Class V Sensitivity

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Metadata:


Identification_Information:
Citation:
Citation_Information:
Originator:
Minnesota Department of Health - Environmental Health - Source Water Protection Unit
Publication_Date: December 20, 2005
Title: Class V Sensitivity
Geospatial_Data_Presentation_Form: vector digital data
Online_Linkage: \\mako\data\owork\classv\c5sens.shp
Description:
Abstract:
The c5sens.shp file shows areas where Class 5 automotive waste disposal wells are likely to present a threat to underground sources of drinking water based on geological conditions. The term "Class 5" refers to a broad category of disposal wells defined under federal regulations. Structures such as the drain fields for septic systems, dry wells, and underground gravel pockets that dispose of fluids used by internal combustion engines are identified as automotive waste disposal wells. Fluids include hydraulic fluid, antifreeze, grease, oil, gasoline, diesel fuel, brake fluid, and transmission fluid. The construction of new Class 5 automotive fluid waste disposal wells is not allowed under either federal or state regulations. Existing wells are not allowed in 1) the wellhead protection areas for public water supply wells or in 2) other sensitive areas. The Minnesota Department of Health is the lead agency for protecting public health and administers state and federal regulations that affect the wellhead protection program. The United States Environmental Protection Agency is responsible for administering federal underground injection control regulations in Minnesota. Together, the two agencies have developed a protocol for assessing where Class 5 automotive waste disposal wells present a threat to underground sources of drinking water. A copy of the document called Methodology for Mapping Areas Not Sensitive to Class 5 Automotive Waste Disposal Wells can be obtained from either the Minnesota Department of Health or the United States Environmental Protection Agency. It defines the subsurface geological conditions that must be present in order to reduce the potential risk that a Class 5 automotive waste disposal well presents to underground to prepare a sensitivity map and includes 1) site-specific data such as drilling logs or records of bedrock outcroppings and 2) interpretations of geologic conditions obtained from geologic maps and reports.
Purpose:
The purpose for doing this is to help local, state, and federal agencies identify priority areas for inventorying these types of underground injection wells and to ensure that, where required, they are properly sealed according to practices specified by the United States Environmental Protection Agency.
Time_Period_of_Content:
Time_Period_Information:
Single_Date/Time:
Calendar_Date: December 20, 2005
Currentness_Reference: publication date
Status:
Progress: Complete
Maintenance_and_Update_Frequency: None planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -97.269688
East_Bounding_Coordinate: -89.397194
North_Bounding_Coordinate: 49.403805
South_Bounding_Coordinate: 43.435423
Keywords:
Theme:
Theme_Keyword_Thesaurus: MDH GIS Data Keyword Thesaurus
Theme_Keyword: Pollution sensitivity
Theme_Keyword: Underground discharge system
Theme_Keyword: Class V injection wells
Place:
Place_Keyword_Thesaurus: MDH GIS Data Place Name Thesaurus
Place_Keyword: Minnesota
Access_Constraints: None
Native_Data_Set_Environment:
Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.1.0.722

Data_Quality_Information:
Lineage:
Process_Step:
Process_Description:
The mapping process is presented as a series of steps that are performed using a geographic information system. Once the initial map has been generated, additional interpretation is sometimes needed because highly variable localized conditions may cause conflicting mapping results. Here, the experience of a qualified geologist is needed to sort out mapping discrepancies and to complete the sensitivity map.

Step 1: Identify areas where clay-rich glacial deposits may occur just beneath the land surface. The principle source for this information is the statewide coverage of landforms that was developed by the Minnesota Geological Survey and the Geology Department at the University of Minnesota at Duluth. Areas where till and superglacial deposits occur are the sediment assemblages selected to broadly define where clay-rich glacial sediments may occur within 30 feet of the land surface. These areas can be further defined by referencing the more detailed mapping of glacial sediments contained in the County Geologic Atlas Series or Regional Hydrologic Assessment Series that have been prepared by the Minnesota Geological Survey. Also, county soil surveys are useful for identifying whether clay-rich materials form the parent materials for the soil classifications used to prepare soil maps. In some areas, lacustrine deposits may be included following a determination of whether they are clay-rich or contain a significant component of sand and silt.

Step 2: Assemble data describing 1) where the depth to bedrock is less than 30 feet, 2) the locations of sinkholes, and 3) exposures of bedrock. These features are not present in all counties, but introduce a much more complicated set of geologic conditions where they occur. The data sources used to determine whether any of these features are present are1) the County Well Index database, 2) the statewide coverage of karst features, and 3) maps showing exposures of bedrock.

Using the data sources listed, a map is prepared to show the areas where the depth to bedrock is less than or greater than 30 feet. It is assumed that the capabilities for clay-rich glacial deposits to reduce contaminant risk from Class 5 automotive waste disposal wells are greatly diminished where bedrock occurs within 30 feet of the land surface. Therefore, these areas are considered to be sensitive.

Step 3: Identify the thickness of clay-rich glacial deposits that occur between 10 and 30 feet of the land surface. The methodology for determining where non-sensitive areas occur excludes any geologic materials that occur within 10 feet of the land surface because they are likely to be 1) fractured by frost and weathering, 2) disturbed by the construction of the Class 5 well, and 3) disturbed by plant roots and animal burrows. Therefore, this depth interval is not included because it is likely that the integrity of any clay-rich materials has been diminished.

Water well logs and test hole records are used to identify the geological materials that are present for the depth intervals of 10-20 and 20-30 feet below the land surface. Classifying the many terms used by drillers to reflect clay-rich materials is determined by a geologist and used in a statistical determination that produces map showing the probability that clay-rich conditions will occur.

Extrapolating between data points introduces uncertainty into the resulting probability map because of 1) the distribution of data points is often not uniform and 2) the detail describing geologic conditions in well logs varies between drilling contractors. For example, a drilling record may indicate that the thickness of glacial deposits is greater than 30 feet but the glacial deposits were lumped into a common term called “glacial drift”. This record was useful for determining the depth to bedrock for step 2 but is too general to be included in this step.

The final results of this step are 1) a coverage of points that indicate the cumulative thickness of clay-rich glacial deposits that occur at depths of 10 to 30 feet below the land surface and 2) a map showing the probability that clay-rich deposits occur at the same depth interval.

Step 4: Integrate the Results of the First Three Steps to Prepare the Initial Sensitivity Map. Areas where clay-rich glacial deposits occur (Step 1) are referenced to the depth to bedrock and local bedrock conditions (Step 2). The resulting map indicates the areas where clay-rich deposits should be at least 30 feet thick. Areas where these conditions are not present are considered to be sensitive to Class 5 automotive waste disposal wells.

Next, the remaining areas are referenced to the point coverage containing the cumulative thickness of clay-rich deposits that occur from 10 to 30 feet. Ideally, this thickness should be 20 feet, but small lenses of sand or gravel may occur within otherwise, clay-rich glacial deposits. These localized conditions should have little impact on the overall evaluation of the 10 to 30 foot interval where nearby data points indicate the full 20 feet consist of clay-rich materials. Therefore, the Minnesota Department of Health uses the probability evaluation to define areas where there is an 80% or greater probability that clay-rich deposits will occur within the 10 to 30 foot depth interval.

Step 5: Reference Site-Specific Data to Confirm Mapping Results. A geographic information system is used to reduce the time required to integrate the maps and data sets that are used to compile a sensitivity map. As a result, extrapolating between data points or overlaying and combining maps may introduce uncertainty into the final results, especially where subsurface geological conditions are variable. Therefore, a geologist must reference the final results to the initial point-source data and determine whether any changes are warranted to reflect any discrepancies that occur. Areas are removed from consideration as non-sensitive where point-source data conflicts with the interpreted mapping results.

Source_Produced_Citation_Abbreviation: MDH
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Bruce Olsen
Contact_Organization:
Minnesota Department of Health - Environmental Health - Source Water Protection Unit
Process_Step:
Process_Description:
County data was aggregated into a statewide file and slivers and mismatches along the county borders were cleaned up. Also a county boundary file was inserted to break up a large polygon into several of more manageable size. County boundary used was from Minnesota DOT.
Source_Produced_Citation_Abbreviation: MDH
Process_Step:
Process_Description:
5 counties (Cook, Koochiching, Lake, Lake of the Woods, & St. Louis) were made all sensitive. The time available to conduct mapping was insufficient to adequately categorize these counties. Data set was dissolved to represent the counties as sensitive.
Source_Produced_Citation_Abbreviation: MDH
Process_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Bruce Olsen
Contact_Organization:
Minnesota Department of Health - Environmental Health - Source Water Protection Unit

Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Vector
Point_and_Vector_Object_Information:
SDTS_Terms_Description:
SDTS_Point_and_Vector_Object_Type: G-polygon
Point_and_Vector_Object_Count: 4707

Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Grid_Coordinate_System:
Grid_Coordinate_System_Name: Universal Transverse Mercator
Universal_Transverse_Mercator:
UTM_Zone_Number: 15
Transverse_Mercator:
Scale_Factor_at_Central_Meridian: 0.999600
Longitude_of_Central_Meridian: -93.000000
Latitude_of_Projection_Origin: 0.000000
False_Easting: 500000.000000
False_Northing: 0.000000
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: coordinate pair
Coordinate_Representation:
Abscissa_Resolution: 0.001024
Ordinate_Resolution: 0.001024
Planar_Distance_Units: meters
Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
Semi-major_Axis: 6378137.000000
Denominator_of_Flattening_Ratio: 298.257222

Entity_and_Attribute_Information:
Detailed_Description:
Entity_Type:
Entity_Type_Label: c5sens.dbf
Entity_Type_Definition: Class V Sensitivity in Minnesota
Attribute:
Attribute_Label: FID
Attribute_Definition: Internal feature number.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain:
Sequential unique whole numbers that are automatically generated.
Attribute:
Attribute_Label: Shape
Attribute_Definition: Feature geometry.
Attribute_Definition_Source: ESRI
Attribute_Domain_Values:
Unrepresentable_Domain: Coordinates defining the features.
Attribute:
Attribute_Label: AREA
Attribute_Definition: Area of the polygon in square meters (derived from software)
Attribute_Definition_Source: MDH
Attribute:
Attribute_Label: PERIMETER
Attribute_Definition: Perimeter of the polygon in meters (derived from software)
Attribute_Definition_Source: MDH
Attribute:
Attribute_Label: C5SENS_ID
Attribute_Definition:
Class V Sensitivity polygon ID (not a unique number due to insertion of counties)
Attribute_Definition_Source: MDH
Attribute:
Attribute_Label: SENS_C
Attribute_Definition: Class V Sensitivity code
Attribute_Definition_Source: MDH
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: S
Enumerated_Domain_Value_Definition: Sensitive to Class V Automotive Waste Disposal Wells
Enumerated_Domain:
Enumerated_Domain_Value: N
Enumerated_Domain_Value_Definition: Not Sensitive to Class V Automotive Waste Disposal Wells
Attribute:
Attribute_Label: ACRES
Attribute_Definition:
Acres of the County polygon (derived from AREA / 4046.8717 ) + 0.001
Attribute_Definition_Source: MDH
Attribute:
Attribute_Label: COUNTY_C
Attribute_Definition: Minnesota county code (1-87)
Attribute:
Attribute_Label: COUNTY
Attribute_Definition: Minnesota County name
Attribute:
Attribute_Label: SC_FIPS
Attribute_Definition: US State/County FIPS code
Attribute_Definition_Source:
Federal Information Processing Standard (FIPS) 6-4 National Institute of Standards and Technology

Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization:
Minnesota Department of Health - Environmental Health - Source Water Protection Unit
Contact_Address:
Address_Type: mailing address
Address: P.O. Box 64975
City: Saint Paul
State_or_Province: MN
Postal_Code: 55164-0975
Contact_Voice_Telephone: (651) 201-4700
Contact_Facsimile_Telephone: (651) 201-4701
Resource_Description: Available electronic data
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Transfer_Size: 32.426

Metadata_Reference_Information:
Metadata_Date: 20051220
Metadata_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Michael N. Baker
Contact_Organization:
Minnesota Department of Health - Environmental Health - Source Water Protection Unit
Contact_Position: GIS Data Administrator
Contact_Address:
Address_Type: mailing address
Address: P.O. Box 64975
City: Saint Paul
State_or_Province: MN
Postal_Code: 55164-0975
Contact_Address:
Address_Type: physical address
Address: 625 N. Robert St
City: Saint Paul
State_or_Province: MN
Postal_Code: 55155
Contact_Voice_Telephone: (651) 201-4651
Contact_Facsimile_Telephone: (651) 201-4701
Contact_Electronic_Mail_Address: michael.baker@state.mn.us
Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998
Metadata_Time_Convention: local time

Generated by mp version 2.8.6 on Tue Dec 20 15:27:37 2005