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OCR for page 64
USE OF THE APPARENT EFFECTS THRESHOLD APPROACH (AET)
IN CLASSIFYING CONTAMINATED SEDIMENTS
Robert Barrick, Harry Beller, Scott Becker, and Thomas Ginn
PTI Environmental Services
ABSTRACT
The Apparent Effects Threshold (AET) approach is a tool
for deriving sediment quality values for a range of biolo-
gical indicators used to assess contaminated sediments. The
AET is the contaminant concentration in sediment above which
adverse effects are always expected for a particular biolog-
ical indicator. Application of this approach in 13 embaym-
ents of Puget Sound, Washington is described. Approximately
85 percent of the 198 benthic infauna stations and 283
amphipod bioassay stations are in accordance with the pre-
dictions of the proposed AET values for these indicators
(i.e., they do not exhibit adverse effects when all concen-
trations are less than AET values, and do exhibit adverse
effects at chemical concentrations above the AET values).
Similarly, approximately 95 percent of 56 oyster larvae
bioassay stations and 56 Microtox bioassay stations are in
accordance with predictions of AET for these indicators
evaluated in a single urban bay and associated reference
area (Commencement Bay and Carr Inlet; additional data for
other embayments are not available). The integration of AET
as one tool for environmental decision making is discussed,
including the need for more than a single number that
defines "clean sediments." Specific management requirements
may dictate that low sediment quality values (e.g., the
lowest AET for a range of biological indicators) be applied
to ensure sensitive identification of potential problems,
while high values (e.g., the highest AET for a range of
biological indicators) be applied to ensure that remedial
action is efficiently focused on problem sediments for which
there is a preponderance of evidence.
INTRODUCTION
Sediments are a primary reservoir of contaminants released by indus-
trial, commercial, and residential activities in coastal urban bays.
The management of contaminated sediments requires that biological or
64
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65
chemical criteria be developed to distinguish effects or concentration
levels above which the sediments are considered to be a problem. Regu-
latory sediment criteria for defining "clean sediments" have not yet
been adopted, but the assessment of toxic effects associated with con-
taminated sediments has been approached by environmental scientists in
two general ways (Figure 1~. .
The first general approach is based on empirical relationships
between laboratory sediment bioassays, in situ biological effects
observed in organisms associated with sediments, and chemical concen-
trations measured in sediments. Examples of this "effects-based"
approach include the Sediment Quality Triad (Long and Chapman, 1985),
the Apparent Effects Threshold (AET) (Barrick et al., 1985), and the
Screening Level Concentration (SLC) (Battelle, 19869. The second
approach emphasizes theoretical models to predict the partitioning of
sediment contaminants to interstitial water (a major exposure pathway
for organisms associated with sediments). The predicted interstitial
water concentrations are then compared to water quality criteria based
on laboratory measurements of biological effects (e.g., the equilibrium
partitioning approach ; Pavlou, 1987~. None of the available approaches
is fully capable of addressing all concerns over interactive effects
among chemicals; hence, field verification using diverse environmental
samples is important to the evaluation of each approach.
The following presentation summarizes the concept of the AET
approach and its application and verification in multiple areas of
Puget Sound, Washington. The information has been abstracted from a
manuscript in preparation (Barrick et al., in prep.~. The AET approach
assumes a dose-response relationship between increasing chemical
contamination and biological effects. Specifically, for each chemical
of concern, the AET is the chemical concentration in sediments above
which statistically significant biological effects are always expected
for one or more biological effects indicator. AET can be developed for
any measured chemical (organic or inorganic) that spans a wide concen-
tration range in the data set used to generate AET. The AET concept
IN SITU Chemistry Field
BENTHIC - ~ Correlation
EFFECTS
Field I LABORATORY | Chemistry Laboratory
Sediment ~ | EXPOSURE | ~ Correlation
FIGURE l Assessment of
sediment quality.
an,
(1 )
SEDIMENT TOO ~ Predicted IW ~ Predicted
CHEMISTRY Par f i lion ing
Chemistry Criteria Effects
(1) Effects-Based (2) Theoretical
(2 ~
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66
can be applied to matched field data for sediment chemistry and any
observable biological effects (e.g., bioassays, benthic infaunal
abundance, bioaccumulation).
By using these different indicators, application of the resulting
sediment quality values addresses a wide range of biological effects in
the management of contaminated sediments. A single biological test or
single concentration for a chemical may not always define "acceptable
contamination." Hence, a range of sediment quality values such as pro-
vided by the AET approach may be necessary to serve the needs of differ-
ent programs.
DESCRIPTION OF AET APPROACH
The focus of the AET approach is to identify concentrations of con-
taminants that are associated exclusively with sediments exhibiting
statistically significant biological effects relative to reference sedi-
ments. The calculation of AET for each chemical and biological indica-
tor is straightforward: -
1. collect "matched" chemical and biological effects data--conduct
chemical and biological effects testing on subsamples of the
same field sample (because of subsampling concerns, benthic
infaunal analyses may require chemical analyses to be conducted
on a separate sediment sample collected concurrently with the
chemical sampled;
I. determine "impacted" and "nonimpacted" stations--statistically
test the significance of adverse biological effects relative to
suitable reference conditions for each sediment sample and bio-
logical indicator;
a. determine AET using only "nonimpacted" stations--for each chemi-
cal, determine the AET for a given biological indicator as the
highest detected concentration among sediment samples that
do not exhibit statistically significant effects (if all values
for the chemical are always undetected in these samples, no AET
can be established for that chemical and biological indicator);
'.. check for tentative AET--verify that statistically significant
biological effects are observed at a chemical concentration
higher than the AET, otherwise the AET is only a tentative mini-
mum estimate (or may not exist.)
A pictorial representation of the AET approach for two chemicals is
presented in Figure 2 based on amphipod bioassay results in Puget
Sound. Two subpopulations of all sediments analyzed for chemistry and
subjected to an amphipod bioassay are represented by bars in the fig-
ures, and include
sediments that did not exhibit statistically significant (P >
0.05) amphipod toxicity ("nonimpacted" stations), and
sediments that exhibited statistically significant amphipod
toxicity in bioassays (nimpacted" stations).
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67
FIGURE 2 The AET approach
applied to sediments tested
for lead and 4-methyl phenol
concentrations and amphipod
mortality during bioassays.
LEAD
~ NO SEDIMENT TOXICITY
me steer = e ~ ~
a~ lee~
- SEDIMENT TOXICITY OeSERVED—
F:~/'',,'/,///~/~/'.~,//,/~
t t ~ 1
SP IS SP-14 . I RS.19
7 - PA
~ ·~' '1
1 1000
APPARENT
CONCENTRATION (~IKg DW) A - HIPOD
TOXICITY
THRESHOLD
~ . . . . .... ! .
10 100
HI
RS-18 I
l
63 - PA
, · ,,4 ~
10,000
MAXIMUM _
OBSERVED
LEVEL AT A
BIOLOGICAL
STATION
OH
4-METHYL PHENOL ~
NO SEDIMENT TOXICITY
1 1
RS 1' RSe18
. . .~
U10 100
, SP!1S
1 300 ppe
sP.lil
......
1000
APPARENT
CONCENTRATION (~g/Kg DW) ~PHIPOD
rot
TH - S - LO
,_
MAXIMUM
OBSERVED
LEVEL AT ~
BK)LOGKAL
STATION
The horizontal axis in each figure represents sedimentary concentra-
tions of contaminant of concern (i.e., lead or 4-methyl phenol) on a
log scale. For the amphipod bioassay under consideration, the AET for
lead is the highest lead concentration corresponding to sediments that
did not exhibit significant toxicity. Above this lead AET, signifi-
cant amphipod toxicity was always observed in the data set. The
AET for 4-methyl phenol was determined analogously.
The Potential Effect Threshold (Figure 2) is the concentration
below which no statistically significant biological effects were
observed in any sample. Note that this threshold for 4-methyl phenol
is equal to the detection limit for the compound. The threshold is
designated as "potential" because toxicity was observed in some, but
not all, of the samples from stations with higher lead or 4-methyl
phenol concentrations. The toxicity effects observed at these stations
could have resulted from other contaminants or physical conditions
(e.g., grain size). Because the potential effect threshold for a chemi-
cal cannot be related in a meaningful way to the observed biological
effects, it is not used to set sediment quality values.
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68
INTERPRETATION OF AET
AET correspond to the sediment concentration of a chemical above
which all samples for a particular biological indicator were
observed to have adverse effects. Thus, AET are based on noncontra-
dictory evidence of biological effects for a given data set. Data are
treated in this manner to reduce the weight given to samples in which
factors other than the contaminant examined (e.g., other contaminants,
environmental variables) may contribute to the biological effect.
For example, sediment from Station SP-14 shown in Figure 2 exhib-
ited severe toxicity, potentially related to a greatly elevated level
of 4-methyl phenol (7,400 times reference levels). The same sediment
from Station SP-14 contained a low concentration of lead that was well
below the AET for lead (Figure 2~. Despite the toxic effects displayed
by the sample, sediments from many other stations with higher lead con-
centrations than Station SP-14 exhibited no statistically significant
biological effects. These results were interpreted to suggest that the
effects at Station SP-14 were more likely associated with 4-methyl
phenol (or a substance with an environmental distribution) than with
lead. A converse argument can be made for lead and 4-methyl phenol in
sediments from Station RS-18. Hence, the AET approach helps to iden-
tify different contaminants that are most likely associated with ob-
served effects at each biologically impacted site. Based on the results
for these two contaminants, effects at 4 of the 28 impacted sites shown
in the figures may be associated with elevated concentrations of
4-methyl phenol, and effects at 7 other sites may be associated with
elevated lead concentrations (or similarly distributed contaminants).
These results illustrate that the occurrence of impacted stations
at concentrations below the AET of a single chemical does not imply
that AET in general are not protective against biological effects, only
that single chemicals may not account for all biological effects. By
developing AET for multiple chemicals, a high percentage of all sta-
tions with biological effects are accounted for with the AET approach
(see "Results of Validation Testify. Nevertheless, unmeasured toxic
chemicals may occur in the environment with a different spatial dis-
tribution than any of the measured chemicals. In such cases, it is
unlikely that the AET approach could regularly predict impacts at sta-
tions where only such chemicals induce toxic effects.
AET can be expected to be most predictive when developed from a
large data base with wide ranges of chemical concentrations and a wide
diversity of measured contaminants. Small data sets that have large
concentration gaps between stations and/or that do not cover a wide
range of concentrations must be scrutinized carefully (e.g., to discern
whether chemical concentrations in the data set exceed reference
concentrations) before generation of the AET is appropriate.
GENERATION OF PUGET SOUND AET
-AET were originally generated for a combined measure of sediment
toxicity (i.e., either amphipod mortality [Swartz et al., 1985] or
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69
oyster larvae abnormality [Chapman and Morgan, 1983] ), and depressions
in the abundance of benthic infauna ~ at high taxonomic levels). These
AET were based on data from 50 to 60 stations sampled during the 1984-
1985 Commencement Bay Remedial Investigation (Barrick et al., 1985~.
In a 1986 project for the Puget Sound Dredged Disposal Analysis (PSDDA)
and Puget Sound Estuary Program (PSEP), AET were generated with a lar-
ger Puget Sound data base (190 samples, including Commencement Bay
data) for individual measures of toxicity (i.e., amphipod mortality,
oyster larvae abnormality, and Microtox bioassays "Williams et al.,
19863), and benthic infaunal depressions (at high taxonomic levels).
Matched biological and chemical data for an additional 10 stations from
a joint state and federal investigation of creosote contamination in
Eagle Harbor in central Puget Sound have also been incorporated (Bar-
rick et al., 19861.
The geographic distribution of samples in this data set is shown in
Figure 3. Detailed descriptions of the specific chemical tests and sta-
tistical analyses for biological indicators is provided elsewhere (Bel-
ler et al., 19861. As the result of additional refinement studies spon-
sored by the Environmental Protection Agency's (EPA) Region 10, the AET
data base has recently been expanded to include additional data on sedi-
ment chemistry, benthic infaunal abundance, and amphipod mortality for
over 100 sediment samples collected in two additional embayments of
Puget Sound, Elliott Bay and Everett Harbor. A report summarizing the
results of this refinement study is available from EPA (PTI, 1988~.
RESULTS OF VALIDATION TESTS
Selected AET generated from a 200-sample Puget Sound data base are
presented for dry-weight normalized chemical data (Table 1~. AET gen-
erated from chemical data normalized to total organic carbon have also
been tested, but are less or no more predictive of observed biological
effects than dry-weight normalized data. Such a result was not expec-
ted based on organic carbon normalization theory, which assumes that
interstitial water is the primary source of nonpolar organic contam-
inants to biota, and that, under equilibrium conditions, the distribu-
tion of nonpolar contaminants between sedimentary organic matter and
water (i.e., KoC) is constant (and predictable).
For contaminated sediments in the environment, organic carbon nor-
malization could be less predictive than dry-weight normalization if
sediment/interstitial water systems are not at equilibrium (e.g.,
because of overriding kinetic factors), if all sediment organic matter
does not have uniform affinity for hydrophobic pollutants, or if inter-
stitial water is not the predominant route of contaminant uptake. Dry-
weight normalization assumes that mass loading of a contaminant in sedi-
ment is a predominant factor influencing toxicity to benthic organisms
(although organic carbon interactions may be a secondary factor). The
AET concept does not favor one of these mechanistic explanations over
the other, but can operate whether one, a combination of the two, or
alternative mechanistic assumptions are appropriate.
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70
:~ ~~o~
~ ~~e'\~ ~~
—~ A'-;/
... ^. ..
. .
.
.r~
O 10 ~ ·. · :-~ '.-~: OLYMPIA ·: 1c
MILES - .-- 7., ·t .- . 1'
`~ /4 MAOISOH~ ~ \;..~. . `~e - Phlox -
FIGURE 3 Location of sampling sites for AET data sets.
OCR for page 71
71
TABLE 1 Continued
NOTES:
aBased on data from Beller et al., 1986 and Eagle Harbor Preliminary
Investigation (Barrick et al., 19861. Data for recent surveys in
Elliott Bay and Everett Harbor are not incorporated in these AET
because the proposed AET values were under review by the Puget Sound
Sediment Criteria Workgroup during preparation of this paper (see PTI,
1988~. Note: ">" indicates that a definite AET could not be estab-
lished because there were no "effects" stations with chemical concen-
trations above the highest concentration among "no effects" stations.
bBased on 160 stations.
CBased on 56 stations (all from Commencement Bay Remedial Investiga-
tion).
dBased on 104 stations.
eBased on 50 stations (all from Commencement Bay Remedial Investiga-
iion).
A higher AET (24,000 ~g/kg for low molecular weight PAH and
13,000 ~g/kg for anthracene) could be established based on data
from an Eagle Harbor station. However, the low-molecular-weight PAH
composition at this station is considered atypical of Puget Sound
sediments because of the unusually high relative proportion of
anthracene. Thus, the low-molecular-weight PAH and anthracene AET
shown are based on the next highest station in the data set.
gThe value shown exceeds the Puget Sound AET established in Beller et
al., (1986) and results from the addition of Eagle Harbor Preliminary
investigation data (Barrick et al., 1986~.
The value shown exceeds AET established from Commencement Bay Reme-
dial Investigation data (Barrick et al., 1985) and results from the
addition of Puget Sound data presented in Beller et al. (1986~.
Measures of Reliability
To meet the needs of ongoing sediment management programs, an ideal
approach for sediment criteria would perform well on both of the fol-
lowing two tests of reliability based on actual field data:
1 . sensitivity- -the proportion of actual environmental problems
that are predicted as problems (i.e., the complement of "false
negatives"; are all sediments exhibiting biological effects
identified using the predictive approach?; and
2. efficiency--the proportion of predicted problems that are actu-
ally environmental problems (i.e., the complement of "false pos-
itives"; are only sediments exhibiting biological effects
identified using the predictive approach?.
The concepts of sensitivity and efficiency are illustrated in Figure
4. Sediment quality values that are highly sensitive may be
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72
FIGURE 4 Measures of
reliability (sensitivity B /
and efficiency).
/
IMPACTED / o
~0
\
\
· ·\ O \
\ O \\. · / 0~
\ A
CORRECTLY PREDICTED ,
SENSITIVITY = C/B x 100
EFFICIENCY = C/A x 100 = 5/7 x 100 = 71%
. -
= 5/8 x 100 = 63%1
1
FOR A GIVEN BIOLOGICAL INDICATOR
A ALL STATIONS PREDICTED TO BE IMPACTED
B ALL STATIONS KNOWN TO BE IMPACTED
C ALL STATIONS CORRECTLY PREDICTED TO BE IMPACTED
environmentally protective but are not necessarily cost-effective.
Sediment quality values that are highly efficient may be cost-effective
and defensible in pursuing high priority remedial action but are not
necessarily protective. The concepts of sensitivity and efficiency will
be used in this paper as an evaluation tool for assessing the relia-
bility of AET.
Test of AET Predictions
As one example of a test of reliability, AET (dry weight) developed
for eight Puget Sound embayments (approximately 200 samples; Beller et
al., 1986) were used to independently evaluate new data from an
additional five embayments (including Eagle Harbor, Elliott Bay,
Everett Harbor, and two reference areas; PTI, 1988~. Stations pre-
dicted to have biological effects were identified as those stations
with one or more chemicals exceeding the AET. Only amphipod bioassay
and benthic infaunal abundance data were collected in these new sur-
veys. Microtox and oyster larvae bioassays have not been conducted
outside of Commencement Bay.
The sensitivity of 1986 benthic infauna AET in correctly identify-
ing impacted stations ranged from 71 to 100 percent, and totaled 81
percent (57/70 impacted stations) for the combined new surveys. This
sensitivity is comparable to that reported overall for the original
surveys used to calculate these AET (82 percent; Belier et al., 1986~.
The predictive efficiency of benthic infauna AET applied to different
geographic areas in the new surveys ranged from 56 to 100 percent and
totaled 74 percent (57/77 predictions) for the combined new surveys.
The sensitivity of 1986 amphipod bioassay AET in correctly
identifying impacted stations generally ranged from 60 to 100 percent,
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73
and totaled 65 percent (35/54 impacted stations) for the new surveys.
This sensitivity is also comparable to an overall sensitivity of 54 per-
cent for the original surveys used to calculate these amphipod bioassay
AET. The predictive efficiency generally ranged from 50 to 100 percent
and totaled 52 percent for the combined new surveys (in the Eagle Har-
bor survey, however, significant amphipod mortality was observed at one
of the five predicted stations).
Recalculation of AET to include this independent data set of five
embayments in the generation of AET automatically results (by defini-
tion of AET) in 100 percent efficiency for both biological indicators.
The sensitivity of the proposed amphipod AET is 58 percent, and the
sensitivity of the proposed benthic infauna AET is 74 percent. There-
fore, for the 13 Puget Sound embayments, approximately 85 percent of
the benthic infauna stations (170 of 198) and amphipod bioassay sta-
tions (238 of 283) are in accordance with the predictions of the pro-
posed AET values for these indicators (i.e., they do not exhibit
adverse effects when all concentrations are less than AET values, and
do exhibit adverse effects at chemical concentrations above the AET
values).
An additional test of the reliability of AET has been conducted as
they might be used in management programs. AET were developed for each
chemical of concern for multiple biological indicators because
different kinds of biological indicators respond in different ways to
the same chemical exposure. For example, an assessment of acute lethal
toxicity to contaminated sediments is expected to result in different
sediment quality values than an assessment of acute or chronic sub-
lethal toxicity to the same sediments. Acute or sublethal responses by
different biological species also can differ. For example, the lowest
AET (LAET) for one chemical (e.g., PCBs) may be established by the
Microtox bioassay and for another chemical (e.g., lead) by benthic
infaunal analyses. The LAET is expected to be protective of a range of
biological effects. Used in combination, the multiple AET can also pro-
vide a preponderance of evidence for associating environmental effects
and chemical contamination. Above the highest AET (HAET) for a range
of biological indicators there is a high degree of confidence that sed-
iments will fail biological testing regardless of the test. In recent
(1988) evaluations with the 300-sample data base for 13 embayments,
LAET were from 90 to 94 percent sensitive in correctly predicting all
known biological effects in the data base (depending on the particular
biological test). By definition, HAET based on this 300-sample data
base were 100 percent efficient in only predicting actual problem sed-
iments (i.e., all of the sediments actually exhibited the predicted
effects).
Application of Puget Sound AET to other coastal areas of the United
States would require validation through at least some site-specific
chemical/biological testing. An initial evaluation based on predic-
tions using Puget Sound AET and comparing with limited biological
effects data from outside of Puget Sound has recently been reported
(PTI, 1987).
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74
APPLICATION OF AET TO SEDIMENT MANAGEMENT IN PUGET SOUND
The reliability of the AET approach (particularly AET normalized to
dry weight) at predicting biological effects indicates its potential
utility as a tool for sediment quality management. Uses for which the
AET approach is well-suited include
determination of the extent and relative priority of potential
problem areas to be managed,
identification of potential problem chemicals in impacted sed-
iments,
prioritization of laboratory studies for determining cause-
effect relationships, and
with appropriate safety factors or other modifications, for use
in regulatory programs and as "trigger levels" for screening
decisions on the need for further chemical or biological testing
of sediments.
Sediment criteria based on definitive laboratory cause-effect
studies and field verification studies will continue to be active
research issues for many years. In the interim, field effects-based
approaches using the AET concept provide decision tools that have the
following characteristics:
2.
3.
. developed empirically from field
provide chemical-specific values,
supported by a variety of biological indicators including acute
lethal and sublethal bioassays and in situ benthic infaunal
analyses reflecting acute and/or chronic effects,
4. driven by statistically significant adverse effects,
5. supported by noncontradictory evidence of adverse effects within
a given data set.
Sediment quality values based primarily on AET have been integrated
into several Puget Sound programs (Figure 5~. These chemical values
are not used in isolation; in all cases site-specific biological
testing is used to supplement or verify the predictions based on sedi-
ment quality values. Problem area and problem chemical identification
was the focus of the Commencement Bay Remedial Investigation, and is
currently a major aspect of the urban bays program of PSEP. This-prob-
lem identification establishes a basis in taxies action plans for prior
itizing potential remedial actions according to the environmental signi
ficance of contamination. Problem identification requires sensitive
sediment quality values to ensure that all potential problems are con-
sidered.
The purpose of subsequent sediment remedial action is to mitigate
contamination in problem areas and thereby to eliminate associated
adverse biological effects. In the Commencement Bay Feasibility Study,
sediment quality values based on the lowest AET for a range of biolog-
ical indicators were developed as potential target cleanup goals (not
considering cost or technical feasibility). These goals correspond to
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75
~ Commencemen t Bay S,uperfund ~
Chemical/ Predictive FS
Biological =~? Relationships c=: > Goals L-1—
Analyses
Site-Specific CLEANUP
Refinement L .,- DECISION
Embayment Puget Sound r PROBLEM
Chem'Cal/8iolo9ical [~no predictions ~ I- ;> DEFINITION
tPuge! Sound Dredged Disposal Analysis|
Tier 1 I.. Tier 2
Need Taste? Id> Chemistry
Predictions
r Tier 3
:> Biological
Confirmation
—A> DISPOSAL
~ DECISION
FIGURE 5 Use of sediment quality values based on AET in Puget Sound
remedial action programs.
those sediment contaminant concentrations that are not predicted to
result in adverse effects according to the biological effects indica-
tors used to generate AET. Although the goals may not be totally pro-
tective of all potential environmental problems, they are sensitive to
currently measurable effects, including effects originally used to iden-
tify problem areas in the remedial investigation.
A higher (i.e., less stringent) level for cleanup was identified as
an alternative to the target cleanup goal. This alternative cleanup
level was recommended for use should the target goal be infeasible at a
particular problem area. The higher concentration alternative would be
more technically or economically feasible than target goals because it
would tend to require smaller volumes of sediment for remedial action.
Instead of using an arbitrary multiple of the target goals, this alter-
native was generally based on the highest AET for the range of biolog-
ical indicators (i.e., the concentration of each chemical above which
all biological effects accounted for by AET are predicted to
occur). This alternative cleanup level is expected to be efficient in
addressing major contaminant problems.
Dredged material disposal guidelines developed by PSDDA incorporate
sediment quality values to address both sensitivity and efficiency con-
cerns (Phillips et al., 1988~. PSDDA guidelines establish a chemical
screening level (SL) above which biological testing must be performed
to establish the suitability of dredged material for disposal at uncon-
fined, open-water sites. The SL is lower or equal to the lowest AET
for a range of biological indicators and is intended to be sensitive
(i.e., fully protective of the environment). Contamination below the
SL is assumed to be acceptable without confirming biological tests. A
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76
maximum level (ML) was also established by PSDDA as the highest AET for
a range of biological indicators. The ML was intended to indicate a
level of chemical contamination above which there was a preponderance
of evidence for adverse effects. Biological testing above the ML is
always expected to confirm the prediction of unacceptable biological
effects, and is not required.
It is recognized that site-specific factors could anomalously
influence predictions of biological effects based on sediment quality
values. Therefore, in evaluating final requirements for sediment remed-
ial action, selected verification of predicted effects is recommended
(extensive biological testing of each sample may not be feasible). For
example, in the Commencement Bay Feasibility Study an option is pro-
vided to appeal the site-specific prediction of biological effects.
This biological testing program is consistent with the intent of other
regional contaminated sediment management programs, including PSDDA
disposal guidelines. Comparable tests and test protocols are recom-
mended, and site-specific biological information overrides predictions
of biological effects based on chemical data. Some specific differ-
ences between regional programs in the interpretation of biological
test results may exist because of differing program goals (e.g., clean-
up of nearshore sediments in a multiuse environment versus assessment
of the suitability of potentially contaminated material for disposal at
a designated deep-water site).
CONCLUSIONS AND RESEARCH RECOMMENDATIONS
Sediment remedial action is controversial because few objective
criteria exist for quantitatively assessing more than the economic
feasibility of remedial actions. A commonly expressed concern is that
cleanup or disposal guidelines based solely on the most sensitive bio-
logical effects would likely be economically or technically infeasible.
In any case, there is a strongly perceived need for a preponderance of
evidence to implement remedial action.
To address these concerns, a range of sediment quality values--
such as those incorporated into existing Puget Sound programs--is recom-
mended. The low end of this range is protective of a wide range of
adverse biological effects. At the high end of this range, a prepon-
derance of evidence exists for the prediction of adverse biological
effects by multiple indicators. These tradeoffs required by balancing
environmental protection and remedial action feasibility are reflected
in the sensitivity and efficiency of sediment quality values, which
should both be evaluated as part of their validation or in any research
effort.
REFERENCES
Barrick, R. C., D. S. Becker, D. P. Weston, and T. C. Ginn. 19850 Com-
mencement Bay Nearshore/Tideflats Remedial Investigation, Final
Report. Prepared for the Washington [State] Department of Ecology
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77
and U. S. Environmental Protection Agency. EPA-910/9-85-134b. Belle-
vue, Wash.: Tetra Tech, Inc. 2 volumes + appendices.
Barrick, R. C., H. R. Belier, and M. Meredith. 1986. Eagle Harbor Pre-
liminary Investigation, Final Report. Prepared for Black & Veatch
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Representative terms from entire chapter:
puget sound
