United States
Environmental Protection
Agency
Office of Water Planning and Standards
Criteria and Standards Division i
Washington, D.C.
Technology Transfer
EPA-625/2-80-027
v>EPA Capsule Report
Lake Restoration in
Cobbossee Watershed
a**-
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Technology Transfer
EPA-625/2-80-027
Capsule Report
Lake Restoration in
Cobbossee Watershed
July 1980
This report was developed by the
Center for Environmental Research Information,
Office of Research and Development,
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268 ',
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Figure 1.
REGIONAL LOCATION
MARANACOOK
LAKE
COCHNEWAGON
LAKE
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I. Introduction
The Clean Lakes program was
initiated in 1975 to implement
section 314 of the Federal Water
Pollution Control Act Amend-
ments of 1972. Section 314
gives the States the responsibil-
ity for protecting and restoring
the quality of freshwater lakes.
The program provides funding .
to assist the States in
classifying their lakes according
to water quality, identifying
methods to control pollution
sources affecting them, and
restoring.those which have
been degraded. To qualify for a
Clean Lakes restoration grant, a
lake must be open and acces-
sible to the public. Furthermore,
the proposed restoration project
must have the potential to yield
long-term public benefits and
not merely temporary or su-
perficial improvement.
This report discusses lake res-
toration in the! watershed of
Cobbossee Stream, which
drains 562 square kilometers
(217 square miles) of Kennebec
County immediately west of Au-
gusta, Maine (Figure 1). The
Cobbossee Watershed contains
28 lakes, three of which
Annabessacook Lake,
Cobbossee Lake, and Pleasant
Pond are classified as eutro-
phic (see Table 1). Lake restora-
tion efforts had been underway
since the 1960's, but despite
substantial progress, including
eliminating industrial and
municipal discharges, nuisance
conditions in the three lakes
persisted. It became obvious
that partial solutions to the
watershed's pollution problems
were not going to be sufficient
to restore lake water quality.
Clean Lakes funds made it pos-
sible to develop and carry out a
comprehensive restoration pro-
gram which included alum
treatment of one of the lakes
and implementation of agricul-
tural pollution control practices
in the direct drainage areas of
all three.
Table 1.
Lake and Watershed Description
Anna-
bessacook Cobbossee
Pleasant
Morphometry ;
Surface Area in hectares (ac)
Mean Depth in meters (ft.)
Maximum Depth in meters (ft.)
575
(1420)
5.3
(17.4)
14.9
(49)
' 2243
(5543)
8.1
(26.5)
30.5
; (ioo)
237
(586)
2.7
(8.8)
7.9
(26)
Total Drainage Area in square kilometers
(mi2) '
Direct Drainage in square kilometers (mi2)
Residence Time (days)
Land Use Characteristics (% direct drainage area)
Forest and Reverting Fields
Developed
Agriculture, Cultivated
Agriculture, Non-cultivated
Other
220
(85)
56.5
(21.8)
81
69
12
16
1
2
340
(131.4)
121.0
: (46.7)
304
i 65
11
20
: o
4
562
(217)
61.1
(23.6)
65
73
8
16
1
2
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2. History of
Restoration
Efforts
Annabessacook Lake has long
had the reputation as one of the
most polluted lakes in the State
of Maine. In the early 1940's,
the first formal complaints of al-
gae blooms on the lake were re-
corded. The lake became "pea
soup" green every summer, of-
ten with thick scums of micro-
scopic algae accumulating on
the surface and heavy mats of
leafy vegetation rotting on the
shorelines. From 1964 through
1971, residents responded by
treating Annabessacook with 30
tons of copper sulfate algicides,
but the effect was short-lived
and diminished with each sea-
son as resistant types of algae
began to predominate.
Phosphorus is the nutrient
controlling algal growth in most
lakes of the northern United
States and Canada, and for
many years the industries and
towns surrounding
Annabessacook Lake discharged
large quantities of phosphorus
in their untreated wastes. These
effluents stimulated the growth
of algae in Annabessacook Lake
and, subsequently, in
Cobbossee Lake and Pleasant
Pond downstream. Although
numerous investigations of the
lake were conducted, no action
was taken to eliminate the dis-
charges until 1970.
The first step toward lake res-
toration was elimination of the
direct discharges of municipal
and industrial effluent to
Annabessacook Lake. In 1967,
Maine's Water Improvement
Commission found that
Annabessacook Lake received
Weeds and Algae in Annabessacook Lake.
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Algal Bloom in Annabessacook Lake.
over 13,600 kilograms (30,000
pounds) of phosphorus per
year, and that the surface wa-
ters of the lake contained
enough phosphorus to produce
about 770,000 kilograms (1.7
million pounds) of algae.
Municipal and industrial dis-
charges from the village areas
of Winthrop, North Monmouth,
and Monmouth Center ac-
counted for 93 percent of this
annual phosphorus input.
To continue discharging into the
lakes would have required
costly advanced wastewater
treatment to remove phos-
phorus. In 1969, the Augusta
Sanitary District chose a more
economical alternative and be-
gan building a trunkline sewer
from Winthrop to the
wastewater treatment plant in
Augusta, a distance of approxi-
mately 19 kilometers (12 miles).
The trunkline became oper-
ational in 1972 and was then ex-
tended, so that by 1976 all point
source discharges of phos-
phorus to the Cobbossee Water-
shed lakes had been eliminated
Annabessacook Lake showed
some improvement as a result
of the diversion of point
sources. However, the lake's
ambient total phosphorus con-
centrations remained above 15
micro-grams per liter (/ug/l), the
generally accepted threshold
level for algal'blooms in north-
ern lakes. Continuing nuisance
growth of algae in
Annabessacook Lake,
Cobbossee Lake, and Pleasant
Pond indicated that the problem
of cultural eutrophication had
not yet been s(olved.
Hypolimnetic aerators were also
installed in Annabessacook Lake
in 1972 and 1974 in an effort to
accelerate its recovery. The in-
tent of the aeration project was
to destratify the lake and mix
the water layers, thereby reduc-
ing light penetration, cooling
the epilimnion, and diluting the
surface algal concentrations. It
was determined that a simple
aeration system could be set up
by lakeshore property owners
for summer use. However, the
aeration project failed to mix
lake water beyond a radius of
50 meters. Because of
Annabessacook's size, the
project did not reduce phos-
phorus levels in the water and
may even have caused a net nu-
trient input by stirring up the
phosphorus-rich sediments at
the bottom of the lake.
Bottom sediments were a major
focus of the early restoration
plans. It was presumed that the
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bottom sediments were made
up primarily of residues from
the many years of sewage dis-
charge into the lake. The shal-
low northern end of
Annabessacook, the former dis-
charge point for municipal and
industrial effluent from Win-
throp, was a particular focal
point for concern. Bubbling
water and foul odprs caused by
decaying vegetation, together
with the proximity of the area to
the old sewage outfalls, pointed
toward this area as a significant
source of nutrient loading
continuing in the lake. However,
sediment sampling indicated
high nutrient levels over the en-
tire lake bottom, not just the
north end. Hopes of restoring
the lake by dredgjng or marsh
propagation in this restricted
area disappeared.
Frustrated by 30 years of failure
in improving water quality in
the Cobbossee chain of lakes,
lakeshore property owners, lo-
cal officials, and concerned citi-
zens began working to develop
a strategy for lake restoration.
Realizing that the causes of lake
water pollution are most often
found not within the lake itself,
but rather in the various land
use activities within the water-
shed that contribute pollutants
through surface runoff or
ground water, they formed the
Cobbossee Watershed District in
1972. The District was designed
to function as a quasi-munici-
pal, special-purpose district, a
governmental agency similar to
a school district or sewer
authority. In a watershed
containing 14 major lakes and
numerous tributary streams and
ponds, with a land area of 620
square kilometers (240 square
miles), it was hoped that this
new unit of government could
pursue a comprehensive ap-
proach which the 10 separate
local governments could not.
The special-purpose lake district
has several advantages for the
resolution of water quality
problems:
Jurisdiction over the entire
watershed, which extends be-
yond the boundaries of any
single municipality;
Taxation powers which free it
from the competition for of-
ten limited tax revenues
raised by a general-purpose
government; and
Specialized technical staff to
deal with lake management
problems and communicate
with their counterparts in
State and Federal agencies.
Since 1973, the District has
been operated by a 13-member
board of trustees, representing
the municipalities and three
water supply districts which
joined. The District raises be-
tween $25,000 and $35,000 per
year by local tax assessments to
support its ongoing water re-
source programs.
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3. Diagnostic
Studies
In June of 1975, a Federal water
quality management (208) plan-
ning grant ^enabled the; District,
in cooperation with Southern
Kennebec Valley Regional Plan-
ning Commission, to undertake
the detailed diagnostic studies
needed to formulate a com-
prehensive restoration plan.
They focused on determination
of annual phosphorus loading
budgets to the lakes.
Since the point sources of phos-
phorus had already been di-
verted, attention turned to
loadings from non-point
sources carried by overland
reductions. Determination of
phosphorus contributions by
various land uses and other
non-point sources would lead to
development of the most effec-
tive alternatives for achieving
needed reductions.
The lakes were sampled every
10 days in 1975, from spring
overturn (mid-April) to fall over-
turn (mid-October), for Secchi
disc visibility and dissolved oxy-
gen and temperature profiles. In
1976, the lakes were sampled
biweekly from spring to fall
overturn for Secchi disc visi-
bility, chlorophyll-a and total
LOADING (%)
Figure 2a.
Annabessacook Lake
Phosphorus Sources.
LOADING (kg)
fi- LAKE [
s* SEDIMENTS:
I5oo ;
AGRICULTURE
1000
UPSTREAM
1000
4200 TOTAL
runoff, atmospheric deposition,
or diffusion from lake bottom
sediments. The relationship of
land use activities and phos-
phorus loadings was a critical
linkage to be examined and
defined. Comparison of present
phosphorus budgets to present
water quality and assimilative
capacities, calculated using lake
modeling techniques, would
then allow assessment of
needed phosphorus loading
phosphorus. Oxygen and tem-
perature profiles were meas-
ured four times per year.
Monitoring of the 12 major trib-
utaries to Pleasant Pond and
Cobbossee and Annabessacook
Lakes occurred monthly during
base flow conditions (July
through August, December
through March) and weekly to
biweekly during spring and fall
runoff periods (April through
June, September through
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LOADING (%)
LOADING (kg)
Figure 2b.
Cobbossee Lake
Phosphorus Sources.
ANNA.LAKE
SEDIMENTATION
»UPSTREAM
4900
ANNA. LAKE,
.; ;,, OTHgR
' " I a>00
SEpilfeNTATlON
1500
ANNA. LAKE
AGRICULTURE
_.
EfrtUE COBBOSSEE 200
AGRICULTURE
2600
November). Parameters
monitored included flow, total
phosphorus, ammonia nitrogen,
total Kjeldahl nitrogen, nitrate-
nitrite nitrogen, dissolved oxy-
gen, turbidity, suspended solids,
and total coliform bacteria.
Morphometric data on the lakes
were calculated from Maine
Fish and Game Qepartment lake
surveys and U.S.[Geological
Survey quadrangle maps. Land
use information was obtained
from air photo interpretation of
1974 U.S. Soil Conservation
Service photographs of the lake
drainages.
Information on shoreline waste
disposal systems, suspected as
a primary contributor to lake
degradation, was obtained
through a door-to-door survey
initiated by the Watershed Dis-
trict in 1974 and Completed dur-
ing the 208 diagnostic studies in
1975.
Phosphorus budgets were
developed from the monitoring
data to help in determining land
use - water quality relationships
(Figure 2). The phosphorus
8900 TOTAL
budget studies gave new insight
to the lakes' problems.
Shoreline septic systems, once
considered a significant contrib-
utor to lake degradation, were
found to contribute less than 1
percent of the phosphorus load-
ing to the lakes. Internal
recycling of phosphorus from
lake bottom sediments was con-
firmed as the major phosphorus
source (34 percent) and primary
impediment to Annabessacook
Lake's improvement and, as
suspected, phosphorus-enriched
water discharged from
Annabessacook Lake contrib-
uted a majority of the total
phosphorus loading to
Cobbossee Lake, directly
downstream.
The most surprising conclusion
of the phosphorus budget stud-
ies was the identification of ag-
riculture as a significant
problem. Runoff from agricul-
tural lands comprised the great-
est single source of phosphorus
to Pleasant Pond and the sec-
ond most significant phos-
phorus source for
Annabessacook and Cobbossee
Lakes. The major agricultural
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Q_
Figure 2c.
Pleasant Pond
Phosphorus Sources.
LOADING (%}
AGRICULTURE
78%
LOADING (kg)
AGRICULTURE
1500.
activity in the watershed is dairy
and poultry farming, and the
widespread practice of spread-
ing manure on frozen and
snow-covered ground was
found to be the cause of the
problem. Measurements of the
phosphorus loss from agricul-
tural lands showed that 65 to 70
percent of the loss occurred in
the winter period from Novem-
ber through April.
Having calculated annual phos-
phorus budgets for each of the
three problem lakes, phos-
phorus loading reductions
needed to restore water quality
had to be determined. This re-
quired defining water quality
goals and standards. The prima-
ry goal established was to re-
duce productivity in the lakes,
i.e., algal growth, to achieve
acceptable water clarity. Regres-
sion analysis of three years of
phosphorus concentration, chlo-
rophyll-a, and Secchi disc visi-
bility data from 26 lakes
indicated that if phosphorus
loadings could be reduced to
achieve an overturn phosphorus
concentration of 15 jjug/l, algal
productivity could be kept to
I930 TOTAL
acceptable levels and summer
Secchi disc visibility would
average 4.3 meters. The District
therefore defined a minimum
standard of 15 |xg/l overturn to-
tal phosphorus for its lakes. Its
strategy for lake restoration,
however, was to endeavor to
achieve average overturn phos-
phorus concentrations of 12
|jig/l. In 1976 the average spring
and fall overturn phosphorus
concentrations in
Annabessacook Lake,
Cobbossee Lake, and Pleasant
Pond were 30 |j,g/l, 18 |xg/l, and
21 |xg/l, respectively.
Using the Dillon-Rigler lake
model, calculations were made
regarding the' maximum annual
phosphorus loadings which
could be received by the lakes
without exceeding phosphorus
concentrations of 12 (j,g/l, i.e.,
their assimilative capacities.
These were then compared to
the loadings estimated in 1976
to quantify needed reductions.
The results indicated necessary
loading reductions of 2,050 ±
250 kg for Annabessacook Lake;
3,100 ±500 kg for Cobbossee
Lake; and 600 kg for Pleasant
Pond.
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4. Evaluation of
Restoration
Alternatives
Agricultural runoff and internal
phosphorus recycling contrib-
uted 60 percent of the total
phosphorus load to
Annabessacook Lake.
Cobbossee Lake received 28
percent of its load from agricul-
ture in its direct drainage and
28 percent from agriculture and
internal loading originating in
the Annabessacook Lake drain-
age. Pleasant Pond received as
much as 75 percent of its total
phosphorus loading from ag-
ricultural drainage. If internal
loading in Annabessacook Lake
could be eliminated and agricul-
tural sources reduced by 50
percent in all three lake drain-
ages, estimates showed that the
phosphorus concentrations in
the lakes should be reduced to
below the critical 15 |o,g/l. Con-
sequently, those sources, rather
than the smaller and more dif-
ficult to control contributions
from septic systems and devel-
oped areas, were selected as
restoration targets.
Phosphorus loading from ag-
ricultural sources could be re-
duced with proper management
of manure, primarily through
stopping winter spreading prac-
tices. Convincing farmers to
stockpile rather than spread ma-
nure could be accomplished
through two approaches: Finan-
cial incentive, by offering cost-
sharing assistance for winter
manure storage facilities; or
regulation, requesting enforce-
ment of Maine pollution laws
prohibiting the direct or indirect
discharge of animal wastes to
State waters. '
A survey of farmers in the three
lake drainages revealed that
most would have severe man-
agement problems if forced to
stockpile manure without an en-
gineered storage facility. The
high cost of these facilities,
from $10,000 to $40,000, had
prevented their construction,
since dairy farmers cannot eas-
ily pass on such added costs to
the consumer. However, most
farmers expressed interest in a
cost-sharing program which
would reduce their cost by 50
percent or more. Section 314 of
the Federal Water Pollution
Control Act was identified as a
means of providing 50 percent
cost-sharing. The Agricultural
Stabilization and Conservation
Service also could contribute
$2,500 per farm. The District
therefore decided to approach
agricultural controls through
financial incentive.
Several techniques were re-
viewed as alternatives for the
control of internal phosphorus
recycling, including:
Dredging
Selective Discharge
Lake Bottom Sealing
Hypolimnetic Aeration
Nutrient Inactivation.
It was determined that dredging
was not cost-effective and could
even increase phosphorus avail-
ability. The use of selective dis-
charge would aggravate the
condition of Cobbossee Lake
immediately downstream. Lake
bottom sealing and
hypolimnetic aeration were
considered impractical consider-
ing the size of the lake. Only nu-
trient inactivation appeared
both feasible and potentially
effective.
Nutrient inactivation involves
chemically treating a lake with
agents which adsorb or chemi-
cally bond to soluble phos-
phorus and remove it from the
water column through precipita-
tion. Although relatively new as
a lake restoration technique, it
is essentially an extension of
existing wastewater and water
supply treatment technologies.
Several agents have been inves-
tigated by lake research scien-
tists, including zirconium and
lanthanum rare earth elements,
fly ash, iron, calcium and alu-
minum. Except for aluminum,
all of these were judged to have
serious limitations due to toxic-
ity or incompatibility with the
pH levels found in
Annabessacook Lake bottom
waters. Aluminum compounds
appeared to be the ones most
likely to effectively remove
phosphorus under conditions
found in the lake, retain phos-
phorus in the sediments follow-
ing precipitation, produce little
adverse effect on aquatic life,
and be effective in the
quantities the District could
afford.
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Manure Containment Structure.
5. Implementing the
Agriculture
Waste
Management
Program
The primary objective was to
prevent spreading of manure on
frozen or snow-covered ground.
In Maine, this necessitates stor-
age capacity for a 6-month
accumulation.,
For most farms, winter storage
of manure meant a drastic
change in the entire manure
handling system the contain-
ment structure, barn-to-storage
transfer mechanism, and re-
moval and application equip-
ment. To assist farmers in
making these costly and com-
plicated changes the Cobbossee
Watershed District recognized
that a combination of skills
would be required in a coordi-
nated effort of local, State, and
Federal agencies interested in
furthering good farm manage-
ment practices for the purpose
of improving water quality. The
effort included financial help
from several agencies U.S.
Environmental Protection
Agency, U.S. Department of Ag-
riculture, Agricultural Stabiliza-
tion and Conservation Service
and Farmers Home Administra-
tion as well as technical as-
sistance from others
Cobbossee Watershed District,
USDA Soil Conservation Ser-
vice, Kennebec County Soil and
Water Conservation District, and
the University of Maine Coop-
erative Extension Service. The
activities of these agencies had
to be coordinated in performing
a wide variety of functions.
Coordinating a cost-sharing
program with Federal pro-
grams administered by two
separate agencies EPA and
USDA
Educating farmers regarding
the project's purposes, proce-
dures for obtaining cost-shar-
ing, sources' of financing, and
availability of technical
assistance
Developing farm" manage-
ment plans including design
of structural pollution con-
trols, stipulation of manure
application rates and timing,
and delineation of stream cor-
ridor buffer zones
Securing the cooperation and
participation of the farmers
Assisting farmers in obtaining
contractors and materials
Assisting contractors in meet-
ing construction
specifications
Inspecting construction
projects to ensure compliance
with specifications
Through the long-standing Fed-
eral Agricultural Conservation
Program, the Agricultural Sta-
bilization and Conservation
Service could offer farmers a
maximum of $2,500 toward a
conservation practice. In 1979
the limit was raised to $3,500.
This alone had not been suffi-
cient assistance to enable farm-
ers to construct needed manure
storage facilities and other
pollution control practices. How-
ever, when this program was
combined with 50 percent cost-
sharing available through the
EPA section 314 Clean Lakes
Program, the resulting financial
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Table 2.
Typical Manure Storage Facilities and Costs (1978)
TYPE FARM
DAIRY
90 milkers
20 youngstock
freestall
DAIRY
28 milkers
20 youngstock
stanchion
MANURE SYSTEM
COMPONENTS
50' x80' x 10'
Concrete Storage
with push-off ramps
and roof
Equipment
40' x 40'
Asphalt Pad with
8' Concrete headwall
and earth sides
Equipment
TOTAL
COST
25,700:
2,000.
9,200.
3,100.
$40,000.
1,200,
6,400.
1,800i
4,400.
$13,800.
FARMER'S
SHARE
$17,500.
$ 4,400.
DAIRY REPLACEMENTS?' x 37' x 4'
20 animals
stanchion
POULTRY LITTER
STACKING SITE
Broilers, 20,000
Concrete storage
Asphalted barnyard
Runoff controls
holding basin
450' diversion
40' x 40'
Concrete Pad
with earth berms
4,850,
2,100.
450.
1,500,.
$ 8,900.
2,900.
3,100.
$ 6,000.
$ 1,950.
$ 500.
Bioassay Prior
to Alum Application.
assistance package became
significant and attracted the
immediate interest of most
farmers in the watershed.
Development of animal waste
management plans which
would meet the pollution con-
trol objectives of the Watershed
District without exceeding man-
agement and financial con-
straints of the farmers was one
of the most challenging aspects
of the project. The restoration
project combined the expertise
of the existing agricultural as-
sistance agencies and the
Cobbossee Watershed District.
The Soil Conservation Service
provided standard engineering
designs for diversions, earthen
lagoons, and concrete contain-
ment structures, which were
modified by the pobbossee
Watershed District to maximize
pollution control. Watershed
District and Kennebec County
Soil and Water Conservation
District personnel then worked
intensively with farmers in
preparing alternative plans for
manure handling and runoff
controls and in soliciting cost
estimates from contractors.
Once a design was selected.
SCS engineers reviewed it and
then inspected and certified all
structural controls, while the lo-
cal SCS conservationists drew
up appropriate management
plans.
Convincing the farmers to
participate voluntarily in the
program was critical to the suc-
cess of the project. The farmer's
share of costs ranged from $500
for small-scale poultry manure
stacking sites to $20,000 for
some large dairy farms (Table
2). Over half of the dairy farm-
ers faced a minimum invest-
ment of their own funds of
$5,000, and one-third were
asked to invest in excess of
$10,000. Consequently, it was
necessary to demonstrate to the
farmers not only the pollution
control benefits, but also the
benefits to farm productivity
and farm management.
By June of 1980, 27 out of 35
farms targeted for controls in
the project area had completed
needed manure management
facilities and runoff controls,
while an additional four had ini-
tiated projects to be completed
in 1980. The total cost of these
controls was $627,000, of which
EPA contributed one-half, ASCS
$85,000, and the farmers the re-
mainder. These 27 farms repre-
sented the major part of the
animal waste problem; they
originally generated 78 percent
of the phosphorus attributed to
livestock manure in the water-
sheds of the three eutrophic
lakes. However, the water qual-
ity effects of this success will
not be fully evident for another
2 to 3 years, since the lakes re-
spond to decreases in phos-
phorus loading over a period of
time. Extensive lake and tribu-
tary monitoring programs are
continuing to assess results.
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6. Nutrient
Inactivation
Treatment
Prior to implementation of nu-
trient inacti.vation treatment,
bioassays and a feasibility study
were conducted to determine
the optimum application rates
of aluminum sulfate. This was a
function of:
Phosphorus removal
efficiency
Residual dissolved aluminum
concentrations
Flow formation characteristics
Change in pH
Potential toxicity to biota.
To prevent harm to aquatic life,
sodium aluminate was used in
the treatment as a buffer to
counteract the potential change
in lake pH caused by alumunum
sulfate. Bioassays were also
conducted to determine the
potential toxicity of the treat-
ment to fish and invertebrates.
After testing various combina-
tions of the two chemicals, an
Che.mical Storage.
Chemical Application Barge.
Alum Application.
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alum-to-aluminate ratio of
1.6:1.0 was selected. This ratio
produced excellent phosphorus
removal (at least 98 percent),
minimal change in pH, and little
residual aluminum.
Lake bottom sediments are usu-
ally regarded as a "sink" for
phosphorus. Generally, when
phosphorus is incorporated in
the bottom sediments, it be-
comes unavailable for stimulat-
ing algal growth. However,
when the lake's hypolimnion
becomes anerobic, significant
amounts of phosphorus may be
released from the sediment and
circulated through the lake.
The area of anoxia increases
with time during the period of
stratification. Thus, to define the
area of the lake in greatest need
of nutrient inactivation treat-
ment, detailed surveys of dis-
solved oxygen concentrations
were conducted. The deepest
area of Annabessacook Lake
usually became anoxic in early
June. By mid-August, all areas
at least 7 meters deep became
anoxic, an area of approxi-
mately 170 hectares (420
acres). The volume of anaerobic
water to be treated was es-
timated at 3.5 x 106 cubic me-
ters (920 million igallons). Thus,
the logistics of the actual ap-
plication were a jmajor chal-
lenge to the project.
Based on the recommended ap-
plication rates, approximately
227,000 liters (60,000 gallons) of
aluminum sulfate and 142,000
liters (37,500 gallons) of sodium
aluminate, with a combined
weight of more than 455,000 kg
(1 million pounds), would be
needed to treat the lake
effectively.
The treatment was carried out
in August 1978, and required
one month to complete. Chemi-
cals were delivered daily by
truck, stored in polyvinyl-lined
swimming pools on shore, and
transferred to a 22,700 liter
(6,000 gallon) tank on the 12 m
(40 foot) barge used for the
chemical application.
Alum was diffused at a depth of
5.2 m (23 feet) into the
hypolimnion at "5 centimeter
(6-inch) intervals along a hori-
zonal 8.8 meter (29-foot) length
of iron pipe, which could be
raised and lowered by a winch.
Valves and flow meters allowed
accurate regulation of discharge
rate in relation to the speed of
the barge.
As with the agricultural compo-
nent of the project, coordination
with other agencies and groups
was an important aspect of the
nutrient inactivation treatment
process. The Watershed District
received technical assistance
from the Maine Department of
Environmental Protection
throughout the project. In addi-
tion, the Annabessacook Lake
Inprovement Association and
the Cobbossee Lake Yacht Club
contributed funds, while
lakeshore property owners and
other interested citizens contrib-
uted many hours of labor, as
well as the use of boats and
property necessary for the stor-
age of chemicals and supplies.
The cost of the treatment is es-
timated at approximately
$200,000 which included
$62,500 for chemicals, equip-
ment and barge rental.
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7. Results
Figure 3.
ANNABESSACOOK LAKE PHOSPHORUS PROFILES- JULY 1977, 1978. 1979
25 50 75 100
150 200 300
TOTAL PHOSPHOROUS-ng«
ANNABESSACOOK LAKE SECCHI DISK TRANSPARENCY
To date, the most significant re-
sponse to the $935,812 restora-
tion project has been seen in
Annabessacook Lake. Best man-
agement practices have been
applied to most of the agricul-
tural operations in its drainage
area. This, coupled with an
apparently dramatic decrease in
internal phosphorus loading fol-
lowing nutrient inactivation, has
reduced total loading of phos-
phorus by an estimated 45
percent in comparison to 1975
conditions. Figure 3 shows the
result in terms of midsummer
total phosphorus concentrations
at various depths in the deepest
part of the lake.
From a lake user's viewpoint,
the immediate' benefit of the
reduction in phosphorus load-
ing and concentration has been
the improvement in water clar-
ity shown in Figure 4. Secchi
disk depths were never less
than 2.0 meters during the 106-
day period for June 1 through
September 15, 1979. Table 3
shows transparency data for
corresponding'periods at other
significant times in Anna-
bessacook's history.
As of early 1980, Cobbossee
Lake has not had adequate time
to respond to the improvements
in the quality of water received
from Annabessacook Lake. Fur-
thermore, additional farm
projects are planned for both
the Cobbossee Lake and Pleas-
ant Pond watersheds during the
summer of 1980 to complete
the necessary controls on ma-
nure runoff. The Cobbossee
Watershed District and the
Maine Department of Environ-
mental .Protection will continue
to monitor these lakes through
July 1981 to assess the results
of the restoration program.
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Table 3.
Annabessacook Lake Visibility.
Secchi Disk
Depth
Public Perception of Water Quality
Days at Given Visibility
(June 1 - September 15)
1972
1977
1979
0 - 0.9 meters gross pollution; lake is totally
unusable for recreation
1-1.9 meters algae blooms still evident; quality is
unacceptable for most uses
2 - 2.9 meters some cpmplaints of declining water
quality; some impairment of water
use
3 - 3.9 meters satisfactory quality; no impairment of
wate.r use
4 - 4.9 meters excellent water quality; a positive
factor encouraging lake use
5 + meters exceptional quality for this lake
43 days 10 days 0 days
63 days 67 days 0 days
0 days 28 days 30 days
0 days 1 day 40 days
0 days 0 days 35 days
0 days 0 days 1 day
106 days 106 days 106 days
Notes on selected years:
1972 - prior to full diversion of municipal/industrial wastewater
1977 - prior to lakes restoration project
1979 - after agricultural waste controls and nutrient inactivation treatment
Annabessacook Lake After Nutrient Inactivation.
USGPO 661-053 9/80
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