HomeMy WebLinkAboutRIGDEN FARM, 1ST FILING, SEVEN OAKS ACADEMY - PDP - 56-98W - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT6G
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APPENDIX A .
VICINITY MAP
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7.
6.2 Drainage Concept
The proposed drainage concepts presented in this report and on the construction plans
adequately provide for stormwater discharge to appropriate conveyance and water quality
facilities.
If, at the time of construction, groundwater is encountered, a Colorado Department of
Health Construction Dewatering Permit will be required.
REFERENCES
1. City of Fort Collins, "Storm Drainage Criteria Manual", (SDCM), dated March,
1986.
2. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria
Manual", Volumes 1 and 2, dated June 2001, and Volume 3 dated September
1999.
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"Drainage and Erosion Control Report for Rigden Farm Filing One P.D.P." by JR
Engineering dated September 30, 1999.
"Drainage and Erosion Control Plan for Rigden Farm Filing One" by JR
Engineering dated September 7, 1999.
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5.
6.
EROSION CONTROL
5.1 General Concept
This site lies within the Moderate Rainfall and Wind Erodibility Zone per the City of Fort
Collins Zone Maps. The potential exists for silt movement from the site and into the
existing swale and streets. Potential also exists for tracking of mud onto existing streets
which could then wash into existing storm systems. The required performance standard
for the site is 79.1 %. During construction and after final paving and building
construction, this figure has been exceeded with the use of silt fence, straw bales and by
using a construction entrance during construction.
The erosion control escrow amount is.$6,279.
5.2 Specific Details
To limit the amount of silt leaving the site several erosion control measures shall be
implemented during construction. Straw bales will be used where appropriate, and all
boundaries shall have silt fence installed. A vehicle tracking pads shall be installed at the
proposed connection to Illinois Drive to control the mud being tracked onto the existing
pavement. During overlot grading, disturbed areas are to be kept in a roughened
condition and watered to reduce wind erosion. The water quality pond will be used as a
sediment trap during construction.
CONCLUSIONS
6.1 Compliance with Standards
All computations that have been completed within this report are in compliance with the
City of Fort Collins Erosion Control Reference Manual for Construction Sites and the
Storm Drainage Design Criteria Manual. Requirements placed on the site related to the
new rainfall criteria have been followed.
No variances are required for the project.
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be extremely flat (0.8% to 1.3%). This shallow slope is provided to minimize .the
migration of the surfacing and was specified by the owner. This basin will drain to the
east and south to a curb cut draining into the parking lot and ultimately to the existing
channel.
Basin 4 includes the east portion of the parking lot and will sheet flow to the southeast to
a curb cut and into the existing channel.
Basin 5 includes the northwest ''/< of the Phase 2 building and the landscape area adjacent
to Illinois Drive. This area will sheet flow to Illinois Drive. Illinois Drive flows to the
north to Custer and the stormwater ultimately reaches the Custer Drive storm sewer
system. This storm sewer flows to Rigden Farm Water Quality Pond 2 and the Foothills
Regional Channel.
Basin 6 includes the Phase 2 playground and the northerly portion of the Phase 1
playground. This area will sheet flow to Custer Drive and then to the storm sewer system
on the south side of Custer Drive.
Basin 7 includes the Phase 1 building's roof. There are four roof drains that will be piped
in PVC storm sewer to the existing inlet at the southwest corner of Custer Drive and Iowa
Drive. The PVC system has been designed to accept the 100-year flow, but in the event
of a failure in the downspouts, the storm flows would sheet flow to Custer Drive and
ultimately reach the same storm sewer system.
Basin 8 includes the landscaped area adjacent to Iowa Drive. This area will sheet flow
into the street. Iowa Drive drains to the north to Custer Drive where storm flows enter
the existing storm sewer system.
4.3 Drainage Summary
All proposed storm flows will ultimately discharge to the existing storm sewer system to
Rigden Farm Water Quality Pond 2 and then to the Foothills Regional Channel. The
flows from this site will be less than the Filing 1 Design flows. Drainage facilities
located outside of the right of way (including the existing channel and proposed roof
drain piping) will be maintained by the owners of the property.
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City of Fort Collins Drainage Criteria and are included in Appendix C of this report.
4. DRAINAGE FACILITY DESIGN
4.1 General Concept
The central and southerly portions of the site (Basins 1-4) will flow overland to the
existing swale.on the south side of the site. This swale discharges into the storm sewer
system described below. There will be minor grading in the drainage easement and
swale. A 4:1 slope will tie to the existing swale 3' north of the existing pan. This swale
was designed in the Filing 1 plans (Swale I -I) to have a 3' bottom and 4:1 side slopes.
The grading proposed will not reduce the design capacity of the channel.
The northerly portion of this site will drain directly to Iowa Drive, Illinois Drive and
Custer Drive; the roof drainage from the east building will be piped to an existing inlet in
Custer Drive. All of these flows eventually will go to the storm sewer system in Custer
Drive. This storm sewer ultimately discharges into Water Quality Pond 2 and the
Foothills Regional Channel. The storm sewer was designed for the developed 100 year
flow.
1 4.2 Specific Flow Routing
A summary of the drainage patterns within each basin is provided in the following
paragraphs.
Basin i includes a small portion of the roof of the west (Phase 2) building. This area will
be required to flow to the south and into the proposed parking lot (Basin 2). It will
discharge into the existing swale on the south side of the site. This channel ultimately
discharges into the Custer Drive storm sewer system, Rigden Farm Water Quality Pond 2
and the Foothills Regional Channel.
Basin 2 includes the west portion of the parking lot and a part of the west building. This
area will flow to the southeast to a proposed curb cut and into the existing swale.
Basin 3 includes the majority of the Phase 1 playground. Because a large part of the
playground will have pea gravel surfacing (for safety reasons) it is required that the area
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development:
For the area flowing to the south (into the existing swale) the Filing 1 report specified
1.44 acres and the C value of 0.67 (Basin 108f). . The C*A value from the Filing 1
Report for the flows to the south is 0.96.
With the Seven Oaks design, 1.28 acres is flowing to the south (Basins 1 through 4) with
a weighted C value of 0.67. The C*A value with the Seven Oaks project for the flows to
the south is 0.86. Because the C values are the same and the acreage flowing to the
south is less than that specified in the Filing 1 Report, the modification to the split was
-_- determined to be acceptable.
For the area flowing to the north (to Custer Drive) the Filing 1 report specified 0.54 acres
and the weighted C value was determined to be 0.84 - 15% of Basin 108bl (C=0.76),
66% of Basin 108b (C=0.88) and 19% of 108c (C=0.79). The C*A value from the
Filing 1 Report for the flows to the north is 0.45.
With the Seven Oaks design, 0.70 acres is flowing to the north (Basins 5 through 8) with
a weighted C value of 0.63. The C*A value with the Seven Oaks project for the flows to
the north is 0.44. Because the C*A value is less than the Filing 1 design, the
additional acreage was determined to be acceptable.
3.3 Hydrologic Criteria
Runoff computations were prepared for the 10-year minor and 100-year major storm
frequency utilizing the rational method.
All hydrologic calculations associated with the basins are included in Appendix B of this
report. Standard Form 8 (SF-8) provides time of concentration calculations for all sub -
basins. Standard Form 9 (SF-9) provides a summary of the design flows for all Sub -
basins and Design -Points associated with this site.
3.4 Hydraulic Criteria
All hydraulic calculations within this report have been prepared in accordance with the
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2.2 Sub -basin Description
This site was studied with the design of Rigden Farm Filing 1. The site includes Basin
108f, and portions of Basins 108b1, 108b and 108c in the Filing 1 Drainage Report.
Basin 108f is designed to flow south into the existing open channel; the other 3 basins are
designed to flow north to Custer Drive and the existing storm sewer on the south side of
Custer Drive. Portions of the Filing 1 Drainage Plan and Report are included in
Appendix E.
3. DRAINAGE DESIGN CRITERIA
3.1 Regulations
This report was prepared to meet or exceed the "City of Fort Collins Storm Drainage
Design Criteria Manual' specifications and the requirements of the Rigden Farm Filing 1
Drainage Plan and Report. Where applicable, the criteria established in the "Urban Storm
Drainage Criteria Manual' (UDFCD), developed by the Denver Regional Council of
Governments, has been used.
3.2 Development Criteria Reference and Constraints
The runoff from this site has been routed to conform to the requirements of the City
Stormwater Department. Detention is not required for this site and water quality facilities
are provided in a pond adjacent to the Foothills Regional Channel.
The Drainage Plan for Rigden Farm Filing 1 specifies that 1.44 acres of this site flow to
the south to the existing swale (Basin 108f) and that the remaining 0.54 acres flow north
to Custer Drive (parts of Basins 108b1, 108b, and 108c).
The layout of the site and the requirements for roof drainage do not allow for the exact
acreage split specified in the Filing 1 report. The proposed project will have 0.70 acres
flowing to Custer Drive and 1.28 acres flowing to the south (the Filing 1 report splits the
flows 0.54 acres and 1.44 acres respectively). It appeared by inspection that the design C
value for the north basin would be considerably less than the Filing 1 design, so to
determine if the design flow spilt to the north and south was acceptable, the C*A value
from the Filing 1 Report was compared to the C*A value proposed with this
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1. GENERAL LOCATION AND DESCRIPTION
1.1 Location
Seven Oaks Academy at Rigden Farm is located in southeast Fort Collins. The legal
description of the site is Tract B of Rigden Farm Filing 1. This project is located in the
northwest quarter of Section 29, Township 7 North, Range 68 West of the Sixth Principal
Meridian, in the City of Fort Collins, Larimer County, Colorado. See the location map in
Appendix A.
The project is bounded on the north by Custer Drive on the west by Illinois Drive, on the
east by Iowa Drive and on the south by the Timberline Church.
1.2 Description of Property
The entire project consists of approximately 2.0 acres of land. Existing streets bound
three sides of the development and the Timberline Church is located to the south. There
is an existing drainage swale in a 30' drainage easement on the south side of the property.
Two commercial buildings (daycare facilities) along with parking, drives and
playgrounds are proposed. The majority of the site will be built now (Phase 1); the west
building and northwest playground will be built in the future (Phase %. The land
currently slopes from northwest to southeast at 1 %. Both Iowa Drive and Illinois Drive
slope north to Custer Drive, Custer Drive slopes to the east and the swale on the south
property line also flows east. There are no mapped floodplains on the property.
1 2. DRAINAGE BASINS AND SUB -BASINS
2.1 Major Basin Description
The proposed development lies within the Foothills Master Drainage Basin and was
studied and designed with Rigden Farm Filing 1. No detention is required for the site
and all of the flows from this site are designed to flow to Water Quality Pond #2 (within
Rigden Farm PUD) and then to the Foothills Regional Channel.
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TABLE OF CONTENTS
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TABLE OF CONTENTS............................................................................................................... iii
1. GENERAL LOCATION AND DESCRIPTION
1.1 Location...................................................................................................................1
1.2 Description of Property............................................................................................1
2. DRAINAGE BASINS AND SUB -BASINS
2.1 Major Basin Description..........................................................................................I
2.2 Sub -Basin Description.............................................................................................2
3. DRAINAGE DESIGN CRITERIA
3.1 Regulations..............................................................................................................2
3.2 Development Criteria Reference and Constraints....................................................2
3.3 Hydrologic Criteria..................................................................................................3
3.4 Hydraulic Criteria....................................................................................................3
4. DRAINAGE FACILITY DESIGN
4.1 General Concept.......................................................................................................4
4.2 Specific Flow Routing.............................................................................................5
4.3 Drainage Summary ...................................................................................................5
5. EROSION CONTROL
5.1 General Concept......................................................................................................5
5.2 Specific Details........................................................................................................6
6. CONCLUSIONS
6.1 Compliance with Standards....................................................................................6
6.2 Drainage Concept.....................................................................................................6
7. REFERENCES....................................................................................................................7
APPENDICES
A Vicinity Map
B Hydrologic Computations
C Hydraulic Calculations
D Erosion Control Calculations
E Excerpts from Other Reports
F Figures and Tables
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North Star
ridesign, inc.
September.30, 2003
' Basil Hamdan
City of Fort Collins Stormwater
700 Wood Street
Fort Collins, CO 80522-0580
RE: Final Drainage and Erosion Control Study for Seven Oaks Academy at Rigden
Farm
Dear Basil,
I am pleased to submit for your review and approval, this Final Drainage and Erosion Control
Study for Seven Oaks Academy at Rigden Farm (Tract B, Rigden Farm Filing 1). I certify that
this report for the drainage design was prepared in accordance with the criteria in the City of Fort
Collins Storm Drainage Manual.
I appreciate your time and consideration in reviewing this submittal. Please call if you have any
questions.
Sincerely,
Michael Oberlander, P.E., L.S.I.
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700 Automation Drive, Unit I Windsor, Colorado 80550
970-686-6939 Phone , 970-686-1 1 88 Fax
FINAL DRAINAGE AND EROSION
CONTROLSTUDY
SEVEN OAKS ACADEMY AT RIGDEN FARM
TRACT B, RIGDEN FARM FILING 1
Prepared for:
Larry Neal
Seven Oaks Academy
3513 Richmond Drive
Fort Collins, Colorado 80526
Prepared by: ,
North Star Design
700 Automation Drive, Unit I
Windsor, Colorado 80550
(970)686-6939
September 30, 2003
Job Number 186-01