United States
Environmental Protection
Agency
Office of Radiation Programs
Eastern Environmental
Radiation Facility
1890 Federal Drive
Montgomery, AL 36109
EPA 520/5-88-019
June 1989
Radiation
Radiological Survey of
San Diego Bay
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EPA 520/5-88-019
Radiological Survey
of
San Diego Bay
Mark 0. Semler
and
Richard L. Blanchard
Eastern Environmental Radiation Facility
1890 Federal Drive
Montgomery, Alabama 36109
March 1989
U.S. Environmental Protection Agency
Office of Radiation Programs
401 M Street SW
Washington, DC 20460
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Table of Contents
Page
List of Figures v
List of Tables v
Preface iv
Introduction 1
Characteristics of the Harbor and Sampling Areas 3
Survey and Analytical Methods 5
Results and Discussion . 12
Conclusions 17
References 19
Appendix:
1. Description of Samples Collected 20
111
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Listof Figures
Page
Figure
1 San Diego Bay and vicinity 2
2 Sampling locations at the Submarine Base, Point Loma .... 6
3 Sampling locations at the U.S. Naval Station - 32nd
Street Pier 7
4 Sampling locations at the piers on North Island 8
List of Tables
Table
1 A summary of samples collected from the three sites
in San Diego Bay 11
2 Summary of natural and fallout radionuclide concentrations
in sediment samples 13
3 Concentrations of Co-60 in harbor sediment samples 13
4 A summary of the gamma-ray exposure rate measurements ... 15
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Preface
The Office of Radiation Programs identifies and evaluates
environmental public health impacts of both natural and man-made radiation
sources. The Eastern Environmental Radiation Facility (EERF) is a fully
integrated participant with other components of the Office in these
efforts. The Facility provides comprehensive capability for evaluating
radiation sources through planning and conducting environmental studies,
nationwide surveillance, and laboratory analysis. The EERF also provides
special analytical support for Environmental Protection Agency Regional
Offices and other federal government agencies, as requested, as well as
technical assistance to the radiological health programs of state and
local health departments.
This report presents results of the survey conducted by EERF
personnel to assess levels of environmental radioactivity resulting from
maintenance and operation of nuclear-powered warships in San Diego Bay,
California. The purpose of the survey was to determine if activities
related to nuclear-powered warships resulted in release of radionuclides
which may contribute to significant population exposure or contamination
of the environment.
Readers of our reports are encouraged to bring comments, omissions,
or errors to our attention.
Charles R. Porter, Director
Eastern Environmental Radiation Facility
vii
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Introduction
Since 1963, the Eastern Environmental Radiation Facility (EERF),
U.S. Environmental Protection Agency (USEPA), in cooperation with the
U.S. Naval Sea Systems Command (NAVSEA) has surveyed facilities serving
nuclear-powered warships on the Atlantic and Pacific coasts and the Gulf
of Mexico. These surveys assess whether the operation of nuclear-powered
warships, during construction, maintenance, overhaul, or refueling, have
created elevated levels of radioactivity. The surveys emphasize sampling
those areas and pathways that could expose the public.
In 1984, NAVSEA requested that EPA survey all active facilities
serving nuclear-powered warships over the next three years. This report
contains the results of the survey conducted in San Diego Bay on the
southern coast of California in 1986. A map of the bay and the
surrounding area of San Diego is shown in Figure 1.
San Diego Bay was previously surveyed by EERF personnel (at that time
the U.S. Public Health Service) in April 1967 (Ca67). During the early
survey, sampling was conducted primarily in the vicinity of the Submarine
Pier on Point Loma. In addition to natural and fallout radionuclides, low
concentrations of Co-60 that were attributed to nuclear-powered ships were
observed in some sediment samples (Ca67). The Submarine Pier was
resurveyed during the recent study conducted from September 15, 1986 to
September 17, 1986. During the latter study, additional sampling was
performed in the vicinity of the 32nd Street Naval Station and near the
northeast corner of the North Island Naval Air Station, These sampling
sites are located in Figure 1 as A, B, and C, respectively.
1
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U.S. NAVAL
AIR STATION
NORTH ISLAND
Nat'l
City
POINT LOMA
N
Figure 1. San Diego Bay and vicinity. Samplingsites are:(A) Submarine Pier; (B) 32nd Street Pier; (C) North
Island Shipyard. Sites of gamma-ray surveys are Shelter Island (D) and Harbor Island (E).
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Characteristics of the Harbor and Sampling Areas
San Diego Bay is a natural landlocked harbor on the coast of Southern
California containing approximately 22 square miles of surface area. The
entrance to the bay is formed by Point Loma on the west and North Island
on the east. The bay has an axial length of 14.7 statute miles with the
main portion of the bay extending in a northwest-southeast direction. The
mean width is 1.26 miles varying from 0.31 miles near the entrance to 2.24
miles at the widest point near the end. The mean tidal range is 4.2 feet
and the current at the entrance has an average velocity of 2.4 feet per
second and an extreme velocity of 4.55 feet per second.
Freshwater inflow for the bay consists of storm runoff and four small
rivers which are dry in the summer. This freshwater flow is so small
there are no stream gauge records showing actual volumes. The average
annual rainfall, 10.30 inches, falls predominantly from October through
May. Due to the absence of extensive silting from freshwater streams, a
minimum of maintenance dredging is required in the bay. The bottom of the
bay is characterized by shells and small gravel. Naval facilities are
located at a number of points around the harbor with the Submarine Base,
fuel and ammunition piers and floating dry dock at Ballast Point on
Point Loma.
Even though commercial fishing is prohibited in the bay, sport
fishing is popular and is centered around the municipal fishing pier on
Shelter Island. The bay is also a popular area for power boating and
sailing. Agriculture is not present along the perimeter of the harbor.
3
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The city of San Diego has an estimated population of 876,000 and the
metropolitan area has a population approaching two million. San Diego's
major industries are aircraft, shipbuilding and tuna fishing. Naval and
marine installations provide employment for a large segment of the total
work force. The water supply for the city of San Diego comes from a group
of reservoirs in the mountainous area of the county and two aqueducts from
the Colorado River.
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Survey and Analytical Methods
Navy personnel helped the EERF survey team identify the most probable
sampling locations, those where radioactivity associated with Naval
nuclear propulsion plants, if it were present, would most likely be
detected. Extensive sampling was conducted in the pier and dry dock areas
of the Submarine Base and the U.S. Naval Station (32nd Street), while
fewer samples were collected near the carrier and cruiser piers at
North Island because of the smaller area and less frequent use of the
site. These are areas where nuclear warships either had been serviced or
were being serviced. Sampling locations are shown in Figures 2, 3, and
4. Samples of bottom sediment were collected at each location, while
samples of water and aquatic life were taken at a few selected locations.
According to past surveys, cobalt-60 is the predominant radioisotope
one would find in environmental media if radioactivity is present as a
result of Naval nuclear propulsion plant operations (Ca77, Se88);
therefore, environmental sampling focused on detecting this radioisotope.
Cobalt-60 content in all samples was determined by gamma-ray
spectroscopy. All water samples were also analyzed for tritium since this
nuclide is known to be produced in the coolant of light water nuclear
reactors.
An underwater gamma scintillation probe with a 10-centimeter by
10-centimeter sodium iodide detector was used with a portable multichannel
pulse height analyzer to help locate areas of radioactivity. All probe
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POINT LOMA
SAN DIEGO BAY
HORTH
NORTH ISLAND
Figure 2. Sampling locations at the Submarine Base, Point Loma.
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NATIONAL
CITY
Pier 11
Pitr 12
SOUTH SAN DIEGO BAY
Figure 3. Sampling locations at the U.S. Naval Station - 32nd Street Pier.
7
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NORTH SAN DIEGO BAY
NORTH ISLAND
CORONADO
Figure 4. Sampling locations at the piers on North Island.
8
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measurements were made for 10 minutes. The underwater probe has been
useful in past surveys of other facilities to select areas for dredge
sampling of bottom sediment and to delineate areas of radioactivity.
However, due to the relatively low sensitivity (as compared to laboratory
measurements) of the probe, sediment samples were collected for laboratory
analysis at all locations of probe measurements. Duplicate samples were
collected for quality assurance purposes at approximately 5 percent of the
sites.
A standard Peterson dredge was used to sample approximately the top
10 centimeters of sediment. These sediment samples were collected at all
locations shown in Figures 2, 3, and 4. At the laboratory these samples
were dried, ground to a fine powder, placed in a 400 cm3 sample counting
container and counted on an intrinsic germanium detector for 1000
minutes. The minimum detectable activity for cobalt-60 in this geometry
is approximately 0.01 picocuries per gram (pCi/g).
Sediment core samples are useful in determining the vertical
distribution of radioactivity in harbor bottom sediment. If radioactive
materials were present from past operations which were subsequently
covered with sediment, it might be observed in the core samples. Core
samples were taken with a 3.8 centimeter diameter by 61 centimeter long
plastic tube. A mechanical driver pushed the tube into the sediment and
capped the ends. Core samples were collected at locations 10 and 62 at
the Submarine Base (Fig. 2) and 51 at North Island (Fig. 4). At the
laboratory the cores were frozen and cut into 2.5 cm sections. The
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individual sections were freeze-dried and counted on an intrinsic
germanium detector to determine the gamma-ray emitting radioisotopes.
The minimum detectable activity for cobalt-60 in this geometry is
approximately 0.1 pCi/g.
Surface water samples were collected from two locations, 1 and 10, at
the Submarine Base and one sample each from the San Diego Naval Station
and North Island sites, locations 36 and 53, respectively. In addition,
two drinking water supplies were sampled. One sample was taken from the
USS MCKEE at the Submarine Base and another at the Holiday Inn near the
bay. The water samples were analyzed for gamma-ray emitters, especially
cobalt-60, and for tritium. The minimum detectable activities for tritium
and cobalt-60 in water are 200 pCi/L and 5 pCi/L, respectively, with the
analysis procedures used.
Aquatic biota were collected only at the submarine base. One sample
each of kelp, fish and algae were collected at locations 2, 10 and 70,
respectively (see Fig. 2). At the laboratory the samples were cut into
small pieces, dried in an oven at 110°C, and counted on an intrinsic
germanium detector for 1000 minutes.
Gamma radiation measurements were made at each sampling location at
the Submarine Base and the US Naval Station (32nd Street) using a
high-pressure ionization chamber (PIC). Shoreline gamma radiation surveys
were also conducted on Harbor Island, Shelter Island, on the sandy beach
10
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opposite Shelter Island and on the beach near the Coast Guard Station at
the north end of the Submarine Base. The shoreline surveys were made one
meter above the ground using portable scintillation survey instruments
that were periodically calibrated with a PIC. A summary of all samples
collected from the three sites in San Diego Bay is presented in Table 1.
Table 1. A summary of samples collected
from the three sites in San Diego
Sampling
Facility Sites
Submarine Base 29
S.D. Naval Station 37
North Island 8
Number of Samples
Water Sediment Cores Aquatic Life
2 29 2 Kelp (1), algae (1),
fish (1)
1 37 0 0
1 810
(^Samples collected September 15-17, 1987. See Appendix 1 for a listing
of all samples collected at each sampling site.
11
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Results and Discussion
Harbor bottom sediment sampling was the most extensive since past
surveys have shown that if radioactivity has been released it usually would
be detected as cobalt-60 in the sediment (Ca77, Se88). Radionuclides tend
to accumulate in the sediment over time which enables detection of events
that may have occurred in the past. Samples were collected from 73
locations at the three sites. Small amounts of Co-60 were detected in
eight sediment samples, seven from the Submarine Base and one from near the
sea wall at North Island. All other radionuclides detected in the 73
sediment samples were either of natural origin or fallout from past nuclear
weapons testing (see Table 2). The underwater gamma scintillation probe,
operated on the harbor floor during sediment sample collection, did not
reflect any areas of radioactivity above background.
The concentrations of Co-60 measured in the 8 sediment samples are
listed in Table 3. These concentrations, ranging from about 0.02 to
0.05 pCi/g, are less than one percent of the total background radioactivity
concentration of harbor sediment samples. These concentrations are also
very small compared to the Co-60 concentrations measured in sediment
samples from the Submarine Base during the 1967 survey. During the early
survey, detectable concentrations of Co-60 in sediment ranged from about
17 pCi/g at the Sub Pier to 0.2 pCi/g off the tip of Ballast Point (Ca67).
These concentrations were nearly three orders of magnitude greater than
those measured during the current survey.
12
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Table 2. Summary of natural and fallout
radionuclide concentrations In sediment samples
Radionuclide
Submarine Base
Naval Station
(32nd Street)
North Island
K-40
Cs-137
Pb-214
Bi-214
Th-232
12 (9-15)
0.083 (0.02-0.15)
0.35 (0.17-0.49)
0.76 (0.31-1.28)
0.30 (0.14-0.45)
13 (11-15)
0.15 (0.02-0.41)
0.42 (0.28-0.58)
1.0 (0.57-1.29)
0.45 (0.26-0.65)
13 (11-15)
0.10 (0.04-0.17)
0.39 (0.29-0.50)
0.85 (0.55-1.14)
0.35 (0.22-0.45)
Notes:
1) Concentrations are pCi/g dry weight.
2) Mean concentrations are given with the range shown in parentheses.
3) Approximate 2 sigma counting errors are: K-40 (3 percent); Cs-137
(13 percent); Pb-214 (6 percent); Bi-214 (7 percent); Th-232
(11 percent).
Table 3. Concentrations of Co-60 in harbor sediment samples
Site
Concentration,
pCi/g dry
Site
Concentration,
pCi/g dry
3
58
59
64
53
Submarine Base
0.022 ± 0.008
0.047 * 0.014
0.027 * 0.014
0.015 * 0.007
65
69
71
North Island
0.030 ± 0.011
0.021 ± 0.009
0.035 ± 0.009
0.029 ± 0.010
13
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These data indicate that little, if any, additional Co-60 has been
recently deposited in the sediments. Radioactive decay during the period
since the initial survey (19.4 years or 3.7 half-lives of Co-60) has
accounted for much of the reduction in the Co-60 activity. Further
reduction of the Co-60 was probably the result of additional sedimentation.
Core samples, taken at locations 10 and 62 at the Submarine Base and 51 at
North Island, did not coincide with any of the locations where Co-60 was
detected in this current survey. Only naturally occurring radioactivity
and traces of Cs-137 from nuclear weapons fallout were observed in the
core samples.
Surface water samples collected from the three sites, two at the
Submarine Base (location Nos. 1 and 10) and one each at the San Diego
Naval Station (location No. 36) and North Island (location No. 53), had
tritium levels below the minimum detectable level of 200 pCi/L. Only
naturally occurring radionuclides were measured in these samples,
primarily K-40 with an average concentration of 330 ± 20 pCi/L. Also, no
detectable radioactivity was found in either of the drinking water samples
collected near the bay.
Only trace quantities of naturally occurring radionuclides were
detected in the three samples of aquatic life that were collected from the
harbor at the Submarine Base. The Cs-137 concentrations were less than
0.05 pCi/g dry weight in all samples. Naturally occurring potassium-40,
the primary radionuclide measured, ranged from 82 pCi/g dry weight in the
kelp to 15 and 11 pCi/g dry weight in the fish and algae samples,
respectively.
14
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Gamma-ray exposure rate measurements were made at the sampling
locations at the Submarine Base and the San Diego Naval Station (32nd
Street). No measurements were made at the North Island Naval Air Station
because of the low utilization of this facility, making it unlikely that
levels above background would be detected. A summary of the gamma-ray
exposure rate measurements is given in Table 4. Exposure rates ranged
between 3.5 and 5.2 nR/hr, averaging 4.1 MR/hr at both sites. Also,
gamma-ray exposure rates were continuously measured while moving south at
3-4 knots from Pier 1 to Pier 12 at the San Diego Naval Station. The
measurements during the traversal survey varied from 3.3 to 4.8 nR/hr.
All exposure rate measurements resemble background levels.
Table 4. A summary of the gamma-ray exposure rate measurements
No. of Gamma-Ray Exposure Rates,
Location of Survey^' Measurements
Average^
Range
Submarine Base 26
San Diego Naval Station
Sampling locations 37
Mobile survey
North Island 0
4.1 ± 0.3
4.1 ± 0.5
~ 3.8
3.6 - 4.8
3.5 - 5.2
3.3 - 4.8
{*}* values are the standard deviation of the means.
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Shoreline gamma-ray exposure surveys were conducted on Harbor Island,
Shelter Island and along the sandy shoreline of the mainland opposite
Shelter Island (see Fig. 1). The shoreline gamma-ray exposure rates
varied between 5 and 7 nR/hr. Four to 6 uR/hr exposure rates were
observed along the beach near the Coast Guard Station at the north end
of the Submarine Base. These exposure rates show no evidence that
contamination exists along shorelines near the sites.
16
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Conclusions
A radiological survey of three sites in San Diego Bay provided the
basis for the following conclusions:
1. Small quantities of Co-60 (0.02-0.05 pCi/g) are present in the
bottom sediments in some areas of the harbor at the Submarine
Base. Most, if not all, of the Co-60 contamination present
probably originated prior to the earlier 1967 survey that
reported Co-60 levels as much as 300 times larger than those
observed in this study. The highest Co-60 concentration
measured is now less than one percent of the normal background
radioactivity in harbor sediment samples.
2. No tritium or gamma-ray emitters, other than trace amounts of
those occurring naturally, were detected in surface water from
the dock areas or in nearby drinking water supplies.
3. Only radionuclides of natural origin and trace amounts of Cs-137
from fallout of previous nuclear weapons tests were detected in
samples of kelp, algae, and fish taken from the harbor at the
Submarine Base.
4. Gamma-ray surveys of the harbors near the docking areas and
along shorelines and beaches near the shipyards failed to detect
any exposure rates above background.
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5. Based on this survey, operations related to nuclear-powered
warship activities have contributed no increases in
radioactivity to the harbors in San Diego Bay that would result
in significant population exposure or contamination of the
environment. Thus, under present conditions Naval operations
within San Diego Bay pose no radiological health problems to the
public.
18
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References
Ca67 Cahill, D.F., McCurry, D.C., and Breakfield, W.D., 1967,
"Radiological Survey of Major California Nuclear Ports-April
1967", U.S. Public Health Service, Southeastern Environmental
Radiological Health Laboratory Report, PB-178-728.
Ca77 Callis, R.S., Windham, S.T., and Phillips, C.R., 1977,
"Radiological Survey of Puget Sound Naval Shipyard, Bremerton,
Washington and Environs", U.S. Environmental Protection Agency
Report, EPA 520/5-77-001.
Se88 Sensintaffar, E.L. and Blanchard, R.L., 1988, "Radiological
Survey of the Norfolk Naval Station, the Norfolk Naval Shipyard,
and Newport News Shipbuilding", U.S. Environmental Protection
Agency Report, EPA 520/5-88-017.
19
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APPENDIX 1
Description of Samples Collected
Sampl i ng
Site No.
Samples Collected
Sampl i ng
Site No.
Samples Collected
Submarine Base, Point Loma
1
2
3
4
5
6
7
8
9
10
56
57
58
59
48
49
50
51
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Sediment, surface water
Sediment, kelp
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment, core,
surface water, fish
Sediment
Sediment
Sediment
Sediment
North
Sediment
Sediment
Sediment
Sediment, core
South San
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
Island
52
53
54
55
Diego Bay
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
Sediment
Sediment
Sediment, core
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment, algae
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment, surface water
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment, surface water
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
Sediment
20
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