HomeMy WebLinkAboutLANDMARK APARTMENTS EXPANSION - PDP - PDP160013 - REPORTS - DRAINAGE REPORTPRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT
June 15, 2016
Landmark Apartments Expansion
Fort Collins, Colorado
Prepared for:
Summit Management Services
730 W. Market Street
Akron, Ohio 44303
330-535-7027
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.
RE: Preliminary Drainage and Erosion Control Report for
Landmark Apartments Expansion
Dear Staff:
Northern Engineering is pleased to submit this Preliminary 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.
Stephanie Thomas, PE
Project Engineer
Landmark Apartments Expansion
Preliminary Drainage Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ................................................................... 1
A. Location ....................................................................................................................................... 1
B. Description of Property ................................................................................................................ 1
C. Floodplain .................................................................................................................................... 3
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 ......................................................................................................................... 6
F. Floodplain Regulations Compliance .............................................................................................. 7
G. Modifications of Criteria .............................................................................................................. 7
IV. DRAINAGE FACILITY DESIGN .................................................................................... 7
A. General Concept .......................................................................................................................... 7
B. Low-Impact Development ............................................................................................................ 9
C. Specific Details ............................................................................................................................. 9
V. CONCLUSIONS ........................................................................................................ 9
A. Compliance with Standards .......................................................................................................... 9
B. Drainage Concept ........................................................................................................................ 9
References ....................................................................................................................... 10
APPENDICES:
APPENDIX A – Hydrologic Computations
APPENDIX B – Hydraulic Computations (NOT INCLUDED WITH PDP)
B.1 – Detention Ponds and Water Quality
B.2 – Storm Sewers (NOT INCLUDED WITH PDP)
B.3 – Inlets (NOT INCLUDED WITH PDP)
APPENDIX C – SWMM Modeling
APPENDIX D – Erosion Control Report
APPENDIX E – FEMA Firmette
APPENDIX F – LID Exhibit and Calculations
Landmark Apartments Expansion
Preliminary 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
Preliminary Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. 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. Bounded 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.
5. This site was originally platted as Young’s Creek.
B. Description of Property
1. The site is approximately 3.67 acres.
Landmark Apartments Expansion
Preliminary Drainage Report 2
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 and pervious pavers.
Landmark Apartments Expansion
Preliminary 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.
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.
Landmark Apartments Expansion
Preliminary Drainage Report 4
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 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. Though 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.
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 connection, associated grading, bridge, and storm
sewer outfalls.
Landmark Apartments Expansion
Preliminary Drainage Report 5
9. A bridge is planned over the drainage channel and floodway. This bridge deck will be
elevated above the base flood elevation. Abutments will be placed outside of the
floodway. No additional construction is planned in 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. 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. 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.
III. DRAINAGE DESIGN CRITERIA
A. Regulations
This project seeks provisions outside of the FCSCM to waive the detention requirement
within the Canal Importation Basin.
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.
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).
Providing pervious pavers to intercept runoff from roof drains. Pervious pavers reduce
runoff and also provide a lower overall imperviousness.
Utilizing large vegetated open areas throughout the site to reduce the overall
impervious area and to minimize directly connected impervious area (MDCIA).
Landmark Apartments Expansion
Preliminary Drainage Report 6
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 riprap 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 riprap 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. EPA Stormwater Management Model (SWMM) modeling was utilized to model peak
flow in the channel before and after development of this site.
4. 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.
5. 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
Landmark Apartments Expansion
Preliminary Drainage Report 7
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.
4. The Landmark Apartments Expansion project does not propose to modify the Canal
Importation Channel within the floodway limits. Limited grading within the southern
flood fringe is expected to accommodate the trail connection and grading to the
buildings. No grading is proposed in the floodway.
F. Floodplain Regulations Compliance
1. 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.
G. Modifications of Criteria
1. This project seeks provisions outside of the FCSCM to waive the detention
requirement within the Canal Importation Basin.
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 basins that flow directly to the canal by-passing any water quality
ponds. Basins designated OS are off-site basins that flow onto the subject property.
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, A2, A3, and A5 are conveyed to a rain
gardens sized for the respective basin. Runoff from Basin A4 is released unto pervious
pavers for LID and Water Quality Treatment. The rain gardens are sized for water
quality utilizing the Urban Drainage BMP spreadsheets.
Runoff produced during a 2-year event will ultimately be captured in inlets and
conveyed to the canal via storm sewer.
Landmark Apartments Expansion
Preliminary Drainage Report 8
Runoff produced during a 100-year event, up to the limits of inlet and storm sewer
capacities, will be captured by inlets and conveyed to the canal by storm sewer.
Additional flow above the inlet/sewer capacities will overtop sidewalks and berms at
rain garden locations and will flow directly into the canal.
Basin B
Basin B consists of proposed multi-family apartments, sidewalk, landscaped areas and
parking. Runoff is captured by a curb cut 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 2-year event will ultimately be treated for water quality and
release via storm sewer to the canal.
Runoff produced during a 100-year event, up to the limits of inlet and storm sewer
capacities, will be captured by inlets and conveyed to the canal by storm sewer.
Additional flow above the inlet/sewer capacities will overtop sidewalks and berms at
the rain garden location and will flow directly into the canal.
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.
These landscape buffers will provide some water quality treatment, but these areas
have not been included in the LID calculations. The majority of the UD basins consist
of landscaping. The concrete trail adjacent the drainage canal is the only impervious
area in the UD basin. Due to the proximity to the canal, this trail was unable to be
captured for additional water quality treatment. The trail is expected to cause very
little concern in regard to water quality.
Basin OS
Basin OS consists of proposed parking, proposed sidewalks, existing single family lots
and existing multifamily development.
Runoff from Basins OS-1, OS-2 and OS-3 will be passed through Basin A safely to the
canal without detention or water quality treatment. Rain gardens are not sized to treat
these areas.
Runoff from Basin OS-4 will continue through the existing parking lot to the sidewalk
chase in Basin A3. This chase will be sized to convey the 2-yr flows from Basin OS-4
along with the 2-yr flows from Basin A3. The rain garden is not sized to
accommodate runoff from Basin OS-4; therefore, flows from Basin OS-4 will safely
bypass to the canal.
Basin OS-5 consists of existing parking lot, proposed parking, and landscaped areas.
Runoff from Basin OS-5 will be captured and treated in the rain garden for Basin B.
The Basin B rain garden will be sized to treat the existing parking lot in Basin OS-5;
thereby, providing additional water quality treatment for existing impervious areas.
Basin OS-6 consists of the proposed cul-de-sac at the end of Hobbit Street. Runoff
from OS-6 will continue as historically to the drainage pan in Hobbit Street, and be
Landmark Apartments Expansion
Preliminary Drainage Report 9
conveyed to the canal via redefined swale. The swale will provide a certain amount of
LID and water quality treatment. This additional treatment has not been included in
the LID treatment calculations. The additional proposed impervious area is less than
the existing impervious area from Basin OS-5 that is now being treated for water
quality.
A full-size copy of the Drainage Plan can be found in the Map Pocket at the end of this
report.
B. Low-Impact Development
The site achieves the requirements set forth by the City of Fort Collins for Low Impact
Development (LID) by providing 88% of total impervious areas as being treated through
an LID treatment. Please see LID Exhibit located in the Appendix.
C. Specific Details
1. Additional details to be provided with the FDP submittal.
V. CONCLUSIONS
A. Compliance with Standards
1. This project seeks provisions outside of the FCSCM to waive the detention
requirement within the Canal Importation Basin.
2. Other than the detention requirement, drainage design proposed with the Landmark
Apartments Expansion project complies with the City of Fort Collins’ Stormwater
Criteria Manual.
3. 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.
4. The drainage plan and stormwater management measures proposed with the
development are compliant with all applicable State and Federal regulations governing
stormwater discharge.
5. The site achieves the requirements set forth by the City of Fort Collins for Low Impact
Development (LID).
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 impacted negatively 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. We have omitted any
runoff reduction that will manifest due to infiltration from rain gardens and pervious
pavers. This is currently unable to be calculated with available soils data.
Landmark Apartments Expansion
Preliminary Drainage Report 10
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.
APPENDIX A
HYDROLOGIC COMPUTATIONS
Landmark Apartments
CHARACTER OF SURFACE1:
Runoff
Coefficient
Percentage
Impervious Project: Landmark Apartments
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: S. Thomas
Asphalt ……....……………...……….....…...……………….………………………………………………………….. 0.95 100% Date: June 14, 2016
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 Cf
= 1.00 100-year Cf = 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
Pavers
(ac)
Area of
Roofs
(ac)
Area of
Single Family
(ac)
Area of
Multi Family
(ac)
Soil Type and Average Slope
Area of
Lawns and
Landscaping
(ac)
2-year
Composite Runoff
Coefficient
Landmark Apartments Expansion
Overland Flow, Time of Concentration:
Landmark Apartments
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
Tc
(min)
Landmark Apartments Expansion
Rational Method Equation: Project: Landmark Apartments
Calculations By:
Date:
Rainfall Intensity:
7 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
7 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
7 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
1 A1 0.62 7 7 5 0.62 0.62 0.77 2.60 4.44 9.95 0.99 1.69 4.75
2 A2 0.32 7 7 5 0.77 0.77 0.97 2.60 4.44 9.95 0.65 1.11 3.11
3 A3 0.37 6 6 5 0.79 0.79 0.98 2.76 4.72 9.95 0.81 1.38 3.64
4 A4 0.97 7 7 5 0.67 0.67 0.84 2.60 4.44 9.95 1.69 2.89 8.10
5 A5 0.18 7 7 5 0.73 0.73 0.91 2.60 4.44 9.95 0.35 0.59 1.66
7 UD-1 0.21 6 6 6 0.26 0.26 0.32 2.67 4.56 9.63 0.14 0.24 0.64
7 North Proposed Basin 2.68 12 12 9 0.66 0.66 0.82 2.05 3.50 8.21 3.61 6.17 18.08
6 B1 0.33 5 5 5 0.78 0.78 0.98 2.85 4.87 9.95 0.73 1.25 3.20
7 UD-2 0.18 7 7 7 0.43 0.43 0.53 2.52 4.31 9.06 0.20 0.33 0.88
7 UD-3 0.02 8 8 7 0.41 0.41 0.51 2.46 4.21 8.80 0.02 0.04 0.11
7 South Proposed Basin 0.53 6 6 5 0.64 0.64 0.81 2.76 4.72 9.95 0.95 1.62 4.29
1 OS-1 0.77 11 11 10 0.30 0.30 0.38 2.13 3.63 7.72 0.49 0.84 2.23
4 OS-2 0.24 12 12 11 0.30 0.30 0.38 2.05 3.50 7.42 0.15 0.25 0.67
4 OS-3 1.05 12 12 11 0.30 0.30 0.38 2.09 3.57 7.57 0.66 1.12 2.98
3 OS-4 1.21 13 13 10 0.46 0.46 0.58 2.02 3.45 7.72 1.13 1.94 5.43
6 OS-5 0.23 5 5 5 0.90 0.90 1.00 2.85 4.87 9.95 0.58 0.98 2.25
7 OS-6 0.24 7 7 7 0.92 0.92 1.00 2.60 4.44 9.06 0.57 0.98 2.16
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)
S. Thomas
Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8
June 14, 2016
Intensity,
i10
(in/hr)
C10
Area, A
(acres)
Intensity,
i2
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 WATER QUALITY POND SIZING
B.2 STORM SEWER (NOT INCLUDED)
B.3 INLET (NOT INCLUDED)
APPENDIX B.1
WATER QUALITY POND
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 51.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.510
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.17 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 26,861 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 374 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 = 250 sq ft
D) Actual Flat Surface Area AActual = sq ft
E) Area at Design Depth (Top Surface Area) ATop = sq ft
F) Rain Garden Total Volume VT= 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 = 374 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 0.27 in MINIMUM DIAMETER = 3/8"
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
June 14, 2016
Landmark Apartments Expansion
Basin A1
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.03 Rain Gardens -A1.xlsm, RG 6/14/2016, 1:37 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
NO SPRINKLER HEADS ON FLAT SURFACE
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
June 14, 2016
Landmark Apartments Expansion
Basin A1
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
UD-BMP_v3.03 Rain Gardens -A1.xlsm, RG 6/14/2016, 1:37 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 71.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.710
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.22 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 30,272 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 564 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 = 14 in 12-INCH MAXIMUM
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 = 376 sq ft
D) Actual Flat Surface Area AActual = sq ft
E) Area at Design Depth (Top Surface Area) ATop = sq ft
F) Rain Garden Total Volume VT= 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 = 564 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 0.33 in MINIMUM DIAMETER = 3/8"
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
June 14, 2016
Landmark Apartments Expansion
Basin A3
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.03 Rain Gardens -A3.xlsm, RG 6/14/2016, 1:38 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
NO SPRINKLER HEADS ON FLAT SURFACE
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
June 14, 2016
Landmark Apartments Expansion
Basin A3
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
UD-BMP_v3.03 Rain Gardens -A3.xlsm, RG 6/14/2016, 1:38 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 58.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.580
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.18 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 42,316 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 648 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 = 11 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 = 432 sq ft
D) Actual Flat Surface Area AActual = sq ft
E) Area at Design Depth (Top Surface Area) ATop = sq ft
F) Rain Garden Total Volume VT= 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 = 648 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 0.35 in MINIMUM DIAMETER = 3/8"
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
June 14, 2016
Landmark Apartments Expansion
Basin A4
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.03 Rain Gardens -A4.xlsm, RG 6/14/2016, 1:38 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
NO SPRINKLER HEADS ON FLAT SURFACE
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
June 14, 2016
Landmark Apartments Expansion
Basin A4
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
UD-BMP_v3.03 Rain Gardens -A4.xlsm, RG 6/14/2016, 1:38 PM
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 79.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.790
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.26 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 24,192 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 520 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 = 10 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 = 346 sq ft
D) Actual Flat Surface Area AActual = sq ft
E) Area at Design Depth (Top Surface Area) ATop = sq ft
F) Rain Garden Total Volume VT= 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 = 520 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 0.32 in MINIMUM DIAMETER = 3/8"
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
June 14, 2016
Landmark Apartments Expansion
Basin B1
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.03 Rain Gardens -B1.xlsm, RG 6/14/2016, 1:38 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
NO SPRINKLER HEADS ON FLAT SURFACE
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
June 14, 2016
Landmark Apartments Expansion
Basin B1
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
UD-BMP_v3.03 Rain Gardens -B1.xlsm, RG 6/14/2016, 1:38 PM
APPENDIX B.2
STORM SEWERS
APPENDIX B.3
INLETS
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
Preliminary 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 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
Project: Landmark Apartments
Calculations By:
Date:
L1 A1 26,861 51% 13,664
L2 A2 14,061 69% 9,730
A3 16,211 72% 11,696
Total L2 30,272 71% 21,425
L3 A4 42,316 58% 24,557
L4 A5 8,019 65% 5,224
L5 B1 14,355 72% 10,346
OS-5 9,837 89% 8,745
Total L5 24,192 79% 19,091
Total Treated 131,660 64% 83,961
UD-1 9,072 1% 78
UD-2 7,931 23% 1,804
UD-3 1,016 22% 220
OS-6 10,406 94% 9,746
Total Proposed
Untreated
28,425 42% 11,848
PROPOSED LID COMPUTATIONS
S. Thomas
June 14, 2016
PROPOSED LID TREATED AREA
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent Impervious
Impervious Area, A
(sf)
PROPOSED LID UNTREATED AREA
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent Impervious
Impervious Area, A
(sf)
374
1,023
13,664
564
564
21,425
648
648
24,557
520
700
19,091
5,224
1,544
3.4
160,085
95,809
71,857
83,961
88%
LID TREATMENT SUMMARY
Total Site Area (sf)
Total Proposed Impervious Area (sf)
75% Required Minimum Area to be Treated
Rain Garden - Basin L1
Total Volume Required (cf)
Total Volume Provided (cf)
Total Impervious Area Treated (sf)
Total Impervious Area Treated (sf)
Total Treated Impervious Area (sf)
Percent Impervious Treated by LID measures
Rain Garden - Basin L2
Total Volume Required (cf)
Total Volume Provided (cf)
Total Impervious Area Treated (sf)
Rain Garden - Basin L3
Total Volume Required (cf)
Total Volume Provided (cf)
Rain Garden - Basin L5
Total Volume Required (cf)
Total Volume Provided (cf)
Total Impervious Area Treated (sf)
Pavers - Basin L4
Total Impervious Area Treated (sf)
Total Paver Area (sf)
Run-on Ratio (x:1)
LID
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what's
R
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
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
( IN FEET )
0
1 INCH = 30 FEET
30 30 60 90
KEYMAP
X
X
X
X
X
X
X
LID TREATMENT SUMMARY
Total Volume Required (cf) 374
Total Volume Provided (cf) 1,023
Total Impervious Area Treated (sf) 13,664
Total Volume Required (cf) 564
Total Volume Provided (cf) 564
Total Impervious Area Treated (sf) 21,425
Total Volume Required (cf) 648
Total Volume Provided (cf) 648
Total Impervious Area Treated (sf) 24,557
Total Volume Required (cf) 520
Total Volume Provided (cf) 700
Total Impervious Area Treated (sf) 19,091
Total Impervious Area Treated (sf) 5,224
Total Paver Area (sf) 1,544
Run-on Ratio (x:1) 3.4
Total Site Area (sf) 160,085
Total Proposed Impervious Area (sf) 95,809
75% Required Minimum Area to be Treated by
LID measures (sf)
71,857
Total Treated Impervious Area (sf) 83,961
Percent Impervious Treated by LID measures 88%
MAP POCKET
DR1 – OVERALL DRAINAGE EXHIBIT
X
X
X
X
X
X X
X X
X X X X
X X X
X X X
X
X X
X X
X X X X X
X X
X X X
X X
X X
X X X X
X X
X X X
X X
X
X X
X X
X
X
X
NBERG DRIVE
TRACT C
YOUNG'S CREEK
OWNER: CITY OF FORT COLLINS
TRACT B
YOUNG'S CREEK
OWNER: CITY OF FORT COLLINS
LOT 1 LANDMARK
SUBDIVISION PUD
OWNER: LANDMARK HOUSING LLC
TRACT B PULSE PUD 1ST
OWNER: NORTH SPRING CREEK
LOT 6 SEAMAN
SUBDIVISION
OWNER: EWAN, JOHN L &
YVONNE S
OS-4
OS-3
OS-1
B1
UD-3
OS-5
OS-6
A1
A2
A3
A4
A5
1
2
4
5
6
EX. 10.00' SEWER EASEMENT
BOOK 1204, PAGE 344
EX. 15.00' UTILITY EASEMENT
REC. NO. 20040037611
EX. 90.00' STORM DRAINAGE EASEMENT
REC. NO. 86072551
CITY OF FORT COLLINS
100-YR FLOODWAY
CITY OF FORT COLLINS
CITY OF FORT COLLINS 100-YR FLOODPLAIN
100-YR FLOODPLAIN
RAIN GARDEN
RAIN GARDEN
RAIN GARDEN
INLET
INLET
INLET
DR1
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what's
R
CityDate Engineer
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
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
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
( IN FEET )
0
1 INCH = 30 FEET
30 30 60 90
KEYMAP
X
X
X
X
X
X
X
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100 2-yr
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
1 A1 0.62 0.62 0.77 6.9 5.0 0.99 4.75
2 A2 0.32 0.77 0.97 6.6 5.0 0.65 3.11
3 A3 0.37 0.79 0.98 5.7 5.0 0.81 3.64
4 A4 0.97 0.67 0.84 6.9 5.3 1.69 8.10
5 A5 0.18 0.73 0.91 6.8 5.0 0.35 1.66
7 UD-1 0.21 0.26 0.32 6.0 5.8 0.14 0.64
6 B1 0.33 0.78 0.98 5.0 5.0 0.73 3.20
7 UD-2 0.18 0.43 0.53 7.1 6.5 0.20 0.88
7 UD-3 0.02 0.41 0.51 7.7 7.2 0.02 0.11
1 OS-1 0.77 0.30 0.38 11.1 10.1 0.49 2.23
4 OS-2 0.24 0.30 0.38 12.1 11.1 0.15 0.67
4 OS-3 1.05 0.30 0.38 12.0 11.0 0.66 2.98
3 OS-4 1.21 0.46 0.58 12.7 10.4 1.13 5.43
6 OS-5 0.23 0.90 1.00 5.0 5.0 0.58 2.25
7 OS-6 0.24 0.92 1.00 7.0 7.0 0.57 2.16
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 "PRELIMINARY DRAINAGE AND EROSION CONTROL REPORT FOR
LANDMARK APARTMENTS EXPANSION BY NORTHERN ENGINEERING, DATED June 15,
2016 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
(in/hr)
100-yr
Tc
(min)
Q C f C i A
6/14/2016 1:36 PM D:\Projects\1257-001\Drainage\Hydrology\1257-001_Conceptual Hydrologic Calculations.xlsx\Runoff
10-yr
Tc
(min)
100-yr
Tc
(min)
7 North Historic Basin No 0.25 0.25 0.31 421 4.99% 19.1 19.1 17.7 N/A N/A N/A 331 1.18% 1.63 3.4 22.5 22.5 21.1
7 South Historic Basin No 0.25 0.25 0.31 85 5.76% 8.2 8.2 7.6 N/A N/A N/A 288 1.01% 1.51 3.2 11.4 11.4 10.8
7 Total Existing Site No 0.25 0.25 0.31 421 4.99% 19.1 19.1 17.7 N/A N/A N/A 331 1.18% 1.63 3.4 22.5 22.5 21.1
1A1 No 0.62 0.62 0.77 183 7.10% 6.3 6.3 4.3 N/A N/A N/A 97 3.61% 2.85 0.6 6.9 6.9 5.0
2A2 No 0.77 0.77 0.97 307 4.72% 6.4 6.4 2.6 N/A N/A N/A 42 4.05% 3.02 0.2 6.6 6.6 5.0
3A3 No 0.79 0.79 0.98 161 2.80% 5.3 5.3 2.0 106 4.06% 4.03 0.4 N/A N/A N/A 5.7 5.7 5.0
4A4 No 0.67 0.67 0.84 46 2.17% 4.2 4.2 2.6 365 1.23% 2.22 2.7 N/A N/A N/A 6.9 6.9 5.3
5A5 No 0.73 0.73 0.91 115 1.35% 6.8 6.8 3.5 N/A N/A N/A N/A N/A N/A 6.8 6.8 5.0
7 UD-1 No 0.26 0.26 0.32 20 19.00% 2.6 2.6 2.4 N/A N/A N/A 331 1.18% 1.63 3.4 6.0 6.0 5.8
7 North Proposed Basin No 0.66 0.66 0.82 307 4.72% 8.6 8.6 5.4 N/A N/A N/A 331 1.18% 1.63 3.4 12.0 12.0 8.8
6B1 No 0.78 0.78 0.98 24 7.50% 1.5 1.5 0.6 244 1.11% 2.10 1.9 N/A N/A N/A 5.0 5.0 5.0
7 UD-2 No 0.43 0.43 0.53 52 12.12% 4.0 4.0 3.3 N/A N/A N/A 288 1.01% 1.51 3.2 7.1 7.1 6.5
7 UD-3 No 0.41 0.41 0.51 25 11.20% 2.9 2.9 2.5 N/A N/A N/A 265 0.38% 0.92 4.8 7.7 7.7 7.2
7 South Proposed Basin No 0.64 0.64 0.81 52 12.12% 2.7 2.7 1.7 N/A N/A N/A 288 1.01% 1.51 3.2 5.9 5.9 5.0
1 OS-1 No 0.30 0.30 0.38 183 7.10% 10.5 10.5 9.5 N/A N/A N/A 97 3.61% 2.85 0.6 11.1 11.1 10.1
4 OS-2 No 0.30 0.30 0.38 199 8.09% 10.5 10.5 9.5 242 1.57% 2.51 1.6 N/A N/A N/A 12.1 12.1 11.1
4 OS-3 No 0.30 0.30 0.38 194 8.14% 10.4 10.4 9.4 242 1.57% 2.51 1.6 N/A N/A N/A 12.0 12.0 11.0
3 OS-4 No 0.46 0.46 0.58 307 4.72% 12.4 12.4 10.2 N/A N/A N/A 42 4.05% 3.02 0.2 12.7 12.7 10.4
6 OS-5 No 0.90 0.90 1.00 51 1.37% 2.5 2.5 1.2 328 1.13% 2.12 2.6 N/A N/A N/A 5.0 5.0 5.0
7 OS-6 No 0.92 0.92 1.00 N/A N/A N/A N/A 185 0.76% 1.74 1.8 402 0.74% 1.29 5.2 7.0 7.0 7.0
PROPOSED TIME OF CONCENTRATION COMPUTATIONS
S. Thomas
June 14, 2016
Design
Point
Sub-Basin
Overland Flow Gutter/Pipe Flow Swale Flow Time of Concentration
(Equation RO-4)
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
6/14/2016 1:36 PM D:\Projects\1257-001\Drainage\Hydrology\1257-001_Conceptual Hydrologic Calculations.xlsx\Tc
10-year
Composite Runoff
Coefficient
100-year
Composite Runoff
Coefficient
Composite
% Imperv.
North Historic Basin 2.68 0.00 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 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 0.00 Clayey | Average 2% to 7% 3.210 0.25 0.25 0.31 0%
A1 0.62 0.19 0.05 0.02 0.00 0.08 0.00 0.00 Clayey | Average 2% to 7% 0.277 0.62 0.62 0.77 51%
A2 0.32 0.06 0.03 0.16 0.00 0.00 Clayey | Average 2% to 7% 0.081 0.77 0.77 0.97 69%
A3 0.37 0.12 0.07 0.09 0.00 0.00 Clayey | Average 2% to 7% 0.087 0.79 0.79 0.98 72%
A4 0.97 0.39 0.12 0.08 0.00 0.00 Clayey | Average 2% to 7% 0.388 0.67 0.67 0.84 58%
A5 0.18 0.00 0.01 0.00 0.04 0.10 0.00 0.00 Clayey | Average 2% to 7% 0.031 0.73 0.73 0.91 65%
UD-1 0.21 0.00 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.206 0.26 0.26 0.32 1%
North Proposed Basin 2.68 0.75 0.28 0.02 0.04 0.51 0.00 0.00 Clayey | Average 2% to 7% 1.070 0.66 0.66 0.82 56%
B1 0.33 0.13 0.04 0.09 0.00 0.00 Clayey | Average 2% to 7% 0.080 0.78 0.78 0.98 72%
UD-2 0.18 0.00 0.05 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.136 0.43 0.43 0.53 23%
UD-3 0.02 0.00 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.018 0.41 0.41 0.51 22%
South Proposed Basin 0.53 0.13 0.09 0.00 0.00 0.09 0.00 0.00 Clayey | Average 2% to 7% 0.234 0.64 0.64 0.81 53%
Total Proposed Site 3.21 0.88 0.37 0.02 0.04 0.60 0.00 0.00 Clayey | Average 2% to 7% 1.304 0.66 0.66 0.82 55%
OS-1 0.77 0.00 0.00 0.00 0.77 0.00 Clayey | Average 2% to 7% 0.000 0.30 0.30 0.38 30%
OS-2 0.24 0.00 0.00 0.00 0.24 0.00 Clayey | Average 2% to 7% 0.000 0.30 0.30 0.38 30%
OS-3 1.05 0.00 0.00 0.00 1.05 0.00 Clayey | Average 2% to 7% 0.000 0.30 0.30 0.38 30%
OS-4 1.21 0.00 0.00 0.00 0.42 0.79 Clayey | Average 2% to 7% 0.000 0.46 0.46 0.58 43%
OS-5 0.23 0.13 0.07 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.018 0.90 0.90 1.00 89%
OS-6 0.24 0.17 0.06 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.009 0.92 0.92 1.00 94%
1. Table RO-11 | Rational Method Runoff Coefficients for Composite Analysis
PROPOSED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
6/14/2016 1:35 PM D:\Projects\1257-001\Drainage\Hydrology\1257-001_Conceptual Hydrologic Calculations.xlsx\Composite C