER SEQUENCE OF CONSTRUCTION 1. REMOVE ALL ACCUMULATED SEDIMENT AND EXCAVATE BIORETENTION FILTER AREA TO PROPOSED DEPTH. USE RELATIVELY LIGHT, TRACKED EQUIPMENT TO AVOID COMPACTION OF THE BASIN FLOOR. AFTER FINAL GRADING IS COMPLETED, DEEPLY TILL THE BASIN FLOOR WITH ROTARY TILLERS OR DISC HARROWS. 2. INSTALL A 6 INCH LIFT OF UNDERDRAIN GRAVEL (VDOT NO. 57) AND LIGHTLY COMPACT WITH LANDSCAPING ROLLER. INSTALL UNDERDRAIN PIPING, CLEANOUTS AND APPURTENANCES IN ACCORDANCE WITH THE PIPE MANUFACTURER SPECIFICATIONS. INSTALL REMAINING UNDERDRAIN GRAVEL. INSTALL PEA GRAVEL CHOKER STONE LAYER. FILL BIORETENTION FILTER AREA WITH BIORETENTION SOIL MIXTURE IN ACCORDANCE TO VIRGINIA BMP CLEARING HOUSE SPECIFICATIONS AS SHOWN IN THE PLANS. 3. INSTALL VEGETATION AND GROUND COVER SPECIFIED IN THE PLANTING PLAN FOR BIORETENTION AREA. INSTALL MULCH LAYER IF CALLED FOR IN THE DESIGN. 4. HAND PLACE LANDSCAPING STONE AT THE BIORETENTION FILTER INLETS AND WEIRS AS SPECIFIED ON THE PLANS AND DETAILS. 5. UPON AUTHORIZATION FROM DESIGNATED INSPECTOR, REMOVE ALL SEDIMENT CONTROLS AND STABILIZE ALL DISTURBED AREAS. BIORETENTION FILTER UNDERDRAIN SPECIFICATIONS UNDERDRAIN MATERIAL TYPES • UNDERDRAIN SYSTEMS SHALL BE COMPOSED OF 6-INCH PVC PIPE (SCHEDULE 40) OR APPROVED EQUAL. UNDERDRAIN CONNECTIONS • PIPE SECTIONS SHALL BE COUPLED USING SUITABLE CONNECTION SOCKET -WELDED JOINTS. FIELD CONNECTIONS TO STORMDRAIN STRUCTURES AND PIPES SHALL BE SEALED WITH POLYMER GROUT MATERIAL THAT IS CAPABLE OF ADHERING TO SURFACES. UNDERDRAIN PIPE SHALL BE CAPPED (AT STRUCTURE) UNTIL COMPLETION OF SITE. • UNDERDRAINS CONNECTED DIRECTLY TO A STORM DRAINAGE STRUCTURE SHALL BE NON -PERFORATED FOR A DISTANCE OF AT LEAST 5 FEET FROM THE STRUCTURE INTERFACE TO AVOID POSSIBLE PIPING PROBLEMS. UNDERDRAIN PERFORATIONS • UNDERDRAIN PERFORATIONS SHALL BE X" PERFORATIONS, 6" CENTER TO CENTER, ALONG TWO OR THREE EQUALLY SPACED LONGITUDINAL ROWS. PERFORATIONS SHALL BE PLACED CLOSEST TO THE INVERT OF THE PIPE TO ACHIEVE MAXIMUM POTENTIAL FOR DRAINING THE FACILITY. NO PERFORATIONS ARE TO BE WITHIN 5 FEET OF WHERE THE UNDERDRAIN SYSTEM CONNECTS TO A STORMDRAIN STRUCTURE. UNDERDRAIN INSPECTION • THE CONTRACTOR SHALL CONTACT THE COUNTY WATER RESOURCES INSPECTOR 24-HOURS PRIOR TO BACKFILLING THE BIOFILTER AND REQUEST AN INSPECTION AND APPROVAL OF THE UNDERDRAIN INSTALLATION AND SOIL MIX. 1 ADDRESS 1st SUBMISSION COMMENTS DMJ 2/27/15 2 UPDATED BIORETENTION ELEVATIONS DMJ 5/01/15 z CL OF EMBANKMENT f �4' MIN. I CUTOFF TRENCH DETAIL NOT TO SCALE 8„1 oG�s, MIN. T ^. ( A - 4 °. .A A ! A. ' CO • d a e 4000 PSI VDOT CLASS A4 GENERAL CONCRETE CONCRETE CRADLE DETAIL NOT TO SCALE 1 4 1 SIGNATURE SET I DMJ 1 6/18/15 1 1 1 1 1 g NO. I SHEET REVISION SHEET REVISION 1L 3 STORMWATER NARRATIVE A VSMP PERMIT WAS OBTAINED FOR THIS SITE PRIOR TO JULY 1, 2014. THEREFORE THIS SITE IS GRANDFATHERED PER 9VAC25-870-48 AND MEETS THE WATER QUALITY REQUIREMENTS OF PART II C SET FORTH IN 9VAC25-870-96. STORMWATER QUALITY AND DETENTION FOR THE IMPROVEMENTS PROPOSED WITH THIS SITE PLAN WILL BE PROVIDED BY THE PROPOSED BIORETENTION FILTER MINIMUM STANDARDS 3.11A. THE REQUIRED TREATMENT VOLUME IS EQUAL TO 1/2" OF RUNOFF FROM THE IMPERVIOUS AREA. THE PROJECT SITE LIES WITHIN THE DEVELOPMENT AREA AND THE REQUIRED OVERALL POLLUTANT REMOVAL RATE IS 49%. BIOFILTER SIZING CALCULATIONS AND BMP COMPUTATIONS ARE PROVIDED ON THIS DRAWING. THE POINT OF ANALYSIS FOR THE PROJECT IS LOCATED AT THE DRAINAGE SWALE ON THE EASTERN PROPERTY LINE AS SHOWN ON DWG. C-19. THE PRE -DEVELOPED DRAINAGE AREA TO THE POINT OF ANALYSIS IS 2.36 ACRES. THE PRE -DEVELOPED FLOWS ARE 2.64 CFS AND 6.73 CFS FOR THE 2-YEAR AND 10-YEAR STORM EVENTS RESPECTIVELY. IN THE POST -DEVELOPED CONDITION THERE ARE TWO SEPARATE DRAINAGE AREAS. 2.65 ACRES WILL BE CAPTURED AND ATTENUATED BY THE PROPOSED BIORETENTION FACILITY AND THERE IS A 1.39 ACRE UNCONTAINED AREA THAT DRAINS TO THE POINT OF ANALYSIS. THE POST DEVELOPED COMBINED FLOWS ARE 2.50 CFS AND 5.35 CFS FOR THE 2-YEAR AND 10-YEAR STORM EVENTS RESPECTIVELY. THE COMBINED FLOWS FOR THE BIORETENTION FILTER ROUTING AND UNCONTAINED DRAINAGE AREAS IN THE POST -DEVELOPED CONDITION ARE LESS THAN THE PRE -DEVELOPED FLOWS AT THE POINT OF ANALYSIS THEREFORE THE SITE IS IN COMPLIANCE WITH MS-19. A ROUTING SUMMARY IS PROVIDED BELOW AND THE ROUTING CALCULATIONS ARE SHOWN ON DWG. C-21. ADEQUACY CALCULATIONS FOR THE EXISTING DOWNSTREAM CHANNEL ARE PROVIDED ON THIS DRAWING. THE CHANNEL ADEQUACY CALCULATIONS INDICATE THAT THE EXISTING VEGETATION IN THE DOWNSTREAM CHANNEL IS ADEQUATE TO PREVENT EROSION. THERE IS NO SIGN OF EROSION IN THE EXISTING CHANNEL IN THE PRE -DEVELOPED CONDITION. BIORETENTION FILTER SIZING CALCULATIONS SURFACE AREA REQUIRED = 2.5% OF IMPERVIOUS AREA IMPERVIOUS AREA = 50,772FT2 REQUIRED SURFACE AREA = 50,772 FT2 x .025 = 1,269 FT2 BIOFILTER SURFACE AREA PROVIDED = 1,290 F72 FOREBAY SIZING CALCULATIONS MIN. SURFACE AREA REQUIRED = 10% OF BIOFILTER SURFACE AREA MIN. SURFACE AREA REQUIRED = 0.10(1,290 FT2) = 129 F72 FOREBAY 1 SURFACE AREA PROVIDED = 207 FT2 FOREBAY 2 SURFACE AREA PROVIDED = 393 F72 POLLUTANT REMOVAL CALCULATIONS THE BMP ANALYSIS AREA FOR THE PROJECT IS THE PROPERTY LIMITS OF THE PARCELS DESIGNATED AS TMP 61A-15 AND 61A-17. THE BMP ANALYSIS AREA IS 2.75 ACRES. CALCULATIONS ARE PROVIDED AS PART OF THIS PLAN. CLASS A1J RIP RAP T A T ITT T T T[r TTT A T TT TITT A TT BIORETENTION SOIL MIXTURE IN ACCORDANCE TO VIRGINIA BMP CLEARINGHOUSE SPECIFICATIONS, LATEST EDITION TOP OF MULCH .�. GRAVEL STONE VDOT NO. PROVIDEAGGREGATE BELOW6" SUMP UNDERDRAIN TH OF "yti, 4 D 7f DAVID M. -TENSE Lic. No. 11484 ��SArIDNAL Fr�O, NOT TO SCALE BIORETENTION FACILITY=425.00 JTION FILTER I NOT TO SCALE 3" MULCH 2' _' 12" 6" DIA. PERFORATED UNDERDRAIN ISSUED FOR CONSTRUCTION 9i 09-03-15 BIORETENTION FILTER SURFACE PERFORMANCE -BASED WATER QUALITY CALCULATIONS APPCNDIX5D PERFORMANCE -BASED WATER QUALITY CALCULATIONS APPENDIX 5D W.rlaha02 SitanNO2 W.clehoot 2, Moulins 2 N,I cf4 Page2af4 Summery ae Situation 2 criteria: torn calculation procedure h= I lhru STEP 3, Workaheet l: STEP Determine the relative peal -development pollutant load(L,j. Applicnblearea(A)-= lS etas L,,o-[0.05+(0.MxI,o)]x Axd28 (Equadon5-21) 4,n =(total prstdevelrpmrnt impervious cover+A) x I W = 3l wM1ere: Lp,,, = mlaEve post -development root phosphoovs load (poonde par Ca.ew = % a I=16% Icy = prsFdevelvpmrnt percent impervious cover (percmO mptessed is I�,y=(total exislirg impervious cove+A") x I W =�% whale numbers) A - applicable urea (acres) I-a.I <I",°y u. %; used L„" = [om+play; x ;j 11] x 2 75 x 228 I,r S-Tsl..,.mw \L % - a.40 pounda,co'cer STEP Dearminc the relative pre -development pollu[an load(LJ. STEP Determine Me relative pvllubnt removal requirementOUL. RR = Ln"-L,.w , (Equation 5-16) RR = its Q- t.1a where: Lr,y-,. = relative pradevelopmeot btal pbospharoua load(pounds per year) L.,"a„a avttaW landeaver condition for specific watershed or locality yr pouMsperyou the Chesapake Bay default value of 16%(pecent expressud in whole cumbers) A applicable arn(auca) STEP Identify beat mamgement praetia(BMP) for then ute. L„y„._o.- o.05+(0.009x Il_)]x. 2,16' x2.20 1. Constrains the required polludentreravel efficiency for the site: pauvda per year EFF-(RR+L_,)x 100 (Equafiaa 5-22) when: EFF - coNtedpalitttaa removal eB"iicievcy(percent expressed it whole tubers) RR = palluavt removal re9uhemmt(prmds per year) Ln„ = alodve postdevelopment rolal phosphorous load (ponds per year) EFF 5D-9 5C-Iv PBCFORMANCERASCD WATER QUALITY CALCULATIONS APPBNDIX50 PERFORMM`CF`BASED WATER QUALITY CALCULATIONS APPENDIX51i Worktheet2: Sifi 2 Page 4ON Workshoet 2, Situation 2 N..3af4 4. Calculate the pollutant land removed by the proposed BMP(s): 2. Select BMP(s) from Table 5-35 and locate on the site: L,,,„,,, - Effat., x Lam (Equation 5-24) BMPL where: L,,,_-Post-developmeotpollutsnt load reraoved by proposed BMP (No. aperyear) BMP 2: Effawe= poBmmt removal efficiency ofBW(expeassedfit deduced f) Lam = rdafivepastdeval.pment toad phosphorous load emeriag BMP 3: proposed BMP (pounds per,aq 3. Denemdnethe polhuant load entering Is proposed BMP(s): L„m_an= 0.56 x a�4-=�f 5s pouMsperycar Lt., - [0.05+(0.009 x I-) x A x 2.28 (Egnafion 5-Im L,:,...amarer _ pounds per yea wham: Le.,r'aletive past-developmrnttoal phosphomva load enmdug L_,,,san x- pounds per year proposed BMP (pounds par year) lam =post-developmevr pwrmt impery ous cvverofa6lP dmtange area (peremtexpreesedmwholeaumbers) S. Celuelme the mml pollutant land removed by the 13141 : A- drainage area of propose I RMP (acres) L..... ...., Last-[0.05+(0009x 44 1]x 26S_x2,2g where L„m,,,,n,a,- totalprputad lead remoyv4beaced sad = 1.49-pound�ptt Year No I L,,,,,„,ee,nn- pollutant load removed by proposed BMP No.2 L:.m.. pollutant load Incurred by proposed BMP No.3 Loan - [0.05+(0.009 • )]---2.28 _a L„m..unwr=pollmmt load Incurred by proposed BMP No.3 = pouoaaperyem L:..e,e,v- 1.5s + + +... Laws - [0.05+(0.009 x x x 2.28 LST pounds"YOur = pouM¢per yew 6. Verify compliance: I,_- RR 5D11 5D- 2 BIORETENTION FACILITY ROUTING SUMMARY DESIGN STORM PRE -DEVELOPED FLOWS (CFS) POST -DEVELOPED COMBINED FLOWS (CFS) 2yr 2.64 2.51 10yr 6.73 5.35 IF SOD CANNOT BE INSTALLED UPON 4e DIA. RCP OUTLET PLACEMENT OF SOIL MIX, INSTALL STRUCTURE W/TRASH RACK PERIMETER SILT FENCE AT TOP OF TOP=433.30 UNSTABILIZED EMBANKMNET SLOPES (TYP) 4" ORIFICE WITH BMP 100YR WSE 434.38 CAGE INV=429.50 x REFER TO LANDSCAPE C-20 C-20 1 OYR WSE 433.24 10, 12" MAX PLANS FOR BIORETENTION TOP OF ICI 2YR WSE 431.11 POl D FILTER PLANTINGS MULCH TOP OF DEPTH x EMBANKMENT III=III I 1 =436.50 11 ELEV.=428.50 1 IMPERVIOUS III1 1- � :::: :.. ......... ..:.. _: ,.;`:...... -.: ....:_:-:::'.:.•:,:.>:. �.-::.:..:.:...:.-:..,...._:.;:'.: III=III ". `,':: ` BIORETENTION CORE . IIIIII11 FILTER SOIL MIX ,._,�..; ........... �...:.-.,:,<: =1 I I-III-III=1 IIIIIIIII=III II 000000000000000 0000000000000000000 0 15" HDPE 6" DIA. DRAINAGE OUTFALL PERFORATED COURSE PIPE UNDERDRAIN 15e O.C. CUTOFF TRENCH WATERTIGHT 81X2' CONCRETE CONNECTION CONCRETE CRADLE BASE TEMPORARY EXCAVATED SUBGRADE SLOPES MAY BE INSTALLED NEAR VERTICALLY TO ENSURE A MINIMUM BOTTOM DEPTH OF 4e IS MAINTAINED FOR THE DRAINAGE COURSE. ALL SLOPES ABOVE MULCH LAYER TO BE NO STEEPER THAN 3:1, UNLESS OTHERWISE SHOWN ON PLANS BIORETENTION FILTER FACILITY DETAIL NOT TO SCALE _ DESIGNED BY: r: PROJECT SET REV. No. LOFTS AT MEADOWCREEK W5 - ENGINEERS FINAL SITE PLAN DRAWN BY: ALBEMARLE COUNTY, VIRGINIA DRAWING NUMBER: rmSURVEYORS II TITLE: STORMWATER MANAGEMENT NARRATIVE PLANNERS C-20 Dlh'R BY: ASSOCIATES a1DB DETAILS AND CALCULATIONS SHEET NUMBER: POB..4119 3040 Avemore Square PI Lynchbd,, VA 24502 clnrinndvdle, VA 22911 WWA NUMBER: FILE NAME: DISCIPLINE: SCALE: DATE: Phone: 434.31&6080 Phone: 434.984.2700 WWW.NM1rOggnCiates.nM 213001.05 300105C_SWM-2.dwg CIVIL H: N/A 00 I Z0/14 24 of 30 V.-N/A w Q O J D_