HomeMy WebLinkAboutMOUNTAIN'S EDGE (FORMERLY 2430 OVERLAND TRAIL - RESIDENTIAL) - PDP - PDP160045 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTPRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT
December 22, 2016
Mountain’s Edge
Fort Collins, Colorado
Prepared for:
Lorson South Land Corp
Jeff Mark
212 N. Wahsatch Avenue, Suite 301
Colorado Springs, CO 80903
719-635-3200
Prepared by:
301 N. Howes Street, Suite 100
Fort Collins, Colorado 80521
Phone: 970.221.4158
www.northernengineering.com
Project Number: 911-007
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
Mountain’s Edge
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
Mountain’s Edge 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
Mountain’s Edge
Preliminary Drainage Report
TABLE OF CONTENTS
I. GENERAL LOCATION AND DESCRIPTION ................................................................... 1
A. Location ....................................................................................................................................... 1
B. Description of Property ................................................................................................................ 1
C. Floodplain .................................................................................................................................... 3
II. DRAINAGE BASINS AND SUB-BASINS ....................................................................... 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 .............................................................................................................. 7
IV. DRAINAGE FACILITY DESIGN .................................................................................... 7
A. General Concept .......................................................................................................................... 7
B. Water Quality Treatment ........................................................................................................... 12
C. Specific Details ........................................................................................................................... 12
V. CONCLUSIONS ...................................................................................................... 12
A. Compliance with Standards ........................................................................................................ 12
B. Drainage Concept ...................................................................................................................... 12
References ....................................................................................................................... 13
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
Mountain’s Edge
Preliminary Drainage Report
LIST OF FIGURES:
Figure 1 – Aerial Photograph ................................................................................................ 2
Figure 2– Proposed Site Plan ................................................................................................ 3
Figure 3 – Existing Floodplains ............................................................................................. 4
LIST OF TABLES:
Table 1 - Historic Rational Basin Summary ............................................................................ 8
Table 2 - Proposed Rational Basin Summary .......................................................................... 9
Table 3 - Detention Pond Summary ..................................................................................... 10
Table 4 - Historic Stormwater Release and Allowable Developed Release.................................. 11
Table 5 - Proposed Stormwater Release ............................................................................... 11
MAP POCKET:
HDR1 – Historic Drainage Exhibit
DR1 - Drainage Exhibit
Mountain’s Edge
Preliminary Drainage Report 1
I. GENERAL LOCATION AND DESCRIPTION
A. Location
1. Vicinity Map
2. A tract located in the southwest quarter of Section 21, Township 7 North, Range 69
West of the 6th Prime Meridian, City of Fort Collins, County of Larimer, State of
Colorado.
3. Bounded to the north by private property, to the west by Overland Trail, to the east by
the Brown Farm Subdivision, and to the south by Drake Road.
4. Significant offsite flows are directed into the site through Dixon Creek. Dixon Creek
traverses the Mountain’s Edge site within the southern half. Additionally, two existing
culverts cross Overland Trail. These culverts convey stormwater runoff from the
property to the west. These off-site flows will be conveyed safely to ultimate outfall
locations within the Mountain’s Edge site.
5. The Mountain’s Edge property has not been studied with the previous proposals or
drainage studies.
B. Description of Property
1. The site is approximately 19.67 acres. This acreage includes a portion of the adjacent
Overland Trail Right of Way.
Mountain’s Edge
Preliminary Drainage Report 2
Figure 1 – Aerial Photograph
2. The existing site is generally comprised of vacant land with natural grasses and
vegetation. A house, gravel drive, and out-structures exist on the site. Off-site basins
include portions of adjacent Overland Trail.
3. The north half of the site is within the Canal Importation Basin. The northern 1/3 of the
site slopes to the northern property line. A portion of the center of the site slopes to the
east and overland flows across the existing single-family lots. The southern half of the
site is located within the Spring Creek Basin and slopes south to the Dixon Creek
drainage channel.
4. A report by Soilogic dated June 11, 2015 lists the soils for the area as consisting of
silty/clayey sand, gravel, cobble and sandy lean clay ranging from 9 to 15 feet below the
ground surface. A Web Soil Survey by the Natural Resources Conservation Service
indicates soils are classified as Hydrologic Soil Group B and have a moderate infiltration
rate. For this study, the soils were modeled as a Soil Group C with a slow infiltration
rate to account for the soil variations within the soil borings.
5. The proposed project site plan is composed of 19 townhome buildings, 17 single-family
lots, public local streets, sidewalk, private asphalt drives, and detention ponds.
6. This site will employ water quality features and runoff reduction facilities including rain
gardens, minimization of directed connected areas of imperviousness, grass swales with
infiltration section, grass buffers, and extended detention basins.
Mountain’s Edge
Preliminary Drainage Report 3
Figure 2– Proposed Site Plan
7. No existing irrigation facilities are known at this time.
8. The project site has not been a part of any known previous drainage study.
C. Floodplain
1. The subject property is not located in a FEMA or City regulatory floodplain.
Mountain’s Edge
Preliminary Drainage Report 4
Figure 3 – Existing Floodplains
II. DRAINAGE BASINS AND SUB-BASINS
A. Major Basin Description
1. The Mountain’s Edge project is located within two major drainage basins. The
northern half of the site is located within the Canal Importation Basin. The southern
half of the site is located within the Spring Creek Basin.
B. Sub-Basin Description
1. Historically, the stormwater runoff and off-site flows within the northern half of the
site generally flow in two directions. Stormwater runoff in the northern 1/3 of the site
generally flows to the northern boundary and is collected within a swale along the
access roadway on the adjacent property. Flows are conveyed to a City
owned/maintained channel in the Brown’s Farm 3rd Subdivision. Stormwater within
the remainder of the northern half of the site overland flows across the existing single-
family lots along the eastern boundary of the site.
2. Historically, stormwater runoff within the southern half of the site overland flows to
the Dixon Creek channel. Once collected in the channel it is conveyed under Drake
Road and ultimately outfalling to Spring Creek.
3. The proposed plan will generally detain developed flows and release to the historical
Mountain’s Edge
Preliminary Drainage Report 5
outfall locations at the historical flow rates.
III. DRAINAGE DESIGN CRITERIA
A. Regulations
There are no optional provisions outside of the FCSCM proposed with the Mountain’s Edge
project.
B. Four Step Process
The overall stormwater management strategy employed with the Mountain’s Edge 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:
Preserving natural areas south of the Dixon Creek. Minimizing site disturbance.
Proposed smaller private streets will allow for greater open space in the center of the
site. This approach allows for a lower percent imperviousness.
Providing vegetated open areas throughout the site to reduce the overall impervious
area and to minimize directly connected impervious areas (MDCIA).
Routing flows, to the extent feasible, through rain gardens, grass-lined channels or
grass buffers to provide additional infiltration.
Providing on-site detention to increase time of concentration, promote infiltration and
reduce loads on existing storm infrastructure.
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 rain gardens and extended detention basins. Water
quality for areas not routed through the rain gardens will be provided within the extended
detention basin volume.
Step 3 – Stabilize Drainageways
This property discharges detained stormwater to an existing drainage channel (Dixon
Creek). The proposed release from this property is expected to require erosion control
mats to stabilize the drainage way at the proposed pipe outfalls. Additionally, any
proposed 4:1 grading will be required to be stabilized with erosion control blankets along
the Dixon Creek. The majority of the Dixon Creek channel will remain undisturbed.
Step 4 – Implement Site Specific and Other Source Control BMPs.
The proposed project will improve upon site specific source controls compared to historic
conditions:
Trash receptacles within home will allow for the disposal of solid waste.
Rain Gardens and extended detention basins to provide for water treatment prior to
flows being released to existing drainageways and storm infrastructure.
Mountain’s Edge
Preliminary Drainage Report 6
Standard Operating Procedures (SOPs) for BMP maintenance of Rain Gardens,
Detention ponds, and associated drainage infrastructure to remove sediment
accumulation regularly.
C. Development Criteria Reference and Constraints
1. The proposed site is a part of the Foothills Drainage Basin. This basin requires a 2-
year historic stormwater release from the developed property.
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. Modified FAA Method calculations were 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 south.
2. All drainage facilities proposed with the Mountain’s Edge 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 Mountain’s Edge 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.
Mountain’s Edge
Preliminary Drainage Report 7
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 Mountain’s Edge drainage design are to maintain the
allowable storm runoffs as outlined within both the Spring Creek and Canal
Importation Basin master plans, and to maintain the historic discharge locations.
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 Mountain’s Edge project site was evaluated. This evaluation
provided the historic 2-yr and 100-yr peak runoff rates for the existing site and
historic discharge locations.
Basin HA
Basin HA is generally the southern half of the property. Stormwater within this portion
of the existing property generally flows via overland to Dixon Creek, from there it is
conveyed to Spring Creek through existing drainage infrastructure. Basin HA is within
the Spring Creek Basin.
Basin HA was subdivided into 3 sub-basins to further aid in design.
Basin HA1 contains the area of the site that will remain mostly undisturbed and
pervious. This area includes Dixon Creek.
Basin HA2 contains area north of Dixon Creek that will be developed with this project.
Basin HA3 contains existing Overland Trail Right of Way proposed to be detained with
this project.
Basin HB
Basin HB is generally the northern half of the property. Stormwater within this portion
of the existing property generally flows via overland the existing single-family
development or to a swale adjacent the existing access road, north of the property
boundary. These stormwater flows are conveyed through existing drainage
infrastructure to the detention ponds within the Brown’s Farm Subdivision. Basin HB
is within the Canal Importation Basin.
Basin HB was subdivided into 3 sub-basins to further aid in design.
Basin HB1 contains the northern 1/3 of the property. This area generally drains to the
northern property line and is collected in a swale along the off-site access road. From
there, flows are conveyed to a City owned and maintained drainage easement through
the Brown’s Farm Subdivision.
Mountain’s Edge
Preliminary Drainage Report 8
Basin HB2 contains existing Overland Trail Right of Way proposed to be detained with
this project.
Basin HB3 contains a portion of the property that generally flows via overland to the
eastern boundary. Stormwater from this location historically flows through the
adjacent single-family lots to Compass Court.
Table 1 - Historic Rational Basin Summary
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 HA1 4.07 0.25 0.31 14.3 13.9 1.96 8.68
1 HA2 4.18 0.25 0.31 31.8 29.9 1.31 5.95
1 HA3 0.33 0.57 0.71 24.0 19.4 0.27 1.33
2 HB1 5.60 0.25 0.31 21.4 20.3 2.18 9.80
2 HB2 0.47 0.57 0.71 15.9 13.5 0.49 2.29
3 HB3 4.66 0.25 0.31 37.2 34.5 1.32 6.06
4. The Mountain’s Edge project divided the site into six (6) major drainage basins,
designated as Basins A, B, C, D, OS and UD. The drainage patterns anticipated for
each basin and sub-basin are further described below.
Basin A
Basin A consists of proposed single-family attached buildings, single-family lots,
sidewalk, roadways, landscape areas and Detention Pond 1. Basin A is subdivided
into 3 sub-basins (A1-A3). Runoff from Basins A1-A3 is detained in Detention Pond
1. Stormwater runoff within Basin A2 is treated for water quality and LID in Rain
Garden 1. Stormwater runoff from Basin A1 and A3 is treated for water quality within
Detention Pond 1. LID treatment for Basin A3 is provided through grass buffers and
grass swales.
Basin B
Basin B consists of proposed single-family attached buildings, single-family lots,
sidewalk, roadways, landscape areas and Detention Pond 2. Basin B is subdivided
into 5 sub-basins (B1-B5). Runoff from Basins B1-B5 is detained in Detention Pond
2. Stormwater runoff for Basins B1-B5 will be treated for water quality within
Detention Pond 2. Stormwater runoff from Basins B1, B2 and B5 is treated for LID
with grass buffers and grass-lined swale with infiltration section. Off-site stormwater
from an existing culvert under Overland Trail, within Basin B1, will be safely routed
through Detention Pond 2 undetained.
Basin C
Basin C consists of proposed single-family attached buildings, sidewalk, roadways,
landscape areas and Detention Pond 3. Basin C is subdivided into 2 sub-basins (C1-
C2). Runoff from Basins C1-C2 is detained in Detention Pond 3. Stormwater runoff
for Basins C1-C2 will be treated for water quality within Detention Pond 3. No LID
treatment is planned for Basin C. Off-site stormwater from an existing culvert under
Mountain’s Edge
Preliminary Drainage Report 9
Basin D
Basin D consists of proposed single-family attached buildings, single-family lots,
sidewalk, roadways, landscape areas and Detention Pond 4. Basin D is subdivided
into 5 sub-basins (D1-D5). Runoff from Basins D1-D5 is detained in Detention Pond
4. Stormwater runoff for Basins D1-D5 will be treated for water quality and LID
within Rain Garden 2. No additional water quality treatment is planned within
Detention Pond 4.
Basin OS
Basin OS1 consists of open space and Dixon Creek. No detention is proposed for this
basin as it is not being developed and generally will remain undisturbed. Some
grading is proposed within this basin to accommodate Detention Pond 4.
Basin UD
Basin UD1 consists of proposed single-family lots, sidewalk, and roadways. Runoff
from Basin UD1 will not be detained. Stormwater runoff for Basin UD1 generally will
be conveyed through existing single-family lots. These existing single-family lots will
generally function as grass buffers and thereby provide LID treatment.
Table 2 - Proposed Rational Basin Summary
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 1.74 0.63 0.79 7.4 5.7 2.77 13.25
2 A2 1.48 0.77 0.96 5.0 5.0 3.26 14.24
3 A3 2.23 0.44 0.55 9.7 8.9 2.20 10.00
4 B1 0.47 0.84 1.00 6.1 5.0 1.04 4.63
5 B2 0.57 0.55 0.69 6.2 5.4 0.84 3.93
6 B3 1.27 0.80 1.00 5.0 5.0 2.90 12.67
7 B4 0.23 0.60 0.75 6.5 5.0 0.35 1.70
8 B5 0.86 0.27 0.34 12.7 12.0 0.47 2.10
9 C1 0.36 0.63 0.79 5.0 5.0 0.65 2.84
10 C2 0.48 0.43 0.54 5.9 5.1 0.58 2.62
11 D1 0.33 0.85 1.00 5.9 5.0 0.76 3.24
11 D2 2.05 0.73 0.91 5.0 5.0 4.24 18.52
12 D3 0.98 0.72 0.90 6.3 5.0 1.89 8.79
13 D4 0.66 0.60 0.74 5.1 5.0 1.12 4.87
14 D5 1.38 0.36 0.45 9.9 9.2 1.11 4.93
15 UD1 0.49 0.36 0.45 11.9 10.5 0.37 1.67
16 OS1 4.07 0.25 0.31 14.3 13.9 1.96 8.68
5. Four (4) detention ponds are proposed with the Mountain’s Edge development. These
ponds will restrict all runoff from the site to historic 2-yr flowrate based on the master
drainage basins, Spring Creek Basin and Canal Importation Basin.
Mountain’s Edge
Preliminary Drainage Report 10
Detention Pond 1
Detention Pond 1 detains developed runoff from Basin A. Detention Pond 1 has a
total 3.34 feet of freeboard from the 100-yr WSEL to the lowest proposed top of
foundation. Additionally, the emergency spill location is 1.58 feet below the lowest
proposed top of foundation. Water Quality is proposed within the pond volume
through an approved outlet structure.
Detention Pond 2
Detention Pond 2 detains developed runoff from Basin B. All minimum opening
elevations (MOEs) will need to be set at least 1 ft above the 100-yr WSEL with final
design. Water Quality is proposed within the pond volume through an approved outlet
structure. Additionally, Pond 2 will be designed to pass off-site flow safely through
the pond undetained.
Detention Pond 3
Detention Pond 3 detains developed runoff from Basin C. Detention Pond 3 has a
total 3.00 feet of freeboard from the 100-yr WSEL to the lowest proposed top of
foundation. The emergency spill for Pond 3 will be directed through an emergency
spill weir designed with final design. Water Quality is proposed within the pond
volume through an approved outlet structure. Additionally, Pond 3 will be designed to
pass off-site flow safely through the pond undetained.
Detention Pond 4
Detention Pond 4 detains developed runoff from Basin D. Detention Pond 4 has a
total 2.40 feet of freeboard from the 100-yr WSEL to the lowest proposed top of
foundation. The emergency spill for Pond 4 will be directed through an emergency
spill weir designed with final design. Water Quality is proposed within the pond
volume through an approved outlet structure.
Table 3 - Detention Pond Summary
Detention Pond Summary | Proposed Condition
Pond
100-yr
Volume
(ac-ft)
100-yr
WSEL
WQCV
(ft3)
WQCV WSEL
Max
Release
(cfs)
1 1.19 5144.86 2,814 5142.63 0.60
2 0.50 5139.56 2,684 5137.73 2.30
3 0.15 5145.28 513 5143.14 0.20
4 1.17 5142.81 863 5137.48 0.80
Mountain’s Edge
Preliminary Drainage Report 11
Total Stormwater Release from Site
The total allowable 100-yr release from the site was evaluated based on historic
Basins HA and HB. These basins correlate with the Spring Creek Basin and Canal
Importation Basin, respectively. The allowable release for the Spring Creek Basin is a
summation of the 100-yr historic runoff from Basin HA1 and the 2-yr historic runoff
from Basins HA2 and HA3. The allowable release for the Canal Importation Basin is a
summation of the 2-yr historic runoff from Basins HB1-HB3.
Table 4 - Historic Stormwater Release and Allowable Developed Release
Historic Stormwater Release
Allowable
Developed 100-
yr Release (cfs)
Pond/ Basin
2-yr Flow
(cfs)
100-yr Flow
(cfs)
HA1 1.96 8.68 8.68
HA2 1.31 5.95 1.31
HA3 0.27 1.33 0.27
TOTAL BASIN
HA 3.54 15.96 10.26
HB1 2.18 9.80 2.18
HB2 0.49 2.29 0.49
HB3 1.32 6.06 1.32
TOTAL BASIN
HB 3.99 18.15 3.99
Total developed 100-yr release in to the Spring Creek Basin (Historic Basin HA) is a
summation of the release rates from Ponds 1, 3, and 4, and the 100-yr flowrate for
Basin OS1. Total developed 100-yr release in to the Canal Importation Basin (Historic
Basin HB) is a summation of the release rate from Pond 2, and the 100-yr flowrate for
Basin UD1.
Table 5 - Proposed Stormwater Release
Proposed Stormwater Release
Pond/ Basin
100-yr Flow
(cfs)
Basin HA
Pond 1 0.60
Pond 3 0.20
Pond 4 0.80
Basin OS1 8.68
Total Basin HA 10.28
Basin HB
Pond 2 2.30
UD1 1.67
Total Basin HB 3.97
Mountain’s Edge
Preliminary Drainage Report 12
The proposed ponds will effectively detain all developed flows from the property to the
2-year historic release for both the Spring Creek and Canal Importation Basins.
A full-size copy of the Drainage Exhibit can be found in the Map Pocket at the end of
this report.
B. Water Quality Treatment
1. A combination of 12-hr Rain Gardens and 40-hr Extended Detention Basins will
provide water quality for the site, including a portion of the Overland Trail right of
way.
2. Water Quality within the Detention Ponds will be provided through approved outlet
structures.
C. 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 Mountain’s Edge project complies with the
City of Fort Collins’ Stormwater Criteria Manual.
2. The drainage design proposed with the Mountain’s Edge project complies with the
City of Fort Collins’ Master Drainage Plan for the Spring Creek Basin and Canal
Importation 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 74% 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 the Fort
Collins Master Drainage Plan 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 the underground water
quality chambers. This is currently unable to be calculated with available soils data.
Mountain’s Edge
Preliminary Drainage Report 13
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. Preliminary Geotechnical Subsurface Exploration Report Proposed Single-Family Residential
Development Herring Property – 2430 South Overland Trail, Fort Collins, Colorado, June 11,
2015, Soilogic, Inc. (Soilogic Project No. 15-1132).
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
Hydrologic Soil Group—Larimer County Area, Colorado
(Mountain's Edge)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/21/2016
Page 1 of 4
4489080 4489140 4489200 4489260 4489320 4489380 4489440 4489500 4489560
4489080 4489140 4489200 4489260 4489320 4489380 4489440 4489500 4489560
488580 488640 488700 488760 488820 488880 488940
488580 488640 488700 488760 488820 488880 488940
40° 33' 24'' N
105° 8' 5'' W
40° 33' 24'' N
105° 7' 50'' W
40° 33' 8'' N
105° 8' 5'' W
40° 33' 8'' N
105° 7' 50'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 100 200 400 600
Feet
0 35 70 140 210
Meters
Map Scale: 1:2,410 if printed on A portrait (8.5" x 11") sheet.
Warning: Soil Map may not be valid at this scale.
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
3 Altvan-Satanta loams, 0
to 3 percent slopes
B 8.7 42.7%
4 Altvan-Satanta loams, 3
to 9 percent slopes
B 11.6 57.3%
Totals for Area of Interest 20.3 100.0%
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
Hydrologic Soil Group—Larimer County Area, Colorado Mountain's Edge
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/21/2016
Page 3 of 4
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Larimer County Area, Colorado Mountain's Edge
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/21/2016
Page 4 of 4
Mountain's Edge
CHARACTER OF SURFACE
1
:
Runoff
Coefficient
Percentage
Impervious Project: Mountain's Edge
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: S. Thomas
Asphalt ……....……………...……….....…...……………….………………………………………………………….0.95 . 100% Date: December 20, 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.
HA1 4.07 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 4.075 0.25 0.25 0.31 0%
Mountain's Edge
Overland Flow, Time of Concentration:
Mountain's Edge
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 HA1 No 0.25 0.25 0.31 87 11.64% 6.5 6.5 6.1 681 0.94% 1.46 7.8 14.3 14.3 13.9
1 HA2 Yes 0.25 0.25 0.31 547 3.21% 25.2 25.2 23.4 583 0.96% 1.47 6.6 31.8 31.8 29.9
1 HA3 Yes 0.57 0.57 0.71 620 2.89% 17.4 17.4 12.8 583 0.96% 1.47 6.6 24.0 24.0 19.4
2 HB1 No 0.25 0.25 0.31 252 5.17% 14.6 14.6 13.5 590 0.94% 1.45 6.8 21.4 21.4 20.3
2 HB2 No 0.57 0.57 0.71 252 5.17% 9.1 9.1 6.7 590 0.94% 1.45 6.8 15.9 15.9 13.5
Mountain's Edge
Rational Method Equation: Project: Mountain's Edge
Calculations By:
Date:
Rainfall Intensity:
1 HA1 4.07 14 14 14 0.25 0.25 0.31 1.92 3.29 6.82 1.96 3.35 8.68
1 HA2 4.18 32 32 30 0.25 0.25 0.31 1.26 2.14 4.56 1.31 2.24 5.95
1 HA3 0.33 24 24 19 0.57 0.57 0.71 1.48 2.52 5.75 0.27 0.47 1.33
2 HB1 5.60 21 21 20 0.25 0.25 0.31 1.56 2.67 5.60 2.18 3.74 9.80
2 HB2 0.47 16 16 13 0.57 0.57 0.71 1.84 3.14 6.92 0.49 0.83 2.29
3 HB3 4.66 37 37 34 0.25 0.25 0.31 1.13 1.93 4.16 1.32 2.25 6.06
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
December 20, 2016
Intensity,
i10
(in/hr)
C10
Area, A
(acres)
Intensity,
i2
(in/hr)
100-yr
Tc
(min)
Q = C f ( C )( i )( A )
12/20/2016 3:48 PM D:\Projects\911-007\Drainage\Hydrology\911-007_Existing_Rational_Calcs.xlsx\Runoff
Mountain's Edge
CHARACTER OF SURFACE
1
:
Runoff
Coefficient
Percentage
Impervious Project: Mountain's Edge
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: S. Thomas
Asphalt ……....……………...……….....…...……………….………………………………………………………….0.95 . 100% Date: December 20, 2016
Concrete …….......……………….….……….………………..….…………………………………………………….0.95 . 90%
Gravel (packed) ……….…………………….….…………………………..………………………………………….0.50 . 40%
Roofs …….…….………………..……………….……………………………………………………………………… 0.95 90%
Single Family Lots 0.30 30%
Lawns and Landscaping
Sandy Soil
Flat <2% ……………………………………………………………………………………………………………… 0.10 0%
Average 2% to 7% ………………………………………………………………………………………………….0.15 . 0%
Steep >7% …………………………………………………………………………………………………………… 0.20 0%
Clayey Soil
Flat <2% ……………………………………………………………………………………………………………… 0.20 0%
Average 2% to 7% ………………………………………………………………………………………………….0.25 . 0%
Steep >7% …………………………………………………………………………………………………………… 0.35 0% 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
Single-Family
Lots
(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.
Mountain's Edge
Overland Flow, Time of Concentration:
Mountain's Edge
Gutter/Swale Flow, Time of Concentration:
Tt = L / 60V
Tc = Ti + Tt (Equation RO-2)
Velocity (Gutter Flow), V = 20·S½
Velocity (Swale Flow), V = 15·S½
NOTE: C-value for overland flows over grassy surfaces; C = 0.25
Is Length
>500' ?
C*Cf
(2-yr
Cf=1.00)
C*Cf
(10-yr
Cf=1.00)
C*Cf
(100-yr
Cf=1.25)
Length,
L
(ft)
Slope,
S
(%)
Ti
2-yr
(min)
Ti
10-yr
(min)
Ti
100-yr
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
Length,
L
(ft)
Slope,
S
(%)
Velocity,
V
(ft/s)
Tt
(min)
2-yr
Tc
(min)
Mountain's Edge
Rational Method Equation: Project: Mountain's Edge
Calculations By:
Date:
Rainfall Intensity:
1 A1 1.74 7 7 6 0.63 0.63 0.79 2.52 4.31 9.63 2.77 4.74 13.25
2 A2 1.48 5 5 5 0.77 0.77 0.96 2.85 4.87 9.95 3.26 5.58 14.24
3 A3 2.23 10 10 9 0.44 0.44 0.55 2.26 3.86 8.21 2.20 3.76 10.00
3 TOTAL BASIN A 5.46 8 8 7 0.59 0.59 0.74 2.40 4.10 8.80 7.73 13.21 35.43
4 B1 0.47 6 6 5 0.84 0.84 1.00 2.67 4.56 9.95 1.04 1.78 4.63
5 B2 0.57 6 6 5 0.55 0.55 0.69 2.67 4.56 9.95 0.84 1.44 3.93
6 B3 1.27 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 2.90 4.96 12.67
7 B4 0.23 7 7 5 0.60 0.60 0.75 2.60 4.44 9.95 0.35 0.61 1.70
8 B5 0.86 13 13 12 0.27 0.27 0.34 2.02 3.45 7.16 0.47 0.81 2.10
8 TOTAL BASIN B 3.40 11 11 10 0.62 0.62 0.77 2.13 3.63 7.88 4.47 7.61 20.64
9 C1 0.36 5 5 5 0.63 0.63 0.79 2.85 4.87 9.95 0.65 1.11 2.84
10 C2 0.48 6 6 5 0.43 0.43 0.54 2.76 4.72 9.95 0.58 0.99 2.62
10 TOTAL BASIN C 0.85 5 5 5 0.52 0.52 0.65 2.85 4.87 9.95 1.25 2.14 5.46
11 D1 0.33 6 6 5 0.85 0.85 1.00 2.76 4.72 9.95 0.76 1.30 3.24
11 D2 2.05 5 5 5 0.73 0.73 0.91 2.85 4.87 9.95 4.24 7.25 18.52
12 D3 0.98 6 6 5 0.72 0.72 0.90 2.67 4.56 9.95 1.89 3.22 8.79
13 D4 0.66 5 5 5 0.60 0.60 0.74 2.85 4.87 9.95 1.12 1.91 4.87
14 D5 1.38 10 10 9 0.36 0.36 0.45 2.26 3.86 8.03 1.11 1.89 4.93
14 TOTAL BASIN D 5.39 10 10 9 0.62 0.62 0.78 2.21 3.78 8.03 7.42 12.68 33.68
15 UD1 0.49 12 12 11 0.36 0.36 0.45 2.09 3.57 7.57 0.37 0.63 1.67
16 OS1 4.07 14 14 14 0.25 0.25 0.31 1.92 3.29 6.82 1.96 3.35 8.68
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
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
Mountain's Edge
911-007
Fort Collins, Colorado
S. Thomas Date: 12/22/2016
Pond No.: 1
Pond 1
100-yr
0.74 WQCV 2814 ft3
Area (A)= 5.46 acres Quantity Detention 49207 ft3
Max Release Rate = 0.6 cfs Total Volume 52021 ft3
Total Volume 1.194 ac-ft
Time Time
Fort 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 40.2 12061 180 11881
10 600 7.72 31.2 18715 360 18355
15 900 6.52 26.3 23709 540 23169
20 1200 5.60 22.6 27151 720 26431
25 1500 4.98 20.1 30182 900 29282
30 1800 4.52 18.3 32873 1080 31793
35 2100 4.08 16.5 34618 1260 33358
40 2400 3.74 15.1 36267 1440 34827
45 2700 3.46 14.0 37745 1620 36125
50 3000 3.23 13.1 39151 1800 37351
55 3300 3.03 12.2 40400 1980 38420
60 3600 2.86 11.6 41600 2160 39440
65 3900 2.72 11.0 42861 2340 40521
70 4200 2.59 10.5 43951 2520 41431
75 4500 2.48 10.0 45091 2700 42391
80 4800 2.38 9.6 46158 2880 43278
85 5100 2.29 9.3 47188 3060 44128
90 5400 2.21 8.9 48218 3240 44978
95 5700 2.13 8.6 49054 3420 45634
100 6000 2.06 8.3 49939 3600 46339
105 6300 2.00 8.1 50909 3780 47129
110 6600 1.94 7.8 51733 3960 47773
115 6900 1.89 7.6 52691 4140 48551
120 7200 1.84 7.4 53527 4320 49207
Detention Pond Calculation | FAA Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
12/22/2016 10:48 AM D:\Projects\911-007\Drainage\Detention\911-007_Detention Pond 1.xlsm\FAA_LarmCnty idf
Mountain's Edge
911-007
Fort Collins, CO
S. Thomas Date: 12/22/2016
Pond No.: 1
Pond 1
WQCV
2814 ft3 5142.63 ft.
Design Storm 100-yr
Required Volume= 52021 ft3 5144.86 ft.
Contour
Elevation (Y-
values)
Contour
Area
Depth
Incremental Area
Avg. End
Cumulative Volume
Avg. End
Incremental Volume
Conic
Cummulative
Volume Conic (X-
values)
ft3 ft. ft3 ft3 ft3 ft3
5,141.60 3 0.00 0 0 0 0
5,141.80 295 0.20 30 30 22 22
5,142.00 1249 0.20 154 184 143 165
5,142.20 2831 0.20 408 592 397 562
5,142.40 5014 0.20 784 1377 774 1337
5,142.60 7597 0.20 1261 2638 1252 2589
5,142.80 10388 0.20 1798 4436 1791 4380
5,143.00 13198 0.20 2359 6795 2353 6733
5,143.20 16023 0.20 2922 9717 2917 9650
5,143.40 18,846 0.20 3487 13204 3483 13133
5,143.60 21,585 0.20 4043 17247 4040 17173
5,143.80 24,006 0.20 4559 21806 4557 21730
5,144.00 26,125 0.20 5013 26819 5012 26742
5,144.20 27,950 0.20 5408 32226 5407 32149
5,144.40 29,486 0.20 5744 37970 5743 37892
5,144.60 30,754 0.20 6024 43994 6024 43915
5,144.80 31,626 0.20 6238 50232 6238 50153
5,145.00 32,455 0.20 6408 56640 6408 56561
5,145.20 33,379 0.20 6583 63224 6583 63144
5,145.40 34,415 0.20 6779 70003 6779 69923
5,145.60 35,573 0.20 6999 77002 6998 76922
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
12/22/201610:48 AM D:\Projects\911-007\Drainage\Detention\911-007_Detention Pond 1.xlsm\Stage_Storage
POND 1
Project: Mountain's Edge
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 5.460 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 48.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.4800 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.201 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.091 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Rain Garden WQCV (ft
3
) = 1167 <-- CALCULATED
Adjusted WQCV (cu-ft) = 2814 <-- CALCULATED (minus Rain Garden)
WQ Depth (ft) = 1.030 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.260 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 4/7 <-- INPUT from Figure 5
number of rows = 3
t (in) = 0.500 <-- INPUT from Figure 5
number of columns = 1.000 <-- CALCULATED from WQ Depth and row spacing
WATER QUALITY CONTROL STRUCTURE PLATE
December 20, 2016
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 69.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.690
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.22 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 64,671 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 1,167 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV = 10 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 892 sq ft
D) Actual Flat Surface Area AActual = 1247 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 1847 sq ft
F) Rain Garden Total Volume VT= 1,289 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = 2.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 1,167 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 4/5 in
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
December 20, 2016
Mountain's Edge - Rain Garden 1
Drake and Overland, Fort Collins, CO
UD-BMP (Version 3.06, November 2016)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
Rain Garden 1.xlsm, RG 12/20/2016, 3:19 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
NO SPRINKLER HEADS ON FLAT SURFACE
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
December 20, 2016
Mountain's Edge - Rain Garden 1
Drake and Overland, Fort Collins, CO
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
Rain Garden 1.xlsm, RG 12/20/2016, 3:19 PM
Mountain's Edge
911-007
Fort Collins, Colorado
S. Thomas Date: 12/22/2016
Pond No.: Pond 2
Pond 2
100-yr
0.77 WQCV 2684 ft3
Area (A)= 3.40 acres Quantity Detention 18868 ft3
Max Release Rate = 2.3 cfs Total Volume 21552 ft3
Total Volume 0.495 ac-ft
Time Time
Fort 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 26.0 7815 690 7125
10 600 7.72 20.2 12127 1380 10747
15 900 6.52 17.1 15362 2070 13292
20 1200 5.60 14.7 17593 2760 14833
25 1500 4.98 13.0 19556 3450 16106
30 1800 4.52 11.8 21300 4140 17160
35 2100 4.08 10.7 22431 4830 17601
40 2400 3.74 9.8 23499 5520 17979
45 2700 3.46 9.1 24457 6210 18247
50 3000 3.23 8.5 25368 6900 18468
55 3300 3.03 7.9 26177 7590 18587
60 3600 2.86 7.5 26955 8280 18675
65 3900 2.72 7.1 27772 8970 18802
70 4200 2.59 6.8 28479 9660 18819
75 4500 2.48 6.5 29217 10350 18867
80 4800 2.38 6.2 29908 11040 18868
85 5100 2.29 6.0 30576 11730 18846
90 5400 2.21 5.8 31243 12420 18823
95 5700 2.13 5.6 31785 13110 18675
100 6000 2.06 5.4 32358 13800 18558
105 6300 2.00 5.2 32987 14490 18497
110 6600 1.94 5.1 33521 15180 18341
115 6900 1.89 4.9 34141 15870 18271
120 7200 1.84 4.8 34683 16560 18123
Detention Pond Calculation | FAA Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
12/22/2016 10:49 AM D:\Projects\911-007\Drainage\Detention\911-007_Detention Pond 2.xlsm\FAA_LarmCnty idf
Mountain's Edge
911-007
Fort Collins, CO
S. Thomas Date: 12/22/2016
Pond No.: Pond 2
Pond 2
WQCV
2684 ft3 5137.73 ft.
Design Storm 100-yr
Required Volume= 21552 ft3 5139.56 ft.
Contour
Elevation (Y-
values)
Contour
Area
Depth
Incremental Area
Avg. End
Cumulative Volume
Avg. End
Incremental Volume
Conic
Cummulative
Volume Conic (X-
values)
ft3 ft. ft3 ft3 ft3 ft3
5,136.80 35 0.00 0 0 0 0
5,137.00 720 0.20 75 75 61 61
5,137.20 2095 0.20 282 357 270 330
5,137.40 3752 0.20 585 942 577 907
5,137.60 5652 0.20 940 1882 934 1841
5,137.80 7358 0.20 1301 3183 1297 3138
5,138.00 8656 0.20 1601 4785 1600 4738
5,138.20 9573 0.20 1823 6607 1822 6560
5,138.40 10171 0.20 1974 8582 1974 8534
5,138.60 10550 0.20 2072 10654 2072 10606
5,138.80 10908 0.20 2146 12800 2146 12752
5,139.00 11270 0.20 2218 15017 2218 14970
5,139.20 11638 0.20 2291 17308 2291 17260
5,139.40 12019 0.20 2366 19674 2366 19626
5,139.60 12482 0.20 2450 22124 2450 22076
5,139.80 13045 0.20 2553 24677 2553 24628
5,140.00 13726 0.20 2677 27354 2677 27305
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
12/22/201610:50 AM D:\Projects\911-007\Drainage\Detention\911-007_Detention Pond 2.xlsm\Stage_Storage
POND 2
Project: Mountain's Edge
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 3.400 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 54.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.5400 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.217 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.062 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Rain Garden WQCV (ft
3
) = 0 <-- CALCULATED
Adjusted WQCV (cu-ft) = 2684 <-- CALCULATED (minus Rain Garden)
WQ Depth (ft) = 1.000 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.251 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 4/7 <-- INPUT from Figure 5
number of rows = 3
t (in) = 0.500 <-- INPUT from Figure 5
number of columns = 1.000 <-- CALCULATED from WQ Depth and row spacing
WATER QUALITY CONTROL STRUCTURE PLATE
December 20, 2016
Mountain's Edge
911-007
Fort Collins, Colorado
S. Thomas Date: 12/22/2016
Pond No.: Pond 3
Pond 3
100-yr
0.65 WQCV 513 ft3
Area (A)= 0.85 acres Quantity Detention 5880 ft3
Max Release Rate = 0.2 cfs Total Volume 6393 ft3
Total Volume 0.147 ac-ft
Time Time
Larimer County
Area II
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 5.5 1649 60 1589
10 600 7.72 4.3 2559 120 2439
15 900 6.52 3.6 3242 180 3062
20 1200 5.60 3.1 3713 240 3473
25 1500 4.98 2.8 4127 300 3827
30 1800 4.52 2.5 4495 360 4135
35 2100 4.08 2.3 4734 420 4314
40 2400 3.74 2.1 4959 480 4479
45 2700 3.46 1.9 5161 540 4621
50 3000 3.23 1.8 5354 600 4754
55 3300 3.03 1.7 5524 660 4864
60 3600 2.86 1.6 5689 720 4969
65 3900 2.72 1.5 5861 780 5081
70 4200 2.59 1.4 6010 840 5170
75 4500 2.48 1.4 6166 900 5266
80 4800 2.38 1.3 6312 960 5352
85 5100 2.29 1.3 6453 1020 5433
90 5400 2.21 1.2 6594 1080 5514
95 5700 2.13 1.2 6708 1140 5568
100 6000 2.06 1.1 6829 1200 5629
105 6300 2.00 1.1 6962 1260 5702
110 6600 1.94 1.1 7074 1320 5754
115 6900 1.89 1.0 7205 1380 5825
120 7200 1.84 1.0 7320 1440 5880
Detention Pond Calculation | FAA Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
12/22/2016 10:51 AM D:\Projects\911-007\Drainage\Detention\911-007_Detention Pond 3.xlsm\FAA_LarmCnty idf
Mountain's Edge
911-007
Fort Collins, CO
S. Thomas Date: 12/22/2016
Pond No.: Pond 3
Pond 3
WQCV
513 ft3 5143.14 ft.
Design Storm 100-yr
Required Volume= 6393 ft3 5145.28 ft.
Contour
Elevation (Y-
values)
Contour
Area
Depth
Incremental Area
Avg. End
Cumulative Volume
Avg. End
Incremental Volume
Conic
Cummulative
Volume Conic (X-
values)
ft3 ft. ft3 ft3 ft3 ft3
5,142.00 9 0.00 0 0 0 0
5,142.20 73 0.20 8 8 7 7
5,142.40 199 0.20 27 35 26 33
5,142.60 389 0.20 59 94 58 91
5,142.80 640 0.20 103 197 102 193
5,143.00 955 0.20 160 357 158 352
5,143.20 1,336 0.20 229 586 228 580
5,143.40 1,746 0.20 308 894 307 887
5,143.60 1,900 0.20 365 1259 364 1251
5,143.80 2,062 0.20 396 1655 396 1647
5,144.00 2,266 0.20 433 2088 433 2080
5,144.20 2,522 0.20 479 2566 478 2559
5,144.40 2,828 0.20 535 3101 535 3093
5,144.60 3,185 0.20 601 3703 601 3694
5,144.80 3,592 0.20 678 4380 677 4371
5,145.00 4,049 0.20 764 5144 764 5135
5,145.20 4,569 0.20 862 6006 861 5996
5,145.40 5,182 0.20 975 6981 974 6971
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
12/22/201610:51 AM D:\Projects\911-007\Drainage\Detention\911-007_Detention Pond 3.xlsm\Stage_Storage
POND 3
Project: Mountain's Edge
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 0.850 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 35.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.3500 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.166 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.012 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Rain Garden WQCV (ft
3
) = 0 <-- CALCULATED
Adjusted WQCV (cu-ft) = 513 <-- CALCULATED (minus Rain Garden)
WQ Depth (ft) = 1.140 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.051 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 1/4 <-- INPUT from Figure 5
number of rows = 3
t (in) = 0.500 <-- INPUT from Figure 5
number of columns = 1.000 <-- CALCULATED from WQ Depth and row spacing
WATER QUALITY CONTROL STRUCTURE PLATE
December 20, 2016
Mountain's Edge
911-007
Fort Collins, Colorado
S. Thomas Date: 12/22/2016
Pond No.: 4
Pond 4
100-yr
0.78 WQCV 863 ft3
Area (A)= 5.39 acres Quantity Detention 49937 ft3
Max Release Rate = 0.8 cfs Total Volume 50800 ft3
Total Volume 1.166 ac-ft
Time Time
Fort 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 41.8 12550 240 12310
10 600 7.72 32.5 19474 480 18994
15 900 6.52 27.4 24670 720 23950
20 1200 5.60 23.5 28252 960 27292
25 1500 4.98 20.9 31405 1200 30205
30 1800 4.52 19.0 34205 1440 32765
35 2100 4.08 17.2 36022 1680 34342
40 2400 3.74 15.7 37737 1920 35817
45 2700 3.46 14.5 39276 2160 37116
50 3000 3.23 13.6 40739 2400 38339
55 3300 3.03 12.7 42038 2640 39398
60 3600 2.86 12.0 43286 2880 40406
65 3900 2.72 11.4 44598 3120 41478
70 4200 2.59 10.9 45733 3360 42373
75 4500 2.48 10.4 46919 3600 43319
80 4800 2.38 10.0 48029 3840 44189
85 5100 2.29 9.6 49101 4080 45021
90 5400 2.21 9.3 50173 4320 45853
95 5700 2.13 9.0 51043 4560 46483
100 6000 2.06 8.7 51964 4800 47164
105 6300 2.00 8.4 52973 5040 47933
110 6600 1.94 8.2 53831 5280 48551
115 6900 1.89 7.9 54827 5520 49307
120 7200 1.84 7.7 55697 5760 49937
Detention Pond Calculation | FAA Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
12/22/2016 10:52 AM D:\Projects\911-007\Drainage\Detention\911-007_Detention Pond 4.xlsm\FAA_LarmCnty idf
Mountain's Edge
911-007
Fort Collins, CO
S. Thomas Date: 12/22/2016
Pond No.: 4
Pond 4
WQCV
863 ft3 5137.48 ft.
Design Storm 100-yr
Required Volume= 50800 ft3 5142.81 ft.
Contour
Elevation (Y-
values)
Contour
Area
Depth
Incremental Area
Avg. End
Cumulative Volume
Avg. End
Incremental Volume
Conic
Cummulative
Volume Conic (X-
values)
ft3 ft. ft3 ft3 ft3 ft3
5,136.60 66 0.00 0 0 0 0
5,136.80 410 0.20 48 48 43 43
5,137.00 857 0.20 127 174 124 167
5,137.20 1333 0.20 219 393 217 384
5,137.40 1832 0.20 316 710 315 699
5,137.60 2,207 0.20 404 1114 403 1102
5,137.80 2,554 0.20 476 1590 476 1578
5,138.00 2,924 0.20 548 2138 547 2126
5,138.20 3,279 0.20 620 2758 620 2746
5,138.40 3,530 0.20 681 3439 681 3426
5,138.60 3,787 0.20 732 4171 732 4158
5,138.80 4,059 0.20 785 4955 784 4942
5,139.00 4,344 0.20 840 5795 840 5782
5,139.20 4,642 0.20 899 6694 898 6681
5,139.40 6,397 0.20 1104 7798 1099 7780
5,139.60 6,892 0.20 1329 9127 1329 9109
5,139.80 7,414 0.20 1431 10557 1430 10539
5,140.00 7,957 0.20 1537 12094 1537 12075
5,140.20 8,522 0.20 1648 13742 1648 13723
5,140.40 9,110 0.20 1763 15505 1763 15486
5,140.60 9,725 0.20 1884 17389 1883 17369
5,140.80 13,580 0.20 2331 19720 2320 19689
5,141.00 14,614 0.20 2819 22539 2819 22508
5,141.20 15,718 0.20 3033 25572 3032 25540
5,141.40 12,761 0.20 2848 28420 2843 28383
5,141.60 13,565 0.20 2633 31053 2632 31015
5,141.80 14,408 0.20 2797 33850 2797 33812
5,142.00 15,302 0.20 2971 36821 2970 36783
5,142.20 16,263 0.20 3156 39977 3156 39939
5,142.40 17,301 0.20 3356 43334 3356 43294
5,142.60 18,413 0.20 3571 46905 3571 46865
5,142.80 19,593 0.20 3801 50706 3800 50665
5,143.00 20,830 0.20 4042 54748 4042 54707
Design Point
POND 4
Project: Mountain's Edge
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 5.390 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 55.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.5500 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.220 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.099 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Rain Garden WQCV (ft
3
) = 3450 <-- CALCULATED
Adjusted WQCV (cu-ft) = 863 <-- CALCULATED (minus Rain Garden)
WQ Depth (ft) = 1.000 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.085 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 1/3 <-- INPUT from Figure 5
number of rows = 3
t (in) = 0.500 <-- INPUT from Figure 5
number of columns = 1.000 <-- CALCULATED from WQ Depth and row spacing
WATER QUALITY CONTROL STRUCTURE PLATE
December 20, 2016
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 55.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.550
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.18 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 234,756 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 3,450 cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume VWQCV USER = cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum) DWQCV = 18 in 12-INCH MAXIMUM
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 2582 sq ft
D) Actual Flat Surface Area AActual = 1446 sq ft ACTUAL FLAT AREA < MINIMUM FLAT AREA
E) Area at Design Depth (Top Surface Area) ATop = 3365 sq ft
F) Rain Garden Total Volume VT= 3,608 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = 2.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 3,450 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 1 1/3 in
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
December 20, 2016
Mountain's Edge - Rain Garden 2
Drake and Overland, Fort Collins CO
UD-BMP (Version 3.06, November 2016)
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
Rain Garden Pond 4.xlsm, RG 12/20/2016, 3:13 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
December 20, 2016
Mountain's Edge - Rain Garden 2
Drake and Overland, Fort Collins CO
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
Rain Garden Pond 4.xlsm, RG 12/20/2016, 3:13 PM
APPENDIX B.2
STORM SEWERS
APPENDIX B.3
INLETS
APPENDIX C
EROSION CONTROL REPORT
Mountain’s Edge
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: Mountain's Edge
Calculations By: S. Thomas
Date: December 22, 2016
L1 A2 64,671 69% 44,326 Rain Garden 1
A3 97,320 24% 23,327 Grass Buffer
Total L1 161,991 42% 67,653
L2 B1 20,289 83% 16,939
B2 24,873 39% 9,698
B5 37,619 17% 6,570 Grass Buffer
Total L2 82,781 40% 33,206
L3 C2 21,094 24% 5,009 Grass Buffer
Total L3 21,094 24% 5,009
L4 D1 14,166 85% 12,078
D2 89,304 67% 60,073
D3 42,668 64% 27,423
D4 28,680 62% 17,666
D5 59,938 20% 12,240
Total L4 234,756 55% 129,480
L5 UD1 21,559 44% 9,544 Grass Buffer
Total L5 21,559 44% 9,544
Total Treated 522,181 47% 244,892
A1 75,924 62% 47,069
B3 55,488 73% 40,496
B4 9,903 58% 5,779
C1 15,762 49% 7,723
Total Proposed
Untreated
157,077 64% 101,066
HA3 14,166 45% 6,375
HB2 20,289 45% 9,130
Total Existing 34,455 45% 15,505
PROPOSED LID COMPUTATIONS
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area,
A
(sf)
LID Treatment
PROPOSED LID UNTREATED AREA
PROPOSED LID TREATED AREA
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area,
A
(sf)
Grass-Lined Swale w/
Infiltration Section
Rain Garden 2
Project: Mountain's Edge
Calculations By: S. Thomas
Date: December 22, 2016
PROPOSED LID COMPUTATIONS
679,258
15,505
345,958
330,453
247,840
244,892
74%
Rain Garden 1 Rain Garden 2
Total Contributing
Area (sf)
64,671 234,756
Percent Impervious 69% 55%
Total Volume
Required (cf)
1,167 3,450
Total Volume
Provided (cf)
1,167 3,450
RAIN GARDEN SUMMARY
LID TREATMENT SUMMARY
Total Site Area (sf)
Total Existing Impervious Area (sf)
Total Proposed Impervious Area (sf)
Total Treated Impervious Area (sf)
Percent Impervious Treated by LID
measures
75% Required Minimum Area to be
Treated by LID measures (sf)
Total Net Proposed Impervious Area (sf)
X X
X
X X X X
X
X
X
X
X X
X
X X X X
X X
X
X
X
X X X X X X X
X X
X
X
X
X
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X
X
X
X
X
X
X
X
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X X
X X X
X
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X
X X X
X
X X
OHE
OHE OHE
OHE
OHE
OHE OHE
OHE
OHE
OHE OHE
OHE OHE
OHE
OHE
OHE
OHE
OHE OHE OHE
OHE OHE OHE OHE OHE
OHE
OHE OHE
G
AS
APPENDIX E
REFERENCES
MAP POCKET
DR1 – OVERALL DRAINAGE EXHIBIT
X
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X
X X
OHE
OHE OHE
OHE
OHE
OHE OHE
OHE
OHE
OHE OHE
OHE OHE
OHE
OHE
OHE
OHE
OHE OHE OHE
OHE OHE OHE OHE OHE
OHE
OHE OHE
G
AS
B M D
T C
F
E
S
S
H2O
H2O
H2O
A1
A2
A3
B3
B1
B2
B4
B5
C1
C2
D1
D2
D3
D4
D5
UD1
OS1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
PRIVATE DRIVE A
PRIVATE DRIVE B (S)
PRIVATE DRIVE B (N)
HILLOCK STREET
PRIVATE DRIVE D
OVERLAND TRAIL
BLUEGRASS DRIVE
PRIVATE DRIVE E
DRAKE ROAD
PROPOSED
INLET
PROPOSED
STORM DRAIN
PROPOSED
INLETS
PROPOSED
STORM DRAIN
REMOVE AND
REPLACE EXISTING
STORM DRAIN
CONNECT TO EXISTING
STORM DRAIN
PROPOSED
OUTLET
STRUCTURE
PROPOSED
OUTLET
STRUCTURE
DETENTION
POND 1
DETENTION
POND 3
DETENTION
POND 4
DETENTION
POND 2
PRIVATE DRIVE C
PROPOSED
OUTLET
STRUCTURE
8" SS
6" W
6" W 6" W
6" W 6" W 6" W 6" W 6" W 6" W 6" W
6" W
8" SS 8" SS
8" SS 8" SS 8" SS
8" SS 8" SS
6" W
6" W
S
6" W
S
S
PROPOSED
OUTLET
STRUCTURE
PROPOSED
INLET
PROPOSED
INLET
PROPOSED
SIDEWALK
CHASE
PROPOSED
SIDEWALK
CHASE
PROPOSED
CURB CUT
RAIN
GARDEN
#1
RAIN
GARDEN
#2
POND 1
SPILL
PATH
POND 1
SPILL
PATH
DIXON CREEK
Sheet
MOUNTAIN'S EDGE These drawings are
instruments of service
provided by Northern
Engineering Services, Inc.
and are not to be used for
any type of construction
unless signed and sealed by
a Professional Engineer in
the employ of Northern
Engineering Services, Inc.
NOT FOR CONSTRUCTION
REVIEW SET
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
E NGINEER ING
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
of 24
DR1
DRAINAGE PLAN
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
City Engineer Date
Date
Date
Date
Date
Stormwater Utility
Parks & Recreation
Traffic Engineer
Date
Water & Wastewater Utility
City of Fort Collins, Colorado
UTILITY PLAN APPROVAL
Environmental Planner 24
( IN FEET )
0
1 INCH = 60 FEET
60 60 120 180
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 Report for Mountains Edge" BY NORTHERN
ENGINEERING, DATED December 22nd, 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
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
1 A1 1.74 0.63 0.79 7.4 5.7 2.77 13.25
2 A2 1.48 0.77 0.96 5.0 5.0 3.26 14.24
3 A3 2.23 0.44 0.55 9.7 8.9 2.20 10.00
4 B1 0.47 0.84 1.00 6.1 5.0 1.04 4.63
5 B2 0.57 0.55 0.69 6.2 5.4 0.84 3.93
6 B3 1.27 0.80 1.00 5.0 5.0 2.90 12.67
7 B4 0.23 0.60 0.75 6.5 5.0 0.35 1.70
8 B5 0.86 0.27 0.34 12.7 12.0 0.47 2.10
9 C1 0.36 0.63 0.79 5.0 5.0 0.65 2.84
10 C2 0.48 0.43 0.54 5.9 5.1 0.58 2.62
11 D1 0.33 0.85 1.00 5.9 5.0 0.76 3.24
11 D2 2.05 0.73 0.91 5.0 5.0 4.24 18.52
12 D3 0.98 0.72 0.90 6.3 5.0 1.89 8.79
13 D4 0.66 0.60 0.74 5.1 5.0 1.12 4.87
14 D5 1.38 0.36 0.45 9.9 9.2 1.11 4.93
15 UD1 0.49 0.36 0.45 11.9 10.5 0.37 1.67
16 OS1 4.07 0.25 0.31 14.3 13.9 1.96 8.68
Detention Pond Summary | Proposed Condition
Pond 100-yr Volume
(ac-ft)
100-yr WSEL WQCV
(ft3)
WQCV WSEL Max Release
(cfs)
1 1.19 5144.86 2,814 5142.63 0.60
2 0.50 5139.56 2,684 5137.73 2.30
3 0.15 5145.28 513 5143.14 0.20
4 1.17 5142.81 863 5137.48 0.80
X
X
X
X
/ / / / / / / /
/ / / / / / / /
X
X
X X X
X
X X X
X X
X X
X
X
X
OHE
OHE OHE
OHE
OHE
OHE OHE
OHE
OHE
OHE OHE
OHE OHE
OHE
OHE
OHE
OHE
OHE
OHE
OHE OHE OHE
OHE OHE OHE OHE OHE
OHE
OHE OHE
/
/ / / / / / /
/ / / / / / / /
/ / / / / / / /
/ / / / / / / /
/ / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / / /
/ / / / / / / / / / / / / / / /
GAS
MM
T
W
VAULT
F.O.
B M D
T C
F
E
S
C
ONTROL
IRR
S
H2O
H2O
H2O
20" W
20" W
20" W
20" W
20" W 20" W
20" W
20" W 20" W
20" W
20" W 20" W
20" W
20" W 20" W
20" W
20" W 20" W
16" W
16" W 16" W
16" W
16" W 16" W
16" W
16" W 16" W
HA1
HA2
HB1
HB2 HA3
1
2
HB3
3
8" SS
6" W
6" W 6" W
6" W 6" W 6" W 6" W 6" W 6" W 6" W
6" W
8" SS 8" SS
8" SS 8" SS 8" SS
8" SS 8" SS
6" W
6" W
S
6" W
S
S
OVERLAND TRAIL
BLUEGRASS DRIVE
DRAKE ROAD
Sheet
MOUNTAIN'S EDGE These drawings are
instruments of service
provided by Northern
Engineering Services, Inc.
and are not to be used for
any type of construction
unless signed and sealed by
a Professional Engineer in
the employ of Northern
Engineering Services, Inc.
NOT FOR CONSTRUCTION
REVIEW SET
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
E NGINEER ING
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
of 23
HDR1
HISTORIC DRAINAGE EXHIBIT
CALL UTILITY NOTIFICATION CENTER OF
COLORADO
Know what'sbelow.
Call before you dig.
R
( IN FEET )
0
1 INCH = 60 FEET
60 60 120 180
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
MOUNTAIN'S EDGE" BY NORTHERN ENGINEERING, DATED DECEMBER 20TH, 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
Tc
(min)
100-yr
Tc
(min)
Q2
(cfs)
Q100
(cfs)
1 HA1 4.07 0.25 0.31 14.3 13.9 1.96 8.68
1 HA2 4.18 0.25 0.31 31.8 29.9 1.31 5.95
1 HA3 0.33 0.57 0.71 24.0 19.4 0.27 1.33
2 HB1 5.60 0.25 0.31 21.4 20.3 2.18 9.80
2 HB2 0.47 0.57 0.71 15.9 13.5 0.49 2.29
3 HB3 4.66 0.25 0.31 37.2 34.5 1.32 6.06
B M D
T C
F
E
S
S
H2O
H2O
H2O
A1
A2
A3
B3
B1
B2
B4
B5
C1
C2
D1
D2
D3
D4
D5
UD1
OS1
PRIVATE DRIVE A
PRIVATE DRIVE B (S)
PRIVATE DRIVE B (N)
HILLOCK STREET
PRIVATE DRIVE D
OVERLAND TRAIL
BLUEGRASS DRIVE
PRIVATE DRIVE E
DRAKE ROAD
PRIVATE DRIVE C
8" SS
6" W
6" W 6" W
6" W 6" W 6" W 6" W 6" W 6" W 6" W
6" W
8" SS 8" SS
8" SS 8" SS 8" SS
8" SS 8" SS
6" W
6" W
S
6" W
S
S
DIXON CREEK
RAIN
GARDEN
#1
RAIN
GARDEN
#2
GRASS SWALE
WITH
INFILTRATION
SECTION
DETENTION
POND 1
DETENTION
POND 3
DETENTION
POND 4
DETENTION
POND 2
GRASS BUFFER
GRASS BUFFER
GRASS BUFFER
GRASS BUFFER
GRASS BUFFER
GRASS BUFFER
GRASS BUFFER
GRASS BUFFER
GRASS BUFFER
L1
A2, A3
L2
B1, B2
L2
B5
L3
C2
L4
D1-D5
L5
UD1
Sheet
MOUNTAIN'S EDGE These drawings are
instruments of service
provided by Northern
Engineering Services, Inc.
and are not to be used for
any type of construction
unless signed and sealed by
a Professional Engineer in
the employ of Northern
Engineering Services, Inc.
NOT FOR CONSTRUCTION
REVIEW SET
301 North Howes Street, Suite 100
Fort Collins, Colorado 80521
E NGINEER ING
N O R T H E RN
PHONE: 970.221.4158
www.northernengineering.com
of 24
LID
(LID) EXHIBIT
LOW IMPACT DEVELOPMENT
( IN FEET )
0
1 INCH = 60 FEET
60 60 120 180
LEGEND:
5013
PROPOSED CONTOUR 93
EXISTING CONTOUR
PROPERTY BOUNDARY
DRAINAGE BASIN BUBBLE
A
LID BASIN BOUNDARY
PROPOSED STORM SEWER
LID TREATMENT MEASURE
DRAINAGE BASIN BOUNDARY
L1
A2, A3
LID BASIN BUBBLE
LID BASIN DESIGNATION
CONTRIBUTING DRAINAGE BASINS
PROPOSED LID TREATED AREA
LID BASIN NODE Sub-Basin(s) Area, A
(sf)
Percent Impervious Impervious Area, A
(sf)
LID Treatment
L1 A2 64,671 69% 44,326 Rain Garden 1
A3 97,320 24% 23,327 Grass Buffer
Total L1 161,991 42% 67,653
L2 B1 20,289 83% 16,939 Grass-Lined Swale w/
B2 24,873 39% 9,698 Infiltration Section
B5 37,619 17% 6,570 Grass Buffer
Total L2 82,781 40% 33,206
L3 C2 21,094 24% 5,009 Grass Buffer
Total L3 21,094 24% 5,009
L4 D1 14,166 85% 12,078 Rain Garden 2
D2 89,304 67% 60,073
D3 42,668 64% 27,423
D4 28,680 62% 17,666
D5 59,938 20% 12,240
Total L4 234,756 55% 129,480
L5 UD1 21,559 44% 9,544 Grass Buffer
Total L5 21,559 44% 9,544
Total Treated 522,181 47% 244,892
PROPOSED LID UNTREATED AREA
LID BASIN NODE Sub-Basin(s) Area, A
(sf)
Percent Impervious Impervious Area, A
(sf)
A1 75,924 62% 47,069
B3 55,488 73% 40,496
B4 9,903 58% 5,779
C1 15,762 49% 7,723
Total Proposed
Untreated
157,077 64% 101,066
HA3 14,166 45% 6,375
HB2 20,289 45% 9,130
Total Existing 34,455 45% 15,505
LID TREATMENT SUMMARY
Total Site Area (sf) 679,258
Total Existing Impervious Area (sf) 15,505
Total Proposed Impervious Area (sf) 345,958
Total Net Proposed Impervious Area (sf) 330,453
75% Required Minimum Area to be Treated
by LID measures (sf)
247,840
Total Treated Impervious Area (sf) 244,892
Percent Impervious Treated by LID measures 74%
RAIN GARDEN SUMMARY
Rain Garden 1 Rain Garden 2
Total Contributing
Area (sf)
64,671 234,756
Percent Impervious 69% 55%
Total Volume
Required (cf)
1,167 3,450
Total Volume
Provided (cf)
1,167 3,450
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
12/22/201610:53 AM D:\Projects\911-007\Drainage\Detention\911-007_Detention Pond 4.xlsm\Stage_Storage
December 20, 2016
Intensity,
i10
(in/hr)
C10
Q = C f ( C )( i )( A )
12/20/2016 3:52 PM D:\Projects\911-007\Drainage\Hydrology\911-007_Proposed_Rational_Calcs.xlsx\Runoff
10-yr
Tc
(min)
100-yr
Tc
(min)
1 A1 No 0.63 0.63 0.79 61 2.34% 5.1 5.1 3.4 N/A N/A N/A 227 0.70% 1.67 2.3 7.4 7.4 5.7
2 A2 No 0.77 0.77 0.96 35 3.54% 2.4 2.4 1.0 N/A N/A N/A 249 0.80% 1.79 2.3 5.0 5.0 5.0
3 A3 No 0.44 0.44 0.55 69 7.35% 5.3 5.3 4.4 163 1.04% 1.53 1.8 264 0.68% 1.65 2.7 9.7 9.7 8.9
3 TOTAL BASIN A No 0.59 0.59 0.74 35 3.54% 3.7 3.7 2.6 163 1.04% 1.53 1.8 264 0.68% 1.65 2.7 8.1 8.1 7.1
4 B1 No 0.84 0.84 1.00 46 2.83% 2.4 2.4 0.9 N/A N/A N/A 358 0.63% 1.59 3.7 6.1 6.1 5.0
5 B2 No 0.55 0.55 0.69 47 10.83% 3.2 3.2 2.4 389 1.99% 2.11 3.1 N/A N/A N/A 6.2 6.2 5.4
6 B3 No 0.80 0.80 1.00 39 3.28% 2.4 2.4 0.8 N/A N/A N/A 349 1.45% 2.41 2.4 5.0 5.0 5.0
7 B4 No 0.60 0.60 0.75 60 2.62% 5.2 5.2 3.7 N/A N/A N/A 216 1.94% 2.79 1.3 6.5 6.5 5.0
8 B5 No 0.27 0.27 0.34 50 2.00% 8.7 8.7 8.0 311 2.41% 2.33 2.2 157 0.52% 1.44 1.8 12.7 12.7 12.0
8 TOTAL BASIN B No 0.62 0.62 0.77 46 2.83% 4.3 4.3 3.0 389 1.99% 2.11 3.1 358 0.63% 1.59 3.7 11.2 11.2 9.8
9 C1 No 0.63 0.63 0.79 35 5.14% 3.0 3.0 2.0 N/A N/A N/A 106 0.47% 1.37 1.3 5.0 5.0 5.0
10 C2 No 0.43 0.43 0.54 52 6.00% 4.9 4.9 4.1 132 2.46% 2.35 0.9 N/A N/A N/A 5.9 5.9 5.1
10 TOTAL BASIN C No 0.52 0.52 0.65 52 6.00% 4.3 4.3 3.4 132 2.46% 2.35 0.9 N/A N/A N/A 5.2 5.2 5.0
11 D1 No 0.85 0.85 1.00 42 2.64% 2.2 2.2 0.9 N/A N/A N/A 639 2.04% 2.86 3.7 5.9 5.9 5.0
11 D2 No 0.73 0.73 0.91 N/A N/A N/A N/A N/A N/A N/A 368 2.42% 3.11 2.0 5.0 5.0 5.0
12 D3 No 0.72 0.72 0.90 78 3.21% 4.2 4.2 2.2 217 1.43% 1.79 2.0 N/A N/A N/A 6.3 6.3 5.0
13 D4 No 0.60 0.60 0.74 18 2.94% 2.8 2.8 2.0 N/A N/A N/A 266 0.94% 1.94 2.3 5.1 5.1 5.0
14 D5 No 0.36 0.36 0.45 57 6.11% 5.7 5.7 5.0 487 1.71% 1.96 4.1 N/A N/A N/A 9.9 9.9 9.2
14 TOTAL BASIN D No 0.62 0.62 0.78 42 2.64% 4.2 4.2 2.8 247 1.23% 1.66 2.5 639 2.04% 2.86 3.7 10.4 10.4 9.0
15 UD1 No 0.36 0.36 0.45 165 3.33% 11.9 11.9 10.5 N/A N/A N/A N/A N/A N/A 11.9 11.9 10.5
16 OS1 No 0.25 0.25 0.31 87 11.64% 6.5 6.5 6.1 681 0.94% 1.46 7.8 N/A N/A N/A 14.3 14.3 13.9
* 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
Design
Point
Sub-Basin
Overland Flow SwaleConcentration Flow Gutter/Pipe Flow Time of
December 20, 2016
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
12/20/2016 3:51 PM D:\Projects\911-007\Drainage\Hydrology\911-007_Proposed_Rational_Calcs.xlsx\Tc
A1 1.74 0.41 0.25 0.55 0.25 Clayey | Average 2% to 7% 0.283 0.63 0.63 0.79 62%
A2 1.48 0.22 0.34 0.00 0.54 Clayey | Average 2% to 7% 0.379 0.77 0.77 0.96 69%
A3 2.23 0.00 0.11 0.00 0.48 Clayey | Average 2% to 7% 1.639 0.44 0.44 0.55 24%
TOTAL BASIN A 5.46 0.64 0.70 0.55 1.27 Clayey | Average 2% to 7% 2.301 0.59 0.59 0.74 48%
B1 0.47 0.37 0.02 0.00 0.00 Clayey | Average 2% to 7% 0.075 0.84 0.84 1.00 83%
B2 0.57 0.00 0.05 0.00 0.20 Clayey | Average 2% to 7% 0.324 0.55 0.55 0.69 39%
B3 1.27 0.29 0.28 0.00 0.43 Clayey | Average 2% to 7% 0.273 0.80 0.80 1.00 73%
B4 0.23 0.09 0.02 0.06 0.00 Clayey | Average 2% to 7% 0.055 0.60 0.60 0.75 58%
B5 0.86 0.00 0.00 0.38 0.00 Clayey | Average 2% to 7% 0.487 0.27 0.27 0.34 17%
TOTAL BASIN B 3.40 0.75 0.37 0.44 0.63 Clayey | Average 2% to 7% 1.213 0.62 0.62 0.77 54%
C1 0.36 0.00 0.07 0.00 0.12 Clayey | Average 2% to 7% 0.165 0.63 0.63 0.79 49%
C2 0.48 0.00 0.07 0.00 0.06 Clayey | Average 2% to 7% 0.356 0.43 0.43 0.54 24%
TOTAL BASIN C 0.85 0.00 0.15 0.00 0.18 Clayey | Average 2% to 7% 0.521 0.52 0.52 0.65 35%
D1 0.33 0.26 0.02 0.00 0.00 Clayey | Average 2% to 7% 0.046 0.85 0.85 1.00 85%
D2 2.05 0.47 0.68 0.23 0.23 Clayey | Average 2% to 7% 0.443 0.73 0.73 0.91 67%
D3 0.98 0.35 0.15 0.00 0.16 Clayey | Average 2% to 7% 0.319 0.72 0.72 0.90 64%
D4 0.66 0.14 0.10 0.30 0.07 Clayey | Average 2% to 7% 0.058 0.60 0.60 0.74 62%
D5 1.38 0.00 0.04 0.27 0.15 Clayey | Average 2% to 7% 0.912 0.36 0.36 0.45 20%
TOTAL BASIN D 5.39 1.22 0.99 0.80 0.60 Clayey | Average 2% to 7% 1.779 0.62 0.62 0.78 55%
UD1 0.49 0.03 0.02 0.44 0.00 Clayey | Average 2% to 7% 0.010 0.36 0.36 0.45 44%
OS1 4.07 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 4.075 0.25 0.25 0.31 0%
TOTAL SITE 19.67 2.63 2.22 2.23 2.68 Clayey | Average 2% to 7% 9.899 0.52 0.52 0.66 40%
Composite Runoff Coefficient with Adjustment
PROPOSED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
12/20/2016 3:50 PM D:\Projects\911-007\Drainage\Hydrology\911-007_Proposed_Rational_Calcs.xlsx\Composite C
3 HB3 Yes 0.25 0.25 0.31 541 0.98% 37.2 37.2 34.5 0 N/A N/A N/A 37.2 37.2 34.5
EXISTING TIME OF CONCENTRATION COMPUTATIONS
S. Thomas
December 20, 2016
Design
Point
Sub-Basin
Overland Flow Swale Flow Time of Concentration
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
12/20/2016 3:48 PM D:\Projects\911-007\Drainage\Hydrology\911-007_Existing_Rational_Calcs.xlsx\Tc
HA2 4.18 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 4.178 0.25 0.25 0.31 0%
HA3 0.33 0.15 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.178 0.57 0.57 0.71 45%
HB1 5.60 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 5.602 0.25 0.25 0.31 0%
HB2 0.47 0.21 0.00 0.00 0.00 Clayey | Average 2% to 7% 0.254 0.57 0.57 0.71 45%
HB3 4.66 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 4.661 0.25 0.25 0.31 0%
1. Table RO-11 | Rational Method Runoff Coefficients for Composite Analysis
Composite Runoff Coefficient with Adjustment
EXISTING COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
12/20/2016 3:47 PM D:\Projects\911-007\Drainage\Hydrology\911-007_Existing_Rational_Calcs.xlsx\Composite C
Survey Area Data: Version 11, Sep 23, 2016
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
(Mountain's Edge)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
12/21/2016
Page 2 of 4
Overland Trail, within Basin C1, will be safely routed through Detention Pond 3
undetained.