API Publ 1628-1996: A Guide for the Assessment, Remediation, and Monitoring of Underground Storage Tanks

Scope and Application of API Publ 1628-1996

API Publication 1628, issued in 1996 by the American Petroleum Institute, provides a comprehensive technical framework for the assessment, remediation, and monitoring of releases from underground storage tanks (USTs). Although superseded by later editions, the 1996 version remains a foundational reference for environmental professionals managing petroleum hydrocarbon releases. The document is intended for use by site assessors, consultants, regulators, and facility owners who must comply with federal and state corrective action programs.

The scope encompasses the entire lifecycle of a release event, from initial detection and site characterization through remediation system design, implementation, and long-term monitoring. It addresses both soil and groundwater contamination, covering light non-aqueous phase liquids (LNAPL), dissolved-phase plumes, and vapor intrusion pathways. Importantly, the publication is a guidance document rather than a prescriptive standard, allowing flexibility in methodology while establishing consistent technical principles.

Technical Requirements and Key Methodologies

Site Characterization

API Publ 1628-1996 emphasizes a phased approach to site characterization. The initial step involves gathering historical data, conducting a thorough site inspection, and developing a conceptual site model (CSM). A key requirement is the proper installation of monitoring wells and soil borings to define the vertical and lateral extent of contamination. The publication recommends a minimum of three to four wells for initial assessment, with additional wells placed downgradient and at the source area. Soil sampling must follow EPA Method 5035 or equivalent, and groundwater samples must be collected using low-flow purging techniques to minimize turbidity.

Remedial Action Objectives

The document establishes that remedial action objectives (RAOs) must be developed based on risk-based corrective action (RBCA) principles. Although the formal RBCA framework was published separately (ASTM E1739), API 1628 incorporates similar risk-based decision logic. RAOs must consider:

• Protection of human health (drinking water standards, vapor intrusion thresholds)
• Ecological receptors and habitats
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