manhole tech brochured

7/27/2019 Manhole Tech Brochured

1/10

PRECAST CONCRETE

MANHOLES

Sustainable Stormwater Solutions


2/10

2 MANHOLE TECHNICAL NATIONAL PRECAST CONCRETE ASSOCIATION

Why Precast Concrete .................................................. 2

Sustainable Benets o Precast Concrete ....................3

LEED Properties o Precast Concrete...........................4

Case Study ..................................................................5

Installation Procedures .................................................6

Testing Procedures .......................................................7

NPCA Plant Certication ............................................... 8

Find a Manhole Producer ..............................................8

Design Notes ................................................................ 9

Additional Resources ................................................. 10

TABLE OF CONTENTS

National Precast Concrete AssociationWith nearly 1,000 member companies, NPCA serves as the

voice o the precast concrete industry in the United States

and Canada. The industry includes a diverse mix o companies,

rom small single-plant manuacturers to multinational

vertically integrated companies that operate in many sectors o

the construction industry. NPCA provides an array o services

to these manuacturers that include technical engineeringsupport, the industrys largest certication program, saety

programming, educational courses and a suite o print and

online publications. In addition to services to members,

NPCA provides specialized technical inormation to owners,

contractors, engineers and designers on precast concrete

products.

Copyright 2012 by National Precast Concrete Association

(NPCA); all rights reserved. No part o this manual may be

reproduced in any orm without permission in writing rom the

National Precast Concrete Association.

1320 City Center Dr., Suite 200, Carmel, IN 46032

800-366-7731 precast.org

WHY PRECASTCONCRETE?Installation is EasyPrecast concrete manholes have become the construction

industrys product o choice over cast-in-place concrete,

brick and other non-concrete products or many reasons, not

the least o which is ease o installation. Precast concrete

manholes can be easily installed on demand and immediately

backlled. There is no need to wait or concrete or mortar to

cure at the job site. The degree o soil compaction around the

manhole and remaining trenches is never a problem, making

installation aster and easier. Contractors are amiliar with how

to handle precast concrete manholes and can easily install

them. Standard sealants and fexible joints are readily available

and are vital to watertightness.

Were Talking Quality Here

Because precast concrete products typically are madein a controlled environment, they exhibit high quality and

uniormity. Variables aecting quality typically ound on a job

site temperature, curing conditions, material quality and

cratsmanship are nearly eliminated in a precast plant.

Rough, Tough and Long-LastingPrecast concrete strengthens with time, while other materials

can deteriorate, experience creep and stress relaxation,

ANATOMY OF

A MANHOLE


3/10


lose strength and/or defect as they age. The load-carrying

capacity o precast concrete is derived rom its own structural

qualities and does not rely on the strength or quality o

the surrounding backll materials. Studies have shown

that precast concrete products can provide a service lie inexcess o 100 years. For severe service conditions, additional

design options are available that can extend the lie o the

precast concrete product. This is extremely important when

calculating lie-cycle costs or a project.

Nasty Weather? No ProblemPrecast concrete increases eciency, because weather will

not delay production o the manholes. In addition, weather

conditions at the job site do not signicantly aect the

schedule, because less time is required to install precast

compared with other construction materials, such as cast-in

place concrete or brick.

Watertight Darn RightASTM C478, Standard Specication or Precast Concrete

Manhole Sections, species the proper manuacture o

quality, watertight precast concrete manholes. Standard

watertight sealants and gaskets are available that are specially

designed or use with precast concrete, making multiple-

seam precast concrete manholes very easy to construct.

Vacuum testing is an easy means o veriying water tightness,

either in the plant or in the eld, as detailed in ASTM C1244,

Test Method or Concrete Sewer Manholes by Negative Air

Pressure (Vacuum) Test Prior to Backll.

Will Sit Tight Without Tie-DownsWith a specic gravity o 2.40 and superior rictional

resistance, precast concrete manholes resist buoyant orces

better than all other manhole materials. Fiberglass has a

specic gravity o 1.86 and HDPE has a specic gravity o

0.97, requiring the use o tie downs and ultimately increasing

project costs and installation headaches. With the many

advantages over alternative products, precast concrete

SUSTAINABLE BENEFITSOF PRECAST CONCRETE

RecyclingPrecast plants reuse ormwork, in itsel a conservationist

practice. Osite casting signicantly reduces construction

waste that would otherwise be generated on the job site.

In addition, cementitious materials used in concrete oten

contain manuacturing byproducts such as fy ash and

blast urnace slag that would otherwise nd their way to

a landll. Wastewater at the plant can be recycled or use

in manuacturing. Steel used or concrete reinorcement is

typically comprised o 95% post-consumer recycled content.

Reduced Site ImpactSince precast concrete manholes are manuactured o site

and delivered on demand, there is a signicant reduction in

truck trac, dust, noise and debris rom ormwork associated

with poured-in-place products. Because precast concrete

manhole components are modular and standardized, they

are installed in a quicker ashion and also result in reduced

construction times and energy usage, less noise and ewer

emissions rom on-site equipment.

Regional Natural MaterialsThe cement used in concrete is made rom common

natural materials such as limestone and clay. Most

cement plants rely on nearby limestone quarries, keeping

transportation distances to a minimum. Aggregates used in

the manuacturing o precast concrete manholes are also

generally extracted and manuactured regionally.

DurabilityConcrete is a very strong and durable material, which is a

signicant sustainable attribute. It will not rust, rot or burn and

has a service lie o in excess o 100 years.


4/10


Precast concrete manholes are a smart choice or projects

applying or LEED certication. Most o the credits shown also

qualiy or additional Innovation in Design points that are tied

to exemplary perormance o the credit listed.

SITE DEVELOPMENT: PROTECT OR

RESTORE HABITAT

(Sustainable Sites Credit 5.1)

Precast concrete manholes are plant cast and are delivered

to the site ready to set so they require very minimal site

disturbance to install.

STORMWATER DESIGN: QUANTITY

CONTROL

(Sustainable Sites Credits 6.1 and 6.2)

Most stormwater management plans will require manholes

in the design to properly handle the stormwater runo.

Precast concrete manholes unction as an integral part o

any stormwater system and can be counted on to perorm

exceptionally or many decades.

CONSTRUCTION WASTE MANAGEMENT:

DIVERT 50% (75%) FROM DISPOSAL

(Materials and Resources Credits 2.1 and 2.2)Precast concrete manholes are plant-cast and are delivered to

the site ready to set, creating minimal to zero amounts o on-

site water material.

RECYCLED CONTENT: 10% (20%) (POST-

CONSUMER PLUS PRE-CONSUMER)

(Materials and Resources Credit 4.1 and 4.2)

Precast concrete manholes may contain supplementary

cementitious materials such as fy ash and blast urnace slag,

adding to the projects recycled content goals.

REGIONAL MATERIALS: 10%

(20%) EXTRACTED, PROCESSED &

MANUFACTURED REGIONALLY

(Materials and Resources Credit 5.1 and 5.2)

The vast majority o materials that go into the manuacturing

o precast concrete manholes are available within a 500-mile

radius o the precast plant.

LEED PROPERTIES OF PRECAST CONCRETE

LEED or New Construction and Major Renovation 2009 Scorecard


5/10


When city ocials in American Fork, Utah, approved

construction o a 175-acre commercial center, a primary

concern or the citys engineers was the environmental eect

it would have on a 45-acre wetland right next door.

PEPG Engineering project engineers designed a sophisticated

stormwater runo treatment system or its new commercial

center, which would be the home or big box stores like The

Home Depot, Wal-Mart, Kohls and a 12-screen Cinemark

Theater. Since the commercial centers runo would

wash straight into the protected Mitchell Hollow Wetland

Conservation area, the challenge was more than just a

regulatory annoyance; it was a legitimate environmental

concern.

Coexisting With ConservationTo avoid the problem o purging during high fows, engineers

specied a two-stage oil and sediment separator. The two-

stage unit includes a bypass or large storm events so that

when fows exceed capacity, water runs through the unit

without disturbing accumulated sediments and oil, keeping

pollutants out o downstream waters.

The system has another eature: a large storage capacity that

incorporates two 60-inch precast concrete manholes instead

o a smaller cast-in-place vault. Since the eectiveness o

most water-scrubbing devices relies on a strict schedule o

cleanup, the separation unit provides a big advantage to the

small towns public works department. On average, the systemrequires cleaning only once a year.

The system includes three components: A primary precast

concrete manhole set in line with the storm sewer pipe, the

separator unit and a second manhole or storage.

Installation is SimpleThe basic installation is simple: Dig, set two manholes, slip

the separation unit in place and backll. Ater the excavator

digs a hole, the utility contractor places one manhole structure

in line with the storm sewer pipe to act as a catch basin and

then to the right or let to act as an overfow storage structure.Since the unit comes in both right-handed and let-handed

congurations, it oers some fexibility around other utilities

and obstacles.

The primary manhole has an outlet large enough or the

separation unit to slip into place, with two pipes dropping into

the catch basin and two outlets. Secondary pipes connect

the unit to the storage manhole, and a reducer connects the

unit to the storm sewer pipe. Gravel backll supports all the

components. Ater manhole rames bring the structures to

nished grade, dirt backll and paving complete the installation.

Precast AdvantagesAccording to Jim Schaeer, project engineer or Ames

Construction, which built most o the utilities or the American

Fork Commercial Center, it took less than a day to install each

system. Its a good thing, given that the project required about

30 manholes. This contrasts sharply with the traditional cast-

in-place system, which can take ve to seven days or each

installation when allowing or curing beore backll.

Project ProfleProject Name: American Fork Commercial Center

Owner: AFCC Limited, Salt Lake City, Utah

Engineer: PEPG Engineering, Draper, Utah

Contractors: HE Davis & Sons, Spanish Fork, Utah Ames

Construction, Salt Lake City, Utah Geneva Rock Products, North

Orem, Utah

Precast Manuacturer: Amcor Precast (a division o Oldcastle

Precast Inc.), Ogden, Utah

CASE STUDY

A Precast Concrete Stormwater Solution

A precast concrete manhole-based stormwater systemprotects the wetlands next to this commercial developmentin American Fork, Utah.


6/10


INSTALLATION PROCEDURES

Liting ApparatusUse approved liting slings that will adequately lit the weight

o the units and that conorm to OSHA standard 29 CFR

1910.184. The use o an approved or rated spreader bar is

preerred. When liting manhole bases and risers, make sure

the chain or cable lengths are long enough to prevent contact

with tongue-and-groove area, and are kept at appropriate liting

angles. Use wooden blocks between sling and manhole wall i

necessary.

Recommended Manhole BeddingUse a minimum o 6 inches o approved bedding material

compacted to 90% proctor in an area not less than the base

area, and preerably 6 inches beyond the outside radius o

the manhole base. The area under incoming and outgoing

pipes should be treated the same way to prevent shearing o

pipes. Local ground conditions may require additional bedding

thickness, according to the engineers recommendations.

Setting Manhole BaseSet the manhole base on graded bedding according to job

specications, making sure boots or pipe openings match

design elevations. Level the top o the manhole base in both

directions.

Pipe ConnectionsFollow the manuacturers recommendations or connections

and check with the manuacturer i precast inverts are

supplied.

Flexible Boot Connections Clean the pipe surace and

inside o boot. Insert the spring line o the pipe fush withthe inside o the manhole wall or as allowed by jurisdiction,

keeping the pipe centered in the connector. Install all take-

up clamps(s) in the groove(s) i provided at the receiving end

o the connector. Tighten the clamps to the recommended

torque, which will vary depending on size and manuacturers

specications. Any grouting that will inhibit the design/

fexibility o the connector should be avoided.

Compression Type Connector Cut a -inch bevel on the

end o the pipe to be inserted into the manhole. Clean the pipe

surace and inside area o the connector. Lubricate the inside

o the connector and exterior o area o the pipe being inserted

with an approved lubricant. Center the beveled end o the pipeinto the connector. Keeping the pipe level, push the pipe into

the connector until it is fush with the inside o the manhole

wall or as required by local specications.

Mortar Joint Locate the pipe into the opening to meet

elevations. Using non-shrink mortar, completely ll voids

around the pipe. Allow proper curing time beore backlling.

Pipe Stubs Any pipe stubs installed in the manhole must be

restrained rom movement to prevent blowout resulting rom

groundwater or any testing. A minimum o a 5-oot stub length

may be required.

Joint InstallationButyl Gasket Use only manuacturer-recommended sizes

or specic diameters. Clean and inspect all tongue-and-groove

suraces. Suraces should be ree rom all dust and debris.

On tongue-up manholes, place the butyl material next to the

vertical surace o the tongue. Wrap the material completely

around the unit overlapping each end. Knead the ends together

to orm a unied splice. Make sure all protective paper is

removed. Lower the bell end o next section making sure the

steps are aligned (i applicable) into the nal position. I the bell

is up, place butyl material next to the vertical surace o the

groove and ollow the above procedure.

Confned O-Ring Clean and inspect joint suraces. Lubricate

the joint surace liberally. Lubricate the O-ring gasket

thoroughly beore placing it into the conned groove space

provided. Run a smooth, round object between the gasket and

tongue around the entire circumerence several times. Lower

the lubricated end o the next section making sure steps are

aligned into nal position. Keep the sections level/plumb while

setting to prevent rolling the gasket and breaking the bell.

Oset and Pre-Lubricated Gaskets Install according to the

manuacturers specications.

Precast Lit Hole Sealing (ull penetration)Liting holes should be sealed by inserting a rubber plug orother approved material into the hole (i supplied) and/or lling

with non-shrink mortar rom both inside and outside.

Backfll Procedure you are vacuum testing, do the test beore backlling.

Detecting leaks at this time is easy and repairs are simple.

Distribute backll around the manhole in equal proportions to

prevent tipping. Compact the ll in lits, the same as with a

standard trench procedure. Backll material should be clean

and ree o large rocks.


7/10


Vacuum testing is a quick, sae and practical way to validate

manhole system integrity. Manhole sections can be tested at

the precast concrete plant prior to delivery or on site prior to

backlling.

Many codes and specications require that a vacuum test be

perormed ater the manhole has been installed and backlled.

Testing ater backlling provides a degree o certainty that a

watertight system has been installed. However, the major

disadvantage is the act that no industry standards exist

or vacuum testing ater the structure has been backlled.

Secondly, it is oten dicult to determine the cause or locate

and repair a system breech once the manhole has been

backlled.

The resolution to this problem is to perorm a vacuum test

beore backlling and, i necessary, ater backlling.

ASTM C1244, Standard Test Method or Concrete Sewer

Manholes by the Negative Air Pressure (Vacuum) Test Prior

to Backll, has been developed to govern the proper vacuum

testing procedure or testing concrete manholes. ASTM C1244

clearly states that a vacuum test is intended to be used as

a preliminary test to enable the installer to demonstrate the

condition o the concrete manhole prior to backll.

When utilizing ASTM C1244, a vacuum o 10 inches Hg is

drawn on the manhole ater all lit holes are plugged, and pipes

entering the manhole are temporarily plugged and securely

braced. The time is measured or the vacuum to drop to 9

inches Hg. The manhole is acceptable i the measured time

meets or exceeds the values presented in Table 1 o ASTM

C1244. I the manhole ails the initial test, it may be repaired

by an approved method until a satisactory test is obtained.

For more details on vacuum testing, please visit preast.org.

TESTING PROCEDURES

Vacuum Test Validates System Integrity


8/10


FIND A PRECASTCONCRETE MANHOLEPRODUCERWhether you need a custom project or standard product, visit

precast.org or call (800) 366-7731 to nd the precast concrete

manuacturers in your area. The Find a Producer button on

our home page leads to a powerul search engine that will link

you to the appropriate NPCA members based on your selection

criteria.

NPCA is happy to provide the data and support that you needto incorporate the latest precast concrete products into your

design. Check the Products & Ino section o our website to

nd inormation based on product lines. Or, contact NPCA

Technical Services directly either by email at [email protected]

or by phone at (800) 366-7731.

Want to reach the precast community, or connect with

engineers, architects, speciers and regulators who have in

interest in precast concrete? Join us on Facebook (acebook.

com/nationalprecast) and plug into the community. Its a daily

discussion o all things precast.

Certiy ExcellenceFrom start to nish, the NPCA Plant

Certication Program sets the highest

standards or plant acilities, production

operations and quality control procedures.

NPCA certied plants are dedicated to

manuacturing rst-class products. To maintain

their NPCA credentials, plants must pass

periodic, on-site certication inspections.

The NPCA Plant Certication Program enables

quality-conscious agencies, architects,

engineers and users to identiy and select

high-quality precast concrete manuacturers.

At no cost to speciers, NPCA certication

prequalies manuacturers as companies

capable o superior workmanship. You save

money, because you do not need to spend

valuable time and resources inspecting aplant to ensure that its products will meet

or exceed your expectations. You also save

time when you work with certied precast plants, because

products arrive on the job site ready or installation. Material

and labor costs are kept in check, because quality control

starts beore the work order reaches the precast plant.

The Certifcation ProcessTo become an NPCA certied plant, a precast concrete

production acility must exceed a level o excellence dened

by NPCA in accordance with relevant industry standards.Plant inspections are perormed by an engineer rom an

independent, nationally accredited rm, and all certication

applicants are graded on all critical aspects o plant operation.

A standard grading schedule is used or all inspections to

ensure uniormity. Inspections are perormed during actual

plant operation.

The NPCA Certifed PlantPrecast concrete plant operators committed to excellence

seek NPCA certication. Plants committed to quality

invest the time and resources necessary to meet the high

standards demanded by the construction industry. Staed

by experienced personnel, plants complying with NPCA

guidelines practice quality assurance at every step o the

production process. These guidelines require procedures and

products to be inspected during each phase o manuacturing

to ensure compliance with rigid industry requirements. As a

result, products rom NPCA certied plants are characterized

by high quality, uniormity and consistency. Each NPCA

certied plant is also required to maintain an active plant

saety program that meets or exceeds local, state, provincial

and ederal laws and the rules and regulations o the U.S.

NPCA PLANT CERTIFICATION

Occupational Saety and Health Administration (OSHA) and

Canadian Centre or Occupational Health and Saety.

NPCA guidelines require certied plants to maintain extensive

records to veriy that materials used in the manuacturing

process conorm to appropriate specications. Work orders,

product drawings, equipment calibration records, aggregate and

concrete test records, batching reports and product inspection

reports are also required as management tools and quality

assurance aids.


9/10


MANHOLE DESIGN NOTES Applicablestandard:ASTMC478,StandardSpecicationforPrecastReinforcedConcreteManholeSections

Typicalsizes:48,60,72,84and96-inchdiameterswithothersizesavailable.

Diameterofthemanholeistypicallybasedonthemaximumpipesizeandtheminimumstructurallegbetweenpipe

holes.

Risersectionstypicallycomeinincrementsof12inches,upto48inches.

Transitionslabsmaybeusedtoreducethemanholediameteroveralargerbasesectiontominimizecosts.

Holesinprecastmanholeconcretesectionsforinuentandeffuentpipeconnectionscanbecastduringpouring,or

cored ater the product has cured. Holes may need to be gasketed with compression or fexible type connectors as

described in ASTM C923 and C1478.

Thebasemaybepouredmonolithicallyormayhaveaseparatebase.Aninvertorowchannelcanalsobepouredintothe

base section i required.

Weldedwirereinforcingorhoopsteeliscommonlyusedinprecastconcretemanholes.Theminimumtotalwall

reinorcing area required is 0.0025 times the internal diameter in inches per vertical oot as noted in ASTM C478.

Baseandtopslabsmusthaveaminimumreinforcementof0.12sq.in./ftineachdirectionfor6i-inchslabthickness.

Jointsinmanholesectionsaredesignedtoresistpassageofsolidsoruidswhiletightenoughtopassvacuumtestingif

required. Rubber gaskets and/or preormed mastic or butyl gaskets are used to seal the joint.

Stepsareinstalledduringthemanufacturingprocess,andmustconformtorequirementsoftheOccupationalSafetyand

Health Standards, U.S. Department o Labor. Standard loads are outlined in ASTM C478 and C497.


10/10


ADDITIONAL RESOURCESASTM A48/A48M, Standard Specication or Gray Iron CastingsASTM A185 / A185M, Standard Specication or Steel Welded Wire Reinorcement, Plain, or Concrete

ASTM A496, Specication or Steel Wire, Deormed, or Concrete Reinorcement

ASTM A497/A497M, Standard Specication or Steel Welded Wire Reinorcement, Deormed, or Concrete

ASTM A536, Standard Specication or Ductile Iron Castings

ASTM A615/A615M, Standard Specication or Deormed and Plain Carbon-Steel Bars or Concrete Reinorcement

ASTM A884, Specication or Epoxy-Coated Steel Wire and Welded Wire Reinorcement

ASTM C443, Standard Specication or Joints or Concrete Pipe and Manholes, Using Rubber Gaskets

ASTM C478, Standard Specication or Precast Reinorced Concrete Manhole Sections

ASTM C497, Standard Test Methods or Concrete Pipe, Manhole Sections, or Tile

ASTM C923, Standard Specication or Resilient Connectors Between Reinorced Concrete Manhole Structures, Pipes, and

Laterals

ASTM C990, Standard Specication or Joints or Concrete Pipe, Manholes, and Precast Box Sections Using Preormed

Flexible Joint Sealants

ASTM C1244, Test Method or Concrete Sewer Manholes by the Negative Air Pressure (Vacuum) Test Prior to Backll

ASTM C1478, Specication or Storm Drain Resilient Connectors Between Reinorced Concrete Storm Sewer Structures,

Pipes, and Laterals

manhole tech brochured

Documents