Risk Assessment, Part Two

We’ll be referring to the table we have available for download for the screening levels for assessment.

For this state, assessment of soil contamination proceeds in a systematic manner (see the Decision Tree document). The sample’s concentration is compared to background levels — either uncontaminated soil from or near the site or state background levels. If the sample’s concentration is lower than the background level, then there is no problem. If the concentration is higher then the next stage of assessment is made. For our samples, arsenic and lead were higher than the maximum concentrations in the state’s background levels. Barium and chromium were lower so those metals aren’t considered a concern. (Canada is currently creating national guidelines for acceptable concentrations of chemicals in soil. These limitations will be in force, even if the soil background concentration is higher.)

The next step is to compare arsenic and lead concentrations to the soil to groundwater screening levels. The EPA recently changed their screening levels (June 2009) and we’re using the EPA’s current screening levels for this region. The sample’s concentrations for lead and arsenic were both higher than the soil to groundwater screening levels (arsenic is also higher for the state’s soil to groundwater screening level — these for some reason are about 20 times higher than the EPA’s). Typically this means that groundwater needs to be tested for these elements.

The next step is to consider residential screening levels. In this case, the arsenic concentration is still higher than the residential screening level, but lead is lower.

In West Virginia an option where soil screening levels are high for residential but don’t exceed the industrial soil screening level, is a deed restriction, so that the property can only be used for industrial activity and not as a place to live, garden or farm. We don’t believe that is an option here since the well pad is on a half acre of a much larger piece of property. The natural gas operator doesn’t own the property, they lease the mineral rights from someone else who owns the mineral rights. Surface rights were severed from the mineral rights some time ago.

Another concern for all the metals — arsenic, barium, chromium and lead — is how much higher their concentrations are than ecological screening levels. In the case of arsenic the eco-ssl is much higher than the residential soil screening level (but the sample’s concentration is higher still), while for barium, chromium and lead the eco-ssl are much lower than residential screening levels.

Our preliminary assessment comes from the laboratory analysis of one spot within an affected surface area of at least 1500 square feet. The matrix has a high chloride concentration which would enable the transport of chemicals through soil to water beyond the confines of the site. It’s entirely possible that laboratory analysis at other points would alter the preliminary assessment’s chemicals of concern and add others. It’s also possible that the pit liner is no longer intact at the bottom further north of the sample location and migration of pollutants has already occurred.

For these reasons, we believe the site deserves a full assessment by a professional though we believe that remediation options for the operator are limited. We hesitate to make recommendations but believe the operator’s preference of doing nothing is not viable because we believe that the site’s unremediated presence is a danger to those living nearby.

October 3, 2009