1.1 Introduction

     The Central Wisconsin Sand Plains region contains some of the

largest and most productive aquifers in the state of Wisconsin.

The sandy glacial outwash soils of the area are highly permeable

and the terrain is relatively flat. These factors combined with a

relatively shallow unconfined aquifer make this region particularly

susceptible to contamination from various land use practices.

     One of the land use practices which is increasingly becoming

a concern involves the residential development of unsewered areas.

Trends in the 1970's and 1980's saw population increases in

suburban areas. As a result, suburban expansion quickly exceeded

beyond the reaches of municipal water and sewage and thus private

sewage systems became common.

     The primary purposes of current private sewage systems are the

disposal of wastewater and the removal of bacteria. Only recently

has consideration been given to the level of chemical treatment

which can be expected from private sewage systems and their

potential for groundwater pollution.

      Soil absorption systems are designed to receive wastewater

from a septic tank and dispose of it below ground where it is

hopefully treated before it reaches the groundwater.         It is

generally recognized that three feet of unsaturated        soil is
required to properly treat sewage effluent to allow adequate

removal of disease causing bacteria, viruses, suspended solids, and

some organic materials.

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