“the weak links in the wastewater collection system

“The Weak Links in the Wastewater Collection System: Manholes and Access Devices”

Antonio V Almeida, PE CMOM 2014 Austin Texas

August 19, 2014

• Manhole Design • The Manhole Paradigm –past,

present & future • Leakage • Location • Corrosion • Structural • Access

• Chambers • Questions

Agenda

The Manhole Design Technical Guidance?

ASCE MOP #60 WEF # FD-5 1930, 1935, 1962, 1982, 2007

(415) (9) Pages

ASCE manual of practice #92 2009 (74) pages

100 years old 1914 (747) (50) pages

VoL II (548) pages

• Provide convenient access to the sewer for observation and maintenance operations.

• Cause a minimum of interference with hydraulics of the sewer. (2 pages)

• Be a durable and generally watertight structure.

• Be strong enough to support applied loads.

The functional

design objective of wastewater collection manholes,

is four-fold:

Wastewater Manhole Design:

WEF Manual of Practice No. FD-5, ASCE MOP No.60 (415pages, 9 pages to manholes) 1982-2013 • Provide convenient access to the sewer for observation and maintenance operations.

• Cause a minimum of interference with hydraulics of the sewer.

• Be strong enough to support applied loads.

• Be a durable and generally watertight structure.

Wastewater Manhole Design Paradigm

• Manhole Paradigm Shift – Do you perceive that this

manhole is watertight? How?

– Do you know when this manhole may not be watertight?

– Do we know the amount that this manhole leaks?

– Is location an issue? Does it matter?

Wastewater Manhole Regulatory Location Requirement

• In the low path of a water course, or

• In an area where ponding of surface water is probable.

Requires that a manhole must not be

located

(TCEQ) Chapter 217.55 (j) – Manholes and Related Structures

Wastewater Manhole Regulatory Location Requirement

• A manhole must not be located in a stream bed or where inundation may occur.

New Proposed

Regulatory Wording


Wastewater Manhole Paradigm

Manhole subjected to ground water above invert (A manhole must not be located in a stream bed or where inundation may occur)

Wastewater Manhole Design

Material Science

Corbel Area • Cover & Frame • Frame seals • Grade Rings

Base Types

Wall and joints

Pipe connections

Wastewater Manhole Leak Resistant Design

Leak prevention- Materials

Traditional – (Difficult to achieve leak prevention goal) • Brick • Block • Concrete

• precast or cast in place

Newer Materials – (Improve leak prevention goal) • Fiberglass

Reinforced Plastic (FRP)

• High Density Polyethylene (HDPE)

• Polymer concrete • PVC


Wastewater Manhole Material Paradigm

Affiliated with the Cretex Companies, Inc., Cretex Specialty Products

Internal mechanical chimney seals

External manhole chimney seals

Applied manhole chimney seals

Manhole adjusting rings

Internal manhole barrel joint seals

Internal pipe joint seals

External joint wrap

Gasketed Pipes

Non-Gasketed Pipes

Arch Pipe

Elliptical Pipe

Manhole adjusting rings

Box Culvert, Single Cell

Manholes, Sanitary Manholes


Newer Materials Lack of Industry Acceptance

Perceived structural weakness

HDPE ASTM F1759

Concrete ASTM C 478

Buoyancy fears


Newer Materials Lack of Industry Acceptance

• Backfill and compaction requirements

• Layup procedures (FRP) • Connection flexibility • Fusion welding (HDPE) • Grade adjustments

Inexperience issues

& Change is Difficult


The Future of Manhole Material Wastewater Manhole Paradigm

Leak Prevention Frame, and Cover

Frame and cover originally not intended to be water tight

New frame and covers offer

machined surfaces with gasket seals that require bolts


Leak Prevention Frame and Grade Ring Seals

• Challenge to meet leak prevention goal

• Not intended to be water tight • Normally not easy to detect • Many products in the market

place

Frame and grade rings

seals


Leak Prevention Frame Seal and Grade Rings

• Support applied loads • Absorb vibration &

temperature movement • Provide leak prevention

The three functions of

the frame seal and

grade rings interface are.


Difficult to achieve long term

Leak Prevention Frame Seal and Grade Rings


Leak prevention-pipe-wall connections

• 10 psig watertight sealing at 7o axial deflection.

• 13psig watertight sealing in straight alignment

ASTM C923:


Leak prevention - Pipe-Wall Connections


Leak Prevention-Wall Joints

Therefore testing for shear or load not required

Joints are designed for axial compression

Steel reinforcement not required in the joint

ASTM C 478


Manhole Types

Manhole Types

Cylindrical manholes “barrel bottom”

Tangential manholes “tee up”


Manhole Type Cylindrical “Barrel bottom” Wastewater Manhole Design

Manhole Type Tangential “Tee up” Wastewater Manhole Design

• Hydrostatic Test • Allowable leakage of 0.025

gallons per foot diameter per foot of manhole depth per hour

• Vacuum Test - common use • A 2.0 minute long test holding

a vacuum of 9.0 inches of mercury

Requires that a new

manhole must pass a

leakage test

(TCEQ) Chapter 217.58 – Testing Requirements for Manholes

Wastewater Manhole Regulatory Leakage Requirement

Wastewater Manhole Regulatory Leakage Requirement

• Section (c) - If a manhole fails a vacuum test, grout must be applied to the exterior of the excavated manhole and the manhole must be retested in accordance with the requirements of this section.

New proposed regulatory wording

for vacuum testing

manholes


Venting

Venting occurred at manhole covers with holes

Venting will occur regardless

Lack of design understanding in venting sewer gas

Inhabited areas

Need access for maintenance

Reduce odor nuisance


Corrosion


Corrosion Resistance Coating and Liners

Cementations products • Micro silica • Alumina calcium • Admixtures

Thermoplastic Liners • Polyethylene • PVC • Polypropylene

Thermoset liners • Cured in place • Panel Inserts • Lay up systems

Polymers • Epoxies • Urethanes • Urea's

Surface Preparation

Material selection

Application limitations

Testing and inspection

Performance expectations not realized


Composite Systems

Coating and liner failures


Corrosion


Wastewater Manhole Regulatory Access

Issues

• At least a 30-inch diameter clear opening.

A manhole where

personnel entry is

anticipated requires

(TCEQ) Chapter 217.55 (l) – Manholes and Related Structures - (1A) manhole covers

Access Paradigm Issues

• Require all new manholes to be at least a 30-inch diameter clear opening or

• Continued with standard manhole lids in the system and restrict personnel entry.

Current User response to

this regulatory

access issue

Wastewater Access

A new paradigm in the making

Access Paradigm Issues

• What is the benefit of providing personnel entry in manholes?

• Especially to pipe system that do not allow personnel access?

Paradigm Shift

Questions ?

Wastewater Access

Wastewater Access Chambers

In 1990, the introduction of the

Wastewater Access Chamber (WAC) in Dallas,

Texas,



OSHA-confined space entry

requirements

TCEQ now 30-inch manhole covers • April 1986 Dallas

Correct use • Improve access for

cleaning and maintenance

• Less cost


Paradigm Shift-Need For Change

Giant step to the perfect

manhole/access chamber

FRP HDPE polymer concrete

Use of Portland

cement based manholes

with protective coatings

internal and external

seals

rubber gasket joints

flexible pipe connectors

Continuous repairs to prevent

extraneous inflow to

manholes corrosion

Change “Change is the law of life and those that look to the past or present are certain to miss the future” by JFK


Questions


“the weak links in the wastewater collection system

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