Summer Lake Management Plan - September 1998 City of Tigard
Summer Lake Management Plan
September 1998
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7080 SW Fir Loop
Portland, Oregon 97223
503.684.9097
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RENE _
DEC 1 1998
City of Tigard
CITY OF TIGARD
SUMMER LAKE
MANAGEMENT PLAN
September 1998
Prepared for:
City of Tigard
Engineering Department
13125 SW Hall Boulevard
Tigard, Oregon 97223
Prepared by:
KCM
KCM, Inc.
7080 SW Fir Loop
Portland, Oregon 97223
(503) 684-9097
Project#2840015
Summer Lake Management Plan
TABLE OF CONTENTS
Title Page No.
1. Introduction 1
2. Evaluation of Management Alternatives 4
Mechanical Control Methods 11
Hydraulic Dredging 11
Mechanical Dredging 12
Diver-Operated Suction Dredging 14
Mechanical Harvesting 15
Rotovation 16
Chemical Control Methods 17
Fluridone 16
Glyphosate 18
Endothall 19
Diquat 19
Aquashade 20
Aluminum Sulfate 20
Biological Control Methods 22
Triploid (Sterile) Grass Carp 22
Waterfowl Management 24
Physical Control Methods 25
Hand-Digging 25
Hand-Cutting 26
Bottom Barrier 27
Artificial Circulation 28
Sediment Oxidation 28
Water-Level Drawdown 28
Watershed Management Measures 29
Landscaping Practices 29
Household and Commercial Practices 30
3. Recommended Management Plan 33
Management Scenarios 33
Recommended Scenario 34
Appendix— Harvester Manufacturer's Specifications
...TABLE OF CONTENTS
LIST OF TABLES
No. Title Page No.
2-1 In-Lake Management Alternatives 5
2-2 Watershed Management Alternatives 10
2-3 Recommended Substitutes for Common Household Products 32
3-1 Summer Lake Management Scenarios 33
LIST OF FIGURES
No. Title Page No.
1-1 Aerial View of Summer Lake and Surroundings 2
2-1 Possible Scheme for Dredging Summer Lake 13
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ii
CHAPTER 1.
INTRODUCTION
Summer Lake, a ponded portion of Summer Creek in the City of Tigard, Oregon, is
surrounded by Summer Lake Park. Figure 1-1 shows an aerial view of the lake. Problems
at Summer Lake in recent years have raised citizen concerns about the park's aesthetics,
the lake's water quality, and the volume of aquatic plants and algae. To address these
concerns, the City commissioned KCM to assist in production of a comprehensive
management plan for the lake. This document presents the recommended plan.
The Summer Lake citizen advisory committee identified the following problems for the
management plan to address:
• Excessive production of rooted aquatic plants, which interfere with
recreational use of the lake
• Nuisance summer and fall algal blooms, which generate odors and
unsightly conditions
• Poor fishing
• Poor water quality in the pond and flowing downstream through lower
Summer Creek to Fanno Creek
• Poor aesthetics
• Lack of wildlife
• Bank damage from nutria (a rodent, also called coypu)
• Too many resident waterfowl
• Lack of bank vegetation.
The beneficial uses of Summer Lake were listed as follows:
• Fish habitat
• Recreation
• Migratory wildlife habitat
• Aesthetics.
The Summer Lake citizen advisory committee developed the following goals for the
management plan (the committee did not rank these goals, and their order here does not
indicate priority):
• Improve water quality; specifically, increase dissolved oxygen, reduce
sediment and nutrient concentrations, and lower the water temperature.
• Improve aesthetic appearance.
• Manage shoreline and island vegetation.
1
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c / City of Tigard Figure 1-1.
lD'L SUMMER LAKE AERIAL VIEW OF SUMMER LAKE
7080 SW Fir Loop MANAGEMENT PLAN AND SURROUNDINGS
Portland, Oregon 97223
...1. INTRODUCTION
• Improve fishery habitat, but not necessarily for recreational fishing
• Control production of aquatic plants and algae.
• Develop best management practices (BMPs) for use in the lake's
watershed.
3
CHAPTER 2.
EVALUATION OF MANAGEMENT ALTERNATIVES
A consideration of management alternatives must take into account the productive state of
the lake, the limited ability of watershed control measures to affect the water quality of the
lake, compatibility with the Fanno Creek Watershed Plan, and the inability to use
herbicides without restrictions. In designing a management plan, not only must the
various alternatives be carefully considered, but the expectations of the residents for the
condition of the lake may need to be revised in light of what is financially, scientifically,
and politically realistic.
Management alternatives for Summer Lake fall into two categories, in-lake measures and
watershed measures. In-lake management activities are designed to decrease nutrients in
the lake and reduce its productivity, or physically remove aquatic macrophytes and algae.
In this chapter, management alternatives for Summer Lake are described, the advantages
and disadvantages considered, and a preliminary cost estimated. Watershed management
activities improve water quality by reducing the quantity of pollutants entering the lake
from point and nonpoint sources in the watershed. Regardless of the amount, all nutrient
inputs to the lake should be minimized.
In-lake and watershed techniques to improve water quality, reduce nutrients, and limit
plant productivity are summarized in Tables 2-1 and 2-2, respectively. Some of the
alternatives are large-scale, entailing substantial labor and equipment costs. Others are
small-scale, low-cost approaches to controlling aquatic macrophytes in localized areas.
Planning and regulatory permits may be required for some activities, and costs associated
with obtaining these permits are not included in the estimates.
A variety of methods (chemical, mechanical, biological, physical) is currently available for
treatment of nuisance aquatic plant populations to protect beneficial uses of a water body.
These methods run the gamut from very intensive removal of target species to less
intensive, short-term control strategies (described as maintenance or cosmetic). Also,
control methods for maximum effectiveness against a target plant species depend on the
particular morphology and structure, physiology, growth requirements, and growth habit
of that species. In other words, control methods that might be successful against one
species may not be effective for another. Currently available treatment methods for aquatic
plant control are evaluated below, both in general and specifically for use in Summer Lake.
Because the primary nuisance plant in Summer Lake is a state Class B noxious species,
the review will focus on aggressive control methods, aimed at long-term management of the
lake environment.
Potential options presented for review are the large-scale treatments: aquatic herbicide
application (e.g. fluridone, endothall, glyphosate), hydraulic dredging, mechanical dredging
coupled with drawdown, sterile grass carp introduction, and mechanical harvesting. Also
considered are methods appropriate for smaller areas: hand-removal, bottom barrier
application, and diver-assisted suction dredging. These techniques vary with respect to
intensity and effectiveness against rooted plants.
4
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
TABLE 2-1.
IN-LAKE MANAGEMENT ALTERNATIVES
Advantages Disadvantages Estimated Costa
Hydraulic dredging • Deepens lake • Punctures organic seal and drains • $3-25/m3
(Removal of lake • Removes nutrient-rich lake • Total:
sediment) sediments and aquatic life • Resuspends sediments $197,000-$2,430,000
• Reduces internal cycling • Temporary destruction of benthic
• Usually long-term solution habitat
(>20 years) • Dredge spoils disposal difficulties
• Removal of entire plant, • Expensive
including roots • Temporary bottom disturbance and
• Additional benefits of increased turbidity in water column
deepening lake,removal of • Not species-specific,for plant
enriched or toxic sediments control
Drawdown • Useful for repair or • Not species-specific • Variable
maintenance of shorelines • May affect wetlands
and structures • Loss of recreation
• May enhance growth of • Dissolved oxygen decrease
emergent plants(waterfowl • Benthic invertebrate impact
habitat)
Diver-operated • Site-specific • Labor intensive • $1,100-2,800/day
dredge • Species-specific • Slow(<0.5 acre per day) (coverage depends on
• No depth constraints • Potential fragment production plant density)
• Used near obstacles • Temporary bottom disturbance and
increased turbidity
Aluminum Sulfate: • Lowers lake phosphorus • Short-term measure • $1,000-2,500/ha-m
Sodium Aluminate content • Temporary decrease in pH and • Total: $5,000 to$15,000
Treatment • Inhibits release of phosphorus alkalinity
(Addition of an from sediments • Potential increase in aquatic
aluminum salt to • Increases water column macrophytes
remove phosphorus) transparency • Effectiveness limited by high
• Reduces occurrence of blue- loading
green algal blooms
Dilution • Reduces nutrient • Requires large quantities of low- • Treatment plant design&
concentrations in the lake by nutrient water construction: $400/m3-d
dilution • High capital and operation costs for • O&M: $13/year/m'-d
• Increases flushing rate treatment plant
• Reduces minor phosphorus
source to lake
Artificial Circulation • Provides aeration and • Does not decrease algal biomass • Construction.: $250,000
oxygenation • May decrease water clarity • O&M: $15,000-25,000/year
• Increases aerobic habitat • May adversely impact coldwater
• Redistributes algal biomass fish
Sediment Oxidation • Reduces internal phosphorus • Not appropriate for Summer Lake • $27,000 to$37,000/ha
loading because iron redox reactions are not
the primary mechanism of
phosphorus release
Aquashade • Non-toxic • Expensive to use in large water • Materials cost:$102/ha-m
bodies • Whole lake: $600
• Repeated application needed • Repeat application at 2-
• Downstream impact week intervals;total April
• Mat increase water temperature to Sept. cost: $15,000
5
Summer Lake Management Plan...
•
TABLE 2-1 (continued).
IN-LAKE MANAGEMENT ALTERNATIVES
Advantages Disadvantages Estimated Costa
Bioenzymes • Non-toxic • High expense • Materials cost:
• Limited effectiveness $l41/ha-m
• Repeat applications needed • Whole-lake cost: $800 for
• Not proven in large-scale maintenance dose,$5,000
applications for initial dose.
Bottom sediment • Non-toxic • Too expensive to use over large • Materials cost:
barriers • Immediate plant removal areas $0.15 to$0.75/sq.ft.
• Materials reusable • Annual inspection and maintenance • Installation:
• Site-specific required $0.25 to$0.80/sq.ft.
• Useful around obstructions • Not species-specific
• Benthic organism impact
• Maintenance required
Grass Carp • Reduces plant biomass • May remove all plants or have little • $4-$7 per fish,planted at
• Non-toxic effect 40-60 fish/ha
• Long-term effectiveness(8- 10 • Permitting not available because of • Total: $1,825($1,000 plus
years) fisheries issues $825 delivery)
• Low cost over life of fish • Containment structures required • Monitoring and
• Triploid fish are sterile • Monitoring needed to assess impact containment structure
of grass carp and restocking costs are additional and
schedule may triple costs
• Potential impacts on nutrient
cycling&water quality
• May stimulate algae blooms
• May negatively impact fishery
• Restocking or removal of over-
stocked fish may be necessary
• May alter composition of plant
community without decreasing total
biomass
Hand Pulling • Site specific • Slow,labor intensive,expensive • $0 with volunteer labor
• Species-specific • Short-term turbidity increase • $500 to$2,800/day for
• Minimum impact on native • Diver visibility can restrict contract divers
plants effectiveness
• Use near obstructions
Hand-cutting • Immediate plant removal • Slow • $100 to$1000 for
• Fragments generated equipment+labor
• Short-term increase in turbidity
Harvest Aquatic • Immediate plant removal to • Reduces internal loading of • $300 to$1,000/acre(May
Plants cutting depth(4 to 8 ft.) nutrients vary with transport costs)
• Minimal bottom disturbance • Fragments produced • Three cuttings per year:
• Materials may be composted • Impact on fish and invertebrates $20,000
• Reduces internal loading of • Slow
nutrients • High initial capital cost
• Operating depth limited
• Operations depend on weather
• Not species-specific
6
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
TABLE 2-1 (continued).
IN-LAKE MANAGEMENT ALTERNATIVES
Advantages Disadvantages Estimated Costa
Rotovation • Winter treatment minimizes • Bottom disturbance/increased • $1,000 to$2,300/ha
summer season recreation turbidity (depends on plant density
impact • Long-term efficacy only on and area of treatment)
perennials
• Bottom obstructions limit use
• Not species-specific
Waterfowl • Reduces nutrient loading • Requires establishment of and • Variable.Minimal for
Management compliance with no-feeding signs,low fences or bushes
ordinances along shoreline. Some
• Landscaping practices by lakeshore staff time required to
residences may need to be modified install signs and for
• Public resistance to disturbing birds enforcement
• Reduces habitat available for • Use ReJeX-It AG-36
migratory birds (methylanthanilate)as
• Deterrent activities need to be bird repellent on grass:
repeated $14/L materials cost
$15,000-$25,000/ha
Copper Sulfate • Effective,inexpensive • Algae can develop tolerance • Materials cost for CuSO4:
Treatment • High doses kill snails to control • Causes shift from green algae to $300/ha-m
(Adds copper to kill "swimmer's itch" blue greens • Cost to treat lake: $1,800
algae) • No water use restrictions • Causes oxygen deficit and,release • Total treatment cost:
• Increases efficacy of other of nutrients and toxins from algae $5,000
herbicides when applied with • Toxic to some fish,invertebrates, • Repeat applications
them and zooplankton species needed at 2-week intervals
• No biomagnification • Potentially inhibit smoltification of for an annual cost of
salmon $125,000
• Requires multiple treatments each
season, algae may recover in 7 to 21
days
• Accumulates in sediment
• Reduced efficacy at high pH because
copper precipitates
• Downstream impact
Cutrine Plus • Effective algicide • Restricted to use in water with • Materials cost:$100/ha-m
(Copper- • Has greater efficacy than carbonate hardness>50 parts per • Cost to treat lake: $5,000
ethanolamine CuSO4 and is less sensitive to million if trout are present ($600 plus labor)
complex) high pH . Same disadvantages as CuSO4 • Repeat applications
• Multiple treatments per year may needed at 2-week intervals
be required for an annual cost of
$125,000
Komeen • Contact herbicide • At recommended dosages fish kills • Materials cost: $300/ha-m
(Copper • Has greater efficacy than have occurred • Cost to treat lake: $5,000
ethylenediamine CuSO4 and is less sensitive to . Same disadvantages as CuSO4 ($1,800 plus labor)
complex) high pH • One season duration of
effectiveness
7
Summer Lake Management Plan...
TABLE 2-1 (continued).
IN-LAKE MANAGEMENT ALTERNATIVES
Advantages Disadvantages Estimated Costa
Diquat • Contact herbicide • Water use restrictions:24 h for •
Materials cost: $225/ha-rn
(6,7-dihydrodipyrido • Effective against many plant swimming, 14 d for domestic use& • Cost to treat lake: $5,000
pyrazinediium species irrigation,recommended 60 d for ($1,500 plus labor)
dibromide) • No bioaccumulation fish consumption&210 d for
potable water
• Persistent,especially in sediments
• Non-to moderate toxicity to most
animals,high toxicity to
amphibians,fish kills have occurred
at recommended application rates
• Is mutagenic,teratogenic under
certain conditions
• Kills plants rapidly and may cause
oxygen deficit,release of nutrients
and toxins
• Repeat applications needed
• Only one season of control
Aquathol K • Contact herbicide • Water use restrictions: 8 d for •
Materials cost: $300/ha-m
(dipotassium • Not persistent,rapidly swimming,35 d for domestic use,3 • Cost to treat lake: $5,000
endothalic acid) degraded by bacteria d for fish consumption ($1,800 plus labor)
• Not toxic to most aquatic • Not very effective against Elodea,
animals generally applied with Komeen to
• No bioaccumulation increase efficacy
• Repeat applications needed
Hydrothol 191 • Contact herbicide at high •
y concentration and algicide at Experimental use as algicide may • Materials cost: $811/ha-m
(dimethylalkylamine low concentration be possible • Cost to treat lake: $10,000
endothalic acid) • Not persistent,rapidly • Water use restrictions:8 d for ($5,000 plus labor)
degraded by bacteria swimming,35 d for domestic use, 3
• No bioaccumulation d for fish consumption
• Toxic to fish at levels used to
control macrophytes
• Repeat applications needed
Sonar • Systemic herbicide • Water use restrictions: no • Materials cost:
(1-methyl-3-phenyl- • Effective for one year or more application within 0.25 miles of $3,200/ha-m
5-(3-trifluoromethyl • Kills plants slowly so oxygen potable water intake,no irrigation • Cost to treat lake: $25,000
phenyl)-4(1N)- deficit,nutrient and toxin for 7 to 30 d ($19,200 plus labor)
pyridinone) release are limited • Will drift to non-target areas due to
• Little or no bioaccumulation high solubility
• Low toxicity to most aquatic • Persist in hydrosoils for extended
animals period
• Repeat applications may be needed
Glyphosate • Systemic herbicide • Non-selective herbicide • $300/acre
• Non-toxic • Emergent plants only
• No label restrictions on
swimming and fishing
Shoreline • Vegetation reduces sediment • None • Minimal to$275/linear m
Stabilization and and nutrient loading • Maintenance costs vary
Revegetation • Attenuates velocity of runoff
• Improves wildlife habitat
8
s
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
TABLE 2-1(continued).
IN-LAKE MANAGEMENT ALTERNATIVES
Advantages Disadvantages Estimated Costa
No Action • Short-term financial savings • Use of lake limited by dense plant
beds and algal blooms
• Potential public health hazard from
toxic blue greens
• Restoration becomes more costly
and less successful in reversing
degraded conditions
• Safety impaired
a. Does not include associated costs such as taxes,permitting,National Environmental Protection Act(NEPA)review,environmental
monitoring,or construction management.Total project cost including permitting is about 1.5 times these estimated costs.O&M=operations
and maintenance cost.
9
•
•
Summer Lake Management Plan...
TABLE 2-2.
WATERSHED MANAGEMENT ALTERNATIVES
Advantages Disadvantages Estimated Costa
Stream and Wetland • Reduces streambank erosion • May require land conversion • Capital: ($0-$2,500)per ha
Buffer Zones and downstream • May require fencing • O&M: Minimal
sedimentation • May require seeding or planting
• Provides shade and lowers
stream temperatures
• Improves fish and wildlife
habitat
• Vegetation assimilates
nutrients and reduces the
mass of nutrients entering the
stream
Improved • Reduces quantity and velocity • Requires regulatory and inspection • Borne by industry
Development of surface runoff personnel
Practices • Reduces erosion and
sedimentation of receiving
waters
• Reduces nutrient and organic
matter loading to surface and
groundwater
Improved Roadside • Reduces sedimentation of • Requires inspection and regulatory • $750/km
Ditch Maintenance receiving waters personnel
• Provides biofiltration
(nutrients removal)prior to
infiltration
• Removes some toxins
Conversion of On- • Reduces nutrient loading • Requires inspection and regulatory • Varies
site Septic System to • Provides an increased level of personnel
Sewer System service • Most of watershed already sewered
Alternative • Reduces nutrient loading • Requires resident participation, • Minimal
Household Practices • Reduces amount of toxins substitution of products, and • May actually provide long-
entering the lake acceptance of nature term savings
• Reduces the amount of runoff
water
Roof Drain • Reduces nutrient loading • Requires conversion of existing roof • Varies
Modifications • Reduces amount of toxins drain systems
entering the lake
• Reduces the amount of runoff
water
Implementation of • Provides education and • Requires committed organization • $3,000 to 8,000 per year
Public Awareness increased watershed
Program awareness
• Does not include associated costs such as taxes,permitting,National Environmental Protection Act(NEPA)review,environmental
monitoring,or construction management.Total project cost including permitting is about 1.5 times these estimated costs. O&M=
operations and maintenance cost.
10
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
Hydraulic suction (barge) dredging, hand removal, bottom barrier, and systemic chemical
applications such as SONAR® (fluridone) and RODEO® (glyphosate) are intensive methods
aimed at killing or removing all of these nuisance aquatic plants, including roots, and are
considered aggressive methods with the potential of achieving long-term reduction. Use of
herbivorous grass carp, offering potential long-term control, is also treated in the review,
but permit restrictions rule out this approach. Depending on target species, scale of
problem, stocking rate, and other site-specifics, effective use of sterile grass carp can range
from eradication of species to no control.
Mechanical harvesting and contact herbicides (e.g., Aquathol) are useful for short-term
removal of large areas of surfacing plants, and are included in the discussion as less
intensive forms of maintenance control. Other types of control methods, such as
mechanical rotovation (bottom tillage), and lake-level drawdown by itself, are not
considered appropriate for use in Summer Lake due to site and species constraints, and are
therefore not discussed. Drawdown by itself is ineffective in western Oregon and
Washington lowland lakes for long-term control of invasive, non-native plants, and may be
useful only when used in conjunction with appropriate dredging methods.
Each treatment alternative is reviewed in terms of its principal mode of action,
effectiveness, human and environmental effects (safety, water quality, non-target
organisms and plants), costs, and other special political and administrative concerns.
Potential mitigation measures are presented along with estimates of mitigation costs,
where possible.
MECHANICAL CONTROL METHODS
Hydraulic Dredging
Principle: This is an intensive technique that involves removal of littoral sediments and
associated rooted aquatic plants using hydraulic dredging equipment. Lake sediment
removal is most often performed by means of a cutter-head hydraulic pipeline dredge
(Cooke et al. 1993). During operation, plants and sediment loosened by the cutter head
travel to the pickup head. The slurry is suctioned up and carried back to the dredge barge
through hoses. The sediment slurry is then piped off-site for disposal.
Control Effectiveness and Duration: Large-scale sediment removal techniques can
often provide multiple benefits to an aquatic system (Cooke et al. 1993). Depending on the
water body, possible enhancements include not only rooted macrophyte control, but also
increased depth of the water body and removal of nutrients or toxic substances. Efficiency
of removal depends on the equipment and sediment type and condition, with conventional
dredges performing well on harder sediment. However, various types of portable hydraulic
dredges available in the U.S. are more effective for small lakes with softer, flocculent
substrate. Longevity of control depends on a number of factors, including sedimentation
rate (the lower the better), watershed-to-surface-area ratios (at least 10:1), and hydraulic
residence times (the longer the better).
Advantages: Dredging removes entire plants, including root systems, so regrowth is
minimized. Plant pieces are collected and retained, and fragmentation spread is minimized
11
Summer Lake Management Plan...
(this is important for control of Brazilian elodea and Eurasian watermilfoil, which spread
by fragments). Hydraulic dredging can be used to cover areas larger than practicable for
diver-operated dredging or diver hand-removal, or where herbicides cannot be used.
Human health and safety concerns are negligible where operations are prudently
conducted.
Drawbacks: Hydraulic dredging is very expensive and highly disruptive to the local
environment. A major problem often involves finding suitable off-site disposal areas and
transporting dredged materials to these sites. As a result, specialized equipment and
materials are required and the process is much more costly. Short-term environmental
effects include resuspension of sediments and localized turbidity increases in the area of
treatment. Release of nutrients and other contaminants from enriched sediments can also
be a problem. In addition, some non-target aquatic organisms and vegetation will be
inadvertently removed during the process. However, if only a portion of the lake bed is
dredged, the impact on benthic aquatic life should be short-lived (Cooke et al. 1993).
Costs: Dredging costs can vary greatly, depending on density and volume of sediment
removed, equipment condition, transport requirements of dredged material, and eventual
use of dredged material (Cooke et al. 1993). Hydraulic dredging costs typically range from
a minimum of $3/m3 to $25/m3 (not including disposal costs), although figures as high as
$50/m3 have been reported in special cases.
Applicability to Summer Lake: The idea behind dredging for long-term aquatic plant
control is to remove enough sediment to deepen the lake bottom at least below the photic
zone (approximately 16 feet) so that plants can no longer receive enough light to grow.
When used in such large-scale applications, this alternative is likely to produce highly
effective immediate and long-term control, but is very costly and can result in extensive
and immediate environmental impact. In Summer Lake, only 1 foot of sediment depth
would have to be dredged to remove plants and roots. This would greatly reduce the cost of
dredging. This alternative could be a highly effective solution. If a dredge spoil disposal site
is found in the vicinity of Summer Lake, the cost of treating a 6.5-acre area of plant beds
would likely be in the neighborhood of $197,000, assuming a cost of $25 per cubic meter,
including planning, engineering, environmental, and permitting costs. Figure 2-1 shows an
example of portions of the lake that could be dredged and where the dredged material
could be used to build up a new island in the lake.
Mechanical Dredging
Principle: Mechanical dredging is the physical excavation of sediments similar to
hydraulic suction (barge-mounted) dredging described above, but using land-based
mechanized equipment (e.g., drag-line dredges). This type of dredging can be used in
conjunction with lake-level drawdown so that the equipment can operate more effectively,
if optimal environmental, operational, and jurisdictional conditions are present.
Advantages, Drawbacks, Costs: Similar to hydraulic dredging, with the added problem
of access and higher costs.
Applicability to Summer Lake: This alternative has limited potential for aquatic plant
control at Summer Lake because of access problems. However, as a partial technique
applied to redefine the shoreline of the lake, it is potentially usable.
12
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SUMMER LAKE Figure 2-1.
POSSIBLE SCHEME FOR
7080 SW Fir Loop
Portland, Oregon 97223 MANAGEMENT PLAN DREDGING SUMMER LAKE
i
Summer Lake Management Plan...
Diver-Operated Suction Dredging
Principle: Diver dredging has been used since the late 1970s in British Columbia as an
improvement over hand removal for sparse colonies of Eurasian watermilfoil. More
recently, this method has been successfully used in several lakes in Washington State for
small-scale removal of non-native watermilfoil plants. The technique employs a small
barge or boat carrying portable dredges with suction heads that are operated by Scuba®
divers to remove individual plants (including roots) from the sediment. Divers physically
dislodge the plants and roots with sharp tools or by hand. The plant/sediment slurry is
then suctioned up and carried back to the barge through hoses operated by the diver. On
the barge, plant parts are sieved out and retained for later off-site disposal. The water
sediment slurry can be discharged back to the lake or piped off-site for upland disposal.
Control Effectiveness and Duration: Diver dredging can be highly effective under the
proper conditions. Efficiency of removal depends on sediment condition, density of aquatic
plants, and underwater visibility. It is best used for localized infestations of low plant
density where fragmentation must be minimized. Depending on local conditions, milfoil
removal efficiencies of 85 to 97 percent can be achieved by diver dredging. This technique is
currently being used for aggressive control of EWM populations in Silver Lake (City of
Everett) and Long Lake (Thurston County).
Advantages: The method is species-selective and site-specific. Disruption of sediments is
minimized. Plant pieces are collected and retained, and spread of fragments is minimized
(which is important for control of milfoil). Diver dredging can be used to cover areas larger
than practicable for hand digging or diver hand removal, or where herbicides cannot be
used. Diver dredging can be conducted in tight places or around obstacles that would
preclude the use of larger machinery.
Drawbacks: Diver-dredging is labor-intensive and expensive. In dense plant beds, the
utility of this method may be much reduced and other methods (e.g., bottom barrier) may
be more appropriate. Returning dredged residue directly to the water may result in some
fragment loss through sieves. Where upland disposal of dredged slurry is used, more
specialized equipment and materials are required and the process is much more costly.
Short-term environmental effects can include localized turbidity increases in the area of
treatment. Release of nutrients and other contaminants from enriched sediments can also
be a problem. In addition, some sediment and non-target vegetation may be inadvertently
removed during the process.
Costs: Dredging costs can vary greatly, depending on the density of plants, equipment
condition, and transport requirements of dredged material. In addition, the use of contract
divers for dredging work is subject to stringent State regulations on certification, safety,
and hourly wage payment, which can affect total project cost. Costs range from a minimum
of$1,100/day to upwards of$2,800/day (not including transport of dredged material). This
corresponds to $6,000 to $20,000 per acre.
Applicability to Summer Lake: Diver-operated dredging may be useful in Summer Lake
to remove small, isolated patches of aquatic plants. Its use in this lake is most appropriate
for small-scale, supplementary work.
14
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
Mechanical Harvesting
Principle: Mechanical harvesting is considered a short-term technique to temporarily
remove plants interfering with recreational or aesthetic enjoyment of a water body.
Harvesting involves cutting plants below the water surface, with or without collection of
cut fragments for onshore disposal. To achieve maximum removal of plant material,
harvesting is usually performed during summer when submersed and floating-leafed
plants have grown to the water's surface.
Conventional single-stage harvesters combine cutting, collecting, storing, and transporting
cut vegetation into one piece of machinery. Cutting machines are also available that
perform only the cutting function. Maximum cutting depths for harvesters and cutting
machines range from 5 to 8.2 feet with a swath width of 6.5 to 12.1 feet. Cooke et al. (1993)
summarize aquatic plant cutters and harvesters available in North America.
Control Effectiveness and Duration: Since harvesting involves physical removal and
disposal of vegetation from the water, the immediate effectiveness in creating open water
areas is quite apparent. The duration of control is variable, however. Factors such as
frequency and timing of harvest, water depth, and depth of cut influence the duration of
control. Harvesting has not proved an effective means of sustaining long-term reductions in
growth of milfoil. Regrowth of milfoil to pre-harvest levels typically occurs within 30 to 60
days (Perkins and Sytsma 1987), depending on water depth and the depth of cut. Aquatic
plant researchers Johnson and Bagwell (1978) and Schiller (1983) also suggest probable
short-term benefits provided by mechanical harvesting of nuisance aquatic plants, but
caution against possible spread of infestation through stem fragmentation.
Advantages: Harvesting is most appropriate for large, open areas with few surface
obstructions. There is usually little interference with the use of a water body during
harvesting operations. Harvesting has the added benefit that removal of in-lake plant
biomass eliminates a possible source of nutrients that can be released during the fall when
aquatic plants die back and decay. This is an important consequence in water bodies with
extensive plant beds and low nutrient inputs from outside sources. Furthermore,
harvesting can reduce sediment accumulation by removing organic matter that normally
decays and adds to the bottom sediments. Depending on species content, harvested
vegetation can be easily composted and used as a soil amendment. Mechanical harvesting
costs can be relatively low compared to other physical or mechanical techniques.
Drawbacks: Since harvesting removes only the upper stem material, regrowth from roots
does occur, requiring annual, or more frequent, harvesting. Cut plant material requires
collection and removal from the water. Harvesting also creates plant fragments.
Harvesting can be detrimental to non-target plants and animals (e.g., fish, invertebrates),
which are removed indiscriminately by the process. Harvesting can also enhance the
growth of opportunistic plant species that invade treated areas. Capital costs for machine
purchase are high and the equipment requires considerable maintenance.
Costs: Harvesting program costs depend on factors such as program scale, composition and
density of vegetation, equipment used, skill of personnel, and site-specific constraints.
Detailed costs are not uniformly reported, so comparing project costs of one program with
15
Summer Lake Management Plan...
another can be difficult. However, average costs of local harvesting operations range from
$200/acre to $1,000/acre, including capital amortization. Because harvesting is mainly a
long-term maintenance operation, costs would continue year after year.
Applicability to Summer Lake: Harvesting in Summer Lake would be expensive due to
limited access and small basin size. However, three to five harvests per year would
improve the aesthetics of the lake.
Rotovation
Principle: A rotovator looks like a harvester, but instead of mowing aquatic plants, it
dislodges the roots by tilling the sediments up to about 20 cm. Rotovators work best in
water 1 to 3 meters deep, and are ineffective in water less than 1 meter deep.
Control Effectiveness and Duration: Rotovating is specifically designed for non-woody
rooted aquatic plants, and is not applicable to most wetland plants. Rotovation is more
expensive than harvesting, but it can keep an area free of plants for up to two years. Plant
density is generally reduced after successive treatments.
Advantages: Rotovation can be done in the winter to provide summer control.
Drawbacks: Disadvantages of rotovation include disturbance of sediments, which can
increase turbidity and release nutrients and contaminants into the water column.
Rotovation may kill fish and benthic invertebrates and temporarily destroy spawning
areas. Rotovation has limited effectiveness against non-rooted plants, such as
Ceratophyllum, and plants that use fragmentation as a dispersal mechanism. Rotovation is
not appropriate for Summer Lake.
Costs: Rotovation costs about $1,000 to $2,300 per hectare, for a capital cost of$140,000.
CHEMICAL CONTROL METHODS
Historically, the use of aquatic herbicides was the principal method of controlling nuisance
aquatic weeds. However, in recent years there has been a move away from widespread
herbicide use, toward more selective herbicide use following a thorough review of
effectiveness, and other environmental, economic, political, and social factors (Ecology
1992).
Three aquatic herbicides commonly used to control aquatic weeds are the systemic
herbicides fluridone and glyphosate, and the contact herbicide endothall. Systemic
herbicides are absorbed by and translocated throughout the plant, which kills the entire
plant, roots and shoots. In contrast, contact herbicides kill the plant surface with which it
comes in contact, leaving roots alive and capable of regrowth. The systemic herbicides,
fluridone has the best potential for use in Summer Lake. Systemic and contact herbicides
are reviewed in more detail below.
16
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
Fluridone
Principle: Fluridone, 1-methyl-3-phenyl-5-[3-trifluoromethyl)phenyl]-4(1H)-pyridinone, is
a slow-acting, systemic herbicide. Fluridone is available as the EPA-registered herbicide
SONAR® (SePRO) for use in the management of aquatic plants in freshwater ponds, lakes,
reservoirs, and irrigation canals. It is formulated as a liquid (SONAR®4AS) sprayed above
or below surface, and in controlled release pellets (SONAR® 5P, SONAR® SRP) spread on
the water surface. Fluridone is effectively absorbed and translocated by both plant roots
and shoots (Westerdahl and Getsinger 1988)
Control Effectiveness and Duration: Fluridone demonstrates good control of
submersed and emergent aquatic plants, especially where there is little water movement.
Its use is most applicable for lake-wide or isolated bay treatments to control a variety of
exotic and native species. Eurasian watermilfoil is particularly susceptible to the effects of
fluridone. Fluridone demonstrates "good" control of Brazilian elodea (Egeria densa),
common elodea (Elodea canadensis), and some pondweeds (Potamogeton spp.) (Westerdahl
and Getsinger 1988). Typical fluridone injury symptoms include retarded growth,
"whitened" leaves, and plant death. The effects of fluridone treatment become noticeable 7
to 10 days after application, with control of target plants often requiring 60 to 90 days to
become evident (Westerdahl and Getsinger 1988). Because of the delayed nature of toxicity,
the herbicide is best applied during the early growth phase of the target plant, usually
spring or early summer.
Advantages: As a systemic herbicide, fluridone is capable of killing the roots and shoots of
aquatic plants, thus producing a more long-lasting effect. Many emergent and submersed
aquatic plants are susceptible to fluridone treatment. As a result of human health risk
studies, it has been determined that use of fluridone according to label instructions does
not pose any threat to human health (Ecology 1992). Fluridone also has a very low order of
toxicity to zooplankton, benthic invertebrates, fish, and wildlife.
Drawbacks: Fluridone is a slow-acting herbicide, and its effects can sometimes take up to
several months to become apparent. This means that the concentration of the herbicide in
the lake must be kept at or above the effective level for as long as eight weeks, which often
requires multiple applications. Because of this long uptake time, fluridone is not effective
in flowing water situations. Also, lakes with high flushing rates (such as Summer Lake)
may reduce the effectiveness of the active ingredient and increase the risks of downstream
impact on non-target plants. Because of the potential for drift out of the treatment zone,
fluridone is not suitable for treating a defined area within a large, open lake.
With fluridone, the potential exists for release of nutrients to the water column and for
consumption of dissolved oxygen from the decay of dying plants. Non-target plants may
also be affected, as many plants show susceptibility to fluridone treatment. Mitigation of
lost non-target vegetation may be necessary. As fluridone-treated water may result in
injury to irrigated vegetation, there are label recommendations regarding irrigation delays
following treatment.
Costs: Treatment costs (materials and application) by private contractor for any of the
formulations are $1,500/acre or more, depending on the scale of treatment.
17
Summer Lake Management Plan...
Applicability to Summer Lake: Proper use of fluridone (at optimal rates and exposure)
offers the most practical, potentially effective means of controlling large infestations of
tenacious weeds. The potential for success is increased with repeated, large-scale, intensive
treatments. Treatment in successive years is a strategy being considered for Summer Lake.
Glyphosate
Principle: Glyphosate (N-(phosphonomethyl)glycine) is a non-selective, broad spectrum
herbicide used primarily for control of emergent or floating-leafed plants such as purple
loosestrife and water lilies. Glyphosate is a systemic herbicide that is applied to the foliage
of actively growing plants. The herbicide is rapidly absorbed by foliage and translocated
throughout plant tissues, affecting the entire plant, including roots. Glyphosate is
formulated as RODEO®(Monsanto) for aquatic application.
Control Effectiveness and Duration: Glyphosate is effective against many emergent
and floating-leafed plants, such as waterlilies (Nuphar and Nymphaea spp.) and purple
loosestrife (Lythrum salicaria). According to the manufacturer, RODEO® is not effective on
submersed plants or those with most of the foliage below water. The herbicide binds tightly
to soil particles on contact and thus is unavailable for root uptake by plants. As a result,
proper application to emergent foliage is critical for herbicidal action to occur. Symptoms of
herbicidal activity may not be apparent for up to 7 days, and include wilting and yellowing
of plants, followed by complete browning and death.
Advantages: As a systemic herbicide, glyphosate is capable of killing the entire plant,
producing long-term control benefits. Glyphosate carries no swimming, fishing, or
irrigation label restrictions. Glyphosate dissipates quickly from natural waters, with an
average half-life of 2 weeks in an aquatic system. The herbicide has a low toxicity to
benthic invertebrates, fish, birds, and mammals.
Drawbacks: As a non-selective herbicide, glyphosate treatment can have an effect on
non-target plant species susceptible to it. While the possibility of drift through aerial
application exists, it is expected to be negligible if application is made according to label
instructions and permit conditions. Use is restricted where glyphosate is applied within 1/2
mile of potable intakes in either flowing or standing waters. Current label restrictions
require that active potable water intakes be shut off for a minimum of 48 hours after
application or until the laboratory-measured glyphosate level in intake water is below 0.7
parts per million.
Costs: Treatment costs (materials and application) by private contractor for any of the
formulations average approximately $300/acre, depending on scale of treatment.
Applicability to Summer Lake: Since glyphosate is most effective against certain
emergent or floating-leafed plants, it is not appropriate for large-scale use in Summer
Lake.
18
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
Endothall
Principle: Endothall is a contact herbicide that is not readily translocated in plant
tissues. Endothall formulations (active ingredient endothall acid, 7-oxabicyclo[2,2,1]
heptane-2,3-dicarboxylic acid) are currently registered for aquatic use in either inorganic or
amine salts. Aqueous or granular forms of the dipotassium salt of endothall, Aquathol (Elf
Atochem), are permitted, with stringent use restrictions on water contact, irrigation, and
domestic purposes over and above label restrictions. Due to its toxicity, the liquid amine
form Hydrothol-191 is not permitted for use in fish-bearing waters in the State of
Washington.
Control Effectiveness and Duration: As a contact herbicide, endothall kills only plant
tissues it contacts, usually the upper stem portions. Thus, the entire plant is not killed. It
is therefore used primarily for short-term control of aquatic plants, not for complete
eradication. Duration of control is a function of contact efficiency and regrowth from
unaffected root masses. Effective reductions in plant biomass can range from a few weeks
to several months. In some circumstances, season-long control can be achieved. Carryover
effectiveness of endothall treatments into the following growth season is not typical.
Advantages: Contact herbicides such as endothall generally act faster than translocating
herbicides such as fluridone; evidence of tissue death is often apparent in 1 to 2 weeks.
There is usually little or no drift impact from proper application of this product. Overall
costs of treatment are less than for fluridone applications over the same area.
Drawbacks: Because the entire plant is not killed, endothall causes only temporary
reductions in aquatic plant growth. As a variety of aquatic plants is susceptible to
endothall, non-target plant impact is possible. The recently amended label for Aquathol K
has no swimming restriction. There are also label restrictions on fish consumption and
non-food crop irrigation.
Costs: As with fluridone applications, endothall treatments vary with total area and
dosage rate. Average costs for a small to moderate area application can run about $500 to
700/acre.
Applicability to Summer Lake: Since endothall kills only the plant tissues it contacts,
usually the upper stem portions, it is most appropriately used for short-term control of
aquatic plants. Thus, endothall treatment would be a short-term management only.
Diquat
Principle: Diquat dibromide (6,7-dihydrodipyrido (1,2-a:2'1'-c) pyrazinediium dibromide)
is a non-selective broad spectrum contact herbicide and algicide. It is effective against
submersed and emergent plants and some types of filamentous algae. Currently the
maximum application rate is 0.074 mg/L; previously it was 1.5 mg/L. Diquat's mode of
action is to generate reactive oxygen radicals, which disrupt photosynthesis.
Control Effectiveness and Duration: Diquat, as a contact herbicide, is effective in
controlling submersed plants. Treatments are effective for 6 to 12 weeks of control.
19
Summer Lake Management Plan...
Advantages: Diquat is a fast-acting contact herbicide that has little or no drift. It kills
only the leaves and stems of the plants it contacts.
Drawbacks: Application of diquat to waters in the State of Washington has not been
permitted since 1992 because of concerns over its toxicity to animals, including humans,
and because a less toxic contact herbicide, endotholl, is available.
Label restrictions include water use restrictions of 3 days for drinking, 6 days for irrigation
of food crops and 5 days for irrigation of non-food crops, and one day for consumption by
livestock. The restriction for swimming of 24 hours was dropped in October 1995. In all
states except Florida, application by individuals is restricted to ponds, lakes, and drainage
ditches that are totally under the control of the product's user and have little or no outflow
of water.
Diquat has no to moderate toxicity to most animals. It has slight to moderate toxicity to
freshwater fish, and is slightly to highly toxic to aquatic invertebrates Additional studies
are needed to determine toxicity to non-target aquatic and terrestrial plants. These risk
assessments were obtained from the EPA's R.E.D. Facts on diquat dibromide (EPA 1995).
Data collected for the 1992 Aquatic Plant EIS for Washington State found the amphipod,
Hyallella, and were sensitive to acute exposure expressed concern about toxicity to
amphibians. The level of concern for endangered species is exceeded for all use patterns of
diquat (EPA 1995).
Diquat kills plants rapidly, so depletion of oxygen from the water column and release of
nutrients and toxins from plants and algae is a potential problem. To protect aquatic
organism, diquat can be applied to no more than one-third to one-half of the dense
macrophyte areas in a water body, and subsequent treatments are prohibited for two
weeks. As with all contact herbicides, repeated applications are needed for long-term
control.
Costs: Material costs for diquat are $225/ha-m, plus labor and monitoring costs.
Aquashade
Aquashade is a non-toxic blue dye that reduces plant productivity by limiting light
penetration of the water column. It is fairly effective in controlling plants and algae in
shallow bodies of water. However, Aquashade is expensive, and application must be
repeated at two-week intervals during the summer.
Materials cost is $102/ha-m or $15,000 to treat the whole lake.
Aluminum Sulfate
Principle: Aluminum sulfate (alum) added to a lake lowers the lake's phosphorus content
by precipitating phosphorus and retarding release of phosphorus from the sediments
(Cooke et al. 1993b). Alum forms a polymer that binds phosphorus and organic matter. The
aluminum hydroxide-phosphate complex (commonly called alum floc) is insoluble and
settles to the bottom, carrying suspended and colloidal particles with it. Water clarity
20
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
typically increases markedly immediately after an alum treatment. Once on the sediment
surface, alum floc retards phosphate diffusion from the sediment to the water.
Control Effectiveness and Duration: Alum is used extensively in the United States to
reduce phosphorus levels in lakes and as a coagulant in drinking water and sewage
treatment plants. Alum treatment of lakes has been successful in controlling phosphorus
release from bottom sediments (Cooke et al. 1993b). In most cases, alum treatments reduce
phosphorus levels for several years; in some lakes for up to 20 years (Garrison and Knauer
1984; Cooke et al. 1993b). When alum treatment was not effective, failure was attributed to
insufficient dose, lake mixing, inadequate reduction in external nutrient inputs, or a high
coverage of macrophytes.
If external phosphorus sources are not controlled, the effectiveness of alum will decrease
with time as nutrient-rich silt and organic material cover the alum layer on the sediments.
The duration of effectiveness is difficult to predict for a specific lake. Long-term water
quality monitoring is required following treatment of a lake with alum to assess the
duration of the treatment's effectiveness.
The appropriate alum dose for a lake depends on the lake's pH and alkalinity, and the
potential for aluminum toxicity (Cooke et al. 1986). As alum is added to a lake, pH and
alkalinity decrease and dissolved aluminum concentrations increase. Hardwater, alkaline
lakes can tolerate higher alum doses than can softwater lakes. Relationships to determine
appropriate alum doses are presented in Kennedy and Cooke (1982) and Cooke et al.
(1993a). The addition of alum to a lake with low to moderate alkalinity, such as Summer
Lake, requires careful testing to ensure that pH and alkalinity are not lowered to levels
that would stress aquatic biota, generally a pH of less than 6. A buffering agent, such as
sodium aluminate or sodium carbonate, can be used to minimize the fall in pH caused by
alum. If the pH falls below 4.5, toxic soluble forms of aluminum such as Al(OH)2+ and A13+
are generated. A buffer for alum will probably be needed in Summer Lake because of the
lake's low alkalinity.
A buffering agent was applied with alum to several northeastern United States lakes, and
to Green Lake in Seattle, with high success in maintaining pH and alkalinity levels
(Dominie 1978; Cobbossee Watershed District 1988; Jacoby et al. 1994). The use of sodium
carbonate in the October 1991 alum treatment of Long Lake (Kitsap County, WA) was
successful in maintaining safe pH and alkalinity levels, as well as in improving lake water
quality (Welch, E.B., 13 October 1992, personal communication).
Other phosphorus inactivation techniques have been used with less success than alum.
Calcium hydroxide [Ca(OH)2] or calcium carbonate (slaked lime) is used in hardwater lakes
in Alberta, Canada, to control nutrient supply and algal growth (Murphy et al. 1990;
Kenefick et al. 1992). However, lime would not offer the same phosphorus-binding benefit
in a softwater lake such as Summer Lake because formation of a hydration shell around
the mineral would retard its dissolution (Cooke et al. in press). Iron, in the form of FeC13 or
FeSO4, has occasionally been used to precipitate phosphorus in streams or drinking water
plants. However, these compounds are potentially toxic and their efficacy in lowering
phosphorus concentrations in lakes is unproved (Cooke et al. 1993b).
21
Summer Lake Management Plan...
Advantages: Alum treatment will not reduce the productivity of rooted macrophytes, and
may actually increase their productivity by improving water clarity (Cooke et al. 1993b).
Increased water clarity allows macrophytes to colonize greater depths, up to 7 m based on
Canfield's estimation (1985), and to grow at higher densities. It is probable that plant beds
would expand if light availability were increased by an alum treatment.
Drawbacks: The improper use of aluminum salts may cause toxic conditions (Cooke et al.
1986). Alum treatments of hardwater lakes have generally not resulted in adverse impacts
to fish (Cooke et al 1993b) or had long-term effects on invertebrate populations (Cooke et
al. 1986; Narf 1990). However, alum treatments may reduce invertebrate populations in
softwater lakes. A decrease in density and species richness of benthic invertebrates was
observed following alum/sodium aluminate treatment of Vermont's Lake Morey, a
softwater lake (alkalinity of 30 to 50 mg CaCO/L), and Green Lake in Seattle, Washington
(alkalinity of about 45 mg CaCO/L) (KCM 1995, Smelzer 1990).
Costs: Costs for alum in 1991 were $0.28/kg and for aluminate, $1.32/kg, including
application. Thus, estimated materials and application cost would be $5,000 to $50,000.
BIOLOGICAL CONTROL METHODS
Interest in using biocontrol agents for nuisance aquatic plant growth has been stimulated
by a desire to find more "natural" means of long-term control as well as to reduce the use of
expensive equipment or chemicals. The possibility of integrating biological controls with
traditional physical, mechanical, or chemical methods is an appealing concept. While
development and use of effective biocontrol agents for aquatic plant management is still in
its childhood, potentially useful candidates have been identified, These include plant-
eating fish or insects, pathogenic organisms, and competitive plants. Control of nuisance
plants using biological agents is a gradual process, although the effects should be long-
lasting.
In the State of Oregon, the only biological method currently available for aquatic plant
control is the introduction of triploid (sterile) grass carp; however, carp introduction is
restricted to irrigation canals.
Triploid (Sterile) Grass Carp
Principle: Grass carp or white amur (Ctenopharyngodon idella Val.) are exotic, plant-
consuming fish native to large rivers of China and Siberia. Known for their high growth
rates and wide range of plant food preference, these fish can control certain nuisance
aquatic plants under the right circumstances. In theory, grass carp are most appropriately
used for lake-wide, low-intensity, long-term control of submersed plants. However,
achieving and sustaining a desired plant density may be difficult if not impossible given
the environmental variability over time at any lake. Appropriate fish stocking rates are
difficult to estimate. Experience has shown that too few result in little or no plant control,
while too many fish may cause all the plants to be eliminated from the water body.
Stocking rates are determined based on climate, water temperature, type and extent of
plant species, and other site-specific constraints.
22
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
Control Effectiveness and Duration: Effectiveness of grass carp in controlling aquatic
weeds depends on feeding preferences and metabolism; rates do appear to be temperature-
dependent (Ecology 1992; Cooke et al. 1993). Triploid grass carp exhibit distinct food
preferences, which apparently vary from region to region in the U.S. Recent research
suggests that feeding preference and rates can also depend on fish age, water chemistry,
and plant composition (Pauley et al. 1994). Laboratory and field studies in Washington
State have shown that some plant species appear to be highly preferred, such as the thin-
leafed pondweeds (Potamogeton crispus, P. pectinatus and P. zosteriformis); other plants
were variably preferred, such as coontail (Ceratophyllum demersum), and some plants
were not preferred, such as waterlily (Nuphar) and watershield (Brasenia schreberi),
although watershield was heavily grazed in Silver Lake. Grass carp appear to graze
Brazilian elodea (Egeria densa) fairly effectively (Miller and Decell 1984; Pine and
Anderson 1991). However, researchers in Washington State report in lab tests that Egeria
densa was highly preferred by large fish, but nearly unpalatable to fingerlings (Pauley et
al. 1994). Preliminary results of grass carp grazing in Silver Lake (Cowlitz County) suggest
a drastic impact within two years on Brazilian elodea and Eurasian watermilfoil, as well as
other species of pondweed, coontail, bladderwort, and watershield (Gibbons 1998). Grass
carp control effectiveness and duration are site-specific. Management studies in
Washington waters indicate that substantial removal of vegetation by sterile grass carp
may not become apparent until 3 to 5 years after introduction.
Advantages: Depending on the problem plant species and other site constraints, proper
use of grass carp can achieve long-term reductions in nuisance growth of vegetation,
although perhaps not immediately. In some cases, introduction of grass carp may result in
improved water quality conditions, where water quality deterioration is associated with
dense aquatic plant growth (Thomas et al. 1990). Compared to other long-term aquatic
plant control techniques (e.g., systemic aquatic herbicides, bottom barriers), costs for grass
carp implantation are relatively low.
Drawbacks: Since sterile grass carp exhibit distinct food preferences, they do not graze all
plants equally well, limiting their applicability. The fish may avoid areas of the water body
experiencing heavy recreational use, resulting in less plant removal. Plant reductions may
not become evident for several years. Overstocking of grass carp could result in eradication
of beneficial plants and may have a serious impact on the overall ecology of the water body.
The full ecological impact of grass carp introductions in Northwest waters is still being
determined. An escape barrier on the lake outlet is currently required to prevent
movement of fish out of the system and avoid impact on downstream non-target vegetation.
Fish loss due to predation, especially by ospreys and otters, is possible. Phytoplankton
production in lakes with grass carp tends to increase, but this increase is not always
observed based on turbidity of water.
Costs: Costs can range from approximately $50/acre to $2,000/acre, at stocking rates
ranging from 5 fish/acre to 200 fish/acre and average cost of $10/fish (range $7.50/fish to
$15.00/fish).
Applicability to Summer Lake: The Oregon Department of Fish and Wildlife does not
permit the introduction of grass carp at this time.
23
Summer Lake Management Plan...
Waterfowl Management
Summer Lake supports abundant waterfowl. Control of phosphorus in bird droppings is
unlikely to have any obvious impact on water quality. However, any reduction in
phosphorus loading will be beneficial. Also, use of the lake by waterfowl may increase in
the future as existing flocks attract more of these gregarious birds. Therefore, discouraging
birds from nesting around the lake or becoming year-round residents will yield long-term
benefits in water quality. The following approaches to bird management are largely taken
from fact sheets prepared by the United States Department of Agriculture, Animal and
Plant Health Inspection Service.
Waterfowl are an important part of lake ecosystems, and a moderate number of birds is
compatible with high water quality goals and is much appreciated by bird watchers.
However, large flocks can exceed the carrying capacity of lakes and increase their
productivity(Scherer et al. 1995). Birds leave accumulations of feathers and droppings that
foul beaches and create potential public health risks since waterfowl can be vectors of
salmonella bacteria and parasites. Canada geese have adapted particularly well to urban
lakes, attracted by the fresh water, lack of disturbance by hunters, and well-manicured
lawns of lakeside residences and parks. Canada geese graze extensively, and can denude
sections of lawns. Their large droppings can impair the aesthetics and recreational uses of
beaches, shorelines, and lawns.
At many lakes, a major attraction to geese and some ducks, especially mallards, is
supplemental food offered by people. Feeding encourages migratory birds to become
residents at a lake, increasing the likelihood of water quality problems and habitat
destruction. Feeding is detrimental to the birds as well, concentrating them and producing
a higher risk from predation (even by pet dogs and cats), disease, and botulism poisoning
from decaying food matter and feces. Young birds fed low-protein diets such as bread and
popcorn can developed deformed wings and lose the ability to fly. Feeding also attracts
rodents, and rats can become a problem. Feeding waterfowl should therefore be strongly
discouraged. This may entail drafting an ordinance that includes the authority to enforce
the regulation.
Several approaches can be used to discourage waterfowl from settling at a lake. These
measures are much more effective if applied as soon as the birds arrive at the lake. Once
birds become acclimated to an area, it is difficult to convince them to leave.
• Shoreline vegetation. Geese graze on short, newly growing grass, and
prefer mowed areas to areas where the grass is allowed to grow long.
Geese are less likely to enter areas where the grass along shorelines has
not been mowed. Alternatively, vegetation along the shoreline can be
changed from grass to a groundcover, such as pachysandra, periwinkle,
and euonymus.
• Barriers. Geese normally walk between the water and feeding areas. Low
fences (0.5 to 0.75 m tall), netting, or bushes along the shoreline are often
enough to discourage waterfowl from entering residential property. Also,
a wire strung 2 to 2.5 m off the ground with attached streamers,
24
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
reflectors, Mylar tape, spirolum whirlers, tin flashers, or balloons will
deter geese because they don't like to walk under things.
• Scarecrows. Any excuse for a scarecrow will work as well as an artistic
one. Birds may become acclimated to scarecrows, especially ones without
any moving parts.
• Terror Eyes. Balloons with concentric black rings that appear to be large
eyes are often successful in scaring waterfowl.
• Chemical repellents. A commercial product, ReJeX-iT, with the active
ingredient, methylanthanilate, is very effective in keeping geese from
grazing an area. However, ReJeX-iT is expensive and must be reapplied
after rain or irrigation.
• Noise devices. Pyrotechnics, automatic exploders, and recorded distress
bird calls are effective, but must be used repeatedly. It is probably not
practical to use this approach in Summer Lake due to noise pollution.
Hunting is very effective, but not practical in residential areas.
• Dogs. Periodic patrols of shorelines by a handler and trained dog is very
effective in discouraging waterfowl from using an area or nesting.
• Addling eggs. Eggs in nests can be addled (killed) by shaking or applying
mineral oil.
• Relocation of waterfowl. This approach is not recommended because the
birds usually return within a short period.
Public resistance to disturbing birds may make implementation of strategies to deter birds
difficult. A public education program can be established to address people's concerns about
the welfare of waterfowl and discourage feeding waterfowl.
PHYSICAL CONTROL METHODS
Hand-Digging
Principle: Hand-digging and removal of rooted, submersed plants is an intensive
treatment option. This method involves digging out the entire plant (stem and roots)with a
spade or long knife, or by hand, and disposing of the residue on shore. In shallow waters
less than 3 feet deep, no specialized gear is required. In deeper waters, hand removal can
best be accomplished by divers using Scuba or snorkeling equipment and carrying
collection bags for disposal of plants. The technique is most appropriately applied to small
areas (i.e., area less than 5,000 square feet).
Control Effectiveness and Duration: Efficacy of plant removal depends on sediment
type, visibility, and thoroughness in removing the entire plant, particularly the roots. A
high degree of control over more than one season is possible where complete removal has
been achieved.
Advantages: The technique results in immediate clearing of the water column of nuisance
plants. The technique is very selective in that individual plants are removed. It is most
25
Summer Lake Management Plan...
useful in sensitive areas where disruption must be kept to a minimum. Because the
technique is highly labor-intensive, it is most suitable for small-area, low plant density
treatments. In these cases, the technique is very useful for aggressive control of sparse or
small pockets of rooted Eurasian watermilfoil. This method can also be useful for clearing
rooted pondweeds or small patches of watershield from areas around docks and beaches.
Drawbacks: The technique is time-consuming and costly, especially where contract divers
may be used. Diver visibility may become obscured by turbidity generated by swimming
and digging activities. Also, it may be difficult for the laborer to see and dig out all plant
roots. Environmental impact is limited to mostly short-term and localized turbidity
increases in the overlying water and some bottom disruption.
Costs: Costs will vary depending on whether contract divers or laborers are used, or if
removal activities are the result of volunteer efforts. In the case of contract divers and dive
tenders, expenses can run upwards of $1,000 to $2,800/day, with the area covered
depending on the density of plants. In other words, this can take three divers 2 to 6 days
per acre of moderate density plants.
Applicability to Summer Lake: Hand digging of plant stems and roots could be used for
small-scale, intensive removal of plants around private dock areas and short shoreline
segments. If root systems are completely removed, this technique provides a more long-
term means of control (as compared to hand-cutting described below). Unfortunately,
Summer Lake has plant beds that are too large to be addressed by hand-removal alone.
Hand-pulling used in conjunction with other control methods, especially for follow-up
efforts, is a likely approach.
Hand-Cutting
Principle: This technique is also a manual method, but differs from hand-digging in that
plants are cut below the water surface (roots generally not removed). Because roots are not
removed, this is a less intensive removal technique. Implements used include scythes,
rakes, or other specialized devices that can be pulled through the weed beds by boat or
several people. Mechanized weed cutters are also available that can be operated from the
surface for small-scale control.
Control Effectiveness and Duration: Root systems and lower stems are often left
intact. As a result, effectiveness is usually short-term as regrowth is possible from the
uncut root masses. Duration of control is limited to the time it takes the plant to grow to
the surface.
Advantages: The technique results in immediate removal of nuisance submerged plant
growth. Costs are minimal.
Drawbacks: Like hand-pulling, this technique is time-consuming. Visibility may be
reduced by turbidity generated by cutting activities. Also, since the entire plant is usually
not removed, this technique does not result in long-term reductions in growth. Duration of
control of rooted plants like EWM would be minimal. Environmental impact is limited to
26
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
mostly short-term and localized turbidity increases in the overlying water and some bottom
disruption. Cut plants must be removed from the water.
Costs: Where volunteer efforts are employed, costs are mostly limited to purchase of a
cutting implement. This can vary from under $100 for the Aqua Weed Cutter (Sunrise
Corp.) to over $1,000 for the mechanized Swordfish (Redwing Products).
Applicability to Summer Lake: Hand cutting of plant stems in Summer Lake would be
appropriate because it does not eradicate the plants. However, 6.5 acres is a very large
area to harvest by hand.
Bottom Barrier
Principle: Barrier material is applied over the lake bottom to prevent plants from
growing, leaving the water clear of rooted plants. Bottom covering materials such as sand-
gravel, polyethylene, polypropylene, synthetic rubber, burlap, fiberglass screens, woven
polyester, and nylon film have all been used with varying degrees of success. Applications
can be made at any depth, with divers often used for deeper water treatments. Usually
bottom conditions (such as the presence of rocks or debris) do not impede most barrier
applications, although pre-treatment clearing of the site is often useful.
Control Effectiveness and Duration: Bottom barriers can provide immediate control of
nuisance plant conditions upon placement. Duration of control depends on a variety of
factors, including the type of material used, application techniques, and sediment
composition. Elimination of nuisance plant conditions for at least the season of application
has been demonstrated for synthetic materials such as Aquascreen and Texel. Where
short-term control is desired for the least expense, burlap has been found to provide up to 2
to 3 years of relief from problematic growth before eventually decomposing (Truelson 1985;
1989). After satisfactory control has been achieved (usually several months), some barrier
materials can be relocated to other areas to increase benefits.
Advantages: Bottom barriers can usually be easily applied to small, confined areas such
as around docks, moorages or beaches. They are hidden from view and do not interfere
with shoreline use. Bottom barriers do not result in significant production of plant
fragments (critical for Eurasian watermilfoil treatment). Bottom barriers are most
appropriately used for localized, small-scale control where exclusion of all plants is
desirable, where other control technologies cannot be used, and where intensive control is
required regardless of cost.
Drawbacks: Depending on the material, major drawbacks to the application of benthic
barriers include some or all of the following: high materials cost, labor-intensive
installation, limited material durability, possible suspension due to water movements or
gas accumulation beneath covers, or regrowth of plants above or below the material.
Periodic maintenance of bottom barrier materials is required to remove accumulations of
silt and any rooting fragments. In some situations, removal and relocation of barriers may
not be possible (e.g., natural fiber burlap does decompose over time). Bottom barriers can
also produce localized depression in populations of bottom-dwelling organisms such as
aquatic insects.
27
Summer Lake Management Plan...
Costs: Costs vary from approximately $0.30/sq. ft (Texel) to $0.35/sq. ft (Aquascreen) for
materials, with an additional $0.25-0.80/sq. ft for installation. Locally, prices for rolled
burlap material (available in fabric stores, outlets) average from $0.15 to $0.25/sq. ft for
materials only.
Applicability to Summer Lake: Because most of the better screening materials are
costly and proper applications can be labor-intensive, bottom barriers are best suited for
spot and limited area treatments. Thus, potential use in Summer Lake would be limited to
small areas; nevertheless, this approach will be an important part of a long-term
integrated management program.
Artificial Circulation
Artificial circulation injects compressed air from a diffuser on the lake bottom. The
objective of artificial circulation is to completely circulate the lake using pumps, jets, or
bubbled air. Stratification is thus prevented or disrupted. The main improvements in water
quality from artificial circulation are aeration and chemical oxidation of substances in the
entire water column (Pastorok et al. 1982). Artificial circulation also expands habitat for
aerobic organisms in lakes where the hypolimnion is anoxic. However, artificial circulation
may decrease water clarity, and would not decrease algal biomass. Algal biomass may even
increase because resuspension of sediments would increase the nutrient concentration in
the water column. Artificial circulation may also adversely impact the cold-water fisheries
by increasing whole-lake temperatures.
Sediment Oxidation
Sediment oxidation is a technique to oxidize the top 15 to 20 cm of anaerobic lake sediment
(Ripl 1976; Cooke et al. 1993b). A solution of calcium nitrate [Ca(NO3)2] is injected into the
sediment to stimulate denitrification and oxidize organic matter. Increased oxidation of
organic matter results in greater binding of sediment phosphorus with iron hydroxide
compounds, and thus lower phosphorus release rates. Very few lakes have been treated
this way, and evidence of success is limited (Cook et al. 1993b).
Water-Level Drawdown
Water-level drawdown controls aquatic macrophytes primarily by exposing the plants to
freezing or desiccation. Drawdown has also been used to consolidate sediments and to
deepen lakes by subsequent dredging or excavation. Drawdown is most effective in
controlling macrophytes in areas with cold climates, and has little or no effect in the
marine climate of western Washington (Cooke et al. 1993b; Olem and Flock 1990). Aquatic
macrophyte control by drawdown in a western Washington lake lasted only one year before
plants returned to pre-drawdown densities (Jacoby et al. 1983).
28
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
WATERSHED MANAGEMENT MEASURES
Landscaping Practices
Shoreline development along Summer Lake has typically replaced native vegetation with
houses, driveways, lawns, gardens, docks, and bulkheads. Problems associated with these
disturbances include nutrient release from fertilizers, detergents, and yard waste; toxic
chemical release from herbicides, pesticides, and paint products; and excess surface runoff
from impervious surfaces or areas of low permeability such as lawns.
Landscaping practices can prevent erosion, reduce runoff, and minimize organic and toxic
chemical use. Preserving native vegetation will reduce erosion, lower landscaping costs,
facilitate infiltration of rain into the soil, and provide wildlife habitat. The following
landscaping and yard maintenance practices are recommended for the long-term
improvement of the waterways.
• Vegetated filter strips, berms, swales, or buffer zones should be maintained
down-gradient of houses, parking areas, driveways, and lawns.
• Yard wastes, such as grass clippings, tree cuttings, ashes, and debris, should
not be discarded in, or close to, the lake, wetlands, or ditches. A good
alternative is to establish a backyard or community compost area that is
protected from surface water. Composting saves money by reducing garbage
disposal costs, and produces soil with a much higher organic content than
commercial potting soils.
• If herbicides, pesticides, or fertilizers are used, apply them carefully and only
when needed. Use less-toxic, short-acting chemicals instead of hazardous,
long-lasting ones. Look for fertilizers with a 3-1-2 ratio of nitrogen to
phosphate to potash, or, better yet, use a phosphorus-free fertilizer. Don't use
combination fertilizer/herbicides; you're probably applying chemicals you don't
need. Avoid application on windy or rainy days. Follow label directions and
use limited quantities. In general, frequent application of small amounts of
chemicals is more effective than applying large amounts once or twice.
• Limit the amount of water running off property by minimizing impervious
areas or areas of low permeability. Impervious areas include concrete or
asphalt driveways, sidewalks, and patios, and houses. Constructing driveways
and walkways with gravel, bricks, interlocking pavers, or pre-cast concrete
lattice pavers can reduce runoff. These modular pavers allow rain to enter the
soil. Planting Corsican mint, moss, or woolly thyme will crowd out weeds and
add beauty. Wood decks are attractive, and the spaces between the decking
allow rain to soak into the ground. Redwood, cedar, or treated wood is as
durable as most paved surfaces. New porous materials, such as porous
asphalt, are also available.
• Plant shrubs and trees to soften the force of the rain as it falls. Lawns and
areas where there is only groundcover are poorly permeable to water. Shrubs
and trees break the force of the rain so that it can infiltrate the ground.
29
Summer Lake Management Plan...
• Don't use landscaping plastic. It blocks diffusion of water and oxygen into the
ground, so runoff is increased and the activity of beneficial microbes in the
soil is reduced. Instead, substitute mulch, such as compost, leaves, grass
clippings, newspaper, or straw. Mulching adds nutrients, makes the soil more
workable, aids water penetration, controls weeds, and improves the moisture-
retaining capacity of the soil. Bark is preferable to plastic, but should not be
used if it could be washed into waterways. The fibers clog drains, increase the
acidity of water, and damage fish gills.
• Direct downspouts from roofs or driveways away from the waterways,
streams, and wetlands. Instead, drain the runoff into properly designed
storage systems, such as french drains, detention basins, or grass lined
swales. Increased infiltration of rain helps supply the waterways with a
steady supply of clean water.
• Stabilize cleared or eroded areas by spreading straw or planting annual
grasses such as rye, cereal rye, and gray oats. The prime times to seed grasses
are from April 20 to June 1, and throughout September.
• Reduce landscape and lawn watering by planting drought-resistant plants.
Water early in the morning using a soaker hose rather than a sprinkler to
reduce evaporation. The second best time to water is early evening, but late
watering may encourage plant diseases if dampness remains frequently
through the night.
• Water infrequently; generally one thorough watering a week is sufficient.
Infrequent watering encourages deep root systems that help plants survive
hot sunny days. Excessive watering decreases the effectiveness of fertilizers,
pesticides, and herbicides, and generates polluted runoff.
• Mow lawns to the proper height. Mowing height determines the degree of
runoff by affecting the depth the roots grow and the density of grass shoots.
Mowing height for perennial ryegrass and fescues should be 4 to 8 cm. Cut
your grass frequently so that no more than the upper third of the blade is
removed.
The aim of many of these recommendations is to conserve water and increase the rate of
groundwater recharge, and maintain a flow through the lake during the summer. Water
conservation by lakeshore residents would improve the water quality of the lake by
decreasing overland flow, which carries nutrients, pesticides, oils and greases, and
sediments.
Household and Commercial Practices
Establishing and maintaining good water quality depends on the willingness and
cooperation of everyone to minimize waste, dispose of toxicants properly, and conserve
water. The following practices should be part of the routine operation of any house or
business.
30
...2. EVALUATION OF MANAGEMENT ALTERNATIVES
• Proper disposal of all hazardous waste
Recycle solvents (e.g., paint thinner, rust remover, turpentine) by
taking them to a household hazardous waste collection service.
Don't wear contact lenses when working with organic solvents. They
can absorb and trap the solvent next to your eye.
Keep unused portions of hazardous products in their original
containers. Preserve the labels for directions and lists of contents as a
reference in case of accidental poisoning. Store chemicals and solvents
in a safe, cool place.
Give unneeded paints (oil-base or water-base) to a friend, neighbor, or
community group to use. To dispose of less than a quart, allow paint
to evaporate in well-ventilated area away from pets and children.
Discard resulting can of dried paint in trash.
Give excess pesticides and herbicides (e.g., weed killers, slug bait,
rose dust, mothballs) to a friend or business to use, or take to a
household hazardous waste collection service.
Use household cleaners (e.g., bleach, furniture polish, spot removers)
according to directions, or give to a friend to use.
Recycle waste oil (most full-service gas stations accept used oil).
Dispose of antifreeze and brake fluid only at hazardous waste disposal
areas.
• When handling paints, solvents, or preservatives, never wash brushes in
areas where the wash water will drain directly into natural receiving
waters.
• Whenever possible, use biodegradable/low phosphate cleaning products.
"Low" phosphate means less than 0.5 percent phosphate by weight in
laundry detergent and less than 4 percent by weight in dishwashing
detergents. The use of detergents within the lake area should be restricted
to low or non-phosphate brands. Ideally, phosphate-containing detergents
should not be made available for purchase within the watershed area.
However, even some biodegradable cleaning products can cause water
quality degradation if they enter the lake in large quantities.
• Reuse and recycle whatever possible.
• Use less toxic products or commercial product substitutes, such as those
listed in Table 2-3.
31
Summer Lake Management Plan...
TABLE 2-3.
RECOMMENDED SUBSTITUTES FOR COMMON HOUSEHOLD PRODUCTS
Household Product Recommended Substitute
Glass cleaner 2 tablespoons of vinegar to 1 quart water.
Oven Cleaner Pour salt on fresh spills in the oven and scrape them off after the
oven cools.A water solution of baking soda will remove grease.
Paint ammonia on spills with a paintbrush.
Refrigerator deodorizer Baking soda.Keeping a refrigerator clean prevents strong smells
from developing.
Air freshener Use vinegar in an open dish or open a window.
Chlorine scouring powder Use a non-chlorine powder or baking soda.
Drain cleaner Plunger followed by a handful of baking soda with 1/2 cup
vinegar;cover drain and let sit for 15 minutes followed by two
quarts of boiling water.
Mothballs Cedar chips enclosed in cotton sachets.Keep only clean clothes in
closet.
Toilet bowl cleaner Scouring powder
Household detergents Simple phosphorus-free soap
Tile cleaner Baking soda
Bleach Borax
Stain remover Rub with cornstarch paste,brush off when dried
Disinfectant cleaner Ammonia
Mildew-stain remover Vinegar solution
Coffeepot cleaner Vinegar solution
• Read labels of all cleaning products carefully and follow directions. Use
products with lowest phosphate content. Make sure that the wastewater
used with detergents (e.g., when washing the car) does not enter the
stream system through storm drains or by overland runoff. Washing the
car in the driveway or parking area will not always prevent the wastewater
from entering the lake. Use the lawn, so that the grass and soil can filter
the wash water.
• Water conservation awareness. The way water is used strongly affects
lakes, wetlands, and streams. Unrestricted use of fresh water not only
threatens water supply, but excess runoff from car washing, lawn
watering, and other activities can speed up the eutrophication process.
Additional water running through the septic field creates a hydraulic
burden. State regulations to address domestic water conservation may be
forthcoming. Possibilities include low-flow faucet aerators (which use 40
percent less water), flow restricters for shower heads, plastic bottles filled
with water for toilet tanks, and water-conserving lawn and garden
sprinklers.
32
CHAPTER 3.
RECOMMENDED MANAGEMENT PLAN
MANAGEMENT SCENARIOS
The advisory committee reviewed the management alternatives described in the previous
chapter and formulated four scenarios to meet the goals defined for the management plan.
The management scenarios are summarized in Table 3-1.
TABLE 3-1.
SUMMER LAKE MANAGEMENT SCENARIOS
Estimated Cost
Activity Year 1 Year 2 Year 3 Year 4 Year 5 5-Year Total
Scenario 1
Harvesting $51,000 $6,000 $6,000 $6,000 $6,000 $75,000
Bottom barriers $8,000 $3,000 $0 $3,000 $0 $14,000
Shade and shoreline $24,000 $2,000 $2,000 $2,000 $2,000 $32,000
Alum treatment $10,000 $0 $0 $10,000 $0 $20,000
Education $2,500 $2,000 $2,000 $2,000 $2,000 $10,500
Total 95,500 $13,000 $10,000 $23,000 $10,000 $151,500
Scenario 2
Systemic herbicide treatment $25,000 $0 $25,000 $0 $25,000 $75,000
Shade and shoreline $24,000 $4,000 $2,000 $4,000 $2,000 $36,000
Alum treatment $10,000 $10,000 $0 $10,000 $10,000 $30,000
Education $2,500 $2,000 $2,000 $2,000 $2,000 $10,500
Total $61,500 $16,000 $29,000 $16,000 $39,000 $161,500
Scenario 3
Contact herbicide treatment $10,000 $10,000 $10,000 $10,000 $10,000 $50,000
Shade and shoreline $24,000 $4,000 $4,000 $4,000 $4,000 $40,000
Alum treatment $10,000 $10,000 $10,000 $10,000 $10,000 $50,000
Education $2,500 $2,000 $2,000 $2,000 $2,000 $10,500
Total $46,500 $26,000 $26,000 $26,000 $26,000 $150,500
Scenario 4
Dredging $100,000 $0 $0 $0 $0 $100,000
Harvesting $0 $51,000 $6,000 $6,000 $6,000 $69,000
Alum treatment $10,000 $10,000 $0 $0 $10,000 $30,000
Shade and shoreline $32,000 $2,000 $2,000 $2,000 $2,000 $40,000
Education $2,500 $2,000 $2,000 $2,000 $2,000 $10,500
Total $144,500 $65,000 $10,000 $10,000 $20,000 $249,500
33
Summer Lake Management Plan...
Each scenario includes four or five basic elements. All are ongoing programs that will
change with environmental conditions and the development of new technology; and all
include public education on BMPs and watershed awareness. In each scenario, the lake
will require some annual activity to meet the management goals and maintain beneficial
uses. The first element of each scenario is the main functional activity in the first year of
implementation. The scenarios'key elements are as follows:
• Scenario 1 calls for harvesting aquatic plants, applying bottom barriers,
providing vegetative shading, adding alum to control algae, and providing
public education.
• Scenario 2 employs a systemic herbicide to kill aquatic plants and includes
shoreline shading, alum addition, and public education.
• Scenario 3 uses a contact herbicide treatment to burn off existing aquatic
plants and includes shoreline shading, alum addition to control algae, and
public education.
• Scenario 4 relies on dredging sediment and harvesting aquatic plants and
includes shoreline shading, alum addition, and public education.
RECOMMENDED SCENARIO
The Summer Lake citizen advisory committee recommends Scenario 1. This approach
requires the purchase of an aquatic plant harvester in the first year to harvest (cut)
aquatic plants to a depth of 4 feet below the water surface. Harvesting will have to be done
three times during the growth season (April through October). A small harvester such as
Aquarius Systems' EH-120 with trail would be purchased at a price of approximately
$45,000 (see appendix for specifications). The estimated operation and maintenance costs
are $6,000 per year. To supplement the harvester in areas that the machine cannot reach,
bottom barriers would be positioned to limit the growth of aquatic plants. A sustainable
vegetative cover on the shoreline and the islands will shade portions of the lake water,
providing some temperature control. To address algal blooms, aluminum sulfate would be
added to the lake to remove phosphorus and limit phosphorus loading from lake sediments.
This would prevent algal blooms and clarify the water. Newsletters and other forms of
communication would be produced to inform the public about the program and to
encourage BMPs.
Table 3-1 provides estimated costs for the first five years of the plan. Years 6 through 20
would be an extension of Years 2 through 5; so the 20-year cost for implementing Scenario
1 would be $375,000, with an average annual cost of$10,000 to $23,000.
The advantage of Scenario 1 is that it allows the system to function as a wetland
environment, with the associated water quality benefits, while still serving as an aesthetic
environment. The program will improve water quality and temperature in the lake, in turn
enhancing downstream conditions and the park's aesthetic setting.
34
...3. RECOMMENDED MANAGEMENT PLAN
If implementation is delayed for administrative, funding or other reasons, treating the lake
with a contact herbicide in the interim could give short-term, immediate relief to current
conditions. The herbicide could be applied in mid-summer to kill off the top of the plants,
creating an open water zone in the lake until a harvester is purchased. This would not
provide long-term benefit but it would generate immediate aesthetic improvements. It is
estimated that it would cost $10,000 for this type of treatment.
35
APPENDIX
HARVESTER MANUFACTURER'S SPECIFICATIONS
Summer Lake Management Plan
September 1998
A Q U A a �'
EH-SERIES AQUATIC PLANT HARVESTING EQUIPMENT
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EH-120 AQUATIC PLANT HARVESTER
Market demand for an economical, highly maneuverable version ,f our top quality line of harvesters inspired us to
introduce the EH-120. Its low profile: twin pontoon styling and 1 500 pound storage capacity make it a
dependable solution to the vegetative problems of small lake and pond owners.
A combination of several proven design features. the EH-120 Incorporates a live storage bed conveyor with the
cut and collect function. This conveyor stores the vegetation and hydraulically discharges the load at a disposal
site on shore.
Unique twin archimedean screws propel the EH-120 These screws which are located in line with the pontoons
enable this unit to maintain a narrow 8' operating width No assembly or disassembly is required making over the
road transport a simple task.
The EH-120 is equipped with the customer's choice of a gas or diesel engine, and all functions are hydraulically
controlled. A thermally cured epoxy finish over a white sandblasted substrate provides excellent protection
against corrosion. Each Harvester comes with a lockable tool box and battery box for added security
Several options are available with the EH-120, including stainless steel and aluminum constructionsunirain
canopy, and stainless steel mesh. Custom options are also available to meet the customer's needs Accessory
equipment available includes: Standard Trailers. Trailer-Conveyors Shore Conveyors. and Hi-Speed Transports
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EH-120 HARVESTER
STANDARD EQUIPMENT SPECIFICATIONS
DIMENSIONS Operating Length 32.33' (9.86 M)
Operating Width 8.17' (2.49 M)
Operating Height .. 5.08' (1.24 M)
Shipping Length .... 32.33' (9.86 M)
Shipping Width 8.17' (2.49 M)
Shipping Height 6' (1.52 M)
Harvester Weight 3,500 lbs. (1,591 KG)
FLOTATION Pontoon Length 22.5' (6.86 M)
Pontoon Diameter 2' (.61 M)
Maximum Displacement 8,026 lbs. (3,648 KG)
Hull Material Steel
Hull Finish Epoxy coating after white sandblast
POWER PAC:: Engine Briggs "rratton 15 h.p. gasoline engine
Hydraulic Pump Variable iolume, pressure compensated
Hydraulic Reservoir 18 US gallons w/temperature & level gauge
Fuel Tanks 2 portable tanks, 6 US gallons (23 Liters) each
CONTROL BRIDGE Hydraulic Controls ningertip levers
Operator Seat '.djustable, ergonomic style
System Controls Full Instrumentation
System Protection Pressure relief valves
HARVESTING HEAD Harvesting Width 4' (1.22M)
Harvesting Depth 0 to 4' (0 - 1.52 M)
Cutter Knives Reciprocating 3" stroke (75 MM)
Shear Fingers Horizontal -forged steel
Vertical- formed steel
Conve `ling 1" x 1" galvanized mesh
LOAD CONTAINER Length 20' (6.1 M)
Width 4.33' (1.32 M)
Volume (Load) ... 130 cubic feet (3.68 Cu M)
Weight (Load) 1,500 lbs. (682 KG)
Conveyor Belting 1"x 1"galvanized mesh
PROP U L S I O N Archimedean Screw (2) Hydraulic drive, independently operated
Forward & Reverse
FASTENERS Fasteners Stainless steel 18/8 throughout
OPTIONS Stainless steel or Aluminum configuration also available
DUE TO CONTINUAL INNOVATION & DESIGN
SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT NOTICE