HomeMy WebLinkAboutMANHATTAN TOWNHOMES - PDP - 34-04 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTNo Text
r
I
i
A
i
I
11
1
APPENDIX A
VICINITY MAP
0
.1
7. REFERENCES
1. City of Fort Collins, "Storm Drainage Criteria Manual", (SDCM), dated March
1999.
2. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria
Manual", Volumes 1 and 2, dated June 2001, and Volume 3 dated September
2001.
6
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 the
' eastern and southern site boundaries shall have silt fence installed. Two vehicle tracking
pads shall be installed at the connections to Manhattan Avenue to control the mud being
I 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 extent of the
disturbance shall be limited and the existing vegetation adjacent to the construction area
shall be maintained to the greatest extent possible.
6. 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. There are no variances requested for this project
at this time.
6.2. Drainage Concept
Conveyance elements have been designed to convey required flows to the existing
detention pond in such a manner as to minimize future maintenance. All basins will be
conveyed to the detention pond via surface flows. No private storm sewers are proposed
with this project. Public storm sewer improvements consist of a proposed 10' Type R
Inlet and RCP pipe located at the low point of Manhattan Avenue.
If, at the time of construction, groundwater is encountered, a Colorado Department of
Health Construction Dewatering Permit will be required.
1
5
1
Basin 5 (0.41 acres) includes the portion of the site adjacent to the existing detention
' pond. This Basin contains portions of 2 townhome buildings and adjacent sidewalks and
landscaping. Runoff from Basin 5 will sheet flow into the existing detention pond.
Runoff from this basin is 1.0 cfs for the 10-year storm and 2.6 cfs for the 100-year storm.
Basin 6 (0.02 acres) is located on the northern edge of the site and contains landscaping
area adjacent to the northernmost townhome building. Runoff from this basin will sheet
flow to the north and will be collected in an existing swale located in the Park South
1 Commercial development. The runoff will then be conveyed to an existing detention
pond located east of the storage units. Runoff from this basin is 0.02 cfs for the minor
storm and 0.06 cfs for the major storm.
,�. 4.3. Drainage Summary
�, Drainage facilities located outside of the right-of-way will be maintained by the home
owner's association. The regional detention facility will be owned and maintained by the
City of Fort Collins. On -site runoff will be routed to the existing regional detention pond
via surface flow. There are no private storm sewer improvements proposed with this
project. The only public storm sewer improvement proposed with this project is a 10'
Type R Inlet and RCP pipe located at the low point of Manhattan Avenue.
5. EROSION CONTROL
5.1. General Concept
This site lies within the Moderate Rainfall and Wind Erodibility Zone per the City of Fort
Collins and into adjacent properties. 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 76.9%. During constructionand after paving, this
figure has been exceeded with the use of silt fence and straw bales. Ground roughing and
straw mulch will also be used to control erosion during construction. All erosion control
calculations are included in Appendix C of this report.
The erosion control escrow amount is $6,500.
4
1 4. DRAINAGE FACILITY DESIGN
4.1. General Concept
Given the close proximity of the regional detention pond, the drainage concept for this
site is to convey the on -site runoff to the detention pond with a minimum of number of
drainage structures. All basins will be routed to the detention pond via surface flow. The
. only drainage structure proposed with this project is a 10' Type R Inlet and RCP pipe at
the low point in Manhattan Avenue.
4.2. Specific Flow Routing
A summary of the drainage patterns within each basin is provided in the following
paragraphs.
Basin 1 (0.23 acres) contains a portion of the northern most building and adjacent
parking. Runoff from this basin sheet flow to the east, then will be conveyed via curb and
lgutter to a proposed 2' curb opening, then into the existing detention pond. Basin 1
runoff is 1.1 cfs for the 10-year minor storm and 2.3 cfs for the 100-year major storm.
Basin 2 (0.24 acres) contains portions of two proposed townhome buildings. Runoff
from this basin sheet flow to the east, then will be conveyed via curb and gutter to a
proposed 2' curb opening, then into the existing detention pond. Basin 2 runoff is 1.0 cfs
for the 10-year minor storm and 2.4 cfs for the 100-year major storm.
Basin 3 (0.89 acres) contains the existing apartment building, portions of three proposed
townhome buildings, the proposed garage building, and adjacent drives, parking and
walks. Runoff from Basin 3 is conveyed to the east via concrete pans and curb and gutter
and enters the pond through a proposed 4' curb opening. Runoff from this basin is 3.4 cfs
for the 10-year storm and 8.8 cfs for the 100-year storm.
Basin 4 (0.42 acres) contains the portion of the site adjacent to Manhattan Avenue,
including portions of three townhome buildings, along with adjacent drives and walks.
Runoff from this basin will sheet flow to the west into Manhattan Avenue. From there,
the runoff will be conveyed via curb and gutter to the south, where it will be collected in
the proposed 10' Type R inlet and piped to the existing detention pond. Runoff from
Basin 4 is 0.9 cfs for the 10-year storm and 2.3 cfs for the 100-year storm.
1 2.2. Sub -basin Description
There are six drainage basins for the proposed site. Runoff from Basins 1, 2, and 3 will
be conveyed to the east through the site and into the detention pond. Basin 4 will sheet
flow to the west into Manhattan Avenue, then to the south into the detention pond.
Runoff from Basin 5 will sheet flow directly into the detention pond. Basin 6 will sheet
flow to the north and will be collected in an existing drainage Swale in the Park South
Commercial development. Runoff will then be conveyed to an existing detention pond
east of the storage units. See Section 4 of this report for a more detailed explanation of
subbasin flows.
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), 2001 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. Neither stormwater detention nor extended water quality
.,� detention are proposed for this site.
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.
3.4. Hydraulic Criteria
All hydraulic calculations within this report have been prepared in accordance with the
City of Fort Collins Drainage Criteria and are included in Appendix B of this report. The
only proposed storm sewer for this project is a 10' Type R Inlet and RCP pipe at the low
point of Manhattan Avenue.
i
,I
1. GENERAL LOCATION AND DESCRIPTION
1.1. Location
The proposed Manhattan Townhomes is located in Fort Collins on the east side of
Manhattan Avenue south of Horsetooth Road. This project is located in the Northeast
Quarter of Section Thirty-five, Township Seven North, Range Sixty-nine West of the
Sixth Principal Meridian, in the City of Fort Collins, Larimer County, Colorado. See the
Vicinity Map in Appendix A.
The site is bounded on the north by existing storage units, on the east by the Colorado &
Southern Railroad tracks, on the south by existing residential development, and on the
west by Manhattan Avenue.
1.2. Description of Property
The project consists of approximately 2.2 acres of land. The proposed improvements on
this site consist of 5 townhome buildings, a garage building, and associated drives, walks,
and parking. Access is obtained on the west from Manhattan Avenue. No portion of the
proposed project is within a designated floodplain area.
Existing development on the site includes an apartment building, parking areas, and
driveways. The eastern portion of the site is a regional detention pond. The existing
detention pond will be resized and re -graded by Icon Engineering as a separate project.
The existing drainage pattern for the eastern portion of the site is to the east into the
existing pond at a slope of approximately 1.5%.
2. DRAINAGE BASINS AND SUB -BASINS
2.1. Major Basin Description
The proposed development lies within the McClelland Mall Creek Drainage Basin. Due
to the location of the regional detention pond, neither on -site stormwater detention nor
extended water quality detention are required for this site. The proposed 100-year water
surface elevation for the pond, according to Icon Engineering, is 4943.0, with a top of
berm elevation of 4944.0. The finished floor of the existing building is at approximately
4943; grading around the building is being proposed to protect it from the adjacent pond.
1
,1,
ITABLE OF CONTENTS
TABLEOF CONTENTS...............................................................................................................
iii
/
1.
GENERAL LOCATION AND DESCRIPTION
1.1 Location...................................................................................................................
I
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....................................................2
3.3 Hydrologic Criteria..................................................................................................2
3.4 Hydraulic Criteria....................................................................................................2
4.
DRAINAGE FACILITY DESIGN
'
4.1 General Concept.......................................................................................................3
4.2 Specific Flow Routing.............................................................................................3
4.3 Drainage Summary ...................................................................................................4
J5.
EROSION CONTROL
5.1 General Concept__,___ ......
5.2 Specific Details........................................................................................................5
........... 4
6.
CONCLUSIONS
6.1 Compliance with Standards....................................................................................5
6.2 Drainage Concept.....................................................................................................5
7.
REFERENCES....................................................................................................................6
APPENDICES
A Vicinity Map
B Hydrologic & Hydraulic Computations
C Erosion Control Calculations
D Figures and Tables
�1
''
1 % North Star
® design, inc.
1`
August 24, 2004
Basil Hamdan
City of Fort Collins Stormwater
700 Wood Street
Fort Collins, CO 80522-0580
I RE
I
I
i
i
1
Final Drainage and Erosion Control Report for Park South 2nd Filing P.U.D.
(Manhattan Townhomes)
Dear Basil,
I am pleased to submit for your review and approval, this Final Drainage & Erosion Control
Report for Park South 2"d Filing P.U.D., hereafter referred to as Manhattan Townhomes. I certify
that this report for the drainage design of Manhattan Townhomes 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.
Prepared by:
J4-�'c J5�
Shane Boyle, EIT
North Star Design, Inc.
Reviewed By:
Patricia Kroetch, PE
North Star Design, Inc.
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
PARK SOUTH 2Nv FILING P.U.D.
(MANHATTAN TOWNHOMES)
Prepared for:
Lagunitas Manhattan, Inc.
3944 JFK Parkway, Suite B200
Fort Collins, CO 80525
Prepared by:
North Star Design
700 Automation Drive, Unit I
Windsor, Colorado 80550
(970)686-6939
August 24, 2004
Job Number 173-05
I