Vista Irrigation District (District) has completed the initial lead service line inventory required by U.S. EPA’s Lead and Copper Rule Revisions. The deadline for the initial inventory is October 16, 2024.

Based on historical records review and field investigation, the District has determined that it has no lead or galvanized requiring replacement (GRR) service lines in its distribution system, including any privately-owned or customer-owned service lines.

The District reviewed all applicable sources of information, including:

·         Construction and plumbing codes, permits and other documentation which indicates approved service line materials used to connect private structures to the distribution system.

·         All water system records, including distribution system maps and drawings, historical records on each service connection, meter installation records, and historical capital improvement projects.

·         Annual Reports (1927-1986) and Board of Director meeting minutes (1923-1986) describing service line audits and changes to the material purchasing policy.

·         Archived service line maintenance and repair records, and archived customer service and work order records describing service line maintenance and repair.

In addition to reviewing the above sources of information, the District used an alternative method to develop the inventory that was approved by the State Water Resources Control Board Division of Drinking Water.

The District used statistical modeling (99% confidence level with a 4% margin of error) with stratified random sampling to develop the initial inventory. Stratified random sampling involves physically verifying a subset of randomly selected service lines in the distribution system; the subset was stratified or divided into groups by decade and weighted based on years when lead services would have been installed in the distribution system (1920-1950). Stratification allows for a sample or subset of service lines to be more representative of the service lines in the distribution system.

After investigating the subset of service lines, if no lead or GRR service lines are discovered, the remaining service lines may be assumed to be non-lead with a certain level of confidence. The District physically verified 982 service lines as non-lead or GRR to establish the confidence level.

The District will continue to document service line material information obtained from normal operations, such as service line maintenance and water main replacement, after October 2024 and will update the initial inventory accordingly.