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	USDA Forest Service 1400 Independence Avenue SW Washington, D.C. 20250-0003 (202) 205-8333

Mount Hood Wilderness

General Information

State(s): Oregon

County(s): Clackamas, Hood River

Forest Service Administrative Unit(s):
Pacific Northwest Region (Region 6) -- Mt. Hood National Forest

Size: 47160 acres

Elevation Range: 1,800 - 9,200 feet

Data:

Documents

Resource Concern Thresholds

AQRV Type: VISIBILITY
Sensitive Receptor	Sensitive Receptor Indicator	Thresholds
Natural Visibilty		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.

AQRV Type: WATER
Sensitive Receptor	Sensitive Receptor Indicator	Thresholds
Lakes with Low Anc	Acid Neutralizing Capacity	For lakes with low acid neutralizing capacity, the condition class of "Severe Deterioration" applies if there is deterioration below ANC of 0 ueq/l.
Lakes with Low Anc	Acid Neutralizing Capacity	For lakes with low acid neutralizing capacity, the condition class of "Significant Deterioration" applies if there is greater than or equal to a 20% decline in ANC.
Lakes with Low Anc	Acid Neutralizing Capacity	For lakes with low acid neutralizing capacity, the condition class of not significant applies if there is less than a 20% decline in ANC.
Lakes with Low Anc	pH	For lakes with low acid neutralizing capacity, the condition class of "Severe Deterioration" applies if pH levels are below 5.3.
Lakes with Low Anc	pH	For lakes with low acid neutralizing capacity, the condition class of "Not Significant" applies if pH levels are above 6.0.
Lakes with Low Anc	pH	For lakes with low acid neutralizing capacity, the condition class of "Significant Deterioration" applies if pH levels are between 5.3-6.0.
Streams	Acid Neutralizing Capacity	For streams that have an initial acid neutralizing capacity of 25-100 ueq/l, the condition class of "Not Significant" applies if there is less than a 25% change in ANC from baseline.
Streams	Acid Neutralizing Capacity	For streams that have an initial acid neutralizing capacity of greater than 100 ueq/l, the condition class of "Significant Deterioration" applies if ANC levels are between 15-25 ueq/l.
Streams	Acid Neutralizing Capacity	For streams that have an initial acid neutralizing capacity of greater than 100 ueq/l, the condition class of "Not Significant" applies if there is less than a 50% change in ANC from baseline.
Streams	Acid Neutralizing Capacity	For streams that have an initial acid neutralizing capacity of 25-100 ueq/l, the condition class of "Significant Deterioration" applies if ANC levels are between 15-25 ueq/l.
Streams	Acid Neutralizing Capacity	For streams that have an initial acid neutralizing capacity of less than 25 ueq/l, the condition class of "Severe Deterioration" applies if there is any change from baseline.
Streams	Acid Neutralizing Capacity	For streams that have an initial acid neutralizing capacity of greater than 100 ueq/l, the condition class of "Severe Deterioration" applies if ANC levels are less than 15 ueq/l.
Streams	Acid Neutralizing Capacity	For streams that have an initial acid neutralizing capacity of less than 25 ueq/l, the condition class of "Not Significant" applies if there is no change from baseline.
Streams	Acid Neutralizing Capacity	For streams that have an initial acid neutralizing capacity of 25-100 ueq/l, the condition class of "Severe Deterioration" applies if ANC levels are less than 15 ueq/l.

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	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.

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)
Haze Index (dv)
For more information on these numbers, click here.