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 maps of nitrate and pesticide leaching classes by examining factors that relate to water movement characteristics of the soil. The pesticide contamination sensitivity data set was created by combining the nitrate map interpretations with information on the distribution of organic matter. (Pesticides are organic compounds that tend to adsorb to soil organic matter, and so have their movement in soil water retarded.)
One of the results is six nitrate and six pesticide leaching classes that group soil associations based on the relative probability of nitrate and pesticide movement through the associated soil profiles. The ranking is qualitative, and is based on the median leaching value of the soil map units that comprise each soil association. Leaching classes include: Excessive, High, Moderate, Somewhat Limited, Limited, and Very Limited. See ISGS EG 148 for the derivation of these classes.
To provide a measure of leaching class variability within each association, leaching class range values were calculated. Four trimmed range values were determined for the leaching classes in each soil association to give an indication of the variability within a specific leaching class. This data set is necessary because each soil association could have only a single leaching class value assigned to it. This item was calculated by sorting the component soil series in order of their leaching characteristic within the association. The trimmed range is the domain of leaching characteristic values between the 90th and 10th quantiles in the sorted list.To reduce the impact of extreme leaching class values on this estimate, the the range values were trimmed so that the upper and lower 10% of values were not included in the calculation. These trimmed range values were used as an overprint on the published map of leaching classes (see cross reference entries).
For example, a particular soil association may have pesticide leaching values that range from "Excessive" to "Somewhat Limited", with a median value of "Moderate". This soil association is assigned an overall leaching value of "Moderate", with a range of 4 (being the values Excessive, High, Moderate, and Somewhat Limited).
The ISGS statewide Stack-Unit map was used to create a map of depth to the uppermost aquifer, which was then combined with the maps of nitrate and pesticide leaching classes to ultimately derive aquifer sensitivity to contamination by nitrate and pesticide 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.
These data are appropriate for use in regional thematic analysis. The data are not appropriate as a geodetic, legal or engineering base. The datasets were not and are not intended as a substitute for surveyed locations, such as can be determined by a registered Public Land Surveyor. Although useful in a GIS, the data have no legal basis in the definition of boundaries or property lines.
In April 2004 the source coverages were transitioned to storage in an Oracle RDBMS using the ArcSDE geodatabase model. The result (this version) is designated edition 20040413. Prior to this time the feature classes were stored as six separate coverages in the ISGS GISDB archive.
The coverage referred to in this documentation as STACK-ST was subsequently imported to the ISGS enterprise (SDE) database and is now known as GISDB_QTGEO.IL_Stack_Units_Py.
Links to these are provided in the Cross References section.
Individuals or entities may make fair use of copyrighted ISGS material, such as reproducing a single figure or table, or using a brief text quotation, without obtaining formal permission, but in all cases the Illinois State Geological Survey must be credited as the source of the material. To reproduce ISGS information beyond the fair use standard, permission must be obtained from the ISGS Information Office, 615 East Peabody Drive, Champaign, Illinois 61820, 217-333-4747, email@example.com. License fees and a license agreement may be required, depending on the proposed usage.
Map information is to be used at a scientifically and cartographically appropriate scale, that is, at a scale no greater than indicated on the map or as described in the documentation of the map or map data. Map information is not appropriate for, and is not to be used as, a geodetic, legal, or engineering base. Map information has no legal basis in the definition of boundaries or property lines and is not intended as a substitute for surveyed locations such as can be determined by a registered Public Land Surveyor.
The data do not replace the need for detailed site-specific studies.
Attributes assumed to be as accurate as the sources.
The information produced from this data set passed the typical ISGS Peer Review associated with the publication of the ISGS EG 148.
The accuracy of this map is insufficient for evaluating the probability of nitrate leaching at specific points. It is the responsibility of the user to determine the appropriateness of this map for specific applications.
The various coverage feature classes were imported using ArcCatalog 8.3. Some unnecessary data fields identifying county FIPS values were dropped.
Prior to import, the spatial reference of the data set was changed to Geographic, decimal degrees, NAD83 in double precision.
Also at this time, this metadata file was created. It is an amalgamation of the metadata files for the six source coverages.
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Illinois Natural Resources Geospatial Data ClearinghouseGenerated by mp version 2.8.25 on Thu Apr 02 09:53:57 2009