SITE REMEDIATION AND
EMERGENCY RESPONSE NEWSLETTER

January 2010
No. 136

Use of Amendments for Contaminated Sediments

Traditional techniques to cap contaminated sediments do not reduce contaminant mass. It has been demonstrated that with the use of amendments, however, sediment capping technologies can both sequester and degrade contaminants in situ.

Stephen Ells of EPA’s Office of Superfund Remediation and Technology Innovation discussed regulatory issues involved in the use of amendments in sediment caps at Superfund sites at the recent DoD Partners in Environmental Technology Technical Symposium & Workshop.

He points out that there are only three technologies in use today for contaminated sediments: capping, dredging and monitored natural attenuation (MNR). The cost of treating contaminated sediments is staggeringly high: $650 million to clean up a segment of the Fox River site, for example, and $74 million for the Portland Harbor site, including EPA oversight costs. Approximately 50 Superfund sediment sites are under investigation today. No decision has been made so far regarding remedial action at these sites.  Therefore, they present an opportunity to use new technologies. EPA guidance on sediment remediation states that there is no presumptive remedy for contaminated sediment sites regardless of contaminant or level of risk.  The focus of all remedies is not mass removal but the reduction of risks. One must understand site conditions most conducive to dredging, capping and MNR. The guidance  includes in situ treatment, such as reactive caps and additives, as an available alternative. Thus, Ells concludes, there is no roadblock against in-situ amendments.

A key measure of the success of in-situ amendments is their long-term effectiveness, and there are no data available yet.

Ells notes the potential benefits of amendments:

  1. Can be used in conjunction with dredging, MNR and capping.

  2. Can be used in locations where dredging is not feasible—under piers and around pilings.

  3. Less impact on benthos than dredging or thick isolation capping.

  4. Minimum impact on flooding potential.

  5. Quicker than standard capping.

  6. Cheaper than current capping.  There is not a great deal of data, but amendments are at least not more expensive than current capping.  They are much cheaper than dredging.

  7. If amendments are not effective in the long-term, not much is lost if one switches to other treatments.

Potential barriers to the use of amendments include the following:

  1. Bias against any remedy other than removal.

  2. Limited track record.  No one wants to be first.

  3. No data on long-term effectiveness.

  4. Fear and uncertainty about adding unnatural materials to the environment.

Are we ready to embrace the use of amendments to remediate contaminated sediments?  Ells says he is not sure, but he is cautiously optimistic. He points out that more long-term monitoring is necessary. 

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