HomeMy WebLinkAbout19 - Design Report - Costco - Catamount Roundabout - Stormwater
406-586-8834 ■ 800-865-9847 (fax) ■ 2090 Stadium Drive ■ Bozeman, Montana 59715 ■ www.dowl.com
TECHNICAL MEMORANDUM
Purpose
The intent of this Technical Memorandum is to:
1. Address City of Bozeman comments of May 7th, 2019
a. Primarily adding a bioretention swale to Catamount and a stormwater pond for the
roundabout at Max and Catron.
Proposed Project
As part of the City’s review of the Planned Unit Development (PUD) and Site Plan (SP) applications the
City is requiring Catamount be widened adjacent to the property to match the existing section width to the
west. Currently, the Catamount Street is 30 feet wide from the north top-back-of-curb (TBC) to the south
edge of asphalt. The new road section will be 50 feet from TBC to TBC. Additionally, the project will
require the construction of new sidewalk along the south side of the street.
The existing impervious area of Catamount Street, adjacent to the Costco parcel is 34,587 FT2 (0.79
acre) including the area in the MDT right-of-way along Valley Center which does not drain to the existing
stormwater system. A temporary retention pond built for Comfort Inn and Suites to the north is receiving
all stormwater from the existing 0.58 acres of Catamount Street and sidewalk excluding the .21 acres of
area of MDT right of way. As part of the Catron Crossing Preliminary Plat approval, the temporary pond is
intended to be replaced by a permanent regional stormwater pond on the north side of the Catron
Crossing Subdivision. The permanent pond is designed to accommodate stormwater flows from the
Catamount Street system but has not been constructed to date. The report indicates this area is included
in this design both graphically and in the narrative discussion, Additionally the run-off coefficients used for
the relevant basins indicate both contain a large area of impervious surface. Relevant excerpts from the
drainage report for the Catron Crossing Subdivision are included in Attachment A.
The proposed project will widen Catamount Street adding 21,992 FT2 (0.50 acre) including the sidewalk
of impervious area. The in-place constraints of the irrigation diversion culvert and structures, wetlands,
and existing improvements, limit the modifications that can be made to the existing road geometry of
Catamount Street. This project proposes a crowned road section to match the existing street geometry to
the west with a transition moving east to a non-crowned street section to accommodate the existing
drainage culvert crossing, the existing grading at intersection with Valley Center, and the existing
approach to the Comfort Inn and Suites.
The existing constraints identified above constrains the geometry and limits the options to modify the
existing drainage pattern currently flowing to the north. The proposed project will split the road into two
basins, a north basin and a south basin, see Figure 1 in attachment B. The south basin will include 0.30
acres of the western road crowned section, (sta 30+12 to 34+00 on Figure 2 in attachment B,) and detain
runoff in a bioretention cell. The basin will have an overflow structure the will outlet via a PVC pipe to the
48-inch CMP culvert passing under Catamount Street to the east. The north basin will drain north as it
currently does and is incorporated into the design of Catron Crossing Subdivision’s stormwater system.
Attachment B Figure 1 delineates the current drainage condition and Figure 2 delineates the post
development condition.
TO: Griffin Nielsen, EIT
FROM: Erik Garberg, PE – Senior Civil Engineer
DATE: 06/14/19
SUBJECT: Bozeman Costco Project - Catamount Stormwater Design Analysis – Revision 2
MEMORANDUM
Page 2 of 4
Hydrology
Existing Conditions:
The existing portion of Catamount Street adjacent to Costco is built as a 28-foot wide asphalt road with
curb, gutter, and sidewalk on the north side only. The roadway drains to existing stormwater inlets which
discharge to a temporary stormwater pond on the Comfort Inn and Suites site, see Figure 1 in attachment
B. The tables below summarize the inputs and outputs of the rational method, for a 10-yr storm event
using City of Bozeman IDF curves for the existing conditions.
Table 1 – Catamount Existing Drainage Inputs and Results
Post Development Condition:
Because of the in-place conditions, the fact that much of the area is already developed with impervious
surface, and a portion of the adjacent area is a basin not under City of Bozeman jurisdiction each post
development basin was analyzed based on its final condition. This means that no deductions were taken
for pre-development flows or volumes. This provides a conservative analysis and ensures the detention
features will contain the design. This also means that the pre and post areas will not align directly. This
is discussed further in the analysis below.
The proposed design will split Catamount Street into three basins. A north basin, south basin, and the
MDT basin see Figure 2 in attachment B. The MDT basin has been reviewed and approved by MDT
through the systems impact process, see Attachment C. The north basin will drain to the north and the
existing stormwater system identified above. The south basin will drain to the south with stormwater
collected in a bioretention cell with an overflow. The proposed project will add 0.50 acres of impervious
surface for a total impervious area of 1.29 (0.5 + 0.79 = 1.29). Both the pre and post development
conditions primarily consist of impervious surface, therefore, the stormwater system has been analyzed
for the overall post development condition excluding any deduction for pre-development flows.
Table 2 – Proposed South Basin Post Development Inputs and Results
Area 1 -South Basin (ac)0.21
Area 2 - North Basin (ac)0.27
Area 3 - Sidewalk (ac)0.1
Area 4 - MDT Basin (ac)0.21
Total Drainage Area (ac)0.79
Run-off Coefficient 0.9
Time of Concentration (min)5
10-yr Peak Runoff (cfs)2.2
10-yr Volume (cuft)671
Catamount Current Addition
Drain Area (ac)0.29
Run-off Coefficient 0.9
Time of Concentration (min)5
10-yr Peak Runoff (cfs)0.82
25-yr Peak Runoff (cfs)0.95
10-yr Volume (cuft)246
South Basin - Post Development
MEMORANDUM
Page 3 of 4
Table 3 – Proposed North Basin Post Development Inputs and Results
Storage volumes are based on 10-yr storm event and the post development condition only.
The south basin will detain stormwater in a bioretention swale with 250 CF of storage and an overflow
structure, see attachment D for the applicable proposed project plans and bioretention swale details.
Stormwater conveyance for the South Basin will be via curb and gutter entering the bioretention swale
through a curb cut in the concrete curb. Using FHWA HEC-22 (2001) – Gutter Flow Analysis the south
gutter, at the controlling design slope of 0.8%, will pass 3.616 CFS with depth of 3.25-incheswhich,
exceeds the calculated 0.95 CFS of stormwater runoff required for the 25-yr design storm event, see
Attachment D for calculations. A 3-feet wide curb cut opening will be installed at the sag with 1:1 side
slope and a height of 0.375 feet from top back of curb to flowline. The curb cut will minimize maintenance
and will not restrict flow during the 25-year storm event. The bioretention swale will have an overflow
structure that discharges to a 15-inch buried PVC pipe. The PVC pipe is sloped to provide a capacity of
1.29 cfs at 80% full. This exceeds the required flow of 0.95 cfs for the 25-year storm event. The PVC
pipe will discharge to a control structure with a concrete weir sized to release stormwater at the pre-
developed runoff rate.
To determine the pre-development runoff rate, the entire area of additional asphalt was compared to the
same area of unimproved land using a rational coefficient of 0.3. Output from this analysis is include in
Table 4 below.
Table 4 – Pre-development Flow New Asphalt Area
A 6-inch x 6-inch rectangular weir will be installed in a flow control manhole to restrict the released
stormwater flow to 0.47 cfs flowing at a depth of 0.43-feet. The weir will be placed in a typical City of
Bozeman outlet structure FIG A-2 in the City’s design manual and constructed.
The flow control manhole will discharge into a buried 48-inch CMP running under Catamount Street. In
previous stormwater/flood hazard analysis detailed in a Memo dated 06/06/2017, DOWL analyzed the
flow of the upstream basin for this culvert. Utilizing the rational value provided in this report, the culvert
will convey 12.2 cfs during a 25-yr event. The 48-inch CMP is sloped at approximately 1.25% and will
have a flow depth of 1-foot for the 25-year storm event and water surface level of 56.70. The flow control
manhole will discharge into the 48-inch culvert at an invert elevation of 56.40. The invert elevation for the
overflow system will be at 58.17. Therefore, the system will have 1.47 ft of hydraulic head to overcome
Drain Area (ac)1.0
Run-off Coefficient 0.9
Time of Concentration (min)5
10-yr Peak Run Off (cfs)2.83
25-yr Peak Run Off (cfs)3.26
10-yr Volume (cuft)849
North Basin - Post Development
Drain Area (ac)0.5
Run-off Coefficient 0.3
Time of Concentration (min)5
10-yr Peak Run Off (cfs)0.47
10-yr Volume (cuft)142
Pre-development Flow for Previous
Impervious Area
MEMORANDUM
Page 4 of 4
0.3 feet of possible back pressure at the discharge, neglecting minor losses in the system. The potential
existing flow in the 48-inch CMP will not significantly impact the function of the discharge piping during a
25-yr storm event. Detail hydraulic calculations are enclosed in Attachment E and relevant flood report
excerpts are contained in Attachment F.
Conclusion
Due to existing constraints identified above, Catamount Street cannot be built with a crown section for its
full length adjacent to the proposed project. A figure detailing the complications of a crowned section is
included in Attachment G. The existing constraints require the stormwater drainage on Catamount to be
split irregularly between a north and south drainage basin. The south basin will drain to the proposed
biorentention cell in the Catamount boulevard with a flow control structure and overflow to the adjacent
48-inch CMP. The north basin will continue to drain to the temporary retention pond until that
construction is finalized and the permanent pond is constructed as detailed in Comprehensive Drainage
Plan Update CATRON CROSSING, September 2018.
These facilities are considered private by the City of Bozeman and will be maintain by the owner per the
provided maintenance plans.
Attachments
Attachment A – Excerpts of Catron Crossing Stormwater Report
Attachment B – Stormwater Basin Delineation
Figure 1 – Catamount Pre-developed Conditions
Figure 2 – Catamount Post-developed Conditions
Attachment C – MDT Approval
Attachment D – Proposed Plans
Attachment E – Stormwater Calculations
Attachment F – Flood Report Excerpts
Attachment G - Road Cross-section Comparison
ATTACHMENT A – EXCERPTS CATRON CROSSING
STORMWATER REPORT
nnr,nr[][1[If ';[Iuuuuuuuu, Morrisoni Maierle»fl9*t**'t luirt^Oti pl»~iRATIONAL METHOD FOR RUNOFF CALCULATIONSCatron Crossing | Post-Development Subbasin 1-K • 25 Year Design Storm FrequencyDeaign Storm Fnquency = | 25 | Years(Enter WQual, 2.5,10, 25,50, or 100)DRAINAGE BASIN CHARACTERISTICSInput values for runoff coeffidents ft-om appropriate tables.RunoffWeightedRunoff FrequencySurfaceDescriptionCatamount StreetArea, AArea, A Coefficient35,1840.808~owCxA-0:767-Coefficient'0.95Factor1.10Adjusted RunoffCoefficientC' = C.o x C,uii x Cf . C»a x C, s 1.00 C" X A1.051.00Totals35,184 0.8080.7670.8080.808IWeighted runoff coefficient, C^ = £C|AJ / Zaj where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type jBASIN TIME OF CONCENTRATIONOverland Flow (Sheet Flow) Travel Time:L/2 TU( = Overland Flow (Sheet Flow) Travel Time (min)Tc-of = ^ ^ ,y {} S = Slope of Flow Course (%)C = Rational Method Runoff Coefficient^1/3L= Length of Basin (ft)C, = Frequency Adjustment FactorLength ofFtowpath(ft)Slope of RunoffFlowpath Coefficient(%)Frequency Travel TimeFactor Ti^fDescription of Overland Flow Course0.95Overiand Flow-Sidewalk1.100.4061.SOOverland Flow-Turf71.500.281.103.30(Average)Channelized Flow Travel Time:L Tt<f= Channelized Flow Travel Time (min) , ,n,/,\2/3 / ^ \i/2 n = Manning's Roughness Coefficient S=Tt'~':f = 60V L ° Le"8t' °' Basin (ft) y= l^6 (^ i-^;} A = Cross-Sectional Area of Channel Flow (ft2)V» Average Velocity of Flow (ft/sec) " ^ / v / P='^s»*4-:—w-s^'Slope of Flowpath(%)Description of Channelized Flow PathConcrete GutterLength ofFlowpath(ft)225Slope of Manning's X-Sectional WettedFlowpath Roughness Flow Area Perimeter-072~Coefficient0.016Average Travel TimeVelocity T^,(ft/sec) (min)T28~g.522.68-T80-TotalsShallow Concentrated Flow Travel Time:2250.720.021.289.522.081.80(Average) (Average) (Average) (Average) (Average)L T|» s shalkw Concentrated Flow Travel Time (min) / r. \i/2 n = Manning's Roughness Coefficient S = Slope of Flowpath (%)' = 601^ L ° l-e"9th of Basin <"' v = ^^~ Rii2/3 f 7^) Rfl = Assumed Hydraulic Radius Based onV= Average Velocity of Row (ft/sec) " ^100^ Land Use / Flow Regime (ft)Description of Shallow ConcentratedFlow CourseShallow Concentrated Flow - Concrete GutterLength of Slope of Manning's HydraulicFlowpath Flowpath Roughness Radius(ft) (%) Coefficient (ft)Average Travel TimeVelocity Tj^c(ft/sec) (min)2880.670.0110.203.771.27Totals2880.67(Average)0.011(Average)0.200(Average)3.775(Average)1.27N:\2tlW25B«wl)oc«Cak3StormW«teAnah«WIPo>K)ndopin«]tRunomBum<1<25-YR_D«aian-Stom.«lMPage 1 of 2Printed: 9/14/20t7-5:15PM
, Morrisoni MaierleDETERMINATION OF BASIN PEAK FLOW RATE S, RUNOFF VOLUMEBasin Time of Concentration, tc:tc = Tt-of + Tt-sc + Tt-cftc = Basin Time of Concentration (min)TM = Overiand Flow (Sheet Flow) Travel Time (min)T,^; = Shallow Concentrated Ftow Travel Time (min)T|<( = Channelized Ftow Travel Time (min)Basin Overland Flow (Sheet Flow) Travel Time, T|<( ;Basin Shallow Concentrated Flow Travel Time, T|<: =Basin Channelized Flow Travel Time, T^=Basin Time of Concentration, tc =Calculation of Peak Flow Rate:Rainfall Intensity Linear InterpolationUpper Rainfall Intensity Value =Lower Rainfall Intensity Value =5 min10minBasin Design Rainfall Intensity, i =3.70 min1.27 min1.80 min6.77 min3.83 in/hr2.46 in/hr3.34 in/hr'•»A -S»»^K(?p = C'iAQp = Basin Peak Flow Rate (ft3/sec or cfs)C' = Basin Adjusted Runoff CoefficientBasin Adjusted Runoff Coefficient, C'= 1.00Basin Rainfall Intensity, i= 3.34 in/hrBasin Area, A = 0.808 acresi s Rainfall Intensity (in/hr)A = Basin Area (acres)Basin Design Peak Flow, Qn =2.70 cfsfip = 60t<. • QyCalculation of Peak Runoff Volume:Rp = Basin Peak Runoff Volume (ft3 or cf)tc = Basin Time of Concentration (min)Basin Time of Concentration, tc:: 6.77 minBasin Peak Flow Rate, Qp» 270 ft3/secQp = Basin Peak Flow Rate (ft'/see or cfs)Basin Peak Runoff Volume, Rn =1,096.13 cfN;l2905\025\D««9nDoca\C«ta\Stifm Water AiulysMlPoit<n«kipmMtRunof ih-01-K_25-YR_D«aign-Storm.xlaxPage2of2Printed: 9/14/2017-5:15PM
nfi[;[1[1[I[1[][][I[]uuuuuuuMomsoni MaierleRATIONAL METHOD FOR RUNOFF CALCULATIONSCatron Crossing | Post-Development Subbasin 1-L - 25 Year Design Storm FrequencyDesign Storm Frequency = | 25 | Yearn(Enter WQual, 2.5.10, 25, 50,or 100)DRAINAGE BASIN CHARACTERISTICSInput values for runoff coefficients from appropriate tables.SurfaceDescriptionAspnalt & uoncreteLandscape AreaBuilding RoofTotalsArea.A15,594RunoffArea, A CoefficientWeightedRunoff FrequencyCoefficientFactor"looe"6,882-^35T0.1840.158-ft95-0.280.95CxA~Q3W~0:05130,482 0.7000.1500.5420.771.10Adjusted RunoffCoefficientC- = C»o x C,,d x Cf . C»n x C, S 1.00 C" x A0.850.850.5960.596Weighted runoff coefficient, C«, = SCjA, / Zaj where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type j\BASIN TIME OF CONCENTRATIONOverland Flow (Sheet Flow) Travel Time:L/2 ^i-ai= Overland Flow (Sheet Flow) Travel Time (min)Tt-ofSl/3S=SlopeofFlowCouree(%)C = Rational Method Runoff CoeffidentL= Length of Basin (ft)C( = Frequency Adjustment FactorLength ofFlowpath(ft)Slope of Runoff Frequency Travel TimeFlowpath Coefficient Factor T^fDescription of Overland Flow CourseOverland Flow - Turf0.281.106.09353.UO62.000.95Overiand Flow - Sidewalk1.100.3862.000.28Overiand Flow - Turf1.102.99(Average)Channelized Flow Travel Time:LTu = Channelized Flow Travel Time (min)Tt~cf =; 601^ L = Len9th °f Basi" (ft>V = Average Velodty of Flow (ft/sec)v1.4861/2 n = Manning's Roughness Coefficient S = Slope of Flowpath (%)2/3 /„ ^ 1/2 n = manning sA = Cross-Sectional Area of Channel Flow (ft2)" ^ ^loo'/ p=Description of Channelized Flow PathConcrete GutterLength ofFlowpath(ft)56Slope of Manning's X-Sectionai WettedFfowpath Roughness Flow Area Perimeter~OS2Coefficient0.0160.928;6oAverage Travel TimeVelocity J^,(ft/sec) (min)1.3;u.bu0.520.020.928.001.57(Average) (Average) (Average) (Average) (Average)Shallow Concentrated Flow Travel Time:1, f^K = Shallow Concentrated Flow Travel Time (min)-sc = ^o^ L = Length of Basin (ft)V = Average Velocity of Flow (ft/sec)T,-s1/2 n = Manning's Roughness Coeffident S = Slope of Flowpath (%)J^86fl,,2/3 f-£-y Rh = Assumed Hydraulic Radius Based onl'=——ff""^ToojLand Use/Flow Regime (ft)Description of Shallow ConcentratedFlow CourseLength of Slope of Manning's HydraulicFlowpath Flowpath Roughness Radius(ft) (%) Coefficient (ft)Average Travel TimeVelocity T,.,,;(ft/sec) (min)Totals0.00(Average)0.000(Average)0.000(Average)0.000(Average)0.00Ni2e05025CMJan Doc*C«ka>St»m Wtto Aiuly»sn>»t-0mk)f»miit Runof(BMh.01-l_25-yR_OMian-3t«mjthxPage1of2Printed: 11/8/2017-9:26 AM
MorrisonMaierlerrtyfHi p^.-wDETERMINATION OF BASIN PEAK FLOW RATE 8, RUNOFFVOLUMEBasin Time of Concentration, tc:tc = T't-0/' + Tt-sc + T[-cf1c = Basin Time of Concentration (min)^^ = Overland Flow (Sheet Flow) Travel Time (min)T|<; = Shallow Concentrated Flow Travel Time (min)Tj^i = Channelized Flow Travel Time (min)Basin Overiand Flow (Sheet Flow) Travel Time, T,^ = 9.45 minBasin Shallow Concentrated Flow Travel Time, T^c = 0.00 minBasin Channelized Flow Travel Time, T|<, = 0.60 minBasin Time of Concentration, t. = 10.05 minCalculation of Peak Flow Rate:Rainfall Intensity Linear InterpolationUpper Rainfall Intensity Value = 10 minLower Rainfall Intensity Value = 15 min^•-.,-^;r-'2.46 in/hr1.89 in/hrBasin Design Rainfall Intensity, i =2.45 jn/hr<2p = C'iAQp= Basin Peak Flow Rate (ft;i/sec or cfs)C' = Basin Adjusted Runoff CoefficientBasin Adjusted Runoff Coefficient, C' = 0.85Basin Rainfall Intensity, ia 2.45 in/hrBasin Area, A = 0.700 acresi= Rainfall Intensity (inflir)A = Basin Area (acres)Basin Design Peak Flow, Qp =1.46 cfsCalculation of Peak Runoff Volume:Rp = Basin Peak Runoff Volume (ft3 or cf)tc = Basin Time of Concentration (min)Basin Time of Concentration, 1c = 10.05 minBasin Peak Flow Rate, Qp= 1.46 ft'/secBasin Peak Runoff Volume, Rn = 880.11 cfQp = Basin Peak Ftow Rate (ft3/sec or cfs)•NSMOM2aDMi»iDoaCak3\Stomi Water Anal»»s\PMt-On«tofimentRunon8aim<14-_2S.YR_D«iian-Sum].>tePage 2 of 2Printed: 11/8/2017-9:26 AM
nr11f]nn-I1[i(In[I[Iu1111[juuI!LuMorrisoni MaierletuKe^Ott f>lfn»'t td»ii!itt^RATIONAL METHOD FOR RUNOFF CALCULATIONSCatron Crossing | Post-Dev. Subbasins 1-K and 1-L • 25 Year Design Storm FrequencyDesign Storm Frequency = | 25 | Yean(Enter WQual, 2.5,10, 25,50,or 100)DRAINAGE BASIN CHARACTERISTICSInput values for runoff coefficients from appropriate tables.SurfaceDescriptionBubbasin 1-KRunoffArea, A Area, A Coefficient(ft2) (acres)WeightedRunoffCoefficientFrequencyFactorSubbasin 1-L,i5,1B4 | U.BUU30,482-0.700-055-0.77~OW-o34TfXC,0.871.10Adjusted RunoffCoefficientC' = C»o x C,C«aXC,£l.OO C'xA0.960.96Totals65,6661.5071.3091.4401.440'Weighted runoff coefficient, C,., = EC|AJ / Zaj where Cj is the adjusted runoff coefficient for surface type j and Aj is the area of surface type jBASIN TIME OF CONCENTRATIONOverland Flow (Sheet Flow) Travel Time:l/z T,^( = Overland Flow (Sheet Flow) Travel Time (min)Tc-of51/3S = Slope of Flow Course (%)C = Rational Method Runoff CoefficientL= Length of Basin (ft)G( = Frequency Adjustment FactorLength ofFlowpath(ft)Slope of RunoffFlowpath Coefficient(%)Frequency Travel TimeFactor T.Description of Overland Flow CourseSubbasin 1-L: Overland Flow - Turf0.281.106.09,353.00Subbasin 1-L; Overiand Flow - Sidewalk62.001.100.950.38Subbasin 1-L: Overland Flow - Turf2.001.100.282.99(Average)Channelized Flow Travel Time:ft&ff:LT,<f s Channelized Flow Travel Time (min)/ = 6QV L ° Len8th of Basin (ft)V = Average Velocity of Flow (ft/sec)v1.4862/3 1/2 n =486 (1\ (-s-\ A = Cross-Sectional Area of Channel Flow (ft2)" ^ ^ ^ ^ P=Wetted-PerinS=SlopeofFlowpath(%)Description of Channelized Flow PathSubbasin 1-L: Concrete GunerLength of Slope of Manning's X-Sectional WettedFlowpath Flowpath Roughness Flow Area Perimeter(ft) (%) CoefficientAverage Travel TimeVelocity T|<|(ft/sec) (min)560.520:016~092-8.00^.31u.bu0.520.020.928.001.570.60(Average) (Average) (Average) (Average) (Average)Shallow Concentrated Flow Travel Time:L T|<;= Shallow Concentrated Flow Travel Time (min) , ^ \i/2 n = Manning's Roughness Coefficient S " Slope of Ftowpath (%)TC~S<::='60V L= Length of Basin (ft) (/= li86./;,,2/3 [-^-y R|,= Assumed Hydraulic Radius Based onV= Average Velocity of Flow (ft/sec) " vll° ^ Land Use / Flow Regime (ft)Description of Shallow ConcentratedFlow CourseLength of Slope of Manning's HydraulicFlowpath Flowpath Roughness Radius(H) (%) Coefficient (ft)Average Travel TimeVelocity T(^(;(ft/sec) (min)Totals0.00(Average)0.000(Average)0.000(Average)0.000(Average)0.00N:l2«)5U25Bnan Oo«ICrt3\Stmi Water Analy«>*Pi»t-0«»do|>m«nt Ri«BnCimbin«<ifl«iin41-K*L_25-YR_DM<frStom.xlMPage lot 2Printed: 11/8tt0l7-9:53 AM
, Morrisoni MaierleDETERMINATION OF BASIN PEAK FLOW RATE & RUNOFFVOLUMEBasin Time of Concentration, 4:tc=Tt-of+Tt-sc+Tt-cfI,; = Basin Time of Concentration (min)T|^ = Overiand Flow (Sheet Flow) Travel Time (min)T^ = Shallow Concentrated Flow Travel Time (min)TM = Channelized Flow Travel Time (min)Basin Overland Flow (Sheet Flow) Travel Time, T^ •Basin Shallow Concentrated Flow Travel Time, T|<; =Basin Channelized Flow Travel Time, T^=Basin Time of Concentration, t<; =Calculation of Peak Flow Rate:Rslnhll Intensity Linear InterpolationUpper Rainfall Intensity Value =Lower Rainfall Intensity Value s9.45 min0.00 min0.60 min10.05 minS sw::^ <i y^WsMWmm--15 min2.46 in/hr1.89 jn/hrBasin Design Rainfall Intensity, i =2.45 jn/hr<2p = C'iAQp = Basin Peak Flow Rate (ft'/sec or ds)C' = Basin Adjusted RunoffCoeffidentBasin Adjusted Runoff Coefficient, C' = 0.96Basin Rainfall Intensity, i = 2.45 in/hrBasin Area, A = 1.507 acresi = Rainfall Intensity (in/hr)A s Basin Area (acres)Basin Design Peak Flow, Qp =3.53 cfsCalculation of Peak Runoff Volume:Rp = Basin Peak Runoff Volume (ft3 or cf)tc = Basin Time of Concentration (min)Basin Time of Concentration, t<;= 10.05 minBasin Peak Flow Rate, Qp= 3.53 ft'/secQp = Basin Peak Flow Rate (ft3/sec or cfs)Basin Peak Runoff Volume, Rn=2,126.93 cfN;l2i05t025tD«aignDoalCafcalStormW«t8fAfM]yiealPoat-Om«b|immtR>in(inCombin«dfliin-014<*L_25-YR.DMi8n-Storm.xiuPage2of2Printed: 11/8/2017-9:53 AM
ATTACHMENT B – PRE AND POST DEVELOPMENT
STORMWATER BASINS
1. Figure 1
2. Figure 2
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CATAMOUNT STREET VALLEY CENTER ROADBBAACOSTCO EXPANSIONBOZEMAN, MONTANAWWW.DOWL.COMPRE-DEVELOPMENT BASINSCATAMOUNT ROAD1
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CATAMOUNT STREET VALLEY CENTER ROADSECTION A - A BBAASECTION B - B
STATION 36+30 (COSTCO)COSTCO EXPANSIONBOZEMAN, MONTANAWWW.DOWL.COMPOST DEVELOPMENT BASINSCATAMOUNT ROAD2
ATTACHMENT C – MDT APPROVAL
1
Erik Garberg
From:Maes, Stephanie <smaes@mt.gov>
Sent:Tuesday, February 05, 2019 10:59 AM
To:Erik Garberg
Cc:Demars, Kyle; Liebel, Duane; Walsh, Joe; Ebert, Jeff
Subject:Costco Expansion - Valley Center Rd/U-1211, Bozeman (65.71.1041.01)
Categories:Filed by Newforma
Erik,
The system impact review is complete, and I returned the Encroachment Application for the subject project to Kyle
DeMars for final approval and permit issuance. Kyle will be your contact from this point forward, and you can reach him
at (406) 556-4704.
Thank you,
Stephanie
Stephanie Maes
Transportation Planning Engineer
Policy, Program & Performance Analysis Bureau
Montana Department of Transportation
P.O. Box 201001
Helena, MT 59620
406-444-6126 | smaes@mt.gov
ATTACHMENT D – PROPOSED PLANS AND DETAILS
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COSTCOWAREHOUSEADDITIONCIVILSITEIMPROVEMENTS406-586-883414108 PE
999LAKEDRIVEISSAQUAH,WA98027TEL:(425)313-8100PREPAREDFORCOSTCOWHOLESALECORPORATIONCATAMOUNT STREET VALLEYCENTERROADSTORMDRAINCATAMOUNTSTREETC8.1.1
COSTCOWAREHOUSEADDITIONCIVILSITEIMPROVEMENTS406-586-883414108 PE
999LAKEDRIVEISSAQUAH,WA98027TEL:(425)313-8100PREPAREDFORCOSTCOWHOLESALECORPORATIONROADWAYDETAILSCATAMOUNTSTREETC8.5
1 TYPICAL SECTION
STATION 30+11.69 TO STATION 32+90.00
2 TYPICAL SECTION
STATION 34+00.00 TO STATION 39+19.73
3 PAVEMENT MARKING DIMENSIONS
NTS
4 36" CONCRETE OUTLET STRUCTURE DETAIL
NTS
MULCH/COMPOST LAYER
BIORETENTION SOIL MEDIA (BSM)
AGGREGATE
NATIVE SOIL
ASPHALT PAVEMENT
CONCRETE
7 CURB INLET
NTS
A A'BB'
ATTACHMENT E – CALCULATIONS
1. 10-yr Pre-development
2. 10-yr Post development north and south
3. 25-yr Post development north and south
4. Outlet weir
5. 48-inch CMP capacity
6. Outlet pipe capacity
7. Biorentention inlet capacity
8. Gutter flow
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v10.514 Thursday, 06 / 6 / 2019
Hyd. No. 1
Pre-development Condition
Hydrograph type = Rational Peak discharge = 0.472 cfs
Storm frequency = 10 yrs Time to peak = 5 min
Time interval = 1 min Hyd. volume = 142 cuft
Drainage area = 0.500 ac Runoff coeff.= 0.3
Intensity = 3.145 in/hr Tc by User = 5.00 min
IDF Curve = Bozeman 10 and 25 IDF.IDF Asc/Rec limb fact = 1/1
0 1 2 3 4 5 6 7 8 9 10
Q (cfs)
0.00 0.00
0.05 0.05
0.10 0.10
0.15 0.15
0.20 0.20
0.25 0.25
0.30 0.30
0.35 0.35
0.40 0.40
0.45 0.45
0.50 0.50
Q (cfs)
Time (min)
Pre-development Condition
Hyd. No. 1 -- 10 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v10.514 Monday, 06 / 3 / 2019
Hyd. No. 1
North Basin
Hydrograph type = Rational Peak discharge = 2.830 cfs
Storm frequency = 10 yrs Time to peak = 5 min
Time interval = 1 min Hyd. volume = 849 cuft
Drainage area = 1.000 ac Runoff coeff.= 0.9
Intensity = 3.145 in/hr Tc by User = 5.00 min
IDF Curve = Bozeman 10 and 25 IDF.IDF Asc/Rec limb fact = 1/1
0 1 2 3 4 5 6 7 8 9 10
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
Q (cfs)
Time (min)
North Basin
Hyd. No. 1 -- 10 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v10.514 Monday, 06 / 3 / 2019
Hyd. No. 1
South Basin
Hydrograph type = Rational Peak discharge = 0.821 cfs
Storm frequency = 10 yrs Time to peak = 5 min
Time interval = 1 min Hyd. volume = 246 cuft
Drainage area = 0.290 ac Runoff coeff.= 0.9
Intensity = 3.145 in/hr Tc by User = 5.00 min
IDF Curve = Bozeman 10 and 25 IDF.IDF Asc/Rec limb fact = 1/1
0 1 2 3 4 5 6 7 8 9 10
Q (cfs)
0.00 0.00
0.10 0.10
0.20 0.20
0.30 0.30
0.40 0.40
0.50 0.50
0.60 0.60
0.70 0.70
0.80 0.80
0.90 0.90
1.00 1.00
Q (cfs)
Time (min)
South Basin
Hyd. No. 1 -- 10 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v10.514 Monday, 06 / 3 / 2019
Hyd. No. 1
North Basin
Hydrograph type = Rational Peak discharge = 3.264 cfs
Storm frequency = 25 yrs Time to peak = 5 min
Time interval = 1 min Hyd. volume = 979 cuft
Drainage area = 1.000 ac Runoff coeff.= 0.9
Intensity = 3.627 in/hr Tc by User = 5.00 min
IDF Curve = Bozeman 10 and 25 IDF.IDF Asc/Rec limb fact = 1/1
0 1 2 3 4 5 6 7 8 9 10
Q (cfs)
0.00 0.00
1.00 1.00
2.00 2.00
3.00 3.00
4.00 4.00
Q (cfs)
Time (min)
North Basin
Hyd. No. 1 -- 25 Year
Hyd No. 1
Hydrograph Report
Hydraflow Hydrographs Extension for AutoCAD® Civil 3D® 2016 by Autodesk, Inc. v10.514 Monday, 06 / 3 / 2019
Hyd. No. 1
South Basin
Hydrograph type = Rational Peak discharge = 0.947 cfs
Storm frequency = 25 yrs Time to peak = 5 min
Time interval = 1 min Hyd. volume = 284 cuft
Drainage area = 0.290 ac Runoff coeff.= 0.9
Intensity = 3.627 in/hr Tc by User = 5.00 min
IDF Curve = Bozeman 10 and 25 IDF.IDF Asc/Rec limb fact = 1/1
0 1 2 3 4 5 6 7 8 9 10
Q (cfs)
0.00 0.00
0.10 0.10
0.20 0.20
0.30 0.30
0.40 0.40
0.50 0.50
0.60 0.60
0.70 0.70
0.80 0.80
0.90 0.90
1.00 1.00
Q (cfs)
Time (min)
South Basin
Hyd. No. 1 -- 25 Year
Hyd No. 1
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Thursday, Jun 6 2019
<Name>
Rectangular Weir
Crest = Sharp
Bottom Length (ft)= 0.50
Total Depth (ft)= 0.50
Calculations
Weir Coeff. Cw = 3.33
Compute by:Known Q
Known Q (cfs)= 0.47
Highlighted
Depth (ft)= 0.43
Q (cfs)= 0.470
Area (sqft)= 0.22
Velocity (ft/s)= 2.19
Top Width (ft)= 0.50
0 .1 .2 .3 .4 .5 .6 .7
Depth (ft)Depth (ft)<Name>
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
Length (ft)Weir W.S.
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Wednesday, Jun 5 2019
Catamount 48-inch CMP
Circular
Diameter (ft)= 4.00
Invert Elev (ft)= 55.71
Slope (%)= 1.25
N-Value = 0.023
Calculations
Compute by:Known Q
Known Q (cfs)= 12.20
Highlighted
Depth (ft)= 0.99
Q (cfs)= 12.20
Area (sqft)= 2.44
Velocity (ft/s)= 4.99
Wetted Perim (ft)= 4.18
Crit Depth, Yc (ft)= 1.02
Top Width (ft)= 3.46
EGL (ft)= 1.38
0 1 2 3 4 5 6
Elev (ft)Depth (ft)Section
54.00 -1.71
55.00 -0.71
56.00 0.29
57.00 1.29
58.00 2.29
59.00 3.29
60.00 4.29
Reach (ft)
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Tuesday, Jun 11 2019
<Name>
Circular
Diameter (ft)= 1.25
Invert Elev (ft)= 1.00
Slope (%)= 0.02
N-Value = 0.009
Calculations
Compute by:Known Depth
Known Depth (ft)= 1.00
Highlighted
Depth (ft)= 1.00
Q (cfs)= 1.290
Area (sqft)= 1.05
Velocity (ft/s)= 1.23
Wetted Perim (ft)= 2.77
Crit Depth, Yc (ft)= 0.45
Top Width (ft)= 1.00
EGL (ft)= 1.02
0 1 2 3
Elev (ft)Section
0.50
1.00
1.50
2.00
2.50
3.00
Reach (ft)
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc.Tuesday, Jun 4 2019
Inlet Sizing
Trapezoidal
Bottom Width (ft)= 3.00
Side Slopes (z:1)= 1.00, 1.00
Total Depth (ft)= 0.38
Invert Elev (ft)= 1.00
Slope (%)= 0.10
N-Value = 0.013
Calculations
Compute by:Known Depth
Known Depth (ft)= 0.38
Highlighted
Depth (ft)= 0.38
Q (cfs)= 2.150
Area (sqft)= 1.28
Velocity (ft/s)= 1.67
Wetted Perim (ft)= 4.07
Crit Depth, Yc (ft)= 0.25
Top Width (ft)= 3.76
EGL (ft)= 0.42
0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5
Elev (ft)Depth (ft)Section
0.75 -0.25
1.00 0.00
1.25 0.25
1.50 0.50
1.75 0.75
2.00 1.00
Reach (ft)
Gutter Flow Analysis
Project Bozeman Costco Addition
Feature Southside of Catamount curb capacity
Version Revision 2
Analyst Erik Garberg
Note Only Case 1 considered for this Analysis
Reference: FHWA HEC-22 (2001)Adjust T (Case 1 and Case 2) or Ts (Case 3)
until computed Q = design Q
Case 1:
N 0.014 Manning n
Sx 0.030 Gutter Cross Slope, ft/ft
S 0.008 Gutter Longitudinal Slope, ft/ft
T 9.000 Spread, ft
Q 3.616 Flow, cfs
A 1.215 Area, sq ft
Y 0.270 Max Depth, ft
V 2.976 Velocity, fps
Case 2:
N 0.000 Manning n
Sx1 0.000 Gutter Cross Slope Next to Curb, ft/ft
Sx2 0.040 Gutter Cross Slope Next to Street, ft/ft
S 0.010 Gutter Longitudinal Slope, ft/ft
T 0.000 Spread, ft
Q #DIV/0! Flow, cfs
Sx 0.000 Equivalent Gutter Cross Slope, ft/ft
A #DIV/0! Area, sq ft
Y #DIV/0! Max Depth, ft
V #DIV/0! Velocity, fps
It is the responsibility of the engineer using this spreadsheet
Case 3:to verify its accuracy and applicability to the specific design.
N 0.000 Manning n
Sw 0.000 Gutter Inside Cross Slope, ft/ft
Sx 0.000 Gutter Outside Cross Slope, ft/ft
S 0.000 Gutter Longitudinal Slope, ft/ft
W 0.000 Gutter Inside Width, ft
Ts 0.000 Gutter Outside Width, ft
Q #DIV/0! Total Flow, cfs
T 0.000 Spread, ft
T/W #DIV/0! Width Ratio
Sw/Sx #DIV/0! Cross Slope Ratio
Eo #DIV/0! Flow Ratio, Qw/Q
Qs #DIV/0! Outside Flow, cfs
Qw #DIV/0! Inside Flow, cfs
Z 0 Depth at Slope Break, ft
A 0.000 Area, sq ft
Y 0.000 Max Depth, ft
V #DIV/0! Velocity, fps
ATTACHMENT F – BASIN HYDROLOGY
406-586-8834 ■ 800-865-9847 (fax) ■ 2090 Stadium Drive ■ Bozeman, Montana 59715 ■ www.dowl.com
Page 1 of 6
Introduction
This memorandum provides a summary of the flood hazard study performed for the drainage
channel located along the west and north border of the Costco property boundary. The channel
begins approximately 1.1 miles south of Costco at Tschache Lane and passes through seven
culverts and one pedestrian bridge before discharging into a 48” CMP culvert located at the
northern end of the Costco property, just south of Catamount Street, see Figure 1. The 48” CMP
culvert discharges into a drainage ditch that flows along the west side of East Valley Center Drive
and under I-90 and eventually discharges into the East Gallatin River to the north. This channel is
spring fed and has flow all year long, but also function as a runoff conveyance channel.
There are existing wetlands and a storm drainage detention pond located in the existing
undeveloped area just north of Costco’s existing parking lot and building, see Figure 1. Costco has
proposed to expand their parking lot into this area requiring a section of the existing drainage
channel to be relocated along with the existing storm drainage detention pond. The existing 48”
CMP outfall culvert will also be extended west to the location where the proposed channel
relocation ends. The City of Bozeman has requested that DOWL complete a flood hazard study
that identifies flood hazards for existing conditions and proposed development.
Hydrology
The contributing drainage area is 65.4 acres and consists mostly of farmland and some minor
developments which results in only 2.3% impervious area. Peak flows were estimated using the
USGS Regression Equations, Rational Method and SCS Method. The USGS Regression Equations
for the Upper Yellowstone – Central Mountain USGS Region (SRIR 2015-5019) were used to
estimate peak flows. A time of concentration of 60 minutes was calculated and used to estimate
peak runoff for both the Rational and SCS Methods. The rainfall intensity for a 60-minute time of
concentration and cumulative 24-hr rainfall depth used to estimate peak flows are provided in
Table 1.
Table 1: Rainfall Data
MEMORANDUM
TO: DOWL: Clint Litle, PE
FROM:
DOWL: Greg Gabel, PE
DATE:
Scott Taylor, E.I.
June 6, 2017
SUBJECT: Costco PUD – Flood Hazard Study
Method 2-Year 10-Year 25-Year 50-Year 100-Year
Rational (in/hr)0.36 0.64 0.78 0.92 1.01
SCS (24 Hr Cum. Depth)1.28 1.95 2.45 2.71 2.88
Page 2 of 6
Page 3 of 6
Runoff coefficients for the Rational Method and curve number for the SCS Method were selected
from Table I-1 in the City of Bozeman Design Manual and Table 7-10 from Chapter 7 of the
Montana Department of Transportation Hydraulics Manual. Runoff coefficients of 0.20 and 0.98
are used to represent farm fields and impervious area, respectively and have a weighted value of
0.22. The soil within the drainage area range from hydrologic soil group B and C and have curve
numbers ranging from 58 to 71 that for farm fields.. A curve number of 98 is used to estimate
runoff from impervious area. The weighted curve number used for the estimate runoff for SCS
method is 63.1. Table 2 shows the computed flows for each hydrologic method used.
Table 2: Computed Flow Comparison
As previously discussed there are seven culverts and one pedestrian bridge that the drainage
channel passes through. Five of these culverts are located upstream and have the potential to
limit the flow to the Costco site. All of these culverts are 36” RCP’s except the one located under
Catron Street which is a 58”x36” RCPA. These 36” RCP culverts have a flow capacity of
roughly 40 cfs before overtopping. When comparing upstream culvert capacities to predicted
flood flows, it appears the Rational Method and USGS Method gives a reasonable estimate. The
SCS method predicts a low estimate and was eliminate from further consideration. DOWL is
recommending the USGS regression predict flood flows over the Rational Method to be
conservative with the flood hazard assessment. In addition there is a high likelihood in the future
that the upstream farmland will be developed and potentially increase the runoff values. DOWL
selected the USGS Method predicted flood flows for evaluating the flood hazards around
the Costco Site.
Hydraulic Modeling
A hydraulic model was developed for the channel reach that borders the western edge of
Costco’s property using HEC-RAS, version 5.0.1. The model extends from the southern border
of Costco’s property to the northern border and includes two culverts and a pedestrian bridge.
The 48” CMP culvert that the drainage ditch discharges into is modeled independently of HEC-
RAS using HY-8. The headwater elevation computed in HY-8 for the 2, 10, 25, 50 and 100-year
flows are used as the fixed downstream tailwater elevation (boundary condition) for each
respective flow in HEC-RAS. Manning roughness values from the channel and overbank areas
are 0.05 and 0.035, respectively. Contraction and expansion coefficients are set to 0.1 and 0.3 for
each cross section except those upstream or downstream of a bridge or culvert, 0.3 and 0.5 are
used for these cross sections. Flow that overtops the channel banks flows away from the model
and is not effective. Ineffective flow limits are placed at the channel banks to conservatively
assume all overtopping flows continue downstream. Cross section data is extracted from both
SCS Method
(cfs)
Rational Method
(cfs)
USGS Method
(cfs)
2-Year 0.0 5.1 0.9
10-Year 1.4 9.1 7.5
25-Year 3.5 12.2 15.5
50-Year 5.9 15.7 24.6
100-Year 7.8 17.9 36.5
Page 4 of 6
surveyed cross sections and the topographic survey completed for the northern part of the
property where the parking lot expansion is proposed. Both an existing and proposed model was
developed to compare the hydraulics of both; each model is explained in further detail below.
Existing Conditions
The 100-year flow is contained within the existing channel until it overtops a low point at
elevation 4661.95 just downstream (north) of the pedestrian bridge, see Figure 1. The existing
channel will pass approximately 20 cfs (between the 25 and 50-year flow) before spilling the low
point and ponding to the north near Catamount Street, see Figure 1. This overtopping flow will
eventually pond at two inlets located in the sag on Catamount Street and enters a storm drain
system. Excess flows will pond above these inlets and overtop the curb to the north and flow
through the parking lot of Comfort Suites and spill into a natural drainage that conveys runoff
into the East Valley Center Drive roadside ditch.
The average existing channel cross section has a bottom width that ranges from 2 to 6 feet, slide
slopes that vary from 4:1 and 6:1 and a depth ranging from 3 to 4 feet. With the exception of the
low point discussed above, the channel has adequate capacity to convey the 100-year flow. The
existing 48” CMP outfall pipe will pass 32.5 cfs before spilling the western channel bank and
flowing to the Catamount Street sag.
Proposed Conditions
The proposed channel centerline is drawn based on a preliminary site design, see Figure 2. The
proposed cross section for the relocated channel section is assumed have a base width of 4 feet,
4:1 side slopes and a depth equal to 4 feet. This geometry was chosen because it closely
represents the existing channel cross section.. The proposed slope of the channel is 0.50 %. The
manning’s roughness value for the proposed channel is set to 0.05 similar to existing conditions.
The inlet elevation of the proposed 48” CMP outfall pipe is assumed to be at elevation 4659.0
feet and was determined by extending the slope (0.49%) of the existing pipe to the proposed
channel connection point. The proposed outfall pipe will pass 56.3 cfs before spilling the
proposed upstream channel bank. This pipe has more capacity than the existing pipe because an
additional 1.3 feet of head is available before bank overtopping. Similar to existing conditions,
the 48” CMP outfall pipe is modeled in HY-8 and used to populate the downstream boundary
condition for the 2, 10, 25, 50 and 100-year flows.
The existing channel bank low point located just downstream of the pedestrian bridge will be
eliminated with the proposed design because a new channel will be constructed through this
reach. Eliminating this low spill point greatly increases the overall capacity of drainage system.
The proposed design has a capacity equal to 53.6 cfs prior to spilling the channel banks,
approximately 33.6 cfs more than existing conditions. The proposed channel section has an
estimated capacity equal to 280 cfs. The capacity of the system as a whole is controlled by the
48” CMP outfall pipe, not the proposed channel geometry.
Conclusion
Relocating the existing drainage channel to the proposed location increases the overall system
capacity by approximately 33.6 cfs. From the stormwater report completed by DOWL on May
18th, 2017 it is known that the peak discharge out of the proposed detention ponds for the 100-
year, 2-hr storm is 1.45 cfs. The proposed drainage channel has adequate capacity to handle the
Page 5 of 6
additional runoff generated from the proposed Costco development expansion and does not
increase flood hazards to the Costco property or adjacent landowners. Because the 48” CMP
outfall controls the system capacity and not the proposed channel, other channel geometries and
alignments can be constructed as long as the top of bank elevation is at a minimum 4-ft above the
proposed pipe invert at the channel end.
Page 6 of 6
ÞÞÞ
Þ ÞÞÞÞ
ÞÞÞÞÞÞÞÞÞÞÞÞÞÞÞÞSource: Esri, DigitalGlobe, GeoEye, i-cubed, Earthstar Geographics,
CNES/Airbus DS, USDA, USGS, AEX, Getmapping, Aerogrid, IGN, IGP,
swisstopo, and the GIS User Community
Drainage Basin
0 1,000 2,000500
Feet
Catron Street
Catamount Street
Cattail Street
Baxter Lane
Tschache LaneNorth 27th AvenueNorth 19th AvenueArea = 65.4 Acres
ATTACHMENT G – CROSS-SECTION FIGURE
WWW.DOWL.COM
CATAMOUNT SECTION AT WEST DRIVEWAY CURB - NON-CROWNED ROADWAY
CATAMOUNT SECTION AT WEST DRIVEWAY CURB - 3% STANDARD CROWN
OPTIONS TO INCREASE COVER OVER NEW PIPE ALIGNMENT
CATAMOUNT DRIVEWAY PROFILE
CROSS-SECTION AND
PIPE COVER ANALYSIS FIGURE 1