Phase II field methods

ASTM E1903-19 leaves exploration and sampling methods to the Phase II Assessor's professional judgment (E1903-19, 7.5.3). It sets the order of the work instead: a conceptual model predicting where target analytes are now, a written sampling plan that tests it, and fieldwork that follows the plan and records where it could not (E1903-19, 6.4.3 to 6.4.5, 7.4 to 7.6).

The conceptual model comes first

The conceptual model is a hypothesis about present conditions: the site's physical setting and the likely spread of target analytes from a known or likely release, built on reasonably ascertainable information and the Phase II Assessor's judgment, for each area to be investigated where target analytes are present or likely present (E1903-19, 3.1.10, 6.4.3). It must be formed before sampling to guide the work and refined as information comes in, and it has three parts (E1903-19, 7.4).

• Target analytes. The model must take in substances tied to past activities at the property, substances from other human activity, and naturally occurring ones; where a release's makeup is unclear, testing for wide groups of analytes is warranted (E1903-19, 7.4.1). It must also account for each analyte's physical state when released or otherwise present, and possible transformations from primary into secondary analytes (E1903-19, 7.4.1.1, 7.4.1.2).
• First entry into the environment. How an analyte first met an environmental medium is a primary guide to where it is now, and so to where samples go (E1903-19, 7.4.2). The Phase II Assessor must judge it from knowledge of the operations tied to the site's current and past uses and of structures, features and containers that could have released substances (E1903-19, 6.4.3.2).
• Behavior, fate and transport. The model must predict where the analytes would be now, given how they entered and what has governed their persistence and movement since, by map or in words (E1903-19, 7.4.3). It should be formed in light of general principles, as the setting and objectives make appropriate: analytes generally persist, and are commonly most concentrated, at their point of entry; migration generally spreads them in three dimensions; and for each area the model should name the entry point, the migration pathways, where along them concentrations are likely highest, and what bounds migration, adding receptors, exposure points and ways of exposure where the objectives need them (E1903-19, 7.4.3 to 7.4.3.4).

The sampling plan

The written plan tests the three-dimensional distribution the model predicts, standing alone or inside a proposal or scope of work with the same elements (E1903-19, 7.5). Its data quality objective is, at a minimum, reproducible chemical testing results for target analytes from locations that bear on the objectives and likely hold the highest concentrations; the work should be framed so another Phase II Assessor could repeat it with consistent results (E1903-19, 6.4.4). Testing must at least seek the analytes the model assigns to the area, and broad categories may be added where the full set is uncertain (E1903-19, 7.5). Results must be interpreted, and conclusions stated, in light of the sampling rationale followed (E1903-19, 7.5).

• Minimum sampling. The plan must allow the media to be collected at each area where target analytes are, or likely are, at their highest concentrations (E1903-19, 7.5.1).
• Beyond the minimum. It may call for more when the question needs the distribution of analytes or their change over time, not only whether a release left them (E1903-19, 7.5.2).
• Health and safety. Unless a separate health and safety plan addresses them, the sampling plan should identify precautions for personnel that satisfy applicable federal or equivalent state or local law, together with requirements imposed by the owner, occupant or user (E1903-19, 7.5.4).
• Techniques. The plan shall identify how representative samples will be collected, using methods suited to both standard practices and the investigation's objectives (E1903-19, 7.5.5). Sampling and testing should follow applicable procedures and protocols, such as EPA's SW-846 or similar agency methods (E1903-19, 6.4.4 Note 1, 2.3). The nonmandatory Appendix X4 lists ASTM standards and EPA documents that may be relevant, such as guides on direct push sampling, soil gas monitoring, chain of custody, monitoring wells, conceptual site models and vapor intrusion (E1903-19, X4.1 to X4.3).
• Field screening. Field screening may guide sample placement by finding physical anomalies underground, routes along which analytes might move, or potential plumes of volatile organic compounds in groundwater (E1903-19, 7.5.6). Field measurements generally differ from laboratory measurements in accuracy and precision; calibrated field analytical equipment can achieve comparable detection and accuracy (E1903-19, 3.1.20, 3.1.20.2). Appropriate QA/QC, such as calibration, must cover the equipment, the screening and its data (E1903-19, 3.1.20.1).
• QA/QC. The plan must include a QA/QC plan, which need not be written but whose provisions the Phase II Assessor must know and follow (E1903-19, 7.5.7). It shall establish procedures, which must be followed, to assure representative samples from the planned media and locations, preserve their integrity during collection and handling, and evaluate test reliability; it should provide for preservation, holding times and a documented chain of custody before samples go to an appropriately accredited laboratory (E1903-19, 7.5.7). Any laboratory used shall be accredited under applicable state requirements, and the Phase II Assessor should require it to report problems or nonroutine events in testing (E1903-19, 4.2.1.3).

Conducting the sampling

Sampling follows the plan and its objectives (E1903-19, 7.6). The field record notes the physical conditions found, such as subsurface soil and groundwater characteristics, and anything that blocked the plan, such as a barrier or too little sample volume (E1903-19, 6.4.5). Deviations must be documented, and justified or reconciled before the investigation ends (E1903-19, 7.5.7, 7.6). If one affects whether the objectives can be met, the Phase II Assessor may, with the user, reconsider or revise the plan or the model (E1903-19, 7.6). At each stage, what has been learned must refine the model as warranted (E1903-19, 7.5); new results must be reconciled with it, the plan changed to match any revision before further sampling, and sampling completed under the revised plan (E1903-19, 7.6).

Related

• What is a Phase II ESA?
• Scoping a Phase II
• Reading Phase II results
• What a Phase II report contains
• Contracting a Phase II
• Likely release and likely presence

This page is general reference for environmental professionals. It does not assess any property. ASTM E1903-19 is the standard and is not reproduced here; the judgment of the Phase II Assessor on the facts governs.