PB89-210421
Long Lake Restoration Project. Final Report
Entrance Engineers, Inc., Kirkland, WA
Prepared for:
Environmental Protection Agency, Seattle, WA
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Dec 80
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PB89-210U21
LONG LAKE
RESTORATION PROJECT
KITSAP COUNTY, WASHINGTON
ENTRANCO Engineers
(NVMOMtNl H ««0 KUKJrCKTAIKX CCNIUTtNTl
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TECHNICAL REPORT DATA
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,1. RECIPIENT'S ACCESSION NO.
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S. REPORT DATE
A. PERFORMING ORGANIZATION CODE
7 AUTHORISI
. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
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12. SPONSORING AGENCY NAME AND AOORESS
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14. SPONSORING AGENCY CODE
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13. SUPPLEMENTARY NOTES
16. ABSTRACT
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LONG LAKE
RESTORATION PROJECT
FINAL REPORT
Prepared for
KITSAP COUNTY, WASHINGTON
Supported by and Submitted to the
U.S. Environmental Protection Agency, Region X
through a Clean Lakes Program Grant
and a
Referendum 26 Lake Restoration Grant
from the State of Washington
Department of Ecology
Olympia, Washington
Prepared by
ENTRANCO ENGINEERS
1515 - 116th Avenue N.E., Suite 200
Bellevue, Washington 98004
December 1980
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PREFACE
This report describes the events that have taken plac^ In a successful
program to Improve water quality and recreation potential of a shallow
lowland lake. Long Lake, 1n KHsap County, Washington, was displaying the
typical eutrophlc status Ir.dlcators of high nutrient concentration! ,
nuisance algal blooms, and extensive aquatic weed growth. After a
comprehensive water quality study and development of a restoration plan,
the following elements were undertaken In order to Improve the condition of
the lake:
1. Land use and drainage control policies 1n the watershed.
2. Dredging of the north bay and outlet of the lake.
3. Summer drawdown of the lake.
4. Chemical treatment of the lake by the application of aluminum
sulfate.
The history of the project and the complete description of results of the
restoration elements will be undertaken In this report.
The total evaluation of this project Is not complete. Further monitoring
1s being conducted by the University of Washington and the net result of
the restoration program w'll not be known for another year. Therefore, the
report will be primarily directed toward the lay reader. A more complete
evaluation of the changes In lake chemistry as a result of the restoration
program will be provided by the University of Washington when their final
monitoring Is complete. Those Individuals who wish to utilize results from
the Long Lake project for Incorporation Into other lake Improvement
programs and need more technical Information prior to the Issuance of the
University of Washington report should contact the University of Washington
or Entrance Engineers for copies of specific quarterly or annual reports.
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ACKNOWLEDGMENTS
This project was managed and conducted by Entrance Engineers of Bellevuc,
Washington for Kltsap County, Washington. The consultants wish to thank
and acknowledge the following groups and Individuals for their efforts 1n
completion of this complicated and Interesting project.
Kltsap County Board of Commissioners
William H. Mahan
Gene Lobe
John Horsley
Kltsap County Public Works Department
Frank Randall
Save Long Lake Committee
George Cressman
Melvln Price
Long Lake Community Club
University of Washington
Eugene Welch
Washington Cooperative Research Fisheries Unit
James Congleton
State of Washington Department of Ecology
Ron P1ne
U.S. Environmental Protection Agency
Ed EldHdge
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SUMMARY
Long Lake, In Kltsap County, Washington, 1s a shallow, lowland lake that
has been displaying the typical eutrophic status Indicators of high
nutrient content, bluegreen algal blooms, and extensive aquatic weed
growth. At the request of local citizens, the County retained help to
conduct a four-season water quality study. The study concluded the lake
was eutrophlc and the County retained Entrance Engineers to develop a lake
restoration plan and prepare a grant application.
Funding for the project was obtained from the Environmental Protection
Agency as a "Clean Lakes National Demonstration Project" and from the State
of Washington Department of Ecology under Referendum 26, "Washington
Futures." The remaining funds were provided by Kltsap County. The total
cost was approximately $1,310,000. A 23-acre park site was obtained or. the
north end of the lake through a grant from the Interagency Committee for
Outdoor Recreation.
The original restoration plan was revised several times In order to meet
the requirements of permit granting agencies, correct funding problems,
make up for project delays, and utilize new monitoring data. The following
elements were finally undertaken 1n order to Improve the water quality of
the lake:
1. Land use and storm drainage control policies
2. Dredging of the north bay and outlet of the lake
3. Summer drawdown of the lake
4. Chemical treatment of the lake by the application of aluminum sulfate
(alum)
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The drainage and land use controls have been practiced on a County-wide
basis for new commercial and residential developments. Stonnwater must be
retained on-s1te and released at pre-development runoff rates to obtain
plat approval. Dredging, drawdown, and alum application were undertaken 1n
the summers of 1978, 1979, and 1980.
Dredging operations removed approximately 60,000 cubic yards of sediment
from the north end of the lake and the outlet channel. Drawdown operations
lowered the lake level approximately 6 feet to promote shoreline sediment
compaction, desslcatlon of weeds, and beach clean-up. The alum treatment
process clarified the water column and covered the lake bottom with a
flocculant blanket to retard phosphorus release from sediments.
Although monitoring will continue for another year, Initial results of the
restoration program appear favorable. The lake shows a notable reduction
in phosphorus concentrations, as well as reduced algal and weed blomass.
1v
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TABLE OF CONTENTS
PAGE
PREFACE 1
ACKNOWLEDGMENTS 11
SUMMARY 111
TABLE OF CONTENTS v
LIST OF FIGURES vl1
LIST OF TABLES 1x
PROJECT BACKGROUND AND HISTORY 1
Land Use/Population 4
Comnunlty Action 6
RehabllKatfve Procedures 7
Current Status II
WATER QUALITY INVESTIGATIONS 11
Introduction 11
Study Program 11
Monitoring Program 13
Monitoring Results 16
DREDGING 28
Introduction 21
Design Considerations 21
Dredging Operations 22
Spoil Restoration 28
Costs 21
Summary and Conclusion 28
LAKE DRAWDOWN 31
Introduction 31
Design Considerations 32
Theory of Operation 35
Operation 35
Shoreline Cleanup 37
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TABLE OF CONTENTS
(Continued)
PAGE
Monitoring and Results 37
Lake Water Quality 37
Macrophyte Surveys 39
Sediment Compaction 41
Water Quality 42
Well Monitoring 42
Auxiliary Water Supply 43
Costs 44
Conclusion 44
CHEMICAL TREATMENT WITH ALUMINUM SULFATE ' 45
Introduction 45
Preliminary Design Considerations 46
System Design 49
Application Procedure 52
Monitoring and Results 56
Costs 60
Conclusion 62
WATER QUALITY EVALUATION 63
Introduction 63
Discussion 63
COMMUNITY EVALUATION 67
LIST OF REFERENCES 68
APPENDIX A
Sampling Location Map
APPENDIX B
University of Washington Annual Report: 9/79-9/80
v1
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LIST OF FIGURES
FIGURE
NUMBER
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
DESCRIPTION
Photograph - Aerial View of Long Lake
Photograph - El odea Densa on Boat Anchor
Diagram - Site Layout for Limits of Dredging Operation
and Location of Spoils Basins
Photograph - Placement of Hydraulic Dredge 1n Lake
Photograph - Hydraulic Dredge Operation 1n North
End of Lake
Photograph - Discharge of Dredge Spoils Into Decant
Basin
Photograph - Alum Treatment System at Basin Connection
Photograph - Dredge Spoil Basin Prior to Restoration
Photograph - Dredge Spoil Basin After Restoration
Photograph - Drawdown Pump Facility in Operation
Photograph - North Shore Beach During Drawdown,
Prior to Clean-up
Photograph - Northshore Beach During Drawdown,
After Clean-up
Photograph - South End of Lake Exposed During
Drawdown
Photograph - Dried Elodea Densa Exposed During
Drawdown
Diagram - Alu.n Distribution Barge
Photograph - Alum Application Barge
Photograph - Alum Application Barge in Operation
Diagram - Alum Treatment Sector Grid Map
Photograph - Secchi Disk Reading after Alum
PAGE
2
5
23
25
25
26
26
29
29
34
38
38
40
40
51
53
53
54
Application 61
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LIST OF FIGURES
(Continued)
FIGURE
NUMBER DESCRIPTION PAGE
ZO Photograph - Core Sample of Bottom Sediments Showing
Layer of Alum Floe 61
21 Graph - Mean Total P Content of Long Lake 64
22 Graph - Mean Chlorophyll-a Concentrations 66
vin
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LIST OF TABLES
TABLE
NUMBER DESCRIPTION PAGE
1 Results of Alum Application Pilot Study 48
2 Long Lake Alum Dosage Quantities 55
2 Results of Pre- and Post-Alum Treatment Monitoring 58
1x
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PUGET SOUND
STATE OF WASHINGTON
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K!lom«t«rt
e
ENTRANCO Engineers
VICINITY MAP
FIGURE
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PROJECT BACKGROUND AND HISTORY
Long Lake 1s located 1n K1f,ap County, Washington, approximately four miles
south of the city of Port Orchard. The 339-acre lake drains a 9.4-square
mile rapidly urbanizing watershed. The tributary system Includes
Salmonberry Creek and several unnamed streams. The lake volume Is 2,180
acre-feet with maximum and mean depths 12 and 6.5 feet, respectively. The
outlet from Long Lake 1s Curley Creek, which flows from the northeast
corner of the lake.
Long Lake Is used primarily for recreation, Including swimming, boating,
water skiing, and fishing. The lake currently contains an active warm
water fishery and Is part of a waterway which harbors a significant
migratory run of salmon. Long Lake Is one of only two lakes In KUsap
County where water skiing 1s allowed (the other 1s Kltsap Lake). Public
access 1s provided by a State of Washington Department of Game boat launch
on the west shore of the lake.
The lake was suffering from an accelerating eutrophlcatlon. Eutrophlcatlon
Is a nutrient enrichment process which results In high productivity.
Eutrophlcatlon happens to all lakes over geologic time; It 1s a natural
aging process which can be accelerated by the activities of man. This
aging process resulted 1n local citizens' realization of the need for a
rehabilitation program.
The condition of the lake had steadily worsened 1n recent years.
Measurements by the U.S. Geological Survey Indicated the depth 1n the lake
had been decreasing from an average depth of 15 feet 1n 1953 to an average
of 6.5 foet 1n 1973. The U.S.G.S. study Indicated maximum depths decreased
from JO feet to 12 feet In the same period. A layer of decayed material
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Figure 1: Aerial view of Long Lake (looking north)
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(detritus) several feet, deep blankets the lake bottom. S1ltat1on, dead
algae, and decayed aquatic weeds are all causes of this f1U1ng-1n process;
peat mining 1n the watershed tuny years ago has also been considered as a
possible cause of lake filling. Recent work by the University of
Washington disputes the rate of filling Indicated by U.S.G.S. measurements.
The University of Washington researchers note a sedimentation rate
significantly lower than Interpreted from U.S.G.S data--.4 cm/year by the
University of Washington versus 12.75 cm/year as back-calculated from the
two U.S.G.S. depth measurements. Many variables exist between the U.S.G.S.
and University measurements, Including:
- Sounding techniques used by U.S.G.S. 1n 1953 and 1973;
- Lake stage at the time of soundings (elevation may Increase by one
meter during prerlpltatlon events);
- Compaction of loose bottom sediments since 1953; and
- Compaction during coring.
The University of Washington measurement techniques of sediment traps and
sediment core dating support each other and seem to verify a lower filling
rate. However, local lifelong residents contend they normally fished In
greater than 20 feet of water twenty years ago. Regardless of depth, no
one denies that the lake was aging at an ever accelerating rate.
The reason water quality In Long Lake had been deteriorating can be
attributed largely to urbanization 1n the watershed. Increased development
In the area resulted 1n removal of vegetation and Increased Impervious
surfaces. Greater volumes of nutrient-rich stormwater were being channeled
Into the lake; nutrients were also being supplied from subsurface flow or
groundwater.
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However, it appears that the majority of nutrients are being recycled from
the lake sediments. As a result of the Increased nutrient supply, foul
smelling and oxygen-depleting bluegreen algal blooms began to occur with
alarming frequency, water clarity diminished, and weed growth became
rampant. Power boating, swimming, and fishing In the lake were being
threatened (see Figure 2). Bacterial contamination was also occurring, as
evidenced by fecal col 1 form counts as high as 4,000 per 100 ml during the
summer of 1973, and over 250 per 100 ml several times 1n recent years.
Washington Administrative Code (WAC) Chapter 173-201 standards allow a
median value of 240 per 100 ml for water contact recreation.
The outlet of the lake (Curley Creek) was plugged with logs, silt, and
weeds, causing the lake level to rise higher than normal during Intense
storms and Increasing retention time In the lake during heavy rains.
LAND USE/POPULATION
Kitsap County as a whole is experiencing a surge 1n population growth. The
County population grew from 135,000 In 1979 to 146,750 In 1980, and growth
Is expected to continue. Much of the projected growth will be concentrated
1n South Kitsap County, particularly 1n the area east of Port Orchard. The
Kitsap County Department of Community Development predicts that population
In South Kitsap will Increase from a 1975 census figure of 26,700 to over
42,000 In 1985. Census figures for 1980 Indicate a population of 37,459 in
South KUsap. As a result, land In the Long Lake watershed will continue
to mike the rural to suburban transition with resultant Impacts to Long
Lake. Several housing developments are either planned or are currently
under construction In the area north of the lake.
The drainage basin 1s Included In two census tract subdlstrlcts or
enumeration districts (ED's). These two ED's—numbers 102 and 111—are
expected to absorb much of the population growth extending south and east
of Port Orchard. The current population of ED's 102 and 111 1s 6,779 and
2,221, respectively (KUsap County Planning Department, April 1979), an
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Figure 2: Typical entanglement of the aquatic weed,
El odea densa on a boat anchor. This is a
major nuisance weed in Long Lake
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Increase from 4,444 and 1,833 1n 1976. The population of the County 1s
relatively young, with 66% of the populace being under 35 years of age.
According to census Information, the drainage basin 1s populated largely by
average to hlgher-than-average Income families with 1-2 children. Demand
for housing will not slacken, nor will demand for recreational facilities
In the area. Swimming, fishing, and power boating rate typically high In
priority for families In this socio-economic classification.
COMMUNITY ACTION
Realizing the deteriorating quality of Long Lake and the resultant Impacts,
Long Lake residents formed the Save Long Lake Committee (SLLC) 1n 1969 to
Investigate measures for lake cleanup and monitor future development on the
lake's shoreline.
The committee organized and paid for an aquatic weed harvesting program 1n
1972, which reduced the lake's weed population for the next two seasons.
However, weed growth soon resumed and algae blooms began to reoccur. The
group attempted no further rehabilitation until 1974, when the Kltsap
County Health Department Issued contamination warnings to swimmers. At the
same time, rapid development along the periphery of the drainage basin
resulted 1n redirection of additional stormwater runoff Into the lake,
worsening existing problems. Realizing the need for governmental
assistance, SLLC requested aid from the Kltsap County Commissioners.
Several public meetings were held at that time to discuss residents'
perceptions of problems and possible solutions. It was determined that
degradation of the lake was a regional rather than strictly local concern
due to the wide geographic area utilizing the lake. The County decided
that professional help was needed.
In October 1974 Kltsap County hired Entrance Engineers and Northwest
Environmental Consultants to prepare a comprehensive four-season (14-month)
water quality study of the lake.
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The Long Lake Community Club and Save Long Lake Committee have continued to
play an active role In promoting community Involvement, fund raising,
lobbying for agency support, and environmental education. Their dedication
has kept the restoration program viable and productive.
RESTORATION PROCEDURES
The four-season water quality study Indicated at the outset that Long Lake
was highly eutrophlc and selected restoration measures would be helpful to
prevent further deterioration of the lake. Entrance Engineers was
requested by KHsap County to assist them 1n pursuing federal and state
grant funds to fund a portion of the rehabilitation costs. The Washington
State Department of Ecology had recently Initiated a lake restoration
program which had been authorized and funded 1n 1971 by the passage of
Referendum 26 (Washington Future Bonds). Several sources of federal funds
were Investigated and applications were submitted for a grant under
Sections 201, 208, and 104h of the 1972 water quality legislation (PL
92-500).
The program offered under Section 104h of the PL 92-500 was "Clean Lake
Demonstration Projects." Application requirements were stringent: the
applicant was required to submit a detailed "Innovative" rehabilitation
plan based on a complete technical analysis of the problem.
The grant application contained an Interim summary report of the water
quality study, as well as a summary of research findings and restoration
alternatives. Two major categories of lake rehabilitation methods were
discussed: methods directed at removing Incoming nutrients and/or
sediments; and methods directed toward the Improvement of 1n-lake
conditions. Programs utilizing methods from each category were proposed,
Including control of runoff, weed control, dredging, dra*1own, and alum
treatment. A cost estimate for the proposed restoration program was
Included.
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In the fall of 1975, Kltsap County was notified that the Long Lake
Restoration Project had been accepted as a Clean Lakes National
Demonstration Project and would be granted 50% of the total project cost of
$711,940 ($355,970). The State of Washington Department of Ecology
verbally committed a 40% grant ($284,776) 1n aid under Referendum 26 when
It was known that the project was financially feasible. Kltsap County
would provide the local portion of the funding.
Entrance Engineers was selected to formulate the restoration plan. At that
time, work began to acquire a 23-acre park site at the north end of the
lake. This acquisition was funded by the Interagency Committee for Outdoor
Recreation (IAC). The park was Intended to provide a public use facility
on the lake, which was part of the requirement for State matching funds.
Public access was already available at the Department of Game boat launch.
In August 1976, a draft environmental impact statement (DEIS) for the
proposed restoration of Long Lake was published by Kltsap County. The
purpose of the project, as stated 1n the DEIS, was to "Improve the lake's
water quality, deepen the lake, and correct and control man's adverse
Impacts on the lake." The objective of the project was to "achieve and
perpetuate a lake which would be attractive and healthy for the natural
flora and fauna and for man's recreational uses." The restoration project
was Initially described as consisting of eight programs: drawdown of the
lake to consolidate the bottom sediments and eradicate weeds; stormwater
treatment by sedimentation ponds; dredging; a pilot spoil disposal program;
alum treatment to inactivate nutrients; zoning of boating limited to deeper
portions of the lake; lake level control; and a monitoring projram. Each
phase was described in detail and analyzed for environmental Impact. The
Draft EIS was Issued 1n August 1976. Comments were accepted until October
1976. Several comments were received from advisory agencies which resulted
in revisions to the restoration plan. Permit-granting agencies such as the
Departments of Fisheries and Game would not approve permits for the project
until certain alterations to the plan were made.
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The Department of Fisheries would not allow dredging of Curley Creek
because of potential damage to salmon spawning areas. They also would not
approve Installation of a permanent lake level control structure, citing
potential negative Impacts to fisheries. The use of herbicides In the lake
was not allowed. As a result, the restoration plan was revised to meet the
approval of participating agencies. The drawdown structure was designed
for temporary pumping operation rather than the original permanent lake
level control design, herbicides were eliminated, and the dredging of
Curley Creek was removed from the Scope of Work. The plan was approved,
and the entire restoration plan package was advertised for bid In April
1977. Only one contractor offered a bid, which was not accepted because
the firm was not bondable and the bid exeeded the budget. The restoration
plan was advertised for bid again In June as separate elements, I.e.,
dredging, drawdown, and alum treatment. Two contractors responded; one
firm was not bondable and the other demanded a higher fee. At the
recommendation of the County Prosecutor, the bids were rejected and It was
decided to wait until the following year to advertise for bids. The 1978
bid advertisement resulted In award of the dredging contract to Marine
Construction and Dredging, Inc. and the drawdown contract was awarded to
Imco General Construction. The alum application was originally Intended to
be done by the consultants during the summer following drawdown.
Proposed stormwater treatment by detention ponds was removed from the
restoration plan because continued monitoring In the drainage basin and the
lake Indicated the majority of nutrients 1n the lake were generated from
Internal recycling rather than surface stormflow. Kltsap County also
adopted a storm drainage management ordinance requiring the Inclusion of
stormwater detention ponds In new residential and commercial developments.
Construction of detention ponds for nutrient control In Long Lake would no
longer be a cost-effective restoration scheme, and the Idea was abandoned.
If the portion of nutrients generated from nonpolnt runoff Is high enough
and can be sufficiently reduced with this type of facility, then this
element may be beneficial to the overall program.
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Ueed harvesting was eliminated from the Initial restoration plan because of
excessive cost. Estimates for weed harvesting rlone would have consumed
over one-half of the project budget. This was not a cost-effective
solution to the lake's water quality problems, but could be a benefit for
future weed control.
Dredging was completed during the summer of 1978. The drawdown structure
was constructed during the same summer, but was completed too late In the
season to Initiate drawdown. Therefore, lake level drawdown was postponed
and finally conducted In the summer of 1979.
It was decided that competitive bidding for the alum application would
provide the most cost-effective and timely treatment. Bids were accepted
1n August of 1980. The contract was awarded to Imco General Construction
and alum application was accomplished during September 1980. Monitoring of
lake water quality has continued throughout the restoration program.
CURRENT STATUS
After many years of work, three grant Increases, and continuous dedicated
community Involvement, the project 1s now complete. The total cost for the
restoration project was $1,310,000. It was the first project funded under
the federal and state programs and has been a good learning experience for
all parties Involved. Even the name, rehabilitation project has been
changed to restoration since the project began 1n the Interest of keeping
the program Identity unique.
The results of this work will be utilized as an example for design purposes
In other lake restoration projects 1n Western Washington and throughout the
United States. Further technical Information will be forthcoming upon
completion of the monitoring and evaluation program being conducted by the
University of Washington.
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WATER QUALITY INVESTIGATIONS
INTRODUCTION
Many Investigations have been conducted In the Long Lake watershed
during the past 5-6 years. These Investigations, or sampling programs,
have been used to monitor trends In lake chemistry, especially with regard
to nutrient enrichment, and to document biological responses to nutrient
loading. Water quality sampling was part of two distinct phases—a study
phase and a monitoring phase. The study phase was used to trace the extent
and source of nutrient enrichment so a eutrophication control and lake
restoration plan could be formulated. The monitoring phase measured the
results of the completed restoration plan. Due to various delays In the
Implementation of certain elements of the restoration plan, the monitoring
program was stretched out for three years beyond Its anticipated limits.
As a result, a tremendous amount of data has been collected and Interpreted
by several principal Investigators. Details of the lake studies and
monitoring programs follow.
STUDY PROGRAM
Initially, to collect enough Information for development of a restoration
plan and prepare a grant application, a four-season water quality study was
conducted by Northwest Environmental Consultants for Kltsap County with the
cooperation of Entrance Engineers. The study began In September 1974 and
terminated In August 1975. The following results were made available from
that study:
1. Total phosphorus and Inorganic nitrogen concentrations In Long Lake
were quite high.
Total Phosphorus as P Total Inorganic Nitrogen as N
Mean - 37 ug/1 Mean - 235 ug/1
Maximum - 60 ug/1 Maximum - 510 ug/1
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2. Bluegreen algal blooms are frequent, with the species Aphanlzomenon and
Anabena most prevalent. (Note: Chlorophyll-a concentrations were not
determined during this study.)
3. There 1s extensive macrophyte growth, dominated by El odea densa and to
a lesser extent, Potomogetan crispus.
4. The major influent stream, Salmonberry Creek, has above normal
concentrations of nutrients.
With this Information and other supportive data, 1t could be stated that
Long Lake was definitely suffering from eutrophlcation with external
sources suspected as a major contributor of nutrients.
In conjunction with the four-season lake and stream study by Northwest
Environmental Consultants were two separate studies by Entrance Engineers
relating to stormwater and sewer system contributions to the lake's
problems. The stormxater runoff was considered a major nonpolnt source of
pollution to Long Lake, and much of the stormwater contribution was
attributed to sediment and nutrients from newly established residential
development in the Long Lake watershed.
The Entrance study of stormwater problems led to the recommendation of a
Stormwater Management Program for Kltsap County utilizing detention/
retention facilities and other drainage Improvements. The program also
recommended the establishment of a public utility for stormwater management
and the collection of fees to pay for Improvements based upon the amount of
Impermeable surface area occupied by each user. Although all the
recommendations of the Entrance study have not been adopted, many
Improvements have been made. The County has proceeded to make it standard
policy for new commercial and residential developments to have stormwater
detention facilities to achieve plat approval. A stormxater public utility
Is still being considered.
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The sewage treatment evaluation was conducted 1n order to access the extent
of la^e nutrient enrichment from septic systems and the economic feasi-
bility of providing a sewage collection system. The collection system
Included an Initial sewer service area around the perimeter of the lake and
two alternative Interceptor lines for transfer of sewage to existing
municipal treatment facilities.
Although analysis of groundwater samples Indicated a high Input of
phosphorus by subsurface flow, the total loading to the lake from human
contributions was not determined sufficient to justify the great expense of
a sewage collection system. Some of the groundwater nutrients were traced
to natural sources. The study did, however, result In an Inspection of the
lakeside on-slte waste disposal systems and a greater consideration for
strict conformance to permit procedures for new septic systems 1n the
wttershed.
MONITORING PROGRAM
In order to evaluate the effectiveness of all the elements of the
restoration plan, two separate monitoring programs were established. One
program was established to measure "1n-lake" responses and was conducted
by the University of Washington's Department of C1v1l Engineering. A
special contract for monitoring and evaluating the restoration techniques
was awarded to the University of Washington by the EPA 1n June 1976.
Entrance Engineers conducted the other program and had the responsibility
of monitoring the streams (Inflow and outflow to Long Lake), the purpose
being to measure the effects of watershed management programs and
construction of the proposed detention ponds on the nonpolnt sources of
pollution. These programs led to a complete evaluation of nutrient Import
to and export from the lake.
To measure Influent loading, five sampling stations were established on
Salmonberry Creek and several other smaller contributing streams,
downstream of different land use areas. Two stations were sampled on
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Curley Creek to evaluate export from the lake. Samples were collected and
evaluated on a monthly basis. Flow recorders with continuous strip charts
to measure gage height were placed on Salmonberry and Curley creeks. Re-
corders were calibrated regularly so actual flows could be calculated from
recorded gage readings. Field measurements for physical characteristics
Included temperature, pH, dissolved oxygen, alkalinity, carbon dioxide
(phenolphthai eln acidity), suspended solids, and conductivity. Samples
were analyzed for total phosphorus and filterable ortho-phosphorus as P,
Kjeldahl nitrogen, ammonia nitrogen, and n1trate-n1trite nitrogen as N.
Commonly accepted practices for field procedure and chemical analysis as
outlined 1n Standard Methods and the EPA manual for water chemistry
analysis were utilized In sample collection and analysis.
Some results of the stream monitoring program conducted by Entrance
Engineers are presented below.
Study Period Summary
7/76-6/77 High dissolved nitrogen contributions are observed In
Salmonberry Creek during the wet season. There Is an
apparent larger contribution of solids and nutrients from
newly developed regions. It was a dry year with a flow
Input of approximately 3.5 times the entire lake replace-
ment volume. A net retention of phosporus and nitrogen
was observed In the nutrient budget (30 kg P and 3,600 kg
N).
7/77-6/78 In the last half of 1977 there was twice the volume of
water entering the lake 0s the entire 7/76-6/77 water
year. The replacement volume flow Input was Increased to
9 times. Inflow showed the usual Increases of dissolved N
and high suspended solids. In-lake phosphorus concentra-
tions exceeded Inflow concentrations which supports the
concept of Internal contributions. A net export of both
phosphorus (300 kg P) and nitrogen (2,400 kg N) was
measured during this time period.
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After this date, further upstream sampling was suspended until such time as
It was necessary to evaluate post construction Improvements (retention pond
construction). The University of Washington continues to monitor the lake
Influent and effluent streams and maintains the flow recorders. Further
results of monitoring programs are discussed In the evaluation of each
restoration element.
In addition to stream monitoring, Entrance Engineers participated 1n the
evaluation of groundwater Input of nutrients and contributions from
precipitation 1n order to fully evaluate external loadings of nutrients to
Long Lake.
The task of monitoring the lake and evaluating the lake response to the
elements of the restoration program was given to the University of
Washington Department of Civil Engineering by separate contract with the
EPA. The University outlined a comprehensive evaluation procedure
Including: (1) physical and chemical constituents of the lake water
column; (2) macrophyte surveys and algal Identification; and (3) analysis
of bottom sediments and lake sedimentation rate. .Variations and extensions
of the above three procedures were carried out by different university
researchers as observed trends posed new questions about the dynamics of
the lake.
The 1n-lake physical and chemical variables measured by the university
researchers Included Total- and Ortho-Phosphorus as P; organic (Kjeldahl),
ammonia, and nitrate-Nitrite nitrogen as N; organic carbon, chlorophyll-a,
alkalinity, dissolved oxygen, temperature, pH and Secchl disk depth.
Phytoplankton cell counts and algal Identification as well as the extent
and make-up of aquatic weeds were the major biological parameters measured.
Some zooplankton enumeration was also occasionally conducted.
Surface, middle, and bottom samples were taken from four 1n-lake stations.
Samples were also collected from two Influent streams and the lake outflow
for comparison to analysis by Entrance Engineers. Samples were normally
collected twice monthly throughout the project.
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MONITORING RESULTS
The Unlvers'ty of Washington monitoring program generated a great deal of
water quality dc-ta which documents the ever changing conditions of Long
Lake. The data were reported on a seasonal basis through a series of
quarterly reports. A brief summation of the highlights of those reports Is
presented In a chronological fashion.
Study Period
7-9/1976
Summary
Chlorophyll-a and Secchl disk readings Indicate the lake
Is In a eutrophlc condition. Macrophytes are abundant
(220 g/m2) with El odea densa- most prevalent. Lake
nutrient concentrations are similar to Inflow concentra-
tions except In south end where dense weed growth occurs,
and during summer months when lake concentrations are
generally higher than Inflow. TP « 50 ug/1 north and
middle, 27 ug/1 south.
10-12/1976 Denser concentration of macrophytes (259 g/m2),
reduced chlorophyll-a and Increased Secchl disk readings.
Sedimentation rate assumed to be u .6 cm/yr. Reduced TP
Influent and lake, north and middle » 39 ug/1, 25 ug/1
south.
1-3/1977
4-6/1977
March bloom of crytomonads resulted In chlorophyll-a peaks
of 100 ug/1. Early Indications of seepage meter
experiments show small nutrient Input attributed to
groundwater. Considerable resuspenslon of sediments.
TP • 41 ug/1 north and middle, 47 ug/1 south.
Potomageton Is appearing as a dominant nuisance weed.
High chlorophyll-a values supported by Increased
concentrations of total P. Indication of high Internal
phosphorus contributions.
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Study Period
7-9/1977
10-12/1977
Summary
Report not available.
Total nitrogen Increased by 3001 over previous year.
Water coloration 1s Increased with winter rains. Winter
decomposition of organic matter and leaching action of
rains strips forest humus of dissolved nitrogenous matter,
adding to lake coloration and N02-N03-N
concentrations.
1-3/1978
Chlorophyll-a concentrations remain high (60 mg/1).
Potomageton praelongus approaching nuisance levels.
Average Total P for entire lake • 57 ug/1.
4-6/1978 Ortho-P and Total-P concentrations fluctuate In contrast
to algal blooms. Algal species dominated by
Apnanlzomsnon. El odea densa remains the dominant
macrophyte, representing 94% of the submergent species.
This ended the series of quarterly reports with an annual report Issued for
the 7/78-7/79 water year. That annual report Included data collected
during a portion of the drawdown operation.
Macrophyte surveys completed during this time period were used for
collection of comparative data to evaluate the effectiveness of summer
drawdown as a method of weed control. High chlorophyll-a and nutrient
concentrations recorded In this report remained similar to previous years.
Research with lake sediments was also presented 1n the annual report.
Sediment cores were taken from the middle of the lake. The cores were
sectioned and dated, based on the concentration of lead (Pb) found. This
association was based upon the Incorporation of lead In gasoline around the
year 193C. As man's activities Increased {* the watershed, lead
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concentrations similarly Increased. Associated vlth the higher lead values
were phosphorus Increases. The background level of lead (about 1930) 1s
about 12 mg Pb/kg sediment, but In recent years lead content Is
approximately five times greater at 60 mg Pb/kg of sediment. The
phosphorus content has also Increased from about 0.061 1n 1930 (.7 ug/kg
sediment) to 0.14% currently (8 dig/kg sediment). In addition, phosphorus
concentrations were 5 to 10 times greater 1n pelagic ssdlments than
littoral sediments.
By June of 1979, the drawdown program had begun. Information from other
reports prepared by the University staff since that time 1s Included 1n
discussion of the dredging, drawdown, and alum treatment results. The
University will continue to monitor the lake until September of 1981.
During the 1977-1978 water year, a report entitled "Studies of Groundwater
Discharges Into Long Lake" was prepared by Tommy Llndell, a visiting
professor at the University of Washington. Llndell utilized "Minnesota
half-barrel" seepage meters to quantitatively and qualitatively evaluate
the groundwater Input to Long Lake. The groundwater exhibited high
concentrations of nutrients with total phosphorus values In excess of 100
ug/1 and total nitrogen of 1050 ug/1. However, due to the low water year,
the study was Inconclusive as to the relative Importance of groundwater
nutrient Input to Long Lake. Estimated groundwater volume was significant
the following year, but nutrient loading was not calculated.
Affiliated with the University of Washington 1n-lake monitoring is the
research being conducted by the Washington Cooperative Fishery Research
Unit. The Coop Is monitoring the effects of the lake restoration on the
fishery population in Long Lake. In their initial monitoring report (June
1978), the Coop made the following observations: (1) largemouth bass and
black crappie populations are low (26 bass and 32 crapple per acre); (2)
both species grew slowly in comparison to other representative lakes; and
(3) fewer numbers of larger fish were observed, which is indicative of a
heavily fished population.
18
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Their July 1979 report showed fish population counts and size similar to
1978. The Coop speculated that the size and number problem may be
attributed to extensive macrophytes and turbidity prompted by algal blooms,
which both limit the ability of the fish to forage.
The evaluation of the effects of the restoration elements on the Long Lake
fish populations continues. Like the University of Washington monitoring,
a complete Intepretatlon of all effects of each element (I.e., alum
treatment) will not be available for another year. There are probably many
synerglstlc effects that cannot presently be measured or duplicated by
experimentation that will take time and further study to properly
Interpret.
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DREDGING
INTRODUCTION
As a lake ages and the waters become enriched with growth-Inducing
nutrients, high productivity leads to the eventual die off and deposition
of much organic material. This nutrient-rich material gradually fills the
lake bottom, forming a layer of sediment. The sediment may contribute to
the continued aging of the lake by releasing nutrients back Into the water
column. Sediments also make an unpleasant substrate for lake usage by
swimmers, and when accompanied by weeds, brush, and debris 1n shallow
water, generally deter other recreational usage.
Long Lake 1s plagued with sediment problems as described above. On the
north end the thick organic deposition and shallow water layer promoted
aquatic weed growth and Invasion by shrubs and brush which are adapted to
wet conditions. Logs, boards, and other debris floating In the lake became
trapped In the north end and often clogged the outlet channel.
The problems previously described resulted 1n the formulation of a plan to
remove sediments from Long Lake by dredging. The Long Lake dredging
program had four major objectives:
1. To remove nutrient-rich sediments and reduce to a limited extent the
diffusion of nutrients to the water column.
2. To clean the lake outlet channel and Improve flushing action during
periods of high Inflow.
3. To provide a channel to facilitate the movement of lakewater to the
drawdown pumps.
4. To provide a deeper lake bottom and clean substrate for a future park
swimming area.
Dredging 1s a mechanical process usually accomplished by two different
techniques—suction or hydraulic dredging and dragline dredging which 1s a
mechanical excavation process. The hydraulic dredge utilizes an auger-type
20
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cutting blade and suction pumps to lift the sediments from the lake bottom
and pump them via pipeline to a disposal area. The dragline dredge scoops
material with a toothed bucket. The bucket has holes which allow most of
*he water to drain Immediately; the bucket is then lifted to a disposal
pile where the dredged material Is dumped. Both of these techniques were
used 1n the Long Lake project.
DESIGN CONSIDERATIONS
Although the dredging operation 1s, 1n Its most simplistic definition, "a
movement of material from one location to another," 1t 1s really a
complicated operation. Some Important considerations In design of a
dredging operation Include:
1. Limits of the dredging operation
2. Estimated volume of material to be dredged
3. Disposal sites and decant or water control operation
4. Protection of water quality
5. Measurement of dredged quantities
To assist In making appropriate determinations for the above design
considerations, a soils engineer was retained to conduct borings and probes
of the sediments 1n Long Lake. Borings and probe work in the Long Lake
sediment were conducted by R1tterhouse-Zeman and Associates. The borings
were logged with relationships to sediment depth and composition. From
this work 1t was evident that the amount of sedimentary muck in the lake
was tremendous, with layers of what the soils engineer called "very soft,
wet, brown muck/sedimentary peat" extending 25 feet in depth or greater in
some places. With this information, it was evident that maximum benefit to
the lake with respect to sediment/nutrient exchange would require a
dredging operation of massive scale. To remove organic muck from almost
the entire lake bottom would create costs and problems that would make such
an undertaking Impracticable.
21
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The dredging limits and estimates cf volume were developed to meet the
previously mentioned objectives of the dredging operation and to remove as
much additional muck as possible with the funds available. Given those
restrictions, the total volume of material to be dredged was calculated to
be 60,000 cubic yards.
Dredge spoils had to be disposed of In the most economical manner while
allowing the dredging contractor to work on a continuous dally basis and
still protect water quality. To do so, dredge spoil basins were designed
that would utilize a decant, constant flow operation. The basins also had
to allow a maximum settling time and provide for the d1str1buti'"t of
chemicals to treat the return flow 1f required before 1t was dischargee to
Curley Creek. Two series of basins with three basins 1n each series were
needed for disposal.
Acreage for the construction of the dredge spufls area had to be obtained
via purchase or easement. Some of the future york i«jna *as utilized for
disposal, and easements from two private property owners were obtained for
the remaining dredge disposal needs. Of the six disposal basins required,
two were used primarily for material settling and four for return water
quality control. A design plan showing limits of dredging and basin
locations 1s provided In Figure 3.
In order to measure post-dredging quantities, bottom contour elevations
were established by a survey team prior to dredging. Shoreline control
points were established and cross-sectional soundings were made on a
50-foot grid pactern. Soundings were made by lowering a weighted aluminum
disc to measure depth from lake surface elevation. The lake surface
elevation was calculated dally from the established datum.
DREDGING OPERATIONS
In June 1978, trees, brush, and other vegetation were cleared from the
disposal areas and berms were constructed from native materials to form
dredge spoil basins. A. dragline was utilized to dredge muck from the
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SODA ASH
DISTRIBUTION
DREDGE
SPOIL
BASIN
NO
DREDGE
SPOIL
BASIN
'NO. 2
ALUM DISTRIBUTION
NO. 1
j! IN-LAKB DREDGING'
I .. - '
' * "
DREDGE SPOIL
BASIN NO. 1
£&»&>
* .i- 4>
ENTRANCO Engineers
-------
DREDGE SPOIL
BASIN NO. 6
SODA ASH DISTRIBUTION
CONNECTION STRUCTURES
BORROW AREA
EASEMENT BOUNDARY
DREDGE SPOIL
BASIN NO. 5
EXISTING SALMON STREAM
(PROTECT FROM SILTATION)
W'SPOIL DISCHARGE
LINE - HIGHWAY
CROSSING
IT OF DREDGING!
FIGURE
LAN DEPICTING LIMITS OF
-OCATION OF SPOILS BASINS
-------
outlet channel and deposit the muck for use in forming the walls of basins
one, two, and three. Approximately 5,000 cubic yards of material was
removed from the outlet channel.
Hydraulic dredging began In July, with the piping of dredje spoils Into
basin number 1. A weir overflow structure and culvert pipe connected Basin
1 to Basin 2. The supernatant from Basin 1 was treated with an aluminum
sulfate (alum) slurry at the connection culvert 1n order to flocculate and
settle suspended material.* The slurry was mixed from dry alum and water
In 200-gallon tanks and distributed at a varying rate per unit volume of
supernatant directly Into the culvert discharge.
Addition of alum was necessitated by a desire to decrease the long
detention time required for settling of suspended dredge spoils. To
produce a supernatant that would meet water quality criteria and allow
continuous flow, alum was added. The alum, however, considerably reduced
the pH of ttie water. The alum treated supernatant from Basin 2 required
the addition of soda ash to raise the pH to allowable limits for
dlscharoe. The soda ash was applied 1n a similar fashion as the alum at
the connection structure between Basins 2 and 3. From Basin 3 the water
was discharged via culvert to Curley Creek. The outflow was regularly
monitored by the resident Inspector for turbidity and pH 1n order to not
violate permit requirements established to maintain water quality.
The dredging operation proceeded as specified until Basin 1 was filled to
capacity. The dredge discharge line was then transferred to the other
series of decant basins—Basins 4, 5, and 6. Basin 4 received the direct
discharge. The supernatant from Basin 4 was treated with alum at the
connection structure and discharged to Basin 5. Basin 5 supernatant was
neutralized with soda ash as it was transferred to Basin 6. From Basin 6
the water was discharged to a small creek and finally to Curley Creek.
Again, water quellty was monitored regularly. Photos of the hydraulic
dredge and dredging operations are shown 1n Figures 4 through 7.
See discussion In the Introduction to the chemical treatment phase of
the project for more description of alum usage.
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"•»»
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Figure 6: Discharge of dredge spoils Into decant basin
Figure 7: Alum treatment system at basin connection
26
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Several shutdowns Mere ordered during the project when monitoring trends
Indicated the water quality of Curley Creek might be violated. pH readings
as low as 5.0 were observed at the discharge point In Curley Creek. State
of Washington water quality standards set 6.5 as the lower limit for pH.
The contractor was then ordered to bring discharge up to standards 1n order
to continue operations.
The hydraulic dredging operations were conducted 1n a priority sequence.
First, the sump for the drawdown pump columns was dredged. This allowed
the construction of the pump support structure while the rest of the
dredging operation continued. Next, the channel was dredged to facilitate
movement of lake water to the drawdown pumps. Finally, the dredge operator
removed as much additional bottom sediments as possible.
The dredge channel extended approximately 200 feet toward the center of the
lake and cut four feet deep Into the lake bottom. Width of the channel cut
varied from 30 to 60 feet. Definite dimensions for the channel were never
established, as the dredging of the north end of the lake was an areawlde
operation. The hydraulic dredging operation took approximately 60 days to
complete (July-September 1978) and removed approximately 60,000 cubic yards
of material.
The post-dredging survey for quantity payment was conducted In the same
manner as the pre-dredging operation. Soundings were taken on a 50-foot
grid pattern using established shoreline control. Survey crews paid
special attention to grade breaks when determining new bottom elevations
Post-dredging soundings were cross-sectioned to compare with pre-dredging
measurements In order to calculate quantities of material removed. An
average depth of four feet of sediment was removed from the north end of
the lake, exposing clean sand and clay substrate.
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SPOIL RESTORATION
Based on the physical composition of the dredged material and the climate
In Western Washington, It was estimated that It would take 2 years for the
dredge spoils to dry sufficiently to regrade. After one year, the spoils
were visibly dry on the surface and, to some extent, had become naturally
revegctated. Probes below the surface, however, revealed an extremely wet,
unworkable material. Finally, 1n late summer 1980, after another year of
exposure and settling, the dredge spoils were dry. The diked areas were
regraded, tilled, and seeded. This restoration effort produced a pasture
area on the leased property (Basins 2, 3, 4, 5, and 6), Including Improved
drainage and new fences. It also provided a level grassy area on the park
property that could be converted to playflelds. Restoration of dredge
spoils was conducted by the KUsap County Public Works Department (Figures
8 and 9).
COSTS
The dredging operation was the single most expensive element of the entire
restoration project. The final costs approached $450,000, which Included
the dragline cleaning of the outlet channel; hydraulic removal of sediments
1n the north bay; dredge disposal area preparation; rental of disposal area
land; and dredge spoil restoration. The costs for dredging of the drawdown
channel are not included above, but are considered part of the drawdown
expense for facilities construction.
SUMMARY AND CONCLUSION
The dredging operation fulfilled all the objectives of the program.
Due to the close affiliation with drawdown, 1t 1s difficult, 1f not
impossible, to assess the merits of the dredging program with respect to
water quality. Certainly, it can be assumed that the cleaning of the
outlet channel and removal of the thousands of yards of nutrient-rich
organics will be beneficial to water quality 1f even to a limited extent.
28
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Figure 8: Dredge spoil basin prior to restoration
Figure 9: Dredge spoil basin after restoration
-------
However, since the dredged area was only equivalent to about S% of the
total lake bottom, and located near the outlet, 1t 1s doubtful that the
dredging operation had much positive effect on total lake water quality
with respect to sediment nutrient release.
The drawdown program could not have been conducted without dredging.
Separate costs for dredging of the drawlown channel are deceivingly low
($67,000). They do not Include the separate portion for equipment
mobilization, dredge spoil area preparation, land rental, and restoration
of dredge spoils absorbed by the dredging contract. Any other means of
getting water to the drawdown pumps would have been similarly expensive.
The benefits of dredging are easiest to assess as Improved access and usage
for public recreation. The north bay of Long Lake could not be used for
swimming, flining, or boat access prior to the dredging operation, but will
now have all those capabilities.
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LAKE DRAWDOWN
INTRODUCTION
The concept of drawdown--lowering of the normal lake water level--has betn
practiced 1n several lake restoration programs. One purpose of drawdown 1s
to stabilize and consolidate the loose organic ooze that makes up the top
layer of bottom sediments. This type of sediment may be easily resuspended
In the lake water and facilitate the release of nutrients. During drawdown
the sediments are dewatered and desiccated by exposure to air and sunlight,
resulting In a change In the structure of the exposed sediments and reducing
the potential for nutrient exchange.
Another purpose of drawdown 1s to control the extent of aquatic weeds.
Winter drawdown on Midwestern lakes has successfully reduced the extent of
aquatic weeds by exposure to freezing temperatures.
The Long Lake drawdown was conducted during summer months because the mild
winter temperatures and great amounts of rainfall In Western Washington
made a winter drawdown Impractical. The concept of summer drawdown was to
achieve sediment consolidation and weed desiccation by the exposure to dry
air and solar radiation, rather than freezing temperatures. A summer
drawdown program was also necessary for the protection of anadromous fish
runs. Salmon and steel head migrate to spawn 1n the Long Lake watershed
from October to January. Juveniles migrate downstream to Puget Sound
during the spring months.
Another practical benefit of drawdown 1s the opportunity for lakeshore
property owners to undertake property Improvements. While the lake 1s
recessed, owners may clean beaches of debris, remove weeds and sediment, and
provide 6 clean substrate. In addition, headwall construction, dock repair
31
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or replacement, and other capital Improvements could be undertaken that
might otherwise by physically or economically Impractical under normal
conditions.
DESIGN CONSIDERATIONS
The original concept of lake drawdown Included the dredging of a channel
from the north end of the lake to a point approximately 2,300 feet
downstream 1n Curley Creek. The channel was designed for two purposes:
(1) to allow lakewater to flow to the drawdown pumps for the Initial
drawdown; and (2) to allow future lake level control by the Installation of
a permanent control structure.
The originally proposed Curley Creek channel dredging would have removed a
natural lake level control point In the stream channel permanently lowering
the level of the lake. Therefore, the manmade lake level control structure
would maintain normal lake level and would allow drawdown of the lake by
gravity flow at any future date.
In spite of the provision for fish passage 1n the control structure, a
permit could not be attelned for Installation of the control device.
Therefore, the pump structure had to be redesigned for the Initial drawdown
to allow fish passage and have the capability to allow future drawdown 1f
desired.
The redesigned drawdown facility was fashioned to Incorporate the dredging
work previously accomplished to allow lakewater to flow to the pumps. The
pumps and a temporary fish ladder were supported on a treated timber pile
support structure, which, along with a sheet pile wall and sandbag coffer
dam, comprised the entire drawdown facility. The drawdown facility was
located at the lake outlet channel (Curley Creek) at the north end of the
lake.
32
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The permanent pump support structure, as constructed, is approximately 60
feet long and 12 feet wide. The structure was designed to withstand loading
forces by heavy vehicles for Installation and removal of the drawdown pumps.
After drawdown operations and pump removal the structure could be finished
with a deck and rail to serve as a recreation facility (fishing pier, boat
dock) until a point 1n time when 1t could be used again, If desired, for
drawdown. The pump structure also served to provide additional structural
support for the sheet pile wall. The drawdown facility 1s shown operating
In Figure 10.
Eighteen hundred square feet of steel sheet pile wall was driven on the
downstream side of the pump structure. The sheet pile was equipped with a
sliding weir plate to allow lake outflow and fish passage until the fish
ladder was installed and operational. A plywood deck was constructed on the
sheet pile wall for access to the fish ladder. To prevent "kick out" of the
sheet pile In the soft lake bottom, the wall was linked by timber braces to
the pump support structure.
A temporary sandbag coffer dam was Installed from the opposite side of the
outlet channel to the end of the sheet pile wall. With the coffer dam
Installed and the sheet pile weir plate closed, no water could flow back
Into the lake.
The drawdown pumps were purchased by KHsap County so they could be
reinstalled If and when future drawdown operations are desired. Three pumps
were obtained for the drawdown operation and installed In the following
sequence on the pump structure:
Pump No. 1 - A 25 HP, 4500 GTM unit for fish ladder supply
Pump No. 2 - A 20 HP, 4500 GPM unit for secondary drawdown
Pump No. 3 - A 30 HP, 6000 GPM unit for primary drawdown
All the pumps were Byron Jackson vertical propeller pumps with fresh water
lubrication. Lubrication was accomplished by In-line filtration of
lakewater.
33
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Figure 10: Drawdown pumps and fish ladder operating at start
of drawdown
34
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F1sh passage was achieved by Installation of a Den11 Model A F1sh Ladder,
consisting of a climbing frame, water supply, and slide. A fence downstream
of the pump discharge was Installed to direct fish to the ladder.
The pump shaft columns extended vertically Into the dredged sump below the
pump structure. The sump was lined with special riprap to maintain a
constant clearance. The pump column Intakes were fixed one foot above the
special riprap, and the Intakes were screened to prevent harm to fish or
damage to pump Impellers from submersed debris. Discharge was directly to
Curley Creek.
The pumps were operated from a master control panel mounted on a utility
pole near the structure. Pump operation and maintenance during drawdown
were Included as a bid Item to be completed by the contractor.
THEORY OF OPERATION
The drawdown was scheduled to lower the lake six feet below the normal water
level (from elevation 118.0 to elevation 112.0). The six-foot drawdown was
calculated to be the most practicable limit 1n order to expose the maximum
amount of lake bottom and still protect the aquatic life 1n the lake and
Curley Creek. A minimum flow of 10 cfs was to be maintained in Curley Creek
at all times during drawdown.
Drawdown was scheduled to be conducted 1n 1978 following the dredging
operation. However, due to delays relating to the dredging program,
equipment deliveries, weather, and other factors, the operation could not be
completed. The structure was constructed and the pumps were Installed and
temporarily operated several days for test purposes, but the drawdown
operation was delayed until 1979.
OPERATION
The actual lake drawdown operation began on June 1, 1979, with the startup
of the fish ladder supply pump. The other pumps were started sequentially
35
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at 24-hour Intervals to graduate total flow and avoid the potential of
downstream scouring. By the end of June (30 days of operation), the lake
had been drawn down 5 feet and the primary drawdown pump was shut down. The
secondary pump was turned off 24 hours later.
The weather during the month of June was very dry and a similar climatic
pattern was predicted for the remainder of the summer. From observations
during the month of June, 1t was ascertained that the 6-foot maximum
drawdown would best be attained gradually during the remainder of the summer
through operation of the fish ladder and evapotransplratlon. Through this
action, the lake level would be less likely to recede beyond the safe limits
with no control on the ability to refill.
The lake finally reached the 6-foot drawdown level (elevation 112.0) during
the first week of August 1979, and remained within Inches of that level
throughout the remainder of August. Forty percent of the lake bottom was
exposed to air and solar radiation. Some control 1n lake level was
established by allowing backflow Into the lake through the sheet pile weir
plate while still maintaining flow 1n Curley Creek. Creek flow at times was
reduced to 1-2 cfs but never less than the proportionate Inflow from
Salmonberry Creek.
The lake gradually refilled throughout the fall months until December 1,
1980, when heavy precipitation elevated the waters above the normal lake
stage. At that time, the final pump was shut down, the weir plate opened,
and the fish ladder, pumps, coffer dam, and other appurtenances, were
removed. The total time span for drawdown operation from pump start-up to
lake refill was six months.
The pumps operated without flaw during the entire drawdown operation.
Lubrication water filters were checked dally and cleaned or replaced If
necessary. Vandalism during the operation was minimal.
36
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SHORELINE CLEANUP
During the months of July, August, and September, residents with waterfront
property *ere encouraged to participate 1n beach Improvements. The Long
Lake Community Club distributed newsletters and the local press carried
articles that prompted owners to remove debris, sediment and weeds from
their beaches. Many residents hired equipment operators to remove muck and
regrade beaches to provide a clean substrate. Although not encouraged, some
owners brought 1n clean sand to Improve swimming areas. Most work by
residents was a manual process of raking, scraping, and shoveling.
The Kitsap County Public Works road crew bladed weeds, muck, and debris from
the north lake shoreline adjacent to the new park property. The master park
plan provides for a swimming beach 1n this area (Figures 11 and 12).
Many residents took advantage of the drawdown operation to undertake other
capital Improvements, which Included: (1) repair, reconstruction, or new
construction of boat docks; (2) Installation of swimming floats and other
water sports facilities; (3) extension of property line fences; and (4)
Installation of bulkheads. A monetary value has not been estimated for
these Improvements, but 1t 1s expected that the drawdown had a considerable
value to property owners beyond the water quality Improvement.
MONITORING AND RESULTS
Lake Water Quality
During drawdown, In addition to lake stage and streamflow, primary
monitoring concerns were directed to lake temperature and dissolved oxygen
(DO) content. These concerns were based upon the increased solar Influence
due to reduced lake volume and the potential for biochemical oxygen demand
from sediment and decaying weeds lying on the exposed shoreline being washed
Into the lake by summer storms.
37
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Figure 11: Northshore beach during drawdown. Note exposed
weeds and debris
Figure 12: North shoreline as shown above after grading to
clean beach of weeds and debris
38
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A drawdown monitoring program was established with the cooperation of the
Department of C1vi1 Engineering and the Fisheries Cooperative Research Unit
of the University of Washington to observe temperature and DO on a diurnal
basis. This procedure was a voluntary addition to the regular sampling
program conducted by these research units. Contingency plans were
established to provide emergency aeration should the dissolved oxygen levels
dip to dangerously low concentrations. Although temperatures In excess of
23° C were recorded, no depletion in dissolved oxygen beyond normal limits
was recorded. The lowest recorded oxygen level was 5.9 mg/1 at 4 a.m. when
^2 levels are expected to be lowest. The planned emergency aeration
system was therefore not Installed.
Macrophyte Surveys
University of Washington personnel established sites at several locations 1n
the lake 1n order to monitor the effects of drawdown on macrophyte standing
crop. These sites were used for pre- and post-drawdown macrophyte surveys.
The pre-drawdown surveys took place 1n June and August 1978, the post-
drawdown surveys 1n July and August 1980. August surveys had also been
conducted during 1976 and 1977, but the 1978 survey Is most pertinent for
comparison.
Visual observations by Inspection of lake shoreline areas Indicated a rapid
deterioration of E. densa exposed during drawdown. The post-drawdown
macrophyte survey by the University confirmed that a substantial reduction
1n plant blomass had occurred. E. densa was definitely decreased,
especially In areas most extensively exposed during drawdown. The total
lake standing crop of macrophytes was reduced by approximately 84% due to
drawdown (see Figures 13 and 14). It was also predicted through sediment
analysis that macrophyte regrowth was more difficult to achieve 1n sediments
that were dried and rehydrated.
Although a reduction In E. densa was attributed to the drawdown operation,
the long-term merits of drawdown for weed control In shallow lakes are not
encouraging. By late summer macrophytes were quickly re-Invading areas
39
-------
Figure 13: South end of lake exposed during drawdown
Figure 14: Dried El odea densa exposed during drawdown
4C
-------
exposed by drawdown. Also, a different species of macrophyte, Potomogeten
crispus, which was not observed since Initial lake studies, was evident as
nuisance patches 1n post-drawdown surveys. Potoroogeton crlspus had never
been noted In measurable quantities in any of the University of Washington
surveys. Other species—Potomogeten praelongus and Elodea canadensls—were
found to be more prevalent after the drawdown. Possibly the E. densa
dieback resulted in a loss of dominating competition. The University
researchers state It Is conceivable that blomass will be back to
pre-drawdown levels by mid-summer 1981.
Drawdown may be best utilized In deep lakes for littoral weed control. For
shallow lakes, a total, drawdown may be the only means of long-term weed
control. Species of 111 lies (I.e., Nuphar) or other plants that are adapted
to survival of drought have to be poisoned or physically removed from the
sediments. •
Sediment Compaction
Sediment compaction as a result of drawdown was determined by University of
Washington researchers. Compaction was measured using three techniques:
(1) pre- and post-drawdown water depth at three control points; (2) analysis
of sediment water content; and (3) sediment elevation as gauged on steel
rods embedded In the lake bottom.
Through these techniques, a determination was made that the extent of
sediment compaction In exposed areas from drawdown was one tenth of a meter.
Laboratory Investigations predicted much greater sediment compaction, but
the laboratory procedures probably did not adequately portray natural
conditions, especially with regard to movement of water from underlying
sediments to the exposed surface. Although not greatly compacted, the
exposed sediments were physically altered and less likely to release
nutrients.
41
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Water Quality
Reduction 1n lake phosphorus content, chlorophyll-a content, and pH have
been attributed to the drawdown. For comparison, pre-drawdown mean total-P
concentrations of 61 ug/1 (1977) and 76 ug/1 (1978) were approximately 501
less after the drawdown, being reduced to a mean of 36 ug/1 In the summer of
1980. Algal Momass as measured by chlorophyll-a content was reduced by a
similar percentage from a mean of 26 ug/1 (1977) and 39 ug/1 (1978) to about
15 ug/1 In 1980. Median pH values of 9.1 (1976), 9.0 (1977), and 8.6 (1978)
were notably higher than the median of 8.1 1n 1980. The pH reduction was
likely a result of the decreased algal blomass primary productivity during
the summer of 1980.
A complete analysis of all water quality parameters, Including a nutrient
budget and assignment of loadings attributed to Internal sources, will be
part of a report submitted by the University at a later date. At this time,
1t does not appear that the reduction In phosphorus concentrations of the
magnitude that occurred can be attributed strictly to sediment exposure and
compaction during drawdown. Certainly, the sediment removed by the north
end dredging operation and Individual beach cleanup also contributed to the
reduced phosphorus values, but that contribution cannot be accurately
measured. The reduction in P attributed strictly to weed desslcation or
removal may also be significant.
Well Monitoring
Lake stage Is the hydraulic control elevation for the groundwater table
around the lake. Since the drawdown would reduce lake stage by six feet, a
program was established to Investigate the shallow wells within a 500-foot
setback of the lakeshore and determine If certain wells would be affected by
drawdown.
Initially, a well and septic system survey was conducted by the Bremerton-
Kltsap County Department of Environmental Health to Identify potential
problems in well supply and possible faulty septic systems. Almost 200
42
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homes were Investigated by the County Inspector with approximately 15 well
systems Identified as having poor supply or previously gone dry during low
water years.
Prior to drawdown, the depth of water 1n the well was measured and recorded.
During drawdown, the wells were monitored on a weekly basis to determine:
(1) If there was any sudden loss In well depth resulting from drawdown; and
(2) 1f an auxiliary water supply need be provided.
Because It was difficult to evaluate the consumptive water use patterns by
homeowners as well as normal well recharge rate and other factors
Influencing well supply, ihe potential for assumed lUblHty relating to the
drawdown operation and loss of water supply was high. A program for
providing an auxiliary water supply was established. During the drawdown,
seven well systems experienced a loss 1n supply requiring the Installation
of the auxiliary water system.
Auxiliary Water Supply
The water supply system consisted of a 1,000-gallon plastic storage tank
suitable for potable water supply. The tanks were connected to the existing
well pump by a one-Inch plastic line. The tanks were filled on a weekly
basis by a tank truck which obtained water from the nearby Annapolis water
district. The tanks were Insta'led by the contractor when monitoring
Indicated that the residents might lose their water supply. Some tanks were
Installed In late July, others not until September. All wells were
receiving sufficient recharge by the end of October. At that time, the
filling program was ended and the tanks were removed.
For connection of the auxiliary water supply to seven systems, a total of
ten supply tanks had to be Installed and maintained. The total cost of this
operation exceeded $30,000.
43
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COSTS
The entire drawdown operation cost over $400,000, Including $67,000 In
dredging costs and $30,000 for the special water supply described above.
The remainder of the expenses was for purchase, Installation, and operation
of pumps, structures, and appurtenances to complete the drawdown.
CONCLUSION
The drawdown was successful 1n providing weed eradication and some sediment
compaction 1n areas exposed during drawdown. However, the recolonlzatlon of
E. densa and the appearance of other competitive weed species 1n exposed
areas within one year of drawdown make the cost/benefit of the operation for
weed control doubtful.
Improved water quality as evidenced by the reduction In phosphorus
concentrations and chlorophyll-a concentrations has been attributed to the
drawdown. The improvements as measured by these parameters appear
significant and are further discussed graphically In the project water
quality evaluation section. Although measured sediment compaction was
minimal, the greatest benefit to water quality from drawdown can likely be
attributed to the physical change In exposed sediments. Instead of being
flocculant, the sediments became caked and even when reflooded with lake
water the altered sediment/water Interface became less effective 1n nutrient
release.
Many valuable Individual property Improvements were undertaken during the
drawdown that probably would not have occurred otherwise. These measures
were extremely Important to promote community Involvement and allow
Individual Input to the lake Improvements.
44
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CHEMICAL TREATMENT WITH ALUMINUM SULFATE (ALUM)
INTRODUCTION
As discussed In the summary of water quality Investigations of Long Lake,
most data indicates the major source of phosphorus that promotes
eutrophlcatlon in the lake comes from Internal recycling rather than
external sources. That is, the transfer of phosphorus from the nutrient-
rich sediments back into the water column.
That nutrient cycle may lead to the rapid death of the lake unless the
cycle is disrupted. Dredging, drawdown, placement of artificial
substrates, and chemical applications may all be used to interrupt the
continual recycling. The use of the chemical, aluminum sulphate
(A^'SO^) • was selected as one of the methods to limit the internal
recycling of phosphorus in Long Lake.
Aluminum sulphate (alum) is a flocculating agent and functions by
chemically reacting with the natural alkalinity of the lake water to form
an aluminum-hydroxide complex. This complex, or floe, resembles snowflakes
in the water column. The floe is denser than water aid settles to the
bottom of the lake, forming a blanket that covers the bottom.
The alum floe acts both physically and chemically to Improve the water
quality. As the floe forms and settles to the lake bottom, 1t acts as a
filter to clear the water of suspended particles (I.e., algae). The alum
floe also functions by complexIng available phosphorus Into an Insoluble
compound, thereby making the water column phosphorus-poor and less likely
to support nuisance algal blooms. The floe blanket on the bottom of the
lake acts as a phosphorus seal by chemically binding with phosphorus made
available by diffusion from the sediment.
45
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Alum has been used for many years as a water treatment agent to floe and
settle suspended material from surface waters used for public water
supplies. It has only been used for the past 7-8 years as an In-lake
treatment medium for phosphorus control. Most notably, alum has been used
for nutrient 1nact1vat1on 1n lakes 1n Wisconsin (Horseshoe, Snake, and
Pickerel lakes), Ohio (Twin Lakes), and 1n Washington (Liberty and Medical
lakes).
Liberty Lake Is a 781-acre lake located In Eastern Washington near the city
of Spokane. It was successfully treated with 105 tons of aluminum sulfate
1n the fall of 1974. The lake had been suffering from massive fall blooms
of bluegreen algae. The alum treatment eliminated major blooms for two
years, but a minor bloom appeared the third year after treatment. It 1s
believed by the principal Investigators of Liberty Lake that nutrient
leachate from on-s1te wastewater disposal systems helped prompt the new
bluegreen algal blooms. The area has since been sewered and a repeat
application of alum 1s scheduled.
Medical Lake received an application of alum during August and September of
1977. The 158-acre lake was treated with 1,031 tons of alum to limit the
amount of phosphorus recycling, and thereby restrict the occurrence of
nuisance algal blooms. Preliminary results Indicate th&i the alum
treatment was successful 1n reducing phosphorus and algal concentrations in
the water and improving water clarity.
The comparison of alum application to Liberty and Medical lakes with Long
Lake will be further discussed throughout this section of the report.
PRELIMINARY DESIGN CONSIDERATIONS
Chemical treatment of Long Lake was considered one viable element for lake
restoration as part of the Long Lake Rehabilitation Plan published in
August of 1976 (Entrance Engineers). At that time, laooratory jar tests
were undertaken with Long Lake water to determine the optimal application
concentration of aluminum sulphate. A series of tests were run with
46
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varying concentrations of alum and the effect of the alum on eight
parameters (temperature, pH, alkalinity, conductivity, turbidity, suspended
solids, apparent color, and ortho-phosphorus). From this series of tests
an alum concentration of 60 mg/1* was determined to have the most effective
floe formation, and removal of suspended sol Ids, nutrient and color. This
concentration also would maintain an alkalinity sufficient to buffer the
water from low pH.
In July of 1980 an on-site pilot study was performed In order to determine
the most effective alum dosage with the current water chemistry. These
field tests were considered to provide results more Indicative of what
would be experienced under full-scale conditions than samples brought into
the laboratory. The optimum concentrations from these tests were used to
estimate appropriate quantities for contract bidding purposes.
During the pilot study, a measured alkalinity of 35 mg/1 CaCO^ prior to
testing dictated the range of alum dosages (Long Lake experiences a normal
range of 25-35 mg/1 CaC03 on an annual basis). The tests were prepared
by using 500 ml of lake water at alum concentrations of 60, 70, and 80
mg/1. (Note: The 1976 tests Indicated 60 mg/1 to be the optimal dosage).
Alkalinity, turbidity, pH, ortho-phosphorus, and total phosphorus were
measured before and after alum application. Measured alum dosages were
flash mixed in the beakers then gently stirred at 10 minute Intervals for
40 minutes. Final water quality measurements were then performed and the
results are presented 1n Table 1.
Turbidity differences 1n the lake versus alum treated waters 1n the test
were not considered to be a completely accurate depiction of full-scale
operation. There was no algal bloom 1n the lake at the time of testing and
the floe had not adequately settled within the testing time frame.
* Concentrations are expressed as mg/1 of commercial grade alum in dry
form, and not as pure
47
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TABLE 1
RESULTS OF ALUM APPLICATION PILOT STUDY
mg/1 ug/1 mg/1 CaCOa NTU
Concentration Ortho-P Total-P pH Alkalinity Turbidity
Lake Mater
60 mg/1 Alum
70 mg/1 Alum
80 mg/1 Alum
6
<5
<5
<5
34
10
10
13
7.7
6.4
6.0
5.5
35
8
5
2
4.5
5.5
6.4
6.5
48
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Lake concentrations of ortho-phosphorus were only 6 ug/1, but all three
alum dosages reduced ortho-P below detectable limits. Total phosphorus
concentrations of 34 ug/1 were reduced to 10 ug/1 1n the 60 ug/1 and 70
ug/1 alum beakers, a 70% reduction In phosphorus. The reduction in the 80
ug/1 beaker was slightly less, resulting 1n a concentration of 13 ug/1.
Alkalinity was reduced from 35 mg/1 CaC03 to 8 mg/1 with a 60 mg/1 alum
dosage, to 5 mg/1 CaC03 W1th a 70 mg/1 alum dosage, and to 2 mg/1
CaC03 with 80 mg/1 of alum. Corresponding resultant pH levels were
6.4, 6.0, and 5.5, respectively, from an Initial value of 7.7.
In order to apply the maximum amount of alum to provide phosphorus removal
while not depressing pH to a point of endangering aquatic organisms, a
concentration of 70 mg/1 alum was considered optimum for full-scale design.
This was based on previous jar tests, the pilot study, and trends observed
In lake chemistry from the University of Washington monitoring reports.
SYSTEM DESIGN
Unlike the previous alum applications where the consultant performed the
studies, designed the application system, and conducted the application,
the Long Lake alum treatment was advertised for competitive bidding.
Criteria for the alum distribution system, procedure of application, and
dosage rates were developed by the consulting engineers and defined In the
specifications and contract documents. For Informational purposes, the
specifications included a description of the application systems used in
both the Liberty Lake and Medical Lake alum treatments. The contractor was
then required to develop and submit his design for approval by the
engineer. Upon approval, he could build the system and provide the
equipment necessary to complete the application according to the
specifications.
The Liberty Lake application was accomplished by the use of a dry alum
distribution system. The system consisted of pontoon barges propelled by
49
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outboard motor and filled with ah alum slurry mixing chamber and pipe
distribution header. Bags of dry alum were mixed onboard with lake water
and the resultant slurry gravity-fed to the distribution header.
The Medical Lake application device Incorporated a system utilizing liquid
alum. The liquid alum was transferred from tank trucks to submersed
storage vessels attached to the application barge. The alum was then
applied to the lake by pumping from the submersed storage tanks to a pipe
dlffuser. The dlffuser was adjustable for either surface or subsurface
application.
The specifications for Long Lake were flexible enough to allow the
contractor to bid and design a system utilizing either dry or liquid alum.
It was anticipated that the low bidder would utilize liquid alum because
the cost per ton of active Ingredient for liquid alum 1s considerably less
than that of dry alum. In fact, the low bidder who was awarded the Long
Lake contract did design his bid around a system utilizing liquid alum.
An artist's concept of the application barge utilized 1n Long Lake Is
provided 1n Figure 15. The contractor obtained a commercial flat bottom
barge previously utilized by a dredging contractor to haul fuel.
Therefore, the barge had a series of empty bilge chambers that were
periodically filled or drained with lake water as necessary to adjust
draft.
Five plastic holding tanks—each with a 1,000-gallon capacity--were set in
tandem on the barge. The back four tanks were plumbed to provide uniform
storage when filled. They were connected by plastic pipe to a pump which
filled the lead tank during application, thereby providing a constant head.
The lead tank gravity fed the liquid alum to a 44-foot long perforated
distribution header. The distribution header was fabricated from 3" PVC
pipe and perforated with 1/8" holes at 3" centers.
50
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1 ALUM DISTRIBUTION HEADER
2 HEADER SUPPORT FRAME
3 HEADER "CLEAN-OUT" CAP
4 SAFETY & SUPPLY STORAGE
5 HEAD SUPPLY TANK
6 FLOWMETER
7 SUPPLY VIEW GAUGE
8 ALUM PUMP
9 SUPPLY TANKS
10 DISTRIBUTION CONTROL VALVE
11 BY-PASS VALVE
12 100 HP OUTBOARD MOTOR
e
B4TRANCO Engneers
ALUM DISTRIBUTION BARGE
1
FIGURE
15
-------
The lead tank was fitted with a clear view gauge to determine the inches of
head at any given moment. The discharge line was fitted with a rotometer
to determine flow 1n gallons per minute.
The barge was propelled by a single 100 horsepower outboard motor and
obtained speeds up to 2 mph fully loaded. The barge had excellent
maneuverability and could be successfully operated by a two-man crew, a
helmsman and bowman (lookout and valve operator).
The fully loaded barge had a maximum draft of 3 feet, and the long
distribution header allowed the applicators to treat the lake to minimum
depth of 2 feet. The velocity of the alum stream on the lake surface
provided sufficient turbulence to "flash mix" the alum and provide good
floe formation. Barge wake and motor operation provided further mixing.
The barge 1n operation 1n shown In Figures 16 and 17.
APPLICATION PROCEDURE
Based upon lake surface area, average depth, and a dosage rate of 70 mg of
alum/liter*, the lake was divided Into 13 sectors, and each sector assigned
a dosage quantity. This quantity was uniformly distributed to the surface
of each sector (see Figure 18 and Table 2).
The sectors were clearly Identified by shoreline control markers and a
series of buoys on each sector line. The alum was applied In two passes In
a Crosshatch pattern to ensure complete coverage. As depicted on the
sector map, the south end of the lake was not treated with alum. Treatment
was omitted in this area to allow the University of Washington researchers
to further evaluate the effects of drawdown on v»eed control and sediment
nutrient release without the Interference of aluminum sulfate.
On a practical note, 1t was evident when encroaching the thick submergent
and emergent weed beds on the south end with the application barge that
70 mg/Hter as dry commercial grade aluminum sulfate (6.3 mg/1 as Al).
52
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Figure 16: Alum application barge after completing a turn.
(Starboard view)
Figure 17: Alum application barge in operation. (Port view)
-------
EDGE OF WATER
ELEV. 118.00
UNTREATED
CONTROL
-LINE OF EQUAL WATER DEPTH
5' INTERVAL
CURLEY-*V
CREEK ^
APPROXIMATE LIMITS OF-
GENERAL DREDGING. NEW
BOTTOM CONTOURS NOT SHOWN.
e
ENTRANCO Engineers
T
ALUM TREATMENT
SECTOR GRID
FIGURE
18
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TABLE 2
LONG LAKE ALUM DOSAGE QUANTITIES
(Based on 70 mg alum/liter)
SECTION
1
2
3
4
ii
6
7
8
9
10
11
12
13
VOLUME
(Acre-Feet)
133
190
172
162
174
140
242
239
183
127
163
149
147
Dry Alum
(Tons)
11.95
17.08
15.46
14.56
15.62
12.62
21.77
21.47
16.44
11.41
15.10
13.35
13.17
DOSAGE
Liquid Alum
(Bulk Tons)
25.10
35.85
32.47
30.58
32.80
26.50
45.72
45.09
34.52
23.96
31.71
28.04
27.66
Liquid Alum
(Gallons)
4,543
6,489
•j.s:.'
5,535
5,937
4,797
8,275
8,161
6,248
4,337
5,740
5,075
5,006
TOTAL
2.226
200.00
420.00
76,020
55
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speed control and application rate would be difficult to manage. This
posed a monitoring problem and potential hazard to aquatic life; therefore,
the application was omitted from this region.
The dosage rate for each sector was calculated by flow rate and barge
speed. This measurement was double checked by comparing full and empty
weight tickets from the loading trucks. (Alum was delivered twice dally
from Allied Chemical 1n Tacoma.) One sector was completed before the barge
moved to the next sector. The applicators covered 1-2 sectors per day,
depending upon hours worked and sector size.
A total of 223 tons of alum were applied to the lake. Design calculations
called for 200 tons; the 23 additional tons were ordered to ensure a
complete coverage In certain areas. The application took eleven working
days to complete.
MONITORING AND RESULTS
The University of Washington Is monitoring the entire restoration project.
The consultant, however, provided Independent water quality monitoring
before, during, and after the alum application. The purposes of this
monitoring Included:
1. Establishment of baseline Information to adjust dosages, maintain pH,
and/or provide additional alkalinity 1f necessary during the alum
application.
?.. Provide maximum retardation of phosphorus transport from sediments.
b. Protect /.ouatlc life.
2. Provide comparative data for Immediate success evaluation of alum
applIcatlon.
3. Provide documentation of results for future applications.
4. Document contractor's conformance to specifications.
56
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Parameters measured prior to and after the alum application Included:
nutrients (N02.No3N, Total KJN, NH3-N, Ortho-P, ToUl-P),
chlorophyll-a, and physical characteristics (pH, DO, temperature,
turbidity, alkalinity, Secchl disk). During the application, the
previously listed physical characteristics were measured on a dally basis,
but the monitoring during application was principally limited to
measurements of pH and alkalinity.
Data analysis of pre- and post-alum application monitoring 1s presented In
Table 3. It is fairly evident from this limited Information that the
anticipated water quality responses to alum treatment of reduced phosphorus
concentrations and Improved water quality did occur. Dissolved phosphorus,
measured as filterable ortho-P, was below detectable limits prior to the
apllcatlon, so phosphorus reduction 1n that fraction could not be deter-
mined. However, total phosphorus concentrations were reduced to less than
half the value measured prior to the alum treatment (from 35 to 15 mg/1).
The Improved clarity after alum treatment 1s recorded 1n several different
parameters. Physically, the Improvements are seen In turbidity reduction
from 8-9 NTU's to 1-2 NTU's and Increased Secchl disk readings (from 1.3
meters to lake bottom >2.7 m, Figure 19). Turbidity and Secchl disk
readings verify the Improved biological condition of the lake water
documented by a dramatic decrease In chlorophyll-a (from 53-7 to .56
mg/m3). A dense bluegreen algal bloom (Anabaena) was almost completely
filtered from the water column by the alum floe. The slight increase in
chlorophyll-a noted between September 25, 1980 and October 30, 1980 (.56 to
1.6 mg/m3) can be attributed to the recurrence In domination by green
algal species (I.e, Volvox). Increased zooplankton activity also was noted
with Increases 1n green algae concentrations.
The removal of the blueg-een bloom by the alum floe would explain the
changes In nitrogen compounds of the lake water. Organic fractions
decreased below detectable limits (KjN from 1.12 mg/1 to <.50 mg/1) but
dissolved nitrogen (ammonia and n1trate/n1trite nitrogen) Increased after
alum applIcatlon.
57
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TABLE 3
RESULTS OF PRE- AND POST-ALUM
TREATMENT MONITORING
PARAMETER*
N02-N03-N (mg/1 as N)
T Kj-N (mg/1 as N)
NH3 (mg/1 as N)
0-P (mg/1 as P)
T-P (mg/1 as P)
Chi a (mg/m3)
Turbidity (NTU's)
Secchi Disk (m)
Alkalinity (mg/1)
Temperature (°C)
pH (units)
Dissolved Oxygen (mg/1 )
PRE -ALUM
TREATMENT
September 3,
1980
<.010
1.12
0.006
<.005
0.033
53.70t
8.3
1.3
42.0
16.0
9.4
10.8
POST-AL'JM TREATMENT
September 25,
1980
0.026
<.50
0.051
<.005
0.015
0.560
2.8
2.7
(bottum)
18.0
14.0
6.2
10.0
October 3C,
1980
0.019
<.50
0.039
<.005
0.016
1.60
1.4
2.7
(bottom)
21.0
10.0
9.0
10.1
December 5,
198C
0.45
N/A
.030
<.005
N/A
.65t
3.3
1.5
(3.5 bottom)
-
3.5
7.4
11.5
* Average concentration of samples taken from both the north and south
ends of Long Lake at surface.
t finc
-------
At the time of printing, all analysis was not complete for the December 5,
1980 post-alum application sampling period. Most notable changes are the
reduced Secctil disk and high dissolved nitrogen concentrations as compared
to the previous period. Both of these phenomena can be attributed to the
late fall runoff which normally carries dissolved organlcs and humlc acids
from decayed vegetation into the lake from the heavily wooded watershed.
Increased nitrate-nitrite concentrations may also be partially attributed to
senescence and mineralization of macrophytes. A visual survey of submersed
macrophytes was attempted, but the dark "root beer" colored water prohibited
any definitive observation.
Again, the future monitoring Information collected by the University of
Washington researchers will provide an overall view of lake chemistry beyond
this time period.
As previously stated, the water quality parameters most frequently monitored
during the alum application were pH and alkalinity. The commercial grade
alum dosage of 70 mg/1 was based upon a lake alkalinity of 35 mg/1. The
alkalinity Immediately prior to application had Increased to 42 mg/1. This
change provided an Increased buffering capacity and less risk of negative
biological effects or the need to add alkalinity (soda ash) if alum overdose
occurred. The initial alkalinity of 42 mg/1 dropped to less than 5 mg/1 at
times during application. Post-application monitoring documents the
recovery that has taken place 1n alkalinity (lf> mg/1 on September 25, 1980
and 21 mg/1 on October 30, 1980).
Similarly, pH took a sudden drop during alum application (from 9.4 units to
between 4.0 and 5.0), but recovered to between 6.0 and 6.5 within one hour
as the lake stabilized. As time passed, the lake pH continued to adjust
(6.2 units on September 25, 1980 and 9.0 units on October 30, 1980). No
uncontrolled application event occurred requiring the addition of base (soda
ash) to recover a drastically suppressed pH.
59
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Observations with SCUBA on September 25 and October 30, 1980 were utilized
to evaluate the homogeneity of the floe blanket on the lake bottom. On
September 25 a floe layer with a depth of approximately 3 cm was observed
to uniformly cover the lake bottom at several dive points. Although
Initially clinging to the leaves of submersed macrophytes, the floe had
fallen and the blanket was visibly uniform on the lake bottom even In thick
weed beds. Hand-driven core samples were taken to document the floe blanket
(see Figure 20). In areas where the alum was first applied, the floe
blanket was already being Incorporated Into the lake bottom by the benthlc
Invertebrates that Inhabit the bottom sediments. Further SCUBA Investiga-
tion and hand coring one month later (October 30, 1980) revealed an almost
complete mixing of alum floe and sediment to make the floe layer nearly
Indiscernible.
F1sh kills were not reported on either the Liberty Lake or Medical Lake alum
applications, but did occur at Long Lake. The Cooperative Fisheries Unit of
the University of Washington reported the death of approximately 60 Suckers,
which are bottom feeders, possibly from Irgestlon of alum floe. The fish,
all of the same age, apparently no longer reproduce 1n Long Lake and their
exact numbers are not known. A number of crapple (Pomoxis sp.) of various
ages were also found dead after the alum treatment. The cause of the fish
kills—whether It was shock to a weak species or the result of a toxic
effect—Is being Investigated and will be Included 1n a later report by the
Fisheries Coop. No trout (Salmo sp.), bass (Mlcropterus sp.). or other
species generally considered more sensitive to adjustments to water quality
were found dead after the alum treatment, nor were any other bottom feeders
(I.e., catfish, Ictalurus sp.).
COSTS
The total payment to the contractor for the alum application was
approximately $98,000.
60
-------
Figure 19: Secchi disk readings to lake bottom were obtained
after alum application
Figure 20: Core samples of bottom sediments taken two wef.
-------
CONCLUSION
Although the initial results of the alum treatment appear favorable to the
water quality of Long Lake, the long-term effects to a lowland shallow lake
have never been demonstrated. The positive effect of alum on Plckeral
Lake, Wisconsin, which Is also shallow and unstratlfied, was short-lived,
possibly due to alum resuspension and drift. This Is not apparent In Long
Lake to date. If the alum application is successful in controlling
internal nutrient recycling and external sources of nutrients do not
Increase, the water quality of Long Lake can then be expected to remain
Improved for years to come. Additional discussion of the results of alum
treatment follow In the Water Quality Evaluation section.
The success of the alum application may depend upon the effect of aquatic
weeds on the water quality of Long Lake. The macrophytes may be active In
"nutrient pumping" or the transfer of dissolved nutrients from sediments
into the water column via the plants. The extent of submersed weed cover
in the lake may also expand due to the alum application. The Improved
water clarity and light penetration may promote weed growth. If so, weed
harvesting or herbicide application may be a long-term maintenance need in
Long Lake.
The University of Washington researchers have shown through unpublished
laboratory tests that E. densa growth 1s suppressed when alum is mixeo with
sediments. The Incorporation of floe with sediments by benthic organisms
may then hypothetically reduce weed growth, however, the alum
concentrations In the University of Washington experiments were ten times
higher.
The evaluation team from the University of Washington will continue to
monitor the lake until August of 1981. Any further plans for harvesting or
additional chemical control of weeds and algae should not be instigated
until the University monitoring 1s finished and evaluated.
62
-------
WATER QUALITY EVALUATION
INTRODUCTION
As stated In the discussion of water quality Investigations, the monitoring
programs were established in order to measure the effectiveness of the
restoration program. The merit of certain restoration techniques must be
demonstrated 1n this project 1n order to recommend their use 1n other lakes
with similar problems and characteristics as Long Lake. Similarly, a
restoration scheme with limited effectiveness and high cost may be a "stop
gap" solution for a problem lake until more data or better resources are
made available.
Monitoring data from the University of Washington and Entrance Engineers
has been utilized to plot trends for certain parameters that have been
observed to date. The graphs depicting these observed trends are shown 1n
Figures 21 and 22 and are discussed below.
DISCUSSION
The University of Washington researchers have stated in their last
quarterly report that the average total phosphorus concentrations in Long
Lake are considerably less following the drawdown than In previous years.
Figure 21 depicts the mean total phosphorus concentrations for the past
four summers. It can be clearly observed 1n Figure 21 that phosphorus
peaks normally occur during the summer months (1977, 1978, 1979), but such
high concentrations Jid not occur In 1980. Equally dramatic In Figure 21
are the reductions 1n total phosphorus that occurred as a direct result of
the alum application. The mean total-P concentration In Long Lake during
the summer of 1080 (June-September) was 36 ug/1, compared to 6) ug/1 In the
summer of 1977, and 76 ug/1 in the summer of 1978. The total-P concentra-
tion following alum treatment was 15 ug/1. Peak concentrations of over 100
ug/1 had been observed in summers prior to drawdown.
63
-------
SUMMER 1978
PRE-DRAWDOWN
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1977
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1978
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INVilirXVtNTAL *SO 1 H A'.S»'O< 1 * I iQN CONSUlUMS
LEGEND
A REPRESENTS U. OF W. VOLUME WEIGHTED
DATA FROM THREE STATIONS
• REPRESENTS ENTRANCO DATA FROM TWO STAT1
-------
SUMMER 1979
DURING DRAWDOWN
POST DREDGING
SUMMER 1980
POST DRAWDOWN
POST-ALUM
APPLICATION
DIJFMAMJJASOND
1980
MEAN TOTAL P CONTENT
OF LONG LAKE
EIGHTED
M TWO STATIONS
FIGURE
21
-------
Figure 22 depicts the mean chlorophyll-a concentrations observed over the
past four years. Algal blomass, as measured by chlorophyll-a, has steadily
decreased since the start of the restoration program. After dredging, mean
concentrations were 5-10 ug/1 less than summer peaks prior to dredging.
After drawdown, mean concentrations peaks were even less. After the
application, ;hlorophyl1-a measurements averaged approximately 1 ug/1. The
University states that bluegreen blooms were rare In 1980, with diatoms and
green algae more abundant than prior years.
The University also notes a lower median pH value following drawdown, which
can probably be related to lower primary productivity. In previous summers
pH values greater than 10.0 have been observed, but the highest value
observed by the University staff was 8.7 1n 1980 (Entrance notes a pK of
9.4 prior to drawdown).
To date, It appears that the combined effects of all the restoration
elements have been beneficial to the lake water quality. The long-term
effects are not yet known, but 1f trends continue tne lake should
demonstrate a marked improvement for years to come. The major unknowns at
this time are:
1. The effect of winter runoff (and flushing action) on the alum
application and thereby, the lake water quality.
- Wet weather Inflows usually carry high concentrations of dissolved
nutrients, especially nitrogen.
- The high volume of inflow in the shallow lake may resuspend sedinents
(and alum floe) and carry It to the outlet, or redistribute to the
center.
- The amount of weed die-off is difficult to determine due to the color
of the lake water from humic acids in the winter runoff.
2. The effect of the alum application on summer macrophyte populations.
3. The long-term effect of the restoration program on fisheries.
The answers to these questions and other questions will have to be
determined upon completion of monitoring In September of 1981.
65
-------
50--
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PRE-DRAWDOWN
PRE-DREDGING
A UNIVERSITY OF WASHINGTON DATA
-SURFACE, KIDDLE £ BOTTOM SAMPLES FROM
THREE STATIONS (NORTH, MID & SOUTH)
• ENTRANCO DATA
-SURFACE SAMPLES FROM TWO STATIONS
(NORTH & SOUTH)
PRE-DRAWDOWN
DURING DREDGING
POST-DREDGING
DURING DRAWDOWN
POST-DRAWDOWN
POST-ALUM \
APPLICATION*
l/l-
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4/1- 17/1- 111/11-11/31-14/14-17/3- 110/17-J 1/9- I 4./J- |6/?0-| 9/6-Ul/2(H 2/7-14/22-1 7/1-1 9/25-1
9/30 12/27| 4/1 6/23 10/3 12/30|3/20 6/12 9/24 11/8 1/10 | 4/8
6/30
1977
9/24 11/8
1979
6/17 9/1
1980
10/30
ENTRANCO Engneers
MEAN CHLOROPHYLL A CONCENTRATIONS I FIGURE
OVER A FOUR YEAR PERIOD I 22
-------
r.OWUHITY EVALUATION
At the November meeting of the Long Lake Community Club, metnber,s of the
group expressed the
-------
REFERENCES
American Public Health Association, 1975. Standard methods for the
examination of water and wastewater, 14th edition. APHA, AWWA, and WPCF,
Washington, D.C.
Battelle-Pacific Northwest Laboratories, 1978. Restoration of eutrophk
Medical Lake, Washington by treatment with aluminum sulfate: preliminary
findings. Prepared for Town of Medical Lake, Washington, 28 pp.
Brcwmari, Michael G., et al, 1977. Interaction of sodium phosphate with
aluminum hydroxide in lakes. Water Resources Center, University of
Wisconsin, 79 pp.
Congleton, James, and Gary Gonyea, 1978-1979. Effects of restoration on
Long Lake fish populations. Progress reports, Washington Cooperative
Fishery Research Unit, College of Fisheries, University of Washington
Cooke, G.O., R.H. Kennedy, 1977. Internal loading of phosphorus. Presented
at the Conference on Mechanisms of Lake Restoration, April 25-28, Madison,
Wisconsin. 23 pp.
Entrance Engineers, 1976. Long Lake rehabilitation demonstration project,
Volume 1: Long Lake rehabilitation plan, 39 pp. Volume 2: Stormwater
management program, 18 pp. Volume 3: Sewage treatment evaluation, 11 pp.
Reports to Kitsap County, Washington
Entrance Engineers, Northwest Environmental Consultants, Systems Architects
Engineers, Inc., 1577. Long Lake rehabilitation demonstration project:
Final environmental impact statement. Prepared for Kitsap County,
Washington, 125 pp.
Entrance Engineers, 1976. Long Lake Rehabilitation Demonstration Project,
Volume 1, Long Lake Rehabilitation Plan. Bellevue, Washington
Entranco Engineers, 1976. Long Lake rehabilitation Demonstration Project,
Volume 2, Stormwater Management Program. Bellevue, Washington.
Entranco Engineers, 1978. Long Lake Rehabilitation Demonstration Project,
Volume 3, Sewage Treatment Evaluation. Bellevue, Washington.
Funk, William H., et al, 1975. Determination, extent, and nature of
nonpolnt source enrichment of Liberty Lake and possible treatment. State
of Washington Water Research Center, Pullman, Washington, 163 pp.
Funk, William H. and Harry L. Gibbons, 1977. Effectiveness of an alum
treatment at Liberty Lake, Washington. Annual Pacific Northwest Pollution
Control Association conference, November 2-4, 1977, 29 pp.
68
-------
Gabrlelson, John 0., 1978. The role of macrophytes In the phosphorus
budget of Long Lake. M.S. thesis, University of Washington. 82 pp.
Hufschmldt, Peter W., 1978. Interactions between macrophytes and
phytoplankton In Long Lake- M.S. thesis, University of Washington. 73 pp.
Llndcll, L. Tormy, 1977. Studies of groundwater discharge to Long Lake.
Department of Civil Engineering, University of Washington.
Perkins, M., et al, 1977-1980. Evaluation of the restoration of Lonp Lake,
quarterly and annual reports. Department of Civil Engineering, University
of Washington.
Plotkin, Stephen, H'79. Changes In selected sediment characteristics due
to drawdown of a shallow eutrophlc lake. M.S. thesis, University of
Washington. 67 pp.
Welch, Eugene B., et al, 1977-1980. Evaluation of the restoration of Long
Lake, quarterly and annual reports. Department of Civil Engineering,
University of Washington.
69
-------
APPENDIX A
-------
• STREAM GAGING LOCATIONS
A ENTRANCO PRE AND POST ALUM
TRFATMENT MONITORING LOCATIONS
• U OF W LAKc SAMPLING LOCATIONS
e
ENTRANCO Engineers
MONITORING LOCATIONS
FIGURE
A
-------
APPENDIX B
-------
Effects of Restoration In Long Lake
Quarterly Reports: September 1979 - September 1980
Mater Column Monitoring:
Water sampling was performed twice monthly during this 12-month period
except during the winter months of December, January and February, when lake
sampling occurred once a month. Secchi depth, temperature, pH, alkalinity,
dissolved oxygen, chlorophyll ji (chl a), total phosphorus (TP), soluble reactive
phosphorus (SRP), total nitrogen, ammonia and nitrate were the variables deter-
mined. During the summer of 1980, primary productivity was also measured for
comparison with pre-drawdown values. The data are summarized in Table 1.
Phosphorus content during 1980 following drawdown during summer 1979 was
substantially reduced (Fig. 1). The mean lake total P concentration, June 1980
through September 1980, is 36 ug 1 compared to past summer means of 61 yg 1
(1977) and 76 ug 1 (1978). During pre-drawdown summers maximum TP levels
exceeded 100 yg 1~ . The P budget for thin time period is presently being
worked on and th« amount of internal loading of P will be quantified. The
data for the water and P budgets are presented in Table 2.
Algal biomass from the summer of 1980 (post-drawdown) also seems to be re-
duced, which, Is reflected in lower chl £ levels. The mean in the summer 1980
was about 15 yg 1~ compared to 26 yg l" in 1977 and 39 yg 1 in 1978.
^
The median pH of 8.1 during summer 1980 is also lower than levels during
prior summers. The median in 1976 was 9.1, 1977, 9.0 and 1978, 8.6. The
decrease in pH in 1980 after drawdown is probably due to the decreased primary
productivity in the lake in summer 1980. pH as high as 10 has been commonly
observed during the summer but during 1980 the highest pH observed was 8.7.
Laboratory experiments with Long Lake sediment suggest that P may be
solubilized and released to the water column at high pH (Fig. 2). Increased
solubilization of hydrous iron oxides under high pH with the subsequent release
73
-------
-2-
of P to the overling water column, may be an important process recycling P
during periods of high productivity. The lower mean P levels in I960, indicat-
ing a decreased internal loading during the summer, may be partly due to the
decreased algal productivity and associated lower pH. The decreased macrophyte
biomass in 1980 over earlier years may also have contributed to the lower pi.
as well as decreasing any direct recycling of P from sediconts due to root uptake
and subsequent plant death and decay. Sediment compaction was small and only
occurred in the exposed shallow regions of the lake. Also, the principal source
of internal loading of P frou the sediments appears to be from the deeper
areas. Therefore, the reduction in internal P loading as is, is not likely
to be due to sediment compaction. However, it seems obvious the drawdown
affected the internal P cycling process in a way that decreased P available in
the summer.
Restoration-Progress:
Refilling of the .lake after the 1979 summer drawdown began in October
and by November 20, 1979, the lake level had returned to normal.
The extent of sediment compaction as determined in exposed areas (about
4CZ CL{ the surface) was only about 0.1 m as estimated by three independent
measurements.
1) Steel rods placed in sediment at 10 sites in the south end of the
lake.
2) Measurements of watar depth at locations of previously known depths.
3) Analysis of sediment water cov.cent
Results of these measurements were contrary to those shown in laboratory
experiments where lake sediment 27 cm in depth compacted by 502 following a
month exposure. The water content of the surface sediment following drawdown
-------
-3-
was nlso higher than expected from results in the laboratory experiments where
water content dropped from 96 to 78Z.
Alum was applied to the lake from September 9, through September 19, 1980
in an attempt to reduce phosphorus levels in the water column nnd prevent its
release from the sediment. The alum was applied at a dosage of 6 tag Al 1
determined by jar tests, and pH and alkalinity considerations. Alum was not
applied to a section of the south end of the lake, which is left as a
control for determining macrophyte reinvasion during the summer of 1981.
Effects of the £lum application on the lake water and sediment characteristics
will be described in a subsequent quarterly report.
Macrophyte Surveys:
Macrophyte surveys were conducted June 27-28, 1980 and August 23-24, 1980.
These, along with data from previously reported surveys, are included here for
comparison in Table 3. The sampling stations are shown in Figure 3.
The June survey demonstrated that a substantial reduction in plant biomass
had occurred in the lake, especially in the southern areas most extensively
exposed during drawdown. E. densa was essentially eliminated in areas that
were previously densely covered.
Compared to June 28, 1978, the June 27, 1980 crop of macrophytes had
_o
decreased by 84 percent (124 + 39 to 87 + 47 g m ). By August 2'*, 1980 the
crop had increased by 5 fold and was only 46? less than the crop estimated on
August 24, 1978 (160 + 39 to 87 + 47 g m~ ). In contrast, the increase
between June 27, 1978 and August 24, 1978 was only 1.3 times. Drawdown definitely
tlc<./ff> • ''•
Inoraiiad the biomass of submersed macrophytes, especially £. densa.
-------
Although the E. dcnsa population was reduced, different macrophyte species,
in particular 1'oun.ioRcton crisp us, colonized the northern areas of the lake
during the spring. Its artal density was not great but it formed highly
visible patches in the northern o.nd of the lake near the edges of previously
exposed sediments as well as in deeper water. Concern was expressed by the
residents and fishermen. Surprisingly, £. crispus was not detected in samples
prior to drawdown. It appeared to die back during the summer but laboratory
observations of turion abundance indicates that this plant nay return during
the fall. In addition to F\ crispus, P_. praelongus and Elodea canadensis are
also present in greater abundance at many of the sampling stations (Table 3).
The late August survey shoved that the biomass increased substantially
during the summer - nearly A times greater increase during those 2 months in
1980 after drawdown than the same period in 1978 before drawdown. Recolonization
by E. densa at some of the stations located along the drawdown low-level con-
tour is occurring. It is conceivable that the biomass will be back to normal by
mid-summer 1981 ac this rate of invasion.
Water lilies (Nuphar) were not affected by the drawdown and seemed to
achieve normal growth patterns and died back during the fall.
-Effects of the alum treatment on macrophyte growth are expected to be
minimal as indicated by laboratory experiments using JL. densa and Long Lake
sediment under the same ':ype of alum treatment at; occurred in the lake. In
fact, it is possible that the alum treatment will increase macrophyte growth
if it is successful in controlling sediment P release and hence phytoplankton
biomass in summer.
Phytoplankton Counts:
Counts and identification to genera of the phytoplankton in Long Lake have
76
-------
-5-
continued during this 12-month period. The data are not completely evaluated,
however, it is obvious that the algal density has been much lower during 1980
and that dense blue-grion blooms were rare. In particular, (;he blue-green
nlgn Aphanizcmcnon was greatly reduced. Diatoms and green algae were more
abundant than in prior years.
In February and March a small cryptomonad outburst occurred. Then in
late April, a substantial diatom (Asterionella) bloom appeared. During the
summer there was other mixed algae community made up of diatoms (e.g., Asterionella,
Fragillaria, and Mclosira). blue-greens (e.g., Anabaena, Aphanizomenon and
GieutrichijQand green algae mainly in the Volvocales. The domir.ence varied
between Astcrionclla, Anahaena and Aphanizomenon during the summer of 1980.
Immediately before the alum treatment a blue-green bloom occurred with high
chlorophyll levels (38 ug 1 I).
Laboratory :Research:
In vitro experiments were performed which compared P release from Long
Lake sediment under a conventional alum layer and from compacted sediment
where alum was mixed into the surface in centimeters. By mixing a higher
allowable dosage of alum into the sediments, inactivation of sediment P is
increased. P release WM analyzed under normal and high pH conditions. In
both sets of experiments, the alum was effective in maintaining low P levels in
the water column at a normal pH. When the pH was raised to 10, P was released
to the water column in the untreated (control) tanks after a lag period of A
to 5 days (Fig. 2). The alum was effective in delaying the release of P at
pH 10 by a couple of weeks. Water column total P in the control tanka was abou:
900 U8 1 after two months and in the alum-treated tanks total P leveled off
77
-------
-6-
around 300 yg 1 ' The substantial release of P from untreated Long Lake sedioent
under high pH conditions suggests the .importance of these sedijients as a source
of P during periods of high productivity and pH in the lake.
The same scries of experiments Is bcinp, performed wich the calcareous sedi-
ments from Moses Lake. These studies may show intereoting differences in P
flux compared to the noncalcareous sediment of Long Lake. In thes^ experiments
also, the alum treatments appear to be effective in reducing water column P
and in delaying its release at high pH.
In addition, the effects of both types of alum treatments on E. densa growth
was examined in vitro. There wj little difference in plant growth between
control and tanks with surface alum applications. However, plants in the tanks
where aluu was mixed into the sediments, grew much slower (growth rate about
it times lower) than the control plants. It is thought that alum mixed into the
sediment in this manner may inhibit macrophyte grovth possibly due to 1) nutrient
limitation, 2) suboptimal pH, 3) Al toxicity. Al toxicity seems to be the most
likely cause of reduced plant growth, however. The suppression of root develop-
ment or elongation is a common symptom of Al tcxicity and this effect was
evident in the "mixed-alum" treatments. Total root biomass was greatly decreased
in treatment tanks relative to the control and to those in tanks with only a
surface application. Nutrient content in digested plant material does not in-
dicate that nutrient limitation is responsible for the reduced growth rates in
tanks with alum mixed into aedimcnts.
J. Jacoby and E. Welch
7f
-------
TOTAL PHOSPHORUS
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FIGURE 1. Mean total P content in Long Lake calculated by volume weighting
of data from three stations
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