HomeMy WebLinkAboutDrainage Reports - 08/19/1991I
OPEAT T OF
Fowr 'LDS UTMLn
4 Final Approved Report
ate �i�
1, .
Final Drainage Report
for
HICKORY HILL VILLAGE AT CUNNINGHAM CORNER
(Tract G)
Fort Collins, Colorado
Prepared for
SHIELDS STREET CORPORATION
3531 Windmill Drive #M/3
Fort Collins, Colorado 80526
Project No: 1234-01-91
Date: May 6, 1991
4836 S. College, Suite 12 Fort Collins, CO 80525 (303)226-5334
T-W. at; I I; I
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PAGE 1
HICKORY HILL VILLAGE AT CUNNINGHAM CORNER
Project No: 1234-01-91
I GENERAL LOCATION AND DESCRIPTION
A. Location
1. Hickory Hill Village (Tract G) at Cunningham Corner is
generally located at the northeast corner of the
intersection of Horsetooth Road and Shields Street (see
vicinity Map attached).
2. It is located in the Southwest Quarter of Section 26, T7N,
R69W of the 6th P.M.
3. The site is bounded on the West by Tract "F" of Willow Grove
at Cunningham Corner, on the Northwest by Richmond Drive, on
the Northeast and East by Windmill Drive and on the South by
Chestnut Village at Cunningham Corner.
B. Description of property
1. Hickory Hill Village (Tract G) contains approximately 4.77
acres. The site is fully serviced by all utilities which are
stubbed to the site at various locations around the
perimeter of the Site.
2. The site slopes moderately toward the northeast toward the
existing Cunningham Corner Detention pond located north of
the site. A storm sewer stub to the site was installed with
the construction of Windmill Drive. The stub to the site was
designed with the consideration of storm runoff contribution
from development of Tract G (See "Storm Water Drainage
Report for Willow Grove at Cunningham Corner" by Taranto,
Stanton & Tagge Consulting Engineers).
3. The site is currently vacant with wild dryland grasses and
other vegetation. It is currently utilized for the storage
of construction materials.
II DRAINAGE BASINS AND SUB -BASINS
A. Major Basin description
1. Cunningham Corner is a part of the Foothills Basin
according to the City of Fort Collins Stormwater Basin map.
B. Sub -basin description
1. Hickory Hill Village (Tract G) at Cunningham Corner is
included in the Cunningham Corner Master Drainage Plan (See
"Storm Water Drainage Report for Willow Grove at Cunningham
Corner" by Taranto, Stanton & Tagge Consulting Engineers and
.subsequent Cunningham Corner drainage reports).
2. The original drainage report for Cunningham Corner indicates
that all Cunningham Corner storm runoff (including Tract G)
will be conveyed to the Cunningham Corner detention pond
located north of Hickory Hill Village (Tract G).
3. Development of Hickory Hill Village (Tract G) will not
change the .basic drainage intent portrayed with the
Cunningham Corner Master Drainage Plan.
PAGE 2
HICKORY HILL VILLAGE AT CUNNINGHAM CORNER
Project No: 1234-01-91
III DRAINAGE DESIGN CRITERIA
A. Regulations:
1. City of Fort Collins Storm Drainage Criteria was used.
B. Development criteria reference and constraints:
1. The Cunningham Corner Master Drainage Plan and existing
conditions around the perimeter of the entire site, dictate
the grading and drainage concept of Hickory Hill Village
(Tract G). Existing site grading and the existing
improvements will be considered in the final grading and
drainage design of Hickory Hill Village at Cunningham
Corner.
C. Hydrological criteria
1. The Rational Method for determining peak flows will be used
for the evaluation of the 2 and 100 year event.
D. Hydraulic criteria
1. Figure 804-1D (Headwater Depth for Concrete Pipe Culverts
with Inlet Control) taken from the State Highway Department
Roadway Design Manual, will be utilized to verify pipe
culvert capacities.
2. The Mannings formula will be utilized for determining
capacities for storm sewers and open channels according to
the requirements of Sections 4, 5 and 7. Mannings "n" values
as indicated in the criteria manual were utilized.
IV DRAINAGE FACILITY DESIGN
A. General concept
1. Generally, all storm runoff will be conveyed from Hickory
Hill Village (Tract G) undetained, northerly and easterly to
the existing Cunningham Corner detention pond via existing
storm sewer facilities adjacent to the site which were
provided with previous development. Refer to the Grading and
Drainage Plan included in the back envelope of this report.
2. A series of site parking lot and landscape area conveyance
swales will direct runoff from a majority of Hickory Hill
Village (Tract G) and a small portion of Chestnut Village
(located south of Hickory Hill Village) to the existing
discharge point which coincides with the low point of
Windmill Drive.
3. Erosion protection will be incorporated at the discharge
points from Hickory Hill Village (Tract G) in order to
protect downstream facilities
4. Detention will not be provided since the Cunningham Corner
detention pond facilitates development of Hickory Hill
Village (Tract G). Consideration to the anticipated_high
water in the detention pond will be made for the
establishment of finished floors for the proposed units.
Detention pond water levels will create a minimal backwater
effect on the Hickory Hill Village (Tract G) site. This is
identified on the Grading and Drainage Plan for Hickory Hill
Village.
PAGE 3
HICKORY HILL VILLAGE AT CUNNINGHAM CORNER
Project No: 1234-01791
V CONCLUSIONS
A. Compliance with standards
1. This report complies with the requirements of the City of
Fort Collins Storm Drainage Criteria Manual and the
Cunningham Corner Master Drainage Plan.
B. Drainage concept
1. No deviations were made from the original Cunningham Corner
drainage intent presented with the "Storm Water Drainage
Report for Willow Grove at Cunningham Corner" by Taranto,
Stanton & Tagge Consulting Engineers and subsequent
Cunningham Corner drainage reports).
2. The grading plan will allow for the effective conveyance of
storm water runoff from the site to existing storm sewer
facilities and ultimately to the Cunningham Corner detention
pond.
3. Onsite detention will not be provided. A detailed
determination of the Tract G runoff coefficient, indicates
that the value for the proposed design is exactly the same
V G4 as that utilized in the original Cunningham Corner reports;
C=0.60 (see appendix for detail on runoff coefficient
determination). The Cunningham Corner detention pond was
designed assuming contribution from this Tract. No
additional detention volume is required.
4. The existing storm sewer provided to the site at the low
point of Windmill Drive consists of an 14"x23" RCP. The stub
will be excavated and a flared end section will be provided
to accept storm runoff generated within Basin I.
5. The existing storm inlet located in Richmond Drive at the
northeast corner of the site will be utilized to convey
Basin II storm runoff to the existing storm sewer system.
One (1) length of 18" storm sewer and an 18" flared end
section will be provided to accept storm runoff generated
within Basin 1I.
VI REFERENCES
1. City of Fort Collins Storm Drainage Criteria Manual
2. "Storm Water Drainage Report for Willow Grove at Cunningham
Corner"; Taranto, Stanton & Tagge Consulting Engineers, dated
February, 1984; TST Project No: 280-063
3. Concrete Pipe Design Manual; American Concrete Pipe Association,
February, 1974.
4. "Urban hydrology for Small Watersheds" Technical Release No. 55,
USDA, SCS Jan. 1975.
APPENDIX I
Composite Runoff Coefficient Determination
Runoff Calculations / storm sewer capacity
PAGE
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STORM WATER DRAINAGE- REPORT
FOR
WILLOW GROVE VILLAGE
AT CUNNINGHAM CORNER
A PLANNED UNIT DEVELOPMENT
IN THE
CITY OF FORT COLLINS, COLORADO
FEBRUARY 1984
'TARANTO, STANTON & TAGGE
CONSUL,PING ENGINEERS
�;:,A„ON FORT COLLINS, COLORADO
CUNNII\'GHAM CORNER - PARCELS C & D
C = .85 C = 1.0 C 1.25
A = 7.3 Acresf18ffice Park)f100
A = 1.1 Acres (Cannercial Area)
AT = 8.4 Acres
D = 400' Cannercial
D = 900' Office Park
Office Park - Parcel C
S Avg.'= 1.0%
Tc10 =
1.87 (1.1 - (.85)(1.0))
9001= = 14 min..
1 1/3
Tc100
- 1.87 (1.1 - .85 (1.25))
900h = 5.6 min.-
1/3
i10 =
3.85 in/hr.
i100• =
7.0 in/hr.
Q10-_(.85)(1)(3.85)(7.3)
= 23.9
cfs
Q10C -
(•85)(1.25)(7.0)(7.3) =
54 cfs
Cannercial Area - Parcel D
Tc10 = 1.87 (1.1 - (.85)(1)) 400 = 9 mi.n.
1 1/3
Tc100 - 1.87 (1.1 - .85(1.25)) 400h = 4 min.
1 1/3
i1 0 '= 4.6 in1hx.
i100 = 7.0 in/hr.
Q10 = (•£5) (1) (4.6) (1.1) = 4.3 cfs
Q100 = (•85)(1.25)(7.0)(1.1) = 8.2 cfs
PARCEL G -
C Developed = .6 Area = 5.0 Acres
D = 700' S Avg. = A.75%
Tc2 = 1.87 (1.1 - (.6)(1.0)) 700 = 17 min.
0.751 3
Tc100 = 1.87 (1.1 - (.6)(1.25)) 700 = 19 min.
0.751/3
i2 = 1.5 in/hr. Q2 = (.6)(1.0)(1.5)(5) = 4.5 cfs.
1100 = 5.3 in/hr. Q100 = (•6)(1.25)(5.3)(5) = 20.0 cfs
I
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APPENDIX II
Figure 3-1; Rainfall Intensity Duration Curve
Figure 3-2; Estimate of average flow velocity for use with Rational
Formula
Figure 44; Culvert capacity for 18" concrete pipe culverts
Figure 61; Culvert capacity for 14x23 concrete pipe culverts
No Text
DRAINAGE CRITERIA MANUAL
RUNOFF
5C
3C
E- 2 C
z
cc
U
W
a 10
z
w
a
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11AM1
II
MENNEE■IN�
.�►.M...
s .5 1 2 3 5. 10 20
VELOCITY. IN FEET PER SECOND
FIGURE 3-2. ESTIMATE OF AVERAGE FLOW VELOCITY FOR
USE WITH THE RATIONAL FORMULA.
*MOST FREQUENTLY OCCURRING_"UNDEVELOPED"
LAND SURFACES IN THE DENVER REGION.
REFERENCE: "Urban Hydrology For Small Watersheds" Technical
Release No. 55, USDA, SCS Jan. 1975.
5 =1-84
URBAN DRAINAGE & FLOOD CONTROL DISTRICT
14
FIGURES
FIGURE 44
CULVERT CAPACITY
18-INCH DIAMETER PIPE
20
is
! 16
14
12
10
8
6
4
2
0
4
241
8 12 16 20 24 28
CULVERT DISCHARGE 0 IN CUBIC FEET PER SECOND
FIGURES 239
20
18
LL
Om ld
Z
0
w
F
014
v
C
0
r-
w
LL
�A
2200 2400
;OND
FIGURE 61
CULVERT CAPACITY
14 x 23-INCH HORIZONTAL ELLIPTICAL
EQUIVALENT 18-INCH CIRCULAR
u
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Manning's n=0.012.
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- ' I - } _
: ...........+
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Outlet Unsubmerged
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1 :.; f-
Approx. Equivalent Circular
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Size Based on Area
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CULVERT DISCHARGE Q IN CUBIC FEET PER SECOND
APPENDIX III
Hickory Hill Village Grading and Drainage Plan (Stuffer Envelope)