HomeMy WebLinkAboutBEEBE CHRISTIAN SCHOOL - PDP - PDP160022 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTDrainage Report
for
BeBee Christian School
2103 Nancy Gray Avenue
Fort Collins, CO 80525
Prepared by: Mike Beach, P.E.
Project #:16‐026‐001
Date: July 13, 2016
Revised: ‐
5255 Ronald Reagan Blvd, Suite 210 Johnstown, CO 80534
(303) 322-6480 EMAIL: mbeach@ridgetopeng.com
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Section Page
1. Project Engineer’s Certification ........................................................................................ 3
2. Project Location & Overview ............................................................................................ 4
3. Drainage Design Criteria ................................................................................................... 5
4. Hydraulic Calculations ....................................................................................................... 6
5. Facility Design .................................................................................................................... 7
6. Conclusion ......................................................................................................................... 8
7. References ......................................................................................................................... 8
Appendix A – Site Vicinity Map
Appendix B – Flood Insurance Rate Map
Appendix C – NRCS Soils Map
Appendix D – Hydrologic Criteria
Fort Collins Rainfall Intensity Curve
Fort Collins Rainfall Intensity Table
Table RO‐3 – Recommended Percentage Imperviousness Values
Appendix E – Hydraulic Calculations
Runoff Coefficients & Imperviousness
Time of Concentration ‐ SF‐2
Rational Method Runoff Flows – SF‐3 (2‐Year Event)
Rational Method Runoff Flows – SF‐3 (10‐Year Event)
Rational Method Runoff Flows – SF‐3 (100‐Year Event)
Detention Volume by Modified FAA Method
Rain Garden Calculations (both Subbasins)
LID Table
Drain Times
Appendix F – Maps
Drainage Plan/Subbasin Map
Appendix G – References
Table of Contents
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Section 1: PROJECT ENGINEER’S CERTIFICATION
I hereby attest that this Final Drainage Report for the design of stormwater management
facilities for BeBee Christian School on 2103 Nancy Gray Ave. was prepared by me, or under my
direct supervision, in accordance with the provisions of the City of Fort Collins Storm Drainage
Design Criteria and Construction Standards for the responsible parties thereof.
__________________________
Mike Beach, P.E.
Registered Professional Engineer
State of Colorado No. 45088
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Section 2: Project Location & Overview
Location
The sites address is 2103 Nancy Gray Avenue, Fort Collins, CO; which is described as a portion
of Outlot A, Spring Creek Farms North, City of Fort Collins, County of Larimer, State of Colorado.
For Recording purposes: Part of the Southeast Quarter of Section 19, TP 7 N, R 68 W of the 6th
PM.
Located along the north side of Nancy Gray Ave. and east of South Timberline Road, the site is
described as above and contains 3.326 acres of undeveloped vacant land. (See Appendix A –
Site Vicinity Map)
Existing Condition
The existing site is covered by native vegetation and slopes predominately towards South
Timberline Road at approximately 0.5% slope. Stormwater runoff collected into an existing
stormwater detention pond along the eastern side of the site. From there the detained water
is released at no more than 2 cfs via outlet structure and conveyed via piping to “Storm 2” as
delineated in previous storm reports. Storm 2 connects to Sidehill Filing 2 Storm system.
Proposed Condition
The intent of the development is to construct a new building of approximately 30,206 SF (in
two phases), asphalt concrete parking, curb and gutter, playground area containing grass and
gravel material, and landscaping. It has been determined by the survey that the existing pond
has sufficient detention capacity for this project.
Floodplain
FEMA Floodplain mapping in this neighborhood is located on map‐panel 08069C1000F,
Effective December 18, 2006, (Not Printed), however it appears the subject property is located
in Zone X, which is outside the 100‐year floodplain. Flood Insurance Rate Map not available for
printing.
Existing Soils
The Natural Resource Conservation Service mapped the historic soils on the site as part of the
Nunn clay loam. The Hydrologic Class is Type ‘C’ Soils. (Appendix C – NRCS Soils Map)
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Section 3: Drainage Design Criteria
Reference Manuals
Storm drainage design criteria is defined in the City of Fort Collins “Storm Drainage Design
Criteria and Construction Standards Manual (FCSDCM) and Amendments, which references to
the “Urban Drainage and Flood Control District” (UDFCD) and the “Urban Storm Drainage
Criteria Manual” (USDCM), Volumes 1, 2, and 3, dated 2008 with revisions (the Manual), are
used and referenced in this report.
Low Impact Development (LID) Requirements
The proposed development is required to meet the City’s current Land Use Code, which
includes:
‐ Treat no less than 50% of any newly added impervious area using one or a
combination of LID techniques.
‐ Treat no less than 25% of any newly added pavement area using a permeable
pavement.
Four Step Process
The City of Fort Collins has adopted the “Four Step Process” that is recommended in Volume 3
of the USDCM for selecting BMP’s in urban redevelopment areas. The goal of this process is to
minimize adverse impacts on receiving waters. The following describe how each step of the
process are incorporated in the proposed development:
Step 1 – Employ Runoff Reduction Practices
By selecting a site that is undeveloped that currently does not have water quality treatment,
the impacts of the proposed development will be less due to the addition of the water quality
capture volume included. The project proposes to install a rain garden with underdrains to aid
in conveyance and infiltration opportunities as well as impermeable pavers within vehicular
traveled areas, which together will reduce the effects of the added impervious area from the
development of the site.
Step 2 – Water Quality Capture Volume (WQCV)
In order to reduce the sediment load and other pollutants leaving the site, it is important to
provide WQCV to minimize the downstream impacts. This project proposes to provide rain
garden prior to the stormwater entering the detention pond, both located on the site. These
facilities are sized to release at or below the historic runoff rates.
Step 3 – Stabilize Drainageways
Since this site is in close proximity to Poudre River it is important to take this Step into
consideration. By providing stormwater detention and water quality and lowering the historic
runoff and providing a metered outflow the project impacts to the drainageway are essentially
reduced. The majority of the drainageway leaving the site is already stabilized.
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Step 4 – Implement Site Specific and Other Source Control BMP’s
The proposed project will contain the following BMP’s:
Rain Garden: All runoff from the site will be directed into and through the proposed
BMP facilities prior to leaving the site. Rain gardens utilize native plants that act as
sponges to reduce the amount of stromwater runoff and absorb contaminants.
Pervious Pavers: Vehicular traveled areas will contain pervious pavers, which allow
rainwater runoff to filter through the spaces between the blocks into the gravel layers
underneath. This reduces the amount of stormwater runoff and absorbs contaminants
that might otherwise enter the local waterways.
Maintenance: In order for BMP’s to remain effective proper maintenance needs are
required. Scheduled visual inspections and routine repair after larger storm events are
critical in the maintenance and effectiveness of the installed BMP’s. The sites owner will
be advised of these practices during installation in order to maximize the efficiency of
the installed BMP’s.
Section 4: Hydraulic Calculations
Criteria
Runoff criteria for the proposed sites was analyzed for the 2‐YR, 10‐YR, and 100‐YR storm
events. The Rational Method is being used for the design of the proposed improvements.
Rainfall Intensities used in the proposed design were determined as a function of the Time of
Concertation for each subbasin. The values used were determined by the City of Fort Collins
Rainfall Intensity/Duration/Frequency curve (Figure 3‐1 and Table 3‐1a (see Appendix D).
Imperviousness
Values from Table RO‐3 (USDCM) were used in determining the sites imperviousness. The
overall proposed site improvements and landscaping equate to a total onsite proposed
Imperviousness of 43%.
Time of Concentration & Runoff Coefficient
The onsite area was separated into two (2) subbasins with slopes varying between 0.5% to
1.5%. The calculated Time of Concentration (TC) for each subbasin are listed in Appendix E. See
Basin Map in Appendix F for more information.
WQCV
The UD‐BMP_v3.03 (UDFCD) spreadsheet was used to calculated the required Rain Garden
water quality capture volume. See Appendix E for design information.
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Detention
The existing detention pond is already constructed and was designed by Stantec with and
allowable release rate of 2 cfs. The Stantec report was not attainable, however the design was
confirmed and discussed in the “Interim Timberline Road Widening – Drake to Prospect”. See
existing report information in Appendix G.
The detention facility Drain Time Spreadsheet has been calculated and is included within
Appendix E of this report. The calculated drain time for 99% of the inflow volume of the pond
with the proposed project and off‐site area included is approximately 6.3 hours for the 100‐
year event, which is below the maximum allowed drain time.
Section 5: Facility Design
The proposed improvements will increase the amount of impervious area; however, measures
have been included in the design to minimize the amount of stormwater released from the site.
Per previous design reports, the outlet structure is designed to release at 2 cfs. Per our report,
the predeveloped 2‐year event at a release is 2.276 cfs per for the entire 3.32‐acre site (see
Appendix E for historic calcs). The runoff will sheet flow until a concentrated point and then be
conveyed via trickle channel or gutters and then deposited into the water quality device or
detention pond.
The site was broken into two developed subbasins for water quality purposes; Subbasin 1.0
(2.294 acres) and Subbasin 2.0 (1.030 acres). OS‐7 (as described below) was also modeled and
included in the detention calculations. See Appendix E for breakdown of the different area
types for each subbasin and Appendix F for the Subbasin Map.
Subbasin 1.0 contains the proposed building, playground area, and minor areas adjacent to the
building. The runoff will be conveyed to the east side of the building and outlet into proposed
rain garden. The rain garden will outlet to the existing detention pond.
Subbasin 2.0 is primarily the parking and paved areas which drains to the east to the existing
detention pond. Since the existing detention pond was already sized for a release of 2 cfs, no
modifications to the steel orifice plate will be required. Currently has one 3.5” diameter orifice.
The existing pond was modeled with the proposed project and the 100‐year WSEL’s is indicated
on the Drainage Plan in Appendix F. Water Quality for this subbasin will be provided via
pervious pavers sized in accordance with the City of Fort Collins criteria. See the LID Table
located in Appendix E and on the Drainage Plan.
OS‐7 – This off‐site basin is included in our report based on previous reports indicating that is
included within this detention pond. Full design calculations are included in order to determine
the required detention volume is being provided within the existing pond.
Since there is only one detention pond modeled with this report we have provided a summary
of the design below. See supporting calculations within the Appendix of this report.
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Area
(ac)
Sub 1.0 2.29 2.22 3.79 9.63 0.009 0.409 0.238 ‐ ‐
Sub 2.0 1.03 1.38 2.38 6.50 Pavers 0.257 0.109 ‐ ‐
OS‐7 0.88 0.77 1.33 3.38 N/A 0.144 0.078 ‐ ‐
Total Site 3.32 3.63 6.19 16.88 ‐ 0.662 0.484 ‐ ‐
Total Basin 4.20 4.34 7.47 19.03 ‐ 0.812 0.630 0.849 2.0
Release
Rate (cfs)
2‐Year
Flow (cfs)
100‐Year
Flow (cfs)
WQCV
(ac‐ft)
100‐Year
Vol. (ac‐ft)
Detention
Req'd (ac‐ft)
Tot. Volume
Provided (ac‐ft)
10‐Year
Flow (cfs)
Section 6: Conclusions
All computations that have been reviewed or completed within this report are in compliance
with the City of Fort Collins Storm Drainage Design Criteria and Construction Standards manual
and the Urban Drainage and Flood Control District Urban Storm Drainage Criteria Manual
Volumes 1 &2.
The proposed drainage concepts presented in this report and on the construction plans
adequately provide for stormwater detention and water quality treatment of impervious areas
by releasing the 100‐Year storm event at the required allowable release rate of 2.0 cfs, which is
less than the Predeveloped 2‐Year runoff rates. The Water Quality design will benefit the site
by reducing the initial discharge from the site and removal of any sediments or other pollutants
generated by the developed site.
Section 7: References
The Natural Resource Conservation Service Soil Survey for Larimer County and the WSS
website.
FEMA FIRM map‐panel 08069C1000F Effective 12/18/2006. – Not Printed.
“City of Fort Collins Stormwater Criteria Manual” dated December 2011
Urban Drainage and Flood Control District Urban Storm Drainage Criteria Manual
(UDFCD), Volumes 1, 2, and 3, dated 2008 with revisions (the Manual).
w Appendix A
Site Vicinity Map
Appendix B
Flood Insurance Rate Map
(Not available to Print)
Appendix C
NRCS Soils Map
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/7/2016
Page 1 of 4
4489690 4489710 4489730 4489750 4489770 4489790 4489810
4489690 4489710 4489730 4489750 4489770 4489790 4489810
496470 496490 496510 496530 496550 496570 496590 496610 496630 496650 496670
496470 496490 496510 496530 496550 496570 496590 496610 496630 496650 496670
40° 33' 32'' N
105° 2' 30'' W
40° 33' 32'' N
105° 2' 20'' W
40° 33' 28'' N
105° 2' 30'' W
40° 33' 28'' N
105° 2' 20'' W
N
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 13N WGS84
0 45 90 180 270
Feet
0 15 30 60 90
Meters
Map Scale: 1:1,020 if printed on A landscape (11" x 8.5") sheet.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Lines
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Soil Rating Points
A
A/D
B
B/D
C
C/D
D
Not rated or not available
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at 1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil line
placement. The maps do not show the small areas of contrasting
soils that could have been shown at a more detailed scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more accurate
calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as of
the version date(s) listed below.
Soil Survey Area: Larimer County Area, Colorado
Hydrologic Soil Group
Hydrologic Soil Group— Summary by Map Unit — Larimer County Area, Colorado (CO644)
Map unit symbol Map unit name Rating Acres in AOI Percent of AOI
73 Nunn clay loam, 0 to 1
percent slopes
C 4.3 97.1%
74 Nunn clay loam, 1 to 3
percent slopes
C 0.1 2.9%
Totals for Area of Interest 4.4 100.0%
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
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/7/2016
Page 3 of 4
Component Percent Cutoff: None Specified
Tie-break Rule: Higher
Hydrologic Soil Group—Larimer County Area, Colorado
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/7/2016
Page 4 of 4
Appendix D
Hydrologic Criteria
RAINFALL INTENSITY-DURATION-FREQUENCY CURVE
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
0.00 10.00 20.00 30.00 40.00 50.00 60.00
STORM DURATION (minutes)
RAINFALL INTENSITY (inches/hour)
2-Year Storm 10-Year Storm 100-Year Storm
Figure RA-16 City of Fort Collins Rainfall Intensity-Duration-Frequency Curves
(13) Section 5.0 is deleted in its entirety.
(14) Section 6.0 is deleted in its entirety.
(15) Section 7.0 is deleted in its entirety.
(16) Section 7.1 is deleted in its entirety.
(17) Section 7.2 is deleted in its entirety.
(18) Section 7.3 is deleted in its entirety.
(19) Section 8.0 is deleted in its entirety.
(20) Table RA-1 is deleted in its entirety.
(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
DRAINAGE CRITERIA MANUAL (V. 1) RUNOFF
Table RO-3—Recommended Percentage Imperviousness Values
Land Use or
Surface Characteristics
Percentage
Imperviousness
Business:
Commercial areas 95
Neighborhood areas 85
Residential:
Single-family *
Multi-unit (detached) 60
Multi-unit (attached) 75
Half-acre lot or larger *
Apartments 80
Industrial:
Light areas 80
Heavy areas 90
Parks, cemeteries 5
Playgrounds 10
Schools 50
Railroad yard areas 15
Undeveloped Areas:
Historic flow analysis 2
Greenbelts, agricultural 2
Off-site flow analysis
(when land use not defined)
45
Streets:
Paved 100
Gravel (packed) 40
Drive and walks 90
Roofs 90
Lawns, sandy soil 0
Lawns, clayey soil 0
* See Figures RO-3 through RO-5 for percentage imperviousness.
C A = K A + ( 1 . 31 i 3 − 1 . 44 i 2 + 1 . 135 i − 0 . 12 ) for CA ≥ 0, otherwise CA = 0 (RO-6)
C CD = K CD + ( 0 . 858 i 3 − 0 . 786 i 2 + 0 . 774 i + 0 . 04 ) (RO-7)
C B = (CA + C CD ) 2
2007-01 RO-9
Urban Drainage and Flood Control District
Appendix E
Hydraulic Calculations
Historic Runoff Coefficients & Percent Impervious Calculated By: RSB
Project - BeBee Christian School Checked By: MRB
Job Number: 16-026-001 Date: 7/10/2016
IMP% Soil Types: Nunn Clay Loam
Table RO-11 (COFC) Roof 0.95 90 Hydrologic Soil Group: C
Table RO-3 (UDSDCM Asphalt 0.95 100
Concrete 0.95 96
Landscaping (flat) 0.20 0
Landscaping (steep) 0.35 0
Gravel & Pavers 0.50 40
Multi-family (attached) 0.65 70
Commercial 0.95 95
Undeveloped Historical 0.20 2
Basin Total Area Roof Paved Gravel Sidewalk Landscape Runoff % Comments
Description (ac) Area (sf) Area (sf) Area (sf) Area (sf) Area (sf) Coeff C Imperv
EX-7 0.880 38333 0 12197 0 0 26136 0.44 32 Off-Site
EX-8 3.320 144619 0 0 0 2660 235224 0.34 2 Site
Total Basin 4.20 182952 0 12197 0 2660 261360 0.36 8
Equations:
Calculated C coefficeints & Percent Impervious are Weighted
C = Summation (Ci*Ai) / At
Ci = Runoff Coefficient for Specific Area (Ai)
Ai = Area of Surface with Runoff Coefficient of Ci
n - Number of different surfaces to be considered
Runoff
Coeff C
Total Area
(sq. ft.)
STANDARD FORM SF-2
Event: 2-Year Historic TIME OF CONCENTRATION
Cf = 1.00 SUBDIVISION: BeBee
CALCULATED BY: MRB DATE: 7/10/2016 REV:
SUB-BASIN INITIAL/OVERLAND TRAVEL TIME t c CHECK FINAL REMARKS
DATA TIME (ti) (t t) (URBANIZED BASINS) tc
DESIG: C AREA LENGTH SLOPE ti LENGTH SLOPE Mannings VEL. tt COMP. TOT. LENGTH tc=(L/180)+10
Ac Ft % Min Ft % n FPS Min tc Ft Min Min
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)
EX-7 0.44 0.88 150 1.0 15.1 340 1 0.025 2.1 2.7 17.8 490 12.7 12.7 Off-Site
EX-8 0.34 3.32 275 1.0 23.5 236 1 0.025 2.1 1.9 25.4 511 12.8 12.8 Site
References/Equations:
Table RO-12 COFC
tc = ti + tt
ti = {1.87(1.1 - C*Cf)*L}/S^0.33
tt = L/Vel
Velocity from Manning's Equation with R=0.1 (per COFC Figure 3-3)
Final tc = Min of ti + tt and/or Urbanized Check
Location: BeBee RATIONAL METHOD PEAK RUNOOF
Calculated By: RSB Event: 2-Year
Date: 7/10/2016 Historic Flow Rate
Cf = 1.00
SUB-BASIN Direct Runoff Comments
DATA
DESIG: C AREA C*Cf tc i Q
Ac min (in/hr) (cfs)
EX-7 0.44 0.88 0.44 12.7 2.00 0.772 Off-Site
EX-8 0.34 3.32 0.34 12.8 2.00 2.276 Site
Total Basin 0.36 4.20 0.36 0.0 2.00 3.048
Q = Cf*C*i*A
Q = Peak Discharge (cfs)
C = Runoff Coefficient
Cf = Frequency Adjustment Factor
I = Rainfall Intensity (in/hr) from COFC IDF Curve (I = 24.221 / (10+tc)^0.7968
A = Drainage Area (ac)
Runoff Coefficients & Percent Impervious Calculated By: RSB
Project - BeBee Christian School Checked By: MRB
Job Number: 16-026-001 Date: 7/10/2016
IMP% Soil Types: Nunn Clay Loam
Table RO-11 (COFC) Roof 0.95 90 Hydrologic Soil Group: C
Table RO-3 (UDSDCM Asphalt 0.95 100
Concrete 0.95 96
Landscaping (flat) 0.20 0
Landscaping (steep) 0.35 0
Gravel & Pavers 0.50 40
Multi-family (attached) 0.65 70
Commercial 0.95 95
Undeveloped Historical 0.20 2
Basin Total Area Roof Paved Gravel Sidewalk Landscape Runoff % Comments
Description (ac) Area (sf) Area (sf) Area (sf) Area (sf) Area (sf) Coeff C Imperv
1.0 2.294 99927 30206 0 11739 2529 54156 0.48 34
2.0 1.030 44867 0 25378 0 2421 18452 0.67 62
OS-7 0.880 38333 0 12197 0 0 26136 0.44 32 Directly to Pond
Total Site 3.32 144793 30206 25378 11739 4950 72608 0.54 43 OS-7 Not Included
Total Basin 4.20 183126 30206 37575 11739 4950 98744 0.52 41 OS-7 Included
Equations:
Calculated C coefficeints & Percent Impervious are Weighted
C = Summation (Ci*Ai) / At
Ci = Runoff Coefficient for Specific Area (Ai)
Ai = Area of Surface with Runoff Coefficient of Ci
n - Number of different surfaces to be considered
Runoff
Coeff C
Total Area
(sq. ft.)
STANDARD FORM SF-2
Event: 2-Year & 10-Year TIME OF CONCENTRATION
Cf = 1.00 SUBDIVISION: BeBee
CALCULATED BY: MRB DATE: 7/10/2016 REV:
SUB-BASIN INITIAL/OVERLAND TRAVEL TIME tc CHECK FINAL REMARKS
DATA TIME (ti
) (tt) (URBANIZED BASINS)
tc
DESIG: C AREA LENGTH SLOPE ti LENGTH SLOPE Mannings VEL. t
t COMP. TOT. LENGTH tc=(L/180)+10
Ac Ft % Min Ft % n FPS Min tc Ft Min Min
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)
1.0 0.48 2.29 175 1.0 15.4 283 0.5 0.016 1.3 3.6 19.0 458 12.5 12.5
2.0 0.67 1.03 95 0.5 9.9 387 0.5 0.015 1.4 4.6 14.5 482 12.7 12.7
OS-7 0.44 0.88 150 1.0 15.1 340 1 0.016 1.3 4.4 19.5 490 12.7 12.7
Total Site 0.54 3.32 100 2.0 8.3 325 0.5 0.016 1.3 4.2 12.5 425 12.4 12.4
Total Basin 0.52 4.20 150 2.0 10.6 340 0.5 0.016 1.3 4.4 15.0 490 12.7 12.7
References/Equations:
Table RO-12 COFC
tc = ti + tt
ti = {1.87(1.1 - C*Cf)*L}/S^0.33
tt = L/Vel
Velocity from Manning's Equation with R=0.1 (per COFC Figure 3-3)
Final tc = Min of ti + tt and/or Urbanized Check
STANDARD FORM SF-2
Event: 100-Year TIME OF CONCENTRATION
Cf = 1.25 SUBDIVISION: BeBee
CALCULATED BY: MRB DATE: 7/10/2016 REV:
SUB-BASIN INITIAL/OVERLAND TRAVEL TIME tc CHECK FINAL REMARKS
DATA TIME (ti) (tt) (URBANIZED BASINS) tc
DESIG: C AREA C*Cf LENGTH SLOPE ti LENGTH SLOPE Mannings VEL. tt COMP. TOT. LENGTH tc=(L/180)+10
Ac Ft % Min Ft % n FPS Min tc Ft Min Min
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)
1.0 0.48 2.29 0.60 175 1.0 12.4 283 0.5 0.016 1.3 3.6 16.0 458 12.5 12.5
2.0 0.67 1.03 0.84 95 0.5 6.0 387 0.5 0.015 1.4 4.6 10.6 482 12.7 10.6
OS-7 0.44 0.88 0.55 150 1.0 12.6 340 1 0.016 1.3 4.4 17.0 490 12.7 12.7
Total Site 0.54 3.32 0.67 100 2.0 6.3 325 0.5 0.016 1.3 4.2 10.5 425 12.4 10.5
Total Basin 0.52 4.20 0.65 150 2.0 8.2 340 0.5 0.016 1.3 4.4 12.6 490 12.7 12.6
References/Equations:
Table RO-12 COFC
tc = ti + tt
ti = {1.87(1.1 - C*Cf)*L}/S^0.33
tt = L/Vel
Velocity from Manning's Equation with R=0.1 (per COFC Figure 3-3)
Final tc = Min of ti + tt and/or Urbanized Check
Location: BeBee RATIONAL METHOD PEAK RUNOOF
Calculated By: MRB Event: 2-Year
Date: 7/10/2016
Cf = 1.00
SUB-BASIN Direct Runoff Comments
DATA
DESIG: C AREA C*Cf tc i Q
Ac min (in/hr) (cfs)
1.0 0.48 2.29 0.48 12.5 2.02 2.22
2.0 0.67 1.03 0.67 12.7 2.00 1.38
OS-7 0.44 0.88 0.44 12.7 2.00 0.77
Total Site 0.54 3.32 0.54 12.4 2.03 3.63
Total Basin 0.52 4.20 0.52 12.7 2.00 4.34
Q = Cf*C*i*A
Q = Peak Discharge (cfs)
C = Runoff Coefficient
Cf = Frequency Adjustment Factor
I = Rainfall Intensity (in/hr) from COFC IDF Curve (I = 24.221 / (10+tc)^0.7968
A = Drainage Area (ac)
Location: BeBee RATIONAL METHOD PEAK RUNOOF
Calculated By: MRB Event: 10-Year
Date: 7/10/2016
Cf = 1.00
SUB-BASIN Direct Runoff Comments
DATA
DESIG: C AREA C*Cf tc i Q
Ac min (in/hr) (cfs)
1.0 0.48 2.29 0.48 12.5 3.45 3.79
2.0 0.67 1.03 0.67 12.7 3.44 2.38
OS-7 0.44 0.88 0.44 12.7 3.44 1.33
Total Site 0.54 3.32 0.54 12.4 3.46 6.19
Total Basin 0.52 4.20 0.52 12.7 3.44 7.47
Q = Cf*C*i*A
Q = Peak Discharge (cfs)
C = Runoff Coefficient
Cf = Frequency Adjustment Factor
i = Rainfall Intensity (in/hr) from COFC IDF Curve (i = 84.682 / (10+tc)^0.7975
A = Drainage Area (ac)
Location: BeBee RATIONAL METHOD PEAK RUNOOF
Calculated By: MRB Event: 100-Year
Date: 7/10/2016
Cf = 1.25
SUB-BASIN Direct Runoff Comments
DATA
DESIG: C AREA C*Cf tc i Q
Ac min (in/hr) (cfs)
1.0 0.48 2.29 0.60 12.5 7.02 9.63
2.0 0.67 1.03 0.84 10.6 7.53 6.50
OS-7 0.44 0.88 0.55 12.7 7.00 3.38
Total Site 0.54 3.32 0.67 10.5 7.55 16.88
Total Basin 0.52 4.20 0.65 12.6 7.01 19.03
Q = Cf*C*i*A
Q = Peak Discharge (cfs)
C = Runoff Coefficient
Cf = Frequency Adjustment Factor
i = Rainfall Intensity (in/hr) from COFC IDF Curve (i = 84.682 / (10+tc)^0.7975
A = Drainage Area (ac)
DETENTION VOLUME CALCULATIONS
RATIONAL VOLUMETRIC (FAA) METHOD
LOCATION: BeBee Christian School
CALCULATED BY: MRB
PROJECT NUMBER: 16-026-001
DATE: 7/10/2016
BASIN: 1.0
Equations: A trib. To pond = 2.294 acre
QD = CiA C100 = 0.60 (C*Cf)
Vi = T*CiA = T*QD Developed C*A = 1.38 acre
Vo =m*QPO*(60*T) QPO = 2.000 cfs
S = Vi - Vo tc = 12.5 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 SS
(min) (in/hr) (ft3) Factor, m (ft3) (ft3) (ac-ft)
5 9.95 13.7 4109 1.00 600 3509 0.081
10 7.72 10.6 6375 1.00 1200 5175 0.119
20 5.60 7.7 9249 0.81 1950 7299 0.168
30 4.52 6.2 11198 0.71 2550 8648 0.199
40 3.74 5.1 12355 0.66 3150 9205 0.211
50 3.23 4.4 13337 0.63 3750 9587 0.220
60 2.86 3.9 14171 0.60 4350 9821 0.225
70 2.62 3.6 15146 0.59 4950 10196 0.234
80 2.38 3.3 15724 0.58 5550 10174 0.234
90 2.22 3.1 16500 0.57 6150 10350 0.238
100 2.05 2.8 16930 0.56 6750 10180 0.234
110 1.93 2.7 17533 0.56 7350 10183 0.234
120 1.80 2.5 17838 0.55 7950 9888 0.227
130 1.60 2.2 17177 0.55 8550 8627 0.198
140 1.40 1.9 16186 0.54 9150 7036 0.162
150 1.20 1.7 14865 0.54 9750 5115 0.117
160 1.15 1.6 15195 0.54 10350 4845 0.111
170 1.10 1.5 15443 0.54 10950 4493 0.103
180 1.05 1.4 15608 0.53 11550 4058 0.093
Required Storage Volume: 10350 ft3
0.238 acre-ft
DETENTION VOLUME CALCULATIONS
RATIONAL VOLUMETRIC (FAA) METHOD
LOCATION: BeBee Christian School
CALCULATED BY: MRB
PROJECT NUMBER: 16-026-001
DATE: 7/10/2016
BASIN: 2.0
Equations: A trib. To pond = 1.030 acre
QD = CiA C100 = 0.84 (C*Cf)
Vi = T*CiA = T*QD Developed C*A = 0.87 acre
Vo =m*QPO*(60*T) QPO = 2.000 cfs
S = Vi - Vo tc = 10.6 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 SS
(min) (in/hr) (ft3) Factor, m (ft3) (ft3) (ac-ft)
5 9.95 8.6 2583 1.00 600 1983 0.046
10 7.72 6.7 4008 1.00 1200 2808 0.064
20 5.60 4.8 5814 0.77 1836 3978 0.091
30 4.52 3.9 7039 0.68 2436 4603 0.106
40 3.74 3.2 7766 0.63 3036 4730 0.109
50 3.23 2.8 8384 0.61 3636 4748 0.109
60 2.86 2.5 8908 0.59 4236 4672 0.107
70 2.62 2.3 9521 0.58 4836 4685 0.108
80 2.38 2.1 9884 0.57 5436 4448 0.102
90 2.22 1.9 10372 0.56 6036 4336 0.100
100 2.05 1.8 10642 0.55 6636 4006 0.092
110 1.93 1.7 11021 0.55 7236 3785 0.087
120 1.80 1.6 11213 0.54 7836 3377 0.078
130 1.60 1.4 10798 0.54 8436 2362 0.054
140 1.40 1.2 10175 0.54 9036 1139 0.026
150 1.20 1.0 9344 0.54 9636 -292 -0.007
160 1.15 1.0 9552 0.53 10236 -684 -0.016
170 1.10 1.0 9708 0.53 10836 -1128 -0.026
180 1.05 0.9 9811 0.53 11436 -1625 -0.037
Required Storage Volume: 4748 ft3
0.109 acre-ft
DETENTION VOLUME CALCULATIONS
RATIONAL VOLUMETRIC (FAA) METHOD
LOCATION: BeBee Christian School
CALCULATED BY: MRB
PROJECT NUMBER: 16-026-001
DATE: 7/10/2016
BASIN: OS-7
Equations: A trib. To pond = 0.880 acre
QD = CiA C100 = 0.55 (C*Cf)
Vi = T*CiA = T*QD Developed C*A = 0.48 acre
Vo =m*QPO*(60*T) QPO = 0.780 cfs
S = Vi - Vo tc = 12.7 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 SS
(min) (in/hr) (ft3) Factor, m (ft3) (ft3) (ac-ft)
5 9.95 4.8 1445 1.00 234 1211 0.028
10 7.72 3.7 2242 1.00 468 1774 0.041
20 5.60 2.7 3252 0.82 765 2487 0.057
30 4.52 2.2 3938 0.71 999 2939 0.067
40 3.74 1.8 4344 0.66 1233 3111 0.071
50 3.23 1.6 4690 0.63 1467 3223 0.074
60 2.86 1.4 4983 0.61 1701 3282 0.075
70 2.62 1.3 5326 0.59 1935 3391 0.078
80 2.38 1.2 5529 0.58 2169 3360 0.077
90 2.22 1.1 5802 0.57 2403 3399 0.078
100 2.05 1.0 5953 0.56 2637 3316 0.076
110 1.93 0.9 6165 0.56 2871 3294 0.076
120 1.80 0.9 6273 0.55 3105 3167 0.073
130 1.60 0.8 6040 0.55 3339 2701 0.062
140 1.40 0.7 5692 0.55 3573 2119 0.049
150 1.20 0.6 5227 0.54 3807 1420 0.033
160 1.15 0.6 5343 0.54 4041 1302 0.030
170 1.10 0.5 5430 0.54 4275 1155 0.027
180 1.05 0.5 5489 0.54 4509 979 0.022
Required Storage Volume: 3399 ft3
0.078 acre-ft
DETENTION VOLUME CALCULATIONS
RATIONAL VOLUMETRIC (FAA) METHOD
LOCATION: BeBee Christian School
CALCULATED BY: MRB
PROJECT NUMBER: 16-026-001
DATE: 7/10/2016
BASIN: Total Site
Equations: A trib. To pond = 3.320 acre
QD = CiA C100 = 0.67 (C*Cf)
Vi = T*CiA = T*QD Developed C*A = 2.22 acre
Vo =m*QPO*(60*T) QPO = 2.000 cfs
S = Vi - Vo tc = 10.5 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 SS
(min) (in/hr) (ft3) Factor, m (ft3) (ft3) (ac-ft)
5 9.95 22.1 6640 1.00 600 6040 0.139
10 7.72 17.2 10303 1.00 1200 9103 0.209
20 5.60 12.5 14948 0.76 1830 13118 0.301
30 4.52 10.1 18098 0.68 2430 15668 0.360
40 3.74 8.3 19966 0.63 3030 16936 0.389
50 3.23 7.2 21554 0.61 3630 17924 0.411
60 2.86 6.4 22902 0.59 4230 18672 0.429
70 2.62 5.8 24477 0.58 4830 19647 0.451
80 2.38 5.3 25412 0.57 5430 19982 0.459
90 2.22 4.9 26666 0.56 6030 20636 0.474
100 2.05 4.6 27360 0.55 6630 20730 0.476
110 1.93 4.3 28334 0.55 7230 21104 0.484
120 1.80 4.0 28828 0.54 7830 20998 0.482
130 1.60 3.6 27761 0.54 8430 19331 0.444
140 1.40 3.1 26159 0.54 9030 17129 0.393
150 1.20 2.7 24024 0.54 9630 14394 0.330
160 1.15 2.6 24557 0.53 10230 14327 0.329
170 1.10 2.4 24958 0.53 10830 14128 0.324
180 1.05 2.3 25225 0.53 11430 13795 0.317
Required Storage Volume: 21104 ft3
0.484 acre-ft
DETENTION VOLUME CALCULATIONS
RATIONAL VOLUMETRIC (FAA) METHOD
LOCATION: BeBee Christian School
CALCULATED BY: MRB
PROJECT NUMBER: 16-026-001
DATE: 7/10/2016
BASIN: Total Basin
Equations: A trib. To pond = 4.200 acre
QD = CiA C100 = 0.65 (C*Cf)
Vi = T*CiA = T*QD Developed C*A = 2.73 acre
Vo =m*QPO*(60*T) QPO = 2.000 cfs
S = Vi - Vo tc = 12.6 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 SS
(min) (in/hr) (ft3) Factor, m (ft3) (ft3) (ac-ft)
5 9.95 27.2 8149 1.00 600 7549 0.173
10 7.72 21.1 12645 1.00 1200 11445 0.263
20 5.60 15.3 18346 0.82 1956 16390 0.376
30 4.52 12.3 22211 0.71 2556 19655 0.451
40 3.74 10.2 24504 0.66 3156 21348 0.490
50 3.23 8.8 26454 0.63 3756 22698 0.521
60 2.86 7.8 28108 0.61 4356 23752 0.545
70 2.62 7.2 30041 0.59 4956 25085 0.576
80 2.38 6.5 31188 0.58 5556 25632 0.588
90 2.22 6.1 32727 0.57 6156 26571 0.610
100 2.05 5.6 33579 0.56 6756 26823 0.616
110 1.93 5.3 34775 0.56 7356 27419 0.629
120 1.80 4.9 35381 0.55 7956 27425 0.630
130 1.60 4.4 34070 0.55 8556 25514 0.586
140 1.40 3.8 32105 0.55 9156 22949 0.527
150 1.20 3.3 29484 0.54 9756 19728 0.453
160 1.15 3.1 30139 0.54 10356 19783 0.454
170 1.10 3.0 30631 0.54 10956 19675 0.452
180 1.05 2.9 30958 0.54 11556 19402 0.445
Required Storage Volume: 27425 ft3
0.630 acre-ft
Sheet 1 of 2
Designer:
Company:
Date:
Project:
Location:
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, Ia Ia = 43.0 %
(100% if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = Ia/100) i = 0.430
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time WQCV = 0.15 watershed inches
(WQCV= 0.8 * (0.91* i3 - 1.19 * i2 + 0.78 * i)
D) Contributing Watershed Area (including rain garden area) Area = 32,450 sq ft
E) Water Quality Capture Volume (WQCV) Design Volume VWQCV = cu ft
Vol = (WQCV / 12) * Area
F) For Watersheds Outside of the Denver Region, Depth of d6 = 0.43 in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region, VWQCV OTHER = 406.1 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 = 271 sq ft
D) Actual Flat Surface Area AActual = 308 sq ft
E) Area at Design Depth (Top Surface Area) ATop = 650 sq ft
F) Rain Garden Total Volume VT= 479 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 = 0.0 ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours Vol12 = 406 cu ft
iii) Orifice Diameter, 3/8" Minimum DO = 1.38 in
Design Procedure Form: Rain Garden (RG)
MRB
Ridgetop Engineering
July 13, 2016
BeBee Christian School
Basin 1
Choose One
Choose One
18" Rain Garden Growing Media
Other (Explain):
YES
NO
UD-BMP_v3.03_Basin 1, RG 7/13/2016, 6:20 PM
Sheet 2 of 2
Designer:
Company:
Date:
Project:
Location:
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
A) Is an impermeable liner provided due to proximity
of structures or groundwater contamination?
6. Inlet / Outlet Control
A) Inlet Control
7. Vegetation
8. Irrigation
A) Will the rain garden be irrigated?
Notes:
Design Procedure Form: Rain Garden (RG)
MRB
Ridgetop Engineering
July 13, 2016
BeBee Christian School
Basin 1
Choose One
Choose One
Choose One
Sheet Flow- No Energy Dissipation Required
Concentrated Flow- Energy Dissipation Provided
Plantings
Seed (Plan for frequent weed control)
Sand Grown or Other High Infiltration Sod
Choose One
YES
NO
YES
NO
UD-BMP_v3.03_Basin 1, RG 7/13/2016, 6:20 PM
Stormwater Facility Name:
Facility Location & Jurisdiction:
User Input: Watershed Characteristics User Defined User Defined User Defined User Defined
Watershed Slope = 0.005 ft/ft Stage [ft] Area [ft^2] Stage [ft] Discharge [cfs]
Watershed Length = 475 ft 0.00 40 0.00 0.01
Watershed Area = 4.20 acres 1.00 1,566 1.00 2.00
Watershed Imperviousness = 43.0% percent 2.00 3,392 2.00 2.00
Percentage Hydrologic Soil Group A = percent 3.00 5,139 3.00 2.00
Percentage Hydrologic Soil Group B = percent 4.00 7,015 4.00 2.00
Percentage Hydrologic Soil Groups C/D = 100.0% percent 5.00 9,027 5.00 2.00
6.00 11,919 6.00 2.00
UDFCD Default 17 7.00 13,506 7.00 2.00
WQCV Treatment Method = hours
After completing and printing this worksheet to a pdf, go to:
https://maperture.digitaldataservices.com/gvh/?viewer=cswdif
create a new stormwater facility, and
attach the pdf of this worksheet to that record.
Routed Hydrograph Results
Design Storm Return Period = WQCV 2 Year 5 Year 10 Year 50 Year 100 Year
One‐Hour Rainfall Depth = 0.53 0.98 1.36 1.71 2.91 3.67 in
Calculated Runoff Volume = 0.137 0.252 0.361 0.757 1.023 acre‐ft
OPTIONAL Override Runoff Volume = acre‐ft
Inflow Hydrograph Volume = 0.136 0.252 0.360 0.756 1.022 acre‐ft
Time to Drain 97% of Inflow Volume = 1.1 1.8 2.4 4.6 6.1 hours
Time to Drain 99% of Inflow Volume = 1.2 1.8 2.5 4.7 6.3 hours
Maximum Ponding Depth = 1.14 2.21 3.03 5.11 6.09 ft
Maximum Ponded Area = 0.042 0.086 0.119 0.214 0.277 acres
Maximum Volume Stored = 0.024 0.093 0.176 0.518 0.760 acre‐ft
Location for 1‐hr Rainfall Depths (use dropdown):
Workbook Protected Worksheet Protected
Stormwater Detention and Infiltration Design Data Sheet
Existing Detention Pond
2103 Nancy Gray Ave, Fort Collins, CO
Drain Times New, Design Data 7/13/2016, 9:55 AM
Doing_Clear_FoYes
CountA= 1
0123
#N/A
#N/A
0123
#N/A
#N/A
Check Data Set 1 Check Data Set 1
Area
Discharge
Stormwater Detention and Infiltration Design Data Sheet
0
5
10
15
20
25
0.1 1 10
FLOW [cfs]
TIME [hr]
100YR IN
100YR OUT
50YR IN
50YR OUT
10YR IN
10YR OUT
5YR IN
5YR OUT
2YR IN
2YR OUT
WQCV IN
WQCV OUT
0
1
2
3
4
5
6
7
0.1 1 10 100
PONDING DEPTH [ft]
DRAIN TIME [hr]
100YR
50YR
10YR
5YR
2YR
WQCV
Drain Times New, Design Data 7/13/2016, 9:55 AM
LID Table
50% On-Site Treatment by LID Requried
New Impervious Area 60,534 sq. ft.
Required Minimum Impervious Area to be Treated 30,267 sq. ft.
Area Treated by Rain Garden (Phase I) 17,942 sq. ft.
Area Treated by Rain Garden (Phase II) 14,508 sq. ft.
Run-on Area 0 sq. ft.
Impervious Area by LID Treatment 32,450 sq. ft.
Actual % On-Site Treated by LID 54%
25% Porus Pavement Requried
New Pavement Area 25,378 sq. ft.
Required Minimum Area of Porus Pavement 6,345 sq. ft.
Porus Pavement Area 2,825 sq. ft.
Run-on Area (up to 3:1 allowed) 4,558 sq. ft.
Total Porus Pavement Area 7,383 sq. ft.
Actual % of Porus Pavement Provided 29%
14 | Page
Appendix F
Maps
PROPOSED
SCHOOL
±17,942
FFE = 4949
JOSEPH ALLEN DR.
S. TIMBERLINE RD.
NANCY GRAY AVE.
DRAINAGE
PLAN
C-2.1
7 Of
PROJECT TITLE
REVISIONS
SHEET TITLE
SHEET INFORMATION
DATE
SEAL
DATE
PREPARED FOR
ENGINEERING R IDGE & CONSULTING T OP
DRAWN BY:
CHECKED BY:
PROJECT NO.:
ROCHE
CONSTRUCTORS
BEBEE
CHRISTIAN
SCOOL
361 71ST AVE.
GREELEY, CO
2103 NANCY GRAY AVE.
FORT COLLINS, CO
16-026-001
MRB
BSA
10
SUBMITTAL
PROJECT
DEVELOPMENT PLAN
7/14/2016
WATER QUALITY TREATMENT LEGEND
Minimum 8" Thick Layer of
CDOT No. 4 Aggregate
Minimum 4" Perforated
PVC Pipe (Optional
Depending on Underlying
Soil Conditions)
12" Ponding Depth
Minimum 12" Thick Layer
of Bioretention Sand Media
(see Bioretention Sand
Media Specification below)
Minimum 6" Thick Layer of
Pea Gravel Diaphragm
Parking/Building
Water Surface
Minimum CDOT
No. 4 Aggregate
Above and Below
PVC Pipe
15 | Page
Appendix G
References
Undisturbed Soil
CONNECT UNDERDRAIN
TO OUTLET PIPE
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
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/7/2016
Page 2 of 4