HomeMy WebLinkAboutDrainage Reports - 06/11/1973EVERGREEN PARK
Project No. 172 242 01
DRAINAGE PLAN & REPORT
Prepared by R. Peter Fabry
Approved by J. Frank Cordova, Jr.
April , 1973
June 11, 1973 (Updated) �� CpRDo`
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VTN COLORADO
6875 East Evans Avenue
Denver, Colorado 80222
(303) 759-4271
INDEX
I. INTRODUCTION AND REPORT
II. AREA MAP (FIGURE 1)
III. CURB CAPACITY CALCULATION (FIGURE 2)
IV. INTENSITY CURVE (FIGURE 3)
V. RUNOFF COEFFICIENTS (FIGURE 4)
VI. DESIGN DATA (FIGURE 5)
VII. DITCH DESIGN (FIGURE 6)
VIII. DRAINAGE PLAN,(FIGURE 7)
IX. PIPE CURVES (FIGURES 8-13)
X. STORM DRAINAGE SYSTEM (FIGURES 14-15)
XI. WIER COEFFICIENTS (FIGURE 16)
EVERGREEN PARK
ON -SITE DRAINAGE. REPORT
Evergreen Park is located just north of the downtown portion of
the City of Fort Collins. The first phase of platting lies
primarily in the W 1/2 NW•1/4 of Section 1, Township 7 North,
Range 69 West of the 6th P.M. (See Figure
In the Drainage Report dated January 5, 1972, by VTN Colorado,
the total drainage area effecting Evergreen Park, plus the total
P.U.D. site, was discussed in terms of the overall drainage plan.
This report will deal with the on -site storm sewer system and
the actual routing.plan•and storage area for the first phase of
platting.
The charts and methods outlined in the Denver Regional Council
of Governments (D.R.C.O.G.) Urban Storm Drainage Criteria Manual
will be used as design criteria for this report. The rational
method will be used to;calculate,runoff quantities (Q=CIA).
The design data and drainage plan are in Figures 5 and 7. The
pipe sizing in Figure 5 is only the preliminary sizing. Figures,
7, 14, and 15 reflect the final hydraulic design.
Storm sewers' -will be concrete pipe and therefore a roughness
coefficient of n=012 will be used. Streets will be asphalt with
concrete six-inch vertical curb and gutter and four -foot sidewalks
e
with a net roughness coefficient of n=0.016. Street capacities
are calculated using Mannings Equation (Q=1.486AR2/3 S1/2)
n
Per the City Engineer of Fort Collins, storm sewers must be
designed for a two-year storm return period with the runoff being
held within the back of walk. The intensity curves for Fort
Collins are shown in Figure 4. The inlet capacity for a Fort
Collins single inlet shall be assumed to be seven cubic feet
per second (per Fort Collins City 'Engineer). This figure is
quite reasonable since all streets requiring storm sewer are
at minimum grade with low runoff velocities; and, therefore,
have good inlet conditions.
The initial storm 'sewer pipes were designed using Mannings
Equation for full flow (See Figure 5). All inlets are assumed
at capacity for pipe design. This adds some conservatism since
several inlets have been added on the downhill sides of streets
which probably will not generate seven cubic feet per second
for a two-year storm. Also, the actual catch basin peak flows
have different times of concentration- which results in the total
system not being at peak capacity at the same time.
The final pipe sizes are designed based on the hydraulic analysis
that appears later in the report. The drainage plan showing pipe
length, diameters, and grades is shown in Figures 7, 14, and 15.
3
At design point P5, the storm runoff will be routed to a pro-
posed lake in a dirt -lined ditch. The lake will serve to pond
part of the increased runoff due to development. (See report
dated January 5, 1972, by VTN Colorado). Another lake is pro-
posed at the southeast corner of Redwood Street and Conifer
Street. (This lake will not receive peak runoffs until future
platting.)
At design point P11, the storm runoff will be routed south in
an overland drainage ditch to Dry Creek. Both ditches at P5
and P11 will be a dirt.,lined ditch with maximum side slopes of
4:1 for maintenance purposes (See Figure 6). Dry Creek will '
be graded southeasterly to carry this ditch flow.
The remaining platted streets will not require storm sewer until
further platting of -that portion of the drainage plan noted as
unplatted. The City Engineer has requested that the construction
and storm sewering of :this portion be delayed until final plat-
ting (See Figure 7). These streets as noted have been platted
at this point since they contain necessary utilities to serve
Phase l of Evergreen Park and their design is critical to the
design of the remaining streets and sanitary and storm sewer
systems.
The required pipes or structures needed to carry Dry Creek and
the Lake Canal under Redwood'St. will also be designed in the
next phase for the same reasons.
4
The pipe required at Josh Ames Ditch crossing shall be a 30-inch
CMP. The Josh Ames is currently carried over the lake canal
approximately 600 feet upstream by a 24-inch pipe.
The total area being developed will drain either into the pi•.o-
posed lake or into Dry Creek. The remaining area to be platted
will drain into the second proposed lake mentioned above.
The two lakes will have a storage volume necessary to pond the
increased runoff due to developing the site. (See January 5,
1973, report.) The overflow ditch from the north pond will have
a controlled outlet to maintain the lake elevation at a height
to allow for major storm runoff ponding. This elevation will be
also set to keep the lake level at or below a height which might
be critical to the storm sewer systems. The analysis of lake
sizes and control elevations appears later in this report.
HYDRAULIC ANALYSIS
Based on. Bureau of Public Roads nomegraphs:
I._ (Figure 8) H14 Depth for. Circular Concrete Pipe
Culverts with Inlet Control January 1963 Revised
May 1964
II. -(Figure 9) Head for Circular Concrete Pipe Culverts
Flowing Full n = 0.012 January 1963
and Concrete Pipe Design Manual Culvert Capacity Graphs (n =
0.012 Projecting Inlet with Outlet Unsubmerged):
I. (Figure 10.)
II. (Figure 11.)
III. (Figure 12.)
IV. (Figure 13.)
21" ¢ pipe
24" pipe
27" pipe
30" pipe
5
Using the manhole and catch basin numbering system shown in
Figures 14 and 15, the hydraulic analysis of the storm sewer
system is calculated below. The system is designed assuming
a catch basin capacity of 6 to 7 CFS per basin with all
basins having peak flow at design. This method will add a
safety factor to the system since the various inlets will have
different time of concentrations for peaks. Since all streets
are designed with cross pans instead of a sump condition, there
will be no ponding conditions during a storm larger than the
two year design. This type of design results in less debris
blocking the inlets due to continuous Elow past the catch basin.
The HW (headwater) values shown in Figures 14 and 15 are the
available head between invert and rim. The actual available
head is three inches more because of the catch basin rim being
depressed below the flow line grade.
AT MH 1 Design Q = 26 cfs D = 30" 1• = 25'
HW = 2.7 (Figure 8 or 13) Inlet Control
TW = HIV + Loss (Upstream)
Tl4 = 2.7 + 0.2 (Assumed) = 2.9 < 5.1
OK
R
AT MH 2 Design Q=13cfs L=157' D=24" TIV=2.9 (MH 1)
HIV= H +ho - SOL = H + TW - SOL (Figure 9)
0.75 + 2.9 - .82 = 2.83 < 4.18 OK
Upstream TW = 2.83 + 0.1 = 2.93
AT MH 3 Design Q=13cfs L=487' D=24" TIV=2.93 (MH 2)
HW = H + TW - SOL
= 1.70 + 2.93 - 1.95 2.68 C 4.13 OK
Upstream TW=2.68 + 0.1 (Assumed Loss) = 2.78
AT CB 4 Design Q=1,3cfs L=72' D=24" TIV=2.9 (,IH 1)
HW = H + TW - SOL = 0.55 + 2.9 - .36 = 3.09 < 3.17 OK
AT CB 5 Design Q=6cfs L=80' D=18" TW=2.78 (MH 3)
HW = H + TW - SOL = 0.45 + 2.78 - 1.36 = 1.87 � 2.42 OK
AT CB 6 Design Q=7cfs L=20'_ D=18" TIV=2•78 (MH 3)
HIV = H + TW - SOL = 0.30 + 2.78 - .76 = 2.32 ,r 2.66 OK
AT MH 4 Design Q=21cfs D=27" L=130'
HIV = 2.6' (Figure 12) Outlet Control
TW = HIV + Loss (Upstream)
TW = 2.6 + 0.2 (Assumed) = 2.8 <-4.04
AT MH 5 Design Q=7cfs D=18" L=4S0 TIV=2.8 (DIH 4)
HIV = H + TW - So L
= 2.0 + 2.8 - 1.8 = 3.0 c 4.04
TW = 3.0 + 0.1 = 3.1 (Upstream)
OK
OK
7
AT
CB1
Design
Q=7cfs D=18" L=45 TW=2.8 (INiH 4)
HIV
= H + TW
- So.L
_ .46 +
2.8 - 1.12 = 2.14 < 2.25
OK
AT
CB2
Design
Q=7cfs D=18" L=15' TW=2.8
(MH
4)
HW=H+TW
- Sol,
= w.32 +
2.8 - .32 = 2.8 c 3.05
OK
AT
CB3
Design
Q=7cfs D=18" L=28' T1V=3.1
(MH
5)
HW
= H + TW
- SoL
=ev.31 +
3.1'- .31 = 3.1 zz 3.17
OK
AT
MH6
Design
Q=21cfs D=24" L-6W -
HW
= 2.8'
(Figure 8 or 11) Inlet Control
TW
2:8 +
0:2 (Losses) ='3.0 < 4.2
OK
AT
MH7
Design
Q=7cfs D=18" L=500' TW=3.0
(MH
6)
HW
=-H +'TW-=
Sol,'
_ 2.1 +
3.0 = 1.0 = 4.1 c5..2
OK
AT
CB9
Design
Q=7cfs D=18" L=47' TW=3.0
(MH
6)
HW=
H+TW
- So _ ..,.
.48 +
3:0 - .20 = 3.28 3.35
OK
0
AT CB 10 Design Q=7cfs D=18" L=34' TW=3.0 (MH 6)
HW=H+TW- SoL
= .48 + 3.0 - .20 = 3.28 -.:: 3.35 OK
AT CB 11 Design Q=7cfs D=18" L=110' TW=4.1 (MH 7)
HW= H+TW - Sol,
= .65 + 4.1 = 0.22 = 4.53 -< 4.71 OK
AT MH 8 Design Q=26cfs D=30" L=lS
HW = 2.7 (Figure 8 or 13) Inlet Control
TW = 2.7 + 0.1 (Losses) = 2.8 c 4.1 OK
AT MH 9 Design Q=26cfs D=30" L=500' TW=2.8 (MH 8)
HW= H+TW - Sol,
= 2.2 + 2.8 - 1.5 = 3.5 �- 4.3 OK
TW = 3.5 + 0.1 (Losses) = 3.6
AT CB 12 Design Q=14cfs D=18" L=78' TW=3.6 (MH 9)
HW = H + TW - Sol,
HW = 1.10 + 3.6 - .78 = 3.92 z 4.20 OK:
AT CB 13 F, 14 Design = 6cfs/ea D=18" L= 200' @ 0.4%
TW = 3.6 (MH 9)
HW = H + TW - SoL
= 0.8 + 3.6 - 0.8 = 3.6 cti4.20 OK
AT CB 7 Design Q=13cfs D=21" L=20'
HW = 2.1' (Figure 8) Inlet Control
TW = 2.1' + 0.1' = 2.2' � 2.99 OK
AT CB 8 Design Q=6.5cfs D=18" L=75' TW=2.4 (CB 7)
HW = H + TW - Sol,
_ .50 + 2.2 - .56 = 2.14 c 2.25 OK
L A K E S
The two lakes proposed for Evergreen Park are to be designed to
allow for storm runoff ponding of the additional runoff due to
development. The total additional runoff to be ponded equals
14.4 acre-feet per City of Fort Collins engineering. (The
volume per Drainage Report dated January 5, 1972, by VTN Colorado
was 13.3 acre-feet.)
The proposed northerly lake (Lake 1) drains approximately 80 acres
or 43% of the total 187 acres. Therefore, this lake must retain
6.2 acre-feet of the required 14.4 acre-feet. The southerly
lake (Lake 2) will retain the remaining 8.2 acre-feet.
The normal lake level of Lake 1 shall be controlled at an eleva-
tion of 4,966.0. This sets the maximum normal lake level below
the invert of the storm sewer entering in a ditch from the west.
The lake outlet shall be through a controlled wier into a ditch
10
leading to Lake 2. At Lake 2, a Wier will control the flow
into Lake Canal.
The 20-year storm runoff from the 187 acres at its present
state of development is 55cfs (See January 5, 1973 Report). .
Since approximately 40cfs runs off the site from the storm
sewer system without any appreciable ponding, the allowable
runoff from,the lakes is 15cfs (55cfs - 40cfs).
The wiers shall be designed for " 10cfs of runoff. Assuming a
broad -crested wier the runoff Q = CLH3/2, where:
Q = runoff, cfs
C = coefficient for wier (See Figure 16)
- L = width,-ft.
H;=.head, ft., _
ca�=
Ii Head $ Depth of Lake
L
BROAD CRESTED WEIR
11
By setting Q = . locfs and assuming values of H, the size of
the two lakes and the required width for the wier (L) can be
determined.
H
H3/2
L
(ft.)
(ft.)
0.8
0.72
5.0
1.0
1.00
4.0
1.2
1.31
3.0
1.4
1.66
12.3
1.6
2.02
1.7
C
Q
Lake 1
Lake 2
(const.)
(cfs)
(acres)
(acres)
2.68
9.65
7.8
10.2 `
2.67
10.28
6.2
8.2
2.65
10.40
5.2
6.8
2.72
10.40
4.4
5.9
3.00
10.30
3.9
5.1 ,
When the grading.plan is finalized, the lake sizes will be set
and the appropriate wier can be selected.
Since Lake 1 feeds into Lake 2, the volume of available
ponding in Lake 2 can be increased to compensate for any reduc-
tions in volume of Lake 1 'as long as a total of 14.4 acre-feet
is maintained for ponding.
31
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CURB CAPACITE5
5.5'
0"
4.51 , 2.01. 25.0• 1 3.0-
9A15E0 ON MANNING-5 EQUATION
A 2 5 V7-
.n
ASSUME n = CO.OKA ,
.q=4.`K y .to-7 .5 XZ-r'S25=780
=,244
32
AT MINIMUM STREET GP-ADI: 5-0.40/a
i
Q = I As(,* '7.8b XC,244)�3 C.o04)�Z
IB eFs (a�) ck +'/o STizEE r a;aAD5
FIGU2E 2
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DRAINAGE CRITERIA MANUAL
RUNOFF
3.6 Continued
TABLE 3-1 (5)
RATIONAL METHOD RUNOFF COEFFICIENTS
Description of Area Runoff Coefficients
Business:
DoYrntown areas 0.70 to 0.95
Neighborhood areas 0.50 to 0.70
Residential:
Single-family areas 0.35 to 0.50
Multi units, detached 0.40 to 0.60
Multi units, attached 0.60 to 0.75
Residential (1/2 acre lots or more) 0.30 to 0.45
Apartment dwelling areas 0.50 to 0.70
Industrial:
Light areas 0.50 to 0.80
f Heavy areas 0.60 to 0.90
Parks, cemeteries 0.10 to 0.25
Playgrounds
0.20
to
0.35
Railroad yard areas
0.20
to
CAD
Unimproved areas
0.10
to
0.30
It is often desirable to develop a composite runoff coefficient based
on the percentage of different types of surface in the drainage area.
This procedure is often applied to typical "sample" blocks as a guide
to selection of reasonable values of the coefficient for an entire
area. Suggested coefficients with respect to surface type are given
In Table 3-2. See the Storm Sewers Part of this Manual for a dis-
cussion of the use of the Rational Method in conjunction with the use
of on site ponding and roof ponding.
1-15-69
1
FIGU?E
i !T \k-- TTV/"-N "-_)
DITCH
N
- MINIMUIYI--DESIGN --- -
DESIGN q`=5OC1=�sTOeMSEwEL-)+3oCFS(r-uiueEi-;-cAT-nw--),
= 80 C FS
-- -- ,A= 2.5X4 ►2X-LX2.5X10 25St—
p = 10.ZX2-r4=Z.4,4
- 35 = 1.4 35
2y.'9
!.2'73
n -
u
AssuA+l>= h =�035 FOP Vier DITCH
----- ----—Q=f,486 -35X1,Z-7 XS��z=t8a05�Z
O, 036
FDl FAH-EiE'AD MMIMDM =O,ZO/0 --
f
_ 175E 1,luNIt`IUM PI?�N 17Gi16N OF 2,5�x�
CHANNSFL WITH 4: ! SIDE SLORF-5-
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DIAMETER OF CULVERT (D) IN INCHES
N N N W W W A A (A 01 0) V V p� t0 l0 r+ •-. r n+ r-�+ �+01 �.+
N 01 cor A V O W O N co O Q1 N COA O 0, O O N W A U1 07
N W O N A m co O
(Q) IN CFS
N W Atno 00 tj O O 000 C3
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HEADWATER DEPTH IN, DIAMETERS,
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DISCHARGE (0) IN CFS
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DIAMETER (D) IN INCHES
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HEAD (H) IN FEET
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VALUES OF NM FOR INLET CONTROL IN FEET ..d VALUES OF NM. S L FOR OUTLET CONTROL IN FEET
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VALUES OF NM FOR INLET CONTROL IN FEET and VALUES OF NMtS,L FOR OUTLET CONTROL IN FEET
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VALUES OF HW FOR INLET CONTROL IN FEET and VALUES OF HW +S.L FOR OUTLET CONTROL IN FEET
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VALUES OF MW FOR INLET CONTROL IN FEET and VALUES OF HW+S.L FOR OUTLET CONTROL IN FEET
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EVr=2G2EE.N PA2V
STORM DRAINAGE PLAN
13INGLE INLET
60 5 TOP- G7.45
INV-G5.03N.W.- 2A?'
SINGLE INLE
c.R 6 ToP- 6
INV.-64.43 H.i
/CON IPEP-
Colorado
003 TOP-GG.59-
INV.-(o3.17 ♦ -M-3.17'
STORM MN 5
RIM - GG9
INV - &OV.8%
51N6L5 INLET
G.E3 2 TOP- 64.4.
INV-(o1.38N•W.- 5.05'
DOUBLE INLET
G.E3.4- TOP-G4-.4.
INV.-61.2Cn EI.W.-3.17
6b'
,4'- 74• @ 0.40 i
STREET
Lil
V
OL
Esi
0
m
z_ a
d
wt°�
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a ctij
I M 11' Z
FIGURE 14
E V ERG2EEN PAP-14
STORM DRAINAGE PL414
5INGLE INLET
G.B.It 7OP-7R.8s
INV-&S.12 O.WV 4.71'
STORM MH 7
RIM -73.1 INV. -67.9
�C
5INGLE INLET
14
VFi
5INGLE INLET
G.6.10 TOP-70,5
U�
INV-G7.! O N•W.-3.45'
STORM MH9
5INGLE INLET
RIM- 72:7
0.13.9 TOP-70.45
-
INV.-G8.40
INV.-io7.10 N.W.-3:39
B IZ 157L EGON E
DR.. STORM MR 5
w
Zti3
m
Go
SINGLE INLET
mN
G.13.8 TOP- 70.09
CO
INV.-GTS44 N W.- 2.25'
2
ci
u
0
nrTGH ,
colorado
FIGURE 15