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Staff explains elevated-tank zones, fire-flow limits and spike in main breaks
Summary
Commission staff described how elevated-tank storage is sized for daily use, peak demand and fire protection, recounted limitations during major fire events, and reported an unusually high number of water-main breaks in recent weeks attributed mainly to corrosion and stray electrical current.
At its Feb. 20 meeting, staff for the Wachterawatt Utility Commission explained how elevated-tank and booster-station storage are sized and described recent operational challenges after a month with a sharp increase in distribution-system failures.
Kelly, a utilities presenter, summarized a schematic showing three tank zones: operating storage at the top (used daily as pumps cycle), equalization storage for peak-hour demand, and a bottom zone reserved for fire protection. Kelly said the Insurance Services Office guidance the utility uses calls for at least 3,500 gallons per minute for three hours to meet typical fire-flow expectations.
Staff emphasized that tanks and reservoirs are sized as a balance between daily operations, peak demands and the practical limits of long-term water quality. "If we had more storage to try to have enough water, if a whole subdivision burned out, we'd have extreme water quality issues because there'd be too much water sitting there that we didn't cycle," Kelly said, explaining why the utility does not size for a single catastrophic event covering an entire subdivision.
Kelly also described an operational surprise staff observed after a recent trailer-home fire: when plumbing is destroyed by heat, water can continue to flow from a meter, increasing water loss during a fire until crews or the utility can shut supply off. Kelly said the commission takes maintenance needs into account and normally takes tanks out of service every five years for maintenance, coordinating with the fire department if multiple hydrants are in use during that work.
In the utilities performance report, staff said the system experienced 25 distribution-system events since the beginning of the year — compared with the utility's annual budgeting assumption of about 30 main breaks per year. Staff said the recent failures show more corrosion-related blowouts (holes from corrosion) and corrosion of stainless bolts, and that similar patterns have been reported by neighboring communities. Possible contributing factors discussed included older buried infrastructure, changes in source-water temperature since switching from a groundwater well to Great Lakes water, stray electrical current in the ground, and, possibly, substandard materials on individual fittings.
To mitigate corrosion, staff said crews install sacrificial anodes (magnesium blocks welded to mains) intended to take corrosion in place of the pipe. Staff said they attempted to send a sample for lab testing to check material quality but could not reach the lab and will attempt testing if another failure allows sampling.
Staff also reported work on operational items including coordination with USIC on locating issues, a new app to track main breaks, continued project design work for 2025 replacements, and efforts to finalize the operation center design and related rezoning and architectural review steps.
Kelly and other staff framed the issues as operational and technical rather than policy decisions; no policy changes were proposed or voted on at the meeting.
