IWA Webinar: Introduction to No-Dig Technologies and the ISTT

Main Ideas and Lessons Conveyed

1) Purpose of the webinar and collaboration context

• The session is an introductory webinar jointly hosted by:
  • International Water Association (IWA)
  • International Society for Trenchless Technology (ISTT / IST)
• They describe a 2025 agreement aimed at mainstreaming trenchless technologies for:
  • water, wastewater, and storm water infrastructure
  • especially for utilities and service providers
• The wider goal is improving underground asset management and addressing urgent challenges like water loss.

2) What “trenchless” and “no-dig” means in practice

• A utility network owner is described as owning a linear system in the ground (pipes) connected to the surface via shafts/manholes.
• Because pipes must function over very long time horizons, the industry needs methods that avoid constant surface disruption.
• Trenchless/no-dig is framed as reducing or avoiding:
  • major excavation and disruption to surfaces
  • impact on traffic, pedestrians, businesses, access, and drainage processes
• Core concept: rely on launch/receiving points rather than long open trenches.

3) IST’s scope and role

• IST is described as a society covering all utilities, not just water:
  • gas
  • district heating
  • electricity
  • water
  • wastewater
  • communications
  • urban drainage
• IST is described as an umbrella for 28 national societies across regions including:
  • North/South America, Europe, China, Australasia
• IST objectives include:
  • advancing the science and practice of trenchless technology
  • promoting education and training for public benefit
  • connecting utilities, engineers, contractors, manufacturers, etc.

4) The “three trunks” of trenchless work (IST framework)

The presentation groups trenchless technologies into three main categories:

A) New installation

• Installing new mains/connections with minimal surface disruption.

B) Rehabilitation (long-term lifecycle focus)

Rehabilitation is divided into three elements:

• Repair localized issues
• Renovation to extend life (upgrades/strengthening/corrosion protection)
• Replacement with a functional equivalent along the same alignment (often “trenchless replacement”)

C) Site investigation (to decide the right method and route)

• Essential to determine:
  • asset condition
  • where to access or route
  • the safest route
  • the best technique

5) Benefits and rationale for trenchless vs open-cut

Key advantages repeatedly emphasized:

• Reduced disruption
  • less road opening and traffic congestion
  • fewer customer complaints (an anecdote: “love you guys” due to fewer complaints)
  • less interruption of drainage during works
  • reduced damage to other utilities during construction
• Health & safety
  • reduced need to dig trenches where workers and public face risks
• Environmental and community impacts
  • less air and noise pollution
  • less excavated waste
  • reduced tree root damage
• Cost and schedule advantages (context-dependent)
  • potential for reduced project costs
  • quicker delivery when road rental is avoided
  • less reinstatement and fewer compensation claims
  • reuse of infrastructure

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Methodology / Structured Frameworks & Technology Lists (Detailed Bullets)

A) How trenchless decisions are approached (IST concepts)

• Step 1: Understand asset condition
  • assess deterioration and operational status
  • use results to plan maintenance/repair/rehab/replacement financially
  • perform periodically, continuously, or using autonomous approaches in the future
• Step 2: Conduct site investigation
  • determine asset location (where pipes are)
  • determine asset environment (what’s around/beneath and how it behaves)
  • use findings to decide safe routing and best technique
• Step 3: Select technology category
  • choose among:
    • New installation
    • Rehabilitation
      • repair
      • renovation
      • replacement
• Step 4: Use evidence/resources
  • reference IST website pages that list technologies
  • encourage owners/consultants to use a “selection matrix” mindset
  • engage the supply chain when the “best match” has been chosen (supply chain will support)

B) Site investigation split: Asset location vs Asset environment

1) Asset location (where the pipe/equipment is)

Examples and methods mentioned:

• drone-delivered LIDAR / GPS 3D modeling of sewer location vs utility maps
• tracing by internal/within-pipe methods such as:
  • internal survey techniques
  • smoke and dye testing (mentioned)
  • sand-impressed signals with sonar retrieval from the surface (sonar-based tracking)
• External/around-pipe methods:
  • ground-penetrating radar
  • seismic techniques
  • sonar techniques (as part of location building)

2) Asset environment (ground conditions affecting performance and construction)

Four areas were referenced:

• Groundwater monitoring
  • depth and seasonal behavior inform design/rehabilitation timing
  • quality matters (including aggressive waters and saline intrusion)
• Thermal environment
  • infrared/thermal imaging used for leak detection context (illustrative example)
• Electromagnetic environment
  • resistivity/probing methods to understand underground conditions (e.g., find clay vs other strata)
• Ground investigation
  • geophysical surveys
  • geochemical surveys
  • soil sampling

C) Asset condition assessment split: visual, structural, operational performance

1) Visual assessment

Uses multiple sensors and delivery platforms:

• fly, walk, crawl, float, dive through pipe systems
• pushed by equipment or by flow of liquid
• dragged by parachute along the pipe line
• fixed sensors
• mentions man-access chambers can be avoided in some cases

Examples:

• crawler CCTV
  • uses AI to interpret/classify damage
• pole zoom camera
  • allows upstream/downstream viewing
  • helps identify roots, leaks, and wildlife presence

2) Structural condition assessment

Methods grouped into:

• wall thickness measurement
• structural response measurement
• external void detection (soil–pipe complex)

Example methods/tools mentioned:

• electromagnetic, acoustic, infrared, impact methods
• “nuclear” methods like X-ray (mentioned)
• smart pig with magnetic sensor for wall thickness changes
• gauges to monitor structural changes

Emphasis:

• voids in surrounding soil matter because the soil supports the pipe.

3) Operational performance assessment

Gravity pipes:

• infiltration/inflow assessment

Pressure pipes:

• leak detection (water, gases)

Methods mentioned:

• leak signature detection
• smoke detection (described as potentially older/simple)
• a method illustrating a small parachute pulling a sensor through the pipe using water flow

Data and AI:

• combining condition/regeneration data into datasets
• AI monitoring for issues like storm sewer overflows

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D) Rehabilitation technology categories (repair / renovation / replacement)

1) Repair (structural or non-structural)

Non-structural repair (examples)

• dealing with infiltration
• grouting methods, including:
  • joint grouting with packers:
    • block pipe ends
    • inject grout into void around a joint
    • cure
    • remove packer
  • joint/lateral connection grouting variations with shaped packers

Structural repair (examples)

• cured-in-place patch repair:
  • insert resin-impregnated felt strip with a packer
  • inflate packer to position patch
  • cure resin
  • deflate/remove packer leaving repaired pipe section
• lateral junction repairs with shaped “sock”/felt configurations

Conceptual takeaway

• Repairs can address leaks/infiltration and structural failures, but patch design must match structural requirements.

2) Renovation (extend life)

Two sub-approaches were contrasted:

Loose-fit lining

• e.g., continuous slip lining
  • pull in a smaller-diameter new pipe
  • existing pipe remains
  • may reduce cross-sectional area
• segmental installation:
  • lower sections into place
  • screw-fix segments together
  • push/install section-by-section

Close-fit lining

• cured-in-place liners (continuous impregnated carrier materials)
• methods leveraging plastics flexibility:
  • squeeze down and pull in, then reform
  • fold and drag through, then inflate
  • spiral wound methods and “melt-in-place” methods mentioned
• surface applied linings
  • sprayed/manual applied
  • bolt-on panels for internal surface
  • example: cement mortar lining applied by a spinning head/vortex spray
  • can be structural or anti-corrosion

3) Replacement (functional equivalent along same alignment)

Trenchless replacement methods mentioned:

• pipe bursting (shatter existing pipe, pull through new)
• pipe splitting
• pipe extraction (remove old pipe and insert replacement behind; example: lead service pipe replacement)

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E) New installation techniques (no/low-dig)

Key methods mentioned:

• Horizontal directional drilling (HDD)
  • drill with a spinning head using slurry
  • directed boring through the ground; supports a range of diameters
• Pipe jacking
  • tunnel head + segments pushed behind into the ground
• Boring (cutting head + auger; soil removed from cutting location)
• Pipe ramming (push pipe in; soil contained within pipe, removed)
• Impact mulling (mole gradually forced through from pit to pit)
• Keyhole drilling / potholing
  • small road/garden cuts to create entry pit (often via vacuum excavation)
  • insert keyhole drilling machine, drill to property, then attach and pull back new pipe
  • finish with long-handled tools for connections
  • described as sometimes bridging into “load dig” style methods (connection-focused, long-handled tool approach)

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Q&A Key Points (Questions Asked and Main Answers)

1) Can trenchless be applied to all soil types (sand/silt)?

• Yes.
• Some technologies are best in soft materials, but others use different drilling/tunneling equipment for harder ground.

2) Can trenchless continue when hard rock/basalt is encountered?

• Site investigation is critical beforehand.
• If obstacles are found, rerouting may be required.
• Large projects may combine approaches:
  • fully trenchless sections
  • excavated segments
  • mixed methods depending on what is encountered.

3) Locating a leak on a water supply pipeline (exact location)

• Depends on pipe diameter/material and constraints for some technologies.
• Suggestions:
  • use IST resources/papers and search the site’s archives
  • consult local utilities that have tried methods
• Example given:
  • some water companies use trained “sniffer dogs” to smell chlorine.

4) Maximum diameter and length for trenchless installation

• General answer:
  • some methods can reach “quite large diameters”
  • for very large diameters, approaches transition toward tunneling
• Example scale mentioned:
  • around 1.5–2 m or more, acknowledging claims could be larger depending on experts/methods.

5) Suitability for upsizing/replacement in hard rock (granite) for vitrified clay / reinforced concrete

• Depends on size and project constraints (including maintaining service).
• Pipe bursting may help enlarge through breaking/enlarging the bore.
• Hard rock may push projects toward tunneling-like approaches or require installing a new larger pipe rather than purely enlarging/pulling through.

6) Trenchless placement of a vacuum sewer pipeline that is not straight

• If bends exist:
  • may need to dig down to insert a bend, then apply trenchless liner/sections on straight runs
• Alternatively:
  • a directional device might allow curved/changed direction during installation
• Example from research:
  • two close 45° bends may require treating as two separate liner shots with a dig-down intervention
• Reminder:
  • manufacturer limitations may require dig-first repairs for certain damage levels.

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Speakers / Sources Featured

Speakers

• Afia Siddiki — host/introducer (IWA), housekeeping rules, agenda, and Q&A facilitation as moderator/host
• Andrea Ross — webinar moderator mentioned in the agenda (IST working group on strategic alliances; based in Germany)
• Andreas Bros (Andreas Cruz) — moderator (moderating the webinar after initial host remarks)
• Dr. Ian Naymith — main presenter; Chair of the UK Society for Trenchless Technology; Chair of IST Technical and Education Committee; also described as a Senior Research Fellow at IKT (Institute for Underground Infrastructure)

Panelists / Audience members in Q&A (asked questions but not named as formal speakers):

• “EI” — asked about soil types
• “Eph” — follow-up about rock/basalt and encountering hard ground
• “Manish” — asked about locating leaks on water supply pipelines
• “Jose” — asked about upsizing/replacement in hard rock and vitrified clay / concrete pipes

Sources / Organizations Referenced

• International Water Association (IWA)
• International Society for Trenchless Technology (ISTT / IST)
• UK Society for Trenchless Technology
• IKT, Institute for Underground Infrastructure
• ISTT/IST website, noted as containing:
  • diagrams
  • ~120+ trenchless technologies listed under new installation/rehabilitation/investigation
  • ~2,000 technical papers archive
  • AI assistant for queries