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Industry rep explains closed-loop cooling: minimal operational discharge but large initial fills possible
Summary
A data-center developer representative told the Janesville council that modern closed-loop cooling systems usually use little municipal water during operation, but initial fills and landscaping irrigation can require millions of gallons; he also highlighted jobs and market growth.
Dale Lewis, director of data center development for Bolt Company, told the Janesville City Council on March 23 that modern AI-scale data centers largely use closed‑loop cooling systems that minimize continuous municipal water withdrawals, though initial fills and landscaping needs can require substantial volumes.
"Closed loop systems ... they don't really use any of your local water. It's like your car radiator," Lewis said, describing how closed systems are sealed, filled with a final chemical/glycol mix by specialist firms (for example Nalco or Ecolab) and managed on‑site by water‑management technicians. He said the ongoing makeup water is mostly to replace entrained air and occasional venting losses, not continuous large draws.
Lewis discussed an example from Microsoft’s Milwaukee (MKE) campus, saying the initial fill at that site was about 2,500,000 gallons. For a hypothetical large Janesville facility using roughly 600 megawatts of power, he estimated an initial fill in the range of 4–5,000,000 gallons, though he emphasized actual volumes depend on system design and the mix of glycol and water.
He described how closed‑loop cooling reduces wastewater from process flow compared with older evaporative or "swamp cooler" designs; however, he said irrigation of landscaping around campuses may use significant water. Lewis also highlighted economic benefits, saying newer AI campuses bring a mix of highly skilled mechanical and IT technician jobs and cited an industry heuristic—about 1.7 on‑site jobs per megawatt—as an example of workforce impact.
Lewis said specialized vendors manage water quality on‑site and, when systems are drained, that water is typically trucked to vendor facilities for filtration and processing before any municipal return. He noted that designs must include containment and be reviewed by regulators before permitting.
Council members asked follow‑ups about initial‑fill estimates; Lewis repeated the Microsoft MKE example and reiterated that Janesville numbers would depend on final engineering and system makeup. No formal permitting decisions were made at the session; presenters provided technical background for future planning and review.
