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PIPING DESIGN LAYOUT TRAININGLESSON 6
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8. UNDERGROUND
8.1 PREFACE
This lesson will cover the procedures required for underground
studies. Two things to keep in mind;first, use Fluor standards as a
guide, and second, the guidelines mentioned in this lesson may
bedifferent than jobs you may have worked on in the past. Some
clients have their own engineeringstandards.
8.1.1 Lesson Objectives
Lessons provide self-directed piping layout training to
designers who have basic piping design skills.Training material can
be applied to manual or electronic applications. Lesson objectives
are:
• To know the types of underground systems.
• To know how to make underground studies avoiding major
mistakes and costly changes.
• To familiarize you with Fluor standards. (Fluor standards are
a guide. The standards used onyour contract may differ.)
8.1.2 Lesson Study Plan
Take the time to familiarize yourself with the lesson sections.
The following information will be requiredto support your
self-study:
• Your copy of the Reference Data Book (R.D.B.)• Fluor Technical
Practices. The following Technical Practices support this
lesson:
000.210.1150000.210.1160000.210.1200000.210.1210000.210.1211000.250.2040
If you have layout questions concerning this lesson your
immediate supervisor is available to assistyou. If you have general
questions about the lesson contact Piping Staff Group.
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8.1.3 Study Aids
Videos on Piping Design Layout Practices supplement your
training. It is suggested that you view thesevideos prior to
starting the layout training. You may check out a copy of the
videos from the KnowledgeCentre (Library).
8.1.4 Proficiency Testing
You will be tested on your comprehension of this lesson.
Proficiency testing will be scheduled three tofour times a year.
Piping Staff will notify you of the upcoming testing schedule.
• Questions are manual fill-in, True-False and short essay
(bring a pencil).• The test should take approximately one hour.•
You may use your layout training Reference Data Book and material
from previous layout training
lessons during the test.• The test facilitator will review your
test results with you at a later date.• Test results will be given
to Piping Staff.
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PIPING DESIGN LAYOUT TRAININGLESSON 6
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8.2 TECHNICAL DUTIES OF LAYOUT PERSON
Develops the following specifications, in accordance with
contract requirements and TechnicalPractices 000.250.1938 and
000.250.1939.
• Gravity sewers - design, layout and testing
• Plant and unit firewater systems. Prepares fire protection
system layouts and data and attendsmeetings pertaining to it.
• Advises general piping supervisor as to the need for any
additional specifications relating tounderground piping by
Civil.
• Reviews piping material specifications and recommends
additions, deletions or changes based ondesign requirements.
Initiates action for the development of purchase descriptions for
anyunderground items that are normally not covered in the piping
material specifications.
• Develops and/or directs the development of the underground
piping standard details, consistentwith contract and material
requirements.
• Develops and/or directs the development of unit underground
layouts and insures they reflect thejob philosophy. Assembles data
and calculations relating to the sizing of the unit sewer
systems.
• Maintains underground workbooks: collections of vital data
relating to the design of U/G systems.
• Coordinates underground piping with other groups and
establishes a two-way flow of information.
• Represents general piping in meetings with vendor, clients,
engineering and other internal groups.
8.2.1 Underground Systems Work Book
It is the responsibility of the underground layout person to
develop and maintain an undergroundsystems work book that
contains:• Schedules• Narrative underground specifications.•
Applicable sections of codes having jurisdiction.
• Piping material information and specifications.• Process data
(P&ID's, flow conditions, quantities and temperature).• Job
instructions and design memos relating to underground piping.•
Calculations and sketches.• Notes on interface meetings.• Questions
and answers.
The above contents are considered minimum and other topics may
be added as necessary
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8.2.2 Prerequisites to Start Underground Piping Layout and
Design
ITEM SOURCE
1. Meteorological Data, Rainfall, Frost Depth Basic Jobsite
Questionnaire 2. Existing Obstructions Client Via Project Manager
3. Sewer Systems, Segregation Process Engineer 4. Soil Conditions
Structural Engineer 5. Paving Structural Engineer 6. Clients Design
Requirements Project Manager 7. Federal, State and Local Codes
Project Manager
Additional Information 8. Schedule Piping Supervisor *9.
Approved Plot Plan(s) Piping Supervisor
10.00 P&ID's Piping Supervisor +11 Preliminary Foundation
Design Sketches Structural Engineer
12. Process Drainage Rates, Temperaturesand Intermittent or
Continuous
Process Engineer
13. Piping Materials Specifications Piping Materials Engineer
14. Fire System Capacity (in spec.) Process Engineer 15. Site
Preparation Drawings Structural Engineer 16. Decision on Location
of Cooling Water
System (above or below ground)Project
* May not be available at start of layout (use best available
info).+ Discuss approximate size with Structural Engineer.
8.3 UNDERGROUND PIPING MATERIALS
Purpose
The purpose of this guide material is to provide the designer
with information relating to some of themore commonly used
underground pipe and fittings.
Scope
The list that follows is for information only and gives the
A.S.T.M. or A.W.W.A. specification reference,size range, and normal
use for each type. For additional information the designer should
refer to thespecifications or manufacturer's catalogs that are
listed. The designer needs to work with the materialengineer for
material selection on the project.
Selection of Pipe
Selection of pipe for underground service depends upon pressure,
temperature, commodity, durability,cost, availability, and client
requirements.
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PIPING DESIGN LAYOUT TRAININGLESSON 6
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8.3.1 Vitrified Clay Pipe
Vitrified clay pipe (standard and extra strength, A.S.T.M.
C-700) is used for gravity pipinghandling surface drainage and
process drainage when this piping is not under concrete pavingor
buildings. It is also used for sanitary sewage to within 5 feet of
an outside wall of a buildingwhere there is no paving and for acid
sewers with acid proof cement joints.
It is available in extra strength in the following sizes:
4"-6"-8"-10"-12"-15"-18"-21"-24"-27"-30"-33"- 36". Joint lengths
vary per manufacturer, but are approx. in 2' or 3' lengths in sizes
up to12" and 3' to 5' lengths in sizes 15" through 36". (Catalogs:
Cantex, Interpace)
8.3.2 Cast Iron Soil Pipe
Cast iron soil pipe (A.S.T.M. A-74) is used for gravity piping
handling surface drainage, processdrainage or sanitary sewage under
concrete paving or buildings. It is available in
2"-3"-4"-5"-6"-8"-10" -12"-15" sizes. Joint lengths available in 5'
& 10' lengths. (Catalogues: Tyler, Cal-Alabama, Rich
Manufacturing).
8.3.3 Cast Iron Water or Pressure Pipe
Cast iron water pipe (A.W.W.A. C-106, 108 & 110) is used for
pressure or sewer systems wherelong runs with few branches are
required. Pipe & A.W.W.A. fittings are available in sizes
2"through 48". Joint lengths vary from 12' to 18' depending upon
the manufacturer. (Catalogs:U.S. Pipe, Mead Pipe.)
8.3.4 Asbestos Cement Pipe (Transite Pipe) (Reference only no
longer used)
Asbestos cement pipe (A.W.W.A. C-400) in conjunction with cast
iron fittings was used forpressurized water service. It had the
advantage of lower installed cost than most other pipingmaterials,
but would not be used in congested areas where it is susceptible to
damage.Available sizes were
4"-6"-8"-10"-12"-14"-16"-18"-20"-24"-30"-36" in pressure classes
100, 150and 200. (Catalogs: Johns-Mansville, Certain-teed.)
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PIPING DESIGN LAYOUT TRAININGLESSON 6
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FIGURE 8-1
FIGURE 8-2
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8.4 DESIGN CONSIDERATIONS
8.4.1 Settlement
The following list identifies problems created by differential
settlement together withrecommended solutions. The degree of the
problem should be determined by discussions withthe Structural
Engineer and a review of the soil report.
Sewer lines connected to manholes -- differential settling of
the manhole and the sewer sometimesbreaks the sewer pipe. A pipe
joint just outside the manhole lessens this danger. If the soil
conditionsare unstable or a high water table could leach sand
bedding out from under the pipe a second jointwithin three feet of
the first should be provided. In these situations cast iron pipe
should be used inplace of vitrified clay pipe. The joints must be
flexible such as a compression joint, mechanical joint, oreven a
lead joint is considered flexible.
Differential settlement involving cooling water branch lines
between large cooling water headers, whichcould settle and
exchangers on piled foundation which may not, could over stress the
piping. Thisproblem can be remedied by locating the headers so that
the branch lines are at least 10 feet long andproviding flexible
connectors (Dresser, Smith-Blair, etc.) at either end of the branch
for steel pipe, or byusing mechanical joints for cast iron
pipe.
For other types of settlement problems these methods just
described should provide a remedy.
Unstable bedding -- when the bottom of the trench is not
sufficiently stable or firm, to prevent vertical orlateral
displacement of the pipe after installation a non-yielding
foundation must be designed.
8.4.2 Crushed rock
The simplest supplementary foundation is to excavate native soil
below grade of bedding material andreplace with a layer of broken
stone, crushed rock, or other coarse aggregate that may produce
thedesired stability under conditions where the instability is only
slight.
8.4.3 Encasement
Under conditions where an extremely unstable area is to be
crossed, and that area represents a veryshort length of line, it is
possible to reinforce the pipe by full concrete encasement and
adequatereinforcing steel to produce a rigid beam.
8.4.4 Piling
In some instances, lines must be constructed for considerable
distances in areas generally subject tosubsidence, and
consideration should be given to constructing them on a timber
platform or reinforcedconcrete cradle supported by piping. Supports
should be adequate to sustain the weight of the fullsewer and
backfill.
The details and requirements for the above should be worked out
in conjunction with the StructuralEngineer based on the
recommendations of the soil report.
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8.4.5 Angle of Repose
Underground lines installed below adjacent foundations should
not undermine the 45o angle of reposeof the foundation (See Figure
# 8-3). Where there is no obvious solution consult with the
StructuralEngineer to see if the actual conditions permit a steeper
angle. It may also be possible to brace thetrench if equipment has
been set, and to protect the pipe against loads by encasement.
FIGURE # 8-3
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8.4.6 Breakage
Precautions must be taken to prevent breakage of pipe due to
construction and maintenanceequipment traffic.
Depth of cover for protection against surface loads is covered
in another section.
Guard posts are provided to protect the above ground features of
the firewater system.
Cleanouts in vitrified clay systems are subject to breakage,
particularly in offsite areas. Wherecleanouts are thus exposed,
protective structures similar to those for the firewater system, as
well asconcrete cradles, must be detailed. Notes on offsite
drawings should state, "INSTALLATION OFCLEANOUTS SHOULD NOT BE
COMPLETED UNTIL PROTECTION SHOWN ON DETAILDRAWING CAN BE
PROVIDED".
Use Cast Iron adjacent to manhole to avoid breakage caused by
differential settlement of loss ofbedding in high water table (See
Figure #8-4).
FIGURE # 8-4
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8.4.7 Stub-Ups
Stub-ups are used to connect underground lines carrying water,
steam, air process liquids and the likewith above ground
facilities. Flanged and welded underground lines should terminate
18 inches abovehigh point finish surface with a flame cut end. The
above ground spool should indicate bevel end orface of flange at
12" above H.P.F.S. (See Figure #8-5). This will permit field
fit-up.
Cathodic protection may be required depending on the soil
conditions.
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8.5 SYSTEM SAFETY CONSIDERATIONS
8.5.1 Purpose of Seals
Seals play a vital role in maintaining safe operation of a
process plant sewer system. Undernormal conditions, sewers are only
partially filled because flow rates are designed for storm
orfirewater quantities. The large vapor spaces in process plant
sewers will frequently containflammable vapors. Liquid seals form
vapor barriers and prevent flame fronts or explosions fromrunning
the full length of the sewer system. Without a sealed sewer system,
a fire in one areacould ignite vapors in a catch basin, which could
flash through the sewer to initiate a fire atsome other
location.
Seals also prevent the release of vapors or gases to the
atmosphere at grade level where theycould create a hazard or
contribute fuel to a fire.
8.5.2 Location of Seals
Catch Basins
Catch basins discharging to any sewers that have the possibility
of containing flammable orhydrocarbon vapors are isolated from the
lateral by one of the following:
(a) Providing an outlet seal at the line where it leaves the
catch basin (See Figure # 8-6a).
(b) Routing the outlet line to a manhole or adjacent catch basin
and providing an inlet seal atthe point of entry (Figure #
8-6b).
Manholes
Laterals leaving a unit are isolated from main or trunk sewers
by providing manholes at junction pointsand routing the lateral
into the manhole at a sealed inlet (Figure # 8-6b).
The plant main sewer may be sectionalized by providing sealed
inlets at those manholes that wouldenable isolation of major
process area groups, storage areas, treatment areas, marine
terminals, etc.Baffle type manholes serve this purpose on larger
sewer runs (Figure # 8-6c).
Drains and Funnels
Groups of drain funnels in fairly close proximity, say up to 30'
apart, are connected to a single branchline which is isolated from
the rest of the system by running it to a catch basin or manhole
and providingan inlet seal at the point of entry.
Generally funnels serving pumps are isolated from the other
funnels on the branch by providing arunning trap between the pump
funnels (Figure # 8-6d).
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Where a sewer system must handle toxic or extremely hazardous
material, each funnel is provided witha "P" trap type seal (See Fig
# 8-6e), and the branch line is connected to the lateral at an
inlet sealedmanhole.
Where a funnel is located close, say within 10' of the catch
basin it is connected to, an inlet seal is notrequired, since a
fire can travel above ground as easily as through the sewer.
8.5.3 Types of Seals
FIGURE # 8-6
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8.5.4 Venting
Sewers in general are designed for gravity flow. In a sealed
system (i.e. without vents), a rise in waterlevel would reduce the
vapor space and cause an increase in pressure. This would reduce
the designcapacity of the sewer. Therefore vents are necessary to
prevent vapor lock and to release vapors to asafe location.
Vents serve to prevent rapid pressure buildup in the sewer
should hot commodities or water enter thesewer and vaporize any
liquid hydrocarbons present.
8.5.5 Location of Vents
Vents are provided at every manhole where the inlet line is
liquid sealed so as to prevent venting to thenext upstream
manhole.
The highest manhole in a system is provided with a vent.
Both chambers of a baffle sealed manhole are provided with
vents.
See the design specification for additional information.
8.6 ON-SITE UNDERGROUND LAYOUT
The purpose of this guide material is to provide the layout
designer with instructions and a standardizedapproach to the layout
of the Underground Piping Systems within a unit.
Scope
This instruction covers the step by step development of the
underground systems layout and points outcritical items with
respect to the design.
General
Specifications covering the layout and design of sewer and
firewater systems are normally prepared foreach contract. These
specifications must be carefully followed as they provide the basis
for design.
8.6.1 Drainage Areas
In process or operating areas, the distance a liquid spill must
travel across the pavement to a catchbasin should be kept to a
minimum. Concrete paved areas are subdivide into drainage areas,
normally3600 sq. ft. (See contract specifications.) Each drainage
area is bounded by a high perimeter anddrains to a catch basin
located at a low point. Figure 8-7.
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PIPING DESIGN LAYOUT TRAININGLESSON 6
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See Figure 8-7.
8.6.2 Drainage Area Sizing Guide
Figure #8-8 may be used as a guide to make a quick evaluation of
the minimum and maximumdrainage area sizes and catch basin
locations based on maintaining required paving slopes at
variousdrops in paving from high to low point.
Drainage areas are based on two considerations: The elevation
difference between high and lowpoints, and the prevention of fire
flow and process spills flowing between adjacent areas. Ideally,
adrainage area should be about 50 to 60 feet square, draining to a
catch basin at or near the center.Equipment requiring curbed areas
shall be noted on the P&ID's or defined in the job
specifications.w
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FIGURE # 8-8
8.6.3 Guidelines
Locate the high point of paving: at perimeter of concrete paving
or edge of road.
at edge of buildings
along major access ways around heater areas, to direct
spillageaway from heater and other equipment.
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When locating catch basins give consideration to the
following:
• locate near center of drainage area if possible.
• do not locate under equipment or piping manifolds.
• do not locate at building entrances or ladder and stairway
landings.
• keep at least five feet clear of equipment work areas, such as
alongside of pumps.
8.6.4 Preliminary Work
In order to avoid design and construction problems resulting
from interferences the following items areshown on the layout.
• Existing concrete obstructions (foundations, sumps, etc.).
• Existing underground electrical ducts and piping systems.
Foundations of columns, heaters, pumps, structures and pipe
supports should be indicated based onwhatever information the
Structural Engineer can provide (or your best guess). Foundation
depths andthickness have an important bearing on the routing of
underground piping (structural engineering. willadvise).
8.6.5 Paving and Surface Drainage
Perimeter of concrete paving to encompass all equipment within
unit area. Paving perimeter isnormally five feet beyond the
furthest projecting equipment. In the interest of economy this
outer limitmay be staggered to suit groups of equipment which do
not project as far. (Keeping the jogs to aminimum.) Drainage
outside the perimeter of the concrete paving is by Civil.
NOTE: Job specifications may dictate that certain equipment
groups handling gases or liquidsthat vaporize at ambient
temperatures may not require concrete paving.
Types and characteristics of paving (verify with your
Civil/Structural Eng.)
• Concrete, 6" thick Process liquid spills truck traffic.•
Concrete, 4" thick Process liquid spills, no truck traffic.•
Asphalt, 3" thick Primary roads.• Asphalt, 2" thick Secondary
roads, general paving and parking areas.• Crushed rock - 3" deep
General area cover.• Concrete sidewalks - 4" thick 3'- 0" wide,
raised 1" above adjacent finished surface.
Paving slope - Minimum 1/8"/ft.
Maximum 1/2"/ft.
Verify with your Civil/Structural engineer
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8.6.6 Types of Catch Basins
Figure 8-9 illustrates four basic types of catch basins and
drain boxes.
• Concrete box per job standards, precast or poured-in-place are
used as area drains and sealboxes in combined sewer (storm and
process water). Liquid level in box should be at orbelow frost
line.
• Concrete pipe may be used for perimeter areas where only a
single outlet is required.
• Dry box type catch basins, are used as area drains for heater
drainage areas in order toremove all hydrocarbon liquids from the
area promptly in event of a tube break. Do not locatedry boxes
under burners. The downstream end of the dry box outlet line shall
be keptseparate from other heaters or equipment areas and sealed in
a catch basin or manhole.(Generally located 50' or more from the
shell of the fired equip.)
• Cast Iron - [Not shown] used as area drain only generally in
separate storm sewer. Not usedin cold climates where they could be
subject to freezing. Not used in crushed rock areas.
Figure 8-9
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8.6.7 Drawings
Process area underground layouts are normally done on a
brownline of the plot plan at a scale of 1" =20' or 1" = 10'. The
initial layout is in the form of a transposition with sufficient
information shown toenable a reasonably accurate material takeoff.
The final layout and design is handled as a part of thedevelopment
of the underground piping drawings. Figure 8-10 shows a portion of
an underground plandrawing.
Figure 8-10
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8.6.8 Sewer System Piping
The unit collection headers for storm, process or combined
sewers (laterals) are usually located underthe pipeway area for
convenience in connecting catch basins and drain funnels on both
sides ofpipeway. If the electrical power duct system is also
located in this area, the layout designers from bothgroups should
work closely to establish easements. Laterals are installed below
frost line.
Normally the slope of the longest path governs the inverts in
the system and the depth of the sewer atthe start, or high end.
Sewer laterals leaving process units are sealed at manholes on
the plant sewer mains. Sealing andventing philosophy for sewers
containing hydrocarbon or flammable vapors is shown on Fig. 8.6a
andFig. 8-6b, and in the section on Manholes in this document.
Sublaterals are routed from the catch basins and/or branches to
the laterals. The connection at thelateral may be at a WYE branch
or at a manhole. In a sewer collecting process drainage,
manholesmay be located along the lateral to serve as seal boxes for
the incoming branches.
Pump and equipment process drains discharge into drain funnels.
A 6" minimum size opening for alldrain funnels is preferred. Where
a 6" opening does not provide sufficient area to
accommodatemultiple drains a larger opening is provided.
Drain funnel requirements are indicated on the P&ID's.
Approximate locations are shown on the initiallayout. Exact
locations are set later by the above ground piping layout. Groups
of funnels in fairlyclose proximity, say 30' apart, are connected
to a single branch line which is run to a catch basin,manhole or
seal box.
Each drain, sublateral or lateral shall be accessible for
rodding out by providing either a cleanout orcatch basin at its
upper terminus.
Limitations for the use of cleanouts are defined in the job
specifications.
Indicate line class, size, and slope for laterals, sublaterals,
and branches. Indicate invert elevation forstart and termination of
unit lateral. Use line sizing criteria provided in conjunction with
Sewer SizingChart, or job specification.
NOTE:It will be necessary for the Layout Designer to consult
with the Process Engineer to determine thesource, nature and
quantity of each process waste stream discharging to the sewer. A
permanentrecord of this information should be maintained for future
reference.
To facilitate construction, maintain a constant slope over long
runs, change line sizes as required, andmaintain common invert
elevations for adjacent parallel lines.
Sanitary sewers within buildings are designed by the Plumbing
Section of the Architectural Group to apoint five (5) feet outside
of the building, at this point you will be given the design
information, e.g.,fixture units being served, gpm and velocity.
Sanitary sewer minimum size is 4". Minimum slope to be1/8" per
foot.
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8.6.9 Manhole and Catchbasin Piping Elevations
Use Figure # 8-11 and the formulas that follow to calculate and
set the elevations of manholes andcatchbasins.
FIGURE # 8-11Where:
x = horizontal distance from inside face of wall to intersection
of invert (or B.O.P.)lines at 22½o bend. (feet)
y = difference in invert (or B.O.P.) elevations between points 2
and 3.
w = sum of:= difference in inlet and outlet line size (D2-D1)
(feet)= minimum liquid seal = .5 feet= D1 x cos 22.5o
(W is tabulated in Table 1 & 2., for lines at 22½o
only.)
s = slope of inlet line (feet/foot)
E = inside diameter or inside face to face of walls for manhole
orcatch basin (feet)
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Procedure
Calculate invert elevation (or B.O.P. for steel pipe
fabrication) at point 1 or 1a.
Deduct "W" which yields invert elevation (or B.O.P.) of seal
pipe at point 2.
Calculate X and Y using equations 1 and 2 that yield invert (or
BOP) and location of point 3.
When seal pipe enters box at an angle other than 22.5o use the
natural tangent of that angle inplace of 0.4142 in equations 1 and
2.
Dimension "W" must be calculated in the above situation using D1
x cos of the angle used, fordimension (c).
Dimension "W" is the sum of (b), (c), and (d) when inlet line is
a branch run at a higher elevationthan the normal flow line of the
system.
DO NOT USE THESE TABLES IF THE LINE ENTERS AT AN ANGLE OTHER
THAN 22.5o.TABLE 1
DIMENSION "W" (FEET)BASED ON INVERT EL. FOR C.I. OR CLAY
PIPE
OUTLET PIPE SIZE4" 6" 8" 10" 12" 14" 15" 16" 18" 20" 24"
4" 0.81 0.97 1.14 1.31 1.47 1.64 1.72 1.81 1.97 2.14 2.476" 0.96
1.13 1.30 1.46 1.63 1.71 1.78 1.95 2.13 2.468" 1.12 1.28 1.45 1.61
1.70 1.78 1.95 2.12 2.45
10" 1.27 1.44 1.60 1.69 1.77 1.94 2.10 2.4412" 1.42 1.59 1.67
1.76 1.92 2.09 2.4214" 1.58 1.66 1.74 1.91 2.08 2.4115" 1.65 1.74
1.90 2.07 2.4016" 1.73 1.90 2.06 2.4018" 1.89 2.05 2.3920" 2.04
2.3724" 2.35
TABLE 2DIMENSION "W" (FEET)
BASED ON B.O.P. FOR STEEL PIPEOUTLET PIPE SIZE
4" 6" 8" 10" 12" 14" 16" 18" 20" 24"4" 0.85 1.02 1.19 1.37 1.53
1.64 1.80 1.97 2.14 2.476" 1.01 1.18 1.35 1.52 1.62 1.79 1.96 2.12
2.468" 1.16 1.34 1.51 1.61 1.78 1.95 2.11 2.45
10" 1.33 1.49 1.60 1.76 1.93 2.10 2.4312" 1.48 1.59 1.75 1.92
2.09 2.4214" 1.58 1.74 1.91 2.08 2.4116" 1.73 1.90 2.07 2.4018"
1.89 2.05 2.3920" 2.04 2.3724" 2.35
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PIPING DESIGN LAYOUT TRAININGLESSON 6
UNDERGROUNDPage 22 of 25
15/30/2002 REV 0
8.6.10 Sewer Sizing Guide
• Purpose
The intent of this instruction is to provide the designer with
an organized approach to sizingsewer lines, and to promote a better
understanding of the hydraulics involved in sewer design.
• Design Basis
The general requirements for the plant sewer systems are
outlined in the design specification. Linesizing is based on the
expected flows in the line plus a safety factor for storm water
flows. Thedesign specification should provide the following:
• Rainfall intensity (inches/hour)
• Maximum fire water flow based on pumping capacity, and fire
protection facilities. (spraysystems, monitors, etc.)
• Definition of waste water system.
8.6.11 Sewer Layout
The Civil Group is responsible for the sewer system layout.
• Generally inverts for the mains can be set by determining
which "path" is the longest. Howeverthis must be analyzed since
shorter paths at steeper slopes may govern.
• On a large plant several trial designs may be required to
determine the most advantageousrouting.
8.6.12 Sewer Sizing Calculation Sheet
The Sewer Sizing Calculation Sheet may be utilized to provide a
permanent record of the hydraulicdesign of the principal sewer
systems. It is used during the layout and design phase to keep
track ofcalculations.
The intent is to use the form for unit laterals, sublaterals and
branches. (See design specification fordefinitions)
Using the chart is actually a "step by step" automatic way to
size the system. The notes that followserve as instructions.
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SEWER SIZING CALCULATION SHEETLine No. _________________________
Layout Dwg No. ______________________
System No. __________________________ Contract No.
______________________
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18FROM TO SQ. FT. SQ.
FT. STORM STORM PROCESS FIRE DESIGN SEWER VELOSITY SLOPE LENGTH
INVERT I.E. I.E. ELEV. APPROX.
MK. MK. PAVED UNPAVED RUNOFF RUNOFF DRANAGE WATER FLOW DIA.
(FT./SEC.) (FT./FT.) (FT.) DROP UPPER LOWER GROUND COVER (GPM)
(GPM) (GPM) (GPM) (IN.) (IN.) (12X13) (FT.) (FT.) UPPER
17-(15+10)
INCREMENT TOTAL 6+7 or 7+8
NOTES:1. STORM RUNOFF BASED ON THE RAINFALL INTENITY OF
______"/HOUR2. FACTOR OF IMPERVIOUSNESS FOR UNPAVED AREAS =
_______3. FIREWATER FLOW IS BASED ON ________GPM PER CATCH BASIN4.
LINE SIZE CHANGES ALONG A RUN SHOULD BE REFLECTED - COLUMN 14 BY AN
APPROXIMATE INCREASE IN THE INVERT DROP
z
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PIPING DESIGN LAYOUT TRAININGLESSON 6
UNDERGROUNDPage 23 of 25
15/30/2002 REV 0
Using the Sewer Sizing Calculation Sheet
• On a copy of the sewer layout, assign identifying letters to
each junction where flow isincreased, breaking the sewer into
individual segments or runs to be separately sized on thechart.
• Column 1: List the identifying letter for the upstream end of
the first run. (The first lineshould be used for the first run in
the system.)
• Column 2: List the identifying letter at the downstream end of
the same run.
• Column 3: Enter the square footage of the paved area with
runoff to the junction pointdesignated in column 1 of the same
line.
• Column 4: Enter the square footage of unpaved areas.
• Column 5: Calculate and list the storm runoff based on areas
listed in columns 3 and 4,using appropriate formulas in the design
specification.
• Column 6: List the total cumulative runoff for run by adding
runoff in column 5 to that listed incolumn 6, in the preceding
line.
• Column 7: List the total cumulative process drainage to the
point listed in column 1.
• Column 8: List the total cumulative firewater flow, based on
requirements in the designspecification.
• Column 9: List the design flow, the total of columns 6 + 7 or
7 + 8 whichever is greater.
• Column 10, 11 and 12: Select and enter the pipe size, flow
velocity and line sloperespectively, using the Pipe Flow Chart in
000.210.1160, Attachment 2, in the PipingEngineering Design Guide,
Vol. 2. In the larger sizes there is a range in choices for
anygiven flow. Selections are a matter of judgement, but consider
the following:
� Velocities of 3 to 4 ft. per sec. are preferred.
� Use lesser slopes where limited by elevations at the terminus
of the system, orwhere excavation is difficult and/or
excessive.
� Use steeper slopes where terrain gradient permits.
• Column 13: Enter the length of run in feet and decimals of a
foot between the pointsdesignated in columns 1 and 2. (For example:
242.25').
• Column 14: Multiply col. 12 x col. 13 to calculate the invert
drop in decimals of a foot, andenter the result. If there is a size
change in the run, add half the difference in nom. pipesize.
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PIPING DESIGN LAYOUT TRAININGLESSON 6
UNDERGROUNDPage 24 of 25
15/30/2002 REV 0
• Column 15: The highest invert elevation at the start of a
system should be based onthe cover requirements and length of the
branches serving the junction point listed. Insubsequent runs if
the line size is larger than in the preceding section, the
invertshould drop accordingly.
• Column 16: The lowest invert elevation, at the end of the
system. Calculate bydeducting the value in column 14 from that in
column 15.
• Column 17 and 18: Self-explanatory, used for reference
only.
Remember to add the required information in notes: 1, 2 &
3.
8.6.13 Utility Water Systems
Cooling water supply and return headers, if underground, are
routed approximately five (5) to ten (10)feet from the exchanger
channel end connections to keep branches short yet still permit for
someadjustment. If there is a choice it is preferable to keep the
main headers out from under concretepaved areas.
Where frost is not a factor the trench depth for the cooling
water headers should be kept to a minimum.As a general rule 3'-0"
cover is adequate protection for truck loading for steel lines 24"
and smaller inunpaved areas. Greater cover may be required for
larger sizes and/or other piping materials. Underconcrete paving
one (1) foot cover may be adequate. (See Civil/Structural Eng.)
Branch lines from the cooling water headers to the exchangers
are taken off the bottom quadrant of theheader if clearance above
will not permit adequate cover. Short branch piping may be routed
in thefrost zone and supply and return need not be at the same
B.O.P.
Provide a minimum clearance of eighteen (18) inches between
cooling water supply and return headers(24" for lines 30" and
larger) to prevent heat transfer.
Utility water headers are located under the pipeway area in
order to keep branches to the utility stationsat pipe support
columns short.
Potable water piping within buildings is designed by the
Plumbing Section of the Architectural Group toa point five (5) feet
outside of the building.
If practical the potable water header and sewer laterals and/or
mains shall not be less than ten (10) feetapart horizontally. If
the requirement cannot be met, the water header shall be placed on
a solid shelfand at all points shall be at least twelve (12) inches
above the top of the sewer line at it's highest point.
Locate unit block valves at plot limits. Protect from
maintenance vehicles with guard posts.
In freezing climates all utility water headers shall have their
top of pipe at or below the frost line.(Firewater shall be 1'-0"
below frostline.)
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PIPING DESIGN LAYOUT TRAININGLESSON 6
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15/30/2002 REV 0
8.6.14 Firewater System
Hydrants are located along plant roads or unit perimeters, so
that a fire at any location in the processunit can be approached
from two directions by men handling fire hoses connected to the
hydrants.
The hose coverage area is based on a nozzle with a 1 1/8" tip
connected to 250 feet of hose. Abrownline of the plot plan should
be marked-up to show monitor and hydrant locations as well as
theircoverage arcs. The Fire Protection Engineer, a plant Fire
Marshall, and local Fire Authorities reviewthis document. (Several
onionskin circles with 250' radius positioned on the plot can
assist indetermining the best hydrant locations.)
Hydrants or monitors should not be located where they will
conflict with exchanger tube pull or othermaintenance activities.
Hydrants or monitor locations that might interfere with
construction erectionactivities should be noted to "install after
equipment has been erected."
Monitors and hose reels are located to protect specific hazards
as outlined in the job specifications.
Water spray systems, when required are designed in accordance
with the National Fire Specification,N.F.P.A. #15. Stub and valve
location is also covered by this standard.
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PURPOSEThis practice provides guidelines for overall storm
drainage design for a project site andapplies to projects being
performed by the Civil Discipline that require storm
drainagedesign.
Information contained herein should be used by the Civil
Engineer as a guide. Many designcriteria, data, charts are
available in text books, handbooks, manuals, but some of them
areshown here. The Design Engineer should stay up to date on
materials, specifications, anddesign criteria.
Each project will have its own set of situations to be analyzed
and addressed with the bestengineering concept. Good engineering
judgment and most economical solutions should beutilized.
For complicated projects, obtain appropriate reference
publication and design storm drainagesystem as specified in the
publication. For very large projects, computer programs
areavailable where time and cost saving is justified. Even for
smaller systems, simple computerprograms are available which
provide quick and accurate results.
SCOPEThis practice utilizes many design criteria, data, charts,
textbooks, handbooks, and manualsavailable for storm drainage
design.
This practice contains types of commonly used hydrology
analysis, hydrology design criteria,the rational method to
determine storm water runoff from a drainage area, hydraulic
designof open channel and closed storm sewers, storage basins, and
design of culverts.
APPLICATIONEach engineer or designer performing storm drainage
design should utilize this guideline oneach project. It is the
overall responsibility of the Lead Engineer to ensure that this
practiceis used for storm drainage design on projects.
GENERALCONSIDERATIONS
Comprehensive storm drainage design includes more than
determination of runoff quantitiesand the layout of a collection or
conveyance system to dispose of the runoff. Integral to thedesign
is the consideration of erosion control and its impact on adjacent
properties. Thedesign of the storm drainage system should be
prepared in conjunction with the gradingdesign since the grading
directly influences the type and design of drainage systememployed.
It is necessary that the drainage philosophy be established before
the gradingdesign is prepared.
The impact of increased/decreased runoff from the project site
to adjacent properties must beconsidered. Further development
within the watershed must also be considered. Stormwatermanagement
is integral to the drainage system design. It is becoming more
commonplace
Practice 670 210 1150Publication Date 20Sep95
Page 1 of 21
FLUOR DANIEL
STORM DRAINAGE
Civil Engineering
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for local/state authorities to require stormwater management
programs in the form ofretention/detention ponds. The rate of
runoff is frequently controlled by statute.
Implementation OfStorm DrainagePractice
Implementation of storm drainage practice includes the
following:Data collectionDefine existing watershedDefine/develop
drainage philosophy for siteDevelop proposed layout of
systemPrepare calculations for systemDesign stormwater management
facilities, if required
Data CollectionReview local/state statutes.- Erosion Control-
Stormwater ManagementEstablish/determine requirements for permit
applications.- Plan Requirements- CalculationsObtain most recent
topographic plans of watershed.- Use USGS to establish general
location and define total watershed.- Use city/county topographic
plans for preliminary design in absence of more
accurate data.- Obtain topographic survey prepared at suitable
accuracy for final design.Obtain rainfall data.- Obtain latest
rainfall data from appropriate governmental agency (weather
bureau).
Define ExistingWatershed
Delineate watersheds on topographic plans.Calculate existing
runoff (Q10, Q25, Q50, and Q100) as required.- Onto site- From
site
Define/Develop Design Philosophy For Site
Consider method of collecting runoff.- Sheet flow versus series
of drainage inlets- Ditches versus underground piping system
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FLUOR DANIEL
STORM DRAINAGE
Civil Engineering
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Establish design criteria.
Develop ProposedLayout Of System
Prepare conceptual grading and drainage plan.Delineate drainage
area for each inlet or section of ditch.
Note!!! For conceptual design, space inlets based on 1 inlet per
10,000 sf.
Prepare CalculationsFor System
Design collection system for design storm frequency.Refine
grading plans and adjust layout of storm drainage.- Check ponding
at inlets. Check capacity of grates.- Consider special inlets with
high capacity grates.- Check ditch flow for depth and velocity.
Consider need for erosion netting, sod, or
rip rap/energy dissipaters. Use available charts for design of
open channels.- Check pipe flow for cleansing/scouring velocity and
depth of flow.- Determine inlet and outlet losses for manholes and
culverts.Pay special attention to details for proper drainage at
the following:- Intersections of roadways- Truck docks- Building
entrances- Rail docks/yards- Pedestrian crossings- Roof drainage
discharge points- Parking lots
Design StormwaterManagement Facilities
Code search- Check state/local/federal requirements.Prepare
calculations/drawings for the following:- Erosion control-
Retention/detention basins- Outflow structures- Emergency
spillways- Earth dams
Practice 670 210 1150Publication Date 20Sep95
Page 3 of 21
FLUOR DANIEL
STORM DRAINAGE
Civil Engineering
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HYDROLOGYANALYSIS
Technical Release 55(TR-55)
Technical Release 55, Urban Hydrology for Small Watersheds,
presents simplifiedprocedures to calculate storm runoff volume,
peak rate of discharge, hydrographs, andstorage volumes required
for floodwater reservoirs. These procedures are applicable in
smallwatersheds, especially urbanizing watersheds, in the United
States.
The model described in TR-55 begins with a rainfall amount
uniformly imposed on thewatershed over a specified time
distribution. Mass rainfall is converted to mass runoff byusing a
runoff CN (curve number). CN is based on soils, plant cover, amount
of imperviousareas, interception, and surface storage. Runoff is
then transformed into a hydrograph byusing unit hydrograph theory
and routing procedures that depend on runoff travel timethrough
segments of the watershed.
Use peak discharge method for up to 2,000 acres of drainage
area. Use tabular method forup to 20 square miles of drainage
area.
In TR-20, the use of TC (Time of Concentration) permits this
method for any size watershedwithin the scope of the curves or
tables, while in TR-55, the procedure is limited to ahomogeneous
watershed. The approximate storage routing curves are
generalizationsderived from TR-20 routings.
Use TR-20 if the watershed is very complex or a higher degree of
accuracy is required.
Use TR-20 if TT (travel time) is greater than 3 hours and time
of concentration TC is greaterthan 2 hours and a drainage area of
individual subareas differ by a factor of 5 or more.
Refer to Civil Engineering software, quick TR-55, and TR-20 for
computer application.
Synthetic UnitHydrograph Method(Chapter 16, Pages16-1 To
16-26)
Over the past 2 decades, the federal, state, county, and local
agencies have made numeroushydrologic investigations of drainage
basins using synthetic unit hydrograph methodology.The synthetic
unit hydrograph method should be used on larger drainage areas.
Rational MethodThe rational method is 1 of the most widely used
techniques for estimating peak runoffs, andis applicable to most of
the drainage problems encountered on Fluor Daniel projects.
The rational formula is Q = CIA
where
Q = Peak runoff, cfs
C = Coefficient of runoff, the rate of direct runoff to
rainfall
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FLUOR DANIEL
STORM DRAINAGE
Civil Engineering
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I = Rainfall intensity, inches per hour, corresponding to the
time of concentration
A = Tributary area, acres
The rational method is commonly used for determining peak
discharge from relatively smalldrainage areas up to 200 acres.
HYDROLOGY DESIGN CRITERIA
Normally, design for a storm frequency of 10 years for projects,
unless otherwise specified bythe client.
Check for storm frequency of 50 years to estimate the
consequences of flooding the site.
For major structures such as culvert under public highway, use a
storm frequency of 50years.
Design major flood control channels and major lift stations for
a storm frequency of 100years.
Stormwater runoff from tank farms is normally not included in
the design. Stormwater isimpounded within the dikes and released
after the peak stormwater runoff has passed.
Design containment storage within containment areas for a storm
frequency of 10 years,24-hour storm for projects, unless otherwise
specified by the client.
Ponding at inlets should be less than 3 inches for a frequency
of 25 years storm.
RATIONAL METHOD
Rational FormulaThe rational formula is Q = CIA. On a
topographic plan of the drainage area, draw thedrainage system and
block off the subareas draining into the system.
Determine A, the area of each subarea in acres.
Coefficient Of RunoffThe coefficient of runoff is intended to
account for the many factors which influence peakflow rate. The
coefficient of runoff primarily depends on the rainfall intensity,
soil type andcover, percentage of impervious area, and antecedent
moisture condition.
Determine the coefficient of runoff C, for appropriate class of
ground surface from thefollowing table. If more than 1 class of
ground surfaces fall in 1 tributary drainage area, usea composite
coefficient of runoff value.
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FLUOR DANIEL
STORM DRAINAGE
Civil Engineering
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Coefficient of Runoff C
Roofs 1.00Pavements
Concrete 1.00Asphalt 1.00
Oiled Compacted Soil 0.80Compacted Gravel 0.70Compacted
Impervious Soil 0.60Natural Bare Soil 0.60Uncompacted Gravel
0.50Compacted Sand Soil 0.40Natural Soil, Grass Cover
0.40Uncompacted Soil 0.20Lawns 0.20
Composite coefficient of runoff C:
A1C1 + A2C2 + A3C3 + −−−−AnCnA1 + A2 + A3 + An
where
A1 A2 A3 ---- An = Areas in acres of different class of
surfacesC1 C2 C3 ---- Cn = Corresponding coefficient of runoff
Time Of Concentration
If rain were to fall continuously at a constant rate and be
uniformly distributed over animpervious surface, the rate of runoff
from that surface would reach a maximum rateequivalent to the rate
of rainfall. The time required to reach the maximum or
equilibriumrunoff rate is defined as the time of concentration.
The time of concentration depends upon the length of the flow
path, the slope, soil cover,and the type of development.
Determine the initial time of concentration using the nomograph
on Attachment 01.
Use a minimum time of concentration of 5 minutes for paved areas
and a minimum time ofconcentration of 10 minutes for unpaved
areas.
PrecipitationThe various precipitation amounts during specified
time periods at recording stations areanalyzed using common models
of probability distributions.
A number of alternative statistical distributions such as Log
Pearson Type III, Pearson TypeIII, Two-Parameter Lognormal,
Three-Parameter Lognormal, and Weibull, Type I, ExtremeValue are
used in flood hazard analysis.
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STORM DRAINAGE
Civil Engineering
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Intensity DurationCurves
Use the intensity duration curves available from federal, state,
county or local agencies forthe project location. If such curves
are not available, construct these curves using WeatherBureau
Technical Paper Number 40 (Continental United States); 42 (Puerto
Rico andVirginia Islands); 43 (Hawaiian Islands); 47 and 52
(Alaska); or NOAA Atlas, Precipitation- Frequency Atlas of the
United States, published by the National Weather Service.
For constructing the curves, given only 1 or 2 points, use the
following conversion factorsbased on 30 minutes as 1.00:
Duration inMinutes Factor
Duration inMinutes Factor
5 2.22 40 0.80
10 1.71 50 0.70
15 1.44 60 0.60
20 1.25 90 0.50
30 1.00 120 0.40
To go from 1 curve to another, use the following factors based
on the 50 year maximumrainfall as 1.000:
1 year 0.428 25 years 0.898
2 years 0.455 50 years 1.000
5 years 0.659 100 years 1.108
10 years 0.762
Rainfall intensity duration curves for more than 100 years can
be constructed using rainfalldata for periods of 2, 5, 10, 25, 50,
and 100 years; and time periods of 20 minutes, 60minutes, 2 hours,
3 hours, 6 hours, 12 hours; and 24 hours using the following
formula:
_ _Xji = Xi + Kj Si Xi
where
j = Return period in yearsi = Specific storm duration in
minutes, hours or daysXji = Precipitation in inches for return
period j and duration iXi = Mean maximum annual storm for duration
iKj = Frequency factor (in standard deviations) for a return period
of j yearsSi = Standard deviation of maximum annual storm for
duration i
For more detailed procedures using this formula, refer to
"Analysis of Data," Pages 7 to 25 ofRainfall Depth Duration
Frequency for California, Department of Water Resources, State
ofCalifornia, November 1982.
A sample set of curves is shown in the sample problems in this
practice.
Practice 670 210 1150Publication Date 20Sep95
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FLUOR DANIEL
STORM DRAINAGE
Civil Engineering
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Using the initial time of concentration, determine "I" intensity
of rainfall in inches per hourfrom the intensity duration curve for
the plant's geographical location using the proper yearlyrainfall
frequency.
Compute Q = CIA.
Refer to sample problems in this practice.
Travel TimeDetermine the size of the channel or pipe required to
carry Q on the slope of the drain.Determine the velocity of
flow.
Measure the length of flow to the point of inflow of the next
subarea downstream. Computethe time of flow for this reach and add
it to the initial time of concentration for the first areato
determine a new time of concentration.
Calculate Q for second subarea, using the new time of
concentration and continue in similarfashion until a junction with
a lateral channel is reached.
Start at the upper end of the lateral and carry its Q to the
junction with the main channel.
Storm Runoff AtJunction
Compute the Q at the junction.
Tributary area with longertime of concentration
Tributary area with shortertime of concentration
QA QB
TA TB
IA IB
Peak Q cfs (cubic feet per second), time of concentration in
minutes, rainfall intensity ininches/hour.
If TA = TB then Qp = QA + QB TP = TA = TB
If QA > QB then Qp = QA + QB IAIB
TP = TA
If QA< QB then Qp = QB + QAIBIA
TP = TB
Qp = Peak Q at junctionTp = Peak time of concentration at
junction
If more than 2 tributary areas are contributing at 1 junction,
combine 2 areas at a time andproceed similarly until tributary
areas are combined.
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FLUOR DANIEL
STORM DRAINAGE
Civil Engineering
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DITCHES ANDCHANNELS
CapacityThe capacity of ditches and channels will be calculated
using the Manning's equation:
Q = 1.486n r2/3s1/2A
where:
Q = Capacity in cfsA = Cross sectional area of flow in square
feet
r = Hydraulic radius = in feetArea of flow
Wetted perimeters = Slope of energy grade line in foot per footn
= Roughness coefficient
Values of roughness coefficient n for ditches and channelsLined
ditches and channelsn = 0.014 for poured concreten = 0.016 for
shotcrete (gunite)n = 0.014 for asphaltn = 0.035 for medium weight
rip rapn = 0.025 for crushed rockn = 0.030 for grassUnlined ditches
and channelsn = 0.020 for very fine sand, silt or loamn = 0.025 for
sand and graveln = 0.030 for coarse gravel
Values of n for other surfaces can be found in Session 7, Pages
7-17 of King and Brater,Handbook of Hydraulics, McGraw-Hill Book
Company, New York; and Chapter 5, Pages110 to 113 of Chow, Ven Te,
Open-Channel Hydraulics, McGraw-Hill Book Company, NewYork,
1959.
Ditches and channels should be designed with the top of the
walls at or below the adjacentground to allow interception of
surface flows.
The minimum velocity of flow should be 2.0 feet per second in
order to prevent the settlingof solids, if there is possibility of
solids flowing in the ditches and channels.
Velocities in unlined ditches and channels must be limited to
prevent cutting or erosion ofthe ditch or channel bottom or sides.
Permissible channel velocities for various types of soilcan be
found in Session 7, Pages 7-19 of King and Brater, Handbook of
Hydraulics,McGraw-Hill Book Company, New York; and Chapter 7, Page
165 of Chow, Ven Te,Open-Channel Hydraulics, McGraw-Hill Book
Company, New York, 1959. If the meanvelocity exceeds that
permissible for that particular kind of soil, the channel should
beprotected with some type of lining.
Freeboard or additional wall heights are to be added above the
calculated water surface.
For ditches and channels with capacities to 50 cfs, add 1.0
feet.
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STORM DRAINAGE
Civil Engineering
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For ditches and channels with capacities from 50 cfs to 200 cfs,
add 1.5 feet.
For ditches and channels with more than 200 cfs capacities,
refer to Chapter 7, Pages 159and 160, of Chow, Ven Te, Open-Channel
Hydraulics, McGraw-Hill Book Company, NewYork, 1959.
For curved alignments, add freeboards above the superelevated
water surface.
It is desirable to provide a depth greater than critical. If not
possible, an energy dissipatormay be required at the end of the
ditch section.
LiningsDitches and channels with a flow velocity that exceeds
permissible velocity will be lined.
Lining of ditches and channels will be poured concrete, gunite,
asphalt, crushed rock, riprap,or other type of slope
protection.
For design procedure of riprap design, refer to Chapter 3, Pages
III-137 to III-150 ofVirginia Erosion and Sediment Control
Handbook, Virginia Department of Conservationand Recreation
Division of Soil and Water Conservation, 1980.
GRAVITY STORMSEWER SYSTEM
CapacityThe capacity of a gravity storm sewer system will be
calculated using the Manning'sequation. Refer to sections covering
Ditches and Channels in this practice.
Closed storm sewers should be deigned to flow full for the
design storm, unless otherwisespecified by the Client.
The gravity storm sewer system will be designed in such a manner
that at the maximumdesign flow, the water level in the most remote
catch basin of the system or subsystem is aminimum of 6 inches
below top of grating. The controlling elevation at a junction of a
main,lateral, or sublateral for calculating the hydraulic gradeline
upstream will be the hydraulicgrade elevation of the main or
lateral at the point or the soffit elevation of the pipe,whichever
is greater.
Values of Manning's n for closed sewers are as follows:
Pipe Material n
Polyvinyl chloride pipe 0.010Steel 0.011Ductile iron 0.013Cast
iron 0.013Cement lined pipe 0.015Concrete pipe 0.013Vitrified clay
pipe 0.013Fiberglass reinforced plastic 0.010Corrugated metal pipe
0.024
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STORM DRAINAGE
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The preferred slope for sewer lines will be approximately 0.01
foot (1/8 of an inch) per foot.The minimum slope will be
approximately 0.005 foot (1/16 of an inch) per foot but may
bedecreased, if necessary, provided the required minimum velocity
is maintained to avoiddisposition of solids.
The minimum pipe size for branch lines will be 4-inch diameter
and 8-inch diameter forcatch basin outlet pipes.
The minimum velocity for closed storm sewers should be 2.0 feet
per second to prevent thesettling of solids.
For concrete sewers where high velocity flow is continuous and
grit erosion is expected to bea problem, use a maximum velocity of
about 10 feet per second.
The alignment chart in Attachment 02 can be used for the
solution of Manning's equation forcircular pipes flowing full.
The graph in Attachment 03 is used for the solution of problems
involving sewers flowingonly partly filled. The following procedure
is used for finding the hydraulic elements of thepipes.
Compute the ratio of q/Q for each line.Find the ratio of h/D and
v/V.From the ratio h/D, calculate h.From the ratio v/V, calculate
v.
q = Actual flow, cfsQ = Quantity if pipe flowing full, cfsh =
Actual depth of flow, feetD = Inside diameter of pipe, feetv =
Actual velocity, fps (feet per second)V = Velocity if pipe were
flowing full, fps
LossesManhole losses will be calculated from the following:
hmh = 0.05 v
2
2gto0.75
v
2
2g
depending upon the inlet and outlet pipe size, elevation and
design.
Bend losses will be calculated from the following equations:
hb = Kb v
2
2g
where
Kb = 2.0
δ90
where δ = Central angle of bend in degrees.
Bend losses should be included for closed conduits; those
flowing partially full as well asthose flowing full.
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STORM DRAINAGE
Civil Engineering
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CULVERTSDrainage culverts are normally corrugated metal pipe,
reinforced concrete pipe, or reinforcedconcrete box as necessary to
meet the requirements for stormwater drainage flow, truckloads, and
depth of fill above the culvert.
Culverts under roads will be designed to support the earth
pressures on the culvert and themaximum wheel load that will be
imposed over it through its design life, plus the applicableimpact,
as defined in AASHTO (American Association of State Highway and
TrafficOfficials) Standard specifications for Highway Bridges. In
the absence of construction ormaintenance vehicles with a greater
wheel load, the culvert will be designed to support awheel load of
16,000 pounds (HS-20 loading). Minimum cover over culverts will
be12-inches for circular corrugated metal pipe, and 18-inches for
reinforced concrete pipe, andcorrugated metal pipe arches.
The minimum size of culvert will be 12-inch diameter for lengths
of 30 feet or less and18-inch diameter for lengths over 30
feet.
Where installation of multiple culverts is required, the minimum
clear distance betweenpipes will be as follows:
Pipe Diameter Minimum Clear Distance
12 inch to 24 inch27 inch to 72 inch78 inch to 120 inch
12 inches1/2 diameter
36 inches
Culverts will have a slope that will provide a minimum velocity
of 2.0 fps. Culverts will besized to pass the 10-year storm flow
with unsubmerged inlet. However, the culvert will bechecked for the
50-year storm with ponding at the entrance not to exceed the top of
the roadsubgrade.
In designing any culvert larger than a 36-inch diameter
single-barrel pipe (for example, archand oval pipe, multiple-barrel
culverts, concrete box), design features such as
headwalls,endwalls, transition structures, and energy dissipators
will be selected strictly on the basis ofculvert performance and be
economically justified.
Procedure for determining culvert size:List the design data.
Refer to sample problems in this practice.Estimate first trial
size.Find headwater depth.
Inlet Control: Using Attachments 04, 05, or 06, determine HW/D
using the appropriateentrance scale. Convert HW/D to HW (headwater)
by multiplying by D (pipe diameter) infeet.
Outlet Control: Using Attachment 07, 08, or 09, determine H
(head) in feet using theappropriate value for k(e) as given in the
following table:
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FLUOR DANIEL
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Entrance Loss Coefficients
Type of EntranceCoefficient
k(e)
Concrete Pipe
Projecting from fill, socket end (groove end) 0.2
Projecting from fill, square cut end 0.5
Headwall or beadwall and wingwallsSocket end of pipe (groove
end)Square endRound radius (radius - 1/2 D)
0.20.50.2
End section conforming to fill slope 0.5
Corrugated Metal Pipe
Projecting from fill (no beadwall) 0.9
Headwall or beadwall and wingwalls, square edge 0.5
Beveled to conform to fill slope 0.7
Flared end section (available from manufacturer) 0.5
Beadwall, rounded edge 0.1
Solve for HW in the following equation:
HW = H + ho − SoL
For TW (tailwater) elevation equal to or greater than the top of
the culvert at the outlet, setho equal to TW.
For TW elevation less than the top of the culvert at the outlet,
use the following equation orTW, whichever is greater, where dc,
the critical depth in feet, is determined fromAttachment 10 or
11.
ho = dc + D2
Compare the headwaters for both inlet and outlet control. The
higher headwater governsand indicates the flow existing under the
given conditions for the trial size selected.
Select culvert size which keeps headwater depth below allowable
limit.
STORMWATERDETENTION ANDRETENTION BASINS
Flood ControlDetention Basin
The primary function of the flood control detention basin is to
store the storm runoff duringpeak flood and reduce the peak
discharge.
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The flood control detention basin is generally the least
expensive and most reliable measure.It can be designed to fit a
wide variety of sites and can accommodate multiple outletspillways
to control multifrequency outflow.
Measures other than flood control detention basins may be
preferred in some locations. Anydevice selected, however, should be
assessed as to its function, maintenance needs, andimpact.
Design flood control detention basins for 50 years storm
frequency.
For flood control detention basin storage volume requirement
calculations procedure, for upto 2,000 acres of drainage area,
refer to Chapter 6 Storage Volume for Detention Basins,Pages 6-1 to
6-11 of Urban Hydrology for Small Watersheds, TR-55, United
StatesDepartment of Agriculture, Soil Conservation Service, January
1975, or use local drainagemanual, if available.
Stormwater RetentionBasin
Regulations require management of storm runoff from industrial
plant sites so as not todischarge toxic or hazardous pollutants to
receiving waters.
The purpose of stormwater retention basins is to store the
stormwater during periods ofstorm runoff and release it at a lower
rate to the treatment process.
Retention pond and storage basin capacities will be determined
based on the totalaccumulated stormwater runoff from the design
storm frequency for duration of 24 hours. Aminimum freeboard of 12
inches will be provided on top of water surface.
Lining for ponds and basins will be as recommended in the
Geotechnical InvestigationReport or as required by process and
environmental criteria for the project.
Sediment ControlBasin
Erosion and sediment control measures are required during
construction to prevent surfacestorm water runoff pollution into
stream channels and water bodies.
The sediment control basin is required to collect and store
sediment or debris from affectedareas.
The sediment control basin collects and holds stormwater runoff
to allow suspendedsediment to settle out.
Design sediment control basins for 10-year storm frequency,
unless regulatory agenciesdictate otherwise.
The surface area of the sediment basin at the height of the rim
of the riser pipe is calculatedby using the following formula:
A =KQVs
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FLUOR DANIEL
STORM DRAINAGE
Civil Engineering
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where
A = Basin surface area square feetQ = Storm runoff cfsK = 1.2Vs
= 0.00096 ft/sec settling velocity for a 0.02 millimeter particle
size.
Particles greater than or equal to the 0.02 millimeter particle
size are to be retained in thebasin.
The sediment storage volume is 75 cu yd per acre of disturbed
construction area. Thesettling zone will be a minimum of 2 feet
deep.
The combined capacities of the riser pipe and spillway are
designed to be sufficient to passthe peak rate of storm runoff of a
10-year storm frequency.
The sediment control basin will need to be periodically cleaned
out to restore the basin to itsoriginal designed volume
capacity.
A concentric antivortex device and trash rack should be provided
on top of the riser pipe.
A concrete base of sufficient weight to prevent flotation of the
riser is attached to the riserpipe with a watertight
connection.
Stone riprap protection should be provided on the spillway to
reduce erosion of the spillwaydike.
A protection fence should be provided around the sediment
control basin for safety.
The sediment control basin may be used after construction as a
permanent stormwatermanagement basin.
For sediment control basin design requirements and procedure,
refer to Chapter 3, PagesIII-59 to III-88 of Virginia Erosion and
Sediment Control Handbook, Virginia Departmentof Conservation and
Recreation Division of Soil and Water Conservation, 1980.
STORM DRAINAGESOFTWARE(AVAILABLEIN IRVINE)
1. Advanced Designer SeriesCivil SoftStorm PlusStorm Drain
Analysis Program
Storm Plus is based on the original computer program F0515P and
was developed inApril 1979. This program was written for use by the
Los Angeles County Flood ControlDistrict or by its contractors on
district projects.
This program computes and plots uniform and nonuniform steady
flow water surfaceprofiles and pressure gradients in open channels
or closed conduits with irregular orregular sections. The flow in a
system may alternate between super critical, subcritical,or
pressure flow in any sequence. The program will also analyze
natural river channels
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STORM DRAINAGE
Civil Engineering
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although the principle use of the program is intended for
determining profiles inimproved Flood Control Systems.
2. Haestad MethodsCivil Engineering SoftwareHEC-1Flood
Hydrograph Package
This computer program was developed by HEC (The Hydrologic
Engineering Center),Corp of Engineers, Department of the Army.
The HEC-1 model is designed to simulate the surface runoff
response of a river basin toprecipitation by representing the basin
as an interconnected system of hydrologic andhydraulic
components.
Each component models an aspect of the precipitation runoff
process with a portion ofthe basin, commonly referred to as a
subbasin. A component may represent a surfacerunoff entity, a
stream channel, or a reservoir. The result of the modeling process
is thecomputation of stream flow hydrographs at desired locations
in the river basin.
HEC-1 has several major capabilities which are used in the
development of a watershedsimulation model and the analysis of
flood control measures. The capabilities are thefollowing:
Automatic estimation of unit graph, interception/infiltration,
and streamflowrouting parameters.Simulation of complex river basin
runoff and streamflow.River basin simulation using a precipitation
depth versus area function.Computation of modified frequency curves
and expected annual damages.Simulation of flow through a reservoir
and spillway for dam safety analysis.Simulation of dam breach
hydrographs.Optimization of flood control system components.
3. Haestad MethodsCivil Engineering SoftwareHEC-2Water Surface
Profiles
This computer program was developed by HEC, Corps of Engineers,
Department of theArmy.
The HEC-2 computer program is intended for calculating water
surface profiles forsteady, gradually varied flow in natural or
manmade channels. Both subcritical andsupercritical flow profiles
can be calculated. The effect of various obstructions such
asbridges, culverts, weirs, and structures in the flood plain may
be considered in thecomputations. The program is also designed for
application in flood plain managementand flood insurance studies to
evaluate floodway encroachments and to designate floodhazard zones.
Also, capabilities are available for assessing the effect of
channelimprovements and levels on water surface profiles.
Practice 670 210 1150Publication Date 20Sep95
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FLUOR DANIEL
STORM DRAINAGE
Civil Engineering
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4. Haestad MethodsCivil Engineering SoftwareHEC-PlotPlotting
Program for HEC-1 and HEC-2
HEC-Plot is an enhanced version of the Plot 2 Program of the US
Army Corps ofEngineers, written by HEC.
Computer Program HEC-Plot was developed to provide a quick and
simple graphicaldisplay of cross section data and computed results
from HEC-1 and HEC-2. TheHEC-Plot Program provides the capability
to plot cross section data, including thechanges to the section
caused by the HEC-2 options that modify section data. HEC-2profiles
and rating curves of the output variables, available on HAESTAD 95
or TAPE95, can be plotted. HEC-Plot also plots HEC-1 output
hydrographs.
5. Haestad MethodsCivil Engineering SoftwareQuick HEC-12Drop
Inlet Design and Analysis
Quick HEC-12 handles the following inlet
types:CurbGrateCombination curb and grate4-inch bridge
ScupperSlotted DrainGrate in trapezoidal ditch
Quick HEC-12 uses the manual procedure outlined by the Federal
HighwayAdministration, Hydraulic Engineering circular Number 12,
Drainage of Highwaypavements, March, 1984.
6. Haestad MethodsCivil Engineering SoftwarePOND-2Detention Pond
Design and Analysis
POND-2 Computer Program is for detention pond design. It
estimates detention storagerequirements, computes a volume rating
table for any pond configuration, routeshydrographs for different
return frequencies through alternative ponds and plots theresulting
inflow and outflow hydrographs. POND-2 is completely compatible
withLINK-2 and can automatically import inflow hydrographs from
QUICK TR-55, TR-20,and HEC-1 computer files.
7. Haestad MethodsCivil Engineering SoftwareQuick TR-55Hydrology
for small watersheds
Quick TR-55 Computer Program was developed based on the SCS
TR-55 UrbanHydrology for small watersheds. The program can generate
and plot hydrographs,compute peak discharges, and perform
predeveloped and postdeveloped analysis.
Practice 670 210 1150Publication Date 20Sep95
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8. Haestad MethodsCivil Engineering SoftwareTR-20Project
Formulation Hydrology
The TR-20 Computer Program is a single-event model which
computes direct runoffresulting from any synthetic or natural
rainstorm. It develops flood hydrographs fromrunoff and routes the
flow through steam channels and reservoirs. The following
majorCivil Engineering software programs from Haestad Methods are
also available:
9. HECWRCFlood Flow Frequency
10. HMR52Probable Maximum Storm
11. WSP-2Water Surface Profiles
12. Hy-4-69Hydraulics of Bridge Waterways
13. WSPRO (Hy-7)Bridge Waterways Analysis Model
14. DAMS 2Structure Site Analysis
15. THYSYSCulverts Storm Sewer and Inlets
16. SWMMStorm Water Management Model
17. HEC-6Scour and Deposition
18. SEDIMOT IIHydrology and Sedimentology
19. HYDRAStorm and Sanitary Sewer Analysis SoftwarePITZER
HYDRA is one of the most practical programs available to analyze
storm and sanitarysewer collection systems. It is structured to
work well on both large municipal systemsand small tracks, with or
without database files and without or within AutoCAD.
HYDRA allows the designer to generate storm flows by the
Rational Method, a modifiedSCS Method (Soil Conservation Service)
or by continuous simulation. The best methodto use depends upon the
situation, available data, and the requirements of
themunicipality.
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STORM DRAINAGE
Civil Engineering
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REFERENCESAASHTO (American Association of State Highway and
Traffic Officials).
Analysis of Data, Pages 7 to 25 of Rainfall Depth Duration
Frequency for California,Department of Water Resources, State of
California, November 1982.
Bureau of Engineering Manual. Part G, Storm Drain Design. City
of Los Angeles,Department of Public Works.
Capacity Charts For the Hydraulic Design of Highway Culverts.
Hydraulic EngineeringCircular Number 10. Mar. 1965.
Chow, Ven Te. Handbook of Applied Hydrology. McGraw-Hill Book
Company. 1964.
Chow, Ven Te. Open-Channel Hydraulics. McGraw-Hill Book Company.
New York.1959.
Design and Construction of Sanitary and Storm Sewers. American
Society of CivilEngineers. WPCF Manual of Practice Number 9.
1972.
Design Manual. Hydraulic. Los Angeles County Flood District.
Design Manual. Orange County Flood Control District.
Engineering Field Manual. United States Department of
Agriculture. SCS. Washington,DC. 1989.
Estimating Probabilities of Extreme Floods: Methods and
Recommended Research.National Research Council. Washington, DC.
1988.
Guide For Sediment Control on Construction Sites in North
Carolina. United StatesDepartment of Agriculture. Soil Conservation
Service, SCS. North Carolina. 1973.
Guidelines For Determining Flood Flow Frequency. Interagency
Advisory Committee onWater Data, Bulletin #17b of the Hydrology
Subcommittee, VA. 1982.
Gumbel, E. J. Statistics of Extremes. Columbia University Press.
New York. 1958.
Hydraulic Charts For the Selection of Highway Culverts.
Hydraulic Engineering CircularNumber 5. Dec 1965.
Hydraulic Design of Improved Inlets For Culverts. Hydraulic
Engineering Circular Number13. Aug 1972.
Hydrology Manual. Los Angeles County Flood Control District.
Hydrology Manual. Orange County Flood Control District.
Hydrology Manual. Riverside County Flood Control and Water
Conservation District.
King and Brater. Handbook of Hydraulics. McGraw-Hill Book
Company. New York.
Kite, G. W. Frequency and Risk Analysis in Hydrology. Water
Resource Publication.Littleton, CO. 1977.
Manual For Erosion and Sediment Control in Georgia. Georgia Soil
and WaterConservation Committee. 1975.
Practice 670 210 1150Publication Date 20Sep95
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STORM DRAINAGE
Civil Engineering
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Manual of Standards For Erosion and Sediment Control Measures.
Association of Bay AreaGovernments. Jun 1981.
Maryland Erosion and Sediment Control Handbook. United States
Department ofAgriculture, SCS. College Park, MD. 1975.
National Engineering Handbook. Drainage of Agricultural Land.
United States Departmentof Agriculture, SCS. Washington, DC.
1971.
National Engineering Handbook. Hydraulics. United States
Department of Agriculture,SCS. Washington, DC. 1975.
National Engineering Handbook. Hydrology. United States
Department of Agriculture.SCS (Soil Conservation Service).
Washington, DC.
NOAA Atlas, Precipitation - Frequency Atlas of the United
States, published by the NationalWeather Service.
Rainfall Depth Duration Frequency For California. Department of
Water Resources. Stateof California. Nov 1982.
Urban Hydrology For Small Watersheds. TR-55. United States
Department of Agriculture.Soil Conservation Service. Jan 1975.
Urban Runoff. Erosion and Sediment Control Handbook. United
States Department ofAgriculture. Soil Conservation Service, SCS.
St. Paul, MN. 1976.
Virginia Erosion and Sediment Control Handbook. Virginia
Department of Conservationand Recreation Division of Soil and Water
Conservation. 1980.
Water Resources Technical Publication. Research Report Number
24. United StatesDepartment of The Interior, Bureau of
Reclamation.
Weather Bureau Technical PaperNumber 40Number 42Number 43Number
47Number 52
ATTACHMENTSAttachment 01:Overland Flow Time
Attachment 02:Alignment Chart For Manning Formula For Pipe
Flow
Attachment 03:Relative Velocity And Flow In Circular Pipe For
Any Depth Of Flow
Attachment 04:Headwater Depth For Concrete Pipe Culverts With
Inlet Control
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Attachment 05:Headwater Depth For CM Pipe Culverts With Inlet
Control
Attachment 06:Headwater Depth For CM Pipe Arch Culverts With
Inlet Control
Attachment 07:Head For Concrete Pipe Culverts Flowing Full
Attachment 08:Head For Standard CM Pipe Culverts Flowing
Full
Attachment 09:Head For Standard CM Pipe Arch Culverts Flowing
Full
Attachment 10:Critical Depth Circular Pipe
Attachment 11:Critical Depth Standard CM Pipe Arch
Attachment 12:Form: 000.210.F8000: Rational Method Calculation
Form
Attachment 13:Form: 000.210.F8001: Peak Q At The Junction
Calculation Sheet
Attachment 14: (12Mar93)Form: 000.210.F5000: Datasheet - Culvert
Design
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FLUOR DANIEL
FORM 000 210 F5000 (12Mar93)Page 1 of 1
DATASHEET - CULVERT DESIGN
Client Name:Project Name:Project Number:
DATE: REV.:
Culvert Station
Hydrology:
( Year Frequency), Q = cfs( Year Frequency), Q = cfs
Q = Design DischargeQ = Check Discharge
NOTES:
1. h =dc + D
2or TW, Whichever is Greater
2. HW = H + h - S L
DESIGN SELECTION
CommentsOutlet ControlInlet ControlQCulvert Identification
Entrance Material Size HW
D
HW(ft)
H h S L HW(ft)
(Note 2)
O
O O
O O
1
2
Elevation
AHW =
HeadwaterMaximum Allowable
Elevation
TW =
Elevation
(Note 1)
S =
L
O
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PURPOSEThis practice establishes the parameters of the various
components involved in the design ofgravity and force main sanitary
sewer systems.
Design of these systems will require compliance with regulations
and standards of variousprivate and public agencies and applicable
federal, state, county and city regulations. Thedesign data,
dimensions, regulations and standards will reflect a considerable
diversitybetween owner and government agencies.
The Civil Engineer must review these various regulations and
standards and select theappropriate ones for the project. This
technical practice should be used in conjunction withtextbooks and
other publications on the subject, such as those listed in the
references. Thedesign engineer should stay updated on materials,
specifications, and design criteria.
SCOPEThis practice includes the following major sections:
SEWAGE FLOWRATESGRAVITY SEWER DESIGNMANHOLESPUMPING
STATIONSSIPHONSHYDRAULIC DESIGNEXAMPLE
PROBLEMREFERENCESATTACHMENTS
APPLICATIONThis practice provides guidelines for the design of
sanitary sewers and applies to all projectsand work assignments
being performed by Fluor Daniel Civil Discipline. The Lead
CivilEngineer on a project is responsible for the use of these
guidelines in designing sanitarysewer systems.
SEWAGE FLOWRATES
Domestic sewage quantities normally are to be computed on a
contributing population basis,except as noted in subparagraph d and
e on page 3-1 of Hydraulic Design of Sewers.
Subparagraph d (Industrial Waste Flows)
Such industries cannot be computed totally on a population or
fixture unit basis.Industrial waste sewers and sanitary sewers will
be designed for the peak industrial flowas determined for the
particular industrial process or activity involved.
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SANITARY SEWER SYSTEMS
Civil Engineering
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Subparagraph e (Fixture Unit Flow) The size of building
connections, including thosefrom theaters, restaurants, chapels,
clubs and other such buildings, will, in all cases, belarge enough
to discharge the flow computed on a fixture unit basis.
The population to be used in design depends upon the type of
area which the sewerserves. If the area is entirely residential,
the design population is based on fulloccupancy. If the area served
is entirely industrial, the design population is the greatest
Average DailyPer Capita
Sewage quantities for different types of installations are shown
on page 3-1 of HydraulicDesign of Sewers. The average daily flow
will be computed by multiplying the resident andnonresident
contribution populations by the appropriate per capita allowances
and adding thetwo flows.
Nonresidents working 8 hour shifts will be allowed 30 gallons
per capita per day.
FlowrateThe average hourly flowrate should be used when
designing sewers to serve small areas ofthe installation where
several buildings or a group of buildings are under consideration
andwhere the majority of sewage is generated by nonresidents or
other short term occupants.
The peak daily or diurnal flowrate is an important factor in
sewer design, especially whenminimum velocities are to be provided
on a daily basis. The peak diurnal flowrate will betaken as 1/2 of
the extreme peak flowrate.
Extreme flowrates of flow occasionally and must be considered.
Sewers will be designedwith adequate capacity to handle extreme
peaks flowrates, ratios of extreme peak flowrates ataverage flow
will be calculated with the use of the following