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HomeMy WebLinkAbout16 - Design Report - South 19th Widening - Stormwater STORMWATER DESIGN REPORT FOR: SOUTH 19TH AVENUE WIDENING BOZEMAN, MT Prepared By: MADISON ENGINEERING Madison Engineering 895 Technology Blvd Ste 203 Bozeman, MT 59718 (406) 586-0262 MAY 2016 = = r ��, LLI L: 01, v Gutter & Inlet Capacity Calculations S. 19th Ave Gutter Capacity Calculations 04.25.16 Allowable Pavement Encroachment Given: T= 9 feet(max per city) T W= 1.5 feet w Ts Ts= 7.5 feet SW= 0.06 ft/ft Sx= 0.03 ft/ft Q• a= 0.96 inches d = 3.24 inches d n = 0.015 So= 0.013 S. 19th Ave ° S. Sw/Sx= 2.00 T/W= 6 Capacity for Gutter equations: Q=QW +Qs Where: Qs= Discharge within the Roadway Qw _E°Q above the depressed section (cfs) QS Qw= Discharge within the depressed _ Q 1—E (gutter) section (cfs) Cf= 0.56 for English units Cr 5 g ' Sx= Pavement cross slope (ft/ft) QS = SX3TSJSQ2 n Ts= Width of flow in the roadway above depressed section So= Gutter longitudinal slope(ft/ft) S"'/S Sw= Gutter depression cross slope (ft/ft) E° = 1+ " 8/3 T= Spread (ft/ft) SN,/Sa W= Width of utter depression ft/ft 1+— — —1 9 P (ft/ft) �T/W�-1 Capacity solution S. 19th Ave So= 0.015 Qs= 2.85 cfs Eo= 0.42 cfs Q= 4.93 cfs Design Flow Q10= 1.98 cfs Q25= 3.48 cfs Design Flow< Capacity OK Q100= 5.14 cfs Summary The gutter capacity is well above the calculated peak flows. Therefore, the pavement encroachment will be less than the allowable(9-feet) by the City of Bozeman. Page 1 of 1 S. 19th Ave Inlet Capacity Calculations 04.25.16 Gutter Section Given: T= 9.0 feet T W= 1.50 feet w T5 Ts= 7.50 feet Sw= 0.06 ft/ft Sx= 0.03 ft/ft Q. a= 0.96 inches a. S. d= 3.24 inches d n = 0.015 Manning's n for curb&gutter So= 0.013 S. 19th Ave Curb Inlet s. From Gutter Capacity Inlet#1 Qw= 2.07 cfs Qs= 2.85 cfs Capacity for Inlet-S. 19th Ave Based on Neenah inlet R-3067-L Weir Equation Q=3.3P(hj s Where: P= perimeter(ft) h= Head (ft) P: 5.90 feet h: 0.35 feet(max per city) Qwier= 4.03 cfs Design Q for inlet#1 2+06.40, RT Q10= 1.98 cfs Q25= 3.48 cfs Q100= 5.14 cfs Inlet Design Ok Page 1 of 1 Storm Drain Calculations S. 19th Ave Roadway Improvements Peak Q Values Storm Information Design Rainfall Freq. 25 OF coefficient a 0.78 OF coefficient b 0.00 OF coefficient n 0.64 Adjustment Factor Cf: 1.1 Peak Q Values for Roadway Q Total Area: 1.148 acres C: 0.90 Average slope: 1.55 Percent Travel Distance 1183.00 feet Total tc: 6.11 minutes intensity at tc 3.36 in/hr peak runoff: 3.48 cfs Q10 = 1.98 cfs Q25 = 3.48 cfs Q100 = 5.14 cfs Page 1 of 1 T N O r M f0 O r M LO 00 O N M h h N CD a $ O O O O C) r r r r N N N N N N N N N N N N N N N N N N d O C II co Y y 0 0 O O M CD O r (D h O O r N N N N N r h (a > d a 00 T O O h W r V O h �-- r O LO O N V h •- O M d m Cl) Oof4CD1- mm V' OI- mCri °� °Dco a L O N IT 10 OD M O ((D � LO 0000 O M O M 0O0 N 0000 m r CN7 M L 0 O N V' O LO 00 r- Mo M � LO M O 0) t- (O NT N 0) (O O O O Cn ❑ (� ,0 r r (V CO V V LO (O h 00 M O O E _ L E LO co In O 00 O O h M O M V CO � O M h L O CO M M O O O O M m O h 0 (O O co CN V N O OOi N � 00 O CO 0) 0 N m � .h- m NNNN N N N V L0000 r V O O r N �' CO O N O O M h r O OD N LO h 0 OLD O 66 66 O O N N M M Q N O L N O O N V h r CO N N LO M N r r N of M -T N O 0 h O O O O O r N " M lO CO h CO O O N h V 0 O O O O CoO O O O O C. 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M 02 11 O� 0) z L) c E 0 (1) 4 a) 0 E E 0. 0 < B B if ry f MEMO DATE: May 23, 2007 TO: Cordell Pool, Stahly Engineering and CONFLUENCE Tracy Poole, Hyalite Capital Incorporated i n c o r p o rated FROM: Ronda Burns, Confluence Inc. RE: Mandeville Creek Hydrology and Hydraulics This memo provides the results of the hydrologic analysis for Mandeville Creek. Three methods were used to evaluate the flood flows for Mandeville Creek through the proposed sub-division: current regression equations developed by the U.S. Geological Survey (USGS), a regional frequency analysis using surrounding gage data, and rainfall runoff calculations performed with the U.S. Army Corps of Engineers (USACE) Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS). The variables used to estimate the flood flows using these three methods and their results are explained below. This memo also summarizes the results of the hydraulic analysis performed using the USACE Hydrologic Engineering Center River Analysis System (HEC-RAS) to size the culverts and map the floodplain through the Mandeville Creek subdivision. USGS REGRESSION EQUATIONS The regression equations developed by the USGS are formulated for different regions within Montana and are based on drainage basin characteristics. Mandeville Creek is located in the Upper Yellowstone—Central Mountain Region. The drainage basin area for Mandeville Creek through the subdivision was determined through the use of topographic information from the USGS map. The drainage basin has an area of 0.43 square miles and is shown in Figure 1. No part of the drainage basin is above 6,000 feet elevation. In addition to basin characteristics the USGS has refined their regression equations to include channel geometry characteristics. From a reference channel, the average bankfull channel width was estimated to be 2.9 feet. The results of the regression calculations based on these characteristics are shown in Table 1. Table 1. Return'Interval 2-year 25-year 100-year Discharge based on basin characteristics (cfs) 3 45 100 Discharge based on channel characteristics (cfs) 5 60 142 Discharge based on combination of 3 48 103 basin and channel characteristics cfs REGIONAL FREQUENCY ANALYSIS FROM GAGE DATA 406-585-9500 This method consists of plotting the drainage area versus estimated flood frequency flow for fax 406-582-9142 p g g q Y nearby gages then drawing a best fit line through this data to determine a relationship. I P.O.Box 1133 used the gages within a 50 mile radius of Bozeman and with drainage basins smaller than 1115 N.7 Ave,Suite 1 2,000 square miles. The resulting graph and equations are shown in Figure 2. Using the Bozeman,MT 59771-1133 q 9 g p q 9 9 drainage area of 0.43 square miles, the results for Mandeville Creek are shown in Table 2. www.confluenceine.com Contract Holder Creative Solutions for Natural Resources MEMO Table 2. Return Interval 2-year 25-year 100-year' Discharge (cfs) 2.3 1 23.6 47.9 RAINFALL RUNOFF CALCULATIONS HEC-HMS uses the selected unit hydrograph method to estimate the runoff from a given storm for a given drainage area. I selected the SCS curve number method. The predominant soil type for the drainage basin is Blackmore Silt Loam which is in hydrologic soil group B. I assumed the antecedent moisture class to be ll. With a land use of meadow (mowed for hay)for 70% of the basin and future land use of residential with 1/8 acre or less average lot size for 30% of the basin, the SCS curve number is 66. Based on this number, the initial loss is 1.03 inches. The basin lag time was estimated to be 122 minutes based on the slope of the basin and the length of the channel within the basin. The SCS has developed 24-hour rainfall distributions for the entire country. Montana is located in the region where the Type II rainfall distribution is applicable. The 24-hour rainfall for the 2-, 25-, and 100-year return intervals for Bozeman measured at Montana State University are shown in Table 3. The results from the HEC-HMS model are also shown in Table 3. Table 3. Return;Interval 2-year 25-year 1'00-year Precipitation (inches) 1.29 2.16 2.67 Discharge (cfs) 13.4 27.6 40.3 HYDROLOGIC SUMMARY Because Mandeville Creek is a low elevation stream with a very small drainage basin system, its hydrology is more dependent on storm events than on snowmelt runoff. The gages used in both the USGS regression equations and in the regional frequency analysis are generally associated with higher elevation, larger drainage basin systems. Due to these differences we believe the results from the rainfall runoff calculations to be the most applicable to the Mandeville Creek subdivision. HYDRAULIC ANALYSIS The hydrologic information and the proposed stream channel geometry and culverts were entered into HEC-RAS. The stream channel will be constructed by grading the proposed alignment down to the stream bed elevation then replacing topsoil along the fringes to create mitigation wetland area next to the channel. The wetland and stream channel corridor is 40 feet wide. The stream channel will meander within this corridor. The proposed stream alignment and profile are shown in Figures 3 and 4, respectively. The stream channel has a top width of 4 feet, and is 1 foot deep. To meet the existing grade, slopes of 5H:1V will be used. Cross-sections for HEC-RAS were created by centering the stream channel geometry in the proposed 40 foot wide wetland corridor and using 5H:1 V slopes to reach the existing ground elevations. Cross-sections were created at least every 50 feet along the stream channel. The typical stream cross-section is shown in Figure 5. A Manning's n-value of 0.04 was used for the stream channel and overbank areas. The HEC-RAS model was run assuming normal depth at the downstream end of the reach. Creative Solutions for Natural Resources MEMO The culverts for Mandeville Creek were sized to meet the City of Bozeman specifications and allow for fish passage. The City of Bozeman requires a culvert to pass the 25-year frequency flow with a headwater depth of no more than 1.5 times the culvert diameter. This criterion results in a 36 inch round equivalent concrete arch pipe culvert. The City also requires an emergency overflow path with a capacity equal to 100% of the culvert. To avoid flooding of the lots upstream of the culverts, it was decided that the culvert diameter should be increased. A 36 inch round equivalent concrete arch pipe has a full flow water area of 6.4 square feet. In order to provide 100% of the capacity for an emergency overflow, a 54 inch round equivalent concrete arch pipe (full flow water area of 14.3 square feet) is necessary. The typical culvert cross-section is shown in Figure 5. Additionally, it is recommended that the slope for the culverts be the same as the average stream bed slope which is 0.0114 ft/ft. The invert of the culvert should be placed 0.5 feet below the stream bed elevation to allow for transport of streambed material into the culvert. For fish passage, the recommended maximum velocity for adult trout passage through a culvert is 3 ft/s for culverts over 100 feet and 4 ft/s for culverts under 100 feet (Design of Road Culverts for Fish Passage, Washington Department of Fish and Wildlife, 2003). During all modeled flood events, the velocities in the channel range between 0.7 and 6.2 ft/s with an average velocity of 3.4 ft/s. The velocities in the culvert are similar to those found in the stream channel and are summarized in Table 4. All culverts are passable at the 2-year return interval flood. Fish passage upstream is not expected to coincide with the peak flows. Alternatively, sustained speeds, a speed that can be maintained for minutes, for adult Cutthroat and Brown trout are given as 6 and 7 ft/sec respectively (Fisheries Handbook of Engineering Requirements and Biological Criteria, Milo C. Bell, USACE, 1990). Table 4. Culvert Length (ft) Velocity US (ft/s) Velocity IDS (ft/s) Q2 Q25 Q100 Q2 Q25 Q100 Alder Creek Dr. 90 3.06 4.02 4.68 2.10 3.94 5.64 Brookdale Dr. 90 3.06 4.02 4.68 2.10 4.02 5.68 Graf St. 120 3.06 4.01 4.61 2.10 3.98 5.62 Volmer St. 90 3.06 4.02 4.68 2.10 3.94 5.68 The extents of the 100-year floodplain boundary for the proposed alignment of Mandeville Creek are shown in Figure 6. The 100-year floodplain is contained within the watercourse setback and does not encroach on any lots or flow over the road. The results of the HEC-RAS model are provided in Appendix A. Creative Solutions for Natural Resources � \ ; � / E oI ! � i, CPO � � � \ R / \ \ \ Lo r \Lu \ § ± z z O O _\ \ \ \ / u / � O c O 0 & / 0 � \ < 2 L W \ \\ \ 2 \ / / / \ / 4 O 4 m / E @L » F- / / E (I-li I \ / I Ln w » � w U)LLI / w W / b z Of O b / \ \ / Z \ LO G- (D\ \® o± g L mz \ � E ¢ > \ � \ \ / ± z 2 3 - -, uj : } � �\ .. .... Mandeville Creek "Arm" Culvert Calculations N 3.. > "t It N CR pl: OR OR 0! 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R r N cl et to 'R t-: CO 0n R T- W -J - &: %: V- V- CL M 11 1� Z L) 'E (D 0 s (D a) E E CL a m 'E 11 0 < B is a Retention Pond Calculations S 19th AVE TEMPORARY STORMWATER RETENTION BASIN CALCULATIONS Calculation of Required Volume for Storm Detention Pond (Reference: Bozeman Stormwater Master Plan-1982) Design Rainfall Freq. 10 year(see page III-5 of master plan) IDF coefficient a 0.64 IDF coefficient b IDF coefficient n 0.65 Pre-development Calculations Post-development Calculations C C Areas(ft): open space 0.20 Areas(ft): open space 0.20 med.res. 0.35 med.res. 0.35 dense res. 0.50 dense res. 0.50 comm.neigh. 0.60 comm.neigh. 0.60 comm.down. 0.80 comm.down. 0.80 industrial 15,610 0.80 industrial 48,100 0.90 (asphalt) Total: 15,610 Total: 48,100 total area: 0.36 acres total area: 1.10 acres composite C: 0.80 composite C: 0.90 Overland t� Overland t� average slope: 1.36 percent average slope: 1.36 percent travel distance: 1184 feet travel distance: 1184 feet tc: 17 minutes tc: 12 minutes Channel t� Channel tc channel tc: minutes channel tc: minutes Total tom: 17 minutes Total tc: 12 minutes intensity at tc(fig 23): 1 A3 in/hr intensity at tc(fig 23): 1.86 in/hr pre-devel peak runoff: 0.41 cfs post-devel peak runoff: 1.85 cfs Detention Pond Calculations: Retention Pond Calculations: design depth of pond 1.50 feet Q=CIA max side slope 4.00 horizontal to 1.00 vertical C= 0.90 (post-development) length/width ratio 3.00 I= 0.41 in/hr(10-yr,2-hr storm) min.particle removed 40 microns(1 micron=1 x 10-6 meters) A= 1.10 acres settling velocity of particle 0.0069 feet/second Q= 0.41 cfs min.pond to settle particle 268 square feet required retention storage(ft)=r 2.918 1 ft' pond dimentions assuming vertical side slopes(actual pond footprint will be larger) design depth 1.50 feet width 95 length/width ratio 1.00 length 48 pond dimensions assuming vertical side slopes Volume held between contours: (actual pond footprint will be larger) Cumulative width 44 Contour Area(ft) Delta V(ft) Volume(ft) length 44 4959.00 1,495 4960.0 2,270 1,883 1,883 4960.5 2,695 1,241 3,124 Design storage at 1.5'depth(ft') Retention pond-25 yr