HomeMy WebLinkAboutSCHRADER PROPANE OFFICE & MINOR VEHICLE REPAIR - PDP - PDP170015 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT
April 11, 2017
Schrader Propane Offices
Fort Collins, Colorado
Prepared for:
Schrader Propane
320 North College Avenue
Fort Collins, CO 80524
970-484-1225
Prepared by:
301 N. Howes Street, Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158
www.northernengineering.com
Project Number: 146-011
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
Schrader Propane Offices
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
Schrader Propane Offices 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
Schrader Propane Offices
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 ................................................................................... 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 .............................................................................................. 6
G. Modifications of Criteria .............................................................................................................. 6
IV. DRAINAGE FACILITY DESIGN .................................................................................... 7
A. General Concept .......................................................................................................................... 7
B. 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 – Erosion Control Report
APPENDIX D – LID Exhibit
APPENDIX E – References
Schrader Propane Offices
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
Schrader Propane Offices
Preliminary Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. Located in the northwest quarter of Section 1, 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 replat of Lots 15 and 16, Block 3, of Evergreen Park.
3. Bounded to the north by industrial lot, to the west by an existing alley, to the south by
undeveloped lot and transmission lines, and to the east by public right of way for Red
Cedar Circle.
4. No significant offsite flows are directed into the site. The majority of off-site flows are
are prevented from entering the site by existing topography.
5. Lots 15 and 16, Block 3 was originally included in the Master Storm Drainage and
Detention Plan for Evergreen Park, prepared by Cornell Consulting Company. The
Drainage Plan for the area has been revised per the North East College Corridor Outfall
Schrader Propane Offices
Preliminary Drainage Report 2
(NECCO) project commissioned by The City of Fort Collins and designed by Ayres
Associates.
6. The NECCO project overrides the existing drainage plan for the Evergreen Park
Subdivision.
B. Description of Property
1. The site is approximately 1.63 acres with 1.06 acres planned for development.
Figure 1 – Aerial Photograph
2. The existing site is comprised of undeveloped land with natural grasses and vegetation.
The southern boundary of the site contains a watermain and overhead electric lines.
3. The majority of the site slopes to the alley and Red Cedar Circle, while gently slopes to
the south. The site generally is very flat except along the eastern boundary.
4. A Web Soil Survey from the Natural Resources Conservation Service lists the soils for the
area as Hydrologic Soil Group C and have a low infiltration rate.
Schrader Propane Offices
Preliminary Drainage Report 3
5. The proposed project site plan is composed of 1 commercial building, four detention
ponds, concrete parking, concrete drives, and gravel yard/parking. This site will employ
water quality features and runoff reduction facilities including rain gardens, pervious
pavers and extended detention basins.
Figure 2– Proposed Site Plan
6. No existing irrigation facilities are known at this time.
7. The project site is within the Evergreen Park Subdivision Drainage Plan and the
NECCO drainage basin. 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.
Schrader Propane Offices
Preliminary Drainage Report 4
Figure 3 – Existing Floodplains
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The Schrader project is located within the Dry Creek Master Drainage Basin.
B. Sub-Basin Description
1. The existing western half of the property generally drains to the western alley. From
there, flows are conveyed along the alley to Conifer Street and to existing downstream
inlets.
2. The existing eastern half of the site generally drains to Red Cedar Circle. From there,
the flows are conveyed along the street curb and gutter to Conifer Street and to
existing downstream inlets.
3. The proposed plan will generally detain developed flows and release to the Red Cedar
Circle curbline.
Schrader Propane Offices
Preliminary Drainage Report 5
III. DRAINAGE DESIGN CRITERIA
A. Regulations
This project is requesting an increased release rate greater than the historic 2-yr. The
detention ponds are proposed to release into the existing street curbline. To create
detention on-site, the site driveway was built up in order to detain above the existing
curbline. As such, runoff from the proposed driveway was unable to be completely
detained and released at the 2-yr historic rate. A small pond is proposed to attenuate the
majority of the driveway flows.
B. Four Step Process
The overall stormwater management strategy employed with Schrader Propane Offices
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
Specific 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:
Routing flows, to the extent feasible, through StormTech Isolator chambers to remove
sediment migration.
Providing on-site detention to increase time of concentration, promote infiltration and
reduce loads on existing storm infrastructure.
Providing gravel parking area in the western portion of the site to reduce the overall
impervious area and to minimize directly connected impervious areas (MDCIA).
Step 2 – Implement BMPs That Provide a Water Quality Capture Volume (WQCV) with
Slow Release
The efforts taken in Step 1 will facilitate the reduction of runoff; however, this
development will still generate stormwater runoff that will require additional BMPs and
water quality. The LID strategies listed above will provide the water quality treatment
required for this project. Additional water quality for this site is provided by the NECCO
drainage project within the downstream extended detention ponds.
Step 3 – Stabilize Drainageways
There are no major drainageways within the subject property. This property discharges to
existing curb and gutter.
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.
Stormtech Underground Chambers 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.
Schrader Propane Offices
Preliminary Drainage Report 6
C. Development Criteria Reference and Constraints
1. The proposed site is a part of the NECCO project. This project requires this site to
discharge runoff from the 100-yr storm event at the historic 2-year release rate.
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 and maximum
release from the site during a 100-yr event.
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 west and east.
2. All drainage facilities proposed with the Schrader Propane Offices 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 Schrader Propane Offices 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. This project is requesting an increased release rate greater than the historic 2-yr.
Schrader Propane Offices
Preliminary Drainage Report 7
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of the Schrader drainage design are to minimize the developed
100-yr event discharge from the site and meet LID treatment requirements.
2. The site is constrained by a lack of accessible drainage outfall. The site has been
designed to store runoff above and release to the existing Red Cedar Circle curb and
gutter.
3. 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.
4. Historic runoff from Schrader Propane Offices project site was evaluated. This
evaluation provided the historic 2-yr, 10-yr, and 100-yr peak runoff rates for the
existing site.
The 1.06 acre site was evaluated to have a historic 2-yr, 10-yr and 100-yr runoff of
0.29 cfs, 0.50 cfs, and 1.32 cfs, respectively. This is higher than the published 0.20
cfs/acre for the Dry Creek Master Drainage Basin 2-yr historic.
5. The Schrader project is divided the site into five (5) major drainage basins, designated
as Basins A, B, C, D and UD.
Basin A
Basin A is a total of 0.62 acres. Basin A consists of proposed building, concrete
drive, gravel parking lot, and detention pond. Runoff from Basin A flows via sheet
flow to a drainage pan and captured in proposed inlets. Stormwater from Basin A is
detained in the combination of Ponds 1, 2 and 3. Basin A is treated for LID within
the underground Stormtech chambers. Total flow during a 100-yr storm from Basin A
is calculated at a 4.07 cfs.
Basin B
Basin B is a total of 0.19 acres. Basin B consists of proposed building, concrete
parking lot, concrete drive, curb and gutter, and landscaped areas. Runoff from
Basins B sheet flows to a curb and gutter and is collect in proposed inlets.
Stormwater from Basin B is detained in the combination of Pond 1, 2 and 3. Total
flow during a 100-yr storm from Basin B is calculated at 1.89 cfs.
Basin C
Basin C is a total of 0.05 acres. Basin C consists of Detention Pond 3. Runoff from
Basin C is detained in Detention Pond 3. Total flow during a 100-yr storm from Basin
C is calculated at 0.16 cfs.
Basin D
Basin C is a total of 0.11 acres. Basin D consists of concrete drive, proposed
building, curb and gutter and detention Pond 4. Runoff from Basin D sheet flows to a
trench drain and is conveyed to Detention Pond 4. Runoff from Basin D is detained in
Detention Pond 4. Total flow during a 100-yr storm from Basin D is calculated at
1.02
Schrader Propane Offices
Preliminary Drainage Report 8
Basin UD
Basin UD1 is a total of 0.06 acres. Basin UD1 consists of concrete drive, sidewalk
and landscaping. Due to the constrained outfall location, the site required to be graded
up from Red Cedar Circle. This area was unable to be captured on-site and conveyed
to the proposed detention ponds. This basin is not detained and runoff will continue to
flow to historic capture points. Total flow during a 100-yr storm from Basin UD1 is
calculated at 0.19 cfs.
Basin UD2 is a total of 0.03 acres. Basin UD2 consists of tie-in grading to existing
ground. This basin is not detained and runoff will continue to flow to historic capture
points. Total flow during a 100-yr storm from Basin UD2 is calculated at 0.06 cfs.
6. Four (4) detention ponds are proposed with the Schrader Propane Offices project.
Detention Pond 1 is located within Basin A. Detention Pond 2 is located within Basin
A. Detention Pond 3 is located within Basin C. Detention Pond 4 is located within
Basin D. Detention Pond 1, 2 and 3 essentially function as one pond connected by
storm sewer and rain garden. Detention Pond 1 will fill up during typical storm
events. Detention Pond 1 will back up into Detention Pond 2 and 3 during larger
storm events.
Detention Pond 1, 2, and 3 Combined
Detention Pond 1, 2 and 3 combined has a total of 0.22 ac-ft storage available. 0.18
ac-ft of storage is required with this project. Water quality control volume for Basin A,
B and C is not included in the pond volume since water quality has been provided via
LID measures upstream. Emergency Overflow from the pond is directed around the
parking lot curb return and down the concrete drive to the Red Cedar Circle. Release
rate from Pond 1, 2 and 3 is proposed at 0.13 cfs.
Detention Pond 4
Detention Pond 4 has a total of 872 cubic feet storage available. 788 cubic feet of
storage is required with this project. Water quality control volume for Basin D is not
included in the pond volume since water quality has been planned downstream in the
NECCO detention ponds. Emergency Overflow from the pond is directed down the
concrete drive to the Red Cedar Circle. Due to the grading constraint on-site, the
depth within Pond 4 was not enough for the amount of volume required for a 2-yr
historic release. The release rate from Detention Pond 4 was increased to fully utilize
the pond without spilling. Release rate from Pond 4 is proposed at 0.08 cfs.
7. Total Stormwater Release from Site
Rational Method/FAA Calculations
100-yr stormwater release from the site is a combination of release from Detention
Pond 1, 2 and 3 Combined (0.13 cfs), Detention Pond 4 (0.08 cfs), Basin UD1 100-
yr runoff (0.19 cfs) and Basin UD2 100-yr runoff (0.06 cfs). The total release from
the site during a 100-yr event, utilizing the rational method and FAA calculations,
would be a total 0.46 cfs.
The historic release from the site was calculated at 0.29 cfs. The proposed total
release from the site is approximately 0.17 cfs above the historic 2-yr release. This
proposed release would fall somewhere between a historic 2-yr and historic 10-yr
release.
Schrader Propane Offices
Preliminary Drainage Report 9
The additional 0.17 cfs release from the site is expected to have no negative impacts
on downstream facilities or structures. Runoff reduction provided by the underground
water quality chambers would help to mitigate this additional discharge from the site.
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 Schrader Propane Offices project complies
with the City of Fort Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with the Schrader Propane Offices complies with the
City of Fort Collins’ Master Drainage Plan for the Dry Creek Drainage Basin, with the
exception of an increased 100-yr release rate from the site.
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 83% 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 within the underground
Stormtech chambers. This is currently unable to be calculated with available soils
data.
Schrader Propane Offices
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. Master Storm Drainage and Detention Plan for Evergreen Park, Cornell Consulting Company.
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
Schrader
CHARACTER OF SURFACE
1
:
Runoff
Coefficient
Percentage
Impervious Project: Schrader
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: S. Thomas
Asphalt ……....……………...……….....…...……………….………………………………………………………….. 0.95 100% Date: June 27, 2016
Concrete …….......……………….….……….………………..….…………………………………………………….. 0.95 90%
Gravel (packed) ……….…………………….….…………………………..………………………………………….. 0.50 40%
Roofs …….…….………………..……………….……………………………………………………………………… 0.95 90%
Pavers…………………………...………………..……………………………………………………………………… 0.40 40%
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 C
f = 1.25
Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Table RO-11
Sub-Basin ID
Sub-
BasinBasin
Area
(ac)
Area of
Gravel
(ac)
Area of
Concrete
Pavement
(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
Schrader
Overland Flow, Time of Concentration:
Project: Schrader
Calculations By:
Gutter/Swale Flow, Time of Concentration: Date:
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 HISTORIC No 0.20 0.20 0.25 173 0.58% 26.6 26.6 25.1 0 n/a N/A N/A 26.6 26.6 25.1
* Time of Concentrations are calculated for the entire basin and used for both the Impervious and Pervious portions of the basins.
June 27, 2016
EXISTING TIME OF CONCENTRATION COMPUTATIONS
Schrader
Rational Method Equation: Project: Schrader
Calculations By:
Date:
Rainfall Intensity:
1 HISTORIC 1.06 27 27 25 0.20 0.20 0.25 1.39 2.37 4.98 0.29 0.50 1.32
June 27, 2016
Intensity,
i10
(in/hr)
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
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
Q = C f ( C )( i )( A )
6/27/2016 4:14 PM D:\Projects\146-011\Drainage\Hydrology\146-011_Existing Hydrologic Calculations.xlsx\Runoff
Schrader
CHARACTER OF SURFACE
1
:
Runoff
Coefficient
Percentage
Impervious Project: Schrader
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: S. Thomas
Asphalt ……....……………...……….....…...……………….………………………………………………………….. 0.95 100% Date: April 3, 2017
Concrete …….......……………….….……….………………..….…………………………………………………….. 0.95 90%
Gravel (packed) ……….…………………….….…………………………..………………………………………….. 0.50 40%
Roofs …….…….………………..……………….……………………………………………………………………… 0.95 90%
Pavers…………………………...………………..……………………………………………………………………… 0.40 40%
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 C
f = 1.25
Runoff Coefficients are taken from the Fort Collins Stormwater Criteria Manual, Table RO-11
Sub-Basin ID
Sub-
BasinBasin
Area
(ac)
Area of
Gravel
(ac)
Area of
Concrete
Pavement
(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
Schrader
Overland Flow, Time of Concentration:
Project: Schrader
Calculations By:
Gutter/Swale Flow, Time of Concentration: Date:
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 0.55 0.55 0.68 83 1.57% 8.1 8.1 6.1 0 n/a N/A N/A 8.1 8.1 6.1
1 A2 No 0.57 0.57 0.71 83 1.57% 7.8 7.8 5.8 0 n/a N/A N/A 7.8 7.8 5.8
2 B1 No 0.86 0.86 1.00 82 1.22% 3.9 3.9 1.6 31 0.65% 1.61 0.3 5.0 5.0 5.0
2 B2 No 0.93 0.93 1.00 82 1.22% 2.7 2.7 1.6 31 0.65% 1.61 0.3 5.0 5.0 5.0
Schrader
Rational Method Equation: Project: Schrader
Calculations By:
Date:
Rainfall Intensity:
1 A1 0.30 8 8 6 0.55 0.55 0.68 2.40 4.10 9.31 0.19 0.39 0.66 1.88
1 A2 0.32 8 8 6 0.57 0.57 0.71 2.46 4.21 9.63 0.22 0.45 0.77 2.19
2 B1 0.05 5 5 5 0.86 0.86 1.00 2.85 4.87 9.95 0.06 0.13 0.22 0.52
2 B2 0.08 5 5 5 0.93 0.93 1.00 2.85 4.87 9.95 0.11 0.21 0.37 0.80
2 B3 0.06 5 5 5 0.95 0.95 1.00 2.85 4.87 9.95 0.08 0.15 0.26 0.57
3 C 0.05 6 6 6 0.24 0.24 0.30 2.67 4.56 9.63 0.02 0.04 0.06 0.16
4 D 0.11 5 5 5 0.75 0.75 0.93 2.85 4.87 9.95 0.12 0.23 0.40 1.02
5 UD1 0.06 19 19 16 0.38 0.38 0.47 1.68 2.86 6.30 0.02 0.04 0.07 0.19
5 UD2 0.03 5 5 5 0.20 0.20 0.25 2.85 4.87 9.95 0.01 0.01 0.03 0.06
Flow,
QWQ
(cfs)
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
PROPOSED RUNOFF COMPUTATIONS
C100
Design
Point
Flow,
Q100
(cfs)
Flow,
Q2
(cfs)
10-yr
Tc
(min)
2-yr
Tc
(min)
C2
Flow,
Q10
(cfs)
Intensity,
i100
(in/hr)
Sub-Basin(s)
S. Thomas
Rainfall Intensity taken from the Fort Collins Stormwater Criteria Manual (FCSCM), Tables RA-7 and RA-8
April 3, 2017
Intensity,
i10
(in/hr)
C10
Q = C f ( C )( i )( A )
4/3/2017 3:06 PM D:\Projects\146-011\Drainage\Hydrology\146-011_Conceptual Hydrologic Calculations.xlsx\Runoff
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
Schrader
146-011
Fort Collins, Colorado
S. Thomas Date: 4/3/2017
Pond No.: Combined Pond 1, 2, and 3
A
100-yr
0.77 Approx. WQCV 0 ft
3
Area (A)= 0.86 acres Quantity Detention 7837 ft
3
(from FAA)
Max Release Rate = 0.13 cfs
Total Volume 0.18 ac-ft
Time Time
Ft.Collins
100-yr
Intensity
Q100
Inflow
(Runoff)
Volume
Outflow
(Release) Volume
Storage
Detention
Volume
(mins) (secs) (in/hr) (cfs) (ft
3
) (ft
3
) (ft
3
)
5 300 9.95 6.6 1977 39 1938
10 600 7.72 5.1 3067 78 2989
15 900 6.52 4.3 3886 117 3769
20 1200 5.60 3.7 4450 156 4294
25 1500 4.98 3.3 4947 195 4752
30 1800 4.52 3.0 5388 234 5154
35 2100 4.08 2.7 5674 273 5401
40 2400 3.74 2.5 5944 312 5632
45 2700 3.46 2.3 6186 351 5835
50 3000 3.23 2.1 6417 390 6027
55 3300 3.03 2.0 6621 429 6192
60 3600 2.86 1.9 6818 468 6350
65 3900 2.72 1.8 7025 507 6518
70 4200 2.59 1.7 7203 546 6657
75 4500 2.48 1.6 7390 585 6805
80 4800 2.38 1.6 7565 624 6941
85 5100 2.29 1.5 7734 663 7071
90 5400 2.21 1.5 7903 702 7201
95 5700 2.13 1.4 8040 741 7299
100 6000 2.06 1.4 8185 780 7405
105 6300 2.00 1.3 8344 819 7525
110 6600 1.94 1.3 8479 858 7621
115 6900 1.89 1.3 8636 897 7739
120 7200 1.84 1.2 8773 936 7837
Detention Pond Calculation | FAA Method
Project Number:
Schrader
146-011
Fort Collins Co
S. Thomas Date: 4/3/2017
Pond No.: Pond 1, 2 and 3 Combined
A
100-yr
0.18 acft 4976.07 ft.
Design Storm WQCV
Required Volume= 0 ft
3 n/a ft.
Contour
Elevation (Y-
values)
Contour Area Depth
Column Not
Used
Incremental
Volume
Total Volume Total Volume
ft
3
ft. ft
3
ft
3
ft
3
acre-feet
4,973.80 4 0.00 0 0 0 0
4,974.00 262 0.20 20 20 0.00
4,974.20 857 0.20 106 126 0.00
4,974.40 1309 0.20 215 341 0.01
4,974.60 1449 0.20 275 616 0.01
4,974.80 1546 0.20 299 915 0.02
4,975.00 1642 0.20 318 1234 0.03
4,975.20 1739 0.20 338 1571 0.04
4,975.40 3262 0.20 492 2063 0.05
4,975.60 6040 0.20 915 2978 0.07
4,975.80 9358 0.20 1526 4504 0.10
4,976.00 13065 0.20 2230 6734 0.15
4,976.20 16475 0.20 2945 9679 0.22
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
Schrader
146-011
Fort Collins, Colorado
S. Thomas Date: 4/3/2017
Pond No.: Pond 4
D
100-yr
0.93 Approx. WQCV 0 ft3
Area (A)= 0.11 acres Quantity Detention 789 ft3 (from FAA)
Max Release Rate = 0.08 cfs
Total Volume 0.02 ac-ft
Time Time
Ft.Collins
100-yr
Intensity
Q100
Inflow
(Runoff)
Volume
Outflow
(Release) Volume
Storage
Detention
Volume
(mins) (secs) (in/hr) (cfs) (ft3) (ft3) (ft3)
5 300 9.95 1.0 305 24 281
10 600 7.72 0.8 474 48 426
15 900 6.52 0.7 600 72 528
20 1200 5.60 0.6 687 96 591
25 1500 4.98 0.5 764 120 644
30 1800 4.52 0.5 832 144 688
35 2100 4.08 0.4 877 168 709
40 2400 3.74 0.4 918 192 726
45 2700 3.46 0.4 956 216 740
50 3000 3.23 0.3 991 240 751
55 3300 3.03 0.3 1023 264 759
60 3600 2.86 0.3 1053 288 765
65 3900 2.72 0.3 1085 312 773
70 4200 2.59 0.3 1113 336 777
75 4500 2.48 0.3 1142 360 782
80 4800 2.38 0.2 1169 384 785
85 5100 2.29 0.2 1195 408 787
90 5400 2.21 0.2 1221 432 789
95 5700 2.13 0.2 1242 456 786
100 6000 2.06 0.2 1264 480 784
105 6300 2.00 0.2 1289 504 785
110 6600 1.94 0.2 1310 528 782
115 6900 1.89 0.2 1334 552 782
120 7200 1.84 0.2 1355 576 779
Detention Pond Calculation | FAA Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
4/3/2017 3:04 PM D:\Projects\146-011\Drainage\Detention\146-011_Conceptual Detention Pond 4.xlsx\FAA_CoFC idf_Pond 1
Schrader
146-011
Fort Collins Co
S. Thomas Date: 4/3/2017
Pond No.: Pond 4
D
100-yr
788.85 ft
3 4975.13 ft.
Design Storm WQCV
Required Volume= 0 ft
3 n/a ft.
Contour
Elevation (Y-
values)
Contour Area Depth
Column Not
Used
Incremental
Volume
Total Volume Total Volume
ft
3
ft. ft
3
ft
3
ft
3
acre-feet
4,974.20 190 0.00 0 0 0 0
4,974.40 529 0.20 69 69 0.00
4,974.60 833 0.20 135 204 0.00
4,974.80 1062 0.20 189 393 0.01
4,975.00 1210 0.20 227 620 0.01
4,975.20 1317 0.20 252 872 0.02
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
1008
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 46.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.156 in
A = 0.62 ac
V = 0.0081 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
352 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
Schrader Propane Offices February 22, 2017
146-011 S. Thomas
Basin A1-A2
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
Basin A
WQ
0.69
5.00 min 291 ft3
0.62 acres 0.01 ac-ft
Max Release Rate = 0.20 cfs
Time (min) Ft Collins WQ
Intensity (in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 1.425 183 1.00 0.20 60 123
10 1.105 284 1.00 0.20 120 164
15 0.935 360 0.67 0.13 120 240
20 0.805 413 0.63 0.13 150 263
25 0.715 459 0.60 0.12 180 279
30 0.650 501 0.58 0.12 210 291
35 0.585 526 0.57 0.11 240 286
40 0.535 549 0.56 0.11 270 279
45 0.495 572 0.56 0.11 300 272
50 0.460 590 0.55 0.11 330 260
55 0.435 614 0.55 0.11 360 254
60 0.410 631 0.54 0.11 390 241
65 0.385 642 0.54 0.11 420 222
70 0.365 656 0.54 0.11 450 206
75 0.345 664 0.53 0.11 480 184
80 0.330 678 0.53 0.11 510 168
85 0.315 687 0.53 0.11 540 147
90 0.305 705 0.53 0.11 570 135
95 0.290 707 0.53 0.11 600 107
100 0.280 719 0.53 0.11 630 89
105 0.270 728 0.52 0.10 660 68
110 0.260 734 0.52 0.10 690 44
115 0.255 753 0.52 0.10 720 33
120 0.245 755 0.52 0.10 750 5
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
A =
Tc =
Project Location :
Design Point
C =
Design Storm
STORM TECH CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
146-011
Schrader Propane Offices
Project Number :
Vault ID
Total
Required
WQ Volume
(cf)
Flow,
WQ
(cfs)
Chamber
Type
Chamber Release
Ratea
(cfs)
Chamber
Volumeb
(cf)
Installed
Chamber w/
Aggregatec
(cf)
Mimimum No.
of Chambersd
Total Release
Ratee
(cfs)
Required
Storage
Volume by
FAA Method
(cf)
Mimimum
No. of
Chambersf
Storage
Provided
within the
Chambersg
(cf)
Total
Installed
System
Volumeh
(cf)
Basin A1, A2 352 0.42 SC-160 0.016 14.70 29.30 13 0.20 291 10 147 381
SC-740
a. Release rate per chamber, limited by flow through geotextile with accumulated sediment.
b. Volume within chamber only, not accounting for void spaces in surrounding aggregate.
c. Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit.
d. Number of chambers required to provide full WQCV within total installed system, including aggregate.
e. Release rate per chamber times number of chambers.
f. Number of chambers required to provide required FAA storage volume stored within the chamber only (no aggregate storage).
g. Volume provided in chambers only (no aggregate storage). This number must meet or exceed the required FAA storage volume.
h. System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required WQCV.
Chamber Configuration Summary
D:\Projects\146-011\Drainage\WatQual\Basin A WQ Chambers.xlsx
1008
Project Title Date:
Project Number Calcs By:
Client
Basins
0.8
WQCV = Watershed inches of Runoff (inches) 86.00%
a = Runoff Volume Reduction (constant)
i = Total imperviousness Ratio (i = Iwq/100) 0.296 in
A = 0.19 ac
V = 0.0047 ac-ft
V = Water Quality Design Volume (ac-ft)
WQCV = Water Quality Capture Volume (inches)
A = Watershed Area (acres)
204 cu. ft.
Drain Time
a =
i =
WQCV =
Figure EDB-2 - Water Quality Capture Volume (WQCV), 80th Percentile Runoff Event
Schrader Propane Offices February 22, 2017
146-011 S. Thomas
Basin B1-B3
0.231
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
WQCV (watershed inches)
Total Imperviousness Ratio (i = Iwq/100)
Water Quality Capture Volume
6 hr
12 hr
24 hr
40 hr
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
WQCV = a ( 0.91 i 3 - 1 . 19 i 2 + 0 . 78 i )
V * A
12
WQCV
÷
ø
Pond No :
Basin B
WQ
1.00
5.00 min 117 ft3
0.19 acres 0.00 ac-ft
Max Release Rate = 0.10 cfs
Time (min) Ft Collins WQ
Intensity (in/hr)
Inflow
Volume
(ft3)
Outflow
Adjustment
Factor
Qav
(cfs)
Outflow Volume
(ft3)
Storage
Volume
(ft3)
5 1.425 81 1.00 0.10 30 51
10 1.105 126 1.00 0.10 60 66
15 0.935 160 0.67 0.07 60 100
20 0.805 184 0.63 0.06 75 109
25 0.715 204 0.60 0.06 90 114
30 0.650 222 0.58 0.06 105 117
35 0.585 233 0.57 0.06 120 113
40 0.535 244 0.56 0.06 135 109
45 0.495 254 0.56 0.06 150 104
50 0.460 262 0.55 0.06 165 97
55 0.435 273 0.55 0.05 180 93
60 0.410 280 0.54 0.05 195 85
65 0.385 285 0.54 0.05 210 75
70 0.365 291 0.54 0.05 225 66
75 0.345 295 0.53 0.05 240 55
80 0.330 301 0.53 0.05 255 46
85 0.315 305 0.53 0.05 270 35
90 0.305 313 0.53 0.05 285 28
95 0.290 314 0.53 0.05 300 14
100 0.280 319 0.53 0.05 315 4
105 0.270 323 0.52 0.05 330 -7
110 0.260 326 0.52 0.05 345 -19
115 0.255 334 0.52 0.05 360 -26
120 0.245 335 0.52 0.05 375 -40
*Note: Using the method described in Urban Storm Drainage Criteria Manual Volume 2.
A =
Tc =
Project Location :
Design Point
C =
Design Storm
STORM TECH CALCULATION; MODIFIED FAA METHOD w/ Ft Collins IDF
Input Variables Results
Required Detention Volume
Fort Collins, Colorado
146-011
Schrader Propane Offices
Project Number :
Vault ID
Total
Required
WQ Volume
(cf)
Flow,
WQ
(cfs)
Chamber
Type
Chamber Release
Ratea
(cfs)
Chamber
Volumeb
(cf)
Installed
Chamber w/
Aggregatec
(cf)
Mimimum No.
of Chambersd
Total Release
Ratee
(cfs)
Required
Storage
Volume by
FAA Method
(cf)
Mimimum
No. of
Chambersf
Storage
Provided
within the
Chambersg
(cf)
Total
Installed
System
Volumeh
(cf)
Basin B1-B3 204 0.50 SC-160 0.016 14.70 29.30 7 0.11 117 5 74 205
SC-740
a. Release rate per chamber, limited by flow through geotextile with accumulated sediment.
b. Volume within chamber only, not accounting for void spaces in surrounding aggregate.
c. Volume includes chamber and void spaces (40%) in surrounding aggregate, per chamber unit.
d. Number of chambers required to provide full WQCV within total installed system, including aggregate.
e. Release rate per chamber times number of chambers.
f. Number of chambers required to provide required FAA storage volume stored within the chamber only (no aggregate storage).
g. Volume provided in chambers only (no aggregate storage). This number must meet or exceed the required FAA storage volume.
h. System volume includes total number of chambers, plus surrounding aggregate. This number must meet or exceed the required WQCV.
Chamber Configuration Summary
D:\Projects\146-011\Drainage\WatQual\Basin B WQ Chambers.xlsx
APPENDIX B.2
STORM SEWERS
APPENDIX B.3
INLETS
APPENDIX C
EROSION CONTROL REPORT
Schrader Propane Offices
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 D
LID EXHIBIT
Project: Schrader
Calculations By:
Date:
LID BASIN NODE Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area, A
(sf)
LID1 Basin A 26,921 46% 12,327
Basin B 8,290 86% 7,125
Total Treated 35,211 55% 19,452
LID BASIN NODE Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area, A
(sf)
LID2 C 2,383 5% 123
D 4,804 65% 3,146
UD1 2,781 21% 586
UD2 1,137 0% 0
Total Proposed
Untreated
11,105 35% 3,856
352
381
Basin B WQCV (ft3) 204
205
46,316
23,307
17,481
19,452
83%
Total Treated Impervious Area (sf)
Percent Impervious Treated by LID measures
Basin B Stormtech Chamber Volume (ft3)
Total Site Area (sf)
Total Proposed Impervious Area (sf)
LID TREATMENT SUMMARY
Stormtech Chambers - Basin LID1
Basin A WQCV (ft3)
Basin A Stormtech Chamber Volume (ft3)
75% Required Minimum Area to be Treated by LID
PROPOSED LID UNTREATED AREA
S. Thomas
April 3, 2017
PROPOSED LID TREATED AREA
PROPOSED LID COMPUTATIONS
APPENDIX E
REFERENCES
Hydrologic Soil Group—Larimer County Area, Colorado
(Schrader Propane Offices)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/6/2016
Page 1 of 4
4494830 4494840 4494850 4494860 4494870 4494880 4494890 4494900 4494910
4494830 4494840 4494850 4494860 4494870 4494880 4494890 4494900 4494910
493580 493590 493600 493610 493620 493630 493640 493650 493660 493670 493680 493690 493700
493580 493590 493600 493610 493620 493630 493640 493650 493660 493670 493680 493690 493700
40° 36' 18'' N
105° 4' 33'' W
40° 36' 18'' N
105° 4' 27'' W
40° 36' 15'' N
105° 4' 33'' W
40° 36' 15'' N
105° 4' 27'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 25 50 100 150
Feet
0 5 10 20 30
Meters
Map Scale: 1:608 if printed on A landscape (11" x 8.5") sheet.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at 1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil line
placement. The maps do not show the small areas of contrasting
soils that could have been shown at a more detailed scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more accurate
calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as of
the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Hydrologic Soil Group
Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
73 Nunn clay loam, 0 to 1
percent slopes
C 1.6 100.0%
Totals for Area of Interest 1.6 100.0%
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive precipitation
from long-duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly
wet. These consist mainly of deep, well drained to excessively drained sands or
gravelly sands. These soils have a high rate of water transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well drained
soils that have moderately fine texture to moderately coarse texture. These soils
have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of water
transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink-swell
potential, soils that have a high water table, soils that have a claypan or clay layer
at or near the surface, and soils that are shallow over nearly impervious material.
These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in their
natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff: None Specified
Hydrologic Soil Group—Larimer County Area, Colorado Schrader Propane Offices
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/6/2016
Page 3 of 4
Tie-break Rule: Higher
Hydrologic Soil Group—Larimer County Area, Colorado Schrader Propane Offices
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/6/2016
Page 4 of 4
MAP POCKET
DR1 – OVERALL DRAINAGE EXHIBIT
W
W W W
W W
W
W W W
W W
W
W W
X X
X X
X X
X X X
X X
X X
X X
X X
X X
X
X X
T
T
E
E
E E
E E
E
E
E
E
E
E
W
W W
W W W
W W
W W W
W W W
W W
E E
E E E E E
E E E E
E E E
E
E
CTV CTV CTV
CTV
CTV CTV
CTV CTV CTV CTV
CTV
CTV
CTV
CTV CTV
T T T T T T T T T T T T T T
SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS
SS SS SS SS
SS SS SS SS SS SS SS SS SS SS SS SS SS SS SS
OHE OHE OHE OHE OHE OHE OHE
OHE OHE OHE OHE OHE OHE OHE OHE OHE OHE OHE OHE OHE OH
E OHE OHE OHE OHE OHE OHE OHE OHE
S
W
EXISTING RIGHT
OF WAY
DETENTION POND 1
100-YR WSEL: 4976.07
RED CEDAR CIRCLE (60' ROW)
EXISTING 75' TRANSMISSION
EASEMENT
ALLEY (20' WIDE ASPHALT)
N:137303.74
E:195116.70
FND NAIL AND BRASS
TAG, LS 14823
N:137542.86
E:195119.39
FND NAIL AND BRASS
TAG, LS 14823
PROPOSED 3' ROW TO BE
DEDICATED TO THE CITY
PROPOSED 9'
PROPOSEDEASEMENT 8' UTILITY
UTILITY EASEMENT
ZERO CURB
WITH APRON
RUNDOWN
VERTICAL
CATCH
CURB
RETAINING
WALL
2.5' HEIGHT
MAX
TRENCH
DRAIN
2' DRAINAGE PAN
DETENTION POND
OUTFALL TO
PROPOSEDCURBLINE
OUTLET STRUCTURE
DETENTION POND
OUTFALL TO
CURBLINE WITH
SIDEWALK CHASE
PROPOSED
STORM SEWER
PROPOSED
STORM SEWER
STORM JUNCTION
AND WATER
QUALITY WEIR
PROPOSED AREA INLET
PROPOSED AREA INLET
STORMTECH
UNDERGROUND
WATER QUALITY
CHAMBERS
STORM JUNCTION
AND WATER
QUALITY WEIR
DETENTION POND 2
100-YR WSEL: 4976.07
PROPOSED INLET
PROPOSED INLET
RETAINING
WALL
1' HEIGHT
MAX
3
2
B1
C
UD1
UD2
A1
B2
A2
B3
D
1
PROPOSED INLET
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
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
( IN FEET )
0
1 INCH = 20 FEET
20 20 40 60
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
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
SCHRADER PROPANE OFFICES BY NORTHERN ENGINEERING, DATED April 11, 2017
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
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
1 A1 0.30 0.55 0.68 8.1 6.1 0.39 1.88
1 A2 0.32 0.57 0.71 7.8 5.8 0.45 2.19
2 B1 0.05 0.86 1.00 5.0 5.0 0.13 0.52
2 B2 0.08 0.93 1.00 5.0 5.0 0.21 0.80
2 B3 0.06 0.95 1.00 5.0 5.0 0.15 0.57
3 C 0.05 0.24 0.30 6.3 5.9 0.04 0.16
4 D 0.11 0.75 0.93 5.0 5.0 0.23 1.02
5 UD1 0.06 0.38 0.47 18.7 16.4 0.04 0.19
5 UD2 0.03 0.20 0.25 5.0 5.0 0.01 0.06
Detention Pond Summary | Proposed Condition
Pond 100-yr Volume
(feet cubed)
100-yr WSEL WQCV
(ft3)
WQCV
WSEL
Max
Release
(cfs)
1, 2, 3 Combined 7837.00 4976.07 n/a n/a 0.13
4 788.00 4975.13 n/a n/a 0.08
Survey Area Data: Version 10, Sep 22, 2015
Soil map units are labeled (as space allows) for map scales 1:50,000
or larger.
Date(s) aerial images were photographed: Apr 22, 2011—Apr 28,
2011
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor shifting
of map unit boundaries may be evident.
Hydrologic Soil Group—Larimer County Area, Colorado
(Schrader Propane Offices)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
6/6/2016
Page 2 of 4
Project Name :
Basin B1-B3
Page 1 of 1
Basin B WQ Chambers.xlsx
ö
ç
è
= æ
12 hr
Project Name :
Basin A1-A2
Page 1 of 1
Basin A WQ Chambers.xlsx
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ç
è
= æ
12 hr
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
4/3/2017 3:03 PM D:\Projects\146-011\Drainage\Detention\146-011_Conceptual Detention Pond 1 and 2.xlsx\FAA_CoFC idf_Pond 1
2 B3 No 0.95 0.95 1.00 62 1.61% 1.9 1.9 1.3 83 0.66% 1.63 0.8 5.0 5.0 5.0
3 C No 0.24 0.24 0.30 42 5.95% 5.7 5.7 5.3 65 0.77% 1.75 0.6 6.3 6.3 5.9
4 D No 0.75 0.75 0.93 62 2.02% 4.1 4.1 2.0 30 4.17% 4.08 0.1 5.0 5.0 5.0
5 UD1 No 0.38 0.38 0.47 200 1.25% 17.8 17.8 15.5 130 1.38% 2.35 0.9 18.7 18.7 16.4
5 UD2 No 0.20 0.20 0.25 10 25.00% 1.8 1.8 1.7 0 n/a N/A N/A 5.0 5.0 5.0
* Time of Concentrations are calculated for the entire basin and used for both the Impervious and Pervious portions of the basins.
April 3, 2017
PROPOSED TIME OF CONCENTRATION COMPUTATIONS
S. Thomas
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
-
=
4/3/2017 3:06 PM D:\Projects\146-011\Drainage\Hydrology\146-011_Conceptual Hydrologic Calculations.xlsx\Tc
100-year
Composite Runoff
Coefficient
Composite
% Imperv.
A1 0.30 0.23 0.02 0.00 0.00 0.02 Clayey | Flat <2% 0.022 0.55 0.55 0.68 45%
A2 0.32 0.25 0.00 0.03 0.00 0.03 Clayey | Flat <2% 0.017 0.57 0.57 0.71 47%
B1 0.05 0.00 0.03 0.00 0.00 0.01 Clayey | Flat <2% 0.007 0.86 0.86 1.00 79%
B2 0.08 0.00 0.04 0.02 0.00 0.03 Clayey | Flat <2% 0.002 0.93 0.93 1.00 88%
B3 0.06 0.00 0.04 0.00 0.00 0.02 Clayey | Flat <2% 0.000 0.95 0.95 1.00 90%
C 0.05 0.00 0.00 0.00 0.00 0.00 Clayey | Flat <2% 0.052 0.24 0.24 0.30 5%
D 0.11 0.00 0.05 0.03 0.00 0.00 Clayey | Flat <2% 0.030 0.75 0.75 0.93 65%
UD1 0.06 0.00 0.01 0.00 0.00 0.00 Clayey | Flat <2% 0.049 0.38 0.38 0.47 21%
UD2 0.03 0.00 0.00 0.00 0.00 0.00 Clayey | Flat <2% 0.026 0.20 0.20 0.25 0%
Basin A 0.62 0.48 0.02 0.04 0.00 0.04 Clayey | Flat <2% 0.039 0.56 0.56 0.69 46%
Basin B 0.19 0.00 0.11 0.02 0.00 0.05 Clayey | Flat <2% 0.009 0.92 0.92 1.00 86%
Basin A, B, C 0.86 0.48 0.13 0.06 0.00 0.09 Clayey | Flat <2% 0.099 0.62 0.62 0.77 52%
Total 1.06 0.48 0.20 0.09 0.00 0.09 Clayey | Flat <2% 0.204 0.60 0.60 0.76 50%
Composite Runoff Coefficient with Adjustment
PROPOSED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
4/3/2017 3:05 PM D:\Projects\146-011\Drainage\Hydrology\146-011_Conceptual Hydrologic Calculations.xlsx\Composite C
S. Thomas
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
-
=
6/27/2016 4:14 PM D:\Projects\146-011\Drainage\Hydrology\146-011_Existing Hydrologic Calculations.xlsx\Tc
100-year
Composite Runoff
Coefficient
Composite
% Imperv.
HISTORIC 1.06 0.00 0.00 0.00 0.00 0.00 Clayey | Flat <2% 1.063 0.20 0.20 0.25 0%
Composite Runoff Coefficient with Adjustment
EXISTING COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
6/27/2016 4:14 PM D:\Projects\146-011\Drainage\Hydrology\146-011_Existing Hydrologic Calculations.xlsx\Composite C