Agriculture Reference
In-Depth Information
more focused approach to cleanup may be in order. For example, if preliminary
investigation indicated that for most of the site's history a metal foundry was
in operation, the first focus should be on metals. If no other contaminants are
identified in the subsequent investigation, a remedial action that best contains
metals may be in order. If a clay layer is identified at the site from test pit
activities and extends laterally beneath the foundry's more porous overburden
material, the clay layer should be sampled to see if any screening levels have
been exceeded. If groundwater has not found beneath the metal-laden mate-
rial, an appropriate interim action removal may be appropriate, followed by a
metal treatment process for any soil or environmental media laden with metal
wastes. For example, metal-laden waste has recently been treated by applying
a buffered phosphate and stabilizing chemicals to inhibit lead leaching and
migration. The technologies for in situ treatment are advancing rapidly.
During and after remediation, water and soil environmental performance
standards must be met, confirmed by sampling and analysis: poststabilization
sampling and TCLP analytical methods to assess contaminant leaching (e.g., to
ensure that concentrations of heavy metals and organics do not violate federal
standards: lead concentrations
5mgL 1 ). Confirmation samples must be
analyzed to verify complete removal of contaminated soil and media in the
lateral and vertical extent within the site.
The remediation steps should be delineated clearly in the final plan for re-
medial action, such as the total surface area of the site to be cleaned up, depth
of soil to be removed, and the total volume of waste to be decontaminated.
At a minimum a remedial action is evaluated on the basis of the current and
proposed land use around the site; applicable local, state, and federal laws and
regulations; and a risk assessment that specifically addresses the hazards and
possible exposures at or near the site. Any plan proposed should summarize
the environmental assessment and the potential risks to public health and the
environment posed by the site. The plan should clearly delineate all remedial
alternatives that have been considered. It should also include data and infor-
mation on the background and history of the property, the results of previous
investigations, and the objectives of remedial actions. Since this is an official
document, the state environmental agency must abide by federal and state re-
quirements for public notice as well as providing a sufficient public comment
period (about 20 days).
The final plan must address all comments. The final plan of remedial ac-
tion must clearly designate the remedial action selected, which will include the
* The vadose zone, also known as the unsaturated zone, is the underground layers above the
water table that may contain water around soil or unconsolidated material particles, but which
also contains air. Thus, unlike the zone of saturation, its void spaces are not completely filled
with water.
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