HomeMy WebLinkAboutDrainage Reports - 06/10/19881
'
FINAL DRAINAGE REPORT
for
'
THE RESIDENCES AT HORSETOOTH C0MMONS
P.U.D.
1
City of Fort Collins
Larimer County
'
Colorado
'
June 1988
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'
Prepared by:
The Engineering Co.
1630 South College Avenue
'
Fort Collins, Colorado
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1 June 7, 1988
1
' City of Fort Collins
300 LaPorte Avenue
Fort Collins, Colorado 80521
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ATTENTION: Stormwater Utility .
' RE: Residences at Horsetooth Commons P.U.D. - Drainage Report
' Gentlemen:
'
We are pleased to submit
herewith a drainage report for the Residences at
Horsetooth Commons. This
report is provided to update the methods of handling
stormwater runoff caused by The Residences as it affects the entire develop-
ment. Several drainage
studies have been done previously for Horsetooth
Commons and The Market at
Horsetooth Commons. We have used information from
those previous studies for
this report.
LIncluded
in the report is
an analysis of stormwater runoff characteristics
caused by improvements to
The Residences at Horsetooth Commons. Methods of
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stormwater conveyance are
also defined in the report.
If you have any questions
concerning the report, please feel free to contact
Us.
1
Respectfully,
1
�
mm�om
J. Brian Z' P. E.
RGj!;ay�
1
THE ENGINEERING CO.
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Final Drainage Report
' for
The Residences at Horsetooth Commons P.U.D.
General
' The purpose of this report is to evaluate the impacts of stormwater flows
caused by the proposed development. The project is generally known as The
Residences of Horsetooth Commons. Horsetooth Commons is located at the north-
west corner of Horsetooth Road and Shields Street. The project has been
replatted and includes approximately 2.86 acres. There is only a slight
decrease in the basin contribution of stormwater flow.. The area of Tract C is
' also affected by the change. However, the affect on the stormwater flows is
minor.
' In preparing this report, we utilized information found on drawings 3 of 9 for
Horsetooth Commons and drawings 2, 39 5 and 7 of The Market at Horsetooth
Commons. Also we have used sheet 5 of 7 from Casa Grande P.U.D. and sheet 5
of 8 from Chapparal P.U.D.
' Site Description
' Presently, The Residences is undeveloped pastureland which slopes to the east
at approximately 1.0 to 1.5%. The property is bordered on the west by the
undeveloped Kingstowne Subdivision and on the north by Casa Grande, which is
presently experiencing active construction.
Design Criteria
' The design criteria for this study was based upon City of Fort Collins - Storm
Drainage Design Criteria and Construction Standards. The rational method is
used to determine flows from the project.
' Where encroachment exceeds allowable limits, continuous grade curb openings
will be used to divert flow off of the roadway and into storm sewer systems.
Proposed Improvements
Hydrology for the 2-year and 100-year storm events was analyzed using the
rational method. Exhibits A and B shows the locations of the basins, which
were analyzed. Only Basins B and C were analyzed as they represent the only
change in area from previous plans. Table 1 shows the 2-year developed flows.
Table 2-shows the 2-year historic flows. Table 3 shows the 100-year developed
' flows.
It is anticipated that the Residences at Horsetooth Commons will be built
before The Market at Horsetooth Commons (Tract D).
Therefore,
detention
'
requirements must be handled as designed with the original
plan for
Horsetooth
Commons. Exhibit B shows the revisions to the detention
facilities
caused by
construction of interior roads within Tract D. Sheet
Commons has also been revised to effect the change. This
3 of 9 for Horsetooth
sheet is included in
the Utility drawings for The Residences, as sheet 5. It
is planned
to install
the storm sewer system as designed for The Market at Horsetooth Commons.
'
Also, the future parking lot will be rough graded to provide detention.
Should the Market at Horsetooth Commons be constructed prior to the Residences
then the parking lot/ drainage plan for The Market will bre used (sheet 3 of
'
10).
'
Detention requirement based on flows from The Residences and Tract D are
32,383 cu.ft. This is based on a release rate of 2.2 cfs as indicated on
sheet 3/10 of the Market. The 100-year flow was routed to determine detention
volumes. Table 4 shows the detention calculations. The grading plan will
'
provide approximately 80,000 cu. ft. of storage. The existing controlled
outlet is in place in outlet A-3. The emergency spillway will be the peri-
meter roads in Tract D. The maximum elevation is 5082.38, before spilling
'
onto Shields Street.
In The Residences, all storm water is to be conveyed to McWilliams Gate. Ten
'
foot (101) curb inlets at the PCR's will remove flow from the street and carry
it through an 18" storm sewer to an existing line which runs under Richmond
Drive. 100-year flows are estimated to be 13.8 cfs. These flows can be
.carried in the existing 24" and 18" storm sewers under McWilliams Gate.
Line B on the north side of Block 1 is a release line for a future detention
pond in Kingstowne P.U.D. A headwall is provided on the west end of the
property. Historic runoff from Kingstowne flow to the northeast across Casa
Grande G.U.D. The storm water conveyence and detention system for Casa Grande
G.U.D. has taken into account historic flows and anticpated release rates from
future detention ponds in the design of their stormwater system. Line "B" is
shown on sheet 5 of 7 of the Casa Grande P.U.D. utility drawings. The future
Kingstowne pond should have an emergency spillway to the north onto Casa
Grande. Their is a planned street immediatly north of the pond which would
accept the flows. The spillway elevation would be lower than the floor
'
elevtions of the northern lots of the Residences, eliminating flooding poten-
tial. McWilliams Gate would also act as an emergency spillway should the
design capacity of the future spillway be exceeded. This would provide
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additional protection to the houses within the Residences.
Line "B" would not be fully utilized until the detention pond for Kingstowne
is constructed. The majority of the historic runoff will flow to the north
before entering line "B".
Tract C is to provide its own detention at the time of specific development.
Calculations and Exhibits are found in the Appendix.
1
RESIDENCES AT HOR5ETOOTH COMMONS - DRAINAGE STUDY JOB: 87-012
APRIL 1968
TABLE - :
HYDROLOGY CALCULATIONS - BASIN INFORMATION ( 2 - YEAR DEVELOPED
!Time of Concentration
Tc = Ti + It
Ti = 1.87 ( 1.1 - C ) Overland length ^.5 / Slope ^.33
It = Travel Length 160 f I channel velocity)
--------------------------------------------------------------------------------------------------
Total Overland Travel Channel Channel
Basin Length length length 51ope Coeff. Ti Slope Velocity Tt Area
I B-1 591 100 481 2.000 0.56 8.02 1.00 2.00 4.01 1.72
B-2 551 100 451 2,000 0.56 8.02 1.01 2.00 3.76 1.07
C 440 440 0 1.000 0.65 17.65 3.05
--------------------------------------------------------------------------------------------------
RESIDENCES AT HORSETOOTH COMMONS - DRAINAGE STUDY JOB: 87-012
APRIL 1488
TABLE -
HYDROLOGY CALCULATIONS
- STORM PLOWS ( 2
- YEAR
DEVELOPED )
------------ 7----------------------------------------
PIoM
Time
Inlet
Time of
Direct
Other
Sue 1
Time
Street
Pipe Conc.
Coeff.
°I°
Area
Runoff
Runoff
Runoff )
( Point
(ft.l
(min.)
(mim.)
(min.) (min.)
°C'
(in/hr)
(acres)
(cfs)
(cfs)
(cfs) 1
--------------------------------------------------------------------------------------------------------------i
I I B-1
581
8.02
4.01
12.02
0.56
2.30
1.72
2.2
2.2
2 B-2
551
8.02
3.76
11.77
0.56
2.36
1.07
1.4
1.10
2.5 (
I 3 C
I
440
17.65
17.65
0.65
2.00
3.05
4.0
4.0 )
I--------------------------------------------------------------------------------------------------------------1
RESI➢ENCES AT HORSETOOTH COMMONS - DRAINAGE STUDY
TABLE - Z
HYDROLOGY CALCULATIONS - BASIN INFORMATION ( 2 - YEAR HISTORIC
---------------------------------------------------------------
!Time of Concentration
JOB: 87-012
ARRIL 1988
1 Tc = Ti + Tt
1 Ti 1.87 ( 1.1 - C ) Overland lenoth ".5 I Slope ^.33
1 It = Travel Lenoth 1 60 } 4 channel velocity)
i--------------------------------------------------------------------------------
1 Total Overland Travel Channel Channel
1 Basin Length length length Slope CDeff. Ti Slope Velocity
1 B-1 581 100 481 2.000 0.3 II.BB 1.00 2.00
B-2 551 100 451 2.000 0.3 11.8B 1.01 2.00
f C 440 440 0 1.000 0.3 31.38
--------------------------------------------------------------------------------
Tt Area
4.01 1.72
3.76 1.07
3.05
RESIDENCES AT HORSETOOTH COMMONS - DRAINAGE STUDY JOB: 87-012
APRIL 1988
TABLE - 2
HYDROLOGY CALCULATIONS - STORM FLOWS ( 2 - YEAR HISTORIC
Flow
Time
1
Inlet
Time of
Direct
Other
Sum 1
Time
Street
PiDe Conc.
Coeff.
"I°
Area
Runoff
Runoff
Runoff 1
1 Point
(ft.)
(min.)
(min.)
(min.) (min.)
"C°
(inlhr)
(acres)
(cfs)
(cfs)
(cfsl 1
1--------------------------------------------------------------------------------------------------------------1
1 I B-1
581
11.86
4.01
15.8E
0.30
2.09
1.72
1.1
1.1 1
I 2 B-2
551
11.88
3.76
15.63
0.30
2.10'
1.07
0.7
1.10
1.8,1
1 3 C
1---------------------------------=----------------------------------------------------------------------------1
440
31.38
31.38
0.30
1.43
3.05
1.3
1.3 1
1
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1
1
1
1
1
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RESIDENCES AT HORSETOOTH COMMONS - DRAINAGE STUDY
TABLE - 3
HYDROLOGY CALCULATIONS - BASIN INFORMATION ( 100 - YEAR DEVELOPED
:Time of Concentration
Tc = Ti f Tt
Ti = 1.87 ( 1.1 - C. ) Overland lenoth ^.5 / Slope ^.33
It = Travel Lenoth / 60 + i channel velocity)
----------------------
JOB: 87-012 .
APRIL 1988
-------------------------------------------------------------------
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Total
Overland
Travel
Channel
Channel
1 Basin
Length
length
length
Slope
Coeff.
Ti
Slope
Velocity Tt
i B-1
5B1
100
481
2.000
0.71
5.79
1.00
2.00 4.01
( B-2
551
100
451
2.000
0.71
5.79
1.0i
2.00 3.76
---C- -----------------------------------------------------------------------------------
440
440
0
1.000
0.71
15.30
Area
1.72
1.07
3.05
1
1
1
1
RESIDENCES AT HORSETOOTH COMMONS - DRAINAGE STUDY JOB: 87-012
APRIL 1988
TABLE
HYDROLOGY CALCULATIONS
- STORM FLOWS ( 100 - YEAR DEVELOPED )
------------------------------------------------------------------
1
Flow Time
;
1
Inlet Time of
Direct
Other Sum )
Time Street Pipe Conc.
Coeff.
'I' Area
Runoff
Runoff Runoff 1
i Point
(ft.) (min.) (mim.) (min.) (min.)
°C'
(in/hr) (acres)
(cfs)
(cfs) (cfs) 1
1-------------------------------------------- =-----------------------------------------------------------------
1
1 I B-1
581 5.79 4.01 9.80
0.71
7.00 1.72
B.5
8.5 1
1 2 B-2
551 5.79 3.76 9.55
0.71
7.00 1.07
5.3
9.50 13.8 1
1 3 C
440 15.30 15.30
0.71
5.90 3.05
12.8
12.8 1
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RESIDENCES AT HORSETOOTH COMMONS
1OB; 88-010
MAY 1980
TABLE - 4
DETENTION FOND DESI6N
----------1--------- -------------1---------------------------
1 I RELEASE RATE 1 INFLOW ➢ATA
1 Storm Release Cumulative 1
1 Duration 1 Rate Volume ) Coeff. °1° Area
1 (min) 1 (cis) (cu. ft.) 1 °C° (inlhr) tacres)
1---------- 1----------------------- 1-----------------------
1 10 1 2.04 1,224.00 1 0.81 6.98 5.24
1 15 + 2.04 1,836.00 1 0.81 5.89 5.24
1 20 + 2.04 2.448.00 : 0.91 5.15 5.24
1 30 + 2.04 3,672.00 1 0.81 4.15 5.24
1 45 + 2.04 5,508.00 0.01 3.20 5.24
1 60 + 2.04 7,344.00 1 0.81 2.60 5.24
1 90 + 2.04 11,016.00 1 0.91 1.BB 5.24
1 120 + 2.04 14,688.00 1 0.81 1.45 5.24
1 180 + 2.04 22,032.00 1 0.81 1.04 5.24
1---------- 1----------------------- 1-----------------------
0
Cumulative 1 Storage 1
Discharge
Volume 1
Volume 1
(cis)
(cu. ft.) 1
(cu. ft.) 1
---------------------------
1--------------- 1
29.6
17.775.55 1
16.551.55 1
25.0
22.499.56 1
20,663.56 1
21.9
26.230.39 1
23,782.39 1
17.6
31,705.67 1
28,033.67 1
13.6
36.671.62 1
31,163.62 1
11.0
39.727.58 1
32,383.58 1
B.0
43,089.15 1
32.073.15 1
6.2
44,311.54 1
29,623.54 1
4.4
47,673.10 1
25,641.10 1
---------------------------1
1
1
sx
= 0,04
T=
12,5
a
s
Se
0/0
1\
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4.7617 cfs
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,s/ems c/-"
No Text
APPENDIX
11
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BLOCK 1 ,._ .._ ___ TRACT
0 0 0 0 0 6 a
STA 3+71.53 P.T. O
STA 3-1. 3 P.T. I i STA 1 +52.62 P.C.
STA 1 +46.69 P.C. .
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ATiE
RICHMOND DRIVE
STA 3+42.09 EXIST
P.T. —
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-- —B C K 2 STA 1 +52.62
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/ 4 VALLEY PAN
H H H H WEFfH fH / , STA 1 +25.00 FL
�j 6' VALLEY PAN
STA /+00 INTERSECTION
RICHMOND DR. McWILLIAMS GATE
STA 1 +52.62 P.C.
STA 1 +25.19 FL
VALLEY PAN
4y EXHIBIT A
;, DRAINAGE IMPROVEMENTS
TRACT C„
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EXHIBIT B �F'��<
l DRAINAGE IMPROVEMENTS A/
7E�
f 3 _C I F
Sf Tna RPs7de.xes of ct'e� 7"
u
AS Cons f�..efed P'lo. T/re MaiLm♦ -
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---
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