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HomeMy WebLinkAbout20070208 Ver 2_More Info Received_20071206~- Soil & Environmental Consultants, PA 11010 Raven Ridge Road Raleigh, North Cazolina 27614 Phone: (919) 846-5.900 Fax: (919) 846-9467 www.SandEC.com, December 5,.2007 S&EC Pi•oject'#4716.W6 DWQ EXP Project #07-0208v2 Department of Environment and Natural Resources Division of Water Quality. Attn: Joseph Gyamfi/Lia Myott E X.(~ ~ 1 - ©a.0 $` V' 2 2321 Crabtree Boulevard, Suite 250 _ Raleigh, NC 27604 Re: Reply to the Division of WaterQuality's Request for More Information Heritage High School-EXPRESS REVIEW PROGRAM Wake Co~inty, NC Dear Mr. Gyamfi and Mrs. Myott: The purpose.of this letter-and supplemental information is to supply the additional information that has been requested by Joseph Gyamfi for•the Heritage High School project. Several conversations on December 3 & 4, 2007, have taken place outlining the dill, use flow provisions that are necessary for the NC Division of Water Quality (NCDWQ) to continue'the review of the subject project. We anticipate that the attached supplemental. information will answer all of the NCDWQ's remaining concerns in order to complete the final review process for Water Quality.Certifieation 3625.and Riparian. Buff. er Authorization. If you have any further questions or any additional explanation is needed, please don't hesitate to .call. Sincerely, Debbie Edwards Environmental Specialist CC: Susan Holt-LS3P .Associates Robert Stutts-Wake County Public School System Attachments: 1) Supplemental Information provided by CLH Design r~ --~, GPI `' ,Ra ", f ~~`AT Charlotte Office: Greensboro Office: 236 LePhillip Court, Suite C 3817-E Lawndale Drive Concord, NC 28025 Greensboro, NC 27455 Phone: (,704) 720-9405 Phone:- (336) 540-8234 ~~ ~ ~~~ ~' ' f i ~ ~ ' `-` ~} . ~, ~., e. -: ~/~~ CLH desl n . a. -Sr~R g ~ p .~~~C MacGregor Park, 125 Edinburgh South, Suite 3I0 Cary, North Carolina 27511 Phone: (919) 319-6716 Fax.• (919) 319-7516 5-Dec-07 TO: Cyndi Karoly - NC Division of Water Quality FROM: Steven J. Miller, PE -CLH Design, PA RE: 401 EXPRESS REVIEW PERMIT HERITAGE HIGH SCHOOL WAKE FOREST, NC CC: Debbie Edwards - S&EC File (1123-print) ~ X.Q o7 - fl a o 8 v 2 Dear Ms. Karoly: Attached please find two (2) copies of revised calculations and four (4) copies of revised drawings C7. l2 &C7.13 requested verbally by Joseph Gyamfi on 4-Dec-07. The attached calculations have been revised as follows: Draw-down calculations of runoff collected in the ponds from the 1-in storm have been revised per our discussions with Joseph. The draw-down orifices have been revised to ensure a draw- down duration of 3-5 days for the first 1-in of rainfall. The discharge velocities from the draw- down of the 1-in rainfall out of the ponds have been calculated at the point where the water leaves the pond barrel pipe and where discharge leaves the riprap apron a the end of the barrel and meets natural ground. Below is a summary of the revised calculation results. Detailed calculations are attached. Pond A Pond A is a dry detention pond. The volume of the 1-in storm is 3,661-cf and discharges at a maximum rate of 0.0017-cfs through a 3/4-in orifice with a maximum head of 1.30-ft above the floor of the pond (or 1.27-ft above the centroid of the orifice). The velocity of the discharge at the end of the pipe was calculated to be 2.21-fps and the velocity at the end of the riprap apron was calculated to be 0.05-fps. The drawdown duration of the 1-in rainfall has been estimated at 4.4-days based on a head 0.42-ft (1/3 of the maximum head of 1.27-ft). Pond B Pond B is a wet detention pond. The volume of the 1-in storm is 34,387-cf and discharges at a maximum rate of 0.179-cfs through a 2.5-in orifice with a maximum head of 1.30-ft above the permanent pool (or 1.20-ft above the centroid of the orifice). The discharge velocity at the end of the pond outlet pipe is 2.27-fps and the velocity at the end of the riprap apron is 0.13-fps. The drawdown duration of the l -in rainfall has been estimated at 3.8-days based on a head 0.40-ft (1/3 of the maximum head of 1.20-ft). 12-5-07-DWQ-S.doc 5-Dec-07 Page 2 Pond C Pond C is a wet detention pond. The volume of the 1-in storm is 13,206-cf and discharges at a maximum rate of 0.060-cfs through a 1.5-in orifice with a maximum head of 1.10-ft above the permanent pool (or 1.04-ft above the centroid of the orifice). The discharge velocity at the end of the pond outlet pipe is 1.57-fps and the velocity at the end of the riprap apron is 0.13-fps. The drawdown duration of the 1-in rainfall has been estimated at 4.4-days based on a head 0.35-ft (1/3 of the maximum head of 1.04-ft). Pond D Pond D is a wet detention pond. The volume of the 1-in storm is 24,379-cf and discharges at a maximum rate of 0.137-cfs through a 2.5-in orifice with a maximum head of 0.80-ft above the permanent pool (or 0.70-ft above the centroid of the orifice). The discharge velocity at the end of the pond outlet pipe is 2.10-fps and the velocity at the end of the riprap apron is 0.19-fps. The drawdown duration of the 1-in rainfall has been estimated at 3.6-days based on a head 0.23-ft (1/3 of the maximum head of 0.70-ft). Pond G Pond G is a wet detention pond. The volume of the 1-in storm is 2,372-cf and discharges at a maximum rate of 0.011-cfs through a 3/4-in orifice with a maximum head of 0.60-ft above the permanent pool (or 0.57-ft above the centroid of the orifice). The discharge velocity at the end of the pond outlet pipe is 2.15-fps and the velocity at the end of the riprap apron is 0.07-fps. The drawdown duration of the 1-in rainfall has been estimated at 4.3-days based on a head 0.19-ft (1/3 of the maximum head of 0.57-ft). * Note that there are no ponds 'E' and 'F'. Thank you very much for your assistance in the permitting of this project. Please contact me directly if you have any questions about these new calculations. Sincerely, -~ 12-5-07-DWQ-S.doc ~xP o~ - aa.og v Z ~~ ~~ ~~ ®~ ~~ ,, `' ~o L :e..•: ~'4rc '' ~,~',r,~nR Q ',,~ oh.. DESK ltii GAL.~GULATI OltiiS GIVILISITE WORK HERITAGE HIGH SCHOOL WAKE FOREST, NORTH CAROLINA DECEMBER, 2006 REV. MAR. 2007 REV. Nov. 2007 REV. DEC. 2007 ~- `~~~~o`~ e ~ f r -~~~~~~ ,~e~ ~(~ EJr^til~~ "~.. a ~~F~ r ,~? 9 -. a - 4 .o ...'~~~J a _ a" '" P >`~''€~'~dto1'~~~'~~~- ~~ / :// CI~H desi n .a. g ~p MacGregor Park, 125 Edinburgh South, Suite 310 Cary, North Carolina 27511 Phone.• (919) 319- 6716 Fax.• (919) 319- 7516 PROJECT NAME Herita a Hi h School LOCATION Wake Forest, NC Drainage Area, (DA) _ Impervious Area (c=0.95) _ Pervious Area (c=0.35) _ Cc = Permanent Water Quality Pool Impervious = Permanent Pool Depth = SA / DA Ratio = Required Surface Area = Temporary Water Quality Pool Design Storm Rainfall Runoff Coeff. (Rv = 0.05 + 0.009 (% Imperv.)) _ Required Volume (design rainfall)(Rv)(DA) _ Surface Area Provided= Surface Area at 1 "Storage Volume= 1"Storage Volume Provided= ~~ ft ~' DATE :~.. 12-4-07 PROJECT NO 1123 BY KAL `'~ 7.39 ac 0.71 ac 6.68 ac 0.41 10% 0.00 ft N/A 0 sf 1.00 in 0.14 in/in 3,661 cf (Typically 1-in) 0 sf 4,877 3,661 cf .~- Temp. Storage Depth above Dewatering Hole = 1.30 ft Diameter of Dewatering Hole = 0.75 in Max. Head Above Dewatering Hole (hmax) = 1.27 ft to centroid of dewatering hole Head used for Dewatering Calculation (h) = 0. 1/3 hmax) Detention (Draw-Down) Time = 4.4 da Tdays=(Temp. Storage Vol / (0.6 " A ` (2"g'`(h))^1/2) 0 (where h =one third temp. storage depth measured to centroid of orifice) Q 1 in/hr (runoff from 1-in/hr storm) = 3.01 cfs Qmax Drawdown= 0.017 Cfs~ (at hmax) s:\1319\0001\calcs\1123-PondSize-Pond A.XLS printed: 12/5/2007 3:52 PM Page 1 of 1 ~- N m N 0 ~- 0.0 4365.0 8729.9 13094.9 17459.9 21824.8 26189.8 30554.7 34919.7 Storage (cult) ~ - ` ` ~ ~ DATE DESIGN PHASE 12/4/07 PRELIM / / PROJECT NAME PROJECT NO CONSTR / / Heritage High School 1123 REVISION / x / LOCATION BY RECORD / / Wake Forest, NC KAL OTHER / / CHECKED BY (SPECIFY) SJM Storm Outlet Structure FES No.= H10 Q~/Qfull = 0.11 Quo/Qfull = 0.75 Pipe Dia= 30 in VNfull = 0.67 VNfull = 1.10 Quo = 31.63 cfs V~o = 9.3 fps Qfull = 42.00 cfs Slope= 5.0 Vfull = 8.50 fps Pipe Inv= 215.00 ft Q~ = 4.65 cfs V~ = 5.7 fps From Fig. 8.06.b.1: Zone = 3 From Fig. 8.06.b.2: D5o = 10 in D~nwc = 15 in - Riprap Class = 1 ~ Apron Thickness 22.5 in a Apron Length 20 ft ~ -~ Apron Width = 3xDia = 8 ft Length Storm Outlet Structure FES No.= POND A Quo/Qfull = 0.11 Pipe Dia= 24 in VNfull = 0.67 Quo = 7.45 cfs V~o = 14.2 fps Qfull = 66.20 cfs OutletSlope= 2.0 Vfull = 21.10 fps Pipe Inv= 263.00 ft Drawdown = 0.017 cfs VDrawdown = 2.21 f (Flowmaster) From Fig. 8.06.b.1: Zone = From Fig. 8.06.b.2: D5o - = 14 in DnnAx = 21 in - - - Riprap Class = 2 { Apron Thickness = 31.5 in ~ Apron Length = 20 ft _ - ~.--+-ength -- 3( Apron Width = 3xDia = 6 ft k ., ~-.. ` ;* ~ .' ~:~ ~~ .,~-t ~~, `- ~ ~ ~~ `~~_ > ~= ~ ~ 4 DATE DESIGN PHASE .-~ ~ "~'{ `~ ~~ _~_~ ~~~~`f~"~ #~ 12/4/07 SD / / PROJECT NAME PROJECT NO DD / / Heritage High School 1123 CD / X / LOCATION BY REV / / Wake Forest, NC KAL OTHER / / CHECKED BY (SPECIFY) X RIPRAP LINING -Permissible Sheer and Capacity Outlet No: DRY POND A Drainage Area, (DA) = 7.39 ac Sta from: Impervious Area (c=0.95) = 0.71 ac Sta to: Pervious Area (c=0.35) = 6.68 ac Section Length: 20 ft Cc = 0.41 Section Slope: 2.00 % One inch/hr storm= 3.01 cfs Riprap Class: 2 (d50= 14") Temp. Storage Depth = 1.30 ft Allowable Sheer: 4.67 Ib/sf Diameter of Dewatering Hole = 0.75 in Allowable Depth: 1.00 ft Drawdown Rate= 0.02 cfs Swale sizing method done by manipulation of Manning's Equation to find the depth of flow that matches the known flow conditions. Performed by trial and error. INPUT DATA Qp = 0.02 cfs flow by drawdown n = 0.797 Class 2 Riprap Manning's Coefficient (dimensionless) S = 0.02 ft/ft longitudinal slope (ft of fall per ft of run) Zreq = 0.06 quantity to equate to Zav M = 0 :1 side slope of channel (ft of run : 1 ft of rise) NORMAL DEPTH AND VELOCITY B D A P R Zav Remark 6 0.50 3.00 7.00 0.43 1.71 deep 6 0.30 1.80 6.60 0.27 0.76 deep 6 0.10 0.60 6.20 0.10 0.13 deep 6 0.06 0.36 6.12 0.06 0.05 OK B = bottom width of trapezoidal channel D = normal depth of flow Zav = Zreq xr~ A = cross-sectional area of flow Can _ ~ R P = wetted perimeter of the channel 1.4g -GIs R = hydraulic radius of the channel Normal Depth, D = 0.06 ft _ Depth O.K. Velocity= 0.05 fps Velocity O.K. STRESS T = yds =shear stress in Ib/sq-ft Y = unit weight of water, 62.4 Ib/cu-ft D = normal depth of flow in ft S =longitudinal slope in ft/ft shear stress, T = 0.07 Ib/sq-ft Sheer O.K. FINAL OUTLET LINING DIMENSIONS length, L= 20 ft width, W = 6 ft Permanent Channel Lining: Class 2 Riprap ~~~~ . ~„~a~~~~~~, ~~~~~ Page 1 ~ ,. ; r ~ ~ ~ I. ~ ' - 4 ~ -'~ ; ~~~' - DATE G~ PROJECT NAME PROJECT NO ~ /I Herita e Hi h School 1123 0 (~ LOCATION BY ~~ Wake Forest, NC KAY •• ~ Drainage Area, (DA) = 16.30 ac Impervious Area (c=0.95) = 9.62 ac Pervious Area (c=0.35) = 6.68 ac Cc = 0.70 Permanent Water Quality Pool Impervious = 59 Permanent Pool Depth = 3.00 ft SA / DA Ratio = 2.37 (from Tbl. 1.1) Required Surface Area = 16,804 sf Temporary Water Duality Pool Design Storm Rainfall 1.00 in (Typically 1-in) Runoff Coeff. (Rv = 0.05 + 0.009 (% Imperv.)) = 0.58 in/in Required Volume (design rainfall)(Rv)(DA) = 34,387 cf Avg. Full Depth Surface Area Provided= Surface Area at 1"Storage Volume= 1 " Storage Volume Provided= Max. Head of Water Above Dewatering Hole = Diameter of Dewatering Hole = Max. Head Above Dewatering Hole (hmax) _ Head used for Dewatering Calculation (h) _ Detention (Draw-Down) Time = 16,900 sf 29,362 sf 34,387 cf 1.30 ft 2.5 in 1.20 ft to centroid of dewatering hole 0.40 f 1 hmax) . days T days=(Temp. Storage Vol / (0.6 * A " (2~g*(h))^i7g}-*~646E~ (where h =one third temp. storage depth measured to centroid of orifice) Q 1 in/nr (runoff from 1-in/hr storm) _ QmaX Drawdown= 11 cfs 0.179 cfs (at hmax) Table 1.1 SA / DA Ratios Permanent Pool Depth (ft) Im envious 3.0 4.0 5.0 6.0 10 0.59 0.49 0.43 0.35 20 0.97 0.79 0.70 0.59 30 1.34 1.08 0.97 0.83 40 1.73 1.43 1.25 1.05 50 2.06 1.73 1,50 1.30 60 2.40 2.03 1.71 1.51 70 2.88 2.40 2.07 1.79 80 3.36 2.78 2.38 2.10 90 3.74 3.10 2.66 2.34 Pond B 0.0 25976.4 51952.8 77929.3 103905.7 129882.1 155858.5 181834.9 207811.3 Storage (cult) ~;.. ~ '~ ~+ DATE DESIGN PHASE ;~,.~ ,; 12/4/07 PRELIM / / _, . ~ _ ~ - PROJECT NAME PROJECT NO CONSTR / / Heritage High School 1123 REVISION / x / LOCATION BY RECORD / / Wake Forest, NC KAL OTHER / / CHECKED BY (SPECIFY) SJM Storm Outlet Structure FES No.= POND B Quo/Qfull = 0.05 Pipe Dia= n VNfull = 0.52 Quo = 6.04 cfs V~o = 6.6 fps Ofull = 122.00 cfs Slope= 1.8 Vfull = 12.70 fps Pipe Inv= 214.0 Drawdown = 0.82 cfs VDrawdown = 2.27 fps (Flowmaster) From Fig. 8.06.b.1: Zone = 3 From Fig. 8.06.b.2: D5o = 10 in DnnAx = 15 in Riprap Class = 1 s Apron Thickness = 22.5 in Apron Length = 28 ft 3 Apron Width = 3xDia = 11 ft _ Length _ I Storm Outlet Structure FES No.= POND C Quo/Qfull = 0.05 Pipe Dia= 30 in VNfull = 0.52 Quo = 2.36 cfs V~o = 4.7 fps Qfull = 44.20 cfs Slope= 4.0 Vfull = 9.00 fps Pipe Inv= 211.00 ft Drawdown = 0.49 cfs VDrawdown = 1.57 fps (Flowmaster) From Fig. 8.06.b.1: Zone = 3 From Fig. 8.06.b.2: D5o - = 10 in DMAx = 15 in - Riprap Class = 1 _ s~ Apron Thickness 22.5 in Apron Length - 20 ft 3 Apron Width = 3xDia = 8 ft _~ Length ~ ~~.~ ~ . ` - ` ~ '~ DATE DESIGN PHASE ~~ ~ • +~ ,. .,. _. 12/4/07 SD / / PROJECT NAME PROJECT NO DD / / Heritage High School 1123 CD / X / LOCATION BY REV / / Wake Forest, NC KAL OTHER / / CHECKED BY (SPECIFY) X R/PRAP LINING -Permissible Sheer and Capacity Outlet No: POND B Drainage Area, (DA) = 16.30 ac Sta from: Impervious Area (c=0.95) = 9.62 ac Sta to: Pervious Area (c=0.35) = 6.68 ac Section Length: 28 ft Cc = 0.70 Section Slope: 1.8 % One inch/hr storm= 11.48 cfs Riprap Class: 1 (d50= 10") Temp. Storage Depth = 1.30 ft Allowable Sheer: 3.33 Ib/sf Diameter of Dewatering Hole = 2.5 in Allowable Depth: 1.00 ft Drawdown Rate= 0.18 cfs Swale sizing method done by manipulation of Manning's Equation to find the depth of flow that matches the known flow conditions. Performed by trial and error. INPUT DATA Qp = 0.18 cfs flow by drawdown n = 0.409 Class 1 Riprap Manning's Coefficient (dimensionless) S = 0.018 ft/ft longitudinal slope (ft of fall per ft of run) Zreq = 0.37 quantity to equate to Zav M = 0 :1 side slope of channel (ft of run : 1 ft of rise) NORMAL DEPTH AND VELOCITY B D A P R Zav Remark 11 0.50 5.50 12.00 0.46 3.27 deep 11 0.40 4.40 11.80 0.37 2.28 deep 11 0.20 2.20 11.40 0.19 0.73 deep 11 0.13 1.43 11.26 0.13 0.36 OK B = bottom width of trapezoidal channel _ ~a° Zreq D = normal depth of flow A = cross-sectional area of flow ~ ~z~ __ Q~ P = wetted perimeter of the channel 1.49 ~ R = hydraulic radius of the channel Normal Depth, D = 0.13 ft ~ Depth O.K. Velocity= 0.13 fps,.' Velocity O.K. AR STRESS T = yds =shear stress in Ib/sq-ft Y = unit weight of water, 62.4 Ib/cu-ft D = normal depth of flow in ft S =longitudinal slope in ft/ft shear stress, T = 0.15 Ib/sq-ft Sheer O.K. FINAL OUTLET LINING DIMENSIONS length, L= 28 ft width, W = 11 ft Permanent Channel Lining: Class 1 Riprap (REF: Malcom, 1991) Page 1 h~ i' ~ DATE ? ~ ... 12-4-07 ~ G~ PROJECT NAME PROJECT NO /~ Herita e Hi h School 1123 ~~ LOCATION BY Wake Forest, NC KAL Drainage Area, (DA) _ Impervious Area (c=0.95) _ Pervious Area (c=0.35) _ Cc = 12.10 ac 3.37 ac 8.73 ac 0.52 Permanent Water Quality Pool Impervious = Permanent Pool Depth = SA / DA Ratio = Required Surface Area = 28 3.00 ft 1.26 6,644 sf Temporary Water Quality Pool Design Storm Rainfall 1.00 in Runoff Coeff. (Rv = 0.05 + 0.009 (% Imperv.)) = 0.30 in/in Required Volume (design rainfall)(Rv)(DA) = 13,206 cf (from Tbl. 1.1) (Typically 1-in) Avg. Full Depth Surface Area Provided= 8,901 sf Surface Area at 1" Storage Volume= 14,147 sf 1"Storage Volume Provided= 13,206 c _--- Max. Head of Water Above Dewatering Hole = 1.10 ft Diameter of Dewatering Hole = 1.5 in Max. Head Above Dewatering Hole (hm~) = 1.04 ft to centroid of dewatering hole Head used for Dewatering Calculation (h) = 0.35 ft_ 1/3 hmax) Detention (Draw-Down) Time 4.4 days ~ j T days=(Temp. Storage Vol / (0.6 " A * (2'`g'`(h))^1 /2) " 8~ (where h =one third temp. storage depth measured to centroid of orifice) Q f in/nr (runoff from 1-in/hr storm) = 6.26 cfs ~maX Drawdown= 0.060 Cfs ) (at hmax) Table 1.1 SA / DA Ratios Permanent Pool Depth (ft) Im envious 3.0 4.0 5.0 6.0 10 0.59 0.49 0.43 0.35 20 0.97 0.79 0.70 0.59 30 1.34 1.08 0.97 0.83 40 1.73 1.43 1.25 1.05 50 2.06 1.73 1.50 1.30 60 2.40 2.03 1.71 1.51 70 2.88 2.40 2.07 1.79 80 3.36 2.78 2.38 2.10 90 3.74 3.10 2.66 2.34 s:\1319\0001\calcs\1123-POndSlze-Pond C.XLS printed: 12/5/2007 3:54 PM Page 1 of 1 Pond C q ~ ° ~ . ~ DATE DESIGN PHASE A ``~ 12/4/07 PRELIM / / 1! w, , PROJECT NAME, e PROJECT NO CONSTR / / Herita a High School 1123 REVISION / x / LOCATION BY RECORD / / Wake Forest, NC KAL OTHER / / CHECKED BY (SPECIFY) SJM Storm Outlet Structure FES No.= POND B Quo/Qfull = 0.05 Pipe Dia= 42 in V/Vfull = 0.52 Quo = 6.04 cfs V~o = 6.6 fps Qfull = 122.00 cfs Slope= 1.8 Vfull = 12.70 fps Pipe Inv= 214.00 ft Drawdown = 0.82 cfs VDrawdown = 2.27 fps (Flowmaster) From Fig. 8.06.b.1: Zone = 3 From Fig. 8.06.b.2: Dso = 10 in DMa~x = 15 in --~ Riprap Class _ 1 s Apron Thickness 22.5 in 27 Apron Length = 28 ft j Apron Width = 3xDia = 11 ft Length I 1 Storm Outlet Structure FES No.= POND C Quo/Qfull = 0.05 Pipe Dia= 30 in V/Vfull = 0.52 Quo = 2.36 cfs V~o = 4.7 fps Qfull = 44.20 cfs Slope= 4.0 Vfull = 9.00 fps Pipe Inv= 211.00 ft Drawdown = 0.49 cfs VDrawdown = 1.57 fps (Flowmaster) From Fig. 8.06.b.1: Zone = From Fig. 8.06.b.2: D5o = 10 in Dnnax = 15 in --T Riprap Class = 1 S Apron Thickness = 22.5 in Apron Length = 20 ft Apron Width = 3xDia = 8 ft - -_~ Length ~..~__ _ ~~~ ~~ '~ ~~~ `~. ~~ ~'~~ ~~ 4,. ~ s.. ~ DATE DESIGN PHASE ,,4 ~ ~ =g. ~ ~,H ~ ~~~~ s?> ~°_: 12/4/07 SD / / PROJECT NAME PROJECT NO DD / / Heritage High School 1123 CD / X / LOCATION BY REV / / Wake Forest, NC KAL OTHER / / CHECKED BY (SPECIFY) X R/PRAP LINING -Permissible Sheer and Capacity Outlet No: POND C Drainage Area, (DA) = 12.10 ac Sta from: Impervious Area (c=0.95) = 3.37 ac Sta to: Pervious Area (c=0.35) = 8.73 ac Section Length: 20 ft Cc = 0.52 Section Slope: 4.0 % One inch/hr storm= 6.26 cfs Riprap Class: 1 (d50= 10") Temp. Storage Depth = 1.10 ft Allowable Sheer: 3.33 Ib/sf Diameter of Dewatering Hole = 1.5 in Allowable Depth: 1.00 ft Drawdown Rate= 0.06 cfs Swale sizing method done by manipulation of Manning's Equation to find the depth of flow that matches the known flow conditions. Performed by trial and error. INPUT DATA Qp = 0.06 cfs flow by drawdown n = 0.409 Class 1 Riprap Manning's Coefficient (dimensionless) S = 0.04 ft/ft longitudinal slope (ft of fall per ft of run) Zreq = 0.08 quantity to equate to Zav M = 0 :1 side slope of channel (ft of run : 1 ft of rise) NORMAL DEPTH AND VELOCITY B D A P R Zav Remark 8 0.50 4.00 9.00 0.44 2.33 deep 8 0.40 3.20 8.80 0.36 1.63 deep 8 0.10 0.80 8.20 0.10 0.17 deep 8 0.06 0.48 8.12 0.06 0.07 OK B = bottom width of trapezoidal channel D = normal depth of flow Zav = 7req A = cross-sectional area of flow ~ Rzr~ _ Can P = wetted perimeter of the channel l,dg R = hydraulic radius of the channel Normal Depth, D = 0. Depth O.K. Velocity= 0.13 fps Velocity O.K. SHEAR STRESS T = yds =shear stress in Ib/sq-ft Y = unit weight of water, 62.4 Ib/cu-ft D = normal depth of flow in ft S =longitudinal slope in ft/ft shear stress, T = 0.15 Ib/sq-ft Sheer O.K. FINAL OUTLET LINING DIMENSIONS length, L= 20 ft width, W = 8 ft Permanent Channel Lining: Class 1 Riprap (REF: Malcom, 1991) Page 1 .r+{- PROJECT NAME Heritaae Hiah School CATION ake Forest. NC KAL -• ~ ~ Drainage Area, (DA) = 20.20 ac Impervious Area (c=0.95) = 6.34 ac Pervious Area (c=0.35) = 13.86 ac Cc = 0.54 Permanent Water Quality Pool Impervious = 31 Permanent Pool Depth = 3.00 ft SA / DA Ratio = 1.39 (from Tbl. 1.1) Required Surface Area = 12,266 sf Temporary Water Quality Pool Design Storm Rainfall 1.00 in (Typically 1-in) Runoff Coeff. (Rv = 0.05 + 0.009 (% Imperv.)) = 0.33 in/in Required Volume (design rainfall)(Rv)(DA) = 24,379 cf Avg. Full Depth Surface Area Provided= Surface Area at 1"Storage Volume= 1" Storage Volume Provided= Max. Head of Water Above Dewatering Hole = Diameter of Dewatering Hole = Max. Head Above Dewatering Hole (hm~) _ Head used for Dewatering Calculation (h) _ Detention (Draw-Down) Time = 16,757 sf 3333 1~~ 24,379 cf 0.80 ft 2.5 in 0.70 ft to centroid of dewatering hole 0.23 ft 1/3 hmax) 3 6 d~ T days=(Temp. Storage Vol / (0.6 ~ A ~ (2~g~(h))^1/2) ~ 86400 (where h =one third temp. storage depth measured to centroid of orifice) Q 1 in/hr (runoff from 1-in/hr storm) _ Qmax Drawdown= Table 1-1 10.87 cfs . 37 Cfs (at hmax) SA / DA Ratios Permanent Pool Depth (ft) Im envious 3.0 4.0 5.0 6.0 10 0.59 0.49 0.43 0.35 20 0.97 0.79 0.70 0.59 30 1.34 1.08 0.97 0.83 40 1.73 1.43 1.25 1.05 50 2.06 1.73 1.50 1.30 60 2.40 2.03 1.71 1.51 70 2.88 2.40 2.07 1.79 80 3.36 2.78 2.38 2.10 90 3.74 3.10 2.66 2.34 '~ DATE 12-4-07 PROJECT NO 1123 s:\1319\0001\calcs\1123-PondSize-Pond D.XLS printed: 12/5/2007 3:54 PM Page 1 of 1 -- i Pond D U.U 30495.9 60991.9 91487.8 121983.8 152479.7 182975.6 213471.6 243967.5 i Storage (cult) r ' " ~ • DATE DESIGN PHASE ® ~ _, ~~~,~-t . =~~ 12/4/07 PRELIM / / PROJECT NAME PROJECT NO CONSTR / / Herita a High School 1123 REVISION / x / LOCATION BY RECORD / / Wake Forest, NC KAL OTHER / / CHECKED BY (SPECIFY) SJM Storm Outlet~tu~ ture FES No.= POND D Quo/Qfull = 0.36 Pipe Dia= in VNfull = 0.91 Quo = 28.37 cfs V~o = 10.1 fps Qfull = 78.60 cfs Slope= 8.3 Vfull = 11.10 fps Pipe Inv= 221. Drawdown = 0.57 cfs VDrawdown = 2.10 fps (Flowmaster) From Fig. 8.06.b.1: Zone = From Fig. 8.06.b.2: D5o = 10 in Dnnax = 15 in Riprap Class = 1 s, Apron Thickness = 22.5 in ~; Apron Length = 24 ft _~ F-_ Length- -1 Apron Width = 3xDia _ 9 ft Storm Outlet Structure FES No.= J2 Q~/Qfull = 0.0 2 Quo/Qfull = 0.12 Pipe Dia= 15 in VNfull = 0.32 VNfull = 0.67 Quo = 0.81 cfs V~o = 3.8 fps Qfull = 6.80 cfs Slope= 5.0 Vfull = 5.60 fps Pipe Inv= 215.00 ft Q~ = 0.11 cfs V~ = 1.8 fps From Fig. 8.06.b.1: Zone = 2 From Fig. 8.06.b.2: D5o = 8 in DnnAx = 12 in Riprap Class = B _ rI Apron Thickness = 18 in Apron Length = 8 ft ~' _ _ _.l ~ Length Apron Width = 3xDia = 4 ft `~'~~ ~` ' ~ -~~~~t~ `~ ~ ' u { ~ DATE DESIGN PHASE ~ .~~r ~?~ , ~ " `. ~~ ~ ~=w . 12/4/07 SD / / PROJECT NAME PROJECT NO DD / / Heritage High School 1123 CD / X / LOCATION BY REV / / Wake Forest, NC KAL OTHER / / CHECKED BY (SPECIFY) X R/PRAP LINING -Permissible Sheer and Capacity Outlet No: POND D Drainage Area, (DA) = 20.20 ac Sta from: Impervious Area (c=0.95) = 6.34 ac Sta to: Pervious Area (c=0.35) = 13.86 ac Section Length: 24 ft Cc = 0.54 Section Slope: 8.3 % One inch/hr storm= 10.87 cfs Riprap Class: 1 (d50= 10") Temp. Storage Depth = 0.80 ft Allowable Sheer: 3.33 Ib/sf Diameter of Dewatering Hole = 2.5 in Allowable Depth: 1.00 ft Drawdown Rate= 0.14 cfs Swale sizing method done by manipulation of Manning's Equation to find the depth of flow that matches the known flow conditions. Performed by trial and error. INPUT DATA Qp = 0.14 cfs flow by drawdown n = 0.409 Class 1 Riprap Manning's Coefficient (dimensionless) S = 0.083 ft/ft longitudinal slope (ft of fall per ft of run) Zreq = 0.13 quantity to equate to Zav M = 0 :1 side slope of channel (ft of run : 1 ft of rise) NORMAL DEPTH AND VELOCITY B D A P R Zav Remark 9 0.50 4.50 10.00 0.45 2.64 deep 9 0.40 3.60 9.80 0.37 1.85 deep 9 0.10 0.90 9.20 0.10 0.19 deep 9 0.08 0.72 9.16 0.08 0.13 OK B = bottom width of trapezoidal channel D = normal depth of flow Zav = Zreq zr~ Qn A = cross-sectional area of flow = ~ R P = wetted perimeter of the channel l,dg R = hydraulic radius of the channel Normal Depth, D = 0.0 Depth O.K. Velocity= 0.19 fps Velocity O.K. STRESS T = yds =shear stress in Ib/sq-ft Y = unit weight of water, 62.4 tb/cu-ft D = normal depth of flow in ft S =longitudinal slope in ft/ft shear stress, T = 0.41 Ib/sq-ft Sheer O.K. FINAL OUTLET LINING DIMENSIONS length, L= 24 ft width, W = 9 ft Permanent Channel Lining: Class 1 Riprap (REF: Malcom, 1991) Page 1 ,. ~ ,,• ~. •~~, ~-, , ~-- _ DATE 12-4-07 PROJECT NAME PROJECT NO o ~~ Herita a Hi h School 1123 __~ LOCATION BY Wake Forest, NC ~~ ~~ ~ Drainage Area, (DA) = 1.91 ac Impervious Area (c=0.95) = 0.62 ac Pervious Area (c=0.35) = 1.29 ac Cc = 0.54 Permanent Water Quality Pool Impervious = 32 Permanent Pool Depth = 3.00 ft SA / DA Ratio = 1.44 (from Tbl. 1.1) Required Surface Area = 1,195 sf Temporary Water Quality Pool Design Storm Rainfall 1.00 in (Typically 1-in) Runoff Coeff. (Rv = 0.05 + 0.009 (% Imperv.)) = 0.34 in/in Required Volume (design rainfall)(Rv)(DA) = 2,372 cf Avg. Full Depth Surface Area Provided= 2,289 sf Surface Area at 1" Storage Volume= 4,533 s 1"Storage Volume Provided= 2,372 cf Max. Head of Water Above Dewatering Hole = 0.60 ft Diameter of Dewatering Hole = 0.75 in Max. Head Above Dewatering Hole (hmax) = 0.57 ft to centroid of dewatering hole Head used for Dewatering Calculation (h) = 0.19 ft (1/3 hmax) Detention (Draw-Down) Time = 4.3 days T days=(Temp. Storage Vol / (0.6 " A' (2*g'(h))^i/2) * 86400 (where h =one third temp. storage depth measured to centroid of orifice) Q 1 in/hr (runoff from 1-in/hr storm) _ QmaX Drawdown= 1.04 cfs .011 cfs (at hmax) Tohlo 1 1 SA / DA Ratios Permanent P ool Depth (ft) Impervious 3.0 4.0 5.0 6.0 10 0.59 0.49 0.43 0.35 20 0.97 0.79 0.70 0.59 30 1.34 1.08 0.97 0.83 40 1.73 1.43 1.25 1.05 50 2.06 1.73 1.50 1.30 60 2.40 2.03 1.71 1.51 70 2.88 2.40 2.07 1.79 80 3.36 2.78 2.38 2.10 90 3.74 3.10 2.66 2.34 s:\1319\0001\calcs\1123-POndSize-Pond G.XLS printed: 12/5/2007 3:53 PM Page 1 of 1 Pond G Storage (cult) 16762.9 19556.7 22350.5 u.u L/y3.8 bb8~.6 8381.4 11175.3 13969.1 ~ - < _ ~ _ ~ , _ °,' ~ ` DATE DESIGN PHASE ~ . > "~.' - ~~~~ , ; -Ej. 12/4/07 PRELIM / / PROJECT NAME PROJECT NO CONSTR / / Heritage High School 1123 REVISION / x / LOCATION BY RECORD / / Wake Forest, NC KAL OTHER / / CHECKED BY (SPECIFY) SJM Storm Outlet Structure FES No.= OND G Quo/Qfull = 0.25 Pipe Dia= in V/Vfull = 0.83 Oro = 8.51 cfs V~o = 15.9 fps Qfull = 33.70 cfs Slope= 21.0 Vfull = 19.10 fps Pipe Inv= 261.00 ft_ - Drawdown = 0.03 cfs Verawdown = _ 2.15 fps (Flowmaster) From Fig. 8.06.b.1: Zone = _ - rm Outlet Structure FES No.= A8 Pipe Dia= 15 in Quo= 1.33 cfs Qfull = 19.60 cfs Vfull = 15.90 fps Q ~ = 0.18 cfs From Fig. 8.06.b.1: From Fig. 8.06.b2: - _, ~` ~ `< _ . ~_ i Length I----._.. _. - __ -' From Fig. 8.06.b.2: Dso = 10 in D enAx = 15 in ~ Riprap Class = 1 s Apron Thickness = 22.5 in Apron Length = 12 ft -- ~_ _ ~e~g~;, ~ I I Apron Width = 3xDia = 5 ft Q~/Qfull = 0.01 Quo/Qfull = 0.07 V~/Vfull = 0.26 V/Vfull = 0.52 V~o = 8.3 fps Slope= 7.0 Pipe Inv= 276.00 ft V~ = 4.1 fps Zone = 3 Dso ~ = 10 in DMAx = 15 in Riprap Class = 1 Apron Thickness = 22.5 in Apron Length = 10 ft Apron Width = 3xDia = 4 ft ~' ~ ~ w ~ ` ` ~ ~ ~ ~ '` s' :; DATE DESIGN PHASE ~, ~ ~ ~ r `' 12/4/07 SD / / PROJECT NAME PROJECT NO DD / / Heritage Hi h School 1123 CD / X / LOCATION BY REV / / Wake Forest, NC KAL OTHER / / CHECKED BY (SPECIFY) X R/PRAP LINING -Permissible Sheer and Capacity Outlet No: POND G Drainage Area, (DA) = 1.91 ac Sta from: Impervious Area (c=0.95) = 0.62 ac Sta to: Pervious Area (c=0.35) = 1.29 ac Section Length: 12 ft Cc = 0.54 Section Slope: 21.00 % One inch/hr storm= 1.04 cfs Riprap Class: 1 (d50= 10") Temp. Storage Depth = 0.60 ft Allowable Sheer: 3.33 Ib/sf Diameter of Dewatering Hole = 0.75 in Allowable Depth: 1.00 ft Drawdown Rate= 0.01 cfs Swale sizing method done by manipulation of Manning's Equation to find the depth of flow that matches the known flow conditions. Performed by trial and error. INPUT DATA Qp = 0.01 cfs flow by drawdown n = 0.409 Class 1 Riprap Manning's Coefficient (dimensionless) S = 0.21 ft/ft longitudinal slope (ft of fall per ft of run) Zreq = 0.01 quantity to equate to Zav M = 0 :1 side slope of channel (ft of run : 1 ft of rise) NORMAL DEPTH AND VELOCITY B D A P R Zav Remark 5 0.50 2.50 6.00 0.42 1.39 deep 5 0.20 1.00 5.40 0.19 0.32 deep 5 0.10 0.50 5.20 0.10 0.10 deep 5 0.03 0.15 5.06 0.03 0.01 OK B = bottom width of trapezoidal channel Zav = Zreq D = normal depth of flow xr~ Qn A = cross-sectional area of flow _ ~ R P = wetted perimeter of the channel l,qg R = hydraulic radius of the channel Normal Depth, D = 0.03 ft Depth O.K. __._ ~ ~_\ Velocity= 0.07 fps Velocity O.K. AR STRESS T = yds =shear stress in Ib/sq-ft Y = unit weight of water, 62.4 Ib/cu-ft D = normal depth of flow in ft S =longitudinal slope in ft/ft shear stress, T = 0.39 Ib/sq-ft Sheer O.K. FINAL OUTLET LINING DIMENSIONS length, L= 12 ft width, W = 5 ft Permanent Channel Lining: Class 1 Riprap (REF: Malcom, 1991) Page 1