and features closely related to that base, includ-
ing woodlands, wetlands, prairies, wildlife
habitat, major lakes and streams and associated
shorelands and floodlands, and historic, scenic,
and recreational sites, when considered together,
result in essentially linear patterns in the
landscape referred to by the Commission as
environmental corridors. "Primary" environ-
mental corridors include a wide variety of
important natural resource and resource related
elements and are, by definition, at least 400
acres in size, two miles long, and 200 feet wide.
In 1985 primary environmental corridors encom-
passed about 299,600 acres, or 17 percent of the
total area of the Region. Yet these corridors
encompassed 65 percent of all woodlands,
80 percent of all wetlands, 93 percent of all
surface waters, and 59 percent of all floodlands
in the Region.
Between 1963 and 1970, there was a slight
decrease of 1,400 acres, or of less than 1 percent,
in the primary environmental corridor area.
Between 1970 and 1985 there was a further
decrease of about 4,900 acres, or of just under
2 percent. These changes were the net effects of
decreases in environmental corridor lands in
certain areas of the Region and increases in
other areas. Decreases in environmental corridor
lands occur, for the most part, as a result of the
conversion of natural areas to intensive urban or
agricultural use. Increases may occur as a result
of reforestation, water impoundment, or the
reversion of agricultural lands to wetlands.
The preservation of primary environmental
corridors in essentially natural, open uses has
since 1966 been one of the most important
recommendations of the adopted regional land
use plan. Such preservation is essential to the
maintenance of a high level of environmental
quality in the Region, to the protection of its
natural beauty, and to the provision of opportu-
nities for certain scientific, educational, and
recreational activities. The exclusion of urban
development from these corridors will also
prevent the creation of serious and costly
developmental problems such as wet and flooded
basements, foundation failures, and excessive
clearwater infiltration and inflow into sanitary
sewerage systems.
Public Sanitary Sewer and Water Supply Ser-
vice: Public utility systems are among the most
important and permanent elements of urban
growth and development. Of particular impor-

tance to sound regional development are central-
ized sanitary sewerage and water supply sys-
tems. Areas served by public sanitary sewers
encompassed about 377 square miles, or about
14 percent of the total area of the Region, in
1985. About 1,508,000 persons, representing
nearly 87 percent of the total resident population
of the Region, were served. Between 1970 and
1985, the area served by sanitary sewers
increased by about 68 square miles, or
22 percent. The population served increased by
about 19,000 persons, or about 1 percent. The
relatively modest increase in population served
by sanitary sewers is the net result of an
increase in the number of persons served in
areas outside Milwaukee County and a decrease
in the number served within Milwaukee County,
where the total resident population decreased by
almost 115,000 persons during the 15-year
period. The proportion of the population served
by sanitary sewers increased in each county in
the Region, including Milwaukee County,
between 1970 and 1985.
In 1985, public water supply service was pro-
vided to a total of 293 square miles, or about
11 percent of the total area of the Region. A total
of about 1,390,000 persons, representing nearly
80 percent of the resident population of the
Region, was served by public water supply
systems. The area of the Region served by public
water supply increased by almost 34 square
miles, or about 13 percent, between 1970 and
1985. The total number of persons in the Region
served by public water supply, however, did not
change significantly, as increases in the popula-
tion served in outlying counties were offset by a
substantial decrease in Milwaukee County.
In general, it may be assumed that sanitary
sewer and water supply service will be made
available as necessary to meet the needs asso-
ciated with increases in, and the redistribution
of, population and economic activity in the
Region through the new plan design year 2010.
The availability of sewer and water supply
service, therefore, need not be considered an
impediment in the design of the year 2010
regional land use plan. With respect to water
supply, it should be noted that Lake Michigan
remains an abundant source of potable water for
portions of the Region located east of the
subcontinental divide, which traverses the

Region in a generally northwesterly-south-
easterly direction. West of that divide, where

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