HomeMy WebLinkAboutMOUNTAIN'S EDGE (FORMERLY 2430 OVERLAND TRAIL - RESIDENTIAL) - PDP - PDP160045 - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE REPORTPRELIMINARY DRAINAGE AND
EROSION CONTROL REPORT
October 9, 2017
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.
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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 .............................................................................................. 7
G. Modifications of Criteria .............................................................................................................. 7
IV. DRAINAGE FACILITY DESIGN .................................................................................... 7
A. General Concept .......................................................................................................................... 7
B. Water Quality Treatment ........................................................................................................... 13
C. SWMM Modeling ....................................................................................................................... 13
D. Specific Details ........................................................................................................................... 14
V. CONCLUSIONS ...................................................................................................... 14
A. Compliance with Standards ........................................................................................................ 14
B. Drainage Concept ...................................................................................................................... 14
References ....................................................................................................................... 15
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 - SWMM Modeling
APPENDIX F – 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 ........................................................................ 10
Table 3 - Detention Pond Summary ..................................................................................... 11
Table 4 - Historic Stormwater Release and Allowable Developed Release.................................. 12
Table 5 - Proposed Stormwater Release ............................................................................... 12
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 12 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, bioswales, 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
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 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 Dixon
Mountain’s Edge
Preliminary Drainage Report 5
Creek (Spring Creek Basin) 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 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. A 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 Spring Creek and Canal Importation Drainage
Basins. 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.
5. The Mountain’s Edge project proposes to discharge developed stormwater runoff for
the site to Dixon Creek at the historic 2-year rates.
Mountain’s Edge
Preliminary Drainage Report 7
F. Floodplain Regulations Compliance
1. As previously mentioned, all structures are located outside of any FEMA 100-year
floodplain, and thus are not subject to any floodplain regulations.
G. Modifications of Criteria
1. The proposed development is not requesting any modifications to criteria at this time.
IV. DRAINAGE FACILITY DESIGN
A. General Concept
1. The main objectives of the Mountain’s Edge drainage design are to maintain the
allowable storm runoffs as outlined within the Spring Creek Basin master plans. This
project will divert all developed runoff to the historic discharge location for the Spring
Creek Basin. The historic discharge location for the Canal Importation Basin will not
be utilized for on-site developed stormwater release from this project.
2. Per the development guidelines, half of any existing adjacent roadway is required to
be detained and treated on-site, as is feasible and reasonable. With this
development, half of Overland Trail (north of Bluegrass) is proposed to be detained
and treated within the Mountain’s Edge project. Overland Trail (south of Bluegrass)
and Drake Road are adjacent to the site, but are not adjacent to the planned
development. As such, detention and treatment of these areas will be significantly
challenging. In order to meet this guideline, extensive storm infrastructure and
disturbance of existing vegetation would be required. With this in mind, these areas
of Overland Trail (south of Bluegrass) and Drake Road are not proposed to be
detained and treated on the Mountain’s Edge site.
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 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 and
treated with this project.
Mountain’s Edge
Preliminary Drainage Report 8
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 historic undefined swale adjacent the existing access road for the
Holiday Twin Drive-In Theater, 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 an undefined swale along the off-site access
road to the Holiday Twin Drive-in Theater. From there, flows are conveyed to a City
owned and maintained drainage easement through the Brown’s Farm Subdivision.
Basin HB2 contains existing Overland Trail Right of Way proposed to be detained and
treated 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
5. The Mountain’s Edge project divided the site into seven (7) major drainage basins,
designated as Basins A, B, C, D, OS, HT 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 6 sub-basins (A1-A6). Runoff from Basins A1-A6 is detained in Detention Pond
1. Stormwater runoff within Basin A1 is treated for water quality and LID in Rain
Garden 1. Stormwater runoff from Basins A2-A6 is treated for water quality within
Detention Pond 1. The stormwater release from Detention Pond 1 will be routed
south, through the site, to Dixon Creek.
Mountain’s Edge
Preliminary Drainage Report 9
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 6 sub-basins (B1-B6). Runoff from Basins B1-B6 is detained in Detention Pond
2. Stormwater runoff for Basins B1-B6 will be treated for water quality within
Detention Pond 2. The stormwater release for Detention Pond 2 will be conveyed
south, through the site, to Dixon Creek. Off-site stormwater from Basin OS1 will be
conveyed through the project to the historic discharge location for the Canal
Importation Basin through a proposed pipe.
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. The
stormwater release for Detention Pond 3 will be conveyed south to Dixon Creek.
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. The stormwater release for Detention Pond 4 will be conveyed
south to Dixon Creek.
Basin UD
Basin UD1 consists of proposed sidewalk and roadways. Runoff from Basin UD1 will
not be detained. Stormwater runoff for Basin UD1 generally will be conveyed through
existing roadways within the Brown’s Farm Subdivision. No LID treatment is planned
for Basin UD1.
Basin UD2 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. Minor
grading is proposed within this basin.
Basin HT1
Basin HT1 is an off-site basin that consists of the existing drive-in theater. Basin HT1
consists of mostly vegetated undeveloped land. HT1 generally gets conveyed in the
small drainage swale on the northside of the Holiday Twin access road until it reaches
the existing ticket booth. At the ticket booth, the flows overtop the existing access
road into an undefined swale along the boundary of Holiday Twin and the Brown Farm
Subdivision.
Basin OS
Basin OS1 is an off-site basin west of Overland Trail. This basin stretches to west to
Horsetooth Reservoir. Based on existing topography, this basin was determined to be
approximately 14.7 acres. During a 100-year event, stormwater from this basin will
be conveyed to a culvert passing under Overland Trail within Basin B1. A SWMM
model was utilized to determine the maximum flow that would pass through the
existing culvert during a 100-year event. The maximum flow was determined to be
Mountain’s Edge
Preliminary Drainage Report 10
16.2 cfs with ponding west of Overland Trail. This flow will be safely passed through
Basin B to the historic undefined swale along the boundary of Holiday Twin and the
Brown Farm Subdivision.
Basin OS2 is an off-site basin west of Overland Trail. This basin stretches to west to
the Dixon Creek Reservoir. This off-site basin contributes to Dixon Creek. Based on
the Fort Collins SWMM model for the Spring Creek Basin, this basin was determined
to be approximately 72.2 acres minus 8.58 acres of historic on-site basin, for a total
63.62 acres. During a 100-year event, stormwater from this basin will be conveyed
to an existing 18” culvert passing under Overland Trail within Basin UD2. The full
100-year flow is restricted by the 18” culvert and stormwater will pool west of
Overland Trail. At a depth of approximately 6 feet above the culvert invert, the water
will bypass the culvert and continue south down a roadside swale on the west side of
Overland Trail. A SWMM model was utilized to determine the maximum flow that
would pass through the existing culvert during a 100-year event. The maximum flow
was determined to be 22.0 cfs with 18.83 cfs continuing south along Overland Trail.
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)
A1 A1 1.45 0.66 0.83 7.1 5.3 2.42 11.93
A2 A2 0.24 0.62 0.77 5.0 5.0 0.42 1.85
A3 A3 0.21 0.60 0.74 5.0 5.0 0.36 1.55
A4 A4 0.23 0.62 0.77 5.0 5.0 0.41 1.77
A5 A5 1.12 0.90 1.00 6.7 5.6 2.60 10.76
A6 A6 2.19 0.47 0.58 10.1 9.1 2.26 10.27
B1 B1 0.50 0.83 1.00 6.3 5.0 1.10 4.93
B2 B2 0.62 0.58 0.72 6.4 5.5 0.97 4.36
B3 B3 1.08 0.80 1.00 5.0 5.0 2.46 10.73
B4 B4 0.27 0.92 1.00 5.0 5.0 0.71 2.72
B5 B5 0.19 0.78 0.98 5.0 5.0 0.42 1.82
B6 B6 1.50 0.27 0.34 16.8 16.1 0.72 3.20
C1 C1 0.14 0.60 0.76 5.0 5.0 0.23 1.02
C2 C2 0.45 0.37 0.47 5.9 5.2 0.46 2.09
D1 D1 0.30 0.85 1.00 5.0 5.0 0.72 2.94
D2 D2 1.66 0.67 0.84 5.0 5.0 3.18 13.87
D3 D3 0.98 0.71 0.89 5.7 5.0 1.92 8.63
D4 D4 0.66 0.58 0.73 5.1 5.0 1.09 4.76
D5 D5 1.41 0.37 0.46 9.8 9.1 1.17 5.19
UD1 UD1 0.05 0.83 1.00 5.0 5.0 0.12 0.52
UD2 UD2 4.07 0.26 0.33 14.2 13.7 2.04 9.07
HT1 HT1 5.51 0.27 0.34 42.7 39.3 1.54 7.11
Mountain’s Edge
Preliminary Drainage Report 11
Detention Pond 1
Detention Pond 1 detains developed runoff from Basin A. Detention Pond 1 has a
total 3.65 feet of freeboard from the 100-yr WSEL to the lowest proposed top of
foundation. Additionally, the emergency spill location is 2.01 feet below the lowest
proposed top of foundation. Water Quality is proposed within the pond volume
through an approved outlet structure. The pond release is routed to Dixon Creek.
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 convey emergency overflow
through the outlet structure. The pond release is routed to Dixon Creek.
Detention Pond 3
Detention Pond 3 detains developed runoff from Basin C. Detention Pond 3 has a
total 4.36 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. The pond release is routed to Dixon
Creek.
Detention Pond 4
Detention Pond 4 detains developed runoff from Basin D. Detention Pond 4 has a
total 2.25 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 provided upstream of the
detention pond within Rain Garden 2. The pond release is routed to Dixon Creek.
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 1.30 5145.90 3,129 5141.85 0.35
2 0.93 5139.59 3,115 5137.68 0.39
3 0.09 5144.65 268 5142.89 0.10
4 1.03 5142.24 n/a n/a 0.60
Mountain’s Edge
Preliminary Drainage Report 12
Total Stormwater Release from Site
The total allowable 100-yr release from the site was evaluated based on the historic
Basins HA and HB. 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
Based purely on a summation of detention pond releases and the basin runoff for
Basin UD2, the total discharge from Mountain’s Edge to Dixon Creek would be 10.51
cfs. This is 0.25 cfs more than the allowable.
Table 5 - Proposed Stormwater Release
Proposed Stormwater Release
Pond/ Basin
100-yr Flow
(cfs)
Basin HA
Pond 1 0.35
Pond 2 0.39
Pond 3 0.10
Pond 4 0.60
Basin UD2 9.07
Total Basin HA 10.51
Basin HB
UD1 0.52
Total Basin HB 0.52
Mountain’s Edge
Preliminary Drainage Report 13
The pond volumes and pond releases were maximized based on a combination of
available storage volume within of the ponds and total release durations based on the
Colorado Revised Statute 37-92-602(8).
Due to the 0.25 cfs discrepancy, a SWMM model was utilized to measure the flow in
Dixon Creek from this site. The SWMM model accounts for the varying times to peak
for the discharges from the ponds and Basin UD2. This SWMM model shows a 100-
year peak flow from the site of 9.63 cfs contributing to Dixon Creek. This is
sufficiently less than the allowable discharge of 10.26 cfs.
The proposed site will generally detain all developed flows from the property to the 2-
year historic release for the Spring Creek Basin. Additionally, any undetained runoff
from the site will comply with the 2-year historic release for the Canal Importation
Basin.
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. SWMM Modeling
1. A SWMM model was created to model multiple drainage concepts that are
challenging to model using standard hydraulic and rational calculations. These
concepts include the following:
• Peak flow from Basin OS2 through the existing pipe under Overland Trail during a
100-yr event. The total flow that spills to the south and bypasses the Dixon Creek
during a 100-yr event.
▪ During a 100-year event, total flow in the existing culvert is 22.0 cfs and
18.83 cfs bypasses the Dixon Creek continuing south along Overland Trail
roadside swale.
• Peak flow from Basin OS1 routed through Basin B and discharged at the boundary
of Holiday Twin Drive-in and Brown Farm Subdivision during a 100-year event.
▪ During a 100-year event, 16.20 cfs is conveyed through the Mountain’s
Edge developing from Basin OS1.
• Total emergency overflow rate for Basin B if the 100-yr orifice for Pond 2 is clogged.
The outlet structure for Detention Pond 2 will be required to convey this flow to
Dixon Creek prior to the pond overtopping.
▪ If the Detention Pond 2 100-year orifice were to become clogged during a
100-year event, the pond fill up and approximately 0.40 cfs would spill
through the outlet structure and continue to Dixon Creek.
Mountain’s Edge
Preliminary Drainage Report 14
• Peak flow from the Mountain’s Edge site contributing to Dixon Creek based on
differing peaking times for the undetained basin and detained basins during a100-
year event.
▪ During a 100-year event, the peak flow from the Mountain’s Edge
development to Dixon Creek is 9.63 cfs. This was determined by
disallowing flows from Basin OS2 through the existing culvert.
• Total flow in Dixon Creek based on the detained flows from Mountain’s Edge,
undetained basins from Mountain’s Edge and upstream undetained off-site Basin
OS2.
▪ During a 100-year event, the peak flow in Dixon Creek, along the Mountain’s
Edge property, is 26.78 cfs. This flow accounts for the undetained basin
UD2, the detention pond releases, and the flow from off-site basin OS2.
D. 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 LID treatment for 49.8% of total impervious areas. This is 0.2%
below the requirements set forth by the City of Fort Collins for Low Impact
Development (LID). 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
not expected to 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 rain gardens. This is
currently unable to be calculated with available soils data.
Mountain’s Edge
Preliminary Drainage Report 15
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
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 SURFACE1:
Runoff
Coefficient
Percentage
Impervious Project: Mountain's Edge
Streets, Parking Lots, Roofs, Alleys, and Drives: Calculations By: S. Thomas
Asphalt ……....……………...……….....…...……………….………………………………………………………….0.95 . 100% Date: September 14, 2017
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
Gravel
(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
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:
A1 A1 1.45 7 7 5 0.66 0.66 0.83 2.52 4.31 9.95 2.42 4.14 11.93
A2 A2 0.24 5 5 5 0.62 0.62 0.77 2.85 4.87 9.95 0.42 0.73 1.85
A3 A3 0.21 5 5 5 0.60 0.60 0.74 2.85 4.87 9.95 0.36 0.61 1.55
A4 A4 0.23 5 5 5 0.62 0.62 0.77 2.85 4.87 9.95 0.41 0.69 1.77
A5 A5 1.12 7 7 6 0.90 0.90 1.00 2.60 4.44 9.63 2.60 4.45 10.76
A6 A6 2.19 10 10 9 0.47 0.47 0.58 2.21 3.78 8.03 2.26 3.87 10.27
A6 TOTAL BASIN A 5.44 9 9 7 0.63 0.63 0.78 2.35 4.02 8.80 8.00 13.66 37.42
B1 B1 0.50 6 6 5 0.83 0.83 1.00 2.67 4.56 9.95 1.10 1.87 4.93
B2 B2 0.62 6 6 6 0.58 0.58 0.72 2.67 4.56 9.63 0.97 1.65 4.36
B3 B3 1.08 5 5 5 0.80 0.80 1.00 2.85 4.87 9.95 2.46 4.20 10.73
B4 B4 0.27 5 5 5 0.92 0.92 1.00 2.85 4.87 9.95 0.71 1.22 2.72
B5 B5 0.19 5 5 5 0.78 0.78 0.98 2.85 4.87 9.95 0.42 0.71 1.82
B6 B6 1.50 17 17 16 0.27 0.27 0.34 1.78 3.04 6.30 0.72 1.23 3.20
B6 TOTAL BASIN B 4.16 14 14 12 0.59 0.59 0.73 1.95 3.34 7.16 4.76 8.14 21.83
C1 C1 0.14 5 5 5 0.60 0.60 0.76 2.85 4.87 9.95 0.23 0.40 1.02
C2 C2 0.45 6 6 5 0.37 0.37 0.47 2.76 4.72 9.95 0.46 0.79 2.09
C2 TOTAL BASIN C 0.58 6 6 5 0.43 0.43 0.54 2.76 4.72 9.95 0.69 1.18 3.11
D1 D1 0.30 5 5 5 0.85 0.85 1.00 2.85 4.87 9.95 0.72 1.22 2.94
D2 D2 1.66 5 5 5 0.67 0.67 0.84 2.85 4.87 9.95 3.18 5.43 13.87
D3 D3 0.98 6 6 5 0.71 0.71 0.89 2.76 4.72 9.95 1.92 3.27 8.63
D4 D4 0.66 5 5 5 0.58 0.58 0.73 2.85 4.87 9.95 1.09 1.86 4.76
D5 D5 1.41 10 10 9 0.37 0.37 0.46 2.26 3.86 8.03 1.17 1.99 5.19
D5 TOTAL BASIN D 5.00 8 8 7 0.59 0.59 0.74 2.40 4.10 9.06 7.10 12.14 33.51
UD1 UD1 0.05 5 5 5 0.83 0.83 1.00 2.85 4.87 9.95 0.12 0.21 0.52
UD2 UD2 4.07 14 14 14 0.26 0.26 0.33 1.92 3.29 6.82 2.04 3.50 9.07
HT1 HT1 5.51 43 43 39 0.27 0.27 0.34 1.03 1.76 3.80 1.54 2.63 7.11
OS1 OS1 14.72 24 24 23 0.33 0.33 0.41 1.48 2.52 5.20 7.06 12.06 31.10
September 14, 2017
Intensity,
i10
(in/hr)
C10
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
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: 9/14/2017
Pond No.: 1
Pond 1
100-yr
0.78 WQCV 3129 ft3
Area (A)= 5.44 acres Quantity Detention 53694 ft3
Max Release Rate = 0.35 cfs Total Volume 56823 ft3
Total Volume 1.304 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 42.2 12666 105 12561
10 600 7.72 32.8 19655 210 19445
15 900 6.52 27.7 24899 315 24584
20 1200 5.60 23.8 28514 420 28094
25 1500 4.98 21.1 31697 525 31172
30 1800 4.52 19.2 34523 630 33893
35 2100 4.08 17.3 36356 735 35621
40 2400 3.74 15.9 38087 840 37247
45 2700 3.46 14.7 39640 945 38695
50 3000 3.23 13.7 41117 1050 40067
55 3300 3.03 12.9 42428 1155 41273
60 3600 2.86 12.1 43688 1260 42428
65 3900 2.72 11.5 45012 1365 43647
70 4200 2.59 11.0 46158 1470 44688
75 4500 2.48 10.5 47354 1575 45779
80 4800 2.38 10.1 48474 1680 46794
85 5100 2.29 9.7 49556 1785 47771
90 5400 2.21 9.4 50638 1890 48748
95 5700 2.13 9.0 51517 1995 49522
100 6000 2.06 8.7 52446 2100 50346
105 6300 2.00 8.5 53464 2205 51259
110 6600 1.94 8.2 54330 2310 52020
115 6900 1.89 8.0 55336 2415 52921
120 7200 1.84 7.8 56214 2520 53694
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
Detention Pond Calculation | FAA Method
Project Number:
Project Location:
Calculations By:
9/14/2017 5:20 PM 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: 9/14/2017
Pond No.: 1
Pond 1
WQCV
3129 ft3 5141.85 ft.
Design Storm 100-yr
Required Volume= 56823 ft3 5145.90 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
5,140.20 68 0.00 0 0 0 0
5,140.40 270 0.20 34 34 32 32
5,140.60 586 0.20 86 119 84 115
5,140.80 985 0.20 157 277 155 271
5,141.00 1482 0.20 247 523 245 516
5,141.20 2098 0.20 358 881 356 872
5,141.40 2847 0.20 495 1376 493 1364
5,141.60 3751 0.20 660 2035 658 2022
5,141.80 4820 0.20 857 2893 855 2877
5,142.00 6006 0.20 1083 3975 1080 3957
5,142.20 7156 0.20 1316 5291 1315 5272
5,142.40 8243 0.20 1540 6831 1539 6811
5,142.60 8948 0.20 1719 8551 1719 8529
5,142.80 9337 0.20 1829 10379 1828 10358
5,143.00 9667 0.20 1900 12280 1900 12258
5,143.20 10003 0.20 1967 14247 1967 14225
5,143.40 10344 0.20 2035 16281 2035 16260
5,143.60 10692 0.20 2104 18385 2104 18363
5,143.80 11045 0.20 2174 20559 2174 20537
5,144.00 11403 0.20 2245 22803 2245 22781
5,144.20 11768 0.20 2317 25121 2317 25099
5,144.40 12,327 0.20 2410 27530 2409 27508
5,144.60 13,276 0.20 2560 30090 2560 30068
5,144.80 14,993 0.20 2827 32917 2825 32893
5,145.00 16,937 0.20 3193 36110 3191 36084
5,145.20 18,981 0.20 3592 39702 3590 39673
5,145.40 22,753 0.20 4173 43875 4168 43841
5,145.60 25,242 0.20 4800 48675 4797 48639
5,145.80 27,817 0.20 5306 53981 5304 53942
5,146.00 30,228 0.20 5805 59785 5803 59745
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 66.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.660
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.21 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 63,123 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 1,086 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 = 12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 833 sq ft
D) Actual Flat Surface Area AActual = 933 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 1577 sq ft
F) Rain Garden Total Volume VT= 1,255 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft
iii) Orifice Diameter, 3/8" Minimum DO = N/A in
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
September 14, 2017
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 9/14/2017, 2:31 PM
POND 1
Project: Mountain's Edge
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 5.440 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 52.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.5200 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.212 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.096 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Rain Garden WQCV (ft
3
) = 1086 <-- CALCULATED
Adjusted WQCV (cu-ft) = 3096 <-- CALCULATED (minus Rain Garden)
WQ Depth (ft) = 1.840 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.236 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 5/9 <-- INPUT from Figure 5
number of rows = 6
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
September 14, 2017
Mountain's Edge
911-007
Fort Collins, Colorado
S. Thomas Date: 9/14/2017
Pond No.: Pond 2
Pond 2
100-yr
0.73 WQCV 3115 ft3
Area (A)= 4.16 acres Quantity Detention 37424 ft3
Max Release Rate = 0.39 cfs Total Volume 40539 ft3
Total Volume 0.931 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 30.2 9065 117 8948
10 600 7.72 23.4 14066 234 13832
15 900 6.52 19.8 17820 351 17469
20 1200 5.60 17.0 20407 468 19939
25 1500 4.98 15.1 22685 585 22100
30 1800 4.52 13.7 24707 702 24005
35 2100 4.08 12.4 26019 819 25200
40 2400 3.74 11.4 27258 936 26322
45 2700 3.46 10.5 28370 1053 27317
50 3000 3.23 9.8 29427 1170 28257
55 3300 3.03 9.2 30365 1287 29078
60 3600 2.86 8.7 31267 1404 29863
65 3900 2.72 8.3 32214 1521 30693
70 4200 2.59 7.9 33034 1638 31396
75 4500 2.48 7.5 33891 1755 32136
80 4800 2.38 7.2 34692 1872 32820
85 5100 2.29 7.0 35467 1989 33478
90 5400 2.21 6.7 36241 2106 34135
95 5700 2.13 6.5 36870 2223 34647
100 6000 2.06 6.3 37535 2340 35195
105 6300 2.00 6.1 38264 2457 35807
110 6600 1.94 5.9 38883 2574 36309
115 6900 1.89 5.7 39603 2691 36912
120 7200 1.84 5.6 40232 2808 37424
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
Detention Pond Calculation | FAA Method
Project Number:
Project Location:
Calculations By:
9/14/2017 2:27 PM 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: 9/14/2017
Pond No.: Pond 2
Pond 2
WQCV
3115 ft3 5137.68 ft.
Design Storm 100-yr
Required Volume= 40539 ft3 5139.59 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
5,137.00 5 0.00 0 0 0 0
5,137.20 1874 0.20 188 188 132 132
5,137.40 5148 0.20 702 890 675 807
5,137.60 9268 0.20 1442 2332 1422 2228
5,137.80 13427 0.20 2269 4601 2257 4485
5,138.00 16787 0.20 3021 7623 3015 7500
5,138.20 18731 0.20 3552 11174 3550 11050
5,138.40 19560 0.20 3829 15004 3829 14879
5,138.60 20203 0.20 3976 18980 3976 18855
5,138.80 20851 0.20 4105 23085 4105 22961
5,139.00 21504 0.20 4235 27321 4235 27196
5,139.20 22162 0.20 4367 31687 4366 31562
5,139.40 22825 0.20 4499 36186 4499 36061
5,139.60 23502 0.20 4633 40819 4633 40693
5,139.80 24227 0.20 4773 45592 4773 45466
5,140.00 24986 0.20 4921 50513 4921 50387
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
9/14/20172:19 PM 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)= 4.160 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 50.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.5000 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.206 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.072 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Rain Garden WQCV (ft
3
) = 0 <-- CALCULATED
Adjusted WQCV (cu-ft) = 3115 <-- CALCULATED (minus Rain Garden)
WQ Depth (ft) = 1.120 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.279 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 3/5 <-- 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
September 14, 2017
Mountain's Edge
911-007
Fort Collins, Colorado
S. Thomas Date: 9/14/2017
Pond No.: Pond 3
Pond 3
100-yr
0.54 WQCV 268 ft3
Area (A)= 0.58 acres Quantity Detention 3429 ft3
Max Release Rate = 0.10 cfs Total Volume 3697 ft3
Total Volume 0.085 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 3.1 935 30 905
10 600 7.72 2.4 1451 60 1391
15 900 6.52 2.0 1838 90 1748
20 1200 5.60 1.8 2105 120 1985
25 1500 4.98 1.6 2340 150 2190
30 1800 4.52 1.4 2548 180 2368
35 2100 4.08 1.3 2683 210 2473
40 2400 3.74 1.2 2811 240 2571
45 2700 3.46 1.1 2926 270 2656
50 3000 3.23 1.0 3035 300 2735
55 3300 3.03 0.9 3132 330 2802
60 3600 2.86 0.9 3225 360 2865
65 3900 2.72 0.9 3322 390 2932
70 4200 2.59 0.8 3407 420 2987
75 4500 2.48 0.8 3495 450 3045
80 4800 2.38 0.7 3578 480 3098
85 5100 2.29 0.7 3658 510 3148
90 5400 2.21 0.7 3738 540 3198
95 5700 2.13 0.7 3803 570 3233
100 6000 2.06 0.6 3871 600 3271
105 6300 2.00 0.6 3946 630 3316
110 6600 1.94 0.6 4010 660 3350
115 6900 1.89 0.6 4084 690 3394
120 7200 1.84 0.6 4149 720 3429
Detention Pond Calculation | FAA Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
9/14/2017 2:20 PM 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: 9/14/2017
Pond No.: Pond 3
Pond 3
WQCV
268 ft3 5142.89 ft.
Design Storm 100-yr
Required Volume= 3697 ft3 5144.65 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
5,142.40 200 0.20 27 36 26 33
5,142.60 389 0.20 59 94 58 91
5,142.80 641 0.20 103 197 102 193
5,143.00 956 0.20 160 357 159 352
5,143.20 1,337 0.20 229 586 228 580
5,143.40 1,748 0.20 308 895 308 888
5,143.60 1,905 0.20 365 1260 365 1253
5,143.80 2,062 0.20 397 1657 397 1650
5,144.00 2,224 0.20 429 2086 429 2078
5,144.20 2,391 0.20 461 2547 461 2539
5,144.40 2,563 0.20 495 3042 495 3035
5,144.60 2,742 0.20 531 3573 530 3565
5,144.80 2,928 0.20 567 4140 567 4132
5,145.00 3,120 0.20 605 4745 605 4737
5,145.20 3,319 0.20 644 5389 644 5381
5,145.40 3,525 0.20 684 6073 684 6065
5,145.60 3,737 0.20 726 6799 726 6791
5,145.80 3,956 0.20 769 7569 769 7560
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
9/14/20172:20 PM 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)= 0.580 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 23.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.2300 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 1.0 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.128 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.006 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Rain Garden WQCV (ft
3
) = 0 <-- CALCULATED
Adjusted WQCV (cu-ft) = 268 <-- CALCULATED (minus Rain Garden)
WQ Depth (ft) = 0.890 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.029 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 1/5 <-- 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
July 25, 2017
Mountain's Edge
911-007
Fort Collins, Colorado
S. Thomas Date: 9/14/2017
Pond No.: 4
Pond 4
100-yr
0.74 WQCV 0 ft3
Area (A)= 5.00 acres Quantity Detention 44698 ft3
Max Release Rate = 0.6 cfs Total Volume 44698 ft3
Total Volume 1.026 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 36.8 11045 180 10865
10 600 7.72 28.6 17138 360 16778
15 900 6.52 24.1 21712 540 21172
20 1200 5.60 20.7 24864 720 24144
25 1500 4.98 18.4 27639 900 26739
30 1800 4.52 16.7 30103 1080 29023
35 2100 4.08 15.1 31702 1260 30442
40 2400 3.74 13.8 33211 1440 31771
45 2700 3.46 12.8 34565 1620 32945
50 3000 3.23 12.0 35853 1800 34053
55 3300 3.03 11.2 36996 1980 35016
60 3600 2.86 10.6 38095 2160 35935
65 3900 2.72 10.1 39250 2340 36910
70 4200 2.59 9.6 40249 2520 37729
75 4500 2.48 9.2 41292 2700 38592
80 4800 2.38 8.8 42269 2880 39389
85 5100 2.29 8.5 43212 3060 40152
90 5400 2.21 8.2 44156 3240 40916
95 5700 2.13 7.9 44922 3420 41502
100 6000 2.06 7.6 45732 3600 42132
105 6300 2.00 7.4 46620 3780 42840
110 6600 1.94 7.2 47375 3960 43415
115 6900 1.89 7.0 48252 4140 44112
120 7200 1.84 6.8 49018 4320 44698
Detention Pond Calculation | FAA Method
Project Number:
Project Location:
Calculations By:
Input Variables Results
Design Point
Design Storm Required Detention Volume
Developed "C" =
9/14/2017 2:21 PM 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: 9/14/2017
Pond No.: 4
Pond 4
WQCV
0 ft3 5135.60 ft.
Design Storm 100-yr
Required Volume= 44698 ft3 5142.24 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
5,135.60 138 0.00 0 0 0 0
5,135.80 452 0.20 59 59 56 56
5,136.00 875 0.20 133 192 130 186
5,136.20 1341 0.20 222 413 220 406
5,136.40 1778 0.20 312 725 311 717
5,136.60 2229 0.20 401 1126 400 1117
5,136.80 2714 0.20 494 1620 494 1611
5,137.00 3208 0.20 592 2213 592 2202
5,137.20 3417 0.20 662 2875 662 2865
5,137.40 3627 0.20 704 3579 704 3569
5,137.60 3841 0.20 747 4326 747 4316
5,137.80 4,061 0.20 790 5116 790 5106
5,138.00 4,287 0.20 835 5951 835 5940
5,138.20 4,518 0.20 880 6832 880 6821
5,138.40 4,754 0.20 927 7759 927 7748
5,138.60 4,996 0.20 975 8734 975 8723
5,138.80 5,243 0.20 1024 9758 1024 9747
5,139.00 5,495 0.20 1074 10832 1074 10820
5,139.20 5,753 0.20 1125 11957 1125 11945
5,139.40 6,017 0.20 1177 13134 1177 13122
5,139.60 6,286 0.20 1230 14364 1230 14352
5,139.80 6,560 0.20 1285 15648 1285 15637
5,140.00 6,841 0.20 1340 16989 1340 16977
5,140.20 7,126 0.20 1397 18385 1397 18373
5,140.40 7,417 0.20 1454 19840 1454 19827
5,140.60 7,713 0.20 1513 21352 1513 21340
5,140.80 12,298 0.20 2001 23354 1983 23324
5,141.00 12,974 0.20 2527 25881 2527 25850
5,141.20 13,659 0.20 2663 28544 2663 28514
5,141.40 14,360 0.20 2802 31346 2802 31315
5,141.60 15,076 0.20 2944 34289 2943 34258
5,141.80 15,806 0.20 3088 37378 3088 37346
5,142.00 16,553 0.20 3236 40614 3236 40582
5,142.20 17,346 0.20 3390 44004 3390 43972
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 51.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.510
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.17 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 217,840 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = 3,035 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 = 12 in
B) Rain Garden Side Slopes (Z = 4 min., horiz. dist per unit vertical) Z = 4.00 ft / ft
(Use "0" if rain garden has vertical walls)
C) Mimimum Flat Surface Area AMin = 2222 sq ft
D) Actual Flat Surface Area AActual = 2334 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 3974 sq ft
F) Rain Garden Total Volume VT= 3,154 cu ft
(VT= ((ATop + AActual) / 2) * Depth)
3. Growing Media
4. Underdrain System
A) Are underdrains provided?
B) Underdrain system orifice diameter for 12 hour drain time
i) Distance From Lowest Elevation of the Storage y = ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = N/A cu ft
iii) Orifice Diameter, 3/8" Minimum DO = N/A in
Design Procedure Form: Rain Garden (RG)
Stephanie Thomas
Northern Engineering
September 14, 2017
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 2.xlsm, RG 9/14/2017, 2:31 PM
POND 4
Project: Mountain's Edge
By: S. Thomas
REQUIRED STORAGE & OUTLET WORKS:
BASIN AREA (acres)= 5.000 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS PERCENT = 51.00 <-- INPUT from impervious calcs
BASIN IMPERVIOUSNESS RATIO = 0.5100 <-- CALCULATED
Drain Time (hrs) 40 <-- INPUT
Drain Time Coefficient 0.8 <-- CALCULATED from Figure Table 3-2
WQCV (watershed inches) = 0.167 <-- CALCULATED from Figure 3-2
WQCV (ac-ft) = 0.070 <-- CALCULATED from UDFCD DCM V.3 Section 6.5
Rain Garden WQCV (ft
3
) = 3035 <-- CALCULATED
Adjusted WQCV (cu-ft) = 0 <-- CALCULATED (minus Rain Garden)
WQ Depth (ft) = 1.000 <-- INPUT from stage-storage table
AREA REQUIRED PER ROW, a (in
2
) = 0.000 <-- CALCULATED from Figure EDB-3
CIRCULAR PERFORATION SIZING:
dia (in) = 0 <-- 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
September 14, 2017
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: September 14, 2017
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area,
A
(sf)
LID Treatment
L1 A1 63,123 66% 41,387
Total L1 63,123 66% 41,387
L2 D1 12,853 86% 10,992
D2 72,150 62% 44,522
D3 42,668 63% 26,699
D4 28,680 60% 17,110
D5 61,489 20% 12,463
Total L2 217,840 51% 111,785
Total Treated 280,963 55% 153,172
LID BASIN NODE Sub-Basin(s)
Area, A
(sf)
Percent
Impervious
Impervious Area,
A
(sf)
A2 10,529 47% 4,964
A3 9,133 44% 4,060
A4 10,041 47% 4,757
A5 48,678 85% 41,408
A6 95,400 28% 26,656
B1 21,602 82% 17,654
B2 27,198 42% 11,537
B3 47,051 74% 34,707
B4 11,903 88% 10,433
B5 8,132 74% 6,013
B6 65,127 14% 9,441
C1 5,930 46% 2,705
C2 19,542 16% 3,130
UD1 2,263 80% 1,810
Total Proposed
Untreated
382,529 47% 179,275
B1 21,602 66% 14,163
D1 12,853 86% 10,992
Total Overland
Trail ROW
34,455 73% 25,155
PROPOSED LID COMPUTATIONS
PROPOSED LID UNTREATED AREA
PROPOSED LID TREATED AREA
Rain Garden 2
Rain Garden 1
AREA NOT REQUIRED TO BE TREATED WITH LID
Project: Mountain's Edge
Calculations By: S. Thomas
Date: September 14, 2017
PROPOSED LID COMPUTATIONS
663,492
25,155
332,447
307,291
153,646
153,172
49.8%
Rain Garden 1 Rain Garden 2
Total Contributing
Area (sf)
63,123 217,840
Percent Impervious 66% 51%
Total Volume
Required (cf)
1,086 3,035
Total Volume
Provided (cf)
1,255 3,154
LID TREATMENT SUMMARY
Total Site Area (sf)
Total Net Proposed Impervious Area (sf)
RAIN GARDEN SUMMARY
Total Overland ROW Impervious Area (sf)
(Basins B1, D1)
Total Proposed Impervious Area (sf)
Total Treated Impervious Area (sf)
Percent Impervious Treated by LID
measures
50% Required Minimum Area to be
Treated by LID measures (sf)
APPENDIX E
SWMM Modeling
SUB-A
SUB-B
SUB-C
SUB-D
HT
OS1 OS2
SUB-UD2
1
2
3
8
9
10
11
BYPASS
OVERFLOWWEIR
OUT1
OUT2
OUT3
OUT4
OUTOS1
OUTOS2
J1
J2
J3
J4
J5
J6 J7
O1
O2
O3
POND1
POND2
POND3
POND4
PONDOS1
PONDOS2
FORTCOLLINS
03/15/2016 00:05:00
SWMM 5.1 Page 1
SWMM Output - All pipes Open.rpt
EPA STORM WATER MANAGEMENT MODEL - VERSION 5.1 (Build 5.1.010)
--------------------------------------------------------------
*********************************************************
NOTE: The summary statistics displayed in this report are
based on results found at every computational time step,
not just on results from each reporting time step.
*********************************************************
****************
Analysis Options
****************
Flow Units ............... CFS
Process Models:
Rainfall/Runoff ........ YES
RDII ................... NO
Snowmelt ............... NO
Groundwater ............ NO
Flow Routing ........... YES
Ponding Allowed ........ NO
Water Quality .......... NO
Infiltration Method ...... HORTON
Flow Routing Method ...... KINWAVE
Starting Date ............ MAR-15-2016 00:00:00
Ending Date .............. MAR-20-2016 06:00:00
Antecedent Dry Days ...... 0.0
Report Time Step ......... 00:05:00
Wet Time Step ............ 00:05:00
Dry Time Step ............ 01:00:00
Routing Time Step ........ 15.00 sec
************************** Volume Depth
Runoff Quantity Continuity acre-feet inches
************************** --------- -------
Total Precipitation ...... 31.524 3.669
Evaporation Loss ......... 0.000 0.000
Infiltration Loss ........ 17.008 1.980
Surface Runoff ........... 14.472 1.684
Final Storage ............ 0.131 0.015
Continuity Error (%) ..... -0.274
Page 1
SWMM Output - All pipes Open.rpt
************************** Volume Volume
Flow Routing Continuity acre-feet 10^6 gal
************************** --------- ---------
Dry Weather Inflow ....... 0.000 0.000
Wet Weather Inflow ....... 14.472 4.716
Groundwater Inflow ....... 0.000 0.000
RDII Inflow .............. 0.000 0.000
External Inflow .......... 0.000 0.000
External Outflow ......... 14.674 4.782
Flooding Loss ............ 0.000 0.000
Evaporation Loss ......... 0.000 0.000
Exfiltration Loss ........ 0.000 0.000
Initial Stored Volume .... 0.204 0.066
Final Stored Volume ...... 0.000 0.000
Continuity Error (%) ..... 0.009
********************************
Highest Flow Instability Indexes
********************************
Link OUTOS2 (2)
*************************
Routing Time Step Summary
*************************
Minimum Time Step : 15.00 sec
Average Time Step : 15.00 sec
Maximum Time Step : 15.00 sec
Percent in Steady State : 0.00
Average Iterations per Step : 1.00
Percent Not Converging : 0.00
***************************
Subcatchment Runoff Summary
***************************
--------------------------------------------------------------------------------------------------------
Total Total Total Total Total Total Peak Runoff
Precip Runon Evap Infil Runoff Runoff Runoff Coeff
Page 2
SWMM Output - All pipes Open.rpt
Subcatchment in in in in in 10^6 gal CFS
--------------------------------------------------------------------------------------------------------
SUB-A 3.67 0.00 0.00 0.74 2.89 0.43 37.08 0.789
SUB-B 3.67 0.00 0.00 0.85 2.78 0.31 23.92 0.759
SUB-C 3.67 0.00 0.00 1.11 2.56 0.04 4.01 0.699
SUB-D 3.67 0.00 0.00 0.77 2.87 0.39 32.77 0.783
HT 3.67 0.00 0.00 2.10 1.58 0.24 11.01 0.430
OS1 3.67 0.00 0.00 2.10 1.57 0.63 26.35 0.427
OS2 3.67 0.00 0.00 2.22 1.45 2.51 99.12 0.395
SUB-UD2 3.67 0.00 0.00 2.10 1.59 0.18 8.73 0.432
******************
Node Depth Summary
******************
---------------------------------------------------------------------------------
Average Maximum Maximum Time of Max Reported
Depth Depth HGL Occurrence Max Depth
Node Type Feet Feet Feet days hr:min Feet
---------------------------------------------------------------------------------
J1 JUNCTION 0.07 1.31 42.01 0 02:09 1.31
J2 JUNCTION 0.09 1.31 40.41 0 02:20 1.31
J3 JUNCTION 0.23 1.38 35.58 0 00:52 1.38
J4 JUNCTION 0.03 1.11 39.33 0 00:50 1.11
J5 JUNCTION 0.01 0.61 46.21 0 01:02 0.61
J6 JUNCTION 0.15 0.33 36.83 0 02:26 0.33
J7 JUNCTION 0.15 0.33 35.33 0 02:29 0.33
O1 OUTFALL 0.02 1.11 36.61 0 00:50 1.11
O2 OUTFALL 0.23 1.38 34.98 0 00:53 1.38
O3 OUTFALL 0.00 0.00 48.00 0 00:00 0.00
POND1 STORAGE 2.31 5.77 45.77 0 02:22 5.77
POND2 STORAGE 0.69 2.67 39.67 0 02:28 2.67
POND3 STORAGE 0.43 3.18 45.18 0 02:09 3.17
POND4 STORAGE 1.29 6.87 43.47 0 02:18 6.87
PONDOS1 STORAGE 0.01 0.96 47.96 0 01:02 0.95
PONDOS2 STORAGE 0.15 6.15 50.15 0 01:37 6.15
*******************
Node Inflow Summary
*******************
Page 3
SWMM Output - All pipes Open.rpt
-------------------------------------------------------------------------------------------------
Maximum Maximum Lateral Total Flow
Lateral Total Time of Max Inflow Inflow Balance
Inflow Inflow Occurrence Volume Volume Error
Node Type CFS CFS days hr:min 10^6 gal 10^6 gal Percent
-------------------------------------------------------------------------------------------------
J1 JUNCTION 0.00 22.10 0 02:09 0 2.27 0.000
J2 JUNCTION 8.73 25.75 0 00:51 0.175 2.44 0.000
J3 JUNCTION 0.00 26.78 0 00:52 0 3.64 0.000
J4 JUNCTION 11.01 25.49 0 00:50 0.236 0.861 0.000
J5 JUNCTION 0.00 16.20 0 01:02 0 0.625 0.000
J6 JUNCTION 0.00 0.74 0 02:26 0 0.799 0.000
J7 JUNCTION 0.00 1.34 0 02:25 0 1.19 0.000
O1 OUTFALL 0.00 25.47 0 00:50 0 0.861 0.000
O2 OUTFALL 0.00 26.78 0 00:53 0 3.64 0.000
O3 OUTFALL 0.00 18.83 0 01:37 0 0.281 0.000
POND1 STORAGE 37.08 37.08 0 00:40 0.428 0.46 0.003
POND2 STORAGE 23.92 23.92 0 00:40 0.314 0.34 0.003
POND3 STORAGE 4.01 4.01 0 00:40 0.0404 0.0441 0.009
POND4 STORAGE 32.77 32.77 0 00:40 0.39 0.396 0.007
PONDOS1 STORAGE 26.35 26.35 0 00:40 0.626 0.626 0.067
PONDOS2 STORAGE 99.12 99.12 0 00:40 2.51 2.51 0.018
**********************
Node Surcharge Summary
**********************
Surcharging occurs when water rises above the top of the highest conduit.
---------------------------------------------------------------------
Max. Height Min. Depth
Hours Above Crown Below Rim
Node Type Surcharged Feet Feet
---------------------------------------------------------------------
J1 JUNCTION 126.00 1.312 3.688
J2 JUNCTION 126.00 1.312 3.688
J3 JUNCTION 126.00 1.379 3.621
J4 JUNCTION 126.00 1.107 1.893
J5 JUNCTION 126.00 0.609 2.391
J6 JUNCTION 126.00 0.333 1.667
J7 JUNCTION 126.00 0.333 1.667
POND1 STORAGE 126.00 5.771 0.029
POND2 STORAGE 126.00 2.673 0.327
Page 4
SWMM Output - All pipes Open.rpt
POND3 STORAGE 126.00 3.175 0.625
POND4 STORAGE 126.00 6.871 0.529
PONDOS1 STORAGE 126.00 0.956 6.044
PONDOS2 STORAGE 126.00 6.147 0.853
*********************
Node Flooding Summary
*********************
No nodes were flooded.
**********************
Storage Volume Summary
**********************
--------------------------------------------------------------------------------------------------
Average Avg Evap Exfil Maximum Max Time of Max Maximum
Volume Pcnt Pcnt Pcnt Volume Pcnt Occurrence Outflow
Storage Unit 1000 ft3 Full Loss Loss 1000 ft3 Full days hr:min CFS
--------------------------------------------------------------------------------------------------
POND1 14.995 25 0 0 58.923 99 0 02:22 0.35
POND2 7.931 16 0 0 42.552 84 0 02:28 0.39
POND3 0.483 6 0 0 5.307 70 0 02:08 0.10
POND4 6.111 10 0 0 48.858 82 0 02:18 0.60
PONDOS1 0.102 0 0 0 11.701 3 0 01:01 16.20
PONDOS2 3.081 2 0 0 148.527 81 0 01:37 40.83
***********************
Outfall Loading Summary
***********************
-----------------------------------------------------------
Flow Avg Max Total
Freq Flow Flow Volume
Outfall Node Pcnt CFS CFS 10^6 gal
-----------------------------------------------------------
O1 2.93 8.66 25.47 0.861
O2 71.75 1.49 26.78 3.639
O3 0.71 11.64 18.83 0.281
-----------------------------------------------------------
Page 5
SWMM Output - All pipes Open.rpt
System 25.13 21.80 61.44 4.781
********************
Link Flow Summary
********************
-----------------------------------------------------------------------------
Maximum Time of Max Maximum Max/ Max/
|Flow| Occurrence |Veloc| Full Full
Link Type CFS days hr:min ft/sec Flow Depth
-----------------------------------------------------------------------------
1 CONDUIT 22.10 0 02:20 3.21 0.03 0.26
2 CONDUIT 25.75 0 00:52 5.08 0.02 0.23
3 CONDUIT 26.78 0 00:53 3.52 0.03 0.28
8 CONDUIT 16.20 0 01:03 3.65 0.27 0.61
9 CONDUIT 25.47 0 00:50 5.20 0.07 0.37
10 CONDUIT 0.74 0 02:29 2.16 0.06 0.17
11 CONDUIT 1.34 0 02:25 6.79 0.03 0.11
BYPASS WEIR 18.83 0 01:37 0.00
OVERFLOWWEIR WEIR 0.00 0 00:00 0.00
OUT1 DUMMY 0.35 0 02:22
OUT2 DUMMY 0.39 0 02:28
OUT3 DUMMY 0.10 0 02:09
OUT4 DUMMY 0.60 0 02:18
OUTOS1 DUMMY 16.20 0 01:02
OUTOS2 DUMMY 22.00 0 01:26
*************************
Conduit Surcharge Summary
*************************
No conduits were surcharged.
Analysis begun on: Mon Oct 09 12:14:38 2017
Analysis ended on: Mon Oct 09 12:14:38 2017
Total elapsed time: < 1 sec
Page 6
SWMM Output - OS2 closed.rpt
EPA STORM WATER MANAGEMENT MODEL - VERSION 5.1 (Build 5.1.010)
--------------------------------------------------------------
*********************************************************
NOTE: The summary statistics displayed in this report are
based on results found at every computational time step,
not just on results from each reporting time step.
*********************************************************
****************
Analysis Options
****************
Flow Units ............... CFS
Process Models:
Rainfall/Runoff ........ YES
RDII ................... NO
Snowmelt ............... NO
Groundwater ............ NO
Flow Routing ........... YES
Ponding Allowed ........ NO
Water Quality .......... NO
Infiltration Method ...... HORTON
Flow Routing Method ...... KINWAVE
Starting Date ............ MAR-15-2016 00:00:00
Ending Date .............. MAR-20-2016 06:00:00
Antecedent Dry Days ...... 0.0
Report Time Step ......... 00:05:00
Wet Time Step ............ 00:05:00
Dry Time Step ............ 01:00:00
Routing Time Step ........ 15.00 sec
************************** Volume Depth
Runoff Quantity Continuity acre-feet inches
************************** --------- -------
Total Precipitation ...... 31.524 3.669
Evaporation Loss ......... 0.000 0.000
Infiltration Loss ........ 17.008 1.980
Surface Runoff ........... 14.472 1.684
Final Storage ............ 0.131 0.015
Continuity Error (%) ..... -0.274
************************** Volume Volume
Page 1
SWMM Output - OS2 closed.rpt
Flow Routing Continuity acre-feet 10^6 gal
************************** --------- ---------
Dry Weather Inflow ....... 0.000 0.000
Wet Weather Inflow ....... 14.472 4.716
Groundwater Inflow ....... 0.000 0.000
RDII Inflow .............. 0.000 0.000
External Inflow .......... 0.000 0.000
External Outflow ......... 11.403 3.716
Flooding Loss ............ 0.000 0.000
Evaporation Loss ......... 0.000 0.000
Exfiltration Loss ........ 0.000 0.000
Initial Stored Volume .... 0.204 0.066
Final Stored Volume ...... 3.268 1.065
Continuity Error (%) ..... 0.034
********************************
Highest Flow Instability Indexes
********************************
All links are stable.
*************************
Routing Time Step Summary
*************************
Minimum Time Step : 15.00 sec
Average Time Step : 15.00 sec
Maximum Time Step : 15.00 sec
Percent in Steady State : 0.00
Average Iterations per Step : 1.00
Percent Not Converging : 0.00
***************************
Subcatchment Runoff Summary
***************************
--------------------------------------------------------------------------------------------------------
Total Total Total Total Total Total Peak Runoff
Precip Runon Evap Infil Runoff Runoff Runoff Coeff
Subcatchment in in in in in 10^6 gal CFS
--------------------------------------------------------------------------------------------------------
SUB-A 3.67 0.00 0.00 0.74 2.89 0.43 37.08 0.789
SUB-B 3.67 0.00 0.00 0.85 2.78 0.31 23.92 0.759
SUB-C 3.67 0.00 0.00 1.11 2.56 0.04 4.01 0.699
SUB-D 3.67 0.00 0.00 0.77 2.87 0.39 32.77 0.783
Page 2
SWMM Output - OS2 closed.rpt
HT 3.67 0.00 0.00 2.10 1.58 0.24 11.01 0.430
OS1 3.67 0.00 0.00 2.10 1.57 0.63 26.35 0.427
OS2 3.67 0.00 0.00 2.22 1.45 2.51 99.12 0.395
SUB-UD2 3.67 0.00 0.00 2.10 1.59 0.18 8.73 0.432
******************
Node Depth Summary
******************
---------------------------------------------------------------------------------
Average Maximum Maximum Time of Max Reported
Depth Depth HGL Occurrence Max Depth
Node Type Feet Feet Feet days hr:min Feet
---------------------------------------------------------------------------------
J1 JUNCTION 0.03 0.17 40.87 0 02:09 0.17
J2 JUNCTION 0.06 0.75 39.85 0 00:45 0.75
J3 JUNCTION 0.20 0.94 35.14 0 00:46 0.93
J4 JUNCTION 0.03 1.11 39.33 0 00:50 1.11
J5 JUNCTION 0.01 0.61 46.21 0 01:02 0.61
J6 JUNCTION 0.15 0.33 36.83 0 02:26 0.33
J7 JUNCTION 0.15 0.33 35.33 0 02:29 0.33
O1 OUTFALL 0.02 1.11 36.61 0 00:50 1.11
O2 OUTFALL 0.20 0.94 34.54 0 00:47 0.93
O3 OUTFALL 0.00 0.00 48.00 0 00:00 0.00
POND1 STORAGE 2.31 5.77 45.77 0 02:22 5.77
POND2 STORAGE 0.69 2.67 39.67 0 02:28 2.67
POND3 STORAGE 0.43 3.18 45.18 0 02:09 3.17
POND4 STORAGE 1.29 6.87 43.47 0 02:18 6.87
PONDOS1 STORAGE 0.01 0.96 47.96 0 01:02 0.95
PONDOS2 STORAGE 5.97 6.29 50.29 0 01:15 6.29
*******************
Node Inflow Summary
*******************
-------------------------------------------------------------------------------------------------
Maximum Maximum Lateral Total Flow
Lateral Total Time of Max Inflow Inflow Balance
Inflow Inflow Occurrence Volume Volume Error
Node Type CFS CFS days hr:min 10^6 gal 10^6 gal Percent
-------------------------------------------------------------------------------------------------
J1 JUNCTION 0.00 0.10 0 02:09 0 0.0441 0.000
J2 JUNCTION 8.73 8.78 0 00:45 0.175 0.219 0.000
J3 JUNCTION 0.00 9.63 0 00:46 0 1.41 0.000
Page 3
SWMM Output - OS2 closed.rpt
J4 JUNCTION 11.01 25.49 0 00:50 0.236 0.861 0.000
J5 JUNCTION 0.00 16.20 0 01:02 0 0.625 0.000
J6 JUNCTION 0.00 0.74 0 02:26 0 0.799 0.000
J7 JUNCTION 0.00 1.34 0 02:25 0 1.19 0.000
O1 OUTFALL 0.00 25.47 0 00:50 0 0.861 0.000
O2 OUTFALL 0.00 9.63 0 00:47 0 1.41 0.000
O3 OUTFALL 0.00 50.82 0 01:15 0 1.44 0.000
POND1 STORAGE 37.08 37.08 0 00:40 0.428 0.46 0.003
POND2 STORAGE 23.92 23.92 0 00:40 0.314 0.34 0.003
POND3 STORAGE 4.01 4.01 0 00:40 0.0404 0.0441 0.009
POND4 STORAGE 32.77 32.77 0 00:40 0.39 0.396 0.007
PONDOS1 STORAGE 26.35 26.35 0 00:40 0.626 0.626 0.067
PONDOS2 STORAGE 99.12 99.12 0 00:40 2.51 2.51 0.061
**********************
Node Surcharge Summary
**********************
Surcharging occurs when water rises above the top of the highest conduit.
---------------------------------------------------------------------
Max. Height Min. Depth
Hours Above Crown Below Rim
Node Type Surcharged Feet Feet
---------------------------------------------------------------------
J1 JUNCTION 126.00 0.173 4.827
J2 JUNCTION 126.00 0.752 4.248
J3 JUNCTION 126.00 0.940 4.060
J4 JUNCTION 126.00 1.107 1.893
J5 JUNCTION 126.00 0.609 2.391
J6 JUNCTION 126.00 0.333 1.667
J7 JUNCTION 126.00 0.333 1.667
POND1 STORAGE 126.00 5.771 0.029
POND2 STORAGE 126.00 2.673 0.327
POND3 STORAGE 126.00 3.175 0.625
POND4 STORAGE 126.00 6.871 0.529
PONDOS1 STORAGE 126.00 0.956 6.044
PONDOS2 STORAGE 126.00 6.286 0.714
*********************
Node Flooding Summary
*********************
No nodes were flooded.
Page 4
SWMM Output - OS2 closed.rpt
**********************
Storage Volume Summary
**********************
--------------------------------------------------------------------------------------------------
Average Avg Evap Exfil Maximum Max Time of Max Maximum
Volume Pcnt Pcnt Pcnt Volume Pcnt Occurrence Outflow
Storage Unit 1000 ft3 Full Loss Loss 1000 ft3 Full days hr:min CFS
--------------------------------------------------------------------------------------------------
POND1 14.995 25 0 0 58.923 99 0 02:22 0.35
POND2 7.931 16 0 0 42.552 84 0 02:28 0.39
POND3 0.483 6 0 0 5.307 70 0 02:08 0.10
POND4 6.111 10 0 0 48.858 82 0 02:18 0.60
PONDOS1 0.102 0 0 0 11.701 3 0 01:01 16.20
PONDOS2 141.600 77 0 0 154.329 84 0 01:15 50.82
***********************
Outfall Loading Summary
***********************
-----------------------------------------------------------
Flow Avg Max Total
Freq Flow Flow Volume
Outfall Node Pcnt CFS CFS 10^6 gal
-----------------------------------------------------------
O1 2.93 8.66 25.47 0.861
O2 71.75 0.58 9.63 1.414
O3 5.62 7.55 50.82 1.440
-----------------------------------------------------------
System 26.77 16.79 77.25 3.715
********************
Link Flow Summary
********************
-----------------------------------------------------------------------------
Maximum Time of Max Maximum Max/ Max/
|Flow| Occurrence |Veloc| Full Full
Link Type CFS days hr:min ft/sec Flow Depth
-----------------------------------------------------------------------------
1 CONDUIT 0.10 0 02:13 0.83 0.00 0.03
2 CONDUIT 8.72 0 00:46 3.88 0.01 0.15
3 CONDUIT 9.63 0 00:47 2.73 0.01 0.19
Page 5
SWMM Output - OS2 closed.rpt
8 CONDUIT 16.20 0 01:03 3.65 0.27 0.61
9 CONDUIT 25.47 0 00:50 5.20 0.07 0.37
10 CONDUIT 0.74 0 02:29 2.16 0.06 0.17
11 CONDUIT 1.34 0 02:25 6.79 0.03 0.11
BYPASS WEIR 50.82 0 01:15 0.00
OVERFLOWWEIR WEIR 0.00 0 00:00 0.00
OUT1 DUMMY 0.35 0 02:22
OUT2 DUMMY 0.39 0 02:28
OUT3 DUMMY 0.10 0 02:09
OUT4 DUMMY 0.60 0 02:18
OUTOS1 DUMMY 16.20 0 01:02
OUTOS2 DUMMY 0.00 0 00:00
*************************
Conduit Surcharge Summary
*************************
No conduits were surcharged.
Analysis begun on: Mon Oct 09 12:12:24 2017
Analysis ended on: Mon Oct 09 12:12:24 2017
Total elapsed time: < 1 sec
Page 6
SWMM Output - Outlet 2 Orifice Clogged.rpt
EPA STORM WATER MANAGEMENT MODEL - VERSION 5.1 (Build 5.1.010)
--------------------------------------------------------------
*********************************************************
NOTE: The summary statistics displayed in this report are
based on results found at every computational time step,
not just on results from each reporting time step.
*********************************************************
****************
Analysis Options
****************
Flow Units ............... CFS
Process Models:
Rainfall/Runoff ........ YES
RDII ................... NO
Snowmelt ............... NO
Groundwater ............ NO
Flow Routing ........... YES
Ponding Allowed ........ NO
Water Quality .......... NO
Infiltration Method ...... HORTON
Flow Routing Method ...... KINWAVE
Starting Date ............ MAR-15-2016 00:00:00
Ending Date .............. MAR-20-2016 06:00:00
Antecedent Dry Days ...... 0.0
Report Time Step ......... 00:05:00
Wet Time Step ............ 00:05:00
Dry Time Step ............ 01:00:00
Routing Time Step ........ 15.00 sec
************************** Volume Depth
Runoff Quantity Continuity acre-feet inches
************************** --------- -------
Total Precipitation ...... 31.524 3.669
Evaporation Loss ......... 0.000 0.000
Infiltration Loss ........ 17.008 1.980
Surface Runoff ........... 14.472 1.684
Final Storage ............ 0.131 0.015
Continuity Error (%) ..... -0.274
Page 1
SWMM Output - Outlet 2 Orifice Clogged.rpt
************************** Volume Volume
Flow Routing Continuity acre-feet 10^6 gal
************************** --------- ---------
Dry Weather Inflow ....... 0.000 0.000
Wet Weather Inflow ....... 14.472 4.716
Groundwater Inflow ....... 0.000 0.000
RDII Inflow .............. 0.000 0.000
External Inflow .......... 0.000 0.000
External Outflow ......... 13.682 4.459
Flooding Loss ............ 0.000 0.000
Evaporation Loss ......... 0.000 0.000
Exfiltration Loss ........ 0.000 0.000
Initial Stored Volume .... 0.204 0.066
Final Stored Volume ...... 0.991 0.323
Continuity Error (%) ..... 0.011
********************************
Highest Flow Instability Indexes
********************************
Link OUTOS2 (2)
*************************
Routing Time Step Summary
*************************
Minimum Time Step : 15.00 sec
Average Time Step : 15.00 sec
Maximum Time Step : 15.00 sec
Percent in Steady State : 0.00
Average Iterations per Step : 1.00
Percent Not Converging : 0.00
***************************
Subcatchment Runoff Summary
***************************
--------------------------------------------------------------------------------------------------------
Total Total Total Total Total Total Peak Runoff
Precip Runon Evap Infil Runoff Runoff Runoff Coeff
Page 2
SWMM Output - Outlet 2 Orifice Clogged.rpt
Subcatchment in in in in in 10^6 gal CFS
--------------------------------------------------------------------------------------------------------
SUB-A 3.67 0.00 0.00 0.74 2.89 0.43 37.08 0.789
SUB-B 3.67 0.00 0.00 0.85 2.78 0.31 23.92 0.759
SUB-C 3.67 0.00 0.00 1.11 2.56 0.04 4.01 0.699
SUB-D 3.67 0.00 0.00 0.77 2.87 0.39 32.77 0.783
HT 3.67 0.00 0.00 2.10 1.58 0.24 11.01 0.430
OS1 3.67 0.00 0.00 2.10 1.57 0.63 26.35 0.427
OS2 3.67 0.00 0.00 2.22 1.45 2.51 99.12 0.395
SUB-UD2 3.67 0.00 0.00 2.10 1.59 0.18 8.73 0.432
******************
Node Depth Summary
******************
---------------------------------------------------------------------------------
Average Maximum Maximum Time of Max Reported
Depth Depth HGL Occurrence Max Depth
Node Type Feet Feet Feet days hr:min Feet
---------------------------------------------------------------------------------
J1 JUNCTION 0.07 1.31 42.01 0 02:09 1.31
J2 JUNCTION 0.09 1.31 40.41 0 02:20 1.31
J3 JUNCTION 0.21 1.37 35.57 0 00:52 1.37
J4 JUNCTION 0.03 1.11 39.33 0 00:50 1.11
J5 JUNCTION 0.01 0.61 46.21 0 01:02 0.61
J6 JUNCTION 0.12 0.33 36.83 0 02:28 0.33
J7 JUNCTION 0.12 0.33 35.33 0 02:31 0.33
O1 OUTFALL 0.02 1.11 36.61 0 00:50 1.11
O2 OUTFALL 0.21 1.37 34.97 0 00:52 1.37
O3 OUTFALL 0.00 0.00 48.00 0 00:00 0.00
POND1 STORAGE 2.31 5.77 45.77 0 02:22 5.77
POND2 STORAGE 2.69 2.76 39.76 0 02:28 2.76
POND3 STORAGE 0.43 3.18 45.18 0 02:09 3.17
POND4 STORAGE 1.29 6.87 43.47 0 02:18 6.87
PONDOS1 STORAGE 0.01 0.96 47.96 0 01:02 0.95
PONDOS2 STORAGE 0.15 6.15 50.15 0 01:37 6.15
*******************
Node Inflow Summary
*******************
Page 3
SWMM Output - Outlet 2 Orifice Clogged.rpt
-------------------------------------------------------------------------------------------------
Maximum Maximum Lateral Total Flow
Lateral Total Time of Max Inflow Inflow Balance
Inflow Inflow Occurrence Volume Volume Error
Node Type CFS CFS days hr:min 10^6 gal 10^6 gal Percent
-------------------------------------------------------------------------------------------------
J1 JUNCTION 0.00 22.10 0 02:09 0 2.27 0.000
J2 JUNCTION 8.73 25.75 0 00:51 0.175 2.44 0.000
J3 JUNCTION 0.00 26.51 0 00:52 0 3.32 0.000
J4 JUNCTION 11.01 25.49 0 00:50 0.236 0.861 0.000
J5 JUNCTION 0.00 16.20 0 01:02 0 0.625 0.000
J6 JUNCTION 0.00 0.74 0 02:28 0 0.476 0.000
J7 JUNCTION 0.00 1.34 0 02:31 0 0.872 0.000
O1 OUTFALL 0.00 25.47 0 00:50 0 0.861 0.000
O2 OUTFALL 0.00 26.51 0 00:52 0 3.32 0.000
O3 OUTFALL 0.00 18.83 0 01:37 0 0.281 0.000
POND1 STORAGE 37.08 37.08 0 00:40 0.428 0.46 0.003
POND2 STORAGE 23.92 23.92 0 00:40 0.314 0.34 0.000
POND3 STORAGE 4.01 4.01 0 00:40 0.0404 0.0441 0.009
POND4 STORAGE 32.77 32.77 0 00:40 0.39 0.396 0.007
PONDOS1 STORAGE 26.35 26.35 0 00:40 0.626 0.626 0.067
PONDOS2 STORAGE 99.12 99.12 0 00:40 2.51 2.51 0.018
**********************
Node Surcharge Summary
**********************
Surcharging occurs when water rises above the top of the highest conduit.
---------------------------------------------------------------------
Max. Height Min. Depth
Hours Above Crown Below Rim
Node Type Surcharged Feet Feet
---------------------------------------------------------------------
J1 JUNCTION 126.00 1.312 3.688
J2 JUNCTION 126.00 1.312 3.688
J3 JUNCTION 126.00 1.374 3.626
J4 JUNCTION 126.00 1.107 1.893
J5 JUNCTION 126.00 0.609 2.391
J6 JUNCTION 126.00 0.334 1.666
J7 JUNCTION 126.00 0.333 1.667
POND1 STORAGE 126.00 5.771 0.029
POND2 STORAGE 126.00 2.760 0.240
Page 4
SWMM Output - Outlet 2 Orifice Clogged.rpt
POND3 STORAGE 126.00 3.175 0.625
POND4 STORAGE 126.00 6.871 0.529
PONDOS1 STORAGE 126.00 0.956 6.044
PONDOS2 STORAGE 126.00 6.147 0.853
*********************
Node Flooding Summary
*********************
No nodes were flooded.
**********************
Storage Volume Summary
**********************
--------------------------------------------------------------------------------------------------
Average Avg Evap Exfil Maximum Max Time of Max Maximum
Volume Pcnt Pcnt Pcnt Volume Pcnt Occurrence Outflow
Storage Unit 1000 ft3 Full Loss Loss 1000 ft3 Full days hr:min CFS
--------------------------------------------------------------------------------------------------
POND1 14.995 25 0 0 58.923 99 0 02:22 0.35
POND2 42.913 85 0 0 44.637 88 0 02:27 0.40
POND3 0.483 6 0 0 5.307 70 0 02:08 0.10
POND4 6.111 10 0 0 48.858 82 0 02:18 0.60
PONDOS1 0.102 0 0 0 11.701 3 0 01:01 16.20
PONDOS2 3.081 2 0 0 148.527 81 0 01:37 40.83
***********************
Outfall Loading Summary
***********************
-----------------------------------------------------------
Flow Avg Max Total
Freq Flow Flow Volume
Outfall Node Pcnt CFS CFS 10^6 gal
-----------------------------------------------------------
O1 2.93 8.66 25.47 0.861
O2 71.75 1.36 26.51 3.316
O3 0.71 11.64 18.83 0.281
-----------------------------------------------------------
Page 5
SWMM Output - Outlet 2 Orifice Clogged.rpt
System 25.13 21.66 61.08 4.458
********************
Link Flow Summary
********************
-----------------------------------------------------------------------------
Maximum Time of Max Maximum Max/ Max/
|Flow| Occurrence |Veloc| Full Full
Link Type CFS days hr:min ft/sec Flow Depth
-----------------------------------------------------------------------------
1 CONDUIT 22.10 0 02:20 3.21 0.03 0.26
2 CONDUIT 25.75 0 00:52 5.08 0.02 0.23
3 CONDUIT 26.51 0 00:52 3.51 0.03 0.27
8 CONDUIT 16.20 0 01:03 3.65 0.27 0.61
9 CONDUIT 25.47 0 00:50 5.20 0.07 0.37
10 CONDUIT 0.74 0 02:31 2.16 0.06 0.17
11 CONDUIT 1.34 0 02:31 6.79 0.03 0.11
BYPASS WEIR 18.83 0 01:37 0.00
OVERFLOWWEIR WEIR 0.40 0 02:28 0.00
OUT1 DUMMY 0.35 0 02:22
OUT2 DUMMY 0.00 0 00:00
OUT3 DUMMY 0.10 0 02:09
OUT4 DUMMY 0.60 0 02:18
OUTOS1 DUMMY 16.20 0 01:02
OUTOS2 DUMMY 22.00 0 01:26
*************************
Conduit Surcharge Summary
*************************
No conduits were surcharged.
Analysis begun on: Mon Oct 09 12:15:17 2017
Analysis ended on: Mon Oct 09 12:15:18 2017
Total elapsed time: 00:00:01
Page 6
APPENDIX F
REFERENCES
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
MAP POCKET
DR1 – OVERALL DRAINAGE EXHIBIT
X
X
X
X
X
X
X
X
X
X
X
X X
X
X X X X
X
X
X
X
X X X
X X
X
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X
X
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X X
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X X X X
X X
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X X X X X X X
X X
X
X
X
X
X
X
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X
X
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X X
X X X
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
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
( 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 October 9, 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)
A1 A1 1.45 0.66 0.83 7.1 5.3 2.42 11.93
A2 A2 0.24 0.62 0.77 5.0 5.0 0.42 1.85
A3 A3 0.21 0.60 0.74 5.0 5.0 0.36 1.55
A4 A4 0.23 0.62 0.77 5.0 5.0 0.41 1.77
A5 A5 1.12 0.90 1.00 6.7 5.6 2.60 10.76
A6 A6 2.19 0.47 0.58 10.1 9.1 2.26 10.27
B1 B1 0.50 0.83 1.00 6.3 5.0 1.10 4.93
B2 B2 0.62 0.58 0.72 6.4 5.5 0.97 4.36
B3 B3 1.08 0.80 1.00 5.0 5.0 2.46 10.73
B4 B4 0.27 0.92 1.00 5.0 5.0 0.71 2.72
B5 B5 0.19 0.78 0.98 5.0 5.0 0.42 1.82
B6 B6 1.50 0.27 0.34 16.8 16.1 0.72 3.20
C1 C1 0.14 0.60 0.76 5.0 5.0 0.23 1.02
C2 C2 0.45 0.37 0.47 5.9 5.2 0.46 2.09
D1 D1 0.30 0.85 1.00 5.0 5.0 0.72 2.94
D2 D2 1.66 0.67 0.84 5.0 5.0 3.18 13.87
D3 D3 0.98 0.71 0.89 5.7 5.0 1.92 8.63
D4 D4 0.66 0.58 0.73 5.1 5.0 1.09 4.76
D5 D5 1.41 0.37 0.46 9.8 9.1 1.17 5.19
UD1 UD1 0.05 0.83 1.00 5.0 5.0 0.12 0.52
UD2 UD2 4.07 0.26 0.33 14.2 13.7 2.04 9.07
HT1 HT1 5.51 0.27 0.34 42.7 39.3 1.54 7.11
OS1 OS1 14.72 0.33 0.41 23.7 23.2 7.06 31.10
Detention Pond Summary | Proposed Condition
Pond 100-yr Volume
(ac-ft)
100-yr WSEL WQCV
(ft3)
WQCV WSEL Max Release
(cfs)
1 1.30 5145.90 3,129 5141.85 0.35
2 0.93 5139.59 3,115 5137.68 0.39
3 0.09 5144.65 268 5142.89 0.10
4 1.03 5142.24 n/a n/a 0.60
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
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
5,142.40 18,224 0.20 3557 47561 3557 47528
5,142.60 19,191 0.20 3741 51302 3741 51269
5,142.80 20,245 0.20 3944 55246 3943 55212
5,143.00 22,280 0.20 4252 59498 4251 59463
Design Point
Design Storm
Require Volume=
Stage - Storage Calculation
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
9/14/20172:21 PM D:\Projects\911-007\Drainage\Detention\911-007_Detention Pond 4.xlsm\Stage_Storage
Project Number:
Project Location:
Calculations By:
Required Volume Water Surface Elevation (WSE)
9/14/20175:19 PM D:\Projects\911-007\Drainage\Detention\911-007_Detention Pond 1.xlsm\Stage_Storage
(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 )
9/14/2017 2:05 PM D:\Projects\911-007\Drainage\Hydrology\911-007_Proposed_Rational_Calcs.xlsx\Runoff
10-yr
Tc
(min)
100-yr
Tc
(min)
A1 A1 No 0.66 0.66 0.83 61 2.34% 4.8 4.8 3.0 N/A N/A N/A 227 0.70% 1.67 2.3 7.1 7.1 5.3
A2 A2 No 0.62 0.62 0.77 33 8.30% 2.6 2.6 1.7 N/A N/A N/A 159 1.39% 2.36 1.1 5.0 5.0 5.0
A3 A3 No 0.60 0.60 0.74 32 16.91% 2.1 2.1 1.5 N/A N/A N/A 124 1.06% 2.06 1.0 5.0 5.0 5.0
A4 A4 No 0.62 0.62 0.77 32 16.91% 2.0 2.0 1.3 N/A N/A N/A 141 1.64% 2.56 0.9 5.0 5.0 5.0
A5 A5 No 0.90 0.90 1.00 65 3.35% 2.0 2.0 1.0 N/A N/A N/A 512 0.85% 1.84 4.6 6.7 6.7 5.6
A6 A6 No 0.47 0.47 0.58 61 4.41% 5.6 5.6 4.6 191 1.72% 1.97 1.6 239 0.47% 1.38 2.9 10.1 10.1 9.1
A6 TOTAL BASIN A No 0.63 0.63 0.78 61 4.41% 4.2 4.2 2.8 191 1.72% 1.97 1.6 239 0.47% 1.38 2.9 8.7 8.7 7.3
B1 B1 No 0.83 0.83 1.00 46 2.91% 2.4 2.4 0.9 N/A N/A N/A 358 0.60% 1.55 3.8 6.3 6.3 5.0
B2 B2 No 0.58 0.58 0.72 47 10.04% 3.1 3.1 2.2 389 1.74% 1.98 3.3 N/A N/A N/A 6.4 6.4 5.5
B3 B3 No 0.80 0.80 1.00 N/A N/A N/A N/A 91 0.86% 1.39 1.1 223 1.79% 2.68 1.4 5.0 5.0 5.0
B4 B4 No 0.92 0.92 1.00 37 3.70% 1.3 1.3 0.7 N/A N/A N/A 175 1.21% 2.20 1.3 5.0 5.0 5.0
B5 B5 No 0.78 0.78 0.98 59 2.42% 3.4 3.4 1.3 N/A N/A N/A 250 1.76% 2.65 1.6 5.0 5.0 5.0
B6 B6 No 0.27 0.27 0.34 35 1.43% 8.1 8.1 7.5 653 0.91% 1.43 7.6 148 1.32% 2.30 1.1 16.8 16.8 16.1
B6 TOTAL BASIN B No 0.59 0.59 0.73 35 1.43% 5.0 5.0 3.6 653 0.91% 1.43 7.6 148 1.32% 2.30 1.1 13.7 13.7 12.3
C1 C1 No 0.60 0.60 0.76 33 8.30% 2.6 2.6 1.8 N/A N/A N/A 71 3.86% 3.93 0.3 5.0 5.0 5.0
C2 C2 No 0.37 0.37 0.47 51 6.61% 5.2 5.2 4.5 115 3.03% 2.61 0.7 N/A N/A N/A 5.9 5.9 5.2
C2 TOTAL BASIN C No 0.43 0.43 0.54 51 6.61% 4.8 4.8 4.0 115 3.03% 2.61 0.7 N/A N/A N/A 5.5 5.5 5.0
D1 D1 No 0.85 0.85 1.00 43 2.79% 2.2 2.2 0.9 N/A N/A N/A 255 1.52% 2.47 1.7 5.0 5.0 5.0
D2 D2 No 0.67 0.67 0.84 N/A N/A N/A N/A N/A N/A N/A 368 2.43% 3.12 2.0 5.0 5.0 5.0
D3 D3 No 0.71 0.71 0.89 68 4.37% 3.7 3.7 2.0 217 1.43% 1.79 2.0 N/A N/A N/A 5.7 5.7 5.0
D4 D4 No 0.58 0.58 0.73 18 2.94% 2.9 2.9 2.1 N/A N/A N/A 266 1.00% 2.00 2.2 5.1 5.1 5.0
D5 D5 No 0.37 0.37 0.46 57 6.11% 5.7 5.7 5.0 487 1.71% 1.96 4.1 N/A N/A N/A 9.8 9.8 9.1
D5 TOTAL BASIN D No 0.59 0.59 0.74 57 6.11% 3.9 3.9 2.8 487 1.71% 1.96 4.1 N/A N/A N/A 8.1 8.1 6.9
UD1 UD1 No 0.83 0.83 1.00 165 3.33% 4.4 4.4 1.6 N/A N/A N/A N/A N/A N/A 5.0 5.0 5.0
UD2 UD2 No 0.26 0.26 0.33 87 11.64% 6.5 6.5 6.0 681 0.94% 1.46 7.8 N/A N/A N/A 14.2 14.2 13.7
HT1 HT1 Yes 0.27 0.27 0.34 500 0.60% 41.1 41.1 37.7 302 4.30% 3.11 1.6 N/A N/A N/A 42.7 42.7 39.3
OS1 OS1 No 0.33 0.33 0.41 20 2.00% 5.1 5.1 4.6 2420 2.10% 2.17 18.6 N/A N/A N/A 23.7 23.7 23.2
* 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 Swale Flow Gutter/Pipe Flow Time of Concentration
September 14, 2017
(Equation RO-4)
( )
3
1
1 . 87 1 . 1 *
S
Ti C Cf L
-
=
9/14/2017 2:05 PM D:\Projects\911-007\Drainage\Hydrology\911-007_Proposed_Rational_Calcs.xlsx\Tc
% Imperv.
A1 1.45 0.39 0.23 0.43 0.20 Clayey | Average 2% to 7% 0.200 0.66 0.66 0.83 66%
A2 0.24 0.00 0.06 0.00 0.07 Clayey | Average 2% to 7% 0.115 0.62 0.62 0.77 47%
A3 0.21 0.00 0.05 0.00 0.05 Clayey | Average 2% to 7% 0.106 0.60 0.60 0.74 44%
A4 0.23 0.00 0.06 0.00 0.06 Clayey | Average 2% to 7% 0.109 0.62 0.62 0.77 47%
A5 1.12 0.21 0.35 0.00 0.48 Clayey | Average 2% to 7% 0.084 0.90 0.90 1.00 85%
A6 2.19 0.00 0.21 0.00 0.47 Clayey | Average 2% to 7% 1.510 0.47 0.47 0.58 28%
TOTAL BASIN A 5.44 0.60 0.95 0.43 1.34 Clayey | Average 2% to 7% 2.124 0.63 0.63 0.78 52%
B1 0.50 0.37 0.04 0.00 0.00 Clayey | Average 2% to 7% 0.087 0.83 0.83 1.00 82%
B2 0.62 0.00 0.08 0.00 0.22 Clayey | Average 2% to 7% 0.330 0.58 0.58 0.72 42%
B3 1.08 0.35 0.23 0.00 0.27 Clayey | Average 2% to 7% 0.233 0.80 0.80 1.00 74%
B4 0.27 0.05 0.07 0.00 0.13 Clayey | Average 2% to 7% 0.013 0.92 0.92 1.00 88%
B5 0.19 0.10 0.04 0.00 0.00 Clayey | Average 2% to 7% 0.044 0.78 0.78 0.98 74%
B6 1.50 0.00 0.01 0.52 0.00 Clayey | Average 2% to 7% 0.965 0.27 0.27 0.34 14%
TOTAL BASIN B 4.16 0.87 0.47 0.52 0.62 Clayey | Average 2% to 7% 1.673 0.59 0.59 0.73 50%
C1 0.14 0.00 0.03 0.00 0.04 Clayey | Average 2% to 7% 0.067 0.60 0.60 0.76 46%
C2 0.45 0.00 0.05 0.00 0.03 Clayey | Average 2% to 7% 0.369 0.37 0.37 0.47 16%
TOTAL BASIN C 0.58 0.00 0.08 0.00 0.07 Clayey | Average 2% to 7% 0.436 0.43 0.43 0.54 23%
D1 0.30 0.24 0.01 0.00 0.00 Clayey | Average 2% to 7% 0.041 0.85 0.85 1.00 86%
D2 1.66 0.45 0.31 0.22 0.22 Clayey | Average 2% to 7% 0.446 0.67 0.67 0.84 62%
D3 0.98 0.35 0.15 0.00 0.14 Clayey | Average 2% to 7% 0.338 0.71 0.71 0.89 63%
D4 0.66 0.12 0.11 0.30 0.06 Clayey | Average 2% to 7% 0.069 0.58 0.58 0.73 60%
D5 1.41 0.00 0.06 0.22 0.16 Clayey | Average 2% to 7% 0.969 0.37 0.37 0.46 20%
TOTAL BASIN D 5.00 1.17 0.64 0.75 0.58 Clayey | Average 2% to 7% 1.864 0.59 0.59 0.74 51%
UD1 0.05 0.03 0.01 0.00 0.00 Clayey | Average 2% to 7% 0.009 0.83 0.83 1.00 80%
UD2 4.07 0.00 0.07 0.00 0.00 Clayey | Average 2% to 7% 4.010 0.26 0.26 0.33 1%
TOTAL SITE 19.31 2.66 2.22 1.69 2.62 Clayey | Average 2% to 7% 10.116 0.53 0.53 0.66 40%
HT1 5.51 0.17 0.00 0.00 0.00 0.00 Clayey | Average 2% to 7% 5.345 0.27 0.27 0.34 3%
OS1 14.72 1.47 0.15 0.00 0.00 0.00 Clayey | Average 2% to 7% 13.248 0.33 0.33 0.41 10%
Composite Runoff Coefficient with Adjustment
PROPOSED COMPOSITE % IMPERVIOUSNESS AND RUNOFF COEFFICIENT CALCULATIONS
9/14/2017 2:05 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
OS1 OS1 14.72 0.33 0.41 23.7 23.2 7.06 31.10
6. Four (4) detention ponds are proposed with the Mountain’s Edge development. These
ponds will restrict all runoff from the developed site to historic 2-yr flowrate based on
the master drainage plan for the Spring Creek Basin.