HomeMy WebLinkAboutTHE OVERLOOK - PDP - PDP160011 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT
March 30, 2016
The Overlook
Fort Collins, Colorado
Prepared for:
Stockover Investments, LLC
1806 Westview Road
Fort Collins, CO 80524
970-556-8132
Prepared by:
301 N. Howes Street, Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158
www.northernengineering.com
Project Number: 1174-001
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
The Overlook
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 The
Overlook 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
The Overlook
Preliminary Drainage Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ................................................................... 1
A. Location ....................................................................................................................................... 1
B. Description of Property ................................................................................................................ 2
C. Floodplain .................................................................................................................................... 3
II. DRAINAGE BASINS AND SUB-BASINS ....................................................................... 4
A. Major Basin Description ............................................................................................................... 4
B. Sub-Basin Description .................................................................................................................. 4
III. DRAINAGE DESIGN CRITERIA ................................................................................... 4
A. Regulations .................................................................................................................................. 4
B. Four Step Process ........................................................................................................................ 4
C. Development Criteria Reference and Constraints ......................................................................... 5
D. Hydrological Criteria .................................................................................................................... 5
E. Hydraulic Criteria ......................................................................................................................... 5
F. Floodplain Regulations Compliance .............................................................................................. 6
G. Modifications of Criteria .............................................................................................................. 6
IV. DRAINAGE FACILITY DESIGN .................................................................................... 6
A. General Concept .......................................................................................................................... 6
B. Specific Details ............................................................................................................................. 8
V. CONCLUSIONS ........................................................................................................ 8
A. Compliance with Standards .......................................................................................................... 8
B. Drainage Concept ........................................................................................................................ 8
References ......................................................................................................................... 9
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 – LID Exhibit
The Overlook
Preliminary Drainage Report
LIST OF TABLES AND FIGURES:
Figure 1 – Aerial Photograph ................................................................................................ 2
Figure 2– Proposed Site Plan ................................................................................................ 3
Figure 3 – Existing Floodplains ............................................................................................. 3
MAP POCKET:
DR1 - Drainage Exhibit
The Overlook
Preliminary Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. Located in the western half of Section 36, Township 7 North, Range 69 West of the
6th Prime Meridian, City of Fort Collins, County of Larimer, State of Colorado. The site
is a part of Lots 3 and 4, Observatory Heights.
3. Bounded to the north by First National Bank 1st PUD, to the west by John F. Kennedy
Parkway, to the south by Larimer County Canal, and to the east by a Private Drive
and Wharf at the Landings PUD Phase 2 Replat.
4. No significant offsite flows are directed into the site. The majority of off-site flows are
are prevented from entering the site by curb and gutter.
5. The Overlook was originally included in the Revised Master Plan and Supplemental
Drainage Report for Fort Collins National Bank PUD, prepared by Cornell Consulting
Company, Revised April 4, 1980.
The Overlook
Preliminary Drainage Report 2
B. Description of Property
1. The site is approximately 3.29 acres. Approximately 0.23 acres of the 3.29 acres is a
parcel of land already developed by the First National Bank PUD; hence this area is
included in the original drainage report and accounted for in the existing detention
pond.
Figure 1 – Aerial Photograph
2. The existing site is comprised of vacant land with natural grasses and vegetation. In the
northeast corner of the site exists an existing parking lot. This existing parking lot will
be demolished with this project and reconfigured in another location.
3. The majority of the site slopes to the north, while an eastern portion slopes to the east.
4. A report by Earth Engineering Consultants dated December 14, 2015 lists the soils for
the area as consisting of lean clay with varying amounts of silt and sand, and
sandstone/siltstone bedrock ranging from 2 to 7 feet below the ground surface. These
soils are classified as Hydrologic Soil Group C and have a low infiltration rate.
5. The proposed project site plan is composed of 2 buildings connected by a walkway.
These buildings are classified as mixed-use with commercial on the first floor and
residential above. This site will employ many water quality features and runoff
reduction facilities including rain gardens, landscape buffers, and extended detention
basins.
The Overlook
Preliminary Drainage Report 3
Figure 2– Proposed Site Plan
6. No existing irrigation facilities are known at this time.
7. The project site is within the First National Bank 1st PUD Master Plan. The proposed
project is not requesting a change in the land use.
C. Floodplain
1. The subject property is not located in a FEMA or City regulatory floodplain.
Figure 3 – Existing Floodplains
The Overlook
Preliminary Drainage Report 4
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The Overlook project is located within the Foothills Drainage Basin, which is located
between Prospect Road and Larimer #2 Canal from north to south and approximately
between Shields Street and Zeigler Road from west to east.
B. Sub-Basin Description
1. The western half of the property generally drains to the center of the property. From
there, flows are conveyed north in a swale to the access road bordering the north side
of the property. Flows within the access road are collected in an inlet at Horsetooth
Road. From there, flows are detained and released to Warren Reservoir.
2. The eastern half of the site generally sheet flows to the eastern boundary. From there,
flows sheet flow to backlot swales and drain pans routing flows around the existing
residential buildings. These flows are also collected in downstream inlets and
detained prior to be released to Warren Reservoir.
3. The proposed plan will generally detain developed flows and release to the detention
ponds north of the site, on the First National Bank property. These ponds have been
sized and included in the previous drainage report.
III. DRAINAGE DESIGN CRITERIA
A. Regulations
There are no optional provisions outside of the FCSCM proposed with The Overlook
project.
B. Four Step Process
The overall stormwater management strategy employed with The Overlook 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 planter boxes with a rain garden filter section at downspout locations from
the building to reduce runoff from the rooftops.
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; however, this
development will still generate stormwater runoff that will require additional BMPs and
water quality. The majority of stormwater runoff from the site will ultimately be
intercepted and treated in proposed water quality ponds.
The Overlook
Preliminary Drainage Report 5
Step 3 – Stabilize Drainageways
There are no major drainageways within the subject property. This property discharges to
existing detention ponds that have been designed to accommodate runoff from this project
as a part of the First National Bank 1st PUD Master Plan.
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 planter boxes for water treatment prior to flows entering the
extended detention basins.
Water Quality measures to protect and prolong the design life of the BMPs delineated
in Step 1.
C. Development Criteria Reference and Constraints
1. The proposed site is a part of the Revised Master Plan and Supplemental Drainage
Report for Fort Collins National Bank PUD, prepared by Cornell Consulting Company,
Revised April 4, 1980. This report states a release rate of 75% of the 2-year release.
This is less than the typical 2-year release requirement.
2. This site is subject to the LID requirements per the City of Fort Collins. Please see the
LID Exhibit located in the Appendix for calculations concerning LID treatment. The
site must either have the following:
75% of total new impervious areas must be treated through an LID (Low Impact
Development) treatment BMP, or
50% of total new impervious areas must be treated through an LID (Low Impact
Development) treatment BMP and 25% of new pavement shall be pervious.
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 SWMM modeling was utilized for detention storage calculations.
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. As previously noted, the subject property historically drains to the north and east.
The north flows are collected in an existing inlet on the private access drive at
Horsetooth Road then conveyed to an existing detention pond that releases to Warren
The Overlook
Preliminary Drainage Report 6
Reservoir.
2. All drainage facilities proposed with The Overlook 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 not located within a FEMA regulatory
floodplain.
4. The Overlook project does not propose to modify any natural drainageways.
F. Floodplain Regulations Compliance
1. As previously mentioned, all structures are located outside of any FEMA 100-year
floodplain, and thus are not subject to any floodplain regulations.
G. Modifications of Criteria
1. The proposed development is not requesting any modifications to criteria at this time.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of The Overlook drainage design are to maintain the allowable
storm runoffs as outlined within the Revised Master Plan and Supplemental Drainage
Report for Fort Collins National Bank PUD.
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. Historic runoff from The Overlook project site was evaluated. This evaluation provided
the historic 2-yr and 100-yr peak runoff rates for the existing site.
Basin H1
Basin H1 has an area of 0.23 acres. This basin contains a portion of the existing
private access road and an existing parking lot. The 2-yr and 100-yr peak runoff rates
from Basin H1 are 0.56 cfs and 2.27 cfs, respectively. Basin H1 has been accounted
for in previous subdivision drainage designs. Therefore, detention of this area is not
proposed.
Basin H2
Basin H2 has an area of 3.04 acres. This basin contains the majority of The Overlook
site. This existing basin contains vacant land. The 2-yr and 100-yr peak runoff rates
from Basin H2 are 1.05 cfs and 4.78 cfs, respectively.
4. The Overlook project divided the site into three (3) major drainage basins, designated
as Basins A, B, and UD. The project further subdivided Basin A in to seven (7) sub-
basins, Basin B into five (5) sub-basins, and Basin UD into five (5) sub-bains. The
drainage patterns anticipated for each basin and sub-basin are further described
below.
Basin A
Basin A is a total of 1.79 acres. Basin A consists of proposed building, parking lot,
sidewalk, landscape areas and rain gardens. Runoff from Basins A1, A2, A3 and A4
The Overlook
Preliminary Drainage Report 7
flow via overland flow and gutter to proposed rain gardens. Runoff from Basin A5 is
collected in trench drains and conveyed to Detention Pond A. Runoff from Basin A7 is
collected in a curb inlet and conveyed to Detention Pond A. Basin A7 contains
Detention Pond A. Total flow during a 100-yr storm from Basin A is calculated at a
routed 12.0 cfs.
Basin B
Basin B is a total of 1.04 acres. Basin B consists of proposed building, parking lot,
sidewalk, landscape areas and rain gardens. Runoff from Basins B1 and B2 are
collected in a storm pipe and curb inlet and are conveyed to a rain garden. Runoff
from Basins B3 and B4 are collected by curb inlets and are conveyed to Detention
Pond B. Basin B5 contains Detention Pond B. Total flow during a 100-yr storm from
Basin B is calculated at a routed 5.97 cfs.
Basin UD
Basin UD is a total of 0.47 acres. This basin is not detained and runoff will continues
to flow to historic capture points.
Basin UD1 and UD5 will continue, as historically, to overland flow to the adjacent The
Wharf Subdivision. Basins UD1 and UD5 have a percent impervious of 1% and 0%,
respectively. Runoff from these basins is considered negligible and similar to historic.
Basins UD2, UD3, and UD4 combine for a developed 54% impervious and total
combined area of 0.41 acres. These basins overland flow to either JFK Parkway or
the Private Access Road. Flows are conveyed along gutters to an inlet located at the
intersection of the Private Access Drive and Horsetooth Road. Total flows during a
100-yr storm from Basins UD2, UD3, and UD4 are a combined routed flow of 2.53
cfs. Historical 100-yr runoff from the existing parking lot (demolished with this
project), was calculated at 2.27 cfs. The proposed undetained runoff is 0.26 cfs more
than historic from the parking lot. Due to the increased runoff, the release rate from
the proposed detention ponds has been restricted to below 75% of 2-year historic
runoff rate.
5. Two (2) detention ponds are proposed with The Overlook development. Detention
Pond A is located within Basin A and Detention Pond B is located within Basin B.
Detention Pond B is routed through Detention Pond A. Release from Detention Pond
A is then conveyed to the existing detention pond on the Bank Property.
Detention Pond A
Detention Pond A has a total of 0.50 ac-ft storage available. 0.48 ac-ft of storage is
required with this project. Water quality control volume for Basin A is included in the
pond volume. Emergency Overflow from the pond is directed north to the existing
access road. Release rate from Pond A is proposed at 0.56 cfs.
Detention Pond B
Detention Pond B has a total of 0.33 ac-ft storage available. 0.25 ac-ft of storage is
required with this project. Water quality control volume for Basin B is included in the
pond volume. Emergency Overflow from the pond is directed east to The Wharf
development. 0.80 ft of freeboard is provided to prevent emergency overflow. The
existing The Wharf development should be able to accommodate any emergency
overflow from the site through a network of drainage pans. Release rate from Pond B
is proposed at 0.19 cfs.
The Overlook
Preliminary Drainage Report 8
Total developed 100-yr runoff from the site is a combination of the undetained flows
from Basins UD2, UD3, and UD4 plus the 0.56 cfs release from Pond A for a total
3.12 cfs. A combination of the Historic 100-yr runoff from Basin H1 plus the 75% of
the 2-yr runoff from Basin H2 totals 3.06 cfs. The proposed developed site is
expected to release 0.06 cfs more than the historic.
The additional 0.06 cfs is considered negligible. This additional flow does not
account for the different peaking times for the release rate from the pond and peak
runoff from the undetained basins. When peaking times are accounted for, this
additional flow is expected to disappear.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
B. Specific Details
1. Additional details to be provided with the FDP submittal.
V. CONCLUSIONS
A. Compliance with Standards
1. The drainage design proposed with The Overlook project complies with the City of
Fort Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with The Overlook project complies with the City of
Fort Collins’ Master Drainage Plan for the Foothills Drainage Basin.
3. There are no regulatory floodplains associated with the development.
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) by providing 76% total impervious areas as being treated through
an LID treatment. Please see LID Exhibit located in the Appendix.
B. Drainage Concept
1. The drainage design proposed with this project will effectively comply with previous
studies and will 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
2. The drainage design is anticipated to be very conservative. We have omitted any
runoff reduction that will manifest due to infiltration from rain gardens. This is
currently unable to be calculated with available soils data.
The Overlook
Preliminary Drainage Report 9
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. Subsurface Exploration Report, JFK Luxury Apartments Fort Collins, Colorado, December 14,
2015, Earth Engineering Consultants, Inc.(EEC Project No. 1152119).
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
The Overlook
CHARACTER OF SURFACE
1
:
Runoff
Coefficient
Percentage
Impervious Project: The Overlook
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: S. Thomas
Asphalt ……....……………...……….....…...……………….………………………………………………………….0.95 . 100% Date: March 29, 2016
Concrete …….......……………….….……….………………..….…………………………………………………….0.95 . 90%
Gravel (packed) ……….…………………….….…………………………..………………………………………….0.50 . 40%
Roofs …….…….………………..……………….……………………………………………………………………… 0.95 90%
Pavers…………………………...………………..……………………………………………………………………… 0.40 22%
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% 2-year Cf = 1.00 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
Pavers
(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.
H1 0.23 0.17 0.03 0.00 0.00 Clayey | Average 2% to 7% 0.029 0.86 0.86 1.00 86%
The Overlook
Overland Flow, Time of Concentration:
The Overlook
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)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
1 H1 No 0.86 0.86 1.00 104 2.40% 3.4 3.4 1.4 267 1.69% 2.60 1.7 5.1 5.1 5.0
2 H2 Yes 0.25 0.25 0.31 526 2.47% 27.0 27.0 25.0 0 N/A N/A N/A 27.0 27.0 25.0
* Time of Concentrations are calculated for the entire basin and used for both the Impervious and Pervious portions of the basins.
EXISTING TIME OF CONCENTRATION COMPUTATIONS
S. Thomas
The Overlook
Rational Method Equation: Project: The Overlook
Calculations By:
Date:
Rainfall Intensity:
1 H1 0.23 5 5 5 0.86 0.86 1.00 2.85 4.87 9.95 0.56 0.96 2.27
2 H2 3.04 27 27 25 0.25 0.25 0.31 1.39 2.37 5.04 1.05 1.80 4.78
EXISTING 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
March 29, 2016
Intensity,
i10
(in/hr)
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
Q = C f ( C )( i )( A )
3/29/2016 12:08 PM D:\Projects\1174-001\Drainage\Hydrology\1174-001_Existing_Rational_Calcs.xlsx\Runoff
The Overlook
CHARACTER OF SURFACE
1
:
Runoff
Coefficient
Percentage
Impervious Project: The Overlook
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: S. Thomas
Asphalt ……....……………...……….....…...……………….………………………………………………………….0.95 . 100% Date: March 29, 2016
Concrete …….......……………….….……….………………..….…………………………………………………….0.95 . 90%
Gravel (packed) ……….…………………….….…………………………..………………………………………….0.50 . 40%
Roofs …….…….………………..……………….……………………………………………………………………… 0.95 90%
Pavers…………………………...………………..……………………………………………………………………… 0.40 22%
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% 2-year Cf = 1.00 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
Pavers
(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.
A1 0.55 0.00 0.01 0.00 0.54 Clayey | Average 2% to 7% 0.000 0.95 0.95 1.00 90%
The Overlook
Overland Flow, Time of Concentration:
The Overlook
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)
2-yr
Tc
(min)
10-yr
Tc
(min)
100-yr
Tc
(min)
1 A1 No 0.95 0.95 1.00 91 12.42% 1.2 1.2 0.8 N/A N/A N/A 5.0 5.0 5.0
1 A2 No 0.31 0.31 0.39 97 0.82% 15.5 15.5 14.0 N/A N/A N/A 15.5 15.5 14.0
2 A3 No 0.91 0.91 1.00 157 5.57% 2.5 2.5 1.3 161 0.78% 1.76 1.5 5.0 5.0 5.0
3 A4 No 0.84 0.84 1.00 58 4.14% 2.3 2.3 0.9 170 0.35% 1.19 2.4 5.0 5.0 5.0
4 A5 No 0.88 0.88 1.00 33 0.91% 2.4 2.4 1.1 N/A N/A N/A 5.0 5.0 5.0
The Overlook
Rational Method Equation: Project: The Overlook
Calculations By:
Date:
Rainfall Intensity:
1 A1 0.55 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 1.49 2.54 5.46
1 A2 0.10 16 16 14 0.31 0.31 0.39 1.84 3.14 6.71 0.06 0.10 0.26
2 A3 0.47 5 5 5 0.91 0.91 1.00 2.85 4.87 9.95 1.23 2.10 4.71
3 A4 0.25 5 5 5 0.84 0.84 1.00 2.85 4.87 9.95 0.59 1.01 2.45
4 A5 0.10 5 5 5 0.88 0.88 1.00 2.85 4.87 9.95 0.26 0.45 1.03
5 A6 0.18 5 5 5 0.85 0.85 1.00 2.85 4.87 9.95 0.43 0.73 1.77
6 A7 0.14 5 5 5 0.25 0.25 0.31 2.85 4.87 9.95 0.10 0.17 0.43
TOTAL BASIN A TOTAL BASIN A 1.79 16 16 14 0.82 0.82 1.00 1.84 3.14 6.71 2.70 4.60 12.00
7 B1 0.32 7 7 5 0.63 0.63 0.79 2.60 4.44 9.95 0.53 0.90 2.53
8 B2 0.27 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.73 1.24 2.67
9 B3 0.12 5 5 5 0.88 0.88 1.00 2.85 4.87 9.95 0.30 0.51 1.18
10 B4 0.11 5 5 5 0.88 0.88 1.00 2.85 4.87 9.95 0.28 0.47 1.10
11 B5 0.22 16 16 15 0.29 0.29 0.36 1.84 3.14 6.62 0.11 0.19 0.51
TOTAL BASIN B TOTAL BASIN B 1.04 16 16 15 0.70 0.70 0.87 1.84 3.14 6.62 1.33 2.26 5.97
13 UD2 0.04 11 11 10 0.42 0.42 0.53 2.17 3.71 7.72 0.04 0.06 0.17
13 UD3 0.10 11 11 10 0.31 0.31 0.39 2.13 3.63 7.72 0.06 0.11 0.29
13 UD4 0.27 5 5 5 0.79 0.79 0.99 2.85 4.87 9.95 0.61 1.04 2.67
TOTAL BASIN UD2-UD4
TOTAL BASIN
UD2-UD4 0.41
11 11 10 0.64 0.64 0.80 2.13 3.63 7.72 0.56 0.95 2.53
12 UD1 0.03 5 5 5 0.26 0.26 0.32 2.85 4.87 9.95 0.02 0.03 0.08
12 UD5 0.03 5 5 5 0.25 0.25 0.31 2.85 4.87 9.95 0.02 0.03 0.09
TOTAL SITE TOTAL SITE 3.29 16 16 15 0.75 0.75 0.94 1.84 3.14 6.62 4.53 7.73 20.38
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)
APPENDIX B
HYDRAULIC COMPUTATIONS
B.1 DETENTION POND SIZING
B.2 STORM SEWER (NOT INCLUDED)
B.3 INLET (NOT INCLUDED)
APPENDIX B.1
DETENTION PONDS AND WATER QUALITY
The Overlook
1174-001
Fort Collins, Colorado
S. Thomas Date: 3/29/2016
Pond No.: Detention Pond A
A
100-yr
1.00 Approx. WQCV 2144 ft3
Area (A)= 1.79 acres Quantity Detention 18632 ft3 (per SWMM)
Max Release Rate = 0.56 cfs Total Volume 20776 ft3
Total Volume 0.48 ac-ft
Detention Pond Calculation | SWMM Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
3/29/2016 12:04 PM D:\Projects\1174-001\Drainage\Detention\1174-001__Detention Pond A.xlsm\FAA_CoFC idf_Pond 1
1174-001
Fort Collins, CO
S. Thomas Date: 3/29/2016
Pond No.: A
A7
100-yr
0.48 acft 5020.23 ft.
Design Storm WQCV
Required Volume= 2144 ft3 5014.87 ft.
Contour
Elevation (Y-
values)
Contour Area Depth
Column Not
Used
Incremental
Volume
Total Volume Total Volume
ft2 ft. ft3 ft3 ft3 acre-feet
5,013.20 7.7 0.00 0 0 0 0
5,013.40 244.02 0.20 20 20 0.00
5,013.60 803.69 0.20 99 119 0.00
5,013.80 1,333.72 0.20 211 330 0.01
5,014.00 1,511.37 0.20 284 614 0.01
5,014.20 1,628.45 0.20 314 928 0.02
5,014.40 1,749.36 0.20 337 1265 0.03
5,014.60 1,875.79 0.20 362 1627 0.04
5,014.80 2,009.54 0.20 388 2015 0.05
5,015.00 2,154.87 0.20 416 2431 0.06
5,015.20 2,237.34 0.20 439 2870 0.07
5,015.40 2,321.15 0.20 455 3325 0.08
5,015.60 2,423.05 0.20 474 3799 0.09
5,015.80 2,538.12 0.20 496 4295 0.10
5,016.00 2,662.90 0.20 520 4814 0.11
5,016.20 2,768.83 0.20 543 5357 0.12
5,016.40 2,883.13 0.20 565 5922 0.14
5,016.60 3,008.11 0.20 588 6510 0.15
5,016.80 3,136.88 0.20 614 7124 0.16
5,017.00 3,270.11 0.20 640 7764 0.18
5,017.20 3,388.00 0.20 665 8429 0.19
5,017.40 3,479.57 0.20 686 9115 0.21
5,017.60 3,564.42 0.20 704 9819 0.23
5,017.80 3,643.25 0.20 720 10539 0.24
5,018.00 3,719.24 0.20 735 11274 0.26
5,018.20 3,801.90 0.20 751 12026 0.28
5,018.40 3,885.54 0.20 768 12794 0.29
5,018.60 3,970.30 0.20 785 13578 0.31
5,018.80 4,059.01 0.20 802 14381 0.33
5,019.00 4,150.05 0.20 820 15201 0.35
5,019.20 4,261.66 0.20 840 16041 0.37
5,019.40 4,375.21 0.20 863 16904 0.39
5,019.60 4,495.27 0.20 886 17790 0.41
5,019.80 4,653.89 0.20 914 18704 0.43
5,020.00 4,838.55 0.20 948 19652 0.45
5,020.20 5,038.34 0.20 987 20639 0.47
5,020.40 5,254.04 0.20 1028 21667 0.50
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
The Overlook
1174-001
Fort Collins, Colorado
S. Thomas Date: 3/29/2016
Pond No.: Detention Pond B
B
100-yr
0.87 Approx. WQCV 906 ft3
Area (A)= 1.04 acres Quantity Detention 9892 ft3 (per SWMM)
Max Release Rate = 0.19 cfs Total Volume 10798 ft3
Total Volume 0.25 ac-ft
Detention Pond Calculation | SWMM Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
3/29/2016 12:06 PM D:\Projects\1174-001\Drainage\Detention\1174-001__Detention Pond B.xlsm\SWMM_CoFC idf_Pond 1
1174-001
Fort Collins, CO
S. Thomas Date: 3/29/2016
Pond No.: B
B
100-yr
0.25 acft 5021.19 ft.
Design Storm WQCV
Required Volume= 906 ft
3 5018.28 ft.
Contour
Elevation (Y-
values)
Contour Area Depth
Column Not
Used
Incremental
Volume
Total Volume Total Volume
ft
2
ft. ft
3
ft
3
ft
3
acre-feet
5,016.60 0.45 0.00 0 0 0 0
5,016.80 41.52 0.20 3 3 0.00
5,017.00 149.92 0.20 18 21 0.00
5,017.20 304.11 0.20 44 66 0.00
5,017.40 469.78 0.20 77 142 0.00
5,017.60 647.54 0.20 111 253 0.01
5,017.80 837.28 0.20 148 401 0.01
5,018.00 1,039.65 0.20 187 588 0.01
5,018.20 1,255.23 0.20 229 817 0.02
5,018.40 1,483.68 0.20 273 1091 0.03
5,018.60 1,726.73 0.20 320 1411 0.03
5,018.80 1,982.69 0.20 370 1781 0.04
5,019.00 2,249.92 0.20 423 2204 0.05
5,019.20 2,531.35 0.20 477 2681 0.06
5,019.40 2,830.40 0.20 535 3217 0.07
5,019.60 3,115.85 0.20 594 3810 0.09
5,019.80 3,393.85 0.20 650 4461 0.10
5,020.00 3,668.01 0.20 705 5166 0.12
5,020.20 3,958.49 0.20 762 5928 0.14
5,020.40 4,328.60 0.20 828 6755 0.16
5,020.60 4,729.31 0.20 905 7660 0.18
5,020.80 5,118.92 0.20 984 8643 0.20
5,021.00 5,472.22 0.20 1058 9701 0.22
5,021.20 5,791.41 0.20 1125 10826 0.25
5,021.40 6,080.43 0.20 1186 12012 0.28
5,021.60 6,351.35 0.20 1242 13254 0.30
5,021.80 6,595.94 0.20 1293 14547 0.33
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
APPENDIX B.2
STORM SEWERS
APPENDIX B.3
INLETS
APPENDIX C
SWMM MODELING
SUBB
SUBA
OUTLETB
OUTLETA
OUT1
PONDB
PONDA
GAGE1
02/26/2016 00:15:00
SWMM 5.1 Page 1
Time Series FC100-YR
Elapsed Time (hours)
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
10
9
8
7
6
5
4
3
2
1
0
SWMM 5.1 Page 1
System Precipitation (in/hr)
Elapsed Time (hours)
0 1 2 3 4 5 6 7
Precipitation (in/hr)
6.0
5.0
4.0
3.0
2.0
1.0
0.0
SWMM 5.1 Page 1
Subcatchment SUBB Runoff (CFS) Subcatchment SUBA Runoff (CFS)
Elapsed Time (hours)
0 1 2 3 4 5 6 7
Runoff (CFS)
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
SWMM 5.1 Page 1
Node PONDA Volume (ft3) Node PONDB Volume (ft3)
Elapsed Time (hours)
0 1 2 3 4 5 6 7
Volume (ft3)
20000.0
18000.0
16000.0
14000.0
12000.0
10000.0
8000.0
6000.0
4000.0
2000.0
0.0
SWMM 5.1 Page 1
S U M M A R Y S T A T I S T I C S
===================================
Object .............. Node PONDA
Variable ............. Volume (ft3)
Event Period ......... Variable
Event Statistic ...... Peak (ft3)
Event Threshold ...... Volume > 0.0000 (ft3)
Event Threshold ...... Separation Time >= 6.0 (hr)
Period of Record ..... 02/26/2016 to 02/26/2016
Number of Events ..... 1
Event Frequency*...... 1.000
Minimum Value ........ 18621.891
Maximum Value ........ 18621.891
Mean Value ........... 18621.891
Std. Deviation ....... 0.000
Skewness Coeff. ...... 0.000
*Fraction of all reporting periods belonging to an event.
SWMM 5.1 Page 1
S U M M A R Y S T A T I S T I C S
===================================
Object .............. Node PONDB
Variable ............. Volume (ft3)
Event Period ......... Variable
Event Statistic ...... Peak (ft3)
Event Threshold ...... Volume > 0.0000 (ft3)
Event Threshold ...... Separation Time >= 6.0 (hr)
Period of Record ..... 02/26/2016 to 02/26/2016
Number of Events ..... 1
Event Frequency*...... 1.000
Minimum Value ........ 9858.642
Maximum Value ........ 9858.642
Mean Value ........... 9858.642
Std. Deviation ....... 0.000
Skewness Coeff. ...... 0.000
*Fraction of all reporting periods belonging to an event.
SWMM 5.1 Page 1
Link OUTLETA Flow (CFS) Link OUTLETB Flow (CFS)
Elapsed Time (hours)
0 1 2 3 4 5 6 7
Flow (CFS)
0.6
0.4
0.2
0.0
SWMM 5.1 Page 1
Table - Node OUT1
Depth Total Inflow
Days Hours (ft) (CFS)
0 00:15:00 0.00 0.02
0 00:30:00 0.00 0.12
0 00:45:00 0.00 0.40
0 01:00:00 0.00 0.48
0 01:15:00 0.00 0.51
0 01:30:00 0.00 0.53
0 01:45:00 0.00 0.54
0 02:00:00 0.00 0.56
0 02:15:00 0.00 0.56
0 02:30:00 0.00 0.56
0 02:45:00 0.00 0.55
0 03:00:00 0.00 0.55
0 03:15:00 0.00 0.54
0 03:30:00 0.00 0.54
0 03:45:00 0.00 0.53
0 04:00:00 0.00 0.52
0 04:15:00 0.00 0.52
0 04:30:00 0.00 0.51
0 04:45:00 0.00 0.51
0 05:00:00 0.00 0.50
0 05:15:00 0.00 0.49
0 05:30:00 0.00 0.49
0 05:45:00 0.00 0.48
0 06:00:00 0.00 0.48
SWMM 5.1 Page 1
APPENDIX D
EROSION CONTROL REPORT
The Overlook
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
LID EXHIBIT
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
200 South College Avenue, Suite 010
Fort Collins, Colorado 80524
N O R T H E RN
PHONE: 970.221.4158 FAX: 970.221.4159
www.northernengineering.com
( IN FEET )
0
1 INCH = 30 FEET
30 30 60 90
KEYMAP
TOTAL SITE IMPERVIOUS AREA: 93,519 SF (2.15 AC) NOT INCLUDING EXISTING
IMPERVIOUS AREA
TOTAL RAIN GARDEN AREA: 1,593 SF
TOTAL RAIN GARDEN RUN-ON AREA (IMPERVIOUS ONLY): 71,487SF (1.64 AC)
OVERALL RAIN GARDEN TO RUN-ON RATIO: 45:1
TOTAL IMPERVIOUS AREA TREATED: 71,487 SF (1.64 AC)
PERCENT OF TOTAL IMPERVIOUS AREA TREATED: 76.4%
MAP POCKET
DR1 – OVERALL DRAINAGE EXHIBIT
HDR1
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
200 South College Avenue, Suite 010
Fort Collins, Colorado 80524
N O R T H E RN
PHONE: 970.221.4158 FAX: 970.221.4159
www.northernengineering.com
( IN FEET )
0
1 INCH = 30 FEET
30 30 60 90
KEYMAP
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
THE OVERLOOK BY NORTHERN ENGINEERING, DATED MARCH 30, 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
DRAINAGE SUMMARY TABLE
DESIGN
POINT
BASIN
ID
TOTAL
AREA
(acres)
C2 C100 2-yr
DR1
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what's
R
CityDate Engineer
Date
Date
Date
Date
Stormwater Utility
Parks & Recreation
Traffic Engineer
Date
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
200 South College Avenue, Suite 010
Fort Collins, Colorado 80524
N O R T H E RN
PHONE: 970.221.4158 FAX: 970.221.4159
www.northernengineering.com
( IN FEET )
0
1 INCH = 30 FEET
30 30 60 90
KEYMAP
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 0.55 0.95 1.00 5.0 5.0 1.49 5.46
1 A2 0.10 0.31 0.39 15.5 14.0 0.06 0.26
2 A3 0.47 0.91 1.00 5.0 5.0 1.23 4.71
3 A4 0.25 0.84 1.00 5.0 5.0 0.59 2.45
4 A5 0.10 0.88 1.00 5.0 5.0 0.26 1.03
5 A6 0.18 0.85 1.00 5.0 5.0 0.43 1.77
6 A7 0.14 0.25 0.31 5.0 5.0 0.10 0.43
7 B1 0.32 0.63 0.79 6.9 5.0 0.53 2.53
8 B2 0.27 0.95 1.00 5.0 5.0 0.73 2.67
9 B3 0.12 0.88 1.00 5.0 5.0 0.30 1.18
10 B4 0.11 0.88 1.00 5.0 5.0 0.28 1.10
11 B5 0.22 0.29 0.36 16.0 14.6 0.11 0.51
13 UD2 0.04 0.42 0.53 10.9 10.1 0.04 0.17
13 UD3 0.10 0.31 0.39 11.1 10.5 0.06 0.29
13 UD4 0.27 0.79 0.99 5.0 5.0 0.61 2.67
12 UD1 0.03 0.26 0.32 5.0 5.0 0.02 0.08
12 UD5 0.03 0.25 0.31 5.0 5.0 0.02 0.09
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
THE OVERLOOK BY NORTHERN ENGINEERING, DATED MARCH 30, 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
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
1 H1 0.23 0.86 1.00 5.1 5.0 0.56 2.27
2 H2 3.04 0.25 0.31 27.0 25.0 1.05 4.78
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
Sub-Basin(s)
S. Thomas
Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8
March 29, 2016
Intensity,
i10
(in/hr)
C10
Q = C f ( C )( i )( A )
3/29/2016 12:11 PM D:\Projects\1174-001\Drainage\Hydrology\1174-001_Proposed_Rational_Calcs.xlsx\Runoff
5 A6 No 0.85 0.85 1.00 95 4.21% 2.9 2.9 1.1 110 1.73% 2.63 0.7 5.0 5.0 5.0
6 A7 No 0.25 0.25 0.31 N/A N/A N/A N/A N/A N/A N/A 5.0 5.0 5.0
TOTAL BASIN A TOTAL BASIN A 15.5 15.5 14.0
7 B1 No 0.63 0.63 0.79 202 5.94% 6.9 6.9 4.6 N/A N/A N/A 6.9 6.9 5.0
8 B2 No 0.95 0.95 1.00 70 17.14% 0.9 0.9 0.6 N/A N/A N/A 5.0 5.0 5.0
9 B3 No 0.88 0.88 1.00 174 5.40% 3.1 3.1 1.4 16 3.13% 3.54 0.1 5.0 5.0 5.0
10 B4 No 0.88 0.88 1.00 138 5.22% 2.8 2.8 1.3 N/A N/A N/A 5.0 5.0 5.0
11 B5 No 0.29 0.29 0.36 179 2.07% 16.0 16.0 14.6 N/A N/A N/A 16.0 16.0 14.6
TOTAL BASIN B TOTAL BASIN B 16.0 16.0 14.6
13 UD2 No 0.42 0.42 0.53 47 4.26% 5.3 5.3 4.5 965 2.07% 2.88 5.6 10.9 10.9 10.1
13 UD3 No 0.31 0.31 0.39 47 4.26% 6.2 6.2 5.6 882 2.27% 3.01 4.9 11.1 11.1 10.5
13 UD4 No 0.79 0.79 0.99 17 4.71% 1.4 1.4 0.5 440 1.93% 2.78 2.6 5.0 5.0 5.0
TOTAL BASIN UD2-UD4 TOTAL BASIN UD2-UD4
11.1 11.1 10.5
12 UD1 No 0.26 0.26 0.32 21 7.62% 3.7 3.7 3.4 N/A N/A N/A 5.0 5.0 5.0
12 UD5 No 0.25 0.25 0.31 16 15.00% 2.6 2.6 2.4 N/A N/A N/A 5.0 5.0 5.0
TOTAL SITE TOTAL SITE 16.0 16.0 14.6
* Time of Concentrations are calculated for the entire basin and used for both the Impervious and Pervious portions of the basins.
PROPOSED TIME OF CONCENTRATION COMPUTATIONS
S. Thomas
March 29, 2016
Design
Point
Sub-Basin
Overland Flow Gutter/Pipe Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
3/29/2016 12:11 PM D:\Projects\1174-001\Drainage\Hydrology\1174-001_Proposed_Rational_Calcs.xlsx\Tc
A2 0.10 0.00 0.01 0.00 0.00 Clayey | Average 2% to 7% 0.091 0.31 0.31 0.39 7%
A3 0.47 0.37 0.07 0.00 0.00 Clayey | Average 2% to 7% 0.028 0.91 0.91 1.00 93%
A4 0.25 0.16 0.05 0.00 0.00 Clayey | Average 2% to 7% 0.037 0.84 0.84 1.00 83%
A5 0.10 0.00 0.09 0.00 0.00 Clayey | Average 2% to 7% 0.010 0.88 0.88 1.00 81%
A6 0.18 0.14 0.02 0.00 0.00 Clayey | Average 2% to 7% 0.027 0.85 0.85 1.00 84%
A7 0.14 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.140 0.25 0.25 0.31 0%
TOTAL BASIN A 1.79 0.66 0.25 0.00 0.54 Clayey | Average 2% to 7% 0.332 0.82 0.82 1.00 77%
B1 0.32 0.12 0.05 0.00 0.00 Clayey | Average 2% to 7% 0.147 0.63 0.63 0.79 53%
B2 0.27 0.00 0.00 0.00 0.27 Clayey | Average 2% to 7% 0.000 0.95 0.95 1.00 90%
B3 0.12 0.06 0.05 0.00 0.00 Clayey | Average 2% to 7% 0.012 0.88 0.88 1.00 86%
B4 0.11 0.07 0.03 0.00 0.00 Clayey | Average 2% to 7% 0.012 0.88 0.88 1.00 87%
B5 0.22 0.00 0.01 0.00 0.00 Clayey | Average 2% to 7% 0.205 0.29 0.29 0.36 5%
TOTAL BASIN B 1.04 0.25 0.14 0.00 0.27 Clayey | Average 2% to 7% 0.376 0.70 0.70 0.87 60%
UD2 0.04 0.00 0.01 0.00 0.00 Clayey | Average 2% to 7% 0.031 0.42 0.42 0.53 22%
UD3 0.10 0.00 0.01 0.00 0.00 Clayey | Average 2% to 7% 0.088 0.31 0.31 0.39 8%
UD4 0.27 0.14 0.07 0.00 0.00 Clayey | Average 2% to 7% 0.063 0.79 0.79 0.99 74%
TOTAL BASIN UD2-UD4 0.41 0.14 0.09 0.00 0.00 Clayey | Average 2% to 7% 0.181 0.64 0.64 0.80 54%
UD1 0.03 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.026 0.26 0.26 0.32 1%
UD5 0.03 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.028 0.25 0.25 0.31 0%
TOTAL SITE 3.29 1.06 0.48 0.00 0.81 Clayey | Average 2% to 7% 0.943 0.75 0.75 0.94 67%
Composite Runoff Coefficient with Adjustment
PROPOSED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
3/29/2016 12:10 PM D:\Projects\1174-001\Drainage\Hydrology\1174-001_Proposed_Rational_Calcs.xlsx\Composite C
March 29, 2016
Design
Point
Sub-Basin
Overland Flow Gutter/Pipe Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
3/29/2016 12:08 PM D:\Projects\1174-001\Drainage\Hydrology\1174-001_Existing_Rational_Calcs.xlsx\Tc
H2 3.04 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 3.038 0.25 0.25 0.31 0%
TOTAL SITE 3.27 0.17 0.03 0.00 0.00 Clayey | Average 2% to 7% 3.067 0.29 0.29 0.37 6%
1. Table RO-11 | Rational Method Runoff Coefficients for Composite Analysis
Composite Runoff Coefficient with Adjustment
EXISTING COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
3/29/2016 12:08 PM D:\Projects\1174-001\Drainage\Hydrology\1174-001_Existing_Rational_Calcs.xlsx\Composite C