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Peer Review on the Data Evaluation and Interpretation Report (DEIR) and Low Resolution Sediment Coring Report (LRC)
Charge for Peer Review 2
Members of this peer review will be tasked to determine whether the scientific analyses conducted for USEPA's Data Evaluation and Interpretation Report (DEIR) and the Low Resolution Sediment Coring Report (LRC) are credible, the conclusions valid, and whether the findings are appropriate to use to support the decision-making process for the Hudson River PCBs Site Reassessment study. The peer reviewers will base their assessment on the review of the DEIR and LRC, as well as additional information found in the Responsiveness Summary issued in December 1998 (responding to several documents including the DEIR) and the Responsiveness Summary for the LRC (which will be released in February 1999). The peer reviewers will also have available for their review the Hudson River Reassessment database, which contains all of the data used in the preparation of the above documents, along with other data.
The DEIR and LRC present the results of the geochemical analyses conducted on the water-column and sediment data collected for the Reassessment, as well as data collected by a number of other agencies and General Electric. It should be noted that there have been several changes in the available data since the time of the release of the DEIR in February 1997. These changes include a better estimate of flow for several reaches of the river, a recalculation of GE's PCB data due to an analytical bias, and the discovery of a sampling bias at the Thompson Island Dam monitoring station. These changes are discussed in the Responsiveness Summaries, and the analyses in the Responsiveness Summaries should supercede those conducted in the reports, as appropriate.
It is important to realize that the geochemical analysis conducted in the DEIR and LRC will be complemented by mass balance modeling and human health and ecological risk assessments to provide a thorough understanding of the fate and transport and impacts of PCBs in the Upper Hudson River. These other reports will address questions regarding the mechanisms that release PCBs from the sediment, toxicity, and bioavailability/biouptake. A peer review was previously conducted for the approach proposed to conduct the modeling for the Reassessment. After the modeling and the risk assessment reports are released, the Agency will also have those documents peer reviewed.
Specific Questions
Data Evaluation and Interpretation Report (DEIR)
1. Is the documented PCB load, which originated from the TI Pool, consistent with a source consisting of historically deposited PCB-contaminated sediments?
2. Are the two-phase and three-phase partitioning coefficients, derived in the DEIR, appropriate and do they properly address the physical parameters of the system (e.g., temperature).
3. Are the conceptual models based on the transect sampling consistent with the data?
4. Does the sampling at the TI Dam-West location impact EPA's conclusion that the sediments of the TI Pool are the major source of PCBs to the freshwater Hudson during low flow conditions considering the analytical corrections made to GE's PCB data? What are the other implications of finding higher concentrations along the shoreline than in the center channel?
5. Are the geostatistical techniques (polygonal declustering and kriging) correctly applied?
6. Are the methods applied in the DEIR (change in molecular weight (MW) and evaluating concentrations of BZ#s 1, 4, 8, 10 and 19 (MDPR)) appropriate standards for determining extent of dechlorination? Are there any significant problems with this approach, or more appropriate approaches?
7. The DEIR finds that the degree of anaerobic dechlorination is primarily a function of original concentration rather than time, and accordingly that there is not significant predictable dechlorination in sediments containing less than approximately 30 mg/kg PCB. Is this reasonable?
Low Resolution Sediment Coring Report (LRC)
1. In the LRC, EPA compared sediment data from cores taken in 1977, 1984 and 1994, which had the PCB analysis conducted by different laboratory methods. How valid are the methods used to establish a consistent basis for comparison?
2. In the upper Hudson River system, it has been well established that there is significant lateral heterogeneity in sediment concentrations. While it was attempted to reoccupy previous locations, some uncertainty is added with respect to the actual sampling location. While the statistical techniques help compensate for this, how does the sediment heterogeneity affect the comparison of cores from two different years? Given the spatial variability, is the finding that there is loss from most of the locations supported by the data?
3. What is the impact of the difference between replicate samples in the 1994 sampling effort (36 percent average variability) on the finding that there was a 40 percent loss of PCB inventory from the highly contaminated sediments in the TI Pool?
4. In the LRC, it was found that Hot Spot 28 contained much more mass than previous estimates. Is the conclusion that this "gain" is primarily due to incomplete characterization in 1977 valid?
5. Does the data set and its interpretation support the conclusion that significant losses have occurred from hot spots below TI Dam?
6. The LRC found that the historically contaminated sediments in the TI Pool were not universally being buried and sequestered from the environment. How much confidence would you place in the LRC evidence against widespread burial?
7. Is the interpretation of the side-scan sonar data appropriate and supported by the analysis of the associated sediment properties?
General Questions
1. Is the data set utilized to prepare the DEIR, LRC and Responsiveness Summaries sufficient to understand the fate and transport of PCBs in the Upper Hudson?
2. Are there any additional analyses that should be done to verify certain findings of the DEIR and LRC?
Recommendations
Based on your review of the information provided, please identify and submit an explanation of your overall recommendation for both the DEIR and LRC.
1. Acceptable as is
2. Acceptable with minor revision (as indicated)
3. Acceptable with major revision (as outlined)
4. Not acceptable (under any circumstance)