PSD, NSR, BACT, LAER, Title V & Offsets

Quick Answer: Attainment area + major source → PSD + BACT. Nonattainment area + major source → NSR + LAER + offsets. Major source thresholds (~100 tpy criteria pollutant) often trigger Title V operating permits. Know BACT vs. LAER stringency and offset credit requirements.

Permitting translates emission estimates into legally enforceable limits. FE Environmental items test which program applies and what technology or offset requirements follow.

Major Source Thresholds (Simplified)

Modifications triggering review compare net emissions increase to pollutant-specific Significant Emission Rates (SER) in handbook tables — can be as low as 40 tpy NOx in some cases.

Prevention of Significant Deterioration (PSD)

Applies to new or modified major sources in attainment areas:

1. BACT — Best Available Control Technology for each regulated pollutant.
2. Air quality analysis — models ambient impacts against NAAQS and PSD increments.
3. Class I area protection — extra scrutiny near national parks/wilderness.

PSD increments cap allowable degradation in clean air areas — separate from NAAQS but constrains growth.

Nonattainment New Source Review (NSR)

In nonattainment areas for a pollutant:

1. LAER — Lowest Achievable Emission Rate; stricter than BACT; cost considered but less limiting.
2. Emission offsets — reductions elsewhere so net air quality improves.
3. Offset ratio — often 1.1:1 or 1.2:1 (more stringent in serious/severe nonattainment).

Offsets must be:

• Surplus — beyond existing requirements.
• Permanent — for life of project.
• Quantifiable and enforceable.

BACT vs. LAER Comparison

Exam trap: LAER is not "less stringent because of economics" — it is more stringent than BACT in most comparisons.

Title V Operating Permits

Title V consolidates all federally enforceable requirements into one permit:

• Emission limits, monitoring, reporting, compliance schedules.
• Five-year term with renewal.
• Public participation and EPA oversight.

Not a technology standard by itself — it administers limits from NSR, MACT, NSPS, etc.

New Source Performance Standards (NSPS)

NSPS under Section 111 set technology-based standards for new stationary sources by category (e.g., turbines, incinerators). Distinct from PSD case-by-case BACT but may overlap in required control level.

Worked Permitting Scenario

Proposal: New cement kiln in severe ozone nonattainment county; PTE 250 tpy NOx, 80 tpy PM.

Acid Rain and Trading Programs

SO2 and NOx cap-and-trade programs (Acid Rain Program, CSAPR) use allowances — separate from local NSR but uses similar mass accounting. Know allowances are mass-based, not technology standards.

Public Participation and Timing

Permits require public notice and comment. Prevention of Significant Deterioration modeling submission timelines affect project schedules — conceptual only on FE.

FE Exam Strategy

Map location attainment status → program → control level → offsets yes/no → Title V yes/no. Use handbook SER tables for modification triggers.

Exam trap: Assuming PSD applies in a nonattainment county — nonattainment NSR replaces PSD for the nonattaining pollutant.

Permitting logic is highly pattern-based on the FE — master the decision tree and BACT/LAER vocabulary.

Significant Emission Rates and Modifications

A major modification at an existing plant triggers NSR when net emissions increase exceeds pollutant-specific Significant Emission Rates (SER) — values in handbook tables (e.g., 40 tpy NOx in some attainment areas). Project netting and plantwide applicability limits (PALs) can avoid NSR if increases stay below caps — conceptual awareness for exam stems describing debottlenecking projects.

Prevention of Significant Deterioration increments limit allowable degradation in Class I, II, III areas — Class I (national parks) most restrictive. Air quality models demonstrate NAAQS and increment compliance for PSD permits.

Operating Permits and Federally Enforceable Limits

Title V permits consolidate requirements but do not replace NSR/MACT/NSPS limits — they make them federally enforceable. Synthetic minor sources accept legally binding caps below major thresholds to avoid Title V and major NSR — caps must be enforceable in permit language.

Offset Banking and Nonattainment Categories

Nonattainment areas classified marginal, moderate, serious, severe, extreme (ozone history) impose stricter offset ratios and compliance schedules. Emission reduction credits must be surplus, permanent, quantifiable, and enforceable — exam scenarios test whether a proposed offset from a closed facility still qualifies.

Class I Increment Example

Class I areas (national parks) have minimal allowable PSD increments for PM and SO₂. A new source in Class I may face more stringent increment analysis than NAAQS alone — conceptual distinction for exam classification questions.

Synthetic Minor Permit

Source limits PTE by enforceable permit conditions (hour caps, throughput limits) to stay below major thresholds — avoids Title V and NSR if legally binding. Potential to emit without limits still counts full capacity.

Emissions Offset Example

New 150 tpy NOx in serious ozone nonattainment with offset ratio 1.15:1 needs 172.5 tpy certified offsets from shuttered or controlled sources in the same nonattainment area — offsets must be surplus, permanent, quantifiable, enforceable.