United States
Environmental Protection
Agency
Water Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S5-87/004 Apr. 1988
Project Summary
A Statistical Abstract of the
Unsewered U.S. Population
This study presents an abstraction of
pertinent data on the unsewered portion
of the total population and associated
dwelling units from the 1970 and 1980
U.S. Censuses. In addition to the overall
trends over the subject decade, the un-
sewered population of each census is
displayed against various demographic
characteristics. These latter characteris-
tics include lot sizes, water supply
sources, number of bedrooms, dwelling
size, age, property value, and inhabitant
characteristics.
This Project Summary was developed
by EPA's Water Engineering Research
Laboratory, Cincinnati, OH, to announce
key findings of the research project that
Is fully documented In a separate report
of the same title (see Project Report
ordering Information at back).
Introduction
The purpose of this statistical abstract
is to provide demographic and housing
characteristics of the unsewered popula-
tion in the U.S. based on 1970 and 1980
census data. These characteristics are
provided to assist the Wastewater Re-
search Division of the U.S. Environmental
Protection Agency, Water Engineering
Research Laboratory in planning research
appropriate to the wastewater facility
needs of the upcoming decades.
In the abstract, unsewered population
and housing units are enumerated for
each state/state group. Small sewage
treatment plants, called "neighborhood
septic tanks" in some localities, are
classified as public sewers. All units in
structures with five or more units are
assumed to be connected to a public
sewer.
Using 1980 census data, unsewered
single-family dwellings in the U.S. are
classified by lot sizes. Within each class,
statistics on the following variables are
provided:
• Total number of dwellings
• Occupancy status (occupied/sea-
sonal/vacant)
• Plumbing status (complete/incom-
plete)
• Source of water supply (public
system or private company/other
sources)
• Number of bedrooms
• Number of bathrooms
• Number of occupants (adults/
children)
• Age of adult occupants
• Age of dwelling
• Property value
• Household income.
Dwellings with lot sizes of less than one
acre are analyzed in greater detail. These
dwellings are classified by location
(rural/urban), source of water supply,
number of bedrooms, dwelling age, and
property value of dwellings. Within each
of these sub-classes, statistics on the
variables listed above are provided.
All elements of the 1980 census data
analysis could not be repeated for the
1970 census due to the unavailability of
the data. For example, 1970 census data
does not provide information on lot sizes.
Rural/urban classification is not made
for all states.* No information is available
on number of bedrooms and household
income, instead the information is avail-
* The eight states for which no rural/urban
classification is made are Alaska. Delaware.
Hawaii, Nevada, Rhode Island, Utah, Vermont,
and Wyoming.
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able on number of rooms and family
income. Keeping these differences in
view, most of the analyses of 1980 census
data are repeated for 1970 census data.
The statistical abstract is divided into
three sections. Section 2 of the report
describes the salient features of single-
family unsewered dwellings in 1970 and
1980. A table showing percentages of
rural population and unsewered housing
units in each state/state group for the 2
years is also provided in the full report.
Section 3 provides detailed analyses of
1980 census data. Section 4 describes
analyses of 1970 census data.
Methodology
Public-use microdata samples obtained
from the Bureau of the Census for 1970
and 1980 were used in the preparation of
the abstract. Public-use microdata sam-
ples are computer tapes that contain
records for a sample of housing units,
with information on the characteristics of
each unit and the people in it. For the
abstract a 1% sample was used for both
the 1970 and 1980 census.
For the 1980 census, each microdata
file is a stratified sample of the population,
actually a subsample of the full census
sample (19.4% of all households), that
received census long-form questionnaires.
Sampling was done household-by-house-
hold in order to allow study of family
relationships and housing unit char-
acteristics. Sampling of persons in
institutions and other group quarters was
done on a person-by-person basis. Vacant
units were also sampled.
In preparing this abstract, a 1 % sample
(1 in 20 of all households completing the
long census form, or 1 % of all households)
of the 1980 census was used for the
following reasons: (1) to see if the classifi-
cation by location (rural/urban) affected
the characteristics of unsewered dwell-
ings, and (2) to study the trend of un-
sewered housing units in the last decade.
The 1% sample identifies 27 states, the
District of Columbia, and 8 groups of
states.
The Census Bureau created six separate
1% samples from the 1970 census. Geo-
graphic areas identified on 1970 micro-
data files were required to have at least
250,000 inhabitants. One geographic
scheme employed in 1970 identified
states, a second identified Standard
Metropolitan Statistical Areas (SMSA's)
with 250,000 or more inhabitants and
similarly large county groups elsewhere,
and the third identified only very large
areas but included records for "neigh-
borhood characteristics."
In the 1970 census, data on sewage
disposal and source of water supply were
available in only one version. Therefore,
the version that identified all 50 states
was used.
Results
The data from the 1970 and 1980
Censuses reveal that the actual number
of dwellings not served by public sewers
is increasing despite the 10-year reduction
in the percentage of dwellings not served
by sewers from 25% to 20%. Several
other comparisons can be made to deter-
mine trends over the decade and the
relative characteristics of various seg-
ments of the unsewered population and
housing units.
The full report was submitted in partial
fulfillment of Contract No. 3-84-2-6908
by Engineering and Economics Research,
Inc. of Reston, VA., under the sponsorship
of the U.S. Environmental Protection
Agency.
This Project Summary was prepared by staff of Engineering & Economics
Research. Inc., Vienna, VA 22180.
James F. Kreissl is the EPA Project Officer (see below).
The complete report, entitled "A Statistical Abstract of the Unsewered U.S.
Population,"(Order No. PB88-113 352/AS; Cost: $14.95, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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