HomeMy WebLinkAboutUNIVERSITY CENTER P.U.D. (WARDS REDEVELOPMENT) - MINOR AMENDMENT / REPLAT - 40-01 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT6.2 Irrigation Ditches
There are no irrigation ditches impacted by the development of this site. (The flow to the
Sherwood Lateral is not changed.)
6.3 Maintenance Agreements
The developer will be responsible for the maintenance of all temporary and permanent
drainage structures.
7. REFERENCES
1. City of Fort Collins, "Storm Drainage Design Criteria and Construction Standards",
(SDDCCS), dated May 1984.
2. "Drainage and Erosion Control Report, University Center PUD", by Bucher, Willis
and Ratliff Corporation, and approved by the City of Fort Collins on July 24, 1998.
3. "Spring Creek Master Drainageway Plan" by Engineering Professionals, Inc., March
1988.
4. Soil Survey of Larimer County Area, Colorado. United States Department of
Agriculture Soil Conservation Service and Forest Service, 1980.
5. Urban Drainage and Flood Control District, "Urban Storm Drainage Criteria
Manual", Volumes 1 and 2, dated March 1969, and Volume 3, dated September
1992.
Final Drainage and Erosion Control Report Page 9
Wards Redevelopment October 3, 2000
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6.
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 ordered 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
All soils exposed during land disturbing activity (stripping, grading, utility installations,
stockpiling, filling, etc.) shall be kept in a roughened condition by ripping or disking along
land contours until mulch, vegetation or other permanent erosion control is installed. No
soils in areas outside project street rights of way shall remain exposed by land disturbing
activity for more than thirty (30) days before required temporary or permanent erosion
control (e.g. seed/ mulch, landscaping, etc.) is installed, unless otherwise approved by the
Stormwater Utility. Vegetation shall not be considered established until a ground cover is
achieved which is demonstrated to be mature and stable enough to control soil erosion as
specified in paragraph 11.3.10 of the City of Fort Collins Storm Drainage Construction
Standards.
MISCELLANEOUS
6.1 Variances
No variances are required or are being requested for this site.
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Wards Redevelopment October 3, 2000
4.
5.
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All hydraulic calculations are included in Appendix B, and the location of all storm drainage
structures is shown on the Drainage and Erosion Control Plan included in the back pocket
of this report.
WATER QUALITY
An existing depression along the western property line of this site acts as a sediment
basin/water quality pond/retention pond. As part of the redevelopment of this site, this area
will be cleaned up so it functions better. In an on -site meeting with Glen Schlueter of the
City of Fort Collins' Stormwater Department, it was stated that this facility was adeqaute for
this site.
For the eastern portion of the site, the existing area inlets are being utilized and the parking
lot is being modified only slightly. Therefore, the implementation of new water quality
structures is not possible.
EROSION CONTROL
5.1 Erosion and Sediment Control Measures
Erosion and sedimentation will be controlled during construction by inlet filters, silt fences,
gravel construction entrances, seeding and mulching. These measures are designed to limit
the overall increase in sediment yield due to construction activities 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. The erosion control cost estimate, effectiveness
calculations and a construction schedule are included in Appendix D.
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.
Final Drainage and Erosion Control Report Page 7
Wards Redevelopment October 3, 2000
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Manual. Rainfall intensity was based on the recently adopted design storm information for
Fort Collins. Details of the hydrologic calculations associated with each subbasin are
included in Appendix A. Table 3.1 provides a summary of the resulting peak flows for all
subbasins and Design Points (DP's) associated with this site. Q 0, in the table includes
applicable carry over flows.
WARDS REDEVELOPMENT
Table 3.1 - Drainage Summary Table
Design
Point
Tributary
Sub -basin
Area
(ac)
C (10)
C (100)
tc (10)
(min)
to (100)
(min)
Q(10not
(eft)
Q(100)tot
(cfs)
1
A
2.57
0.92
1.00
5.0
5.0
11.5
25.6
2
B
0.53
0.92
1.00
5.0-
5.0
2.4
5.3
3
c
0.03
0.95
1.00
5.0
5.0
0.2
0.3
4
0
0.01
0.67
0.83
5.0
5.0
0.0
0.1
5
E
0.01
0.67
0.83
5.0
5.0
0.0
0.1
6
F
1.64
0.82
1.00
5.0
5.0
6.6
16.3
7
G
0.04
0.53
0.66
5.0
5.0
0.1
0.3
8
H
1.24
0.87
1.00
5.0
5.0
5.2
12.3
9
1
0.23
0.10
0.13
5.0
5.0
0.1
0.3
10
J
0.31
0.95
1.00
5.0
5.0
1.4
3.1
3.4 Allowable Street Flow Capacities
The proposed development of this site does not affect any street flows. Therefore, street flow
calculations are not included in this report.
3.5 Storm Drainage Structure Design
Storm drainage structures for this site include sidewalk culverts, curb cuts and existing area
inlets and storm drainage pipes. The capacity of sidewalk culverts and curb cuts was
determined using the computer program F1owMaster, which uses Manning's Equation. The
sidewalk culverts and curb cuts have capacity to convey peak flows from the 100-year storm
within criteria set fourth by the SDDCCS Manual.
For the storm pipe design, the computer program StormCAD, developed by Haestad
Methods, Inc. was used. StormCAD considers whether a culvert 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).
Final Drainage and Erosion Control Report Page 6
Wards Redevelopment October 3, 2000
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chase has been added to allow the flows to enter Subbasin I and be collected in the
existing area inlet. (The existing area inlets in Subbasins F, H, and I all interact to
provide collection for this site.)
Runoff from Subbasin G, the very northeast corner of the site, are conveyed via
sheet flow northerly to the existing parking lot/property north of the Wards
Redevelopment site. The amount of runoff generated from this basin did not change
from historic amounts.
Runoff from Subbasin H is conveyed via sheet flow and gutter flow across the
existing parking and drive area to an existing sump condition area inlet in the
existing parking lot just north of the southeast corner of subject site. Said area inlet
is located in an existing low area that acts as a small detention area as the release of
flows is controlled by the capacity of the existing pipe in College Avenue, the size
of the outfall pipe and the size of the inlet. In the event that the area around said inlet
overflows, a sidewalk chase has been added to allow the flows to enter Subbasin I
and be collected in the existing area inlet.
Runoff from Subbasin I is conveyed via sheet flow to an existing sump condition
area inlet in the existing parking lot. Said area inlet is located in an existing low area
that acts as a small detention area as the release of flows is controlled by the capacity
of the existing pipe in College Avenue, the size of the outfall pipe and the size of the
inlet. In the event that the area around said inlet overflows, a sidewalk chase has
been added to allow the flows to enter Subbasin F and/or H and be collected in the
existing area inlets. For the interim condition, said existing inlet will be left as is.
When this lot is developed, the inlet will be relocated to fit with the proposed layout
and the inter -relationship between the existing area inlets will be addressed.
Runoff from Subbasin J is conveyed via sheet flow to an existing sump condition
area inlet ion College Avenue just north of the southeast corner of the site in the
continuous right turn lane on College Avenue.
3.3 Hydrologic Analysis of the Proposed Drainage Conditions
The Rational Method was used to determine the 10-year and 100-year peak runoff rates for
each subbasin. Runoff coefficients were assigned utilizing Table 3-2 of the SDDCCS
Final Drainage and Erosion Control Report Page 5
Wards Redevelopment October 3, 2000
and the proposed building envelope. The flows are still routed as historically with the flows
from the eastern portion of the site conveyed to the existing area inlets and the flows from
the western portion of the site conveyed to the railroad swale and eventually into the
Sherwood Lateral.
A qualitative summarization of the drainage patterns within each sub -basin is provided in the
following paragraphs.
Runoff from Subbasin A is conveyed via roof drains and sheet flow across the rear
parking and drive area to the aforementioned depression along the western portion
of subject site. Said depression acts as a sediment basin/water quality pond/retention
pond. In the major storm event, said depression overtops and the flows enter the
existing swale along the east side of the railroad tracks, is diverted northerly and
conveyed in said swale to the Sherwood Lateral. The amount of runoff generated
from this basin does not change from historic amounts.
Runoff from Subbasin B is conveyed via sheet flow and gutter flow across the
existing parking and drive area north of the northwest corner of the existing building
to the aforementioned depression along the western portion of subject site. Said
depression acts as a sediment basin/water quality pond/retention pond. In the major
storm event, said depression overtops and the flows enter the existing Swale along
the east side of the railroad tracks, is diverted northerly and conveyed in said Swale
to the Sherwood Lateral. The amount of runoff generated from this basin does not
change from historic amounts.
,! Runoff from Subbasins C, D and E are conveyed via sheet flow northerly to the
existing parking lot/property north of the Wards Redevelopment site. The amount
of runoff generated from these basins, a total of 0.05 acres, does not change from
historic amounts.
Runbff from Subbasin F is conveyed via sheet flow and gutter flow across the
existing parking and drive area to an existing sump condition area inlet in the access
drive to this site from College Avenue. Said area inlet is located in an existing low
{ area that acts as a small detention area as the release of flows is controlled by the
capacity of the existing pipe in College Avenue, the size of the outfall pipe and the
size of the inlet. In the event that the area around said inlet overflows, a sidewalk
Final Drainage and Erosion Control Report Page 4
;� Wards Redevelopment October 3, 2000
negative impact on the Spring Creek Major Drainage Basin as the site is currently almost
entirely impervious. In fact, the redevelopment of this site will slightly reduce the runoff
with the proposed additional landscape areas.
A portion of this site was included in the "Drainage and Erosion Control Report, University
Center PUD", prepared by Bucher, Willis and Ratliff Corporation, and approved by the City
of Fort Collins on July 24, 1998.
2. EXISTING SITE DRAINAGE
The existing drainage for this site consists of the flow being split between the east and west
portions of the site. The flows from the eastern portion of the site enter three (3) existing
sump condition area inlets within the parking and drive area. Said inlets are conveyed to an
existing storm sewer system in College Avenue which outlets directly into Spring Creek.
The flows from the western portion of the site are conveyed westerly towards the railroad
tracks. Immediately adjacent to the west edge of the existing parking lot, there is an existing
depression/ponding area that the runoff enters. This depression acts as a sediment
basin/water quality pond. When this area fills with runoff, it overtops and the flows enters
an existing swale along the railroad tracks. The flows are then conveyed northerly in said
swale to the Sherwood Lateral.
The soil on this site is Nunn clay loam, which consists of nearly level soils on high terraces
and fans (USDA, 1980). 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 in Hydrologic Group C.
3. PROPOSED DRAINAGE PLAN
3..1 Off -site Flow Routing
No off -site flows enter this site.
3.2 On -Site Flow Routing
The site was graded so that stormwater runoff is directed away from the existing building
Final Drainage and Erosion Control Report Page 3
Wards Redevelopment October 3, 2000
1. INTRODUCTION
1.1 Project Description
The Wards Redevelopment is the redevelopment of the existing Montgomery Wards site
adjacent to the University Mall. This site contains approximately 6.6 acres. The proposed
-- redevelopment will include adding a new fagade to the building, adding a future building lot
to the eastern portion of the site, and upgrading the parking lot and landscaping.
The site is located in the southwest corner of Rutgers Avenue and South College Avenue,
in Fort Collins, Colorado. It is bounded by College Avenue on the east, the University
Center on the south, Burlington Northern railroad tracks on the west, and an existing
commercial center on the north. The site lies in Section 23, Township 7 North, Range 69
West -of the Sixth Principal Meridian, in the City of Fort Collins, Larimer County, Colorado.
A vicinity map is included after the Table of Contents of this report.
1.2 Purpose and Scope of Report
This report defines the proposed drainage and erosion control plan for the proposed Wards
Redevelopment. The drainage plan includes consideration of all on -site and tributary off -site
runoff.
1.3 Design Criteria
This report and associated calculations were prepared to meet requirements established in
the "City of Fort Collins Storm Drainage Design Criteria and Construction Standards"
(SDDCCS), dated May 1984 and updated January 1997. The new rainfall criteria as
amended by Ordinance 42.1999 was used for the 10-year and 100-year design storms.
Runoff computations were made using the rational method. Where applicable, the criteria
established in the "Urban Storm Drainage Criteria Manual" (UDFCD), 1984, developed by
the Denver Regional Council of Governments, has been utilized.
1.4 Master Drainage Plan and Related Drainage Reports
This site is included in the Spring Creek Major Drainage Basin and a report entitled "Spring
Creek Master Drainageway Plan" was prepared by Engineering Professionals, Inc., in March
1988. It is not anticipated that the proposed redevelopment of the Wards site will have a
Final Drainage and Erosion Control Report Page 2
Wards Redevelopment October 3, 2000
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VICINITY MAP
N.T.S.
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TABLE OF CONTENTS
LETTER OF TRANSMITTAL
PAGE
TABLEOF CONTENTS.................................................................................................................I
1.
INTRODUCTION.................................................................................................................. 2
1.1 Project Description.............................................................................................................. 2
1.2 Purpose and Scope of Report .............................................................................................. 2
1.3 Design Criteria.................................................................................................................... 2
1.4 Master Drainage Plan and Related Drainage Reports......................................................... 2
2.
EXISTING SITE DRAINAGE............................................................................................... 3
3.
PROPOSED DRAINAGE PLAN........................................................................................... 3
3.1 Off -site Flow Routing......................................................................................................... 3
3.2 On -Site Flow Routing......................................................................................................... 3
3.3 Hydrologic Analysis of the Proposed Drainage Conditions ............................................... 5
3.4 Allowable Street Flow Capacities....................................................................................... 6
3.5 Storm Drainage Structure Design....................................................................................... 6
4.
WATER QUALITY................................................................................................................ 7
5.
EROSION CONTROL........................................................................................................... 7
5.1 Erosion and Sediment Control Measures............................................................................ 7
5.2 Dust Abatement.......................:.......................................................................................... 7
5.3 Tracking Mud on City Streets............................................................................................. 8
.:
5.4 Maintenance........................................................................................................................8
5.5 Permanent Stabilization...................................................................................................... 8
6.
MISCELLANEOUS............................................................................................................... 8
6.1 Variances.............................................................................................................................8
6.2 Irrigation Ditches................................................................................................................ 9
6.3 Maintenance Agreements.................................................................................................... 9
7.
REFERENCES.....................................................................................................:................. 9
APPENDIX A - HYDROLOGIC CALCULATIONS
APPENDIX B - STORM DRAINAGE STRUCTURE DESIGN
APPENDIX C -EROSION CONTROL
Final Drainage and Erosion Control Report Page i
Wards Redevelopment October 3, 2000
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October 3, 2000 ft)
J•R ENGINEERING
Mr. Basil Hamdan A Subsidiary of Westrian
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, CO 80521
RE: Final Drainage and Erosion Control Report for Wards Redevelopment
Dear Basil:
We are pleased to submit to you for your review and approval, this Final Drainage and Erosion
Control Study for the Wards Redevelopment. All computations within this report have been
completed in compliance with the City of Fort Collins Storm Drainage Design Criteria.
We appreciate your time and consideration in reviewing this submittal. Please call if you have any
questions.
Sincerely,
q� b
"..
David W. Klockeman,
Division Manager
Attachment
2620 East Prospect Road, Suite 190, Fort Collins, CO 80525
970-491-9888 • Fax 970-491-9984 • www.jrengineeringxom
FINAL DRAINAGE AND EROSION
CONTROL REPORT
WARDS REDEVELOPMENT
UNIVERSITY MALL PUD REPLAT NO.2
October 3, 2000
Prepared by
JR ENGINEERING
2620 E. Prospect Rd., Suite 190
Fort Collins, Colorado 80525
(970)491-9888
Prepared for
ZTI Group
2120 South College Avenue
Fort Collins, Colorado 80525
(970)493-4105
Previous revision dates
None
Job Number 9059.03