Environmental regulatory agencies apply traditional risk assessment processes to estimate an amount of chemical in the environment that could cause an adverse health outcome to humans and ecological receptors.  The estimated chemical concentration is derived from scientific studies of the chemical’s toxicity combined with upper range values of exposure that a person, plant, or animal (i.e., receptor) may experience.  As is often stated, if there is no exposure there is no risk; hence, risk-based cleanup decisions at sites of environmental contamination are largely influenced by estimates of how often a receptor could be exposed to the chemical and the actual chemical concentrations in the environment.  It is the intertwining of these two variables that should be factored into the development environmental sampling plans – exposure data collection.

At HMA, risk-based decision-making centers on collecting data from locations within environmental media (soil, groundwater, soil vapor) that best represent concentrations that receptors could ingest, contact (dermal) or breathe in. Data collection at the exposure point is ideal for current risk determination, data should also be collected along transport pathways lying between the source of contamination and the receptor. Thus, the emphasis on the value of data collection to discern the mechanisms leading to receptor exposures – referred to as the conceptual site model. In the risk assessment process, practitioners at HMA are mindful of three elements of environmental sampling to foster risk-based decisions – data generation (data design acquisition), data interpretation (risk analysis), and data use (response warranted?). Risk assessment and data collection are inseparable (mutually inclusive) in the sense that the goal of site risk evaluations should be to align risk reduction strategies (i.e., risk management) toward unacceptable exposures and proportionate to financial resources.

With these guiding tenets in mind, HMA utilizes a number of investigatory and CSM-building techniques to achieve this overarching goal of risk reduction and optimal resource allocation.  Among these are:

Incremental Sampling Methodology (ISM)
HMA frequently uses ISM to best represent concentrations that the receptor is likely to be exposed to in a particular decision unit or area.

High Resolution Site Characterization
When appropriate, HMA uses various High-Resolution techniques to provide comprehensive spatial understanding of contaminant mass.  These efforts often include traditional drilling and sampling and direct push techniques and other data dense techniques such as Membrane Interface Probe with Hydraulic Profiling Tool (MIP w/ HPT).

Saturated Soil Sampling and Analysis
Particularly for chlorinated solvent sites, HMA is a proponent of coincident saturated soil and groundwater sampling to better understand contaminant mass distribution.