HomeMy WebLinkAboutAVAGO TECHNOLOGIES BLDG. 4 WEST EXPANSION - MJA/FDP - FDP130006 - SUBMITTAL DOCUMENTS - ROUND 2 - DRAINAGE REPORTAVAGO TECHNOLOGIES – BUILDING 4 WEST
ANNEX EXPANSION AND SITE
DEVELOPMENT
DRAINAGE REPORT
CITY OF FORT COLLINS, COLORADO
REV, MAY 21st, 2013
MARCH 25TH, 2013
MARTIN/MARTIN PROJECT NO. 13.0091
PREPARED FOR: AVAGO TECHNOLOGIES (APPLICANT)
4380 ZIEGLER ROAD
FORT COLLINS, CO 8025-9790
(970) 288-0344
PAUL TANGUAY
PREPARED BY: MARTIN/MARTIN, INC.
12499 WEST COLFAX AVENUE
LAKEWOOD, COLORADO 80215
PHONE: (303) 431-6100
PRINCIPAL IN CHARGE: MATTHEW B. SCHLAGETER, P.E.
PROJECT MANAGER: PETER S. BUCKLEY, P.E.
PROJECT ENGINEER: BRET M. SMITH, E.I.T. II
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TABLE OF CONTENTS
A. INTRODUCTION ..................................................................................... 2
A1. LOCATION ............................................................................................................. 2
A2. PURPOSE................................................................................................................ 3
A3. EXISTING CONDITIONS AND PROPOSED DEVELOPMENT ...................... 3
B. DRAINAGE BASINS................................................................................ 4
B1. MAJOR DRAINAGE BASIN DESCRIPTION ..................................................... 4
B2. SUB-BASIN DESCRIPTIONS............................................................................... 5
B3. SWMM MODEL COMPLIANCE.......................................................................... 5
C. DRAINAGE DESIGN CRITERIA........................................................... 8
C1. REFERENCES ....................................................................................................... 8
C2. HYDROLOGIC CRITERIA ................................................................................... 8
C3. HYDRAULIC CRITERIA....................................................................................... 8
C4. VARIANCES FROM CRITERIA .......................................................................... 9
D. DRAINAGE FACILITY DESIGN........................................................... 9
D1. GENERAL CONCEPT........................................................................................... 9
D2. SPECIFIC DETAILS ........................................................................................... 10
E. STORMWATER QUALITY.................................................................... 14
F. CONCLUSIONS...................................................................................... 18
F1. COMPLIANCE WITH STANDARDS................................................................. 18
F2. SUMMARY OF CONCEPT.................................................................................. 18
LIST OF REFERENCES............................................................................ 19
G. APPENDIX ............................................................................................. 20
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A. INTRODUCTION
A1. LOCATION
The Avago Technologies - Building 4 West Annex Expansion and Site Development
(hereafter referred to as “PROJECT”) site is located on the Hewlett-Packard Campus
(hereafter referred to as “CAMPUS”) in Lot 2 of the Preston-Kelley 2
nd
Subdivision,
found in the Southwest ¼ of Section 33, Township 7 North, Range 68 West of the 6
th
Principal Meridian, City of Fort Collins, County of Larimer, State of Colorado. The
PROJECT address is 4380 Ziegler Road. The overall site consists of 8.80 acres of
disturbed area. The overall area evaluated for the purposes of this drainage report consists
of 24.24 acres.
The overall CAMPUS is bound to the north by Hidden Pond Drive, to the east by the
Fossil Creek Drainage Ditch, to the south by East Harmony Road, and to the West by
Ziegler Road. The PROJECT site is bound to the north by an existing field and
Technology Parkway, to the east by the existing Hewlett Packard Building 4, to the south
by existing landscaped areas and an asphalt parking lot, and to the West by Technology
Parkway. Refer to the vicinity map below and in the Appendix.
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A2. PURPOSE
The following outlines the intent of this Compliance Drainage Report:
• Illustrate hydrologic compliance with the “Final Drainage and Erosion Control
Study for Hewlett-Packard Building 4” report produced by The Sear-Brown
Group dated March 22, 1999 (hereafter referred to as “BUILDING 4 REPORT”).
Per an email dated 2/14/2013 from Wes Lamarque of the City of Fort Collins
Stormwater Utility Department, compliance with the BUILDING 4 REPORT
forms the basis of drainage design for the PROJECT. Refer to the Appendix for a
copy of the email.
Hydrologic Compliance is illustrated in Section B3. SWMM COMPLIANCE of
this report
• Illustrate compliance with the Low Impact Design (“LID”) policies for Water
Quality found in City of Fort Collins Municipal Code, Section 3.4.3 Water
Quality.
Compliance with the City’s LID policies is illustrated in Section E.
STORMWATER QUALITY of this report.
• Quantitatively and qualitatively establish drainage design on the site.
A3. EXISTING CONDITIONS AND PROPOSED DEVELOPMENT
According to the “Geotechnical Engineering Report” produced by Terracon Consultants,
Inc., dated September 4, 2012, the existing soils consist of fill materials consisting of
sandy lean clay with various amounts of sand and gravel, and in-situ poorly graded sand
with gravel. Based on the results of borings, claystone bedrock is located at a maximum
depth of exploration of 39.7 feet. Groundwater was observed at a maximum elevation of
4982.6’, and a minimum depth of 18’ below existing grade. The soils on site are typically
SCS Type C Hydrologic Soils. A USDA web soil survey of the CAMPUS states that the
soils consist mostly of Nunn clay loam. A copy of the web soil survey is referenced in the
Appendix.
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The existing site topography generally slopes from west to east at approximately 0.7
percent. Native grasses or existing asphalt drives and parking cover a large majority of
the site.
The proposed development will include the construction of an expansion to the existing
Building 4, private asphalt and concrete drives, and utility infrastructure necessary to
service the proposed building. The footprint of the building expansion covers
approximately 80,000 SF. Additionally, drainage facilities designed to improve
Stormwater Quality are proposed for the site in accordance with Section 3.4.3 Water
Quality of the City of Fort Collins Municipal Code.
B. DRAINAGE BASINS
B1. MAJOR DRAINAGE BASIN DESCRIPTION
The CAMPUS lies entirely within the Fox Meadows Drainage Basin which is
approximately bounded by Horsetooth Road on the north, Harmony Road on the south,
the Cache de La Poudre River and I-25 on the east, and Lemay Avenue on the west. A
Master Plan for the Fox Meadows Drainage Basin was prepared by Resource
Consultants, Inc., in 1981. In this master report, the CAMPUS is located within Basin H.
This area was studied again by Nolte and Associates in 1990 when a master drainage plan
was prepared for the CAMPUS (this report hereafter referred to as “MASTER”). The
MASTER did not alter any of the assumptions or conclusions which were made in the
Fox Meadows Master Drainage Plan.
The majority of the proposed PROJECT site discharges north to a regional channel. This
regional channel located along County Road 9 and the north boundary of the CAMPUS
was recommended in the MASTER report and was designed and built with the Hewlett-
Packard Building 5 project. The channel was designed for the 100-year storm and
discharges to the North Pond on the CAMPUS. Stormwater detention and water quality
treatment for the CAMPUS is provided by four on-site ponds located in the SE corner of
the CAMPUS. These ponds are constructed as Extended Detention Basins (EDBs). The
North Pond is a dry bottom pond. The South Pond, Southwest Pond, and Dam Pond are
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wet ponds. Added water quality benefits are gained via the regional channel along the
north side of the campus which is constructed as a Grass Swale. This channel provides
initial water quality treatment to the north-flowing basins in the PROJECT area prior to
treatment in the CAMPUS ponds.
B2. SUB-BASIN DESCRIPTIONS
The northern portion of the PROJECT site is located within Basin 32 of the MASTER
report. Basin 32 discharges to a regional channel located along County Road 9 and the
north boundary of the CAMPUS. The regional channel was recommended in the
MASTER report and was designed and built with the Hewlett-Packard Building 5
project. The channel was designed for the 100-year storm and discharges to the north
regional detention pond on the CAMPUS. It was modified during Building 4 construction
to ensure that uncontrolled spilling into the Fossil Creek Ditch from the regional
detention ponds does not occur during the 100-year storm.
A portion of the southern end of the PROJECT site is located within Basin 34 of the
MASTER. This Basin discharges south and travels east via storm sewer to a regional
detention pond located in the southeast portion of the CAMPUS.
B3. SWMM MODEL COMPLIANCE
The PROJECT site is designed in order to maintain the same amount of pervious area
specified in the BUILDING 4 REPORT. An analysis comparing proposed development
with the development specified in the BUILDING 4 REPORT confirms that there is no
net increase in impervious area for the PROJECT site. Additionally, the City requested
that the calculated composite “C” factor remain in compliance with the BUILDING 4
REPORT. The allowable composite “C” factor within the proposed development is 0.44
per the BUILDING 4 REPORT. The proposed development will result in a net composite
“C” factor of 0.43 (indicating a slightly less percent imperviousness than the allowable
imperviousness from the BUILDING 4 REPORT).
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BLDG 4 REPORT APPROVED BASINS WITHIN PROPOSED
DEVELOPMENT
Basin
Imperviou
s "C"
Pervious
"C"
A, Imp
(ac)
A, Perv
(ac)
A, total
(ac)
% Imp % Perv
Composit
e "C"
4 0.95 0.25 0.19 1.44 1.67 11 86 0.32
5 0.95 0.25 0.12 0.65 0.77 16 84 0.36
6 0.95 0.25 0.00 6.75 6.75 0 100 0.25
14 0.95 0.25 0.25 0.18 0.43 58 42 0.66
17 0.95 0.25 0.56 1.40 1.96 29 71 0.45
18 0.95 0.25 0.05 0.85 0.90 6 94 0.29
19 0.95 0.25 0.10 2.75 2.85 4 96 0.27
20 0.95 0.25 0.08 0.30 0.38 21 79 0.40
22 0.95 0.25 0.79 0.22 1.01 78 22 0.80
22A 0.95 0.25 0.72 0.15 0.87 83 17 0.83
23 0.95 0.25 0.49 0.25 0.74 67 34 0.72
24 0.95 0.25 0.56 0.07 0.63 89 11 0.87
24A 0.95 0.25 0.35 0.02 0.37 95 5 0.91
24B 0.95 0.25 0.25 0.06 0.31 81 19 0.81
25 0.95 0.25 0.48 0.17 0.65 74 26 0.77
25A 0.95 0.25 0.42 0.12 0.54 78 22 0.79
26 0.95 0.25 0.27 0.03 0.30 90 10 0.88
27 0.95 0.25 0.04 0.00 0.04 100 0 0.95
36 0.95 0.25 0.16 0.17 0.33 48 52 0.59
37 0.95 0.25 0.29 0.04 0.33 88 12 0.87
38 0.95 0.25 0.23 0.09 0.32 72 28 0.75
40 0.95 0.25 0.05 0.01 0.06 83 17 0.83
39 0.95 0.25 0.00 2.02 0.00 0 100 0.25
SITE Σ 6.49 17.74 24.23 27 73 0.44
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BLDG 4 WEST ANNEX EXPANSION AND SITE DEVELOPMENT
PROJECT BASINS
Basin
Imperviou
s "C"
Pervious
"C"
A, Imp
(ac)
A, Perv
(ac)
A, total
(ac)
% Imp % Perv
Composit
e "C"
A1 0.95 0.25 0.67 0.00 0.67 100 0 0.95
A2 0.95 0.25 0.05 0.20 0.25 19 81 0.38
A3 0.95 0.25 0.76 0.00 0.76 100 0 0.95
A4 0.95 0.25 0.07 2.18 2.26 3 97 0.27
A5 0.95 0.25 0.31 0.00 0.31 100 0 0.95
A6 0.95 0.25 0.09 1.70 1.79 5 95 0.29
A7 0.95 0.25 0.45 2.06 2.51 18 82 0.38
A8 0.95 0.25 0.19 0.03 0.22 88 12 0.86
A9 0.95 0.25 0.13 0.03 0.15 83 17 0.83
A10 0.95 0.25 0.16 0.03 0.19 86 14 0.85
A11 0.95 0.25 0.22 2.18 2.40 9 91 0.31
B1 0.95 0.25 0.00 0.09 0.09 0 100 0.25
B2 0.95 0.25 0.30 0.72 1.02 29 71 0.45
B3 0.95 0.25 0.46 1.35 1.81 25 75 0.43
B4 0.95 0.25 0.23 0.32 0.55 42 58 0.54
B5 0.95 0.25 0.07 0.18 0.25 27 73 0.44
B6 0.95 0.25 0.19 0.60 0.79 24 76 0.42
B7 0.95 0.25 0.19 0.47 0.66 28 72 0.45
C1 0.95 0.25 0.90 0.12 1.02 88 12 0.87
C2 0.95 0.25 0.05 1.57 1.62 3 97 0.27
C3 0.95 0.25 0.29 1.68 1.97 15 85 0.35
C4 0.95 0.25 0.00 0.69 0.69 0 100 0.25
OS-A 0.95 0.25 0.57 1.68 2.25 26 74 0.43
SITE Σ 6.35 17.89 24.24 26 74 0.43
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C. DRAINAGE DESIGN CRITERIA
C1. REFERENCES
C1.1 Jurisdictional
This drainage report has been prepared in compliance with the following criteria:
i) Article VII, Stormwater Utility, City of Fort Collins Municipal Code, latest
revision (“hereafter referred to as the “CRITERIA”),
ii) Section 3.4.3, Water Quality, City of Fort Collins Municipal Code, latest
revision, and
iii) “Urban Storm Drainage Criteria Manual” latest revision (hereafter referred to
as the “MANUAL”).
C1.2 Drainage Studies, Outfall Systems Plans, Site Constraints
The proposed design is in accordance with the MASTER report and BUILDING 4
REPORT.
The site is part of the Fox Meadows Master Drainage Plan (Basin H).
C2. HYDROLOGIC CRITERIA
Design runoff is calculated using the rational method as established in the MANUAL.
The 100-year, one-hour point rainfall data is 2.86 inches per the CRITERIA. Composite
runoff coefficients are based upon a value of 0.95 for imperviousness areas, and 0.25 for
pervious areas in accordance with the BUILDING 4 REPORT.
C3. HYDRAULIC CRITERIA
Final pipe sizes and water surface profiles have been calculated using the Neo-UDSewer
program, latest edition per the MANUAL. Water surface profiles for Storm Line A have
been set at 4917.25 per the BUILDING 4 REPORT. During the 100-year storm, water in
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the northern section of the site will pond to this water surface elevation. The extent of
ponding is shown on the drainage plan.
C4. VARIANCES FROM CRITERIA
No variances from the CRITERIA are requested at this time.
D. DRAINAGE FACILITY DESIGN
D1. GENERAL CONCEPT
D1.1 Major On-Site Basins
Proposed Basin A includes the majority of the Building 4 Expansion roof, portions of the
north access drive extension, and existing native areas. Basin A discharges via a grass
swale to a 24” FES located at design point A7. From A7, flow continues northeast via
storm sewer to the regional channel. From the regional channel, runoff enters the
CAMPUS North Pond, which then flows into the South Pond, which then flows into the
Dam Pond before flowing off-site.
Basin B discharges south to existing storm sewer via a series of swales, a trench drain, a
proposed Type C inlet, and DIP storm pipe. Basin B includes the northern edge of the
proposed Building 4 Expansion roof, proposed loading dock, proposed access drive, and
landscaped areas. On-site storm sewer conveys flow into the CAMPUS Southeast Pond,
which then flows into the South Pond, which then flows into the Dam Pond before
flowing off-site.
Basin C discharges north via existing inlets and storm sewer to the regional detention
channel. Basin C enters the regional detention channel farther west (upstream) than Basin
A, and then flows downstream in the same manner as runoff from Basin A.
D1.2 Major Off-Site Basins
Basin OS-A consists of approximately 2.25 acres of existing landscaped area and
portions of an existing parking lot located south of the proposed PROJECT site. Basin
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OS-A discharges southwest via overland flow and curb and gutter, following existing
drainage patterns.
D2. SPECIFIC DETAILS
D2.1 Basin A
Sub-Basin A1 consists of approximately 0.67 acres of the proposed Building 4 Expansion
roof. Runoff from Sub-Basin A1 discharges through a roof drain lambs tongue into a rock
box at Design Point A1. The rock box is designed to improve downstream water quality
by promoting sedimentation and filtration. From the rock box, discharge enters a 3’ wide
concrete channel which flows west via a sidewalk chase. From the concrete channel,
discharge enters a level spreader. Once runoff has overtopped the level spreader, sheet
flow occurs to Design Point A2 where runoff from Sub-Basin A1 meets runoff from Sub-
Basin A2 in the proposed grass swale.
Sub-Basin A2 consists of approximately 0.25 acres of mostly landscaped area. Runoff
from Sub-Basin A2 sheet flows to Design Point A2, where discharge enters the grass
swale and meets runoff from Sub-Basin A1.
Sub-Basin A3 consists of approximately 1.76 acres of the proposed Building 4 Expansion
roof. Runoff from Sub-Basin A3 discharges through a roof drain lambs tongue into a rock
box at Design Point A3. The rock box is designed to improve downstream water quality
by promoting sedimentation and filtration. From the rock box, discharge enters a 3’ wide
concrete channel which flows west via a sidewalk chase. From the concrete channel,
discharge enters a level spreader. Once runoff has overtopped the level spreader, sheet
flow occurs to Design Point A4 where runoff from Sub-Basin A1 meets runoff from
Design Point A2 and Sub-Basin A4 in the proposed grass swale.
Sub-Basin A4 consists of approximately 2.26 acres of landscaped area and existing native
area. Runoff from Sub-Basin A4 sheet flows to Design Point A4, where discharge enters
the grass swale and meets runoff from Sub-Basin A3 and Design Point A2.
Sub-Basin A5 consists of approximately 0.31 acres of the proposed Building 4 Expansion
roof. Runoff from Sub-Basin A5 discharges through a roof drain lambs tongue into a rock
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box at Design Point A5. The rock box is designed to improve downstream water quality
by promoting sedimentation and filtration. From the rock box, discharge enters a 3’ wide
concrete channel which flows west via a sidewalk chase. From the concrete channel,
discharge enters a level spreader. Once runoff has overtopped the level spreader, sheet
flow occurs to Design Point A6 where runoff from Sub-Basin A5 meets runoff from
Design Point A4 and Sub-Basin A6 in the proposed grass swale.
Sub-Basin A6 consists of approximately 1.79 acres of landscaped area and existing native
area. Runoff from Sub-Basin A6 sheet flows to Design Point A6, where discharge enters
the grass swale and meets runoff from Sub-Basin A5 and Design Point A4.
Sub-Basin A7 consists of approximately 2.51 acres of landscaped area, existing native
area, and proposed concrete pavement. Runoff from Sub-Basin A7 discharges to Design
Point A7 via storm sewer. Runoff enters the storm sewer via a 24” FES located at the
downstream end of the grass swale, or one of two Type C Inlets located in the concrete
pavement. At Design Point A7, runoff from Sub-Basin A7 combines with runoff from
Design Point A6.
Sub-Basin A8 consists of approximately 0.22 acres of mostly paved area. Runoff from
Sub-Basin A8 enters existing storm sewer via an existing inlet at Design Point A8.
Sub-Basin A9 consists of approximately 0.15 acres of mostly paved area. Runoff from
Sub-Basin A9 enters existing storm sewer via an existing inlet at Design Point A9.
Sub-Basin A10 consists of approximately 0.19 acres of mostly paved area. Runoff from
Sub-Basin A10 enters existing storm sewer via an existing inlet at Design Point A10.
Sub-Basin A11 consists of approximately 2.40 acres of mostly pervious area. Runoff
from Sub-Basin A11 enters existing storm sewer via a series of proposed swales and area
inlets.
Runoff from Sub-Basins A8, A9, A10, and A11 combines with runoff from Design Point
A7 at Design Point A. From Design Point A, runoff enters the regional channel and flows
to the existing regional detention pond.
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D2.1 Basin B
Sub-Basin B1 consists of approximately 0.09 acres of proposed landscaping. Runoff from
Sub-Basin B1 discharges south to a proposed swale at Design Point B1. From the grass
swale, runoff is carried to a proposed Type C Inlet.
Sub-Basin B2 consists of approximately 1.02 acres of landscaped area, existing native
area, and proposed pavement. Runoff from Sub-Basin B2 enters the storm sewer system
at Design Point B2 via a proposed 18” trench drain and Type C Inlet. At Design Point
B2, runoff from Sub-Basin B2 meets discharge from Sub-Basins B1.
Sub-Basin B3 consists of approximately 1.81 acres of existing and proposed landscaping,
paved parking, and paved drives. Runoff from Sub-Basin B3 travels via an existing
concrete swale to Design Point B3 and combines with discharge from Design Point B2.
Sub-Basin B4 consists of approximately 0.55 acres of mostly landscaped area. Runoff
from Sub-Basin B4 enters storm sewer at Design Point B4 via an existing area inlet.
Sub-Basin B5 consists of approximately 0.44 acres of mostly landscaped area. Runoff
from Sub-Basin B5 enters the storm sewer system via an area inlet at Design Point B5
and combines with discharge from Design Point B4.
Sub-Basin B6 consists of approximately 0.79 acres of mostly landscaped area. Runoff
from Sub-Basin B6 enters the storm sewer system via an area inlet and combines with
runoff from Design Point B5 at Design Point B6.
Sub-Basin B7 consists of approximately 0.66 acres of mostly landscaped area. Runoff
from Sub-Basin B7 enters the storm sewer system via an area inlet and combines with
runoff from Design Point B6 at Design Point B7.
Runoff from Sub-Basins B4, B5, B6, and B7 combines with runoff from Design Point B3
at Design Point B. From Design Point A, runoff continues south and east to a regional
detention pond.
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D2.1 Basin C
Sub-Basin C1 consists of approximately 1.02 acres of existing asphalt parking lot. Runoff
discharges southeasterly via sheet flow and curb and gutter to an existing inlet at Design
Point C1. At Design Point C1, runoff enters the storm sewer system and flows north.
Sub-Basin C2 consists of approximately 1.62 acres of proposed landscaped area which is
to be built in place of an existing parking lot which is to be demolished. The demolition
of the existing asphalt parking lot is the main strategy used to maintain compliance with
the imperviousness values and composite “C” factor found in the BUILDING 4
REPORT. Runoff from Sub-Basin combines with runoff from Sub-Basin C1 at Design
Point C2, an existing storm sewer inlet. From Design Point C2, runoff flows north via
existing storm sewer.
Sub-Basin C3 consists of approximately 1.97 acres of existing native area and a portion
of the eastern half of Technology Way. Runoff travels via sheet flow and curb and gutter
to an existing inlet at Design Point C3.
Runoff from Sub-Basin C3 combines with runoff from Design Point C2 at Design Point
C. From Design Point A, runoff enters the regional channel and flows to the existing
regional detention pond.
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E. STORMWATER QUALITY
Water Quality is provided by the regional detention ponds located on the CAMPUS;
however, in accordance with City of Fort Collins Municipal Code, Section 3.4.3 Water
Quality, this development has followed Low-Impact-Design (“LID”) principles in order
to increase the water quality for stormwater discharge from the developed site. The
following specific LID features are incorporated into the drainage design for this project:
Grass Swale: The site has been designed with an approximately 450’ long grass
swale which has been designed in accordance with the Grass Swale Best
Management Practice Fact Sheet and Design Spreadsheet from the MANUAL.
The Grass Swale will except and treat runoff from Sub-Basins A1-A7. The Grass
Swale will be a densely vegetated trapezoidal channel with low-pitched side
slopes and a relatively broad cross section which will convey flow in a slow and
shallow manner, thereby facilitating sedimentation and filtering while limiting
erosion. An underdrain system has been provided for the Grass Swale in order to
encourage infiltration and limit ponding.
Rock Box: Runoff from roof drains will discharge via lamb’s tongues at the
building face into one of five proposed rock boxes. Rock boxes are constructed of
a single CDOT Type D Inlet approximately 48” in height. Rock Boxes are
designed to facilitate sedimentation, provide minimal detention, and provide
energy dissipation for roof drain runoff. The Rock Box utilizes a layer of rip-rap
or cobble at its top in order to first slow down and dissipate roof drain flows.
Next, these flows filter down through approximately 3’ of 1-2” crushed rock in
order to encourage sedimentation and filtration. An orifice plate mounted to the
front of the rock box provides for the slow discharge rate out of the rock box.
From the rock box outlet, runoff enters a concrete lined chase which directs runoff
towards another LID feature, the level spreader.
Level Spreaders have been incorporated into the drainage design in order to
provide another feature which encourages infiltration, and limits erosion by
limiting flow velocities and concentration. The level spreader functions by
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providing a small sedimentation basin (approximately 3” depth) for flows
discharging from the proposed concrete channels. This sedimentation basin
discharges over the 40’ long level spreader at a constant elevation, thereby
creating sheet flow as runoff discharges towards the grass swale. This has the
added benefit of increasing infiltration during sheet flow, and limiting the erosive
potential of the runoff by spreading the discharge.
Grass Buffer: Downstream from the level spreaders, sheet flow runs through a
grass buffer before entering the grass swale. Grass Buffers play an important role
in LID by enabling infiltration and slowing runoff. The Grass Buffer provides the
benefits of filtering sediment and trash; and reducing directly connected
impervious area.
Nyloplast Sedimentation Basin / Sediment Trap: At the request of the City, a
Nyloplast Sedimentation Basin has been installed at the downstream end of the
proposed Grass Swale in order to provide an additional means for sedimentation
before entering the storm sewer system. The Nyloplast Sedimentation Basin will
consist of a 24” Nyloplast Drainage Basin in a concrete collar. The Basin will
have 2’ of sump in order to allow for settlement before runoff enters the storm
sewer system via the proposed 24” FES.
Multiple Roof Drains and Disconnecting Impervious Area (DCIA): The roof
drainage from the Building 4 Expansion has been purposely broken up into
multiple discharge points along the perimeter of the building in order to
disconnect impervious areas which lengthens runoff times of concentration and
allows for multiple localized areas for water quality treatment.
Permanent site stabilization will be provided through the installation and maintenance of
asphalt or concrete paving and permanent landscaping at the time of final site
development. Final stabilization will be achieved once a uniform vegetative cover has
been established with a density of at least 70-percent of pre-disturbance levels.
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Detention and water quality for the entire CAMPUS will continue to be provided in the
regional water quality and detention ponds. Additionally, the LID features mentioned
previously will enhance the water quality of discharge from the PROJECT site.
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F. CONCLUSIONS
F1. COMPLIANCE WITH STANDARDS
The Drainage Report for the Avago Building 4 Expansion and Site Development project
has been prepared in compliance with the BUILDING 4 REPORT, MASTER,
CRITERIA, MANUAL, and the City of Fort Collins Municipal Code, Section 3.4.3
Water Quality. The proposed drainage design is consistent with both existing and
developed conditions.
F2. SUMMARY OF CONCEPT
Developed runoff will be collected and conveyed by a system of overland flow, grass
swales, concrete channels, and proposed and existing storm sewer. Runoff will ultimately
be conveyed to existing regional detention and water quality ponds located on the
CAMPUS. LID principles will improve the water quality for stormwater runoff from the
developed site. Development of the site will not adversely impact downstream properties
or drainage facilities.
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LIST OF REFERENCES
1. “Updated Hydrology for the Fox Meadows Basin”. Resource Consultants. 1987.
2. “Master Drainage Report for Hewlett-Packard Site”. Nolte and Associates. 1990.
3. “City of Fort Collins Municipal Code”. Latest revision
4. “Hewlett-Packard Building 5 Drainage Report”. Sear-Brown Group. 1996.
5. “Hewlett-Packard Building 4 Drainage Report”. Sear-Brown Group. 1999.
6. “Symbios Logic Site Development”. Sear-Brown Group. 1997
7. “Detailed Hydraulic Study, Regional Detention Facilities, Hewlett-Packard Company”.
Sears Brown Group. 2000.
8. “Geotechnical Engineering Report, Avago Technologies B4 West Annex”. Terracon
Consultants, Inc. September 4, 2012
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G. APPENDIX
miles
km
1
1
Grass Buffer T-1
November 2010 Urban Drainage and Flood Control District GB-1
Urban Storm Drainage Criteria Manual Volume 3
Photograph GB-1. A flush curb allows roadway runoff to sheet flow
through the grass buffer. Flows are then further treated by the grass
swale. Photo courtesy of Muller Engineering.
Description
Grass buffers are densely vegetated
strips of grass designed to accept sheet
flow from upgradient development.
Properly designed grass buffers play a
key role in LID, enabling infiltration and
slowing runoff. Grass buffers provide
filtration (straining) of sediment.
Buffers differ from swales in that they
are designed to accommodate overland
sheet flow rather than concentrated or
channelized flow.
Site Selection
Grass buffers can be incorporated into a
wide range of development settings.
Runoff can be directly accepted from a
parking lot, roadway, or the roof of a
structure, provided the flow is distributed in a uniform manner over the width of the buffer. This can be
achieved through the use of flush curbs, slotted curbs, or level spreaders where needed. Grass buffers are
often used in conjunction with grass swales. They are well suited for use in riparian zones to assist in
stabilizing channel banks adjacent to major drainageways and receiving waters. These areas can also
sometimes serve multiple functions such as recreation.
Hydrologic Soil Groups A and B provide the best infiltration
capacity for grass buffers. For Type C and D soils, buffers still
serve to provide filtration (straining) although infiltration rates are
lower.
Designing for Maintenance
Recommended ongoing maintenance practices for all BMPs are
provided in Chapter 6 of this manual. During design the
following should be considered to ensure ease of maintenance
over the long-term:
Where appropriate (where vehicle safety would not be
impacted), install the top of the buffer 1 to 3 inches below the
adjacent pavement so that growth of vegetation and
accumulation of sediment at the edge of the strip does not
prevent runoff from entering the buffer. Alternatively, a
sloped edge can be used adjacent to vehicular traffic areas.
Amend soils to encourage deep roots and reduce irrigation
requirements, as well as promote infiltration.
Grass Buffer
Functions
LID/Volume Red. Yes
WQCV Capture No
WQCV+Flood Control No
Fact Sheet Includes
EURV Guidance No
Typical Effectiveness for Targeted
Pollutants3
Sediment/Solids Good
Nutrients Moderate
Total Metals Good
Bacteria Poor
Other Considerations
Life-cycle Costs Low
T-1 Grass Buffer
GB-2 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
Benefits
Filters (strains) sediment and
trash.
Reduces directly connected
impervious area. (See Chapter 3
for quantifying benefits.)
Can easily be incorporated into a
treatment train approach.
Provides green space available
for multiple uses including
recreation and snow storage.
Straightforward maintenance
requirements when the buffer is
protected from vehicular traffic.
Limitations
Frequently damaged by vehicles
when adjacent to roadways and
unprotected.
A thick vegetative cover is
needed for grass buffers to be
effective.
Nutrient removal in grass buffers
is typically low.
High loadings of coarse solids,
trash, and debris require
pretreatment.
Space for grass buffers may not
be available in ultra urban areas
(lot-line-to-lot-line).
Design and adjust the irrigation system (temporary or
permanent) to provide water in amounts appropriate for
the selected vegetation. Irrigation needs will change from
month to month and year to year.
Protect the grass buffer from vehicular traffic when using
this BMP adjacent to roadways. This can be done with a
slotted curb (or other type of barrier) or by constructing a
reinforced grass shoulder (see Fact Sheet T-10.5).
Design Procedure and Criteria
The following steps outline the grass buffer design procedure
and criteria. Figure GB-1 is a schematic of the facility and its
components:
1. Design Discharge: Use the hydrologic procedures
described in the Runoff chapter of Volume 1 to determine
the 2-year peak flow rate (Q2) of the area draining to the
grass buffer.
2. Minimum Width: The width (W), normal to flow of the
buffer, is typically the same as the contributing basin (see
Figure GB-1). An exception to this is where flows become
concentrated. Concentrated flows require a level spreader
to distribute flows evenly across the width of the buffer.
The minimum width should be:
𝑊𝑊 =
𝑄𝑄2
0.05
Equation GB-1
Where:
W = width of buffer (ft)
Grass Buffer T-1
November 2010 Urban Drainage and Flood Control District GB-3
Urban Storm Drainage Criteria Manual Volume 3
Photograph GB-2. This level spreader carries concentrated flows into a
slotted pipe encased in concrete to distribute flows evenly to the grass buffer
shown left in the photo. Photo courtesy of Bill Wenk.
Use of Grass Buffers
Sheet flow of stormwater through a
grassed area provides some benefit in
pollutant removal and volume
reduction even when the geometry of
the BMP does not meet the criteria
provided in this Fact Sheet. These
criteria provide a design procedure
that should be used when possible;
however, when site constraints are
limiting, this treatment concept is
still encouraged.
4. Buffer Slope: The design slope of a grass buffer in the
direction of flow should not exceed 10%. Generally, a
minimum slope of 2% or more in turf is adequate to
facilitate positive drainage. For slopes less than 2%,
consider including an underdrain system to mitigate
nuisance drainage.
5. Flow Characteristics (sheet or concentrated):
Concentrated flows can occur when the width of the
watershed differs from that of the grass buffer.
Additionally, when the product of the watershed flow
length and the interface slope (the slope of the watershed
normal to flow at the grass buffer) exceeds approximately
one, flows may become concentrated. Use the following
equations to determine flow characteristics:
Sheet Flow: FL(SI) ≤ 1 Equation GB-2
Concentrated Flow: FL(SI) > 1 Equation GB-3
Where:
FL = watershed flow length (ft)
SI = interface slope (normal to flow) (ft/ft)
6. Flow Distribution: Flows delivered to a grass buffer must be sheet flows. Slotted or flush curbing,
permeable pavements, or other devices can be used to spread flows. The grass buffer should have
relatively consistent slopes to avoid concentrating flows within the buffer.
A level spreader should be used when flows are concentrated. A level spreader can be a slotted drain
designed to discharge flow through the slot as shown in Photo GB-2. It could be an exfiltration
trench filled with gravel, which allows water to infiltrate prior to discharging over a level concrete or
rock curb. There are many ways to design and construct a level spreader. They can also be used in
series when the length of the
buffer allows flows to re-
concentrate. See Figure GB-2 for
various level spreader sections.
T-1 Grass Buffer
GB-4 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
Photograph GB-3. This level spreader includes the added benefit of a
sedimentation basin prior to even distribution of concentrated flows
from the roadway into the grass buffer. Photo courtesy of Bill Wenk.
Photograph GB-4. Maintenance access is provided via the ramp
located at the end of the basin. Photo courtesy of Bill Wenk.
Photos GB-3 and GB-4 show a level
spreader that includes a basin for
sedimentation. Concentrated flows
enter the basin via stormsewer. The
basin is designed to drain slowly
while overflow is spread evenly to
the downstream vegetation. A small
notch, orifice, or pipe can be used to
drain the level spreader completely.
The opening should be small to
encourage frequent flows to overtop
the level spreader but not so small
that it is frequently clogged.
7. Soil Preparation: In order to
encourage establishment and long-
term health of the selected vegetation,
it is essential that soil conditions be
properly prepared prior to
installation. Following site grading,
poor soil conditions often exist.
When possible, remove, strip,
stockpile, and reuse on-site topsoil.
If the site does not contain topsoil,
the soils should be amended prior to
vegetation. Typically 3 to 5 cubic
yards of soil amendment (compost)
per 1,000 square feet, tilled 6 inches
into the soil is required in order for
vegetation to thrive, as well as to
enable infiltration of runoff.
Additionally, inexpensive soil tests
can be conducted to determine
required soil amendments. (Some
local governments may also require
proof of soil amendment in
landscaped areas for water
conservation reasons.)
8. Vegetation: This is the most critical
component for treatment within a grass buffer. Select durable, dense, and drought tolerant grasses to
vegetate the buffer. Also consider the size of the watershed as larger watersheds will experience
more frequent flows. The goal is to provide a dense mat of vegetative cover. Grass buffer
performance falls off rapidly as the vegetation coverage declines below 80% (Barrett et al.2004).
Grass Buffer T-1
November 2010 Urban Drainage and Flood Control District GB-5
Urban Storm Drainage Criteria Manual Volume 3
Turf grasses such as Kentucky bluegrass are often selected due to these qualities1
9. Irrigation: Grass buffers should be equipped with irrigation systems to promote establishment and
survival in Colorado's semi-arid environment. Systems may be temporary or permanent, depending
on the type of vegetation selected. Irrigation application rates and schedules should be developed and
adjusted throughout the establishment and growing season to meet the needs of the selected plant
species. Initially, native grasses require the same irrigation requirements as bluegrass. After the
grass is established, irrigation requirements for native grasses can be reduced. Irrigation practices
have a significant effect on the function of the grass buffer. Overwatering decreases the permeability
of the soil, reducing the infiltration capacity and contributing to nuisance baseflows. Conversely,
under watering may result in delays in establishment of the vegetation in the short term and unhealthy
vegetation that provides less filtering and increased susceptibility to erosion and rilling over the long
term.
. Dense native turf
grasses may also be selected where a more natural look is desirable. Once established, these provide
the benefit of lower irrigation requirements. See the Revegetation chapter in Volume 2 of this manual
with regard to seed mix selection, planting and ground preparation. Depending on soils and
anticipated flows, consider erosion control measures until vegetation has been established.
10. Outflow Collection: Provide a means for downstream conveyance. A grass swale can be used for
this purpose, providing additional LID benefits.
Construction Considerations
Success of grass buffers depends not only on a good design and long-term maintenance, but also on
installing the facility in a manner that enables the BMP to function as designed. Construction
considerations include:
The final grade of the buffer is critical. Oftentimes, following soil amendment and placement of sod,
the final grade is too high to accept sheet flow. The buffer should be inspected prior to placement of
seed or sod to ensure appropriate grading.
Perform soil amending, fine grading, and seeding only after tributary areas have been stabilized and
utility work crossing the buffer has been completed.
When using sod tiles stagger the ends of the tiles to prevent the formation of channels along the
joints. Use a roller on the sod to ensure there are no air pockets between the sod and soil.
Avoid over compaction of soils in the buffer area during construction to preserve infiltration
capacities.
Erosion and sediment control measures on upgradient disturbed areas must be maintained to prevent
excessive sediment loading to grass buffer.
1
Although Kentucky bluegrass has relatively high irrigation requirements to maintain a lush, green aesthetic, it also withstands
drought conditions by going dormant. Over-irrigation of Kentucky bluegrass is a common problem along the Colorado Front
Range, and it can be healthy, although less lush, with much less irrigation than is typically applied.
T-1 Grass Buffer
GB-6 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
PLAN
PROFILE
Figure GB-1. Typical Grass Buffer Graphic by Adia Davis.
Grass Buffer T-1
November 2010 Urban Drainage and Flood Control District GB-7
Urban Storm Drainage Criteria Manual Volume 3
Figure GB-2. Typical Level Spreader Details
Grass Swale T-2
November 2010 Urban Drainage and Flood Control District GS-1
Urban Storm Drainage Criteria Manual Volume 3
Photograph GS-1. This grass swale provides treatment of roadway
runoff in a residential area. Photo courtesy of Bill Ruzzo.
Description
Grass swales are densely vegetated
trapezoidal or triangular channels with
low-pitched side slopes designed to
convey runoff slowly. Grass swales
have low longitudinal slopes and broad
cross-sections that convey flow in a slow
and shallow manner, thereby facilitating
sedimentation and filtering (straining)
while limiting erosion. Berms or check
dams may be incorporated into grass
swales to reduce velocities and
encourage settling and infiltration.
When using berms, an underdrain
system should be provided. Grass
swales are an integral part of the Low
Impact Development (LID) concept and
may be used as an alternative to a curb and
gutter system.
Site Selection
Grass swales are well suited for sites with low to moderate slopes.
Drop structures or other features designed to provide the same
function as a drop structures (e.g., a driveway with a stabilized
grade differential at the downstream end) can be integrated into
the design to enable use of this BMP at a broader range of site
conditions. Grass swales provide conveyance so they can also be
used to replace curb and gutter systems making them well suited
for roadway projects.
Designing for Maintenance
Recommended ongoing maintenance practices for all BMPs are
provided in Chapter 6 of this manual. During design, the
following should be considered to ensure ease of maintenance
over the long-term:
Consider the use and function of other site features so that the
swale fits into the landscape in a natural way. This can
encourage upkeep of the area, which is particularly important
in residential areas where a loss of aesthetics and/or function
can lead to homeowners filling in and/or piping reaches of
this BMP.
Grass Swale
Functions
LID/Volume Red. Yes
WQCV Capture No
WQCV+Flood Control No
Fact Sheet Includes
EURV Guidance No
Typical Effectiveness for Targeted
Pollutants3
Sediment/Solids Good
Nutrients Moderate
Total Metals Good
Bacteria Poor
Other Considerations
Life-cycle Costs Low
3
T-2 Grass Swale
GS-2 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
Provide access to the swale for mowing equipment and
design sideslopes flat enough for the safe operation of
equipment.
Design and adjust the irrigation system (temporary or
permanent) to provide appropriate water for the selected
vegetation.
An underdrain system will reduce excessively wet areas,
which can cause rutting and damage to the vegetation
during mowing operations.
When using an underdrain, do not put a filter sock on the
pipe. This is unnecessary and can cause the slots or
perforations in the pipe to clog.
Design Procedure and Criteria
The following steps outline the design procedure and criteria
for stormwater treatment in a grass swale. Figure GS-1
shows trapezoidal and triangular swale configurations.
1. Design Discharge: Determine the 2-year flow rate to be
conveyed in the grass swale under fully developed
conditions. Use the hydrologic procedures described in
the Runoff Chapter in Volume 1.
2. Hydraulic Residence Time: Increased hydraulic
residence time in a grass swale improves water quality
treatment. Maximize the length of the swale when
possible. If the length of the swale is limited due to site
constraints, the slope can also be decreased or the cross-sectional area increased to increase hydraulic
residence time.
3. Longitudinal Slope: Establish a longitudinal slope that will meet Froude number, velocity, and
depth criteria while ensuring that the grass swale maintains positive drainage. Positive drainage can
be achieved with a minimum 2% longitudinal slope or by including an underdrain system (see step 8).
Use drop structures as needed to accommodate site constraints. Provide for energy dissipation
downstream of each drop when using drop structures.
4. Swale Geometry: Select geometry for the grass swale. The cross section should be either
trapezoidal or triangular with side slopes not exceeding 4:1 (horizontal: vertical), preferably flatter.
Increase the wetted area of the swale to reduce velocity. Lower velocities result in improved
pollutant removal efficiency and greater volume reduction. If one or both sides of the grass swale are
also to be used as a grass buffer, follow grass buffer criteria.
Benefits
Removal of sediment and
associated constituents through
filtering (straining)
Reduces length of storm sewer
systems in the upper portions of a
watershed
Provides a less expensive and
more attractive conveyance
element
Reduces directly connected
impervious area and can help
reduce runoff volumes.
Limitations
Requires more area than
traditional storm sewers.
Underdrains are recommended for
slopes under 2%.
Erosion problems may occur if not
designed and constructed
properly.
Grass Swale T-2
November 2010 Urban Drainage and Flood Control District GS-3
Urban Storm Drainage Criteria Manual Volume 3
Native grasses provide
a more natural aesthetic
and require less water
once established.
Use of Grass Swales
Vegetated conveyance elements provide some benefit in pollutant removal and volume reduction
even when the geometry of the BMP does not meet the criteria provided in this Fact Sheet. These
criteria provide a design procedure that should be used when possible; however, when site
constraints are limiting, vegetated conveyance elements designed for stability are still encouraged.
5. Vegetation: Select durable, dense, and drought tolerant grasses. Turf grasses, such as Kentucky
bluegrass, are often selected due to these qualities1
once established. Turf grass is a general term for any
grasses that will form a turf or mat as opposed to bunch
grass, which will grow in clumplike fashion. Grass
selection should consider both short-term (for
establishment) and long-term maintenance requirements,
given that some varieties have higher maintenance
requirements than others. Follow criteria in the
Revegetation Chapter of Volume 2, with regard to seed
mix selection, planting, and ground preparation.
. Native turf grasses may also be selected where a
more natural look is desirable. This will also provide the benefit of lower irrigation requirements,
6. Design Velocity: Maximum flow velocity in the swale
should not exceed one foot per second. Use the Soil
Conservation Service (now the NRCS) vegetal retardance
curves for the Manning coefficient (Chow 1959).
Determining the retardance coefficient is an iterative
process that the UD-BMP workbook automates. When
starting the swale vegetation from sod, curve "D" (low retardance) should be used. When starting
vegetation from seed, use the "E" curve (very low vegetal retardance).
7. Design Flow Depth: Maximum flow depth should not exceed one foot at the 2-year peak flow rate.
Check the conditions for the 100-year flow to ensure that drainage is being handled without flooding
critical areas, structures, or adjacent streets.
Table GS-1. Grass Swale Design Summary for Water Quality
1
Although Kentucky bluegrass has relatively high irrigation requirements to maintain a lush, green aesthetic, it also withstands
drought conditions by going dormant. Over-irrigation of Kentucky bluegrass is a common problem along the Colorado Front
Range. It can be healthy, although less lush, with much less irrigation than is typically applied.
Design Flow Maximum
Froude Number
Maximum
Velocity
Maximum
Flow Depth
2-year event 0.5 1 ft/s 1 ft
T-2 Grass Swale
GS-4 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
8. Underdrain: An underdrain is necessary for swales with longitudinal slopes less than 2.0%. The
underdrain can drain directly into an inlet box at the downstream end of the swale, daylight through
the face of a grade control structure or continue below grade through several grade control structures
as shown in Figure GS-1.
The underdrain system should be placed within an aggregate layer. If no underdrain is required, this
layer is not required. The aggregate layer should consist of an 8-inch thick layer of CDOT Class C
filter material meeting the gradation in Table GS-2. Use of CDOT Class C Filter material with a
slotted pipe that meets the slot dimensions provided in Table GS-3 will eliminate the need for
geotextile fabrics. Previous versions of this manual detailed an underdrain system that consisted of a
3- to 4-inch perforated HDPE pipe in a one-foot trench section of AASHTO #67 coarse aggregate
surrounded by geotextile fabric. If desired, this system continues to provide an acceptable alternative
for use in grass swales. Selection of the pipe size may be a function of capacity or of maintenance
equipment. Provide cleanouts at approximately 150 feet on center.
Table GS-2. Gradation Specifications for Class C Filter Material
(Source: CDOT Table 703-7)
Sieve Size Mass Percent Passing Square Mesh Sieves
19.0 mm (3/4") 100
4.75 mm (No. 4) 60 – 100
300 µm (No. 50) 10 – 30
150 µm (No. 100) 0 – 10
75 µm (No. 200) 0 - 3
Table GS-3. Dimensions for Slotted Pipe
Pipe Diameter Slot
Length1
Maximum Slot
Width
Slot
Centers1
Open Area1
(per foot)
4” 1-1/16” 0.032” 0.413” 1.90 in2
6” 1-3/8” 0.032” 0.516” 1.98 in2
1 Some variation in these values is acceptable and is expected from various pipe
manufacturers. Be aware that both increased slot length and decreased slot centers
will be beneficial to hydraulics but detrimental to the structure of the pipe.
Grass Swale T-2
November 2010 Urban Drainage and Flood Control District GS-5
Urban Storm Drainage Criteria Manual Volume 3
Photograph GS-2. This community used
signage to mitigate compaction of soils post-
construction. Photo courtesy of Nancy Styles.
9. Soil preparation: Poor soil conditions often exist following site grading. When the section includes
an underdrain, provide 4 inches of sandy loam at the invert of the swale extending up to the 2-year
water surface elevation. This will improve infiltration and reduce ponding. For all sections,
encourage establishment and long-term health of the bottom and side slope vegetation by properly
preparing the soil. If the existing site provides a good layer of topsoil, this should be striped,
stockpiled, and then replaced just prior to seeding or placing sod. If not available at the site, topsoil
can be imported or the existing soil may be amended. Inexpensive soil tests can be performed
following rough grading, to determine required soil amendments. Typically, 3 to 5 cubic yards of soil
amendment per 1,000 square feet, tilled 4 to 6 inches into the soil is required in order for vegetation to
thrive, as well as to enable infiltration of runoff.
10. Irrigation: Grass swales should be equipped with irrigation systems to promote establishment and
survival in Colorado's semi-arid environment. Systems may be temporary or permanent, depending
on the type of grass selected. Irrigation practices have a significant effect on the function of the grass
swale. Overwatering decreases the permeability of the soil, reducing the infiltration capacity of the
soil and contributing to nuisance baseflows. Conversely, under watering may result in delays in
establishment of the vegetation in the short term and unhealthy vegetation that provides less filtering
(straining) and increased susceptibility to erosion and riling over the long term.
Construction Considerations
Success of grass swales depends not only on a good
design and maintenance, but also on construction
practices that enable the BMP to function as designed.
Construction considerations include:
Perform fine grading, soil amendment, and seeding
only after upgradient surfaces have been stabilized
and utility work crossing the swale has been
completed.
Avoid compaction of soils to preserve infiltration
capacities.
Provide irrigation appropriate to the grass type.
Weed the area during the establishment of vegetation
by hand or mowing. Mechanical weed control is
preferred over chemical weed killer.
Protect the swale from other construction activities.
When using an underdrain, ensure no filter sock is placed on the pipe. This is unnecessary and can
cause the slots or perforations in the pipe to clog.
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This unofficial copy was downloaded on Feb-06-2013 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Feb-06-2013 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Feb-06-2013 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Feb-06-2013 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Feb-06-2013 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
This unofficial copy was downloaded on Feb-06-2013 from the City of Fort Collins Public Records Website: http://citydocs.fcgov.com
For additional information or an official copy, please contact City of Fort Collins Utilities 700 Wood Street Fort Collins, CO 80524 USA
PROJECT INFORMATION
PROJECT NAME:
PROJECT NO:
DESIGN BY:
REVIEWED BY:
JURISDICTION:
REPORT TYPE:
DATE:
C2 C5 C10 C100 % IMPERV
0.25 0.00 0.00 0.25 0%
0.95 0.00 0.00 0.95 100%
24.24 0.43 0.00 0.00 0.43 26.2%
AREA
(ACRES) C2 C5 C10 C100
0.67 0.95 0.00 0.00 0.95 100%
0.00 0.25 0.00 0.00 0.25 0%
0.67 0.95 0.00 0.00 0.95 100.0%
AREA
(ACRES) C2 C5 C10 C100
0.05 0.95 0.00 0.00 0.95 100%
0.20 0.25 0.00 0.00 0.25 0%
0.25 0.38 0.00 0.00 0.38 18.7%
AREA
(ACRES) C2 C5 C10 C100
0.76 0.95 0.00 0.00 0.95 100%
0.00 0.25 0.00 0.00 0.25 0%
0.76 0.95 0.00 0.00 0.95 100.0%
AREA
(ACRES) C2 C5 C10 C100
0.07 0.95 0.00 0.00 0.95 100%
2.18 0.25 0.00 0.00 0.25 0%
2.26 0.27 0.00 0.00 0.27 3.3%
AREA
(ACRES) C2 C5 C10 C100
0.31 0.95 0.00 0.00 0.95 100%
0.00 0.25 0.00 0.00 0.25 0%
0.31 0.95 0.00 0.00 0.95 100.0%
AREA
(ACRES) C2 C5 C10 C100
0.09 0.95 0.00 0.00 0.95 100%
1.70 0.25 0.00 0.00 0.25 0%
1.79 0.29 0.00 0.00 0.29 5.1%
SUB-BASIN COMPOSITE
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
SUB-BASIN
PERVIOUS
TOTAL SITE COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
PERVIOUS
AVAGO
13.0091
BMS
PSB
FORT COLLINS
FINAL
05/09/13
JURISDICTIONAL STANDARD
AREA
(ACRES) C2 C5 C10 C100
0.45 0.95 0.00 0.00 0.95 100%
2.06 0.25 0.00 0.00 0.25 0%
2.51 0.38 0.00 0.00 0.38 18.1%
AREA
(ACRES) C2 C5 C10 C100
0.19 0.95 0.00 0.00 0.95 100%
0.03 0.25 0.00 0.00 0.25 0%
0.22 0.86 0.00 0.00 0.86 87.8%
AREA
(ACRES) C2 C5 C10 C100
0.13 0.95 0.00 0.00 0.95 100%
0.03 0.25 0.00 0.00 0.25 0%
0.15 0.83 0.00 0.00 0.83 82.8%
AREA
(ACRES) C2 C5 C10 C100
0.16 0.95 0.00 0.00 0.95 100%
0.03 0.25 0.00 0.00 0.25 0%
0.19 0.85 0.00 0.00 0.85 85.9%
AREA
(ACRES) C2 C5 C10 C100
0.22 0.95 0.00 0.00 0.95 100%
2.18 0.25 0.00 0.00 0.25 0%
2.40 0.31 0.00 0.00 0.31 9.1%
AREA
(ACRES) C2 C5 C10 C100
0.00 0.95 0.00 0.00 0.95 100%
0.09 0.25 0.00 0.00 0.25 0%
0.09 0.25 0.00 0.00 0.25 0.0%
AREA
(ACRES) C2 C5 C10 C100
0.30 0.95 0.00 0.00 0.95 100%
0.72 0.25 0.00 0.00 0.25 0%
1.02 0.45 0.00 0.00 0.45 29.3%
AREA
(ACRES) C2 C5 C10 C100
0.46 0.95 0.00 0.00 0.95 100%
1.35 0.25 0.00 0.00 0.25 0%
SUB-BASIN COMPOSITE 1.81 0.43 0.00 0.00 0.43 25.3%
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
B3
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
B2
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
B1
IMPERVIOUS
PERVIOUS
AREA
(ACRES) C2 C5 C10 C100
0.23 0.95 0.00 0.00 0.95 100%
0.32 0.25 0.00 0.00 0.25 0%
0.55 0.54 0.00 0.00 0.54 42.0%
AREA
(ACRES) C2 C5 C10 C100
0.07 0.95 0.00 0.00 0.95 100%
0.18 0.25 0.00 0.00 0.25 0%
0.25 0.44 0.00 0.00 0.44 27.0%
AREA
(ACRES) C2 C5 C10 C100
0.19 0.95 0.00 0.00 0.95 100%
0.60 0.25 0.00 0.00 0.25 0%
0.79 0.42 0.00 0.00 0.42 24.4%
AREA
(ACRES) C2 C5 C10 C100
0.19 0.95 0.00 0.00 0.95 100%
0.47 0.25 0.00 0.00 0.25 0%
0.66 0.45 0.00 0.00 0.45 28.4%
AREA
(ACRES) C2 C5 C10 C100
0.90 0.95 0.00 0.00 0.95 100%
0.12 0.25 0.00 0.00 0.25 0%
1.02 0.87 0.00 0.00 0.87 88.3%
AREA
(ACRES) C2 C5 C10 C100
0.05 0.95 0.00 0.00 0.95 100%
1.57 0.25 0.00 0.00 0.25 0%
1.62 0.27 0.00 0.00 0.27 3.0%
AREA
(ACRES) C2 C5 C10 C100
0.29 0.95 0.00 0.00 0.95 100%
1.68 0.25 0.00 0.00 0.25 0%
1.97 0.35 0.00 0.00 0.35 14.6%
AREA
(ACRES) C2 C5 C10 C100
0.00 0.95 0.00 0.00 0.95 100%
0.69 0.25 0.00 0.00 0.25 0%
SUB-BASIN COMPOSITE 0.69 0.25 0.00 0.00 0.25 0%
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
C4
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
C3
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
C2
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
AREA
(ACRES) C2 C5 C10 C100
0.57 0.95 0.00 0.00 0.95 100%
1.68 0.25 0.00 0.00 0.25 0%
2.25 0.43 0.00 0.00 0.43 25.5%
24.24 0.43 0.00 0.00 0.43 26.2%
SUB-BASIN COMPOSITE
TOTAL SITE COMPOSITE
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
OS-A
IMPERVIOUS
PERVIOUS
SUB-BASIN SURFACE CHARACTERISTICS
5/9/2013 5:04 PM
COMPOSITE_C-VALUES
G:\SCHLAGETER\13.0091-Avago Bldg 4 Expansion and Site Develoment\ENG\DRAINAGE\RATIONAL METHOD\RATIONAL METHOD.xls
CALCULATED BY: JOB NO:
CHECKED BY: PROJECT:
DATE:
FINAL
tc
AREA LENGTH SLOPE ti LENGTH SLOPE VEL. tt COMP. TOT. LENGTH
ac ft ft/ft min ft ft/ft fps Min tc ft min min
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15)
A1 A1 0.00 0.67 0 0.0000 0.0 200 0.0200 20 2.83 1.2 1.2 200.0 11.1 5.0
A2 A2 0.00 0.25 125 0.0450 13.5 0 0.0000 20 0.00 0.0 13.5 125.0 10.7 10.7
A3 A3 0.00 0.76 0 0.0000 0.0 200 0.0200 20 2.83 1.2 1.2 200.0 11.1 5.0
A4 A4 0.00 2.26 485 0.0100 43.7 0 0.0000 20 0.00 0.0 43.7 485.0 12.7 12.7
A5 A5 0.00 0.31 0 0.0000 0.0 200 0.0200 20 2.83 1.2 1.2 200.0 11.1 5.0
A6 A6 0.00 1.79 500 0.0130 40.7 0 0.0000 20 0.00 0.0 40.7 500.0 12.8 12.8
A7 A7 0.00 2.51 285 0.0250 24.8 100 0.0030 15 0.82 2.0 26.8 385.0 12.1 12.1
A8 A8 0.00 0.22 70 0.0200 13.2 0 0.0000 20 0.00 0.0 13.2 70.0 10.4 10.4
A9 A9 0.00 0.15 70 0.0200 13.2 0 0.0000 20 0.00 0.0 13.2 70.0 10.4 10.4
A10 A10 0.00 0.19 70 0.0200 13.2 0 0.0000 20 0.00 0.0 13.2 70.0 10.4 10.4
A11 A11 0.00 2.40 140 0.0200 18.7 0 0.0000 20 0.00 0.0 18.7 140.0 10.8 10.8
B1 B1 0.00 0.09 0 0.0000 0.0 200 0.0200 20 2.83 1.2 1.2 200.0 11.1 5.0
B2 B2 0.00 1.02 130 0.0500 13.3 160 0.0100 15 1.50 1.8 15.1 290.0 11.6 11.6
B3 B3 0.00 1.81 135 0.0110 22.4 135 0.0075 20 1.73 1.3 23.7 270.0 11.5 11.5
B4 B4 0.00 0.55 65 0.0590 8.9 0 0.0000 20 0.00 0.0 8.9 65.0 10.4 8.9
B5 B5 0.00 0.25 85 0.0280 13.0 0 0.0000 20 0.00 0.0 13.0 85.0 10.5 10.5
B6 B6 0.00 0.79 140 0.0250 17.4 0 0.0000 20 0.00 0.0 17.4 140.0 10.8 10.8
B7 B7 0.00 0.66 140 0.0250 17.4 0 0.0000 20 0.00 0.0 17.4 140.0 10.8 10.8
C1 C1 0.00 1.02 120 0.0140 19.5 220 0.0085 20 1.84 2.0 21.5 340.0 11.9 11.9
C2 C2 0.00 1.62 200 0.0163 23.9 110 0.0066 20 1.62 1.1 25.0 310.0 11.7 11.7
C3 C3 0.00 1.97 150 0.0177 20.1 0 0.0000 20 0.00 0.0 20.1 150.0 10.8 10.8
C4 C4 0.00 0.69 310 0.0070 39.3 0 0.0000 20 0.00 0.0 39.3 310.0 11.7 11.7
OS-A OS-A 0.00 2.25 200 0.0200 22.3 100 0.0000 20 0.00 0.0 22.3 300.0 11.7 11.7
*Velocity (V) = CvSw0.5
TABLE RO-2
*Table RO-2, UDFCD (V.1), Chapter 5, Page RO-6
in which: Cv = Conveyance Coefficient (See Table Above)
Sw = Watercourse Slope (ft/ft)
10
Grassed Waterway 15
BASIN
DESIGN
POINT
C5
Paved Areas and Shallow Paved Swales 20
Heavy Meadow 2.5
Tillage / Field 5
Short Pasture and Lawns 7
Nearly Bare Ground
Type of Land Surface Conveyance Coefficient, Cv
(tt) (URBANIZED BASINS)
tc=(L/180)+10
Cv
tc CHECK
REMARKS
BMS
PSB
05/09/13
DATA
SUB-BASIN
TIME (ti)
INITIAL/OVERLAND TRAVEL TIME
CALCULATED BY: BMS JOB NO: 13.0091
CHECKED BY: PSB PROJECT: AVAGO
DATE: 05/09/13 DESIGN STORM: 2-YEAR
ONE-HR PRECIP: 0.82
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)
A1 A1 0.67 0.95 5.0 0.64 2.78 1.77 5.0 0.64 2.78 1.77
A2 A2 0.25 0.38 10.7 0.10 2.16 0.21 10.7 0.73 2.16 1.58 DP A2
A3 A3 0.76 0.95 5.0 0.72 2.78 2.01 5.0 0.72 2.78 2.01
A4 A4 2.26 0.27 12.7 0.61 2.01 1.23 12.7 2.06 2.01 4.15 DP A4
A5 A5 0.31 0.95 5.0 0.29 2.78 0.82 5.0 0.29 2.78 0.82
A6 A6 1.79 0.29 12.8 0.52 2.00 1.04 12.8 2.88 2.00 5.76 DP A6
A7 A7 2.51 0.38 12.1 0.95 2.05 1.95 20.0 3.83 1.61 6.18 DP A7
A8 A8 0.22 0.86 10.4 0.19 2.19 0.41 10.4 0.19 2.19 0.41
A9 A9 0.15 0.83 10.4 0.13 2.19 0.28 10.4 0.13 2.19 0.28
A10 A10 0.19 0.85 10.4 0.16 2.19 0.35 10.4 0.47 2.19 1.03
A11 A11 2.40 0.31 10.8 0.74 2.15 1.60 10.8 1.22 2.15 2.62 DP A11
B1 B1 0.09 0.25 5.0 0.02 2.78 0.06 5.0 0.02 2.78 0.06
B2 B2 1.02 0.45 11.6 0.46 2.09 0.95 11.6 0.48 2.09 1.00 DP B2
B3 B3 1.81 0.43 11.5 0.78 2.10 1.63 11.6 1.26 2.09 2.63 DP B3
B4 B4 0.55 0.54 8.9 0.30 2.32 0.69 8.9 0.30 2.32 0.69
B5 B5 0.25 0.44 10.5 0.11 2.18 0.24 10.5 0.41 2.18 0.89 DP B5
B6 B6 0.79 0.42 10.8 0.33 2.15 0.71 10.8 0.74 2.15 1.60 DP B6
B7 B7 0.66 0.45 10.8 0.30 2.15 0.64 10.8 1.04 2.15 2.24 DP B7
C1 C1 1.02 0.87 11.9 0.89 2.07 1.84 11.9 0.89 2.07 1.84
C2 C2 1.62 0.27 11.7 0.44 2.08 0.91 11.9 1.33 2.07 2.74 DP C2
C3 C3 1.97 0.35 10.8 0.69 2.15 1.48 11.9 2.02 2.07 4.17 DP C3
C4 C4 0.69 0.25 11.7 0.17 2.08 0.36 11.9 2.19 2.07 4.52 DP C4
OS-A OS-A 2.25 0.43 11.7 0.97 2.08 2.02 11.7 0.97 2.08 2.02 TOTAL OS-A
12.8 5.05 2.00 10.11 TOTAL DP A
11.6 2.30 2.09 4.80 TOTAL DP B
11.9 2.19 2.07 4.52 TOTAL DP C
I. One-Hr Precipitation Values for the City OF Fort Collins
Return Period: 2-YEAR 5-YEAR 10-YEAR 100-YEAR
Depth In Inches: 0.82 2.86
*Equation RA-3, UDFCD (V.1), Chapter 4, Page RA-6
*Rainfall Intensity: In Which: I = Rainfall Intensity (Inches Per Hour)
P1 = 1-Hour Point Rainfall Depth (Inches)
tc = Time Of Concentration (Minutes)
AREA REMARKS
(AC)
RUNOFF
COEFF
tc
(MIN)
BASIN DESIGN POINT
DIRECT RUNOFF TOTAL RUNOFF
tc
(MIN)
S(CxA)
(AC)
I
(IN/HR)
Q
(CFS)
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
CxA
(AC)
I
CALCULATED BY: BMS JOB NO: 13.0091
CHECKED BY: PSB PROJECT: AVAGO
DATE: 05/09/13 DESIGN STORM: 100-YEAR
ONE-HR PRECIP: 2.86
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)
A1 A1 0.67 0.95 5.0 0.64 9.70 6.19 5.0 0.64 9.70 6.19
A2 A2 0.25 0.38 10.7 0.10 7.53 0.72 10.7 0.73 7.53 5.52 DP A2
A3 A3 0.76 0.95 5.0 0.72 9.70 6.99 5.0 0.72 9.70 6.99
A4 A4 2.26 0.27 12.7 0.61 7.01 4.27 12.7 2.06 7.01 14.46 DP A4
A5 A5 0.31 0.95 5.0 0.29 9.70 2.84 5.0 0.29 9.70 2.84
A6 A6 1.79 0.29 12.8 0.52 6.99 3.62 12.8 2.88 6.99 20.09 DP A6
A7 A7 2.51 0.38 12.1 0.95 7.14 6.81 20.0 3.83 5.63 21.54 DP A7
A8 A8 0.22 0.86 10.4 0.19 7.62 1.41 10.4 0.19 7.62 1.41
A9 A9 0.15 0.83 10.4 0.13 7.62 0.97 10.4 0.13 7.62 0.97
A10 A10 0.19 0.85 10.4 0.16 7.62 1.21 10.4 0.47 7.62 3.60
A11 A11 2.40 0.31 10.8 0.74 7.51 5.59 10.8 1.22 7.51 9.13 DP A11
B1 B1 0.09 0.25 5.0 0.02 9.70 0.22 5.0 0.02 9.70 0.22
B2 B2 1.02 0.45 11.6 0.46 7.28 3.33 11.6 0.48 7.28 3.49 DP B2
B3 B3 1.81 0.43 11.5 0.78 7.31 5.69 11.6 1.26 7.28 9.16 DP B3
B4 B4 0.55 0.54 8.9 0.30 8.08 2.42 8.9 0.30 8.08 2.42
B5 B5 0.25 0.44 10.5 0.11 7.60 0.84 10.5 0.41 7.60 3.11 DP B5
B6 B6 0.79 0.42 10.8 0.33 7.51 2.49 10.8 0.74 7.51 5.57 DP B6
B7 B7 0.66 0.45 10.8 0.30 7.51 2.24 10.8 1.04 7.51 7.81 DP B7
C1 C1 1.02 0.87 11.9 0.89 7.21 6.40 11.9 0.89 7.21 6.40
C2 C2 1.62 0.27 11.7 0.44 7.25 3.17 11.9 1.33 7.21 9.56 DP C2
C3 C3 1.97 0.35 10.8 0.69 7.49 5.17 11.9 2.02 7.21 14.53 DP C3
C4 C4 0.69 0.25 11.7 0.17 7.25 1.25 11.9 2.19 7.21 15.78 DP C4
OS-A OS-A 2.25 0.43 11.7 0.97 7.27 7.04 11.7 0.97 7.27 7.04 TOTAL OS-A
12.8 5.05 6.99 35.25 TOTAL DP A
11.6 2.30 7.28 16.73 TOTAL DP B
11.9 2.19 7.21 15.78 TOTAL DP C
I. One-Hr Precipitation Values for the City OF Fort Collins
Return Period: 2-YEAR 5-YEAR 10-YEAR 100-YEAR
Depth In Inches: 0.82 0.00 0.00 2.86
*Equation RA-3, UDFCD (V.1), Chapter 4, Page RA-6
*Rainfall Intensity: In Which: I = Rainfall Intensity (Inches Per Hour)
P1 = 1-Hour Point Rainfall Depth (Inches)
tc = Time Of Concentration (Minutes)
AREA REMARKS
(AC)
RUNOFF
COEFF
tc
(MIN)
STANDARD FORM SF-3
STORM DRAINAGE SYSTEM DESIGN
(RATIONAL METHOD PROCEDURE)
CxA
(AC)
I
(IN/HR)
Q
(CFS)
BASIN DESIGN POINT
DIRECT RUNOFF TOTAL RUNOFF
tc
(MIN)
S(CxA)
(AC)
I
PROJECT:
JOB NO: 01/13/00
DATE: 05/09/13
DESIGN AREA % Q2 Q100
POINT (ACRES) IMP. (CFS) (CFS)
A1 A1 0.67 100.0% 0.95 0.95 1.77 6.19
A2 A2 0.25 18.7% 0.38 0.38 0.21 0.72
A3 A3 0.76 100.0% 0.95 0.95 2.01 6.99
A4 A4 2.26 3.3% 0.27 0.27 1.23 4.27
A5 A5 0.31 100.0% 0.95 0.95 0.82 2.84
A6 A6 1.79 5.1% 0.29 0.29 1.04 3.62
A7 A7 2.51 18.1% 0.38 0.38 1.95 6.81
A8 A8 0.22 87.8% 0.86 0.86 0.41 1.41
A9 A9 0.15 82.8% 0.83 0.83 0.28 0.97
A10 A10 0.19 85.9% 0.85 0.85 0.35 1.21
A11 A11 2.40 9.1% 0.31 0.31 1.60 5.59
B1 B1 0.09 0.0% 0.25 0.25 0.06 0.22
B2 B2 1.02 29.3% 0.45 0.45 0.95 3.33
B3 B3 1.81 25.3% 0.43 0.43 1.63 5.69
B4 B4 0.55 42.0% 0.54 0.54 0.69 2.42
B5 B5 0.25 27.0% 0.44 0.44 0.24 0.84
B6 B6 0.79 24.4% 0.42 0.42 0.71 2.49
B7 B7 0.66 28.4% 0.45 0.45 0.64 2.24
C1 C1 1.02 88.3% 0.87 0.87 1.84 6.40
C2 C2 1.62 3.0% 0.27 0.27 0.91 3.17
C3 C3 1.97 14.6% 0.35 0.35 1.48 5.17
C4 C4 0.69 -0.3% 0.25 0.25 0.36 1.25
OS-A OS-A 2.25 25.5% 0.43 0.43 2.02 7.04
SITE COMPOSITE 24.24 26.2% 0.43 0.43 23.20 80.90
BASIN
RUNOFF SUMMARY
C2 C100
AVAGO
RUNOFF_SUMMARY
5/9/2013 5:04 PM
G:\SCHLAGETER\13.0091-Avago Bldg 4 Expansion and Site Develoment\ENG\DRAINAGE\RATIONAL METHOD\RATIONAL
METHOD.xls
PROJECT INFORMATION
PROJECT NAME:
PROJECT #:
DATE:
Basin
Impervious
"C"
Pervious "C" A, Imp (ac) A, Perv (ac) A, total (ac) % Imp % Perv
Composite
"C"
4 0.95 0.25 0.19 1.44 1.67 11 86 0.32
5 0.95 0.25 0.12 0.65 0.77 16 84 0.36
6 0.95 0.25 0.00 6.75 6.75 0 100 0.25
14 0.95 0.25 0.25 0.18 0.43 58 42 0.66
17 0.95 0.25 0.56 1.40 1.96 29 71 0.45
18 0.95 0.25 0.05 0.85 0.90 6 94 0.29
19 0.95 0.25 0.10 2.75 2.85 4 96 0.27
20 0.95 0.25 0.08 0.30 0.38 21 79 0.40
22 0.95 0.25 0.79 0.22 1.01 78 22 0.80
22A 0.95 0.25 0.72 0.15 0.87 83 17 0.83
23 0.95 0.25 0.49 0.25 0.74 67 34 0.72
24 0.95 0.25 0.56 0.07 0.63 89 11 0.87
24A 0.95 0.25 0.35 0.02 0.37 95 5 0.91
24B 0.95 0.25 0.25 0.06 0.31 81 19 0.81
25 0.95 0.25 0.48 0.17 0.65 74 26 0.77
25A 0.95 0.25 0.42 0.12 0.54 78 22 0.79
26 0.95 0.25 0.27 0.03 0.30 90 10 0.88
27 0.95 0.25 0.04 0.00 0.04 100 0 0.95
36 0.95 0.25 0.16 0.17 0.33 48 52 0.59
37 0.95 0.25 0.29 0.04 0.33 88 12 0.87
38 0.95 0.25 0.23 0.09 0.32 72 28 0.75
40 0.95 0.25 0.05 0.01 0.06 83 17 0.83
39 0.95 0.25 0.00 2.02 0.00 0 100 0.25
SITE Σ 6.49 17.74 24.23 27 73 0.44
Basin
Impervious
"C"
Pervious "C" A, Imp (ac) A, Perv (ac) A, total (ac) % Imp % Perv
Composite
"C"
A1 0.95 0.25 0.67 0.00 0.67 100 0 0.95
A2 0.95 0.25 0.05 0.20 0.25 19 81 0.38
A3 0.95 0.25 0.76 0.00 0.76 100 0 0.95
A4 0.95 0.25 0.07 2.18 2.26 3 97 0.27
A5 0.95 0.25 0.31 0.00 0.31 100 0 0.95
A6 0.95 0.25 0.09 1.70 1.79 5 95 0.29
A7 0.95 0.25 0.45 2.06 2.51 18 82 0.38
A8 0.95 0.25 0.19 0.03 0.22 88 12 0.86
A9 0.95 0.25 0.13 0.03 0.15 83 17 0.83
A10 0.95 0.25 0.16 0.03 0.19 86 14 0.85
A11 0.95 0.25 0.22 2.18 2.40 9 91 0.31
B1 0.95 0.25 0.00 0.09 0.09 0 100 0.25
B2 0.95 0.25 0.30 0.72 1.02 29 71 0.45
B3 0.95 0.25 0.46 1.35 1.81 25 75 0.43
B4 0.95 0.25 0.23 0.32 0.55 42 58 0.54
B5 0.95 0.25 0.07 0.18 0.25 27 73 0.44
B6 0.95 0.25 0.19 0.60 0.79 24 76 0.42
B7 0.95 0.25 0.19 0.47 0.66 28 72 0.45
C1 0.95 0.25 0.90 0.12 1.02 88 12 0.87
C2 0.95 0.25 0.05 1.57 1.62 3 97 0.27
CUB
BUILDING 4
BUILDING 4
FAB
EXISTING FAB
BUILDING 2
CHEMICAL
BUILDING
CHEM
BLDG
EXIST
EXIST
CHEM BLDG
PIV DETAIL (NTS)
0.00 4.00 8.00 12.00 16.00 20.00 24.00 28.00 32.00 36.00
4912.20
4912.50
4912.80
4913.10
4913.40
4913.70
4914.00
4914.30
4914.60
HGL
EGL
Project Description
Friction Method Manning Formula
Solve For Discharge
Input Data
Roughness Coefficient 0.013
Channel Slope 0.00500 ft/ft
Normal Depth 0.50 ft
Bottom Width 3.00 ft
Rating Curve Plot
CONCRETE CHANNEL CAPACITY
3/22/2013 4:39:06 PM
Bentley Systems, Inc. Haestad Methods Solution Bentley Center 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 1
Project Description
Solve For Discharge
Input Data
Headwater Elevation 4.00 ft
Crest Elevation 2.90 ft
Tailwater Elevation 0.00 ft
Weir Coefficient 3.00 US
Crest Length 2.00 ft
Number Of Contractions 0
Rating Curve Plot
ROCK BOX - RATING CURVE FOR 100-YR WEIR
3/22/2013 1:19:17 PM
Bentley Systems, Inc. Haestad Methods Solution Bentley Center 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 1
Project Description
Solve For Discharge
Input Data
Headwater Elevation 4.00 ft
Centroid Elevation 0.08 ft
Tailwater Elevation 0.00 ft
Discharge Coefficient 0.60
Opening Area 2.75 in²
Rating Curve Plot
ROCK BOX - RATING CURVE FOR WATER QUALITY PLATE
3/22/2013 1:20:30 PM
Bentley Systems, Inc. Haestad Methods Solution Bentley Center 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 1
WSEL WQ 1 WQ 2 WQ 3 WQ 4 WQ 5 WQ 6 WQ 7 WQ 8 WQ 9 WQ 10 WQ 11 WEIR COMPOSITE
0.00 0.00
0.05 0.00
0.10 0.012999 0.01
0.15 0.024319 0.02
0.20 0.03184 0.03
0.25 0.037898 0.04
0.30 0.043112 0.04
0.35 0.047761 0.012999 0.06
0.40 0.051995 0.024319 0.08
0.45 0.05591 0.03184 0.09
0.50 0.059568 0.037898 0.10
0.55 0.063014 0.043112 0.11
0.60 0.066281 0.047761 0.012999 0.13
0.65 0.069395 0.051995 0.024319 0.15
0.70 0.072374 0.05591 0.03184 0.16
0.75 0.075236 0.059568 0.037898 0.17
0.80 0.077993 0.063014 0.043112 0.18
0.85 0.080656 0.066281 0.047761 0.012999 0.21
0.90 0.083233 0.069395 0.051995 0.024319 0.23
0.95 0.085733 0.072374 0.05591 0.03184 0.25
1.00 0.088162 0.075236 0.059568 0.037898 0.26
1.05 0.090526 0.077993 0.063014 0.043112 0.27
1.10 0.09283 0.080656 0.066281 0.047761 0.012999 0.30
1.15 0.095078 0.083233 0.069395 0.051995 0.024319 0.32
1.20 0.097274 0.085733 0.072374 0.05591 0.03184 0.34
1.25 0.099422 0.088162 0.075236 0.059568 0.037898 0.36
1.30 0.101524 0.090526 0.077993 0.063014 0.043112 0.38
1.35 0.103584 0.09283 0.080656 0.066281 0.047761 0.012999 0.40
1.40 0.105603 0.095078 0.083233 0.069395 0.051995 0.024319 0.43
1.45 0.107584 0.097274 0.085733 0.072374 0.05591 0.03184 0.45
1.50 0.10953 0.099422 0.088162 0.075236 0.059568 0.037898 0.47
1.55 0.111442 0.101524 0.090526 0.077993 0.063014 0.043112 0.49
1.60 0.113321 0.103584 0.09283 0.080656 0.066281 0.047761 0.012999 0.52
1.65 0.11517 0.105603 0.095078 0.083233 0.069395 0.051995 0.024319 0.54
1.70 0.116989 0.107584 0.097274 0.085733 0.072374 0.05591 0.03184 0.57
1.75 0.118781 0.10953 0.099422 0.088162 0.075236 0.059568 0.037898 0.59
1.80 0.120546 0.111442 0.101524 0.090526 0.077993 0.063014 0.043112 0.61
1.85 0.122286 0.113321 0.103584 0.09283 0.080656 0.066281 0.047761 0.012999 0.64
1.90 0.124001 0.11517 0.105603 0.095078 0.083233 0.069395 0.051995 0.024319 0.67
1.95 0.125693 0.116989 0.107584 0.097274 0.085733 0.072374 0.05591 0.03184 0.69
2.00 0.127362 0.118781 0.10953 0.099422 0.088162 0.075236 0.059568 0.037898 0.72
2.05 0.12901 0.120546 0.111442 0.101524 0.090526 0.077993 0.063014 0.043112 0.74
2.10 0.130637 0.122286 0.113321 0.103584 0.09283 0.080656 0.066281 0.047761 0.012999 0.77
2.15 0.132243 0.124001 0.11517 0.105603 0.095078 0.083233 0.069395 0.051995 0.024319 0.80
2.20 0.133831 0.125693 0.116989 0.107584 0.097274 0.085733 0.072374 0.05591 0.03184 0.83
2.25 0.1354 0.127362 0.118781 0.10953 0.099422 0.088162 0.075236 0.059568 0.037898 0.85
2.30 0.136951 0.12901 0.120546 0.111442 0.101524 0.090526 0.077993 0.063014 0.043112 0.87
2.35 0.138485 0.130637 0.122286 0.113321 0.103584 0.09283 0.080656 0.066281 0.047761 0.012999 0.91
2.40 0.140002 0.132243 0.124001 0.11517 0.105603 0.095078 0.083233 0.069395 0.051995 0.024319 0.94
2.45 0.141502 0.133831 0.125693 0.116989 0.107584 0.097274 0.085733 0.072374 0.05591 0.03184 0.97
2.50 0.142987 0.1354 0.127362 0.118781 0.10953 0.099422 0.088162 0.075236 0.059568 0.037898 0.99
2.55 0.144457 0.136951 0.12901 0.120546 0.111442 0.101524 0.090526 0.077993 0.063014 0.043112 1.02
2.60 0.145911 0.138485 0.130637 0.122286 0.113321 0.103584 0.09283 0.080656 0.066281 0.047761 0.012999 1.05
2.65 0.147352 0.140002 0.132243 0.124001 0.11517 0.105603 0.095078 0.083233 0.069395 0.051995 0.024319 1.09
2.70 0.148778 0.141502 0.133831 0.125693 0.116989 0.107584 0.097274 0.085733 0.072374 0.05591 0.03184 1.12
2.75 0.150191 0.142987 0.1354 0.127362 0.118781 0.10953 0.099422 0.088162 0.075236 0.059568 0.037898 1.14
2.80 0.151591 0.144457 0.136951 0.12901 0.120546 0.111442 0.101524 0.090526 0.077993 0.063014 0.043112 1.17
2.85 0.152978 0.145911 0.138485 0.130637 0.122286 0.113321 0.103584 0.09283 0.080656 0.066281 0.047761 1.19
2.9 0.154352 0.147352 0.140002 0.132243 0.124001 0.11517 0.105603 0.095078 0.083233 0.069395 0.051995 1.22
ROCK BOX - COMPOSITE OUTLET RATING CURVE
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00
HEAD (FT)
DISCHARGE (CFS)
Project Description
Solve For Headwater Elevation
Input Data
Discharge 7.00 ft³/s
Headwater Elevation 0.44 ft
Crest Elevation 0.25 ft
Tailwater Elevation 0.00 ft
Crest Surface Type Gravel
Crest Breadth 0.50 ft
Crest Length 27.00 ft
Cross Section Image
LEVEL SPREADER WEIR
3/22/2013 5:01:31 PM
Bentley Systems, Inc. Haestad Methods Solution Bentley Center 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 1
Sheet 1 of 1
Designer:
Company:
Date:
Project:
Location:
1. Design Discharge
A) 2-Year Peak Flow Rate of the Area Draining to the Grass Buffer Q2
= 2.0 cfs
2. Minimum Width of Grass Buffer WG
= 40 ft
3. Length of Grass Buffer (14' or greater recommended) LG
= 15 ft
4. Buffer Slope (in the direction of flow, not to exceed 0.1 ft / ft) SG
= 0.100 ft / ft
5. Flow Characteristics (sheet or concentrated)
A) Does runoff flow into the grass buffer across the
entire width of the buffer?
B) Watershed Flow Length FL
= ft
C) Interface Slope (normal to flow) SI
= ft / ft
D) Type of Flow CONCENTRATED FLOW
Sheet Flow: FL
* SI
< 1
Concentrated Flow: FL
* SI
> 1
6. Flow Distribution for Concentrated Flows
7 Soil Preparation
(Describe soil amendment)
8 Vegetation (Check the type used or describe "Other")
9. Irrigation
(*Select None if existing buffer area has 80% vegetation
AND will not be disturbed during construction.)
10. Outflow Collection (Check the type used or describe "Other")
Notes:
FORT COLLINS, CO
PER LANDSCAPE
40' LEVEL SPREADER TO BE USED TO DISTRIBUTE FLOW
ACROSS GRASS BUFFER
Design Procedure Form: Grass Buffer (GB)
BMS
MARTIN/MARTIN, INC.
AVAGO BLDG 4 EXPANSION
March 22, 2013
Existing Xeric Turf Grass
Irrigated Turf Grass
Other (Explain):
Choose One
Choose One
Grass Swale
Street Gutter
Storm Sewer Inlet
Other (Explain):
None (sheet flow)
Slotted Curbing
Level Spreader
Choose One
Sheet 1 of 1
Designer:
Company:
Date:
Project:
Location:
1. Design Discharge for 2-Year Return Period Q2
= 6.04 cfs
2. Hydraulic Residence Time
A) : Length of Grass Swale LS
= 462.0 ft
B) Calculated Residence Time (based on design velocity below) THR
= 9.1 minutes
3. Longitudinal Slope (vertical distance per unit horizontal)
A) Available Slope (based on site constraints) Savail
= 0.003 ft / ft
B) Design Slope SD
= 0.003 ft / ft
4. Swale Geometry
A) Channel Side Slopes (Z = 4 min., horiz. distance per unit vertical) Z = 10.00 ft / ft
B) Bottom Width of Swale (enter 0 for triangular section) WB
= 5.00 ft
5. Vegetation
A) Type of Planting (seed vs. sod, affects vegetal retardance factor)
6. Design Velocity (1 ft / s maximum) V2
= 0.85 ft / s
7. Design Flow Depth (1 foot maximum) D2
= 0.63 ft
A) Flow Area A2
= 7.1 sq ft
B) Top Width of Swale WT
= 17.6 ft
C) Froude Number (0.50 maximum) F = 0.24
D) Hydraulic Radius RH
= 0.40
E) Velocity-Hydraulic Radius Product for Vegetal Retardance VR = 0.34
F) Manning's n (based on SCS vegetal retardance curve E for seeded grass) n = 0.052
G) Cumulative Height of Grade Control Structures Required HD
= 0.10 ft
AN UNDERDRAIN IS
8. Underdrain REQUIRED IF THE
(Is an underdrain necessary?) DESIGN SLOPE < 2.0%
9. Soil Preparation
(Describe soil amendment)
10. Irrigation
Notes:
PER LANDSCAPE
Design Procedure Form: Grass Swale (GS)
BMS
MARTIN/MARTIN, INC.
March 22, 2013
AVAGO BLDG 4 EXPANSION
FORT COLLINS, CO
Choose One
Temporary Permanent
Choose One
Grass From Seed Grass From Sod
Choose One
YES NO
UD-BMP_v3.02.xls, GS 3/22/2013, 5:29 PM
Other (Explain):
Choose One
Yes No
Choose One
Permanent
None*
Temporary
UD-BMP_v3.02.xls, GB 3/22/2013, 5:22 PM
2.95 0.155715 0.148778 0.141502 0.133831 0.125693 0.116989 0.107584 0.097274 0.085733 0.072374 0.05591 0.067082 1.31
3 0.157065 0.150191 0.142987 0.1354 0.127362 0.118781 0.10953 0.099422 0.088162 0.075236 0.059568 0.189737 1.45
3.05 0.158404 0.151591 0.144457 0.136951 0.12901 0.120546 0.111442 0.101524 0.090526 0.077993 0.063014 0.348569 1.63
3.1 0.159732 0.152978 0.145911 0.138485 0.130637 0.122286 0.113321 0.103584 0.09283 0.080656 0.066281 0.536656 1.84
3.15 0.161049 0.154352 0.147352 0.140002 0.132243 0.124001 0.11517 0.105603 0.095078 0.083233 0.069395 0.75 2.08
3.2 0.162355 0.155715 0.148778 0.141502 0.133831 0.125693 0.116989 0.107584 0.097274 0.085733 0.072374 0.985901 2.33
3.25 0.163651 0.157065 0.150191 0.142987 0.1354 0.127362 0.118781 0.10953 0.099422 0.088162 0.075236 1.242377 2.61
3.3 0.164937 0.158404 0.151591 0.144457 0.136951 0.12901 0.120546 0.111442 0.101524 0.090526 0.077993 1.517893 2.91
3.35 0.166212 0.159732 0.152978 0.145911 0.138485 0.130637 0.122286 0.113321 0.103584 0.09283 0.080656 1.811215 3.22
3.4 0.167478 0.161049 0.154352 0.147352 0.140002 0.132243 0.124001 0.11517 0.105603 0.095078 0.083233 2.12132 3.55
3.45 0.168735 0.162355 0.155715 0.148778 0.141502 0.133831 0.125693 0.116989 0.107584 0.097274 0.085733 2.447346 3.89
3.5 0.169982 0.163651 0.157065 0.150191 0.142987 0.1354 0.127362 0.118781 0.10953 0.099422 0.088162 2.788548 4.25
3.55 0.17122 0.164937 0.158404 0.151591 0.144457 0.136951 0.12901 0.120546 0.111442 0.101524 0.090526 3.144281 4.62
3.6 0.172449 0.166212 0.159732 0.152978 0.145911 0.138485 0.130637 0.122286 0.113321 0.103584 0.09283 3.513972 5.01
3.65 0.173669 0.167478 0.161049 0.154352 0.147352 0.140002 0.132243 0.124001 0.11517 0.105603 0.095078 3.897114 5.41
3.7 0.174881 0.168735 0.162355 0.155715 0.148778 0.141502 0.133831 0.125693 0.116989 0.107584 0.097274 4.293251 5.83
3.75 0.176085 0.169982 0.163651 0.157065 0.150191 0.142987 0.1354 0.127362 0.118781 0.10953 0.099422 4.701968 6.25
3.8 0.17728 0.17122 0.164937 0.158404 0.151591 0.144457 0.136951 0.12901 0.120546 0.111442 0.101524 5.12289 6.69
3.85 0.178468 0.172449 0.166212 0.159732 0.152978 0.145911 0.138485 0.130637 0.122286 0.113321 0.103584 5.555673 7.14
3.9 0.179647 0.173669 0.167478 0.161049 0.154352 0.147352 0.140002 0.132243 0.124001 0.11517 0.105603 6 7.60
3.95 0.180819 0.174881 0.168735 0.162355 0.155715 0.148778 0.141502 0.133831 0.125693 0.116989 0.107584 6.455579 8.07
4 0.181983 0.176085 0.169982 0.163651 0.157065 0.150191 0.142987 0.1354 0.127362 0.118781 0.10953 6.922138 8.56
C3 0.95 0.25 0.29 1.68 1.97 15 85 0.35
C4 0.95 0.25 0.00 0.69 0.69 0 100 0.25
OS-A 0.95 0.25 0.57 1.68 2.25 26 74 0.43
SITE Σ 6.35 17.89 24.24 26 74 0.43
BLDG 4 EXPANSION
13.0091
5/9/2013
BLDG 4 REPORT APPROVED BASINS WITHIN PROPOSED DEVELOPMENT
PROPOSED BASINS WITHIN DEVELOPMENT
5:05 PM5/9/2013 APPROVED BASIN COMPOSITE.xls
B. SMITH
MARTIN/MARTIN INC.
(IN/HR)
Q
(CFS)
( )
( ) 0 .786
10
28 . 5 1
c
t
P
I
+
= ×
100-YEAR
5/9/2013 5:04 PM
G:\SCHLAGETER\13.0091-Avago Bldg 4 Expansion and Site Develoment\ENG\DRAINAGE\RATIONAL METHOD\RATIONAL METHOD.xls
(IN/HR)
Q
(CFS)
( )
( ) 0 .786
10
28 . 5 1
c
t
P
I
+
= ×
2-YEAR
5/9/2013 5:04 PM
G:\SCHLAGETER\13.0091-Avago Bldg 4 Expansion and Site Develoment\ENG\DRAINAGE\RATIONAL METHOD\RATIONAL METHOD.xls
(RATIONAL METHOD PROCEDURE)
TIME OF CONCENTRATION SUMMARY
13.0091
AVAGO
STANDARD FORM SF-2
TOC
5/9/2013 5:04 PM
G:\SCHLAGETER\13.0091-Avago Bldg 4 Expansion and Site Develoment\ENG\DRAINAGE\RATIONAL METHOD\RATIONAL METHOD.xls
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
C1
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
B7
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
B6
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
B5
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
B4
IMPERVIOUS
PERVIOUS
SUB-BASIN SURFACE CHARACTERISTICS
5/9/2013 5:04 PM
COMPOSITE_C-VALUES
G:\SCHLAGETER\13.0091-Avago Bldg 4 Expansion and Site Develoment\ENG\DRAINAGE\RATIONAL METHOD\RATIONAL METHOD.xls
SUB-BASIN
SUB-BASIN SURFACE CHARACTERISTICS
PERCENT
IMPERVIOUSNESS
A7
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS
PERCENT
IMPERVIOUSNESS
A8
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS
PERCENT
IMPERVIOUSNESS
A9
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS
PERCENT
IMPERVIOUSNESS
A10
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS
SUB-BASIN COMPOSITE
COMPOSITE RUNOFF COEFFICIENTS PERCENT
IMPERVIOUSNESS
A11
IMPERVIOUS
PERVIOUS
5/9/2013 5:04 PM
COMPOSITE_C-VALUES
G:\SCHLAGETER\13.0091-Avago Bldg 4 Expansion and Site Develoment\ENG\DRAINAGE\RATIONAL METHOD\RATIONAL METHOD.xls
A1
IMPERVIOUS
IMPERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
A2
IMPERVIOUS
PERVIOUS
SURFACE CHARACTERISTICS
PERCENT
IMPERVIOUSNESS
A3
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS
PERCENT
IMPERVIOUSNESS
A4
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS
PERCENT
IMPERVIOUSNESS
A5
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
SUB-BASIN SURFACE CHARACTERISTICS
COMPOSITE RUNOFF COEFFICIENTS
PERCENT
IMPERVIOUSNESS
A6
IMPERVIOUS
PERVIOUS
SUB-BASIN COMPOSITE
COMPOSITE RUNOFF COEFFICIENTS
5/9/2013 5:04 PM
COMPOSITE_C-VALUES
G:\SCHLAGETER\13.0091-Avago Bldg 4 Expansion and Site Develoment\ENG\DRAINAGE\RATIONAL METHOD\RATIONAL METHOD.xls
Based primarily on data from the
International Stormwater BMP Database
(www.bmpdatabase.org).
Q2 = 2-year peak runoff (cfs)
3. Length: The recommended length (L), the distance along
the sheet flow direction, should be a minimum of 14 feet.
This value is based on the findings of Barrett et al. 2004 in
Stormwater Pollutant Removal in Roadside Vegetated
Strips and is appropriate for buffers with greater than 80%
vegetative cover and slopes up to 10%. The study found
that pollutant removal continues throughout a length of 14 feet. Beyond this length, a point of
diminishing returns in pollutant reduction was found. It is important to note that shorter lengths or
slightly steeper slopes will also provide some level of removal where site constraints dictate the
geometry of the buffer.
3
Based primarily on data from the
International Stormwater BMP Database
(www.bmpdatabase.org).