HomeMy WebLinkAboutBELLA VIRA FILING 2 - MJA/FDP - FDP140001 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORT1501 Academy Ct. Ste. 203 Fort Collins, Colorado 80524 (970) 530-4044
Preliminary Drainage Addendum
Bella Vira –––– Filing 2
FortCollins Fort Collins, , CO
Prepared for:
Bella Vira Town Homes Inc.
1313 Fairway Five Drive
Fort Collins, CO 80525
December 31, 2013
Drainage Addendum
Bella Vira – Filing 2
Fort Collins, CO
1 U13012-DrainageAddendum-Preliminary.doc
December 31, 2013
City of Fort Collins
Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80521
RE: Bella Vira – Filing 2
Fort Collins, Colorado
Project Number: U13012
Dear Staff:
United Civil Design Group, LLC. is pleased to submit this Preliminary Drainage Addendum for
the Bella Vira – Filing 2 site in Fort Collins, Colorado. In general, this summary serves to
document the stormwater impacts associated with the proposed project and to verify that the
project does conform to the intent and requirements set forth in the approved final drainage
report prepared by Jim Sell Design (JSD) entitled “Final Drainage and Erosion Control Report for
Bella Vira”, and dated December 21, 2007.
Site Location and Project Description
The development site (referred herein as ”the site”) is located in Fort Collins and is described
as Tract A within the south half of Section 17, Township 7 North, Range 69 West of the Sixth
P.M., City of Fort Collins, Larimer County, Colorado. The site has a platted area of 3.47 acres
and is bounded by Overland Trail to the east, West Elizabeth Street (currently under
construction) to the north, and The Ponds at Overland Trail Second Filing to the west and
south. See the attached Drainage Plan for additional information.
The planned development for the site will consist of the following:
• The construction of six (6) single family attached buildings with twenty-five (25)
units.
• The construction of a private drive and parking stalls in support of the building
construction.
• The construction of utilities to support the proposed buildings including sanitary,
water and storm drainage.
Existing Conditions
Hydrology
The site, which is located within the Canal Importation Basin, currently exists mainly as
agricultural farm land and is currently covered with grasses and weeds. Storm runoff
Drainage Addendum
Bella Vira – Filing 2
Fort Collins, CO
2 U13012-DrainageAddendum-Preliminary.doc
from the site currently drains towards the south and west to an existing City regional
detention pond located within Tract C of the Bella Vira Subdivision just west of the site.
Floodplain
A small portion of the southern site is located within a City-regulatory moderate risk
floodway adjacent to the Pleasant Valley and Lake Canal. No improvements are being
proposed within this area.
Detention
The City regional detention pond located within Tract C of Bella Vira Subdivision just
west of the site provides both detention and water quality for the site.
Developed Conditions
In part, the intent of this Drainage Addendum is to verify that the Filing 2 project conforms to
the intent and requirements set forth in the JSD Final Drainage Report for this site. As such,
the following sections of this Addendum compare the proposed design for Filing 2 to the
design as shown in aforementioned report.
Hydrology
Basin A as shown in the attached Drainage Plan collects the vast majority of the
developed flows from the site and routes them via swales and storm sewer to the City
regional pond west of the site. Basin A largely corresponds to Basins 20-21b, 25-27, and
29 as were shown in the approved JSD report. A summary of the results of the analysis
of Basin A as compared to the JSD basins is as follows:
Comparison Summary Table
Basin A JSD Basins
Overall Area (acres) 3.16 3.54
Impervious Area (acres) 1.75 2.08
Q2 (cfs) 5.67 6.07
Q100 (cfs) 24.21 26.87
As shown in the above table, the proposed improvements for Filing 2 of Bella Vira result
in lower overall and impervious areas and resulting flowrates from those shown in the
approved JSD report. Therefore, the proposed Filing 2 improvements appear to meet
the intent and requirements set forth in the original JSD report and it is anticipated that
the Filing 2 improvements will not have a negative impact to the downstream
improvements as designed by JSD.
Drainage Addendum
Bella Vira – Filing 2
Fort Collins, CO
3 U13012-DrainageAddendum-Preliminary.doc
Storm Sewer
Storm Sewer Line 1 is located in the center of the proposed development and collects
water from Basins A1 and A4-A6. In order to eliminate as much surface water as
possible through Basin A5, several downspouts within Basin A6 are being collected and
piped directly into the storm drain. Due to the collection of some roof areas, the minor
flows that are to be collected, and the desire to eliminate as much surface flow through
Basin A1 due to erosion concerns, Storm Line 1 has been designed to convey the 100-
year flows away from the site and into the downstream pond.
Detention and Water Quality Requirements
As previously mentioned, the site is provided with detention and water quality from the
City regional pond just west of the site. With the Filing 2 improvements not exceeding
those assumed during the design of the regional facility, no further detention or water
quality improvements are required with Filing 2.
Low Impact Development (LID) Requirements
In February of 2013, City Council adopted the LID policy and criteria. Filing 2 of Bella
Vira is required to meet the newly adopted criteria. Per the criteria, the site must:
• 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.
In communication with City personnel, this site, as it was originally approved prior to
the LID requirements, will not be required to provide the permeable pavement if the
development proposes to treat more than 50% of the newly added impervious area.
For this development, Basin A contains all the impervious area associated with the
project which totals 1.75 acres. In order to accommodate the above mentioned
requirement, the development is proposing to treat the newly added impervious area
as follows:
• The upstream basins of A4-A6 (totaling 1.31 acres of impervious area) will be
treated with a series of grass lined swales prior to entering the storm drain
system. Once in the storm drain system, the entirety of the impervious area
within said basins will be treated within Inlet 1-2 using a Snout BMP along
with an associated bioskirt. Refer to the Drainage Plan and Construction
Documents for additional information.
• Basin A2 (with 0.22 acres of impervious area) will be treated with a grass line
swale prior to entering a bioswale with underdrain proposed at the
downstream end of the basin. This bioswale (which has total length of 135-
feet) will treat the entirety of the impervious area within the basin prior to
directing the runoff to the downstream pond.
Drainage Addendum
Bella Vira – Filing 2
Fort Collins, CO
4 U13012-DrainageAddendum-Preliminary.doc
In total, the development is proposing to collect and treat 1.53 acres of the newly
added impervious area using a series of LID techniques. The percentage of the
impervious area within the site being treated with LID techniques totals 87%. Due to
the percentage of the site that is proposed to be treated, and based upon
communication with City personnel, the development team is proposing to not provide
any pervious pavement with Filing 2 of this project.
Four Step Process
With the adoption of the USDCM, the City has also adopted the “Four Step Process”
that is recommended in Volume 3 of the USDCM in selecting structural BMPs for the
redeveloping urban areas. The following portions of this addendum describe each step
and how it has been utilized for this project:
Step 1 – Employ Runoff Reduction Practices
The objective of this step is to reduce runoff peaks and volumes and to employ the
technique of “minimizing directly connected impervious areas” (MDCIA). This project
accomplishes this by:
• Providing grass buffers throughout the site between impervious areas to
minimize directly connected impervious areas.
• Routing flows through a series of vegetated swales to increase time of
concentration, promote infiltration and provide initial water quality.
• Routing a portion of the site through a bioswale to promote infiltration and
provide additional water quality.
Step 2 – Provide Water Quality Capture Volume (WQCV)
The objective of providing WQCV is to reduce the sediment load and other pollutants
that exit the site. For this project WQCV is provided within the regional pond located
west of the site, so no additional WQCV is required.
Step 3 – Stabilize Drainageways
The site is adjacent to the Pleasant Valley and Lake Canal. The project is not directly
stabilizing this manmade drainageway; however, the project is indirectly maintaining
the existing stability of the drainageway by directing the vast majority of onsite flows
away from the canal and to the existing regional pond west of the site. Additionally,
this project will pay stormwater development and stormwater utility fees which the City
uses, in part, to maintain the stability of the City drainageway systems.
Step 4 – Consider Need for Industrial and Commercial BMPs
This step is generally considered for industrial and commercial sites. As this
development is proposing single family attached dwellings only, no specialized BMPs
have been considered for this project.
Drainage Addendum
Bella Vira – Filing 2
Fort Collins, CO
5 U13012-DrainageAddendum-Preliminary.doc
Standard Operating Procedures (SOPs)
In order for physical stormwater Best Management Practices (BMPs) to be
effective, proper maintenance is essential. Maintenance includes both routinely
scheduled activities, as well as non-routine repairs that may be required after
large storms, or as a result of other unforeseen problems. Standard Operating
Procedures should clearly identify BMP maintenance responsibility. BMP
maintenance is typically the responsibility of the entity owning the BMP.
Identifying who is responsible for maintenance of BMPs and ensuring that an
adequate budget is allocated for maintenance is critical to the long-term success
of BMPs. Maintenance responsibility may be assigned either publicly or
privately. For this project, the privately owned BMPs shown in Appendix C of
this Addendum are to be maintained by the property owner, homeowner’s
association (HOA), or property manager.
Conclusions
In conclusion, the drainage system proposed within this Drainage Addendum provides
adequate conveyance of the developed stormwater runoff from the proposed development to
existing discharge locations and drainage systems. In addition, the calculations provided show
that the proposed drainage system does meet the intent and requirements set forth in the
original JSD Final Drainage Report. It should also be noted that with this addendum and the
corresponding design, every attempt has been made to minimize any negative impacts on the
downstream receiving waters. With the incorporation of the LID techniques throughout the
development, the site will discharge a lower sediment load and less runoff than the design
originally proposed with the Bella Vira Subdivision project.
We understand that review by the City of Fort Collins is to assure general compliance with
standardized criteria contained in the Fort Collins Stormwater Criteria Manual (FCSCM). This
addendum was prepared in compliance with technical criteria set forth in both the Urban
Drainage and Flood Control District (UDFCD) Urban Storm Drainage Criteria Manual and the
FCSCM.
If you should have any questions or comments as you review this drainage summary, please
feel free to contact us at your convenience.
Sincerely,
United Civil Design Group, LLC
Kevin Brazelton, PE
Engineering Manager
APPENDIX A
Hydrology Calculations
Bella Vira Filing 2
Fort Collins, CO Runoff Summary
Area Q2
Q100
(acre) (cfs) (cfs)
A1 A1 0.28 27% 0.45 0.57 0.35 1.55
A2 A2 0.60 35% 0.51 0.64 0.87 3.82
A3 A3 0.46 29% 0.46 0.58 0.60 2.62
A4 A4 0.78 80% 0.86 1.00 1.90 7.73
A5 A5 0.64 69% 0.77 0.96 1.39 6.07
A6 A6 0.32 47% 0.60 0.76 0.56 2.42
OS1 OS1 0.27 2% 0.25 0.31 0.16 0.68
OS2 OS2 0.10 2% 0.25 0.31 0.06 0.27
Onsite Total 3.44 47% 0.61 0.76 5.67 24.21
19 19 0.35 78% 0.82 1.00 0.82 3.52
23 23 0.06 82% 0.84 1.00 0.15 0.63
Proposed Basins -Filing 2
Modified Phase 1 Basins
C100
C2
Basin Design Point %I
Calculations by: KRB
Date: 12/19/2013 D:\Dropbox\Projects\U13012 Bella Vira\Drainage\Hydrology\U13012-Runoff_Final.xlsx
Bella Vira Filing 2
Fort Collins, CO Runoff Coefficients and % Impervious
Roof (1) Concrete(1) Asphalt(1) Landscape(1)
%I = 90% %I = 90% %I =100% %I=2%
C = 0.95 C = 0.95 C = 0.95 C = 0.25
acres sf sf sf sf sf C2 C100
Proposed Basins -Filing 2
A1 A1 0.275 11993 3354 107 0 8532 27% 0.45 0.57
A2 A2 0.599 26113 9764 4 0 16345 35% 0.51 0.64
A3 A3 0.455 19839 6023 0 0 13816 29% 0.46 0.58
A4 A4 0.777 33850 12253 11276 5807 4514 80% 0.86 1.00
A5 A5 0.637 27743 8057 6773 5630 7283 69% 0.77 0.96
A6 A6 0.322 14038 7028 86 0 6924 47% 0.60 0.76
OS1 OS1 0.270 11750 0 0 0 11750 2% 0.25 0.31
OS2 OS2 0.104 4523 0 0 0 4523 2% 0.25 0.31
Onsite Total 3.440 149849 46479 18246 11437 73687 47% 0.61 0.76
Modified Phase 1 Basins
19 19 0.354 15403 0 4961 7501 2941 78% 0.82 1.00
23 23 0.064 2776 0 557 1766 453 82% 0.84 1.00
Notes:
(1) Recommended % Imperviousness Values from USDCM Vol 1 - Ch 5 - Table RO-3. Increased Lawns from 0% to 2% Impervious.
(2) Runoff C2
is based on UDFCD Eq RO-8 per City Amendment to Chapter 5. Runoff C100 is based upon Table RO-12 per City Amendment to Chapter 5.
Composite Runoff
Basin Coefficients (2)
Areas
Composite
Imperviousness
(%I)
Total Total
Design
Pt.
Calculations by: KRB
Date: 12/19/2013 D:\Dropbox\Projects\U13012 Bella Vira\Drainage\Hydrology\U13012-Runoff_Final.xlsx
Bella Vira Filing 2
Fort Collins, CO Time of Concentration
Area Length Slope ti
(2)
Length Slope
Velocity
(3) t
t
(4) Check
tc?
Total
Length
tc
(5)
acres ft % min ft % fps min min
u =
urban
ft min min
Proposed Basins -Filing 2
A1 A1 0.28 Roof 0.73 15 2 2.1 90 12 20 6.9 0.2 2.3 u 105 11 5
A2 A2 0.60 Roof 0.73 20 2 2.4 560 3.5 20 3.7 2.5 4.9 u 580 13 5
A3 A3 0.46 Roof 0.73 20 2 2.4 85 11.5 20 6.8 0.2 2.6 u 105 11 5
A4 A4 0.78 Walk 0.73 35 5.6 2.2 335 2.9 20 3.4 1.6 3.9 u 370 12 5
A5 A5 0.64 Roof 0.73 25 2 2.6 305 3.5 20 3.7 1.4 4.0 u 330 12 5
A6 A6 0.32 Roof 0.73 25 2 2.6 110 1.5 20 2.4 0.7 3.4 u 135 11 5
OS1 OS1 0.27 Lawn 0.09 55 4 8.5 10 2 20 2.8 0.1 8.6 u 65 10 9
OS2 OS2 0.10 Lawn 0.09 80 11 7.4 30 2.5 20 3.2 0.2 7.5 u 110 11 8
Modified Phase 1 Basins
19 19 0.35 Street 0.90 10 2 0.9 130 1.7 20 2.6 0.8 1.7 u 140 11 5
23 23 0.06 Street 0.90 35 2 1.7 60 3.5 20 3.7 0.3 2.0 u 95 11 5
Notes:
(1)
C5
based initial ground type and Table RO-5
(4)
tt
=L/(V*60 sec/min)
(2)
ti
= [1.8(1.1-C5
)L
1/2
]/S
1/3
, S= slope in %, L=length of overland flow (400' max)
(5)
tc
check (for urban or developed areas only) = total length/180 + 10
(3)
V=Cv
S
0.5
, S=watercourse slope in ft/ft, UDFCD Equation RO-4
(6)
min tc
= 5 min
Initial
Ground
Type
C5
Bella Vira Filing 2
Fort Collins, CO Rational Method Peak Runoff
Final
tc
(6) I2 I100 Q2 Q100
sf min in/hr in/hr cfs cfs
Proposed Basins -Filing 2
A1 A1 11,993 5 0.45 0.57 2.85 9.95 0.355 1.548
A2 A2 26,113 5 0.51 0.64 2.85 9.95 0.875 3.816
A3 A3 19,839 5 0.46 0.58 2.85 9.95 0.600 2.620
A4 A4 33,850 5 0.86 1.00 2.85 9.95 1.897 7.732
A5 A5 27,743 5 0.77 0.96 2.85 9.95 1.391 6.070
A6 A6 14,038 5 0.60 0.76 2.85 9.95 0.555 2.424
OS1 OS1 11,750 9 0.25 0.31 2.30 8.03 0.155 0.677
OS2 OS2 4,523 8 0.25 0.31 2.40 8.38 0.062 0.272
Onsite Total 149,849 5.673 24.210
Modified Phase 1 Basins
19 19 15,403 5 0.82 1.00 2.85 9.95 0.823 3.518
23 23 2,776 5 0.84 1.00 2.85 9.95 0.152 0.634
0.975 4.153
Design
Pt.
Peak Discharge
Area
Basin Runoff Coefficients Rainfall Intensity
C2 C100
Calculations by: KRB
Date: 12/19/2013 D:\Dropbox\Projects\U13012 Bella Vira\Drainage\Hydrology\U13012-Runoff_Final.xlsx
APPENDIX B
Hydraulic Calculations
Project =
Inlet ID =
Design Information (Input)
Length of a Unit Inlet Lu
= 10.00 ft
Local Depression, if any (not part of upstream Composite Gutter) alocal
= 3.00 inches
Height of Curb Opening in Inches H = 6.00 inches
Side Width for Depression Pan Wp
= 3.00 ft
Clogging Factor for a Single Unit (typical value = 0.1) Co
= 0.20
Angle of Throat (see USDCM Figure ST-5) Theta = 63.4 degrees
Orifice Coefficient (see USDCM Table ST-7) Cd
= 0.67
Weir Coefficient (see USDCM Table ST-7) Cw
= 3.00
Total Number of Units in the Curb Opening Inlet No = 1
Curb Opening Inlet Capacity in a Sump
As a Weir
Design Discharge on the Street (from Street Hy ) Qo
= 7.4 cfs
Water Depth for the Design Condition Yd
= 8.37 inches
Total Length of Curb Opening Inlet L = 10.00 ft
Capacity as a Weir without Clogging Qwi
= 26.9 cfs
Clogging Coefficient for Multiple Units Coef = 1.00
Clogging Factor for Multiple Units Clog = 0.20
Capacity as a Weir with Clogging Qwa
= 23.4 cfs
As an Orifice
Capacity as an Orifice without Clogging Qoi
= 18.5 cfs
Capacity as an Orifice with Clogging Qoa
= 14.8 cfs
Capacity for Design with Clogging Qa
= 14.8 cfs
Capture Percentage for this Inlet = Qa
/ Qo
= C% = 100.00 %
Note: Unless additional ponding depth or spilling over the curb is acceptable, a capture
percentage of less than 100% in a sump may indicate the need for additional inlet units.
CURB OPENING INLET IN A SUMP
Bella Vira - Filing 2
Inlet 1-2
Storm Inlet 1-1.xls, Curb-S 12/19/2013, 2:02 PM
Bella Vira - Filing 2
Fort Collins, CO Area Inlet Capacity
INLET ID: Inlet 1-7 (Basin A6)
Governing Equations:
Inlet capacity equation at low flows (weir calculation):
Where:
P = 2(L + W)
H = depth of water above the flowline
Inlet capacity equation at higher flows (orifice calculation):
Where:
A = open area of the inlet grate
H = depth of water above the centroid of the cross-sectional area (A)
Input Parameters:
Grate: 15" Nyloplast (1599CGD)
Wier Perimeter: 3.93
Open Area of Grate (ft
2
): 0.80 Q2 = 0.56 cfs
Flowline Elevation (ft): 5127.62 Q100 = 2.42 cfs
Allowable Capacity: 50%
Depth vs. Flow:
Depth Above Inlet
(ft)
Elevation
(ft)
Shallow
Weir Flow
(cfs)
Orifice
Flow
(cfs)
Actual
Flow
(cfs)
0.00 5127.62 0.00 0.00 0.00
0.10 5127.72 0.19 0.68 0.19
0.21 5127.83 0.56 0.98 0.56 Q2
0.10 5127.72 0.19 0.68 0.19
0.30 5127.92 0.97 1.18 0.97
0.40 5128.02 1.49 1.36 1.36
0.50 5128.12 2.08 1.52 1.52
0.60 5128.22 2.74 1.67 1.67
0.70 5128.32 3.45 1.80 1.80
0.80 5128.42 4.22 1.93 1.93
0.90 5128.52 5.03 2.04 2.04
Q = 3 . 0 P H 1 . 5
Q = 0 . 67 A ( 2 gH ) 0 . 5
Calculations by: KRB
Date: 12/19/2013 D:\Dropbox\Projects\U13012 Bella Vira\Drainage\Inlets\U13012-Area Inlets.xlsx
Bella Vira-Filing 2
Fort Collins, CO
Riprap Sizing at Pipe Outlets
Circular
D or Da,
Pipe
Diameter
(ft)
H or Ha,
Culvert
Height
(ft)
W,
Culvert
Width
(ft)
Yt/D Q/D1.5 Q/D2.5 Yt/H Q/WH0.5
Storm Line 1 Outlet 16.23 1.50 0.60 0.40 8.83 5.89 N/A N/A 1.80 5.89 3.25 7.04 Type L 10.00 7.50 1.5
Circular
Pipe
(Figure MD-21)
Rectangular
Pipe
(Figure MD-22) Spec
Min. Width
of
Riprap
(ft)
2*d50,
Depth
of
Riprap
(ft)
for L/2
Froude
Parameter
Q/D2.5
Max 6.0
or
Q/WH1.5
Max 8.0
Riprap
Type
(From
Figure
MD-21 or
MD-22)
Urban Drainage
pg MD-107
Culvert Parameters
Box Culvert
Pipe Designation
Design
Discharge
(cfs)
L=
1/(2tanq)*
[At/Yt)-W]
(ft)
INPUT CALCULATE
Channel Report
Hydraflow Express Extension for AutoCAD® Civil 3D® 2013 by Autodesk, Inc. Thursday, Dec 19 2013
Swale - Upstream Basin A5 (Between Buildings 5&6)
User-defined
Invert Elev (ft) = 5126.64
Slope (%) = 1.75
N-Value = 0.025
Calculations
Compute by: Known Q
Known Q (cfs) = 1.80
(Sta, El, n)-(Sta, El, n)...
( 0.00, 5128.50)-(0.10, 5128.00, 0.013)-(7.50, 5127.96, 0.013)-(13.00, 5126.64, 0.025)-(24.00, 5128.00, 0.025)-(24.10, 5132.75, 0.013)
Highlighted
Depth (ft) = 0.35
Q (cfs) = 1.800
Area (sqft) = 0.75
Velocity (ft/s) = 2.40
Wetted Perim (ft) = 4.35
Crit Depth, Yc (ft) = 0.36
Top Width (ft) = 4.29
EGL (ft) = 0.44
-5 0 5 10 15 20 25 30
Elev (ft) Depth (ft)
Section
5125.00 -1.64
5126.00 -0.64
5127.00 0.36
5128.00 1.36
5129.00 2.36
5130.00 3.36
5131.00 4.36
5132.00 5.36
5133.00 6.36
Sta (ft)
APPENDIX C
Standard Operating Procedures
STANDARD OPERATING PROCEDURES (SOPs)
A. Purpose
In order for physical stormwater Best Management Practices (BMPs) to be effective,
proper maintenance is essential. Maintenance includes both routinely scheduled
activities, as well as non-routine repairs that may be required after large storms, or as a
result of other unforeseen problems. Standard Operating Procedures should clearly
identify BMP maintenance responsibility. BMP maintenance is typically the responsibility
of the entity owning the BMP.
Identifying who is responsible for maintenance of BMPs and ensuring that an adequate
budget is allocated for maintenance is critical to the long-term success of BMPs.
Maintenance responsibility may be assigned either publicly or privately. For this project,
the privately owned BMPs shown in Section B below are to be maintained by the property
owner, homeowner’s association (HOA), or property manager.
B. Site-Specific SOPs
The following stormwater facilities contained within Bella Vira – Filing 2 are subject to SOP
requirements:
- Vegetated Swales
- Bioswale
- Snout BMP
The location of said facilities can be found on the Utility Plans for Bella Vira – Filing 2.
Inspection and maintenance procedure and frequencies, specific maintenance
requirements and activities, as well as BMP-specific constraints and considerations shall
follow the guidelines outlined in Volume 3 of the Urban Drainage and Flood Control
District (UDFCD) Urban Storm Drainage Criteria Manual for the Vegetated Swales and
Bioswale. Inspection and maintenance procedure and frequencies, specific maintenance
requirements and activities for the Snout BMP shall adhere to guidelines provided by the
manufacturer.
SOP Maintenance Summary Table
Stormwater Facility /
BMP
Ownership /
Responsibility
Maintenance Reference
Vegetative Swales Private
Follow applicable guidelines for
Vegetative Swales within UDFCD.
Bioswale Private
Follow applicable guidelines for
Bioretention and Vegetative Swales within UDFCD.
Snout BMP Private
Follow applicable guidelines for
Snout BMP provided by the manufacturer.
The complete UDFCD BMP maintenance references listed above can be found in Chapter
6 of Volume 3. The complete Snout BMP maintenance references “Maintenance
Considerations for SNOUT Stormwater Quality Systems”, and can be found on
www.bmpinc.com. Applicable excerpts for "Routine" maintenance requirements for each
BMP can be found below. Additionally, it is strongly recommended that the Guidelines
for Use of Pesticides, Herbicides and Fertilizers (UDFCD Fact Sheet S-8), and the
Landscape Maintenance procedures (UDFCD Fact Sheet S-9) be followed, not just within
the drainage facilities themselves, but for the entire development.
Vegetative Swales Routine Maintenance Table (Summary from Chapter 6 of UDFCD)
Required
Action
Maintenance Objective Frequency of Action
Lawn mowing
and Lawn care
Maintain irrigated grass at 2 to 4 inches tall
and nonirrigated native grass at 6 to 8 inches
tall. Collect cuttings and dispose of them
offsite or use a mulching mower.
Routine – As needed.
Debris and Litter
removal
Keep the area clean for aesthetic reasons,
which also reduces floatables being flushed
downstream.
Routine – As needed by
inspection, but no less than two
times per year.
Sediment
removal
Remove accumulated sediment near culverts
and in channels to maintain flow capacity.
Replace the grass areas damaged in the
process.
Routine – As needed by
inspection. Estimate the need to
remove sediment from 3 to 10
percent of total length per year,
as determined by annual
inspection.
Inspections
Check the grass for uniformity of cover,
sediment accumulation in the swale, and near
culverts.
Routine – Annual inspection is
suggested.
Bioswale Routine Maintenance Table (Summary from Chapter 6 of UDFCD)
Required Action Maintenance Objective Frequency of Action
Lawn mowing and
vegetative care
Occasional mowing of grasses and weed
removal to limit unwanted vegetation.
Maintain irrigated turf grass as 2 to 4 inches
tall and nonirrigated native turf grasses at 4
to 6 inches.
Routine – Depending on aesthetic
requirements.
Debris and Litter
removal
Remove debris and litter from bioswale area
to minimize clogging of the sand media.
Routine – Including just before annual
storm seasons (that is, April and May),
end of storm season after leaves have
fallen, and following significant rainfall
events.
Landscaping
removal and
replacement
The bioretention sand media and landscaping
layer will clog with time. This layer will need
to be removed and replaced, along with all
turf and other vegetation growing on the
surface, to rehabilitate infiltration rates.
Every 5 to 10 years, depending on
infiltration rates needed to drain the
WQCV in 12-hours or less. May need to
do it more frequently if exfiltration rates
are too low to achieve this goal.
Inspections
Inspect bioswale area to determine if the
sand media is allowing acceptable infiltration.
Routine – Bi-annual inspection of
hydraulic performance.
Snout BMP Routine Maintenance Table (Summary from Manufacturer Recommendations)
Required Action Maintenance Objective Frequency of Action
Monitoring
Monitor new installation after site has been
stabilized. Measure sediment depth and note
surface pollutants in the structure.
Routine – Monthly for first year. Determine
yearly schedule from monitoring performed.
Sediment removal
Remove sediment from sump. Maintenance is
best completed with a vacuum truck.
Routine – Optimally completed when sump is
half full of sediment. Routine schedule should
be determined during first year monitoring.
Structures should also be cleaned if a spill or
other incident causes a larger than normal
accumulation of pollutants.
Floatable and trash
removal
Remove floatables and trash from sump.
Routine - Optimally completed when 6" of
floating material accumulates on surface above
APPENDIX D
Drainage Plan
A1
FF=29.90
FF=29.90
FF=29.20
FF=28.50
FF=32.75
FF=33.80
FF=35.30
FF=36.50
FF=36.60
FF=35.90
FF=34.20
FF=33.30
FF=31.80
FF=30.90
FF=28.20 FF=29.70 FF=30.40 FF=31.10
FF=27.50
FF=27.90
FF=27.90
FF=29.30
FF=29.30
FF=30.40
FF=30.40
PROPOSED BIOSWALE
WITH UNDERDRAIN
Basin Design
Point
Area
%I C2 C100
Q2 Q100
(acre) (cfs) (cfs)
Proposed Basins -Filing 2
A1 A1 0.28 27% 0.45 0.57 0.35 1.55
A2 A2 0.60 35% 0.51 0.64 0.87 3.82
A3 A3 0.46 29% 0.46 0.58 0.60 2.62
A4 A4 0.78 80% 0.86 1.00 1.90 7.73
A5 A5 0.64 69% 0.77 0.96 1.39 6.07
A6 A6 0.32 47% 0.60 0.76 0.56 2.42
OS1 OS1 0.27 2% 0.25 0.31 0.16 0.68
OS2 OS2 0.10 2% 0.25 0.31 0.06 0.27
Onsite
Total 3.44 47% 0.61 0.76 5.67 24.21
Modified Phase 1 Basins
19 19 0.35 78% 0.82 1.00 0.82 3.52
23 23 0.06 82% 0.84 1.00 0.15 0.63
PREPARED FOR: DATE SUBMITTED:
The engineer preparing these plans will not be responsible for, or
liable for, unauthorized changes to or uses of these plans. All
changes to the plans must be in writing and must be approved by
the preparer of these plans.
CAUTION
BELLA VIRA TOWNHOMES INC. 12/31/2013
BELLA VIRA - FILING 2
21
U13012
PRELIMINARY
PLANS
NOT FOR CONSTRUCTION
Civil Engineering & Consulting
1501 Academy Court, Suite 203
Fort Collins, CO 80524
(970) 530-4044
www.unitedcivil.com
NONE KEVIN
D:\DROPBOX\PROJECTS\U13012 BELLA VIRA\CADD\CP
C6.00_DRAINAGE PLAN.DWG
12/23/2013 4:02:12 PM
KRB
DRAINAGE PLAN
C6.00
N/A
CHECKED BY: 30'
CHECKED BY:
CHECKED BY:
CHECKED BY:
CHECKED BY:
APPROVED:
1. EXISTING UNDERGROUND AND
OVERHEAD PUBLIC AND PRIVATE
UTILITIES AS SHOWN ARE INDICATED
ACCORDING TO THE BEST INFORMATION
AVAILABLE TO THE ENGINEER.
2. EXISTING INFORMATION AS SHOWN ON
THIS PLAN IS PER DESIGN INFORMATION
PROVIDED BY JIM SELL DESIGN AS
SHOWN IN THE PHASE 1 CONSTRUCTION
PLANS ENTITLED "BELLA VIRA
SUBDIVISION" AND DATED DECEMBER 7,
2007. AT THE TIME OF THIS SUBMITTAL,
CONSTRUCTION OF THE PHASE 1 BELLA
VIRA IMPROVEMENTS IS NOT YET
COMPLETE. CONTRACTOR SHALL FIELD
VERIFY ACTUAL CONDITIONS AT ALL
INTERFACES WITH PHASE 1
IMPROVEMENTS PRIOR TO THE
COMMENCEMENT OF FILING 2
CONSTRUCTION.
LEGEND
NOTES
D-101
BASIN DESIGNATION
BASIN AREA (ACRE)
2 - YR RUNOFF COEFF.
100 - YR RUNOFF COEFF.
BASIN BOUNDARY
DESIGN POINT
FLOW DIRECTION
0 30' 60'
SCALE: 1" = 30'
15'
static water level. Routine schedule should be
determined during first year monitoring.
Structures should also be cleaned if a spill or
other incident causes a larger than normal
accumulation of pollutants.
Bio-Skirt service or
replacement
Maintain/replace Bio-Skirt. "Maintenance"
includes wringing out of the unit to remove
accumulated oils and then washed in an
industrial washing machine with warm water.
The Bio-Skirt may then be re-deployed as long
as the material maintains it's structural
integrity.
Routine – Optimally completed when more than
2/3 of the boom is submerged, indicating a
nearly saturated state. At a minimum, annual
service or replacement is required.
Yt,
Tailwater
Depth
(ft)
At=Q/V
(ft)
Expansion
Factor
1/(2tanq)
(From
Figure
MD-23 or
MD-24)
OUTPUT
Spec
Min. Length
of
Riprap
(ft)
Calculations by: KRB
Date: 12/19/2013 D:\Dropbox\Projects\U13012 Bella Vira\Drainage\Riprap\Riprap Calcs Spreadsheet.xls
(1)
Cv
ti+tt
Final
tc
(6)
tc Check for Urbanized
Basin
Initial Overland Flow Time (ti) Travel/Channelized Time of Flow (tt)
Design
Pt.
Calculations by: KRB
Date: 12/19/2013 D:\Dropbox\Projects\U13012 Bella Vira\Drainage\Hydrology\U13012-Runoff_Final.xlsx