HomeMy WebLinkAboutScan of Stormwater Reports DESIGN REPORT
STORMWATER MANAGEMENT
ROSA APARTMENTS MASTER SITE PLAN
Prepared for:
Rosa Construction, Inc.
125 Central Avenue, Ste. 1 A
Bozeman, MT 59718
Prepared by:
C&H Engineering and Surveying, Inc.
1091 Stoneridge Drive, Bozeman, MT 59718
(406) 587-1115
Project Number: 16723
November 2016
{
INTRODUCTION
The Rosa Apartments Master Site Plan project proposes to develop Lot 1 of Traditions Phase 3
into multiplex 3-story apartment buildings. The property is currently located in the City of
Bozeman and is zoned as R-4 with an Open Space lot along the western edge of the site.
Construction of Oak Street to City standards is underway and stormwater improvements have
been completed including installation of a 36"by 58"RCP arch culvert that flows under the Oak
Street right-of-way conveying Baxter Ditch. There is a detention pond in the northwest of the
site located in the open space which will collect drainage from the site and also from the Oak
Street right of way and Rosa Way public access and utility easement. This pond discharges
through an existing outlet structure to Baxter Ditch to the west. A combination of site grading,
curb and gutter, storm inlets and piping, on-site retention, and the existing detention pond will be
used to manage stormwater runoff on the site. Supporting stormwater calculations and a
breakdown of each drainage area are included in Appendix B for reference. Previous reports
pertinent to the Rosa Apartments Master Site plan have also been included at the end of this
section and these include: Rosa Subdivision (June 2006) and Traditions Phase 3 Oak Street
Improvements (June 2015)
CONTRIBUTING DRAINAGE AREAS TO EXISTING
STORMWATER DETENTION POND
The site was split into three drainage basins as shown on the attached Drainage Area Map included
in Appendix A. All drainage from Drainage Areas 1 and 2, Oak Street, Twin Lakes Avenue,
Sherwood Way and Rosa Way flow into the existing detention pond located in the open space area
to the west of the site. The weir in the existing detention pond outlet structure has been sized to
account for all flow from the future fully developed site and is adjustable up to 8 inches in width
per the 14170 Oak Street Improvements stormwater report dated August 2015. All gutter
capacities were checked along Oak Street and Twin Lakes Avenue in the original stormwater
report submitted for the Oak Street Improvements project and there is a gutter flow spreadsheet
included in Appendix B which assesses the gutter capacity of Rosa Way. The existing detention
pond has a volume of 10,798 cubic feet at 1.5' in depth. This pond will be resized to 12,058 cubic
feet during construction of Rosa Way.
At full buildout Drainage Area 2 will be collected by a catch basin located in the northwest of the
north parking area and Drainage Area 1 will flow into storm inlets: CB3 and CB4 located at the
northwestern end of Drainage Area 1 near the parking area and Rosa Way intersection. All catch
basins and inlets will convey stormwater via a 15" pipe to the existing detention pond. The 15"
diameter PVC pipe has a 4.91 cubic feet per second capacity which will be adequate to convey
drainage from each individual catchment. The pipe capacity spreadsheet has been included in
Appendix B located at the end of this report.
f
APPENDIX A
DRAINAGE AREA MAP
C
1Pl.-.El POLE
1 .1—.—r;Yet— ` 1 µ`F.— —__ --_ _-- :.F.0 E__lll.'.�•�. . fiY --- C�ir— —_ -- --_ .. ...__-.— r= .. �-- •i_ .
1 ,' GILDER 474, EST--( AK STREET 474j z
_ _ __
CREEK
C�"F
.s_ mr r.ji`�i .G
1L Vcrll1 J L52 LS
,x A53 SF 9, t
/ O I �i tr-Eabr BLDGI Aa SF BLOG2 _I — — — -- _ -- —— — — -- — 91 8
415o SF e.150 SF i to'n
sr-
/ ].lex SF
�a Yt='_nFST - 1.
\.4740
111
,
11 \ I ,167• I e.150 SF ra
5aMS SF
I II j I
I
Q BLOG4
\ II II �,
M
�� 1 III IIII I ${j DRAINAGE aOGIO 'III 1
\1 111 I11 o, m SF
AREA 2 I II I A
1 I Il 11` 3,t5F i II
I I i
—
_ T
1 1111 II`1 { P /G7 A3 .. 310 SF
1.17
1395F 45 _ x.329'SF ill I IIi fLnhJ C'[f?5 'e;:=i
„ 4744 Al II 1—
s
n1 p1
t2( - 1 x II __—
'�bf
I DRAINAGE BumPK I
I I 8.1m s' I r I I
\ 5a 0 AREA 1
1 ✓ BLOG8
C. `` 1J 41 t5I.S5
`LSS
BT
1 ui t 3.7ax
\ i 1 �
I_ .1 x 1 1.eo,s.. 5 1 ,l 1 _I p
OPEN SP E t 1a� ; t 9 i ,3 I C`_I
49.05 Sq.FL
p ....._ ._. I I L
1.139 I
BLDG7
c rr r_1 ;; s 43eGs6F L59 LOT 5 e,15o Sc
' FL J"l': 4T4+`a I Rye SF 9.M SF li
—
t132.05-�- —
67t-4-20a'4rl4` M1 ---�---- — — — —
•pa cp/50 —11 -- SHERWOOD WAY
s11- —_ J-•�.. •s��.—mot { :c rnu +—.:;— - --- J —
T Issue Date:
C. —
I
APPENDIX B
SUPPORTING CALCULATIONS
c
DETENTION POND (Twin Lakes, Rosa Way, Drainage Area 1, Sherwood Way, West Oak)
REQUIRED VOLUME
2. Calculate Area and Weighted C Factor(Post-Development)
Contributing Area C Area(ft2) C*Area
Oak Street 0.82 26588 21802 Composite ROW: C
Twin Lakes Avenue 0.73 22204 16209 Coak= ((0.95*38)+(0.2*7))/45 0.83
Rosa Way 0.82 39298 32224 CT"i.= ((0.95*21.5)+(0.2*7))/30 0.73
Sherwood Way a82 15709 12881 CSherwood= ((0.95*21.5)+(0.2*7))/30 0.73
Drainage Area 2 0.72 145564 104679
Drainage Area 1 a78 138001 107310 Cosa= ((0.95*41)+(0.2*7))/60 0.67
Total 387364 295106
A=Area(acres) 8.8927
C=Weighted C Factor 0.76
3. Calculate T, (Pre-Development)
Tc Overland Flow
Tc=1.87(1.1-CCf)D12/Slr3
---------------------------------------------
;Storm
S=Slope of Basin(%) 1 ;Return(yrs) Cf
C=Rational Method Runoff Coefficient 0.2 2 to 10 1
Cf=Frequency Adjustment Factor 1.1 111 to 25 1.1
D=Length of Basin(ft) 886 126 to 50 1.2
51 to 100 1.25
Tc(Pre-Development)(minutes) 49
--------------------------------------------
4. Calculate Rainfall Intensity(Duration=Pre-Development Tc)
i=0.64e-"(10-yr Storm, Fig. 1-3,COB Design Standards)
x=storm duration(hrs) 0.82 (Tc Pre-Development)
i=rainfall intensity(in.1hr.) 0.73
5. Calculate Runoff Rate(Pre-Development)
Q=CiA
C=Rational Method Runoff Coefficient 0.2:(open land)
i=rainfall intensity(in./hr.) 0.73 (calculated above)
A=Area(acres) 8.89 (calculated above)
Q=Runoff Rate (Pre-Development)(cfs) 1.30
6. Calculate Required Pond Volume
Total Area(acres)= 8.89 acres
Weighted C= 0.76
Discharge Rate(cfs)= 1.30 cfs(Equal to Pre-Development Runoff Rate)
Duration(min) Duration(hrs) Intensity Q.'"(cfs) Runoff Release Required
(in/hr) Volume Volume Storage(W)
59 0.98 0.65 4.38 15517 4597 10920'
70 1.17 0.58 3.92 16474 5455 11020
71 1.18 0.57 3.89 16556 5533 11024
72 1.20 0.57 3.85 16637 5610 11027
73 1.22 0.56 3.82 16718 5688 11030'
74 1.23 0.56 3.78 16798 5766 11031
75 1.25 0.55 3.75 16877 5844 11033
76 1.27 0.55 3.72 16955 5922 11033
77 1.28 0.54 3.69 17033 6000 11033
78 1.30 0.54 3.66 17110 6078 11032
79 1.32 0.54 3.63 17187 6156 11031
80 1.33 0.53 3.60 17262 6234 11029
81 1.35 0.53 3.57 17338 6312 11026
82 1.37 0.52 3.64 17412 6390 11023
83 1.38 0.52 3.51 17486 6468 11019
OUTLET STRUCTURE SLOT
Q=CLH 312
QExISTING POND=Discharge(cfs) 2.71
QPOND 1=Discharge(cfs) 1.30
{ QTOTALAT POND 1 WEIR=Discharge(cfs) 4.01
C=Weir Coefficient 3.33 (per COB Design Standards)
H=Head(ft) 1.5;
L=Horizontal Length(ft) 0.66
L=Slot Width(inches) 7.9
i
DRAINAGE AREA ROSA WAY
Contributing Area C Area(f 2) C * Area
ROW 0.82 35358 289041
Total 35358 28993.6
C=Weighted C Factor 0.81;
A=Area(acres) 0.81
Required Gutter/Pipe Capacity (257yr Storm)
Tc Overland Flow
Tc= 1.87 (1.1-CCf)D"/S1/3
Storm
S = Slope of Basin (%) 0.5 Return Cf
C=Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf=Frequency Adjustment Factor 1.1 11 to 25 1.1
D =Length of Basin (ft) 15 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow(minutes)= 6.52
Tc Gutter Flow
Tc=L/V/60
V = (1.486/n)R /3 Sv2
n=Mannings Coefficient _003'
R=Hydraulic Radius A/P (ft) 0_13 (0.15'below top of curb)
S = slope (ft/ft) 0.010
L=length of gutter(ft) 520
V=mean velocity(ft/s) 3.001
Tc Gutter Flow(minutes)= 2.89
Tc Total (Overland+ Gutter) = i; y 9.4-1
Q = CIA
C=Weighted C Factor 1 0.82!(calculated above)
I= 0.78 Tc o.64(in/hr) 2.551
A=area(acres) 0.81:
Qrequired (Cfs)_ __.1.70'
Provided Gutter Capacity(flowing at 0.15' below ton of curb)
Q =(1.486/n)AR2i3 '
n=Mannin s Coefficient `"'
-0.01311
A=area(ft2) 1.24
P =wetted perimeter ft
R=Hydraulic Radius A/P (ft) 0.131
S =slope (ft/ft) 0.005
Qprovided (Cfs) _ - 2.631
GUTTER IMSADEQUATE CAPACITY
i
DRAINAGE AREA 1
r-,
Contributing Area C Area(ft) C * Area
Drainage Area 1 0.7776 138001 , 107310'
Total 138001 107310
C=Weighted C Factor
A=Area(acres) 3.17
Required Gutter/Pipe Capacity (257yr Storm)
Tc Overland Flow
Tc= 1.87 (1.1-CC)D1/2/Sii3
Storm
S = Slope of Basin (%) 0.5 Return Cf
C=Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf=Frequency Adjustment Factor 1.1 11 to 25 1.1
D =Length of Basin (ft) 159 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow(minutes) = 21.241
Tc Gutter Flow
Tc=LN160
V=(1.486/n)R2' S"
n=Mannings Coefficient 0.013
R=Hydraulic Radius A/P (ft) 0.13 (0.15'below top of curb)
S =slope (ft/ft) 0.010
L=length of gutter(ft) 365
V=mean velocity (ft/s) 3.00.
Tc Gutter Flow(minutes)= 2.03
Tc Total (Overland+Gutter)= 23.27
Q= CIA
C=Weighted C Factor 0.78 (calculated above)
I= 0.78 Tc o.6a(in/hr) 1.43
A=area(acres) 3.17
Qrequired (efs) = 3.52
r
DRAINAGE AREA 2
Contributing Area C Area(ft) C * Area
Drainage Area 1 0.71913 145564 104679!
Total 145564 104679!
C =Weighted C Factor 0.72
A=Area(acres) 3.34'
Required Gutter/Pipe Capacity (25-yr Storm)
Te Overland Flow
Tc= 1.87 (1.1-CCf)D1/2/S1/3
Storm
S = Slope of Basin (%) 0.5 Return Cf
C=Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf=Frequency Adjustment Factor 1.1 11 to 25 1.1
D =Length of Basin (ft) 150 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow(minutes)= 20.63
Tc Gutter Flow
Tc=LN/60
V =(1.486/n)W" S"
n=Mannings Coefficient 0.013
R=Hydraulic Radius A/P (ft) 0.13;(0.15'below top of curb)
S = slope (ft/ft) 0.018
L=length of gutter(ft) 532
V=mean velocity(ft/s) 3.97'
Tc Gutter Flow(minutes)= 2.24
Tc Total (Overland+ Gutter)= 22.87:
Q = CIA
C= Weighted C Factor 0.72 (calculated above)
I= 0.78 Tc o.6a(in/hr) 1.45'
�; A=area(acres) 3.34
Qrequired (CfS) = 3.48
MANNING'S EQUATION FOR PIPE FLOW
Project: 12" Storm pipe Location: Storm Inlets
By: ADM Date: 7/23/2015
Chk. By: Date:
Clear Data
0 Entry Cells
INPUT
________ D= 15 inches
d= 14.07 inches
Mannings Formula d 10 n= 0.013 mannings
D 0= 57.7 degrees
Q=(1.486/n)ARhv3S l iz
S= 0.005 slope in/in
R=A/P
A=cross sectional area
P=wetted perimeter V=(1.49/n)Rh2J3S112
S=slope of channel Q=V X A
n=Manning's roughness coefficient
Solution to Mannings Equation Manning's n-values
Wetted Hydraulic
Area,ft2 Perimeter,ft Radius,ft velocity ft/s flow,cfs PVC 0.013
1.20 3.30 0.36 4.11 4.91 PE(<9"dia) 0.015
PE(>12"dia) 0.02
PE(9-12"dia) 0.017
CMP 0.025
ADS N12 0.012
HCMP 0.023
Concl 0.013
INSPECTION AND MAINTENANCE FOR
STORMWATER MANAGEMENT FACILITIES
The Property Owners Association shall be responsible for the maintenance of the stormwater
drainage facilities within the Rosa Apartments.
Storm Water Facilities:
1. Drainage swales slope toward storm inlet structures and yard drains.
2. Existing detention pond to the west of the site located in the open space.
Post Construction Inspection:
1. Observe drain time for a storm event after completion of the facility to confirm that the
desired drain time has been obtained. If excessively slow infiltration rates are observed
then excavate a minimum 5 ft by 5 ft drain to native gravels (or native well-draining
material) and backfill with well-draining material (pit-run).
2. Observe the stormwater catch basins after installation and clear any material or
obstructions in the drainage slots. Inspect the drywells after a storm event to insure
proper drainage.
3. Factors responsible for clogging should be repaired immediately.
Semi-Annual Inspection:
1. Check detention pond following three days of dry weather after a storm event exceeding
1/4 inch of precipitation. Failure for water to percolate or pass through out let structure
within this time period indicates clogging or poor-draining soils. Replace/repair as
necessary.
2. Remove grass clippings, litter, and debris from drainage swales, catch basins, and
detention pond. Flush and/or vacuum drywells or stormwater pipes if excessive material
is observed in the facilities.
Standard Maintenance:
1. Remove sediment and oil/grease from retention ponds.
2. Inspect and remove debris from drainage swales, catch basins, and detention ponds.
3. Monitor health of vegetation and revegetate as necessary to maintain full vegetative
cover.
4. Inspect for the following issues: differential accumulation of sediment, drain time, signs
of petroleum hydrocarbon contamination(odors, oil sheen in pond water), standing water,
trash and debris.
Sediment accumulation:
In most cases, sediment from a detention pond does not contain toxins at levels posing a
hazardous concern. However, sediments should be tested for toxicants in compliance with
current disposal requirements and if land uses in the drainage area include commercial or
industrial zones, or if visual or olfactory indications of pollution are noticed. Sediments
containing high levels of pollutants should be disposed of in accordance with applicable
regulations and the potential sources of contamination should be investigated and contamination
practices terminated.
i
ST ORMWAT'IER MANAGEMENT
DESIGN REPORT
TRADITIONS SUBDIVISION PHASE 3
OAK ST RE ET IMPROVEMENTS
Prepared for:
Rosa Const►•tiction, Inc.
125 Central Avenue, Bozeman, MT 59718
Pre�2ared by:
C&H Engineering and Surveying, Inc.
1091 Stoneridge Drive, Bozeman, MT 59718
�'��, ' _•`.:a��-2% .. '�;' fit,'
Project Number. 14170.1
�� JUNE 2015
INTRODUCTION
Oak Street improvements are proposed during construction of Traditions Subdivision Phase 3 and
will connect West Oak Street from Boulder Creek Subdivision to Twin Lakes Avenue at the
boundary of Flanders Creek Subdivision. The 7.89-acre Lot R1, with frontage along Oak Street,
is situated in the Northeast Quarter of the Southeast Quarter of Section 4, Township 2 South,
Range 5 East of P.M.M., City of Bozeman, Gallatin County, Montana. Lot RI is a restricted use
lot and zoned R4. This report considers the management of stormwater with Lot R1 in its current
undeveloped state but also provides adequate detention to accommodate the anticipated buildout
of the lot in sizing overflow structures and detention pond volume. A future subdivision or site
plan will address stormwater management on the developed Lot RI in more detail and additional
stormwater management will be implemented if found to be necessary.
C&H Engineering developed spreadsheets were used for all calculations in this report including
pipe outlet capacities, gutter flow depth and detention pond sizing. Each drainage area,
composite "C" value, total acreage and storm peak runoff was calculated using a C&H
Engineering developed Excel spreadsheet. Data was taken from the Flanders Creek Stormwater
Report and revisions dated June 2005 to model the existing storm sewer facilities in order to
interface the existing system with the proposed. All excel spreadsheet printouts and other sources
can be found at the end of this report.
STORMWATER MANAGEMENT
Design of the stormwater facilities for this project was based on the City of Bozeman Design
Standards and Specifications Policy, March 2004 including Addendums 1 through 5. The future
site plan for Lot RI was incorporated into the detention pond volume as described in the detention
pond section of this report. For the purposes of determining the volume for Pond 1 the Lot R1
area was assumed to have a future runoff coefficient of 0.7. In the future site plan excess runoff,
which cannot be detained in Pond 1, will be retained on site or an additional detention pond will
need to be designed. Pond 1 is currently shown at its maximum size on Figure D1 found at the
end of this report. The inlet at the corner of Twin Lakes Avenue and Oak Street (Inlet FC-14) is
proposed to be removed during Oak Street improvements. FC-14 currently is piped to a
temporary retention pond located in the Oak Street right of way;this structure will be removed and
r
t
Design Report-Page 2 of 5
the contributing drainage area will be graded to drain from the current location of FC-14 to
proposed Storm Inlet 1A. There is a small section of Oak Street on the far west of the proposed
street(Oak West) which accounts for 4,263 square feet of Oak Street (C=0.82). This small area
will be temporarily drained to Pond 1 until completion of Boulder Creek Subdivision. A
temporary swale is shown on the construction plans for management of this runoff.
DRAINAGE AREA 1
Drainage Area 1 consists of a portion of Oak Street to the north of Lot Rl and a portion of Twin
Lakes Avenue east of Lot Rl, as shown on Figure D1. Drainage Area 1 will contribute runoff to
Pond 1 via Storm Inlet I located on the south side of Oak Street at the low point in the street
profile. This inlet will be piped to a proposed 48-inch manhole (Storm Inlet 2A) via a 15-inch
PVC storm sewer pipe under the curb in Oak Street. From Storm Inlet 2A a 15-inch PVC pipe
will connect with a new 60-inch manhole (SDMH 1) proposed to be installed at the existing
30-inch RCP pipe draining from east to west along the south side of Oak Street in the existing 15
foot stormwater easement. The existing 30-inch RCP pipe is an outlet pipe currently used for the
ii
19,000 cubic foot existing detention pond that was installed with Flanders Creek Subdivision
(existing pond). A 30-inch PVC pipe will be installed downstream from SDMH 1. This pipe
will be the inlet pipe for a new detention pond (Pond 1)proposed to detain runoff from Drainage
Area 1. A composite "C" runoff coefficient was calculated for Drainage Area 1 along with the
post-development time of concentration. The proposed 15-inch,30-inch and 36-inch storm sewer
pipes discussed above all have adequate capacity as calculated on the storm sewer pipe capacity
spreadsheets. Additionally all existing and proposed gutter capacities were checked to verify
adequate freeboard while flowing at the COB maximum gutter flow depth of 0.15 feet below the
top of curb. As can be seen in the attached spreadsheets all gutters have adequate capacity.
STORMWATER DETENTION AT POND 1
Pond 1 is proposed in the designated open space area along the west side of Lot Rl. This pond
will retain and release runoff from Drainage Area 1 and it has been oversized for future use
following buildout of the Lot RI site. The exact drainage area contribution to this pond from Lot
RI will be determined in the future site plan. Design water depth for the detention pond
Design Report-Page 3 of 5
calculations was limited to 1.5 feet, which is the maximum allowed pond water depth in the COB
stormwater design standards without safety fencing. Drainage area 1 has a total area of 1.14 acres
and a composite "C" runoff coefficient of 0.82. The pre-developed runoff rate was calculated to
be 0.17 ft%ec. (See end of the report for detailed calculations). The storage volume was
computed by increasing the storm duration and computing the runoff volume minus the release
volume. The release rate is equal to the pre-developed runoff rate. The maximum storage
required occurs at a storm duration of 85 minutes and is equal to 1,579 cubic feet. Detention Pond
#1 has a volume of 10,623 cubic feet as shown on the construction drawings. This volume
accounts for the area of Lot Rl (7.89 acres) with a C coefficient of 0.7, the 1.14 acres from
Drainage Area 1 plus the small contribution from Oak West. As shown on the spreadsheet
entitled Detention Pond#1 (Oak Street, Twin Lakes and Lot R1 included) found at the end of this
report the required volume of Pond 1 is 10,299 cubic feet. Therefore the pond as shown on Figure
D 1 will be sized to have ample volume to detain the required runoff from Oak Street, Twin Lakes
Avenue, and from the completed Lot Rl.
OUTLET STRUCTURE AND PIPING—POND 1 AND EXISTING POND
An outlet structure and piping will be installed in the north end of Detention Pond#1. The outlet
structure will be sized per the City of Bozeman Design Standards and will be adjusted to a weir
width of 5.6 inches. Discharge to Baxter Ditch will be limited to 2.88 ft3/sec.which includes 2.71
ft3/sec., the pre-development runoff release rate of the existing pond's 5.3-inch weir, plus the
pre-development runoff release rate of 0.17 ft3/sec. from Drainage Area 1. An adjustable outlet
weir will be used in the outlet structure at Pond 1 in order to increase the overflow rate in the future
if additional detention volume is required during development of the future site plan design. The
weir notch will have a maximum width of 8-inches which will handle the pre-development runoff
from Lot Rl, Drainage Area 1 and the current release rate of the outlet weir on the existing pond.
The outlet pipe for the new pond will be sized as a 36-inch PVC pipe with a 0.54% slope
(maximum capacity = 52.72 ft3/sec.). The outlet pipe has been oversized to handle overflow
drainage from Drainage Area 1, Lot Rl and the existing pond. The capacity of this pipe exceeds
the required design flow rate of 35.41 ft3/sec., which includes the existing outlet structure's
overflow rate, Q25 of 20.29 ft3/sec. (Flander's Creek Stormwater Design Report and revisions
l
Design Report-Page 4 of 5
dated June 2005), plus 15.12 ft3/sec. which is the total amount of overflow from Drainage Area 1
-and the anticipated maximum overflow contribution from Lot R1. The detention pond outlet pipe
therefore will provide sufficient overflow capacity from the proposed detention pond to the Baxter
Ditch outfall in a major storm event for the current design and the weir width can be easily adjusted
to handle additional flows from Lot R1 as required.
i
Design Report-Page 5 of 5
�4 MARK A.
ammm
Na 95111ES
F.L LR!E,
P.; :N(E)=i::4..4 I yam(9( (YLPo�EyO
/ rl IY(c)-..4
%S<._4 ..•A^wT(ETTfa'ESF'1113
THIS DRUH+CE AREA I COS TRACT52 3t• t '
I WCLUDED IN B011LDETi F._ O':G('•,).4735 CT ANXRSON NSA FERN h BAXTER F.L CM:1 i
CREE](STOPIMATER I r.L RI(E, 4T35,}: RANCH HO101N0 LTD -.1 R:(S 0'"n Sheet 1 OJ
! �p0� 1 �'-r_LGi:Orr 2244707 -1 A
t:aT:k`'lUH STORY�T 2A 4r STA 1+67.30(23.05%) o
I Y:44 ].cR FOE CARE
.E,*-.t.O=W,TP.TOLE ' /^� n W tl
1; ,r tNS1Al1 NEW 3K RCP I/ OW(SYn. 4 94(1 _A Ct;POLC'` - C R
F,ARm FND SECIpN f R A736. S)
—,Aa Cti .:NC AK - Y
�_C•rf-. v-_'•:�1=riff— v,c_ i++E r.K_ i.E ry,_ Cwi .iC r'1E _ _
� 1 �� l,E A4 O1':
,C'w�•.S_K--1'r A`�``�Ji" Y �•'y� 7��c .-7�et
c so
�'_E.YYtCT•�_T.^T -F.. i - _ P. .RE:.Y0. [5 n F
G t , g 4
a, vrrr s;- v�--r •jai'4a-_..-�. r— i I —- c rt+s L '� 1 $1
1103 t 1 .) i I F ) -0_ µ v1:Er-
IVJ:-�` LN7�6[[C0I tly` r \ FJ OJT t _ / t -- 1 ` T s_—cam—- -- �I I
I _ Az2 r/j ABI�NDDH'tSJ• °�;,i,],:•ef:..,�— /' 2- W ✓
tRENI 6_• SE%EF.E<;E•.•ENT r.t,cur cn; _._... . --} !
FY PCVit•d,T E' S
Mn 1 no-Irta aruErtn)srA I+u.so aar" I 1 � @
I _I tWj t..':: ttt I o X 1L+_itET.::.'.i:<
\ \\\ I fi W(E}4736.7t1(SC) r._W(E!-t7:'iC EK Crime rO-ii l'' I I I I �' i B
0ETEMX)N OVM1Ei to fiV) A 6/66 007.,(. l i ..I rL Ot INE}4736.78(W) .` sN <t.00 I• ].: 1C WER SLOT
\\\�R / 73gg�,,.5554(DK)rJ ` PDNo ZI a OUT(S):4736.75(31T) •..-.L tur(T.
WI{IfFI 56'c / VOl-AT 1 STORY Mn 1A(4S)STA 4+31.54(26.119'L)'
(OFPM.,0. WSTALL NEW 3tr RCP Po+1:4]}9.9J
�'�EIEV.AT OF F1AIS➢END mD7wN FL OUT(W):4737.70(IS) 1 �:
POND 47 2 FL.475632
S ,
��•: ) / ' CIi:��Y1=Nit1;E EA',.'.vENT �I^p
'D,0 Ijl ! I j ('�j r�T,e'''(q �, 1 F'
1 00� r I I Fi_AtdLCPE• (:PE=V I W
LK'.`:,Irt`I SUBDIVISION -
t\\ V.' �I 31•TmDE Sr.—<L7:E= `•1 ( 1-
r I
�\ � �•' �, 1 z� I ' � I I a
—.`
\.`. 343.676 SF _
ON
I11 lAi RI
t=LANDERS Ul%faY----- -- ''�
- -------------- ------
�
I\
1 ;UPI1
DID g E 2 rL 1 'I}
III II t•�:� 1 .� I I I ' V1 �/1
II �Ez rAH; •,P:
Ir.L O —555, O
SHERWOOD r
tri,
N
lasm Date 8I24115
Scale In Feet
50 O 50 ®1.0
15 0 Is ) DRAINAGE MAP
Scale In Meterx C1,0 SGlE Y�50'
#14170.1
DETENTION POND #1 (Twin Lakes and Oak Street Only)
REQUIRED VOLUME
2. Calculate Area and Weighted C Factor(Post-Development)
Contributing Area C Area (ft2) C *Area
ROW 0.82 49504 40593
OS/Park 0.2 0 0
Lot R1 0.7 0 0
Laurel Parkway 0.81 0 0
Durston ROW 0.68 0 0
Total 49504 40593
A =Area(acres) 1.1365
C= Weighted C Factor 0.82
3. Calculate T, (Pre-Development)
Tc Overland Flow
Tc= 1.87 (1.1-CCf)D"2/Sv3
Storm
S = Slope of Basin (%) 1 ;Return (yrs) Cf
C= Rational Method Runoff Coefficient 0.2 12 to 10 1;
Cf= Frequency Adjustment Factor 1.1 111 to 25 1.1
D= Length of Basin (ft) 886 ;26 to 50 1.2;
51 to 100------------ 1.25
c(Pre-Development)(minutes) 49
4. Calculate Rainfall Intensity(Duration =Pre-Development Tc)
i= 0.64x 0.65 (10-yr Storm, Fig. 1-3, COB Design Standards)
x=storm duration (hrs) 0.82 (Tc Pre-Development)
i=rainfall intensity(in.1hr.) 0.73
5. Calculate Runoff Rate(Pre-Development)
Q = CiA
C = Rational Method Runoff Coefficient 0.2 (open land)
i= rainfall intensity(in./hr.) 0.73 (calculated above)
A=Area (acres) 1.14 (calculated above)
Q=Runoff Rate (Pre-Development)(cfs) 0.17
6. Calculate Required Pond Volume
Total Area (acres) = 1.14 acres
Weighted C= 0.82
Discharge Rate (cfs)= 0.17 cfs (Equal to Pre-Development Runoff Rate)
Duration(min) Duration(hrs) Intensity Q.'"(cfs) Runoff Release Required
(in/hr) Volume Volume Storage (ft3)
78 1.30 0.54 0.50 2354 777 1577
79 1.32 0.54 0.50 2364 787 1577
80 1.33 0.53 0.49 2375 797 1578
81 1.35 0.53 0.49 2385 807 1578
82 1.37 0.52 0.49 2395 817 1579
83 1.38 0.52 0.48 2405 827 1579
84 1.40 0.51 0.48 2415 836 1579
85 1.42 0.51 0.48 2425 846 1579
86 1.43 0.51 0.47 2435 856 1579
87 1.45 0.50 0.47 2445 866 1579
88 1.47 0.50 0.46 2455 876 1579
89 1.48 0.50 0.46 2465 886 1579
90 1.50 0.49 0.46 2474 896 1578
91 1.52 0.49 0.45 2484 906 1578
92 1.53 0.48 0.45 2494 916 1577
OUTLET STRUCTURE SLOT
Q=CLH 3/2
�r
QExISTING POND= Discharge (cfs) 2.71
QPOND 1 = Discharge (cfs) 0.17
QTOTALATPOND 1 WEIR= Discharge (cfs) 2.88
C=Weir Coefficient 3.33 (per COB Design Standards)
H = Head (ft) 1.5
L= Horizontal Length (ft) 0.47
L =Slot Width (inches) 5.6
f
DETENTION POND #1 (Oak Street, Twin Lakes and Lot R1 included)
REQUIRED VOLUME
2. Calculate Area and Weighted C Factor(Post-Development)
Contributing Area C Area (ft2) C *Area
ROW 0.82 53767 44089
OS/Park 0.2 0 0
Lot R1 0.7 343838 240687
Laurel Parkway 0.81 0 0
Durston ROW 0.68 0 0
Total 397605 284776
A =Area(acres) 9.1278
C= Weighted C Factor 0.72
3. Calculate T, (Pre-Development)
Tc Overland Flow
Tc= 1.87 (1.1-CC)D112/Sv3
Storm
S= Slope of Basin (%) 1 f Return (yrs) Cf
C = Rational Method Runoff Coefficient 0.2 12 to 10 1;
Cf= Frequency Adjustment Factor 1.1 111 to 25 1.1
D = Length of Basin (ft) 886 ;26 to 50 1.2;
f 151 to 100__--- 1.25;
Tc(Pre-Development) (minutes) 49 -------
4. Calculate Rainfall Intensity(Duration =Pre-Development Tc)
i = 0.64x o.s5 (10-yr Storm, Fig. 1-3, COB Design Standards)
x=storm duration (hrs) 0.82 (Tc Pre-Development)
I=rainfall intensity(in.1hr.) 0.73
5. Calculate Runoff Rate(Pre-Development)
Q= CiA
C = Rational Method Runoff Coefficient 0.2 (open land)
i= rainfall intensity(in./hr.) 0.73 (calculated above)
A=Area (acres) 9.13 (calculated above)
Q =Runoff Rate (Pre-Development)(cfs) 1.33
_ 6, Calculate Required Pond Volume
Total Area (acres) = 9.13 acres
Weighted C = 0.72
Discharge Rate (cfs) = 1.33 cfs (Equal to Pre-Development Runoff Rate)
Duration(min) Duration(hrs) Intensity Q.'" (cfs) Runoff Release Required
(in/hr) Volume Volume Storage (ft )
58 0.97 0.65 4.28 14885 4639 10246
59 0.98 0.65 4.23 14974 4719 10255
60 1.00 0.64 4.18 15063 4799 10264
61 1.02 0.63 4.14 15150 4879 10271
62 1.03 0.63 4.10 15236 4959 10277
63 1.05 0.62 4.05 15322 5039 10283
64 1.07 0.61 4.01 15407 5119 10288
65 1.08 0.61 3.97 15490 5199 10292
66 1.10 0.60 3.93 15573 5279 10295
67 1.12 0.60 3.89 15656 5359 10297
68 1.13 0.59 3.86 15737 5439 10298
69 1.15 0.58 3.82 15818 5519 10299
70 1.17 0.58 3.79 15897 5599 10299
71 1.18 0.57 3.75 15977 5679 10298
72 1.20 0.57 3.72 16055 5759 10296
73 1.22 0.56 3.68 16133 5839 10294
74 1.23 0.56 3.65 16210 5919 10291
75 1.25 0.55 3.62 16286 5999 10287
76 1.27 0.55 3.59 16362 6079 10283
OUTLET STRUCTURE SLOT
Q=CLH 3/2
QEXISTING POND= Discharge (cfs) 2.71
QPOND 1 = Discharge (cfs) 1.33
QTOTAL AT POND 1 WEIR= Discharge(cfs) 4.04
C =Weir Coefficient 3.33 (per COB Design Standards)
H = Head (ft) 1.5
L= Horizontal Length (ft) 0.66
L =Slot Width (inches) 7.9
DETENTION POND #1 (Temp. Drainage from Oak West)
REQUIRED VOLUME
2. Calculate Area and Weighted C Factor(Post-Development)
Contributing Area C Area (ft2) C*Area
ROW 0.82 4263 3496
OS/Park 0.2 0 0
Lot R1 0.7 0 0
Laurel Parkway 0.81 0 0
Durston ROW 0.68 0 0
Total 4263 3496
A =Area (acres) 0.0979
C=Weighted C Factor 0.82
3. Calculate T, (Pre-Development)
Tc Overland Flow
Tc= 1.87 (1.1-CCf)D1/2/Sii3
Storm
S= Slope of Basin (%) 1 !Return (yrs) Cf
C = Rational Method Runoff Coefficient 0.2 12 to 10 1;
Cf= Frequency Adjustment Factor 1.1 11 to 25 1.1
D = Length of Basin (ft) 886 ;26 to 50 1.21
51 to 100------------ 1.25
Tc(Pre-Development) (minutes) 49
4. Calculate Rainfall Intensity(Duration =Pre-Development Tc)
i= 0.64x o.65 (10-yr Storm, Fig. 1-3, COB Design Standards)
x=storm duration (hrs) 0.82 (Tc Pre-Development)
i=rainfall intensity(in.1hr.) 0.73
5. Calculate Runoff Rate(Pre-Development)
Q = CiA
C = Rational Method Runoff Coefficient 0.2 (open land)
i= rainfall intensity(in./hr.) 0.73 (calculated above)
A=Area (acres) 0.10 (calculated above)
Q =Runoff Rate (Pre-Development) (cfs) 0.01
6. Calculate Required Pond Volume
Total Area (acres) = 0.10 acres
Weighted C = 0.82
Discharge Rate (cfs)= 0.01 cfs (Equal to Pre-Development Runoff Rate)
Duration(min) Duration(hrs) Intensity Q.'" (cfs) Runoff Release Required
(in/hr) Volume Volume Storage (ft3)
70 1.17 0.58 0.05 195 60 135
71 1.18 0.57 0.05 196 61 135
72 1.20 0.57 0.05 197 62 135
73 1.22 0.56 0.05 198 63 135
74 1.23 0.56 0.04 199 63 136
75 1.25 0.55 0.04 200 64 136
76 1.27 0.55 0.04 201 65 136
77 1.28 0.54 0.04 202 66 136
78 1.30 0.54 0.04 203 67 136
79 1.32 0.54 0.04 204 68 136
80 1.33 0.53 0.04 204 69 136
81 1.35 0.53 0.04 205 69 136
82 1.37 0.52 0.04 206 70 136
83 1.38 0.52 0.04 207 71 136
84 1.40 0.51 0.04 208 72 136
85 1.42 0.51 0.04 209 73 136
86 1.43 0.51 0.04 210 74 136
87 1.45 0.50 0.04 211 75 136
88 1.47 0.50 0.04 211 75 136
89 1.48 0.50 0.04 212 76 136
90 1.50 0.49 0.04 213 77 136
91 1.52 0.49 0.04 214 78 136
92 1.53 0.48 0.04 215 79 136
93 1.55 0.48 0.04 216 80 136
94 1.57 0.48 0.04 216 81 136
95 1.58 0.47 0.04 217 81 136
96 1.60 0.47 0.04 218 82 136
97 1.62 0.47 0.04 219 83 136
98 1.63 0.47 0.04 220 84 135
DRAINAGE AREA LOT k 1
Contributing Area C Area(ft) C * Area Composite ROW
ROW 0.81957 0 0
((0.95 43)+(0.2 17))/60
OS/Park 0.2 0 0 0.8195652
Lot RI 0.7 346141 242299
Total 346141 242299
C=Weighted C Factor 0.70
A=Area(acres) 7.95
Required Gutter/Pipe Capacity (25-yr Storm)
Tc Overland Flow
Tc= 1.87 (1.1-CCf)D1i2/S1i3
Storm
S = Slope of Basin(%) 0.5 Return C f
C =Rational Method Runoff Coefficient 0.35 2 to 10 1
C f=Frequency Adjustment Factor 1.1 11 to 25 1.1
D=Length of Basin (ft) 15 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow(minutes)= 6.52
Tc Gutter Flow
Tc=LN160
V= (1.486/n)R" S"
n=Mannings Coefficient 0.013
R=Hydraulic Radius A/P (ft) 0.13 (0.15'below top of curb)
S = slope (ft/ft) 0.010
L=length of gutter(ft) 670
V=mean velocity(ft/s) 3.00
Tc Gutter Flow(minutes)= 3.72
Tc Total (Overland+ Gutter)= 10.25
Q =CIA
( C=Weighted C Factor 0.70 (calculated above)
I=0.78 Tc 0.64(in/hr) 2.42
Drainage Area#LOT R1
A= area(acres) 7.95
Qrequired (cfs) = 13.44
Provided Gutter Capacity (flowing at 0 15' below ton of curb)
Q= (1.486/n)Ale'S"
n=Mannings Coefficient 0.013
A=area(f 2) 1.24
P =wetted perimeter(ft) 9.23
R=Hydraulic Radius A/P (ft) 0.13
S =slope (ft/ft) 0.01
Qprovided (efS)= 3.72
CAPACITY PROBLEM
Drainage Area#LOT R1
DRAINAGE AREA 1 (TWIN LAKES WEST AND OAK STREET)
Contributing Area C Area(ft 2) C * Area Composite ROW
ROW 0.81957 45504 37293 ((0.95*43)+(0.2*l7))/60
OS/Park 0.2 0 0 0.8195652
Lot Rl 0.7 0 0
Total 45504 37293.5
C =Weighted C Factor 0.82
A=Area(acres) 1.04
Required Gutter/Pipe Capacity (257yr Storm)
Tc Overland Flow
Tc= 1.87 (1.1-CCf)Dli2/S1/3
Storm
S = Slope of Basin (%) 0.5 Return Cf
C=Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf=Frequency Adjustment Factor 1.1 11 to 25 1.1
D =Length of Basin(ft) 15 26 to 50 1.2
Tc Overland Flow(minutes)= 6.52 51 to 100 1.25
Tc Gutter Flow
Tc=L/V/60
V= (1.486/n)R2i3 Sv2
n=Mannings Coefficient 0.013
R=Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S = slope (ft/ft) 0.005
L= length of gutter(ft) 968
V=mean velocity(ft/s) 2.12
Tc Gutter Flow(minutes) = 7.61
Tc Total (Overland+ Gutter)= 14.13
Q=CIA
( C= Weighted C Factor 0.82 (calculated above)
I=0.78 Tc 0.64(in/hr) 1.97
A=area(acres) 1.04
Qrequired (efS) = 1.68
Provided Gutter Capacity (flowing at 0 15' below ton of curb)
Q = (1.486/n)AR"'S"
n=Mannings Coefficient 0.013
A=area(f 2) 1.24
P =wetted perimeter (ft) 9.23
R=Hydraulic Radius A/P (ft) 0.13
S = slope (ft/ft) 0.01
Qprovided (CfS) = 3.72
GUTTER IMSADEQUATE CAPACITY
i
DRAINAGE AREA OAK WEST
Contributing Area C Area(ft) C * Area Composite ROW
ROW 0.81957 4263 3494 ((0.95*43)+(0.2*17))/60
OS/Park 0.2 0 0 0.8195652
Lots 0.35 0 0
Total 4263 3493.81
C =Weighted C Factor 0.82
A=Area(acres) 0.10
Required Gutter/Pipe Capacity (25-yr Storm)
Tc Overland Flow
Tc= 1.87 (1.1-CCf)D1i2/S1/3
Storm
S = Slope of Basin (%) 0.5 Return C f
C=Rational Method Runoff Coefficient 0.35 2 to 10 1
Cf=Frequency Adjustment Factor 1.1 11 to 25 1.1
D =Length of Basin (ft) 15 26 to 50 1.2
51 to 100 1.25
Tc Overland Flow(minutes)= 6.52
Tc Gutter Flow
Tc=LN/60
V=(1.486/n)R2i3 S"
n=Mannings Coefficient 0.013
R=Hydraulic Radius A/P (ft) 0.13 (0.15' below top of curb)
S =slope(ft/ft) 0.005
L=length of gutter(ft) 88
V=mean velocity(ft/s) 2.12
Tc Gutter Flow(minutes)= 0.69
Tc Total (Overland+ Gutter)= 7.22
Q =CIA
C= Weighted C Factor 0.82,(calculated above)
I= 0.78 Tc o.64(in/hr) 3.03
Drainage Area#OAK WEST
A=area(acres) 0.10
Qrequired (Cfs) = 0.24
Provided Gutter Capacity (flowing at 0.15' below ton of curb)
Q= (1.486/n)AIe'S"
n=Mannings Coefficient 0.013
A= area(f z) 1.24
P =wetted perimeter(ft) 9.23
R=Hydraulic Radius A/P (ft) 0.13
S = slope (ft/ft) 0.005
Qprovided (efS) = 2.63
GUTTER IMASADEQUATE CAPACITY
Drainage Area#OAK WEST
DESIGN REPORT
STORM WATER
MANAGEMENT
ROSA
SUBDIVISION
Prepared for:
JOHN ROSA
Prepared by:
C & H Engineering and Surveying, Inc.
205 Edelweiss
Bozeman, MT 59718
(406) 587-1115
Project Number: 05230
June, 2005
STORM WATER MANAGEMENT
Summary
STORM WATER run-off from Rosa Subdivision will be directed to several storm water
detention areas located throughout 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
four 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 Rosa Way. Drainage area 43 will
drain to two detention ponds located at the north portion of the parks#6 &7,by the intersection
of Sherwood Way and Rosa Way. Drainage area#4 will drain to a detention pond located near
the intersection of Rosa Way and Oak Street. All proposed ponds will have an outlet pipe to
Baxter Ditch to ensure that the ponds drain after 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
r
DRAINAGE AREA#1
Drainage Area#1 consists of a total of 266,080 ft2, with 86,910 ft2 of that being right of way,and
179,170 ft2 of medium density lots. Drainage area#1 will be divided into three 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 each catch basin.
The time of concentration for sub-area#1-1 is calculated below:
Time of Concentration
Overland flow(115 ft @ 1.0%, C=0.35) = 14.3 min.
Gutter flow(400 ft @ 0.95% avg. slope on Rosa Way)
V=(1.486/n)W"Sv2 (n=0.013, A=1.24 ft, P=9.23, R"'=0.2623, S"2=0.0982)
V=2.95 ft/s
T=400 ft/2.95 ft/s/60s/min =2.3 min
Total Time of Concentration = 16.6 minutes(0.28 hours)
For a 25-year storm event Its= 0.78X-•64= 0.78(0.28)--64= 1.76 in/hr
Q25 Lots= CIA=0.35(1.76 in/hr)(0.9361 acres) = 0.58 cfs
Q25 r/w= CIA=0.70(1.76 in/hr)(0.3586 acres)= 0.44 cfs
Q25 Total=(0.58+0.44) = 1.02 cfs=Total flow rate entering catch basin#1
The time of concentration for sub-area#1-2 is calculated below:
Time of Concentration
Overland flow(155 ft @ 1.0%, C=0.35) = 16.7 min.
Gutter flow(470 ft @ 0.50% avg. slope on Brookside Lane)
V= (1.486/n)W"Sv2 (n=0.013, A=1.24 ft, P=9.23, R2"=0.2623, S"2=0.0707)
V=2.12 ft/s
T=470 ft/2.12 ft/s/60s/min =3.7 min
Gutter flow(470 ft @ 0.95% avg. slope on Rosa Way)
V= (1.486/n)R213SI12 (n=0.013, A=1.24 ft, P=9.23, R2"=0.2623, Si2=0.0982)
V=2.95 ft/s
T=240 ft/2.95 ft/s/60s/min = 1.4 min
Gutter flow(280 ft @ 0.60% avg. slope on Glenwood Drive)
V=(1.486/n)R213Si12 (n=0.013, A=1.24 ft, P=9.23, R2"=0.2623, Sv2=0.0775)
V=2.32 ft/s
T=280 ft/2.32 ft/s/60s/min =2.0 min
Total Time of Concentration =23.8 minutes (0.40 hours)
For a 25-year storm event Its= 0.78X--64= 0.78(0.40)-.64= 1.40 in/hr
Q25 Lots = CIA=0.35(1.40 in/hr)(3.1770 acres)= 1.56 cfs
Q25 r/w= CIA= 0.70(1.40 in/hr)(1.2709 acres) = 1.25 cfs
Q25 Total=(1.56+1.25) =2.81 cfs=Total flow rate entering catch basin#2
The time of concentration for sub-area#1-3 is calculated below:
Time of Concentration
Overland flow(13.5 ft @ 2.0%, C=0.46) =3.2 min.
Gutter flow(300 ft @ 0.60% avg. slope on Glenwood Drive)
( V= (1.486/n)R2i3Sli2 (n=0.013,A=1.24 ft, P=9.23, W"=0.2623, Sv2=0.07746)
V=2.32 ft/s
T= 300 ft/2.32 ft/s/60s/min =2.2 min
Total Time of Concentration =5.4 minutes (0.09 hours)
For a 25-year storm event 125= 0.78X-•64= 0.78(0.09)--64= 3.64 in/hr
Q25 r/w=CIA= 0.70(3.64 in/hr)(0.3656 acres) = 0.93 cfs
Q25 Total= 0.93 cfs=Total flow rate entering catch basin#3
Q25 Total for Storm Sewer#1 = (1.02+2.81+0.93) =4.76 cfs
The capacity of the curb and gutter, at a 0.60% slope, with a depth of water 0.15' below top of
curb is calculated as follows:
Q=(1.486/n)AR2"Sv2
n= 0.013 for Concrete
A= 1.24 ft2
P = 9.23 ft
V� ' R=A/P= 1.24/9.23 =0.1343 ft
R"' =0.2623 ft
S =0.0060 ft/ft
S v2= 0.0775 ft/ft
Q = (1.486/0.013)(1.24)(0.2623)(0.0775)=2.88 cfs.
2.81 cfs < 2.86 cfs — Gutter capacity is adequate
DRAINAGE AREA#2
Drainage Area#2 consists of a total of 490,865 ft2, with 79,295 ft2 of that being right of way,
263,990 ft2 of park land, and 147,580 ft2 of medium density lots. Drainage area#2 will be
divided into four subareas, three for each area that contributes to a catch basin that will be
utilized,plus the portion of the park that will drain into the detention pond. 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#2-1 is calculated below:
Time of Concentration
Overland flow(115 ft @ 1.00%, C=0.35) = 14.3 min.
Gutter flow(830 ft @ 1.00% avg. slope on Rosa Way)
V=(1.486/n)R2i3Sli2 (n=0.013,A=1.24 ft, P=9.23, W"=0.2623, S"2=0.1000)
V=3.00ft/s
T= 830 ft/3.00 ft/s/60s/min =4.6 min
Total Time of Concentration = 18.9 minutes (0.32 hours)
For a 25-year storm event Its= 0.78X-•64=0.78(0.32)-"64= 1.62 in/hr
Q25 Lots= CIA= 0.35(1.62 in/hr)(1.7553 acres)= 1.00 cfs
Q25 r/w= CIA=0.70(1.62 in/hr)(0.6123 acres) = 0.69 cfs
Q25 Total= (1.00+0.69) = 1.69 efs=Total flow rate entering catch basin#4
The time of concentration for sub-area#2-2 is calculated below:
Time of Concentration
Overland flow(110 ft @ 1.00%, C=0.35) = 14.0 min.
�" Gutter flow(830 ft @ 1.0% avg. slope on Rosa Way)
V=(1.486/n)R2/3S'/2 (n=0.013, A=1.24 ft, P=9.23, R2/3=0.2623, S'/2=0.1000)
t V= 3.00 ft/s
T= 830 ft/3.00 ft/s/60s/min =4.6 min
Total Time of Concentration = 18.6 minutes(0.31 hours)
For a 25-year storm event Its=0.78X--64= 0.78(0.31)-•64 = 1.65 in/hr
Q25 Lots= CIA= 0.35(1.65 in/hr)(1.656 acres)=0.96 cfs
Q25 r/w=CIA= 0.70(1.65 in/hr)(0.9431 acres)= 1.09 cfs
Q25 Total= (0.96+1.09) =2.05 cfs=Total flow rate entering catch basin#5
The time of concentration for sub-area#2-3 is calculated below:
Time of Concentration
Overland flow(13.5 ft @ 2.0%, C=0.46) =3.2 min.
Gutter flow(150 ft @ 0.60% avg. slope on Annie Street)
V= (1.486/n)R2/3S'/2 (n=0.013, A=1.24 ft, P=9.23, R2/3=0.2623, S'/2=0.07746)
V=2.32 ft/s
T= 150 ft/2.32 ft/s/60s/min = 1.1 min
Total Time of Concentration =4.3 minutes (0.09 hours)
For a 25-year storm event Its = 0.78X--64= 0.78(0.07)--64=4.21 in/hr
Q25 r/w= CIA=0.70(4.21 in/hr)(0.2649 acres)=0.78 cfs
Q25 Total= 0.78 cfs=Total flow rate entering catch basin#6
Q25 Total for Storm Sewer#2= (1.69+2.05+0.78) =4.52 cfs
DRAINAGE AREA#3
Drainage Area#3 consists of a total of 421,020 ft2,with 85,620 ft2 of that being right of way,
151,785 ft2 of park land, and 183,615 ft2 of medium density lots. Drainage area#3 will be
divided into three 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(13.5 ft @ 2.0%, C=0.46) =3.2 min.
Gutter flow(115 ft @ 0.60% avg. slope on Sherwood Way)
V= (1.486/n)W/3S112 (n=0.013, A=1.24 ft, P=9.23, W"=0.2623, S"2=0.07746)
V=2.32 ft/s
T= 115 ft/2.32 ft/s/60s/min = 0.8 min
Total Time of Concentration =4.0 minutes(0.07 hours)
For a 25-year storm event Its = 0.78X-.64=0.78(0.07)-•64=4.30 in/hr
Q25 r/w= CIA= 0.70(4.30 in/hr)(0.1625 acres) =0.49 cfs
Q25 Total= 0.49 cfs=Total flow rate entering catch basin#7 & 8
Q25 Total for Storm Sewer#3 = 0.49 cfs
The time of concentration for sub-area#3-2 is calculated below:
Time of Concentration
Overland flow(115 ft @ 1.0%, C=0.35) = 14.3 min.
Gutter flow(320 ft @ 1.10% avg. slope on Rosa Way)
V=(1.486/n)R2'3S'/2 (n=0.013, A=1.24 ft, P=9.23, R2"=0.2623, S"2=0.1049)
V=3.14 ft/s
T=320 ft/3.14 ft/s/60s/min = 1.7 min
Gutter flow(200 ft @ 0.60% avg. slope on Sherwood Way)
V=(1.486/n)R213S'/2 (n=0.013, A=1.24 ft,P=9.23, R2"=0.2623, S"2=0.0775)
V=2.32 ft/s
T=200 ft/2.32 ft/s/60s/min = 1.4 min
Total Time of Concentration = 17.4 minutes (0.29 hours)
For a 25-year storm event I25 =0.7M.14= 0.78(0.29)-•64= 1.72 in/hr
Q25 Lots= CIA= 0.35(1.72 in/hr)(0.7118 acres)= 0.43 cfs
Q25 r/w= CIA=0.70(1.72 in/hr)(0.7375 acres)=0.89 cfs
Q25 Total =(0.43+0.89)= 1.32 cfs=Total flow rate entering catch basin#9
The time of concentration for sub-area#3-3 is calculated below:
Time of Concentration
Overland flow(145 ft @ 1.0%, C=0.35) = 16.1 min.
Gutter flow(620 ft @ 0.80% avg. slope on Parkview Avenue)
V= (1.486/n)R213S112 (n=0.013, A=1.24 ft, P=9.23, R2"=0.2623, S"2=0.0894)
V=2.68 ft/s
T= 620 ft/2.68 ft/s/60s/min =3.9 min
Gutter flow(270 ft @ 0.60% avg. slope on Parkview Avenue)
V= (1.486/n)R213S112 (n=0.013, A=1.24 ft, P=9.23, R2"=0.2623, Sv2=0.0775)
V=2.32 ft/s
T=270 ft/2.32 ft/s/60s/min = 1.9 min
Total Time of Concentration =21.9 minutes (0.37 hours)
For a 25-year storm event I25 =0.78X-.64=0.78(0.37)".64= 1.47 in/hr
Q25 Lots= CIA= 0.35(1.47 in/hr)(3.5035 acres) = 1.80 cfs
Q25 r/w= CIA= 0.70(1.47 in/hr)(1.0655 acres)= 1.10 cfs
Q25 Total= (1.80+1.10) =2.90 cfs=Total flow rate entering catch basin#10
Q25 Total for Storm Sewer#3 = (1.32+2.90)=4.22 cfs
DRAINAGE AREA 94
Drainage Area#4 consists of a total of 474,050 ft2, with 143,825 ft2 of that being right of way,
40,660 ft2 of park land, and 289,565 ft2 of high density lots. Drainage area#4 will be divided
into three 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#4-1 is calculated below:
Time of Concentration
Overland flow(13.5 ft @ 2.0%, C=0.46) =3.2 min.
Gutter flow(625 ft @ 1.20% avg. slope on Rosa Way)
r-.
V= (1.486/n)R2"S"2 (n=0.013, A=1.24 ft, P=9.23, R2i3=0.2623, S"2=0.1095)
V=3.28 ft/s
T= 625 ft/3.28 ft/s/60s/min =3.2 min
Total Time of Concentration =6.4 minutes(0.11 hours)
For a 25-year storm event Its= 0.78X--64=0.78(0.1 ly.14=3.20 in/hr
Q25 r/w= CIA=0.70(3.20 in/hr)(0.5342 acres) = 1.20 cfs
Q25 Total = 1.20 cfs=Total flow rate entering catch basin#11
The time of concentration for sub-area#4-2 is calculated below:
Time of Concentration
Overland flow(280 ft @ 1.0%, C=0.60) = 13.8 min.
Gutter flow(262.5 ft @ 0.60% avg. slope on A Street)
V= (1.486/n)W"Sv2 (n=0.013, A=1.24 ft, P=9.23, R2i3=0.2623, S"2=0.0775)
V=2.32 ft/s
T=262.5 ft/2.32 ft/s/60s/min = 1.89 min
Total Time of Concentration = 15.7 minutes (0.26 hours)
For a 25-year storm event Its =0.78X--64 =0.78(0.26)-.64= 1.85 in/hr
Q25 Lots= CIA= 0.60(1.85 in/hr)(1.4415 acres)= 1.60 cfs
Q25 r/w= CIA= 0.70(1.85 in/hr)(0.47 acres) =0.61 cfs
Q25 Total =(1.60+ 0.61)=2.21 cfs=Total flow rate entering catch basin#15
Time of Concentration
Overland flow(280 ft @ 1.0%, C=0.60) = 13.8 min.
Gutter flow(262.5 ft @ 0.60% avg. slope on A Street)
V=(1.486/n)R2i3SIi2 (n=0.013,A=1.24 ft, P=9.23,R2i3=0.2623, Sv2=0.0775)
V=2.32 ft/s
T=262.5 ft/2.32 ft/s/60s/min = 1.89 min
Total Time of Concentration = 15.7 minutes (0.26 hours)
For a 25-year storm event Its =0.78X--64 =0.78(0.26)-'64= 1.85 in/hr
Q25 Lots= CIA= 0.60(1.85 in/hr)(1.2609 acres) = 1.40 cfs
Q25 r/w= CIA= 0.70(1.85 in/hr)(0.47 acres) = 0.61 cfs
Q25 Total = (1.40+ 0.61) =2.01 cfs=Total flow rate entering catch basin#12
Q25 Total for Storm Manhole#2= (2.21 +2.01)=4.22 cfs
The time of concentration for sub-area#4-3 is calculated below:
Time of Concentration
Overland flow(280 ft @ 1.0%, C=0.60) = 13.9 min.
Gutter flow(300 ft @ 1.20% avg. slope on Rosa Way)
V=(1.486/n)R2i3Sli2 (n=0.013,A=1.24 ft, P=9.23, R2"=0.2623, Sv2=0.1095)
V= 3.28 ft/s
T= 300 ft/3.28 ft/s/60s/min = 1.5 min
Total Time of Concentration = 15.4 minutes (0.26 hours)
For a 25-year storm event I25=0.78X-.64= 0.78(0.26)--64 = 1.85 in/hr
r.
Q25 Lots= CIA= 0.60(1.85 in/hr)(1.9050 acres)=2.11 cfs
Q25 r/w= CIA= 0.70(1.85 in/hr)(0.6319 acres) =0.82 cfs
Q25 Total = (2.11+0.82)=2.93 cfs=Total flow rate entering catch basin#13
The time of concentration for sub-area#44 is calculated below:
Time of Concentration
Overland flow(280 ft @ 1.0%, C=0.60) = 13.9 min.
Gutter flow(300 ft @ 1.60% avg. slope on Rosa Way)
V= (1.486/n)W"Sv2 (n=0.013, A=1.24 ft, P=9.23, R2"=0.2623, Sv2=0.1265)
V=3.79 ft/s
T=300 ft/3.79 ft/s/60s/min = 1.3 min
Total Time of Concentration = 15.2 minutes (0.25 hours)
For a 25-year storm event I25 = 0.78X-.64= 0.78(0.25)--64= 1.89 in/hr
Q25 Lots= CIA=0.60(1.89 in/hr)(1.7423 acres)= 1.98 cfs
Q25 r/w= CIA= 0.70(1.89 in/hr)(0.8160 acres)= 1.08 cfs
Q25 Total = (1.98+1.08) =3.06 cfs=Total flow rate entering catch basin#14
Q25 Total for Storm Sewer#4 =(1.20+4.42+2.93+3.06)= 11.61 cfs
Drainage Area#1
15" PVC from Catch Basin 91 to Catch Basin#2
This pipe carries the storm water from drainage sub-area#1-1. As previously calculated we
should anticipate a flowrate of 1.02 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
0.40 feet with a velocity of 3.00 ft/sec.
15" PVC from Catch Basin#2 to Catch Basin 93
This pipe carries the storm water from drainage sub-areas 1 A & 1-2. As previously calculated
we should anticipate a flowrate of(1.02 +2.81) = 3.83 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 0.88 feet with a velocity of 4.17 ft/sec.
15" PVC from Catch Basin#3 to Pond #1
This pipe carries the storm water from drainage sub-areas 1-1, 1-2 & 1-3. As previously
calculated we should anticipate a flowrate of(1.02 +2.81+0.93)=4.76 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 1.08 feet with a velocity of 4.22 ft/sec.
Detention Pond#1
The total area served by Detention Pond#1 is 6.11 acres with a weighted C-factor of 0.464 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 1.07 cfs. Calculations are
also enclosed in the Appendix for sizing the detention pond by varying the storm duration and
holding the release rate at 1.07 cfs. The required storage for Detention Pond#1 is 3,215 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#1 will be 2.09 inches in width.
These calculations are included with the calculations for sizing the pond.
Drainage Area#2
15" PVC from Catch Basin#4 to Catch Basin #5
This pipe carries the storm water from drainage sub-area 2-1. As previously calculated we
should anticipate a flowrate of 1.69 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
0.53 feet with a velocity of 3.44 ft/sec.
15" PVC from Catch Basin#6 to Catch Basin #5
This pipe carries the storm water from drainage sub-area 2-3. As previously calculated we
should anticipate a flowrate of 0.78 cfs from a 25-year storm event. Calculations are enclosed in
the Appendix for a 15" PVC pipe at 0.75% slope. The 15-inch pipe will flow at a depth of
0.32 feet with a velocity of 3.21 ft/sec.
15" PVC from Catch Basin 45 to Storm MH#1 to Detention Pond#2
This pipe carries the storm water from drainage sub-area 2-1, 2-2, &2-3. As previously
calculated we should anticipate a flowrate of(1.69+0.78+2.05) =4.52 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 1.01 feet with a velocity of 4.24 ft/sec.
Detention Pond#2
The total area served by Detention Pond#2 is 11.270 acres with a weighted C-factor of 0.326
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 1.801 cfs.
Calculations are also enclosed in the Appendix for sizing the detention pond by varying the storm
duration and holding the release rate at 1.801 cfs. The required storage for Detention Pond#2 is
3,610 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#2 will be 3.53
inches in width. These calculations are included with the calculations for sizing the pond.
l
Drainage Area #3
15" PVC from Catch Basin 97-8 to Pond 93
This pipe carries the storm water from drainage sub-area 3-1. As previously calculated we
should anticipate a flowrate of 0.49 cfs from a 25-year storm event. Calculations are enclosed in
the Appendix for a 15" PVC pipe at 1.00% slope. The 15-inch pipe will flow at a depth of
0.23 feet with a velocity of 3.10 ft/sec.
Detention Pond #3
The total area served by Detention Pond#3 is 2.23 acres with a weighted C-factor of 0.367 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 0.367 cfs.
Calculations are also enclosed in the Appendix for sizing the detention pond by varying the storm
duration and holding the release rate at 0.367 cfs. The required storage for Detention Pond#3 is
525 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 .72 inches in
width. These calculations are included with the calculations for sizing the pond.
15" PVC from Catch Basin#10 to Catch Basin #9
This pipe carries the storm water from drainage sub-area 3-3. As previously calculated we
should anticipate a flowrate of 2.90 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
0.72 feet with a velocity of 3.94 ft/sec.
15" PVC from Catch Basin #9 to Pond #4
This pipe carries the storm water from drainage sub-area 3-2 & 3-3. As previously calculated
we should anticipate a flowrate of(2.90+1.32) =4.22 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 0.95 feet with a velocity of 4.22 ft/sec.
Detention Pond#4
The total area served by Detention Pond#4 is 7.440 acres with a weighted C-factor of 0.3.96
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 1.11 cfs.
Calculations are also enclosed in the Appendix for sizing the detention pond by varying the storm
duration and holding the release rate at 1.11 cfs. The required storage for Detention Pond#4 is
3,340 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#4 will be 2.18
inches in width. These calculations are included with the calculations for sizing the pond.
Drainage Area 94
15" PVC from Catch Basin#14 to Catch Basin #13
This pipe carries the storm water from drainage sub-area 4-4. As previously calculated we
should anticipate a flowrate of 3.06 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
0.75 feet with a velocity of 3.99 ft/sec.
15" PVC from Catch Basin#12 to Storm MH#2
This pipe carries the storm water from drainage sub-area 4-2. As previously calculated we
should anticipate a flowrate of 2.21 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
0.61 feet with a velocity of 3.69 ft/sec.
15" PVC from Catch Basin#15 to Storm MH#2
This pipe carries the storm water from drainage sub-area 4-2. As previously calculated we
should anticipate a flowrate of 2.01 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
0.58 feet with a velocity of 3.60 ft/sec.
15" PVC from Storm MH#2 to Catch Basin#13
This pipe carries the storm water from drainage sub-area 4-2. As previously calculated we
should anticipate a flowrate of 4.22 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
1.39 feet with a velocity of 4.23 ft/sec.
18" PVC from Catch Basin 913 to Catch Basin #11
This pipe carries the storm water from drainage sub-area 4-2, 4-3, &4-4. As previously
calculated we should anticipate a flowrate of(4.22+2.93+3.06) = 10.21 cfs from a 25-year storm
event. Calculations are enclosed in the Appendix for a 18" PVC pipe at 1.00% slope. The
18-inch pipe will flow at a depth of 1.20 feet with a velocity of 6.77 ft/sec.
18" PVC from Catch Basin#11 to Detention Pond#5
This pipe carries the storm water from drainage sub-area 4-1, 4-2, 4-3, &4-4. As previously
calculated we should anticipate a flowrate of(1.20+4.22+2.93+3.06) = 11.41 cfs from a 25-year
storm event. Calculations are enclosed in the Appendix for a 18" PVC pipe at 1.50% slope.
The 18-inch pipe will flow at a depth of 1.10 feet with a velocity of 8.22 ft/sec.
Detention Pond #5
The total area served by Detention Pond#5 is 10.88 acres with a weighted C-factor of 0.596 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 1.61 cfs.
Calculations are also enclosed in the Appendix for sizing the detention pond by varying the storm
duration and holding the release rate at 1.61 cfs. The required storage for Detention Pond#5 is
9,200 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#5 will be 3.16
inches in width. These calculations are included with the calculations for sizing the pond.
Rosa Subdivision: Stormwater Addendum
DRAINAGE AREA#1 (Now includes Durston Road)
Drainage Area#1 consists of a total of 297,279 ft2, with 118,109 ft2 of that being right of way
and 179,170 ft2 of high density lots. Drainage area#1 will be divided into three 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 each catch basin.
The time of concentration for sub-area#1-1 is calculated below:
Time of Concentration
Overland flow(115 ft @ 1.0%, C=0.60) = 14.3 min.
Gutter flow(400 ft @ 1.30% avg. slope on Rosa Way)
V= (1.486/n)W"Sv2 (n=0.013, A=1.24 ft, P=9.23, R2"=0.2623, 5112=0.114)
V=2.51 ft/s
T=400 ft/2.51 ft/s/60s/min =2.66 min
Total Time of Concentration = 16.96 minutes(0.28 hours)
For a 25-year storm event Its= 0.78X-.64=0.78(0.28)-.64= 1.76 in/hr
Q25 Lots= CIA= 0.35(1.76 in/hr)(0.9361 acres) = 0.58 cfs
Q25 r/w= CIA=0.70(1.76 in/hr)(0.5084 acres)=0.63 cfs (includes Durston Road)
Q25 Total =(0.58+0.63) = 1.21 cfs=Total flow rate entering catch basin#1
Capacity of curb and gutter at 0.9%Average slope (Rosa Way&Durston Road)
Q= (1.486/n)AR2/3S112
n= 0.013 for Concrete
A= 1.24 ft2
P= 9.23 ft
R=A/P = 1.24/9.23 = 0.1343 ft
R " = 0.2623 ft
S = 0.009 ft/ft
SU2= 0.09487 ft/ft
Q =(1.486/0.013)(1.24)(0.2623)(0.09487)=3.53 cfs.
Total flow in gutter along Rosa Way and Durston Road
Q = 1.21 cfs
1.21 cfs s 3.07 cfs - Gutter capacity is adequate
The time of concentration for sub-area#1-2 is calculated below:
Time of Concentration
Overland flow(155 ft @ 1.0%, C=0.35)= 16.7 min.
Gutter flow(470 ft @ 0.5% avg. slope on Brookside Lane)
V= (1.486/n)R2i3S112 (n=0.013, A=1.24 ft,P=9.23, W"=0.2623, Sv2=0.0707)
V=2.12 ft/s
T=470 ft/2.12 ft/s/60s/min =3.7 min
Gutter flow(470 ft @ 1.30% avg. slope on Rosa Way
V= (1.486/n)RIIISIi2 (n=0.013, A=1.24 ft, P=9.23, R"'=0.2623, Sv2=0.1140)
V=3.42 ft/s
T=470 ft/3.42 ft/s/60s/min =2.3 min
Gutter flow(470 ft @ 0.601/o avg. slope on Glenwood Drive
V= (1.486/n)R2i3S"2 (n=0.013, A=1.24 ft, P=9.23, W"=0.2623, S"2=0.0982)
V=2.32 ft/s
T=280 ft/2.32 ft/s/60s/min =2.0 min
Gutter flow(470 ft @ 0.50% avg. slope on Durston Road
V= (1.486/n)R2i3SIi2 (n=0.013,A=1.24 ft, P=9.23, R2i3=0.2623, S"2=0.0707)
V=2.12 ft/s
T=470 ft/2.12 ft/s/60s/min =3.69 min
Total Time of Concentration=28.4 minutes (0.47 hours)
For a 25-year storm event I25=0.78X--64= 0.78(0.47)-•64= 1.26 in/hr
Q25 Lots=CIA= 0.35(1.26 in/hr)(3.1770 acres) = 1.40 cfs
Q25 r/w= CIA= 0.70(1.26 in/hr)(1.8373 acres) = 1.62 cfs (includes Durston Road)
Q25 Total= (1.40+1.62)=3.02 cfs=Total flow rate entering catch basin#2
The time of concentration for sub-area#1-3 is calculated below:
Time of Concentration
Overland flow(13.5 ft @ 2.0%, C=0.46) =3.2 min.
Gutter flow(300 ft @ 0.60% avg. slope on Glenwood Drive)
V= (1.486/n)R2i3Sv2 (n=0.013, A=1.24 ft, P=9.23, R2"=0.2623, Sv2=0.0982)
V=-2.32 ft/s
T=300 ft/2.32 ft/s/60s/min =2.2 min
Total Time of Concentration=5.4 minutes (0.09 hours)
For a 25-year storm event Its=0.78X-•64=0.78(0.09),64 =3.64 in/hr
Q25 r/w=CIA=0.70(3.64 in/hr)(0.3656 acres)=0.93 cfs
Q25 Total= 0.93 cfs=Total flow rate entering catch basin#3
Q25 Total for Storm Sewer#1 = (1.21 +3.02+0.93) = 5.16 cfs
Drainage Area#1
15" PVC from Catch Basin#1 to Catch Basin#2
This pipe carries the storm water from drainage sub-area#1-1. As previously calculated we
should anticipate a flowrate of 1.21 cfs from a 25-year storm event. Calculations are enclosed
for a 15" PVC pipe at 0.50% slope. The 15-inch pipe will flow at a depth of 0.44 feet with a
velocity of 3.14 ft/sec.
15" PVC from Catch Basin #2 to Catch Basin 93
This pipe carries the storm water from drainage sub-areas 1-1 & 1-2. As previously calculated
we should anticipate a flowrate of(1.21 +3.02)=4.23 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 0.95 feet with a velocity of 4.23 ft/sec.
18" PVC from Catch Basin#3 to Pond#1
This pipe carries the storm water from drainage sub-areas 1-1, 1-2 and 1-3. As previously
calculated we should anticipate a flowrate of(1.21 +3.02+ 0.93) = 5.16 cfs from a 25-year
storm event. Calculations are enclosed in the Appendix for a 18" PVC pipe at 0.30% slope.
The 15-inch pipe will flow at a depth of 1.11 feet with a velocity of 3.68 ft/sec.
Detention Pond #1
The total area served by Detention Pond#1 is 6.82 acres with a weighted C-factor of 0.489 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 1.192 cfs.
Calculations are also enclosed in the Appendix for sizing the detention pond by varying the storm
duration and holding the release rate at 1.192 cfs. The required storage for Detention Pond 41 is
3,900 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#1 will be 2.34
inches in width. These calculations are included with the calculations for sizing the pond.
r' i
Shoat I of 1
CO.LOQ
XOAON
U bSM V1 101
L
MIC> U U I L f
661
—Lf' s SL 101
j 'i bs 0A 01101
1�§
i- 9101 -- -
i 11 1 3t 101
!�
V7,,1Q1
ol 01
6 101\ 'z
lu b 3zfb
101
Lo
v
vt 3Z 101
Coco
Co 0
101'. f
z
ez I
DD0'9
4.
101
—w
U bS 79jr
V1 iol £l 101
G�101
coitj M
E
jr \\0Z 101
MJB-AREik z 161-
Wdr dD
--- - ---- ----
09
U) (o �Vofiz
0
LjO.Loo
azz L,L 0.t ON]
z
35(-11-88000M
d, L2 B V
0 ffi st OT
12
<
IIII
ji. 0 >: F,
W -0 6 C)
DRAINAGE PLAN
SCALE I-20V
Scale In Feet
200 0 200
I Dmv(W Date G127105
60 0 60
Scale In Meters D 1
#047701