United States
Environmental Protection
Agency
Office Of Water
(4503F)
EPA841-F-94-001
January 1994
Number 7 7
TMDL Case Study
Lake Chelan, Washington
Key Feature:
Project Name:
Location:
Seope/Si/e:
Land Type:
Type of Activity:
Pollutants:
TMDL Development:
Data Sources:
Data Mechanisms:
Monitoring Plan:
Control Measures:
A phosphorus TMDL to protect a
threatened lake
Lake Chelan
EPA Region X/Chelan County,
Washington
Lake, watershed 2,393 km2
Ecoregion 10, high mountains
Forest, agriculture, urban
Phosphorus, bacteria
PS, NPS
State and local
Steady-state model
Yes
Increased public sewerage,
development limits, boat sewage
pump-outs, agricultural and
stormwater management
Washington State
Puget Sound
FIGURE 1. Location of Lake Chelan in central Washington
Summary: Lake Chelan, located in the Northern Cascades of central Washington State (Figure 1), is classified as ultra-
oligotrophic. It has extremely low nutrient levels and a high degree of clarity. Although it is not on Washington's 303(d)
list, increasing development pressures have raised concerns about maintaining the lake's high water quality. During 1989,
in an effort to protect this unique and highly valuable natural resource, the Washington State Department of Ecology
(DOE) conducted the Lake Chelan Water Quality Assessment which determined the nutrient loading limits that will
maintain the lake's ultra-oligotrophic condition.
In 1990, the Lake Chelan Water Quality Committee, which is composed of representatives from local public-agencies,
prepared a water quality plan based on the assessment. The plan included a list of action items for controlling nutrients
and bacteria from 6n-site septic systems, underground sewer lines, agricultural runoff, and urban stormwater runoff. The
water quality plan also included a TMDL for total phosphorus in Lake Chelan. To support the Committee's effort, DOE
conducted the technical TMDL analyses for several options, based on potential development patterns in different portions
of the basin. The most-likely option was chosen and a phosphorus TMDL of 51 kg/day was submitted to and approved by
EPA Region X. The TMDL includes load allocations of 0.5 kg/day for future growth, 6.3 kg/day for existing sources,
and 44.2 kg/day, for background loads (Pelletier, 1991). The Lake Chelan Water Quality Committee is responsible for
implementing the water quality plan in order to meet the TMDL. The committee is currently investigating various control
approaches such as sewer line replacement, sewer system extension, boat sewage pump-out facilities, agricultural runoff
management, and stormwater management.
Contact: Steve Butkus, Washington State Department of Ecology, Water Quality Program, PO Box 47600,
Olympia, Washington 98504-7600, phone (206)407-6482
Recycled/Recyclable
Printed with Soy/Canda Ink on paper that
contains at least 50% recycled fiber
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BACKGROUND
Lake Chelan is located in the northern Cascades,
approximately 100 miles east of Seattle and 50 miles
south of the Canadian border. Lake Chelan serves as a
water supply for more than 6,000 residents, provides
irrigation water for approximately 18,000 acres, and
produces hydroelectric power (Beck and Assoc., 1991).
It is also an important location for water-related
recreation and fisheries production. It is considered one
of the most pristine bodies of water in North America,
with a high degree of clarity and extremely low nutrient
levels.
Lake Chelan is over 50 miles long with an average width
of 1 mile. It has a surface area of 52 mi- (134 km2) and
a watershed of approximately 924 mi2 (2393 km2). Lake
Chelan discharges to the Chelan River at a small
hydroelectric dam in the city of Chelan (Figure 2). The
dam, which was constructed in 1927, raised the level of
the lake by 24 feet. Beyond the dam, the Chelan River
flows only a few miles before emptying into the
Columbia River. The average annual discharge from
Lake Chelan is 2,050 cubic feet per second (cfs); its
bulk detention time (i.e., the average amount of time it
takes for the all of the water in the lake to be
exchanged) is approximately 10.6 years (Patmont et al.,
1989).
Lake Chelan has two distinct basins, which are
distinguished mainly by their bathymetry. The upper
basin is extremely deep and approximately 38 miles in
length. The maximum recorded depth is 1,486 feet
although some local residents maintain that the lake "has
no bottom." The lower basin, which is bordered by the
city of Chelan, is approximately 12 miles long and has
an average depth of approximately 141 feet (Patmont et
al., 1989).
The upper basin is very remote and accessible only by
boat or plane. Consequently, the vast majority of its
watershed remains heavily wooded and undisturbed.
Most of the watershed is public land, including the Lake
Chelan National Recreation Area, the Sawtooth
Wilderness, the Wenatchee Forest, and portions of the
North Cascades National Park and Glacier Peak
Wilderness. Land use in the lower watershed is a
mixture of forest, apple orchards, and urban land.
Table 1 summarizes the distribution of land uses in the
watershed as a whole.
The total resident population of the Chelan basin was
approximately 6,600 in 1987. However, the population
changes seasonally due to fluctuations in the farm labor
force, tourism, and recreation. Nearly all of the
residents live in the lower basin, primarily in the city of
Chelan and the town of Manson. In the upper basin,
Chelan
FIGURE 2. Schematic of the Lake Chelan watershed
approximately 130 people live in the villages of
Stehekin, Lucerne, and Holden. Between 1910 and
1950, a mine operated in the Holden area and the upper
basin was more populated. The lower basin reported a
12.5 percent population increase between 1970 and
1980, a growth rate that is likely to continue or increase
in the future because of the basin's recreational appeal
(Patmont et al., 1989).
ASSESSING AND CHARACTERIZING
THE PROBLEM
Targeting and Prioritizing
Identifying and protecting threatened good-quality waters
are important to the TMDL program. Although Lake
Chelan is not currently classified as water quality-limited
and does not appear on Washington's 1992 section
303(d) list, there is concern that, without comprehensive
planning, increasing development in the watershed could
degrade water quality. It is for this reason that, in
April, the Lake Chelan Water Quality Committee
developed a phosphorus TMDL for Lake Chelan.
Monitoring and Data
In 1989, Washington's Department of Ecology (DOE)
conducted the Lake Chelan Water Quality Assessment.
This intensive study was designed to (1) provide baseline
water quality data; (2) evaluate the suitability of on-site
wastewater disposal systems within the developing lower
basin; and (3) estimate the potential sources and impacts
of nutrients, bacteria, and other chemicals of concern.
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T&BL.E 1. Land use within the
(Patmontet al., 1989)
Lake Chelan watershed
Land Use
Lake Chelan
Other Water Bodies
Forested Public Lands
Forested Private Lands
Agriculture - Orchard
Agriculture - Nonorchard
Residential
Roadways
Commercial and Public Buildings
TOTAL
Area
(mi-)
52
1.5
772
63
18
12
2.3
2.3
0.38
923.9
Percent of
Total
5.6
0.2
83.9
6.8
2.0
1.3
0.3
0.2
0.0
100
The State's report detailed the lake's present condition
and supplied most of the technical information for
developing this TMDL (Patmont et al., 1989). Table 2
summarizes the lake's water quality characteristics for
several parameters of concern.
Phosphorus
Phosphorus is the principal nutrient controlling algal
growth in Lake Chelan. This was determined through
analysis of water column and particulate matter nitrogen-
to-phosphorus ratios (Table 2). Both ratios indicated
that phosphorus is the nutrient limiting algal growth.
The Lake Chelan Water Quality Assessment estimated
that from 75 to 90 percent of the phosphorus input to the
lake comes from natural sources, largely forest runoff
and direct precipitation. Of the remaining 10 to 25
percent attributable to anthropogenic sources, roughly
half comes from agricultural activities, primarily
orchards. A large portion of the total agricultural runoff
loads are attenuated in three small lakes located in
orchard areas approximately 1 mile north of the lake's
north shore. However, loading values associated with
the runoff from orchard operations have not been
quantified (Beck and Assoc., 1991).
The remaining phosphorus loads in the basin are
attributable to stormwater runoff and septic system
inputs (Patmont et al., 1989). Homes using on-site
waste disposal contribute approximately 0.08 kg
P/day/1,000 homes. This includes phosphorus from the
septic system and from lot runoff. Homes on public
sewer systems are estimated to contribute only to the
runoff component, or 0.001 kg P/day.
Chinook salmon net pens are the only point source of
phosphorus in the watershed. Net pens are large,
floating, barge-like structures that contain dense
populations of fish being raised for market. The fish,
which are fed with special preprocessed food packs, are
estimated to contribute 0.01 kg P per day per 2,000 Ib
offish (Beck and Assoc., 1991).
Bacteria
In addition to phosphorus enrichment, pathogens from
septic systems pose a health concern for those who use
the lower basin as a source of drinking water. At the
lake outlet, fecal streptococcus, fecal coliform, and total
coliform are within state and federal criteria for water
contact recreational use; however, values do regularly
exceed the State's potable water standard of
1 count/100 ml (Patmont et al., 1989). The Chelan-
Douglas Health District chlorinates water prior to
distribution.
The Management Plan
In 1990, the City of Chelan, Chelan County, the Chelan
County Public Utility District, the Lake Chelan Sewer
District, and the Lake Chelan Reclamation District
formed the Lake Chelan Water Quality Committee.
With funding from the .Washington Centennial Clean
Water Fund, the Committee prepared the Lake Chelan
Water Quality Plan, which specifies steps to ensure that
Lake Chelan maintains its present ultra-oligotrophic
status. Since urbanization is a major concern in the
watershed, the plan's primary .recommendations are to
TABLE 2. Average spring/summer values for selected
water quality parameters for Lake Chelan, Washington
Parameter
Secchi Disk Depth (m)
Temperature (°C)
pH
Dissolved Oxygen (mg/L)
Total Suspended Solids (mg/L)
Sp. Conductance (umho/cm)
Total Phosphorus (ug/L)
Total Nitrogen (ug/L)
Total Coliibrm (0/100 ml) .
Particulalc N:P
Water Column N:P
Average
Epiliihnetic Value
(95% CI)
12.1 +/- 0.5
13.2 +/- 0.4
7.67 +/- 0.02
10.6 +/- 0.1
0.1 +/-0.0
56.7 +/-0.1
3.01 +/- 0.18
103 +/- 6
2.2 +/- 0.5
> 15:1-
30:1 +/- 3:1
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expand existing sewerage facilities and to extend services
to presently unsewered areas. Specific concerns are as
follows (Beck and Assoc., 1991):
Qn-site wastewater management - Older on-site systems
may not perform satisfactorily. For certain situations,
hookup to public sewers may become mandatory.
Stormwater management - Runoff from newly developed
areas may increase pollutant loadings to the lake. New
ordinances for stormwater and drainage standards are
being developed.
Agricultural activities - Runoff from agriculture impacts
the lake; monitoring to determine potential impacts may
be considered, as may improved farmer education and
the increased development of farm plans.
Boat sewage disposal - As boat recreation increases, so
will potential for pollution. A task force to develop an
improved program for regulation and education,
additional facilities, and new licensing provisions have
been proposed.
TMDL DEVELOPMENT
The goal is to preserve the ultra-oligotrophic condition
of Lake Chelan. Additional total phosphorus (TP)
loadings to the lake (over the 1986-87 load) are
considered acceptable only if there is less than a
5 percent chance that such additions will cause in-lake
(lower basin) TP concentrations to exceed 4.5 /tg/L,
which is & generally accepted value for the ultra-
oligotrophic classification. Management goals are
expressed in terms of their effect on the lower basin
because the lower basin is relatively shallow and
consequently more prone to the effects of increased
phosphorus loads. DO& conducted these analyses as
technical support for the Lake Chelan Water Quality
Committee's water quality plan.
Using a steady-state mass balance model and Monte
Carlo analysis techniques, DOE calculated that the 4.5
/
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TABLE 3. Summary of load allocation strategies for future development in the upper and lower basins of Lake Chelan
(Pelletier, 1991) .
OPTION 1:
No growth in
upper basin
OPTION 2:
Mixture of growth
in upper and
lower basins
OPTION 3:
No growth in
lower basin
LOAD ALLOCATIONS (kg P/day)
Existing (1986-87)
land uses in lower
basin
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6,3
6.3
Future. growth in
lower basin
0.50
0.47
0.45
0.40
0.34
0.29
0.24
0.19
0.14
0.08
0.00
Future growth in
the upper basin
0.00
0.05
0.10
0.20,
0.30
0.40
0.50
0.60
.0.70
0.80
0.96
Background load
from upper basin
watershed and
precipitation
44.2
44.2
44.2
44.2
44.2
44.2
44.2
' 44.2
44.2
44.2 '
44.2
TMDL
- 51.0
51.0
51.0
51.1
51.1
51.2
51.2
51.3
51.3
51.4
5'1.5
Wengreen, Public Utility District #1 of Chelan County,
personal communication, September 22, 1993):
Wastewater treatment - Although the Chelan Treatment
Plant discharges into the Columbia River, the collector
pipe for the Lake Chelan Sewer District runs under the
lake shore. This has sparked significant water quality
and health concerns. Negotiations are underway
regarding the replacement of the sewer collector line for
the district.
Stormwater - Proposed regulations for stormwater
management are currently being developed by the City
of Chelan and Chelan County.
Boat Sewage - One new boat sewage pump-out station
has been installed, bringing the total in the lake to three.
Additional, pump-outs are being investigated.
LONG-TERM MONITORING
The Lake Chelan Water Quality Plan includes a long-
term water quality monitoring strategy. The plan states
that permanent stations will be chosen and selected
parameters will be monitored on a repeating year cycle.
This has not yet occurred; however, the Lake Chelan
Reclamation District has received a $176,000 grant
(75 percent cost share) to initiate a short-term "Irrigation
Water Management and Drain Monitoring" project in the
watershed.
The drain monitoring portion of the plan will assess
water quality trends and. runoff from agricultural drains
to evaluate pollutant loading during worst case
conditions. At a minimum, the following parameters
will be evaluated: flowi fecal coliform, total suspended
solids, turbidity, dissolved oxygen, temperature, pH,
TP, ammonia nitrogen, nitrites, nitrates, and
conductivity. DOE also conducts monthly TP sampling
at the lake outlet.
The irrigation water management portion of the project
will involve extensive soils analysis to determine the
optimum procedure for managing irrigation rate, timing,
and duration. The goal is to help growers minimize the
amount of water leaving the site either through runoff or
deep percolation (DOE, 1993).
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TABLE 4. Load allocations for four Lake Chelan development scenarios (Beck and Assoc., 1991)
Scenario 1: Sewer system extended, but proportion of homes on septic remains the same
This scenario assumes that net pens remain at their current size, agricultural lands do not increase in size, and
the percentage of homes on septic systems remains the same.
Source Type
Homes using on-site disposal
Homes on sewer systems
Chinook net pens
Agricultural activities
Allowable Load
0.16 kg P per day
0.33 kg P per day
0.01 kg P per day
0.00 kg P per day
Development Potential
800 new residential units
3,300 new residential units
2000 Ib of fish (existing)
No additional acres
Scenario 2: Comprehensive sewerage
This scenario assumes that a comprehensive sewer plan is developed and implemented. This would result in
the construction of very few, if any, on-site sewer systems in the future.
Source Type
Homes on sewer systems
Chinook net pens
Agricultural activities
Allowable Load
0.49 kg P per day
0.01 kg P per day
0.00 kg per day
Development Potential
4,900 new residential units
2,000 Ib of fish (existing)
No additional acres
Scenario 3: Sewer systems not extended
This scenario assumes that sewer systems are not expanded beyond their current service areas and that sewered
homes are built until the capacity of the treatment plant is reached.
Source Type
Homes on sewer systems
Homes with on-site disposal
Chinook net pens
Agricultural Activities
Allowable Load
0.23 kg P per day
0.26 kg P per day
0.01 kg P per day
0.00 kg per day
Development Potential
2,300 new residential units
1,440 new residential units
2000 Ib of fish (existing)
No additional acres
Scenario 4: Agricultural land converted to home sites
This scenario assumes that some agricultural lands are converted to home sites. This is considered highly
probable and will likely occur in conjunction with any of the first three scenarios.
Conversion to homes with sewer systems
Conversion to homes with on-site septic systems
1 additional home for every 0.24 acre converted
1 additional home for every 2.0 acres converted
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TABLE 5. Summary of required actions (Beck and
Assoc., 1991)'
Agency/ Action Item
WQ Advisory Committee
• Plan approval
• Expand and formali/.e committee
• Establish boat sewage task force
• Submit sewer hookup ordinances .
• Establish on-site wastewater task
force
• Submit stormwater ordinances
• Submit amended boat registration
rates
City of Chelan
• Prepare stormwater management plan
• Construct interim facilities
• Relocate primary facilities and
expand wastewater plant
Chelan Public Utility District
• Relocate interceptor
• Construct lakeside/primary plant
. interceptor
• Construct Minneapolis Beach/Yacht
Club interceptor
• Construct Yacht Club/Fields Landing
interceptor
Chelan County
• Prepare stormwaler management plan
Lake Chelan Reclamation District
• Extend sewer past Willow Point
Chelan County Conservation District
• Conduct agricultural drain monitoring
• Prepare farm plans
Washington State Parks
• Construct 25 Mile Creek wastewaler
facilities
WSU Cooperative Extension
• Establish education programs for
growers
Chelan County Fire Marshall
• Survey storage lank practices
Cost
($ 1990)
A
t)
a
a
A
150,000
350,000
6,700,000
3,500,000
850,000
4,630,000
3,620,000
150,000
1,390,000
75,000
2,160,000
A
"
REFERENCES
Beck, R.W., and Associates. 1991. Lake Chelan water
quality plan. Report to the Lake Chelan Water Quality
Committee, Wenatchee, Washington.
DOE. 1992. Lake Chelan TMDL summary. TMDL
Number 47-001. Washington State Department of
Ecology, Olympia, Washington.
DOE. 1993. Centennial dean water fund grant
agreement between the State of Washington Department
of Ecology and Lake Chelan Reclamation District.
Washington State Department of Ecology, Olympia,
Washington.
Patmont, C.R., G.J. Pelletier, E.B. Welch, and C.C.
Ebbesmeyer. 1989. Lake Chelan water quality
assessment. Prepared by Harper Owes, Inc. for
Washington State Department of .Ecology, Olympia,
Washington.
Pelletier, G. 1991. Lake Chelan TMDL for total
phosphorus.. Memorandum of April 5 to B. Hashim and
J. Milton. Washington State Department of Ecology,
Olympia, Washington.
USEPA. 1991. Guidance for water quality-based
decisions: The TMDL process. EPA 440/4-91-001.
United States Environmental Protection Agency, Office
of Water, Washington, DC.
This case study was prepared by Research Triangle
Institute, Research Triangle Park, NC, in conjunction with
EPA, Office of Office of Wetlands, Oceans, and
Watersheds, Watershed Management Section. To obtain.
copies, contact your EPA Regional 303(d)/TMDL
Coordinator.
Funds from each agency's ongoing programs.
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