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Engineers flag Fairborn lift station, trunk-line limits in Murray wastewater master plan
Summary
Consultants told the city the wastewater system shows about 600,000 gallons/day infiltration; the Fairborn Lift Station has limited holding time and sits near Cottonwood Creek, and modeled growth could raise ERUs from roughly 14,400 to as many as 43,500 at maximum build-out, prompting prioritized capacity and monitoring projects.
Consulting engineers presented the draft Murray wastewater master plan to the City Council on July 7, identifying several capacity and reliability priorities and outlining how the city’s hydraulic model will guide future projects.
Ridley Griggs, a project engineer and project manager with the consulting firm identified in the presentation, said the team used flow meters, elevation surveys and hydraulic modeling to size current capacity and forecast future needs. The consultants estimated current infiltration—groundwater and other unintended inflows—at about 600,000 gallons per day and said that rate has been stable compared with the previous assessment five years ago.
“Any time when we’re out tubing and surveying the system, we find a pipe that has significant infiltration coming into it, we move that at the top of our list,” Griggs said, explaining their prioritization method.
The consultants called out the Fairborn Lift Station as a critical vulnerability: it handles roughly one-quarter to one-third of the city’s flow, has limited wet-well holding time for emergencies, and is located about a half-hour upstream of Cottonwood Creek, increasing the consequences of a multi-pump failure. The team recommended redundancy, increased holding capacity where feasible, and a project to divert some flow by gravity to reduce pump reliance and improve reliability.
Griggs and Ben Ford (who introduced the topic) described other near-term projects, including capacity upgrades on the South State Street corridor and replacements or spot checks for undersized pipes in redevelopment areas. The plan separates growth-driven capacity projects (timed to redevelopment) from ongoing repair-and-replacement work; the report notes an existing annual pipe-lining budget of about $300,000 to extend pipeline life.
To quantify future demands, the team uses equivalent residential units (ERUs). The report estimated roughly 14,400 ERUs now, with a maximum-build scenario approaching 43,500 ERUs—numbers the presenters said should be viewed over a long horizon and tied to where and when development actually occurs.
Council members asked whether the plan included recently annexed areas; the presenters said the analysis covers the Murray City collection system east of 9900 East and does not include the annexed area, which is served mostly by nearby improvement districts. Staff also said they plan sampling with Central Valley to evaluate commercial grease trap loadings and to consider a possible surcharge or rate structure change so commercial generators pay their relative share of treatment costs.
Consultants emphasized that cost estimates are preliminary until designs are produced and that timelines will shift as development patterns change. The presentation closed with a recommended list of prioritized projects tied to modeling results and monitoring data; no final council action was taken at the meeting.
