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HomeMy WebLinkAboutInfrastructureDesignReport Inf�rastructi:Ire nI Dec.;ig "Re port (Water, Sanitary Sewer. 9: Storm SeNNrer) Oak & Cot.-tonwoodApartments Lots ,4 & 5, Block 5 :Flanders Creek SUbdivision Located in the SE -1/4 of Section 4, 1 . 2S.9 R. 5E., P.M.M. City of Bozeman, Gallatin County, Montana Prepared By: IF •� e �a o Cotterman n 15873ES Q .�� CENS�� �J Revised July 2022 tiFFR_LPN� SAMI'AKY ;Sll XVI;'IR Sanitary se'A'er service for the Oak and Cottonwoods Apartments projry,t will be provided by extension of a new 8-inch nnain through the hrirnar;i east-west clrive aisle. The sewer Will connect: -to the existing main found in Twin L*E)s Avenue. 4-inch sewer services will be extended to each building from the new 8-inch sewer main. The original Flanders Creek Subdivision infrastructure design assurned a total average daily flow raise of 4.20 gallons pE;r minute I;gprn) far Block 5. The downstream sani:arlY sewE;r lift station, located to the, m!st along Oak Street within Laurel Glen Subdivision, is approaching its ultimate capacity. To apleviate future capacity issues a new sewer interceptor line is proposr�d, an4:t currently under construction, v it:h the Northwest Crossing Subdivision. The int:erce: ptor line will connect to thE! Oak Street sewer main at the i rite n_.ection with Rosa Way diverting flows nort[Mard through the Northwest Crossing Subdivision a tirriately discharging into the Norton East Ranch outfall sewer. The Oak: & C,ottonwood Apartment project proposes a total of 84 2-bedroom apartrmmts. Estimated Average Daily SE-:wer- Flow: 8,-fir✓o bedroom living units 2 17 personsldwelling unit: 611-A clpdpc (84 units)(2- 17 persons/clwE:)ling unit)(64.4 clpdpc)= 11,739 gpd (8.15 gpm) Qrric::r 13-h 2 � PE,a;king Factor =--- == ---P (P = Population in thousands) Qave 44P /2 18+(0.1823)L/2 Peaking Factor 4+1,0.99?,3)1/2 = 4.16 Assume(] Infiltration == 150 gallons/acrelday x '3.12.92 acres, = 469.4 gpd — NlaX. Flow, Qmax == (Oavg x Peaking Factor) + Infiltration _ (11,739 gpd x 4.16) + 469A gpd ;49 304 gpd (Q.�_)7E� �cf� The capacity of an 8--inch main, at minimum slope, is checked using Manning's Equation: Qruu (1.486/0.0'13)faR `20 - Mlanning"s n = 0.013 for PVC. Pipe M nirnurr•i Slope = O.G04 ft/ft A = (rr;r = (3.1416)(i).; ,,)2 0.3491 ft2 P = 2(,Tr)r = 2(3.1416i(G.33) = 2.0944 ft R = AIP = 0.3491/2.0944 = 0.1667 ft R2i3 0302.9 ft S = 0.004 ft/ft S1/2 ,= 0.06326 ft/ft Cruii _ (1 .4861'0.0'13)(0.349'I)(0.3029)(O.C)6:'';;1a) = 0.76 ,rfs 0ira),A)fuu = 0.0763 c,fs/O.'76 = 0.10 or 1 Ci% The estirnaik!d peak sanitary sewer flow rate ge!n(,ratE.d from this project ,arnounts to '10%0 of the capacity of the proposed 8" sanitary S(YXer main. The clown atrearn mains proposed within the Northwest Crossing Subclivi:si,on and the Norton East: Ranch oirtfcrll sewer were sized to accommodate, the proposed sanitary sev+,,er frorn this site. WATER.S Y'iIMM Water will be. provided to the Oak sand Cottonwood project by oxtension of two existing 8- inch water main lines currently stubbed into the property. The existing 8-inch stub fron') Flanders Way into Lot 5 will bE, extended to the Ekinch stub from Cotonwood Road to provide r looped system. ThE; Cl-inch main will be extended through the project within a proposed easernent within 1:!ie main drive aisle. All structures, will b(.+ served with both 2° domestic water service lines and 2 fire service Imes. Water s,arvice lines were sized wring the fixture e,ount method outlined in the Uniforrn Plumbing Code. The fixture count:totals and corresponding minimum pile size per U C Table 6"10.::; an(J -fable (310.4 for each 12-cnit Ir)uilding are attached in Appendix A: 1:2-pi ex = 264 fi):tUrE7s -- Meter & Street Service = 1.!5.-inc:h minimum Building Supply & Branch ,. 2-inch Maximum Allowable Service Length = 272 feet 2-inch Type K Copper water se.�rvice lines and metE:rs will be provide(~ to each building) for domestic: service. Supply Ind branch lines will also be 2-inch diam,,Aer after the meter. Pressure and flow data fron flow tests performed on nearby hydrant::. on Sherwood Lane were provided to us by the City of Bozeman Water Department. The adjoining fire hydrants WE-)re f,ourld to havE" ai static pressure of 86 psi under normal flow conditions .and a residual pressure of 132 psi while an adjacent (hydrant was flowing 1,300 gallons per minute out of the 2.5-inch orifice (30 psi pitot pressure). This information was used for the development of a pump curve to be used in our model at the connection point. The connection point was modcIled with ?he abowe-mentioned pump and a reservoir. The pump report showing the pump curve and associatedequations are included in Appendix A. VWxmi.]DI'',"I'RIBLTTION �i�'S'117EM SI EFING INPUT DATA Average D,.tily Residential Usage 170 gallons per capita per day Average Pc ipulation Density - 2.11 personsidWelling unit Minimum Fire Hydrant Flow = 1,500 gpm (hear Appendix III.-A of :he U.I=.C.) Residual Pressure Required 20 psi for Fire. Flcw Peakin 1_17actors: Average D;ay Demand (Peaking Factor _ 1) Maximum E)ay :Demand (Peaking Factor = 2.3) Maximum Hour Demand (Peaking Factor = '3.0) Demands: Average D,ay Demand 8.4du x 2.11 personsidu x 170gpcpd =30,131 gpd(20.92 gpm) Maximum IDay Demand == ";0,1'131 gpd x 2.3 = 69,301 gpd (48.13 clpm.) Peaty; Hour Demand -- 30,121 gpd x 3.0 = !a0,3!:a2 gpd (G2.1 rlpm) A model of the proposed system has been prepared using EPANET 2.0 software, to analyze the performance of the! system during average daily., m<axinnum daily and peak hour flows ,.ind to verify adequate pressure and flow for firefighting during max. daily flow:... In order to model the system, each junction nocle of the water distribution system was assessed a demand based on its service area. The table showi beloiv quantifies the demands placed at the junction nodes and -demands for Average Day, Maximum Day and Peaty; Hour. The peaking factor for each case is 1, 2.3 and 3.0 reapectively. DAl(d; &COTTONWOOD WA'rER SYSTE7111 JUNCTION # AVG. DAY 1161AX. DAY PEAK: HOUR NODE UNITS GPM GPM GPM 2 24 5.9783 13.750;2�- ---�-17.935 4 12 2.989:2 6.8751 8.9675 `- 5 12 2.989:2 6.8751 ___.--- 8.9675 --- 7 12 2.989;2 6.8751-------_-.- .Y- 8.9675------------ --- 8 24 5.9783 -_— 13.7502 _ 17.935 ---_ TOTAL. 84 20.92 48.13 62.71 DISTRIBITT ON MA➢:N The results of -the EPANET analysis, at average da61y, maximurn daily and peak Hour demand;, ,are: attached in Appendix A. The 1_)ro13es(:)d 8-inch DIP water main provides adequate, flow and pressure under all demand scenarios. The ability of the system to provide fire flows while meeting rninimum press-,ure requirements was checked by placing a 1,500-gprn demand at the fire hydrant location (n6) and check ng that all nodes maintain at least: the minimum 20 psi residual pres:_;ure under maxiiTrum daily demand. Residual pressures within the system under a 1,500 gpm fire flow were calculated to be within the range frorrc 7 psi to 81 psi. The results of the analysis with a fire flow placed at the hydrant location at max daily flaw are included in Appendix A. Also included aire analysis results at maximum daily clernand with 1 500 gpm fire flow demands placed near each of they 4 corners of the hrcject near existing hydrant locations. These resr.ilts show pressure and flow consistent'uAfith the results from the interior hydrant, further confirming that tine existing waiter system has adequate pressure arid flow to meet the m nimurn fire flow equirements. STORM V VAT ER MA NA,(3rLME MI' Attached in Appendix B are relevant sections of the Storm Water Design Report prepared for Flanders C;r(:,ek Subdivision. The project site is io,:,ated within Drainage Basin #3 and highlighted on the "Basin 3 Drainage Area Map". The original IDetE:Mtion Basin #3 calculations are also attached highlighting the post--development rUinoff coefficient assumecl for the site P=0.60, ror lots zoned R-A). Runoff from Lots 4 & 5 was assurned to discharge directly into the "Common Area" cletention ponds loc,_rted immediately to the north of the lots and into ad Jacent roadway, which also convey storm water to the "Common Area" ponds. The storm water runoff patterns for the Oak and Cottonwood Apartrnents project is proposed to be consistent with that assumed with the subdivision infrastructure design. The loulk: of the runoff from t_ot:_, .4 & 5 will run to two retention areas proposed on the north side of the property. These retention ponds will s,EM,Fe as an initial storage and settling basin. "Neillow structures and pipes will be provided to allow overfloW into the existing detention basins in the adjacern: "Common Area". Peripheral storm water runoff from Lots 4 and 5 will flow into the adjacent roadways and landscapf_! areas which will also convey water to the existing 1"Ammon Area" clete-ntion pond. Lots 4 & 5 ::ontain a gross area of 136,305 square feet. The prof-I-osed c:levelopment will include: Roof Area (C=0.85) -- 31,305 sq ft ConGrE:te/Asphalt Area (('>0.90) = 69,299 s,q ft L,_rnd's.caping (C=0.30) -= 35,701 sq ft The Cornpcis,ite C coefficient fat- :he proposed devEfloped area is: C = (CI.85(31,305) + 0.90(tHli,299) + 0.301(3.131701)) / 136,305) C = 0.73 The proposed site developnrient includes a slightly higher impervious area than that which was assumed with the original Flanders Creek Subdivision infrastructure design report (".' of 0.73 vs. C of 0.60). To avoid unplanned iIrip,act5 to the existing storm water infrastructueE; we are proposing to construct Mo re':ention arE'as to rE:tain the difference on-site. Attached in Appendix B is 4orrn Water De,_ign Calculations" spreadsheet comparing the 10-yE3ar storm water volumes for the assurned site runoff (,C:=C,.60) and the proposed site runoff (G=0.73). The ralc:jlations show that an on-site retention volume of 1,207 cubic feet is rerluired to limit the off-site flows to tine original projection. The proposed shallow storm water retention ponds will provide a volume of 1,; 02 cubic feet which is more than s.uffic:ierrt to make.! up for the addiition,al rcinoff from this project. The ponds are designecl with overflow structures so that when the ponris reach their capacity level the storm w;:IAer aril enter the overflow structure and be piped to the existing detention pond found to the north of the site. Calculations ,are: also provided in the Appendix B spreadsheet for each oar the 5 individw it drainage basin.s,. .Again, the c.alc;ulations show mat the combination of existing detention pond plus proposed retention basins provide sutflcient storm water capacity to ensure that the original design cap,:_rcities ,:are not exceeded. We will also check that the ponds ,are sized to cal tur:a the runoff generated from the fire 0.50 inches of rainfall from a 24--hiour storm. The site is located within Flanders Creel. Drainag(., Area #3 which was calculated with the original subdivision to contain a contributing ,area of 897,021) square feet with a c,ornp.7site runoff coefficient of 0.:524. A half inch of rain falling on Flanders Creek: Drainage Area #3 equates -to a total runoff volume of IS,,585 cubic feel. of water (897,020 x CI.!524 x 0.5'712 = 19,5135). The existing "Common )"-kr"E'.a° detention hondis provide a storable volume of 19,000 rabic feet and, the proposed on-site retention areas add 1,502 cubic feet to this volume for a total storage volume of 20,32.7 cubic feet. This total volume is more than adequalte to capture this first 0.5-inches of rainfall. STORMS WAVER CON%FEYs4h1C:E STRucTURE SIZING Storm water conveyance structures proposed with this project include sidewalk drainage chases and underground stor n sewer pipes. These structures are located within Drainage.' Areas #1, #2 and #3. Sl:orm waiver ronvayEance structures are sized to convey the minimum of a 25-year storm event in accordance: with Cite/ of Bozeman Design Requirements. Drainage Area #1 contains a total area of 32,187 square fey::4 (0.7389 acrE'.). For simplicity we will conservatively assume that all runof'from this drainage area enters the storm water conveyance structure::,. Time.-of +":cricentration Overla-id flow(35 ft (S) 2% on grass, C=0.3) =: 6.0 min(see Figure 1-1, Appendix B) Overt and flow(155 ft @ 1.6`'o on asphalt, C=0.9) = 4.0 minl,see Figure 1-1, App. B) TotaN Time of Concentr Rion = 10 minutess(0.167 hours) For a 25-year storm event 125 = 0.78X-.64 = 0.713(0.1(37)-64 == 2.46 in/hr Q25 ::. CIA = D.76(2.46 in/hr)(0.7389 acres) = 1 .38 c;fs Attached in Appendix B are results, from a channel flow calculator showing the proposed 1' wide ,sidewalk chase at :G% slope will flow at a depth of 3.4 inches; with a velocity cif 4.94 ft/sick during the peak flow from a 25-year storm event. Calculations for the 10-inch storm pipe conveying storm water fromi the sidewalk chase to the underground retention storacae are also includes in Appendix B. The pipe will carry the flow from a 25--year storm event at a dE1pth of 4.5c) inches and velocity of 5.66 ft/sec. Drainage Area #2 contains a total area of 31,234 square feat (0.7182 acre). For simplicity we will conservatively assume that all runoff from this drainage area enters, the storm welter conveyance structures. Time of Concentration Overland flow(45 ft 20,,0 on grass, C=0.3) _: 6.0 min(see Figur(: 1-1. Appendix B) Overland flow(100 ft L% on asphalt, C=0.9) = 4_0 imin(se�e Figi.re 1-1, App. 13) Total Time of Concentration = 10 minutes(0.167 hours) For a 25--year storrn event 1,,,5 = 01.78X`1 = 0.7i N.1(37)-64 = 2.46 in/hr Q25 == CIA = D.69(2.46 in/hr)(0.718.2 acres) = 1 .22 cfs Attached in Appendix B are results from a channel 11cw calculator showing the proposed 1' wide :Sidewalk chase at 2% slope will flow at a depth of 3.112 Inches v✓ith a velocity cf 4.76 ft/sec during the peak flow from a 25-year storm event. Calculations for the grass lined Swale conveying slorrn water from the sidewalk chase to retention pond #2 are also i ncluded in Appendix B. The swale w ll carry the flow from a 25-year storm event at a depth of .:3 inches and vr_!Iocity of 1.6 ft/s,e!c. Also attached in Appendix 13 are results from a Ma.nning's pipe calculator showing that the proposed 10-inch n_aention pond #2 overflow pipe will floMr, with no surcharging, at a depth of 5.32 inches with of velocity of 4.13 ft/sEelc: during the! peak flow from a 25-year storm event. Drainage Area #3 contains s total area of 45,01C1 square feet (1 .0.335 acre). For simplicity we will conservatively assurne that all runoff from this drainage area enters the storm w,eIter conveyance struci:ures. Time of Concentration Overland Flow(30 ft (a) 2% on grass, C=0.3) = Es.O min(see Figure 1-1, Appendix B) C,vertand flow(215 ft @D 2% on asphalt, C=0.9) = 5.0 min(s;.-e Figure 1-1, App. 13) Total Time of Concentration = 11 minut,es(0.183 hours) Fora 25 year storm event Iz5 = 0,r'$ 64 = 0.78(0.183)-64 = 2.31 in/hr Q25 = CIA = 1177(2.31 in/hr)(1.0,335 acres) = 1.84 cfs Attached in Appendix I3 are results from a Manning's pipe calci.lator showing that the proposed Drainage Area #3 storm sewer pipe will flow, with no surcharging, at a depth of 5.53 inches with of velocity ,af 4.:20 ft/sec during the peak flow from a 2115--year storm event. The proposed cn-site storm water facilities are to h-e maintained by the Oak & Cottonwood Apartments owners and their property management team. Attached in Appendix C is a copy of thE! "Storm Water Maintenance Plan" oAlining the owners maintenance responsibilities for the on-site retention ponds and conveyance structures. The existing off-site s'torrn water conveyancE., and detention facilitie's are to continue to be maintained by the Flanders Creek :)'ubdivision property owner's assoc ation. The owner's association maintenance responsibilities are spelled cut in the subdivision covenants and homeowners association dccuments. Appendix .A • EPANET Input ; 8: Hydraulic Analysis Results • City of Bozeman Wal::er Service Calculation Work,heets BOZ ; , ^ I'T Y OF BOZIMAN Ai Fire .Flow Request For;rn .� N — i * *i� PHONE(406)5$2-3200 FAX(906)5t32-32{)S 411 O Zi �'�"� -• 8�:"'`mil Ghuping Our ruturc Toged-vc 7t.te results of the fire flow information thatyou requested areas follows: Rosa :1.8 plex Twin I.ah:e,,;,. HD #:1737 Static-86PSI, Residual - 82PS'1 H U# :1731 Pitot- 60P:31 Flowing 1300 GPM on a 2.5° nozzle. Fire Flow test performed on 11/2/2021. r, 4870 0 483+) 4870 4830) -r- J W H`�b#1731 HD#173 L + iD11 Win 1090 1%�'S ,:, + S 08 If you have questions or need further infclrrnation feel free to email. Data Disclaimer: Water dis.rtb.ttiun information is calculated using hydr•auhc modeling software and is subject to variation.Actual field conditions may vary.This information provided to the requestor for evaluation purposes only, without warranty of any kind,including,but not limited to any expressed or implied warranty arising by contract, stature,or law.In no event regardless of cause,shall the City be liable for any direct,indirect,spec;:al,punitive or consequential damages of any kind whether such damages arise under contract,tort,strict liability or inequity. 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Commercial (2018 IBC) City/if Bozeman Water Service Calculation Worksheet Project Address: ak-1 [moor: ri Property Owner: _ _ 'at4_------- General Contractor: ------------------------------------------------------------------------------- Permit Number: _______________ Proposed Water Meter Size: __-____________ UPC Table 610.3 Standard Design Water Supply Fixture Units Appliances and Fixtures Fixture Units # of Fixtures Total Bathtub/Combination Tub/Shower 4.0 X Soaker Tub 10.0 X = -------- -------- Shower (per head) 2.0 X ________ _ -------- Clothes washer 4.0 X 1 = LI.O__ Dishwasher 1.5 X � _ L5___ Hose Bibb 2.5 X = -------- -------- Additional Hose Bibb (each) 1.0 X -------- _ _______- Drinking Fountain 0.5 X ________ _ -------- Service /Mop Basin 3.0 X ________ _ ___-__-- Lavatory Sink 1.0 X __a__-_ Kitchen Sink 1.5 X _J____ Laundry Sink 1.5 X = Water closet (1.6 GPF) 2.5 X -------- _ -------- Water closet (1.6 GPF - Flushometer tank) 2.5 X _a---- Water closet (flushometer valve) Table Values ________ _ -------- Urinal (flushometer valve) Table Values ________ _ -------- Total Number of Fixture Unit - F— Vet x �4� s Fixture Unit Tables for Determining Water Pipe & Meter Size Pressure Range - 46-60 PSI Circle the length in feet to the farthest fixture & applicable service, meter & branch sizes below based on the total number of fixture units detailed above. UPC Table 610.4 Maximum Allowable Length in feet Meter & Supply& 60' 80' 100, ISO, 200' Service Branches 20 19 17 14 11 39 36 33 28 23 1" 1" 39 39 36 30 25 1%" 39 39 39 39 39 1" 1%" 78 76 67 52 44 1'/2" 1%" 78 78 78 66 52 1" 134"/2" 85 85 85 85 85 1'/2" 1'/2" 151 151 151 128 105 2" 1'/2" 151 151 151 ISO 117 1'/2" 2" 370 340 318 2 240 318 If count is over 370 fixtures, water demand does not meet table 610.4 submitted by a registered Montana mechanical engineers design, signed and stamped. 04.29.20 Appendix B • Storm Water Design Calculations • Drainage Area Exhibit • Site Grading & Drainage Plan • Flanders Creek Subdivision — Drainage Area #3 Calculations Storm Water Design Calculations Project: Oak&Cottonwood Apartments Date: 8/6/2021 From City of Bozeman Design Standards: Q=CIA Rainfall Intensities(from figures 1-2&1-3) V=7200Q 110=0.4079 in/hr(10 yr,2 hr event) Q=runoff(cfs) 125=0.5005 in/hr(25 yr,2 hr event) C=Weighted C factor 150=0.5822 in/hr(50 yr,2 hr event) I=Rainfall Intesity(in/hr) 1100=0.6348 in/hr(100 yr,2 hr event) A=Area(acres) V=Volume(ft3) Composite Runoff Coefficient Calculation Area ft2 Area(acres) C factor Hardscape= 69,299 1.5909 0.90 Roof= 31,305 0,7187 0.85 Landscaping= 35,701 0.8196 0.30 Total Area= 136,305 3.1291 Weighted C= 0.73 *The original Flanders Creek Subdivision assumed a composite runoff coefficient of 0.60 Total On Site Retention Required(Post Development minus Pre Development) For a 10-year storm event: Pre Development Post Development Area= 136,305 ft2 Area= 136,305 ft2 Q10= 0.7658 cfs Q10= 0.9335 cfs Vrgd= 5,514 ft3 V,qd= 6,721 ft3 Total On Site Retention Required=6,721 ft3-5514 ft3= 4 this volume will be provided with 2 retention ponds handling runoff from Drainage Area#1 &#2 4 Total On-Site Retention Provided=1,502 cubic feet (this is>the 1,207 cubic feet required) Individual Drainage Area Checks: Drainage Area#1 -Composite Runoff Coefficient Calculation Area ft2 Area(acres) C factor Hardscape= 16,600 0.3811 0.90 Roof= 8,945 0.2053 0.85 Landscaping= 6,642 0.1525 0.30 Total Area= 32,187 0.7389 Weighted C= 0.76 4 Post Development Area= 32,187 ft2 Q10= 0.2298 cfs Vrqd= 1,654 ft3 4 Retention Provided=445 cubic feet 4 Overflow to Existing Pond=1,209 cubic feet Drainage Area#2-Composite Runoff Coefficient Calculation Area ft2 Area(acres) C factor Hardscape= 14,200 0.3260 0.90 Roof= 6,708 0.1540 0.85 Landscaping= 10,376 0.2382 0.30 Total Area= 31,284 0.7182 Weighted C= 0.69 4 Post Development Area= 31,284 ft2 Q10= 0.2022 cfs Vrqd= 1,456 ft3 4 Retention Provided=1,057 cubic feet 4 Overflow to Existing Pond=399 cubic feet Drainage Area#3-Composite Runoff Coefficient Calculation Area(ft2 Area(acres) C factor Hardscape= 28,960 0.6648 0.90 Roof= 6,708 0.1540 0.85 Landscaping= 9,351 0.2147 0.30 Total Area= 45,019 1.0335 Weighted C= 0.77 4 Post Development Area= 45,019 ft2 Q10= 0.3237 cfs V,qd= 2,331 ft3 Runoff to Existing Pond=2,331 cubic feet Drainage Area#4-Composite Runoff Coefficient Calculation Area ft2 Area(acres) C factor Hardscape= 2,594 0.0596 0.90 Roof= 4,472 0.1027 0.85 Landscaping= 4,722 0.1084 0.30 Total Area= 11,788 0,2706 Weighted C= 0.64 Post Development Area= 11,788 ft2 Q10= 0.0707 cfs Vrqd= 509 ft3 Runoff to Existing Pond=509 cubic feet Drainage Area#5-Composite Runoff Coefficient Calculation Area ft2 Area(acres) C factor Hardscape= 6,945 0.1594 0.90 Roof= 4,472 0.1027 0.85 Landscaping= 4,610 0.1058 0.30 Total Area= 16,027 0.3679 Weighted C= 0.71 4 Post Development Area= 16,027 ft2 Q-= 0.1071 cfs Vrqd= 771 ft3 Runoff to Existing Pond=771 cubic feet 4 Total Post Development Runoff= 6,721 ft' -) Total On Site Retention Provided= 1,502 ft3 4 Total Runoff to Existing Pond= 5,219 ft3 I ss U �ZV614t4lG= 90 1200 I I I I I I I I I I I ( I I I 140 I I 1 1 1 1 I I 1 I I y I I 1 1 I I y I I y A Iv I I 1000 I I ► I I I ' . I i t ! I I z, 1 I I ! i 1 1 I 120 I I II IWI / II I I 1 I log I I I I I I I I I I_o I I I I v I i I . I I ( l l i l to I I I h I I I I I I I I 1 i i I I I I I i I I I Ii I � I Boo ► I ► 1 1 1 1 I tI I A I I I I 1 I ! I I I l00 l l l f l l i I I 1 1 - 1 11 1 i 1 1 I z W I I I I I II I I I 1 1 I I I I I f l � I I I I t l l I I I II I Q z I i l l I I I I I I I I I W 60O I I I I I I I I 60 z U LU I I I I I I z N_ I ► I I V Y V/ Y V JV1 I II I I I o a I I I II A 4 Al I i VI f 1 16 I I I o I I I I I I I I I I aoo 60I I I Yl I I o z II I I a I I I I I I W w 200 I ! I I I I a0 0 I I I I -}o I 11 1 1 I I ! a I I I I I I I I I I 20 I I ►c I I I I I I I I L9 M,ti i I l l l l l i l l l I I y""''• 0 FIGURFC;-I TIME OF CQNC�NTRATIQN (Rational Formula' YY Drainage Area #1 Sidewalk Chase Channel Design - lft wide channel flowing 1 . 3E Channel Type: Rectangular Dimensions : Base Dimension: 1 . 00 Wetted Perimeter: 1 . 56 Area of Wetted Cross Section: 0 .28 Channel Slope: 2 . 0000 Manning' s n of Channel : 0 . 0135 Discharge: 1 . 38 cfs Depth of Flow: 0 .28 feet Velocity: 4 . 94 fps Channel Lining: Smooth Concrete Pam= 1 cif Channel Report Drainage Area #1 Swale Trapezoidal Results Bottom Width (ft) =2.000 Flow Depth(ft) =0.269 Left Side Slope(Z:1) =4.000 Q(cfs) = 1.384 Right Side Slope(Z:1) =4.000 Area(sq ft) =0.827 Channel Depth(ft) =0.500 Wetted Perim (ft) =4.218 Slope (%) = 1.000 Hydraulic Radius(ft) =0.196 Manning's n =0.030 Velocity(ft/s) = 1.673 Critical Depth(ft) =0.212 Top Width(ft) =4.151 EGL(ft) = 0.312 2.00 i 1.00 77 a a> 0.00 -1.00 4.00 -3.00 -2.00 -1.00 0.00 1.00 2.00 3.00 4.00 Reach(ft) Drainage Area #1 - 10" Pipe @ 1% Slope Flow Rate (CFS) : 1 . 38 Pipe Diameter (in) : 10 . 00 Manning' s n: 0 . 013 Length (ft) : 24 . 00 Slope (ft/ft) : 0 . 0100 Travel Time(min) : 0 . 09 Flow Depth (in) : 5 . 75 Velocity(fps) : 4 .26 PACTA 1 of 1 -N/ %ll AffvL*A L*, & 211/. ot�- rs, (c 1ao' Z'", or- a�.s�4- c= 0,-TO zoo I I I I I I I ( I I I I I I I I 140 7-1 1 1 1 1 1 1 0 I I I7 I 1 I i R l I l l l l uI I y I I 1000 I I I I I I I `! all 1 i t I I I I Z I I ! I l f l 120 i I I I 1will 11 1 1 I All i o1 w Boo i i i i i i i t I 100 z i i I I I I I if I I I 1 1 z I ly I IY I I I I I I I ►� I I I I I I I I I ! I I I I I I I a z ( I i t I I I 1 1 1 1 1 1 6Go I I I I I I I I I I I I 80 W I I 11 I I I I I I I z IIIII I y I I I I i I U i t l i � I I I Ic► I I I I o W 400 I I { I I I I I I 1 60 ! I Iy y v vI I I I X t;- I 1 1 I Al A A V I I ' o z I l iv v I A 1 i I J ui 200 1 1Al VI IV I I I I 40 0 -�oI 1 4 I I i I i 0 I - 20 VMS FIGURE I-I TIME OF CONCENTRATION (Rational Formula) 3n Drainage Area #2 Sidewalk Chase Channel Design Channel Type: Rectangular Dimensions: Base Dimension: 1.00 Wetted Perimeter: 1.51 Area of Wetted Cross Section: 0.26 Channel Slope: 2.0000 Manning' s n of Channel: 0.0135 Discharge: 1.22 cfs Depth of Flow: 0.26 feet Velocity: 4.76 fps Channel Lining: Smooth Concrete Freeboard: 0.30 feet Channel Report Drainage Area #2 Swale Trapezoidal Results Bottom Width (ft) =2.000 Flow Depth (ft) =0.252 Left Side Slope(Z:1) =4.000 Q (cfs) = 1.220 Right Side Slope(Z 1) =4.000 Area(sq ft) =0.757 Channel Depth(ft) =0.500 Wetted Perim (ft) =4.076 Slope(%) = 1.000 Hydraulic Radius(ft) =0.186 Manning's n =0.030 Velocity(ft/s) = 1.611 Critical Depth (ft) =0.196 Top Width (ft) =4.014 EGL(ft) =0.292 2.00 i 1.00 s a a� i 0.00 I� -1.00 -4.00 -3.00 -2.00 -1.00 0.00 1.00 2.00 3.00 4.00 Reach(ft) Drainage Area #2 - 10" Pipe @ 1% slope Flow Rate (CFS) : 1 .22 Pipe Diameter (in) : 10 . 00 Manning' s n: 0 . 013 Length (ft) : 8 . 00 Slope (f-t/ft) : 0 . 0100 Travel Time (min) : 0 . 03 Flow Depth (in) : 5. 32 Velocity (fps) : 4 . 13 )1 � -*-s A(,?k :Jot i on. 8✓ s (C= 0.30) i o JN C=0.10 i2oo I I I I I I I I I I I I I i I 140 I I I I I I I Il I T I I I yI I l l l l l l y i I 11 I I Iv I I ( l l 1000 I ° I vi t ! I I I a I ° 1 ! I I I I I I 120 f 1 I I I I W I I I I I I I I °\ 11 I 1 I I 1 to I1 I I A X V I I I I I I i ' w I I I I I I I I I I � I + �� Z 8O0 p , I I I I I I I 1 ! 1 1 1 1 1 1 1 1 1 1 -I _---.;---- I_ .i _ LL 1 I I I I I I I I I I I I I I I a l l f I I I I 600 I I I I I I I I 80 w I I I I I Ali A I I I v I z N I I I 1 1 I I I 1 1 I I I ° i t I i I I I I IG 400 1 1 I I I I I IIII I II I X LXI o z l i t 1 I I t 1 � J f ' u.! w 20o I I I I I 40 0 I IK X I adaf 1 1 ! I I I I I ! I ( I I I 0 I I i I I I I ! I ( 20 I - I I Icy 0 FIGURE 1-1 TIME OF CONCENTRATION (Rational Formula) YY Drainage Area #3 - 10" Pipe @1% slope Flow Rate (CFS) : 1 . 84 Pipe Diameter (in) : 10 . 00 Manning' s n: 0 . 013 Length (ft) : 23 . 60 Slope (ft/ft) : 0 . 0100 Travel Time (min) : 0 . 09 Flow Depth (in) : 7 . 00 Velocity(fps) : 4 . 51 PAf7A 1 Af -- o -- — r _ -_-----------------------'-__ peon poomuopoo - --- - -- -_. ---------- !I; I it i i I I I,i II. 7[G�9 ;�pOQ �.t igoni fi... e 1 I 8t i =t _'i� Q I ' P��• - --g E- I/ 11 '5 w i o -"I anuany�aaJO scar TTV 4 Fla' W =1 3 m B. r 8 ... �� Nt LL 0 -7 Lu CD ix rr — - 'anuany -sa)je-j Ulm _. -- - - - - --- - w w O eO z w U Lu N z 0 -71 DESIGN REPORT STORM WATER MANAGEMENT FLANDERS CREEK SUBDIVISION Prepared for: DENNIS BALIAN Prepared by: C & H Engineering and Surveying, Inc. 205 Edelweiss Bozeman, MT 59718 (406) 587-1115 Project Number: 05189 Nc,s 6 June, 2005 N AL- STORM WATER MANAGEMENT Summary STORM WATER run-off from Flanders Creek Subdivision will be directed to several storm water detention areas located through out the site. Sheet D1, enclosed in the Appendix, highlights the individual drainage areas that drain to each storm water pond. The subdivision was divided into three separate watersheds, that will be directed to their own detention pond. Drainage area#1 will drain to a point at the southern boundary of the central park,near the intersection of Parkview Avenue and Glenwood Drive. Drainage area#2 will drain to a pond on the norther boundary of the central park,near the intersection of Annie Street and Parkview Avenue. Drainage area #3 will drain to two detention ponds located at the north property line, by the intersection of Cottonwood Road and Oak Street. All proposed ponds will have an outlet pipe to Baxter Ditch to ensure that the ponds drain during storm water events. Inlets will be placed to intercept the storm water runoff at intervals to ensure that the curb capacity is not exceeded, and to rout the storm water to the desired storm water detention area. The storm water runoff rate was calculated with the rational formula as shown. A runoff coefficient(C) of 0.35 was used for the lots Zoned R3, and 0.60 was used for the larger R4 and R-O lots as recommended by the City of Bozeman Design Standards, and a composite C value was used for the right of way due to the higher percentage of impervious area. COMPOSITE RUNOFF COEFFICIENT The runoff coefficient for the R/W Area at 60 ft. wide: C,I,= [(0.90x43 ft)+(0.20xl7 ft)]/60 ft =0.70 iV i 1 DRAINAGE AREA#3 Drainage Area#3 consists of a total of 897,020 ft',with 253,215 ft2 of that being right of way, 52,431 ft'of ponds/openspace, 291,290 ft'of medium density lots and 300,084 ft' of high density lots. Drainage area#3 will be divided into five subareas, one for each catch basin that will be utilized. The time of concentration for each sub-area needs to be calculated to determine the intensity of storm that will contribute to the catch basin. The time of concentration for sub-area#3-1 is calculated below: Time of Concentration Overland flow(140 ft @ 1.0%, C=0.50) = 15.8 min. Gutter flow(580 ft @ 1.10% avg. slope on Cottonwood Road) V=(1.486/n)R113SV2 (n=0.013, A=1.24 ft,P=9.23,R''=0.2623, S'12=0.1049) V=3.14 ft/s T= 580 ft/3.14 ft/s/60s/min =3.1 min Gutter flow(260 ft @ 0.60%avg. slope on Sherwood Way) V=(1.486/n)R2�3S12 (n=0.013, A=1.24 ft,P=9.23,W'3=0.2623, S"2=0.0775) V=2.32 ft/s T=260 ft/2.32 ft/s/60s/min = 1.9 min Total Time of Concentration =20.8 minutes(0.35 hours) For a 25-year storm event I25 =0.78X--"=0.78(0.35)-.64 = 1.53 in/hr Q25 Medium Density Lots=CIA=0.35(1.53 in/hr)(3.4023 acres)= 1.82 cfs Q25 r/w=CIA=0.70(1.53 in/hr)(1.6478 acres) = 1.76 cfs Q25 Total=(1.82+1.76)=3.58 cfs=Total flow rate entering catch basin#6 The time of concentration for sub-area#3-2 is calculated below: Time of Concentration Overland flow(135 ft @ 1.0%, C=0.35) = 15.5 min. Gutter flow(585 ft @ 0.85%avg. slope on Parkview Avenue) V=(1.486/n)W5S''2 (n=0.013,A=1.24 ft, P=9.23, R"'=0.2623, S`n=0.0922) V=2.76 ft/s T=585 ft/2.76 ft/s/60s/min =3.5 min Gutter flow(245 ft @ 0.60% avg. slope on Sherwood Way) V=(1.486/n)R2"S'7 (n=0.013, A=1.24 ft, P=9.23,R2"3=0.2623, S'n=0.0775) V=2.32 ft/s T=245 ft/2.32 ft/s/60s/min = 1.8 min Total Time of Concentration =20.8 minutes (0.35 hours) For a 25-year storm event I25=0.78X--'=0.78(0.35)--64= 1.53 in/hr Q25 Medium Density Lots=CIA=0.35(1.53 in/hr)(3.2849 acres)= 1.76 cfs Q25 r/w =CIA=0.70(1.53 in/hr)(1.2770 acres)= 1.37 cfs Q25 Total=(1.76+1.37) =3.13 cfs=Total flow rate entering catch basin#7 The time of concentration for sub-area#3-3 is calculated below: Time of Concentration Overland Flow(140 ft @ 1.0%, C=0.60) =9.7 min. Gutter Flow (143.5 ft @ 0.75% avg. slope on Twin Lakes Drive) V= (1.486/n)R23S'n (n=0.013, A=1.24 ft, P=9.23, Rsi3=0.2623, 512=0.08660) V=2.60 ft/s T= 143.5 ft/2.60 ft/s/60 s/min =0.92 min. Total Time of Concentration = 10.62 minutes(0.177 hours) For a 25-year storm event 125=0.78XC-64=0.78(0.177)--14=2.36 in/hr Q25 High Density Lots=CIA=0.60(2.36 in/hr)(0.8744 acres)= 1.24 cfs Q25 r/w=CIA=0.70(2.36 in/hr)(0.20 acres)=0.33 cfs Q25 Total =(1.24+0.33) = 1.57 cfs=Total flow rate entering catch basin#8 Time of Concentration Overland Flow(140 ft @ 1.0%, C=0.60) =9.7 min. Gutter Flow(218.42 ft @ 0.75% avg. slope on Twin Lakes Drive) V=(1.486/n)R213SIl (n=0.013,A=1.24 ft, P=9.23, R2'3=0.2623, S"2=0.08660) V=2.60 ft/s T=218.42 ft/2.60 ft/s/60 s/min = 1.40 min. Total Time of Concentration = 11.1 minutes (0.185 hours) For a 25-year storm event I25=0.78XC-'=0.78(0.185)--4=2.30 in/hr Q25 High Density Lots =CIA=0.60(2.30 in/hr)(1.1937 acres) = 1.65 cfs Q25 r/w=CIA=0.70(2.30 in/hr)(0.30 acres) =0.48 cfs Q25 Total=(1.65 +0.48)=2.13 cfs=Total flow rate entering catch basin #9 The capacity of the curb and gutter, at a 0.75% slope, with a depth of water 0.15'below the top of curb is calculated as follows: Q=(1.486/n)ARZ`Sv2 n=0.013 for Concrete A= 1.24 ft2 P=9.23 ft R=A/P = 1.24/9.23 =0.1343 ft R"3 =0.2623 ft S =0.0075 ft/ft S'n=0.08660 ft/ft Q = (1.486/0.013)(1.24)(0.2623)(0.08660)=3.21 cfs. 1.57 cfs s 2.13 cfs s 3.21 cfs - Gutter capacity is adequate Q25 Total for Storm Sewer#3 =(3.58+3.13+1.57+2.13) =10.41 cfs The time of concentration for sub-area#34 is calculated below: Time of Concentration Overland flow(140 ft @ 1.0%, C=0.60) =9.7 min. Gutter flow(340 ft @ 0.75% avg. slope on Twin Lakes Drive) V=(1.486/n)R2/3S"2 (n=0.013, A=1.24 ft, P=9.23, R2�3=0.2623, 512=0.08660) V=2.60 ft/s T=340 ft/3.67 ft/s/60s/min =2.2 min Gutter flow(260 ft @ 0.87% avg. slope on A Street) V=(1.486/n)R2/3S"2 (n=0.013, A=1.24 ft, P=9.23, R2"=0.2623, S"2=0.0933) V=2.78 ft/s T=260 ft/2.78 ft/s/60s/min = 1.6 min Gutter flow(350 ft @ 1.5% avg. slope on Parkview Avenue) V=(1.486/n)R2/3S'n (n=0.013, A=1.24 ft,P=9.23,R?'=0.2623, S"2=0.1225) V=3.67 ft/s T=350 ft/3.28 ft/s/60s/min = 1.6 min Total Time of Concentration = 15.1 minutes (0.25 hours) For a 25-year storm event 125=0.78X'-64=0.78(0.25)--64= 1.89 in/hr Q25 High Density Lots=CIA=0.60(1.89 in/hr)(2.008 acres) =2.28 cfs Q25 r/w= CIA=0.70(1.89 in/hr)(1.5327 acres)=2.03 cfs Q25 Total =(2.28+2.03)=4.31 cfs=Flow rate entering catch basin#10 Time of Concentration(Oak Street) Gutter flow(600 ft @ 0.5% avg. slope on Oak Street) V=(1.486/n)R2"3S'"2 (n=0.013, A=1.24 ft, P=9.23, R2�3=0.2623, S'"2=0.07071) V=2.63 ft/s T= 600 ft/2.63 ft/s/60s/min =4.72 min Total Time of Concentration =4.72 minutes(0.079 hours) For a 25-year storm event 125 =0.78X'-64=0.78(0.079)-.64=3.95 in/hr Q25 r/w=CIA= 0.70(3.95 in/hr)(0.8276 acres) =2.29 cfs Q25 Total =2.29 cfs=Flow rate entering catch basin#10 Q25 Total for Storm Sewer#4 =4.31 cfs+2.29 cfs=6.6 cfs The capacity of the curb and gutter, at a 1.5% slope for Parkview Avenue,with a depth of water 0.15'below the top of curb is calculated as follows: Q=(1.486/n)AR"S'"2 n=0.013 for Concrete A= 1.24 ft2 P = 9.23 ft R=A/P = 1.24/9.23 =0.1343 ft Rv3 =0.2623 ft S =0.015 ft/ft S 12=0.1225 ft/ft Q=(1.486/0.013)(1.24)(0.2623)(0.1225)=4.55 cfs. 4.31 cfs _< 4.55 cfs - Gutter capacity on Parkview Avenue is adequate The capacity of the curb and gutter, at a 0.5% slope for Oak Street, with a depth of water 0.15' below the top of curb is calculated as follows: Q=(1.486/n)AR"'S'n n=0.013 for Concrete A= 1.24 ft' P = 9.23 ft R=A/P= 1.24/9.23 =0.1343 ft R2/3=0.2623 ft S =0.015 ft/ft S"2=0.07071 ft/ft Q=(1.486/0.013)(1.24)(0.2623)(0.0707 1)=2.63 cfs. , 2.29 cfs <_ 2.63 cfs — Gutter capacity on Oak Street is adequate The time of concentration for sub-area#3-5 is calculated below: Time of Concentration Gutter flow(615 ft @ 1.1% avg. slope on Cottonwood Road) V=(1.486/n)R2/3S12 (n=0.013, A=1.24 ft, P=9.23, R2/3=0.2623, S"2=0.1049) V= 3.14 ft/s T= 615 ft/3.14 ft/s/60s/min = 3.3 min Total Time of Concentration =3.3 minutes (0.06 hours) For a 25-year storm event 125 =0.78X-.64=0.78(0.06)--' =4.721 in/hr Q25 r/w=CIA= 0.70(4.721 in/hr)(0.9936 acres) = 3.28 cfs Q25 Total for Storm Sewer#5 =3.28 cfs=Flow rate entering catch basin#11 The capacity of the curb and gutter, at a 1.1% average slope for Cottonwood Road, with a depth of water 0.15'below the top of curb is calculated as follows: Q=(1.486/n)AR2/3S112 n=0.013 for Concrete A= 1.24 ft' P=9.23 ft R=A/P= 1.24/9.23 =0.1343 ft R2/3 =0.2623 ft S =0.011 ft/ft Drainage Area#3 15" PVC from Catch Basin #6 to Storm MH #1 This pipe carries the storm water from drainage sub-area 3-1. As previously calculated we should anticipate a flowrate of 3.58 cfs from a 25-year storm event. Calculations are enclosed in the Appendix for a 15" PVC pipe at 0.50% slope. The 15-inch pipe will flow at a depth of 0.83 feet with a velocity of 4.12 ft/sec. 15" PVC from Catch Basin#7 to Storm MH#1 This pipe carries the storm water from drainage sub-area 3-2. As previously calculated we should anticipate a flowrate of 3.13 cfs from a 25-year storm event. Calculations are enclosed in the Appendix for a 15" PVC pipe at 0.50% slope. The 15-inch pipe will flow at a depth of 0.76 feet with a velocity of 4.01 ft/sec. 18" PVC from Storm MH#1 to Catch Basin #8 to Storm MH#2 to Catch Basin #9 These pipes carry the storm water from drainage sub-areas 3-1 &3-2 &part of 3-3. As previously calculated we should anticipate a flowrate of(3.58 + 3.13 + 1.57)=8.28 cfs from a 25-year storm event. Calculations are enclosed in the Appendix for a 18" PVC pipe at 0.60% slope. The 18-inch pipe will flow at a depth of 1.26 feet with a velocity of 5.24 ft/sec. 24" PVC from Catch Basin #9 to Detention Pond #3 This pipe carries the storm water from drainage sub-areas 3-1 &3-2 & 3-3. As previously calculated we should anticipate a flowrate of(3.58 +3.13 + 1.57+2.13)= 10.41 cfs from a 25- year storm event. Calculations are enclosed in the Appendix for a 24" PVC pipe at 0.50%slope. The 24-inch pipe will flow at a depth of 1.18 feet with a velocity of 5.42 ft/sec. 15" PVC from Catch Basin #10 to Detention Pond#3 This pipe carries the storm water from drainage sub-area 3-4. As previously calculated we should anticipate a flowrate of 6.60 cfs from a 25-year storm event. Calculations are enclosed in the Appendix for a 15" PVC pipe at 1.0% slope. The 15-inch pipe will flow at a depth of 1.05 feet with a velocity of 5.99 ft/sec. 15" PVC from Catch Basin #11 to Detention Pond#3 This pipe carries the storm water from drainage sub-area 3-5. As previously calculated we should anticipate a flowrate of 3.28 cfs from a 25-year storm event. Calculations are enclosed in the Appendix for a 15" PVC pipe at 0.50% slope. The 15-inch pipe will flow at a depth of 0.78 feet with a velocity of 4.05 ft/sec. Detention Pond#3 The total area served by Detention Pond#2 is 20.593 acres with a weighted C-factor of 0.524 after development. The storage basin can have a release rate equal to the pre-development flow. The calculations for the pre-development time of concentration and flows are included in the Appendix. The pre-development flow (acceptable release rate) is 2.71 cfs. Calculations are also enclosed in the Appendix for sizing the detention pond by varying the storm duration and holding the release rate at 2.71 cfs. The required storage for Detention Pond#3 is 15,175 cubic feet. The weir must also be sized to insure the discharge never exceeds the allowable release rate. The weir in the discharge structure for Detention Pond#3 will be 9.77 inches in width. These calculations are included with the calculations for sizing the pond. DRAINAGE CALCULATIONS Watershed#3 Pre-Developed Conditions Flow Length = 1285.00 Slope (%) = 1.16 C coeficient= 0.20 Cf = 1.00 Tc = (1.87'(1.1-C'Cf)(L)(112))/(s)(11) Tc(min)= 57.41821 Storm Return Interval = 10 I (in/hr)for 10 year storm 1=0.64t(-0.65) 0.658561 RATIONAL METHOD FOR CALCULATING FLOW RATE Rational Method = Q =C'I'A C coeficient= 0.20 Cf = 1.00 I (in/hr)= 0.66 Area (ft) = 897020.00 =Area (AC)= 20.5927 Total Runoff For 10yr Storm (W/s)= 2.712305 Detention Pond #3 Flanders Creek Subdivision Park C = 0.20 R3 Zone C = 0.35 R-O Zone C = 0.60 Right of Way C= 0.70 Area (Ft2)= 52431.00 Area (Ft2) = 291290.00 Area(Ft2)= 300084.00 Area (Ft2) = 253215.00 Area (ac)= 1.20 Area (ac) = 6.69 Area(ac) = 6.89 Area (ac) = 5.81 Total Area (ac) = 20.59 Weighted C = 0.524 Release Rate(cfs)= 2.712 Tc Method 10 Year Storm Total Total Runoff Release Required Storm Intensity Q Volume Volume Storage length(min) (In/Hr) (ft3/s) (ft) (ft) (ft) 15 1.58 16.994 15294.25 2441.07 12853.17 20 1.31 14.095 16914.40 3254.77 13659.64 25 1.13 12.192 18288.38 4068.46 14219.92 �i 30 1.00 10.830 19493.45 4882.15 14611.30 35 0.91 9.797 20574.06 5695.84 14878.22 40 0.83 8.983 21558.43 6509.53 15048.90 II 45 0.77 8.321 22465.73 7323.22 15142.51 50 0.72 7.770 23309.65 8136.91 15172.73 55 0.68 7.303 24100.34 8950.61 15149.73 II 60 0.64 6.902 24845.58 9764.30 15081.28 65 0.61 6.552 25551.47 10577.99 14973.48 70 0.58 6.244 26222.89 11391.68 14831.21 90 0.49 5.303 28633.94 14646.45 13987.49 120 0.41 4.398 31667.20 19528.60 12138.60 OUTLET CONTROL STRUCTURE SIZING Allowable Flow Rate Q(cfs) = 2.712 'Head above Weir Notch (ft) = 1.00 Weir Coefficient= 3.33 Length of Weir (ft)= 1.00 Weir Equation = Q =(C)*(L)*(H)(3i2) Required Length (ft)= 0.814506 Required Length (in)= 9.7741 DRAINAGE CALCULATIONS Watershed#3-1 Flow Length = 146.00 Slope(%) = 1.00 C coeficient= 0.35 Cf = 1.10 Tc=(1.87*(1.1-C"Cf)(L)1"2))/(s)("3) Tc(min)= 15.82 Storm Return Interval = 25 (in/hr)for 25 year storm 1=0.78t(-o.sa� 1.830695 DRAINAGE CALCULATIONS Watershed #3-2 Flow Length = 135.00 Slope(%)= 1.00 C coeficient= 0:35 Cf = 1.10 To= (1.87`(1.1-C"Cf)(L)("'))/(s)("3) To(min)= 15.54 Storm Return Interval = 25 1 (in/hr)for 25 year storm 1=0.78t("0,64) 1.852124 DRAINAGE CALCULATIONS Watershed#3-3 Flow Length = 140.00 Slope(%)= 1.00 C coeficient= 0.60 Cf = 1.10 Tc = (1.87*(1.1-C*Cf)(L)w2>)/(s)(1/3) Tc(min)= 9.74 Storm Return Interval = 25 1 (in/hr)for 25 year storm 1=0.78t("0.64) 2.497825 DRAINAGE CALCULATIONS Watershed#34 Flow Length = 140.60 Slope(%) = 1.00 C coeficient= 0.60 Cf = 1.10 Tc=(1.87*(1.1-C*Cf)(L)('JZ))/(s)t'13) Tc(min)= 9.74 Storm Return Interval = 25 I (in/hr)for 25 year storm 1=0.78t(-1s4) 2.497825 s N s i s Z —--W*vt-Oak St so i l7 to � I N w W '0 A Street C RO W ,D . ....._. RO RO RO RO I � _____ _____ �T o oc 3wffi�'•SYSor�4n 00 �� g DRAINAG AREA 2 I wJon Street 3 I 1 I C nwood Drive N a GE I, I O o IIn 1-7 4 !p Duraton Road. N N O O O 9MMAWAM MAS TSRS' PLAN �IHCffiS cGw 0 ROSA "DWOON GRADING/DRANAGE RM ` •��"° CL i s BOZEMAN, MONTANA Appendix C • Storm Water Maintenance Plan STORM WATER MAINTENANCE PLAN Lots 4 & 5, Block 5, Flanders Creek Subdivision Oak & Cottonwood Apartments City of Bozeman, Montana THE FOLLOWING PROPERTY OWNER'S RESPONSIBILITIES FOR ROUTINE INSPECTION AND MAINTENANCE ARE TO BE PERFORMED BY THE LANDOWNER (L&S PROPERTIES) OR THEIR DESIGNATED AGENT. SHOULD THE PROPERTY CHANGE OWNERSHIP THESE RESPONSIBILITIES SHALL PASS TO THE NEW PROPERTY OWNER(S). 1. Routine Maintenance Activities (1-3 month interval) • Designate no cut zones in the bottom of basins • Remove trash, leaves, grass clippings and debris from inlets, swales & ponds • Remove any obstruction to flow • Establish a chemical free zone in and around the basins • Inspect for uniform ponding, and that water disappears within three days of rain events • Inspect inlets, piping, swales & outlet structures for sediment buildup and/or evidence of erosion • Check for eroded or channelized areas. Repair immediately, find the cause and take action to prevent further erosion. • Inspect structures and pond area for oil sheens • Inspect ponds and swales for undesirable vegetation or noxious weeds 2. Annual Maintenance Activities (Annually) • Cut vegetation to 6" and remove clippings • Re-establish vegetation on eroded and barren areas • Remove excess sediment build-up in inlets, piping, swales, ponds and outlet structures. • Update maintenance plan and inspection log • Repair/Replace eroded or damaged rip rap aprons • Clear and remove accumulated winter sand in parking lots and structures 3. Long Term Maintenance Activities (5-10 year interval) • Consult a qualified professional to inspect and return storm water basin back to initial design found on the subdivision and/or site plan engineering plans. • Dredge basin if sediment buildup is greater than 6" • Re-establish vegetation • Repair or replace damaged storm water structures and/or piping • Repair/Replace eroded or damaged rip rap aprons • Re-grade swales to ensure proper drainage. \20006\Storm Water Maintenance PIan.Doc