HomeMy WebLinkAboutKNICKERS PRELIMINARY PUD - 10 91 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTFinal Drainage Report
for
LOUDEN CREEK GOLF COURSE
Fort Collins, Colorado
Prepared for
KNICKERS, INC.
PREUMINAmvn
Project No: 1230-1-91
Date: March 4, 1991
4836 S. College, Suite 12 Fort Collins, CO 80525 (303)226-5334
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APPENDIX B
Figure 3-1; City of Fort Collins Rainfall -Intensity -Duration curves
Figure 3-2; Travel Time Velocity Curves, Urban Drainage and Flood Control
District
Figure 804-ID; Culvert capacity nomograph, Colorado Department of Highways
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# MOST FREQUENTLY OCCURRING "UNDEVELOPED"
LAND SURFACES IN THE DENVER REGION:
REFERENCE: "Urban. Hydrology For. Small ,Watersheds" Technical
Release No. 55, USDA, SCS Jan. 1975.
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APPENDIX C
Louden Creek Golf Course Drainage Plan (Stuffer Envelope)
I GENERAL LOCATION AND DESCRIPTION
A. Location
1. The Louden Creek Golf Course is located in South Fort
Collins in the Northeast one -quarter of Section 14, T6N,
R69W of the 6th P.N. It is located adjacent to Colorado
State Highway 287. It is on the west side of 287.
2. The site is bounded partially on the north by the Hermitage
Annexation and partially by unplatted property, on the west
and south by unplatted property and on the east by Colorado
State Highway 287.
B. Description of property
1. Louden Creek Golf Course contains approximately 33.27 acres.
2. The property is currently utilized as pasture/grassland and
is covered primarily with dryland wild grasses. Stablesand
other equestrian related appurtenances exist on the site.
3. Development will consist of a 3 par, 9 hole golf course with
supplemental recreational facilities.
4. The site slopes moderately from west to east with slopes
reaching in the area of 6X to 7X nearing the east side of
the property.
5. The North Louden Ditch crosses the property. It will remain
unaffected and incorporated into the design of the golf
course. It will not be considered as a storm water
conveyance facility with this project.
II DRAINAGE BASINS AND SUB -BASINS
A. Major Basin description
1. Louden Creek Golf Course is contained within the Fossil
Creek Drainage Basin.
2. The North Louden Ditch is located on the property and has
the potential to intercept storm runoff from the west. The
assumption that the ditch will be flowing at capacity will
be made for all rainfall events.
B. Sub -basin description
1. The property is contained within a sub -basin consisting of
approximately 144 acres. Runoff from the property, including
offsite contribution to the property from the west,
concentrates at a point near the Southeast corner of the
property. A 24" RCP conveys storm runoff from the property,
under Highway 287, to Robert Benson Reservoir. Robert Benson
Reservoir is directly adjacent to Highway 287 on the east
side.
2. There will be absolutely no change to historic flow patterns
due to development of the Golf Course. Runoff will continue
to flow to the east, concentrate at the existing 24" RCP,
and be conveyed under Highway 287 to Robert Benson Reservoir
via the existing 24" RCP.
III DRAINAGE DESIGN CRITERIA
A. Regulations:
1. City of Fort Collins Storm Drainage Criteria was used.
B. Development criteria reference and constraints
1. Although the North Louden Ditch is located on the property,
it will be assumed to be flowing full for peak runoff
calculations for the 'two. storm frequency events under
consideration.
III DRAINAGE DESIGN CRITERIA (continued)
B. Development criteria reference and constraints (continued)
2. Highway 287 and the existing 24" RCP under Highway 287
appear to be the main potential stormwater design
constraints. The 24" RCP was installed with the construction
of Highway 287. Highway Department Construction plans
indicate flow values and contributing area acreage to the
24" RCP. However, no backup drainage report for the values
indicated on the Highway Department plans was available from
the Highway Department.
C. Hydrological criteria
1. The Rational Method for determining peak flows was used for
the evaluation of the 2 and 100 year event.
2. The Cumulative Runoff method (Mass Curve) for determining
potential detention storage requirements will be utilized.
This method will also be used to determine the potential
detention storage which will occur due to the existing 24"
RCP outlet restriction from the property.
D. Hydraulic criteria
1. The 1990 Highway Department Roadway Design Manual culvert
nomographs were used to determine the Highway 287 24" RCP
culvert capacity with certain Headwater to Diameter (HW/D)
ratios.
IV DRAINAGE FACILITY DESIGN
A. General concept
1. Generally, there will be no change to historic flow
patterns. All storm runoff will continue to be conveyed to
the existing 24" RCP located at the southeast portion of the
property. Refer to the Drainage Plan included in the back
envelope of this report.
2. Temporary erosion protection is anticipated at the existing
24" RCP until golf course plantings take hold. Possible
erosion control upstream of the North Louden Ditch is also
anticipated. Immediate planting will occur to establish golf
course fairways as soon as possible.
A. Specific Details
1. The 24" RCP remains the primary storm drainage facility_
affecting the site.
a. The RCP size restricts the release of stormwater from
the site to less than historic flows, based on the
contributing area established with this report.
b. The 24" RCP causes the potential for excessive storm
backwaters on this site, prior to overflowing the curb
into Highway 287. "
V CONCLUSIONS
A. Compliance with standards
1. All drainage calculations and facility design comply with
the requirements of the City of Fort Collins Storm Drainage
Criteria Manual and the current storm drainage system
intent.
B. Drainage concept
1. The drainage concept for the Louden Creek Golf Course
remains unchanged from the existing drainage situation.
V CONCLUSIONS (continued)
B. Drainage concept (continued)
2. All grading of golf course fairways will :include the
provision for adequate conveyance of storm water runoff
through the site and to the existing 24" RCP.
3. There will be absolutely no additional potential downstream
impact due to the development of this project.
4. The potential for storm water flow over the curb into
Highway 287 exists (for current conditions) for less
frequent storms which generate more runoff. This is because
the existing 24" RCP restricts the conveyance of total
historic flows (for the total anticipated contributing area)
to the 2-year storm.
a. 2-year storm calculated flow to 24" RCP = 39.4 cfs
b. 24" RCP capacity with HW/D of 4.25 = 42.5 cfs
5. The detention volume determination with the cumulative
runoff method amd the existing 24" &CP release, does not
indicate that this project be required to provide that
amount of storm water detention.
C. Erosion Control
1. The affected areas of the site during earthwork operations,
will be restricted to the fairways and will be minimal
relative to the total area of the project.
2. Temporary erosion control protection will be provided at the
existing 24" RCP until golf course plantings take hold.
Erosion control upstream of the North Louden Ditch will be
provided to only the extent of the affected area. Immediate
appropriate seeding and planting will occur to establish
golf course fairways as soon as possible.
VI REFERENCES
1. City of Fort Collins Storm Drainage Criteria Manual
2. "Roadway Design Manual", Colorado Department of Highways, 1990.
3. Colorado Department of Highways construction plans for Highway
287; 1978.
APPENDIX A
Exhibit A, portion of U.S.G.S. Loveland Quadrangle Map; U.S.G.S.,
Photorevised 1984
Runoff Calculations
Mass Curve for detention potential (Cumulative Runoff Method)
Stage -Storage Curve for existing conditions
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