Aquifer Sensitivity to Contamination by Nitrate Leaching in Illinois

This data set was designed for statewide evaluation of
agrichemical leaching characteristics and associated
aquifer sensitivity to contamination. It was created to
classify soils and aquifer settings according to predictions
of leaching potential. The classifications have not been
validated by the results of water quality sampling and
accordingly, the reliability of these aquifer sensitivity
ratings as predictors of water quality has not been evaluated.

This is a statewide Arc/Info data set for evaluating the potential
for contamination of shallow aquifers by nitrate. The sources of
this data set were published and digitized at 1:250,000; however,
the soils map and depth to aquifer map (stack-unit map) were
generated from source data mapped at 1:15,000 and 1:64,000,
respectively. This aquifer sensitivity map was published at
1:500,000. Nominal scale is 1:250,000.

Two statewide data sets were identified as containing
information that would be useful for producing aquifer
sensitivity maps: a soil association map (and database)
and a map of geologic materials to a depth of 50 feet
(Stack-unit map). The soil association map and database
were used in an interpretive mapping model that generated
a map of nitrate leaching classes by examining factors that
relate to water movement characteristics of the soil.

The Stack-Unit map was used to create a map of depth to the
uppermost aquifer, which was then combined with the map of
nitrate leaching classes. This combined map was interpreted
based on the sensitivity of aquifers (to create a map of
aquifer sensitivity) to contamination by nitrate leaching.
Six aquifer sensitivity classes are indicated: Excessive, High,
Moderate, Somewhat limited, Limited, and Very limited.

Disturbed land and surface water areas are also shown.

These data are to be used in conjunction with ISGS Environmental
Geology report 148. This data set is one of a suite of six
related data sets (listed below). Full citation details are
available in the Cross References section.

Aquifer Sensitivity to Contamination by Nitrate Leaching in Illinois
Nitrate Leaching Classes of Illinois Soils (this data set)
Nitrate Leaching Class Ranges

Aquifer Sensitivity to Contamination by Pesticide Leaching in Illinois
Pesticide Leaching Classes of Illinois Soils
Pesticide Leaching Class Ranges

This coverage includes county lines. These lines are not directly
relevant to the data, but are necessary for technical reasons.
Without the additional county lines, some of the polygons exceed
the maximum allowable vertex limit in ARCPLOT. This problem is
solved by the additional county lines, which serve to divide polygons
with too many vertices into smaller units. Accordingly, to remove
the county lines from maps created with ARCPLOT, the DROPLINE
command must be used on conjunction with the COUNTY_NAME
polygon item.