HomeMy WebLinkAboutEAST PARK DISTRICT MAINTENANCE FACILITY - MJA200003 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTSeptember 23, 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 absolutely necessary, we recommend double-sided printing.
September 23, 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 submittal for the proposed East
Park District Maintenance Facility development.
This report has been prepared in accordance to 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 Garcia 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 ....................................................................................................................... 5
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 ......................................................................................... 6
A. General Concept ............................................................................................................................... 6
B. Specific Details .................................................................................................................................. 6
V. CONCLUSIONS ............................................................................................................. 7
A. Compliance with Standards .............................................................................................................. 7
VI. REFERENCES ............................................................................................................... 8
EROSION CONTROL REPORT ............................................................................................ 15
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Detention Pond Computation
APPENDIX C – Erosion Control Report
LIST OF FIGURES:
Figure 1 – Aerial Photograph ................................................................................................ 2
Figure 2– Proposed Site Plan ................................................................................................ 3
Figure 3 – Existing Floodplains ............................................................................................. 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 Dr. 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 direction, 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 & 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 1/3rd 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 life-safety or emergency response critical facilities are proposed.
It should be noted that the Cache La Poudre River is in the midst of a remapping
process that may affect this property. Discussions with City staff have indicated that the
existing elevations on the project site would place the project within the updated 100-yr
floodplain. To ensure that the project site remains out of the updated floodplain, the
building has been elevated above the anticipated base flood elevation.
East Park District Maintenance Facility
Preliminary Drainage Report 4
Figure 3 –Area Floodplain Mapping
2. While the area refenced above does fall outside of the current100-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 land owners 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 Emergency Action Plan, on the levee system(s) providing protection for 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 the Bucking Horse Subdivision Filing
Two, which is located in the foothills Drainage Basin. All of Bucking Horse Filing Two
was intended to be conveyed into existing Detention Pond 215, which is located due
west of the subject property. This Pond was designed and approved with Bucking Horse
Filing 1. According to the updated Foothills Master Drainage Plan by Anderson
Consulting Engineers, (ACE) dated July 15, 1999, Onsite detention for Basin 57 was
limited to the 100-year developed discharge of 85 CFS. In Bucking horse filing two the
release rate was revised and reduced to 83 CFS. Therefore, the release rate 1.19 CFS
from the site will not increase from the original allowable discharge by ACE. (please
refer to Section B.-Specific Details down below)
East Park District Maintenance Facility
Preliminary Drainage Report 5
B. Sub-Basin Description
1. The subject property historically drains overland from west to northeast, southeast &
South. In this preliminary submittal a detention pond is proposed on the southeast side
of the property. Because of the grade differential between the detention pond 215 water
surface elevation and existing site topography, we believe is not practical for this site to
drain to detention pond 215, without a considerable fill volume. 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 2-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 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 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
1. No modifications are requested at this time.
East Park District Maintenance Facility
Preliminary Drainage Report 6
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. The site has been broken into 4 onsite sub-basins for preliminary design purposes.
Anticipated drainage patterns for proposed drainage basins are described below.
Basin 1
Basins 1 consist of asphalt and landscape areas. This basin will generally drain via
overland flow to a concrete pan and into LID features which are discussed below and
will then drain via internal storm piping systems generally southeast into the proposed
detention pond on the southeast corner of the project. The proposed detention pond will
release to an Existing Storm designed with Bucking Horse Filing 1 located along the
north east boundary of the property.
Basin 2
Basin 2 consists primarily of open space and concrete walks areas. This basin will
generally drain via overland flow to Environmental Dr. and will then drain via curb and
gutter to existing drainage facilities to the south.
Basins OS1 and OS2
Basins OS1 and OS4, as shown on the Drainage Exhibit, consist of portions 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. According to Final Drainage Report Bucking Horse Filing One, Dated September 19,
2012 by Norther Engineering. the design SWMM for the overall subdivision was
updated. Pond 3 was added to the model, and the basin parameters and conveyance
routing were updated to reflect the new design proposed with Bucking Horse Filing One.
2. The new watershed area to be treated in Pond 215 was roughly 178.1 acres with an
approximate imperviousness of 46%. The resultant WQCV for a 40-hour dry EDB was
3.48 ac-ft. According to survey information provided by Washburn Land Surveying,
Pond 215 achieved a volume of 3.48 ac-ft at an elevation of approximately 4882.11-ft.
The original design called for a WQCV of 3.34 ac-ft at an elevation of 4882.23-ft.
Therefore, the existing outlet works should remain sufficient at 28.3 Cfs . Likewise, the
new total required volume of 33.1 ac-ft (29.6 ac-ft detention storage plus 3.5 ac-ft
WQCV) occurs at an elevation of approximately 4885.31-ft, and required no
modification of the existing top of pond or spillway
3. According to Final Drainage Report Bucking Horse Filing Two, Dated December 17,
2012 by Norther Engineering. The second major revision to the SWMM model comes
with the Bucking Horse First and Filing Two developments. Basin areas and percent
imperviousness have been updated to be consistent with the development plan(s)
currently proposed. This includes the addition of Basin 100 and Pond 3 to correctly
East Park District Maintenance Facility
Preliminary Drainage Report 7
model the development now proposed on the Jessup Farm parcel. However, the water
quality requirements for Basin 100 have now been shifted from Pond 3 to Pond 215.
4. The WQCV (i.e., 3.34 ac-ft to 3.48 ac-ft) resulted in no change to the WSEL. Therefore,
the existing outlet structure will not need to be adjusted. Combined with the necessary
detention storage volume of 28.8 ac-ft, the total new required volume in Pond 215 is
roughly 32.3 ac-ft. With 32.4 ac-ft of volume currently provided at an elevation of
4885.25-ft, the existing pond is sufficient and has a new peak discharge from Pond
215 of 83.0 cfs. Less than the 85 cfs. defined in the (ACE).
5. 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.
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 Norther
Engineering.
8. Final Drainage Report Bucking Horse Filing Two, Dated December 17, 2012 by Norther
Engineering
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 41413 0.95 0.00 0.00 0.00 0.00 0.95 0.25 0.25 0.31 2.0%
H2 100904 2.32 0.00 0.00 0.00 0.00 2.32 0.25 0.25 0.31 2.0%
Developed Basins:
d1 142317 3.27 0.29 1.13 0.15 0.22 1.48 0.60 0.60 0.75 51.2%
d2 14563 0.33 0.01 0.04 0.00 0.00 0.29 0.35 0.35 0.44 15.9%
OS1 3616 0.08 0.00 0.04 0.00 0.00 0.04 0.63 0.63 0.79 55.0%
OS2 5427 0.12 0.00 0.04 0.00 0.00 0.09 0.45 0.45 0.57 30.4%
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.
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 0.95 21 21 20 0.25 0.25 0.31 1.56 2.67 5.68 0.37 0.63 1.69 0.19
H2 H2 2.32 26 26 24 0.25 0.25 0.31 1.42 2.42 5.09 0.82 1.40 3.68 0.41
Developed Basins:
d1 d1 3.27 8 8 7 0.60 0.60 0.75 2.46 4.21 8.80 4.85 8.29 21.70 2.43
d2 d2 0.33 5 5 5 0.35 0.35 0.44 2.85 4.87 9.95 0.33 0.57 1.45 0.17
OS1 OS1 0.08 5 5 5 0.63 0.63 0.79 2.85 4.87 9.95 0.15 0.25 0.65 0.07
OS2 OS2 0.12 5 5 5 0.45 0.45 0.57 2.85 4.87 9.95 0.16 0.27 0.70 0.08
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
September 17, 2020
Intensity,
i10
(in/hr)
Rainfall Intensity taken from the City of Fort Collins Storm Drainage Design Criteria (CFCSDDC), Figure 3.1
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
WQ Flow
(cfs)
Q = C f ( C )( i )( A )
APPENDIX B
WATER Detention Pond Computation
COG
Pond No : South
d1
100-yr
0.75
Area (A)= 3.27 acres 23923 ft
3
Max Release Rate = 1.19 cfs 0.55 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 24.40 7321 357.0 6963.7
10 600 7.720 18.93 11360 714.0 10646.0
15 900 6.520 15.99 14391 1071.0 13320.3
20 1200 5.600 13.73 16481 1428.0 15052.8
25 1500 4.980 12.21 18320 1785.0 16535.2
30 1800 4.520 11.09 19954 2142.0 17811.5
35 2100 4.080 10.01 21013 2499.0 18514.0
40 2400 3.740 9.17 22014 2856.0 19157.6
45 2700 3.460 8.49 22911 3213.0 19698.3
50 3000 3.230 7.92 23765 3570.0 20194.7
55 3300 3.030 7.43 24523 3927.0 20595.5
60 3600 2.860 7.01 25251 4284.0 20966.9
65 3900 2.720 6.67 26016 4641.0 21375.1
70 4200 2.590 6.35 26678 4998.0 21680.3
75 4500 2.480 6.08 27370 5355.0 22014.9
80 4800 2.380 5.84 28017 5712.0 22305.4
85 5100 2.290 5.62 28643 6069.0 22573.7
90 5400 2.210 5.42 29268 6426.0 22842.1
95 5700 2.130 5.22 29776 6783.0 22992.8
100 6000 2.060 5.05 30313 7140.0 23172.9
105 6300 2.000 4.91 30902 7497.0 23404.5
110 6600 1.940 4.76 31402 7854.0 23547.8
115 6900 1.890 4.64 31983 8211.0 23772.1
120 7200 1.840 4.51 32491 8568.0 23922.7
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
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 = 3.270 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 51.20 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.51 <-- CALCULATED
WQCV (watershed inches) = 0.210 <-- CALCULATED from USDCM Vol.3, Figure 3-2
WQCV (ac-ft) = 0.069 <-- CALCULATED from USDCM Vol.3, EQ 3-3
WQ Depth (ft) = 3.000 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in2) = 0.195 <-- 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 = 77.8 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.778
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.25 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 76,686 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 1,611 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 = 5.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 1193 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
September 23, 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_North-RG_UD-BMP_v3.06.xlsm, RG 9/23/2020, 9:24 AM
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
September 23, 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_North-RG_UD-BMP_v3.06.xlsm, RG 9/23/2020, 9:24 AM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 24.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.240
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.10 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 71,612 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 627 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 = 344 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
September 23, 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_South-RG_UD-BMP_v3.06.xlsm, RG 9/23/2020, 9:26 AM
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
September 23, 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_South-RG_UD-BMP_v3.06.xlsm, RG 9/23/2020, 9:26 AM
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 AVENUE
UD
UD
UD UD UD
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
60' ROW
100' ROW
GREAT WESTERN
RAIL ROAD
PROPOSED
AREA DRAIN
SOUTH RAIN GARDEN
EXISTING 36"x96"
STORM DRAIN
CONNECT
TO EXISTING STORM
PROPOSED
OUTLET
STRUCTURE
EXISTING
DETENTION
POND 215
15' EASEMENT
PROPOSED
CONCRETE PAN
20' UTILITY
EASEMENT
10' WATER LINE
EASEMENT
15' SANITARY SEWER
EASEMENT
PROPOSED POND
OUTLET
PROPOSED
CURB OPENING
DETENTION POND:
DETENTION VOLUME = 0.55 AC-FT
WQCV. VOLUME = 0.07 AC-FT
TOTAL VOLUME REQUIRED = 0.62 AC-FT
MAXIMUM RELEASE RATE, 2-Yr. HISTORIC = 1.19 CFS.
GREAT WESTERN RAILROAD
OWNER
SIDE HILL RESIDENTIAL
ASSOCIATION
OWNER
AGGEREGATE
INDUSTRIES-WCR INC
NORTH RAIN GARDEN
OS2b
OS2
0.12 ac
2
0.33 ac
1
3.27 ac
OS1
0.08 ac
d2
d1
OS1a
FFE=88.00
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
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)
NOTES:
1. REFER TO THE PRELIMINARY DRAINAGE REPORT FOR EAST PARK DISTRICT
MAINTENANCE FACILITY, DATED SEPTEMBER 21, 2020 FOR ADDITIONAL
INFORMATION.
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 0.95 0.25 0.31 21.4 19.9 0.37 1.69
H2 H2 2.32 0.25 0.31 25.7 24.1 0.82 3.68
Developed Basins:
d1 d1 3.27 0.60 0.75 7.8 7.1 4.85 21.70
d2 d2 0.33 0.35 0.44 5.0 5.0 0.33 1.45
OS1 OS1 0.08 0.63 0.79 5.0 5.0 0.15 0.65
OS2 OS2 0.12 0.45 0.57 5.0 5.0 0.16 0.70
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_DRNG.dwg, 9/23/2020 9:58:27 AM, 1:1
P:\1748-002\Dwg\Drng\1748-002_LID.dwg, 9/23/2020 9:37:13 AM, 1:1
Date : September 17, 2020
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 0.31 218 1.45% 20.7 20.7 19.2 60 0.50% 1.41 0.7 0 0.00% N/A N/A 21 21 20
H2 H2 No 0.25 0.25 0.31 270 1.65% 22.1 22.1 20.5 304 0.50% 1.41 3.6 0 0.00% N/A N/A 26 26 24
Developed Basins:
d1 d1 No 0.95 0.95 1.00 100 2.00% 2.2 2.2 1.5 474 0.50% 1.41 5.6 0 0.00% N/A N/A 8 8 7
d2 d2 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
September 17, 2020
Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
C Cf L
Ti
= −
10-year Cf = 1.00
September 17, 2020