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APPENDIX A
MAPS AND FIGURES
7. 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. "Final Report for the Hydrologic Model Update for the Foothills Basin Master
Drainage Plan", April 27, 1999, Anderson Consulting Engineers, Inc.
4. "Foothills Basin (Basin G) Drainage Master Plan", February 1981, Resource
Consultants, Inc.
5. "Overall Drainage Plan for the Rigden Farm O.D.P.", JR Engineering, November
1999.
6. Soil Survey of Larimer County Area, Colorado. United States Department of
Agriculture Soil Conservation Service and Forest Service, 1980.
7. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria
Manual", Volumes 1 and 2, dated March 1969, and Volume 3, dated September
1992.
Preliminary Drainage and Erosion Control Report Page 10
Lois Lane August 28, 2000
control soil erosion to the satisfaction of the City Inspector and to survive severe weather
conditions.
Preliminary Drainage and Erosion Control Report Page 9
Lois Lane August 28, 2000
1
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 firmish 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.
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
Preliminary Drainage and Erosion Control Report Page 8
Lois Lane August 28, 2000
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,
hL = K*(VZ/2g)
Where hL = headloss
K = headloss coefficient
V = average velocity (ftls)
g = gravitational constant (32.2 ft/s2)
The storm pipe design was performed for two different scenarios, the first being the runoff
from the site into the North Tributary Storm Sewer (NTSS) and the second being for the
ultimate build -out of Rigden Farm in the northwest corner of the development. This was
done to ensure that the system for this project could be extended to include the commercial
areas proposed in the northwest comer of Rigden Farm. The pipe design for the future
development is included in Appendix E of this report.
5. EROSION CONTROL _
5.1 Erosion and Sediment Control Measures
Erosion and sedimentation will be controlled on -site by use of inlet filters, silt fences, straw
bale barriers, gravel construction entrances, 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. Straw bale dikes will be placed along
proposed swales. Erosion control effectiveness, rainfall performance calculations and a
construction schedule will be provided with the final report.
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Lois Lane August 28, 2000
Table 3.1 Drainage Summary
Design
Point
Tributary
Sub -basin
Area
(ac)
C (2)
c (100)
tc (2)
(min)
tc (100)
(min)
Q(2)tot
(efs)
Q(100)tot
(cfS)
1
101
1.51
0.64
0.80
6.8
5.1
2.5
11.8
2
102
1 0.17
0.75
0.93
1 5.0
1 5.0
1 0.4
1 6.1
3
1 103
1 0.25
0.79
1 0.99 1
5.0 1
5.0
1 0.6
1 2.5
4. HYDRAULIC ANALYSIS
1 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
curb or the street crown for local streets. The 2-year storm was used as the initial storm for
street capacity calculations. During the major storm, the depth of water over the crown or
curb is limited to six inches. 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 UDINLET 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. If for some reason these inlets were plugged, the flow would pond until it overtopped
the curb and sheet flowed into the roadside ditch for Drake Road between Lois Lane and
Rigden Parkway. These flows would then enter a culvert to be conveyed to the temporary
detention pond. All inlet locations and sizes are shown on the. Utility Plans for the
construction of this project.
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Lois Lane August 28, 2000
3.4 Hydrologic Analysis of the Proposed Drainage Conditions
The Rational Method was used to determine both 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:
Q = CfCIA
(1)
where Q is the maximum rate of runoff in cfs, A is the total area of the basin in acres, Cf 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
tC=ti+tt
(2)
where tc is the time of concentration in minutes, ti is the initial or overland flow time in
minutes, and 4 is the conveyance travel time in minutes. The initial or overland flow time
is calculated with the SDDCCS Manual equation:
ti = [1.8 /(1.1 - CCr)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 Cf 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. A summary of these calculations for the
three basins is included in Table 3.1 below.
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Lois Lane August 28, 2000
Design Point 1 , from which it will flow to the NTSS, and then continue to the detention
pond. The undeveloped portion of Rigden Farm in the northwest corner of the development
will continue to flow southeast as it has done historically.
The ultimate storm sewer design for Rigden Farm and the portion of Drake Road that bounds
it was designed to convey the runoff into the NTSS and then into the detention pond. This
process will begin with the construction of storm pipe from Lois Lane to the NTSS. The
storm pipe between Lois Lane and Rigden Parkway has been sized at a 54" diameter pipe to
convey the developed flows for the system proposed in the drainage reports for Rigden Farm
O.D.P. and Filing One, P.D.P. The calculations for the storm sewer system at total build -out
are included in Appendix E. These calculations use the areas for basins in the Rigden Farm
O.D.P. report with a maximum "C" value of 1.00.
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 of drainage
facilities identified in this section are included in the following sections.
Runoff from Subbasin 101 will be conveyed via sheet flow and gutter flow to the
sump inlet located at Design Point (DP) 1. This storm flow will join flow from sub -
basin 102 to enter the NTSS.
Runoff from Subbasin 102 will be conveyed via sheet flow and gutter flow to a
proposed sump inlet located at DP 2. Flow will join that from sub -basin 101 and enter
the NTSS that outlets into the temporary detention pond at the corner of Ziegler Road
and Drake Road.
Runoff from Subbasin 103 will be conveyed via sheet flow and gutter flow to DP 3.
From here, flow will be directed westerly on Limon Drive to an inlet that will deliver
the runoff to Pond 218, located in Filing One of Rigden Farm.
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Lois Lane August 28, 2000
3. LOCAL DEVELOPED DRAINAGE DESIGN
3.1 Method
The Rational Method was used to determine both 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 Appendix B of this report.
3.2 General Flow Routing
Flows within this site will take the form of overlot, gutter, and pipe flow. The proposed
drainage patterns from the Rigden Farm drainage plans have been maintained as much as
possible.
The proposed drainage facilities for this site consist of proposed sump inlets, swales and
drainage pipes. The southern portion of Lois Lane will drain to Limon Drive and then west
to an existing inlet. The northern portion of the proposed street will drain to sump inlets on
Lois Lane. From here runoff will be carved to the North Tributary Storm Sewer (NTSS).
The NTSS delivers stormwater to a temporary pond at the corner of County Road 9, now
Ziegler Road, and Drake Road during the interim conditions. When the NTSS and Rigden
Farm Second Filing is completed, the temporary detention pond will be replaced by a
permanent detention pond.
Storm sewer service for the rest of the undeveloped area in the northwest portion of Rigden
Farm and the southern half of Drake Road will not be interrupted by the construction of Lois
Lane. Before Lois Lane is constructed, any runoff from Drake Road west of Rigden
Parkway will enter a culvert under Rigden Parkway to flow to the temporary detention pond.
When Lois Lane is constructed, the flow pattern is altered. The portion of Drake Road
'between Lois Lane and Rigden Parkway will continue to flow through the culvert under
Rigden Parkway to the temporary detention pond at the intersection of Ziegler Road and
Drake Road. The portion of Drake Road west of Lois Lane is ultimately supposed to enter
the NTSS and be delivered to the detention pond at Ziegler Road and Drake Road. The street
vertical design and the grading around it was performed to direct flows to the sump inlet at
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Lois Lane August 28, 2000
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. Where applicable, the criteria established in the "Urban Storm Drainage
Criteria Manual" (UDFCD) dated 1984, developed by the Denver Regional Council of
Governments have been utilized.
1.5 Master Drainage Basin
Lois Lane lies in Reach 2 of the Foothills Drainage Basin. The master 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 street is also included in the "Overall Drainage Plan for Rigden Farm
O.D.P." by JR Engineering, dated November 24, 1999 which incorporates the previously
mentioned reports. In the Rigden Farm O.D.P. report the Foothills Drainage Basin models
were updated with the proposed build -out of Rigden Farm including the regional pond to be
built at the corner of Drake and County Road 9 (now Ziegler Road). As presented in the
report, the southern half of Lois Lane was modeled to drain south onto Limon Drive and into
Pond 218. The northern half of Lois Lane was projected to drain to the north and enter the
North Tributary Storm Sewer.
2. HISTORIC (EXISTING) DRAINAGE
The historic (existing) flows for the Lois Lane site consist of the flows from the site and
some offsite flows from the west and north, including Drake Road. The drainage pattern for
the property is via overland flow in a southeasterly direction at approximately 1 percent
slope. The "Overall Drainage Plan for the Rigden Farm O.D.P." and "Drainage and Erosion
Control Report for Rigden Farm Filing One, P.D.P." directed the general direction of
stormwater from the Rigden Farm development and therefore, historic runoff calculations
are not included as part of this report.
Preliminary Drainage and Erosion Control Report Page 2
Lois Lane August 28, 2000
1. INTRODUCTION
1.1 Project Description
Lois Lane is a proposed approximately 560 lineal foot residential local road at Rigden Farm
P.U.D. The road connects to Drake Road to the north and Limon Drive to the south. Rigden
Parkway is the first road directly east of Lois Lane. The street lies in a portion of the North
half of Section 29, Township 7 North, Range 68 West of the Sixth Principal Meridian, in the
City of Fort Collins, Larimer County, Colorado. A location map is provided in Appendix
A.
1.2 Existing Site Characteristics
The site is primarily covered with native grasses and farmland. The site currently drains in
a southeasterly direction at a 1 to 2 percent slope. The soil on the site is predominately Nunn
clay loam (soil numbers 73 and 74) with 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. The other soil group found in the site area in
limited amounts is Satanta loam (soil number 96), categorized as Hydrologic Group B.
Medium runoff and moderate wind and water erosion characterize this soil group.
1.3 Purpose and Scope of Report
This report defines the proposed drainage and erosion control plan for Lois Lane. The plan
includes consideration of all on -site and tributary off -site runoff and the design of all
drainage facilities required for this street. This drainage plan is consistent with the design
concepts of the drainage report prepared for Rigden Farm Overall Development Plan
(O.D.P.).
Preliminary Drainage and Erosion Control Report Page 1
Lois Lane August 28, 2000
TABLE OF CONTENTS
PAGE
TRANSMITTAL LETTER............................................................................................................. i
TABLEOF 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......................................................:...........................................4
3.4 Hydrologic Analysis of the Proposed Drainage Conditions...........................................5
4. HYDRAULIC ANALYSIS....................................................................................................6
4.1 Allowable Street Capacity ...............................................................................................6
4.2 Inlet Sizing......................................................................................................................6
4.3 Storm Sewer System.......................................................................................................7
5. EROSION CONTROL...........................................................................................................7
5.1 Erosion and Sediment Control Measures........................................................................7
5.2 Dust Abatement...............................................................................................................8
5.3 Tracking Mud on City Streets.........................................................................................8
5.4 Maintenance....................................................................................................................8
5.5 Permanent Stabilization..................................................................................................8
7. REFERENCES.........................................................................................I............................10
Appendix A: Maps and Figures
Appendix B: Hydrologic Calculations
Appendix C: Street Capacity Calculations
Appendix D: Pipe and Inlet Calculations
Appendix E: Pipe Calculations for Future Development
Appendix F: Other Reports
J•R ENGINEERING
A Subsidiary of Westrian
August 28, 2000
Mr. Basil Hamdan
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
RE: Preliminary Drainage and Erosion Control Report for Lois Lane a Portion of Rigden
Farm Filing 3.
Dear Basil,
We are pleased to submit to you for your approval, this Preliminary Drainage and Erosion Control
Report for Lois Lane, a residential road at Rigden Farm P.U.D. 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,
JR ENGINEERING
Prepared by,
�I Amber Reed, E.I.T.
Design Engineer I
I
attachments
Reviewed by,
Kent Bruxvoort, P.E.
Project Manager
2620 East Prospect Road, Suite 190, Fort Collins, CO 80525
970-491-9888 • Fax: 970-491-9984 • wJrengineering.wrn
PRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT
Lois Lane a Portion of
Rigden Farm Filing 3
Prepared for:
Wheeler Commercial
1027 W. Horsetooth Road, Suite 200
Fort Collins, Colorado 80526
(970)225-9305
Prepared by:
JR Engineering
2620 E. Prospect Road, Suite 190
Fort Collins, Colorado 80525
(970)491-9888
August 28, 2000
Job Number 9164.11