JOHN MARTIN RESERVOIR, Colo. – The U.S. Army Corps of Engineers’ John Martin Dam received significant maintenance and minor repairs in a recently completed conduit project.
On June 1, 2020, three employees from the USACE Albuquerque District’s office in Albuquerque, New Mexico, two employees from the USACE Albuquerque District’s Trinidad Project maintenance staff, and four members of a confined space rescue team contracted from ROCO, joined the John Martin team in performing work on the conduits at John Martin Dam.
Routine repairs and maintenance of the dam is essential to ensure the proper function of dam operations and to prevent potential risks to floodplains.
Extensive exposure to moist conditions and turbulent water flow promotes corrosion, spalling, and cavitation damage on the conduit liner and gate leafs.
“A spall is defined as flakes of material that are broken off of a larger solid body. Concrete spalling typically begins when the steel reinforcing embedded within the concrete member rusts. These expansive forces can cause the concrete to delaminate or to crack, spall, and break off. Cavitation is the formation of an empty space within a solid object or body or turbulence created in a liquid,” said Christopher Gauger, John Martin project office manager.
These long-term deteriorating conditions not only compound damage but pose a threat to dam operations and safety as well.
John Martin Dam has six conduits and all were found to need maintenance and repairs. In the past, two conduits were inspected and repaired on an annual rotation schedule. In the early 2000s a safety determination was made that restricted access to the conduits without a confined space rescue team in place to protect employees. This halted the regularly scheduled maintenance and allowed for accumulated debris and mineral buildup in the conduit air vents. Due to the timing of the annual rotation cycle, conduits 1 and 5 last received maintenance in 2009.
The degree of deterioration and the scope of repairs needed was unknown because staff had not been allowed access to the conduits for several years.
Recent issues with vent malfunctions, conduit operations, and the clear evidence of cavitation and corrosion made the need for inspections and maintenance on the conduits a priority. There had been irregularities noted in air vent operations. Also noted was failure with the chapman valves, which are air flow exchange valves which allow the water to flow with less turbulence; and a lack of air flow in the bellmouth vents, the tapered opening in the end of the ventilation ducts.
Conduit 1 was removed from service in December 2019. John Martin staff believed that due to unusual sounds emitting from the air vents, there was significant cavitation damage. Given this, the anticipation was growing among the staff to assess the condition of the conduits and make any necessary repairs.
After careful consideration, several factors led to the determination that this would be a project handled in-house, and John Martin staff would no longer require the work to be contracted out. Once scheduling, training, and contracting a rescue team were completed, work was ready to begin.
With the confined space rescue team in place at the conduit entrances, the three employees from the Albuquerque District office inspected the conduits, June 1-3, 2020. Their priority was to examine the emergency gates, service gates, conduit liners, gate slots, air vent openings, and other potential areas with possible damage or corrosion. The emergency gates were fully closed during this time, while the service gates remained partially opened to assist with visibility and access to the service gate air vents.
Inspection results found that significant corrosion was present. There was visible damage downstream of the service gates caused by the turbulent waters created during gate openings when releases occur.
Delamination and section loss was evident on much of the liners and gate surfaces throughout all six conduits. Delamination is a mode of failure where a material fractures into layers.
Pitting and corrosion was present in localized areas. The steel liners also exhibited significant chipping, rust, and spalling on the outermost existing surface, exposing bare metal.
All of the conduits exhibited moderate leakage from the bottom of the emergency gates and two conduits also showed leakage from the top of the gates. Gate slots were also found to be in poor condition, exhibiting heavy corrosion and gouging as well as moderate to severe cracking.
The air vents in each conduit showed a significant amount of mineralization and debris buildup which was restricting airflow. Debris included shards of delaminated material, driftwood, rocks, and large pieces of construction lumber – thought to be remnants from the original construction of the dam.
After each conduit was carefully inspected, the two sets of air vents inside each conduit were ready to be cleaned. The removal of mineralization and debris buildup allows the vents to function as designed.
Debris was successfully cleared out of the air vent holes in all six conduits. It was originally anticipated to take approximately three weeks, but was completed in four days.
The rescue team was contracted for a three-week duration and the speedier maintenance allowed time for further repairs to be made, including cavitation repairs using a metal repair product that goes by the trade name Belzona.
Water releases were managed to allow proper, dry conditions for the Belzona to be applied per the manufacturer’s guidelines. Repairs were primarily focused on cavitation damage both downstream of the service gate and in high-flow areas where the most turbulent of flows occur during releases. This has been a typical repair historically in similar Albuquerque District dams.
Repairs were made by mechanically roughening each surface, removing free material. After cleaning and prepping the surfaces, Belzona was applied and allowed to cure. The Belzona repairs will need to be routinely monitored and a more corrosion resistant material may be necessary on the sections of liner where cavitation continues to cause damage to the sidewalls.
While the conduits were found to be in fair condition, routine maintenance and repairs were required to ensure mission capability. Recommendations derived from assessing the conditions during the inspection included extensively cleaning the liners and gates, exposing the steel in order to apply a new protective coating due to the heavy corrosion.
Mineralization and debris buildup in the air vents needs to continually be cleaned out. It is standard operating procedure to clean the air vents regularly to prevent mineralization from clogging the holes and restricting air flow. Blockage and reduced air flow compromises the conduits’ ability to effectively transport water downstream.
To ensure the air vents provide adequate air flow, it was recommended that access holes be installed in the vent grates where maintenance personnel can access the air vent chambers to remove captured debris.
Working as a USACE team brought in a wide range of expertise. Continuing to collaborate with other USACE employees will not only help reduce costs for similar projects but will help other projects gain knowledge as many Albuquerque District dams have similar maintenance needs and repairs. Maintaining in-house expertise in air vent maintenance, conduit repairs, Belzona application, and repair techniques can be valuable for all projects in the Albuquerque District.
It was also recommended that USACE utilize training for a confined space rescue team that projects can rely upon. With USACE providing a rescue team that can assist projects throughout the district, costs can be reduced even more.
John Martins’ conduit project was an excellent example of careful planning, utilization of resources, and teamwork between project offices. Pursuing USACE values such as teamwork will allow for professional growth, and encourage employees to share skills and expertise, allowing similar projects to be completed in-house and continuing to reduce costs.
“The success of this project has demonstrated substantial benefits by retaining and utilizing institutional knowledge and indicates real potential for reducing costs for future USACE projects,” said Gauger.
Christopher Gauger, John Martin project office manager; Joshua Ellison, civil engineer, USACE-Albuquerque District; and Katie Schober, park ranger, John Martin Reservoir; also contributed to the article.