Fairfax staff propose zoning standards and safety rules for large battery energy storage systems

County zoning staff presented a draft zoning ordinance amendment that would add use‑specific standards for large battery energy storage systems (BESS), including thresholds, setback rules, emergency planning and decommissioning requirements.

Jackie Camp (Zoning Administration) told the committee staff are proposing to treat large‑scale BESS as part of the light utility facility use with a new, specific definition and an energy‑capacity threshold range under consideration from greater than 600 kilowatt‑hours (kWh) — drawn from NFPA 855 guidance — up to 10 megawatt‑hours (MWh) based on municipal examples. Systems below the chosen threshold would be accessory uses and subject to building, electrical and fire code standards; systems above the threshold would be principal uses requiring site‑specific review.

Proposed standards and safety measures Staff proposed use‑specific standards intended to manage noise and safety and to address community concerns: setbacks (a staff proposal of roughly 100 feet from property lines and 200 feet from residential uses), increased transitional screening, an emergency operations plan and a decommissioning plan for disposal and restoration. Staff also proposed requiring adequate public water supply for fire protection in locations where needed and said they were researching financial security mechanisms (bond, escrow or letter of credit) to ensure decommissioning costs are covered.

Fire and code considerations Chief John Walzer (Fire and Rescue) briefed the committee on firefighting limitations for lithium‑ion systems: thermal runaway produces flammable gases and, while water cooling is often the only reliable mitigation, runoff from firefighting is an environmental concern because of hazardous byproducts. He explained that fire code standards apply at lower energy levels (the fire code regulates lithium‑ion BESS above 20 kWh) and that applicants could pursue performance‑based hazard mitigation analyses to justify systems beyond prescriptive thresholds.

Board discussion and outstanding issues Supervisors asked about by‑right allowances in industrial districts, accessory BESS in residential settings, temporary/emergency deployments, urban or underground installations, and whether the draft should include an explicit emergency‑use exemption. Staff acknowledged the technology is evolving and may prompt adjustments; they signaled openness to adding clear emergency provisions and to further research on thresholds and financial security before public hearings this fall.