Soil Pile Disposition Assessment Section 5 - Identification and Initial Screening of Corrective Measure Technologies

Section 5 - Identification and Initial Screening of Corrective Measure Technologies

This section identifies and describes each corrective measure technology that potentially has applicability in meeting corrective action objectives. The evaluation is based on technical, environmental, human health, and institutional concerns.

A number of technologies are available to address potential contamination of excavated soils at SWMUs B-8, B-20/21, B-24, B-28, and the DD Area. A list of potential technologies is presented and screened to reduce the number of technologies and identify viable candidates to be considered for further evaluation. This screening was accomplished using intuitive, obvious, or subjective evaluations of each technology�s applicability to the site conditions and ability to satisfy corrective action objectives.

The corrective action objective is to remediate existing contamination (soil stockpiles generated during sifting operations) or otherwise demonstrate a lack of threat to current and/or potential occupants or users of the facility as prescribed by the EPA. As indicated in Section 3, the excavated surface soils have been impacted with heavy metals. The common metals that are present above background conditions for stockpiles at all five sites include copper and zinc. Additionally, barium, lead, and mercury were reported in the excavated soils at one to four of the SWMUs. Cadmium was detected above background in one sample collected from the B-20/21 stockpiles. A summary of metals exceeding background levels is provided in Table 5.1 below. SVOCs were reported in one sample collected from a DD stockpile but the results are below PCLs.

In soil, metals are found in one or more of several �pools� of the soil (Shuman, 1991). The metal �pools� are described as:

In situations where metals have been introduced into the environment through human activities, metals are associated with the first five �pools�. The aqueous fraction, and those fractions in equilibrium with this fraction, i.e., the exchange fraction, is of primary importance when considering the migration potential of metals associated with soils.

Based on the acceptance of various technologies, six corrective measure technologies are presented for preliminary evaluation.

Remedial alternatives are developed from the technologies and feasible process options that can address the objectives for the SWMUs of concern. The basic objectives used to identify potential alternatives are to remediate, remove, or contain contamination. Each remedial alternative can consist of one or several remedial technologies which can be classified into one of five groups, including no action, institutional controls, removal, containment, or treatment. Treatment can be in situ or ex situ.

Table 5.2 presents a summary of the potential remedial technologies reviewed for remediating the affected soils. Further discussion of the remedial technologies that are potentially viable is presented in Section 6.

The no action alternative assumes that no further remedial activities will be undertaken at the site. This alternative does not include monitoring of conditions that would detect when changes are occurring at the site. It is the lowest cost alternative and requires the least activity.

Institutional Controls (ICs) (http://www.epa.gov/superfund/policy/ic/index.htm) are used to supplement engineering controls when residual contamination restricts the unimpeded use of a site or a groundwater aquifer. ICs are intended to maintain the integrity of remedies and minimize the potential exposure to contamination. Examples include easements, zoning restrictions, and deed notices. ICs are implemented during or immediately following remedy implementation consistent with the requirements of the decision document, and are maintained as long as needed to prevent exposure or protect the remedy. Site managers must work closely with States, Federal agencies, and local governments, as appropriate, to ensure ICs are implemented, maintained, and enforced.

Commercially available technologies for contaminant source containment are available for sites where complete contaminant source removal is not currently technically feasible and/or contaminants and site conditions do not lend themselves to clean up by natural processes.

General Response Action	Remedial Technology	Process Options	Description		Screening Comments	Effectiveness	Implementability	Cost	Retain for Further Consideration
No action	None	None	Leave soil as is. No further monitoring or investigation.		Consideration required by the National Contingency Plan (NCP). Contamination is not mitigated.	Not effective	Not applicable (NA)	None	Yes, as a benchmark for judgment of other technologies.
Institutional control	Deed restrictions	None	All deeds for property within contaminated area would include restrictions on land use only.		Contamination is not mitigated. May not comply with chemical-specific applicable or relevant and appropriate requirements (ARARs).	Effective. However, does not meet remedial goals.	May be readily implemented	Low	No, due to screening comments
Source containment	Capping	Low permeability caps and/or liners	Source sites capped with low permeability clays, geomem-brane, asphalt, concrete or a combination to prevent surface water infiltration and creation of leachate.	Requires long-term monitoring and deed restrictions.		Generally effective in limiting further waste migration.	Easily implemented	Moderate	Yes, due to cost and implementability
Source removal	Excavation	None	Removal of contaminated soil would require excavation and transporting to a disposal facility.	Soils may require treatment to meet land disposal restriction requirements.		Most effective in source and hot spot control.	Easily implemented	Moderate	Yes, due to cost and implementability
		Landfill	Receives excavated contaminated soils for placement into controlled/permitted landfill.	Risks are continual for the owner of the waste placed into a landfill cell.		Effective for solids.	Easily implemented	Moderate to High	Yes, due to effectiveness and implementability
Ex situ treatment	Physical treatment	Solidification	Contaminants are physically bound or enclosed within a stabilized mass. This technology includes; bituminization, emulsified asphalt, modified sulfur cement, polyethylene extrusion, and pozzolan/portland cement technologies.	Potential to result in a significant increase in waste volume.		Highly effective for metals	Easily implemented	Moderate	Yes, due to effectiveness and implementability
		Soil Washing � Density Separation	Water based process for scrubbing soils to remove contaminants. Density separation concentrates contaminants through particle size and gravity separation techniques.	Heavy metal particles can be removed from the soil matrix and the larger soil fractions returned to the site for continued use. Smaller soil fraction and washing fluid may require further treatment or off-site disposal.		Effective	May not be readily implemented	Moderate to High	Yes, due to effectiveness
	Chemical treatment	Stabilization	Chemical reactions are induced between the stabilizing agent and the contaminants to reduce their mobility.	Environmental conditions may affect long-term immobilization of contaminants.		Highly effective for metals	Easily implemented	Moderate	Yes, due to effectiveness and implementability

General Response Action	Remedial Technology	Process Options	Description	Screening Comments	Effectiveness	Implement-ability	Cost	Retain for Further Consideration
In situ treatment	Chemical/physical treatment	Vitrification	Electric current is used to melt soil at extremely high temperatures thus immobilizing most inorganics.	Future usage of the site may �weather� the materials and affect ability to maintain immobilization of contaminants.	Effective	Not readily implemented	Very high	No, due to costs
		Soil Flushing	Extraction of contaminants from the soil with water or other suitable aqueous solutions.	Soil flushing is accomplished by passing the extraction fluid through in-place soils using an injection or infiltration process. Extraction fluids must be recovered from the underlying aquifer and, when possible, they are recycled.	Not Effective	Not readily available	Very high	No, due to effectiveness
		Phytoremediation	Use of genetically engineered plants (Indian Mustard) to uptake mobile lead from impacted soils.	Treatment of biomass as hazardous waste may be required.	Can be effective at removing ionic species of lead. Not effective on metallic form of lead.	Easily implemented; however, operations and maintenance intensive.	Very high	Yes, due to implementability
		Electrokinetics	Uses electric current to osmotically transport contaminants to anode or cathode wells.	Contaminants may need to be mobilized from the soil matrix with the addition of weak acids.	Can be effective.	Not readily available	Very high	No, due to costs

Capping is a common source containment technology. The involvement of local and state governments in the corrective action decision-making process is necessary to ensure that remedy decisions are consistent with local land use plans and zoning requirements, as well as allow for any deed restrictions or necessary controls on the use of the site if contaminants remain.

Source removal refers to excavation of contaminated soils, or pumping of contaminated groundwater, and disposal off-site. When a well-defined, concentrated, continuing source is present, such as a leaking tank or highly contaminated soil, source removal is the most effective way to prevent ongoing release of contamination.

Ex situ treatment refers to aboveground treatment systems, including source removal technologies that can eliminate or stop potential pathways of contamination. Material that has been treated ex situ can be disposed off-site, reused or recycled, or put back in place.

In situ treatment refers to in-the-ground treatment of contaminants and is often preferable to ex situ treatment because treatment costs are generally lower, there is less potential for exposure, and there are no disposal issues associated with in situ treatment. However, in situ treatment is generally more difficult to implement and monitor than ex situ treatment processes. In situ treatment can be divided into chemical/physical treatment and biological treatment, which includes phytoremediation. Many treatments have the same functional bases as the ex situ processes, but instead are employed without excavation of surface or subsurface soils.

	Barium	Cadmium	Copper	Lead	Mercury	Zinc
SWMU B-8 Piles	X		X	X		X
SWMU B-20/21 Piles	X	X^*	X	X		X
SWMU B-24 Piles	X		X	X		X
SWMU B-28 Piles	X		X			X
SWMU DD Area Piles			X	X	X	X
* Detected above background in one sample only.