Understanding Petroleum Releases in Soil & Groundwater

When petroleum is released from an underground storage tank, its components behave differently in soil, groundwater, and soil gas — some dissolve readily, some volatilize, and some biodegrade under natural conditions. API has funded decades of research to characterize this behavior. The Technical Bulletins below summarize key findings on topics including natural attenuation, plume behavior, and risk evaluation at petroleum release sites.

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• Technical Protocol for Evaluating the Natural Attenuation of MtBE – API Publication 4761
• API Technical Bulletins

Petroleum Vapor Intrusion (PVI)

Vapor intrusion (VI) occurs when vapors from subsurface contamination migrate into overlying buildings. The BioVapor model is a screening tool that estimates indoor air concentrations from subsurface petroleum vapor sources, accounting for aerobic biodegradation in the vadose zone.

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LNAPL Management

Light non-aqueous phase liquid (LNAPL) is often present at petroleum release sites. API has developed tools to help practitioners and regulators evaluate LNAPL mobility, estimate recoverability, and make risk-informed decisions.

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Groundwater Monitoring & Site Closure

Tracking groundwater quality over time is essential for demonstrating that a site is stable and progressing toward closure. API’s GWSDAT tool provides statistical and spatial analysis of groundwater monitoring data to support closure decisions. The video resources below provide introductions to key concepts in site assessment and closure.

Related Assets

• GWSDAT (Groundwater Spatiotemporal Data Analysis Tool)
• Instructional Youtube videos