SUMMARY OF THE REMEDIATION TECHNOLOGIES DEVELOPMENT FORUM
SEDIMENTS REMEDIATION ACTION TEAM
NATURAL RECOVERY SUBGROUP CONFERENCE CALL

April 23, 2001
11:00 a.m–12:30 p.m.

On April 23, 2001, the following members of the Remediation Technologies Development Forum’s (RTDF’s) Sediments Remediation Action Team, Natural Recovery Subgroup, met in a conference call:

John Davis, The Dow Chemical Company (Subgroup co-chair)
Mike Erickson, Limno-Tech, Inc.
Victor Magar, Battelle Memorial Institute
Christine Hartnett of Eastern Research Group, Inc. (ERG), was also present.

PERFORMING A NATURAL RECOVERY PROJECT AT THE ANACOSTIA RIVER

Reviewing Available Documents

John Davis noted that the Natural Recovery Subgroup is interested in performing a project at the Anacostia River, a site contaminated with polycyclic aromatics, polychlorinated biphenyls, and metals. During the Subgroup’s last conference call, he said, call participants agreed that their first step should be to identify locations in the river where natural recovery is viable. (These will be locations where sediment transport conditions are depositional and ongoing sources are absent.) To identify these locations, Davis said, the Subgroup agreed to (1) analyze GeoSea Consulting’s sediment transport report, and (2) determine where combined sewer overflows (CSOs) and other point sources are located. Davis asked call participants how far they had gotten on these tasks. Erickson said that he does not have a complete copy of the GeoSea Consulting report; Davis agreed to send him a Web address for the report. Victor Magar said that he is still reviewing the report. Call participants agreed to continue the review process and discuss their findings during the next Subgroup conference call.

Boat Trip on the Anacostia River

Davis said that several members of the RTDF Sediments Remediation Action Team plan to tour the Anacostia River, by boat, on May 15, 2001. Erickson and Magar said that they plan to attend. Before the tour, they agreed, it would be useful to identify potential sites for natural recovery; that way, the Subgroup can be a bit more focused during the trip and take note of the accessibility of candidate sites.

Erickson expressed interest in inviting Mike Sullivan on the boat trip, noting that Sullivan has modeled CSOs and possesses significant knowledge about outfalls along the Anacostia River. Call participants agreed that it would be useful to talk to Sullivan. Both Erickson and Davis agreed to contact Dick Jensen to determine whether all of the boat’s seats have already been filled.

Davis said that the Subgroup’s goal is to define a systematic approach that can be used to demonstrate whether natural recovery is occurring. Ideally, he said, the approach defined by the Subgroup will be applied to a range of sites, not just the Anacostia River. Erickson said that he advocates a phased approach, in which simple and inexpensive assessment techniques are used in preliminary investigations and more advanced and expensive analyses are undertaken once researchers gain confidence that the site is a strong candidate for natural recovery. Call participants agreed that a phased approach would be useful. Davis expressed interest in creating a table listing different investigation phases, the data that should be collected during each phase, and the questions that must be answered during each phase. Erickson agreed to draft a preliminary version of the table and to send it to Subgroup members for comment. He will incorporate any comments that he receives and bring the most updated version of the table to the May 15 Anacostia River boat trip. Subgroup members will be able to refine the table further when they meet face-to-face.

Davis asked call participants to identify topics that must be explored during natural attenuation projects. The following were identified as important issues:

• Assessing bed stability, diffusion, and dispersion. Erickson said that it is essential to know whether sediments in a study area are likely to be buried or dispersed. In a burial-driven system, he said, burial-dominated natural attenuation occurs, but some diffusion and dispersion can result. This leads to reductions in contaminant concentrations. In erosional environments, Erickson continued, advective diffusion or dispersion processes may dominate and drive attenuation. When performing demonstration projects, Erickson said, it is important to focus on burial-driven sites. Sediment transport analysis can be used to determine the depositional structure of a site. In addition, radionuclide-dated cores can provide useful information about long-term accumulation rates and mixing depths. Also, Erickson said, interesting information can be obtained using sonar recorders that track bed elevation at a fixed position. This method can be used to monitor bed elevation, measure velocity, and track the total suspended solid that passes by a certain fixed point.
  
  
• What are the contaminant loading rates? Erickson said that he would ask Sullivan for information about contaminant loading rates at the Anacostia River. Having this information in hand, he said, will help with site selection.
  
  
• Determining whether sources are ongoing. Call participants agreed that demonstration projects should not be attempted in areas with continuing sources.
  
  
• Determining how long a source has been shut down. Erickson noted that some of the CSOs at the Anacostia River have been shut down for quite some time; others are still active, but will be shut down in the very near future. Magar expressed interest in studying sites where sources had been inactivated long ago, as well as sites where the sources are newly shut down. If he could only choose one type of site to study, however, he would choose the former.
  
  
• Davis agreed to send Erickson the Web site for GeoSea Consulting’s sediment transport report.
  
  
• Davis will identify a date for the next Subgroup conference call. The regular Subgroup members will be notified of the call’s date and time. In addition, Patrick McLaren, of GeoSea Consulting, will be invited to participate.
  
  
• Erickson and Davis will contact Dick Jensen to determine whether there are any empty slots available for the May 15 boat trip. If so, Sullivan will be invited to go on the trip.
  
  
• Erickson will create a table that lists different investigation phases involved in natural recovery projects, the data that should be collected during each phase, and the questions that must be answered during each phase. He agreed to draft a preliminary version of the table and send it to Subgroup members for comment. He will incorporate comments that he receives and bring the most updated version of the table with him on the May 15 Anacostia River boat trip.