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PSD / NSR Modification Calculator

Local federal emissions-increase prompts before state, permit, and qualified air-review decisions

Free source-aware PSD/NSR modification screen for environmental managers, engineers, and consultants who need transparent arithmetic before formal air-permitting review. Enter user-reviewed baseline and projected emissions for NOx, SO2, VOC, CO, PM, PM10, PM2.5, and Lead. The screen compares each row against local federal significant-emission-rate prompts and keeps the unresolved PSD, NNSR, netting, source-category, state SIP, and permit-review gaps visible.

Pro Tip: Treat baseline and projected emissions as source-supported inputs, not values created by this screen. Verify the project description, emissions units, lookback period, demand-growth treatment, emissions method, controls, enforceable limits, and state or local program rules before using the output in any regulated context.

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PSD / NSR Modification Calculator
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How It Works

  1. Enter Baseline Prompts

    Input source-supported baseline emissions in tons per year for each pollutant. The app does not determine baseline actual emissions, lookback periods, demand-growth exclusions, or accepted methods.

  2. Enter Projected Prompts

    Input source-supported projected emissions after the project. Keep capacity, fuel, control, operating, and emission-method assumptions documented outside the calculator.

  3. Set Review Context

    Select the major/minor source prompt and ozone attainment context. These choices do not determine major-source status, area classification, state SIP treatment, or NNSR requirements.

  4. Review Source Boundaries

    Use the local review prompts, source pointers, and residual data gaps to prepare for qualified environmental, legal, state, local, or EPA review.

Built For

  • Environmental managers organizing source-supported project emissions before permit strategy review
  • Consultants checking arithmetic in baseline versus projected emissions worksheets
  • Plant engineers documenting unresolved data gaps before capital-project gate reviews
  • Operations staff comparing reviewed fuel, equipment, or control-change scenarios before environmental signoff

Assumptions

  • Emission increases are calculated as projected emissions minus baseline emissions for each pollutant.
  • Federal PSD significant-emission-rate prompts are local source-aware values from the cited eCFR source pointers.
  • Serious, severe, and extreme ozone nonattainment prompts apply only to local NOx/VOC major-source context in this screen.
  • State, tribal, local, permit, and agency rules may differ from the local federal prompts.

Limitations

  • Does not calculate emissions from raw activity data or choose emission factors.
  • Does not determine baseline actual emissions, projected actual emissions, actual-to-potential, hybrid tests, demand-growth treatment, or project aggregation.
  • Does not perform contemporaneous netting, offsets, PAL, synthetic-minor, BACT, LAER, modeling, public-notice, or permit-completeness review.
  • Does not determine state SIP acceptance, minor NSR applicability, construction authorization, or agency acceptance.

References

  • 40 CFR 51.166 - Prevention of Significant Deterioration of Air Quality
  • 40 CFR 51.165 - Permit Requirements
  • 40 CFR 52.21 - Prevention of Significant Deterioration of Air Quality
  • EPA New Source Review Laws and Statutes

Frequently Asked Questions

They are federal source-pointer values used by this app as local review prompts. Actual PSD or NSR treatment depends on major-source status, source category, project test, significant emissions increase, significant net emissions increase, netting, state SIP rules, permit terms, and agency review.
No. Baseline actual emissions require source-specific records, methods, lookback period review, emissions-unit treatment, demand-growth treatment, and applicable rule analysis. Enter only values that have been developed and documented outside this screen.
The app uses PSD prompts for attainment or unclassifiable context and local NOx/VOC prompts for selected ozone nonattainment contexts. It does not decide whether PSD, NNSR, minor NSR, Title V, HAP, GHG, PAL, synthetic-minor, or state-only rules apply.
No. Netting depends on contemporaneous increases and decreases, creditability, enforceability, surplus treatment, source boundaries, pollutant treatment, and agency acceptance. Decrease rows in the app are only prompts for review.
Disclaimer: This screen provides preliminary arithmetic prompts only. It does not determine PSD, NSR, NNSR, minor NSR, Title V, HAP, GHG, PAL, synthetic-minor, permit, construction-start, or agency-approved status. Verify every value and method with current federal rules, state/local SIP requirements, permits, source data, agency guidance, and qualified environmental/legal review.

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