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The Lead Pipe Problem (and Opportunity)

A systemic lack of documentation detailing where lead service lines (LSLs) are used to deliver water to homes is a challenge that plagues many cities across North America. This is particularly acute in the eastern Provinces and mid-Western States of Canada and the U.S.  

In many cities, lead services were still the default material type used through the 1950’s, and in some cases into the 1980’s. Furthermore, incomplete records of replaced services have left thousands of properties with completely unknown pipe material. The EPA alone estimates the population of LSLs in the U.S. to be near 10M. On a utility level, the scale of infrastructure that must be located, inspected, documented, and replaced is truly monumental.

On top of a lack of documentation, homeowners are often responsible to replace the private side of the service themselves through independent contracting, while the utility must replace the public side. Site inspections which may require entering private residences or excavation to determine pipe materials are often difficult to coordinate, thus increasing cost.

Legacy Approaches

To address this issue, in 2021, the US Environmental Protection Agency revised its policies for utilities and community water systems so that they must, effective October 2024, have initial steps in place to develop a complete inventory of Lead Service Lines (LSLs). The Lead and Copper Rule Improvements (2023) added further intensity to these efforts, requiring every lead service to be located, and removed, over the next decade.

So how would utilities try to establish the material type of a service, or understand if it is an LSL? There are several methodologies currently being used to identify LSL’s which we will briefly review.

  • The first source would be historical records, if they exist, on where lead is and is not.
  • The second would be customer driven data, such as inspection reports, insurance, or any other documentation provided by a homeowner which could validate the existence of a lead service.
  • Another method is water quality sampling, where higher concentrations of lead could indicate a lead service, but could also be due to other sources, such as lead-brass fixtures like faucets and valves or lead soldered to join pipes pre-1990.
  • If pipe is exposed, the natural softness and pliability of lead makes it easy to scratch, and it’s non-magnetic, but then again copper is also non-magnetic.
  • Camera testing could be used to attempt to visually identify lead services but is difficult and requires access to insert equipment into the service line.
  • Data science methods using historical geography-based data is a fascinating approach to predict the location of lead services but is inherently unreliable unless it’s founded on a solid data base to train learning algorithms. It could be used more as a higher-level search tool but wouldn’t likely operate on a case-by-case basis.
  • Finally, you can always just excavate down to the buried pipe and see if it’s lead, whether by scratch test or visual inspection.

Each of these options poses one or several problems, whether it be expense, intrusiveness, reliability, or consistency in some cases.

Time for a Novel Approach

By applying acoustic theory to water service lead identification, we are effectively trying to use the different physical properties of the different service material types, to manifest themselves by acting as a medium for transporting acoustic waves. As you can imagine, a peice of copper service (light, thin-walled, ringy) will act very differently to a piece of lead service (heavy, thick-walled, absorbant).

There are different ways that could theoretically be used to determine material:

  • Velocity testing: Measure the speed of structural waves. Requires two points of measurement, so access to the inside of the residence is required. Would be difficult to perform an assessment if the pipe has multiple materials
  • Frequency spectrum analysis (FSA): Excite service at the fundamental resonant frequencies and measure the responses.
FIG1: Leadfinder1000 early prototype

Our approach leverages frequency spectrum analysis, which when applied correctly allows us to avoid two direct points of measurement on the service. Therefore, no entry is required into the home, a huge benefit to the utility for approaching this challenge with scale. Executed through a shaker and deployment of a series of sensors in proximity to the service, will be able to capture the representative characteristics of the service type below each sensor. We believe that our methodology will determine the presence and extent of mixed services, for example a stranded piece of lead between two pieces of copper.

One of our testing protocols involves shaking the service via the curb stop a predetermined frequency, known to excite a response from either the copper, or the lead, based on emprical data collected in the field. The excited frequency transmits down the service and into the soil, such that a series of sensors can capture the representative response along the service. Applying mathematical techniques to process the data, such as a time averaged Fast Fourier Transform (FFT), we are able to see a profile of the signal response at a point in question, for our target frequencies.

FIG2: Time Average FFT of Lead and Copper

Initial testing makes us confident that we are able to determine the material make up of services along the water main to private home, including the presence of mixed material types.

Acoustics in the broader infrastructure technology market

The application of acoustic principles for determining the condition of a pipeline (or other) asset, or for determining the presence of location of a leak on a pipeline (or other) asset, has become common practice wihtin the municipal water sector. These principles, and the exciters (noise sources) and sensors (signal receivers) that manefest in products and applications, have been applied by acoustic engineers and product companies on a variety of applications across a diverse set of sectors, including oil & gas, mining, transport, civil, aviation, and many more. Our SonicFinder1000 product is applying similar principles to the challenge of locating buried, un-marked plastic water and gas services.