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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 |
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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. |
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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 |
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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 |
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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 |
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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 |
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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 |
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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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