Errata (If you have a hardcopy
of the original report, you may download and print corrected
Appendix B tables from the Errata page. All on-line
html and pdf tables have been corrected.)
The U.S. Nuclear Regulatory Commission (NRC) and the U.S.
Environmental Protection Agency (EPA), through a subcommittee
of the Interagency Steering Committee on Radiation Standards
(ISCORS), are sponsoring a joint survey to collect information
concerning radioactive materials in sewage sludge and ash
from sewage treatment plants (referred to in the industry
as publicly owned treatment works (POTWs)). Sanitary sewer
disposal of radioactive material and sludge reconcentration
became an issue in the 1980s with the discovery of elevated
levels of radioactive materials in sewage sludge/incinerator
ash at several POTWs. Although neither
the NRC nor the Agreement States have seen further problems
associated with POTW reconcentration of radioactive materials
since NRC’s regulations were revised in 1991, NRC and
EPA are working together to conduct a survey of radioactive
materials in sewage sludge and ash from POTWs.
The objectives of this joint NRC/EPA sewage sludge/ash survey
are to: (1) obtain data on the levels of radioactive materials
in sludge and ash at POTWs from across the country; (2) estimate
the extent to which radioactive contamination comes from either
NRC/State licensees or naturally-occurring radioactivity;
and (3) support potential rulemaking decisions by NRC or EPA,
if necessitated by the survey results. However, because of
the design limitations, the survey alone may not be sufficient
for rulemaking.
The intent is that the names of the POTWs will not be associated
with the analysis results in publicly available records and
reports. The reason for the anonymous survey is to encourage
the cooperation of POTWs. However, if elevated levels of radioactive
materials are detected that are determined to be a potential
health and safety concern, as determined by NRC, further investigation
will be conducted to determine the appropriate course of action.
The voluntary survey consists of two components - a questionnaire
and a program to sample and analyze sewage sludge and incinerator
ash. Questionnaires will be sent to selected POTWs associated
with NRC and Agreement State licensees that have the greatest
potential to discharge radioactive materials in accordance
with existing regulations and to POTWs in all areas of the
country, including areas of relatively high background radioactivity.
Using the information from the questionnaires, NRC and EPA
will identify approximately 300 POTWs to be sampled. It is
expected that it will take several months for both agencies
to analyze the results from the questionnaire and a year to
complete the analysis of samples to be received from the POTWs.
This report summarizes the results at nine POTW sites where
the questionnaire methods and sampling and analytical procedures
were tested. The survey was refined based on the experiences
at the test cases and public comments on the survey. The results
of the full survey will be published as a joint NRC/EPA report
for use by POTW operators, Federal agencies, States, and local
officials.
The sewage sludge/ash survey is being coordinated by a subcommittee
of ISCORS, which was formed in 1995 to coordinate resolution
of interagency issues related to radiation protection. The
ISCORS Sewage Subcommittee is assisting NRC and EPA in the
development of the survey, including analysis procedures and
the selection of facilities to sample.
The NRC contractors and EPA's National Air and Radiation
Environmental Laboratory (NAREL) in Montgomery, Alabama, will
analyze the sewage sludge and ash samples. These labs have
also assisted ISCORS with the survey design. For example,
the labs collaborated to ensure that the analytical laboratory
procedures and quality assurance programs that both labs plan
to use will produce consistent, accurate, and reliable laboratory
measurements.
NRC requested Office of Management and Budget (OMB) approval
for this survey. Notices were published in the Federal Register
on January 6, 1997, and December 2, 1997, to solicit public
comments on the survey effort. This information request was
approved by OMB (clearance number 3150-0189), with an expiration
date of June 30, 2001.
Specific amounts and concentrations of radioactive material
are legally authorized to be disposed into the sanitary
sewage collection system by Federal and State regulations.
In 1991, NRC revised its sewer disposal criteria, partially
in response to evidence that certain radioactive materials
were reconcentrating in sewage sludge or incinerator ash.
The revised NRC regulations further limited the radioactive
materials that NRC licensees are allowed to discharge to
POTWs, which should preclude contamination at POTWs. The
current NRC regulations in 10 CFR 20.2003 permit disposal
of specific quantities of soluble material into a sanitary
sewer. NRC plans to use the survey information in assessing
whether to apply further restrictions to the licensed radioactive
material that is being discharged to sanitary sewage collection
systems.
The EPA standard for the use and disposal of sewage sludge
(biosolids) in 40 CFR Part 503 does not include limits for
radioactive material. POTW operators have requested that
EPA regulations address radioactive materials so POTWs would
have a basis to restrict discharges of radioactive materials
to the sewage collection system. EPA plans to use the survey
results to evaluate the need to include limits on radioactive
materials in biosolids standards.
Sources of Radioactive Materials
One possible source of radioactive material entering a
POTW involves naturally-occurring sources such as groundwater,
which can contain elevated levels of radioactive materials
in some parts of the U.S., as well as drinking water treatment
residuals disposed of into the sanitary sewage collection
system. Another possible source is the authorized disposal
by users of radioactive materials (such as NRC and Agreement
State licensees) of man-made radioactive materials into
the sanitary sewage collection system. The removal of contaminants
by various methods at POTWs, and the reduction of the volume
of solids that contains these contaminants (e.g. incineration
of sludge), can cause reconcentration of radioactive materials
in the treatment facility's sewage sludge or ash.
Background information on the nature of radioactivity in
sewage sludge can be found in reports published by NRC in
1992 and 1994 entitled "Evaluation of Exposure Pathways
to Man From Disposal of Radioactive Materials Into Sanitary
Sewer Systems" (NUREG/CR-5814) and "Reconcentration
of Radioactive Material Released to Sanitary Sewers in Accordance
with 10 CFR 20" (NUREG/CR-6289), respectively. Another
useful background document is a report entitled "Radioactivity
of Municipal Sludge" issued by EPA during the development
of the first round rulemaking of the 40 CFR Part 503 sewage
sludge technical rule.
Congressional Interest
This survey responds, in part, to a recommendation in the
General Accounting Office (GAO) report, "Actions Needed
to Control Radioactive Contamination at Sewage Treatment
Plants," published in May 1994. The GAO report recommended
that NRC determine the extent of elevated levels of radioactive
materials at POTWs and establish acceptable limits for radioactive
materials in sewage sludge and ash.
A joint House/Senate hearing was held in 1994 to officially
release and address questions raised in the GAO report.
The hearing was stimulated by concerns associated with elevated
levels of radioactive materials in incinerator ash at a
major sewage treatment plant in the Cleveland, Ohio, area.
The GAO stated that, over the past 20 years, NRC documented
about a dozen situations where elevated levels of radioactive
materials were identified in sewage sludge or sludge incinerator
ash; but, there has been no national survey of radiation
levels present in sewage sludge or sludge incinerator ash
to determine if this is a widespread problem.
At the time of the hearing, EPA was planning to conduct
a second National Sewage Sludge Survey (NSSS) to support
its efforts to develop the second round of the 40 CFR Part
503 sewage sludge technical regulations. EPA's planned survey
would have included the collection of data on concentrations
of radioactive materials in a representative sampling of
POTW sludges from across the country. (The first national
survey conducted in the late 1980s did not include analysis
of radioactive material.)
Testimony presented by both NRC and EPA during the 1994
hearing noted that there was no indication of a widespread
problem in this area and the Cleveland incident appeared
to be an isolated incident. Based on limited information
on radiation levels in sewage sludge and ash across the
country, it appeared that reconcentration of radioactive
materials may have been associated with authorized insoluble
industrial releases from both NRC and Agreement State licensees,
which was documented and used as a basis of the GAO report.
These problems occurred prior to the revision to NRC’s
regulations in 1991.
Industry Interest
In 1996, the Association of Metropolitan Sewerage Agencies
(AMSA) conducted a confidential voluntary survey of concentrations
of radioactive materials in some of its members' POTW sewage
sludges and ashes. The objective was to develop a better
estimate of the concentration of radioactive materials in
sewage sludges and sludge incinerator ashes. Samples from
55 wastewater plants in 17 States were supplied voluntarily
and analyzed for radioactive materials. These plants were
distributed across the country and ranged in size from small
to among the largest POTWs. The most significant levels
of radioactive material were the potassium and radium isotopes,
which are naturally-occurring radioactive materials. The
restricted nature of the AMSA survey limited its usefulness
in assessing regional background levels of radioactive materials
or the effects of licensees that dispose of radioactive
material into sanitary sewers.
Current Plans
EPA is not currently planning to move forward with a second
NSSS. Based on EPA’s plans and the limitations of the
AMSA survey, NRC and EPA decided to jointly fund a survey
of POTW sewage sludges and ash to assess the potential need
for NRC and/or EPA rulemaking. The survey information will
also be referenced in a joint NRC/EPA guidance document
for POTWs, which is currently under development by the ISCORS
Sewage Subcommittee. This guidance would provide information
to help POTW operators determine sources of radioactive
materials at POTWs, describe sampling and analysis procedures,
and advise whether a response is needed to the presence
of radioactive material in sludge.
The objectives of this joint NRC/EPA sewage sludge/ash survey
are to: (1) obtain data on the levels of radioactive materials
in sludge and ash at POTWs from across the country; (2) estimate
the extent to which radioactive contamination comes from either
NRC/State licensees or naturally-occurring radioactivity;
and (3) support potential rulemaking decisions by NRC or EPA,
if necessitated by the survey results. However, because of
the design limitations, the survey alone may not be sufficient
for rulemaking. These limitations include: (1) it is a voluntary
survey, (2) a small number of samples are collected at each
POTW, (3) the samples are collected in a snapshot in time,
and (4) the survey is biased to POTWs associated with facilities
with the greatest potential to discharge radionuclides and
to POTWs in areas of higher concentrations of naturally-occurring
radioactive material (NORM). Therefore, the survey results
will not be a statistically valid representation of radionuclide
levels in sludges nationwide.
The survey consists of two components - a questionnaire and
a program to sample and analyze sewage sludge and incinerator
ash.
Development of the Questionnaire
NRC and EPA developed a questionnaire (Appendix
A) to request information from POTWs, such as their
sludge treatment processes and disposal practices. The questionnaire
also requests the zip codes for their collection systems
so NRC can identify the licensees associated with each POTW.
NRC will request from each Agreement State a list of licensees
for the zip codes associated with each POTW. In 1996, the
questionnaire was sent to nine test sites to assess the
questions and to obtain a better basis for estimating the
actual cost (burden hours) to the POTWs.
POTWs That Were Selected to Receive the Questionnaire in
sewage sludge and ash at POTWs across the United States
(the 50 States, the District of Columbia, and Puerto Rico).
To maximize its effectiveness, the survey will focus on
the POTWs associated with licensees with the greatest potential
to discharge radioactive material to the sanitary sewer
and POTWs in areas known to have high levels of naturally-occurring
isotopes such as radium, thorium, and uranium. With these
objectives in mind, the list of POTWs to be sent the questionnaire
was developed as follows:
Select POTWs associated with NRC and Agreement State
licensees that have the greatest potential for discharge.
NRC developed a list of licensees that have the greatest
potential for discharge, and EPA established a list of
POTWs associated with these licensees.
Select POTWs in areas known to have higher concentrations
of NORM in ground and surface water, or that are associated
with facilities that may potentially discharge NORM into
the sewage collection system.
Include POTWs with incinerators because radioactive
materials are expected to be at higher concentrations
in ash than in sludge. There are about 180 POTWs with
active incinerators. However, the number of POTWs with
incinerators varies from State to State, and if all the
incinerators are sampled, some States will include a disproportionately
high number of samples. For these reasons, the survey
plans to sample no more than a few POTWs with incinerators
in each State.
Ensure that the POTWs on the list developed in Steps
1 and 2 are from all geographic areas of the United States
(Coastal Plain, Appalachians, etc.) to reflect the regional
differences in NORM. If the list developed in Steps 1
and 2 has only a few POTWs in any of the geographic areas,
add POTWs from the 479 POTWs which responded to the questionnaire
in the first EPA national survey, which was conducted
in the late 1980's. The list of POTWs from the 1980's
survey was chosen because it includes POTWs for various
flow rates, percent industrial flow, and use and disposal
practices and is a group of nationally representative
POTWs.
Add POTWs requested by other ISCORS members and the
States.
Include a small group of POTWs with low potential for
elevated radioactive materials for comparison purposes.
NRC and EPA will jointly send the questionnaire to about
600 POTWs. The Association of Metropolitan Sewerage Agencies
and the Water Environment Federation will provide a letter
to be included with the questionnaire and will send a guidance
document prepared by the National Biosolids Partnership
(1999) and regulatory alert to the POTWs preceding the mailing
of the questionnaires to help introduce the POTWs to the
voluntary survey effort and provide assistance in conducting
radiation surveys of their treatment facilities and industrial
contributors.
The POTWs will be requested to voluntarily complete and
return the completed questionnaires to NRC. NRC will then
develop the list of licensees associated with each POTW
from the zip codes in their collection system and assign
each POTW to a geographic area. This information will be
entered into an electronic database so that NRC and EPA
can select the POTWs to be sampled. NRC will send letters
to the POTWs that returned the questionnaire with lists
of licensees in their service area. NRC will also develop
a sample return tracking system to follow up on non-respondents.
Selection of POTWs for Sampling and Analysis
From the responses to the questionnaire, about 300 POTWs
will be chosen for sampling and analysis. Based on the responses
to the questionnaires, the POTWs will be assigned to the
categories listed below. A number of POTWs will be sampled
from each category. The actual number of samples to be taken
from each category will be determined based on the responses
to the questionnaire. It is the goal of this survey to obtain
a representative number of POTWs from each category during
the course of the survey. It is recognized that some factors,
such as seasonality, may need to be studied further.
Type of NRC/Agreement State licensees that could dispose
into the sewage collection system
1. Academic
2. Medical
3. Manufacturing and Distribution
4. Research and Development
5. Other licensees
6. No licensees that discharge to the sewage collection
system
Geographic area
1. Coastal Plain
2. Appalachians
3. North Central
4. Central
5. Rockies and Basin and Range
6. Colorado Plateau
7. California
8. Pacific Northwest, Alaska, Hawaii
Sample Collection and Analysis
The sampling will take place over a one-year period. In
areas of high NORM, sampling may be adjusted during some
seasons, because there may be seasonal effects to the concentrations
of NORM at POTWs.
Each month, over a one-year period, NRC and EPA will jointly
send the NRC contractor a list of the POTWs to be sent letters
and sample collection materials. The NRC contractor will
contact the POTW operators to review the sampling instructions
and then mail the letters and sample collection packages
to the POTWs. Since POTWs routinely take representative
sludge and ash samples to monitor pollutants, the POTWs
will use similar procedures to collect samples for this
survey. The POTWs will return their samples to the NRC contractor
who will assign a code to each POTW to ensure confidentiality.
It is assumed that each POTW will, on average, send two
samples of processed sludges and/or ashes, so the total
number of samples collected from all POTWs participating
in the survey will be about 600. It is expected that each
laboratory will analyze about 300 samples.
The physical sampling and analysis procedure that will
be used in this survey is described in the Quality Assurance
Project Plan for this project. All analyses will be performed
using methods typically used for environmental monitoring
samples. All the samples will receive gamma spectroscopy,
gross alpha, and gross beta analyses. The gross alpha and
beta analyses are considered screening analyses. To use
resources most efficiently, additional isotope-specific
analyses will only be performed on samples with the highest
expected concentrations of the isotopes. Each month about
ten percent of the samples (about 2 or 3 samples at each
lab) will receive additional isotope-specific alpha or beta
analysis; the action level for this additional analysis
will be chosen based on the highest observed gross alpha
and gross beta results from the survey samples analyzed
that month.
Additional isotope-specific analysis will be conducted
for the following radioactive materials:
Radium, thorium and uranium are naturally-occurring radioactive
materials. Uranium and plutonium are also found in the effluents
from processes in nuclear facilities that are used to produce
nuclear fuel for research or power reactors. Strontium is
a medical isotope. Plutonium will be analyzed only for POTWs
with fuel-cycle or weapons research and development facilities
in the collection system. Carbon-14 is both naturally occurring
and man-made and is discharged by radiopharmaceutical and
research facilities. Tritium is discharged by academic,
manufacturing, and weapons research and development facilities.
During the survey, the laboratories will send the analysis
results to the ISCORS Sewage Subcommittee in individual
monthly letter reports that discuss the samples analyzed
that month and report any lab or field problems. The reviews
of these monthly letter reports could lead to changes in
the analysis procedures or in the selection of POTWs to
be sampled.
An NRC contractor will enter the sample analysis results
into an electronic data base and analyze the results. The
ISCORS Sewage Subcommittee has formed a working group to
perform dose modeling studies to help evaluate the potential
risks associated with the radioactive materials measured
in the survey. At the conclusion of the sample analyses,
the laboratories will report their results to the subcommittee
in a final report. The ISCORS Sewage Subcommittee will prepare
a final report on the survey results.
The questionnaire was sent to the nine test sites to obtain
current site-specific information about the sludge treatment
process and disposal practices of each facility. As a result
of the experiences with the tests sites and public comments
on the January 6, 1997 Federal Register notice, minor changes
were made to the questionnaire.
Originally, it was estimated that it would take two hours
to complete the questionnaire. For most of the test sites,
the respondents took 20 minutes or less. Two respondents needed
two hours because of the large number of zip codes in the
collection system.
The revised questionnaire is attached in Appendix
A.
Following the evaluation of the responses to the questionnaires,
each test site was sent sample collection packages to obtain
sewage samples for analysis at the laboratories. Samples from
the nine test POTWs were analyzed by both laboratories to
ensure comparability, consistency in sample handling, and
validity of analytical methods.
To assist in the evaluation of sample collection procedures
used in the survey, the laboratory staffs observed sample
collection procedures at two of the test sites. Most test
sites sent two sets of sludge or ash samples (one to each
laboratory).
A joint NAREL and NRC contractor report presents the findings
of the radioanalytical results of various sewage sludge/ash
matrices that were analyzed from the test sites. The report
compared the analytical results between the laboratories and
made recommendations for changes to be implemented before
beginning the full survey. All the samples received gamma
spectroscopy and gross alpha and beta analyses. For the test
cases, all the samples also received additional isotope-specific
alpha or beta analysis, although these analyses will only
be performed on about ten percent of the samples in the full
survey. For the test sites, both labs analyzed all the samples
for all the radioactive materials for inter-lab comparisons.
The results of the analysis of the test samples are discussed
in Appendix B.
The results from the test sites provide the beginning of
the data base for the survey. By comparing each month’s
lab results (by radioactive isotope and for the gross alpha
and gross beta results) to the data collected to date, it
should be possible to determine the higher concentrations
of radioactive materials. As expected from other studies,
the incinerator ash samples in the test sites contained higher
concentrations of some radioactive materials than the non-ash
samples.
The following changes in the laboratory analysis resulted
from the experiences with the test sites and recommendations
from the laboratories:
In general, the laboratories found good agreement between
their gamma analyses. Thus the final survey will not require
that split samples be analyzed by both labs, as was done
with the test survey.
The gross
alpha and gross beta analyses did not provide as good
agreement, due to differences in calibration and/or analysis
procedures at the labs. Although gross alpha and gross beta
measurements are useful as gross screening tools, their
accuracy should not be assumed to be better than about an
order of magnitude. Therefore, the general magnitude of
the results should be evaluated rather than detailed comparisons
between individual measurements. For example, if every month,
the top few samples were to be screened for further analysis
using either gross alpha or gross beta results, the same
samples would be selected using either laboratory’s
data.
Although C-14 is naturally occurring, it is also man-made,
and there are licensees (radiopharmaceutical and research
facilities) that could potentially discharge C-14 to sewage
collection systems. Because C-14 will not be detected readily
by the sludge screening (gross beta) analyses, the screening
analyses would not be useful for determining which samples
to analyze for C-14. Instead, the association of a POTW
with a facility that could discharge C-14 will be used to
determine a limited number of samples to be analyzed for
C-14.
Both of the laboratories as well as the subcommittee recommended
that tritium be excluded from the analysis because tritium
does not reconcentrate due to its chemical behavior in sewage
collection systems. However, since tritium was detected
in several samples, the laboratories will analyze for tritium
until the results indicate that this analysis can be discontinued.
Return time to the labs should be minimized for detection
of short-lived nuclides, as well as for sample preservation
(avoidance of sample deterioration). The survey will continue
to use overnight shipments of samples to the labs.
The turnaround time at the POTWs was often not very good.
This caused sample batching problems for the labs, which
in turn caused increased turnaround times and more analysis
expense. Therefore, the sampling instructions and phone
calls to the POTWs will emphasize the need for quick sampling
and return. A turnaround time of no more than one week is
needed for efficient laboratory operation.
All samples will be analyzed using gross alpha, gross
beta and gamma spectroscopy analytical techniques; ten percent
of the samples will receive additional isotopic-specific
alpha or beta analyses.
Ainsworth, C. C., Hill, R. L., Cantrell, K. J., Kaplan,
D. I., Norton, R. L., Aaberg, R. L., 1994, "Reconcentration
of Radioactive Material Released to Sanitary Sewers in Accordance
with 10 CFR Part 20," NUREG/CR-6289, U.S. Nuclear Regulatory
Commission, Washington, D.C. 20555.
EPA, 40 CFR Part 503, "Standards for the Use or Disposal
of Sewage Sludge."
EPA, 1986, "Radioactivity of Municipal Sludge."
EPA, 1989, "POTW Sludge Sampling and Analysis Guidance
Document."
EPA, 1990, "Suggested Guidelines for the Disposal of
Drinking Water Treatment Wastes Containing Naturally Occurring
Radionuclides."
EPA/NAREL and ORISE, 1998, "Report to the ISCORS Subcommittee
on the Sewage Nuclide Concentration Test Samples," November
13, 1998.
GAO, 1994, Nuclear Regulation, "Action Needed to Control
Radioactive Contamination at Sewage Treatment Plants."
Kennedy, Jr., W. E., Parkhurst, M. A., Aaberg, R. L., Rhoads,
K. C., Hill, R. L., Martin, J. B., 1992, "Evaluation
of Exposure Pathways to Man from Disposal of Radioactive Materials
into Sanitary Sewer Systems," NUREG/CR-5814, U.S. Nuclear
Regulatory Commission, Washington, D.C. 20555.
National Biosolids Partnership, 1999, Characteristics of
Radioactivity Sources at Wastewater Treatment Facilities;
A Guidance Document for Pretreatment Coordinators.
NRC, 10 CFR Part 20, "Standards for Protection Against
Radiation."
NRC, January 6, 1997, Federal Register, Agency Information
Collection Activities: Proposed Collection; Comment Request,
page 771.
NRC and EPA, May 29, 1997, Draft Guidance of Radioactive
Materials in Sewage Sludge/Ash at Publicly Owned Treatment
Works (POTWs).
NRC, December 2, 1997, Federal Register, Agency Information
Collection Activities: Submission for OMB Review; Comment
Request, pages 63730-63731.
