U.S. ENVIRONMENTAL PROTECTION AGENCY
A Study on Disposal of Campground Wastes
Adjacent to Waldo Lake, Oregon
Working Paper #7
by
John R. Tilstra*, Kenneth W. Malueg
and Charles F. Powers
National Eutrophication Research Program
February 1973
PACIFIC NORTHWEST ENVIRONMENTAL RESEARCH LABORATORY
An Associate Laboratory of
National Environmental Research Center—Corvallis
-------
A Study on Disposal of Campground Wastes
Adjacent to Waldo Lake, Oregon
Working Paper #7
by
John R. Tilstra*, Kenneth W. Malueg
and Charles F. Powers
National Eutrophication Research Program
February 1973
~Present address: Environmental Protection Agency, Region VIII
Denver Federal Center, Denver, Colorado 80203
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CONTENTS
Page
INTRODUCTION 1
The Septic Tank Treatment System 2
Physical Characteristics 2
METHODS 4
Constructing the Flow Network 6
Tracer Studies 9
Sample Collection and Analyses 9
Effluent Flow Augmentation 10
RESULTS 10
DISCUSSION 17
CONCLUSIONS 21
REFERENCES 22
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INTRODUCTION
Proper treatment and disposal of human and domestic wastes
has long been a serious public concern, particularly in densely
populated areas. More recently, this problem has affected an
increasing number of recreational lakes and streams in sparsely
populated areas, including the vast national forests of the western
United States.
The forest lands are undergoing rapid development for recreational
use, including construction of new campgrounds and service roads. The
design of new campground waste treatment systems generally conforms
to existing state and federal pollution control regulations, but the
disposal of treatment effluents in the vicinity of recreational waters
may create unique problems. For many campground situations treated
effluents are disposed through soil absorption systems, and in some
cases the receiving aquifers are hydraulically associated with campground
supply and recreational waters.
Our investigation pertains to a cooperative study by the U. S.
Forest Service, Pacific Northwest Region, the Federal Water Quality
Administration (now the Environmental Protection Agency), and the
Pacific Northwest Water Laboratory (now the Pacific Northwest Environmental
Research Laboratory) during June to October, 1970. The study site was
a new campground septic tank treatment and disposal system at Islet
Campground, adjacent to Waldo Lake, Oakridge Ranger District, Willamette
National Forest, Oregon. Our primary objectives were to introduce
1
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expedient methods for characterizing the ground water flow regime in
areas either considered for or actively used for disposal of septic
tank effluents by soil absorption, and to determine the effectiveness
of a rocky volcanic soil upon the breakdown and retention of phosphorus
and nitrogen from a septic tank effluent.
The Septic Tank Treatment System
The septic tank treatment system is the most common domestic waste
treatment system for remote installations. The system involves two
basic components, the septic tank and the underground drainage field
or soil absorption system. The septic tank provides three basic functions
(1) removal of solids, (2) biological treatment, and (3) sludge and scum
storage. The septic tank does not accomplish a high degree of bacterial
removal, and accomplishes essentially no chemical removal. Its principal
purpose is to condition the sewage, by clarification, to reduce clogging
of the drainage field. The soil is responsible for removing harmful
bacteria and chemical constituents from the effluent; therefore,
considerable emphasis must be placed on selection of appropriate disposal
areas.
Physical Characteristics
The comfort station in this investigation utilizes a 5,000 gal.
septic tank, an effluent distribution pipe, and three underground
lateral drain pipes (each 50 ft in length and 4 in. I. D.) as shown
in Fig. 1. The drainfield is forested and is mantled with a soil zone
varying between 1 1/2 and 2 1/2 ft. in thickness. A zone of consolidated
2
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WALDO
LAKE
COMFORT
STATION
APPROXIMATE SCALE
Figure 1. Waldo Lake Campground Study Area.
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bedrock (basalt-rhyolite intermediate), which ranges from moderately
permeable to impermeable and from 11 to 16 ft in thickness, immediately
underlies the soil (Fig. 2). Beneath this bedrock layer is a 4 to
6 in. zone of highly fractured bedrock and pumice granules, constituting
the upper-most aquifer for most of the drainfield. Bedrock of unknown
composition, permeability, and thickness underlies this aquifer. The
land surface of the drainfield slopes toward the Waldo Lake shoreline
at a mean gradient of 4 degrees.
METHODS
Guidelines commonly used in the selection of a suitable subsurface
sewage effluent disposal site are given in the Manual of Septic-Tank
Practice, U.S.D.H.E.W. (1), as follows:
The first step in the design of subsurface sewage disposal
systems is to determine whether the soil is suitable for the
absorption of septic tank effluent and, if so, how much area
is required. The soil must have an acceptable percolation
rate, without interference from ground water or impervious
strata below the level of the absorption system. In general,
two conditions should be met:
(1) The percolation time should be within the range of
those specified in Table 1, p.8.' '
(2) The maximum seasonal elevation of the ground water
table should be at least 4 ft. below the bottom of
the trench or seepage pit.
Unless these conditions can be satisfied, the site is unsuitable
for a conventional subsurface sewage disposal system.
Refer to U.S.D.H.E.W. (1)
4
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Comfort
Station
Septic
Tank
Waldo
Lake
OTTT
Fractured
Bedrock £
t>n
Impermeable
Bedrock
TOWS
J fractured zone V
^ Lower Bedrock Layer
Figure"2. An East-West Cross Section of the Drainfield Showing the Stratigraphy and Areas
of Extensive Fracturing.
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The above guidelines, which were satisfied by the comfort
station selected for this study, emphasize the importance of soil
percolation rate and capacity tests as related to waste accomodation
by the soil and to design of the disposal system. Methods described
in our study, except for the chemical quality sampling, augment the
above guidelines for the proper selection of disposal sites by
introducing expedient tests which serve to predict the immediate
fate and pollutional possibilities of waste disposal at many considered
sites. However, it should be early recognized that a developed
disposal field was selected for method demonstration in our study
because other objectives were related to the chemical transformations
of disposed wastes.
Constructing the Flow Network
Ten test holes were drilled into the drainfield and developed
into observation wells as shown in Figs. 3 and 4. All test holes,
except "G", were drilled to the depth where the hole first encountered
water, using a track-mounted, rotary-percussion rock drill. Test
hole "G" was intentionally terminated in dry bedrock in order to
determine the occurrence and magnitude of flow along the soil-bedrock
interface, and to confirm the impermeability of the upper bedrock horizon.
Test holes were drilled during June 23-29, 1970, shortly after
the winter snows were sufficiently melted to permit access to the
area. The wells were mapped with an alidade and plane table, and a
Jlpi rit level was used for determining the elevations of well heads
6
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Comfort
Station
I
Waldo
Lake
W«U 'ft
7.
Well T
Well I
Impermeable
Bedrock
Lower Bedrock Layer
Figure 4. An East-West Section of the Drainfield Showing Hydraulic Separation of Aquifers
Shaded areas designate extent of saturation.
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and the lake surface. The reference elevation was that of a permanent
USGS staff gage near the lake outlet. A steel tape and chalk were
used to measure the water level elevations in the wells.
Tracer Studies
On July 23, following a four-week stabilization period for the newly
developed wells, two gallons of a fluorescent dye concentrate (Rhodamine
W.T)(a) were injected into the comfort station septic system through a
lavatory drain. This particular fluorescent dye possesses one of the
lowest soil absorption coefficients of presently available dyes;
-9
detectability limits are in the 10 g/1 range using a Turner Model
111 Fluorometer.(b) The dye was used to determine flow velocity of the
septic tank effluents and to verify flow pathways as indicated
by the piezometric gradient.
The effectiveness of this subsurface tracer was verified by
injecting a second tracer, 10 lbs of sodium chloride in solution form
on July 28. . Sodium chloride has been widely used as a subsurface
tracer where non-clay soils are involved, but detection sensitivity
(10~6 g/1) has always been a severe limitation.
Sample Collection and Analyses
Water samples were collected from individual wells using a vacuum
pump and an in-line pyrex glass suction flask. Where possible, two
one-liter water samples were collected. One was treated with mercuric
(a) (b) ^se a trade name product does not necessarily imply
government endorsement.
9
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chloride for preservation prior to nitrogen and phosphorus analysis;
the other was left untreated and used for chloride determination and
fluorescent dye measurements. All analyses were performed at the
Pacific Northwest Water Laboratory, Corvallis, Oregon, according to
the latest FWPCA methodology, USDI (2).
Effluent Flow Augmentation
The Manual of Septic-Tank Practice indicated that a campground
comfort station with flush toilets and a 100 person daily use rate
will result in 2,500 gpd of liquid wastes. The average daily use
rate of the comfort station during our study was estimated at 25
persons per day, which is perhaps 25 percent of the design capacity
of the station. Therefore, waste flow was augmented with approximately
1 gpm of fresh water into the waste system (by leaving a faucet
partially open) to more nearly approximate the design waste volume.
RESULTS
Water level elevations, well logs, phosphorus and nitrogen analysis,
and tracer measurements of individual wells were collectively used
to define the hydrology of the drainfield. Fig. 4 shows the aquifers
and stratigraphy of the drainfield by a section through wells "A",
"E\ and "I".
Water level in the wells was measured on July 21, 28, 31; August
5, 12, 18; and September 2. These data are summarized in Fig. 5.
Water levels in wells "A" and "I" behaved differently from those
in the other wells. Levels in well "A" (the well nearest the comfort
10
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101
WALDO WELL and LAKE WATER LEVELS
«
>
UJ
at o
Lake Elevation*:
^773T
8/17
Lolt
<
£
—5i
-10"
WECL A B C D E F H
INCLUSIVE MEASUREMENT DATES
7/21/70 to 9/2/70
Figure 5. Water Level Elevations for Observation Wells and Waldo
Lake. Elevation bars for each measurement_site are in
chronological order. Small x denotes missing data..
11
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station) averaged about 10 feet above the lake datum baseline, and
fluctuated randomly with respect to observed lake levels. Water levels
in well "I", on the other hand, were nearly identical with lake levels
throughout the period of observation. In the remaining wells, water
levels were always significantly below lake datum baseline, and in
well "J" the water was about twice as low as in the others.
Fluorescence measurements of the well water (Fig. 6) were made
on July 23, 24, 25, 28, and 31; August 5, 12, and 18; and September
2. The measurements are expressed in concentration units referenced
to the 30X scale on the fluorometer. Readings of less than 10 are
not regarded conclusively as that of true fluorescence owing to background
turbidity interference. The fluorescent dye reached well "A" within
24 hours following dye injection, wells "B", "C", "D", "E", and "F"
within 5 days, and wells "H" and "J" within one month. Dye was not
detected in well "I" or in the lake water at the shoreline.
Chloride measurements (Fig. 7) were made on July 25, 28, and
31; August 5, 12, and 18; and September 2. When compensation is
made for the five day interval between the dye and chloride injection
dates, the chloride concentration peak corresponds chronologically
to the fluorescence peak for each well. The addition of the tracer
probably did not largely increase the chloride concentrations already
present in the sewage effluents.
Most of the wells had moderately high nitrogen concentrations
(Table 1). Analyses from well "A" showed high total Kjeldahl-nitrogen
12
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10
10
u
o
-------
100
50
WELL: A
B
H
]J
I
INCLUSIVE MEASUREMENT DATES
7/25/70 to 9/2/70
Figure 7. Chloride Measurements for Observation Wells. Chloride
concentration bars for each measurement site are in
chronological order. Small x denotes missing data.
14
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Table 1. Chemical Analyses of Water
as mq/1 Nitrogen
as mq/1 Phosphorus
Total
Well
Ammonia
Ni tri te
Ni trate
Kjeldahl
Ortho-
Total-
Date
Code
Nitrogen
Ni trogen
Ni trogen
Ni trogen
Phosphate
Phosphate
o
A
4.40
.004
.016
6.5
.018
.121
CM
D
.44
.200
2.00
.6
.006
.030
CM
H
.05
.100
2.80
1.1
.003
2.80
I
.02
.001
.002
.3
.018
.120
A
10.0
.020
.130
12.1
.003
.780
C
: .04
.003
1.30
.003
.110
O
D
—
.400
8.00
.5
.003
N
E
.900
12.0
.4
.045
3.04
CSJ
F
.01
.100
4.00
.1
.006
.295
H
.02
.100
3.60
.7
.006
.420
I
.08
.010
.008
.4
.024
.470
J
.03
.001
.300
•5
.015
.750
A
10.4
.005
.012
13.8
.003
3.20
B
.90
.021
2.60
2.8
.138
4.40
C
.08
.017
3.60
.2
.003
.007
o
D
—
.520
9.30
.5
.006
2.00
N
E
—
1.01
14.4
.1
.003
2.00
LO
CSJ
F
.02
.005
6.80
.6
.003
5.28
hv
H
.03
.002
5.40
.1
.003
2.64
I
.05
.001
.004
.3
.063
2.40
J
.01
.001
.187
1.1
.006
8.40
A
D
33.0
.020
.020
41.1
.014
14.4
D
C
.06
.006
1.70
1.3
.001
.380
O
1^.
D
—
.500
9.90
.3
.001
.080
r>
E
.900
13.0
.1
.058
w
CM
F
.28
.100
9.90
2.4
.007
H
.03
,.100
5.50
.3
.007':
18.8
I
.01
.001
.001
.2
.004
.600
lake
.03
.001
.010
.3
.003
.028
A
D
35.2
.040
.040
39.1
.009
.038
o
fs,
D
C
_ _ _
.040
7.60
.1
.001
.006
\
D
.560
14.0
.3
.005
.030
en
E
1.00
14.0
1.1
.032
.154
r-.
F
.80
.320
9.60
1.6
.007
.147
H
.04
.003
6.40
.3
.010
.042
I
.01
.001
.010
.2
.006
.016
15
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Table 1. (Conti nued)
as mg/1 Nitrogen as mq/1 Phosphorus
Total
Well
Ammoni a
Ni tri te
Ni trate
Kjeldahl
Ortho-
Total -
Date
Code
Ni trogen
Nitrogen
Ni trogen
Ni trogen
Phosphate
Phosphate
A
16.0
.006
.003
28.2
.001
.025
B
—
—
3.4
.088
C
.002
2.70
1 .2
.002
.007
o
D
.038
4.40
2.6
.001
.005
E
.007
1 .80
4.1
.002
.006
C\J*
F
.026
4.80
.1
.001
.014
o>
H
.007
7.50
.3
.031
.033
I
.02
.001
.002
.3
.001
.060
J
4.70
.004
2.40
5.1
.008
.357
A
9.00
.007
.001
10.7
.001
.009
B
2.60
.025
2.50
8.2
.002
.034
C
1.10
.004
3.00
2.3
.001
.016
o
rs.
D
2.42
.050
3.80
6.3
.005
.012
c\T
E
7.00
.008
1.70
13.5
.002
.012
eg
F
.96
.007
4.00
.3
.002
.007
CTi
H
1.20
.006
6.30
1.2
—
.060
J
2.40
.006
4.20
5.7
.002
.010
1 ake
1 .00
.001
.100
1.2
.002
.011
16
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and relatively low nitrate concentrations. Analyses of all other
wells generally showed initial high nitrate concentrations and relatively
low total Kjeldahl. Later in the simmer total Kjeldahl nitrogen
generally became the most abundant nitrogen form.
Phosphorus data showed considerable variation among individual
wells and with respect to time, and did not indicate any significant
trend. Ortho-phosphorus concentrations in well "A" were in most
cases as low, if not lower, than concentrations in wells more distant
from the sewage effluent discharge areas.
DISCUSSION
All the wells except wells "A" and "I" tapped the main aquifer
in the highly fractured zone between the two principal bedrock layers
and ranged considerably in water yield. The fractured zone was probably
the interface of separate lava flows and the local variation in permeability
due to differences in size, extent, and hydrualic linkage of individual
fractures. Wells "E", "F", and "J" could not be pumped dry at a rate
of 1 gpm for 10 minutes, whereas, well "B" never yielded more than a
fraction of a gallon.
Wells "A" and "I" were supplied by two separate aquifers. The
well "A" aquifer probably consisted entirely of disposed sewage effluents,
as indicated by chemical analysis (Table 1). Well "A" was not a high-
yielding well (maximum of 2 gal. at 1 gpm pumpage rate) and was located
in an area where the upper bedrock zone was fractured. The well "I"
aquifer was perched and was apparently recharged by the lake, as
17
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indicated by comparing lake and well water level elevations (Fig.
5). (A perched aquifer is an underground water body, usually of
small size, which overlies, but is hydraulically separate from, the
main aquifer.) The continuous decrease of measured lake surface
elevation closely corresponded with the decrease of water surface
elevation in well "I".
The main aquifer sampled by wells other than "A" and "I" was
evidently not connected to the lake, since water elevations in those
wells showed no correspondence to lake levels (Fig. 5). The elevation
of the main ground water aquifer near the lake shoreline was several
feet lower tha;i the lake water surface, thereby indicating that septic
tank effluents incorporated with native ground water did not enter
the lake during the study period (July—September, 1970). This is
confirmed by our failure to detect dye at any time in well "I", the
single well which appeared to be linked hydraulically to the lake.
However, since the aquifer has limited permeability, the possibility
exists that septic tank failure, inadequate maintenance, and/or
bacterial biomass may eyentually lead to the complete clogging of
the fractures in the aquifer and upper bedrock zone, in which case
the septic tank effluents would probably flow along the soil-bedrock
interface and directly into the lake. Reference to Fig. 5 confirms
that the addition of sewage effluents through the summer definitely
raised the water level elevation of wells "C", "D", "E", "F". "H\
and "J" (note the rapid return to lowered levels following the end
of summer campground use). The presence of waste effluents in these
18
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wens was confirmed by the fluorescent dye and increased chloride
concentrations found there. The fate of the septic tank effluent
was further elucidated by the nitrogen analyses. The high total
Kjeldahl nitrogen and relatively low nitrate concentrations at
well "A" indicated that the well probably sampled raw septic tank
effluents because septic tank contents are characteristically anaerobic.
The initially high nitrate concentrations in the other wells indicated
that some nitrification occurred early in the study (indicating desirable
aerobic microbiological activity), but the increase in Kjeldahl
nitrogen as the season progressed was symptomatic of deterioration
of the aerobic aquifer as a result of partial clogging of the aquifer
fractures.
Caution should also be exercised here and in similar situations
involving aquifers of limited permeability with respect to the disposal
of septic tank effluents during a time when the aquifer is receiving
a high rate of natural recharge, such as during snowmelt runoff or
during a wet, rainy summer. This would greatly reduce the capacity
of the aquifer to accommodate artificial recharge, such as that involved
in the underground disposal of septic tank effluents. Under these
conditions the probable route of the effluents would again be along
the soil-bedrock interface and directly into the lake.
The disposal field and associated underground hydrology described
herein may or may not be typical of present or proposed disposal
sites in the Cascade Range or other parts of the western United States
19
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forest lands. On lands of volcanic origin and where composite lava
flows occur, fractures provide a principal means for underground water
movement. If the fractures in the present study were more extensive,
the lake probably would be hydrualically connected to the adjacent
underground aquifer. On the other hand, if the fracturing were less
extensive, the disposed septic tank effluents probably would move
along the soil-bedrock interface horizontally toward and into the
lake. Each of the above hypothetical situations presents an almost
certain lake pollution condition.
20
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CONCLUSIONS
1. Septic tank effluents incorporated with native ground water did
not enter Waldo Lake during the study period, July - September,
1970; the main aquifer was evidently not connected to the lake.
2. The aquifer is of limited permeability (it is contained in a
highly fractured zone between two bedrock layers), and the
possibility exists that septic tank failure, inadequate
maintenance, and/or bacterial biomass could eventually lead to
complete clogging of the fractures with the resultant flow of
septic tank effluents along the soil-bedrock interface into the
lake.
3. Because of the limited permeability of the aquifer, its capacity
to accommodate septic tank effluents would be greatly reduced
during times of high natural recharge, such as during snow melt or
a wet summer. Under such conditions the effluents would probably
pass along the soil-bedrock interface into the lake.
4. Many recreational lakes in the Western United States are located
in volcanic areas where rock fractures provide a principal means
for underground water movement. The fragility of most of these
lakes, together with inherent possibilities for entrance of
effluents into lakes situated in volcanic soils, indicates that
special precautions should be taken in the design and location of
waste disposal systems located adjacent to such lakes.
21
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REFERENCES
S. Department of Health, Education, and Welfare. Public
Health Service Publication No. 526. Manual of Septic-
Tank Practice, Revised (1967). 92 p.
S. Department of the Interior. Federal Water Pollution
Control Administration. Analytical Techniques for the
National Eutrophication Research Program, June (1969).
141 p.
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