Challenges in Design and
Construction of LDWM
Presented by:
Rafael Ortega, PE
Lockwood, Andrews & Newnam, Inc.
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Rafael Ortega, PE
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Vice President
Lockwood, Andrews & Newnam, Inc.

Agenda
Introduction
Design Issues
ROW Concerns
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Technical Specifications
Critical Installation and Constructability

Design Issues

Urban Environment
Anticipating issues ahead of time
Reducing unknowns
Constructability
Innovative solutions
– How to do more with less funding

Goal of Urban Project
Minimize impact to traffic
Avoid disturbance to adjacent structures
Reduce surface restoration
Limited staging or work area
Avoid utility conflicts
– Maintain services
– Reduce outages
– Avoid relocations

Understanding “What it Takes
What Takes”
Project requirements
Site visits – key to more
complete designs

Subsurface Utility Engineering
Critical in an urban environment
Increase contractors’ level of confidence
– Design package
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– Bidding
– Construction

Geotech Investigation
Soil conditions vary along alignment
Determine limits of soil variations
Subsurface conditions impact:
Sb f diti i t
– Long-term performance of pipeline
Long-
– Specifications
– Tunneling criteria
– Construction claims

Traffic Control
Key to project acceptance by stake holders
The more detailed the less disruption
Optimize h i
O ti i phasing:
– Minimize duration of impacts
– Provide for progressive transitions

ROW Concerns

Main Alternatives
Greenspoint Mall IAH Airport
Greens Rd.
World Houston
Lauder
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Route Evaluation Factors
Limits of City jurisdiction
ROW Acquisition
Distinct Neighborhoods
Di ti t N i hb h d
Type of Construction Environment
–DDevelopment type
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– Contamination

Easement Breakdown
Aldine
Easements Lauder Greens
Bender
Residential 37 26 8
Commercial 28 51 14
Undeveloped Tracts 14 27 21
TOTAL 79 104 43
Estimated structures impacted 2 5 0

Public Coordination
Businesses
Bus routes
School year
Emergency access
Special event traffic

Technical Specifications

AWWA Standards
Minimum requirements
Alternatives w/in standards
Responsibility of specifier to address project
issues

Rigid vs. Flexible
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Width of Trench
– Practical Space Required
– Larger Pipe = Larger Width
All Pipe Not Created Equal

All Pipe Not Created Equal
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Made to Order
Material
Mt il
Properties
– less fo gi ing
forgiving
Design
Considerations

Nonmetallic Materials
PVC, FRP, HDPE
PVC FRP
Speed of installation
Alternatives in stray current areas
Alt ti it t
Steel or DIP bends and outlets
–V l
Valves, fittings, and outlets
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– Vertical and horizontal

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Fusing Operation
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Pipe Comparison Summary
Gasket
Field Joint
Pipe Corrosion Modifications Field Welding Bonding
Pipe Material Design Joint Type Protection Allowed? Allowed? Req’d?
Ductile Iron
D til I R/F G Y Y N Y
Steel F G or W Y Y Y Y or N
FRP F G or W N Y N N
Fused/
HDPE F Flanged N Y Y N
PCCP R G or W Y N Y Y or N
Bar Wrapped F G or W Y N Y Y or N
F = Flexible R = Rigid G = Gasket W = Welded Y = Yes N = No

Critical Installation
and Constructability

Challenges During Construction
Pipe material availability
Private utility relocations
Competition for contractor’s
resources
Construction phased to
C t ti h dt
avoid impacting operations

Construction Issues
Verify densities of pipe bedding
Lay pipe continuously
Do t
D not remove stulls prior to backfill
t ll i t b kfill
Perform internal inspections during construction

Bedding Requirements
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Pipe Embedment
– Bottom shaping
– Compaction at haunches
Movement of trench support
Use of special embedment material (depth)
Trench dams

Backfill Critical
Effectiveness of compaction critical
– Loading capability
– Deflection affects coating and linings
E’ = Modulus of Soil
– % Compaction
– Type of Soil
– Greatest Affect on Wall Thickness

Improper Installation

Proper Backfilling

Joint Grout
Mortar
Spigot
Lining
Ring

Closure Considerations
Butt Strap
– Requires true alignment
– 12 wide w/ 4” minimum overlap required
12” 4
– Welding of prestressed wires
Grouting Requirements
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– Wire mesh
– Non-shrink grout
Non-
– Interior and exterior welds

Butt Strap
Butt-Strap
Closure Piece
Cl Pi Poorly Grouted
P l G td

Exterior Joint Grout
Diaper;
– w/ ethafoam backing
– Width
Installation
– Grout mix and testing
– Bottom joint recess (similar to bell form)
– Rod and set time required
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Ungrouted Exterior Joint

Annular Space Issues
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Flotation of Pipe
Grouting Monitoring
– M it i key
Monitoring k
– Pressure and volume
– Potential exists w/ low-density grout
low-

Grouting Pressure Problems
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Testing of Line
Impacted by potential contamination from
existing section
Water discharge receptors
– Capacity
– Locations
Schedule considerations
– Fill rates
– Required interconnects – temporary and permanent

Unavoidable Change Orders
Debris encountered in excavations
Longer work duration
Unanticipated services
U ti i t d i
– Active
– abandoned

Questions ?