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Final Drainage Report
- Colorado Iron & Metal
IX. APENDICES ,
Appendix I - Hydrologic Calculations
■ Runoff Curve Number
■ Time of Concentration and Peak Discharge
Appendix 11 - Hydraulic and Detention Calculations
■ Water Quality Calculations
■ Detention Pond Sizing Worksheet
■ Pond Stage -Storage Worksheet
■ Storm Sewer Calculations
■ Sediment and Erosion Control Opinion of Probable Cost
Appendix III - Mapping and Plans
■ FEMA Firmette
■ City Floodplain Map
■ Drainage and Erosion Control Plan (24"x36")
Final Drainage Report
Colorado Iron & Metal
VI1. CONCLUSIONS
A. Compliance with standards
I. All drainage design conform to the criteria and requirements of City of Fort Collins
Storm Drainage and Design Criteria and Construction Standards.
2. Proposed drainage improvements conform to the concepts and recommendations of
the Dry Creek Basin master plan.
3. Proposed sediment/erosion control measures conform to the recommendations of
City of Fort Collins Storm Drainage and Design Criteria and Construction Standards
and generally accepted erosion control procedures.
B. Drainage Concept
1. The proposed drainage plan concept for the project will be effective for the control of
stormwater runoff and water quality for the proposed site and conforms to City of
Fort Collins standards.
VII1. REFERENCES
• City of Fort Collins Storm Drainage and Design Criteria and Construction Standards
• The Dry Creek Basin Master Plan
• Urban Storm Drainage Criteria Manual Volume I: Urban Drainage and Flood Control District,
Denver, Colorado, March, 1969.
• Urban Storm Drainage Criteria Manual Volume 2; Urban Drainage and Flood Control District,
Denver, Colorado, March, 1969.
• Urban Storm Drainage Criteria Manual Volume 3. Best Management Practices; Urban Drainage
and Flood Control District, Denver, Colorado, September, 1999.
Final Drainage Report
Colorado Iron & Metal
VI. SEDIMENT/EROSION CONTROL
A. General Concept
I. Temporary erosion control measures will be installed with this project. These
measures will include:
a. Silt fence along the property lines.
b. Gravel filters at the locations of point discharges from the site.
c. Water trucks and soil terracing to address construction dust abatement.
d. Vehicle tracking pad at the construction entrance.
e. The detention pond will act as a sediment basin during construction.
2. Permanent sediment\erosion control measures will consist of paving, concrete .
hardscape, and landscaping to stabilize the disturbed areas.
3. Maintenance of all sediment\erosion control devices will remain the responsibility
of the contractor until the project is completed.
4. An Engineer's opinion of probable cost for the erosion/sediment control measures
is located in the appendix.
Final Drainage Report
Colorado Iron & Metal
topography towards the existing detention pond on Lot I, and ultimately to the
borrow ditch along the west side of Lemay.
` C. Specific Details - Stormwater Quality
I. Water quality will be provided in accordance with Best Management Practices as
presented in the Urban Storm Drainage Criteria Manual Volume 3 Best Management
Practices; Urban Drainage and Flood Control District, Denver, Colorado, September,
1999.
2. Permanent structural BMP's consists of extended detention within the proposed
detention pond.
D. Specific Details - Swales
1. There are no swales requiring analysis within the project site.
w
E. Specific Details - Inlets and Storm Sewer
w I. The detention pond discharges through a 15" pipe (storm sewer A) which runs
through the Odell Brewery property directly to the south. Ultimately, this pipe
discharges to the existing borrow ditch along the north side of Lincoln Avenue. An
off -site easement will be provided for this pipe by separate instrument.
2. The discharge through storm sewer A is 1.22 CFS, which is the release discharge
from the detention pond. The pipe sizing calculations are included in the appendix,
and indicate that capacity in the proposed pipe is more than adequate.
3. Storm sewer B is a 15" HDPE pipe to provide positive drainage from the northern
portion of the detention pond. This pipe is not intended to convey the 100-year
event. It is simply in place to provide positive drainage for low flows.
F. Specific Details - Curb Cuts
1. Three curb cuts are proposed along the southern flowline of Buckingham Street.
These are located within sumps with very small drainage basins. Each curb cut will be
2' wide, connected to a sidewalk culvert with a 2' wide, 6" deep concrete U channel
at 0.5% slope.
Final Drainage Report
Colorado Iron & Metal
V. DRAINAGE FACILITY DESIGN
A. General Concept
I. The general direction of storm water flow is from north to south.
2. Storm water from Buckingham Street is carried through curb cuts and sidewalk
culverts to the parking areas within the site. These flows are then conveyed
through the site, along with flows from the site itself.
3. Portions of the site will continue to drain to the existing detention pond. As
previously discussed, the total drainage area to this existing pond will be
substantially decreased as a result of this development. No revised analysis is,
included for this existing pond, since the only proposed change is to reduce the
drainage area.
4. Newly developed areas, with a portion of the existing developed area (drainage
basin A) will flow to a new detention pond located near the southwest corner of
the property.
B. Specific Details — Detention
I. The drainage area to the new detention pond is 6.09 acres. The additional developed
area within the site will be treated for detention and water quality by a new detention
pond. The required water quality volume is 0.200 acre-feet and the required
detention volume is 1.651 acre-feet, for a total pond volume of 1.851 acre-feet. .This
volume is provided in the proposed detention pond at elevation 4943.23'.
2. The detention pond drains to a new storm drain pipe which flows southerly and into
the borrow ditch along the north side of Lincoln Avenue. This proposed pipe (storm
drain A) is 15" in diameter. An off -site easement will be obtained from the owner of
the property to the south to contain this new storm drain line.
3. As stated previously, the existing drainage area to the existing detention pond is being
reduced significantly. This reduction will allow the existing pond to function at a
higher level of performance when compared to existing.
4. An emergency spillway is proposed to convey emergency flow from the site towards
the southeast. The proposed design of the spillway is a trapezoidal channel with a
bottom width of 60' and side slopes of 33:1, with a weir elevation of 4944.20'. Since
the spillway discharges to natural ground, the Manning's Equation was used to
determine the spillway capacity. The results indicate that the spillway can convey the
100-year discharge from this drainage basin (39.7 CFS) at a normal depth of 0.34'.
The flow velocity is quite low at 1.64 FPS, so the erosion potential in this area is
insignificant. This area is proposed to be covered with gravel.
5. Once the emergency overflow discharge passes through the pond spillway, it generally
flows towards the south and east. This emergency flow is directed by existing
Final Drainage Report
Colorado Iron & Metal
IV. DRAINAGE DESIGN CRITERIA
A. Development Regulations
I. Design criteria from the City of Fort Collins Storm Drainage and Design Criteria and
Construction Standards were followed for this drainage report.
B. Development Criteria Reference and Constraints
I. The proposed storm water release rate is 0.20 cfs/acre, in accordance with the Dry
Creek Master Plan. The drainage area of the portion of the site draining to the new
detention pond (drainage basin A) is 6.09 acres. This equates to a release rate of 1.22
CFS.
C. Hydrological Criteria
I. Peak flow rates for the 100-year storm are calculated in accordance with the City of
Fort Collins Storm Drainage and Design Criteria and Construction Standards. Please
see these calculations in the Hydrology section of Appendix 1.
D. Hydraulic Criteria
I. The City of Fort Collins Storm Drainage and Design Criteria and Construction
Standards are used to determine the adequacy of the hydraulic structures associated
with the project
2. Analyses are performed using methodologies presented in Urban Storm Drainage
Criteria Manual Volumes I and 2 Urban Drainage and Flood Control District,
Denver, Colorado, September, 1999. Please see the various computation
spreadsheets in the Hydraulics section of Appendix I.
Final Drainage Report
Colorado Iron & Metal
Ill. DRAINAGE BASINS AND SUB -BASINS
A. Major Basin Description
1. The project site lies within the City of Fort Collins Dry Creek Basin.
2. The project site is located outside the Dry Creek and Cache La Poudre River 100-
year floodplains, but is inside the Cache La Poudre River 500-year floodplain. Copies
of the FEMA FIRM panel 08069C0983G, dated June 17, 2008, and the City Floodplain
Mapping are included in the appendix
B. Existing Conditions
I. As mentioned, the project site is currently partially developed. The existing
development was part of the "Vanworks Subdivision Second Filing". The construction
plans for that subdivision included Lots I, 2 and 3. A detention pond was constructed
within Lot I to mitigate storm water flows from all three lots. The original
engineering plans were prepared by Shear Engineering and are dated March 1998.
2. The existing detention pond is located in the rear portion of Lot I, which is located
immediately east of the project site. The pond discharges through a control structure
to a Swale which connects to the borrow ditch along the west side of Lemay Avenue.
Lots 2 and 3 are included in drainage basin A, which was shown to have a drainage
area of 14.76 acres and a composite runoff coefficient of 0.48.
C. Developed Conditions
1. The proposed use is a metal recycling and fabrication facility. The proposed project
consists of the renovation of the existing building, construction of two new buildings,
one new driveway, concrete and asphalt drive aisles and parking areas. The new
buildings consist of a metal shop building and a building to house the bailer used in the
paper recycling process.
2. Portions of the project site will continue to drain to the existing detention pond
which was originally constructed for the entire site. In general, this includes the
existing building, the existing pavement on the east side of the building, and a portion
of the southern half of Buckingham Street. It should be noted that the existing pond
was originally designed to mitigate all these existing improvements plus some existing
areas that will be redirected to the new detention pond described below.
3. A large portion of the development site and a portion of the south portion of
Buckingham Street drains to a new detention pond located in the southwest corner of
the site. This new detention pond drains through a proposed storm drain in a
southerly direction to the borrow ditch along the north side of Lincoln Avenue. This
has the effect of reducing the drainage area to the existing pond by 5.57 acres.
Therefore, the only impact to the existing, previously approved pond is a reduction of
drainage area in the proposed condition.
Final Drainage Report
Colorado Iron & Metal
I. INTRODUCTION
This report presents the pertinent data, methods, assumptions, and references used in
analyzing and preparing the final drainage, erosion control and water quality design for the
Colorado Iron & Metal project (the "project').
11. GENERAL LOCATION AND DESCRIPTION
A. Property Location
I. The project is located on Lots 2 and 3 of Vanworks Subdivision Second Filing,
consisting of 8.74 acres. The street address of the project is 903 Buckingham Street
Fort Collins, Colorado, as shown below:
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Vicinity Map, NTS
B. Property Description
I. The project site is currently partially developed. Existing improvements consist of a
large metal building, with two driveways and associated parking and hardscape. The
project was originally developed in the late I990's as part of the "Vanworks
Subdivision Second Filing".
2. The site is relatively flat, with a gentle slope from north to south. There are no
subsurface drainage facilities near the site, and the surrounding topography is generally
flat.
Final Drainage Report
Colorado Iron & Metal
TABLE OF CONTENTS
1.
INTRODUCTION..........................................................................I......I............. 3
11.
GENERAL LOCATION AND DESCRIPTION..............................................3
A.
Property Location..................................................................................................................................... 3
B.
Property Description................................................................................................................................3
III.
DRAINAGE BASINS AND SUB-BASINS......................................................4
A.
Major Basin Description..........................................................................................................................4
B.
Existing Conditions....................................................................................................................................4
C.
Developed Conditions.............................................................................................................................4
IV.
DRAINAGE DESIGN CRITERIA....................................................................5
A.
Development Regulations........................................................................................................................5
B.
Development Criteria Reference and Constraints............................................................................5
C.
Hydrological Criteria................................................................................................................................5
D.
Hydraulic Criteria.....................................................................................................................................5
V.
DRAINAGE FACILITY DESIGN.....................................................................6
A.
General Concept.......................................................................................................................................6
B.
Specific Details — Detention....................................................................................................................6
C.
Specific Details—Stormwater Quality.................................................................................................7
D.
Specific Details — Swales..........................................................................................................................7
E.
Specific Details — Inlets and Storm Sewer...........................................................................................7
F.
Specific Details — Curb Cuts..................................................................................................................7
VI.
SEDIMENT/EROSION CONTROL................................................................8
A:
General Concept.......................................................................................................................................8
VII.
CONCLUSIONS...............................................................................................9
A.
Compliance with standards.....................................................................................................................9
B.
Drainage Concept....................................................................................................................................9
VIILREFERENCES.................................................................................................... 9
IX. APENDICES.....................................................................................................
10
Final Drainage Report
Colorado Iron & Metal
ENGINEER'S CERTIFICATION
I hereby state that this Final Drainage and Erosion Control report for the Colorado Iron & Metal
project was prepared by me or under my direct supervision for the owners thereof and meets or
exceeds the criteria in the City of Fort Collins Storm Drainage Design Criteria and Construction
Standards.
�7 ---------------- ------------------------
Stacy J. Gowing
Registered Professional Engineer
State of Colorado No: 34290
Final Drainage, Erosion Control and Water Quality Report
For
Colorado Iron &'Metal.
Fort Collins, Colorado
Prepared for:
GTC INVESTMENTS, LLC
1400 EAST MULBERRY STREET
C/O KENT GARVIN
FORT COLLINS, CO 80524
Prepared by:
ENGINEERING
908 LAPORTE AVENUE
FORT COLLINS, CO 80521
970-219-2834
MAY 30, 2012