HomeMy WebLinkAboutRIGDEN FARM, THE COLONY - PDP - 56-98AC - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT8. REFERENCES
1. City of Fort Collins, "Storm Drainage Design Criteria and Construction Standards"
(SDDCCS), May 1984.
2. "Drainage and Erosion Control Report for Rigden Farm Filing One, P.D.P.", JR
Engineering, September 1999.
3. "Drainage and Erosion Control Report for with Rigden Farm, 7th Filing, The
Willow", JR Engineering, Revised January 14, 2002
4. "Final Report for the Hydrologic Model Update for the Foothills Basin Master
Drainage Plan", April 27, 1999, Anderson Consulting Engineers, Inc.
5. "Foothills Basin (Basin G) Drainage Master Plan", February 1981, Resource
Consultants, Inc.
6. "Overall Drainage Plan for the Rigden Farm O.D.P.", JR Engineering, November
1999.
7. Soil Survey of Larimer County Area, Colorado. United States Department of
Agriculture Soil Conservation Service and Forest Service, 1980.
8. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria
Manual", Volumes 1 and 2, dated June 2001, and Volume 3, dated September 1999.
Drainage and Erosion Control Report
Rigden Farm, Tract C
. "5" .
March, 2005
Stabilized construction entrances are required per the detail shown on the Erosion Control
Plan, with base material consisting of 6" coarse aggregate. The contractor will be
responsible for clearing mud tracked onto city streets on a daily basis.
5.4 Maintenance
All temporary and permanent erosion and sediment control practices must be maintained and
repaired as needed to assure continued performance of their intended function. Straw bale
dikes or silt fences will require periodic replacement. Sediment traps (behind straw bale
barriers) shall be cleaned when accumulated sediments equal approximately one-half of trap
storage capacity. Maintenance is the responsibility of the developer.
5.5 Permanent Stabilization
A vegetative cover shall be established within one and one-half years on disturbed areas and
soil stockpiles not otherwise permanently stabilized. Vegetation shall not be considered
established until a ground cover is achieved which is demonstrated to be mature enough to
control soil erosion to the satisfaction of the City Inspector and to survive severe weather
conditions.
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Rigden Farm, Tract C March, 2005
The storm pipe calculations were performed to ensure that the existing systems would not be
adversely impacted by the additional flows from Rigden Farm Tract C. Because all flows
were reduced from the assumed flows calculated with Rigden Farm, 71h Filing, The Willow,
the riprap provided at the outlet of all impacted storm pipes was not resized and therefore, no
calculations for riprap sizing were provided in the appendices.
5. EROSION CONTROL
5.1 Erosion and Sediment Control Measures
Erosion and sedimentation will be controlled on -site by use of silt fences, inlet protection,
gravel construction entrances with vehicle tracking control, and seeding and mulch. The
measures are designed to limit the overall sediment yield increase due to construction as
required by the City of Fort Collins. During overlot and final grading the soil will be
roughened and furrowed perpendicular to the prevailing winds. Erosion control
effectiveness, rainfall performance calculations and a construction schedule with surety
calculations will be provided in Appendix F during final submittal.
5.2 Dust Abatement
During the performance of the work required by these specifications or any operations
appurtenant thereto, whether on right-of-way provided by the City or elsewhere, the
contractor shall furnish all labor, equipment, materials, and means required. The Contractor
shall carry out proper efficient measures wherever and as necessary to reduce dust nuisance,
and to prevent dust nuisance that has originated from his operations from damaging crops,
orchards, cultivated fields, and dwellings, or causing nuisance to persons. The Contractor
will be held liable for any damage resulting from dust originating from his operations under
these specifications on right-of-way or elsewhere.
5.3 Tracking Mud on City Streets
It is unlawful to track or cause to be tracked mud or other debris onto city streets or rights -of -
way unless so approved by the Director of Engineering in writing. 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.
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Rigden Farm, Tract C March, 2005
curb or the street crown for local streets. During the major storm, the depth of water over the
crown or curb is limited to six inches. The 2-year storm was used as the minor storm and the
100-year storm was used as the major storm for street capacity calculations. See the street
capacity calculations in Appendix C for more detailed information.
4.2 Inlet Sizing
Inlets were sized using the computer program UDWLET that was developed by James C. Y.
Guo of the University of Colorado at Denver. Computer output files for the inlet sizing are
provided in Appendix D of this report. Inlets were designed to receive the 100-year peak
flows. The existing Type R inlets were calculated using a 50% grate clogging factor and a
10% curb opening clogging factor. The existing Type C Area inlet was also calculated with a
50% grate clogging factor. All inlet locations and sizes are shown on the Utility Plans for the
construction of this project. The "turtle -back" grate and frame is Neenah Type R-4360-D,
and will accept the 0.2 cfs of flow from Swale A with a 50% grate clogging factor. (See
Appendix D for inlet capacity calculation.)
4.3 Storm Sewer System
' For the storm pipe design, the computer program StormCAD, developed by Haestad
Methods, Inc. was used. StormCAD considers whether a storm pipe is under inlet or outlet
control and if the flow is uniform, varied, or pressurized and applies the appropriate
equations (Manning's, Kutter's, Hazen -Williams, etc). StormCAD also takes into account
tailwater effects and hydraulic losses that are encountered in the storm structures. It
calculates the losses through an inlet or manhole by allowing the user to assign a coefficient
for the equation,
Where hL = headloss
K = headloss coefficient
V = average velocity (ft/s)
g = gravitational constant (32.2 ft/sz)
Drainage and Erosion Control Report Page 6
f Rigden Farm, Tract C March, 2005
where Q is the maximum rate of runoff in cfs, A is the total area of the basin in acres, Cr is
the storm frequency adjustment factor, C is the runoff coefficient, and I is the rainfall
intensity in inches per hour for a storm duration equal to the time of concentration. The
frequency adjustment factor, Cr, is 1.0 for the initial 2-year storm and 1.25 for the major 100-
year storm. The runoff coefficient is dependent on land use or surface characteristics.
The rainfall intensity is selected from Rainfall Intensity Duration Curves for the City of Fort
Collins (Figure 3.1 of SDDCCS). In order to utilize the Rainfall Intensity Duration Curves,
the time of concentration is required. The following equation is used to determine the time
of concentration
t,=ti+tt
(2)
where tc is the time of concentration in minutes, ti is the initial or overland flow time in
minutes, and tt is the conveyance travel time in minutes. The initial or overland flow time is
calculated with the SDDCCS Manual equation:
ti = [1.87(l.1 - CCt)L0.5J/(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 Cr are as defined previously.
All hydrologic calculations associated with the sub -basins shown on the attached drainage
plan are included in Appendix B of this report.
4. HYDRAULIC ANALYSIS
4.1 Allowable Street Capacity
The theoretical street and gutter capacity was calculated using Manning's equation for open
channel flow. Allowable gutter flows and maximum street capacities for both the initial and
major storms were estimated and evaluated based on the specifications set forth in the
SDDCCS Manual. During the initial storm, runoff was not allowed to overtop either the
Drainage and Erosion Control Report Page 5
Rigden Farm, Tract C March, 2005
Runoff from Sub -basin 101 will be conveyed via overland flow to the gutter of
Kansas Drive and then flow north to the gutter of Custer Drive (design point 1) where
it will flow eastward to existing design point 4 of the Rigden Farm Filing One P.D.P
on Custer Drive, where an existing sump inlet will ultimately convey these flows south
to the existing Water Quality Pond 1.
Runoff from Sub -basin 102 will be conveyed via overland flow to Swale A (design
I point 2) where an existing manhole lid will be replaced by an open grate. The capacity
of the open grate in a sump was checked. The pipe capacity was re -run with StormCad
and the system showed no negative impacts, (See Appendix D for grate calculation and
Appendix E for StormCad calculations). This flow will then be piped via existing
storm pipe to the existing Water Quality Pond 2.
Runoff from Sub -basin 103 will flow east via overland flow to the gutter of Kansas
lDrive to design point 3, where gutter flow will carry the flows south along Kansas
Drive and then east along Parkfront Drive to an existing sump inlet at design point 17
of Rigden Farm, 7th Filing, The Willow. The flow is then conveyed via existing storm
pipe to the existing Water Quality Pond 2.
lRunoff from Sub -basin 104 will be conveyed via overland and gutter flow to the
existing area inlet at design point 4. The flow will then be conveyed southward via
existing pipe system to existing Water Quality Pond 2. The flows to the existing area
inlet were checked and do not show any negative impacts to the inlet or the pipe
system installed with Rigden Farm, 7th Filing, The Willow (see Appendix D for grate
calculation and Appendix E for StormCad calculations).
3.4 Hydrologic Analysis of the Proposed Drainage Conditions
The Rational Method was used to determine the 2-year and 100-year peak runoff values for
each sub -basin. Runoff coefficients were assigned using Table 3-2 of the SDDCCS Manual.
The Rational Method is given by:
IQ = CtCIA (1)
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Rigden Farm, Tract C March, 2005
and routing of storm water within the site and therefore, historic runoff calculations are not
included as part of this report.
3. LOCAL DEVELOPED DRAINAGE DESIGN
3.1 Method
The Rational Method was used to determine the 2-year and 100-year flows for the sub -basins
indicated in this drainage report. Drainage facilities were designed to convey the 100-year
peak flows. A detailed description of the hydrologic analysis is provided in Section 3.4 and
the calculations are found in Appendix B of this report.
3.2 General Flow Routing
The proposed drainage patterns from the Overall Drainage Plan for the Rigden Farm O.D.P.
l have been maintained as closely as possible with this development. Flows within this site
will take the form of overland, gutter, swale and pipe flow. The proposed drainage facilities
for this site consist of. a proposed swale, sidewalk chases, erosion control and utilizing
existing drainage pipe systems. The following summarizes proposed flow routing within the
site. The Drainage and Erosion Control Plan, attached in the map pocket, depicts the
locations of basins, design points, swales and existing storm systems.
Most of the runoff from the parcel will be conveyed to the south where it will then be
collected by a couple of existing inlets and storm pipes, constructed with Rigden Farm, 7th
�. Filing, The Willow. From here, the storm pipes outlet into Water Quality Pond 2, designed
with Rigden Farm Filing One P.D.P.
3.3 Proposed Drainage Plan
A qualitative summary of the drainage patterns within each sub -basin and at each design
point is provided in the following paragraphs. Discussions of the detailed design
methodologies for the drainage facilities identified in this section are included in the
following sections.
Drainage and Erosion Control Report Page 3
Rigden Farm, Tract C March, 2005
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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 and updated April 1997. Where applicable, the criteria established in the
"Urban Storm Drainage Criteria Manual" (UDFCD), developed by the Denver Regional
Council of Governments have been utilized.
1.5 Master Drainage Basin
Rigden Farm, Tract C lies in Reach 2 of the Foothills Drainage Basin. The master drainage
basin study for this area is the "Foothills Basin (Basin G) Master Drainage Plan" by Resource
Consultants, Inc.,1981. Another applicable report is the "Final Report for Hydrologic Model
Update for the Foothills Basin Master Drainage Plan" by Anderson Consulting Engineers,
Inc. (ACE) dated July 15, 1999. The proposed site is also included in the O.D.P. by JR
Engineering, dated November 24, 1999. The ACE model incorporates the proposed build
out of the Rigden Farm subdivision as defined in the O.D.P. report.
2. HISTORIC (EXISTING) DRAINAGE
The historic (existing) flows draining to or through the site consist primarily of on -site flows.
The overall drainage pattern for the entire site is via overland flow in a southerly direction at
slopes that range from 0.5 to 3 percent. The site currently drains into Water Quality Ponds 1
& 2 designed with the "Final Drainage and Erosion Control Report for Rigden Farm Filing
One, P.D.P." These Water Quality Ponds outlet directly into the Foothills Regional Channel.
The Foothills Regional Channel (FRC) was modeled with HEC-RAS in the Final Drainage
and Erosion P.D.P. and Rigden Farm, Tract C, is not changing flows from the O.D.P. and
therefore not modeling the FRC.
The "Overall Drainage Plan for the Rigden Farm O.D.P." and the "Final Drainage and
Erosion Control Report for Rigden Farm Filing One, P.D.P." addressed the historic quantities
Drainage and Erosion Control Report
Rigden Farm, Tract C
Page 2
March, 2005
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' 1. INTRODUCTION
1.1 Project Description
Rigden Farm, Tract C is located in the north half of Section 29, Township 7 North, Range 68
West, City of Fort Collins, Larimer County, Colorado. The site is approximately 3 acres. A
location map is provided in Appendix A. The site is bound by Custer Drive to the north, the
' Willow Subdivision to the south and east, and vacant undeveloped land to the west.
I1.2 Existing Site Characteristics
The site is primarily covered with native grasses. The parcel currently drains in a southerly
direction at slopes ranging from 0.5% to 3%. The site discharges into existing Water Quality
Ponds 1 & 2 designed in Rigden Farm Filing One P.D.P. documents. The soil is
predominately Nunn clay loam (soil number 73) having slopes from 0 to 5% as shown on the
soil map included in Appendix A (USDA SCS, 1980). Nunn clay loam consists of nearly
' level soils on high terraces and fans. Pertinent characteristics of this soil include slow to
medium runoff, a slight hazard of wind erosion, and a moderate hazard of water erosion.
Nunn clay loam is categorized as Hydrologic Group C.
' 1.3 Purpose and Scope of Report
This report defines the proposed drainage and erosion control plan for Rigden Farm, Tract C.
The plan includes consideration of all on -site runoff and the design of all drainage facilities
required for this project site. This drainage plan is consistent with the design concepts of the
' drainage reports prepared for Rigden Farm Overall Development Plan (O.D.P.) and Rigden
Farm, 7`h Filing, The Willow and with the design concepts of the Drainage and Erosion
' Control Report for Rigden Farm Filing One, Project Development Plan (P.D.P.).
Drainage and Erosion Control Report Page t
Rigden Farm, Tract C March, 2005
TABLE OF CONTENTS
PAGE
TRANSMITTAL LETTER.................................................................................. i
TABLE OF CONTENTS.............................................................................................................. ii
1. INTRODUCTION..................................................................................................................I
1.1 Project Description..........................................................................................................1
1.2 Existing Site Characteristics...........................................................................................1
1.3 Purpose and Scope of Report ..........................................................................................1
1.4 Design Criteria................................................................................................................2
1.5 Master Drainage Basin....................................................................................................2
2. HISTORIC (EXISTING) DRAINAGE................................................................................2
' 3. LOCAL DEVELOPED DRAINAGE DESIGN...................................................................3
3.1 Method............................................................................................................................3
3.2 General Flow Routing.....................................................................................................3
3.3 Proposed Drainage Plan..................................................................................................3
3.4 Hydrologic Analysis of the Proposed Drainage Conditions............................................4
4. HYDRAULIC ANALYSIS.....................................................................:..............................5
4.1 Allowable Street Capacity...............................................................................................5
4.2 Inlet Sizing......................................................................................................................6
4.3 Storm Sewer System.......................................................................................................6
5. EROSION CONTROL...........................................................................................................7
5.1 Erosion and Sediment Control Measures........................................................................7
5.2 Dust Abatement...............................................................................................................7
5.3 Tracking Mud on City Streets.........................................................................................7
5.4 Maintenance....................................................................................................................8
5.5 Permanent Stabilization..................................................................................................8
8. REFERENCES
..................................................................................9
Appendix A: Maps and Figures
Appendix B: Hydrologic Calculations
Appendix C: Street Capacity Calculations
Appendix D: Inlet Calculations
Appendix E: Storm Pipe and Swale Calculations
Appendix F: Erosion Control (Calculations to be included at Final Submittal)
Appendix G: Excerpts from Other Reports
J-R ENGINEERING
it!^: es U�ian Cm:;paiq
March 2, 2005
f Mr. Basil Hamdan
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
RE: Final Drainage and Erosion Control Report-Rigden Farm, Tract C
Dear Basil:
We are pleased to submit to you for your review this Preliminary Drainage and Erosion Control
Report for Rigden Farm, Tract C. All computations within this report have been completed in
compliance with the City of Fort Collins Storm Drainage Design Criteria.
We greatly appreciate your time and consideration in reviewing this submittal. Please call if you
have any questions.
Sincerely,
Prepared by,
Erika Schneider
Design Engineer II
Reviewed by,
Lee Watkins, P.E.
Project Manager
2620 East Prospect Road, Suite 190, Fort Collins, CO 80525
970-491-9888 • Fax: 970-491-9984 • w Jrengineering.com
PRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT
The Colony at Rigden Farm
Prepared for:
The Colony at Rigden Farm
25338 Foothills Drive
Golden, Colorado 80401
(303) 289-1992
Prepared by:
JR Engineering
2620 E. Prospect Road, Suite 190
Fort Collins, Colorado 80525
(970)491-9888
February 15, 2005
Job Number 39422.00