United States
                     Environmental Protection
                     Agency
Environmental Research
Laboratory
Corvallis OR 97333
                     Research and Development
EPA-600/S3-84-097  Nov. 1984
&EPA          Project  Summary

                     Effect  of Dredging
                     Lilly Lake,  Wisconsin
                     Russell C. Dunst, James G. Vennie, R. B. Corey, and A. E. Peterson
                       Lilly Lake is located in southeastern
                     Wisconsin. It has a surface area of 37 ha
                     and in 1977 had a maximum depth of
                     1.8 m and a calculated infilling rate of
                     0.5 cm per year. The basin contained up
                     to 10.7 m of lightweight,  organic sedi-
                     ments. Recreational activity was severe-
                     ly restricted due to periodic winter fish
                     kills and dense growths of macrophytes
                     throughout the summer. During  the
                     open water periods of 1978 and 1979,
                     683,000 m3 of sediment were removed
                     with a 30-cm  cutterhead dredge and
                     transported via pipeline to two disposal
                     sites. The dredging operation deepened
                     the lake to  a maximum of 6.6 m and
                     afforded  an excellent opportunity to
                     evaluate the inlake and disposal site
                     effects of the project. The inlake portion
                     of the investigation included an assess-
                     ment of water quality, aquatic biology,
                     sediments, and hydrology before, dur-
                     ing, and after completion of dredging.
                     The evaluation of sediment disposal
                     emphasized the impact on the nearby
                     groundwater system and the value of
                     using hydrosoilsto enhance agricultural
                     crop production. The study  began in
                     July, 1976 and extended through 1981,
                     with some  work continuing into  the
                     summer of 1982.
                       This Project Summary was developed
                     by EPA's Environmental Research Labo-
                     ratory, Corvallis, OR, to announce key
                     findings of the research project that is
                     fully documented in a separate report of
                     the same title (see Project Report order-
                     ing information at back).

                     Introduction
                       Lilly Lake is a 37 ha, natural, seepage
                     lake located in southeastern Wisconsin.
                     In the early 1970s, it was 1,8 m deep and
                     infilling at a rate of 0.5 cm/yr. The basin
                     contained up to 10.7 m of light-weight,
                     organic sediments, with a water content
of 90-98%.  During July-October 1978
and May-August 1979, 683,900 m3 of
sediment were removed with a 30-cm
cutterhead dredge, deepening the lake to
6.6 m.  Inlake  water  quality, aquatic
biology,  sediment characteristics, and
hydrology were investigated before, dur-
ing, and after completion of the project
(1976-82).
  Before dredging began, winter fish kills
were common, and rooted macrophytes
grew over the entire basin, reaching the
surface in most areas. The fish population
was dominated by slow growing bluegills,
and natural reproduction of gamef ish was
poor. Had oxygen resupply/production
been eliminated  during the winter, dis-
solved oxygen concentrations would have
approached zero within 25 days. Water
quality was satisfactory in the summer.
Chlorophyll a levels averaged under 5
fjg/L, and at least 22  genera of algae
were present. Chlorophyceae were domi-
nant in terms of numbers and biomass.
Macrophytes were represented by 12
submergent species, with a combined
lakewide weighted average biomass of
685 and 335 g/m2 in  1976 and 1977,
respectively. These plants strongly influ-
enced inlake dynamics and were a major
problem in recreational usage of the lake.
In 1977, groundwater inflow contributed
17 and 2% of the water and phosphorus
loading to the lake, respectively.
  During the dredging activity, lake levels
dropped  1.5 m.  This produced an in-
creased groundwater inflow, including a
halt in the outflow, with flow reversal in
all of the previous outflow areas. As a
result, inlake water chemistry showed
more similarity to that of the groundwater,
which is illustrated by increases in con-
ductivity and total alkalinity. Because of
sediment disturbance,  there were also
increases in ammonia nitrogen, total
phosphorus, and biological oxygen  de-

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mand (5-day)  levels.  However, intake
dissolved oxygen concentrations were not
affected, and,  in general, water quality
remained within tolerable limits. The fish
population did  not appear to be stressed
by the prevailing conditions. Initially, the
algal population increased, peaking at 33
Aig/L of chlorophyll a. Changes were also
measured for gross primary productivity,
numbers of algal cells, and total biomass;
however, the population did not undergo
any major change in diversity or relative
composition. Apparently in response to
the algal  expansion,  the zooplankter
Bosmina longirostris greatly increased in
number during the same period.
  Since completion of  the dredging pro-
ject, the lake has refilled to pre-treatment
levels.  Compared  to earlier concentra-
tions, magnesium, sodium, potassium,
chloride, conductivity, and total alkalinity
were higher while total phosphorus was
lower. In 1981  sediment oxygen demand
and ammonia nitrogen release rates were
similar to 1977. Nevertheless,  the inlake
water storage was increased by 2.3X, and
winter dissolved oxygen levels remained
above 7  mg/L at all depths. The ammonia
nitrogen was  apparently being  quickly
converted to other nitrogen forms (as in
1977), because only insignificant levels
were found in the water column. Soluble
reactive phosphorus  release into the
water column  was minimal due to the
toxic conditions, although  it would be-
come a significant  phosphorus source
under anoxia. In 1981, the lake was still
polymictic, but thermal gradients  up to
8°C  were present  on occasion. Low
dissolved oxygen levels were found near
the bottom during these periods of re-
duced  mixing. Bottom temperatures
reached 24°C; however, summer maxima
were depressed at all depths due to the
increased water volume.
  By 1981, average summer chlorophyll
a levels were again under 5 /ug/L.  Algal
diversity and density were similar to the
pre-dredging levels of 1978. There was a
shift in species composition, represented
by the  appearance of  six genera of
Chrysophyceae. These were co-dominant
with the Chlorophyceae in terms of bio-
mass. The benthic invertebrate commun-
ity was relatively sparse both before and
after dredging; however, numbers and
diversity were greater in 1981. The
populations of Hyalella azteca and Peri-
coma sp. were down,  but Oligochaetes,
Caenis sp., and several genera of chiron-
omids responded to the improved inlake
conditions. Many of the latter are known
to be good fish  food organisms. Dredging
and drawdown was a major disruption for
the rooted submergent vegetation. In
1980, species  diversity was reduced to
six, and the lake bottom was  inhabited
primarily by a macrophytic algae, Chara
sp. This is often a pioneer species for new
habitat. By 1982 the Chara sp. was being
replaced by rooted macrophytes, and the
diversity of species had increased some-
what. The plant community  was still
evolving, but the existing characteristics
included: (1) growth over 75% of the lake
area, to a depth of 3.7 m; (2) top 1.2-1.8 m
of the water column weed-free, except in
the shallow, near shore area; (3) lakewide
weighted  average  biomass under 100
g/m2; and (4) lower biomass over sand
versus muck bottom. The lower biomass
over sand was also true before dredging
but is important because of the greatly
enlarged area of  sand bottom post-
treatment.
  Although dredging removed  the phos-
phorus-rich upper sediments, resulting in
a major  reduction  in most phosphorus
forms (especially sodium hydroxide ex-
tractable phosphorus), the sediments
were still the most important reservoir of
phosphorus within the lake.  However,
phosphorus transport directly into the
water column was minimal, based on a
combination of measurement and predic-
tive equation.  Groundwaters  furnished
46% of the water loading in 1981 but only
9% of  the phosphorus. Several models
were used with the water and phosphorus
loadings  before and after dredging to
predict a chlorophyll a level for the lake.
All of  the  models suggested  that low
chlorophyll a concentrations  would be
present in the lake, correlating well with
actual  measurements.
  The lake sediments were transported
via pipeline to  two disposal  sites. The
primary site, a modified abandoned gravel
pit, was used in 1978 and 1979, eventu-
ally receiving about 540,000 m3 of sedi-
ment. The  remainder of the sediments
were  placed in a low diked area  on
agricultural land. This site was used in
1979 only. Changes to the groundwater
systems were monitored with observation
wells at both sites plus private drinking
water wells at the gravel pit. Parameters
of interest  at both  sites included water
levels,  nitrate plus nitrite nitrogen, am-
monia  nitrogen, pH, and conductivity. In
addition, chemical  oxygen demand was
measured  at the  diked area and the
following at the gravel pit site: chloride,
total organic nitrogen, total  dissolved
phosphorus, total phosphorus, arsenic,
barium,  cadmium, copper, iron, lead,
mercury, selenium, silver,  zinc, and
chromium.
  The results were similar at each of the
disposal sites. The response time for i
particular well was related to soil perme-
ability and distance from the diked area oi
gravel pit basin. The greatest impact was
observed in wells located adjacent to the
sites, especially  where permeable soils
were present. Impact duration was short
because the lake sediments quickly inhib-
ited  continued seepage of  water  away
from the sites. In general, the surrounding
groundwater systems were  not affected
significantly as a result of lake sediment
disposal. In 1983, the modified gravel pit
was still retaining water; however, the
sediments at the diked area were  land-
spread, dried, and incorporated into the
terrestrial soils during 1980-81. By 1983
the area was growing corn.
  Laboratory, greenhouse and field stu-
dies, begun in 1980 and terminated in
1982, were set up to determine the effects
of applications of sediment from the lake
on  agricultural  crops. The laboratory
studies  included a survey of sediments
from 11 other Wisconsin  lakes, and the
greenhouse study included three  addi-
tional sediments  so that chemical proper-
ties and plant responses to this sediment
could be compared with chemical proper-
ties and crop responses from other sedi-
ments.
  The sediment survey included analyses
of the 12 sediments for pH, total carbon,
chemical oxygen demand, loss on ignition,
total nitrogen, ammonia nitrogen, total
phosphorus, organic phosphorus, phos-
phorus extracted with 0.5A4 sodium bi-
carbonate,  phosphorus equilibrated in
0.01M calcium chloride, and total zinc,
manganese, copper, cadmium and lead.
A study  of nitrogen and phosphorus
released  or immobilized  on incubation
was also included. Lilly Lake sediment
hadthe highest pH, total carbon, chemical
oxygen demand, loss on  ignition, total
nitrogen and nitrogen release on three
month's incubation. It also  showed the
greatest decrease in phosphorus equili-
brating in calcium chloride after incuba-
tion. The sediments showed  wide ranges
in many  of the  factors, particularly in
those associated with  pH and  organic
matter content.
  The four sediments used in the green-
house study were selected to give wide
ranges in pH (5.1 to7.7), chemical oxygen
demand(3.5to28.7 mg/L), total nitrogen
(0.35 to 2.69 mg/L) and  carbon/phos-
phorus ratio(64-1420). Sediment concen-
trations equivalent to 0, 10, 30, 90 and
270 mT/ha were established in 1.5 dm3
pots of Plainfield sand and Withee silt

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loam. Corn was planted and harvested
after eight weeks.
  Factors investigated in the greenhouse
experiment included yield, tissue concen-
trations of nitrogen, phosphorus, potas-
sium, calcium, magnesium, sulfur, iron,
manganese,  copper,  zinc, boron, and
plant uptake of nitrogen, phosphorus and
potassium. Statistical analyses showed
highly significant differences associated
with the soil used for all factors "except
yield and copper concentration.  Differ-
ences associated with sediment source
were significant at the 5% level or greater
for all factors except phosphorus, potas-
sium and boron concentrations. However,
only concentrations and uptakes of nitro-
gen showed differences that were great
enough to be important from a practical
standpoint. The New Richmond flowage
sediment did increase the zinc concentra-
tion  in the plant tissue more  than the
other sediments, but  the concentration
was not excessive.
  Although there was a sizable, signifi-
cant variation in nitrogen concentration
and uptake associated with the different
sediments, there was no effect of applica-
tion  rate beyond  the first increment.
Application rate did significantly  affect
calcium, magnesium, sulfur and manga-
nese concentrations, but except for man-
ganese the effects were not great. I ncreas-
ing rates of high pH Lilly Lake sediment
decreased manganese concentrations in
the plant, whereas increasing rates of the
acidic Lake Tomah sediment increased
manganese concentrations.
  The field studies were set up on a Fox
silt loam in 1980. Lilly Lake sediment
additions equivalent to 0, 22.4, 44.8 and
39.6 mT/ha of dry sediments were made.
There were four  replicates in a  latin
square design. Sudan grass was planted
and was harvested twice. Even though
the site was an old alfalfa field, significant
yield and nitrogen uptake responses over
the control were obtained in both har-
vests. There were no significant differ-
ences between different rates of sediment
application.
  The field experiment of 1981 and 1982
was on a Hebron silt loam at a different
site because sediment from an adjoining
lagoon was spread over the original site.
The same experimental design was used
at the new site which was previously in'
pasture, and corn was grown both years.
No significant differences in yield, or in
nitrogen or phosphorus concentrations or
uptakes occurred in 1981. Grain yields
could not be obtained in 1982 because of
cow damage, but concentrations of the
following elements were determined in
ear leaves at silking and in the corn grain:
nitrogen, phosphorus, potassium, calci-
um, magnesium, sulfur, zinc, iron, copper,
aluminum, manganese, cobalt, arsenic,
cadmium and lead. The only significant
effect associated with sediment addition
was an increase in the nitrogen concen-
tration in the grain at the  highest sedi-
ment rate.
  Both the greenhouse and field  results
suggest that, of the factors measured, the
only beneficial  effect  to crops from the
application of Lilly Lake sediment would
be an  increase in nitrogen availability
which  would probably  continue to be
effective  for a number of years.  No
harmful effects of sediment application
were apparent.

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     Russell C. Dunst and James G. Vennie are with the Wisconsin Department of
       Natural Resources, Madison, WI53707;R. B. Corey and A. E. Petersonare with
       the University of Wisconsin, Madison, Wl 53701.
     Spencer A. Peterson is the EPA Project Officer (see below).
     The complete report, entitled "Effect of Dredging Lilly Lake, Wisconsin," {Order
       No. PB 85-117 042; Cost: $ 13.00, subject to change) will be available only from:
             National Technical Information Service
             5285 Port Royal Road
             Springfield, VA 22161
             Telephone: 703-487-4650
     The EPA Project Officer can be contacted at:
             Environmental Research Laboratory
             U.S. Environmental Protection Agency
             Corvallis. OR 97333
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