Practices for Controlling Tunnel Leaks (2024)

• Alaska DOT and Public Facilities (AK)
• Arizona DOT (AZ)
• Colorado DOT (CO)
• Connecticut DOT (CT)
• Delaware DOT (DE)
• District of Columbia DOT (DC)
• Florida DOT (FL)
• Georgia DOT (GA)
• Idaho DOT (ID)
• Illinois DOT (IL)
• Kentucky Transportation Cabinet (KY)
• Maryland Transportation Authority (MD)
• Massachusetts DOT (MA)
• Minnesota DOT (MN)
• Missouri DOT (MO)
• Nebraska DOT (NE)
• Nevada DOT (NV)
• New Hampshire DOT (NH)
• New Jersey DOT (NJ)
• New York State DOT (NY)
• North Carolina DOT (NC)
• Ohio DOT (OH)
• Oklahoma DOT (OK)
• Oregon DOT (OR)
• Pennsylvania DOT (PA)
• South Carolina DOT (SC)
• South Dakota DOT (SD)
• Tennessee DOT (TN)

• Virginia DOT (VA)
• Washington State DOT (WA)
• Wisconsin DOT (WI)
• West Virginia DOT (WV)
• Wyoming DOT (WY)

Q1.-Q5. These questions identified the DOT and person completing the summary and will not be printed herein.

Q6. Does your DOT have any tunnels or long enclosed roadways (>300ft in length) such as deck structures over depressed roadways?

Q7. In addition to your DOT’s tunnel inventory, does your DOT have tunnel-type structures with specialized systems for lighting, fire protection, or other systems?

Q8. How many tunnels in your state’s tunnel inventory are owned by your DOT?

Q9. How many of your DOT’s tunnels and tunnel-type structures have water infiltration or have experienced water infiltration in the past ten years?

Q10. What problems does the water infiltration cause, or has it caused in your DOT’s tunnels? (Check all that apply)

Other responses:

• Nuisance.
• Tile failures.
• Leakage varying from staining to surface saturations with few areas of active dripping.

Q11. What techniques does your DOT use to manage these secondary challenges?

Responses below are not tied to the responding state.

• Icicles are removed manually. Ice melt is applied to slick surfaces. Drainage is flushed annually.
• Localized repairs on structural deterioration and functional system deterioration.
• Collection systems, large collection system, and Drainage material with plumbing.
• The Department includes Maintenance forces during the bridge inspections in order to capitalize on the lane closure to perform repairs/cleanup.
• Joints injection.
• Each tunnel typically has a special plan of action procedure in place.
• Routine monitoring, pressure injection of cracks, conduit plug, joint repair, divert to “collection area.”
• Cleared roadway drainage issue to minimize water infiltration.
• Added secondary trough to catch water leaking into tunnel.
• We have tried different expanding joint type products with little success.
• Routine monitoring and removal of icicles. Attempts have been made to seal tunnel with limited success. (2)
• Consistently wash the tunnels, flush drainage system, and repair/replace areas of deterioration by a standby, on-call, specialized contractor.
• Epoxies inject the cracks where water appears to be infiltrating.
• Drains behind new tunnel liners.
• Some tunnel owners have a dedicated tunnel maintenance contract to perform minor repairs and maintenance. Flushing inlets within the tunnel, general preventative maintenance and knocking down ice as it forms at locations of leaks.
• Tunnels are bare rock tunnels (6) and one rock tunnel with shotcrete. Really is no big issues for our tunnels.
• Use a contractor to mitigate the issues such as sealing the leaks and making the structural repairs.
• Historically these issues have not been of great concern. Slippery roadways are treated with deicer along with outside roadway. Icicles are removed prior to becoming excessively large. One structure had a heating system installed to prevent water freezing in liner. More recent construction has created issues with infiltration to conduits, still being addressed in contract. Leaks of concern are typically addressed with targeted epoxy or foam sealant injection. Leaks not of concern are handled via tunnel drainage system.
• Maintenance response to mitigate hazards as appropriate at the time.
• Inspection.
• None at this time.

Q12. How many tunnel-type structures exist within your state that are not owned by your DOT?

Q13. How many of the non-DOT owned tunnel-type structures have experienced water infiltration issues?

Q14. How many of your DOT’s tunnel-type structures currently have water infiltration or have experienced water infiltration in the past ten years?

Q15. If GPR, thermography, LiDAR scan or photogrammetry were used, how effective were these non-destructive testing (NDT) methods in detecting leak locations?

Q16. What is the primary source of water into your DOT’s tunnels or long enclosed roadways? (Check all that apply)

Other responses consisted of:

• Leakage from the glacier above.
• Deck park irrigation system.
• Flood event.
• Still investigating.

Q17. What methods has your DOT used to identify the source of water infiltration? (Check all that apply).

Other responses consisted of:

• Visual/NTIS/In-Depth inspection. (4)
• None or N/A. (9)
• Judgment. (1)

Q18. What methods has your DOT used to identify the location of water infiltration? (Check all that apply).

Q19 TO Q39. DOTs were asked to provide information regarding their tunnels with the most water infiltration currently or within the past ten years.

Q40. Which of the following methods has your DOT utilized to mitigate water infiltration in existing tunnels? (Check all that apply)

Other responses consisted of:

• Shotcrete with drains.
• None or N/A. (8)
• Clearing storm water drain behind abutment.

Q41. Which of the following methods has been successful as a long term (>10 years) remediation for water infiltration? (Check all that apply)

Other responses consisted of:

• Shotcrete with drains.
• None or N/A. (11)
• Still Investigating

Q42. Which method has been most successful for your DOT in resolving leaks?

Other responses consisted of:

• Still investigating.
• No remediation attempted.
• None or N/A. (8)

Q43. What problems has your DOT experienced attempting to mitigate leakage in your tunnels?

Responses below are not tied to the responding state. Similar responses were combined with (#) at the end of each bullet representing the number of states who had a similar comment.

• The best and most cost-effective solution is to collect and control the water. (2)
• Seasonal flows, Durability of mitigation systems, Freeze/Thaw, Ice.
• Could not access top of tunnel to reseal joint after pavement was placed over tunnel.
• Investigating the source. (3)
• Excavating can be difficult with traffic interruption impacts.
• Roof leaks – Roof shape (generally flat roofs) and type of roof.
• Tunnel joints – Difficult to reliably seal the joints. (3)
• Cost of repairs.
• After crack injection/sealing one location a leak forms in adjacent location. (3)
• Porous rock.
• Nothing out of the ordinary.
• No mitigation techniques have proven successful in the long term. (2)
• No attempts to mitigate leakage have been attempted at this time. (3)
• N/A (5)

Q44. Has your DOT experienced any unintended consequences from the techniques used to remediate water infiltration?

Q45. Describe the unintended consequence noted in the prior question.

Responses below are not tied to the responding state.

• Sealing one location can inadvertently create leak in new location. (2)

Q46. What information would be most valuable to your DOT as a tunnel owner with regard to water infiltration?

Responses below are not tied to the responding state. Similar responses were combined with (#) at the end of each bullet representing the number of states who had a similar comment.

• Information on better ways to contain and control water. (4)
• Effective remedies/lessons learned to address leakage for various liner types/repair methods. (7)
• Inspection/Condition assessment of different repair methods.
• Effectiveness/Lessons Learned from maintenance methods (flushing underdrains, etc.)
• What NDT evaluation techniques work the best and what are the limitations? (2)
• What condition becomes a safety issue?
• Know the history of the tunnel prior to repairs.
• Knowing the source.
• With our 6 unlined rock tunnels and 1 shotcrete lined rock tunnel - water infiltration is not a problem or concern. Natural groundwater and or surface run off is the source of the water through natural cracks/joints in the underlying rock.
• Make sure when the tunnel is being constructed that all joints are sealed properly. (2)
• To remain on top of the situation, particularly in the winter. To continue washing the tunnel liners to properly see if any structural damage exists, and to monitor the source of water through dyes and thermography. You can replace joint material every year, but the source of water, needs to be redirected, or mitigated, first.
• Recommendations on preventing groundwater infiltration into electrical conduits which travel from tunnel to ground and back to tunnel. Conduits collect ground water at some point in that ground interface. This is very tunnel specific. In general, leaking is a relatively minor concern for which we have good repair solutions when needed.
• Unknown or N/A (8)

Q47. What is the threshold for leakage at which your DOT would initiate water remediation?

Responses below are not tied to the responding state. Similar responses were combined with (#) at the end of each bullet representing the number of states who had a similar comment.

• Deterioration of structural elements. (5)
• Icicles over traffic (2)
• Aesthetics/losing tile
• Varies per specific tunnel
• No set threshold, depends on leak location
• Prefer preventive options, but some difficult to access locations may be an issue
• Impacting traffic operation/speed reduction warranted. (5)
• High flow or ponding water. (5)
• As soon as it is visible.
• Under review.
• A leak which causes a secondary issue that cannot be mitigated such as functional system safe performance and longevity. (3)
• Safety Issue/traffic hazard. (5)
• None or N/A (9)

Q48. Does your DOT have specific acceptance criteria for leakage into a tunnel structure which is part of the new tunnel design criteria?

Q49. What is your DOT’s acceptance criteria for leakage in a new tunnel per the question above?

• Below is the bulleted response from one responding DOT.
  • Maximum overall infiltration 1gpm per 1000 feet of tunnel. >
  • Local infiltration limit 0.25 gallons per day for 10 square feet of area, and no more than 1 drip per minute at any location.
  • No drips shall be permitted over the driving surfaces or where they have the potential to cause damage to equipment, malfunctioning of any electrical power, signaling, lighting, control, communication equipment, or compromise electrical clearances.
  • No water ingress shall cause entry of soil particles into the tunnel.
  • The interface between Cut-and-Cover Tunnel section with Bored Tunnel and other structures, (i.e. building structures, emergency egress structures, etc.) shall be designed and constructed such that the joint between the two structures is fully watertight.

Q50. Does your DOT have specific criteria for a tunnel leakage remediation/rehabilitation project for acceptance of the leakage remediation work?

Q51. What is your DOT’s acceptance criteria for a tunnel leakage remediation/rehabilitation project per the previous question?

Responses below are not tied to the responding state.

• Use of project specific special provisions that are developed for each project individually. A recent tunnel rehab included references to the following ASTM D Standards: 3574-95, 3475-955, 2369, 2196 and 756.
• We have a contract in place to seal and coat the areas when they start leaking.
• Under review.

Q52. Would you be willing to participate in a brief interview to learn more about your experience with tunnel leakage and remediation?