A Coastal City Uses Pipe Condition Assessment Tools to Optimize its Capital Improvement Program
Like many of its peers, the City of Santa Monica, California, was faced with the challenges associated with old and aging water infrastructure. The City’s Public Works Department recognized the need for pipeline assessment to diagnose the source and extent of their operational deficiencies and minimize risk.
The Public Works Department elected to develop a capital improvement plan based on actionable and defensible data to prioritize and maximize capital expenditure. It was assumed that mainline pipes were most problematic, and that age was a significant contributing factor to their operational shortcomings. The department, however, did not have the means to make a diagnosis that would support the decision-making process and therefore outsourced the assignment to a specialist team of pipeline diagnostic experts.
After researching the various inspection technologies available on the market, the City appointed Aquam Pipe Diagnostics (APD), a pipeline service and technology provider, to execute video inspection and condition assessment services in an effort to investigate the current state of its potable water pipelines. The diagnostics company was tasked with developing a strategy and selecting a technology that would best assess the condition of the preferred potable water pipelines identified by the City. The strategy was designed based on the project objectives and expectations of the City in terms of data output. The purpose was to identify precarious sections of pressurized water mains that may require some level of intervention in terms of rehabilitation and replacement as part of future capital improvement programs.
A Look at the System
The City of Santa Monica owns and maintains 205 miles of water distribution mains, ranging from 4- to 36-in. in diameter, and distributes 12 million gallons of water per day to approximately 86,000 residential and commercial customers.
A pre-inspection survey was conducted to understand site conditions, identify and assess access points, develop a contingency plan and identify any necessary enabling works that were required prior to mobilization to the project site. In addition, the specialist team held regular dialogues with the City to clearly communicate and understand the scope of the work, set clear objectives, and determine the best tools available to optimize data output.
Having a thorough understanding of the pipe and asset configuration, along with system constraints and field conditions, were crucial for selecting the best available technology. The different pipe diameters ranging from 20 in. and smaller, the varieties of pipe materials, as well as the volatile operational conditions were all dominant considerations that influenced the decision-making process in tool selection.
It was also a requirement that the inspection tool could be inserted under pressure through a fire hydrant and would provide visual assessment of the condition of the pipe and leak detection data. Leaks, corrosion, evidence of tuberculation and any other visible pipe wall defects that would suggest deterioration, were all of particular interest to the City.
Forty locations were identified for assessment and involved the utilization of fire hydrants as access points. These pipes ranged from 4- to 20-in. in diameter, all varying in materials, age, and operational pressures. Wet barrel fire hydrants were selected as insertion points, and encompassed a minimum of 50 ft upstream and downstream on deployment.
APD utilized a CCTV for visual condition assessment coupled with acoustic leak detection to complete the project and performed the inspections when the pipes were still in service, causing no disruption to supply.
A Look at the Results
The City of Santa Monica’s collaboration with APD yielded results that contradicted the City’s working assumptions for renewal and replacement. It was concluded that age is not a reliable indicator of pipeline condition and is not a solid foundation on which to base capital disbursement.
In one instance, a 102-year-old pipe, which the department had prioritized for replacement, had no obvious signs of degradation and appeared structurally sound, and therefore required no replacement at this stage.
In contrast, the inspection also found a 30-year-old pipe that was not factored into the capital improvement plan but was presenting conditions that would warrant replacement. With regard to overall condition of the main lines, it was discovered that the hydrant laterals were in worse condition and in some cases, the tuberculation was so excessive that the inspection had to be abandoned as access was significantly restricted or impossible. In these cases, alternative locations were designated.
The inspection program also revealed that the unlined cast iron pipe closest to the Pacific Ocean was in poor condition in comparison to sections of pipe that were located further inland. Lined pipe in the same area was minimally affected except for evidence of tuberculation and corrosion activity on joints that were not lined.
Discrepancies and defects in mapping were also identified and annotated with the facilitation of GIS and spatial updates to the City’s GIS system. Such inconsistencies included misalignment of pipes and inaccurate pipe location, identification and location of lost or unknown valves, actual and recorded valve conditions and operabilities, pipe material changes and previous repairs, to name but a few.
In utilizing the data from the inspection program, the City is in a better position to minimize unnecessary expenditure on remediation and repair of low-priority pipes and focus investment of resources and time on high risk areas. In a climate where the funding for water infrastructure replacement and renewal is not abundant, condition assessment technologies and data have proved to be the compass for an effective asset management strategy for owners and operators of water distribution systems alike.
Through the implementation of this program, the City of Santa Monica can feel more confident in establishing a sound remediation plan with a better return on investment for the future.