SERA
United States
Environmental Protection
Agency
Municipal Environmental Research^
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-82-048 August 1982
Project Summary
Stormwater Management to
Improve Lake Water Quality
Martin P. Wanielista, Yousef A. Yousef, and James S. Taylor
Many investigators have identified
the urban environments as those pro-
ducing high levels of water pollutants
relative to other land uses. In a 59
hectare (146 acre) urban watershed in
Orlando, Florida, the Stormwater sys-
tem discharges to an 11 hectare (27
acre) lake. The lake water quality is
characterized by frequent algal
blooms, odor, and in general, reduced
recreational activities. The lake is one
of the focal points of the city's recre-
ational/social programs.
Stormwater management proce-
dures were established based on the
runoff sampling program and a target
mass pollutant reduction of storm-
water runoff with special emphasis on
phosphorus. Management of storm-
water for the removal of phosphorus
was accomplished by diversion for
retention (filtration) of the first flush of
pollutants.
Lake water quality will be managed
by the reduction of Stormwater mass,
bottom mud inactivation, and littoral
zone plantings. Approximately half of
the water column phosphorus concen-
tration was estimated to originate in
the bottom muds and return to the
water column primarily during anoxic
conditions. Thus, a coagulant cover-
age of the bottom muds will be used.
The coagulant possibilities are alum
sludge or alum.
This Project Summary was devel-
oped by EPA's Municipal Environmen-
tal Research Laboratory. Cincinnati.
OH, to announce key findings of a
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
Stormwater may be a significant
source of surface water pollution in
urban areas. Lake impacts have been
and continue to be studied on an
international level by the National Eutro-
phication Research Program in the
United States and an international
program with United States participa-
tion.
This summary presents Stormwater
impacts on an urban lake and recom-
mendations for Stormwater and lake
management. The impact was first
defined by visual observation and storm-
water was the major pollution source.
There was no point sources of industrial
or domestic wastewaters. Samples were
taken of Stormwater, lake water, and
bottom muds and estimates made of
mass loading and impacts to determine
a combination of management practices.
Some elevations of best management
practices (BMP's) for urban Stormwater
had been completed before this work.
The critical relationship between a BMP
and receiving water quality, however,
had not been well documented, except
for some dissolved oxygen responses in
rivers.
Watershed and Lake
Characteristics
The drainage area is the Lake Eola
watershed in Orlando, Florida. The
Stormwater system, which is separate
from the sewage system, drains a
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watershed of approximately 59 hectares
(146 acres), composed of 33.7 hectares
(83.2 acres) of commercial and 25.3
hectares (62.8 acres) of residential areas
discharging to an 11-hectare (27-acre)
lake. In addition, 4.5 hectares (11.2
acres) of parkland surrounds the lake
and are not considered part of the
watershed because of infrequent runoff
to the lake. Streets and parking lots
comprise approximately 19.7 hectares
(49 acres) of the watershed within a
total of about 49.3 hectares (122 acres)
of impervious lands. The pervious area
is only 9.7 hectares (24 acres), most of
which is in the residential areas. The
land use is illustrated in Figure 1.
Visual observation of the watershed
indicates a total of 35 parking lots with
an area of about 12 hectares (29 acres)
discharging stormwater. Parking areas
were identified to select possible areas
for management of stormwater dis-
charged to the land-locked lake. One of
the parking lots was designated a samp-
ling location for runoff waters and is
usually maintained between 26.5
meters (87.0 ft) and 27 meters (88.5 ft)
above sea level by well discharge and
pumping. It is a shallow lake with a
mean depth of approximately 3 meters
(9.84 ft) and about 73 percent of the
total volume located within the 0 to 3
meter (0 to 9.84 ft) frustrum layers.
Most urban lakes in central Florida
(more than 5,000) have similar physical
characteristics.
Benefits
The benefits of the lake and its
surroundings are evident but difficult to
quantify. The lake is a focal point of
Orlando with frequent music concerts,
arts and crafts shows, tourist visits,
children's park, and relaxation areas,
and is one of the main reasons the
downtown area continues its economic
security. The property surrounding the
lake brings top value because of its
location. The dollar benefits from lake
activity are estimated at $2.3 million per
year.
Lake Impacts
From visual observation and analytical
data. Lake Eola has persistent algal
blooms virtually year round. Populations
of the macroscopic algae, Chara, and
the filamentous green algae, Spirogyra,
covered up to 30 percent of the lake
surface during the summer rainy sea-
son. Lake Eola water was found to be
somewhat alkaline with pH ranging
from 8.4 to 9.5 (indicative of the rate of
algal production). The average annual
value and the measured range of values
for pH, chlorophyll-a, inorganic and
organic carbon, and Secchi disc trans-
parency are shown by Table 1.
The average values shown in Table 1
are similar to values reported in the
literature for eutrophic lakes.
L_
1
Legend
Commercial
Residential
Parkland
Sampling locations
Sub- watershed
Figure 1. Lake Eola watershed land uses and sampling locations.
2
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Table 1. Values for Selected Parameters Measured in Lake Eola, Florida, Between
July 1978 and August 1979
Parameter
Chlorophyll-a
Organic carbon
Inorganic carbon
pH
Secchi disc
No. of
Samples
64
67
68
57
32
Average
Value
25.4
10.9
18.8
8.85
106
Standard
Units Deviation
mg/m3
mg/L
mg/L
cm
8.8
6.7
6.4
—
13.0
Range of
Values
9.0 -
3.0 -
13.8 -
8.40-
90
36.4
29.1
40.6
9.5
120
Concentrations of dissolved oxygen in
Lake Eola, although usually at or above
saturation near the surface, drop period-
ically during the spring and summer
months to less than 1 mg/L in deep
areas of 4 meters (13.1 ft) or greater.
Phosphorus from the bottom sediments
is released up to a level of 250 mg/m2
after 2 months of anoxic conditions.
This anaerobically released phosphorus
has the potential for increasing water
column phosphorus by 11.6 /ug P04~3-
P/L, about 50 percent of the average
orthophosphorus concentration in the
lake(23//g/L).
Extensive bioassay experiments indi-
cate that when the concentration of
orthophosphorus in Lake Eola was less
than 0.10 mg/L, algal production was
regulated by adding orthophosphorus
alone. Above this concentration, appar-
ently an excess of phosphorus was
available, and algal growth was regu-
lated by the N/P ratio. In most cases,
however, the concentration of orthophos-
phorus was below0.04 mg/L, and most
likely algal production was limited by
the concentrations of added phosphorus
alone.
In addition to the enhanced algal
growth conditions experienced during
the summer rainy months, runoff enter-
ing the lake after prolonged periods of
drought may produce severe toxic effects
on aquatic life in Lake Eola. Contami-
nants are allowed to accumulate within
the watershed, and when a storm event
occurs, the mass loading to the lake is
many times larger than experienced
during frequent rainfall periods of time.
This influx of toxic and oxygen demand-
ing wastes can be lethal to many forms
of aquatic life.
Evidence of such a phenomenon was
recorded in March 1979 when a rain
event followed a dry period of 6 weeks.
oncentrations of organic carbon as
.ligh as 400 mg/L were measured in
stormwater runoff entering the lake
during this event. Two days later, dis-
solved oxygen concentrations had been
reduced from saturation near the sur-
face to 4 mg/L at a depth of 1 meter and
to near zero below 2 meters. Numerous
large-mouth bass averaging 1 to 2 kg
were found floating in the water, and
large masses of dead filamentous algae
had accumulated in thick mats over
much of the lake's surface. During 1979,
a total of six fish kills were reported. One
dead bass (about 2 kg) floating at the
surface was brought to the laboratory,
processed and analyzed for metal con-
centrations in selected organs (heart,
gall bladder, liver, stomach) and flesh. It
appeared that nickel and lead concen-
trated in the gills, iron concentrated in
the heart, and zinc and copper concen-
trated in the liver. At this time, however,
it is not known that these metals were
directly responsible for the fish kill.
A pathogen isolation study was con-
ducted for 1 year with the collection of
129 water and sediment samples. Four-
teen were composites of runoff, 32
were bottom samples, and 83 were lake
water. Clostridium was isolated from
the bottom sediments of the lake and
Salmonella was isolated from the lake
water samples.
Domestic ducks in the Lake Eola
waters and park areas number approxi-
mately 20, with decreasing populations
noted over the past 5 years. Microbiol-
ogists at the Orange County Pollution
Control Agency have speculated during
site visits, that gas production from the
anaerobic sediments is increased in the
summer months. This anaerobiosis pro-
motes growth of the botulism organism
that produces a toxin that, in turn,
concentrates in the small insect larvae
of the sediments. When ducks eat the
larvae they can die. After the autopsy of
two dead ducks, botulism was the
reported cause of death.
Stormwater
Stormwater pollutants and flowrates
were first estimated by sampling storm-
water relative to the hydrograph. In this
hydrograph-related sampling program,
eight rainfall/runoff events were quan-
tified. Next, a composite sampling pro-
gram was completed with seven rain-
fall/runoff events. One major question
was the percentage of dissolved pollu-
tant materials present in the runoff. The
sampling program indicated that the
dissolved nutrients and organics were
approximately 50 percent or more of the
total, while the dissolved fraction of lead
was 20 percent. From the 15 runoff
samples, estimates were made for aver-
age mass loading (as discharged) and
average concentrations. Priority pollu-
tants were measured. Estimates of
loading rates from both commercial and
residential areas were calculated from
the runoff studies.
The Lake Eola site loading data were
compared with the loadings of SWMM/
level I analysis and other national data.
The suspended solids (SS) and BOD
data (Table 2) appear to agree, but total
nitrogen loadings are higher in the Lake
Eola watershed. Possible reasons are
that the residential areas should be
classified as commercial when consider-
ing loading rate data, the landscaping
maintenance places an additional nitro-
gen load, and the heavy rainfall (130 cm)
is greater than the national average.
Most likely, a combination of these
reasons caused the increase.
The commercial and residential land
use pollution contribution to the total
was estimated to be 98 percent for SS,
96 for BOD, 95 for total organic carbon,
94 for total Kjeldahl nitrogen (TKN), and
91 for total phosphorus (TP). Total
contribution was defined as the sum of
the contributions from stormwater, at-
mosphere, and ducks resident on the
lake.
The sampling program and the lake
impact work led to the following conclu-
sions: (1) stormwater is the major
external source of lake related pollution;
(2) phosphorus and other stormwater
pollutants require removal; and(3) sedi-
mentation was possibly not the choice
method for stormwater management
because of the large percentage of
dissolved pollutants.
Target Phosphorus Reduction
The major question is to what degree
should the bottom sediment and storm-
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Table 2. Loading Rate Comparisons fkg/ha-yrj
Data Source
SS 5005
roc
TN
TKN POt-P TP
Lake Eola
Commercial
Residential
1076
827
196
87
1167
757
32.0
40.5
27.8
36.1
1.7
3.1
3.5
6.2
SWMM/Levell
Commercial
Residential
1255
922
181
45
16.7
7.4
4.3
1.9
National A verages
Commercial
Residential
941
470
97
39
14.5
6.6
3.0
2.0
water be treated to economically reduce
nutrient enrichment, fish and duck kills,
and algal activity to an acceptable level?
Using the trophic state models, a target
reduction level of phosphorus loadings
into the oligotrophic/mesotrophic level
may reduce algal blooms. In addition, a
chlorophyll-a mean concentration of 7
/ug/L may indicate a mesotrophic state.
Table 3 illustrates the target level and
need for an approximate 90 percent
reduction in phosphorus load and con-
centration.
In the National Eutrophication Study,
total phosphorus concentration of less
than 10/ug/L in the water column was
noted as a target reduction to classify
lakes as oligotrophic. A combination of
stormwater treatment and bottom sedi-
ment inactivation may produce a water
column concentration of less than 10
fjg/L. The bottom sediments were esti-
mated to contribute 11.6 yi/g/L of the
average water column concentration of
23//g/L
Stormwater Management
Selection
Each stormwater management prac-
tice that could be defined in terms of
cost and efficiency and was practical for
the watershed was evaluated for storm-
water control. Selecting the best combi-
nation of practices that met cost and
efficiency constraints (least cost) could
be aided by a computer analysis.
Cost-efficiency curves (present value
dollars versus removal quantities) were
developed for each subwatershed of
Lake Eola. Removal efficiencies were
used from the literature and nonpoint
urban runoff programs. These efforts in
the central Florida area had defined the
efficiencies and costs for diversion/
percolation basins, swales, underdrains,
and vacuum sweeping nonpoint source
management methods. In the highly
impervious urban areas, the cost of land
is expensive, and land intensive activ-
ities (detention and retention basins)
are sometimes not aesthetically pleas-
ing. Thus, street sweeping diversion
with retention underground, and catch-
basin cleaning appeared probable for
the Lake Eola area. Dutch drains, rooftop
storage, coagulation, filtration, and
solids concentrators were other manage-
ment methods being investigated. These
methods formed the basis for determin-
ing optimal combinations of practices. A
linear programming network routing
model was incorporated into a computer
program, and the cost-efficiency curves
were estimated by "piecewise" linear
approximation.
Table 3. Target Reductions
Models Before
Vollenweider 2.33 g-P/m2/yr
Dillon 0.49g-P/m2
Larsen-Mercier 0.48 mg/L
OECD/ chlorophyll1 269 mg-P/m3
Target Reduction Levels
0.2 g-P/m2/yr
0.05g-P/m2
0.05 mg/L
70 mg-P/m3
'Reduction corresponding to a chlorophyll-a of 7 fjg/L.
4
One limitation on stormwater control
was the use of private property. Thus, it
was decided to do all management
within the city right-of-way. The alter-
natives considered for management of
the stormwater were:
1. diversion of stormwater to the
sanitary sewer system for treat-
ment;
2. street cleaning by both broom and
vacuum sweepers;
3. diversion of stormwater into perco-
lation basins;
4. conversion of inlets to catchbasins;
5. coagulant addition with sedimen-
tation (detention);
6. silt removal from lake, and draw-
down every 5 years;
7. natural "living filter" treatment
through littoral zones;
8. fabric bag filters;
9. detention systems (on-line pass
through);
10. "best" combination of any or all of
the above alternatives; and
11. diversion of stormwater into infil-
tration trenches near the lake.
The first alternative was eliminated
because it was not considered as a
general solution for other areas and it
required the replacing of over 7.00C
meters (22,950 ft) of sanitary sewei
lines, thus the capital cost of pipe anc
pumping stations was over $600,000.
A "column study" was done to exam
ine detention and detention after coagu-
lation as a method for improving watei
quality. Because a significant amount o
the pollutants in stormwater were in the
dissolved or colloidal state, coagulatior
with detention may be necessary t<
remove these types of pollutants. Deten
tion with significant holding times wil
remove suspended materials. The reduc
tion reported ranged from a high of 5:
percent for TSS to a low of 20 percen
for lead. Alum coagulation improvei
stormwater quality more than detentioi
alone. Reductions of TP and TSS afte
alum coagulation were in excess of 91
percent. Standard isoconcentration line
and regression equations relating per
cent removal to time, settling velocity
and the logarithm of time were devel
oped. The regression equations are eas
to use and were developed within
predictive error of less than 5 percen
The detention systems were judged to
expensive because of land area require
and the chemical costs. Detention afte
coagulation, however, may be feasibl
for other locations.
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Before the percolation alternatives
could be considered, the infiltrative
capacity of the soils was estimated by
defining the type of soils and the loca-
tion of the water table. The water table
is at least 2 meters (6.56 ft) below the
ground surface for a ground elevation of
29 meters (95 ft) or higher. Borings
close to the lake indicate the water table
is near elevation 27 meters (88 ft). In
addition, sandy soil is available to about
6.5 meters (20 ft) below ground level.
Percolation of stormwater is possible for
parking lot and street drainage for those
areas whose ground elevation is above
29 meters (95 ft).
All alternatives were evaluated for
estimated cost and yearly pollutant
removal efficiencies. The cost for the
natural "Living Filter" areas was esti-
mated from local contractors and the
city of Orlando records. Native vegeta-
tion was selected and has been used in
other lakes. All other cost data were
obtained from recently bid sewer pro-
jects.
The selected solution was based on
minimum present value cost and maxi-
mum removal efficiencies. The fabric
bag alternative had a lower capital cost,
but poor removals relative to other
alternatives. The location of the best
management practices was near parking
lots and immediately before lake dis-
charge. Parking lot and street diversion
were designed to percolate the first 0.6
to 1.25 cm (0.25 to 0.5 in.) of every
storm chosen, resulting in a removal
efficiency of 90 percent on a yearly
basis. The resulting capital cost for
stormwater management and lake res-
toration was approximately $6,2507
hectare ($2,5007 acre) of watershed.
Results and Conclusions
Presented here are the results and
conclusions separated into the areas of
stormwater, lake impacts, sediments,
and selection of management practices.
Stormwater
The stormwater pollutants and quanti-
ties were first estimated by sampling
stormwater relative to the hydrograph.
Eight rainfall/runoff events were quan-
tified in this manner. Next, a composite
sampling program was initiated meas-
uring seven rainfall/runoff events. From
the 15 runoff samples, estimates were
made for mass loading (as discharged)
and average concentrations. Loading
rate and average concentration data
were estimated for 19 water quality
parameters, including data for 10
metals. Results of the sampling program
are:
1. The dissolved portion of storm-
water pollutants was equal to or
greater than 50 percent of the
total except for zinc, lead, and
chromium.
2. Loading rates of SS, BOD5, and
dissolved phosphorus were com-
parable to national averages. Load-
ing rate data for nitrogen are
higher than national averages.
3. The relative loading rates for each
external (not including lake recy-
cle) source of pollution were esti-
mated. Stormwater produced the
greatest percentage of the total
loadings.
Lake Impacts
During this research, monthly water
quality analyses were performed in Lake
Eola and bioassay experiments were
conducted to determine the effect of
nutrients and stormwater additions on
algal productivity in this lake system.
Coagulation of stormwater to remove
nutrients and limit algal production was
also studied. From the results obtained
in this research, the following conclu-
sions were reached;
1. The input of stormwater in Lake
Eola has damaged this aquatic
system. Persistent algal blooms
exist virtually year round. Bottom
sediments have become covered
with a layer of loose flocculant
material and anoxic conditions
exist in areas more than 4 meters
(13.12 ft) deep during the spring
and summer.
2. When the concentration of ortho-
phosphorus in Lake Eola is less
than 0.10 mg/L, algal production
is regulated by the addition of
orthophosphorus alone. Above
this concentration, it appears that
an excess of phosphorus is avail-
able, and algal growth is regulated
by the N:P ratio. In most cases,
however, the concentration of
orthophosphorus is below 0.04
mg/L, and algal production is
limited by the concentration of
added phosphorus alone.
3. Although nitrogen was able to
stimulate algal production in lim-
ited bioassay experiments, it will
probably not be a limiting resource
in Lake Eola when considered over
a period of years because of the
large numbers of nitrogen-fixing
blue-green algae that are charac-
teristic of eutrophic systems.
4. Adding stormwater runoff to Lake
Eola water in any concentration
increases algal production. A mix-
ture of 25 percent stormwater
runoff produces the largest stand-
ing crop.
5. Coagulating stormwater runoff
with alum reduces concentrations
of both orthophosphorus and ni-
trate nitrogen by 80 to 95 percent
and re moves certain heavy metals.
"3. Coagulating stormwater runoff
significantly reduces phosphorus
and most metals. Thus, the treated
stormwater is less toxic to aquatic
organisms and algae growth is
reduced.
7. Dry weather storm sewer flow has
a negligible effect on algal produc-
tion in Lake Eola.
8. Maximum algal growth in bioassay
experiments generally occurred
after 6 to 11 days of incubation.
When stormwater runoff is added
to Lake Eola water, however, a
growth lag is often experienced
that may extend the time required
to reach maximum yield to as
many as 18 days.
9. Continuous stormwater inputs
into Lake Eola during the rainy
season greatly enhances algal
growth because of the constant
input of nutrients and dilution of
toxic components. Inputs of storm-
water after a long dry spell may
inflict serious toxic effects on
aquatic life.
10. Concentrations of copper and zinc
in Lake Eola are sufficient to
cause incipient inhibition of algal
production. Average stormwater
runoff concentrations of copper,
zinc, and lead are sufficient to
produce complete inhibition or
algicidal effects.
11. Human pathogens were identified
in the lake. Clostridium was iso-
lated from bottom samples and
Salmonella from water samples.
Sediment
During this study, sediment phos-
phorus was characterized and the mag-
nitude and effect of anaerobically re-
leased phosphorus were studied to
determine the effects on the productivity
of Lake Eola and the related eutrophica-
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tion. Based on the results of this re-
search, the following conclusions were
reached:
1. The major source of phosphorus
entering Lake Eola is from storm-
water runoff. The major phos-
phorus sink is the sediments. Both
components greatly exceed the
quantity of phosphorus stored in
the water column at any time.
2. The input of stormwater runoff
has severely affected the natural
decomposition cycle in the Lake
Eola ecosystem, resulting in an
accumulation of partially decom-
posed organic matter with a con-
stantly high oxygen demand.
3. Flocculent sediment particles of
smaller size and density contain
considerably more phosphorus
than larger and more dense parti-
cles. In Lake Eola, flocculent, deep
water particles contained about
61 percent more phosphorus than
discrete, dense sand particles from
the shallow areas.
4. A thick mat of decomposing algal
cells covers the sand placed over
the sediments in the Lake Eola
restoration project of 1973 be-
cause the source of phosphorus
was not controlled.
5. Aerobic phosphorus release be-
cause of turbulent agitation of the
sediments is most likely an insig-
nificant phosphorus source, but
may serve to maintain lake water
phosphorus levels when productiv-
ity has depleted the phosphorus in
the water column.
6. The hypolimnion of Lake Eola
remains anaerobic from mid-May
to mid-August, corresponding to
the wet season and the associated
increase of stormwater runoff
during this period. This anaerobic
condition enhances phosphorus
release from the bottom sedi-
ments.
7. Anaerobically released phos-
phorus, when mixed out of the
hypolimnion, has the potential for
increasing water column phos-
phorus by 11.6 fjg P04~3-P/L,
which amounts to 50 percent of
the average orthophosphorus con-
centration in the lake (23 /jg/L).
Selection of Management
Practices
Many stormwater practices are avail-
able and tested in many geographical
regions. Unfortunately, few of these
practices have been documented rela-
tive to their removal efficiencies for
selected water quality measures. Diver-
sion of the first-flush of stormwater has
been documented. If the first-flush is
percolated through soil, direct surface
discharge of pollutants is eliminated. If
soil conditions and water table permit
percolation, then diversion for storage
and treatment by percolation is possible.
There appears, however, to be a need
for more documentation on other prac-
tices. The following conclusions expand
upon our existing knowledge.
1. Percolation is possible after storm-
water diversion in urban areas.
Perforated pipe under sidewalks
and parking lots within municipal
right-of-way should be examined.
2. Diversion of the first 0.64 cm (0.25
in.) of every stormwater runoff
event will produce long-term re-
moval efficiencies of at least 80
percent.
3. Sedimentation will remove sus-
pended materials. The reduction
reported herein ranged from a high
of 52 percent for TSS to a low of 20
percent for lead.
4. Alum coagulation plus detention
improved stormwater quality more
than detention only. Of the water
quality parameters investigated,
only the nitrogen forms and Ca
were not reduced by alum coagula-
tion. The reduction of TP and TSS
after alum coagulation and deten-
tion was in excess of 90 percent.
5. Standard isoconcentration lines
and regression equations relating
the percent removal of any of the
water quality variables were devel-
oped as linear or semi-log func-
tions of settling velocity or deten-
tion time. The regression equations
were developed using an alpha
error of less than 5 percent. The
regression equations are easy to
use.
6. Phosphorus release experiments
using alum stormwater sludge,
lakewater, and lake sediment indi-
cated that the phosphorus re-
moved by alum coagulation of
stormwater would be retained in
the solid form in a simulated lake
environment for aerobic or anoxic
conditions with or without gentle
mixing.
After defining the stormwater man-
agement practices for the watershed, a
computer program "MANAGE" was
used as a methodology for the choice of
the least cost combination. As a general
methodology, however, more work was
needed to estimate localized cost-
efficiencies for stormwater manage-
ment practices. Incorporating mathe-
matical programming methods to this
work allows one to select a combination
of practices that will remove a maximum
amount of pollutants at least cost.
Implementation Steps
Based on citizen concern and histori-
cal water quality data on fish and duck
kills, oxygen depletion, and algal blooms,
it was evident that the factor causing
the water quality impact had to be
identified. Trophic state analysis indi-
cated that the lake was estimated as
eutrophic. In laboratory tests, algal
productivity was related to stormwater.
Also, the bottom sediments were shown
to contribute to the phosphorus concen-
tration in the water column.
Based on the runoff quality and
quantity data along with lake limnologi-
cal data, an implementation plan for
stormwater management was devel-
oped. Since phosphorus is most likely
the limiting nutrient, it will be controlled.
The two major sources of phosphorus
are stormwater and lake bottom mud
recycling. By reducing stormwater phos-
phorus mass inputs, littoral zone plant-
ing, and coagulant coverage of bottom
muds, it is predicted that the effects of
stratified conditions (anaerobic) will be
minimized and algal blooms will be
reduced.
The stormwater management will be
done by diversion/percolation of parking
lot runoff and limited street runoff
approximately 24.0 hectares (60 acres)
In addition, most of the areas no
managed with this method will be
diverted for filtration before discharge t(
the lake, approximately 27.0 hectares
(66 acres).
The full report was submitted ir
fulfillment of Grant No. R-805580 b'
the University of Central Florida unde
sponsorship of the U.S. Environmenta
Protection Agency.
-------
Martin P. Wanielista, Yousef A. Yousef, and James S. Taylor are with the
University of Central Florida, Orlando, FL 32816.
Richard P. Traver is the EPA Project Officer (see below).
The complete report, entitled "Stormwater Management to Improve Lake Water
Quality," (Order No. PB 82-227 711; Cost: $21.00, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Oil and Hazardous Materials Spills Branch
Municipal Environmental Research Laboratory-Cincinnati
U.S. Environmental Protection Agency
Edison, NJ 08837
•&U. S. GOVERNMENT PRINTING OFFICE: 1982/559-092/0459
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United States Center for Environmental Research pees pg|d
Environmental Protection Information Environmental
Agency Cincinnati OH 45268 Protection
Agency
EPA 335
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