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HomeMy WebLinkAboutDrainage Reports - 10/15/2015dwilesco Project & Construction Services October 14, 2015 Dan Mogen City of Fort Collins Utilities Stormwater Engineering 700 Wood Street Fort Collins, CO 80521 1315 Oakridge Drive, Suite 120 Fort Collins, CO 80525 ditescoservices.com City of Fort Collins A ro ed Plans Approved by: Date:%s/2ot5� RE: Drainage Memorandum - CSU Research Boulevard Parking Lot Drake Road Turn Lane Project Dear Dan: The purpose of this drainage memorandum is to summarize the proposed drainage design and provide calculations for the additional impervious area runoff. Approximately 3,210 square feet of asphalt and concrete will be added due to the construction of a right-hand turn lane from westbound Drake Road onto northbound Research Boulevard. Please refer to the attached Drainage Exhibits including the rational method and other hydrologic calculations. The expanded turn lane area is less than one -tenth of an acre in size and is contained within the Drake Road right of way. The project spans from Research Boulevard east to the Larimer #2 Ditch Crossing of Drake Road. Work includes milling and overlay of the existing bike lane, excavation of the current shoulder, placement of base course and asphalt paving, as well as a new concrete pavement, curb, gutter and sidewalk. Work also includes installation of directional ramps, roadway striping, and traffic pole relocation. Existing drainage will be re-routed from its historical pattern which currently outlets to the Larimer #2 ditch via overland flow. Storm water drainage currently runs from west to east through the intersection and will be maintained in its current general path along the new edge of roadway to a proposed curb inlet, where it will enter a 14"x23" horizontal elliptical reinforced concrete pipe and outlet to a storage pond on CSU property. The pond will outlet into the Larimer #2 ditch at a reduced flow rate. We have calculated the additional impervious drainage tributary area using the Urban Area Drainage Criteria Manual (Fort Collins Amended) and found that the increase in stormwater runoff due to new pavement installation is an approximate 8.15% increase from the existing condition in the tributary basin (See Exhibits 5 and 6 for Calculations). Currently the tributary area is approximately 0.9 acres with a flow of 8.96 CFS during a 100 year storm event with a 5 minute return interval. The addition of the turn lane adds 0.074 acres with a corresponding flow of 0.74 CFS at 100 year storm event for a total of 9.69 CFS. The 5 year storm event flows for existing and proposed conditions are 3.25 CFS and 0.27 CFS respectively. The 2 year storm event flows are 2.57 CFS and 0.21 CFS, respectively. For inlet sizing and Page 1 of 16 pond storage capacity, a 100-year storm event of one hour duration was used for calculations. A summary of the results can be seen in Exhibit 7. During a meeting between Colorado State University (CSU) and City of Fort Collins Stormwater staff on September 21, 2015, CSU agreed to provide offsite storage of drainage runoff from storm events in a detention pond on CSU property adjacent to the Larimer Ditch located north of the project. This will be a shallow pond with a total detention capacity for a 100 year storm event, equal to 0.153 acre-feet located west of the Larimer #2 Ditch right of way and north of the existing City of Fort Collins drainage easement. The pond will outlet through a 12-in pipe with a restrictor plate into_the Larimer #2 ditch at a rate of 1.8 CFS at maximum flow with an outlet flap valve to prevent water in the ditch from entering the pond. Future development plans for the area in which the proposed 0.153 acre-ft pond will be situated include a larger retaining pond to contain rainfall on future planned impervious areas on CSU property. At the time of that development, CSU will modify the system to direct stormwater away from the Larimer #2 ditch and into the CSU storm system. The additional volume into the CSU system will be incorporated into CSU's stormwater surface flow model and credit tallied appropriately per the process outlined in the Stormwater IGA. For the current project, inlet location will be "in -line" with the curb and gutter. In the expected future condition, the inlet will be in a "sump condition" and will handle additional surface drainage from the area bounded by the centerline crown of Drake Road and the mid -span of the future Larimer #2 Drake Crossing Bridge. In summary, CSU will be providing onsite water quantity detention for the project and tributary drainage area in order to provide the City of Fort Collins more flexibility in designing the new Larimer #2 Drake Crossing as a City capital project in the future. If you have any questions regarding this submittal, please do not hesitate to contact me -by email at bill.renz@ditescoservices.com or by phone at 970-219-0157. Thank you for your attention and assistance in this matter. Sincerely, `�. QOREGlSlFR�.i�� pQ?�,� Md f F,P •.O Vl1 - o U #32�]9�6CC- �'2 Bill Renz, El Ditesco �'�� SS;ottMW Enc. Calculations, UDFCD Worksheets Cc: Gene Ellis, CSU Utilities Services Manager Laura Bently, CSU Project Manager Keith Meyer, Ditesco Page 2 of 16 N Q O N GJ O.0 m G1 Q C fD f9 4! C m m N Q ri x W a) bD m C m L NO 2� �o"l� - / Spi I 1 11' I I I II I E . N I i � I 1 N lz� - I O I O .- O 6 N(DO O CO � Q) N I a Q('')N QM �I I II I I I II I II ol., z I e., � x�l ��1 Ir I III Qol 'LNI I I I �I i � I II I 1 s w I I I - n Q¢ Q_ I ')0 I o L a� I } L d I I I I �• r V/131nO8 HOH%f3S3N i 11- irL� III a w 0 m w m m a C N f0 CO L O .� Y c O u ra u .E O 4- 2 I (V t X W N W m C ro Drainage Exhibit 3 - Runoff Coefficients Table RO3—Recommended Percentage Imperviousness Values Land Use or Surface Characteristics Percentage Imperviousness Business: Commercial areas 95 Neighborhood areas 85 Residential: Single-family ' Multi -unit (detached) 60 Multi -unit (attached) 75 Half -acre lot or larger ' Apartments 80 Industrial: Light areas 80 Heavy areas 90 Parks, cemeteries 5 Playgrounds 10 Schools 50 Railroad yard areas 15 Undeveloped Areas: Historic flow analysis 2 Greenbelts, agricultural 2 Off -site flow analysis (when land use not defined) 45 Streets: Paved 100 Gravel (packed) 40 Drive and walks 90 Roofs 90 Lawns, sandy soil 0 Lawns, clayey soil 0 ' See Fiaures RO-3 through RO-5 for percentage Imperviousness. The composite "c" value for the Rational Method Basin Streets Paved Area (scift) Composite No. "C=1.00" "C" New Turn Lane 3,210 1.00 Page 5 of 16 Drainage Exhibit 4 - Intensity/Duration/Frequency Table Table RA-7 -- City of Fort Collins Rainfall Intensity -Duration -Frequency Table for Use with the Rational Method (5 minutes to 30 minutes) Duration (min) 5 2-Year Intensity (in/hr) 2.85 10-Year intensity (itVhr) 4.87 100-Year Intensity (in/hr) 9.95 6 2.67 4.56 9.31 7 2.52 4.31 8.8 8 2.4 4.1 8.38 9 2.3 3.93 8.03 10 2.21 3.78 7.72 11 2.13 3.63 7.42 12 2.05 3.5 7.16 13 1.98 3.39 6.92 14 1.92 3.29 6.71 15 1.87 3.19 6.52 16 1.81 3.08 6.3 17 1.75 2.99 6.1 18 1.7 2.9 5.92 19 1.6.5 2.82 5.75 20 1.61 2.74 5.6 21 1.56 2.67 5.46 22 1.53 2.61 5.32 23 1.49 2.55 5.2 24 1.46 2.49 5.09 25 1.43 2.44 4.98 26 1.4 2.39 4.87 27 1.37 2.34 4.78 28 1.34 2.29 4.69 29 1.32 2.25 4.6 30 1.3 2.21 4.52 Table RA-8 - City of Fort Collins Rainfall Intensity -Duration -Frequency Table for Use with the Rational Method (31 minutes to 60 minutes) Duration (min) 31 2-Year Intensity (inAW) 1.27 10-Year Intensity (in/hr) 2.16 100-Year Intensity (iNtu) 4A2 32 124 2.12 4.33 33 122 2.08 4.24 +4 1.19 2.04 4.16 35 1.17 2.0 4.08 36 1.15 1.96 4.01 37 1.16 1.93 3.93 38 1.11 1.89 3.97 39 1.09 1.86 3.8 40 1.07 1.83 3.74 41 1.05 1.8 3.68 42 I At 1.77 3.62 43 1.02 1.74 3.56 44 1.01 1.72 3.51 45 0.99 1.69 3.46 46 0.98 1.67 3.41 47 0.96 1.64 3.36 48 0.95 1.62 3.31 49 0.94 1.6 3.27 50 0.92 1.58 3.23 51 0.91 1-% 3.18 52 0.9 1.54 3.14 53 0.89 1.52 3.1 54 0.88 1.5 3.07 55 0.97 1.48 3.03 56 0.86 1.47 2.99 57 0.85 1.45 2.96 58 0.94 1.43 292 59 0.83 1.42 2.89 60 0.82 1.4 2.86 Page 6 of 16 c O a=+ L c u c O u O v E Ln L L X W v d4 m c L w 9 E m Lo 0 cn U 0 x J N U m 0 T m a N J l0 U N M m 0 W w 0 n w m m a CSU Drake Turn Lane Storm Drainage Design Design Storm: 2 year 5 min. Time of Concentration Site Calculations: Drainage Exhibit 6 - Rational Method Project Location: CSU Drake Turn Lane Calculated By: RW Date: 813/2015 Direct Runoff Basin No. Sub -basin Area (Ac) Total Contrib. Area CS Area (Ac) Area (Ac) I Final tc C2xA I I (Ac) (in/hr) Q (cfs) Design Q (cfs) New Turn Lane 0.074 0.074 1 1.00 1 4.63 1 0.07 2.85 0.21 0.21 l Existing 0.90 0.90 1.00 4.63 0.90 2.850 2.57 2.57 CSU Drake Turn Lane Storrs Drainage Design Design Storm: 5 year 5 min. Time of Concentration Site Calculations: Project Location: CSU Drake Turn Lane Calculated By: RW Date: 8/3/2015 Direct Runoff Basin No. Sub -basin Area I (Ac) Total Area (Ac) Contrib. Area C5 Area (Ac) I Final tc C2xA I I I (Ac) (in/hr) Q (cfs) Design Q (cfs) New Turn Lane 1 0.074 0.074 1.00 4.66 1 0.07 3.6 0.27 0:27 Existing 0.90 0.90 1.00 4.66 0.90 3.6 3.25 325 CSU Drake Turn Lane Storrs Drainage Design Design Storm: 100 year 5 min. Time of Concentration Site Calculations: Project Location: CSU Drake Turn Lane Calculated By: RW Date: 8/3/2015 Direct Runoff Basin No. Sub -basin Area (Ac) Total Area (Ac) Contrib. Area C100 Area (Ac) Final tc C2xA I I (Ac) (in/hr) Q (cis) Design Q (cfs) New Turn Lane - 0.074 0.074 1.00 4.63 0.07 9.95 0.7 0.74 Existing 0.90 0.90 1.00 4.63 0.90 9.95 9.0 1 8.96 Page 8 of 16 Q I'll'iO11011oiOII II a 1-111-11,*ONN IOI IMI I�I II it IOI INI I� fA cN VN ... � O h I() N CO n N N N 0 v O O r O C C L m C C c O O O O O O O O O O C C N O O O O O C a- O O O O O C X W l7 V a � O COj. i O O l9 i V Q v p O 0 O C C O fb,O0 C •O L 0 O 03 a m c a m LO c w Q d 4 J Z l N O CD W } C M G d J 2 W 6 C } O O %o w 0 tio w m m d Drainage Exhibit 8 — Detention Volume iv =m*QPO*(6" RaiiM ratensdy from I alimer Area I IDF Curve A tnb. To pond 097 am Develor Qpo=! IM_fame Cfs tc 5 min Storm R-infin QD vat In outflow VOL Out Storage Storage Duration, T Intensity, i (e15) Ali Adjustment 170 S S (Inin) (ft) Factor, m (ft) —(rr) 3 995 9.7 2907 1.00 540 2367 0054 to 7-72 75 4512 0.75 810 3703 0-085 20 5-69 5.3 65-45 0.63 1350 5195 0.119 1 30 452 4.4 7924 059 IM 6FA 0-139 40 3-74 35 9743 U6 2430 6313 0-145 50 3-23 3-1 943E 055 2970 6M 0-14S 60 2-86 2-8 IONS 0,54 3510 651E 0.150 70 2-Q 2.6 10718 054 4050 6668 0.153 SO 238 2-3 11127 0-53 4590 6537 0-150 go 222 22 11676 053 3130 6546 0-130 100 2-05 10 11990 0.53 5670 6310 0.145 Ito 193 19 12497 0.52 6210 6197 0-142 120 1.80 1.8 12623 0-52 6750 5973 0-135 130 1.60 16 12156 0-52 7290 4366 0-112 140 1-40 1.4 11454 0-52 7530 362.4 0-083 150 120 12 10519 0-52 8370 2149 0-049 160 IA5 1.1 10753 0.52 8910 IM 0.042 170 1 1.10 1.1 10.928 0-51 9450 1478 0-034 1S0 105 10 11045 0-51 9990 1055 0-024 IgNwred Storage Volume: 6668 ---------- Page 10 of 16 Drainage Exhibit 9 — Pond Sizing STAGE -STORAGE SIZING FOR POLYGONAL. ELLIPTICAL, OR IRREGULAR PONDS Project. Drake Turn Lane Basin ID'. Pond pv, M SW f DIM ._._.__.�._... stsy.. Desion Information (InouO: Mnof Pond Bottom. W = 37.00 ft Right Triangle OR... Length of Pond Bottom. L = 40.00 ft Isosceles Triangle OR., Dam Side -slope (H V). Z, = 4.00 tuft Rectangle X OR... Circle / Ellipse OR_ Megular (Use Ovende values in cells G32:052) MINOR, MAJOR Storage Requirement from Sheet'Modi6ed FAA' 0 153 cre-ft. Stage -Storage Relationship: Storage Requirement from Sheet 'Hydrograph` _ _ aue-ft. Storage Requirement from Sheet'Full-Spectrum': I acre-ft. Labels for W GCV. Minor. 8 Major Storage Stages nnouti Stage ft Side Slope (H:V) ft/R Below EL ,nut Pond Width at stage ft (output) Pond Length at Stage ft aut ui Surface Area at Stage fe (output) Surface Area at Stage fly User Overide Volume Below Stage ft' loutput) Surface Area at Stage aere4 cut ui Volume Below Stage acr lit (output) Target Volumes for W GCV, Minor. 8 Major Storage Volumes Pond Bottom 5033.00 3Z00 40.00 1,480.0 0.034 0.000 6033.50 4.00 41,00 44.00 1804.0 821 0.D41 0.019 5034.00 400 45.00 48.00 2.160.0 1 812 O.D50 0.042 5034.50 400 49.00K6800 2.548.0 2.989 0.058 0.069 5035 00 4.00 53.00 2,968.0 4.368 0,068 _ 0.100 5035 -': 4.00 57.00 3 420,0 5,965 0.079 _ 0.137 1DO-Year Event : 00 58.60 3.6098 6.668 0.083 0.153 Spillway 61.DO 3904.0 7,795 0.090 0-179 To of Berm - 3Pi 400 65.00 4 420.0 9 876 0.101 0.227 #Nl /A _ #WA #N/A IM#A #WA #N/A #WA _ #N/A #WA #WA #WA #WA #WA #WA #WA #WA _ #WA #NIA #WA #N!A #NA #MA #WA #N/A #WA #WA #N/A _ #WA #N/A MA #NIA *VA #NIA #WA #NIA #WA #N/A MA 11N/A #WA #N/A MA #NIA #NIA MA _ #WA MA #N/A _ _ _ MA I _ #WA #N/A MA iN4/A #NIA #NIA ##A #W_A_ MA #NIA _ #WA #N/A #NIA #NA #WA #WA #WA #N/A #WA #N/A #N/A Page 11 of 16 p,0J.C. Bann tD STAGE -STORAGE SIZING FOR POLYGONAL. ELLIPTICAL. OR IRREGULAR PONDS 503700 5035 00 5035.00 > 503- o0 d Z Y W Ta) V• N 503300 503200 5031.00 STAGE -STORAGE CURVE FOR THE POND 0.05 010 015 020 0.25 Storage (acre-feet) Page 12 of 16 Drainage Exhibit 10-Spillway STAGE -DISCHARGE SIZING OF THE SPILLWAY Project: Drake Tum Lane Basin ID: Pond Design Information (input): Bottom Length of Weir L =M28 feet Angle of Side Slope Weir Angle =degrees Elev for Weir Crest EL. Crest =feet Coef. for Rectangular Weir C. = Coal. for Trapezoidal Weir C- = Calculation of Spillway Capacity ioutputl: Water Surface Elevation ft. !linked; Rect. Weir Flowrate cfs four*.., Triangle Weir Flowrate cfs out; Total Spillway Release cfs ,output`) Total Pond Release cfs lout -,ui/ 5033.00 0.00 0.00 0.00 0.00 5033.50 0.00 0.00 0.00 0.20 5034.00 0.00 0.00 0.00 0.40 5034.50 0.00 0.00 0.00 1 1.00 5035.00 0.00 0.00 0.00 1.47 5035.50 0.00 0.00 0.00 1.64 5036.00 0.00 0.00 0.00 1.80 5036.50 9.90 1.98 11.88 13.82 5037.00 28.00 11.20 39.20 41.28 #N/A #NIA MA #N/A #N/A #NIA #N/A #N/A #N!A #N/A #N/A #NIA #N/A #N/A #N/A #N/A #N/A #NIA #NIA #NIA #WA #N/A #N/A #N/A #NIA #N/A #N/A #NIA #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A MA #N/A #N/A #N/A #WA #NiA #N/A #NIA #N/A #N/A #N/A #NIA #N/A #N/A #N/A #N/A #N/A #N/A #NIA #N/A #N/A #N/A #N/A #NIA #N/A #N/A #N/A #N,'A #NIA #WA #NIA #N/A #NIA #N/A #NIA #NIA MA #N/A #N/A #N/A #N/A #N/A *N/A #N/A #N/A #N/A #N/A #N/A #NIA #N/A #N/A #N/A #NiA #N/A #N/A #N/A #N/A MIA #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A MA #NIA #N/A #N/A #N/A #NIA *NIA #N/A #N/A #NIA #NiA MIA #NIA #N/A #NIA #N/A #N/A #N/A #NIA #NIA #NIA #N/A #NIA #N/A #NIA #N/A #N/A #N/A #NIA #N/A #N/A #NIA #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #NIA #NIA #NIA #N/A #N/A #N/A !NA #N!A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #WA #N/A #N/A #N/A #N/A #WA #N/A #N/A #N/A #N/A Page 13 of 16 STAGE -DISCHARGE SIZING OF THE SPILLWAY Project: Drake Tum Lane Basin ID: Pond 0.000 5040.00 5039,00 5038.00 503TD0 m m m 5036.00 m m 5035.00 ?d 5034-00 5033.00 503200 5031.00 STAGE -STORAGE -DISCHARGE CURVES FOR THE POND Storage (Acre -Feet) 0 D50 0 100 0.150 0200 0 250 0 300 5030.00 ' I I T 0.00 5.00 10.00 15.00 2000 25.00 30.00 35.00 40.00 45.00 Pond Discharge (efs) TOTAL DISCHARGE —SPILLWAY DISCHARGE POND STORAGE Page 14 of 16 Drainage Exhibit 11— Outlet Pipe Restriction RESTRICTOR PLATE SIZING FOR CIRCULAR VERTICAL ORIFICES Project! Drake Tum Lane Basin ID'. Pond x Sizina the Restrictor Plate for Circular Vertical Orifices or Pipes flnout) Water Surface Elevation at Design Depth Pipe/Vertical Orifice Entrance Invert Elevation Required Peak Flow through Orifice at Design Depth PipeNertical Orifice Diameter (inches) Orifice Coefficient Full -Bow Capacity (Calculated) Full -flow area Half Central Angle in Radians Full -flow capacity Calculation of Orifice Flow Condition Half Central Angle (O<Theta<3.1416) Flow area Top width of Onfice (inches) Height from Invert of Onfice to Bottom of Plate (feet) Elevation of Bottom of Plate Resultant Peak Flow Through Onfice at Design Depth Width of Equivalent Rectangular Vertical Orifice Elev WS = Elev Invert - 0= Dia = C, _ #1 Vertical Onfice 02 Vertical Orifice 5.035.80 0.033.00 1 80 12.0 0.60 feet reel cis inches At = 0.79 I sq It Theta = 3.14 red Of = 5.7 cis Percent of Design Flow = 319% Theta ==5.033.33feet red A,sq If T.=inches Y. afeel Elev Plate Bottom Edge = Oo acfs Equivalent Width -1 0.70 1 Ifeet Page 15 of 16 Drainage Exhibit 12 — Inlet Sizing INLET IN A SUMP OR SAG LOCATION Project a Drake Turn Lane Inlet lD a Type R Inlet -r Lo (C)—� H-Curb H-Vert `, Wo V \ La (6) of Ine! l DoWcS; do (addtoaw to coreruous gXV de=sslon'a' Irom'Q-Ai Ler of Unt Inlets (Grate or Curo Opening( m Derr, at Fowfns (outside of local depreswn) Information ;th of a Unit: Crate h of a Urn Grate Opening Ratio for a Grate (typical vaues. 0. 15.0,90) gN Facto for a Segb Grata (typcal vake 0.50 - 0.70) e Weir Coefficient (typical value 2.15 - 3.60) Ontice Coefficient (typical value 0.60 - 0.60) 1 Opmtkrg kiomrawn th of a Unit Curb Opening rt of Vertical Cum Opening in Inches N of Curb Orifice Throat n Inches t of Throat Isee USDCM Figure ST-51 Widen for Depression Pan (typically the gutter width of 2 foot) ping Factor for a Single Curb Opening (typical vale 0.10) Opening Weir Coeffroert (lypral vekre 2.3-3.7) Doering Orifice Coeffdml ilyptcal vahr 0 60 - 0 70) Inlet Interception Capacity (assumes clogged condition) MINOR MAJOR Irld Type = CDOT Type R Curb Opening ae:a = 3oo No = 1 Ponding Depth - 6.0 6.0 MINOR MAJOR (nerds Inches 0 Ptak. DwNr L,(G)- WA feet Wo= NIA feet Ara = N/A Q (G)= NIA N!A C. (G) - WA C lG)- NIA MINOR MAJOR Le(C)= H, H , = Tema - Wr= C,(C)= C. (C)= Cr(C)= Q. Oxucrr.:claan 5.DD 6.00 6.00 63,40 2.00 0.10 0.10 3.6D 0.67 feet nches inches degrees feet Notes: Inlet sizing calculations performed using 100-year event with 1 hour duration Proposed condition is Inlet on Continuous Grade Future Expected Condition is Inlet in a Sump or Sag Location Page 16 of 16