United States
Environmental Protection
Agency
Office of Water Planning and Standards
Criteria and Standards Division
Washington, D.C.
Technology Transfer
EPA-625 2-80-026
Capsule Report
Restoration of
Lake Temescal
• :
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Beach at Lake Temesc?
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Technology Transfer EPA-625/2-80-026
Capsule Report
Restoration of
Lake Temescal
July 1980
This report was developed by the
Center for Environmental Research Information,
Office of Research ai-d Development,
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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SAN FRANCISCO
_P
Figure 1.
San Francisco Bay Area and Lake Temescal.
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I. Introduction
The Clean Lakes Program was
initiated in 1975 to implement
section 314 of the Federal Water
Pollution Control Act Amend-
ments of 1972. Section 314
gives the States the responsibil-
ity for protecting and restoring
the quality of freshwater lakes.
The program provides funding
to assist the States in
classifying their lakes according
to water quality, identifying
methods to control pollution
sources affecting them, and
restoring those which have
been degraded. To qualify for a
Clean Lakes restoration grant, a
lake must be open and acces-
sible to the public. Furthermore,
the proposed restoration project
must have the potential to yield
long-term public benefits and
not merely temporary or su-
perficial improvement.
This report discusses the res-
toration of Lake Temescal, a 4-
hectare (10-acre) man-made
lake which is the main attraction
of a regional recreation area
within the city limits of Oakland,
Calif. (Figure 1). One of the few
public beach and swimming
sites within the populous San
Francisco metropolitan area, it
is 4.8 kilometers (3 miles) from
downtown Oakland, and readily
accessible by public transit.
Lake Temescal began to deterio-
rate rapidly during the 1970's.
Four separate water quality
problems were identified as
causing the deterioration. Bac-
terial contamination threatened
to prevent swimming al-
together. High nutrient con-
centrations resulted in severe
blooms of algae. Water clarity
was reduced by algae and sus-
pended sediment, resulting in
unattractive and sometimes haz-
ardous conditions for swim-
mers. Rapid accumulation of
sediment, eroded from dis-
turbed areas in the steeply-slop-
ing watershed, had reduced the
lake's depth by 75 percent. If
these conditions persisted, it
was apparent that public use of
Lake Temescal was going to be
sharply restricted within several
years and would eventually
cease completely.
Loss of this particular recrea-
tional resource was a matter of
serious concern because of its
great popularity. A peak day
during the 4-month swimming
season brings as many as 3,000
people to the lake's beach and
swimming area. In 1977, in spite
of the already obvious decline
in water quality, 750,000 user-
days were recorded for the rec-
reation area, and beach use
alone exceeded 150,000. With
so many people depending on it
for some part of their recrea-
tion, Temescal's continuing
deterioration was going to have
a significant socioeconomic im-
pact. Consequently, the East
Bay Regional Park District de-
cided to embark on a restora-
tion program.
Restoration of Lake Temescal
entailed a combination of in-
lake and watershed measures:
dredging to restore depth and
volume, detention and partial
diversion of stream flows to re-
duce bacterial counts and sedi-
ment inputs, and watershed
management to eliminate pollu-
tion sources. The in-!ake activi-
ties were completed in 1979.
Watershed management began
in the same year and is still in
progress.
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2. Problem
Assessment
Fiqure 2.
In 1976, 46 percent of the water
samples collected from Lake
Temescal violated the California
total coliform bacteria standard
for contact recreation. Of addi-
tional samples collected in the
lake's watershed to identify the
nature and sources of the
contamination, more than 85
percent exceeded both total and
fecal coliform standards. The
Alameda County Health Care
Services Agency concluded that
swimming in 1977 should be
permitted only on a month-to-
month basis, conditional on sat-
isfactory reports of
bacteriological quality.
The volume of sediment carried
by the lake's two tributaries was
another factor which contrib-
uted to hazardous swimming
conditions. During 1975, for
example, water transparency as
measured by the depth at which
a Secchi disk could be seen
from the surface, ranged from
38 to 107 centimeters (15 to 42
inches). Turbidity was always
worse along the bathing beach,
where accumulated silt was
continually disturbed by swim-
mers. Recognizing that poor
visibility had contributed to
drownings in other U.S. lakes
by impeding supervision and
rescue, county health officials
recommended in early 1977 that
"if a major rehabilitation pro-
gram so as to provide a safe
LAKE TEMESCAL SILTATION 1907-1977
swimming area is not to be ini-
tiated, other public uses of the
lake be developed which do not
include swimming."
Algal blooms were partly
responsible for the reduced
water clarity. Dominant species
included blue-green algae which
are common in eutrophic lakes
and have often been implicated
in fish kills; the blooms oc-
curred because of high phos-
phorus and nitrogen
concentrations.
Rapid accumulation of sediment
was Lake Temescal's most se-
rious problem, from the stand-
point of its long-term usefulness
as a recreational resource.
When developed in 1868, the
lake was reported to have been
approximately 24 meters (80
feet) deep. Figure 2 illustrates
how its depth has changed. The
earliest bathymetric map, dated
1907, shows a maximum depth
of 11 meters (36 feet). In spite
of dredging conducted in 1963
and 1968, the maximum depth
was a mere 5.5 meters (18 feet)
by 1973. It has been estimated
that more than 71,000 cubic me-
ters (94,000 cubic yards) of sedi-
ment — 39 percent of the lake's
1963 volume — were deposited
between 1963 and 1973. This
was accompanied by formation
of deltas at the mouth of each
tributary. Sediment sources in-
cluded natural erosion in steep
terrain, erosion at highway and
residential construction sites,
streambank erosion resulting
from increased runoff, and ero-
sion of poorly designed and
managed road cuts and drain-
age systems.
Lake Temescal is a lake which
undergoes thermal stratification,
and summertime dissolved oxy-
gen concentrations approach
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Eroded Slope at
Construction Site
zero in the deepest layer
(hypolimnion). The oxygen
depletion has two adverse ef-
fects on recreation: it prevents
the establishment of some spe-
cies of fish and leads to produc-
tion of hydrogen sulfide gas at
the bottom of the lake. Bubbles
of H2S rising to the surface have
made swimming unpleasant
from time to time.
The 1976 watershed bacteri-
ological survey detected several
points of sewer line overflow or
leakage and one malfunctioning
septic system, and steps were
taken to abate these discharges.
However, it was obvious that
this was only a partial solution;
surface runoff and storm sewer
discharges to the two tributar-
ies, Caldecott and Temescal
Creeks, were responsible for
much of Lake Temescal's
deterioration.
Caldecott Creek drains 256 hec-
tares (633 acres) of the lake's
769 hectare (1,900 acre) water-
shed (Figure 3). Freeway and
tunnel construction activities
there spanned several years in
the 1960's and were accom-
panied by severe erosion. For a
time, the creek received acid
and detergent used to clean
Caldecott Tunnel, but this has
been diverted by agreement
with the California Department
of Transportation. However,
highway runoff containing bac-
teria, sediment, organic matter,
and other pollutants is a major
component of Caldecott Creek's
discharge during storms.
Temescal Creek, with a water-
shed of 513 hectares (1,267
acres), drains existing and
developing residential areas,
many of which are on slopes
exceeding 45 percent. It trans-
ports sediment, bacteria, and
nutrients into the lake. It also
experienced the results of se-
vere erosion during highway
construction between 1971 and
1973.
Figure 3.
Lake
Temescal
Watershed.
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3. Development of
Restoration and
Management
Alternatives
East Bay Regional Park District
applied for a Clean Lakes Dem-
onstration Grant in June 1976.
The proposed project, as it was
then defined, consisted of
dredging the deeper part of the
lake, forming a dike with the
dredged material to transform
the upstream third of the lake
into a large sediment trap for
Caldecott and Temescal Creeks,
and isolating the swimming
area with an impermeable bar-
rier and a circulation-filtration
system. An aeration system and
a bottom water withdrawal
structure were to be installed.
The objectives of these in-lake
measures were to eliminate
health hazards to swimmers;
alleviate nuisance conditions
caused by algae, turbidity, and
hydrogen sulfide production in
the lake; and reduce the dif-
ficulty and cost of maintenance
dredging. The project's cost was
estimated at $609,450.
Other alternatives which had
been considered at this early
stage included dredging alone,
bypass of dry-season stream
flows to control coliform bac-
teria, bypass of rainy-season
flows to reduce sediment influx,
and taking no action. Dredging
alone would have had to be re-
peated regularly and offered
only dilution as a means of
reducing coliform counts and
nutrient concentrations. Each of
the bypass alternatives would
have alleviated only part of Lake
Temescal's problem, and either
would have made water level
and flow maintenance difficult.
To take no action was clearly
unacceptable, since it was prob-
able that swimming would be
prohibited within 1 or 2 years,
and most other uses would be
lost in no more than 15 years.
EPA awarded the Clean Lakes
Demonstration Grant on March
31, 1977, and East Bay Regional
Park District initiated its water
quality monitoring program and
feasibility study. Several
modifictions to the project re-
sulted almost immediately.
An on-site study of bacterial
die-off rates showed that an
average of 98 percent of total
coliform and 93 percent of fecal
coliform in a given sample
would die during the course of
72 hours (Figure 4). This sug-
gested detention as a more
cost-effective method of control,
and the concept of isolating and
filtering swimming area water
was dropped from further
consideration. The proposed
desilting basin could be used to
effect the necessary detention.
The East Bay Regional Park Dis-
trict had realized since the
beginning of the project that the
feasibility of the in-lake desilting
basin could not be confirmed
without detailed geologic and
soils analyses. Three borings,
extending as deep as 33 feet
into the lake bottom, were
made in November 1977. They
showed the lake bottom sedi-
ments to be very soft clays and
silts of low bearing capacity, un-
able to support the weight of
the dike as proposed without
risking substantial settlement or
failure. A dike could be con-
structed at the intended location
in the lake, but the dredged ma-
terial would be unsuitable and
rocky fill would have to be im-
ported. The engineering geolo-
gists recommended that a less
costly alternative be explored.
The District and its consultants
re-examined and eventually se-
lected the concept of diversion
of dry-weather flows from both
creeks for bacteria and nutrient
loading control, supplemented
by a detention structure on
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Temescal Creek to allow bac-
teria die-off and sediment set-
tling. Dredging remained in the
work plan. The aeration system
was deleted; high operating
costs and poor performance at
other shallow lakes in the
United States were the main
considerations in that decision.
The bottom withdrawl structure
was also eliminated when it
was determined that if water
level was to be maintained, the
limited inflow during summer
months would not allow
enough water to be released
from the hypolimnion to signifi-
cantly improve the water
quality.
The project was amended in
June of 1979 to include a major
watershed management compo-
nent. Designated the "Lake
Temescal Pollution Identification
and Source Control Program," it
was designed to provide data
which could be used in develop-
ing and implementing ap-
proaches to reduce the
generation of pollutants in the
drainage basin. If successful, it
would help protect the invest-
ment made in in-lake restora-
tion measures by slowing the
rate of future deterioration.
Figure 4.
500
300
100
50
i
i
30
10
5
3
24 48
DETENTION TIME IHoirsl
72
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4. Implementation
Dredged
Material Disposal.
Caldecott Creek
Diversion.
Temescal Creek Weir
and Detention Pond.
Figure 5 shows the structural
portion of the restoration
project as it was implemented.
The construction phase began
early in 1979 and was com-
pleted in time for the swimming
area to be reopened to the pub-
lic on July 4.
Using a 100-ton crane and
clamshell or dragline, 36,000 cu-
bic meters (47,200 cubic yards)
of sediment were removed from
the lake. The spoil was loaded
directly into end-dump trailers
for hauling to another park be-
ing developed by the District. At
the disposal site, the material
was dumped in an area sur-
rounded by grassed berms to
dry for eventual use as fill.
A pond with an earth dam pro-
tected by a concrete apron was
built at the mouth of Caldecott
Creek, and a pump station was
constructed to direct all dry-sea-
son flows to a discharge point
downstream of the lake's outlet.
A detention pond with a weir
and removable flashboards was
constructed at the mouth of
Temescal Creek. The Temescal
pond was sized to provide 72-
hour detention for the mean
summer creek-flow.
Smaller pumps were installed at
the Temescal Creek pump sta-
tion since not all dry-weather
flows there are diverted.
Temescal runoff is detained to
allow time for bacterial die-off
and then released to the lake,
unless the pond level becomes
too high or monitoring shows
that water quality has not im-
proved sufficiently. Water which
cannot be released is used to ir-
rigate the adjacent meadow or
pumped to the Caldecott Creek
detention pond and thence to
the discharge point downstream
of the lake. Both pump stations
are provided with silt traps, and
all equipment is underground
(Figure 6).
During the rainy season, when
there is no swimming at Lake
Temescal, stream flow is not di-
verted. The earth dam at the
mouth of Caldecott Creek is
taken out, allowing all flow to
enter the lake. Flashboards are
removed as necessary from the
Temescal Creek weir to allow
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Erosion and Sedimentation Controls.
storm flows to pass safely while
still being detained sufficiently
to undergo some desilting.
The source identification and
control program began early in
1979, as a cooperative effort by
the U.S. Geological Survey and
East Bay Regional Park District.
USGS installed gaging stations
and rain gages, provided sedi-
ment sampling and flow meas-
uring equipment, and
performed some laboratory
analyses. Automatic water sam-
plers were used at the mouths
of the two creeks, while sam-
ples were collected by hand
during storm events at the sta-
tions higher in the watershed. A
number of land developers co-
operated with the District by im-
plementing erosion controls.
This permitted comparisons of
the amounts of sediment being
transported from controlled and
uncontrolled sites.
The District has no direct regu-
latory authority over land devel-
opment in Lake Temescal's
watershed and must rely on the
City of Oakland and Alameda
County to enforce best manage-
ment practices. Project per-
sonnel meet often with the
Assoua'..;:.:•• ?' / .-.ica Hnv-
ernments and the Alamc
County Flood Control District,
both of which are involved in
areawide water quality manage-
ment planning, to develop best
management practices in the
most usable form for the water-
shed. They also work closely
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Figure 6.
Pump Station.
Figure 5.
Detention and
Diversion System.
with the Oakland and Alameda
County planning agencies to
promote incorporation of man-
agement practices in City and
County ordinances.
The total cost of the Lake
Temescal Restoration Project
was $998,254. East Bay Re-
gional Park District provided
$244,486 of the funds to match
EPA's $315,618 grant. An addi-
tional $64,000 of matching
money was made available to
the District under the California
Urban and Coastal Park Act. The
remainder of the match was
taken from a special appropri-
ation paid to the District via the
State transportation fund. The
appropriation, $359,150, was
passed because freeway
construction by the California
Department of Transportation
had been a major factor in the
lake's rapid sedimentation and
deterioration after 1960. The
balance of the appropriation
was used to cover increases in
dredging costs, which had dou-
bled since the application had
been prepared. The U.S. Geo-
logical Survey, under a coopera-
tive agreement, contributed
$15,000 toward the source iden-
tification and control program.
SILT TRAP
TYPICAL PUMP STATION
SCREENED INTAKE
CALDECOTT CREEK
DIVERSION
PUMP STATION
IRRIGATION DIVERSION
PUMP
STATION
MESCAL CREEK
RETENTION BASIN
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5. Results and
Benefits
The first and most obvious re-
sult of the restoration project is
that Lake Temescal was usable
for swimming in 1979. More-
over, the public evidently saw it
as more attractive as a swim-
ming site. Receipts from the
modest beach-use fees ($1.00
per adult, $.50 per child) in 1979
amounted to more than 90
percent of 1978 beach revenues,
in spite of the fact that the lake
was closed during the first 2
months of the season because
dredging and construction had
not been completed. This sug-
gests that average daily use in-
creased by approximately 50
percent over 1978 usage rates, a
substantial public benefit.
One of the reasons for this re-
sult is that the beach was never
closed in 1979. In the few years
prior to the project, the beach
had been closed an average of
four times per season because
of coliform standards violations.
Diversion of Caldecott Creek
flows eliminated coliform inputs
from that portion of the water-
shed. The Temescal Creek
detention pond proved quite
effective in reducing bacteria
counts, as the August 1979 data
in Table 1 demonstrate.
Nutrient concentrations appear
to have been little affected by
the dredging, diversion, and
detention pond. Blue-green al-
gae decreased somewhat in
numbers in 1979 compared to
1978, but algal blooms contin-
ued to occur, adversely affect-
ing water clarity.
Turbidity remained high until
late September, when the lake
destratified and clarity improved
dramatically. Disturbance during
dredging and construction was
probably partially responsible
for the turbidity. Sampling dur-
ing 1980 should provide better
data for use in assessing the re-
sults of the project from the
standpoint of water clarity.
It is, of course, too soon to
measure the impact of the
project on sedimentation rates
in the lake. A good qualitative
indication, though, is the large
amount of material that has col-
lected in the Temescal Creek
detention pond. After less than
1 year, the pond already needs
cleaning (this can be easily
done using a large back-hoe). In
the absence of the pond, this
material would have been
deposited in the lake.
Table. 1.
Effectiveness of Temescal Creek Detection Pond, August 1979
Fecal Coliform Count (colonies/100 ml)
Date
8/1
8/7
8/16
8/21
8/29
Above Pond
1220
1476
520
2400
3933
Below Pond
160
313
297
43
263
Percent
Reduction
87
79
57
98
93
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Recreation on Lake Temescal.
Although quite new, the source
identification and control pro-
gram has already yielded
beneficial results. Using data
from sub-basin sampling, flow
measurements, and rainfall
records, estimates of sediment
production by land use type
were developed. Site specific
sampling has provided data
which can be usecJ to determine
the effectiveness of various ero-
sion control moas -res which
would be applicable ir tV
watershed. These results ... _^
used tooothor in r1- ^elopinr:
TIC ..lei e'c<=i' •; r- ' '••' i _ • .
o for iocai gc <- •'• s
onstrating the .;. \- , i .olb Ly a
' "• "\<.l< .. In some
USGPO661-054 9/80
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This report has been reviewed by the Clean Lakes Section, Criteria and
Standards Division, U.S. Environmental Protection Agency and approved for
publication. Mention of trade names or commercial products does not consti-
tute endorsement or recommendation for use.
Single copies of this report are available from:
Center for Environmental Research Information
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
Thisrepu, v;-s prepared for the U.S. r-ivrunmenT3' Pro' ?ciior>A> ••_
'O.H jrt fcvas. ir-.-j-.G"!, Pen,-;a. -'•iG='-g"?-jf-c *^ch':;:^> M.-irr
, . :e'o ^ >\ tps; 3a- f -i.. -r-\ '••,.-. ris.tr
/,d. . ,crmation or reference material may be requested from:
Denn. ^ '^~'
j-.. , I7:,/ \v pur< r
11500 Skyline Boulevard
Oakland, Calif. 94619
Clean Lakes Program
Office of Water Planning and
-mental Protection Agency
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