Saturday, February 20, 2010

FIRESIDE CHAT: Hudson River PCB Dredging Phase 1 Evaluation

A two-day public meeting of the Hudson River PCB Dredging Peer Review Panel was held at the Gideon Putnam Hotel in Saratoga Springs, New York on Wednesday and Thursday 17-18 February. My oral comments to the Panel on Wednesday alluded to analysis of GE’s ‘bucket files’ (1), which are computer registers recording each closure of a dredge bucket in each delineated five-acre work area (‘Certification Unit’, or CU) in the Phase I dredging area. From my analysis of these GE files I concluded that the preponderance of sediment disturbed by dredge buckets was left in mobile form on the river bottom, not placed in waiting barges.

The GE bucket files are available for free via download from GE's dredging website, as Table G-1 in Appendix G of GE’s draft Phase I Dredging Evaluation Report. The pdf format in which the 44-page file is provided, however, precludes numerical analysis of the data without extensive manipulation. To conduct my analysis, I converted the file into a Microsoft Excel (.xls) file. As the pdf version originally provided by GE contained built-in impediments to such conversion, the Excel version that I prepared represents the product of days of labor. The Excel version, therefore, is being offered for sale (click on the Title field above to be taken to the purchase page if you are interested).

Using the bucket closure file, I analyzed the number of bucket closures in each five-acre dredging Certification Unit, and related this to separately-reported information about the volume of sediment placed in barges. This analysis is presented in the SYNTHESIS tab of the xls file that I created. Finally, I abbreviated this analysis by combining all CUs to create a BRIEF tab, or see figure below.

The figure summarizes the quantitative support for my oral statement that the preponderance of dredge-disturbed sediment is left on the river bottom, not barged. My written comments to be submitted formally to the Panel (via the facilitator) will show, further, that PCB in these sediments is more mobile than in the original buried state, which ironically is the physical state that EPA’s strategy of capping dredge prisms seeks to restore. From the river bottom, resting sediment piles produced by Phase I dredging gradually (perhaps over years) can and will erode. Some sediment will travel downstream, to be measured by GE in the EPA-mandated ‘resuspension’ monitoring program.

The preponderance of PCB, however, may not go downstream. EPA’s criterion of ‘benefit’ of the dredging project therefore is illogical. The ‘benefit criterion’ allows no increase in downstream transport of resuspended sediment during the planned six-year duration of the project. Instead, under the benefit criterion, downstream transport may be increased by dredging in the short term only in amounts that will be offset by future decreases over the longer term, meaning the project duration. This benefit criterion is illogical because it assumes incorrectly that potential dredging impacts consist of nothing more than downstream transport of resuspended sediment, whereas this appears to constitute a relatively minor contributor to total potential dredging impacts.

Specifically, EPA’s benefit criterion fails to consider demonstrated increases in the amount of PCB released to other ecosystem compartments. The amount of such release may greatly outweigh the amount resuspended and addressed by EPA’s “benefit” criterion. Much if not most dredge-moblized PCB-tainted sediment will enter ecosystems, including migrating species of fish and birds, and much will enter the air. For example, whereas resuspension has approximately doubled in downstream areas, PCB concentration in fish tissue (filets) already has increased approximately fivefold, and organs such as the liver might have increased even more; the liver represents the filter for toxins consumed by the fish.

A major concern relates to risks potentially posed to human health. Apart from participation of people as ecosystem components at the top of the food chain, I am concerned about airborne PCB, which is derived from PCB released to the water and largely unmeasured. In that regard, I will urge the Panel to demand delivery of the results of personal monitoring samples taken on dredge platforms (minus employee identifying information). These samples generated the only data of which I am aware that reflects airborne PCB levels produced by dredging, at the location of dredge platforms. These samplers all operated with sensitivity to the occupational airborne PCB limit of 1,000 ug/M3, which is over 9,000 times EPA’s residential limit of 11 ug/M3… so these samples all had better be negative, but nobody I spoke with has been willing to say that they were indeed consistently negative. Rather, EPA told me that the data belong to GE, and GE told me that the data belong to its contractors. Information of possibly critical concern to the public clearly has been ‘compartmentalized’ out of public view… and members of the pubic and the Peer Review Panel have an opportunity to demand an end to such compartmentalization.

EPA asserts that portable air monitors placed on each shoreline adjacent to each dredge platform should do the air monitoring job. This is not the case. These monitors do not receive aerosols that fall back to the river before reaching shore. They do receive air, but the air they receive comes from all directions, 360 degrees, and only rarely from the direction of their adjacent dredge platform. The 24-hour samples recorded, therefore, all are massively diluted, not reflective of airborne PCB levels over the river. Finally, these monitors routinely are withdrawn downstream with their adjacent dredge platforms and, at the end of Phase I, they are withdrawn from service altogether… all very likely long before PCB release from the river surface to the air reaches a maximum or a steady state.

In short, the monitors are withdrawn before they can characterize the evolution of PCB release to the air over the six-year planned life of the project and beyond. Indeed, as the acreage of dredged river increases, the number of monitors per acre declines, but the fraction of river surface contributing to air levels over the river and on shore increases… never to be measured because the monitors that could have measured these evolving levels were withdrawn from service. I call this ‘hit-and-run dredging’. My formal comments to the Panel, therefore, will assert the need for a permanent array of air monitors to capture the evolution of PCB release levels as the fraction of river bottom dredged increases, and as PCB-tainted sediments are restratified and processed by physical, chemical, and biological processes of degradation, mobilization, and eventual release to ecosystems and the atmosphere.

Given the Phase I experience of massive sediment mobilization by clamshell dredging, I have raised the issue of whether dredging should continue with Phase II. This issue is specifically precluded from Peer Review Panel consideration, but it should be added to the purview of the Panel. If Phase II is to be implemented, alternative technologies should be considered, such as use of dredging enclosures (one technology of this sort is termed ELB, for Environmental Lunch Box) and/or hydraulic dredging (also termed vacuum or suction dredging).

As a final issue I introduce the movie version of Isaac Asimov’s wonderful Sci-Fi novel “I Robot.” The holographic image of the deceased robot inventor advises that “My responses are limited… You must ask the right question.” In evaluating Phase I of the Hudson River PCB dredging project, some of the wrong questions have been asked; and wrong, irrelevant, or only partially relevant answers therefore obtained. I give several examples of how the wrong questions can be and should be converted to the right questions:

WRONG: What is the composition of PCB sheens found during dredging?
RIGHT: Where is the source of the sheens, and what is their composition, volume, and potential for mobilization with further (clamshell) dredging?

WRONG: What is the optimum number of dredge passes needed to complete and close a five-acre dredging Certification Unit?
RIGHT: What is the minimum number of dredge bites (or ‘cuts’), and therefore the minimum degree of mobilization of PCB-tainted sediments, associated with completing and closing a five-acre dredging Certification Unit?

WRONG: What strategies can be employed to keep resuspension and downstream transport of PCB-tainted sediments within acceptable limits defined by EPA’s benefit criterion?
RIGHT: What strategies can be employed to keep dredging impacts, including resuspension and downstream transport, within acceptable limits?

WRONG: What concentrations of airborne PCB are measured by mobile detectors on opposite shores adjacent to dredge platforms?
RIGHT: What are the anticipated maximum, steady state, and evolving air impacts of PCB dredging at Hudson River communities during active dredging, between dredging Phase I and Phase II, and following dredging completion as modeled for a perod of years, and as confirmed by a permanent array of air monitors if further dredging goes forward?

Issues raised above are amplified and technically supported in earlier posts on this blog.


1. GE. Phase I Evaluation Report: Hudson River PCBs Superfund Site. Draft report prepared for General Electric Company (Albany, New York) by: Anchor QEA (Glens Falls, New York) and Arcadis (Syracuse, New York); 191 pages plus tables, figures, and appendices; Appendix G, Table G-1, 44 pages; January 2010.