Jefferson County committee outlines draft rules for data centers on air pollution, wastewater and stormwater

Jefferson County officials and outside engineering consultants on Dec. 10 described a suite of proposed rules aimed at limiting local impacts from large commercial data centers, including tighter air‑quality reporting for diesel backup generators, mandatory wastewater impact assessments and stronger stormwater controls.

County staff outlined draft requirements that would force applicants to submit air‑quality impact assessments, generator testing schedules coordinated with the county, semiannual compliance reports and third‑party audits at the owner’s expense. Will Caldran, an engineer with air‑quality permitting experience, told the committee that “the main thing we’re talking about is these diesel generators,” and said permits are typically written to keep sites below federal major‑source thresholds that are commonly described as under 250 tons per year for key pollutants.

On wastewater, consultants and staff stressed that the cooling technology determines the risk. Samantha McKee, a project scientist with stormwater and compliance experience, said water‑cooled systems “require a higher water demand and then also would produce wastewater,” potentially requiring on‑site pretreatment or industrial‑user permits if municipal treatment plants lack capacity. Staff proposed that applications include a wastewater impact assessment covering expected daily and peak flows, total dissolved solids (TDS), chloride, discharge temperature and proposed pretreatment systems. The draft language cited a numeric baseline: “cooling system wastewater … shall not exceed 1,000 milligrams per liter TDS,” with chlorides and a 104°F discharge temperature identified as additional controls.

Stormwater requirements in the draft focus on quantity and quality: sites—typically 70–90% impervious—would need stormwater management plans with hydrologic modeling for 1‑, 2‑, 10‑, 25‑ and 100‑year storms; post‑development peak runoff would have to be less than predevelopment; and BMPs (bioretention, filters or infiltration) would be required for generator yards, fueling areas and chemical‑storage locations. Mike Cook, the county’s stormwater manager, emphasized inspection and maintenance: “These O and M’s have to be maintained or they fail,” and staff proposed flow equalization tanks and access for third‑party inspections.

Council members pressed staff on enforcement and deterrents. One councilmember proposed tying financial penalties to a data center operator’s estimated outage costs, arguing this would be a stronger disincentive than conventional fines. Staff said enforcement typically relies on permit limits, nonresettable runtime meters on engines, manufacturer emission factors and periodic inspections; the county also proposed the right to require third‑party audits paid by the owner.

The committee discussed renewables and site requirements. Rather than mandating a single technology (for example, rooftop solar), several members favored a performance or percentage approach—e.g., a renewable‑energy target with multiple compliance paths—to preserve flexibility as technologies evolve. Staff said heat‑reclamation and off‑site renewable procurement could factor into compliance.

Members asked staff to add decommissioning and bonding language to address future cleanup and obsolescence; staff agreed to draft decommissioning/exit‑clause language and to advance community benefit agreement and workforce development clauses for the next meeting.

There was no final regulatory vote. Staff said draft regulations will be posted to the county’s data‑center page on jeffcomo.gov and that a full draft ordinance is tentatively slated for the Planning & Zoning Commission on March 12, with potential county action afterward. The committee scheduled a follow‑up meeting for Jan. 7 to review community benefit language, workforce development clauses and draft regulatory text.