HomeMy WebLinkAboutLINCOLN PARK (FORMERLY LINCOLN MIXED-USE PDP), 1110 E. LINCOLN - PDP - 40-94G - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT1.
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GENERAL LOCATION AND DESCRIPTION
1.1. Location
The Lincoln Avenue Mixed Use development is located in the northeast quarter of
Section 7, Township 7 North, Range 68 West of the Sixth Principal Meridian, in the City
of Fort Collins, County of Larimer, and State of Colorado. See the Vicinity Map located
in Appendix A.
The project is bounded on the north and east by undeveloped agricultural land, on the
west by existing Lemay Avenue, and on the south by existing Lincoln Avenue. There is
also an existing bank building located adjacent to the property on the southwest corner.
1.2. Description of Property
The entire project consists of approximately 15.5 acres of land. Existing development on
this property includes a house and several small outbuildings. Existing drainage patterns
for the site are generally to the southeast with slopes ranging from approximately 0.5% to
1.0%. Runoff from this site flows to the existing roadside ditch along Lincoln Avenue.
Proposed development for the site includes six commercial/office buildings, sixteen
multifamily buildings (6, 7, & 8-plexes), a clubhouse, pool, and three detached garage
structures, along with associated walks, parking, and drives. Access for the proposed
development will be from Lincoln Avenue on the south and Lemay Avenue on the west.
DRAINAGE BASINS AND SUB -BASINS
2.1. Major Basin Description
The proposed development lies within the Dry Creek Drainage Basin as delineated by the
City of Fort Collins. Portions of the property lie within both the FEMA Poudre River
100-year floodplain and the City of Fort Collins 100-year Dry Creek floodplain. No
portion of this site is within the Poudre River or Dry Creek 100-year floodway
boundaries.
A small portion of the site along the western property line lies within the FEMA Poudre
River 100-year. floodplain and the site is encompassed by the FEMA Poudre River 500-
year floodplain. Floodplain information has been provided by the City of Fort Collins,
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DATE: 6/10/05
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AT LINCOLN & LEMAY design, inc.
700 Automation Drive, Unit I
o DESIGNED BY: TLN Windsor, Colorado 80550
VICINITY MAP Phone: 970-686-6939
JOB NO.: 173-02 Fax: 970-686-1188
APPENDIX A
VICINITY MAP
A
6.
it
CONCLUSIONS
6.1. Compliance with Standards
All computations within this report are in compliance with the City of Fort Collins
Erosion Control Reference Manual for Construction Sites, the Storm Drainage Design
Criteria Manual, and Chapter 10 of the City Code (Flood Prevention and Protection). No
drainage variances are being requested for this project at this time.
6.2. Drainage Concept
The proposed drainage concepts presented in this report and on the construction plans
adequately provide for stormwater quality treatment of proposed impervious areas.
Conveyance elements have been designed to convey the 100-year storm runoff to the
proposed retention/detention ponds and to minimize future maintenance.
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.
3. City of Fort Collins Code, Chapter 10, City of Fort Collins Web Site under
Municipal Code Section www.fcgov.com/ciiyclerk/codes". Information obtained
on 6/21 /04.
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Basin 3 is located in the southeastern corner of the site and contains the portion of the site
that will drain into Pond 3. Runoff from this basin will be conveyed to Pond 3 via a
combination of surface and subsurface flow. The detained release from Pond 3 will be
piped to the Lincoln Avenue storm sewer, which will convey the runoff to the northern
Lincoln Avenue roadside ditch and ultimately to Dry Creek.
4.3. Drainage Summary
Drainage facilities located outside of the right-of-way (including the ponds, proposed
storm drain systems, and the pond outlet structures) will be maintained by the owners of
the property. The storm. system in the proposed rights -of -way will be owned and
maintained by the City of Fort Collins.
5. EROSION CONTROL
5.1. General Concept
rThis 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 along the north side of Lincoln Avenue. A 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 74.7%. 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 the retention pond as a sediment trap during construction.
The erosion control escrow amount is $21,000.
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 silt
fence will be installed around the entire property boundary. Vehicle tracking pads shall
be installed at the proposed connections to Lemay Avenue and Lincoln Avenue to control
the mud being tracked onto existing pavement. During overlot grading, disturbed areas
are to be kept in a roughened condition and watered to reduce wind erosion. The
retention pond will be used as a sediment trap during construction.
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4. DRAINAGE FACILITY DESIGN
r4.1. General Concept
Where possible, runoff from the proposed development will be routed to the proposed
retention/detention ponds by surface flow. Where necessary, and at pond outlets, storm
sewer has been used to adequately convey storm runoff to the retention/detention ponds.
Three ponds are proposed with.this development. In the interim condition, Ponds 1 and 3
will act as retention ponds. These ponds will be allowed to release downstream at the 2-
year historic rate once the water in the Lincoln Avenue roadside ditch has dissipated. In,
the ultimate condition, Ponds 1 and 3 will be reconfigured and will act as detention ponds
with a release rate equal to the 2-year historic runoff rate. Pond 2 will act as a detention
pond and will release into Pond 3 in both design conditions. These ponds have been
from
modeled in series and Pond 3 has been adequately sized to accommodate the release
Pond 2. Calculations for both the interim and ultimate conditions are included in the
Appendices of this report.
4.2. Specific Flow Routing
A summary of the drainage - patterns within each basin is provided in the following
paragraphs.
Basin 1 is located on the western edge of the site and contains the portion of the site that
will drain into Pond 1. Runoff from this basin will be conveyed to the detention pond via
surface flow and curb openings. The detained release from Pond 1 will be piped to an
existing storm sewer that runs south through the site. From there, the runoff is conveyed
to the storm sewer in Lincoln Avenue and ultimately to the northern Lincoln Avenue
roadside ditch which will convey the runoff to Dry Creek.
Basin 2 is located in the northeastern corner of the site and contains the portion of the site
that will drain into Pond 2. Runoff from this basin will be conveyed to Pond 2 via a
combination of surface and subsurface flow. The detained release from Pond 2 will be
conveyed to Pond 3 via a proposed storm sewer. Pond 2 has been designed to act as a
detention pond in both the interim and ultimate conditions and has been designed in
series With Pond 3. Pond 3 has been designed to accommodate the release from Pond 2
in both the interim and ultimate conditions.
e
3.2. Development Criteria Reference and Constraints
The runoff from this site has been routed to conform to the requirements of the City of
Fort Collins Stormwater Department and Larimer County Engineering. In the interim
condition, two retention ponds and a detention pond are proposed and will provide 2
times the storage capacity required for the 3-hour 100-year storm event. Manually
operated valves will be placed on the outlet structures for Ponds 1 and 3 so that the ponds
will act as retention during the storm event. The valves would only be opened after the
flow in the existing swale has dissipated. This valve will be operated and maintained by
the Home Owner's Association.
3.3. Hydrologic Criteria
Runoff computations were prepared for the 2-year and 10-year minor and 100-year major
storm frequencies for the ultimate condition and for -the 100-year major storm frequency
for the interim, condition. All calculations were completed utilizing the rational method
for determining peak runoff. All hydrologic calculations associated with the basins are
included in Appendix B of this report.
Detention and retention volumes were determined using the FAA Method. Water quality
volume was calculated using.the method recommended in the "Urban Storm Drainage
Criteria Manual" and will only be incorporated in the ultimate pond design, except for
Pond 2, which will be used as a detention pond with extended water quality detention in
both design conditions.
3.4. Hydraulic Criteria
Hydraulic elements have been designed to adequately convey the 100-year storm runoff
from this site to the proposed retention/detention ponds. All hydraulic calculations within
this report have been prepared in accordance with the City of Fort Collins Drainage
Criteria and are included in Appendix C of this report.
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Floodplain Administrator for the FEMA and City of Fort Collins 100-year floodplain
boundaries for the Poudre River. None of the proposed buildings are located within the
Poudre River 100-year floodplain. The FEMA 100-year and 500-year Poudre River
floodplains are located on the FIRM Panel number 080101 0179E.
W The southeastern corner of this site is also within the City of Fort Collins Dry Creek 100-
year floodplain and the site is encompassed by the City of Fort Collins 500-year Dry
Creek floodplain. All or portions of ten of the proposed buildings lie within the Dry
Creek 100-year floodplain. The 'foundation for all structures is expected to be slab on
grade and all buildings have been designed with a minimum opening elevation of at least
1.5' above the 100-year base flood elevation. A floodplain use permit will be required for
each building prior to a CO being issued. Floodplain information for the Dry Creek
floodplain has been provided by the City of Fort Collins.
2.2. Sub -basin Description
Runoff from this site currently flows southeast to the existing swale along the north side
of Lincoln Avenue. The existing drainage patterns will be altered with the development
of this site. Runoff will be routed to three ponds. In the interim condition, Ponds 1 and 3
will act as retention ponds and the release will be manually controlled by a valve in the
outlet structure. Runoff will be gravity released into the existing storm system along
Lincoln Avenue when the storm has passed and water downstream has dissipated. In the
ultimate condition, these ponds will be reconfigured and the manual valve will be
removed so that the ponds will act as detention ponds, with a release rate equal to the 2-
year historic runoff. In both the interim and ultimate . conditions, Pond 2 has been .
designed in series with Pond 3. Pond 3 has been sized to accept the runoff from Pond 2
in both design conditions.
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. Where applicable, the criteria established in the
"Urban Storm Drainage Criteria Manual" (UDFCD), 1984, developed by the Denver
Regional Council of Governments, has been used. This site is also in compliance with
Chapter 10 (Flood Prevention and Protection) of the City of Fort Collins Municipal Code.
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TABLE OF CONTENTS
TABLE
OF CONTENTS...............................................................................................................
iii
1.
GENERAL LOCATION AND DESCRIPTION
1.1 Location ......................
1
1.2 Description of Property ............................................................................................I
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....................................................3
3.3 Hydrologic Criteria..................................................................................................3
3.4 Hydraulic Criteria....................................................................................................3
4.
DRAINAGE FACILITY DESIGN
4.1 General Concept.......................................................................................................4
4.2 Specific Flow Routing.............................................................................................4
4.3 Drainage Summary ...................................................................................................5
5.
EROSION CONTROL
5.1 General Concept........:.............................................................................................5
5.2 Specific Details........................................................................................................5
6.
CONCLUSIONS
6.1 Compliance with Standards....................................................................................6
6.2 Drainage Concept.....................................................................................................6
7. REFERENCES....................................................................................................................6
APPENDICES
A Vicinity Map
B Hydrologic Computations
C Hydraulic Calculations
D Pond Sizing Calculations
E Erosion Control Calculations
F Figures and Tables
G Floodplain Permits and Boundaries
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11 North Star
riAama, design, inc.
June 17, 2005
Basil Hamdan
City of Fort Collins Stormwater
700 Wood Street
Fort Collins, CO 80522-0580
0
RE: Final Drainage and Erosion Control Report for Lincoln Avenue Mixed Use
Dear Basil,
I am pleased to submit for your review and approval, this Final Drainage and Erosion Control
Report for the Lincoln.Avenue Mixed Use. 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,
Shane Boyle, EIT
North Star Design, Inc.
ii
North Star Design, Inc.
President
700 Automation Drive, Unit I Windsor, Colorado 80550
970-686-6939 Phone • 970-686-1 1 88 Fax
FINAL DRAINAGE AND EROSION
CONTROL REPORT
FOR
LINCOLN AVENUE MIXED USE
Prepared for:
Lagunitas Lincoln, Inc.
3944 JFK Parkway, Suite B200
Fort Collins, CO 80525
Prepared by:
North Star Design, Inc.
700 Automation Drive, Unit I
Windsor, Colorado 80550
(970) 686-6939
June 17, 2005
Job Number 173-02