United States
Environmental Protection
Agency
 Environmental Research
 Laboratory
 Duluth MN 55804
Research and Development
 EPA/600/S3-85/045 Jan. 1986
Project  Summary
An  Evaluation  of
Environmental Stress
Imposed by a  Coal  Ash  Effluent

(Catherine E. Webster, Anne M. Forbes, and John J. Magnuson
  Effluent discharged from the coal ash
settling basin of the Columbia Electric
Generating Station (Wisconsin) modi-
fied water chemistry (resulting in in-
creased concentrations of trace metals,
suspended solids and dissolved mate-
rials) and substrate quality (precipitation
of a chemical  floe) in the receiving
stream, the ash pit drain.
  A sequence  of macroinvertebrate
community responses to this effluent
was documented: (1) decline in total
abundance and taxa 4 months after
effluent discharge began in 1974; (2)
loss of most macroinvertebrates  in
1977; and (3) recovery of the commun-
ity by 1980, although a shift in domi-
nance to more tolerant species, lower
total abundance and a slight decline in
diversity suggested continued sublethal
influence of the coal ash effluent. The
variation in the severity of stress sug-
gested by these changes was attribut-
able to a series of generating station
activities related  to coal treatment,
effluent discharge characteristics, and
dredging of accumulated floe in the
upstream drainage ditch. The effluent
response threshold (1,000 yumhos con-
ductivity), accurately predicted the re-
covery of ash pit drain  macroinverte-
brates when effluent concentrations fell
below threshold. As acute toxicity did
not completely explain the reductions in
macroinvertebrate  abundance, we
examined  behavioral  avoidance of
modified  habitats  as  an alternative
hypothesis. Results from two studies,
one a comparison of macroinvertebrate
drift rates in coal  ash  modified and
reference conditions in  laboratory
streams, the second, measurement of
in-situ reponses to intermittent effluent
discharge, did not support the hypoth-
esis. However, these studies did provide
evidence for sublethal effects when coal
ash effluent concentrations were below
the response threshold.
  This Project Summary was developed
by  EPA's Environmental Research
Laboratory, Duluth, MN, to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).

Introduction
  Discharge of coal ash  supernatants
from wet storage ponds at  coal-fired
power plants  can  have  a  significant
impact on aquatic ecosystems (Cherry et
al. 1979, Coutant et al. 1978). Acute and
sublethal impacts on aquatic organisms
can occur in response to one or more of
the stresses typical ly associated with coal
ash effluent discharge: (1) the addition of
elements to the ecosystem,  including
some potentially toxic heavy metals; (2)
increases in suspended solids; (3) changes
in pH and chemical balance; (4) sedimen-
tation of  chemical solids; and (5) absorb-
tion  of P by fly ash interfering  with
nutrient cycling (Guthrie et al. 1982, Roy
etal. 1981).
  The Columbia Electric  Generating
Station near Portage, Wisconsin, consists
of two coal-fired operating units,  each
capable of producing 527 MW per day. Fly
ash from Unit I and bottom ash from both
units are slurried into a series of settling
basins. Following acidification, the coal
ash effluent is discharged into a stream,
the ash pit drain, situated in a floodplain
of the Wisconsin River. This discharge

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'9*.
       severely modified stream habitats through
       precipitation of a chemical floe and in-
       creased concentrations of suspended and
       dissolved materials and some potentially
       toxic heavy metals(Magnuson et al. 1980,
       Andren et  al.  1977).  Conductivity, ele-
       vated in the coal ash effluent by adding
       NaHCOa to the pulverized coal, provided
       an easily monitored measure of effluent
       strength. Magnuson  et al (1980) and
       Forbes  et al. (1981) found that stream
       habitats receiving effluent concentrations
       exceeding 1,000 //mhos conductivity ex-
       hibited  lower  macroinvertebrate densi-
       ties.
         The summary incorporates results from
       several studies (Webster, 1983; Webster
       et  al.  1981;  Forbes  et al.  1981; and
       Magnuson et al.  1980)  to  document
       changes in stream macroinvertebrate
       community structure from the pre-opera-
       tion state through severe stress and later
       recovery. The influence of generating
       station activities on the severity of stress
       is  discussed.  Also presented are  the
       results of a laboratory study investigating
       an alternative behavioral mechanism
       explaining depletion of the community by
       habitat avoidance through increased drift.
       A final  study attempted  to  verify  the
       laboratory  drift results in the field by
       monitoring changes in  macroinvertebrate
       distributions during an intermittent pat-
       tern of effluent discharge.

       Materials and Methods

       Behavioral Response
       Methods to Coal Ash Effluent

       Drift Experiment
         Examinations of the effects of pollution
       on stream macroinvertebrates have gen-
       erally focused on acute toxicity.  Less
       attention has  been  directed toward in-
       vestigating behavioral  responses to sub-
       lethal habitat modifications by pollutants.
       Behavioral drift has been recognized as a
       mechanism by which macroinvertebrates
       can avoid unfavorable environments
       (Corkum et al. 1977).  Since declines in
       abundance and species diversity in ash
       pit drain habitats receiving the coal ash
       effluent could not be completely explained
       by direct toxicity, we  hypothesized that
       the field distributions might be at least
       partially explained by  habitat  avoidance
       through an increased drift response.
         We measured macroinvertebrate drift
       in plexiglas laboratory streamscontaining
       combinations  of substrate  and water
       collected from two  sites,  one contami-
       nated by the coal ash effluent (APD-1)
and the other an unaffected reference
site in Rocky Run Creek (RRC-2) (Figure
1). A third treatment of  food  addition
(Acer saccharum leaves  incubated in
Rocky Run Creek  for  4  months) was
included to investigate possible food
limitation in the coal ash effluent-modified
substrates.
  Treatment combinations were random-
ly assigned  to  the eight laboratory
streams. Substrates were added to the
stream channels(11 x 52 cm) to a depth of
2 cm and  the streams filled with the
appropriate treatment waters to a depth
of 9  cm.  Shredded leaf  material was
partially  buried  at the surface of the
substrates in those streams that received
the food treatment. A total of 37 individ-
uals(1 OAsellus racovitzai,  10 Gammarus
pseudolimnaeus, TOCorixidae, 5 Ephem-
eroptera, and 2 Trichoptera) were placed
in the upstream third  of each stream
channel  and allowed  to acclimate to
experimental conditions without current
for 2  h.  After starting water circulation
(generated by airstones), the drift nets at
the end of each  channel were emptied
and drifting organisms counted  after 1 h
and every 3 h thereafter for 48 h. Two
replicate experiments were run in March
1979 in a controlled environment room.
Temperature (5.0°C) and photoperiod
(12L12D) approximated field conditions.
Laboratory streams were illuminated by
15-W fluorescent lamps.
  The effects  of the three treatments
(substrate, water and food) at two levels
each  on macroinvertebrate drift were
analyzed using a 23 factorial design. Only
48 h drift data for Asellus racovitzai and
Gammarus pseudolimnaeus were ana-
lyzed as the high drift rates of other taxa
precluded use of ANOVA.

Substrate Choice Experiment
  In August 1979, the substrate prefer-
ences of Gammarus pseudolimnaeus
offered a choice between sediments from
the coal  ash effluent-modified  site  and
from the reference site were investigated.
Plexiglas chambers (30 x 16 x 11  cm)
contained substrates on either  side of a
2.0cm high longitudinal divider. Twenty
chambers were randomly placed in  re-
spect to a light source (15-W incandescent
lamps) in a constant temperature water
bath.  Ten chambers received only refer-
ence substrates and served as controls.
The other 10 chambers contained  two
substrates randomly assigned to the right
or left side.  On one side, 2.0  cm of
reference substrate was added; on the
other, ash  effluent-modified substrates
were layered over reference substrates.
All chambers contained fresh reference
site water and were aerated. Experimental
conditions  of temperature (22°C)  and
photoperiod  (14L:100) approximated
ambient field conditions.
  Ten Gammarus pseudolimnaeus were
introduced  into each chamber, five per
side. At the end of 48 h  the chamber
halves were  separated  by a plexiglas
divider and the Gammarus settling on
each  side were recovered. Data were
pooled separately for treatment and for
control chambers and analyzed using Chi
square.

Responses to Intermittent
Coal Ash Discharge
  The intermittent discharge of coal ash
effluent from the generating station  pro-
vided an opportunity to measure macro-
invertebrate  responses to an  abrupt
change in water quality.  In September
1979, we collected samples on the last 2
days  of a  2-week  pause in effluent
discharge and on days 1, 2, 4, and  8 of
discharge. Three sites were sampled: a
reference site in Rocky Run Creek (RRC-
2) and two modified sites, APD-1  and
APD-2 (Figure 1). Triplicate samples for
macroinvertebrates were collected at
each  site with  a  PONAR dredge. In
addition, we measured conductance,
methyl orange  alkalinity, turbidity, pH,
total filterable  residue (TFR), current
speed, water depth, and percent floe in
the top 8 cm of sediment.
  Multiple regression and ANOVA were
used  to detect significant changes in
macroinvertebrate abundance related to
effluent discharge.  Two  models were
compared.  Model I  had  independent
variables for site (APD-1, APD-2  and
RRC-2) and time (before and after  dis-
charge began). Model II  included the
above variables plus an  independent
variable for the site by time interaction.
The  model providing  better fit to the
dependent variable (measures of macro-
invertebrate  abundance  and species
richness) was determined by calculating
the F-ratio between the regression sum
of squares from the ANOVA of the two
models. Two alternative hypotheses were
tested: (Ho) the site by time interaction
was  not significant (i.e., non-significant
F-ratio) and, thus, any changes  in the
invertebrate community  following the
resumption of effluent discharge could
not be distinguished from natural vari-
ability exhibited at the reference site; (Hi)
the site by time interaction was significant
(significant F-ratio) and the changes at
the experimental sites following resump-

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tion of effluent discharge were measur-
ably different from the reference site and
could be attributed  to exposure to the
effluent. Where F-tests were significant,
a multiple comparison  test  identified
individual sites with significant differ-
ences in before vs.  after macroinverte-
brate populations. This test provides 95%
confidence  intervals  for  a  particular
difference in means between two treat-
ments within an ANOVA.
  The dependent variables analyzed in
this fashion were total macroinvertebrate
abundance, Isopoda,  Amphipoda  and
Trichoptera abundances, and number of
taxa. The taxa from the three replicate
PONARs were pooled for each date. Other
variables were  calculated as the mean
from the three replicate PONARs follow-
ing transformation to natural logs [In (x +
1)].
                             Effects on Community Structure
                              Magnuson  et  al.  (1980) documented
                             changes in macroinvertebrate community
                             structure from  the preoperation year
                             (1974) through subsequent post-opera-
                             tion years (1975, 1977).  We followed
                             their methods  in 1980 to determine
                             whether  recovery  had  taken place  in
                             response  to lowered effluent concentra-
                             tions. Site APD-1   (Figure 1),  highly
                             impacted  by  the effluent in 1977, was
                             chosen for the 1980 study.
                              Two types  of artificial substrate sam-
                             plers were used. Basket samplers made
                             of closed cylinders of chicken wire (20 x
                             30 cm)filled with 4.5 kg of limestone rock,
                             were suspended 10 cm above stream
                             sediments at  APD-1. Macroinvertebrates
                             were collected monthly from May through
                             September in 1974, 1975 and 1980. A
                             modified Hester-Dendy artificial substrate
                                                          APD-1
Figure 1.
Columbia Electric Generating Station study site. Sampling locations marked with
closed circles. Arrows denote direction of flow. The star marks the point of coal ash
effluent discharge from the settling basin into the effluent ditch (dashed line) which
joins with the ash pit drain /solid line).
consisting of a Tuffy®* scrub pad held
between two, 8-cm diameter masonite
plates with an eyebolt,  was used to
evaluate differences between macroin-
vertebrate populations upstream (APD-3)
and downstream (APD-1) of the effluent
in June 1977 and June 1980. Samplers
were suspended 20 cm over stream
sediments and allowed to colonize for 1
week.

Results

Behavorial Responses to
Coal Ash Effluent
  The hypothesis that aquatic macroin-
vertebrates would drift at higher rates in
laboratory streams with modified condi-
tions was not supported by the patterns of
drift observed for Gammarus andAsel/us.
The  highest drift  occurred in stream
chambers containing substrate and water
from the reference site. Asellus racovitzai
drifted more in response to food addition
compared to no food addition and in
reference substrates compared to modi-
fied substrates. The significant response
to substrate should be considered as part
of the substrate-water interaction. Drift
was significantly higher in streams where
substrate and water were from the refer-
ence  site compared to all other stream
chambers, while drift in  streams with
modified substrate  and reference water
was significantly lower. Except for a non-
significant effect of food addition, Gam-
marus pseudolimnaeus exhibited similar
responses. Drift increased in  the refer-
ence  substrate and the substrate-water
interaction was significant. Again, the
highest  drift occurred in laboratory
streams  containing both  substrate and
water from the reference site.
  In the substrate choice experiment, the
hypothesis tested was that Gammarus
pseudolimnaeus would display no pref-
erence  for  modified substrates. Chi-
square analysis of data from the control
chambers showed that amphipods did not
discriminate between  chamber sides
(right vs. left or position in respect to light
source)after48 h. Likewise, nodifference
was observed between  modified  and
reference substrates (X2 = 0.40 for pooled
data from 10 chambers).

Responses to Intermittent
Coal Ash Discharge
  Changes in water  chemistry at the
experimental sites following effluent dis-
                                                                               'Mention of trade names or commercial products
                                                                                does not constitute endorsement or recommendation
                                                                                for use.

-------
charge paralleled those reported in earlier
studies (Magnuson et al. 1980). Conduc-
tivity, turbidity and total filterable solids
(TFR) increased, while pH and alkalinity
declined.  Water  temperature, current
speed, stream depth  and floe (%) in
sediments did not  show appreciable
changes. At the reference site,  stream
habitat variables  were relatively stable
throughout the study period.
  Correlations between water chemistry
parameters and effluent discharge rate
suggested differences in response time at
the two experimental sites. At site APD-1
all the water chemistry parameters were
significantly correlated  with discharge
rate. In contrast, at APD-2, located further
downstream, only turbidity and TRF were
significantly correlated  with discharge
rate.  Other parameters (conductivity,
alkalinity  and pH)  were  more  closely
related to the discharge rate  of  the
previous day. Thus, while organisms at
APD-2 may have been exposed to some
precursor  of the effluent in the form of
increased  suspended material when dis-
charge began on October 5, there was a
lag of 1 day in exposure to the chemical
components of the  coal  ash effluent.
Figure 2 shows daily values for conductiv-
ity and total filterable residue at each site
during the study period.
  Beginning October 6, the second day of
coal ash effluent discharge, macroinver-
tebrate abundance increased  at APD-1
(Figure 2). This  was due primarily to
higher densities of Asellus racovitzaiand
secondarily to  the  amphipods Hyallela
azteca and Crangonyx sp. Of the remain-
ing 27 taxa sampled at the site, four were
not collected following effluent discharge,
while nine were  present only after dis-
charge began. Most of these taxa were
rarely encountered; only Phryganea sp.,
Oecetis sp. and Nemotelus sp. were col-
lected in more than three PONAR sam-
ples. In contrast to the response at APD-
1, total macroinvertebrate abundance at
APD-2 declined following effluent  dis-
charge (Figure 2). This decline began on
October 5 when the amount of suspended
material  increased, but there was no
chemical  alteration  of  water  quality.
Decreases in densities of Hyallela azteca
and, to a lesser extent, Asellus racovitzai
accounted for much of the response. Of
the  12 other taxa collected at this  site,
only Cheumatopsyche sp., Chironomidae
and Hydroptilidae were present  in three
or more PONAR samples. No appreciable
differences between before  and after
populations for these taxa were apparent.
The macroinvertebrate community at the
reference site, RRC-2 remained relatively
stablethroughout the study period(Figure
2). As at the two experimental sites, the
dominant macroin vertebrates were Asel-
lus racovitzai and  Hyallela azteca. The
remaining  community  members were
comprised of 10 less common taxa.
  Model II provided better fit to the total
macroinvertebrate  abundance, Isopoda,
Amphipoda and Trichoptera data than did
Model  I (Table 1). The site by  time
interaction explained no additional vari-
ation of the number of taxa. Upon further
analyses with the  multiple comparison
test, only  a few individual site-specific
changes were  significant; increases at
APD-1  and decreases at APD-2 in total
                            Table 1.   Macroinvertebrate Response to
                                      Resumption of Coal Ash Effluent
                                      Discharge*
Dependent
Variable
Total abundance
Number of taxa
Isopoda
Amphipoda
Trichoptera
F-ratio
(2.9) d.f.
27.00
1.61
6.53
26.69
4.93
Level of
Significance
P < 0.001
NS
P<0.05
P < 0.001
P < 0.05
                            'Given are the F-ratios.  comparing the re-
                             gression sum of squares from the A NOVA of
                             the two models and the level of significance
                             (NS = not significant) of these F ratios for five
                             dependent variables.
                             Ash Pit Drain
                     3.7km                5.4km
                                                  Reference
                                                     Site
      8
      •c
         800
         400
          40
          20
    j,   7000

    | I  700
    .> o
    I N   70
          20
      |   10
      I
                                        Conductivity
                                    Total Filterable Solids
      +-~4-
                                           I    I   I
                                    Macroinvertebrates
                                           Taxa
                                                                i    i   r   i
                                                                    i   i   i
-202468-2
                                                     8-202468
                                       024
                                          Time
                              (Days before and after initiation of
                                    effluent discharge)

 Figure 2.    Changes in conductance,  total filterable solids, macroinvertebrate density and
            number of taxa upon resumption of coal ash effluent discharge. A sh pit drain sites
            3.7 km and 5.4 km refer to APD-1 andAPD-2, respectively. The vertical dashed line
            indicates the first day of discharge. Macroinvertebrate density (log scale) shows
            number of individuals in each of three basket samplers indicated by dots; the solid
            line connects the median. Macroinvertebrate taxa represent pooled value for three
            samples.

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individuals and Amphipoda  abundance
following  effluent  discharge. Although
Model II provided better fit for Isopoda and
Trichoptera data, variability within cells
apparently  masked any  site-specific
changes. No significant before vs. after
differences were measured at RRC-2.
Effects on Community Structure
  The following sequence of macroinver-
tebrate responses to habitat modification
by the coal  ash  effluent was observed
from colonization of artificial substrates:
(1) decline in total abundance and number
of taxa 4 months after effluent discharge
began in 1974; (2) near disappearance of
all macroinvertebrates in 1977; and (3)
recovery of most taxa in  1980. The
macroinvertebrate  community in  1980,
while similar in taxonomic composition to
the 1974 pre-operation community, ex-
perienced significant shifts in absolute
abundance as well as in relative abun-
dances  of individual taxa. The resulting
community was  characterized by  lower
total  abundance  and domination by
Asellus  racovitzai.
  The shift from a community dominated
by hydropsychid caddisflies in 1974-1975
to one dominated by the isopod Asellus
racovitzai in 1980, was one of the most
striking  responses documented at the
site. Hydropsychid caddisflies function as
collector-filterers, constructing  nets
which retain algae, detritus, animals, and
small particles carried by stream currents.
The  accumulation of a  chemical floe
coating  stream substrates substantially
reduced the available habitat for  these
caddisfly larvae and probably played an
important role in their disappearance in
1977. In contrast, densities of the isopod
Asellus  racovitzai greatly increased after
recovery.  Numerous  individuals  were
collected in 1979 PONAR samples and in
1980 basket samplers. Substrate modifi-
cation may not have been as detrimental
to Asellus racovitzai as the  Hydropsy-
chidae.
  The comparison  between colonization
of substrates at the upstream  (APD-3)
and downstream (APD-1) sites in the ash
pit drain in  June  1977 and  1980, are
shown  in Figure 3.  While there were
dramatic differences between the two
sites  in total  macroinvertebrate abun-
dance and number of taxa  in 1977, no
substantial differences in these param-
eters were apparent in 1980.
  Forbes et al. (1981) derived a biological
response threshold  based  on  effluent
conductivity from a series of laboratory
and field  studies.  Ash  pit drain sites
receiving  concentrations of coal ash
chemicals exceeding 1,000 //mhos con-
ductance were unsuitable for macroin-
vertebrate  colonization.  As shown  in
Figure 3, effluent concentrations at site
APD-1 in  1977  clearly  exceeded the
habitable limit. Conductivity was nearly
2,500 //mhos, significantly higher than
the 1,000 //mhos response threshold. The
lack of invertebrates mirrors the severity
of environmental  stress.  When  effluent
concentrations fell  below the 1,000
//mhos threshold in 1980, total abundance
and number of taxa were similar  to
upstream values.

Discussion
  Environmental stress in the coal ash
drainage system of the Columbia Electric
Generating Station was evaluated using
a combination of biological and chemical
indicators.  Severly stressed sites were
characterized by a substantially reduced
macroinvertebrate fauna and by coal ash
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Figure 3.
1977   1980

Comparison between conductiv-
ity, macroinvertebrate abun-
dance and number of taxa at
upstream (APD-3) and down-
stream (APD-1 j sites in the ash
pit drain in 1977 and 1980.
effluent concentrations exceeding the
biological  response threshold of 1,000
//mhos conductivity (Forbes et al. 1981). A
temporal variation  in  the  intensity of
environmental stress was detected at the
study site over the 7-yr study period. A
partial recovery was documented 3 years
after a depauperate fauna was observed.
  Conductivity provided an easily moni-
tored indicator of effluent strength within
the drainage system. The major sources
of conductivity  in  the effluent were
sodium  bicarbonate (1975-78) and am-
monium bisulfate (1979-80) added to the
pulverized coal to increase the efficiency
of electrostatic  precipitator operation.
The transport  of these compounds  with
the fly ash through the coal ash settling
ponds and into the ash pit drain elevated
conductance values in proportion to the
concentration  of the effluent. Thus, the
main generating station activities influ-
encing  conductivity  values were the
frequency and rate of discharge(Table 2).
The highest  conductivity values  (median
1805 //mhos)  were measured in 1977
when discharge volume per day and the
frequency of discharge were at or  near
peak. Only five of 25 conductivity obser-
vations  made during that year were less
than the 1,000 A/mhos biological response
threshold. By 1979 and 1980, when the
frequency and rate of discharge  had
declined, conductivities rarely exceeded
this.
  The extent of floe deposits varied over
the study period similar to conductivity.
The thick layers of floe that accumulated
on  stream  substrates  in  1977 were
substantially diminished by 1979  and
were rarely observed in backwater pools
in 1980. The reductions of floe formation
by 1979 were associated with declines in
effluent discharge (Table 2). Removal of
accumulated floe in the effluent ditch
immediately below the discharge point by
generating station personnel also prob-
ably reduced the downstream transport
of precipitated materials. The switch from
HjSCu addition to CO2 bubbling for efflu-
ent pH  control in 1979 may also have
lessened precipitation  of the dissolved
metals which formed the floe.
  Macroinvertebrate community struc-
ture at the ash pit drain study site reflected
the severity of  environmental stress
predicted by the  chemical indicators. In
1977 when conductivities were predom-
inantly above threshold and floe deposits
were extensive, only a few macroinverte-
brates colonized artificial substrates. Both
chemical and  biological indicators  em-
phasized the severely stressed conditions
at site APD-1  during that year. When

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Table 2.   Observations of Conductivity and Extent of Floe Deposits at Site APD-1 and
          Generating Station Activities Potentially Influencing Ash Pit Drain Habitats.
          Discharge Rates are Mean Daily Discharge forYear; Conductance isMedianforYear.
Station Operations
Year
1975
1977
1979
1980
Discharge
(10s liter/day)
14
19
10
9
Coal
Treatment
None
NaHCOa
NHtHS04
NH,HSOt
pH
Control
H£0<
H£0t
H,$0<
CO4
Floe
Removal
No
No
Yes
Yes
Indicators
Conductance
(umhos)
400
1800
600
500
Floe Deposits
No observation
Extensive
Diminished
Rare
conductivities declined below threshold
and floe deposits diminished in 1979-80,
many macroinvertebratetaxa recolonized
the previously depauperate site.
  No evidence was found for behavioral
avoidance of coal ash-modified habitats
in the 1979 laboratory drift study or from
in situ responses to intermittent discharge
patterns. Contrary to the hypothesis that
macro!nvertebrates avoid habitats modi-
fied  by  the coal  ash effluent through
increased drift, the drift of Gammarus
pseudolimnaeus and Asellus racovitzai
was uniformly lower in laboratory streams
where substrate, water, or both were
from the modified site. This result sug-
gests that these species were affected by
chemical constituents of  the  coal ash
effluent present in sediments and in the
water even though concentrations were
less than threshold. Habitat modifications
were less severe  in  1979 and the fall in
situ study demonstrated that a community
dominated  by  Asellus  racovitzai and
Hyallela azteca had recolonized the ash
pit drain. The coal ash-modified  habitat
simulated in the laboratory streams may
not  have represented the severity of
environmental  stress that occurred in
1977 or accurately reproduced the field
condition.
  The reduced drift  response  measured
in the laboratory in  1979 could have
resulted from a preference for the modi-
fied over the reference conditions or from
a reduction in activity in modified habitats.
Preference for the modified habitat seems
unlikely. When  presented a choice,
Gammarus pseudolimnaeus did not dis-
tinguish between modified and reference
substrates. The coal ash effluent, which
contained  sublethal concentrations of
several heavy metals, may have depressed
the physiological activity of the  stream
invertebrates studied. Sublethal  effects
on arthropod physiology following expo-
sure to  the same  effluent have been
documented (Magnuson et al. 1980).
  Intermittent discharge of effluent may
also sublethally influence ash  pit drain
macroinvertebrates already acclimated to
coal ash chemicals. Although responses
were inconsistent, significant changes in
abundance were  observed  at  the two
experimental sites. Densities increased
at site APD-1  after effluent discharge
resumed. This site, located below a culvert
and closer to the discharge point, may
have served as a refuge for invertebrates
disturbed at  upstream locations. In con-
trast, macroinvertebrate abundances de-
creased at site APD-2  located further
downstream in a floodplain forest, a less
stable habitat subject to seasonal fluctu-
ations in water levels.
  Much attention has been focused on
other serious  environmental  problems
associated with the  operation of coal-
fired power plants, including emissions of
sulfur oxides contributing to acidic depo-
sition,  release  of thermal  discharges,
entrainment, and chlorine toxicity. Envi-
ronmentally sound disposal of two of the
major byproducts of coal consumption—
power plant aggregate (bottom ash and
slag) and fly ash—is likely to become an
equally pressing concern as the volume
of waste  being  generated increases.
Although the Federal Clean  Water Act of
1977 prevents newly constructed coal-
fired power plants from using wet storage
of ash residues, this method of disposal
was prevalent prior to passage of the Act.
  Coal ash wastes have been identified
as potentially hazardous pollutants due to
their  high suspended solids load,  toxic
element concentrations, and  extremely
acid or alkaline nature. The impacts on
the aquatic ecosystems to which they are
discharged can be considerable.  While
this and  other studies demonstrate  a
relatively  rapid recovery from a severely
stressed  condition,  loss  of sensitive
species and sublethal effects may occur
at lower  exposure levels.  The  results
support the  need for strict control on the
amount of effluent discharged into lotic
environments.

References
Andren, A., M. Anderson, N. Loux, and R.
  Talbot. 1977. Aquatic chemistry, p. 9-
  35. In: Documentation of environmental
  change related to the Columbia Electric
  Generating  Station. Eleventh Semi-
  Annuaf Report. Report 92. Institute for
  Environmental Studies,  University of
  Wisconsin-Madison.
Cherry, D. S., S. R. Larrick, R. K. Guthrie,
  E. M. Davis, and F. F. Sherberger. 1979.
  Recovery of invertebrate and vertebrate
  populations in a  coal  ash stressed
  drainage system. J. Fish. Res. Bd. Can.
  36:1089-1096.
Corkum, L. D., P. J. Pointing, and J. J. H.
  Ciborowski. 1977.  The influence of
  current velocity and substrate on the
  distribution and drift of two species of
  mayflies (Ephemeroptera). Can. J. Zool.
  55:1970-1977.

Coutant, C. C., C. S. Wasserman, M. S.
  Chung, D. B. Rubin, and M. Manning.
  1978. Chemistry and biological hazard
  of a coal ash seepage stream. J. Water
  Poll. Control Fed. 50:747-753.
Forbes, A. M., J. J. Magnuson, and D. M.
  Harrell. 1981. Effects of habitat modifi-
  cations  from coal ash effluents on
  stream macroinvertebrates. p.  241-
  249. In: LA. Krumholz(ed.)Warmwater
  Streams Symposium. American Fisher-
  ies Society. Washington, DC.
Guthrie, R. K., E. M. Davis, D. S. Cherry,
  and J. R. Walton. 1982.  Impact of coal
  ash from electric power production on
  changes in water quality. Water Res.
  Bull. 19:135-138.
Magnuson, J. J.,  A. M. Forbes,  D. M.
  Harrell, and J. D. Schwarzmeier. 1980.
  Responses of stream invertebrates to
  an ash pit effluent. Wisconsin Power
  Plant  Impact Study. EPA/600/3-80/
  081. U.S. Environmental  Protection
  Agency. Cincinnati, OH.
Roy, W.  R., R. G. Thiery, R. M. Schuller,
  and J. J. Suloway. 1981. Coal fly ash: A
  review of the literature and proposed
  classification system with emphasis on
  environmental impacts.  Environ. Geol.
  Notes 96. Illinois Institute of Natural
  Resources. Chicago, IL 69 p.
Webster, K. E. 1983. Responses of stream
  macroinvertebrates to environmental
  stress imposed by a coal ash effluent.
  M.S. Thesis. University of Wisconsin,
  Madison, Wl. 88 p.
Webster, K. E.,  A. M. Forbes, and J. J.
  Magnuson. 1981. Behavioral responses
  of stream macroinvertebrates to habitat

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modification  by a coal ash effluent.
p.  408-414.  In: L A.  Krumholz (ed.)
Warmwater  Streams Symposium.
American Fisheries Society. Washing-
ton, DC.
                                                                               7

                                                                              U. S. GOVERNMENT PRINTING OFFICE: 1986/646-116/20748

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                                            Katharine E. Webster, Anne M. Forbes, and John J.  Magnuson are with the
                                              University of Wisconsin, Madison, Wl 53706.
                                            Gary £. Glass is the EPA Project Officer (see below).
                                            The complete report, entitled "An Evaluation of Environmental Stress Imposed by
                                              a Coal Ash Effluent:  Wisconsin Power Plant Impact Study," (Order No. PB
                                              85-213 429/AS; Cost: $10.00, subject to change) will be available only from:
                                                   National Technical Information Service
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                                                   Springfield, VA22161
                                                    Telephone: 703-487-4650
                                            The EPA Project Officer can be contacted at:
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Environmental Protection
Agency
Center for Environmental Research
Information
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