HomeMy WebLinkAbout7_Appendix E_Stormwater APPENDIX E
STORM1A/Al'E12 DRAINAGE REPORT
DESIGN REPORT
STORMWATER MANAGEMENT
BOULDER SUBDIVISION
Prepared for:
Four Corners Construction, LLC.
125 Central Avenue, Bozeman, MT 59718
Prepared by:
C&H Engineering and Surveying, Inc.
1091 Stoneridge Drive, Bozeman, MT 59718
(406) 587-1115
Project Number: 12662
APRIL 2014
INTRODUCTIONINTRODUCTIONTR�9DTJy� DUCTIGN
Design Report-Page 2 of 11
The Boulder Creek Subdivision is a proposed 63 lot subdivision located east of Laurel Parkway
and north of Annie Street. The 35.34-acre development is situated in the south half of Section 4,
Township 2 South, Range 5 East of P.M.M., Gallatin County, Montana. This project will require
connection to existing City of Bozeman water and sanitary sewer system.
STQRM'WATER MANAGEMENT
Storm water runoff from the subdivision will be conveyed to one of three detention facilities. A
plan view of the site highlighting the drainage areas and the storm water features is included in
Appendix A at the end of the report.
The southern half of the site will discharge into Detention Pond 5 running northwest near the
western subdivision boundary. This detention pond.is proposed to discharge into Baxter Creek.
The northwest section of the site will discharge to Detention Pond 6. This detention pond is
proposed to discharge into Baxter Creek. The northeastern section of the site will discharge to
Detention Pond 7. This detention pond is proposed to discharge into Baxter Ditch.
DETENTION POND 5
Detention Pond 5 has a volume of 6668 ft3 and will service Drainage Area#5 with a total area of
12.91 acres. The pre-development release rate is first calculated to ensure that post-development
discharge rates from the pond do not exceed pre-development rates.
Pre-Development Release Rate
The time of concentration (Te) is calculated as the flow time from the pre-developed most
hydraulically remote point in the drainage to the proposed discharge point. Pre-developed flow
conditions include overland flow over open land (C=0.20). The Tc is then used to calculate the
pre-development release rate.
Flow Iine length= 1,050 ft
Slope= 1.30%
Tc=49.97 mins, 0.833 hrs
Design Report-Page 3 of I
Ito=Intensity (10-yr freq.) = 0.64(TC)(-0.65)=0.721 in/hr
Q i o=CIA= (0.20) (0.721 in/hr) (12.91 acres) = 1.86 cfs
Drainage Area 45
The storm water runoff surface areas for Drainage Area #5 are calculated as follows. All runoff
"C"coefficients are from the City of Bozeman's DSSP.
Contributing Areas:
Right-of-way(C=0.73) =99,732 ft2
Open Land (C=0.20) =239,201 ft2
Lot Area(C=0.5) _ =226,620 ft2
Total = 562,553 ft2
= 12.91 acres
The composite runoff coefficient for the R/W Area is calculated as follows,this coefficient applies
to all R/W areas in the subdivision:
CR/w= [(0.95 x 42 ft)+ (0.20 x 18 ft)] /60 ft =0.73
The composite runoff coefficient for all of Drainage Area#1 is calculated as:
Ccomp= [(0.73 x 99,732 ft2)+ (0.20 x 239,201 ft2)+ (0.50 x 226,620 ft2)] /562,553 ft2=0.41
The maximum required storage is calculated in the table shown in Appendix A by varying the
storm duration with the associated storm intensity, and holding a release rate of 1.86 cfs with a C
coefficient of 0.41 for the entire drainage area.
Detention Pond 5 will have a volume of 6668 ft'which is adequate to handle the runoff from the
drainage area.
Inlet Pipe Sizing
The storm sewer pipes are designed to handle a 25-year storm event. The post-development time
of concentration is first calculated to determine the peak discharge:
Overland flow(1050 ft @ 1.30% slope, C=0.41)
Total Time of Concentration=36.03 min (0.601 hrs) Design Report-Page 4 0,f II
For a 25-year storm event, I25 = 0.78X-0-64=0.78 (0.601)-0.64= 1.081 in/hr
Q25 = CIA = 0.41 (1.08 in/hr) (12.91 acres) = 5.72 cfs
A 14-inch PVC Schedule 40 pipe is proposed for the storm sewer pipe for Drainage Area#5. The
capacity of a 14-inch PVC at the proposed slope is checked using Manning's equation:
Qfuli = (1.486/n)AR2/3Sv2
Manning's n=0.013 for PVC
Slope = 0.0165 ft/ft
A=area= (3.14/4)d 2=(3.14/4)(14/12)2= 1.0684 ft2
P =perimeter=2(3.14)r=2(3.14)(7/12) = 3.6633 ft
R=hydraulic radius =A/P= 1.0684/3.6633 = 0.2916 ft
R2/3 =0.4380 ft
S1!2=0.1285 ft/ft
Qfu(1_ (1.486/0.013)(0.1.0684)(0.4380)(0.1285) =6.87 cfs
The 14-inch PVC will be adequate to handle the storm water discharge rates to the detention pond.
Outlet Control Structure Sizin
The outlet control structure in Detention Pond 5 needs to limit the release rate to the
predevelopment runoff rate of 1.86 cfs. The slot width is sized using the following equation:
Q =CLH3/2
The maximum pond depth is 1.5 ft which represents the maximum head.
Therefore:
L= (1.86 cfs)/(3.33 x 1.53/2)=0.3040 ft
The weir needs to be 3.65"wide in order to limit the release rate to 1.86 cfs.
Outlet Structure Pine Sizing
The outlet structure discharge pipe must be sized to handle the maximum flow of 1.86 cfs into the
structure. A 10-inch PVC pipe is proposed for the discharge pipe. The capacity of a 10-inch PVC
line is calculated as follows: Design Report-Page 5 of 11
Qftai =(1.486/n)AR213Su2
Manning's n =0.013 for PVC Pipe
Minimum Slope =0.0165 ft/ft
A =area= (3.14/4)d 2=(3.14/4)(10/12)2= 0.5451 ft2
P =perimeter=2(3.14)r=2(3.14)(5/12)=2.6180 ft
R=hydraulic radius =A/P = 0.5451 /2.6180=0.2082 ft
R2f3 =0.3513 ft
S =0.0165 ft/ft
S12=0.1285 ft/ft
Qfuu=(1.486/0.013)(0.5451)(0.3513)(0.1285) =2.80 cfs
The 10-inch PVC pipe will be adequate to handle the discharge rates from the outlet structure.
DETENTION POND 6
Detention Pond 6,located in the northwestern area of the subdivision,is proposed to have a storage
volume of 11,397 ft3, and will service Drainage Area #6 with a total area of 494,476 ft2. The
detention pond will discharge to Baxter Creek.
Pre-Development Release Rate
The time of concentration (Tc) is calculated as the flow time from the pre-developed most
hydraulically remote point in the drainage to the proposed discharge point. Pre-developed flow
conditions include overland flow over open land (C=0.20). The Tc is then used to calculate the
pre-development release rate.
Flow line length= 850 ft
Slope= 1.25%
Tc=45.55 rains, 0.759 hrs
ito=Intensity (10-yr freq.)=0.64(Tc)(461)= 0.766 in/hr
Qio= CIA =(0.20) (0.766 in/hr) (11.35 acres) = 1.74 cfs
Drainage Area #6 Design Report- Page 6 of 11
The storm water runoff surface areas for Drainage Area 46 are calculated as follows:
Contributing Areas:
Right-of-way(C=0.73) = 152,927 ft2
Open Land (C=0.20) =48,759 ft2
Lot Area(C=0.50) =292,790 ft2
Total =494,476 ft2
= 11.3516 acres
The composite runoff coefficient for all R/W areas is 0.735 as calculated above. The composite
runoff coefficient for all of Drainage Area#6 is calculated as:
Ccomp = [(0.73 x 152,927 ft2) + (0.20 x 48,759 ft2) + (0.50 x 292,790 ft2)] /494,476 ft2=
0.54
The maximum required storage is calculated in the table shown in Appendix A by varying the
storm duration with the associated storm intensity, and holding a release rate of 1.74 cfs with a C
coefficient of 0.54 for the entire drainage area.
Detention Pond 6 will have a volume of 11,397 ft3 which is adequate to handle the runoff from the
drainage area.
Inlet Pine Sizing
The storm sewer pipes are designed to handle a 25-year storm event. The post-development time
of concentration is first calculated to determine the peak discharge:
Overland flow (850 ft @ 1.25% slope, C=0.54)
Total Time of Concentration=25.61 min(0.427 hrs)
For a 25-year storm event, Its =0.78X-0-64=0.78 (0.427)"0.64= 1.345 in/hr
Q25=CIA= 0.54 (1.345 in/hr) (11.35 acres)= 8.24 cfs
A 16-inch PVC Schedule 40 pipe is proposed for the storm sewer pipe for Drainage Area#6. The
capacity of a 16-inch PVC at the proposed slope is checked using manning's equation:
Design Report-Page 7 of 11
Qf„u = (1.486/n)ARzi3Slr2
Manning's n = 0.013 for PVC
Slope =0.0165 ft/ft
A=area= (3.14/4)d 2= (3.14/4)(16/12)2= 1.3956 ft2
P =perimeter=2(3.14)r=2(3.14)(8/12)=4.1867 ft
R=hydraulic radius=A/P = 1.3956/4.1867 =0.3333 ft
R2" =0.4790 ft
Si/2= 0.1285 ft/ft
Qf,,u= (1.486/0.013)(1.3956)(0.4790)(0.1285) =9.82 cfs
The 16-inch PVC will be adequate to handle the storm water discharge rates to the detention pond.
Outlet Control Structure Sizing
The outlet control structure in Detention Pond 6 needs to limit the release rate to the
predevelopment runoff rate of 1.74 cfs. The slot width is sized using the following equation:
Q=CLH312
The maximum pond depth is 1.5 ft which represents the maximum head. Therefore:
L= (1.74 cfs) /(3.33 x 1.5312) =0.2844 ft
The weir needs to be 3.41"wide in order to limit the release rate to 1:74 efs.
Outlet Structure Pine Sizing
The outlet structure discharge pipe must be sized to handle the maximum flow of 1.74 cfs into the
structure. A 10-inch PVC pipe is proposed for the discharge pipe. The capacity of a 10-inch PVC
line is calculated as follows:
Qf„u = (1.486/n)AR2i3Sv2
Manning's n =0.013 for PVC Pipe
Minimum Slope = 0.0165 ft/ft
A= area= (3.14/4)d 2= (3.14/4)(10/12)2=0.5451 ft2
P =perimeter=2(3.14)r=2(3.14)(5/12)=2.6180 ft
Design Report- Page 8 of I 1
R=hydraulic radius= A/P = 0.5451 /2.6180= 0.2082 ft
R2" =0.3513 ft
S = 0.0165 Mt
Sv2 = 0.1285 ft/ft
Qeuet= (1.486/0.013)(0.5451)(0.3513)(0.1285) =2.80 efs
The 10-inch PVC pipe will be adequate to handle the discharge rates from the outlet structure.
DETENTION POND 7
Detention Pond 7 is proposed to have a storage volume of 2,252 ft3,and will service Drainage Area
#7 with a total area of 172,781 W. The detention pond will discharge to the Baxter Ditch.
Pre-Development Release Rate
The time of concentration (Tc) is calculated as the flow time from the pre-developed most
hydraulically remote point in the drainage to the proposed discharge point. Pre-developed flow
conditions include overland flow over open land (C=0.20). The Tc is then used to calculate the
pre-development release rate.
Flow line length= 575 ft
Slope= 1.35%
Tc= 36.52 mins, 0.609 hrs
lio =Intensity (10-yr freq.)=0.64(Tc)t-0.61>=0.884 in/hr
Q i o= CIA= (0.20) (0.884 in/hr) (3.97 acres) = 0.70 efs
Drainal4e Area #7
The storm water runoff surface areas for Drainage Area#7 are calculated as follows:
Contributing Areas:
Right-of-way (C=0.73) = 14,803 ft2
Open Land (C=0.20) =45,586 ft2
Lot Area(C=0.50) = 112,392 ft2
Total = 172,781 ft2
Design Report-Page 9 of 11
= 3.9665 acres
The composite runoff coefficient for all R/W areas is 0.73, as calculated above. The composite
runoff coefficient for all of Drainage Area 43 is calculated as:
Ccomp= [(0.73 x 14,803 ft)+(0.20 x 45,586 ft)+ (0.50 x 112,392 ft)] /172,781 fl2=0.44
The maximum required storage is calculated in the table shown in Appendix A by varying the
storm duration with the associated storm intensity, and holding a release rate of 0.70 cfs with a C
coefficient of 0.44 for the entire drainage area.
Detention Pond 7 will have a volume of 2,252 R3 which is adequate to handle the runoff from the
drainage area.
Inlet Pipe Sizing
The storm sewer pipes are designed to handle a 25-year storm event. The post-development time
of concentration is first calculated to determine the peak discharge:
Overland flow(575 ft @ 1.35%slope, C=0.44)
Total Time of Concentration=24.99 min(0.417.hrs)
For a 25-year storm event, I25 =0.78X-0-64=0.78 (0,417)-0•64= 1.366 in/hr
Q25 = CIA= 0.44 (1.366 in/hr) (3.97 acres) =2.38 cfs
A 10-inch PVC Schedule 40 pipe is proposed for the storm sewer pipe for Drainage Area V. The
capacity of a 10-inch PVC is checked using Manning's equation:
Qui = (1.486/n)AR2i3Sii2
Manning's n =0.013 for PVC
Slope = 0.0165 ft/ft
A= area=(3.14/4)d 2= (3.14/4)(10/12)2=0.5451 ft2
P=perimeter= 2(3.14)r=2(3.14)(5/12) =2.62 ft
R=hydraulic radius=A/P =0.5451 i 2.62 =0.2083 ft
R211 =0.3496 ft
Design Report-Page 10 of J 1
S"2=0.1285 ft/ft
Qeuai = (1.486/0.013)(0.5451)(0.3496)(0.1285) =2.80 cfs
The 10-inch PVC will be adequate to handle the storm water discharge rates to the detention pond.
Outlet Control.Structure Sizing
The outlet control structure in Detention Pond 7 needs to limit the release rate to the
predevelopment runoff rate of 0.70 cfs. The slot width is sized using the following equation:
Q=CLH"2
The maximum pond depth is 1.5 ft which represents the maximum head.
Therefore:
L= (0.70 cfs)/(3.33 x 1.92)=0.1144 ft
The weir needs to be 1.37"wide in order to limit the release rate to 0.70 cfs.
Outlet Structure Pipe Sizing
The outlet structure discharge pipe must be sized to handle the maximum flow of 0.70 cfs into the
structure.An 8-inch PVC line is proposed for the discharge pipe.As calculated above,the capacity
of an 8-inch PVC line flowing full is 1.5431 cfs, which is adequate to handle the anticipated
discharge rate.
Design Report-Page 11 of 11
AREA 5-DETENTION POND
Pre-Developed'Condition
Overland Flow Time
Flow Length= 1050.00
Slope(0/0)= 1 1.30
C coeficiebt 0.20
Cf = 1.00
To=(1.87-(1.1
To(min)= 49.96865
Total Basin To(hr)= 0.833
Rational Method For Calculating Flow Rate
Storm Return Interval= 10
I(in/hr)for 10 year storm 1=0.64t(0 651 0,721
Rational Method: Q,=C*I*A
C coefficient= 0.20
1(in/hr)= 032
Area(ft)= 562553.00
Area(ac)= 12.9144
Total Runoff For 1 Oyr Storm(ft%)= 1.86 =Basin To
Post Developed Weighted C Calculation
Landscaped C= 0.2 ROW C= 0,73 Lot C= 0.5
Area(ft)= 239201 Area(W)= 99732 Area(ft)= 226620
Area(ac)= 5.49 Area(ac) 2.29 Area(ac) 5.20
Weighted C= 0.41
Weighted C= 0.41
Total Area= 12.91 acres
Release Rate = 1.86 efs
Storm Storm. Runoff Release Required
l-ength(min) Len gth(hrs Intensity Q(future) Volume Volume Storage
17 0.28 1,45 7.76 7916.24 1&99J02 6017:22
18 0.30 1.40 7.48 076.20 2Q10.72 6065.47
19 0.32 1.35 7.22 8230-48 2122.43 0108.05
20 0.33 1.31 U.8 8379,58 2234.14 6145,44
21 0,35 1,27 6.76 8523.90 2345.84 6178.06
22 0,37 1.23 6.56 8663.92 2457.55 6206.27
23 0'38 1.19 6.38 �8799.67 2569.26 6230.41
24 0A0 1.16 6.20 89�31.73 2680.96 6250.76
25 0,42 1.13 6.04 906026 2792,67 6267.59
26 0A3 1.10 5.89 918549 2004,38 6281A 1 1
27 0.45 1.08 5.75 930.63 3010.00 6291.54
28 0.47 1.05 5.61 9426.8.6 3127,7,9 6299.06
29 0.48 1.03 5.48 9648.35 3239.50 6303.85
31 0.52 0,98 5.25 9768.73, 3462,91 630 02
32 0.53 0.96 5.14 9877.89 3574.62 6303.27
33 0155 0,94 5.04 9984.85 3686,33 6298.52
34 0.57 0.93 4.95 10089.72 3798.03 629,1,69
35 0.58 0.01 4,86 10192.61 3909.74 6282.87
36 0.60 0.89 4.77 1029160 4021.45 6272.16
37 0:62 0.88 4.68 10392.79 4133.15 6259.84
38 0.63 0,86 4.60 10490.25 4244.86 6245.39
39 0.65 0.85 4.52 101586:06 4356.57 6229.49
'
- AREA S ~i�����i�g
` -
Post-Developed Conditions
Overland Flow Time
Flow Length= 1850.00
Smpo (ro = 1.30
Ccoeficient 0.41
Cf = .1O
Tc= /1.G7^(1-1-C^CO(L)<1'2>\/(e)("m)
To(min)= 38.0.3295
Total Basin Tc(hh= 0.001
Rational Method For Calculating Flow Rate
Storm Return Interval 25
\ (in/hr)for 25 year storm |=D.7Ot(u-wV 1.081
Rational Method: {J= C°|*A
Coneffioient= 8.41
< � l (in/hr)= 1.08
-~- Araa (ft) = 502553.00
\_ Anae(ac) = 12.9144
Total Runoff For 2Sv Storm *t3/s\ = 5.72 = BeanTc
�~~�
AREA 6-DETENTION PONE)
Pre-Developed Conditions
Overland Flow Time
Flow Length= 850.00
Slope{%)= 1.25
C.coeficient= 0.20
Cf = 1.00
Tc=
Tc(min)= 45.5502
Total Basin Tc(hr)= 0.759
Rational Method For Calculating Flow Rate
Storm Return interval= 1.0
(in/hr)for 10 year storm i=0.64t(-") 0.766
Rational Method: Q=C*I*A
C coefficient= 0.20
1(inthr)= 0.77
Area(ft)= 494476.00
Area(ac)= 11,3516
Total Runoff For 10yr Storm(ft3/s)= 1.74 =Basin Tc
Post Developed Weighted C Calculations
Landscaped C= . 0.2 ROW C= 0.73 Lot C= 0.5
Area(fe)= 48759 Area(fe)= 152927 Area(fe)= 292790
Area(ac)= 1.12 Area(ac)= 3.51 Area(ac)= 6.72
Weighted C= 0.54
Weighted C= 0.64
Total Area= 11.35 acres
Release Rate = 1.74 cfs
Storm Storm Runoff Release Required
Length(min) Len th hrs Intensity Q future Volume Volume Storage
21 0,35 1.27 7.76 '9868.45 2189.86 7618.60
22 0.37 1.23 7.55 9969,46 2294,14 7675.33
23 0.38 1.19 7.34 10125.78 2396.41 7727.37
24 0.40 1.16 7A 4 10277.74 2502.69 7775.05
25 0.42 1.13 6.95 10425.64 2606.97 7818.67
26 0:43 1.10 6.78 10569.74 2711.25 7858.49
27 .0.45 1.08 6.61 10710.29 2815.63 7894,76
28 0:47 1.05 6.46 1,0847.49 2019.81 7927.68
29 0.48 1.03 6.31 1098154 3024.:09 79,57.45
30 0.50 1,.00 6.17 11112.61 3128.37 7984.25
31 0.52 0.98 6.04 11240.88 3232.65 8008.23
32 0.53 0,96 5.92 11366.4.9 3336.93 80A56
33 0,56 0.04 6.80 11489.57 3441.20, 8448.36
34 0,57 0.93 5.69 11610,24 3545.48 8064.76
35 0.58 0.91 5.59 1172&64 3649.76 8078.88
36 0.60 0.89 5.48 11844.85 8754.04 8090,81
37 0.62 0,88 5139 11958.99 3858132 8100.67
38 0.63 0:86 519 12071.13 3962.60 8108.53
39 .0.66 0:85 5.21 12181.38 4066.88 8;114.50
40 0.67 0.83 5.12 12289.80 4171.16 811*8.64
41 0.68 0.82 5.104 12390A7 4275.44 8121.04
43 0.72 0,79 4.89 120,04.85 4483,99 8120.86
44 0.73 0,78 4.81 12706.68 4588.27 8118.41
45 0.75 0.77 4.74 12807.02 4692.55 9114.47
46 0.77 0,76 4.68 12905:92 4796.83 8109.09
47 0.78 0.75 4.61 13003A3 4901.11 8102.32
48 0.80 0.74 4.55 13099.60 60.05.39 8094.22
`
)
AREA 6 'inlet sizing
Post-Develooed Conditions
Overland Flow Time
Flow Lan�� =
_�_ 850.0,0
Slope 1.25
`,uoevme/u= 0.54
Cf =
1.10
Te= (1.87~Y1.1-C*Cf (L)('m) /�`vU«@
Tchnh1\= 25.80933
Total Bas|DTc(hr) 0.427
StormRational Method For Calculating Flow Rate
" .~owx/ mu*vu/= 25
| Un/hr for 25 year storm 1=0. 1.345
Rational Method: C>= C*I*4
Ccoefficient= 0.54
/ | (��h=
` ' 1.05
`
Area ='- y� 494476.00
` °«eu \mc/ = 11.3618
Total Runoff For 25yr Storm (*»/s) = 824 = 8esinTo
`
-
``''
AREA 7-DETENTION POND
Ere-Developed Conditions
Overland Flow Time
Flow Length= 575.00
Slope 1.35
C coekient= 0.20
Cf = 1.00
Tc.=(1.87*(J.I-C*Co(�)(112))/(s)(111)
Tc(min)= 36.5.1518
Total Basin Tc(hr)= 0.609
Rational Method For Calculating Flow Rate
Storm Return Interval= 10
I(in/hr.)for 10 year storm 1=0.64t"") 0.884
Rational Method: Q=C*I*A
C coefficient= 0,20
1(in/hr)= 0,88
Area(fC)= 172781.00
Area(801)= 3,9665
Total Runoff For 10yr Storm(ft%)= 0.70 =Basin Te
post Developed Weighted C Calculations
Landscaped C= 0.2 ROW C= 013 Lot C= 0.5
Area(fe)= 4558.6 Area(W)= 14808 Area(ft)= 112392
Area(ac)= 1.05 Area(ac)= 0.34 Area(ac)= 2.58
Weighted C= 0.44
Weighted C= 0.44
Total Area= 3.97 acres
Release Rate 0.70 cfs
Storm Storm Runoff Release Required
Length min) Length(hrs Intensity Q(future) Volume Volume Storage
14 0-23 1.65 2.88 241,9.25 688.96 1830,29
16 0.25 1.58 2.75 2478.$8 6,31.03 1847.35
16 0.27 1 i5i 2.64 2535.00 673.10 1861.90
17 0,28 1.45 2.54 2589.36 715.17 1874.19
18 020 1.40 2.4.5 2641 k8 757,23 1884.45
19 0.32 135 2.36 2692.15 799:30 189Z64
20 0.33 1.31 2.28 2740.92 841-37 1890.64
21 0,35 1.27 2.21 2708.12 883.44 1,904.68
22 0.37 1.23 2.15 2833.89 925,51 1908.38
23 0.38 1.19 2,09 2878.33 967,58 101.0.75
2
26
2.7 0.45 1.08 1.88 3044.48 1185.85 1908,62
28 0.47 11.05 1.84 3083.48 1177.92 1905.55
20 0.48 1.03 179 3121:58 1219.99 1901.59
30 0.50 1.00 1.75 3158.84 1262.0,6 .1896.78
31 0.52 0.98 1,72 3195.30 1304.13 1891.17
32 0.53
U6 1.68 3231.01 1346.20 1884A1
33 0.55 0.94 1.65 3265.99 1388.26 1877.73
34 0,57 0.93 1.62 33000 1480,33 1869.96
AREA 7 - inlet sizing
Post-Develooed Conditions
Overland Flow Time
Flow Length= 575.00
Slope(%) = 1.35
C coeficient= 0.44
Cf = 1.10
Tc= (1.87*(1.1-C*Cf)(L)("2))/(s)('/3)
Tc(min)= 24.99261
Total Basin Tc(hr) = 0.417
Rational Method For Calculatinq Flow Rate
Storm Return Interval= 25
1 (in/hr)for 25 year storm 1=0.78t(-0.64) 1.360
Rational Method: Q = C*I*A
C coefficient= 0.44
1 (in/hr)= 1.37
Area (ft)
172781.00
Area (ac) = 3,9665
Total Runoff For 25yr Storm (ff1s)= 2.38 Basin Tc
DRAINAGE PLAN
BOULDER CREEK SUBDIVISION
LOCATED IN THE S 112 OF SECTION 4, T. 2 S., R. 5 E.
OF P.M.M., CITY OF BOZEMAN, GAL LA TIN COUNTY, A40NTANA
LEGEND
IIIIIIIII M= DRAINAGE AREA BOUNDARY V,
E 1/4 GCQ SEC 4
DRAINAGE ARROW
FF
LOT 5 LOT-4 L0T 3 LOT
an
LN 2,
q
SAMA ANE
WN
LOT 7
LOT 3
LOT-6
E N
# T 6 54 ably
OPEN J=6
I 1 1!%.1 PWAI
MD Pusuc Kcm
I Tr D RA
LOT 5 mn%
tlx." LOT 5 P AT M.ON
AT C
4,
L
LOT 4
wz� L&S 4 2
LOT 3
LOT 3
E 2
2
LOT 2
4�3 W LOT ttis.QY LOT 1
LOT I
LOT I
,17
a726
SHER OD WAY
fl LOT I LOT I LOT I LOT I
LOT'1 LOT 2 LOT,3
VAA
LOT 2 LOT 2 LOT 2 LOT.2
wzx
�:W 4
WOOD 'YA,
14
40
Ems
LOT 3
N,
LOT 3 LOT LOT�3
=4 t-' Z-1
PUBLIC PARK 1
7&s�
LOT 4
447
OT LOT 4
v
PRWATE CO
PWATE COMON
1px
O�M SPACE I
QC�a 'KCE�
�3 LOT 5 C_
VA4
Pid"ATE COMMON
LOT 6 LOT a
LOT 6
P.
ffi Ad E-
RW",
LOT LOT 7 7 LOT 1 RA #1 , W.7.
EXISTING POND "Z.1
P
LOT 8 LOT a LOT 8
Scale In Feet
80 0 80 LOT 9 ,T 9 LOT 4
S
24 0 24
Scale In Meters r
!%-Wmgjw- a73a.730
_
DRAWING DATE: 5/7/14
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