Navigating Unknowns: Strategies for Completing Your Water Service Line Inventory
How to Finish Your Service Line Inventory after the Initial Records Review is Complete.
Posted on September 29, 2023 120Water
Many water systems are in the process of developing their initial service line inventory, which is due October 16, 2024. Developing inventories involves reviewing required and available information related to service lines and organizing the information in a state-approved database or template. Once that process is complete, many systems find a combination of known (e.g., Lead, Galvanized Requiring Replacement (GRR), or Non-lead) and unknown service lines.
Dealing with Unknown Services Lines
Inventories that contain unknowns can be submitted to the state and are considered ‘in compliance’ with the inventory requirements. However, there are disincentives to having unknown service lines in an inventory, including the following:
- Annual inventory re-submissions,
- Annual customer notifications,
- Submission of a Lead Service Line Replacement Plan, and
- Including unknowns in Lead Service Line Replacement calculations.
Strategies for Completing the Service Line Inventory
Water systems should submit inventories with all non-lead service lines as soon as possible to end the inventory submission and associated compliance obligations. This can be accomplished through conducting state-approved investigations for all remaining unknown service lines and replacing any Lead or GRR service lines.
However, investigating every unknown service line is often impractical and can be very time and resource-intensive. State regulators also understand this issue and have begun to release predictive/statistical policies to help systems accelerate the process of classifying unknowns.
Many of these policies contain different guidance for two common situations encountered by utilities:
Scenario #1) Non-LSL systems:
After the initial records review to classify service line materials, a utility has some unknowns, but the records review DID NOT produce evidence of any LSLs1, and the utility does not believe that LSLs were ever installed in their system.
Scenario #2) LSL Systems:
After the initial records review to classify service line materials, a utility has some unknowns, and the records review DID produce evidence of LSLs1 in their system.
Common Requirements for Predictive/Statistical Policies
The good news for Non-LSL systems is that some state policies provide a simplified approach to classifying the entire system as non-lead through verification of a specific number of unknowns. State policies also provide streamlined approaches for LSL Systems, but the process is more complex. These policies generally start with a set of similar requirements listed below. However, this list is a generalization, and the specific details can be complex; each state policy should be reviewed for full requirements.
- Review records to understand the numbers of “known” vs. “unknown” service lines.
- Identify how many “unknown” service lines to verify. See Table 1 below.
- Randomly select unknowns to verify. See page 5 in Oregon Policy for random number generation details.
- Conduct verifications of the random service lines and evaluate the results.
- If there are no records of LSLs1 or evidence of LSLs1 from the random verification set, then you can classify the remaining “unknowns” as non-lead, and your inventory would be complete, containing all non-lead service lines.
- If LSLs1 are found in your records review or through the random verification process, more evaluation or a different process is needed.
Examples of States with available Predictive/Statistical policies:
- Virginia: Guidance for Statistical Methods and Predictive Modeling
- Colorado: Initial Service Line Inventory Development Policy
- Oregon: Statistical Guidance for Evaluating Unknown Service Lines
- Washington: Statistical Guidance for Group A PWS Evaluation of Unknown Service Lines
- California: Verification Strategies Based on System Size
Water systems in states without a formal predictive/statistical policy should contact their state to understand what frameworks they accept and how that may help accelerate their inventory process.
Resources for Accelerating Your Inventory Process
Maps have been developed by 120Water and Blue Conduit to help track state-specific inventory resources in your state. 120Water has partnered with Blue Conduit to bring best-in-class solutions to predictive/statistical analysis. Contact 120Water for questions on how to take the next step with your inventory and what predictive/statistical analysis might look like for your system.
1Consult your state for how they are handling GRR in a predictive/statistical policy as state approaches differ
Verify the number of unknown service lines in the right column based on the number of system unknowns in the left column. The table represents a 95% confidence level with +/-5% margin of error.
|Number of “Unknown” Service Lines||Number to Verify|
|Fewer than 1,500||20% of unknown lines|
|225,000 or more||384|