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General Information
State(s): Minnesota
County(s): Cook, Lake, Saint Louis
Forest Service Administrative Unit(s):
Eastern Region (Region 9) -- Superior National Forest
Size: 810088 acres
Elevation Range: 1,260 - 2,301 feet
Data:
Documents
Resource Concern Thresholds
| AQRV Type: VISIBILITY |
| Sensitive Receptor |
Sensitive Receptor Indicator |
Thresholds |
| Natural Visibilty |
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For sources generally further than 50 km from a Class I area, the visibility threshold for concern is not exceeded if the 98th %ile change in light extinction is <5% for each year modeled, when compared to the annual average natural condition value for that Class I area. |
| Plume Blight |
Absolute Contrast |
Higher level near-field screening and refined analysis: no further analysis will likely be requested if a new or modified source can show that impacts from a new or modified source will stay with the threshold of DeltaE <1.0 and |C| <0.02 modeled against natural conditions. |
| Plume Blight |
Absolute Contrast |
For near field sources (within 50 km of a Class I area), no additional analysis will be requested If screening analysis of a new or modified source can demonstrate that its emissions will not cause a plume with hourly estimates of DeltaE (color difference index) greater than or equal to 2.0 or the absolute value of the contrast greater than or equal to 0.05 when modeled against natural conditions. |
| Plume Blight |
Color Difference Index |
Plume blight near-field refined analysis: no further analysis will likely be requested if a new or modified source can show that impacts from a new or modified source will stay with the threshold of DeltaE <1.0 and |C| <0.02 when modeled against natural conditions. |
| Plume Blight |
Color Difference Index |
For near field sources (within 50 km of a Class I area), no additional analysis will be requested If screening analysis of a new or modified source can demonstrate that its emissions will not cause a plume with hourly estimates of DeltaE (color difference index) greater than or equal to 2.0 or the absolute value of the contrast greater than or equal to 0.05 when modeled against natural conditions. |
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| AQRV Type: WATER |
| Sensitive Receptor |
Sensitive Receptor Indicator |
Thresholds |
| Aquatic Organisms |
Chemistry |
Total sulfur plus 20% of nitrogen deposition at levels exceeding 12 kg/ha-yr may cause ANC loss that would impact aquatic organisms. Levels below 9 kg/ha-yr are not expected to significantly impact aquatic organisms. |
| Aquatic Organisms |
Chemistry |
Based on the Acid Deposition Control Act passed by Minnesota, the sulfur deposition limit that would protect the most sensitive lakes and streams from acidification was set at 11 kg/ha/yr. Higher levels would be damaging. Below 6 kg/ha/yr, no damage to aquatic organisms is expected. |
| Perennial Lakes and Streams |
Chronic Acid Neutralizing Capacity |
To maintain healthy biological functioning in perennial lakes and streams, the chronic acid neutralizing capacity must be >= 25 ueq/l. ANC's below 10 ueq/L (the red line) are expected to cause adverse effects. |
| Perennial Lakes and Streams |
Episodic Acid Neutralizing Capacity |
To maintain healthy biological functioning in perennial lakes and streams, the episodic acid neutralizing capacity must be >= 0 ueq/l. |
| Perennial Lakes and Streams |
Metals (Hg) Concentration |
In perennial lakes and streams, the concern threshold for mercury in fish tissue is .05 parts per million mercury in wet weight, skin-on filet. |
Pollutant Exposure Concern Thresholds
| Pollutant Exposures |
Level Name |
Thresholds |
| N |
EXCEEDANCE |
The Deposition Analysis Threshold for nitrogen deposition is 0.005 kg/ha/yr. Below this, estimated impacts from a source greater than 50km from a FLM Class I Area are considered negligible. |
| Q |
QOverD |
For new or modified sources locating greater than 50 km from a Class I area, its impacts will be considered negligible with respect to Class I AQRVs if its total SO2, NOx, PM25, PM10, and H2SO4 annual emissions in tons/yr, based on 24-hr maximum allowable emissions, divided by the distance (km ) from the Class I area (Q/D) is 10 or less. For sources operating less than a year, the emissions must be adjusted to reflect what the emissions would be if the source operated year-round. |
| S |
DEPOSITION |
Based on the Acid Deposition Control Act passed by Minnesota, the sulfur deposition limit that would protect the most sensitive lakes and streams from acidification was set at 11 kg/ha/yr. Higher levels would be damaging. Below 6 kg/ha/yr, no damage to aquatic organisms is expected. |
| S |
EXCEEDANCE |
The Deposition Analysis Threshold for sulfur deposition is 0.005 kg/ha/yr. Below this, estimated impacts from a source greater than 50km from a FLM Class I Area are considered negligible. |
| S20PctN |
DEPOSITION |
Total sulfur plus 20% of nitrogen deposition at levels exceeding 12 kg/ha-yr may cause ANC loss that would impact aquatic organisms. Levels below 9 kg/ha-yr are not expected to significantly impact aquatic organisms. |
Natural Background Visibility
| Site Specific Rayleigh scattering coefficient: |
Clearest 20% Natural |
Clearest 20% 2000-2004 Baseline |
Haziest 20% Natural |
Haziest 20% 2000-2004 Baseline |
Average Annual Natural |
Annual Average 2000-2004 Baseline |
| Standard Visual Range (km) |
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| Haze Index (dv) |
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| For more information on these numbers, click here. |
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