Library / State agency
Virginia Department of Environmental Quality
OnboardedVAAir permits for generator fleets are the third-ranked delay driver. About 8,000 diesel generators were permitted at Virginia data centers as of 2024. Pathway durations (4–6 / 6–12 / 12–24 months) are consultant estimates; DEQ's own figure for a complete Title V application is 18 months. The generator-count thresholds used as pathway triggers below are planning proxies for potential-to-emit, not regulatory thresholds.
Sources (6)
| Document | Version | Effective | Notes |
|---|---|---|---|
| DEQ Air Permit Guidance APG-576: data center generator permitting | — | 2026-04-09 | Presumptive NOx limit 0.60 g/hp-hr; most data center units treated as non-emergency. |
| DEQ Clarification 2025-03: construction activities permitted before air permit issuance | — | — | Limits pre-air-permit construction of the emissions units and directly related structures. |
| DEQ water permitting: Virginia Water Protection (VWP) permit program and water withdrawal permitting | — | — | VWP covers state wetlands/stream impacts (joint permit application with the Corps). Withdrawal permit need depends on source, volume and location; Loudoun is outside the eastern Virginia groundwater management areas. |
| VPDES General Permit for Discharges of Stormwater from Construction Activities (9VAC25-880) | — | — | Coverage required for one acre or more of land disturbance; registration through the VSMP authority. |
| Virginia Air Permit Regulations for Stationary Sources (9VAC5-80): minor NSR, state major NSR, PSD and Title V | — | — | Pathway is set by potential to emit after enforceable hours/fuel limits, not by unit count. |
| Virginia HB 507 (2024) data center generator emissions — Va. Code § 10.1-1322.6 | — | 2026-07-01 | Tier 4 (or equivalent) required for generator permit applications received on or after July 1, 2026. |
Requirement classes (11)
Triggers are evaluated against project inputs; durations are typical working days.
| Code | Title | Gate | Category | Asset classes | Trigger | Days | Veto | Predecessors | Source / clause |
|---|---|---|---|---|---|---|---|---|---|
| DEQ-AIR-SCREEN | Generator fleet emissions inventory and permit pathway determination Potential-to-emit calculation for the proposed generator fleet (count, kW, tier, hours) to pick the permit pathway: synthetic minor, state major + Title V, or PSD. This is the single highest-leverage air decision; the fleet spec from the tenant must be frozen first. Evidence: Emissions inventory spreadsheet; pathway memo from the air consultant; DEQ pre-application meeting notes. | Entitlement | Air | Data center | Applies when generators are proposed (generator count >= 1) | 30 | TEN-GEN | Virginia Air Permit Regulations for Stationary Sources (9VAC5-80): minor NSR, state major NSR, PSD and Title V — | |
| DEQ-AIR-MAJOR | Air permit — state major NSR plus Title V operating permit State major new source review construction permit followed by a Title V operating permit. Consultant estimate 6–12 months; DEQ cites 18 months for a complete Title V application. Public notice and comment apply, which is where opposition groups engage. Trigger uses 21–80 generators as a planning proxy. Evidence: Issued state major NSR permit; Title V application receipt and issued operating permit. | Permit | Air | Data center | Applies to mid-size fleets (21–80 generators; proxy threshold, estimate) | 190 | DEQ-AIR-SCREEN, DEQ-TIER4 | Virginia Air Permit Regulations for Stationary Sources (9VAC5-80): minor NSR, state major NSR, PSD and Title V 9VAC5-80 (state major NSR; Title V operating permits) | |
| DEQ-AIR-PSD | Air permit — Prevention of Significant Deterioration (PSD) major source Federal PSD review for fleets whose potential to emit exceeds the major-source threshold even with limits: BACT, modeling, Class I analysis. Consultant estimate 1–2 years. Trigger uses more than 80 generators as a planning proxy; a campus of this size usually phases permits to stay out of PSD. Evidence: Issued PSD permit; BACT determination; modeling report accepted by DEQ. | Permit | Air | Data center | Applies to very large fleets (more than 80 generators; proxy threshold, estimate) | 375 | DEQ-AIR-SCREEN, DEQ-TIER4 | Virginia Air Permit Regulations for Stationary Sources (9VAC5-80): minor NSR, state major NSR, PSD and Title V 9VAC5-80 (PSD permits) | |
| DEQ-AIR-SM | Air permit — synthetic minor (minor NSR with enforceable limits) Minor new source review permit with federally enforceable hours and fuel limits keeping the fleet below major-source thresholds. Consultant estimate 4–6 months. Trigger uses generator count <= 20 as a planning proxy for PTE; the air consultant's pathway memo overrides it. Evidence: Issued minor NSR permit with limits; public comment record if applicable. | Permit | Air | Data center | Applies to small fleets (1–20 generators; proxy threshold, estimate) | 100 | DEQ-AIR-SCREEN, DEQ-TIER4 | Virginia Air Permit Regulations for Stationary Sources (9VAC5-80): minor NSR, state major NSR, PSD and Title V 9VAC5-80 (minor NSR permits) | |
| DEQ-TIER4 | Tier 4 generator requirement (applications on or after July 1, 2026) Va. Code § 10.1-1322.6 (HB 507) requires Tier 4 or equivalent emission performance for data center generator permit applications received on or after July 1, 2026; DEQ APG-576 sets a presumptive NOx limit of 0.60 g/hp-hr. Confirm the procured units meet it before the application is filed; a non-Tier 4 spec is a re-design. Evidence: Manufacturer emission certification (Tier 4 / 0.60 g/hp-hr NOx) for the specified units. | Permit | Air | Data center | Applies when generators are proposed (generator count >= 1); application date on/after 2026-07-01 | 10 | DEQ-AIR-SCREEN | Virginia HB 507 (2024) data center generator emissions — Va. Code § 10.1-1322.6 Va. Code § 10.1-1322.6; DEQ APG-576 (Apr 9, 2026) | |
| DEQ-VWP | Virginia Water Protection (VWP) permit for wetland and stream impacts State permit for impacts to wetlands and streams, filed as a joint permit application with the Corps Section 404 request. DEQ issues it as the state 401 certification counterpart; small impacts may qualify for a VWP general permit. Evidence: VWP permit or general permit authorization; compensatory mitigation credit purchase. | Permit | Water | all | Applies when wetlands are present on the site | 120 | FED-404-DELIN | DEQ water permitting: Virginia Water Protection (VWP) permit program and water withdrawal permitting — | |
| DEQ-WATER-DISCHARGE | Cooling water discharge authorization (VPDES or sewer-authority pretreatment) Authorization for cooling tower blowdown and process discharge: VPDES individual permit if to surface water, or an industrial pretreatment/discharge permit from the sewer authority if to sanitary sewer. Evidence: VPDES permit or sewer authority discharge permit with limits. | Permit | Water | all | Applies when a process/cooling discharge is proposed (discharge gpd > 0) | 90 | DEQ-WATER-WITHDRAW | DEQ water permitting: Virginia Water Protection (VWP) permit program and water withdrawal permitting — | |
| DEQ-WATER-WITHDRAW | Water withdrawal permit / supply confirmation for cooling Confirmation that the cooling water supply is permitted: DEQ withdrawal permit for surface or groundwater sources, or a capacity commitment letter from the municipal supplier. The 300,000 gpd trigger is a planning threshold, not a regulatory one. Water is a political gate in the arid West and an opposition theme in Virginia. Evidence: DEQ withdrawal permit or municipal supplier capacity/availability letter sized to peak day demand. | Permit | Water | all | Applies to large withdrawals (>= 300,000 gallons/day; planning threshold, estimate) | 180 | LC-PREAPP | DEQ water permitting: Virginia Water Protection (VWP) permit program and water withdrawal permitting — | |
| DEQ-AIR-PRECON | Pre-permit construction limits confirmed (DEQ Clarification 2025-03) Written confirmation from DEQ or the air consultant of which construction activities may proceed before the air permit issues (site work and shell generally yes; generator pads, fuel systems and exhaust no). Protects the grading/foundation early start from an enforcement problem. Evidence: Consultant/DEQ memo listing permitted pre-issuance activities, filed with the grading permit. | Construction | Air | Data center | Applies when generators are proposed (generator count >= 1) | 5 | DEQ-AIR-SCREEN | DEQ Clarification 2025-03: construction activities permitted before air permit issuance — | |
| DEQ-VPDES-CGP | VPDES construction stormwater general permit coverage (SWPPP) Registration statement and stormwater pollution prevention plan for the construction general permit, submitted through Loudoun as VSMP authority. Required for one acre or more of disturbance. Evidence: DEQ coverage letter with permit number; SWPPP on site. | Construction | Stormwater | all | Applies when land disturbance is one acre or more (site acreage >= 1) | 15 | LC-SWM, LC-ESC | VPDES General Permit for Discharges of Stormwater from Construction Activities (9VAC25-880) 9VAC25-880 (construction general permit) | |
| DEQ-VSMP | Post-construction stormwater compliance (nutrient credits / BMP maintenance) VSMP water-quality compliance for the built condition: on-site BMPs plus purchase of nutrient credits for any remaining phosphorus load, and the recorded BMP maintenance agreement. Often resolved at the last minute before the grading permit; schedule it with the SWM plan. Evidence: Nutrient credit purchase certificate; recorded maintenance agreement. | Construction | Stormwater | all | Applies when land disturbance is one acre or more (site acreage >= 1) | 20 | LC-SWM | VPDES General Permit for Discharges of Stormwater from Construction Activities (9VAC25-880) Virginia Stormwater Management Program Regulation (9VAC25-870), water quality criteria |