County Geologic Atlas Program


Todd County Geologic Atlas Part B

NRSFSNPY metadata

Sensitivity to Pollution of the Near Surface Materials


Minnesota DNR Waters
County Geologic Atlas and Regional Hydrogeologic Assessment Program

Description of data created for Todd County Geologic Atlas, Part B
County Geologic Atlas Series C-18

Metadata created using Minnesota Geographic Metadata Guidelines version 1.2
Metadata content prepared 2010-12-02


Go to Section:
1. Identification Information
2. Data Quality Information
3. Spatial Data Organization Information
4. Spatial Reference Information
5. Entity and Attribute Information
6. Distribution Information
7. Metadata Reference Information
 

 

Section 1

Identification Information - - - - - - top

Originator

Minnesota DNR Waters - County Geologic Atlas and Regional Hydrogeologic Assessment Program

Title

NRSFSNPY

 

System Name

 

Abstract

Near-surface pollution sensitivity in Todd County, Minnesota. The sensitivity to pollution assessment of the near-surface materials estimates the time of travel for water to travel from the land surface to a depth of ten feet.

 

Purpose

County Geologic Atlas and Regional Hydrogeologic Assessment Program,
Todd County Geologic Atlas, Part B, County Geologic Atlas Series C-18

Time Period of Content Date

November, 2010

Currentness Reference

Publication date

Progress

Complete

Maintenance and Update Frequency

None Planned

Spatial Extent of Data

Todd County, Minnesota

Bounding Coordinates

East

-94.6

West

-95.2

North

46.4

South

45.8

 

Place Keywords

Minnesota, Todd County

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 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

See Metadata Reference Information section, below

Browse Graphic File Name

 

Browse Graphic File Description

 

Associated Data Sets

Todd County Geologic Atlas, Part A, County Geologic Atlas Series C-18, published by the Minnesota Geological Survey, 2007. More information and downloadable data for Part A available on the MGS ftp site.The preceeding link is to a non-DNR site

 

Section 2

Data Quality Information - - - - - - top

Attribute Accuracy

 

Logical Consistency

Data are topologically correct using ArcGIS 9.3

Completeness

Complete

Horizontal Positional Accuracy

unknown

Vertical Positional Accuracy

not applicable

Lineage

This file is the most correct combination of soil and surficial geology attributes and represents the final grid for a near-surface sensitivity calculation.

This file was created by combining the estimated infiltration time for soil units with the estimated infiltration rate for the underlying surficial geology units, the soil?s parent material. Field [TRVL_TIME] is the best estimate of travel time of water (in hours) to move from the surface to a depth of 10 feet.

The sensitivity to pollution assessment for near-surface materials estimates the time of travel for water to travel from the land surface to a depth of ten feet, and is shown in Figure 13, Plate 10. Soil properties are used to estimate the travel time from land surface to a depth of three feet and surficial geology properties are used to estimate the travel time from a depth of three feet to ten feet. The near-surface materials sensitivity assessment was created by estimating infiltration rates through soils and surficial geology units based on the Natural Resources Conservation Service (NRCS) hydrologic rating for soils and the geologic unit texture of deeper parent materials, from Plate 3, Part A, Surficial Geology. Estimates of infiltration rates are shown in Table 1, Plate 10. The NRCS defines hydrologic groups based on a somewhat complicated system, but it is primarily based on the soil unit?s texture and the presence or absence of dense, low permeability layers.

The near-surface materials sensitivity rating is determined by using the minimum transmission rates for the soil and surficial geologic units to calculate the estimated travel time. For this calculation, the water table is assumed to be 10 feet below the land surface throughout the county. The GIS polygons from both the soil survey and the surficial geologic map are converted to grids with a 30 meter cell size. Each cell in the respective grids is assigned a minimum transmission rate as explained above. The travel time for the upper 3 feet is calculated using the minimum transmission rate of the soil unit. The travel time for 3 feet to 10 feet below land surface is calculated using the minimum transmission rate of the surficial geologic unit. The total travel time to 10 feet is then used to estimate the near-surface materials geologic sensitivity (Figure 2, Plate 10). Some soil units have not been assigned a hydrologic group (for example gravel pits) and therefore have no assigned minimum transmission rate. If a minimum transmission rate was not available for a soil unit, then the surficial geology unit minimum transmission rate was used to calculate the travel time for the entire 10-foot distance.

Soils with a dense material layer are primarily from a dense basal till parent material. These soils have a hydrologic group rating of C or C/D. This implies that these soil layers are less sensitive than most other layers. These soils may transmit water through vertical fractures much more quickly than through the matrix material. Therefore, an overlay polygon representing the soils with dense material layers is shown in feature class soils_dense. The sensitivity rating calculated for these areas of dense soils may be too low, if vertical fractures exist.

The [infiltration rate grid] was calculated using the combine command from spatial analyst. It combined grids [soils_rate_int] and [sgpg_rate_int], where [soils_rate_int] is the infiltration of water through soil (from 0 to 3 feet below land surface) and [sgps_rate_int] is the infiltration rate of water through the underlying surficial geologic material (soil parent material) from 3 to 10 feet. To facilitate the use of integer grids, both infiltration rates are stored as inches/hour * 100.

The travel time to a 10-foot depth, field [TRVL_TIME], was calculated using the following field calculation:

Dim TTime As Double
If [SOILS_RATE_INT] = 0 Then
If [SGPG_RATE_INT] <> 0 Then TTime = ROUND((1000 *12) / [SGPG_RATE_INT], 0)
elseif [SGPG_RATE_INT] = 0 Then TTime = -9999
endif
elseif [SGPG_RATE_INT] = 0 Then TTime = -9999
else TTime = ROUND((300 *12) / [SOILS_RATE_INT] + (700 *12) / [SGPG_RATE_INT], 0)
endif

Field [SOILS_RATE_INT] is from [min_t_rate] in soils.shp. It is the infiltration rate in inches/hour * 100. (To use an integer grid, it was necessary to multiply the infiltration rate by 100.)

Field [SGPG_RATE_INT] is from [min_t_rate] in sgpg_cat_py. It is the infiltration rate in inches/hour * 100. (To use an integer grid, it was necessary to multiply the infiltration rate by 100.)

Field [TRVL_TIME] is the estimated travel time from the surface to 10 feet below the surface in hours. If the value is this field is -9999, then the cell should be considered null. -9999 was used when both [mintratcor] in soils.shp and [min_t_rate] in sgpg_cat_py were equal to 0. It was used when water is at the surface, so infiltration to 10 feet is meaningless. If the soil data are null, but [min_t_rate] is not null, then [min_t_rate] from sgpg_cat_py was used to calculate the travel time for the 10 feet of travel.

Sensitivity ratings are based on hours of travel to a depth of ten feet and are applied as follows:

Hours Travel Time

Sensitivity Rating

0 to 320 hours
320 to 1000 hours
1000 to 1800 hours
1800 to 3200 hours
Greater than 3200 hours

Very High
High
Moderate
Low
Very Low

The final raster was converted to a polygon shapefile.

Sensitivity interpretation was based on estimated time of travel ranges as follows:

Map color

Sensitivity Rating

Time of travel range

Red
Orange
Yellow
Light Green
Dark Green

Very High
High
Moderate
Low
Very Low

Hours to weeks
Weeks to months
Months
Months
Months to a year

Source Scale Denominator

100000

 

Section 3

Spatial Data Organization Information - - - - - - top

Native Data Set Environment

ArcGIS 9.3

Geographic Reference for Tabular Data

Not Applicable

Spatial Object Type

Vector

Vendor Specific Object Types

polygon

Tiling Scheme

state

 

Section 4

Spatial Reference Information - - - - - - top

Horizontal Coordinate Scheme

UTM

Ellipsoid

GRS1980

Horizontal Datum

NAD83

Horizontal Units

meters

Distance Resolution

meters

Altitude Datum

n/a

Altitude Units

n/a

Depth Datum

n/a

Depth Units

n/a

Cell Width

0

Cell Height

0

Latitude Resolution

0

Longitude Resolution

0

UTM Zone Number

15

SPCS Zone Identifier

0

County Coordinate Zone Identifier

0

Coordinate Offsets or Adjustments

n/a

Map Projection Name

n/a

Map Projection Parameters

n/a

Other Coordinate System's Definition

n/a

 

Section 5

Entity and Attribute Information - - - - - - top

Entity and Attribute Overview

 

Entity and Attribute Detailed Citation

HTML Table (Not Available)

NRSFSNPY

 

 

 

Rating

 

"nsVH" is very high
"nsH" is high
"nsM" is moderate
"nsL" is low
"nsVL" is very low

 

 

Section 6

Distribution Information - - - - - - top

Publisher

Minnesota DNR Waters

Publication Date

2010

Contact Person Information

See Metadata Reference Information section, below

Distributor's Data Set Identifier

NRSFSNPY

Distribution Liability

This 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 Name

shapefile

Transfer Format Version Number

 

Transfer Size

 

Ordering Instructions

Download ArcGIS shapefiles from:
Todd County Geologic Atlas, Part B: Metadata for GIS and Digital Data

Online Linkage

Todd County Geologic Atlas, Part B: Metadata for GIS and Digital Data

 

Section 7

Metadata Reference Information - - - - - - top

Metadata Date

2010-12-02

Contact Person Information

GIS Specialist, Atlas/Assessment Program
Minnesota DNR - Division of Waters
500 Lafayette Road
Saint Paul, MN 55155
Phone: (651) 259-5693
FAX: (651) 296-0445
E-mail:

Metadata Standard Name

Minnesota Geographic Metadata Guidelines

Metadata Standard Version

1.2

Metadata Standard Online Linkage

http://www.lmic.state.mn.us/gc/stds/metadata.htm

 

 

 

 

 

 

 

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