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February 26, 2009 - ASCE Comments - on National Tunnel Inspection Standards

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The Federal Highway Administration
Advance Notice of Proposed Rulemaking
National Tunnel Inspection Standards
FHWA Docket No. FHWA-2008-0038
73 FR 68365 (November 18, 2008)


The American Society of Civil Engineers is pleased to submit the following comments in response to the Advance Notice of Proposed Rulemaking regarding the proposed establishment of National Tunnel Inspection Standards.

1. Definition of a Tunnel- The NTIS would apply to structures receiving Federal-aid highway funds that meet the NTIS definition of a “tunnel”. What requirements should the FHWA incorporate into the definition of a “tunnel”?

A. Should the definition of a tunnel contain a minimum length requirement?

From a practical point of view, there will need to be a minimum length requirement for a tunnel structure. If the current definitions for bridges and culverts are reviewed, it would seem appropriate that a minimum length of 20 feet should be considered.

B. Should the definition of a tunnel contain requirements other than tunnel length?

Yes. Length is one parameter that should be included, but the definition of tunnel should also be sufficient to exclude culverts and “tunnel-like” structures simply created by bridges such as an overpass. While most tunnel structures also include ventilation, drainage, lighting and other mechanical and electrical systems, these systems should not be required for a structure to be considered a tunnel. For structures meeting the definition of a tunnel, the lack of such systems should be considered in the evaluation. Further, it may be helpful to clarify that a tunnel is a below-grade structure.

As all tunnels are intimately connected with geologic materials, regardless of the construction method (i.e., bored, drill and blast, cut and cover, etc.), and some, such as hard rock tunnels, have little or no man-made structural components. The definition should include a mention of the role the geologic materials play in the makeup of tunnels.

Train tunnels should be excluded from the definition as these structures will not likely be capable of receiving Federal-aid highway funds. However, combined tunnels that carry both vehicular and train (including light rail) may need to be included as part of the definition. Consideration should also be given to including pedestrian and bike facilities built with Federal-aid Highway funds.

C. The National Fire Protection Association defines a tunnel as an "enclosed roadway for motor vehicle traffic with vehicle access that is limited to portals." The American Association of State Highway and Transportation Officials (AASHTO) Technical Committee for Tunnels (T-20) defines tunnels as "enclosed roadways with vehicle access that is restricted to portals regardless of type of structure or method of construction. Tunnels do not include highway bridges, railroad bridges or other bridges over a roadway. Tunnels are structures that require special design considerations that may include lighting, ventilation, fire protection systems, and emergency egress capacity based on the owner's determination.” Should the FHWA adopt one of these definitions, or another definition of a tunnel?

AASHTO T-20 currently has a definition for tunnels. The NTIS definition should be based on the current AASHTO definition with appropriate expansion. However, the NTIS should make a distinction between tunnels that require ventilation, fire protection, emergency egress etc. and those that do not. The “inspection” requirements for the tunnels in the former category require a more thorough multidiscipline approach.

2. Inspection Procedures- Inspections should assess the condition of all structural elements of a tunnel and assess the condition and performance of a tunnel’s structural, mechanical, electrical, hydraulic and ventilation systems including operational procedures. If unlined rock tunnels exist in the inventory, inspection of these tunnels will consist significantly of the condition of the rock mass exposed in the tunnel. Inspection of the rock mass should follow an established system, such as the Q-System, the Rock Mass Rating (RMR), or the Rock Structure Rating (RSR), together with an assessment of the current conditions of the rock mass. Special attention would be paid to changes in conditions of openness of rock joints, changes in groundwater seepage quantities, and reports of rockfall inside the tunnels.

A. Should the NTIS adopt the inspection techniques and standards in the Highway and Rail Transit Tunnel Inspection Manual?

In addition to the inspection and standards currently defined in the Highway and Rail Transit Tunnel Inspection Manual, the NTIS should fully consider the best practices for tunnel inspections as reported in NCHRP 20-07 Task 261 as guidance in developing the standards.

B. What additional sources of inspection standards should the FHWA consider?

In addition to the information in NCHRP 20-07 Task 261, the FHWA should consider inspection standards or guidelines that may be available within state DOT organizations, the European community, and other private (or quasi-private) tunnel agencies. While inspection is critically important, other activities should also be considered as part of a tunnel safety assurance program. Examples include testing of critical life safety systems, coordination of first responders, and testing of tunnel leak water for its corrosivity. In view of the wide variety of safety systems and tunnel complexity, the NTIS should include criteria for development of tunnelspecific programs. For new structures, the program would be developed as part of the tunnel design and construction. For existing structures, the tunnel -specific program could be developed based on a one-time safety audit.

C. Should inspections include evaluation of emergency response and non-emergency operational procedures?

Yes. While many aspects of the proposed NTIS will pattern after the current NBIS, this is one area where the scope of inspections and review process will need to be broadened to include not only the emergency and non-emergency operational procedures, but also include all components of the tunnel structure such as emergency exit paths, ventilation structures, interior tunnel finishes, and all mechanical, electrical and communications systems. Consideration should be given to establishing multiple inspections with set frequencies and criteria.

D. Are there any special inspection procedures for new tunnels that should be included in inspection manuals for all new tunnels?

Yes. NCHRP 20-07 Task 261 may provide a detailed summary of these best practices. Items for consideration by NTIS should include:
Inspection of both structural and non-structural elements in the tunnel;
Inspection of all emergency egress paths;
Inspection of all ventilation shafts and support structures including machine rooms;
Inspection of drainage systems; and
Installation and maintenance of line and grade makers to monitor tunnel position and movement.

New tunnels should be designed with inspection in mind and provide access to all critical components. Documentation of construction of new tunnels may include results of geotechnical instrumentation monitoring. If operation of the completed tunnel includes ongoing monitoring and reporting of
instrumentation data, review of these data should be included in the inspection procedure.

We would note that delamination, especially overhead, is now a far more major concern with tunnels than it is with bridges and requires the depth of inspections to be defined. And each common overhead system requires specific standards to assure that any element that may break loose is identified.

3. Frequency of Inspection- The inspection of highway tunnels likely would include collecting information on the condition of all structural elements and systems.

A. What tunnel elements and systems should be inspected routinely?

At a minimum, tunnel inspections should include:
All structural elements including tunnel perimeter, roadway and roof ;
All non-structural elements including tunnel finishes (ceiling panels);
All emergency access/exit structures;
All ventilation structures including shafts and fan housing structures;
All mechanical systems (ventilation, emergency ventilation and smoke exhaust, fire suppression, drainage pumps); and
All electrical systems (lighting, emergency lighting, traffic control, alarms), and all communications systems (traffic monitoring, smoke sensor, fire sensors, voice communications).

B. What inspection frequency should be established for these elements and systems?

Because tunnel inspections will include a broad spectrum of structural, mechanical and electrical systems, the inspection frequency may need to be varied depending on the complexity of the systems, the age of the systems and the operational characteristics of the tunnel facility. The FHWA should fully consider the best practices as identified in NCHRP 20-07 Task 261, the European Scan Tour conducted by the FHWA (FHWA-PL-06-016, June 2006) and other resources as may be identified.

C. Should a minimum frequency for tunnel inspection be established?

A minimum inspection frequency should be established for each facility based on a combination of tunnel complexity, age and operational characteristics. The NTIS should consider establishing categories for tunnels and define a minimum inspection frequency for each category.

D. Is there a need to identify various types of inspections? If so, what types of inspections should be defined?

The FHWA should consider having the NTIS establish minimum inspections for all components and systems in a tunnel structure.

E. Should the frequency of each type of inspection vary according to the type of inspection? Yes. The frequency of inspections for mechanical and electrical systems may need to be more closely tied to operational characteristics and system maintenance. Systems that are actively operated by theowner may not need to be inspected as frequently as mechanical and electrical systems that are operated only in an emergency mode.

Overhead items require more frequent inspections than much of the remainder, and structural systems should be inspected with the same frequency of a bridge (at a minimum every 2 years), and more frequently if necessary. For example, long, subaqueous tunnels may not benefit from an interior based visual inspection which provides no information on the conditions present on the exterior of the tunnel. Unlike bridge inspection programs, the tunnel inspection standard may best be served by a series of tunnel categories to help define the inspection frequency.

There are geotechnical aspects of tunnel sites that may place them in higher risk categories, such as regions of relative higher seismic activity, high groundwater levels, aggressive ground conditions (chemical agents), nearby mining activities, methane gas, etc. Using a risk-based approach would address these issues.

For non-seismic zones, inspections of geotechnical related items should be initially established on a minimum schedule, but may be adjusted to a longer frequency if historic inspection data indicate low risk of problems. For seismic zones, an inspection should be made immediately following an earthquake.

A risk factor for unlined rock tunnels in areas with groundwater and exposed to freezing conditions, is the action of ice wedging to loosen individual rock blocks which may fall from the roof or ribs of the tunnel. Especially where tunnels are built with relatively little cover (vertical dimension of ground between the tunnel crown and the overlying ground surface), documentation of new development above the tunnel should be included in the inspection data. New development above tunnels (including mining) may impact factors such as changes in stress in the ground over the tunnel, changes in weathering or alteration of the ground above the tunnel, and alteration of drainage of surface water and groundwater into the ground above the tunnel. As mentioned above, climate, especially freezing weather would be a factor in a risk-based inspection system.

F. Should we establish a risk-based frequency to account for the complexity of each tunnel?

Yes. At present, the AASHTO T-20 Technical Committee recommends the risk-based approach and the FHWA should consider this approach for the NTIS.

G. What factors (e.g., age, traffic, length, ventilation, urban or rural location) should be included in a risk-based frequency inspection system?

Not all factors would have the same weight and the weighting of individual factors may vary from one structure to another. A risk-based approach should consider the following factors:
Tunnel age;
Traffic volume;
Tunnel complexity (mechanical and electrical systems);
Tunnel importance (location, detour length);
Emergency characteristic (including evacuation times); and
Repair feasibility (submerged tunnel, rock tunnel).

4. Equipment and System and Inspection- The NTIS likely would include requirements for inspection procedures for structural, mechanical, electrical hydraulic and ventilation systems, and other major tunnel elements. For several of these elements and systems, the inspections could include the following provisions:

A. The mechanical inspection could consist of verifying the condition and operation of tunnel mechanical equipment and systems. Examples of mechanical equipment and systems include, but are not limited to, ventilation fans, control room air conditioning and heating, plumbing systems and tunnel drainage and waterproofing systems.


B. The structural inspection could include suspended ceilings, structural attachments, lining, exposed rock, roadway slabs, and tunnel finishes.

Agree. The ventilation shafts, mechanical rooms and emergency exit paths may also need to be included as part of the structural systems. Rock mass reinforcing elements (e.g. rock bolts) should also be included in the inspection.

C. The safety inspection could consist of verifying the condition and operation of various safety equipment and systems, such as variable message signs, overhead warning systems, carbon monoxide detection systems, fire protection systems, signage, geometry, traffic signals, and normal operations and emergency response procedures.

Agree. Many of these items should be covered under normal maintenance and system testing requirements. For example, local fire departments may require the fire protection systems to be tested on a specific schedule.

D. The security inspection could consist of verifying the condition and operation of security equipment and systems that are used to detect and coordinate responses to natural or manmade emergencies. These systems include video cameras, monitors, alarms, telephones, security gates, and portal flood gates.

Agree. Intercom and/or Public Address systems, AM or FM transmitter systems and any other communications systems should be included as well.

E. The electrical inspection could consist of verifying the condition and operation of electrical equipment and systems used for power distribution, emergency power, and lighting.

Agree. The specific requirements for physical testing of these systems may depend on how frequently the systems are tested as part of the normal operational characteristics of the tunnel.

5. Qualifications and Training for Inspectors

A. Should the qualification requirements for transit tunnel inspectors contained in the Highway and Rail Transit Tunnel Inspection Manual be adopted as the qualifications required for Federal-aid highway tunnel inspectors? Are the qualifications in the Highway and Rail Transit Tunnel Inspection Manual sufficiently specific for all tunnel elements and systems?

Tunnel inspectors should be persons who are familiar with tunnel design and construction and who are experienced in evaluation of existing structural and life safety systems. The current qualifications for transit tunnel inspectors may be adequate for the structural components but may not be adequate for the mechanical, electrical and communications systems. The qualifications for inspectors in theseareas will need to be developed based on the specific areas of expertise. All inspection teams should have access to appropriate experts on an as need basis.

Consideration should be given to adopting the Team Leader and Team Member qualifications contained in Highway and Rail Transit Tunnel Inspection Manual, with the following comments:
-A Team Leader for each discipline should have a consistent minimum number of years of inspection experience.
-Successful completion of a Comprehensive Tunnel Inspection Training Course should be a prerequisite for both Team Leader and Team Member positions.

The Highway and Rail Inspection Manual does not include an individual with geotechnical qualifications. For regions with unlined or partially unlined rock tunnels, relatively high seismic risk, and complex geology, an inspector with a geotechnical/geologic background should be included in the inspection team. The inspector should be a licensed geologist/engineer, with experience in design and construction of tunnels and with excavations and support of rock-masses in underground openings.

B. What education and training should be required for tunnel inspectors? Should the NTIS incorporate a requirement for periodic training for tunnel inspectors?

Yes. Training should be established as part of the implementation of the NTIS. NHI style training may be the most effective in terms of both initial training and then refresher training.

Consideration should be given to adopting the education and training requirements contained in the Highway and Rail Transit Tunnel Inspection Manual with the addition that the Team Member has a high school diploma as the minimum education requirement. Tunnel Inspector periodic or refresher training (every 3-5 years) should be offered to supplement a Comprehensive Tunnel Inspection Training Course.

C. What experience should be required for tunnel inspectors? Should there be multiple levels of qualifications depending upon the role of the team member (i.e. leader, inspector) and the type of inspection?

Yes. The experience of inspectors will have to be defined as part of the NTIS. Provided tunnels are grouped into categories based on complexity and systems, it may be possible to define the expertise required for specific teams. Consideration should be given to adopting the experience requirements contained in Highway and Rail Transit Tunnel Inspection Manual, and the levels of qualifications should depend on the role of the inspector (Team Leader and Team Member) and the type of inspection (initial, in-depth, periodic). Different types of tunnels may require certain inspection expertise. By defining “special” element inspections, it may be possible to simplify Team Leader and Team Member requirements.

6. Recordkeeping

A. Should States be required to keep records of all highway tunnel inspections performed within the State? If not, where and with whom should the inspection records reside?

Yes. States should maintain the records for inspections. A reporting system similar to the NBIS should be developed and implemented for the NTIS. The FHWA should consider a requirement in NTIS that data be stored in an electronic database.

B. Are inspection record requirements such as those contained in the Highway and Rail Transit Tunnel Inspection Manual sufficient for the NTIS?

No. The NRTTI do not currently provide condition codes (or ratings) for individual elements in a tunnel. A new system should be considered that would encompass the full spectrum of structural, mechanical and electrical components to be inspected.

C. For how long should tunnel inspection records be maintained?

For the life of the structure.

7. Rating

A. Should the NTIS incorporate a condition-based rating system for Federal-aid highway tunnels, under which the tunnels in the best condition receive a high rating and the tunnels in the poorest condition receive a low rating?

No. The NTIS rating system must be element level based and must be able to individually rate each of the primary systems including structural, mechanical, electrical, communications etc. Consideration should be given to creating the equivalent of an AASHTO sufficiency rating based on database input on general and condition-based data. Adoption of a condition-based rating system would provide a method for weighting the importance of the various systems.

B. Should a tunnel rating system be the basis for possible funding decisions?

The rating system should be a guide for FHWA and individual states in prioritization. Other factors may be relevant.

8. National Tunnel Inventory Database

A. What tunnel data elements should be collected for all Federal-aid highway tunnels (e.g., tunnel name, age, and length, finishes, width, and height, number of lanes, ventilation, truck traffic, and automobile traffic)?

Like the NBIS, the NTIS should include basic inventory data such as described. This data will also need to include geometric information, lane clearances, overburden characteristics, and the complete description of the mechanical systems. In addition, the basic inventory data should also include a comprehensive description of the operational and maintenance characteristics of the tunnel and data involving water and groundwater may be useful.

The database should also include:
- Information on the type(s) of temporary ground support installed in the tunnels, which may be hidden by the final tunnel liner;
- Type(s) and number(s) of geotechnical instrumentation installed and monitored in the tunnel;
- Documentation of previous ground support problems in the tunnel;
- Documentation of remedial repairs associated with ground support in the tunnel;
- Documentation of the performance of the tunnel during an earthquake; and
- Documentation of any structural modifications made to the tunnel.

B. How often should data be collected and reported?

The basic inventory data should be gathered and reported as part of the implementation of the NTIS and should be reviewed and updated at the time of each inspection.

C. Should this data be reported to the FHWA?
Yes. Both the basic inventory data and the latest inspection data should be reported to the FHWA.

D. Should a tunnel be indentified using a tunnel inventory number (TIN) in a manner similar to how bridges are identified under the NBIS?


E. What criteria should be used to assign a TIN?

Like the BINS tag, the TIN tag should describe the location by county and route. We note that their may be merit to incorporating the TIN system into the BIN system, to ensure a structure doesn’t slip through the cracks.

9. Organization of Inspection Team

A. How should the inspection teams be organized?

The NTIS should include specific guidelines for the make-up and organization of the inspection teams for each category of tunnel. Provided there is some type of training and certification required, the teams should be led by a qualified person who is also a Registered Professional Engineer. As part of the NTIS, there should be one person designated to lead the team and be responsible for the reporting of all disciplines.

If it is determined that it is not feasible to assemble qualified teams of tunnel inspectors in all 50 states, then it may be incumbent on the federal government to make one or more teams available to the states for tunnel inspections.

B. Should inspection teams be established with differing levels of responsibility?

Yes. The teams should be as required for each category of tunnel and should be compromised of a Team Leader and Team Member from the following disciplines:
* Civil (Structural/Geotechnical);
*Electrical; and
*Others –(Track…Third Rail…Catenary…Signals…Communications)

C. Should one person on the team have overall responsibility for the program?

Yes. A Chief Inspector with overall responsibility for the tunnel inspection team should be identified.

10. Technical References 

What technical publications, if any, should be incorporated by reference?

-FHWA/FTA Highway and Rail Transit Tunnel Inspection Manual, March 2003
-FHWA Bridge Inspection Reference Manual (BIRM)
-AASHTO Manual for Condition Evaluation of Bridges
-AREMA Fatigue Standards
-AREMA Manual for Railway Engineering, Chapter 9, Part 1, Subsections 1.2 and 1.5
-29 CFR, OSHA Standards
-FHWA Inspection of Fracture Critical Bridge Members
-FHWA Manual on Uniform Traffic Control Devices
-23 CFR 650, Subpart C, National Highway Bridge Inspection Standards
-There is a FHWA Tunnel Training Manual currently in development and it may be appropriate to include a reference to this document.
-The outcome of NCHRP20-07 Task 261.
-Possibly, appropriate NFPA documents.

11. Quality Control/Quality Assurance (QC/QA)

Should QC/QA procedures similar to the procedures required under the NBIS be implemented for the NTIS?


12. Cost of Inspections

The FHWA requests information regarding the costs associated with tunnel inspection, particularly the typical inspection costs per linear foot of tunnel.

No comment.

13. Tunnel Repairs

The FHWA requests information associated with tunnel rehabilitation projects (e.g., costs of repairs, dates of work, scope of work).

No comment.

14. Research- The FHWA and others have conducted extensive research related to tunnel design, construction, rehabilitation and inspection. The following is a list of research projects related to tunnel safety that either have been conducted or are ongoing.

A. The Memorial Tunnel Fire Ventilation Test Program
B. Prevention and Control of Highway Tunnel Fires…
C. Underground Transportation Systems in Europe: Safety, Operations an Emergency Response…
D.NCHRP Project 04-37, Long-Term Performance of Epoxy Adhesive Anchors
E.NCHRP Project 20-07/Task 261, Best Practices for Implementing Quality Control and Quality Assurance for Tunnel Inspection
F.FHWA Control of Highway Tunnel Fire Workshop

We welcome information regarding other existing or ongoing research related to tunnel inspection.
What additional research should be undertaken?

- The FHWA should consider development of a risk-based inspection protocol for tunnel structures.
- Tunnel structures can represent sophisticated systems that combine multiple structural systems and mechanical, electrical and communications systems. The proposed NTIS standards must take into account the wide range of tunnel types and the varying levels of sophistication in these structures.
- Development of the NTIS should include an implementation phase. The implementation phase may utilize a pilot program to inspect and rate a sample of tunnel structures. This effort would allow the NTIS to be fine tuned prior to broad based implementation.
- Development of the NTIS should include development of appropriate training and certification.
- Since there are limitations to all inspections, and given the wide variety of possible tunnel conditions, tunnel specific inspection protocols should be developed pursuant to recommendations from the tunnel designers and/or as a result of post-construction inspections and investigations. One possible outcome from the NTIS inspections may be recommendations for further study, analysis or testing.
- The FHWA should consider establishing criteria for leakage in a tunnel.
- The NTIS should make specific recommendations to designers to incorporate inspectability in all aspects of the design. This would include both providing access to all areas that will need to be inspected, but also to providing that access in areas that are safe to access during normal tunnel operations. Further, designers should take into account the sizes of physical spaces to ensure that inspectors can move safely and easily through the spaces.
- Since tunnels rely on drainage, the NTIS inspections should provide some requirement that all drainage systems be physically inspected to ensure the free flow of water. These inspections could be accomplished using remote camera devices.
- The FHWA should consider requiring designers to include calibrated recording devices on drainage pumps to allow for accurate monitoring of drainage water pumped from a tunnel.

The following groups may be helpful in preparing the inspection standards:

-The Transportation Research Board (Tunnel Committee);
-The Underground Technology Research Council; and
-The Underground Construction Association.

Thank you for your attention to our comments. If you have any questions, please contact Steven Fier of the ASCE Government Relations Department at 202-789-7841 or at

Respectfully submitted,

The American Society of Civil Engineers

February 13, 2009