HomeMy WebLinkAboutFORT COLLINS LOVELAND WATER DISTRICT - PDP - 23-98 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTst
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VICINITY MAP
APPROXIMATE SCALE: 1" = 2000'
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APPENDIX A
MAPS AND FIGURES
6.0 REFERENCES
1
2.
3
4
n
City of Fort Collins, "Storm Drainage Design Criteria and Construction Standards,"
(SDDCCS), dated May 1984.
Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria
Manual", Volumes 1 and 2, dated March 1969, and Volume 3 dated September
1992.
Master Drainageway Planning Study for the Fossil Creek Drainage Basin by
Simons, Li & Associates dated August 1982.
Final Drainage Report for the Fossil Creek Design Center, P.U.D. by Stewart &
Associates, Inc. dated May 16, 1989.
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1
and soil stockpiles not otherwise permanently stabilized. Vegetation shall not be
considered until a ground cover is achieved which is demonstrated to be mature enough to
control soil erosion to the satisfaction of the City and to survive severe weather conditions.
Erosion control calculations, cost estimate, and schedule is included in the appendix of this
report.
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1
1
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1
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Rainfall Wind
Soil Designation Erodibility Zone Erodibility Zone
Altvan-Santata Loams Moderate Moderate
5.3 . Erosion and Sediment Control Measures
Erosion and Sedimentation will be controlled on -site by the use of silt fence, construction
entrances and overexcavation of the detention ponds during construction to act as sediment
traps.
5.4 Dust Abatement
During the performance of the work or any operations appurtenant thereto, the Contractor shall
-carry out proper efficient measures wherever and as necessary to prevent or reduce dust
nuisance, and to prevent dust which has originatedfrom his operations from damaging crops,
orchards, cultivated fields, and dwellings, or causing a nuisance to persons. The Contractor
will be responsible for any damage resulting from dust originating from his operations.
5.5 Tracking Mud on City Streets
Wherever construction vehicles access routes or intersect paved public roads, provisions must
be made to minimize the transport of sediment (mud) by runoff or vehicles tracking onto the
paved surface. Stabilized construction entrances are required per the detail shown on the Plan,
with base material consisting ofb" coarse aggregate. The contractor will be responsible for
clearing mud tracked onto city streets on a daily basis.
5.6 Maintenance
All temporary and permanent erosion and sediment control practices must be maintained and
repaired as needed to assure continued performance of their needed function. Maintenance
is the responsibility of the contractor.
5.7 Permanent Stabilization
A vegetative cover shall be established within one and one-half years on disturbed areas
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1 4.
DESIGN
AREA
AREA
C10
C10o
Tc (10)
Tc (100)
Q(10),
Q (100)
POINT
DESIG.
(ACRES)
(MIN)
MIN)
(CFS)
(CFS)
1
1
3.17
0.40
0.50
9.3
8.4
6.73
13.99
2
2
0.71
0.57
0.71
6.8
5.5
2.07
4.41
3
0.17
0.88
1.0
5.0
5.0
0.86
1.56
4
0.59
0.27
0.34
10.8
10.8
0.70
1.39
RUNOFF DETENTION AND RELEASE '
The site will contain two detention ponds, detention pond 1 is located at the southwest corner
of Tractt C and detention pond 2 is located in Lot 1. Both ponds are designed to detain runoff
from the 100-year storm from the site. Detention Pond 1 will release into detention pond ?.
at agate of °1 A cfs and will -be controlled by 5.2" diameter orifice plate. Detention Vond 2 will
release into the existing storm system in Snead Drive at a rate of 1.5 cfs and will be controlled
by a 6.4" diameter orifice plate. Calculations are included in the appendix of this report.
5. EROSION CONTROL
5.1 Introduction
This section represents the Erosion Control Report for Fort Collins -Loveland Water District
and was prepared to meet the regulatory requirements of the City of Fort Collins. This report
was prepared following the guidelines and regulations set forth in the SDDCCS Manual.
The proposed improvements cover all of Lot 1 and grading will be completed in Tract C.
1 No grading or improvements are proposed on Tracts A or B.
The general topography of this site consists of undisturbed soil with native vegetative ground
' cover. Slopes range from three to ten percent.
' 5.2 Soil Description
' In accordance with the Soil Conservation Service's {SCS) "Soil Survey of Fort Collins Area,
Colorado," the soils on -site consist of the following:
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1
3.4 Hydrologic Analysis of the Proposed Drainage Conditions
The Rational Method was used to determine both 10-year and 100-year peak runoff values for
-each Sub -basin. Runoff coefficients were assigned utilizing Table 3-2 of the SDDCCS
Manual.
As stated above, the Rational Method was used for all hydrologic analyses for the project site.
The Rational Method utilizes the equation:
Q=CfCIA (1)
where Q is the flow in cfs, C is the runoff coefficient, Cf is the storm frequency adjustment
factor, I is the rainfall intensity in inches per hour, and A is the total area of the basin in acres.
The frequency adjustment factor, Cf is 1.0 for the initial 10-year storm and 1.25 for the major
100-year storm.
The appropriate rainfall intensity information was developed based on rainfall intensity -
duration curves in Figure 3-1 of this Manual.
In order -to utilize the rainfall intensity -curves, the time of concentration is required. The
following equation was used to determine the time of -concentration:
t'=ta+tt
(2)
where t, is the time of concentration in minutes, to is the initial or overland flow time in
minutes, and t, is the travel time in the ditch,channel, or gutter in minutes. The initial or
overland- low time is calculated with the equation:
to = [1.87(1.1- CCf)Lo.5J/(S)0.33
(3)
where L is the length of overland flow in feet {limited to a maximum of 500 feet), S is the
average slope of the basin in percent, and C and Cf ar-e as defined previously.
All hydrologic calculations associated with the sub -basins shown are attached in the Appendix
of this report. Table 3.1 provides a summary of the design flows for all Subbasins and Design
Points (DP's) associated with this site.
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1 the site through an existing irrigation lateral. This flow is diverted to the east property line and
is not conveyed through proposed detention facilities.
3.3 Onsite Flows
Approximately 2 acres of this 5-acre site has been rezoned to allow for the development of the
FCLWD building and the remainder of the site will remain undeveloped. Drainage within the
developed area will surface flow to detention ponds with the exception of two basins, which
will direct discharge. All grading has been designed to carry flows in a positive direction
away from structures to the proposed drainage facilities. A qualitative summary of the
drainage patterns within each developed sub -basin is provided in the following paragraphs.
Detention and -release rates are described in Section 4, "Runoff Detention and Release".
Sub -basin 1 is approximately 3.7 acres and contains a portion of the east half of Snead Drive. ..
the FCL WD building and the storage yard. Runoff from Sub -basin 1 is conveyed by surface
flow to Detention Pond #1 at the southeast comer of Tract C. Release from this detention
pond flows into Detention Pond 42 and is restricted to 1.0 cfs by an orifice plate.
Sub -basin 2 contains the drop off lane, the parking lot on the south of -the building and the
green area between Snead Drive and the drop off lane. Sub -basin 2 contains approximately
0.7 acres and runoff from this sub -basin is carried overland to detention pond #2. Detention
pond #2 also receives discharge from detention pond #1 and releases to the inlet and storm
system in Snead Drive. The discharge from this pond is limited to 1.5 cfs by an orifice plate.
Sub -basin 3 is a small basin along the west property line and contains approximately 0.17
acres. This sub -basin contains the east half of Snead Drive that is released downstream
undetained.
Sub -basin 4 is along the south property line of the site and is primarily maintained as native
grasses. This basin will release downstream undetained as it has historically done. The
amount of runoff released downstream will be dramatically reduced because of the on site
detention. A perforated pipe will also be installed along the south property line in an attempt
to alleviate downstream concerns and to help mitigate groundwater issues downstream.
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2.
3.
1.5 Master Drainage Basin
This site is located in the Fossil Creek Master Drainage Basin. The Master Drainageway
Planning Study forthe Fossil Creek Drainage Basin prepared by Simons, Li & Associates, Inc.
dated August 1982 does not require on -site storm water detention for this -site. On -site
detention will be provided for this site to lower the discharge from the site and improve
downstream conditions.
EXISTING DRAINAGE SYSTEM
Fossil Creek Design Center installed a storm system in Snead Drive that will be utilized for
the detention discharge from this site. An inlet on the west side of Snead Drive collects flows
from the Fossil Creek Design Center from a 15" pipe and also collects flows from Snead
Drive. These flows are discharged to a swale to the south through a 27" pipe. The Swale
carries flows south to a 30" pipe under Fossil Creek Parkway and into Fossil Creek.
Detention discharge from the FCLWD site will be routed via pipe to the existing inlet in
Snead Drive and then south in the existing swaleto the pipe under Fossil Creek Parkway.
Our research and field survey determined that the pipe under Fossil Creek Parkway was
installed approximately 3 feet too high and the slope is flatter that was designed. This
construction error has reduced the capacity of this pipe. The pipe will have the capacity to
convey flows from the FCLWD site with this development but with any future development
east or west of Snead Drive, this pipe will require upsizing or an additional pipe will need to
be installed under Fossil Creek Parkway.
DEVELOPED FLOWS
3.1 Criteria
The Rational Method was used to determine both the 10-year and 100-year flows for the sub -
basins indicated in this drainage report. A description of the hydrologic analysis is provided
in Section 3.6 of this report.
3.2 Off -site Flows
A portion of the east half of Snead Drive will be routed through this site and into the proposed
detention area. Offsite flows from the property to the north will continue to be routed through
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1. INTRODUCTION
' 1.1 Project Location
The proposed Fort Collins -Loveland Water District (FCLWD) building is located adjacent to
the east side of Snead Drive, north of Fossil Creek Parkway and south of Fairway Lane. The
site location can also be described as a portion of the Southwest Quarter of Section 1,
Township 6 North, Range 69 West of the Sixth Principal Meridian, City of Fort Collins,
County of Larimer, State of Colorado.
The site is approximately 5 acres, and is bounded on the north, east and south by residential
developments and on the west by Snead Drive and the Fossil Creek Design Center. (See
FIGURE 1 - VICINITY MAP.)
1.2 Site Characteristics
The general topography of the site consists :primarily of undisturbed soil with native
vegetation. In general the site slopes to the southeast at slopes varying from 3 to 10 percent.
The Soil Survey of Larimer County Area, Colorado indicates the soils for this site are
comprised of Altvan-Santanta loams which have the potential for moderate wind and water
erosion.
1.3 Purpose and Scope of Report
This report defines the proposed drainage and erosion control plan for the proposed Fort
Collins -Loveland Water District, including consideration of all on -site and off -site runoff.
1.4 Design Criteria
This report was prepared to meet or exceed the submittal requirements established in the City
of Fort Collins' "Storm Drainage Design Criteria and Construction Standards" (SDDCCS),
dated May 1984. Runoff computations were prepared for the 10-year and 100-year storm
frequency utilizing the rational method.
Where applicable, the criteria established in the "Urban Storm Drainage Criteria Manual"
(UDFCD), 1984, developed by the Denver regional Council of Governments, has been
utilized.
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TABLE OF CONTENT'S
TABLE OF CONTENTS
2.
INTRODUCTION
PAGE
1.1 Project Location..............................................................................1
1.2 Site Characteristics..........................................................................1
1.3 Purpose and Scope of Report ..............................................................1
1.4 Design Criteria..............................................................................1
1.5 Master Drainage Basin...................................................................................2
EXISTING DRAINAGE SYSTEM ...... :.....................................................................2
3. DEVELOPED FLOWS
3.1 Criteria..............................................................................................:..................:...2
3.2 Off -Site Flows..........................................................................................................2
3.3 Onsite Flows...........................................................................................................3
3.4 , Hydrologic Analysis of the Proposed Drainage Conditions....................................4
' 4.
RUNOFF DETENTION AND RELEASE.......................................................5
5.
EROSION
CONTROL ..............................................................................5
5.1
Introduction..............................................................................................................5
5.2
Soil Description.......................................:...............................................................5
5.3
Erosion and Sediment Control Measures................................................................6
5.4 _Dust
Abatement.......................................................................................................6
5.5
Tracking Mud on City Streets ...................... :...........................................................
6
5.6
Maintenance .............................................................................................................6
5.7
Permanent Stabilization ................... .........................................................................
6
6.
REFERENCES....................................................................:..................8
APPENDIX
A
MAPS AND FIGURES
APPENDIX B HYDROLOGIC CALCULATIONS
APPENDIX C DETENTION POND CALCULATIONS
APPENDIX D ORIFICE PLATE CALCULATIONS
APPENDIX E EROSION CONTROL CALCULATIONS
APPENDIX F FOSSIL CREEK DESIGN CENTER DRAINAGE REPORT
No Text
FINAL DRAINAGE AND EROSION
CONTROL STUDY
FOR
FORT COLLINS-LOVELAND WATER DISTRICT
Prepared for:
FORT COLLINS-LOVELAND WATER 17ISTRICT
47,00 South College Avenue
Fort Collins, CO 80525
970-226-3104
Prepared by:
JR Engineering, Ltd.
2620 East Prospect Road, Suite 190
Fort Collins, Colorado 80525
(970) 491-9888
April 21, 1998
Job Number 9097.03
FINAL DRAINAGE AND EROSION
CONTROL STUDY
FOR
FORT COLLINS-LOVELAND WATER DISTRICT
Engineering, Ltd,