# Near surface sensitivity

This page last updated: 11/25/2025
Metadata created using Minnesota Geographic Metadata Guidelines

Go to Section:

1. Overview
2. Data Quality
3. Data Organization
4. Coordinate System
5. Attributes
6. Distribution - Get Data
7. Metadata Reference

## Section 1: Overview

Originator:Minnesota Department of Natural Resources
Title: Near surface sensitivity
Abstract: This dataset estimates the pollution sensitivity of near-surface materials from the transmission time of water through 3 feet of soil and 7 feet of geology, to a depth of 10 feet from the land surface.
Purpose: Houston County Groundwater Atlas, Part B
Time Period of Content Date:
Currentness Reference: Source material were obtained in 2020
Progress: Complete
Maintenance and Update Frequency: None Planned
Spatial Extent of Data: Houston County, Minnesota
Bounding Coordinates: -91.731
-91.217
43.853
43.493
Place Keywords: Houston County, Minnesota
Theme Keywords: Pollution sensitivity, near surface
Theme Keyword Thesaurus: None
Access Constraints: None
Use Constraints: 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 Minnesota 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 Person Information: CGA, GIS Specialist
Minnesota DNR - Ecological and Water Resources
500 Lafayette Rd
Saint Paul, MN 55155-4025
Phone: 651-259-5693
Email: county.groundwater.atlas.dnr@state.mn.us
Browse Graphic: None available
Associated Data Sets: Houston County Geologic Atlas, Part A, published by the Minnesota Geological Survey (MGS). More information and downloadable data for Part A available on the MGS site: http://www.mngs.umn.edu/county_atlas/countyatlas.htm
Minnesota Hydrogeology Atlas HG-02: http://www.dnr.state.mn.us/waters/programs/gw_section/mapping/platesum/mha_ps-ns.html

## Section 2: Data Quality

Attribute Accuracy: 1:100,000
Logical Consistency: Data are topologically correct using ArcGIS Pro 3.3
Completeness: Complete
Horizontal Positional Accuracy:
Lineage: The pollution sensitivity of near-surface materials is an estimate of the time it takes for water to infiltrate the land surface to a depth of 10 feet. It is intended to estimate the time of travel through the unsaturated zone to reach the water table, which for the purposes of this method, is assumed to be 10 feet below land surface everywhere.
The matrix texture of a geological unit is determined from the fraction of the material that is less than 2 millimeters in size, and is described by the percent sand, silt, and clay of this fraction. The matrix texture is used as a proxy for estimating the transmission rate, as coarse-grained materials have transmission rates greater than fine-grained materials because of the larger and more connected pore spaces between the grains. The transmission rate is estimated with a two-layer approach using two primary inputs: NRCS data for the soil layer (0 to 3 feet) and the surficial geologic map for underlying geologic materials (3 to 10 feet). The published saturated hydraulic conductivity rates are converted to unsaturated rates. The transmission rate of the soil layer is derived from the Hydrologic Soil Group, which is a proxy for texture. Special conditions override this approach for regions where the regionally unique geology dominates.
Pollution sensitivity of near-surface materials was derived from the following datasets:
- NRCS soil survey tabular and spatial data, using the hydrologic soil groups for transmission rate determination. SSURGO was the primary source of soil data.
- Surficial geology coverage was delineated from the county surficial geology map from the MGS. Residuum (Qr) transmission rate was modified to 0.50 in/hr per discussion with MGS.
Transmission rates for the soil layer and the surficial geology layer are determined by correlating the hydrologic soil group and the matrix texture, respectively, with the transmission rates shown in Table 2 in HG-02: files.dnr.state.mn.us/waters/groundwater_section/mapping/mha/hg02_report.pdf.
The general approach used to create the maps is as follows: (A) GIS polygons from soil and surficial geologic units are converted to rasters with 30-meter cells, with their transmission rates as the cell value. (B) Conditional statements are used to calculate travel time given the availability of soil and surficial geology data at a specific location where soil and surficial geology raster cells are coincident.
The two-layer model was applied to large portions of the state. However, special conditions override this approach for regions where unique geological environments dominate: karst, bedrock at or near surface, north-central peatlands, and large areas of disturbed land. The delineation of karst is from GW-01 Minnesota Regions Prone to Surface Karst Feature Development. The bedrock at or near surface and the disturbed lands are from surficial geology maps. The north-central peatlands are delineated from the Ecological Land Type Associations of Minnesota. Not all of these conditions necessarily exist within the county.

## Section 3: Spatial Data Organization (not used in this metadata)

## Section 4: Coordinate System

Horizontal Coordinate Scheme: Universal Transverse Mercator
UTM Zone Number: 15
Horizontal Datum: NAD83
Horizontal Units: meters
Vertical Datum:
Vertical Units:
Depth Datum:
Depth Units:

## Section 5: Attributes

Overview:
Detailed Citation:
Table Detail:

houston_near_surface_sensitivity
Field Name | Valid Values | Definition | Definition Source
--- | --- | --- | ---
RATING | enumerated | geologic sensitivity rating of the near surface materials as defined by vertical travel time |
| nsH | high: hours to a week |
| nsM | moderate: a week to weeks |
| nsL | low: weeks to months |
| nsVL | very low: months to a year |
| water | not rated |
| bedrock | bedrock at or near surface |
| karst | area prone to karst feature development |

## Section 6: Distribution

Publisher: Minnesota Department of Natural Resources, Ecological and Water Resources Division
Publication Date: 11/25/2025
Contact Person Information: Holly Johnson, GIS Specialist
Minnesota Department of Natural Resources
500 Lafayette Rd
St. Paul, MN 55155-4025
Phone: 651-259-5693
Email: holly.je.johnson@state.mn.us
Distributor's Data Set Identifier: houston_near_surface_sensitivity
Distribution Liability: These data were prepared from publicly available information only. Every reasonable effort has been made to ensure the accuracy of the factual data on which these files are 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 Department of Natural Resources.
Ordering Instructions: Download zip file of metadata and feature classes by clicking "I AGREE" below.
PDFs of the County Groundwater Atlas plates can be downloaded at: http://www.dnr.state.mn.us/waters/groundwater_section/mapping/status.html
Online Linkage: I AGREE to the notice in "Distribution Liability" above. Clicking to agree will either begin the download process, link to a service, or provide more instructions. See "Ordering Instructions" above for details.

## Section 7: Metadata Reference

Metadata Date: 11/25/2025
Contact Person Information: Holly Johnson, GIS Specialist
Minnesota Department of Natural Resources
500 Lafayette Rd
St. Paul, MN 55155-4025
Phone: 651-259-5693
Email: holly.je.johnson@state.mn.us
Metadata Standard Name: Minnesota Geographic Metadata Guidelines
Metadata Standard Version: 1.2
Metadata Standard Online Linkage: http://www.mngeo.state.mn.us/committee/standards/mgmg/metadata.htm

This page last updated: 11/25/2025
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