Tunnel FAQ

Can a tunnel have multiple uses?

Yes, especially in an environment where multiple government agencies and/or utilities are willing to cooperate. For example, a new highway tunnel can also be built to accommodate duct banks for power, cable, fiber optics and other technologies; essentially becoming a utility corridor or ‘Utilidor.’ The SMART Tunnel in Kuala Lumpur is a highway tunnel that doubles as a flood control tunnel during periods of heavy storms/flooding. More and more water tunnels are being evaluated for power generation where practical. Tunnel use is limited only by creativity and political will.

When should I consider a tunnel for my infrastructure?

Tunnels are a practical, reliable and cost-effective in the long term. Use examples include:

• A tunnel through high snow-covered mountains is likely to be more cost effective and practical than a major highway crossing the mountains at the surface.
• A new surface highway across a developed metropolis (or busy rail yard) would likely be technically infeasible due to existing infrastructure. A highway tunnel could be built instead.
• Open cut sewer installations at depths greater than about 20 to 30 feet are typically more expensive than a tunneled alternative. This is particularly true in poor ground, in congested commercial or residential areas and/or areas with extensive underground utilities.
• A tunnel may be the best option in an urban environment where real estate, right-of-way, and environmental impacts can be significantly reduced by the smart use of underground space.

In addition, tunnels can free up surface space for more productive use. They are increasingly being used to eliminate surface roads or unsightly decrepit bridge structures that cut off one part of a city with another. This is creating new green spaces and chances for more beneficial surface use and development.

Aren’t tunnels more expensive than conventional construction?

Typically yes, but you would not build a tunnel unless there were factors making it a more cost effective/technically feasible solution to your infrastructure needs. For example, if surface space restrictions and existing utilities make a surface highway or shallow grade separation impractical.

Aren’t tunnels way too risky and dangerous?

There was a time when that was true but with the modernization of equipment and the proliferation of experienced tunnel contractors and designers, tunnels are as safe as any other construction method. The industry is much better now at assessing and mitigating project risks, resulting in safer and more successful tunnel projects.

How safe are tunnels in an earthquake?

Tunnels move with the same frequency as the shaking ground and are one of the safest places to be in an earthquake. Design takes expected seismicity into account and tunnels are typically planned to remain operational in the event of seismic activity.

Furthermore, you are not subject to falling glass or building debris in a tunnel as you would be walking amongst high rise buildings.

It’s just a circle on a drawing… How hard can it be to design?

The proper design of the tunnel and associated connections, appurtenant structures, and systems requires skilled individuals from a broad range of general Civil, Structural, Geotechnical, Mechanical, Electrical and other engineering disciplines with a thorough understanding of such things as:

• Soil (and rock)/structure interaction.
• Groundwater control
• Ground modification methods
• Shoring systems
• Underground gasses
• Geotechnical and structural instrumentation
• Current codes and regulations specific to the tunnel application
• Proper ventilation, lighting , fire and life safety design for occupied tunnels
• Surge control, air entrainment and ventilation for water/wastewater tunnels
• Environmental considerations and requirements

My local wastewater (or highway design) consultant has little to no expertise when it comes to tunnels, but they have served me well for 30 years. Why shouldn’t I trust them to design my upcoming tunnel?

Tunnel engineering is a specialist field and should be undertaken by individuals and firms who are well versed in the geosciences and have extensive experience in underground design and construction. In this way, you have some certainty that the underground risks are understood, mitigated, and allocated in an acceptable way. You would not have your sewer or highway consultant design a sports stadium or a new sports car. Why would you have them delve into tunnel design and construction without the requisite experience and skillsets?

That said, local knowledge is important and non-local tunnel design firms often join forces with local firms familiar with the local ground conditions, permitting authorities and other information specific to a given locality.

My tunnel consultant (or contractor) promises certain experienced staff but I never see them on the project. What can I do?

Sometimes there are legitimate reasons for this, such as health or family reasons. Other times firms promise the ‘A team’ and deliver the ‘D team.’ This is an indication that the firm could be over-committed and may not have the resources to perform the number of projects it is currently undertaking. To discourage this behavior, consider putting clauses in your contract along these lines:

• No changing of promised key staff without prior written permission from the client/owner. “Key” in this case refers to named individuals in oversight or lead positions in the firms’ proposed organization chart.
• Penalties (some dollar amount) for changing key staff without owner/client permission. These should be large enough to discourage the behavior. A contractor penalty should typically be higher than that of a consultant due to the magnitude of the respective fees; i.e. a contractor who stands to make orders of magnitude more profit than a consultant can easier absorb the same penalty amount.
• Termination clause for changing key staff without owner/client permission.

These clauses will always get attention from a contractor or designer or CM consultant when weighing one competing staffing need on a project vs. another project. Ideally it will prevent over-committed firms from proposing on your work.

What is more important when selecting a tunnel consulting firm (or tunnel contractor)? Firm experience or individual experience?

Both are important. It is most important that the individuals are experienced since they do the work, not the firm or the firm’s reputation. However, selecting a firm with a reputation for successful tunnel work provides a better chance that the firm’s individuals will be provided adequate resources and material. When selecting, don’t just ask for the consultant’s or contractor’s references; check them! But be aware you will not likely be provided bad references. Checking deeper at a past client could either reinforce a good recommendation or uncover bad recommendations and poor past performance.

My local (state) bylaws will not allow me to pre-qualify contractors. How can I make sure I get a qualified tunnel contractor to build my project?

Some states have allowed prequalification with a waiver for sufficiently unique or complex projects, so don’t immediately assume it is impossible. That said, even in the best case it will take time to get a waiver, so allow for this.

Assuming you cannot get a waiver, minimum qualifications can be stated in the contract and evidence of the qualifications can be required with the bid. Most agencies are free to not award to a contractor that does not meet the minimum requirements. However, far too often, the contractor without the required qualifications is also the low bidder; sometimes by a significant amount. Agencies and their governing Boards must then decide whether to gamble that the risk of choosing a contractor with questionable qualifications will cost them more than the difference between the enticingly low bid price and the next highest bid. All too often owners have accepted a low bid from a non-qualifying contractor in order to ‘save’ 20 to 30% over the next high bid, only to pay 50 to 100% in additional claims during construction.

One word of caution. When developing minimum experience requirements for contractors (or designers) make sure that the requirements are reasonable. Requirements that are overly and unnecessarily restrictive eliminate competition from highly qualified firms and individuals.

Should I have my designer do Construction Management/Administration for my tunnel, or should I hire another firm? Should I self-perform?

There are several schools of thought on this.

Both 1 and 2 above can be true to some degree, but in the end it is the staff involved, and their professionalism, that should be judged and not the philosophy.

1. Some owners feel that putting the designer in charge of construction administration is like having the “fox guard the henhouse.” They fear that the designer will have pride of authorship and not want to admit mistakes. This behavior has certainly occurred in the past and can lead to conflict on site and ultimately delays and claims. For this reason, these owners self-perform or hire an independent firm.
2. Other owners believe that after a year or two of working on every detail of the project, there is no one better to oversee construction administration than the design firm.

If you can answer “yes” to most of the following questions, consider leaving your design firm in place for Construction Management services. If not, consider hiring an independent firm, or staffing up your agency if your program is long enough to allow acquiring appropriate staff:

• Does your design firm have staff with the right construction experience and availability to do the job?
• Does the named Resident Engineer have the right temperament to work with the contractor and the owner’s staff? To interface with the public if the agency desires? Personality conflicts are a major reason for disputes during construction. Patience and fairness when administering the contract, and sometimes compromise, are required.
• Have you gotten favorable reference checks on key proposed staff? Check references on their past 2 or 3 projects and not just the names they give you. A few quick phone calls to their past clients can often unearth patterns of good or bad performance.

On a final note, a blend of Owner and Designer staff can be ideal and many owners opt for this arrangement. This works especially well when an owner’s representative is on site full time to make quick decisions regarding contract performance, for example. Note that using your design firm should cost you less (no re-procurement of a CM team) and you will not have the conflicts and differences of opinion that normally develop when more than one consulting firm is involved. However, the wrong firm or personnel can lead to much larger claims and overruns down the road.

Should I package my upcoming tunnel as a Design/Build?

Consider the following:

• If you are a public agency, it may not be legal for you to procure work in this fashion. Check your local laws and your agency charter.
  • Note that even if it is not allowed, some agencies, municipalities and/or states have changed their rules in the past when approached on case-by-case basis.
• What are you trying to accomplish with design/build? Are you trying to save time? Are you hoping for a less expensive out-turn cost? Are you trying to avoid all risk?
  • Design/Build can be an excellent way to achieve time and cost savings, and ‘early contractor involvement’ aka ‘alliance contracting’ is one particularly effective way to do so. Some owners, however, are not familiar with design/build and hire consultants to perform a base design or a set of bridging documents for bidding that are far too developed for any design/build innovation. Often these designs take more time and cost more money to produce than traditional design/bid/build. Some projects could have been completely constructed by the time an owner and his consultant finally produce bid documents.
  • Some owners feel they are shedding all risk by using design/build. This is simply not the case, and a more proactive approach to risk management is a far better option that an ill-advised attempt to shed risk that others should not be reasonably expected to assume such as unknown ground risk.

This topic is far too broad to cover in a few paragraphs. Several national organizations publish Industry guidelines and ‘best practices’ which can provide more information. Feel free to consult with the UCA Executive Committee or a trusted consulting firm familiar with this issue.

I have heard that Green Infrastructure (GI) such as tree lawns, green roofs and porous pavements can do the same job as a “Gray” tunnel for controlling Combined Sewer Overflows (CSO). Is this true?

When trying to reduce combined sewer overflows, tunnels are much more cost- and time-effective than GI. Similar levels of control using GI, if even possible, take much longer and cost much more than tunneled storage solutions, and a typical owner cannot on their own modify the impermeable surfaces of a city to an extent that a CSO tunnel would not be required. However, GI practices do capture some ‘first flush’ flows and should be encouraged for any new development, and some sewer agencies are willing to spend a little more on their projects in order to provide parks and other ‘leave-behinds’ for their customers. However, note that:

• Many municipalities are putting forward green infrastructure as a means to delay or eliminate required CSO tunnels, and regulatory agencies are complicit in this. This is a short-term political expedient at best. Later, when the required tunnels are eventually built, they will cost the rate payers much more due to escalation.
• ‘Gray’ CSO Tunnels are maintained by the agency who builds them and can be mostly maintenance free. Who maintains an urban retention basin? Regional agencies have no authority to maintain City tree lawns. Cities responsible for CSO reduction can and do maintain such facilities but their annual maintenance budgets rise disproportionately to the benefit received.
• Some practitioners are building permeable pavements or installing wick drains in areas of deep impermeable glacial clay geology. These soils do not allow sufficient infiltration and when the small amount of storage is filled by the first rain, the facility may never accept another drop. Wick drains can also lead to unintended consequences such as cross contamination of soil layers, contamination of aquifers, or ground settlement.

Most tunnel contractors are big national or international firms. How can I make sure that my $300,000,000 tunnel project puts local people to work?

Tunnel contractors are very familiar with the requirements, and benefits, of using local firms and individuals to support the project. Still, many clients use a contractual clause requiring the main contractor to include a certain percentage of local people and firms and/or local small and disadvantaged businesses on their team.

I’m concerned about negative publicity on a tunnel project, particularly ground settlement and building damage – how can I avoid this?

With the tunneling equipment available today, a competent designer and contractor should be able to design and build in an urban environment with negligible settlement or damage; and they should be able to prove it by providing instruments in the ground and on existing structures. When the odd project makes the news for excessive settlement and damage to existing infrastructure it can be tied to a number of factors, all of which can be avoided by selecting competent designers, contractors and construction management staff, and providing for ground exploration programs that meet industry standard of care.

Are tunneling standards and methods similar between the U.S. and Europe? And Asia/Australasia?

Means and methods are largely similar. Standards and specifications (and contract law) differ between countries. The UCA is part of the International Tunneling Association (ITA) consisting of member organizations in countries around the world. The ITA has several Working Groups who work collaboratively to develop international standards and guidelines.