HomeMy WebLinkAboutSPRING CANYON COMMUNITY PARK - FDP - 20-05/A - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTconstruction of the Spring Canyon Park will include wattle dikes and straw bale dikes set
across all flowpaths determined by the general grading plan. The wattle dikes are placed in
the flow paths for each 2 ft of vertical drop to slow the conveyance of water and prevent
significant erosion before vegetation is installed. The straw bales dikes are to be used in the
constructed portion of the Spring Creek channel. Silt fencing is to be added around the
construction site to prevent sediment form leaving the site during construction. Drop inlet
protection will be installed around each inlet, grated manhole lid, and pond outlet structure to
prevent sediment from leaving the project site and entering Spring Creek or downstream
stormwater facilities. Straw mulch will be applied after seeding to prevent erosion from
runoff and help establish plant cover. ,A vehicle -tracking pad is to be installed at the south
entrance of the project site to prevent mud from being carried off site on vehicle tires.
Vehicle tracking pads must also be provided at any other access locations to the worksite.
All disturbed areas not in the roadway or greenbelt shall have temporary vegetation seed
applied within 30 days of initial disturbance. After seeding, hay or straw mulch shall be
applied over the seed at a rate of 1.5 to/ac minimum, and the mulch shall be adequately
anchored, tacked, or crimped into the soil. Those roads that are to be paved as part of the
development must have a 1-inch layer of gravel mulch applied at a rate of at least 135 to/ac
immediately after over lot grading is completed. The pavement structure shall be applied
with in 30 days after the utilities have been installed.
If the disturbed areas will not be constructed upon within one growing season, a permanent
seed shall be applied. After seeding, a hay or straw mulch shall be applied over the seed at
a minimum rate of 1.5 to/ac, and the mulch shall be adequately anchored, tacked or crimped
into the soil. In the event a portion of the roadway pavement surface and utilities will not be
constructed for an extended period of time after over lot grading, a temporary vegetation
seed and mulch shall also be applied to the roadway areas as previously discussed.
10 Ayres Associates
realigned along the west side of the park to channelize flows and merge Spring Creek with
the proposed park topography.
A separate HEC-RAS model was developed to analyze the flow entering Pond A through the
inflow weir located immediately upstream of the diversion culvert. The purpose of this
analysis was to determine the embankment configuration that ensures water flows into the
pond without losing a portion across the left bank, back into Spring Creek. The HEC-RAS
model included a cross section at the weir, spilling into the pond and three cross sections
located a distance of 400 feet downstream into the pond. The results indicate the proposed
embankment on the left bank has a minimum of 1.0 ft of freeboard along its entire length.
The HEC-RAS model is included in the Appendix.
The 100-year velocities through the reach were evaluated to assess the overall channel
stability with the proposed improvements. Generally, high velocities occur in the vicinity of
the drop structures. Riprap revetment will be constructed upstream and downstream of the
structures to provide local erosion protection. There are also other locations along the main
channel where the velocities are sufficient to erode natural channel bed material. These
areas result from the Parks Department's desire for the channel to be graded around
existing trees and other natural features. The high velocity occurring at cross section 37689
is a result of the channel being graded around a group of trees that the Parks Department
would like to protect. This causes a constriction point in the channel and consequently
higher velocities to occur. These high velocity areas will be further examined to determine if
minor changes in the channel are feasible or if erosion control measures are necessary. If
erosion control measures are necessary, installation of a turf reinforcement mat will be
recommended.
For more information on the floodplain analysis please refer to the Spring Canyon Park
Hydraulic Analysis and Design Report dated September 2005.
5. EROSION CONTROL
Construction of the Spring Canyon Park will require implementation of erosion control BMPs
to minimize the amount of sediment carried offsite by wind and water. Drainage from the
park property flows into Spring Creek and erosion control practices must be implemented to
minimize the impacts.
The Rainfall Performance Standards for Spring Creek Park, during and after construction,
were calculated to be 79.8 and 93.9, respectively. Therefore the erosion plan shall be
developed to contain 79.8% and 93.9% of the rainfall sediment that would normally flow off a
bare ground site during a 10-year rainfall event for both pre- and post -construction
conditions. The Effectiveness values for the site during and after construction were
determined to be 84.2 and 96.9, respectively. These values demonstrate that the developed
Erosion Control Plan contains at least the minimum amount of rainfall sediment on -site
required during and after construction, therefore, the erosion control plan below meets the
City of Fort Collins requirements. The erosion control calculations can be found in the
appendix.
The erosion control methods to be implemented during the construction of the Spring
Canyon Park is located on the Erosion Control Sheet. The City of Fort Collins erosion and
sediment control construction notes are included on this sheet. Erosion control BMPs for
9 Ayres Associates
UDFCD criteria manual. All lines discharging to a pond or to Spring Creek will require riprap
to prevent local scour and erosion. The spillways for both ponds A and B will be protected
with Erosion Control Fabric to protect the weir from erosion and possible breach.
4. SPRING CREEK FLOMPLAIN ANALYSIS
The construction of the SCCP will significantly impact the floodplain, drainage patterns, and
flow characterization of Spring Creek throughout the park property. The land use throughout
the project site will be typical of urban parks and contain a mix of athletic fields, parking lots,
recreational facilities, and maintained open space. The reach of Spring Creek that flows
through the park will be constrained to a well-defined channel to control flow and minimize
the impact of flood events on park property. The proposed channel alignment will intercept
flows south of the park site and direct them along the west edge of the property before
merging with the existing Spring Creek channel adjacent to Cottonwood Glen Park. The
proposed trapezoidal channel will have a bottom width of approximately 30 feet and typical
side slopes of 6:1. To lessen the impact of the natural grade, two 3-foot drop structures
were incorporated into the design of the channel to control velocities and prevent channel
erosion. The channel side slope grading and top width were varied to present a more natural
appearance through the park. In addition, the channel configuration was aligned to protect
the large existing cottonwood trees located along the channel banks. Within the park, the
proposed Spring Creek channel was designed to contain major storm events, up to a 100
year event, and significantly reduce overbank flooding. All local storm drainage from the
park property will be routed to Spring Creek through a stormsewer system described in
Section 3.
The upstream reach of Spring Creek, south of the park, on City of Fort Collins Natural Areas
property, will merge with the proposed Spring Creek channel. The creek will continue north
onto park property, and run along the west edge of the property. Near the north edge of the
park, a diversion structure is designed to divert flow from Spring Creek and into the
proposed regional detention pond. Stormwater will be detained in the pond to minimize
downstream impacts on Spring Creek during large rainfall events. The diversion structure
will consist of a 4- by 6-foot box culvert in the main channel that will allow up to 210 cfs to
continue down the Spring Creek channel. The backwater caused by the box culvert will
cause excess flows to be diverted over the east bank of the channel into the regional
detention pond. Discharges from the detention pond return to Spring Creek via an overflow
spillway and a 15-inch stormsewer pipe.
Flood Hydrology and Boundary Conditions
Hydrology for the proposed conditions (PR) model was taken from the Spring Canyon Park
drainage design, developed according to City of Fort Collins storm drainage criteria. The
ModSWMM model was updated with the proposed grading, land use, and drainage facilities
and used to model developed conditions hydrology for the park. The updated SWMM
results were used in HEC-RAS as boundary conditions for the 2-, 10-, and 100-year
proposed conditions models.
Proposed Conditions
After the EC model was established, the cross sections were regenerated to reflect the
SCCP and Spring Creek channel grading. For the PR model, the proposed channel was
M
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discharge downstream of the box culvert diversion structure. Further, approximately 19.4
acres of the storm water flows from element 347 travel through a channel that runs into
Spring Creek. During the construction of the SCCP, this channel will be re -graded and lined
with a turf reinforcement blanket. The flows will travel down the channel to a low point where
they will be collected with a 36-inch RCP. The stormsewer pipe will then take water to
Spring Creek immediately downstream of the box culvert. This pipe is labeled as
Stormsewer H.
ModSWMM element 147 also contributes flow from the foothills to Spring Creek. The flows
from this basin enter Spring Creek upstream of the box culvert diversion structure.
PV&L and SPRING CREEK INTERSECTION
Currently, low flows from Spring Creek are conveyed under the PV&L Canal through a 12-
inch corrugated metal culvert. Flows exceeding the capacity of this culvert (approximately 5
cfs) overtop Spring Creek and merge with flows in the PV&L canal, and ultimately spill over
the north bank of the canal back into the Spring Creek drainage. With the construction of
Spring Canyon Park, it is proposed that this pipe be replaced with a 1.5- by 6-foot reinforced
concrete box culvert. The culvert will have the capacity to pass approximately 77 cfs prior to
overtopping into the PV&L Canal. This pipe is labeled as Stormsewer G.
3.4 Hydraulic Analysis
Each of the storm sewer trunklines and the associated laterals were analyzed with the HEC-
22 energy grade line method. This provided the basis for all pipe sizing, taking into account
the tailwater conditions and headloss associated with the different hydraulic structures. The
HEC-22 worksheet is included as part of the Appendix. Inlets for the storm sewer system
were sized using UD-Inlet v1.04(CASFM).xls; a spreadsheet developed by UDFCD applying
methods outlined in the USDCM. Area inlets were sized using a combination of the weir and
orifice equations.
All inlets for the storm sewer system for the Spring Canyon Community Park are
summarized in Table 4.
Table 4. Storm Sewer Inlet Summary for Spring Canyon Community Park.
Inlet
Inlet Type
No. of
Inlets
On -Grade or
Sump.
Q,00
(cfs)
Al
Type R
3
Sump
39.8
A2
Type R
3
Sump
17.6
D1
Type C
1
Sump
4.3
D2
Type 13-Combo
1
Sump
10.3
Pond A outlet
Type C
1
Sump
10.5
Pond B outlet
Type C
1
---
54.9
The 100-year discharge from Pond B will be 109 cfs.
To prevent local scour at storm sewer outlets, it is necessary to include riprap revetment as
outlet protection. Riprap revetment design will be based on procedures outlined in the
7 Ayres Associates
I. controlled spillway into Spring Creek. The spillway will be lined with erosion control fabric to
prevent erosion during large storm events.
Detention for the water quality pond was determined using the Urban Drainage Flood Control
District (UDFCD) method. This method incorporates the total impervious percentage of area
draining into the pond and calculates the water quality capture volume in inches, the depth of
the average runoff, and the total upstream tributary area.
The total volume captured by detention Pond B is 0.50 acre-feet. At this volume, water will
rise to an elevation of 5125.93 feet. All flows exceeding this WSEL will enter a grated inlet
that discharges through a 30-inch RCP storm sewer pipe, Storm C, into Spring Creek. Weir
flow will occur when the WSEL exceeds 5127.0 feet.
POND C
[ Basin 3 drains to a small depression. This depression is known as Pond C. The goal of
t Pond C was to detain water during the winter months for a small skating rink on the site.
This pond has a box outlet structure equipped with a waterman gate at the end of Storm E.
When the gate is open the stormwater will flow to the proposed storm sewer, but when the
gate is closed ponding will occur.
A summary of the pond storage characteristics is included in Table 3 below.
Table 3. Detention Summary for Onsite Detention Facilities.
Pond
WSEL
Volume
. Storm Event
Pond A"
5118.40 ft
49.2 ac-ft
1 00-ear
Pond B
5125.93 ft
0.50 ac-ft
10-year
"Pond A begins to spill over the spillway to the west at 5,116.5 ft
`* Pond B begins to spill over the spillway to the west at 5127.0 ft
STORM SEWER SYSTEM
The storm drainage system for the park consists of one main storm sewer trunkline, Line A.
This line extends from its outlet point at Pond B just north of the parking lot/road to a low
spot at the southeast corner of the site. This storm system �picks_up basins 1 through 8. ' Line A starts upstream as a 24-inch RCP, it then travels west where it picks up flows from
basins 1 and 3 where it becomes a 30-inch RCP. A couple hundred feet downstream it
reaches inlet A2 where flows from basins 7 and 8 join the system. At this point the storm
sewer becomes a 48-inch RCP. The storm sewer discharges into Pond B.
Line B is a small 24-inch RCP stub -out. The purpose of this pipe is to provide a future tie-in
for a detention pond on Basin 13. This pond may or may not be constructed, but by
providing a stub -out the developer can choose to construct the pond at a later date without
encroaching on the future floodplain of Spring Creek. If the pond were to be constructed, it
would act as a water feature and basins 12 and 13 would drain to it.
Several other basins contribute stormwater to Spring Creek. In addition to flow from Pond A,
approximately 87.1 acres from the foothills west of the park (ModSWMM element 347) also
6 Ayres Associates
Pond A is a 49.2 acre-foot regional detention pond contained entirely on SCCP property.
Several drainage basins contribute stormwater flows to Pond A. The majority of the tributary
flow to Pond A results from the overtopping of Spring Creek just west of the basketball
courts. This is a designed Spring Creek overflow, created by the proposed 4- by 6-foot high
reinforced concrete box culvert (RCBC), line I, diversion structure just downstream of the
spill location. The culvert was designed to allow up to 157 cfs into Spring Creek during a low
flow event. During higher flows in Spring Creek, a portion of the flow will spill northeast to
Pond A, with a maximum spill into the pond of 1,290 cfs (during the 100-year storm event).
At this discharge, the culvert will allow 210 cfs to pass into the Spring Creek channel. In
addition, runoff from Basins 12, 13 and 14 will travel by overland flow to Pond A. Erosion
control fabric will line the spillway to protect the weir from erosion and possible breach.
Discharge from Pond A will ultimately be carried to Spring Creek through a 15-inch storm
sewer pipe, Storm F, and an overflow spillway located downstream of the RCBC diversion
structure (Figure 3.1). The spillway embankment has an elevation of 5116.5 and will have a
maximum overtopping depth of 1.9 feet, which results in a 100-year water surface elevation
is at 5118.4. The volume of the pond at 5118.4 feet is approximately 49.2 acre-feet. The
15-inch RCP was designed to allow nuisance flows through the pond before the spillway
begins to release water. During the 100-year storm 10.5 cfs will discharge into Spring Creek
through the pipe and the spillway will allow a maximum of 700.2 cfs to return to Spring
Creek.
The pond was modeled using the Spring Creek Master Drainage Plan ModSWMM model.
The purpose of this detention facility is to decrease the amount of flow in Spring Creek
downstream of Spring Canyon Park. By optimizing Pond A and the downstream pond at
Taft Hill Road (ModSWMM element 304), the downstream overflow at Shields Street
(ModSWMM element 902) was minimized.
The pond spillway and 15-inch outlet pipe were modeled in HY-8 Culvert and a rating curve
was developed. The flows leaving the detention pond through the discharge pipe, and
through the spillway were added together to obtain a total flow leaving the facility. This
rating curve was placed into ModSWMM.
In the event that a greater than 100-year storm occurs, two emergency release mechanisms
are in place. On Spring Creek, at the box culvert diversion point, the 100-year water surface
elevation is 1 foot below the overtopping elevation of the culvert/bridge structure. If the
water surface reaches this elevation, the water will simply overtop the structure and flow into
the downstream part of Spring Creek. In addition, the spillway within the regional detention
pond (Pond A) has enough freeboard to allow emergency spills to be contained at higher
n depths across the weir.
POND B
Basins 1 through 11 contribute flow either through the storm sewer system or by overland
flow to Pond B located upstream of the RCBC diversion structure. Pond B is designed as a
grass lined pond, with a water quality discharge control structure to provide extended
duration detention for water quality. This structure will detain minor storm events for 40
D hours providing a mechanism for pollutants to settle out of the stormwater runoff before
flows are discharged into Spring Creek. The water quality structure contains a grated inlet
that will allow flows up to the 10-year storm event to pass through the pond and into Spring
DCreek. Flows greater than the 10-year storm event will overtop the pond, through a
D5 Ayres Associates
development planned in this, therefore the storm water generated from this basin will
continue in its current designation.
Runoff from Basin Run-1 is captured by the grouted boulder rundown that discharges to
Spring Creek from the west.
The rational method calculations contain four distinct impervious values describing land uses
within the park. These land uses consist of undeveloped areas (typically mowed grass),
gravel areas, ponds, asphalt and concrete paving. The impervious values for these areas
are 20%, 50%, 5%, and 95%, respectively. The natural grassland in the Run-1 drainage
basin is composed of rocky soil and dryland vegetation. The impervious value for this area
was calculated as 40%. The basin parameters and hydrologic calculations are included in
the Appendix for the 10- and 100-year storm events. This data is summarized in Table 2.
Table 2. Rational Method Parameters and Results by Basin Number.
Basin
No.
Drainage
Area (ac)
Percent
Impervious (%)
Q10
(cfs)
Q100
(cfs)
1
2.78
58
7.8
17.5
2
5.09
40
9.3
17.6
3
0.92
25
1.4
2.6
4
1.44
81
5.1
10.3
5
1.11
25
1.4
2.8
6
0.37
35
0.7
1.5
7
5.17
45
10.8
21.4
8
5.21
37
9.3
18.4
9
2.69
60
7.3
15.1
11
1.31
30
2.0
4.1
12
2.55
24
3.2
6.4
13
2.60
27
3.6
7.1
14
42.8
21
38.5
74.9
15
0.58
71
2.5
4.9
16
1.10
73
4.8
9.2
17
1.96
73
8.5
16.4
18
0.96
32
4.6
3.1
19
0.95
20
1.4
2.7
20
0.43
90
2.3
4.0
21
53.6
20
80.4
154.7
Run-1
19.27
40
N/A
53.5
3.3 Proposed Drainage Plan
A discussion of the detailed design of drainage facilities is included in this section. Attached
to this report are the Drainage and Erosion Control Plan Sheets. Storm drainage on the
Spring Canyon Community Park will follow the flowpaths determined by the, grading plan.
Flow tends to concentrate in a series of inlets that drain to a storm sewer network. Drainage
will eventually make its way to Pond A (north central park site) or Pond B (west central park
site), where runoff discharged from the project site will be held at controlled release rates.
�rZ6I:1111Vt1
Ayres Associates
plan for Spring Canyon Community Park. The proposed locations of the regional detention
pond, water quality pond and the pond outfalis to Spring Creek, are indicated on the
proposed plan sheets. Also shown are the locations of the minor storm drainage facilities
that include curb inlets, grate inlets, combined inlets, storm sewer pipes, and minor drainage
swales. Section 3.3 of this report presents a specific description of the proposed drainage
plan for the park.
The design of inlets was performed based on the methodologies outlined in the Urban Storm
Drainage Criteria Manual (USDCM) published by the Urban Drainage and Flood Control
District (UDFCD) in Denver, Colorado. Storm sewers were designed using methods
established in the Hydraulic Engineering Circular Number 22 Urban Drainage Design
Manual, also known as HEC-22. Hydrologic calculations for the design of the local drainage
facilities were performed using the rational method, as described in the Fort Collins manual.
A detailed description of the design of the local drainage facilities is provided in Section 3.3.
The water quality pond was sized in accordance with methods outlined in Volume 3 of the
USDCM. The regional detention pond was sized using ModSWMM. The rational method
analysis was used to determine the 10- and 100-year runoff for the subbasins that contribute
to each pond. Details of the proposed conditions hydrology are included in Section 3.2.
3.2 Proposed Conditions Hydrology
The proposed Spring Canyon Community Park was subdivided into 20 individual sub -basins
with regard to topography and flow contribution. These basins are numbered 1 through 21;
(minus 10) and were incorporated into rational method calculations performed according to
the City of Fort Collins Storm Drainage Design Criteria and Construction Standards manual.
Basins 1 through 11, approximately 26 acres, will drain, via a storm sewer system, overland
flow or curb and gutter, to water quality Pond B located on basin 11, just northwest of the
proposed Hockey rink location.
Basins 12, 13, and 14 are largely pervious area that will be used for recreational purposes
(i.e., soccer and baseball). The basins drain north to a large regional detention facility at the
north corner of the site, Pond A. Pond A does not provide water quality due to the small
amount of impervious land contributing to the pond. This land will generate minimal
amounts of pollutants, of which most will be settled out prior to discharge into Spring Creek.
Basins 15 and 16, approximately 1.7 acres, drain to Spring Creek with no water quality or
detention. The flow from these basins during the minor storm event is a total of 7.3 cfs.
Water quality has not been provided for these basins. Basin 15, 2.5 cfs, is a picnic area and
should not generate many pollutants while basin 16, 4.8 cfs, discharges to a small grass field
prior to entering Spring Creek.
Basin 17 contains a parking lot. The storm water generated from this basin will flow
overland to an existing pond to the north, Pond D
Basin 18 contains mainly a grassy swale that flows to Spring Creek.
Basin 19 will be undisturbed by the development of Spring Canyon Park. Basin 20 is a small
portion of Horsetooth Road that will be re -graded with the development of Spring Canyon
Park. Both basins currently flow offsite where they join existing storm systems.
Basin 21 contains the land that was not captured in Basins 1 through 20. This basin
contains a small amount of grading as well as the re -alignment of Spring Creek. There is no
Ayres Associates
In the western portion of the Park site, Spring Creek is a poorly defined channel that also
appears to have been excavated to convey nuisance stormwater flows to the north. Several
large deciduous trees have grown adjacent to the Spring Creek channel. On the far north
end of the Park site, the Spring Creek channel becomes more defined, and bends to the
northeast. At its confluence with the Pleasant Valley and Lake Canal (PV&L), Spring Creek
is conveyed in a 12-inch pipe under the canal, with any excess flows being conveyed over
the ditch. It should be noted that at this location, the canal appears to have been dug
primarily from excavation, meaning the downstream bank does not appear to be a fill -slope,
but instead native soil. With the existing condition climate and irrigation practices, the Spring
Creek channel does not have a consistent base flow until downstream of the PV&L Canal.
On the southern boundary of the. Park, Horsetooth Road has been extended west to
Horsetooth Court. Runoff from Horsetooth Road, Horsetooth Court and releases from the
Springfield Subdivision detention pond are all conveyed on the south side of Horsetooth
Road west to the valley low point.
In the southwest corner of the proposed Park site, there is an existing fenced -in dog park.
The vegetation in this park site has been predominantly removed in this area, resulting in a
more hard -packed earth, rather than grassed vegetation that characterizes the surrounding
Park site.
On the western boundary of the Park, the northern frontage of the Spring Creek channel is
bounded on the west by Cottonwood Glen Park, a neighborhood park constructed in 2000.
The drainage patterns on the Cottonwood Glen Park generally direct water from west to
east. A portion of the runoff is intercepted by a landscape/irrigation lake and released to
Spring Creek. The remainder of the runoff is discharged directly to Spring Creek.
The Spring Creek Master Drainage Plan provided a big -picture hydrologic analysis of the
Spring Creek Basin, including the Park site. The hydrologic modeling was completed in
MODSWMM and is representative of developed conditions with existing drainage facilities.
The discharge in Spring Creek at various design points in the vicinity of the Park site are
given in Table 1.
Table 1. 100-Year Discharge From Spring Creek Master Plan MODSWMM Model.
Location
Model Node
Discharge
Horsetooth Road
961
1,412
Mid -point of Spring Canyon Community Park
962
1,680
Pleasant Valley and Lake Canal
338
1,871
Model SCDEV100.OUT provided by City of Fort Collins, March 24, 2005
3. PRELIMINARY DRAINAGE PLAN FOR THE SPRING CANYON
COMMUNITY PARK
3.1 General
The preliminary drainage plan for the Spring Canyon Community Park has been developed
to provide a drainage system that meets the requirements established in the City of Fort
Collins Storm Drainage Design Criteria and Construction Standards manual. This has been
accomplished by designing a series of inlets, storm sewers, underdrains, and detention
ponds that will collect, convey, and detain runoff. Sheet C2.3 and C2.4 show the drainage
2 Ayres Associates
1. INTRODUCTION
The Spring Canyon Community Park (SCCP) project consists of approximately 136 acres
located on the north side of West Horsetooth Road (LCR-40) and east of the Pineridge
Natural Area in Fort Collins, Colorado. Figure 1 shows a vicinity map of the project site.
The proposed development would convert an agricultural use area (alfalfa hay) to a
recreational park with numerous athletic facilities, recreational opportunities, and maintained
multi -use open areas.
Figure 1. Vicinity map of the Spring Canyon Community Park.
2. EXISTING DRAINAGE CONDITIONS
The existing Spring Canyon Community Park development site is primarily undeveloped.
For decades, the property has been used as flood -irrigated grassland. The regularity of the
existing ground contours shows evidence of a historic reworking of the land, with a ground
slope of approximately 1.0% from south to north. Around the southern portion of the site,
the Taft Lateral is a periodic irrigation channel that is fed from a pressurized pipe system,
with an outlet near the western terminus of Horsetooth Road. Through the middle of the
site, a small drainage collector channel has been excavated to convey excess irrigation and
stormwater flows north to Spring Creek.
Ayres Associates
TABLE OF CONTENTS
1. introduction................................................................................................................... 1
2. existing drainage conditions..........................................................................................1
3. preliminary drainage plan for the spring canyon......................:.....................................2
3.1 General..................................................................................................................2
3.2 Proposed Conditions Hydrology.............................................................................3
3.3 Proposed Drainage Plan........................................................................................4
3.4 Hydraulic Analysis.................................................................................................. 7
4. SPRING CREEK FLODDPLAIN ANALYSIS..................................................................8
5. erosion control.............................................................................................................. 9
TECHNICALAPPENDIX................................................................................................... --
LIST OF FIGURES
I Figure 1. Vicinity map of the Spring Canyon Community Park............................................1
LIST OF TABLES
Table 1. 100-Year Discharge From Spring Creek Master Plan MODSWMM Model . ........... 2
Table 2. Rational Method Parameters and Results by Basin Number.................................4
Table 3. Detention Summary for Onsite Detention Facilities ............................................... 6
Table 4. Storm Sewer Inlet Summary for Spring Canyon Community Park ......................... 7
Ayres Associates
DRAFT
PRELIMINARY DRAINAGE REPORT
FOR
SPRING CANYON COMMUNITY PARK
Prepared for
City of Fort Collins
Stormwater Utility
215 North Mason
Fort Collins, Colorado 80524
/MIRES
ASSOCIATES
P.O. Box 270460
Fort Collins, Colorado 80527
(970) 223-5556, FAX (970) 223-5578
Ayres Project No. 32-0890.00 (Task 5)
SP-CAN6T.DOC
October 2005