HomeMy WebLinkAboutEAST PARK DISTRICT MAINTENANCE FACILITY - MJA200003 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTNovember 4, 2020
PRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT FOR
East Park District Maintenance Facility
Fort Collins, Colorado
Prepared for:
City of Fort Collins
Attn: Matt Schaefer
PO Box 580
Fort Collins, Colorado 80522
Prepared by:
200 South College Avenue, Suite 10
Fort Collins, Colorado 80524
Phone: 970.221.4158 Fax: 970.221.4159
www.northernengineering.com
Project Number: 1748-002
This Drainage Report is consciously provided as a PDF.
Please consider the environment before printing this document in its entirety.
When a hard copy is necessary, we recommend double-sided printing.
November 4, 2020
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Preliminary Drainage and Erosion Control Report for
East Park District Maintenance Facility
Dear Staff:
Northern Engineering is pleased to submit this Preliminary Drainage and Erosion Control Report for
your review. This report accompanies the Project Development Plan (PDP) submittal for the
proposed East Park District Maintenance Facility development.
This report has been prepared in accordance with Fort Collins Stormwater Criteria Manual (FCSCM)
and serves to document the stormwater impacts associated with the proposed project. We
understand that review by the City is to assure general compliance with standardized criteria
contained in the FCSCM.
If you should have any questions as you review this report, please feel free to contact us.
Sincerely,
Northern Engineering Services, Inc.
Carlos Ortiz García Shane Ritchie, PE
Project Engineer Project Manager
East Park District Maintenance Facility
Preliminary Drainage Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ........................................................................ 1
A. Location................................................................................................................... 1
B. Description of Property ............................................................................................... 2
C. Floodplain ................................................................................................................ 3
II. DRAINAGE BASIN AND SUB-BASIN ................................................................................ 4
A. Major Basin Description ............................................................................................. 4
B. Sub-Basin Description ............................................................................................... 4
III. DRAINAGE DESIGN CRITERIA ........................................................................................ 5
A. Regulations .............................................................................................................. 5
B. Hydrological Criteria .................................................................................................. 5
C. Hydraulic Criteria ...................................................................................................... 5
D. Modifications of Criteria ............................................................................................. 5
IV. DRAINAGE FACILITY DESIGN ......................................................................................... 5
A. General Concept ....................................................................................................... 5
B. Specific Details ......................................................................................................... 6
V. CONCLUSIONS ............................................................................................................. 7
A. Compliance with Standards ........................................................................................ 7
VI. REFERENCES ............................................................................................................... 8
APPENDICES
APPENDIX A – Hydrologic Computations
APPENDIX B – Detention Pond Computation
APPENDIX C – Erosion Control Report
APPENDIX D – Preliminary LID Design Information
LIST OF FIGURES
Figure 1 – Aerial Photograph ................................................................................................ 2
Figure 2 – Proposed Site Plan ............................................................................................... 3
Figure 3 – Area Floodplain Mapping ...................................................................................... 4
MAP POCKET
Proposed Drainage Exhibit
East Park District Maintenance Facility
Preliminary Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. The project site is located in the Southeast ¼ of Section 20, Township 7 North, Range
68 West of the 6th Principal Meridian, City of Fort Collins, County of Larimer, State of
Colorado.
3. The project site is located just north of Environmental Drive and south of the Great
Western Railroad.
4. The East Park District Maintenance Facility is located on the southeast side of Detention
Pond 215. An existing storm drain runs along the east boundary of the site, directing
water out of Detention Pond 215. This pond conveys runoff from the existing Bucking
Horse Filings 1-4 and was intended to also convey runoff from the current site.
5. Offsite flows are minimal, and they enter the site from the west. Refer to the Drainage
Exhibit for offsite basins location.
East Park District Maintenance Facility
Preliminary Drainage Report 2
B. Description of Property
1. The project area is roughly 3.60 acres.
Figure 1 – Aerial Photograph
2. The subject property is an undeveloped parcel with native ground cover. The existing
ground slopes in three different directions; the north side of the site slope with a mild to
moderate grade (i.e., 1 - 3±%) through the interior to the northeast, and the south
middle portion of the site slope with a mild to moderate grade (i.e., 1 – 2.5±%) through
the interior to a low point located at the southeast corner of the site and, a small portion
of area on the south side of the site slope south with a mild to moderate grade (i.e., 1 –
2±%). General topography slopes from the west to the northeast, southeast, and south.
3. A soils report (Project No. FC09344-125) was completed by CTL Thompson, Inc. on
May 4, 2020. The report contains the results of a complete geotechnical subsurface
exploration as well as pertinent geotechnical recommendations.
4. The proposed project site plan is composed of one building, parking areas, and open
spaces. Please see Figure 2, on the following page, showing the proposed site plan.
East Park District Maintenance Facility
Preliminary Drainage Report 3
Figure 2 – Proposed Site Plan
5. There are existing Utility Easements crossing the property at a northeast bearing on the
east one-third side of the site.
C. Floodplain
1. The East Park District Maintenance Facility is located within a FEMA Moderate Risk
Flood Hazard Area for the Cache la Poudre River. This area is designated as Zone X on
Firm Panel 0992G, Revised May 2, 2012. Therefore, it falls outside of the regulated
100-year floodway and floodplain fringe. Chapter 10 of the City of Fort Collins
Municipal Code does regulate critical facilities within this Moderated Risk Flood Hazard
Zone. However, no critical facilities are proposed.
It should be noted that FEMA is remapping the Cache Poudre River in the next one to
two years in a process that may affect this property. Discussions with City staff have
indicated that the existing elevations on the project site could place the project within
the updated 100-year floodplain. To ensure that the proposed building remains out of
the updated floodplain, the finished floor of the building, and all ductwork, heating,
ventilation, electrical systems, etc. will be elevated 24 inches above the Base Flood
Elevation (BFE). This elevation is known as the Regulatory Flood Protection Elevation
(RFPE). RFPE = BFE + 24 inches.
Preliminary results from the new modeling indicate the BFE will be 4885.1 and the
RFPE would be 4887.1
East Park District Maintenance Facility
Preliminary Drainage Report 4
Figure 3 – Area Floodplain Mapping
2. While the area referenced above currently falls outside of the current 100-year
floodplain, it should be noted that the subject property is protected from the 1% annual
chance or greater flood hazard by a levee system. Overtopping or failure of any levee
system is possible. Current and future landowners should check with the local floodplain
administrator at the City of Fort Collins to obtain more information, such as the
estimated level of protection provided (which may exceed the 1% annual chance level)
and the Emergency Action Plan, on the levee system(s) protecting this area. To mitigate
flood risk in residual risk areas, property owners and residents are encouraged to
consider flood insurance and floodproofing or other protective measures. For more
information on flood insurance, interested parties should visit the FEMA Website.
II. DRAINAGE BASIN AND SUB-BASIN
A. Major Basin Description
1. The East Park District Maintenance Facility lays in Basin 57 of the Foothills Drainage
Basin. According to the updated Foothills Master Drainage Plan by Anderson Consulting
Engineers, (ACE) dated July 15, 1999, the project site was was limited to a 100-year
developed discharge of 85 CFS, which equated to the 2-yr historic rate.
B. Sub-Basin Description
The subject property is located within the Bucking Horse development, and has historically
drained overland from west to northeast, southeast, and south. The property was included
in the Pond 215 design, and had both detention and water quality accounted for. Because
of the grade differential between the Detention Pond 215 water surface elevation and
East Park District Maintenance Facility
Preliminary Drainage Report 5
existing site topography, we believe it is not practical for this site to drain to Detention Pond
215. As such, the project site is proposed to follow the existing drainage pattern to the
southeast and be released into the existing storm drain along the east side of the property. A
more detailed description of the project drainage patterns follows in Section IV.A., below.
III. DRAINAGE DESIGN CRITERIA
A. Regulations
There are no optional provisions outside of the FCSCM proposed with the proposed project.
B. Hydrological Criteria
1. The City of Fort Collins Rainfall Intensity-Duration-Frequency Curves, as depicted in
Figure RA-16 of the FCSCM, serve as the source for all hydrologic computations
associated with the proposed development. Tabulated data contained in Table RA-7 has
been utilized for Rational Method runoff calculations.
2. The Rational Method has been employed to compute stormwater runoff utilizing
coefficients contained in Tables RO-11 and RO-12 of the FCSCM.
3. Two separate design storms have been utilized to address distinct drainage scenarios.
The first event analyzed is the “Minor” or “Initial” Storm, which has a two-year
recurrence interval. The second event considered is the “Major” Storm, which has a
100-year recurrence interval.
4. No other assumptions or calculation methods have been used with this development
that are not referenced by the current City of Fort Collins criteria.
C. Hydraulic Criteria
1. As previously noted, the subject property maintains historic drainage patterns.
2. All drainage facilities proposed with the project are designed in accordance with the
criteria outlined in the FCSCM and/or the Urban Drainage and Flood Control District
(UDFCD) Urban Storm Drainage Criteria Manual.
3. As previously mentioned, this project is not subject to any floodplain regulations.
D. Modifications of Criteria
No modifications are requested at this time.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of the project drainage design are to maintain existing drainage
patterns and to ensure no adverse impacts to any adjacent properties.
2. Onsite detention and water quality treatment will be provided within the detention pond
located at the southeast corner of the project. The pond will treat the majority of
developed runoff prior to discharge into the existing storm pipe.
3. The site has been broken into four onsite sub-basins for preliminary design purposes.
Anticipated drainage patterns for proposed drainage basins are described below.
East Park District Maintenance Facility
Preliminary Drainage Report 6
Basin 1
Basin 1 consists of concrete, gravel, landscape areas, and a portion of the building area.
This basin will generally drain via overland flow to a concrete pan and into a rain garden
and will then drain via storm drain and inlets into the proposed detention pond located
on the southeast corner of the project. The proposed detention pond will release to an
existing storm drain pipe designed with Bucking Horse Filing One located along the east
boundary of the property.
Basin 2
Basin 2 consists of asphalt and landscape areas and a portion of the building area. This
basin will generally drain via overland flow across the parking lot to a curb cut and into
a rain garden and will then drain via storm drain and inlets into the proposed detention
pond on the southeast corner of the project. The proposed detention pond will release to
an existing storm drain pipe designed with Bucking Horse Filing One located along the
east boundary of the property.
Basin 3
Basin 3 consists primarily of open space. This basin will generally drain via overland
flow to the northeast and will not be detained.
Basin 4
Basin 4 consists primarily of open space and concrete walks areas. This basin will
generally drain via overland flow to Environmental Drive and will then drain via curb and
gutter to existing drainage facilities to the south and will not be detained.
Basins OS1 and OS2
Basins OS1 and OS2, as shown on the Drainage Exhibit, consist of open space and
concrete walks along the east side of Detention Pond 215 that drain onto the current
site. Some of OS1 runoff will not receive LID treatment, and the detention will pass this
flow over the spillway. OS2 runoff will receive LID Treatment, and the detention will
pass this flow over the spillway.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
B. Specific Details
1. The detention pond volume of 0.55 AC-FT was calculated using the FAA Method. The
requirements for this basin are to detain the difference between the 100-year developed
inflow rate and the historic two-year release rate. A historic two-year release rate of
1.64 CFS was calculated for the overall East Park District Maintenance Facility site (3.6
acres).
2. City code requires LID treatment for all projects, and this project is proposing to meet
the requirement using rain gardens. The rain gardens are situated towards the bottom of
the paved areas and will treat stormwater prior to it entering the detention facility. This
configuration will treat 96.2% of the onsite impervious area, far exceeding the City
requirement to treat more than 75% of the site.
3. Water quality for the project will be provided by the rain gardens. A water quality
volume of 0.07 AC-FT was calculated using the Mile High Flood District method for
Rain Garden sizing and then by adding 20% to that volume.
4. The allowable release rate from the entire Bucking Horse project was identified by
Anderson Consulting Engineers (ACE) in their original report dated July 15, 1999 as 85
East Park District Maintenance Facility
Preliminary Drainage Report 7
cfs. Bucking Horse Filing Two used a release rate of 83 CFS, leaving 2 cfs of available
release from the basin without exceeding the original design. The proposed release rate
for the project is less, therefore the project is in conformance with the previous designs.
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with the proposed project complies with the City of Fort
Collins’ Stormwater Criteria Manual, as well as previous drainage studies from which
downstream stormwater infrastructure was constructed
2. The drainage design proposed with this project complies with requirements for the
Foothills Basin.
3. The drainage plan and stormwater management measures proposed with the proposed
development are compliant with all applicable State and Federal regulations governing
stormwater discharge.
4. Additional information and detail will be provided with future submittals, as is
customary during the Final Plan review and approval process.
East Park District Maintenance Facility
Preliminary Drainage Report 8
VI. REFERENCES
1. City of Fort Collins Landscape Design Guidelines for Stormwater and Detention
Facilities, November 5, 2009, BHA Design, Inc. with City of Fort Collins Utility
Services.
2. Fort Collins Stormwater Criteria Manual, City of Fort Collins, Colorado, as adopted by
Ordinance No. 174, 2011, and referenced in Section 26-500 (c) of the City of Fort
Collins Municipal Code.
3. Larimer County Urban Area Street Standards, Adopted January 2, 2001,
Repealed and Reenacted, Effective October 1, 2002, Repealed and Reenacted,
Effective April 1, 2007.
4. Soils Resource Report for Larimer County Area, Colorado, Natural Resources
Conservation Service, United States Department of Agriculture.
5. Urban Storm Drainage Criteria Manual, Volumes 1-3, Urban Drainage and Flood
Control District, Wright-McLaughlin Engineers, Denver, Colorado, Revised April
2008.
6. Preliminary Geotechnical Exploration Report, Bucking Horse Development -
Southeast (Johnson Farm, Working Farm, Urban Estate), Fort Collins, Colorado,
July 19, 2012, Earth Engineering Consultants, Inc. (EEC Project No.
1122025C)
7. Final Drainage Report Bucking Horse Filing One, Dated September 19, 2012,
by Northern Engineering.
8. Final Drainage Report Bucking Horse Filing Two, Dated December 17, 2012, by
Northern Engineering
APPENDIX A
Hydrologic Computations
APPENDIX B
WATER Detention Pond Computation
APPENDIX C
Erosion Control Report
APPENDIX D
Preliminary LID Design Information
MAP POCKET
DRAINAGE EXHIBITS
East Park District Maintenance Facility
Preliminary Erosion Control Report
EROSION CONTROL REPORT
A comprehensive Erosion and Sediment Control Plan (along with associated details) will be included
with the final construction drawings. It should be noted, however, that any such Erosion and
Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of
the BMPs depicted, and additional or different BMPs from those included may be necessary during
construction, or as required by the authorities having jurisdiction.
It shall be the responsibility of the Contractor to ensure erosion control measures are properly
maintained and followed. The Erosion and Sediment Control Plan is intended to be a living
document, constantly adapting to site conditions and needs. The Contractor shall update the
location of BMPs as they are installed, removed, or modified in conjunction with construction
activities. It is imperative to appropriately reflect the current site conditions at all times.
The Erosion and Sediment Control Plan shall address both temporary measures to be implemented
during construction, as well as permanent erosion control protection. Best Management Practices
from Volume 3, Chapter 7 – Construction BMPs will be utilized. Measures may include, but are not
limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways,
and inlet protection at existing and proposed storm inlets. Vehicle tracking control pads, spill
containment and clean-up procedures, designated concrete washout areas, dumpsters, and job site
restrooms shall also be provided by the Contractor.
Grading and Erosion Control Notes can be found on the Utility Plans. The Final Plans will contain a
full-size Erosion Control sheet as well as a separate sheet dedicated to Erosion Control Details. In
addition to this report and the referenced plan sheets, the Contractor shall be aware of, and adhere
to, the applicable requirements outlined in the Development Agreement for the development. Also,
the Site Contractor for this project will be required to secure a Stormwater Construction General
Permit from the Colorado Department of Public Health and Environment (CDPHE), Water Quality
Control Division – Stormwater Program, prior to any earth disturbance activities. Prior to securing
the said permit, the Site Contractor shall develop a comprehensive StormWater Management Plan
(SWMP) pursuant to CDPHE requirements and guidelines. The SWMP will further describe and
document the ongoing activities, inspections, and maintenance of construction BMPs.
APPENDIX A
Hydrologic Computations
CHARACTER OF SURFACE:
Runoff
Coefficient
Percentage
Impervious Project: 1748-002
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: COG
Asphalt ……....……………...……….....…...……………….………………………………….. 0.95 100% Date:
Concrete …….......……………….….……….………………..….………………………………… 0.95 100%
Gravel ……….…………………….….…………………………..……………………………….. 0.50 40%
Roofs …….…….………………..……………….…………………………………………….. 0.95 90%
Pavers…………………………...………………..…………………………………………….. 0.50 40%
Lawns and Landscaping
Sandy Soil ……..……………..……………….…………………………………………….. 0.15 2%
Clayey Soil ….….………….…….…………..………………………………………………. 0.25 2% 2-year Cf = 1.00 100-year Cf = 1.25
Basin ID
Basin Area
(s.f.)
Basin Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Roofs
(ac)
Area of
Gravel
(ac)
Area of
Lawn, Rain
Garden, or
Landscaping
(ac)
2-year
Composite
Runoff
Coefficient
10-year
Composite
Runoff
Coefficient
100-year
Composite
Runoff
Coefficient
Composite
% Imperv.
Historic Basins:
H1 43021 0.99 0.00 0.00 0.00 0.00 0.99 0.25 0.25 0.31 2.0%
H2 113859 2.61 0.00 0.00 0.00 0.00 2.61 0.25 0.25 0.31 2.0%
Developed Basins:
1 77380 1.78 0.00 1.07 0.09 0.22 0.40 0.74 0.74 0.92 70.1%
2 67113 1.54 0.29 0.13 0.06 0.00 1.06 0.47 0.47 0.58 31.9%
3 8526 0.20 0.00 0.00 0.00 0.00 0.20 0.25 0.25 0.31 2.0%
4 3860 0.09 0.00 0.00 0.00 0.00 0.08 0.28 0.28 0.35 6.1%
OS1 4040 0.09 0.00 0.05 0.00 0.00 0.04 0.62 0.62 0.78 54.4%
OS2 5002 0.11 0.00 0.03 0.00 0.00 0.08 0.44 0.44 0.55 28.6%
Overland Flow, Time of Concentration:
Project: 1748-002
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt
= L / 60V
Tc
= Ti
+ Tt
(Equation RO-2)
Velocity (Gutter Flow), V = 20·S
½
Velocity (Swale Flow), V = 15·S
½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf
=1.00)
C*Cf
(10-yr
Cf
=1.00)
C*Cf
(100-yr
Cf
=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
Rational Method Equation: Project: 1748-002
Calculations By:
Date:
From Section 3.2.1 of the CFCSDDC
Rainfall Intensity:
Historic Basins:
H1 H1 0.99 5 14 13 0.25 0.25 0.31 2.85 3.29 6.92 0.70 0.81 2.14 0.35
H2 H2 2.61 25 25 23 0.25 0.25 0.31 1.45 2.47 5.20 0.94 1.61 4.25 0.47
3.60
Developed Basins:
1 1 1.78 5 5 5 0.74 0.74 0.92 2.85 4.87 9.95 3.73 6.38 16.30 1.87
2 2 1.54 5 5 5 0.47 0.47 0.58 2.85 4.87 9.95 2.05 3.50 8.94 1.02
3 3 0.20 5 5 5 0.25 0.25 0.31 2.85 4.87 9.95 0.14 0.24 0.61 0.07
4 4 0.09 5 5 5 0.28 0.28 0.35 2.85 4.87 9.95 0.07 0.12 0.31 0.04
OS1 OS1 0.09 5 5 5 0.62 0.62 0.78 2.85 4.87 9.95 0.16 0.28 0.72 0.08
OS2 OS2 0.11 5 5 5 0.44 0.44 0.55 2.85 4.87 9.95 0.14 0.25 0.63 0.07
3.601
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
WQ Flow
(cfs)
RUNOFF COMPUTATIONS
C100
Design
Point
Flow,
Q100
(cfs)
Flow,
Q2
(cfs)
10-yr
Tc
(min)
2-yr
Tc
(min)
C2
Flow,
Q10
(cfs)
Intensity,
i100
(in/hr)
Basin(s)
COG
November 3, 2020
Intensity,
i10
(in/hr)
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
Q = C f ( C )( i )( A )
APPENDIX B
WATER Detention Pond Computation
COG
Pond No : South
100-yr
0.73
Area (A)= 3.60 acres 23008 ft
3
Max Release Rate = 1.64 cfs 0.53 ac-ft
Time Time
100-yr
Intensity
Q100
Inflow
(Runoff)
Volume
Outflow
(Release)
Volume
Storage
Detention
Volume
(mins) (secs) (in/hr) (cfs) (ft
3
) (ft
3
) (ft
3
)
5 300 9.950 26.15 7845 492.0 7352.6
10 600 7.720 20.29 12173 984.0 11188.9
15 900 6.520 17.13 15421 1476.0 13945.1
20 1200 5.600 14.72 17660 1968.0 15692.2
25 1500 4.980 13.09 19631 2460.0 17171.2
30 1800 4.520 11.88 21381 2952.0 18429.4
35 2100 4.080 10.72 22517 3444.0 19072.7
40 2400 3.740 9.83 23589 3936.0 19652.9
45 2700 3.460 9.09 24551 4428.0 20122.8
50 3000 3.230 8.49 25465 4920.0 20545.3
55 3300 3.030 7.96 26277 5412.0 20865.4
60 3600 2.860 7.52 27058 5904.0 21153.9
65 3900 2.720 7.15 27878 6396.0 21481.8
70 4200 2.590 6.81 28587 6888.0 21699.4
75 4500 2.480 6.52 29328 7380.0 21948.5
80 4800 2.380 6.25 30022 7872.0 22150.3
85 5100 2.290 6.02 30692 8364.0 22328.4
90 5400 2.210 5.81 31363 8856.0 22506.6
95 5700 2.130 5.60 31907 9348.0 22558.5
100 6000 2.060 5.41 32482 9840.0 22642.1
105 6300 2.000 5.26 33113 10332.0 22780.8
110 6600 1.940 5.10 33649 10824.0 22824.9
115 6900 1.890 4.97 34272 11316.0 22955.7
120 7200 1.840 4.84 34816 11808.0 23007.7
Developed "C" =
1.35
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
DETENTION POND CALCULATION; FAA METHOD
Project Number : 1748-002
Date : November 3, 2020
WATER QUALITY CAPTURE VOLUME DESIGN CALCULATIONS
40-Hour Extended Detention
Project: 1748-002
By: COG
Date: 09/17/20
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA = 3.600 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 48.51 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.49 <-- CALCULATED
WQCV (watershed inches) = 0.202 <-- CALCULATED from USDCM Vol.3, Figure 3-2
WQCV (ac-ft) = 0.073 <-- CALCULATED from USDCM Vol.3, EQ 3-3
WQ Depth (ft) = 3.000 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in2) = 0.205 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 4/8 <-- INPUT from Figure 5
n = 9 <-- INPUT from Figure 5
t (in) = 1/4 <-- INPUT from Figure 5
number of rows = 1 <-- CALCULATED from WQ Depth and row spacing
APPENDIX C
Erosion Control Report
East Park District Maintenance Facility
Preliminary Erosion Control Report
EROSION CONTROL REPORT
A comprehensive Erosion and Sediment Control Plan (along with associated details) will be included
with the final construction drawings. It should be noted, however, that any such Erosion and
Sediment Control Plan serves only as a general guide to the Contractor. Staging and/or phasing of
the BMPs depicted, and additional or different BMPs from those included may be necessary during
construction, or as required by the authorities having jurisdiction.
It shall be the responsibility of the Contractor to ensure erosion control measures are properly
maintained and followed. The Erosion and Sediment Control Plan is intended to be a living
document, constantly adapting to site conditions and needs. The Contractor shall update the
location of BMPs as they are installed, removed or modified in conjunction with construction
activities. It is imperative to appropriately reflect the current site conditions at all times.
The Erosion and Sediment Control Plan shall address both temporary measures to be implemented
during construction, as well as permanent erosion control protection. Best Management Practices
from the Volume 3, Chapter 7 – Construction BMPs will be utilized. Measures may include, but are
not limited to, silt fencing along the disturbed perimeter, gutter protection in the adjacent roadways
and inlet protection at existing and proposed storm inlets. Vehicle tracking control pads, spill
containment and clean-up procedures, designated concrete washout areas, dumpsters, and job site
restrooms shall also be provided by the Contractor.
Grading and Erosion Control Notes can be found on the Utility Plans. The Final Plans will contain a
full-size Erosion Control sheet as well as a separate sheet dedicated to Erosion Control Details. In
addition to this report and the referenced plan sheets, the Contractor shall be aware of, and adhere
to, the applicable requirements outlined in the Development Agreement for the development. Also,
the Site Contractor for this project will be required to secure a Stormwater Construction General
Permit from the Colorado Department of Public Health and Environment (CDPHE), Water Quality
Control Division – Stormwater Program, prior to any earth disturbance activities. Prior to securing
said permit, the Site Contractor shall develop a comprehensive StormWater Management Plan
(SWMP) pursuant to CDPHE requirements and guidelines. The SWMP will further describe and
document the ongoing activities, inspections, and maintenance of construction BMPs
APPENDIX D
Preliminary LID Design Information
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 70.1 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.701
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.22 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 77,380 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 1,421 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV = 12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 5.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 1085 sq ft
D) Actual Flat Surface Area AActual = 1236 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 2005 sq ft
F) Rain Garden Total Volume VT= 1,621 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = N/A ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft
iii) Orifice Diameter, 3/8" Minimum DO = N/A in
Design Procedure Form: Rain Garden (RG)
Carlos Ortiz
Northern Engineering
October 26, 2020
East Park District Maintenance Facility
North Rain Garden
UD-BMP (Version 3.06, November 2016)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
1748-002_RG-North_UD-BMP_v3.06.xlsm, RG 10/26/2020, 5:04 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Carlos Ortiz
Northern Engineering
October 26, 2020
East Park District Maintenance Facility
North Rain Garden
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
1748-002_RG-North_UD-BMP_v3.06.xlsm, RG 10/26/2020, 5:04 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 33.7 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.337
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.13 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 56,411 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 611 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV = 12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 380 sq ft
D) Actual Flat Surface Area AActual = 892 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 1612 sq ft
F) Rain Garden Total Volume VT= 1,252 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = N/A ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft
iii) Orifice Diameter, 3/8" Minimum DO = N/A in
Design Procedure Form: Rain Garden (RG)
C. Ortiz
Northern Engineering
October 26, 2020
East Park District Maintenance Facility
South Rain Garden
UD-BMP (Version 3.06, November 2016)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
1748-002_RG-South_UD-BMP_v3.06.xlsm, RG 10/26/2020, 5:07 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
C. Ortiz
Northern Engineering
October 26, 2020
East Park District Maintenance Facility
South Rain Garden
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
1748-002_RG-South_UD-BMP_v3.06.xlsm, RG 10/26/2020, 5:07 PM
SD
SD SD SD
SD
X X
X
X
X
X
X
X
X
X
X
NORTH RAIN GARDEN
REQUIRED VOLUME: 1,611 CU. FT.
MINIMUM FLAT AREA: 1193 SF
PROVIDED VOLUME: 1,621 CU. FT.
PROVIDED FLAT AREA: 1,236 SF
TREATMENT AREA: 59,666 SF
SOUTH RAIN GARDEN
REQUIRED VOLUME: 627 CU. FT.
MINIMUM FLAT AREA: 344 SF
PROVIDED VOLUME: 1,252 CU. FT.
PROVIDED FLAT AREA: 892 SF
TREATMENT AREA: 17,166 SF
EAST PARK DISTRICT
MAINTENANCE FACILITY
SHEET NO:
P:\1748-002\DWG\DRNG\1748-002_LID.DWG
301 N. Howes Street, Suite 100
Fort Collins, Colorado 80521
E NGINEER ING
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
DRAWING REFERENCE:
LID TREATMENT EXHIBIT A. Reese
1 in = 80 ft
September 23, 2020 LID-1
DRAWN BY:
SCALE:
ISSUED:
( IN FEET )
0
1 INCH = 80 FEET
80 80
LEGEND
UNTREATED AREA
PERMEABLE PAVER AREA
PAVER TREATMENT AREA
East Park District Maintenance On-Site LID
Treatment
Project Summary
Total Impervious Area 79,864 sf
Target Treatment Percentage 75%
Minimum Area to be Treated by LID measures 59,898.00 sf
Rain Garden
Rain Garden Treatment Area 76,832 sf
Total Treatment Area 76,832 sf
Percent Total Project Area Treated 96.2%
MAP POCKET
DRAINAGE EXHIBITS
ENVIRONMENTAL DRIVE
UD
UD
UD
UD
UD
UD
E
E
E E
X X
SD
SD SD SD
SD
SD SD SD
SD
SD SD SD
SD
SD SD
SD
SD
/
/ / / / / / /
/ / / / / / / /
X X X X
X
X
X
X X
X
X
X
X
X
X X
X
X
X
X
X
X
X
X
X X
X
X X X X X X X X X
X
X
X
X X
X
X
X
X
X
X
X X X
X
X
X
X X
X
X X X X X
X X X X X
X
X
X
X
X
X
TF
EM
60' ROW
100' ROW
GREAT WESTERN
RAIL ROAD
EXISTING
DETENTION
POND 215
DETENTION POND:
DETENTION VOLUME = 0.53 AC-FT
WQCV. VOLUME = 0.07 AC-FT
TOTAL VOLUME REQUIRED = 0.60 AC-FT
MAXIMUM RELEASE RATE, 2-Yr. HISTORIC = 1.64 CFS.
GREAT WESTERN RAILROAD
OWNER
SIDE HILL RESIDENTIAL
ASSOCIATION
OWNER
AGGEREGATE
INDUSTRIES-WCR INC
OS2
OS2
0.11 ac
4
0.09 ac
1
1.78 ac
OS1
0.09 ac
2
1
OS1
FFE=88.00
NYLOPLAST
INLET BASIN
NYLOPLAST
INLET BASIN
NYLOPLAST
INLET BASIN
NYLOPLAST
INLET BASIN
CONCRETE
WEIR
CONCRETE
WEIR
2
1.54 ac
PROPOSED
AREA DRAIN
SOUTH RAIN GARDEN
EXISTING 36"x96"
STORM DRAIN
CONNECT
TO EXISTING STORM
PROPOSED
OUTLET
STRUCTURE
PROPOSED
CONCRETE PAN
PROPOSED POND
OUTLET
PROPOSED
CURB OPENING
NORTH RAIN GARDEN
3
0.20 ac
DRAINAGE
EASEMENT
PROPOSED
AREA DRAIN
PROPOSED
AREA DRAIN
EXISTING WETLAND
BOUNDARY
APPROXIMATE TOP
OF DITCH BANK
10' PROPOSED
DRAINAGE EASEMENT
10' PROPOSED
DRAINAGE EASEMENT
3
4
PROPERTY
BOUNDARY
SLOPE PROTECTION
(SCOUR-STOP)
SLOPE PROTECTION
(SCOUR-STOP)
Sheet
EAST PARK DISTRICT MAINTENANCE FACILITY These drawings are
instruments of service
provided by Northern
Engineering Services, Inc.
and are not to be used for
any type of construction
unless signed and sealed by
a Professional Engineer in
the employ of Northern
Engineering Services, Inc.
NOT FOR CONSTRUCTION
REVIEW SET
E NGINEER ING
N O R T H E RN
FORT COLLINS: 301 North Howes Street, Suite 100, 80521
GREELEY: 820 8th Street, 80631
970.221.4158
northernengineering.com
of 11
DR1
PRELIMINARY DRAINAGE EXHIBIT
11
NORTH
( IN FEET )
1 inch = ft.
30 0 30 Feet
30
60 90
NOTES:
1. REFER TO THE PRELIMINARY DRAINAGE REPORT FOR EAST PARK DISTRICT
MAINTENANCE FACILITY, DATED NOVEMBER 4TH, 2020 FOR ADDITIONAL
INFORMATION.
2. THIS PROPERTY IS LOCATED IN THE FEMA_REGULATED, 500_YEAR POUDRE RIVER
FLOODPLAIN. ANY DEVELOPMENT WITHIN THE FLOODPLAIN MUST COMPLY WITH
THE SAFETY REGULATIONS OF CHAPTER 10 OF CITY MUNICIPAL CODE.
3. ESSENTIAL SERVICES CRITICAL FACILITIES AND AT_RISK POPULATION CRITICAL
FACILITIES ARE PROHIBITED IN THE 500_YEAR FLOODPLAIN.
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100
2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
Historic
Basins:
H1 H1 0.99 0.25 0.31 5.0 13.1 0.70 2.14
H2 H2 2.61 0.25 0.31 24.7 23.0 0.94 4.25
Developed
Basins:
1 1 1.78 0.74 0.92 5.0 5.0 3.73 16.30
2 2 1.54 0.47 0.58 5.0 5.0 2.05 8.94
3 3 0.20 0.25 0.31 5.0 5.0 0.14 0.61
4 4 0.09 0.28 0.35 5.0 5.0 0.07 0.31
OS1 OS1 0.09 0.62 0.78 5.0 5.0 0.16 0.72
OS2 OS2 0.11 0.44 0.55 5.0 5.0 0.14 0.63
LEGEND:
PROPOSED CONTOUR
PROPOSED STORM SEWER
PROPOSED SWALE
EXISTING CONTOUR
PROPOSED CURB & GUTTER
PROPERTY BOUNDARY
PROPOSED INLET
DESIGN POINT A
FLOW ARROW
DRAINAGE BASIN LABEL
DRAINAGE BASIN BOUNDARY
PROPOSED SWALE SECTION
1 1
B2
1.45 ac
BASIN
DESIGNATION
BASIN
AREA (AC)
CALL 2 BUSINESS DAYS IN ADVANCE BEFORE YOU
DIG, GRADE, OR EXCAVATE FOR THE MARKING OF
UNDERGROUND MEMBER UTILITIES.
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
P:\1748-002\Dwg\Drng\1748-002_LID.dwg, 9/23/2020 9:37:13 AM, 1:1
Project Location : Fort Collins, CO.
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Historic Basins:
H1 H1 No 0.25 0.25 0.31 89 1.45% 1.2 13.2 12.3 132 2.00% 2.83 0.8 0 0.00% N/A N/A 5 14 13
H2 H2 No 0.25 0.25 0.31 270 1.65% 22.1 22.1 20.5 304 1.00% 2.00 2.5 0 0.00% N/A N/A 25 25 23
Developed Basins:
1 1 No 0.95 0.95 1.00 26 5.57% 0.8 0.8 0.5 403 0.91% 1.91 3.5 0 0.00% N/A N/A 5 5 5
2 2 No 0.95 0.95 1.00 14 8.03% 0.5 0.5 0.3 192 1.55% 2.49 1.3 0 0.00% N/A N/A 5 5 5
3 3 No 0.25 0.25 0.31 25 6.04% 4.3 4.3 4.0 28 4.85% 4.40 0.1 0 0.00% N/A N/A 5 5 5
4 4 No 0.25 0.25 0.31 10 2.00% 4.0 4.0 3.7 10 2.00% 2.83 0.1 0 0.00% N/A N/A 5 5 5
OS1 OS1 No 0.25 0.25 0.31 10 2.00% 4.0 4.0 3.7 10 2.00% 2.83 0.1 0 0.00% N/A N/A 5 5 5
OS2 OS2 No 0.25 0.25 0.31 10 2.00% 4.0 4.0 3.7 10 2.00% 2.83 0.1 0 0.00% N/A N/A 5 5 5
TIME OF CONCENTRATION COMPUTATIONS
Gutter Flow Swale Flow
Design
Point
Basin
Overland Flow
COG
November 3, 2020
Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
C Cf L
Ti
= −
COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
Runoff Coefficients are taken from the City of Fort Collins Storm Drainage Design Criteria and Construction Standards, Table 3-3. % Impervious taken from UDFCD USDCM, Volume I.
10-year Cf = 1.00
November 3, 2020