HomeMy WebLinkAboutSPRING CREEK PLACE (FORMERLY STATION, 2105 S. COLLEGE AVE.) - PDP - PDP160020 - SUBMITTAL DOCUMENTS - ROUND 3 - DRAINAGE REPORTCity of Fort Collins
Spring Creek Place
(2105 South College Avenue)
Preliminary Drainage Report
OCTOBER 2016 | VERSION 3
Prepared By:
4582 South Ulster Street, Suite 1500
Denver, CO 80237
Daniel L. Skeehan, P.E.
Registered Professional Engineer
State of Colorado No. 46391
2
INTRODUCTION
The proposed 2105 South College Avenue Project is located within the Northeast Quarter of Section 23,
Township 7 North, Range 69 West of the Sixth Principal Meridian, City of Fort Collins, County of Larimer,
Colorado. The site is bound by an existing self-storage business and undeveloped land to the north, an
existing drive aisle and retail development to the east, an existing parking lot and retail development to the
south and the MAX Spring Creek Bus Station to the west. A vicinity map is provided below.
PROPOSED DEVELOPMENT
This project will be developed on a platted tract located in the northeast quarter of Section 23, Township 7
North, Range 69 West of the 6th PM. The site is approximately 2.22 acres and contains two existing
buildings with associated surface parking. The site is divided topographically with half of the site sloping to
the northeast and the other half sloping to the northwest at 1% to 5%. The soil on the site is 73% Nunn
loam (73), which is classified as Hydrologic Soil Group C; and 27% Altvan-Satanta loams (4), which is
classified as Hydrologic Soil Group B. The soil Classification Map can be found in Appendix A.
The site is currently zoned C-G (General Commercial). The proposed land uses for this site will consist of
standard multi-family residential housing and structured parking.
Preliminary Drainage Report
2105 S. College Ave – Fort Collins, Colorado
3
HISTORIC DRAINAGE
The existing Site drains to the northwest and northeast at slopes of 1% to 5%. There are currently no
existing on-site water quality or detention improvements. The Site and the surrounding area are considered
part of the Spring Creek Drainage Basin and ultimately outfall to the Poudre River to the northeast of the
site. The majority of existing flows for this site are conveyed into an existing inlet at the northwest corner
of the site which flows into a vegetated swale until it is intercepted by Spring Creek. This system was
installed as part of the MAX BRT system, and select portion of the associated drainage report are included
in Appendix C. Additional flows either surface flow into an existing irrigation ditch or surface flow to an
existing curb inlet in S. College Avenue. Flows captured within S. College Avenue travel through an existing
underground storm drainage system and ultimately discharge into Spring Creek.
The site is located within City of Fort Collins Federal Emergency Management Agency (FEMA) Flood
Insurance Rate Map Number 08069C0987G, revised May 2, 2012 and is designated as an area outside
of the 500-year floodplain. The FEMA Firmette is included in Appendix A.
DESIGN CRITERIA
The City of Fort Collins “Amendments to the Urban Drainage and Flood Control District Criteria Manual,”
(Criteria Manual) and the “Urban Drainage and Flood Control District Urban Storm Drainage Criteria
Manual” Volumes 1, 2, and 3 (Drainage Manual), with latest revisions, were used to prepare the storm
calculations. Weighted impervious values were calculated and used for the site area in accordance with
the Criteria Manual and Drainage Manual.
Hydrologic Criteria
The existing and proposed imperviousness of the site was determined in order to evaluate the Project’s
potential impacts on stormwater runoff. A topographic survey and knowledge of the Site was utilized for
this analysis. The existing and proposed imperviousness of the Site were determined to be 93% and 84%
respectively. This analysis is included in Appendix B. A drainage area map representing the existing
conditions has been included in Appendix D, and the proposed conditions has been included in Appendix
C.
The 2-year and 100-year storm events were used in determining rainfall and runoff for the proposed site.
Table RA-7 of the Criteria Manual was used to determine rainfall data for the storm events and has been
included in Appendix B. The 5-minute rainfall intensities used for the calculations at the site were 2.85
inches per hour and 9.95 inches per hour for the 2 and 100-year events, respectively. Table RO-10 from
the Criteria Manual was utilized to obtain the runoff coefficients based upon the character of surface,
resulting coefficient values of 0.85 and 0.90 for the 2 and 100-year events, respectively.
As the imperviousness of the Site is decreasing with redevelopment, on-site detention is not required.
However, due to limited available capacity in the receiving off-site storm conveyance systems, detention
may be required to mitigate flows to any receiving off-site storm conveyance system that exceed capacity.
The proposed development contemplates increasing the discharge to the west, requiring on-site detention
to mitigate the increased discharge. Detention for the proposed development will be provided by an onsite
underground detention facility to be located in the northwest corner of the site. Required volumes for the
detention facility were determined using the Modified Rational Formula-based FAA Method as outlined
4
within Volume 2, Chapter 10, Section 3.2.3 of the Criteria Manual. Standard release rates were also
determined as outlined by Volume 1, Chapter 1, Section 1.6 of the Criteria Manual.
Hydraulic Criteria
The design will include a private storm sewer system connecting into existing public storm sewer inlet at
the northwest of the site, adjacent to the MAX bus facility. The storm sewer and inlets will be designed to
provide for the 100-year event. Calculations for the private storm sewer system and HGL will be completed
using StormCAD and included in the Final Drainage Report. There are no major drainage ways located on
the proposed site.
Water Quality Treatment Criteria
Applicable water quality design criteria is referenced from Volume 3, Section 3.0 of the Drainage Manual.
Permanent best management practices associated with the water quality treatment design will be per the
Criteria Manual and discussed in further detail in the Drainage Plan section.
WQCV Watershed Inches = a*(0.91i3-1.19i2+.78i)
=0.8*(0.91(0.84) 3-1.19(0.84)2+.78(0.84))
=0.284 watershed inches
WQCVother= (WQCV/0.43)*(d6)
= (0.284/0.43)*0.43
=0.284 ac-ft
V = (WQCV/12)*(A)
= (0.284/12)*2.22
=0.053 ac-ft (2,309 ft3)*
i = Composite Tributary Imperviousness [%]
A = Area [ac]
a = Coefficient of drain time (a = 0.8 for 12-hour drain time)
d6 = depth of average runoff producing storm from Figure 3-1 from Urban Storm Drainage Criteria
Manual Volume 3
*Per Volume 3, Chapter 3, Section 3.1 of the Criteria Manual 75% of any newly developed or
redeveloped area must be treated using one or a combination of LID techniques.
DRAINAGE PLAN
GENERAL CONCEPT
The site was divided into seven onsite sub-basins which are described in greater detail in the following
section. BMPs were selected utilizing the four step process outlined in Volume 3, Chapter 1, Section 4 of
the Drainage Manual:
Preliminary Drainage Report
2105 S. College Ave – Fort Collins, Colorado
5
1. Employ runoff reduction practices - The redevelopment on an urban site provides limited
opportunities to employ runoff reduction practices. Site has been developed to install landscaping
wherever pavement (or building) is not required.
2. Implement BMPs that provide a water quality capture volume with a slow release – Majority of site
will be treated by two water quality BMPs; an existing mechanical separator that was installed as
part of the MAX improvements located immediately downstream of the western connection point
and an underground chamber/filtration system to be install as part of this development.
3. Stabilize streams – Not applicable. This development is not adjacent to a stream, nor directly
impact the downstream water body (Spring Creek).
4. Implement site specific and other source control BMPs –Trash containers, recycling containers,
and the majority of vehicular parking will be located inside the parking structure to reduce potential
for contamination discharges.
Runoff generated by the majority of these drainage basins will be conveyed into a proposed storm sewer
system and will be treated by a WQ BMP before being detained within a proposed underground detention
facility. Flows from the underground detention facility will outfall into an existing storm drain inlet located in
the northwest corner of the site near the MAX Spring Creek Bus Station. A proposed drainage area map
which shows the limits of these sub-basins has been provided in Appendix C. Calculations related to the
preliminary sizing of the storm sewer pipes have been included in Appendix B.
SPECIFIC DETAILS
WQCV Device
Water quality for the proposed development is currently provided by an off-site WQ BMP located at the
Max Station. In addition, a Low Impact Development (LID) system is proposed and will be provided by
means of a proposed underground chamber/filtration system/proprietary device which will treat 0.040 ac-ft
(1,742 ft3) or 75% of the required 0.053 ac-ft (2,309 ft3) water quality volume. The proposed device is still
being specified, but the ADS StormTech system is being considered. An impervious liner may be
required to prevent saturation of soils adjacent to building foundation. Based on conversations with Staff,
we understand this proposed system may be used to meet the City’s LID requirements by treating 75% of
the total WQCV (Volume 3, Section 3.1 of the Criteria Manual). The proposed underground
chamber/filtration system is in addition to the existing mechanical separator located downstream of the
western point of connection, at the Max Station, resulting in a redundant system.
Detention Facility
The underground detention facility has been sized and designed using the Modified FAA method as outlined
by Volume 2, Chapter 10, Section 3.2.3 of the Criteria Manual with City of Fort Collins precipitation data
and requires 0.115 acre-feet (5,010 ft3) for the 1.65 acres contributing runoff area. The volume provided in
the proposed water quality and underground detention facility will meet or exceed the required 0.115 ac-ft
volume. The proposed water quality and detention facility will discharge at a rate of 4.37 cfs and 8.79 cfs
for the 2 and 100-year events respectively. These values were determined by finding the historical flow
rates to the existing inlet in the northwest corner of the site (Existing basin B1 Q100 = 9.47 cfs). Proposed
flows to this storm sewer structure will include a combination of overland flows and flows which will have
passed through the combined Water Quality BMP and Detention Facility. To determine the proposed
discharge release rates from the Detention Facility, the overland flows from sub-basin 25 (SB25 Q100 = 0.68
cfs), described below, were subtracted from the historical flows. Flows from the detention facility will be
regulated using a combination of a restrictor plate and an orifice. Supporting calculations related to the
6
sizing of the detention facility using the Modified FAA method are available in Appendix B. Calculations
and sizes for the 2 and 100-year detention outlets will be included in the Final Drainage Report.
The remaining 0.34 acres (sub basin 10, Q100 = 2.89 cfs) will continue to surface drain to the east into South
College Avenue. This is a decrease from the existing 1.21 acres (existing sub-basin B2, B3, B4; totaling
Q100 = 11.40 cfs) that drain into South College Ave. The improvements to this area are minimal and consist
of utility connections, pavement replacement, and hardscape and landscape immediately adjacent to the
building.
Inlets
There are four proposed inlets on the project site. All inlets and storm sewer will be designed to convey
the 100-year storm event. The type of inlet for each is indicated in Table 1. Discussion of each inlet by
sub-basin follows the table.
Table 1. Inlet Types
Design
Point
Sub-basin
Structure
Type
CB-3 15 Sump Inlet
CB-2 20
On-Grade
Inlet
CB-4 30 Sump Inlet
CB-5 35 Sump Inlet
Sub-basin 05
Sub-basin 05 is 1.43 acres and consists of building/roof area. Runoff within this sub-basin will collect at
roof drains that tie into the private underground storm sewer that discharges to the Underground Detention
Facility. The runoff coefficients for this sub-basin are 0.95 and 1.00 for the 2-year and 100-year storm,
respectively.
Sub-basin 10
Sub-basin 10 is 0.13 acres and consists of parking, sidewalk and landscaped areas. Runoff within this sub-
basin will enter inlet CB-6 and be conveyed to the Underground Detention Facility through a private
underground storm sewer. The runoff coefficients for this sub-basin are 0.74 and 0.79 for the 2-year and
100-year storm, respectively.
Preliminary Drainage Report
2105 S. College Ave – Fort Collins, Colorado
7
Sub-basin 15
Sub-basin 15 is 0.09 acres and consists of a paved fire lane drive aisle. Runoff within this sub-basin will
enter inlet CB-3 and be conveyed to the Underground Detention Facility through a private underground
storm sewer. The runoff coefficients for this sub-basin are 0.94 and 0.99 for the 2-year and 100-year storm,
respectively. If inlet CB-3 were to plug, the runoff for this basin would flow north onto an existing access
drive following its historic path to the Sherwood Lateral.
Sub-basin 20
Sub-basin 20 is 0.05 acres and consists of a paved fire lane drive aisle. Runoff within this sub-basin will
enter inlet CB-2 and be conveyed to the Underground Detention Facility through a private underground
storm sewer. The runoff coefficients for this sub-basin are 0.95 and 1.00 for the 2-year and 100-year storm,
respectively. If inlet CB-2 were to plug, the runoff for this sub-basin would flow west into the existing inlet
CB-1 following its historic path.
Sub-basin 25
Sub-basin 25 is 0.23 acres and consists of sidewalk and landscaped areas. Runoff within this sub-basin
will enter inlet CB-1 and be conveyed off-site through a private underground storm sewer. The runoff
coefficients for this sub-basin are 0.28 and 0.32 for the 2-year and 100-year storm, respectively. If inlet
CB-1 were to plug, the runoff for the basin would flow north following its historic path to Sherwood Lateral.
Sub-basin 30
Sub-basin 30 is 0.05 acres and consists of sidewalk and landscaped areas. Runoff within this sub-basin
will enter area inlet CB-4 and be conveyed to the Underground Detention Vault through a private
underground storm sewer. The runoff coefficients for this sub-basin are 0.67 and 0.72 for the 2-year and
100-year storm, respectively. If inlet CB-4 were to plug, the runoff for the basin would flow west and north
following its historic path to the Sherwood Lateral.
Sub-basin 35
Sub-basin 35 is 0.07 acres and consists of sidewalk and landscaped areas. Runoff within this sub-basin
will enter inlet CB-5 and be conveyed to the Underground Detention Facility through a private underground
storm sewer. The runoff coefficients for this sub-basin are 0.69 and 0.74 for the 2-year and 100-year storm,
respectively. If inlet CB-5 were to plug, the runoff for the basin would flow west and north following its
historic path to the Sherwood Lateral.
Sub-basin 40
Sub-basin 40 is 0.21 acres and consists of parking, sidewalk and landscaped areas. Runoff within this sub-
basin will surface flow onto S. College Avenue following its historical drainage path. The runoff coefficients
for this sub-basin are 0.92 and 0.97 for the 2-year and 100-year storm, respectively.
8
IMPLEMENTATION AND PHASING
The Project will disturb over 10,000 square feet of stabilized ground; therefore, a Stormwater Management
Plan is required. Construction will be implemented in two phases due to the size of the project and types
of improvements required for the Project. The Stormwater Management Plans and Details will be provided
in the Project Construction Documents.
CONCLUSIONS
COMPLIANCE WITH STANDARDS
The 2105 S. College Avenue project is in compliance with City of Fort Collins criteria for storm drainage
design. The “Fort Collins Amendments to the Urban Drainage and Flood Control District Criteria Manual”
and the Urban Drainage Flood Control District “Urban Storm Drainage Criteria Manual Volumes 1, 2, and
3 have been utilized in the design of the storm sewer. The private onsite storm sewer system for this site
will provide conveyance for the 100-yr storm event.
SUMMARY OF CONCEPT
The onsite drainage basins use private roof drains, storm inlets, and curb and gutter to collect and convey
runoff generated within the project site to an existing storm sewer in the northwest corner of the site. With
the exception of flow in sub-basins 10 and 25, all stormwater runoff will be collected and routed through a
WQ BMP and onsite underground detention facility before entering the existing storm sewer system in the
northwest corner of the site. This design will provide LID Water Quality for a minimum of 75% of the site,
or all of the sub-basins except for 10 and 25, as well as limit damages due to erosion. In addition, all flows
that enter the underground detention facility will be routed through an existing off-site water quality BMP.
REFERENCES
Fort Collins Amendments to the Urban Drainage and Flood Control District, City of Fort Collins.
Urban Storm Drainage Criteria Manual, Volume 1-3, Urban Drainage and Flood Control District, Denver,
CO; January 2016, with latest revisions.
APPENDICES
A. Firmette and NRCS Data
B. Hydrology and Hydraulics
C. Proposed Drainage Map
D. Existing Drainage Map
9
APPENDIX A
Hydrologic Soil Group—Larimer County Area, Colorado
(2105 S. College Ave)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/13/2016
Page 1 of 4
4489880 4489900 4489920 4489940 4489960 4489980
4489880 4489900 4489920 4489940 4489960 4489980
493260 493280 493300 493320 493340 493360 493380 493400 493420
493260 493280 493300 493320 493340 493360 493380 493400 493420
40° 33' 38'' N
105° 4' 46'' W
40° 33' 38'' N
105° 4' 39'' W
40° 33' 34'' N
105° 4' 46'' W
40° 33' 34'' N
105° 4' 39'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 40 80 160 240
Feet
0 10 20 40 60
Meters
Map Scale: 1:847 if printed on A landscape (11" x 8.5") sheet.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at 1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil line
placement. The maps do not show the small areas of contrasting
soils that could have been shown at a more detailed scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more accurate
calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as of
the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Hydrologic Soil Group
Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
4 Altvan-Satanta loams, 3
to 9 percent slopes
B 0.6 26.6%
73 Nunn clay loam, 0 to 1
percent slopes
C 1.7 73.4%
Totals for Area of Interest 2.4 100.0%
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 2105 S. College Ave
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/13/2016
Page 3 of 4
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Larimer County Area, Colorado 2105 S. College Ave
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/13/2016
Page 4 of 4
10
APPENDIX B
33
(11) Section 4.0 is amended to read as follows:
4.0 Intensity-Duration-Frequency Curves for Rational Method:
The one-hour rainfall Intensity-Duration-Frequency tables for use the Rational Method
of runoff analysis are provided in Table RA-7 and in Table RA-8.
Table RA-7 -- City of Fort Collins
Rainfall Intensity-Duration-Frequency Table
for Use with the Rational Method
(5 minutes to 30 minutes)
2-Year 10-Year 100-Year
Duration
(min)
Intensity
(in/hr)
Intensity
(in/hr)
Intensity
(in/hr)
5 2.85 4.87 9.95
6 2.67 4.56 9.31
7 2.52 4.31 8.8
8 2.4 4.1 8.38
9 2.3 3.93 8.03
10 2.21 3.78 7.72
11 2.13 3.63 7.42
12 2.05 3.5 7.16
13 1.98 3.39 6.92
14 1.92 3.29 6.71
15 1.87 3.19 6.52
16 1.81 3.08 6.3
17 1.75 2.99 6.1
18 1.7 2.9 5.92
19 1.65 2.82 5.75
20 1.61 2.74 5.6
21 1.56 2.67 5.46
22 1.53 2.61 5.32
23 1.49 2.55 5.2
24 1.46 2.49 5.09
25 1.43 2.44 4.98
26 1.4 2.39 4.87
27 1.37 2.34 4.78
28 1.34 2.29 4.69
29 1.32 2.25 4.6
30 1.3 2.21 4.52
34
Table RA-8 -- City of Fort Collins
Rainfall Intensity-Duration-Frequency Table
for Use with the Rational Method
(31 minutes to 60 minutes)
2-Year 10-Year 100-Year
Duration
(min)
Intensity
(in/hr)
Intensity
(in/hr)
Intensity
(in/hr)
31 1.27 2.16 4.42
32 1.24 2.12 4.33
33 1.22 2.08 4.24
34 1.19 2.04 4.16
35 1.17 2.0 4.08
36 1.15 1.96 4.01
37 1.16 1.93 3.93
38 1.11 1.89 3.87
39 1.09 1.86 3.8
40 1.07 1.83 3.74
41 1.05 1.8 3.68
42 1.04 1.77 3.62
43 1.02 1.74 3.56
44 1.01 1.72 3.51
45 0.99 1.69 3.46
46 0.98 1.67 3.41
47 0.96 1.64 3.36
48 0.95 1.62 3.31
49 0.94 1.6 3.27
50 0.92 1.58 3.23
51 0.91 1.56 3.18
52 0.9 1.54 3.14
53 0.89 1.52 3.1
54 0.88 1.5 3.07
55 0.87 1.48 3.03
56 0.86 1.47 2.99
57 0.85 1.45 2.96
58 0.84 1.43 2.92
59 0.83 1.42 2.89
60 0.82 1.4 2.86
40
Table RO-10
Rational Method Minor Storm Runoff Coefficients for Zoning Classifications
Description of Area or Zoning Coefficient
R-F 0.3
U-E 0.3
L-M-In 0.55
R-L, N-C-L 0.6
M-M-N, N-C-M 0.65
N-C-B 0.7
Business:
C-C-N, C-C-R, C-N, N-C, C-S 0.95
R-D-R, C-C, C-L 0.95
D, C 0.95
H-C 0.95
C-S 0.95
Industrial:
E 0.85
I 0.95
Undeveloped:
R-C, T 0.2
P-O-L 0.25
For guidance regarding zoning districts and classifications of such districts please refer to
Article Four of the City Land Use Code, as amended.
096291001 2105 SOUTH COLLEGE AVENUE 10/4/2016
2105 S. College Sub-Basin Characteristics
Existing Site Area (sf) Area (Ac) Basin % Landscape Roof Pavement IWEIGHTED C2 C100
Entire Site 96,692 2.22 100.0% 2320 31330 63042 92.77% 0.93 0.98
Proposed Site Area (sf) Area (Ac) Basin % Landscape Roof Pavement IWEIGHTED C2 C100
5 60,492 1.39 62.6% 0 60492 0 95.00% 0.95 1.00
10 5,668 0.13 5.9% 1488 0 4180 75.31% 0.74 0.79
15 4,076 0.09 4.2% 59 0 4017 93.91% 0.94 0.99
20 2,335 0.054 2.4% 0 0 2335 95.00% 0.95 1.00
25 9,897 0.23 10.2% 8284 0 1613 17.16% 0.28 0.32
30 2,139 0.05 2.2% 736 0 1403 63.00% 0.67 0.72
35 2,835 0.07 2.9% 910 0 1925 65.15% 0.69 0.74
40 9,248 0.21 9.6% 357 0 8891 91.41% 0.92 0.97
Total 96,690 2.22 100% 11834 60492 15473 75.16% 0.76 0.81
Landuse I C2 C100
Landscape 2% 0.15 0.19
Permeable Pavement 65% 0.45 0.56
Roof 95% 0.95 1.00
Drives and Walks 95% 0.95 1.00
Paved Streets 95% 0.95 1.00
K:\DEN_Civil\096291001_Fort Collins - College & Rutgers\_Project Files\Eng\Drainage\CALCS.xls
096291001 2105 SOUTH COLLEGE AVENUE 10/4/2016
2105 S. College Sub-Basin Characteristics - Proposed
2-Year Design Storm Runoff Calculations
(Rational Method Procedure)
DRAIN AREA RUNOFF T(c) C x A I Q
BASIN ac. COEFF min in/hr cfs
5 1.39 0.95 5.0 1.3193 4.90 6.46
10 0.13 0.74 5.0 0.0963 4.90 0.47
15 0.09 0.94 5.0 0.0878 4.90 0.43
20 0.054 0.95 5.0 0.0509 4.90 0.25
25 0.23 0.28 5.0 0.0637 4.90 0.31
30 0.05 0.67 5.0 0.0331 4.90 0.16
35 0.07 0.69 5.0 0.0451 4.90 0.22
40 0.21 0.92 5.0 0.1951 4.90 0.96
Net Runoff: 9.3
100-Year Design Storm Runoff Calculations
(Rational Method Procedure)
DRAIN AREA RUNOFF T(c) C x A I Q
BASIN ac. COEFF min in/hr cfs
5 1.39 1.00 5.0 1.3887 9.40 13.05
10 0.13 0.79 5.0 0.1024 9.40 0.96
15 0.09 0.99 5.0 0.0925 9.40 0.87
20 0.054 1.00 5.0 0.0536 9.40 0.50
25 0.23 0.32 5.0 0.0727 9.40 0.68
30 0.05 0.72 5.0 0.0354 9.40 0.33
35 0.07 0.74 5.0 0.0481 9.40 0.45
40 0.21 0.97 5.0 0.2056 9.40 1.93
Net Runoff: 18.8
BASIN INFORMATION DIRECT RUNOFF
BASIN INFORMATION DIRECT RUNOFF
K:\DEN_Civil\096291001_Fort Collins - College & Rutgers\_Project Files\Eng\Drainage\CALCS.xls
096291001 2105 SOUTH COLLEGE AVENUE 8/11/2016
2105 S. College Sub-Basin Characteristics - Existing
2-Year Design Storm Runoff Calculations
(Rational Method Procedure)
DRAIN AREA RUNOFF T(c) C x A I Q
BASIN ac. COEFF min in/hr cfs
B1 1.01 0.95 5.0 0.9566 4.90 4.69
B2 0.46 0.95 5.0 0.4372 4.90 2.14
B3 0.30 0.95 5.0 0.2829 4.90 1.39
B4 0.45 0.95 5.0 0.4321 4.90 2.12
Net Runoff: 10.3
100-Year Design Storm Runoff Calculations
(Rational Method Procedure)
BASIN INFORMATION
DRAIN AREA RUNOFF T(c) C x A I Q
BASIN ac. COEFF min in/hr cfs
B1 1.01 1.00 5.0 1.0069 9.40 9.47
B2 0.46 1.00 5.0 0.4603 9.40 4.33
B3 0.30 1.00 5.0 0.2978 9.40 2.80
B4 0.45 1.00 5.0 0.4548 9.40 4.28
Net Runoff: 20.9
DIRECT RUNOFF
DIRECT RUNOFF
BASIN INFORMATION
K:\DEN_Civil\096291001_Fort Collins - College & Rutgers\_Project Files\Eng\Drainage\CALCS.xls
Equations: A trib. To pond = 1.78 acre
QD = CiA C100 = 0.97
Vi = T*CiA = T*QD Developed C*A = 1.73 acre
Vo =m*QPO*(60*T) QPO = 8.79 cfs
S = Vi - Vo tc = 5 min
Rainfall intensity from Larimer County Area 1 IDF Curve
Storm Rainfall QD Vol. In Outflow Vol. Out Storage Storage
Duration, T Intensity, i (cfs) Vi Adjustment Vo S S
(min) (in/hr) (ft3) Factor, m (ft3) (ft3) (ac-ft)
5 9.95 17.2 5154 1.00 2637 2517 0.058
10 7.72 13.3 7998 0.75 3956 4042 0.093
20 5.60 9.7 11603 0.63 6593 5010 0.115
30 4.52 7.8 14048 0.58 9230 4818 0.111
40 3.74 6.5 15498 0.56 11867 3631 0.083
50 3.23 5.6 16731 0.55 14504 2227 0.051
60 2.86 4.9 17777 0.54 17141 637 0.015
70 2.62 4.5 19000 0.54 19778 -778 -0.018
80 2.38 4.1 19725 0.53 22415 -2690 -0.062
90 2.22 3.8 20698 0.53 25052 -4353 -0.100
100 2.05 3.5 21237 0.53 27689 -6451 -0.148
110 1.93 3.3 21993 0.52 30326 -8332 -0.191
120 1.80 3.1 22377 0.52 32963 -10586 -0.243
130 1.60 2.8 21548 0.52 35600 -14052 -0.323
140 1.40 2.4 20305 0.52 38237 -17932 -0.412
150 1.20 2.1 18647 0.52 40874 -22226 -0.510
160 1.15 2.0 19062 0.52 43511 -24449 -0.561
170 1.10 1.9 19372 0.51 46148 -26775 -0.615
180 1.05 1.8 19580 0.51 48785 -29205 -0.670
Required Storage Volume: 5010 ft3
0.115 acre-ft
Scenario: Base
CO-9
27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 1 of 1
+1-203-755-1666
10/4/2016
Bentley StormCAD V8i (SELECTseries 4)
StormCAD 2016_1004.stsw Bentley Systems, Inc. Haestad Methods Solution Center [08.11.04.54]
FlexTable: Conduit Table
Invert (Start)
(ft)
Velocity
(ft/s)
Capacity (Full
Flow)
(cfs)
Flow
(cfs)
Slope
(Calculated)
(ft/ft)
Length (Unified)
(ft)
Label Start Node Stop Node
CO-5 CB-5 CB-4 242.0 0.005 0.45 4.53 2.36 5,015.10
CO-1 CB-2 O-2 4.1 0.005 0.50 2.49 0.64 5,012.72
CO-4 CB-4 CB-Roof 192.6 0.007 0.78 5.33 0.64 5,013.92
CO-3 CB-Roof O-1 5.0 0.000 13.83 0.00 11.27 5,012.61
CO-8 CB-6 MH-12 33.0 0.005 0.96 9.51 3.45 5,014.20
CO-9 MH-12 O-3 35.0 0.005 1.83 7.32 3.44 5,014.04
CO-10 CB-3 MH-12 22.9 0.002 0.87 1.66 2.14 5,014.09
Hydraulic Grade
Line (Out)
(ft)
Elevation
Ground (Stop)
(ft)
Invert (Stop)
(ft)
Hydraulic Grade
Line (In)
(ft)
Elevation
Ground (Start)
(ft)
5,020.27 5,016.27 5,013.91 5,020.68 5,016.26
5,016.70 5,016.00 5,012.70 5,016.50 5,016.00
5,020.68 5,016.26 5,012.61 5,019.00 5,016.23
5,019.00 5,016.23 5,012.61 5,016.70 5,016.00
5,016.39 5,014.56 5,014.04 5,017.33 5,014.55
5,017.33 5,014.55 5,013.87 5,016.00 5,014.38
5,016.33 5,014.60 5,014.04 5,017.33 5,014.55
27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 1 of 1
+1-203-755-1666
10/4/2016
Bentley StormCAD V8i (SELECTseries 4)
StormCAD 2016_1004.stsw Bentley Systems, Inc. Haestad Methods Solution Center [08.11.04.54]
FlexTable: Catch Basin Table
Headloss
Coefficient
(Standard)
Intercepted
Fixed Flow
(cfs)
Flow (Total Out)
(cfs)
External CA Inlet Type
(acres)
Hydraulic Grade
Line (In)
(ft)
Elevation (Rim)
(ft)
Label
CB-5 5,020.27 5,016.27 0.Capture000 Full 0.45 0.45 0.500
CB-2 5,016.70 5,016.00 0.Capture000 Full 0.50 0.50 0.600
CB-3 5,016.33 5,014.70 0.Capture000 Full 0.87 0.87
CB-4 5,020.68 5,016.26 0.Capture000 Full 0.78 0.33 0.600
CB-Roof 5,019.00 5,016.23 0.Capture000 Full 13.83 13.05
CB-6 5,016.39 5,014.66 0.Capture000 Full 0.96 0.96
27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 1 of 1
+1-203-755-1666
10/4/2016
Bentley StormCAD V8i (SELECTseries 4)
StormCAD 2016_1004.stsw Bentley Systems, Inc. Haestad Methods Solution Center [08.11.04.54]
Profile Report
Engineering Profile - Profile - 1 (StormCAD 2016_1004.stsw)
27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 1 of 1
+1-203-755-1666
10/4/2016
Bentley StormCAD V8i (SELECTseries 4)
StormCAD 2016_1004.stsw Bentley Systems, Inc. Haestad Methods Solution Center [08.11.04.54]
Profile Report
Engineering Profile - Profile - 1 (StormCAD 2016_1004.stsw)
27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 1 of 1
+1-203-755-1666
10/4/2016
Bentley StormCAD V8i (SELECTseries 4)
StormCAD 2016_1004.stsw Bentley Systems, Inc. Haestad Methods Solution Center [08.11.04.54]
Profile Report
Engineering Profile - Profile - 2 (StormCAD 2016_1004.stsw)
5,010.00
5,015.00
5,020.00
-0+50 0+00 0+50
Station (ft)
CB-2
Rim: 5,016.70 ft
Invert: 5,012.72 ft
O-2
Rim: 5,016.50 ft
Invert: 5,012.70 ft
CO-1: 4.1 ft @ 0.005 ft/ft
Circle - 12.0 in
27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 1 of 1
+1-203-755-1666
10/4/2016
Bentley StormCAD V8i (SELECTseries 4)
StormCAD 2016_1004.stsw Bentley Systems, Inc. Haestad Methods Solution Center [08.11.04.54]
Profile Report
Engineering Profile - Profile - South (StormCAD 2016_0811.stsw)
27 Siemon Company Drive Suite 200 W Watertown, CT 06795 USA Page 1 of 1
+1-203-755-1666
8/11/2016
Bentley StormCAD V8i (SELECTseries 4)
StormCAD 2016_0811.stsw Bentley Systems, Inc. Haestad Methods Solution Center [08.11.04.54]
Project Description
Friction Method Manning Formula
Solve For Discharge
Input Data
Roughness Coefficient 0.010
Channel Slope 0.00500 ft/ft
Normal Depth 1.50 ft
Diameter 1.50 ft
Results
Discharge 9.66 ft³/s
Flow Area 1.77 ft²
Wetted Perimeter 4.71 ft
Hydraulic Radius 0.38 ft
Top Width 0.00 ft
Critical Depth 1.20 ft
Percent Full 100.0 %
Critical Slope 0.00524 ft/ft
Velocity 5.46 ft/s
Velocity Head 0.46 ft
Specific Energy 1.96 ft
Froude Number 0.00
Maximum Discharge 10.39 ft³/s
Discharge Full 9.66 ft³/s
Slope Full 0.00500 ft/ft
Flow Type SubCritical
GVF Input Data
Downstream Depth 0.00 ft
Length 0.00 ft
Number Of Steps 0
GVF Output Data
Upstream Depth 0.00 ft
Profile Description
Profile Headloss 0.00 ft
Average End Depth Over Rise 0.00 %
Normal Depth Over Rise 100.00 %
Downstream Velocity Infinity ft/s
Spring Creek Place - Discharge Pipe (proposed BMP to existing inlet)
8/11/2016 4:49:10 PM
Bentley Systems, Inc. Haestad Methods Solution BentleCyenter FlowMaster V8i (SELECTseries 1) [08.11.01.03]
27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 1 of 2
Kimley-Horn and Associates, Inc.
GVF Output Data
Upstream Velocity Infinity ft/s
Normal Depth 1.50 ft
Critical Depth 1.20 ft
Channel Slope 0.00500 ft/ft
Critical Slope 0.00524 ft/ft
Spring Creek Place - Discharge Pipe (proposed BMP to existing inlet)
8/11/2016 4:49:10 PM
Bentley Systems, Inc. Haestad Methods Solution BentleCyenter FlowMaster V8i (SELECTseries 1) [08.11.01.03]
27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 Page 2 of 2
Kimley-Horn and Associates, Inc.
11
APPENDIX C
T
A BIG A SELF
STORAGE
(N.A.P.)
VACANT LAND
(N.A.P.)
SPRING CREEK
STATION
MATTRESS
FIRM
(N.A.P.)
WHOLE FOODS
(N.A.P.)
R
SPRING CREEK PLACE
FORT COLLINS, CO
DANIEL L. SKEEHAN
NORTH COLORADO PE No. 46391
LEGEND
PROPOSED DRAINAGE AREA MAP
N
COLLEGE AVE.
C&S RR
COLUMBIA RD.
O'DEA
ELEMENTARY
SCHOOL
COLORADO
STATE
UNIVERSITY ZONE:
RL
ZONE:
CG
ZONE:
CSU
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Survey Area Data: Version 10, Sep 22, 2015
Soil map units are labeled (as space allows) for map scales 1:50,000
or larger.
Date(s) aerial images were photographed: Apr 22, 2011—Apr 28,
2011
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor shifting
of map unit boundaries may be evident.
Hydrologic Soil Group—Larimer County Area, Colorado
(2105 S. College Ave)
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
1/13/2016
Page 2 of 4