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Understanding API Publication 351-1999: Environmental Performance Measures for Terminal Operations
A Detailed Overview of the 1999 API Publication on Environmental Indicators for Marine and Onshore Terminals
Scope and Objectives of API Publication 351-1999
API Publication 351-1999 (commonly referred to as API Publ 351) provides a standardized framework for measuring and reporting environmental performance at marine and onshore terminals handling petroleum products. Published in 1999, this non-consensus document—classified as an API publication—was developed to assist terminal operators in identifying key environmental aspects, establishing performance indicators, and promoting continuous improvement in environmental management.
The scope of the publication covers terminals involved in the receipt, storage, handling, and transfer of crude oil, refined products, and liquefied gases. It addresses environmental aspects such as air emissions, wastewater discharges, waste management, spill prevention and response, and resource consumption. While the document does not prescribe binding requirements, it offers guidance on metrics that reflect operational efficiency and environmental stewardship.
API Publ 351-1999 is intended for use by terminal management, environmental professionals, regulatory bodies, and third-party auditors. It aligns with broader environmental management systems (e.g., ISO 14001) and can serve as a basis for internal and external reporting.
Tip: API Publ 351-1999 is a vital resource for terminals starting or refining their environmental performance metrics. Refer to it alongside current regulatory requirements to avoid outdated criteria.
Technical Requirements and Key Performance Indicators
The core of API Publ 351-1999 is a set of environmental performance measures organized into logical categories. Each indicator is defined in terms of calculation method, unit of measure, and data source. The publication emphasizes that indicators should be objective, measurable, consistent, and comparable over time.
Air Emissions
Metrics include total VOC emissions from loading/unloading operations (e.g., marine vapor collection system efficiency), SOx, NOx, and particulate matter from combustion sources (boilers, heaters, engines). Fugitive emissions from valves and seals are also addressed. The recommended unit is mass per throughput (e.g., kg VOCs/1000 m3 transferred).
Water and Effluent
Key indicators cover volume and quality of ballast water, bilge water, and stormwater discharges. Parameters such as oil content (ppm), biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total suspended solids (TSS) are typically tracked. The publication suggests limits based on local discharge permits.
Waste Management
Metrics include hazardous waste generation rate (kg/tonne throughput), recycling efficiency percentage, and volume of residues (e.g., sludges, burnt oil). The document encourages minimizing waste generation and promoting reuse/recycling.
Spills and Releases
Number and volume of accidental hydrocarbon spills, both to water and land, are tracked per year. The indicator “spill rate per unit throughput” allows benchmarking. Emergency response time and recovered volume percentages are also suggested.
| Performance Category | Indicator | Unit | Typical Reference Baseline |
|---|---|---|---|
| Air Emissions | VOC emissions per throughput | kg/1000 m³ | 0.1–0.5 kg/1000 m³ |
| Water Discharge | Oil content in effluent | mg/L | ≤15 ppm |
| Waste Generation | Hazardous waste per tonne | kg/tonne throughput | <0.1 kg/tonne |
| Spill Performance | Spill volume per 10⁶ m³ handled | m³ | <0.02 m³/10⁶ m³ |
Caution: The baselines in API 351‑1999 are illustrative. Operators must adjust thresholds to align with local permits and commercial objectives.
Implementation Highlights
Successful adoption of API Publ 351-1999 requires integration into existing management systems. The document outlines a step‑by‑step process:
- Define operational boundaries – determine which facilities and activities are in scope.
- Select relevant indicators – choose from the menu of metrics that match the terminal’s environmental aspects.
- Establish data collection procedures – specify frequency, responsibility, and quality control.
- Calculate performance values – use standard formulae to normalize by throughput or other factors.
- Analyze trends – compare against historical data, targets, and industry benchmarks.
- Report and review – internal reporting to management and external disclosure if required.
The publication also stresses the importance of consistent application across time and among different terminals within the same company. Many operators use the metrics for sustainability reporting (e.g., GRI, IPIECA) or to demonstrate compliance with environmental permits.
Success factor: Terminals that implemented the API 351 framework report improved environmental transparency and better identification of cost‑saving opportunities through waste reduction and energy efficiency.
Compliance and Regulatory Integration
API Publication 351-1999 is not itself a regulatory standard, but it supports compliance with many international and national regulations. Its indicators align with the U.S. EPA’s performance track, MARPOL Annex I (ballast water), Annex VI (air emissions), and local coastal management programs.
Regulatory bodies may accept API 351‑based reporting as part of environmental audit protocols. However, operators must ensure that the chosen indicators meet local legal requirements—for example, discharge limits for oil content (typically 15 ppm) which are stricter than the broader baseline suggested in the publication.
Compliance notes:
- Update cycles: Since 1999, several API recommended practices have evolved (e.g., RP 50, RP 55). Users should check for newer editions or replacements.
- Data comparability: To gain maximum benefit, facilities should use consistent definitions and measurement periods.
- Third‑party verification: Some terminals opt for independent assurance of the reported indicators to increase credibility.
Important: Relying solely on API 351‑1999 without updating to current regulatory limits may result in non‑compliance. Always verify against the latest regional legislation.
Frequently Asked Questions
Q: Is API Publ 351-1999 still valid today?
A: API 351-1999 remains a useful reference for environmental performance measurement at terminals, but it has not been formally reaffirmed or replaced in recent years. For up‑to‑date guidance, combine it with current API standards (e.g., API Stewardship activities) and regulatory requirements. The document is available as a scanned copy through the API portal.
A: API 351-1999 remains a useful reference for environmental performance measurement at terminals, but it has not been formally reaffirmed or replaced in recent years. For up‑to‑date guidance, combine it with current API standards (e.g., API Stewardship activities) and regulatory requirements. The document is available as a scanned copy through the API portal.
Q: What is the difference between an API Publication and an API Recommended Practice (RP)?
A: API Publications are non‑consensus documents that present useful information or guidance, whereas RPs are developed through formal consensus and may be recognized by regulatory agencies. API 351‑1999 provides guidance without establishing mandatory requirements.
A: API Publications are non‑consensus documents that present useful information or guidance, whereas RPs are developed through formal consensus and may be recognized by regulatory agencies. API 351‑1999 provides guidance without establishing mandatory requirements.
Q: Which terminals can use API 351‑1999?
A: The publication is designed for both marine terminals (loading/unloading ships and barges) and onshore terminals (rail, truck, pipeline). It can be adapted to small‑ or large‑scale facilities.
A: The publication is designed for both marine terminals (loading/unloading ships and barges) and onshore terminals (rail, truck, pipeline). It can be adapted to small‑ or large‑scale facilities.
Q: Does the framework support ISO 14001 integration?
A: Yes. The indicators directly support the “monitoring and measurement” and “evaluation of compliance” elements of an ISO 14001 environmental management system. Many operators use API 351 metrics as part of their EMS documentation.
A: Yes. The indicators directly support the “monitoring and measurement” and “evaluation of compliance” elements of an ISO 14001 environmental management system. Many operators use API 351 metrics as part of their EMS documentation.
© 2026 — Technical review of API Publication 351-1999. This article is intended for informational purposes and does not replace the original standard.