ENVIRONMENTAL CLAIMS JOURNAL
, VOL. , NO. , –
Excessive PCBs in the Hudson River: Attributable to
Incompleteness of Dredging, or to Seven Years of Dredging?
Robert A. Michaelsaand Uriel M. Okob
aRAM TRAC Corporation; bRecycle Management
GE recently completed a seven-year US EPA-mandated clamshell
dredging project to remediate PCB contamination of the Hud-
son River. Post-project PCB levels in water and sh, however,
are higher than anticipated, suggesting to some the need to
extend the project to remove more PCB-bearing sediments.
Our investigation of the eectiveness of the dredging project
revealed that a previously unconsidered physical process must
mobilize sediments as a result of dredge bucket closure. We also
used computerized dredging data (‘bucket les’) to estimate
the fraction of dredged sediments returned to the river instead
of being deposited into waiting barges. We conclude that
excessive post-project PCBs in the Hudson River predominantly
are attributable to sediment mobilization by clamshell dredges.
We predict that proposed extension of the dredging project
would prolong mobilization processes, allowing PCBs to spread
widely and enter ecosystems that include people, endangered
sh such as sturgeon, and endangered birds such as bald eagles.
GE (the General Electric Company) recently completed a seven-year US EPA-
mandated clamshell dredging project to remediate PCB (polychlorinated biphenyl)
contamination of the Hudson River. Post-project PCB levels in water and sh,
however, are higher than anticipated, for example in 2016 requiring the New York
State Department of Health (NYS DOH 2016) to recommend further restriction of
sh consumption. NYS DOH issued a “Don’t Eat” sh consumption advisory for
walleye sh taken from the Hudson River downriver, between the Rip Van Winkle
Bridge at Catskill and the Tappan Zee Bridge. This advisory is more stringent than
the previous advisory, which recommended limiting intake of walleye to one meal
per month. The current advisory was based upon new data showing elevated levels
of PCBs in these sh.
CONTACT Robert A. Michaels email@example.com;firstname.lastname@example.org Rosendale Road, Schenectady,
Color versions of one or more of the ﬁgures in the article can be found online at www.tandfonline.com/becj.
© Taylor & FrancisGroup, LLC
116 R. A. MICHAELS AND U. M. OKO
In 2007 the U.S. Environmental Protection Agency (US EPA) required GE to
remediate the Hudson River PCB Superfund Site via dredging. Also in 2007, we
reported pro-dredging bias in the form of errors in US EPA’s baseline health risk
assessment (HRA) for Hudson River PCBs; indeed, all nine identied errors were
made in the dredging-friendly direction rather than randomly (Michaels and Oko
2007). Permissive HRA ndings that resulted from these errors constituted a neces-
sary condition for US EPA to conclude that dredging could be accomplished within
acceptable health and environmental risk parameters, and to require GE to employ
dredging for remediation of the site. The original purpose of site remediation via
clamshell dredging was to reduce safely and substantially the long-term downstream
transport of PCBs (Peer Review Panel 2010; US EPA 2002).
In 2010 we evaluated dredging Phase 1, consisting of a one-year attempt, in
2009, to demonstrate the feasibility of clamshell dredging as a multiyear remedy for
the Hudson River PCB Superfund Site (Michaels and Oko 2010). The 2010 paper
reported failure (of GE) to complete a signicant fraction of the planned Phase 1
feasibility of implementing Phase 2 within acceptable environmental and health risk
parameters. Similar conclusions were drawn by US EPA’s peer review panel for Hud-
son River PCB dredging (Peer Review Panel 2010). Others more generally have char-
acterized conventional clamshells as more typically used for navigational rather than
for environmental dredging (for example, Bridges et al. 2008; Palermo et al. 2008):
Although conventional dredges normally used for navigation dredging (e.g., conventional
clamshells or cutterheads) can be eective for environmental dredging, evolving tech-
nologies for dredge and dredgehead designs (e.g.,enclosedbuckets,articulatedxed-
arm mechanical, swinging ladder cutterheads, and articulated ladder cutterheads) may
oer better performance for environmental dredging. (Palermo et al. 2008, 257; empha-
Accordingly, we recommended consideration of hydraulic dredging as originally
proposed, or other alternatives to conventional clamshells (Michaels and Oko 2010).
Indeed, US EPA specication of clamshell dredging in the Hudson River is unusual,
as most PCB dredging from U.S. waters has relied upon hydraulic dredges, which
were used, for example, in the New Bedford Harbor in Massachusetts, the Cumber-
land Bay in Plattsburgh, New York, and the Fox River in Green Bay, Wisconsin.
Notwithstanding the above, US EPA required GE to initiate Phase 2 in 2011, after
a one-year hiatus in 2010 for project evaluation, culminating in our paper (Michaels
and Oko 2010) and the peer review panel’s adverse report (Peer Review Panel 2010).
The scope of Year 1 of Phase 2, in 2011, included completion of the undredged Phase
1 area. As we reported, Phase 1 not only failed but, more fundamentally, it lacked
the potential to succeed in demonstrating the feasibility of Phase 2, because Phase
and (2) conning dredge-disturbed PCB-contaminated sediments to within iso-
lated ‘hot spots,’ despite river currents capable of carrying mobilized PCB liquids,
dissolved molecules, colloids, and suspended particulates downstream to areas in
which future dredging was not planned.
EXCESSIVE PCBS IN THE HUDSON RIVER 117
Phase 1 diered from Phase 2 in being conducted largely at one side (the east
side) of Rogers Island, where sediment transport was slowed by a nearby stone dam
and sediment curtain. Phase 1 also predominantly involved bank-to-bank dredging.
Phase 2 involved widely separated PCB hot spots and faster moving open river water.
Redeposition of mobilized PCB-containing sediments in the Phase 1 area was fol-
lowed generally by redredging, thereby minimizing the impact of dredge-disturbed
sediment ow and mobilization beyond the dredging zone. Thus, US EPA’s autho-
rization to conduct Phase 2 based upon Phase 1 constituted a non sequitur.
Failure of Phase 1 to meet engineering performance standards (EPSs) and health
risk criteria (Peer Review Panel 2010) was ominous for Phase 2 (Michaels and Oko
2007,2010;PeerReviewPanel2010). Implementation of Phase 2 for two years, in
2011 and 2012, and its continuation in 2013 and for years thereafter until comple-
tion, together raised ve emerging and unique issues that we evaluate here, including
1. Sediment mobilization: US EPA accuracy in estimating PCB-contaminated
sediment mobilized by dredging;
2. PCB mobilization: Possible PCB loss by desorption from resuspended sedi-
3. Storms: Possibly changing frequency of sediment-mobilizing high-ow
4. Endangered species: Endangered species classication of Hudson River stur-
geon and bald eagles; and
5. Autism: Progress of research into possible PCB causation of autism.
Our investigation included reviewing literature, making site visits, attending meet-
ings, and evaluating several exposure and toxicology issues. We conducted three
site visits to observe and photograph dredging, each time visiting US EPA’s eld
oce in Fort Edward, interviewing US EPA and GE personnel and contractors,
analyzing dredging data, attending public meetings, and examining scientic and
regulatory documents (for example, Harza 1992;NYSDEC2000,2003;PSEGNY
2001;Shavit,etal.2003;UNEP2003, and other sources in References). Our analy-
sis adopts methods of health risk assessment (HRA), critical evaluation of project-
related scientic information sources (for example, GE 2009,2010a,2010b,n.d.;
US EPA 1999,2000a,2000b,2001,2006,2010a,2010b,2010c,2010d,2010e,2012,
n.d.a,n.d.b), and objective scientic peer review. The latter are not a priori methods,
and they are not described in detail here. Rather, they consist of diverse methods that
are generally typical of peer review by scientists seeking to remain objective. Most
essentially, these methods consist of our own disciplined, critical evaluation of the
scientic merit with which numerous methods were selected for use and applied
prior to dredging, during dredging Phase 1, and during Phase 2.
The scope of our assessment therefore includes our own peer review of GE and
US EPA methods, ndings, and conclusions, such as those reported orally in public
meetings, and in written public communications on GE (n.d.)andUSEPA(n.d.a,
118 R. A. MICHAELS AND U. M. OKO
n.d.b) Web sites for Hudson River dredging, and more formally in GE (2009,2010a,
sideration by the public, specic interested parties, and members of the Hudson
River dredging project peer review panel (Peer Review Panel 2010). Members of the
public and other readers of our assessment can judge for themselves whether and
to what degree we succeeded in applying the methods of HRA and of peer review
objectively. We hope that we have done so completely.
Mobilization of dredge-disturbed sediment was ࣙ100 times higher than measured
by US EPA’s engineering performance standard (EPS) for resuspension, and no EPS
exists to detect, quantify, or reduce downstream sediment redeposition. Much PCB
adsorbed to dredge-disturbed sediment desorbs within minutes of mixing into river
water. This fugitive molecular and colloidal PCB is transported downstream, but
missed in routine resuspension monitoring. Complicating matters, the frequency
and intensity of storms is increasing. Invisible to EPSs, storms may scour fugitive
PCB-contaminated sediment, and transport it downstream gradually and episodi-
cally, over years or decades. Long-term downstream transport of PCB poses risks to
endangered species, possibly including extirpation of sensitive sturgeon from the
Hudson River. Finally, recent animal research links PCBs to developmental pro-
cesses that, in humans, are thought to underlie autism causation, but US EPA has
failed to address potential autism risks.
Issue 1, sediment mobilization: US EPA accuracy in estimating PCB-contaminated
sediment mobilized by dredging
Sediment mobilization by dredge jaw closing. Sediment resuspension arising from
bucket (clamshell) dredging is reported to “result from the impact, penetration, and
removal [of the dredge bucket] from the bottom sediments; leakage while raising it
through and out of the water column; and washing during movement through the
water column” (Zappi and Hayes 1991,citingBarnard1978). Resulting “suspended
can range from 20 to 1,100 mg/L” (Zappi and Hayes 1991,citingMcLellanetal.
1989). A process contributing to sediment mobilization that apparently has been
neither addressed nor described previously is generation of a suction force behind
closing dredge jaws.
Specically, the sediment fraction mobilized has been calculated previously rel-
ative to a full dredge bucket, but that parameter fails to account for the mobiliz-
ing eects of closing dredge jaws on sediment that is situated outside of the bucket.
Dredge bucket jaws are constructed of rigid walls of steel that are suspended beneath
EXCESSIVE PCBS IN THE HUDSON RIVER 119
Figure . Hudson River dredge showing bucket suspended beneath superstructure.
a rigid nonsolid steel superstructure (Fig. 1). The jaws of a typical 5-cubic-yard
(3.85-cubic-meter) bucket used in the Hudson River each have an open cross-
sectional area of 88 square feet (9.8 square meters) measuring 7.1 feet (2.2 meters)
in width and approximately 4.4 feet (1.3 meters) in height, producing a solid cross-
sectional area of >30 square feet (3 square meters). The superstructure adds another
6 feet (1.8 meters) of height, producing a total of over 10 feet (3 meters).
The total cross-sectional area that moves through river water during closing of
each dredge jaw therefore is approximately 50 square feet (4.6 square meters), most
(0.5 meter), visible as the abraded area at the bottom of the bucket depicted in Fig. 1).
The angle of attack changes (becomes more vertical) as the bucket closes and, of
course, the velocity of jaw movement through the water is greatest toward the bot-
tom, which also is the solid portion of the dredge bucket.
As the bucket jaws close, physics requires that they create three strong currents.
One current results from compression of water and sediment situated between the
closing bucket jaws. It forces water and sediment out of the dredge bucket. The other
two currents result from suction of water and sediment situated in the reduced-
pressure zone behind each dredge jaw. These latter two currents exert a force that
drags water and sediment, causing them to follow behind moving dredge jaws as
they close. All three forces create turbulence. The compressive force, especially
because it drives water and sediment upward through the open top of dredge jaws,
120 R. A. MICHAELS AND U. M. OKO
produces turbulent eddies of sediment typically extending to the river surface, read-
ily visible and varying from gray to black, depending upon location in the river.
The inward-directed suction force exerted in the reduced-pressure zone behind
manifested (for example) by race cars drafting close behind another car to accelerate
by using the powerful suction force created by the lead car’s evacuation of air behind
it. The suction force also is made visible as opaque diesel exhausts ow over the tops
of moving trucks and are sucked turbulently downward in the trailing low-pressure
zone. Physics demands that loose or uncompacted sediment situated outside each
opposing jaw of dredge buckets likewise must be sucked o the river bottom during
bucket closure. The swirling sediment then is left in the river as the dredge buckets
Sediment mobilization is quantied by comparison of sediment volumes placed
in barges with sediment volumes dredged in each bucket closure. Bucket closures
are recorded automatically via computers on board dredge platforms, and published
as the ‘bucket les’ (GE 2010b;MichaelsandOko2010;USEPA2010a). Sediment
that is mobilized behind closing dredge jaws, however, is routinely not quantied
in the bucket les, because such sediment is not dredged and not placed in barges.
For example, consider a typical ve-cubic-yard dredge bucket that penetrates to a
sediment depth designed to ll it to 80 percent of full capacity. Its eld capacity
would be four cubic yards (0.8×5 cubic yards). If only two of the four cubic yards
are barged, by subtraction the inferred mobilization also is two cubic yards, or 50
percent of eld capacity.
The mobilization fraction calculated as above excludes turbulent sediment mobi-
lization due to suction generated by each closing dredge jaw. Accordingly, the actual
mobilization fraction is higher by the amount disrupted outside each dredge bucket
jaw. Physics demands that the compressive force exerted to the interior of dredge
bucket walls equal the suction force exerted outside. A reasonable approximation,
therefore, is that uncounted sediment mobilization outside dredge buckets roughly
equals the amount of sediment that is mobilized within buckets. This approximation
also is conservative, inasmuch as the sediment that can be mobilized includes that
situated behind each of two dredge jaws. This added mobilization factor gives rise
to the possibility of the sediment mobilization fraction exceeding 100 percent of the
dredge bucket eld capacity. That is, dredge buckets cannot mobilize more sediment
than they contain, unless (as described above) they also mobilize sediment that they
do not contain.
Estimation of sediment mobilization fraction. We previously made two indepen-
dent quantitative estimates of the fraction of sediment mobilized when a dredge
bucket descends to the river bottom, closes, lifts its load, and transfers its load to
awaitingbarge(MichaelsandOko2010). One estimate, based upon the dierence
between sediment volume enclosed by an open versus a closed dredge bucket, was
a mobilization fraction of approximately 80 percent. The other, based upon analysis
of published bucket les versus published barged-sediment data, was approximately
EXCESSIVE PCBS IN THE HUDSON RIVER 121
75 percent during Phase 1, Year 1. These values exclude consideration of the new
factor described above, i.e., suction creating turbulence behind closing dredge jaws.
A related factor, likewise unquantied (in Michaels and Oko 2010,andalso
herein), is failure of bucket closure, that is, turbulent mobilization of sediments
by descending dredge jaws that cannot close when they encounter obstacles on
the river bottom (such as bicycles, automobile tires, logs, boards, rocks, concrete
blocks, rebar, and other construction debris). When dredge buckets fail to close, the
onboard computer does not record the data in the bucket les. Indeed, for this rea-
son, the fraction of bucket descents that result in nonclosure is unknown, notwith-
standing that these bucket descents mobilize sediment in the river. Most essentially,
notwithstanding our inability to quantify some parameters precisely, the factors
described above, along with bucket geometry and computerized bucket data, indi-
cate that dredge buckets dumped more material back into the river than into waiting
barges. That material remains mobile via physical processes or, if taken up by biota,
through ecosystem dynamics.
The two factors described above, though we cannot quantify them exactly, at the
least add conservatism to our previously published estimates of 75–80 percent sedi-
ment mobilization per bucket closure. This fraction was applicable to dredge buck-
ets, but was signicantly (but likewise to an unquantied degree) reduced when con-
sidering overall sediment mobilization in Phase 1, because of bank-to-bank dredg-
ing. Such redredging in Phase 1, however, is not a feature of Phase 2 (except in its
rst year, 2011, which included bank-to-bank dredging of the uncompleted Phase
1 area), because Phase 2 addresses widely spaced PCB hot spots. Sediments that are
portion of the river bottom that will never be dredged (or redredged). Phase 2 hot
spot dredging comprises the preponderance of the forty-mile (sixty-four-kilometer)
stretch of the Upper Hudson River that is included in the dredging project, making
the per-bucket mobilization fraction highly relevant for Phase 2. Given the prepon-
derant scope of Phase 2, the per-bucket mobilization fraction is relevant in evaluat-
ing the Hudson River dredging project in its entirety.
Issue 2, PCB mobilization: Possible PCB loss by desorption from resuspended
Estimation of PCB mobilization fraction. Apart from the sediment mobilization
fraction addressed above is the related issue of the possibly dierent PCB mobiliza-
tion fraction. PCB might be mobilized by desorption from dredge-disturbed sed-
iment as particle surfaces encounter relatively PCB-free river water. To the degree
that this occurs, PCB may be mobilized from dredge-disturbed sediment as it falls
back to the river bottom or remains suspended (resuspended) in the water column.
Such desorption produces free PCBs in the molecular and colloidal phase, which
are transported downstream with river water. Free PCB in river water no longer is
adsorbed to clay or silt particles. Sampling of clay or silt particles in routine resus-
pension monitoring would not capture free PCBs in dissolved or colloidal form.
122 R. A. MICHAELS AND U. M. OKO
“PCB in colloidal form constitutes the most mobile form of PCB in water, being
aected only minimally by settling, physical retention or adsorption” (Paquin 2001).
To develop a more realistic picture of resuspension, we estimate, roughly but
quantitatively, the amount of fugitive free PCB that clamshell dredging might have
created in Phase 2. Fugitive PCB originates, and primarily is carried by, ne particles
we used data on hydraulic dredging to derive information on the size distribution
and resuspension of such sediment in moving water like the Hudson River. Avail-
able literature (Nau-Ritter et al. 1982) indicates that approximately 30 percent of
PCB adsorbed to resuspended sediment particles desorbs and enters river water in
dissolved or colloidal form within minutes of resuspension. Further, most ne par-
ticles (‘nes’) remain resuspended for hours to weeks before settling, during which
(Schneider 2005). We assume that much or most of the 70 percent is captured by
routine resuspension monitoring. The 30 percent that quickly enters the aqueous
phase, however, would not be captured in routine particle monitoring for verica-
tion of compliance with US EPA’s EPS for resuspension.
The mass of PCB corresponding to loss of 30 percent desorbed from particles of
dredge-disturbed sediment to the aqueous phase is missed in monitoring PCB con-
centration in water, due to river ow variation. We approximate it as follows. We do
not know the exact size distribution of resuspended particles, but laboratory devel-
opment of a dredging elutriate test (DiGiano et al. 1995) revealed that turbulence
mixes a wide range of particle sizes into the water column, but denser particles set-
tle preferentially, leaving behind an elutriate (supernatant) of less dense resuspended
particles, of which 90 percent were ࣘ10-µm (micrometer, or micron) diameter.
The most common size class was 4 µm. Accordingly, we similarly assume spheri-
cal particles of diameter 4 µm. Although the particles are resuspended, we assume
a heavier-than-water specic gravity of 1.8, which, as they are small, can be main-
tained in suspension by turbulence in river water. This specic gravity is somewhat
lower than 2.6 previously reported for Hudson River sediments (Gruendell 1966;
Michaels and Oko 2010), as we also assume here that relatively lighter resuspended
particles are enriched in relatively less dense organic matter.
Our 4-µm spherical particle model is only a rough guide. Fine particles resus-
pended after dredge disturbance actually are nonspherical, and some are more
porous than others, whereas we assume hard spheres. Both properties increase sur-
face area. For example, clay, an important constituent of silt, is both porous and
nonspherical, with particle surface areas of 200–600 m2/g (square meters/gram).
Our hard-sphere model therefore is conservative, because porous-nonspherical par-
ticles have more surface area, can adsorb more PCB, and thus can desorb more PCB
to river water.
The high surface area of small sediment particles such as clay disproportion-
ately carries resuspended PCB (DiGiano et al. 1995; Anchor Environmental 2003;
Michaels and Oko 2010). We assume that each resuspended hard-spherical particle
is coated initially with a monolayer of PCB molecules. We also assume an average
EXCESSIVE PCBS IN THE HUDSON RIVER 123
Tab le . PCB desorption from resuspended sediment in ten-acre Phase- Year- Hudson River dredg-
Mass of PCB rapidly desorbed from a resuspended spherical sediment particle of diameter four microns
radius of -micron (µm) diameter spherical particle µm
surface area of spherical particle of -µm diameter: πr. sq. µm
area occupied by one molecule of (decachlorinated) PCB sq. angstroms
area occupied by one molecule of (decachlorinated) PCB . E- sq. µm
PCB molecules in monolayer on one -µm-diameter particle . E+ PCB molecules
molecular weight (MW) of the PCB molecule g/mole
number of PCB molecules per mole (Avogadro’s number) . E+ PCB molecules
moles of PCB monolayer adsorbed to -µm diameter particle . E- moles
mass of PCB molecules on one -µm diameter particle . E- g
fraction of PCB rapidly desorbed and entering river in aqueous Phase . …
mass of PCB rapidly desorbed to water, per -µm diameter particle . E- g/.-µm particle
Mass of a resuspended spherical sediment particle of diameter microns
volume of spherical particle of -µm diameter: / πr. E+ cu. µm
conversion, cubic µmtoliter(=, cu. cm) . E- cu. µm/liter
volume of spherical particle of -µm diameter: / πr. E- liters
speciﬁc gravity of -µm diameter spherical particle . g/mL =kg/liter
conversion, g/mL to g/cu. m . E- (g/cu. m)/(g/mL)
speciﬁc gravity of -µm diameter spherical particle . E+ g/cu. m
mass of spherical particle of -µm diameter . E- kg/.-µm particle
mass of spherical particle of -µm diameter . E- g/.-µm particle
Number of spherical sediment particles of diameter four microns ﬁtting into a ﬁve-cubic yard dredge bucket
conversion, cubic yards to cubic meters . E- cu. m/cu. yd.
volume of -cubic yard dredge bucket . E+ cu. m
ﬁeld capacity if ﬁlled to percent of full capacity . E+ cu. m
volume of spherical sediment particle of -µm diameter . E+ cu. µm
conversion, cubic µmtocubicm .E- cu.m/cu.µm
volume of spherical sediment particle of -µm diameter . E- cu. m
no. of -µm spherical sediment particles per -cubic yard bucket . E+ particles/bucket
Allowable resuspension in ten-acre Phase- Year- dredging area, under US EPA’s percent-EPS
mass of sediment particles per -cubic yard dredge bucket . E+ kg
US EPA engineering performance standard (EPS) for resuspension percent
allowable resuspended particle mass, in accordance with EPS . kg/-cu. yd. bucket
bucket closures in ten-acre area dredged in Phase Year , closures/ acres
allowable resuspended particle mass, in ten-acre Phase- Year- area . E+ kg/ acres
Mass of PCB rapidly desorbed to water from resuspended particles in ten-acre Phase- Year- area
-µm diameter spherical particles per gram . E+ particles/gram
-µm particles resuspended in ten-acre Phase- Year- area . E+ particles
mass of PCB adsorbed as monolayer on resuspended particles . E+ kg of PCB adsorbed
mass of PCB rapidly desorbed from resuspended particles . E+ kg of PCB desorbed
∗Scientiﬁc notation: . x + tabulated as . E+.
PCB molecular weight of 240 grams/mole. Tab le 1 (above) shows the following cal-
culated parameter values:
1. themassofamonolayerofPCBona4-µm spherical particle is 2.00×10−15
2. themassofaparticleof4-µm diameter and specic gravity 1.8 is 6.03×10−11
3. an 80 percent-full 5-cu. yd. dredge bucket can contain 9.13×1016 4-µm
124 R. A. MICHAELS AND U. M. OKO
Figure . At Waterford: GE projected years needed to match no-dredging, assuming zero dredge
mobilization of PCB other than ‘resuspension’.
4. US EPA’s 2 percent-EPS allows resuspension of 2.44×107kg in the ten-acre
Phase 1, Year 1 dredging area; and
5. the estimated mass of PCB desorbed to the river in aqueous phase is 810 kg.
GE estimates show that the break-even point, at which dredging will have reduced
PCB mobilization as much as it has increased it during the dredging project, would
be twenty years, assuming compliance with US EPA’s 2 percent-EPS for resuspen-
sion. This would bring the break-even year to 2032 (Fig. 2). Under GE’s highest
mobilization assumption, 5 percent of sediment is released back to the river “at the
dredgehead,” in which case dredging will require forty-six years to match the eec-
tiveness of the no-action remediation alternative. That is, no benet can be expected
until the year 2057 at the earliest, optimistically assuming no delays and, critically (see
Discussion), no mobilization of PCB sediments other than ‘resuspension’.
Issue 3, storms: Possibly changing frequency of sediment-mobilizing high ow
After the rst season of dredging, GE reported (Carson 1962;DiGianoetal.1995;
Gardiner et al. 1996) that sediment samples outside the dredged area “show that
dredging caused wide-spread redistribution of PCB-containing sediments on the
surface of the river bottom.” High-ow events already have driven some of this
dredge-mobilized sediment downstream (see, e.g., Islam et al. 2012, 24). Indeed,
recent years have evinced a trend toward increasing frequency and intensity of
storms (Matonse and Frei 2012, 25), including extreme events such as Hurricane
Katrina in 2005, Irene in 2011, and Sandy in 2012, all attaining extraordinary energy,
largely from warmer ocean water in their path (see, e.g., Trenberth 2007).
EXCESSIVE PCBS IN THE HUDSON RIVER 125
Evident global climate change (whatever may be the less-well-known contribu-
tion of civilization to it) has been manifest in a concomitant trend toward more
frequent high-ow events in rivers and streams, resulting from rainfall, tidal surges,
and ooding. Indeed, Matonse and Frei (2012) investigated whether the hydrolog-
ical impacts of Hurricane Irene and Tropical Storm Lee continue a historical trend
toward increasing frequency of extreme hydrological events in New York State’s
Catskill Mountains and Hudson River Valley region. They found
a marked increase in the frequency of extreme hydrologic events during the last one to two
decades. This increasing trend is more evident during the late summer and early fall, the
season of the most extreme precipitation events.
This trend, therefore, can be extrapolated to the future, and incorporated into Super-
fund remediation project assumptions, including assumptions for Hudson River
Tropical Storms Irene and Lee caused 100-year and 500-year ooding, in which
the Mohawk River carved new channels up to forty-ve-feet deep. The storms
exerted comparable impacts on the Hudson River. For example, the storms deliv-
ered an extraordinary amount of fresh water to the Hudson River watershed, along
with a U.S. Geological Survey (USGS) estimate of nearly three million tons (2.7×106
kg) of sediment (Wall and Homan 2012, 18).
Potential eects of swift river ow include scouring of PCB-laden sediment
exposed by dredging to downstream areas, washing away of plantings designed to
stabilize the river bottom and reestablish ecosystems, disruption of caps placed over
residual PCB-containing sediments, ooding, and depositing PCB sediment on the
shore as ‘ood mud.’ Islam et al. (2012, 17), investigating the impact of Tropical
Storm Irene-associated precipitation on the Hudson River and estuary ecosystem,
reported the following:
Continuous monitoring data at the PCB superfund site at Fort Edward, NY…showed sig-
nicant and coincident increases in sediment ux (22 metric ton/hr to 2400 metric ton/hr)
3/s to 480 m3/s) following Irene. In addition, in-situ particle size
measurements suggest that signicant amounts of small particles (<70 µmdiameter)were
transported during the ood event.
Moreover, the contribution of these extreme storm eects to the overall loading is com-
parable to that of long-term sediment transport under ordinary conditions. This suggests
that eects of episodic events should be considered as part of ecosystem management dur-
ing activities such as navigational channel dredging, remediation projects, and long-term
water usage and discharge control.
Issue 4, endangered species: Endangered species classication of Hudson River
US EPA reported that PCB concentrations in sh tissue in the Upper Hudson River
increased vefold after the rst year of dredging (US EPA 2010a,2010e,2012,n.d.a,
n.d.b). US EPA reported more recently that PCB concentrations in sh tissue in
the Upper Hudson River sampling area have returned to normal, presumably due
to a combination of contaminated sediment removal and downstream transport
126 R. A. MICHAELS AND U. M. OKO
of residuals (Id.2010e,2012,n.d.a,n.d.b). Indeed, US EPA’s Hudson eld oce
director David King acknowledged orally at a conference at Marist College (January
16, 2013) that twenty to thirty years might be required for PCB levels in sh tissue to
decline again to levels safe for human consumption. Resuspended PCB transported
downstream is assumed (by us and by US EPA) eventually to reach the Lower
Hudson River, which is the principal habitat of two species of sturgeon (Shepherd
2006;USDOC2012). Indeed, such transport is more than theoretical, but has been
documented empirically. Hudson River Natural Resource Trustees reported (NYS
et al. 2013) that PCB transport (mostly prior to dredging) already has resulted in
PCB contamination of the Lower Hudson River:
The Hudson River Natural Resource Trustees are conducting a natural resource damage
assessment (NRDA) to investigate natural resource injuries that may have occurred due
to the release of polychlorinated biphenyls (PCBs) from General Electric (GE) facilities
at Hudson Falls and Fort Edward, NY. This report summarizes available information on
PCB contamination in the Hudson River ecosystem, including historic information, but
focusing particularly on data collected and analyzed between 2002 and 2008 as part of
ongoing NRDA activities. The Hudson River, for greater than 200 miles below Hudson
Falls, NY, is extensively contaminated with PCBs. Surface waters, sediments, oodplain
soils, sh, birds, wildlife, and other biota are all contaminated with PCBs. (NYS et al. 2013,
1; emphasis added)
The shortnose sturgeon (Acipenser brevirostrum) was listed as endangered in
1967, though (in 2006; Shepherd 2006)itappearedtoberecoveringinasmuchasit
has not been a target of shing since 1967. The U.S. Department of Commerce, on
February 6, 2012, added the Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus)to
the Endangered Species List (US DOC 2012). The Commerce Department must pro-
tect sturgeon habitat—principally the Hudson River (Shepherd 2006)—as required
by the federal Endangered Species Act. Loss of habitat is a big part of the problem of
loss of sturgeon, inasmuch as the principle alternative loss factor, shing for either
species of sturgeon, has been prohibited for well over a decade, since a moratorium
on harvesting wild Atlantic sturgeon was imposed in 1998 after decades of over-
shing. Commercial landings of Atlantic sturgeon crashed before the moratorium
was imposed (Fig. 3;Shepherd2006). The Lower Hudson River, below the Federal
Dam at Troy, evidently will be impacted by PCBs for years or decades as contami-
nated dredge-mobilized sediments are scoured and transported downstream from
an increasing area of river bottom in the Upper Hudson River, at Fort Edward and
to the south.
susceptible to PCB contamination (US EPA 2010c). According to US EPA (previous
to the ocial Endangered Species classication of the Atlantic sturgeon): “Fragile
populations of threatened and endangered species in the Lower Hudson River, rep-
resented by the bald eagle and shortnose sturgeon, are particularly susceptible to
adverse eects from future PCB exposure.”
By “future PCB exposure” US EPA (2010c) meant future exposure if dredging
does not occur, but dredging did occur. PCB levels in Lower Hudson River water
presumably will vary over space and time as they increase gradually to an
EXCESSIVE PCBS IN THE HUDSON RIVER 127
Figure . Total commercial landings of Atlantic sturgeon in the United States historically.
Source: G. Shepherd. . Status of ﬁshery resources oﬀ the northeastern United States. Atlantic and
shortnose sturgeons: Atlantic (Acipenser oxyrhynchus), shortnose (Acipenser brevirostrum. National
Oceanic and Atmospheric Administration (NOAA), Northeast Fisheries Science Center (NEFSC),
Resource Evaluation and Assessment Division, http://www.nefsc.noaa.gov/sos/spsyn/af/sturgeon/
undetermined maximum over a period of years or decades, during which annual
sturgeon reproductive cycles will be stressed. The degree of stress, and ability of
already-stressed sturgeon populations to withstand it, both remain unknown.
Modeling of the dynamics of three million tons of sediment loading into the Hud-
son River following Tropical Storms Irene and Lee, undertaken by Ralston, Geyer,
and Warner (2012, 11), revealed the following:
The simulated sediment transport showed surprisingly little sediment export—most of the
sediment delivered by the storms was trapped in the tidal river north of West Point, accord-
ing to the model.
Similar dynamics may be expected from PCB-bearing sediments mobilized by
dredging. That is, estuaries can trap sediments and the toxins that they harbor, to
the detriment of ecosystems including Hudson River sturgeon occurring below the
Federal Dam at Troy.
Issue 5, autism: Research into possible PCB causation of autism
PCBs are known neurotoxicants (ATSDR 2000). Moreover, PCBs have been impli-
cated in causation of Parkinson’s disease (Goldman et al. 2016), ADHD (Keil and
Lein 2016), and autism ((Keil and Lein 2016; Landrigan et al. 2012;Waymanetal.
2012a,2012b). PCBs also are known developmental neurotoxicants at environmen-
tal levels of exposure (ATSDR 2000). Based upon prospective epidemiology studies,
maternal exposure to PCBs during pregnancy has been linked to dyslexia, attention
decit hyperactivity disorder (ADHD), and loss of cognition (reduced IQ; Winneke
2011). More recent (animal) studies now link PCBs to DNA methylation (Keil and
Lein 2016) and to specic developmental processes that, in humans, are thought to
128 R. A. MICHAELS AND U. M. OKO
Figure . Autism prevalence trend.
underlie causation of autism (Landrigan et al. 2012;Waymanetal.2012a,2012b),
most notably the following:
1. stimulation of calcium signaling in the brain that alters nerve cell dendrite
2. increased dendrite growth and branching; and
3. alteration of synapse formation in developing brains (in animal bioassays).
The prevalence of autism has been increasing dramatically in recent decades
eight; Autism Speaks n.d.; Landrigan et al. 2012;USDOH2012) and nearly one of
fty-four boys (Autism Speaks n.d.). A substantial portion of the increase in autism
prevalence evidently is attributable to environmental factors. Boys are nearly ve
timesmorelikelythangirlstohaveautism(AutismSpeaksn.d.), suggesting sex-
linked inheritance of susceptibility factors, as boys have just a single (maternal) X
chromosome that, if damaged, lacks potential compensation from genes in a coun-
terpart (paternal) X chromosome as is the case in girls, who inherit an X chromo-
some from each parent.
Discussion, conclusions, and recommendations
Issue 1, sediment mobilization: US EPA accuracy in estimating PCB-contaminated
sediment mobilized by dredging
US EPA’s engineering performance standard (EPS) pointedly refers to “resuspen-
sion,” not “mobilization.” These terms might seem intuitively synonymous but,
EXCESSIVE PCBS IN THE HUDSON RIVER 129
in US EPA parlance, resuspension denotes just a miniscule fraction of dredge-
mobilization of sediment. A signicant sediment mobilization discrepancy there-
fore exists between sediment that is mobilized by dredging versus the much smaller
compliance with the US EPA resuspension EPS. The discrepancy arises from the fact
that the preponderance of dredge-resuspended sediment falls back to the riverbed,
and remains on the river bottom, still mobile, but unrecorded by GE or US EPA
because its resuspension typically is episodic over years to decades and, in the main,
has not yet occurred.
US EPA (2010d,2010e,n.d.a) EPSs limit dredge mobilization of sediments to
a maximum of 2 percent “at the dredgehead.” Results of US EPA modeling using
HUDTOX, however, clearly indicated that the 2-percent EPS, even for resuspension
alone, could not be attained at the dredgehead; indeed, it was redened upward sim-
ply by changing (at least doubling) the estimated mass of PCB to be dredged (and
also the allowable resuspension fraction), and therefore the amount (mass) of allow-
able PCB resuspension:
[The Record of Decision] originally estimated the PCB mass to be removed as approxi-
mately 70,000 kg, and the total project cumulative load standard was set at just below 1
percent of this total, or 650 kg. Based on the Phase 1 experience and additional sampling
results, the estimated PCB mass for the entire project has been revised to the range 140,000
to 200,000 kg. (US EPA 2010d, 4–2).
The sediment mobilization problem also was highlighted by US EPA’s Hudson
River Dredging Peer Review Panel. The panel’s initial draft report (Peer Review
Panel 2010), published to elicit comments, made an interesting error that was fol-
lowed by a more interesting response by US EPA. The panel’s comment no. 6 stated
[EPA’s] incomplete analysis done for the 2004 EPS does not consider near-eld and far-eld
PCB deposition rates on the sediment bed surface.
Thus, according to the peer review panel, US EPA failed to consider sediment
mobilization at the dredgehead (“near eld”), where dredged sediments are mobi-
lized. US EPA’s response to Hudson River Dredging Peer Review Panel comment no.
in handling data that might interfere with Agency plans:
EPA did simulate near-eld suspended matter transport and settling in its near-eld mod-
eling analysis. The HUDTOX model runs did not reect the near-eld settled solids but did
incorporate an estimate of dredging-related suspended solids transport 1,000 meters down-
stream of the dredge. This analysis was the basis for the EPA forecasts of dredging-related
resuspension. (US EPA 2010b; emphasis added)
Thus, US EPA apparently could not meet the 2-percent (originally 1-percent)
EPS limit at the dredgehead, so it declined to apply its HUDTOX modeling results
at the dredgehead to forecast dredging-related resuspension quantitatively. Instead,
130 R. A. MICHAELS AND U. M. OKO
1,000 meters downstream of dredging. Inasmuch as nearly all dredge-disturbed
bottom near the dredgehead, the use of HUDTOX results from 1,000 meters down-
stream ignores roughly 99 percent of resuspension occurring at the dredgehead.
This is at best misleading and, indeed, the expert peer review panel was misled
as indicated by its incorrect criticism (quoted above) that US EPA had failed to
model resuspension at the dredgehead (in the “near eld”). The Agency did do the
modeling, but (as US EPA stated) declined to use the results.
As explained, sediment mobilization via dredging includes resuspension (at
the dredgehead or wherever estimated) as well as the preponderance of dredge-
disturbed sediment that falls back to the riverbed and is not barged (which we
approximated conservatively at 75–80 percent of the amount initially excavated).
This sediment drops back to the river bottom, still mobile, but it is excluded from
US EPA’s resuspension parameter. US EPA’s statement quoted above therefore
shows that the Agency justied dredging by ignoring gradual erosion from the
river bottom of dredge-mobilized PCB-bearing sediments, which reasonably would
be expected to occur over a period of years to decades. The Agency thereby also
ignored inevitable, though gradual, entry of PCBs from these sediments into down-
stream water, ecosystems, and air. Thus, in fty years US EPA conceivably might
nd the river to be in much the same condition from GE dredging up sediments
The modeling and data handling issues raised above presumably would have
come under scrutiny by US EPA’s Hudson River PCB Dredging Peer Review Panel,
but US EPA explicitly prohibited the panel from opining whether dredging should
continue, or whether Phase 2, if undertaken, could meet project health goals.
Nonetheless, the Peer Review Panel (2010) rejected US EPA’s response, quoted
above, concluding in its nal report:
Phase 1 showed that the 2004 EPS [engineering performance standards] for Resuspension,
Residuals, and Productivity were not met individually or simultaneously during Phase 1
and cannot be met under Phase 2 without substantive changes. EPA and GE proposed
changes to the EPS, but the Panel nds that the new proposed standards from either party
would not contribute to the successful execution of Phase 2. (Id., 84)
The sediment mobilization discrepancy discussed above represents more than
merely a dierence between a predicted versus a measured parameter value. It repre-
sents a fundamental inconsistency in US EPA’s past justication of the need to dredge
versus US EPA’scurrent characterization of the performance of the dredging project.
The need for dredging was justied by the observed, persistent mobility of PCB sed-
iments requiring, according to US EPA, their removal via dredging. In contrast, in
mobility. Mobility in the dredging project is newly quantied by the miniscule frac-
tion of mobilized (resuspended) PCB that is detected at signicant distance down-
stream. Thus, US EPA has ignored nearly all sediment and PCB mobilization in
EXCESSIVE PCBS IN THE HUDSON RIVER 131
evaluating compliance with the engineering performance standard for resuspension.
In ignoring mobility of PCB-containing dredge-mobilized sediments for gauging
compliance with the resuspension EPS, US EPA has ignored a much larger degree
of PCB sediment mobility than that which constituted US EPA’s most essential basis
for requiring, in 2007, remediation of the Hudson River PCB Superfund Site via
the only example of misleading use of modeling or monitoring data by US EPA, and
should be viewed in this broader context. One example will suce. In seeking to
justify dredging, US EPA had prepared a baseline health risk assessment (HRA; US
EPA 1999,2000a,2000b) that excluded all mono- and di-chlorinated PCB congeners
based upon a misleading premise, specically, that these congeners do not bioaccu-
mulate in sh tissue, which contributes to human exposure to PCBs (Michaels and
Oko 2007). The mono- and di-chlorinated congeners, even if they bioconcentrate
less dramatically than the higher-chlorinated congeners, still are present in sh tis-
sue. They should have been present in the HRA.
In the 1960s, Rachel Carson’s Silent Spring (1962) famously raised awareness
of environmental risks posed by DDT, which is a nearly identical twin of PCBs
(Michaels and Oko 2010). Both DDT and PCBs contribute to human health risk
by entering air, water, and ecosystems that include food chains terminating in con-
sumption of sh and birds by people. Higher-chlorinated PCBs degrade via dechlo-
rination, resulting in build-up of the mono- and di-chlorinated congeners. Their
omission from US EPA’s HRA, therefore, contributed signicantly to obtaining its
dredging-permissive results. Indeed, when US EPA came under attack by environ-
mental groups for favoring a dredging plan that would remove only one hundred
thousand pounds of PCB, US EPA responded by adding back the mono- and di-
chlorinated PCB congeners that initially had been excluded when assessing poten-
tial health risks. US EPA thereby claimed that the actual amount of PCBs that would
be dredged under its “revised” plan would be one hundred fty thousand pounds,
indicating that, in US EPA’s own view, the mono- and di-chlorinated congeners that
were omitted from the baseline HRA would contribute 50 percent more than the
one hundred thousand pounds of PCB actually included in the inventory on which
the HRA was based (Michaels and Oko 2007).
We conclude that US EPA estimation of mobilization of dredge-disturbed PCB-
contaminated sediment has been grossly inaccurate. Sediment resuspension has
been mismeasured and evidently not limited to within the applicable EPS of 2
percent of the amount of PCB dredged at the dredgehead. Environmental per-
formance standards that address the broader issues of sediment mobilization and
spreading to new areas of the river bottom remain nonexistent, notwithstanding
peer review panel ndings that such EPSs are needed. We also conclude, therefore,
that any extension of the dredging project as demanded recently by many in the
environmental community should be predicated upon agency remediation of these
132 R. A. MICHAELS AND U. M. OKO
Issue 2, PCB mobilization: Possible PCB loss by desorption from resuspended
Comparison with US EPA mobilization assumptions. US EPA engineering perfor-
mance standards (EPSs; US EPA 2010d,2010e) limit dredge mobilization of PCB
in sediments to ࣘ2 percent “at the dredgehead,” which roughly is at the dredging
platform. A 2010 US EPA (2010e) factsheet explicating Tec hnic a l Req u i rem e nts fo r
Phase 2 of Hudson River Dredging states, for example:
the amount of PCBs actually excavated from the river bottom, as measured at designated
locations downstream of where the dredging is taking place.
As shown in Ta ble 1 (in Findings), this limit routinely has been exceeded sub-
stantially, in part because measurement at downstream locations does not reect
the amount of PCB excavated at the dredgehead, and that eventually will ow down
the river. Even if the 2-percent limit were not exceeded at all, however, GE esti-
mates (Fig. 2,inFindings) shows that the break-even point, at which dredging will
have reduced PCB mobilization as much as it has increased it during the dredging
project, would be forty-six years. That is, no benet can be expected until the year
2057 at the earliest, optimistically assuming no delays and, critically, no mobilization
of PCB sediments other than resuspension.
Issue 3, storms: Possibly changing frequency of sediment-mobilizing high-ow
The documented trend toward more frequent and more intense storms and result-
ing sediment mobilization (see Findings) can be and should be extrapolated to the
future, and incorporated into Superfund remediation project assumptions, includ-
ing assumptions for Hudson River PCB dredging. US EPA reported in 2011 that
high river-ow caused by Tropical Storms Irene and Lee did not elevate con-
centrations of resuspended sediment above acceptable guidelines specied in the
EPS for resuspension. However, the EPS, as already shown, dramatically under-
estimates PCB mobilization, and therefore constitutes a poor measure of that
When storms greatly increase river ow, uncompacted PCB sediments disturbed
by dredging are scoured from the river bottom. They enter the swiftly moving water
column, and are transported downstream. This downstream transport may be invis-
ible to US EPA’s EPS for resuspension because the increased river ow simultane-
ously dilutes the scoured sediments. This dilution reduces PCB concentrations that
can be measured in river water, thereby masking the increased scouring of sediment
and elevation of the rate of its downstream transport.
Swift river ow events increase downstream transport of PCB sediments to a
greater degree if dredging is not suspended during their occurrence. Such episodes
presumably would increase the pace of downstream contamination of water,
EXCESSIVE PCBS IN THE HUDSON RIVER 133
ecosystems, and air. US EPA’s EPS for resuspension fails to measure these eects,
and no EPS exists to measure the resulting increase in the area of newly contami-
nated river bottom. Future high-ow events, over years to decades, will continue to
transport dredge-mobilized PCB sediments episodically downstream, where they
river ow, virtually all dredge-disturbed PCB sediment conceivably could be driven
downstream by storms and other high-ow events without contravening US EPA’s
EPS for resuspension. Thus, any extension of dredging should be predicated upon
adoption of EPSs that eectively quantify and limit long-term scouring of dredge-
disturbed sediments and resulting increases in the area of newly contaminated river
Issue 4, endangered species: Endangered species classication of Hudson River
In 1999, more than a decade prior to addition of the Atlantic sturgeon to the Endan-
gered Species List, US EPA issued an addendum to its baseline ecological risk assess-
ment for the Lower Hudson River (49). The addendum, updated in 2010, evaluated
future risks posed up to the year 2018 by PCB transport from the Upper Hudson
River to ecosystems in the Lower Hudson River, between the Federal Dam at Troy
and the Battery in New York City. As a baseline assessment, it assumes no dredg-
ing; indeed, it assumes “the absence of remediation.” Its major conclusions (US EPA
— Fish in the Lower Hudson River are at risk from future exposure to PCBs. Fish that
eat other sh (i.e., which are higher on the food chain), such as the largemouth bass and
— Fragile populations of threatened and endangered species in the Lower Hudson River,
represented by the bald eagle and shortnose sturgeon,areparticularlysusceptibleto
adverse eects from future PCB exposure [emphasis added];
— The future risks to sh and wildlife are greatest in the upper reaches of the Lower Hud-
son River and decrease in relation to decreasing PCB concentrations down river. Based on
modeled PCB concentrations, many species are expected to be at risk through 2018 (the
entire forecast period).
Dredging will continue to increase transport of PCBs from the Upper Hudson
River to the Lower Hudson River to a degree exceeding the no-action alterna-
tive for the full forecast period. The conclusions of the Ecological Risk Assessment
Addendum, therefore, reect consistency of US EPA’s (2010c) conclusion of record
with our own: that endangered sturgeon, endangered bald eagles, and other species
are at risk from continued dredging and PCB mobilization, and therefore with the
general principle that environmental health is crucial for food chains and the safety
of the human food supply (Hulme 2013).
134 R. A. MICHAELS AND U. M. OKO
ing Peer Review Panel (2010). The panel concluded in 2010 that US EPA had failed
to set an allowable sediment-loading limit, failed to gather data needed do this, and
failed to develop models to predict transport of dredge-mobilized sediment and
PCB bioaccumulation based upon Hudson River hydrodynamics. Thus, US EPA
sampling of resuspended PCB was insucient, because US EPA failed to sample
or model the vastly larger quantity of dredge-mobilized PCB resting on the river
bottom. US EPA, therefore, cannot assure the public that transport of sediment
already mobilized by dredging will not increase downstream PCB loads gradually
and episodically for decades, threatening ecosystems in the Lower Hudson River.
gered sturgeon and bald eagles can survive decades of increased PCB transport to
the Lower Hudson River. Continued dredging therefore should be predicated upon
development of appropriate EPSs and compliance with them, which together might
Issue 5, autism: Research into possible PCB causation of autism
Treatment of children severely impaired by autism is palliative rather than cura-
tive; that is, children with autism typically become adults with autism (Landrigan
et al. 2012). Impacts on families of children with autism may be devastating physi-
cally, psychologically, and nancially. Economic impacts to society likewise are enor-
mous (Landrigan et al. 2012;AutismSpeaksn.d.), and may be exacerbated since the
American Psychiatric Association in 2013 changed its diagnostic mental illness def-
initions, combining people with severe autism and others with milder forms (such
as those with Asperger’s Syndrome) into a single autism spectrum disorder (ASD)
category (Jabr 2012).
The issue of whether the ocially completed GE Hudson River dredging project
should be extended to remediate remnant PCBs must be viewed in the context of
US EPA’s longstanding special mandate regarding children’s health, embodied by US
EPA’s (2001)Children’s Health Risk Initiative. In 1997 the Oce of Children’s Health
Protection was instituted within US EPA. Its mission was and remains “to make
children’s health protection a fundamental goal of public health and environmental
protection …[by] ensuring strong standards that protect children’s health.”
Long-term remediation projects undertaken under the federal Superfund Act or
its state equivalents are subject to ve-year reviews. As dredging Hudson River PCBs
was mandated in 2007, the rst ve-year review of the project was undertaken as
required in 2012 (US EPA 2012). Accordingly, one of us (Michaels) informed US
EPA of the emerging link between PCBs and possible causation of autism and, in a
ative to numerous river communities alongside the path of the dredging project. The
ve-year review (US EPA 2012), however, neither addressed this issue substantively,
nor alluded to it. Indeed, the word autism was absent from the eighty-two-page
report. Given the high and increasing prevalence of autism (Fig. 4;AutismSpeaks
EXCESSIVE PCBS IN THE HUDSON RIVER 135
n.d.), and its seriousness, cost, and apparent linkage to environmental agents that
may include maternal exposure to PCBs during pregnancy, extending the dredging
project should be predicated upon satisfactory consideration of this emerging pub-
lic health issue. The next ve-year review of the dredging project is underway, for
release in 2017.
Will further clamshell dredging fulll the purpose of dredging?
resuspension to ࣘ2% of the amount excavated. Consider a numerical illustration
based upon the parameters quantied (at least approximately) earlier: 1,000 kg of
PCB-contaminated sediment is excavated at the dredgehead. The EPS for resuspen-
sion is ࣘ2percent,whichisࣘ20 kg. If 25 percent (ࣘ250 kg) is barged, then 75 per-
cent (ࣘ750 kg) is mobilized, drastically contravening the 20-kg EPS. If, as reported
orally by US EPA, 99 percent (750 kg x 0.99 =742.5 kg) falls back to the river bot-
tom near the dredgehead, then just 1 percent (7.5 kg) remains in the water column.
If US EPA measured resuspension at the dredgehead, all of this resuspension would
be captured in the measurement (742.5 +7.5 =750 kg).
A downstream measurement that is made after separation of the 1 percent
remaining in the water column from the 99 percent falling back to the river bot-
tom near the dredgehead would capture only the 7.5 kg remaining in the water
column. The location of such a measurement, according to US EPA HUDTOX
modeling, appears to be ࣙ1,000 m downstream. The resuspension value obtained
at this location (7.5 kg in the example) complies with the EPS for resuspension
(20 kg for every 1,000 kg excavated). Measuring or modeling resuspension 1,000 m
downstream of dredging, therefore, in this example drastically contravenes the
EPS for resuspension by overlooking 742 kg of dredge-disturbed sediment that
The above numerical example also illustrates that clamshell dredging has failed
to fulll US EPA’s main, original purpose of dredging: to reduce safely and substan-
tially the long-term downstream transport of dredge-disturbed PCB sediments. The
742 kg of sediment that has fallen back to the river bottom in the above example
still is mobile, in the sense that it can be and (if not redredged) eventually will be
transported downstream via episodic high-ow events over years to decades. This
redeposited mobile PCB sediment, as illustrated earlier, is invisible to the EPS for
resuspension. The EPS, in turn, therefore is blind to long-term health and environ-
mental risks potentially posed to downstream ecosystems.
Any long-term project, especially if unusually expensive, must be evaluated period-
ically to assess the degree to which it is fullling its purpose. If it is not fullling its
purpose, it must be redesigned or terminated. Clamshell dredging was and remains a
136 R. A. MICHAELS AND U. M. OKO
bad idea for the Hudson River, and has been shown incapable of fullling its original
purpose of reducing safely and substantially the long-term downstream transport of
PCBs. Our overall conclusion, therefore, is that excessive post-project PCBs in the
Hudson River predominantly are attributable to sediment mobilization by clamshell
dredges. We predict that proposed extension of the dredging project would prolong
mobilization processes, allowing PCBs to spread widely and enter ecosystems that
include people,endangered sh such as sturgeon, and endangered birds such as bald
Recommendations. We recommend that the design of any extended or future
PCB dredging be improved to comply with US EPA’s EPS limiting short-term
resuspension to ࣘ2 percent of PCB in sediment excavated, and adopt EPSs also
limiting long-term downstream deposition of residual sediments outside of dredge
zones. Increasing storm frequency and intensity must be incorporated into predic-
tion of dredging-associated sediment transport. EPSs must limit transport to within
levels shown sustainable for survival and reproduction of sturgeon, eagles, and other
endangered species in the long-term, well beyond several years needed for comple-
tion of dredging. US EPA likewise must address the potential of dredging to increase
the incidence of autism in aected river communities and, if necessary, adopt health
protective EPSs. Finally, hydraulic dredging, originally proposed, should be con-
sidered as an alternative to conventional clamshells for extending and completing
remediation of the Hudson River PCB Superfund Site.
About the authors
Robert A. Michaels is president of Schenectady-based RAM TRAC Corporation, and a toxicol-
ogist specializing in assessment and management of risks to public health potentially posed by
environmental contaminants. He has served numerous corporate clients, the U.S. Congressional
Oce of Technology Assessment, and public interest organizations such as the Natural Resources
Defense Council (NRDC). Dr. Michaels chaired the State of Maine Scientic Advisory Panel,
and for twenty years chaired the Certication Review Board of the Academy of Board Certied
Environmental Professionals (ABCEP); he now serves as an ABCEP trustee. Michaels has been
secretary of the National Fire Protection Association (NFPA) Committee on Classication and
Properties of Hazardous Chemicals, board member of the National Association of Environmental
Professionals, and member of the Editorial Advisory Boards of Springer-Verlag and Cambridge
University Press journals. In 2004 he was awarded ABCEP’s Kramer Medal recognizing his pro-
fessional contributions. Uriel M. Oko is an independent consulting engineer in Albany, New York.
He specializes in environmental remediation, cathodic protection for prevention of corrosion and
material failures. At the Missouri University of Science and Technology he investigated surface
behavior of mine tailings water that had been contaminated with heavy metal ions: zinc, lead,
copper and mercury. He has designed remediation systems for pollution abatement of aquifers,
stripping systems for the removal of MTBE (methyl-tert-butyl ether) and other volatile organic
compounds from water, and cathodic protection systems for underground pipelines and storage
tanks. Dr. Oko has served as an expert witness in litigation of industrial accidents. Prominent
cases have involved metallurgical examination of collapsed bridge sections, fugitive chlorine gas
from a water treatment plant, and collapsed scaolds, cranes, and ladders.
EXCESSIVE PCBS IN THE HUDSON RIVER 137
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