Stearns County Geologic Atlas, Part B

GWSL3PY metadata


Minnesota Geographic Metadata Guidelines
Metadata Entry Template

Version 1.0.4 - July 1, 1997

A State Version of the FGDC Content Standards for Geospatial Metadata

***
Description of data created for
The Stearns County Geologic Atlas
by
DNR Waters, Groundwater Mapping Unit


Data Set Name: GWSL3PY

Metadata Entered By: Randy McGregor

Date: 8/18/99


Section 1Identification Information
OriginatorHua Zhang, DNR Waters
TitleGWSL3PY
Minnesota Clearinghouse ID 
AbstractSensitivity to pollution of groundwater 
PurposeCounty Geologic Atlas Program: Atlas C-10 Part B, Plate 10, Sensitivity of Ground Water Systems to Pollution
Time Period of Content Date1997 - 1999
Currentness ReferenceComplete
ProgressComplete
Maintenance and Update FrequencyNone planned
Spatial Extent of DataStearns County, Minnesota
West Bounding Coordinate333,072 
East Bounding Coordinate418,103 
North Bounding Coordinate5,071,100 
South Bounding Coordinate5,015,216 
Place KeywordsStearns County, Minnesota, Midwestern United States
Theme KeywordsGround Water, Pollution Sensitivity
Theme Keyword Thesaurus 
Access Constraints 
Use ConstraintsUsers may wish to verify critical information; sources include both the references here and information on file in the offices of the Minnesota Geological Survey and the Department of Natural Resources. Every effort has been made to ensure the interpretation shown conforms to sound geologic and cartographic principles. This map should not be used to establish legal title, boundaries, or locations of improvements.
Contact PersonSee METADATA CONTACT PERSON (below)
Contact Organization"
Contact Person Position"
Contact Address"
Contact City"
Contact State or Province"
Contact Postal Code"
Contact Voice Phone"
Contact Fax Phone"
Contact E-mail Address"
Browse Graphic File Name 
Browse Graphic File Description 
Associated Data SetsCounty Geologic Atlas Program: C-10 Part A, Produced by the Minnesota Geologic Survey
Section 2Data Quality Information
Attribute Accuracy 
Logical ConsistencyData are topologically correct using ARC/INFO 7.1.1
CompletenessComplete
Horizontal Positional AccuracyN.A.
Vertical Positional AccuracyN.A.
LineageFour coverages - 1) depth to water table, 2) subsurface permeability, 3) outline of till areas, and 4) surficial geology from MGS - were combined, using the ARC command, 'union.'

DESCRIPTION OF EACH LAYER


Depth to Water Table
  1. A TIN was made from a simplified potentiometric surface of the water table line coverage (see metadata for 'psfwt'), using the ARC command, 'arctin,' with the 'line' option. 'Simplified,' means that contours that ended 'in mid air,' i.e., those whose continuation could not be determined, had been deleted.
  2. A lattice was made from this TIN with the ARC command, 'tinlattice' using the item, 'elev (elevation of the potentiometric surface)' with defaults.
  3. This lattice was subtracted from the surface elevation DEM using GRID to create a depth-to-water-table grid.
  4. The resulting depth-to-water-table grid was filtered with a 'low' pass with 5 iterations, then contoured at 10 ft. intervals, using the ARC command, 'latticecontour,' with default settings.
  5. The contour lines were enclosed within the county boundary to create a polygon coverage. This was done by using the ARCEDIT command, 'get' to attach the county boundary coverage to the contour coverage, with 'intersectarcs' set to 'all.' Contour bits and pieces that dangled outside the county border were deleted, and the coverage was built with the 'polygon' option.
  6. Values from the depth to water grid were attached to polygon labels of this coverage using the ARC command 'latticespot.' The resulting depth to water value which is attached to each polygon label was used to calculate depth range values. i.e., If a polygon label's depth to water value is '10.8,' then that label is given a range value of '10 to 20' ft. This works because all of the polygons in this coverage are bounded by equipotential lines at 10 ft. intervals. The value of a point ANYWHERE within a given polygon is NECESSARILY between two 10 ft. intervals. A polygon label with a depth to water value of .69 would be given a range value of '0 to 10,' meaning that the polygon defines an area within Stearns County where the estimated depth to water is at least 0, and at most 10 ft.
  7. The resulting depth to water coverage was combined with a simplified version of NWI polygons, using the ARC command, 'union' to create a coverage that contains both DNR Waters-created depth to water polygons and NWI polygons. The NWI data was simplified by deleting all polygons less than 20,000 sq. meters, and dissolving the result on the item 'system,' leaving outlines of wetland types rather than outlines of very single wetland.
  8. This coverage was, in turn, combined with the polygons from Stearns County Soil Survey Data Set polygon coverage, where depth to the water table was less than 6 ft to create the final water table near the surface polygon coverage. (Note: this data set was compiled at a larger scale than that of all of the other data, and the greater detail of its polygons might artificially enhance the appearance of precision of the pollution sensitivity coverage. The pollution sensitivity coverage is no more accurate than the 1:100,000 scale manuscripts that comprise most of the layers that went into it! Contact Stearns County Environmental Services at (320) 656-3613 for more information about The Stearns County Soil Survey Data Set) The item 'nearsurf' was added and given a value of 'Y' when one of the following conditions were met:
    • Depth to the water table is less than 6 ft. based on Stearns County Soil Survey Data Set (Step 8).
    • All wetlands (Step 7)
    • Estimated depth to the water table is less than 20 ft. (Steps 1 to 6)
Subsurface Permeability

A 1:100,000 scale manuscript showing selected CWI points colored according to 'score' value ranges was prepared in ARCVIEW and plotted on paper. 'Score' values are numbers indicating the estimated thickness of the subsurface impermeable layer. These cumulative scores were calculated by Hua Zhang from CWI Well Log data of about 4100 wells in Stearns County.

Each well log was examined by a computer program written by Hua Zhang that assigned a permeability unit score based on the thickness and types of geologic materials in the upper 50 feet. The unit scores range from 0 to 1, with 0 indicating highest permeability (i.e, gravel or sand)., and 1 lowest (i.e., clay or shale).

Then, a cumulative score was calculated by summation of the unit scores of all individual layers within 50 feet of the land surface. The calculated cumulative score ranges from 0 to 50. A well with clay material in the whole upper 50 feet, for example has a cumulative score of 50. A well with gravel or sand in the whole upper 50 feet has a cumulative score of 0.

The cumulative scores of all wells were plotted on paper at a scale of 1:100,000. Hua Zhang drew contour lines around groups of points having:

  • a preponderance of cumulative score values greater than 40 (relatively low subsurface permeability)
  • a preponderance of cumulative score values between 20 and 40 (relatively high subsurface permeability).
As a supplemental visual aid, he referenced a 1:100,000 paper plot of each of the following:
  • digitally generated contour lines that had been made from a GRID of cumulative score values
  •  MGS' surficial geology polygon coverage from the Stearns County Geologic Atlas, Part A, Plate 3.
The contour lines were digitized in ARCEDIT, the county boundary was acquired with the ARCEDIT command 'get' (intersectarcs all), and the coverage was built as a polygon coverage.

Outline of till areas

This coverage was made in order to create a geographic area of till so that peat over till could be differentiated from peat that is NOT over till. It was derived from the MGS surficial geology coverage. Map units 'dc' 'P' 'st' 'stp' 'stt' 'dsc' 'dst' 'drt' 'dlt' 'thd' 'dt' 'wt' (till areas) were selected and put (ARCEDIT command 'put') into a new coverage. A dissolve was performed to eliminate all interior lines, resulting in a coverage that shows an outline of till areas, rather than each till polygon.

This process creates polygons within which many peat areas fall when a union that includes MGS surficial geology is performed. These peat areas can then be delineated by selecting those which fall "within" till areas and those which do not. However, many peat polygons are on "edges" of till areas, and would therefore not have ended up "inside" the till area outline created by this processes. In fact, it is difficult to know whether or not a given peat polygon on the "edge" of a till area should be considered 'peat over till,' or 'peat not over till.' Hua Zhang selected several "edge" peat polygons which were subsequently added to the till outline coverage, in effect broadening the geographic scope of this (till) coverage so that it subsumes those polygons after the union is performed. Other "edge" peat polygons were considered 'peat NOT over till, along with the peat polygons that are completely outside of till areas.

Surficial Geology from the Minnesota Geological Survey (SGPG)

This polygon coverage was created by the MGS, and is displayed on Plate 3 of The Stearns County Geologic Atlas, Part A. Relative permeability of different geologic types was estimated by Hua Zhang, and used in assessing pollution sensitivity values. See Ratings Matrix on Stearns County Geologic Atlas, Part B, Plate 10 for more detailed information.

COMBINING, DISSOLVING, SIMPLIFYING, AND ADDING ITEMS


The above four layers were combined using the ARC command 'union.' The item 'senrating' was added (See Enity and Attribute information below), and was calculated using an ARC AML based on criteria outlined in Plate 10 of The Stearns County Geologic Atlas, Part B.

The coverage was dissolved on the item 'senrating, and polygons 20,000 sq meters or smaller were removed with the ARC command 'eliminate.' Finally, the item 'sensymbol' was added and calculated as shown in 'Entity and Attribute Information' (below).
 

Source Scale Denominator1:100,000
Section 3Spatial Data Organization Information
Native Data Set EnvironmentARC/INFO 7.1.1
Geographic Reference for Tabular Data 
Spatial Object TypeVector
Vendor Specific Object TypesPolygon
Tiling SchemeCounty
Section 4Spatial Reference Information
Horizontal Coordi651te SchemeUTM
EllipsoidGRS 1980
Horizontal DatumNAD83
Horizontal UnitsN.A.
Altitude DatumN.A.
Altitude UnitsN.A.
Depth DatumN.A.
Depth UnitsN.A.
Cell WidthN.A.
Cell HeightN.A.
UTM Zone Number15
Coordinate Offsets or AdjustmentsNone
Distance Resolution 
Section 5Entity and Attribute Information
Entity and Attribute Overview 
Entity and Attribute Detailed Citation 
Table NameField NameBegin ColumnDefinition Description 
gwsl3py.pat    Polygon Attribute Table
 SENRATING25 Pollution sensitivity rating based on estimated vertical travel time for water-borne surface contaminants to reach the aquifer.
    'NR'Not rated (Mostly open water)
    'VH'Very high - Hours to months
    'H'High - Weeks to years
    'M'Medium - Years to decades
    'L'Low - More than a century
 SENSYMBOL272,2,i Pollution sensitivity rating as a number
    0Not rated
    1Very high
    2High
    3Medium
    4Low
Section 6Distribution Information
PublisherMinnesota Department of Natural Resources
Publication Date1999
Online Linkage 
Distributor Contact PersonSee METADATA CONTACT PERSON (below)
Distributor Organization"
Distributor Position"
Distributor Address"
Distributor City"
Distributor State or Province"
Distributor Postal Code"
Distributor Voice Phone"
Distributor Fax Phone"
Distributor

E-mail Address

"
Distributor's Data Set Identifier  
Distribution LiabilityThis map was prepared from publicly available information only. Every reasonable effort has been made to ensure the accuracy of the factual data on which this map is based. However, the Department of Natural Resources does not warrant the accuracy, completeness, or any implied uses of these data.

Users may wish to verify critical information; sources include both the references here and information on file in the offices of the Minnesota Geological Survey and the Department of Natural Resources. Every effort has been made to ensure the interpretation shown conforms to sound geologic and cartographic principles. This map should not be used to establish legal title, boundaries, or locations of improvements.

Transfer Format NameARC/INFO, ArcExport, INFO
Transfer Format Version Number7.1.1
Transfer Size 
Ordering InstructionsDownload Arc/INFO export file or ARCVIEW shapefile from Stearns County Geologic Atlas, Part B: Metadata for GIS and Digital Data
Section 7Metadata Reference Information
Metadata Date 
Metadata Contact PersonRandy McGregor
Metadata Contact OrganizationMinnesota Department of Natural Resources
Metadata Contact PositionGIS Specialist
Metadata Contact Address500 Lafayette Road
Metadata Contact CitySt. Paul
Metadata Contact State or ProvinceMN
Metadata Contact Postal Code55155 - 4032
Metadata Contact Voice Phone(651) 297 - 4591
Metadata Contact Fax Phone(651) 296 - 0445
Metadata Contact
E-mail Address
[email protected]
Metadata Standard NameMinnesota geographic Metadata Guidelines
Metadata Standard Version1.0.4
Metadata Standard Online Linkage