HomeMy WebLinkAboutLANDMARK APARTMENTS EXPANSION - FDP190002 - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE REPORTFINAL DRAINAGE AND
EROSION CONTROL REPORT
May 3, 2019
Landmark Apartments Expansion
Fort Collins, Colorado
Prepared for:
Redwood Construction, Inc.
2082 Michelson Drive, 4th Floor
Irvine, CA 92612
(949) 299-0875
Prepared by:
301 N. Howes Street, Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158
www.northernengineering.com
Project Number: 1257-001
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.
301 N. Howes Street, Suite 100, Fort Collins, CO 80521 970.221.4158 www.northernengineering.com
May 3, 2019
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Final Drainage and Erosion Control Report for
Landmark Apartments Expansion
Dear Staff:
Northern Engineering is pleased to submit this Final Drainage and Erosion Control Report for your
review. This report accompanies Project Development Plan submittal for the proposed Landmark
Apartments Expansion 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.
Danny Weber, PE
Project Engineer
Landmark Apartments Expansion
Final Drainage Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ................................................................... 1
A. Location ............................................................................................................................................. 1
B. Description of Property ..................................................................................................................... 2
C. Floodplain.......................................................................................................................................... 4
II. DRAINAGE BASINS AND SUB-BASINS ....................................................................... 5
A. Major Basin Description .................................................................................................................... 5
B. Sub-Basin Description ....................................................................................................................... 5
III. DRAINAGE DESIGN CRITERIA ................................................................................... 5
A. Regulations........................................................................................................................................ 5
B. Four Step Process .............................................................................................................................. 5
C. Development Criteria Reference and Constraints ............................................................................ 6
D. Hydrological Criteria ......................................................................................................................... 6
E. Hydraulic Criteria .............................................................................................................................. 7
F. Floodplain Regulations Compliance .................................................................................................. 7
G. Modifications of Criteria ................................................................................................................... 7
IV. DRAINAGE FACILITY DESIGN .................................................................................... 8
A. General Concept ............................................................................................................................... 8
B. Conformance with Water Quality Treatment ................................................................................... 9
C. Conformance with Low Impact Development (LID) .......................................................................... 9
D. Specific Details .................................................................................................................................. 9
V. CONCLUSIONS ...................................................................................................... 10
A. Compliance with Standards ............................................................................................................ 10
B. Drainage Concept ............................................................................................................................ 10
References ....................................................................................................................... 11
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations
B.1 – Storm Sewers
B.2 – Inlets
B.3 – Swales and Weirs
APPENDIX C – SWMM Modeling
APPENDIX D – Erosion Control Report
APPENDIX E – FEMA Firmette
APPENDIX F – LID Exhibit and Calculations
Landmark Apartments Expansion
Final Drainage Report
LIST OF TABLES AND FIGURES:
Figure 1 – Aerial Photograph ................................................................................................ 2
Figure 2 – Proposed Site Plan ............................................................................................... 3
Figure 3 – Existing Floodplains ............................................................................................. 4
MAP POCKET:
DR1 - Drainage Exhibit
Landmark Apartments Expansion
Final Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. The Landmark Apartments Expansion is located in the northwest quarter of Section
23, Township 7 North, Range 69 West of the 6th Prime Meridian, City of Fort Collins,
County of Larimer, State of Colorado. The site includes Lots 1, 2, 3, 4 and Tracts A,
D, E, and F of Young’s Creek Subdivision. The site is replatted as Lots 1 and 2,
Landmark Apartments.
3. The project site is bordered to the north by Prospect Road, to the west by the existing
Landmark Apartments development, to the south by vacant land, and to the east by a
single-family development.
4. Offsite flows from the existing single-family development are expected but should be
relatively small due to the low imperviousness. Off-site flows will be passed through
the site undetained as they are currently.
5. This site was originally platted as Young’s Creek.
Landmark Apartments Expansion
Final Drainage Report 2
B. Description of Property
1. The platted site is approximately 3.00 acres. This area does not include the City-
owned tract that currently encompasses the major drainage channel.
Figure 1 – Aerial Photograph
2. The existing site is comprised of vacant land with natural grasses and vegetation. The
Canal Importation Channel bisects the site from the western boundary to the south
boundary of the site.
3. The majority of the site slopes to the south, while a portion of the site, south of the
channel, slopes to the north.
4. A report by Soilogic, Inc. dated February 24, 2016 lists the soils for the area as
consisting of lean clay with varying amounts of silt and sand. These soils are classified
as Hydrologic Soil Group C and have a low infiltration rate.
5. The proposed project site plan is composed of 5 multi-family residential buildings. This
site will employ water quality features and runoff reduction facilities including rain
gardens.
Landmark Apartments Expansion
Final Drainage Report 3
Figure 2 – Proposed Site Plan
6. No existing irrigation facilities are known at this time.
7. The proposed project is not requesting a change in the land use.
Landmark Apartments Expansion
Final Drainage Report 4
C. Floodplain
1. The subject property is bisected by both a FEMA and City regulatory floodplain.
Development within the floodplain will be limited and subject to regulations set forth
by the City of Fort Collins City Code Chapter 10 and FEMA.
2. The FEMA floodplain associated with this site is shown in FEMA Map Number
08069C0979H. See appendix for FEMA firmette.
3. The City of Fort Collins floodplain per the ‘Canal Importation Basin Master Drainage
Plan Hydraulic Evaluation and Mapping Update’ by Anderson Consulting Engineers,
Inc, dated July 22, 2014 is more dominant over the site. As such, all grading and
finished floor elevations are in relation to the City of Fort Collins floodplain and base
flood elevations.
Figure 3 – Existing Floodplains
4. This site is not subject to City of Fort Collins published erosion buffers.
5. Multi-family apartments are proposed as slab on grade. No residential structures are
proposed in the floodway or flood-fringe. Although these structures will be subject to
additional requirements. Specifically, all duct work, heating, ventilation and air
conditioning systems, hot water heater, electrical, and the lowest floor of the building
are a minimum of 18 inches above the Base Flood Elevation (BFE). That minimum is
known as the regulatory flood protection elevation (RFPE).
6. Non-residential structures can be flood proofed instead of elevated to the regulatory
flood protection elevation.
Landmark Apartments Expansion
Final Drainage Report 5
7. No garages are proposed with this site.
8. Any and all construction activities in the floodway or flood fringe must be preceded by
an approved Floodplain Use Permit. If the construction is in the floodway, a no-rise
certification must be approved prior to construction. Specifically, a floodplain use
permit will be required for the trail connections, associated grading, bridge and
abutments, and storm sewer outfalls. The Turf Reinforcement Mats (TRMs) will
require a No-Rise Certification if construction of improvements disturbs the floodway.
9. A bridge is planned over the drainage channel and floodway. This bridge deck will be
elevated >12-inches above the base flood elevation. Abutments will be placed
outside of the floodway.
10. If a structure requiring a Certificate of Occupancy is proposed in the floodplain, a
FEMA elevation or floodproofing certificate will be completed and approved before the
Certificate of Occupancy is issued. No structures requiring a Certificate of Occupancy
are proposed in the floodplain.
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The Landmark Apartments Expansion project is located within the Canal Importation
Basin, which is located south of Laporte Avenue, north of Drake Road, west of Shields
Street, and East of the foothills.
B. Sub-Basin Description
1. Historically, the northern portion of the site drains south to the Canal Importation
Channel and the southern portion of the site drains north to the Canal Importation
Channel.
2. The Canal Importation Channel runs south and connects with Spring Creek.
3. Due to proximity to the Canal Importation Channel and location within the Canal
Importation Drainage Basin, no stormwater detention is proposed on this site. The
flow volumes and times of concentration for on-site basins are very small compared to
the regional flow through the Canal Importation Channel. The peak runoff from this
site will be conveyed through the channel prior to the peak flows from the major basin
upstream of the site. This detention waiver is discussed later in this report.
III. DRAINAGE DESIGN CRITERIA
A. Regulations
There are no optional provisions outside of the FCSCM proposed with the Landmark
Apartments Expansion. See Modifications of Criteria for detention waiver in accordance
with FCSCM.
B. Four Step Process
The overall stormwater management strategy employed with Landmark Apartments
Expansion project utilizes the “Four Step Process” to minimize adverse impacts of
urbanization on receiving waters. The following is a description of how the proposed
development has incorporated each step.
Landmark Apartments Expansion
Final Drainage Report 6
Step 1 – Employ Runoff Reduction Practices
Several techniques have been utilized with the proposed development to facilitate the
reduction of runoff peaks, volumes, and pollutant loads as the site is developed from the
current use by implementing multiple Low Impact Development (LID) strategies including:
Providing rain gardens throughout the site to reduce the overall impervious area and to
minimize directly connected impervious areas (MDCIA).
Utilizing large vegetated open areas throughout the site to reduce the overall
impervious area and to minimize directly connected impervious area (MDCIA).
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with
Slow Release
The efforts taken in Step 1 will facilitate the reduction of runoff. Additionally, the majority
of stormwater runoff from the site will ultimately be intercepted and treated in rain gardens
prior to release to the drainage channel.
Step 3 – Stabilize Drainageways
Buried ScourStop® pads will be installed at the stormwater outfalls into the Canal
Importation Channel. These pads will fortify the outfall and reduce any erosion within the
channel. Additional buried pads will be provided on-site at locations where steep grades
within swales could produce erosion.
Step 4 – Implement Site Specific and Other Source Control BMPs.
The proposed project will improve upon site specific source controls compared to historic
conditions:
Localized trash enclosures within the development will allow for the disposal of solid
waste.
Rain gardens and vegetated open areas for water treatment prior to flows entering the
drainage channel.
Channeling runoff from parking lots through rain gardens for water quality treatment.
C. Development Criteria Reference and Constraints
1. No previous studies were utilized with this project.
2. Low-Impact Development and water quality facilities make up the majority of this
drainage concept and report.
3. This project will be subject to the design guidelines as set forth by the Fort Collins
Stormwater Criteria Manual (FCSCM) and the Urban Drainage and Flood Control
District Criteria Manual.
D. 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 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. The Rational Formula-based Federal Aviation Administration (FAA) procedure has not
been utilized for detention storage calculations since detention is not required for the
project.
Landmark Apartments Expansion
Final Drainage Report 7
4. EPA Stormwater Management Model (SWMM) modeling was employed to model peak
flow in the channel pre- and post-development of this site.
5. Three 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. The third storm computed, for comparison
purposes only, is the 10-year event.
6. No other assumptions or calculation methods have been used with this development
that are not referenced by current City of Fort Collins criteria.
E. Hydraulic Criteria
1. The northern portion of the site drains south to the Canal Importation Channel. The
southern portion of the site drains north to the Canal Importation Channel.
2. All drainage facilities proposed with Landmark Apartments Expansion project are
designed in accordance with criteria outlined in the FCSCM and/or the Urban
Drainage and Flood Control District’s (UDFCD) Urban Storm Drainage Criteria
Manual.
3. As stated previously, the subject property is bisected by both a FEMA and City
regulatory floodplain. Development within the floodplain will be limited and subject
to regulations set forth by the City and FEMA.
F. Floodplain Regulations Compliance
4. As stated previously, the subject property is bisected by both a FEMA and City
regulatory floodplain. Any and all construction activities in the floodway or flood
fringe must be preceded by an approved Floodplain Use Permit. If the construction is
in the floodway a no-rise certification must be approved prior to construction.
5. The vast majority of the project is located outside of the floodplain and will not be
subject to any floodplain regulations. However, consideration has been given to the
floodplain elevations as they relate the to the proposed building and the finished floors
have been elevated >18-inches above Base Flood Elevation (BFE) as if it were
subject to the same criteria of being within the floodplain.
6. The Landmark Apartments Expansion project proposes to slightly modify the Canal
Importation Channel within the floodway limits. This will be limited to cutting only (no
filling) to allow for Turf Reinforcement Mats at storm outfalls. A no-rise certification
will be required for this activity.
7. Rain gardens used for on-site water quality treatment were elevated to protect from
contamination during the peak flow through the floodplain.
8. A pedestrian bridge is proposed across the FEMA and City floodplain. The low steel
of the bridge deck is elevated >12-inches above BFE. See Landmark Apartments
Expansion Utility Plans for more information.
G. Modifications of Criteria
1. This project pursues the Fort Collins Stormwater Criteria Manual Chapter 6, Section
2.5 - Alternative to Quantity Detention (“Beat the Peak”) provision due to the site’s
adjacency to the Canal Importation Channel. Pre- and post-development hydraulic
SWMM model results are provided in Appendix C of this report that demonstrates no
significant increase in peak flow through the Canal Importation Channel without on-
Landmark Apartments Expansion
Final Drainage Report 8
site detention. This approach has been supported by City Staff and approved during
the Preliminary Design process.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of the Landmark Apartments Expansion drainage design are to
provide water quality for stormwater runoff and safely convey stormwater runoff to the
Canal.
2. A list of tables and figures used within this report can be found in the Table of
Contents at the front of the document. The tables and figures are located within the
sections to which the content best applies.
3. The Landmark Apartments Expansion project is divided into three (4) major drainage
basins, designated as Basins A, B, UD and OS. Basin A is on-site and located north
of the canal. Basin B is on-site and located south of the canal. Basins designated
UD are on-site and off-site basins that flow directly to the canal. Basins designated
OS are existing off-site basins that are considered in this report.
Basin A
Basin A consists of proposed multi-family apartments, sidewalk, landscaped areas,
pavers and parking. Runoff from roofs will be conveyed through curb cuts and swales
to rain gardens. Sidewalk chases, curb cuts, and swales are the main mode of water
conveyance around the site. Basins A1-A6 are treated by 3 on-site rain gardens. The
rain gardens are sized for water quality utilizing the Urban Drainage BMP
spreadsheets.
Runoff produced during a 100-year event will be captured by inlets and conveyed to
the canal by storm sewer.
Basin B
Basin B consists of proposed multi-family apartments, sidewalk, landscaped areas and
parking. Runoff is captured by a curb cut and storm sewer and conveyed to the rain
garden. The rain garden in Basin B is sized for water quality utilizing the Urban
Drainage BMP Spreadsheet.
Runoff produced during a 100-year event will be captured by inlets and conveyed to
the canal by storm sewer.
Basin UD
Basin UD consists of proposed concrete trail, and landscaped areas. Runoff during
both 2-year and 100-year events will flow directly to the canal over landscaped areas.
The concrete trail adjacent the drainage canal is the only impervious area in the UD
basin. Due to the proximity to the canal, this off-site trail was unable to be captured
for additional water quality treatment, however, the trail is expected to cause very little
concern in regard to water quality.
Basin OS
OS basins consist primarily of off-site parking, sidewalks, single family lots and
existing multifamily development. Since these basins flow through or near the site,
they will be considered in this report.
Landmark Apartments Expansion
Final Drainage Report 9
Runoff from Basins OS1 and OS2 will be passed through Basin A safely to the canal
without detention as they currently do. The rain gardens were sized to include water
quality for these offsite basins.
Runoff from Basins OS3 and OS4 will be collected by a crosspan at the edge of the
proposed development. This crosspan will direct flows to a curb cut that empties into
the canal.
Basins OS5, OS6, OS7, and OS8 consist of streets, parking, buildings, and
landscaped areas. Runoff from these off-site basins will route to the east end of
Hobbit St and be conveyed by a low-slope grass swale as it currently does prior to
discharging into the canal.
A full-size copy of the Drainage Plan can be found in the Map Pocket at the end of this
report.
B. Conformance with Water Quality Treatment
1. City Stormwater Criteria requires that 100% of on-site runoff must receive some form
of water quality treatment. This project proposes water quality treatment using 4
bioretention cells (aka Rain Gardens) located throughout the site. These rain gardens
are also considered a LID treatment method. Due to the physical constraints
associated with an infill project of this nature, some small areas along the perimeter
of the site cannot be captured. In lieu of these areas, this project will treat off-site
basins that route through the site and size the rain gardens appropriately. In total,
the project is treating 107% of the site’s impervious area for water quality.
C. Conformance with Low Impact Development (LID)
1. The Landmark Apartments Expansion will conform to the City’s Stormwater
requirement to treat a minimum 75% of the on-site impervious areas using a LID
technique. As previously mentioned, this site is providing water quality treatment of
off-site basins. These areas are also being treated for LID, which is in excess of what
is required for LID criteria. In total, the project is treating 107% of the site’s
impervious area using a LID technique. Please see the LID Exhibit located in the
Appendix F.
D. Specific Details
1. Inlets were designed utilizing either Urban Drainage spreadsheets for curb inlets or
area inlets spreadsheets. All inlets were designed to collect the 100-year flow.
2. Low Impact Development (LID) calculations and techniques are based on the Urban
Drainage spreadsheet for Best Management Practices (UD-BMP).
3. Storm sewers were modeled utilizing Hydraflow for AutoCAD. All storm lines were
designed to convey the full 100-year flow.
4. In lieu of riprap, Turf Reinforcement Mats (TRMs) were designed for the storm outfalls
as recommended by Fort Collins Stormwater Criteria.
Landmark Apartments Expansion
Final Drainage Report 10
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with the Landmark Apartments Expansion project
complies with the City of Fort Collins’ Stormwater Criteria Manual.
2. The subject property is bisected by both a FEMA and City regulatory floodplain.
Development within the floodplain will be limited and subject to regulations set forth
by the City and FEMA.
3. The drainage plan and stormwater management measures proposed with the
development are compliant with all applicable State and Federal regulations governing
stormwater discharge.
4. The site achieves the requirements set forth by the City of Fort Collins for Low Impact
Development (LID) and Water Quality.
B. Drainage Concept
1. All drainage facilities proposed with Landmark Apartments Expansion project are
designed in accordance with criteria outlined in the FCSCM and/or the Urban Drainage
and Flood Control District’s (UDFCD) Urban Storm Drainage Criteria Manual.
2. The drainage design proposed with this project will effectively limit any potential
damage or erosion associated with its stormwater runoff. All existing downstream
drainage facilities are expected to not be negatively impacted by this development.
3. The proposed development will not have any impact on the Master Drainage Plan
recommendations for the Canal Importation Basin.
4. The drainage design is anticipated to be very conservative. This report has omitted
any runoff reduction that will manifest due to infiltration from rain gardens. This is
currently unable to be calculated with available soils data.
Landmark Apartments Expansion
Final Drainage Report 11
References
1. 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.
2. Geotechnical Subsurface Exploration Report Landmark Apartments Expansion Southeast of
West Prospect Road and South Shields Street, Fort Collins, Colorado, February 24, 2016,
Soilogic, Inc. (Soilogic Project No. 16-1024).
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. Canal Importation Basin Master Drainage Plan Hydraulic Evaluation and Mapping Update,
Anderson Consulting Engineers, Inc; July 22, 2014
APPENDIX A
HYDROLOGIC COMPUTATIONS
Landmark Apartments
CHARACTER OF SURFACE1:
Runoff
Coefficient
Percentage
Impervious Project: Landmark Apartments Expansion
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: D. Weber
Asphalt ……....……………...……….....…...……………….………………………………………………………….0.95 100% . Date: 5/3/2019
Concrete …….......……………….….……….………………..….…………………………………………………….0.95 90% .
Gravel (packed) ……….…………………….….………………………….0.50 .………………………………………….40% .
Roofs …….…….………………..……………….……………………………………………………………………… 0.95 90%
Pavers…………………………...………………..……………………………………………………………………… 0.40 40%
Land Use
Existing Multi-family ……....……………...……….....…...……………….0.55 …………………………………………… 50%
Existing Single Family …….......……………….….……….……………….0.30 .….……………………………………… 30%
Lawns and Landscaping
Sandy Soil
Flat <2% ……………………………………………………………………………………………………………… 0.10 0%
Average 2% to 7% ………………………………………………………………………………………………….0.15 0% .
Steep >7% …………………………………………………………………………………………………………… 0.20 0%
Clayey Soil
Flat <2% ……………………………………………………………………………………………………………… 0.20 0%
Average 2% to 7% ………………………………………………………………………………………………….0.25 0% .
Steep >7% …………………………………………………………………………………………………………… 0.35 0% 10-year C
f = 1.00 100-year C
f = 1.25
Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Table RO-11
Sub-Basin ID
Sub-
BasinBasin
Area
(ac)
Area of
Asphalt
(ac)
Area of
Concrete
(ac)
Area of
Gravel
(ac)
Area of
Roofs
(ac)
Soil Type and Average Slope
Area of
Lawns and
Landscaping
(ac)
2-year
Composite Runoff
Coefficient
10-year
Composite Runoff
Coefficient
100-year
Composite Runoff
Coefficient
Composite
% Imperv.
Landmark Apartments Expansion
Overland Flow, Time of Concentration:
Project: Landmark Apartments Expansion
Calculations By:
Date:
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = Ti + Tt (Equation RO-2)
Velocity (Gutter Flow), V = 20·S½
Velocity (Swale Flow), V = 15·S½
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,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Landmark Apartments Expansion
Rational Method Equation: Project: Landmark Apartments Expansion
Calculations By:
Date:
Rainfall Intensity:
N North Historic Basin 2.68 22 22 21 0.25 0.25 0.31 1.53 2.61 5.46 1.02 1.75 4.56
S South Historic Basin 0.53 11 11 11 0.25 0.25 0.31 2.13 3.63 7.57 0.28 0.49 1.27
T Total Existing Site 3.21 22 22 21 0.25 0.25 0.31 1.53 2.61 5.46 1.23 2.09 5.48
A1 A1 0.55 5 5 5 0.68 0.68 0.84 2.85 4.87 9.95 1.07 1.82 4.66
A2 A2 0.25 5 5 5 0.63 0.63 0.78 2.85 4.87 9.95 0.45 0.77 1.96
A3 A3 1.04 8 8 8 0.66 0.66 0.82 2.40 4.10 8.38 1.63 2.79 7.13
A4 A4 0.31 5 5 5 0.92 0.92 1.00 2.85 4.87 9.95 0.82 1.41 3.13
A5 A5 0.23 5 5 5 0.75 0.75 0.94 2.85 4.87 9.95 0.49 0.83 2.13
A6 A6 0.10 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 0.23 0.40 1.01
N UD1 0.11 5 5 5 0.25 0.25 0.31 2.85 4.87 9.95 0.08 0.13 0.34
N North Proposed Basin 2.60 5 5 5 0.69 0.69 0.86 2.85 4.87 9.95 5.08 8.68 22.17
B1 B1 0.32 5 5 5 0.79 0.79 0.99 2.85 4.87 9.95 0.71 1.21 3.10
S UD2 0.15 8 8 8 0.48 0.48 0.60 2.40 4.10 8.59 0.18 0.30 0.79
S South Proposed Basin 0.47 5 5 5 0.69 0.69 0.86 2.85 4.87 9.95 0.92 1.57 4.02
T Total Proposed Site 3.07 5 5 5 0.69 0.69 0.86 2.85 4.87 9.95 6.00 10.25 26.18
OS1 OS1 0.46 11 11 10 0.30 0.30 0.38 2.13 3.63 7.72 0.29 0.50 1.34
OS2 OS2 1.31 12 12 11 0.35 0.35 0.44 2.05 3.50 7.42 0.94 1.60 4.23
OS3 OS3 0.29 11 11 10 0.36 0.36 0.45 2.17 3.71 7.88 0.23 0.39 1.04
OS4 OS4 4.14 20 20 19 0.57 0.57 0.72 1.63 2.78 5.84 3.86 6.59 17.28
OS5 OS5 0.24 5 5 5 0.84 0.84 1.00 2.85 4.87 9.95 0.58 0.99 2.40
OS6 OS6 1.07 10 10 10 0.71 0.71 0.89 2.21 3.78 7.88 1.68 2.87 7.48
OS7 OS7 0.28 5 5 5 0.94 0.94 1.00 2.85 4.87 9.95 0.74 1.26 2.74
OS8 OS8 0.12 7 7 6 0.31 0.31 0.39 2.60 4.44 9.31 0.10 0.17 0.45
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
PROPOSED 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)
Sub-Basin(s)
Urban Drainage and Flood Control District Volume 1, Chapter 6, January 2016
Time of Concentration: Project:
Tc = Ti + Tt (Equation 6-2) Calculations By:
Date:
Overland Flow, Time of Concentration:
(Equation 6-3, adequare for distances up to 300 ft in urban areas and 500 feet in rural areas)
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V (Equation 6-4)
First Design Point Time of Concentration in Urban Catchments (tc max):
(Equation 6-5)
Velocity (Gutter Flow), V = 20·S½
Velocity (Swale Flow), V = 15·S½
Calculated Tc
at First Design Point
Time of
Concentration
Ti
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Comp. Tc
(min)
A1 A1, A2, & OS1 (Rain 10.4 0 0.00% 0.00 N/A 0 0.00% 0.00 N/A 10.4
A3 A1-A3 & OS1-OS2 10.4 0 0.00% 0.00 N/A 310 0.80% 1.34 3.9 14.3
OS3 OS3 & A6 10.0 0 0.00% 0.00 N/A 0 0.00% 0.00 N/A 10.0
OS4 OS3, OS4, & A6 18.8 0 0.00% 0.00 N/A 0 0.00% 0.00 N/A 18.8
OS7 OS5-OS7 7.5 120 1.00% 2.00 1.0 0 0.00% 0.00 N/A 8.5
OS8 OS5-OS8 8.5 0 0.00% 0.00 N/A 215 0.50% 1.06 3.4 11.9
DEVELOPED TIME OF CONCENTRATION FOR COMBINED BASINS
Landmark Apartments Expansion
D. Weber
May 3, 2019
Design
Point
Basins
Additional Gutter / Pipe Flow Additional Swale Flow
( )
3
1
5
Rational Equation: Q = CiA Project:
Calculations By:
Date:
Rainfall Intensity:
A1 A1, A2, & OS1 1.26 10.4 0.53 0.53 0.66 2.21 3.78 7.72 1.5 2.5 6.4
A3 A1-A3 & OS1-OS2 3.61 14.3 0.50 0.50 0.62 1.92 3.29 6.71 3.5 5.9 15.1
OS3 OS3 & A6 0.40 10.0 0.47 0.47 0.59 2.26 3.86 7.88 0.4 0.7 1.8
OS4 OS3, OS4, & A6 4.48 18.8 0.57 0.57 0.71 1.68 2.86 5.84 4.3 7.3 18.5
OS7 OS5-OS7 1.59 8.5 0.77 0.77 0.96 2.40 4.10 8.38 2.9 5.0 12.8
OS8 OS5-OS8 1.71 11.9 0.74 0.74 0.92 2.09 3.57 7.29 2.6 4.5 11.5
Flow,
Q10
(cfs)
Flow,
Q100
(cfs)
C10 C100 Notes
Intensity,
i2
(in/hr)
Intensity,
i10
(in/hr)
Intensity,
i100
(in/hr)
Flow,
Q2
(cfs)
DEVELOPED RUNOFF COMPUTATIONS FOR COMBINED BASINS
Landmark Apartments Expansion
D. Weber
May 3, 2019
Rainfall Intensity taken from the City of Loveland Storm Drainage Criteria (Addendum to the USDCM Volume 1, 2, and 3) Adopted September 1, 2002 Figure 502
Design
Point
Basin(s)
Area, A
(acres)
Tc
(min)
C2
5/6/2019 12:59 PM D:\Projects\1257-001\Drainage\Hydrology\1257-001_Rational.xlsx\Combined Runoff
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 - STORM SEWERS
B.2 - INLETS
B.3 - SWALES AND WEIRS
APPENDIX B.1
STORM SEWERS
APPENDIX B.2
INLETS
Project:
Calculations By:
Date:
INLET 1-2 15.10 15.10 0.00 CDOT Type C Close Mesh Grate 33"x40"
INLET 3-2 0.70 0.70 0.00 Single Combination Inlet 2'x3'
INLET 3-4 1.30 1.30 0.00 Nyloplast Drain Basin w/ Dome Grate 15"
INLET 4-2 3.10 3.10 0.00 Nyloplast Drain Basin w/ Dome Grate 24"
INLET 6-2 6.27 6.27 0.00 CDOT Type C Close Mesh Grate 33"x40"
D. Weber
1257-001
Q100
Total
(CFS)
Q100
Unintercepted
(CFS)
INLET SUMMARY TABLE
Design
Point
Inlet Type
Design Inlet
Label
Notes
Q100
Intercepted
(CFS)
Inlet Size
May 3, 2019
D:\Projects\1257-001\Drainage\Inlets\Inlet Summary.xls\Inlet Interception Summary
Area Inlet Performance Curve:
Landmark Apartments Expansion - Inlet 1-2
Governing Equations:
At low flow depths, the inlet will act like a weir governed by the following equation:
* where P = 2(L + W)
* where H corresponds to the depth of water above the flowline
At higher flow depths, the inlet will act like an orifice governed by the following equation:
* where A equals the open area of the inlet grate
* where H corresponds to the depth of water above the centroid of the cross-sectional area (A)
The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown.
However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation
will cross at a certain flow depth. The two curves can be found below:
If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir.
Input Parameters:
Type of Grate: CDOT Type C Close Mesh Grate
Shape Rectangular
Length of Grate (ft): 3.33
Width of Grate (ft): 2.75
Open Area of Grate (ft
2
): 7.54
Flowline Elevation (ft): 5012.250
Allowable Capacity: 50%
Depth vs. Flow:
Depth Above Inlet (ft)
Elevation
(ft)
Shallow
Weir Flow
(cfs)
Orifice
Flow
(cfs)
Actual
Flow
(cfs)
0.00 5012.25 0.00 0.00 0.00
0.10 5012.35 0.58 6.41 0.58
0.20 5012.45 1.63 9.06 1.63
0.30 5012.55 3.00 11.10 3.00
0.40 5012.65 4.61 12.81 4.61
0.50 5012.750 6.45 14.33 6.45
0.60 5012.85 8.48 15.69 8.48
0.70 5012.95 10.68 16.95 10.68
0.80 5013.05 13.05 18.12 13.05
0.90 5013.15 15.57 19.22 15.57
1.00 5013.250 18.24 20.26 18.24
Q100
0.00
5.00
10.00
15.00
20.00
25.00
0.00 0.20 0.40 0.60 0.80 1.00 1.20
Discharge (cfs)
Stage (ft)
Stage - Discharge Curves
Series1
Series2
Project =
Inlet ID =
Design Information (Input) MINOR MAJOR
Type of Inlet Inlet Type =
Local Depression (additional to continuous gutter depression 'a' from 'Q-Allow') alocal
= 2.00 2.00 inches
Number of Unit Inlets (Grate or Curb Opening) No = 1 1
Water Depth at Flowline (outside of local depression) Flow Depth = 6.0 6.0 inches
Grate Information MINOR MAJOR
Length of a Unit Grate Lo
(G) = 3.00 3.00 feet
Width of a Unit Grate Wo
= 1.73 1.73 feet
Area Opening Ratio for a Grate (typical values 0.15-0.90) Aratio
= 0.43 0.43
Clogging Factor for a Single Grate (typical value 0.50 - 0.70) Cf
(G) = 0.50 0.50
Grate Weir Coefficient (typical value 2.15 - 3.60) Cw
(G) = 3.30 3.30
Grate Orifice Coefficient (typical value 0.60 - 0.80) Co
(G) = 0.60 0.60
Curb Opening Information MINOR MAJOR
Length of a Unit Curb Opening Lo
(C) = 3.00 3.00 feet
Height of Vertical Curb Opening in Inches Hvert
= 6.50 6.50 inches
Height of Curb Orifice Throat in Inches Hthroat
= 5.25 5.25 inches
Angle of Throat (see USDCM Figure ST-5) Theta = 0.00 0.00 degrees
Side Width for Depression Pan (typically the gutter width of 2 feet) Wp
= 2.00 2.00 feet
Clogging Factor for a Single Curb Opening (typical value 0.10) Cf
(C) = 0.10 0.10
Curb Opening Weir Coefficient (typical value 2.3-3.6) Cw
(C) = 3.70 3.70
Curb Opening Orifice Coefficient (typical value 0.60 - 0.70) Co
(C) = 0.66 0.66
MINOR MAJOR
Total Inlet Interception Capacity (assumes clogged condition) Q
a = 3.6 3.6 cfs
Inlet Capacity IS GOOD for Minor and Major Storms (>Q PEAK) Q
PEAK REQUIRED = 0.2 0.7 cfs
INLET IN A SUMP OR SAG LOCATION
Landmark Apartments Expansion
Inlet 3-2 (Design Point A2)
CDOT/Denver 13 Combination
H-Vert
H-Curb
W
Lo (C)
Lo (G)
Wo
WP
Inlet 3-2 (Design Point A2).xlsm, Inlet In Sump 12/12/2018, 8:15 AM
Area Inlet Performance Curve:
Landmark Apartments Expansion - Inlet 3-4
Governing Equations:
At low flow depths, the inlet will act like a weir governed by the following equation:
* where P = 2(L + W)
* where H corresponds to the depth of water above the flowline
At higher flow depths, the inlet will act like an orifice governed by the following equation:
* where A equals the open area of the inlet grate
* where H corresponds to the depth of water above the centroid of the cross-sectional area (A)
The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown.
However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation
will cross at a certain flow depth. The two curves can be found below:
If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir.
Input Parameters:
Type of Grate: Dome
Grate Diameter (in) 15
Flowline Elevation (ft): 5020.12 Depth Needed
Q10 (cfs): 0.00
Q100 (cfs): 1.30 0.37
Depth Interval (ft) 0.1
Open Area of Grate (in
2
): 122.07
Allowable Capacity: 50%
Depth vs. Flow:
Depth Above Inlet (ft)
Elevation
(ft)
Shallow
Weir Flow
(cfs)
Orifice
Flow
(cfs)
Actual
Flow
(cfs)
0.00 5020.12 0.00 0.00 0.00
0.10 5020.22 0.19 0.72 0.19
0.20 5020.32 0.53 1.02 0.53
0.30 5020.42 0.97 1.25 0.97
0.40 5020.52 1.49 1.44 1.44 <-Q100
0.50 5020.62 2.08 1.61 1.61
0.60 5020.72 2.74 1.76 1.76
0.70 5020.82 3.45 1.91 1.91
0.80 5020.92 4.21 2.04 2.04
0.90 5021.02 5.03 2.16 2.16
1.00 5021.12 5.89 2.28 2.28
0.00
1.00
2.00
3.00
4.00
5.00
6.00
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
Discharge (cfs)
Stage (ft)
Stage - Discharge Curves
Weir Flow
Area Inlet Performance Curve:
Landmark Apartments Expansion - Inlet 4-2
Governing Equations:
At low flow depths, the inlet will act like a weir governed by the following equation:
* where P = 2(L + W)
* where H corresponds to the depth of water above the flowline
At higher flow depths, the inlet will act like an orifice governed by the following equation:
* where A equals the open area of the inlet grate
* where H corresponds to the depth of water above the centroid of the cross-sectional area (A)
The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown.
However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation
will cross at a certain flow depth. The two curves can be found below:
If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir.
Input Parameters:
Type of Grate: Dome
Grate Diameter (in) 24
Flowline Elevation (ft): 5012.00 Depth Needed
Q10 (cfs): 0.00
Q100 (cfs): 3.10 0.48
Depth Interval (ft) 0.1
Open Area of Grate (in
2
): 270.64
Allowable Capacity: 50%
Depth vs. Flow:
Depth Above Inlet (ft)
Elevation
(ft)
Shallow
Weir Flow
(cfs)
Orifice
Flow
(cfs)
Actual
Flow
(cfs)
0.00 5012.00 0.00 0.00 0.00
0.10 5012.10 0.30 1.60 0.30
0.20 5012.20 0.84 2.26 0.84
0.30 5012.30 1.55 2.77 1.55
0.40 5012.40 2.38 3.19 2.38
0.50 5012.50 3.33 3.57 3.33 <-Q100
0.60 5012.60 4.38 3.91 3.91
0.70 5012.70 5.52 4.23 4.23
0.80 5012.80 6.74 4.52 4.52
0.90 5012.90 8.05 4.79 4.79
1.00 5013.00 9.42 5.05 5.05
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00
Discharge (cfs)
Area Inlet Performance Curve:
Landmark Apartments Expansion - Inlet 6-2
Governing Equations:
At low flow depths, the inlet will act like a weir governed by the following equation:
* where P = 2(L + W)
* where H corresponds to the depth of water above the flowline
At higher flow depths, the inlet will act like an orifice governed by the following equation:
* where A equals the open area of the inlet grate
* where H corresponds to the depth of water above the centroid of the cross-sectional area (A)
The exact depth at which the inlet ceases to act like a weir, and begins to act like an orifice is unknown.
However, what is known, is that the stage-discharge curves of the weir equation and the orifice equation
will cross at a certain flow depth. The two curves can be found below:
If H > 1.792 (A/P), then the grate operates like an orifice; otherwise it operates like a weir.
Input Parameters:
Type of Grate: CDOT Type C Close Mesh Grate
Shape Rectangular
Length of Grate (ft): 3.33
Width of Grate (ft): 2.75
Open Area of Grate (ft
2
): 7.54
Flowline Elevation (ft): 5013.500
Allowable Capacity: 50%
Depth vs. Flow:
Depth Above Inlet (ft)
Elevation
(ft)
Shallow
Weir Flow
(cfs)
Orifice
Flow
(cfs)
Actual
Flow
(cfs)
0.00 5013.50 0.00 0.00 0.00
0.10 5013.60 0.58 6.41 0.58
0.20 5013.70 1.63 9.06 1.63
0.30 5013.80 3.00 11.10 3.00
0.40 5013.90 4.61 12.81 4.61
0.50 5014.000 6.45 14.33 6.45
0.60 5014.10 8.48 15.69 8.48
0.70 5014.20 10.68 16.95 10.68
0.80 5014.30 13.05 18.12 13.05
0.90 5014.40 15.57 19.22 15.57
1.00 5014.500 18.24 20.26 18.24
Q100
0.00
5.00
10.00
15.00
20.00
25.00
0.00 0.20 0.40 0.60 0.80 1.00 1.20
Discharge (cfs)
Stage (ft)
Stage - Discharge Curves
Series1
Series2
APPENDIX B.3
SWALES AND WEIRS
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 12 2018
Curb Cut - Design Point A1 (100-yr)
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 6.00
Total Depth (ft) = 0.50
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Q
Known Q (cfs) = 6.40
Highlighted
Depth (ft) = 0.47
Q (cfs) = 6.400
Area (sqft) = 2.81
Velocity (ft/s) = 2.28
Top Width (ft) = 6.00
0 1 2 3 4 5 6 7 8
Depth (ft) Curb Cut - Design Point A1 (100-yr) Depth (ft)
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
Length (ft)
Weir W.S.
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 12 2018
Curb Cut - Design Point A3 (10-yr)
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 8.00
Total Depth (ft) = 0.50
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Q
Known Q (cfs) = 5.90
Highlighted
Depth (ft) = 0.37
Q (cfs) = 5.900
Area (sqft) = 2.93
Velocity (ft/s) = 2.02
Top Width (ft) = 8.00
0 1 2 3 4 5 6 7 8 9 10
Depth (ft) Curb Cut - Design Point A3 (10-yr) Depth (ft)
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
Length (ft)
Weir W.S.
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 12 2018
Curb Cut - Design Point B1 (100-yr)
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 4.00
Total Depth (ft) = 0.50
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Q
Known Q (cfs) = 3.10
Highlighted
Depth (ft) = 0.38
Q (cfs) = 3.100
Area (sqft) = 1.51
Velocity (ft/s) = 2.05
Top Width (ft) = 4.00
0 .5 1 1.5 2 2.5 3 3.5 4 4.5 5
Depth (ft) Curb Cut - Design Point B1 (100-yr) Depth (ft)
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
Length (ft)
Weir W.S.
Culvert Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 12 2018
Sidewalk Chase - Design Point A4
Invert Elev Dn (ft) = 99.87
Pipe Length (ft) = 6.50
Slope (%) = 2.00
Invert Elev Up (ft) = 100.00
Rise (in) = 5.4
Shape = Box
Span (in) = 24.0
No. Barrels = 1
n-Value = 0.013
Culvert Type = 90D Headwall,
Chamfered or Beveled Inlet Edges
Culvert Entrance = 90D headwall w/3/4-in chamfers
Coeff. K,M,c,Y,k = 0.515, 0.667, 0.0375, 0.79, 0.2
Embankment
Top Elevation (ft) = 100.50
Top Width (ft) = 6.00
Crest Width (ft) = 10.00
Calculations
Qmin (cfs) = 1.41
Qmax (cfs) = 3.13
Tailwater Elev (ft) = Critical
Highlighted
Qtotal (cfs) = 1.41
Qpipe (cfs) = 1.41
Qovertop (cfs) = 0.00
Veloc Dn (ft/s) = 3.71
Veloc Up (ft/s) = 2.83
HGL Dn (ft) = 100.06
HGL Up (ft) = 100.25
Hw Elev (ft) = 100.41
Hw/D (ft) = 0.91
Flow Regime = Inlet Control
Culvert Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 12 2018
Sidewalk Chase - Design Point OS3
Invert Elev Dn (ft) = 99.90
Pipe Length (ft) = 5.00
Slope (%) = 2.00
Invert Elev Up (ft) = 100.00
Rise (in) = 5.4
Shape = Box
Span (in) = 24.0
No. Barrels = 1
n-Value = 0.013
Culvert Type = 90D Headwall,
Chamfered or Beveled Inlet Edges
Culvert Entrance = 90D headwall w/3/4-in chamfers
Coeff. K,M,c,Y,k = 0.515, 0.667, 0.0375, 0.79, 0.2
Embankment
Top Elevation (ft) = 100.50
Top Width (ft) = 4.00
Crest Width (ft) = 12.00
Calculations
Qmin (cfs) = 1.80
Qmax (cfs) = 1.80
Tailwater Elev (ft) = Critical
Highlighted
Qtotal (cfs) = 1.80
Qpipe (cfs) = 1.80
Qovertop (cfs) = 0.00
Veloc Dn (ft/s) = 3.91
Veloc Up (ft/s) = 3.07
HGL Dn (ft) = 100.13
HGL Up (ft) = 100.29
Hw Elev (ft) = 100.48
Hw/D (ft) = 1.07
Flow Regime = Inlet Control
Culvert Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 12 2018
Sidewalk Chase - Design Point OS7
Invert Elev Dn (ft) = 99.86
Pipe Length (ft) = 7.00
Slope (%) = 2.00
Invert Elev Up (ft) = 100.00
Rise (in) = 5.4
Shape = Box
Span (in) = 24.0
No. Barrels = 2
n-Value = 0.013
Culvert Type = Rectagular Concrete
Culvert Entrance = Tapered inlet throat
Coeff. K,M,c,Y,k = 0.475, 0.667, 0.0179, 0.97, 0.2
Embankment
Top Elevation (ft) = 100.50
Top Width (ft) = 6.00
Crest Width (ft) = 25.00
Calculations
Qmin (cfs) = 2.90
Qmax (cfs) = 12.80
Tailwater Elev (ft) = Critical
Highlighted
Qtotal (cfs) = 2.90
Qpipe (cfs) = 2.90
Qovertop (cfs) = 0.00
Veloc Dn (ft/s) = 3.63
Veloc Up (ft/s) = 2.85
HGL Dn (ft) = 100.06
HGL Up (ft) = 100.25
Hw Elev (ft) = 100.38
Hw/D (ft) = 0.85
Flow Regime = Inlet Control
Culvert Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 12 2018
Sidewalk Chase - Design Point OS8
Invert Elev Dn (ft) = 99.96
Pipe Length (ft) = 7.50
Slope (%) = 0.53
Invert Elev Up (ft) = 100.00
Rise (in) = 11.4
Shape = Box
Span (in) = 24.0
No. Barrels = 1
n-Value = 0.013
Culvert Type = 90D Headwall,
Chamfered or Beveled Inlet Edges
Culvert Entrance = 90D headwall w/3/4-in chamfers
Coeff. K,M,c,Y,k = 0.515, 0.667, 0.0375, 0.79, 0.2
Embankment
Top Elevation (ft) = 101.00
Top Width (ft) = 6.50
Crest Width (ft) = 16.00
Calculations
Qmin (cfs) = 5.00
Qmax (cfs) = 12.80
Tailwater Elev (ft) = Critical
Highlighted
Qtotal (cfs) = 5.00
Qpipe (cfs) = 5.00
Qovertop (cfs) = 0.00
Veloc Dn (ft/s) = 4.46
Veloc Up (ft/s) = 4.31
HGL Dn (ft) = 100.52
HGL Up (ft) = 100.58
Hw Elev (ft) = 100.95
Hw/D (ft) = 1.00
Flow Regime = Inlet Control
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 12 2018
Swale - Design Point A3
Trapezoidal
Bottom Width (ft) = 2.00
Side Slopes (z:1) = 4.00, 4.00
Total Depth (ft) = 1.65
Invert Elev (ft) = 5011.85
Slope (%) = 2.00
N-Value = 0.030
Calculations
Compute by: Known Q
Known Q (cfs) = 20.10
Highlighted
Depth (ft) = 0.85
Q (cfs) = 20.10
Area (sqft) = 4.59
Velocity (ft/s) = 4.38
Wetted Perim (ft) = 9.01
Crit Depth, Yc (ft) = 0.88
Top Width (ft) = 8.80
EGL (ft) = 1.15
0 2 4 6 8 10 12 14 16 18 20
Elev (ft) Depth (ft)
Section
5011.00 -0.85
5011.50 -0.35
5012.00 0.15
5012.50 0.65
5013.00 1.15
5013.50 1.65
5014.00 2.15
Reach (ft)
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Monday, Mar 11 2019
Swale - Design Point OS3 (100-yr)
User-defined
Invert Elev (ft) = 15.17
Slope (%) = 2.00
N-Value = 0.035
Calculations
Compute by: Known Q
Known Q (cfs) = 2.40
(Sta, El, n)-(Sta, El, n)...
( 0.00, 16.43)-(10.10, 15.35, 0.035)-(19.10, 15.17, 0.035)-(24.10, 15.67, 0.035)
Highlighted
Depth (ft) = 0.24
Q (cfs) = 2.400
Area (sqft) = 1.65
Velocity (ft/s) = 1.45
Wetted Perim (ft) = 11.98
Crit Depth, Yc (ft) = 0.21
Top Width (ft) = 11.96
EGL (ft) = 0.27
-5 0 5 10 15 20 25 30
Elev (ft) Depth (ft)
Section
14.50 -0.67
15.00 -0.17
15.50 0.33
16.00 0.83
16.50 1.33
17.00 1.83
Sta (ft)
Channel Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 12 2018
Swale - Design Point OS8 (100-yr)
Triangular
Side Slopes (z:1) = 4.00, 4.00
Total Depth (ft) = 2.00
Invert Elev (ft) = 100.00
Slope (%) = 0.50
N-Value = 0.030
Calculations
Compute by: Known Q
Known Q (cfs) = 17.10
Highlighted
Depth (ft) = 1.30
Q (cfs) = 17.10
Area (sqft) = 6.76
Velocity (ft/s) = 2.53
Wetted Perim (ft) = 10.72
Crit Depth, Yc (ft) = 1.03
Top Width (ft) = 10.40
EGL (ft) = 1.40
0 2 4 6 8 10 12 14 16 18 20
Elev (ft) Depth (ft)
Section
99.50 -0.50
100.00 0.00
100.50 0.50
101.00 1.00
101.50 1.50
102.00 2.00
102.50 2.50
103.00 3.00
Reach (ft)
HY-8 Culvert Analysis Report
Crossing Discharge Data
Discharge Selection Method: Specify Minimum, Design, and Maximum Flow
Minimum Flow: 15.1 cfs
Design Flow: 15.1 cfs
Maximum Flow: 15.1 cfs
Table 1 - Summary of Culvert Flows at Crossing: Crossing 1
Headwater Elevation
(ft)
Total Discharge (cfs) Culvert 1 Discharge
(cfs)
Roadway Discharge
(cfs)
Iterations
5013.58 15.10 0.00 15.08 1
5013.58 15.10 0.00 15.08 1
5013.58 15.10 0.00 15.08 1
5013.58 15.10 0.00 15.08 1
5013.58 15.10 0.00 15.08 1
5013.58 15.10 0.00 15.08 1
5013.58 15.10 0.00 15.08 1
5013.58 15.10 0.00 15.08 1
5013.58 15.10 0.00 15.08 1
5013.58 15.10 0.00 15.08 1
5013.58 15.10 0.00 15.08 1
5012.86 0.00 0.00 0.00 Overtopping
Rating Curve Plot for Crossing: Crossing 1
Table 2 - Culvert Summary Table: Culvert 1
Total
Discharge
(cfs)
Culvert
Discharge
(cfs)
Headwater
Elevation (ft)
Inlet Control
Depth (ft)
Outlet
Control
Depth (ft)
Flow
Type
Normal
Depth (ft)
Critical
Depth (ft)
Outlet Depth
(ft)
Tailwater
Depth (ft)
Outlet
Velocity
(ft/s)
Tailwater
Velocity
(ft/s)
15.10 0.00 5013.58 0.000 0.000 2-M2c 0.000 0.000 0.000 0.850 0.105 0.000
15.10 0.00 5013.58 0.000 0.000 2-M2c 0.000 0.000 0.000 0.850 0.105 0.000
15.10 0.00 5013.58 0.000 0.000 2-M2c 0.000 0.000 0.000 0.850 0.105 0.000
15.10 0.00 5013.58 0.000 0.000 2-M2c 0.000 0.000 0.000 0.850 0.105 0.000
15.10 0.00 5013.58 0.000 0.000 2-M2c 0.000 0.000 0.000 0.850 0.105 0.000
15.10 0.00 5013.58 0.000 0.000 2-M2c 0.000 0.000 0.000 0.850 0.105 0.000
15.10 0.00 5013.58 0.000 0.000 2-M2c 0.000 0.000 0.000 0.850 0.105 0.000
15.10 0.00 5013.58 0.000 0.000 2-M2c 0.000 0.000 0.000 0.850 0.105 0.000
15.10 0.00 5013.58 0.000 0.000 2-M2c 0.000 0.000 0.000 0.850 0.105 0.000
15.10 0.00 5013.58 0.000 0.000 2-M2c 0.000 0.000 0.000 0.850 0.105 0.000
15.10 0.00 5013.58 0.000 0.000 2-M2c 0.000 0.000 0.000 0.850 0.105 0.000
********************************************************************************
Straight Culvert
Inlet Elevation (invert): 5012.75 ft, Outlet Elevation (invert): 5012.70 ft
Culvert Length: 10.00 ft, Culvert Slope: 0.0050
********************************************************************************
Culvert Performance Curve Plot: Culvert 1
Water Surface Profile Plot for Culvert: Culvert 1
Site Data - Culvert 1
Site Data Option: Culvert Invert Data
Inlet Station: 0.00 ft
Inlet Elevation: 5012.75 ft
Outlet Station: 10.00 ft
Outlet Elevation: 5012.70 ft
Number of Barrels: 1
Culvert Data Summary - Culvert 1
Barrel Shape: Circular
Barrel Diameter: 0.00 ft
Barrel Material: Concrete
Embedment: 0.00 in
Barrel Manning's n: 0.0120
Culvert Type: Straight
Inlet Configuration: Square Edge with Headwall
Inlet Depression: None
Table 3 - Downstream Channel Rating Curve (Crossing: Crossing 1)
Flow (cfs) Water Surface Elev (ft) Depth (ft)
15.10 5012.70 0.85
15.10 5012.70 0.85
15.10 5012.70 0.85
15.10 5012.70 0.85
15.10 5012.70 0.85
15.10 5012.70 0.85
15.10 5012.70 0.85
15.10 5012.70 0.85
15.10 5012.70 0.85
15.10 5012.70 0.85
15.10 5012.70 0.85
Tailwater Channel Data - Crossing 1
Tailwater Channel Option: Enter Constant Tailwater Elevation
Constant Tailwater Elevation: 5012.70 ft
Roadway Data for Crossing: Crossing 1
Roadway Profile Shape: Irregular Roadway Shape (coordinates)
Roadway Surface: Paved
Roadway Top Width: 0.50 ft
Crossing Front View (Roadway Profile): Crossing 1
Weir Report
Hydraflow Express Extension for Autodesk® AutoCAD® Civil 3D® by Autodesk, Inc. Wednesday, Dec 12 2018
Weir - Design Point OS4 (100-yr)
Rectangular Weir
Crest = Sharp
Bottom Length (ft) = 30.00
Total Depth (ft) = 0.50
Calculations
Weir Coeff. Cw = 3.33
Compute by: Known Q
Known Q (cfs) = 18.50
Highlighted
Depth (ft) = 0.32
Q (cfs) = 18.50
Area (sqft) = 9.74
Velocity (ft/s) = 1.90
Top Width (ft) = 30.00
0 5 10 15 20 25 30 35 40
Depth (ft) Weir - Design Point OS4 (100-yr) Depth (ft)
-0.50 -0.50
0.00 0.00
0.50 0.50
1.00 1.00
Length (ft)
Weir W.S.
APPENDIX C
SWMM MODELING
01/01/2013 00:01:00
SWMM 5 Page 1
S U M M A R Y S T A T I S T I C S
===================================
Object .............. Link 43
Variable ............. Flow (CFS)
Event Period ......... Variable
Event Statistic ...... Peak (CFS)
Event Threshold ...... Flow > 0.0000 (CFS)
Event Threshold ...... Event Volume > 0.0000 (ft3)
Event Threshold ...... Separation Time >= 6.0 (hr)
Period of Record ..... 01/01/2013 to 01/01/2013
Number of Events ..... 1
Event Frequency*...... 0.993
Minimum Value ........ 518.730
Maximum Value ........ 518.730
Mean Value ........... 518.730
Std. Deviation ....... 0.000
Skewness Coeff. ...... 0.000
*Fraction of all reporting periods belonging to an event.
SWMM 5 Page 1
S U M M A R Y S T A T I S T I C S
===================================
Object .............. Link 43
Variable ............. Flow (CFS)
Event Period ......... Variable
Event Statistic ...... Peak (CFS)
Event Threshold ...... Flow > 0.0000 (CFS)
Event Threshold ...... Event Volume > 0.0000 (ft3)
Event Threshold ...... Separation Time >= 6.0 (hr)
Period of Record ..... 01/01/2013 to 01/01/2013
Number of Events ..... 1
Event Frequency*...... 0.993
Minimum Value ........ 518.810
Maximum Value ........ 518.810
Mean Value ........... 518.810
Std. Deviation ....... 0.000
Skewness Coeff. ...... 0.000
*Fraction of all reporting periods belonging to an event.
SWMM 5 Page 1
APPENDIX D
EROSION CONTROL REPORT
Landmark Apartments Expansion
Final Erosion Control Report
A comprehensive Erosion and Sediment Control Plan (along with associated details) is 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 Sheet CS2 of the Utility Plans. The Utility
Plans at final design will also contain a full-size Erosion Control Plan 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 any existing
Development Agreement(s) of record, as well as the Development Agreement, to be recorded prior
to issuance of the Development Construction Permit. 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,
before commencing any earth disturbing 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 E
FEMA FIRMETTE
APPENDIX F
LID EXHIBIT AND CALCULATIONS
T
T
E
E
E
E
E
E
X
X
X
X
X
X X X
X X
X X X
X X
X
X
X
X X
X
X
X
X
T T T
E
E
W
W
W
W
W W
WW
WW
ET
FO
FO
FO
DC DC
CC
VAULT
ELEC
S
S
S
S
WV
S
WV
WV
WV
E
X
X
X
S
S
S
S
Project: Landmark Apartments Expansion
Calculations By:
Date:
1 A1, A2, & OS1 55,001 38% 20,900 Rain Garden 1
2 A3 & OS2 102,379 32% 32,761 Rain Garden 2
3 A4-A6 28,037 78% 21,869 Rain Garden 3
4 B1 13,772 74% 10,191
Rain Garden 4
Total Treated 199,189 43% 85,722
A - 1,600 100% 1,600 None
B - 400 100% 400 None
Total Untreated 2,000 100% 2,000
C - 8,529 100% 8,529 Rain Gardens
Total Treated 8,529 100% 8,529
640
676
20,900
1,075
1,127
32,761
591
654
21,869
270
337
10,191
87,722
65,791
85,722
8,529
94,251
107%
Sub-Basin(s)
Area, A
(sf)
Percent Impervious
Impervious Area, A
(sf)
LID Treatment
Proposed On-site Impervious Area (sf)
Proposed On-site Treated Area (sf)
Percent Treated by LID measures
Proposed Additional Off-site Treated Area (sf)
Proposed Total Treated Area (sf)
Total Volume Required (cf)
Total Volume Provided (cf)
Total Impervious Area Treated (sf)
Total Volume Required (cf)
Total Volume Provided (cf)
Total Impervious Area Treated (sf)
Rain Garden 4
Percent Impervious LID Treatment
Rain Garden 3
LID TREATMENT SUMMARY
Rain Garden 1
Total Volume Required (cf)
Total Volume Provided (cf)
Total Impervious Area Treated (sf)
Rain Garden 2
Total Volume Required (cf)
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 38.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.380
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.14 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 55,001 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 640 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 = 0.0 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 = 427 sq ft
D) Actual Flat Surface Area AActual = 436 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 915 sq ft
F) Rain Garden Total Volume VT= 676 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 = 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)
Danny Weber
Northern Engineering
May 3, 2019
Landmark Apartments Expansion
Rain Garden 1
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.03 Rain Garden - 1.xlsm, RG 5/6/2019, 1:12 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 32.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.320
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 = 102,379 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 1,075 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 = 0.0 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 = 717 sq ft
D) Actual Flat Surface Area AActual = 879 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 1375 sq ft
F) Rain Garden Total Volume VT= 1,127 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 = 24.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 1,075 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 0.45 in
Design Procedure Form: Rain Garden (RG)
Danny Weber
Northern Engineering
May 3, 2019
Landmark Apartments Expansion
Rain Garden 2
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.03 Rain Garden - 2.xlsm, RG 5/6/2019, 1:12 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 78.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.780
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 = 28,037 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 591 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 = 0.0 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 = 394 sq ft
D) Actual Flat Surface Area AActual = 409 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 899 sq ft
F) Rain Garden Total Volume VT= 654 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 = 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)
Danny Weber
Northern Engineering
May 3, 2019
Landmark Apartments Expansion
Rain Garden 3
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.03 Rain Garden - 3.xlsm, RG 5/6/2019, 1:13 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 74.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.740
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.24 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 13,772 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 270 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 = 0.0 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 = 9 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 = 180 sq ft
D) Actual Flat Surface Area AActual = 326 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 573 sq ft
F) Rain Garden Total Volume VT= 337 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 = 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)
Danny Weber
Northern Engineering
May 3, 2019
Landmark Apartments Expansion
Rain Garden 4
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.03 Rain Garden - 4.xlsm, RG 5/6/2019, 1:14 PM
MAP POCKET
DR1 – OVERALL DRAINAGE EXHIBIT
UD
UD UD
UD
UD
UD
E
E
E
E E E
E E E
E
E E
E
E
E E
E
E
E
8" SS 8" SS
8" SS 8" SS
E
E
X
X
X
X
X X X
X
X
X
X
X
X X
X
X
X
X
X
E
W
W
W
W
W W
WW
WW
ET
FO
FO
6" SS 6" SS 6" SS
6" SS
6" SS
DC DC
CC
VAULT
ELEC
S
S
S
S
S
S
S
S
CONTROL
IRR
CONTROL
IRR
CONTROL
IRR
WV
WV
H
Y
D
WV
WV
WV
S
WV
WV
WV
E E E E
G
G
G
G
X
X
X
S
S
S
S
S
S
D
D
UD UD UD
UD UD
UD
UD UD
UD
UD
UD
UD
UD
UD
UD
V.P.
OS4
OS2
OS1
UD2
B1
OS5
OS7
A1
A2
A4
A3
A1
A2
A4
A3
B1
UD1
OS3
OS1
OS2
A5
A5
OS8
OS6
OS3
OS4
A6
A6
OS5
OS6
OS7
OS8
N
S
T
INLET 1-2
CONCRETE FES 1-1
INLET 3-2 STMH 3-2
INLET 3-4
CONCRETE FES 3-1
INLET 4-2
OUTLET COLLAR 4-1
OUTLET 5-1
CONCRETE FES 6-1
CITY OF FORT COLLINS
100-YR FLOODWAY
CITY OF FORT COLLINS
100-YR FLOODPLAIN
RAIN GARDEN 1
RAIN GARDEN 3
RAIN GARDEN 4
RAIN GARDEN 2
HOBBIT STREET
54' RIGHT OF WAY
W. PROSPECT ROAD
102' RIGHT OF WAY
WALLENBERG DRIVE
STUART STREET
54' RIGHT OF WAY
LOT 1 LANDMARK
SUBDIVISION PUD
OWNER: LANDMARK HOUSING LLC
LOT 3 ARTHUR C.
SHEELY FIRST
SUBDIVISION
OWNER: DEVORE, JANICE S.
LOT 3 ARTHUR C. SHEELY
FIRST SUBDIVISION
OWNER: HANSCH, EDWARD C & DEBRA J
LOT 3 ARTHUR C. SHEELY FIRST
SUBDIVISION
OWNER: HUFBAURER, RUTH
LOT 2 ARTHUR C. SHEELY
FIRST SUBDIVISION
OWNER: FONTE, STEVEN J & SARAH C
LOT 1 ARTHUR C. SHEELY
FIRST SUBDIVISION
OWNER: HOGESTAD, PER M & VEDA V
TRACT B
PULSE PUD FILING ONE
OWNER: NORTH SPRING CREEK
PROPERTIES LLC
LOT 6 SEAMAN
SUBDIVISION
OWNER: EWAN, JOHN L &
YVONNE S
INLET 6-2
FEMA100-YR FLOODPLAIN
STA:720 ELEV:5011.15
STA:905 ELEV:5011.89
STA:983 ELEV:5012.08
STA:1075 ELEV:5012.31
STA: 1136 ELEV: 5012.53
STA:805 ELEV:5011.42
Sheet
LANDMARK APARTMENTS EXPANSION 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
301 North 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
of 34
KEYMAP
DC DC
CC
LEGEND:
5013
PROPOSED CONTOUR 93
EXISTING CONTOUR
PROPERTY BOUNDARY
EXISTING STORM SEWER
1. THE SIZE, TYPE AND LOCATION OF ALL KNOWN UNDERGROUND UTILITIES ARE
APPROXIMATE WHEN SHOWN ON THESE DRAWINGS. IT SHALL BE THE
RESPONSIBILITY OF THE CONTRACTOR TO VERIFY THE EXISTENCE OF ALL
UNDERGROUND UTILITIES IN THE AREA OF THE WORK. BEFORE COMMENCING
NEW CONSTRUCTION, THE CONTRACTOR SHALL BE RESPONSIBLE FOR LOCATING
ALL UNDERGROUND UTILITIES AND SHALL BE RESPONSIBLE FOR FOR ALL
UNKNOWN UNDERGROUND UTILITIES.
2. REFER TO THE "FINAL DRAINAGE AND EROSION CONTROL REPORT FOR LANDMARK
APARTMENTS EXPANSION" BY NORTHERN ENGINEERING, DATED MAY 3, 2019 FOR
ADDITIONAL INFORMATION.
NOTES:
FLOW PATH
DRAINAGE BASIN BUBBLE
A
DESIGN POINT A
BASIN BOUNDARY
PROPOSED STORM SEWER
FOR DRAINAGE REVIEW ONLY
NOT FOR CONSTRUCTION
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
City Engineer Date
Date
Date
Date
Date
Stormwater Utility
Parks & Recreation
Traffic Engineer
Date
APPROVED:
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
Water & Wastewater Utility
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
Environmental Planner
( IN FEET )
0
1 INCH = 50 FEET
50 50 100 150
DR1
DRAINAGE PLAN
34
NORTH
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C10 C100
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q10
(cfs)
Q100
(cfs)
A1 A1 0.55 0.68 0.68 0.84 5.1 5.1 5.0 1.07 1.82 4.66
A2 A2 0.25 0.63 0.63 0.78 5.0 5.0 5.0 0.45 0.77 1.96
A3 A3 1.04 0.66 0.66 0.82 8.5 8.5 8.2 1.63 2.79 7.13
A4 A4 0.31 0.92 0.92 1.00 5.0 5.0 5.0 0.82 1.41 3.13
A5 A5 0.23 0.75 0.75 0.94 5.0 5.0 5.0 0.49 0.83 2.13
A6 A6 0.10 0.80 0.80 1.00 5.0 5.0 5.0 0.23 0.40 1.01
N UD1 0.11 0.25 0.25 0.31 5.0 5.0 5.0 0.08 0.13 0.34
B1 B1 0.32 0.79 0.79 0.99 5.0 5.0 5.0 0.71 1.21 3.10
S UD2 0.15 0.48 0.48 0.60 8.5 8.5 7.8 0.18 0.30 0.79
OS1 OS1 0.46 0.30 0.30 0.38 11.2 11.2 10.4 0.29 0.50 1.34
OS2 OS2 1.31 0.35 0.35 0.44 12.4 12.4 11.5 0.94 1.60 4.23
OS3 OS3 0.29 0.36 0.36 0.45 10.7 10.7 10.0 0.23 0.39 1.04
OS4 OS4 4.14 0.57 0.57 0.72 19.6 19.6 18.8 3.86 6.59 17.28
OS5 OS5 0.24 0.84 0.84 1.00 5.0 5.0 5.0 0.58 0.99 2.40
OS6 OS6 1.07 0.71 0.71 0.89 10.1 10.1 9.6 1.68 2.87 7.48
OS7 OS7 0.28 0.94 0.94 1.00 5.0 5.0 5.0 0.74 1.26 2.74
OS8 OS8 0.12 0.31 0.31 0.39 6.6 6.6 6.3 0.10 0.17 0.45
Total Volume Provided (cf)
Total Impervious Area Treated (sf)
PROPOSED ADDITIONAL OFF-SITE TREATED AREA
Location
LID Treatment
Impervious Area, A
(sf)
75% Required Minimum Area to be Treated
LID COMPUTATIONS
D. Weber
May 3, 2019
PROPOSED ON-SITE TREATED AREA
LID Basin Sub-Basin(s)
Area, A
(sf)
Percent Impervious
Impervious Area, A
(sf)
PROPOSED ON-SITE UNTREATED AREA
Location Sub-Basin(s)
Area, A
(sf)
S
S
D
D
V.P.
UD
UD
UD
UD
UD
UD
UD
UD
E E
E
E
E
E E E
E
E
E
E
E E
E
E E
E E
E E E
HOBBIT STREET
54' RIGHT OF WAY
W. PROSPECT ROAD
102' RIGHT OF WAY
WALLENBERG DRIVE
STUART STREET
54' RIGHT OF WAY
TRACT C
YOUNG'S CREEK
OWNER: CITY OF FORT COLLINS
LOT 1 LANDMARK
SUBDIVISION PUD
OWNER: LANDMARK HOUSING LLC
LOT 3 ARTHER C.
SHEELY FIRST
SUBDIVISION
OWNER: DEVORE, JANICE S.
LOT 3 ARTHER C. SHEELY
FIRST SUBDIVISION
OWNER: HANSCH, EDWARD C & DEBRA J
LOT 3 ARTHER C. SHEELY FIRST
SUBDIVISION
OWNER: HUFBAURER, RUTH
LOT 2 ARTHER C. SHEELY
FIRST SUBDIVISION
OWNER: FONTE, STEVEN J & SARAH C
LOT 1 ARTHER C. SHEELY
FIRST SUBDIVISION
OWNER: HOGESTAD, PER M & VEDA V
TRACT B PULSE PUD 1ST
OWNER: NORTH SPRING CREEK
PROPERTIES LLC
LOT 6 SEAMAN
SUBDIVISION
OWNER: EWAN, JOHN L &
YVONNE S
RAIN GARDEN 1
RAIN GARDEN 2
RAIN GARDEN 3
RAIN GARDEN 4
LID BASIN 2
TOTAL AREA: 102,379 SF
TOTAL IMPERVIOUS AREA: 32,761 SF
LID TREATMENT: RAIN GARDEN
LID BASIN 3
TOTAL AREA: 28,037 SF
TOTAL IMPERVIOUS AREA: 21,869 SF
LID TREATMENT: RAIN GARDEN
LID BASIN 4
TOTAL AREA: 13,772 SF
TOTAL IMPERVIOUS AREA: 10,170 SF
LID TREATMENT: RAIN GARDEN
LID BASIN 1
TOTAL AREA: 55,001 SF
TOTAL IMPERVIOUS AREA: 20,900 SF
LID TREATMENT: RAIN GARDEN
LID BASIN 6
TOTAL AREA: 36,199 SF
TOTAL IMPERVIOUS AREA: 1,898 SF
LID TREATMENT: NONE
LOCATION A
UNTREATED ON-SITE
AREA=1,600 SF
LOCATION B
UNTREATED ON-SITE
AREA=400 SF
LOCATION C
ADDITIONAL OFF-SITE TREATED
AREA TOTAL=8,529 SF
LID
LID TREATMENT EXHIBIT
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
Sheet
LANDMARK APARTMENTS EXPANSION 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
301 North 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
of 34
KEYMAP
DC DC
CC
( IN FEET )
0
1 INCH = 40 FEET
40 40 80 120
LEGEND:
UNTREATED ON-SITE AREA
NORTH
ADDITIONAL OFF-SITE TREATED AREA
LID TREATMENT SUMMARY
Rain Garden 1
Total Volume Required (cf) 640
Total Volume Provided (cf) 676
Total Impervious Area Treated (sf) 20,900
Rain Garden 2
Total Volume Required (cf) 1,075
Total Volume Provided (cf) 1,127
Total Impervious Area Treated (sf) 32,761
Rain Garden 3
Total Volume Required (cf) 591
Total Volume Provided (cf) 654
Total Impervious Area Treated (sf) 21,869
Rain Garden 4
Total Volume Required (cf) 270
Total Volume Provided (cf) 337
Total Impervious Area Treated (sf) 10,191
Proposed On-site Impervious Area (sf) 87,722
75% Required Minimum Area to be Treated by LID measures (sf) 65,791
Proposed On-site Treated Area (sf) 85,722
Proposed Additional Off-site Treated Area (sf) 8,529
Proposed Total Treated Area (sf) 94,251
Percent Treated by LID measures 107%
Q = 3 . 0 P H 1 . 5
Q = 0 . 67 A ( 2 gH ) 0 . 5
Stage (ft)
Stage - Discharge Curves
Weir Flow
Orifice Flow
Q = 3 . 0 P H 1 . 5
Q = 0 . 67 A ( 2 gH ) 0 . 5
Orifice Flow
Q = 3 . 0 P H 1 . 5
Q = 0 . 67 A ( 2 gH ) 0 . 5
Q = 3 . 0 P H 1 . 5
Q = 0 . 67 A ( 2 gH ) 0 . 5
0 . 395 1 . 1
S
C L
Ti
−
=
( )
( ) o
t
c
i S
L
t i
60 24 12
18 15
+
= − +
5/6/2019 12:59 PM D:\Projects\1257-001\Drainage\Hydrology\1257-001_Rational.xlsx\Combined Tc
D. Weber
Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8
May 3, 2019
Intensity,
i10
(in/hr)
C10
Q = C f ( C )( i )( A )
5/6/2019 12:59 PM D:\Projects\1257-001\Drainage\Hydrology\1257-001_Rational.xlsx\Runoff
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
N North Historic Basin No 0.25 0.25 0.31 421 5.0% 19.1 19.1 17.7 N/A N/A N/A 331 1.2% 1.63 3.4 22.5 22.5 21.1
S South Historic Basin No 0.25 0.25 0.31 85 5.8% 8.2 8.2 7.6 N/A N/A N/A 288 1.0% 1.51 3.2 11.4 11.4 10.8
T Total Existing Site No 0.25 0.25 0.31 421 5.0% 19.1 19.1 17.7 N/A N/A N/A 331 1.2% 1.63 3.4 22.5 22.5 21.1
A1 A1 No 0.50 0.50 0.63 50 7.0% 4.1 4.1 3.3 260 5.0% 4.47 1.0 0 0.0% N/A N/A 5.1 5.1 5.0
A2 A2 No 0.25 0.25 0.31 30 10.0% 4.0 4.0 3.7 40 1.0% 2.00 0.3 140 6.0% 3.67 0.6 5.0 5.0 5.0
A3 A3 No 0.25 0.25 0.31 25 5.0% 4.6 4.6 4.3 0 0.0% N/A N/A 310 0.8% 1.34 3.9 8.5 8.5 8.2
A4 A4 No 0.95 0.95 1.00 115 5.0% 1.8 1.8 1.2 100 3.0% 3.46 0.5 0 0.0% N/A N/A 5.0 5.0 5.0
A5 A5 No 0.95 0.95 1.00 95 2.5% 2.0 2.0 1.3 0 0.0% N/A N/A 30 2.0% 2.12 0.2 5.0 5.0 5.0
A6 A6 No 0.95 0.95 1.00 40 20.0% 0.7 0.7 0.4 120 2.0% 2.83 0.7 0 0.0% N/A N/A 5.0 5.0 5.0
N UD1 No 0.25 0.25 0.31 30 20.0% 3.2 3.2 3.0 0 0.0% N/A N/A 0 0.0% N/A N/A 5.0 5.0 5.0
N North Proposed Basin No 0.00 0.00 N/A N/A N/A N/A N/A N/A N/A 5.0 5.0 5.0
B1 B1 No 0.95 0.95 1.00 40 2.0% 1.4 1.4 0.9 0 0.0% N/A N/A 130 0.5% 1.06 2.0 5.0 5.0 5.0
S UD2 No 0.25 0.25 0.31 45 2.0% 8.5 8.5 7.8 0 0.0% N/A N/A 0 0.0% N/A N/A 8.5 8.5 7.8
S South Proposed Basin No 0.00 0.00 N/A N/A N/A N/A N/A N/A N/A 5.0 5.0 5.0
T Total Proposed Site No 0.00 0.00 N/A N/A N/A N/A N/A N/A N/A 5.0 5.0 5.0
OS1 OS1 No 0.25 0.25 0.31 200 8.0% 11.2 11.2 10.4 0 0.0% N/A N/A 0 0.0% N/A N/A 11.2 11.2 10.4
OS2 OS2 No 0.25 0.25 0.31 200 6.0% 12.4 12.4 11.5 0 0.0% N/A N/A 0 0.0% N/A N/A 12.4 12.4 11.5
OS3 OS3 No 0.25 0.25 0.31 150 8.0% 9.7 9.7 9.0 0 0.0% N/A N/A 150 3.0% 2.60 1.0 10.7 10.7 10.0
OS4 OS4 No 0.25 0.25 0.31 175 8.0% 10.5 10.5 9.7 770 0.5% 1.41 9.1 N/A N/A 19.6 19.6 18.8
OS5 OS5 No 0.95 0.95 1.00 130 4.0% 2.0 2.0 1.3 0 0.0% N/A N/A 0 0.0% N/A N/A 5.0 5.0 5.0
OS6 OS6 No 0.25 0.25 0.31 30 2.0% 6.9 6.9 6.4 460 1.4% 2.37 3.2 0 0.0% N/A N/A 10.1 10.1 9.6
OS7 OS7 No 0.95 0.95 1.00 20 2.0% 1.0 1.0 0.7 120 1.0% 2.00 1.0 0 0.0% N/A N/A 5.0 5.0 5.0
OS8 OS8 No 0.25 0.25 0.31 10 5.0% 2.9 2.9 2.7 0 0.0% N/A N/A 230 0.5% 1.06 3.6 6.6 6.6 6.3
PROPOSED TIME OF CONCENTRATION COMPUTATIONS
D. Weber
May 3, 2019
Design
Point
Sub-Basin
Overland Flow Gutter/Pipe Flow Swale Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
C Cf L
Ti
−
=
5/6/2019 12:59 PM D:\Projects\1257-001\Drainage\Hydrology\1257-001_Rational.xlsx\Tc
North Historic Basin 2.68 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 2.675 0.25 0.25 0.31 0%
South Historic Basin 0.53 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.535 0.25 0.25 0.31 0%
Total Existing Site 3.21 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 3.210 0.25 0.25 0.31 0%
A1 0.55 0.20 0.06 0.03 0.07 Clayey | Average 2% to 7% 0.201 0.68 0.68 0.84 59%
A2 0.25 0.07 0.00 0.00 0.07 Clayey | Average 2% to 7% 0.116 0.63 0.63 0.78 51%
A3 1.04 0.46 0.06 0.00 0.08 Clayey | Average 2% to 7% 0.437 0.66 0.66 0.82 57%
A4 0.31 0.12 0.08 0.00 0.10 Clayey | Average 2% to 7% 0.014 0.92 0.92 1.00 90%
A5 0.23 0.00 0.06 0.00 0.11 Clayey | Average 2% to 7% 0.065 0.75 0.75 0.94 64%
A6 0.10 0.00 0.01 0.00 0.07 Clayey | Average 2% to 7% 0.021 0.80 0.80 1.00 71%
UD1 0.11 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.109 0.25 0.25 0.31 0%
North Proposed Basin 2.60 0.85 0.26 0.03 0.50 Clayey | Average 2% to 7% 0.963 0.69 0.69 0.86 59%
B1 0.32 0.14 0.01 0.00 0.09 Clayey | Average 2% to 7% 0.073 0.79 0.79 0.99 74%
UD2 0.15 0.00 0.05 0.00 0.00 Clayey | Average 2% to 7% 0.103 0.48 0.48 0.60 30%
South Proposed Basin 0.47 0.14 0.06 0.00 0.09 Clayey | Average 2% to 7% 0.175 0.69 0.69 0.86 59%
Total Proposed Site 3.07 0.99 0.32 0.03 0.59 Clayey | Average 2% to 7% 1.138 0.69 0.69 0.86 59%
OS1 0.46 0.00 0.02 0.00 0.01 Clayey | Average 2% to 7% 0.423 0.30 0.30 0.38 7%
OS2 1.31 0.00 0.00 0.00 0.18 Clayey | Average 2% to 7% 1.128 0.35 0.35 0.44 13%
OS3 0.29 0.00 0.00 0.00 0.05 Clayey | Average 2% to 7% 0.248 0.36 0.36 0.45 14%
OS4 4.14 1.10 0.00 0.00 0.80 Clayey | Average 2% to 7% 2.235 0.57 0.57 0.72 44%
OS5 0.24 0.17 0.03 0.00 0.00 Clayey | Average 2% to 7% 0.036 0.84 0.84 1.00 84%
OS6 1.07 0.37 0.16 0.00 0.17 Clayey | Average 2% to 7% 0.369 0.71 0.71 0.89 62%
OS7 0.28 0.21 0.06 0.00 0.00 Clayey | Average 2% to 7% 0.005 0.94 0.94 1.00 96%
OS8 0.12 0.00 0.01 0.00 0.00 Clayey | Average 2% to 7% 0.114 0.31 0.31 0.39 8%
A1, A2, & OS1 (Rain Garden 1) 1.26 0.27 0.08 0.00 0.15 Clayey | Average 2% to 7% 0.764 0.53 0.53 0.66 38%
A1-A3 & OS1-OS2 3.61 0.73 0.14 0.00 0.42 Clayey | Average 2% to 7% 2.330 0.50 0.50 0.62 34%
OS3 & A6 0.40 0.00 0.01 0.00 0.12 Clayey | Average 2% to 7% 0.269 0.47 0.47 0.59 29%
OS3, OS4, & A6 4.48 1.10 0.01 0.00 0.92 Clayey | Average 2% to 7% 2.450 0.57 0.57 0.71 43%
OS5, OS7, & OS8 0.64 0.38 0.10 0.00 0.00 Clayey | Average 2% to 7% 0.155 0.78 0.78 0.98 74%
OS5-OS7 1.59 0.75 0.25 0.00 0.17 Clayey | Average 2% to 7% 0.410 0.77 0.77 0.96 71%
OS5-OS8 1.71 0.75 0.26 0.00 0.17 Clayey | Average 2% to 7% 0.523 0.74 0.74 0.92 67%
A3 & OS2 (Rain Garden 2) 2.35 0.46 0.06 0.00 0.27 Clayey | Average 2% to 7% 1.565 0.48 0.48 0.60 32%
A4-A6 (Rain Garden 3) 0.64 0.12 0.14 0.00 0.28 Clayey | Average 2% to 7% 0.100 0.84 0.84 1.00 78%
1. Table RO-11 | Rational Method Runoff Coefficients for Composite Analysis
PROPOSED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
5/6/2019 12:59 PM D:\Projects\1257-001\Drainage\Hydrology\1257-001_Rational.xlsx\Composite C