ill., photos; Cover title; "September, 1985."; Includes bibliographical references (p. 50-51)
Visibility in Oregon's Wilderness and National Park Lands EXECUTIVE SUMMARY Introduction This Executive Summary presents results obtained from visibility monitoring within Oregon's wilderness areas and Crater Lake National Park during the summer's of 1982-1984• This document has been prepared to assist the Department, Federal Land Managers and public bodies with the management of visibility within Oregon's class I areas. The reader should note that the comments and conclusions found in this document are based on data gathered during the three summer periods of 1982-1984, Insufficient historical data has been gathered to determine if these data are representative of long term visibility conditions, A. Legislative History The Clean Air Act Amendments of 1977, Section 169 (A) established a national visibility protection goal for "Prevention Of Any Future And The Remedying Of Any Existing Impairment Of Visibility In Mandatory Class I Federal Areas Which Impairment Results From Manmade Air Pollution-w This requirement of the Act applies to 11 of Oregon's Wilderness Areas and Crater Lake National Park, Visibility protection has not been afforded to any of the 22 new wilderness areas established under the 1984 Oregon Wilderness Act since these areas have not been redesignated by the Department as class I areas. The regulations promulgated by the Environmental Protection Agency (EPA) required that the Department adopt a Visibility Protection Plan designed to meet the requirement of the Clean Air Act by no later than August, 1986 and approved by EPA no later than December, 1986. A draft of the plan must be submitted to EPA by December, 1985• B. Oregon's Class I Areas Oregon's wilderness lands and Crater Lake National Park are important recreational and economic assets to the State of Oregon. Visitors to these areas purchase recreational equipment and incur travel costs which add about $17.4 million per year to the State's economy. The areas of highest visitation include Crater Lake National Park (210,000 visitor days/year), the Mt. Jefferson Wilderness (110,600), the Three Sisters Wilderness (155,400) and the Eagle Cap Wilderness (99,600). Nearly 96% of the use occurs between mid-June and mid-September. For convenience, the Mt. Jefferson, Mt. Washington and Three Sisters Wilderness Areas are collectively referred to in this report as the Central Cascade Wilderness Areas. c. Visibility Monitoring in Oregon The Department established a visibility monitoring program, in cooperation with the U.S. Forest Service and the National Park Service during the summer of 1982 at locations near Mt. Hood, the Central AD2155.1 Page i Cascade Wilderness Areas and the Eagle Cap Wilderness Areas, A site was also established at Crater Lake, During the summer of 1984, additional sites were established by the U.S. Forest Service near the Kalmiopsis, Diamond Peak and Strawberry Mountain Wilderness Areas. The monitoring systems included measurements of standard visual range (SVR), particle light scattering, fine particle mass and aerosol chemistry; wind direction and speed as well as an extensive program of daily photography of selected visibility targets. The data is intended to provide information on the visual clarity of the atmosphere, the magnitude and duration of impaired visibility, the chemical composition of the particles causing the visibility loss and, through receptor modeling, estimates of specific source impacts on visibility. D. Visibility in Oregon’s Class I Areas Visibility in Oregon's class I areas is often impaired by uniform haze and, to a lesser extent, ground based layered haze. Many of the uniform haze episodes appear to be associated with impacts from dispersed field and forest slash burning activity. Discrete plume blight impairment associated with well defined plumes is uncommon. For purposes of this report, significant visibility impairment is defined as the standard visual range (SVR) which results from a 4$ contrast ratio change at the 90th percentile of the SVR distribution. In terms of light scattering, this definition translates to a threshold value of 0.6 X 10 M . Manmade impairment ranges from an average of 4$ of the daylight hours at Crater Lake to 17? at Mt. Hood and 33$ of the daylight hours within the Central Oregon Wilderness Areas. These data indicate that manmade visibility impairment in Oregon's class I areas may be related to the proximity of the class I lands to sources of manmade air pollution. Periods of impairment have been further subdivided into 3 categories: perceptible, moderate and heavy impairment. The findings reported below are based on these criteria: 1. Mt. Hood Wilderness Median visual range within the Mt. Hood Wilderness Area averages 120 km (74 miles) during the summer months, affording a view of Mt. Jefferson, 80 km (50 miles) to the south. During periods of heavily impaired visibility, minimum visual ranges of 18 km (11 miles) have been recorded. On exceptionally clear days, however, the visual approaches 230 km (138 miles). Visibility is impaired by natural and manmade sources 60-70$ of the July-September daylight hours. About 15-20$ (140 hours) of the daylight hours were impaired to some extent by manmade sources. About 50$ of the manmade impairment was in the "just perceptible" impairment category, while 33$ of the hours were moderate, and 10$ (16 hours) were heavy impairment hours. One-third of these periods occurred on Saturdays or Sundays. About 30$ of the impairment hours are caused by dispersed plume impacts while 70$ are related to regional haze. AD2155.1 Page ii 2. Central Oregon Wilderness Areas Median visual range within the Central Cascade Wilderness Areas was somewhat greater than that found in the Mt. Hood Wilderness, averaging 150 km (92 miles). Minimum visual ranges similar to those found at Mt. Hood were reported, but the visual range on exceptionally clear days was about 250 km (155 miles), or about 20 km greater. As in the Mt. Hood area, visibility in these Central Oregon Wilderness Areas was impaired 60-70% of the time by natural and manmade sources. Manmade sources contributed to impairment an average of 34% of the daylight hours within these three wilderness areas, one-third of which is caused by regional haze. Approximately 160 hours (50%) of the impairment hours are within the moderate and heavy categories. The frequency of weekend impairment is similar to that found for Mt. Hood, about one-third of the total hours. During the summer of 1984, 60% of the periods of heavy impairment occurred on a Saturday or Sunday. 3. Eagle Cap Wilderness Area The visibility within the Eagle Cap Wilderness was among the best in Oregon with a median summer visual range of 165 km (102 miles). Excellent visual range (270 km or nearly 170 miles) occurs about 10% of the time. The visibility was occasionally impaired on the south boundary of the wilderness by agricultural and slash burning. Further monitoring information is required along the northerly boundary of the wilderness to assess impairment conditions before a determination of significant impairment can be made. 4. Diamond Peak, Kalmiopsis and Strawberry Mountain Wilderness Areas One summer of monitoring information within these areas is insufficient to determine if visibility within these wilderness areas is impaired. Preliminary results indicate that the visual range within these wilderness areas is quite good, with median summer visual ranges of from 148-165 km (90-102 miles). Further monitoring is required to identify the extent and sources of impairment, if any. 5. Crater Lake National Park The best visibility within the State of Oregon is found at Crater Lake National Park, averaging 169 km (105 miles) to the north and south. During the clearest 10% of the time, visitors to the Park may experience visual ranges in the order of 280 km or 170 miles. Integral vistas, tentatively identified by the Park Service, south to Mt. Shasta and west toward the Bear Creek Valley are, however, impaired by uniform haze. While visibility within the Park was impaired during the summer of 1984, additional work is required to evaluate the importance of integral vistas and the degree of protection that should be afforded to them. AD2155.1 Page iii 6. Other Oregon Wilderness Areas The other Federal Class I Wilderness Areas within Oregon which are not discussed here (Sky Mountain, Mountain Lakes, Hells Canyon and the Gearhart Mountain Wilderness Areas) have not yet been included in the Department or Forest Service visibility monitoring programs as recreational use of these lands is small in comparison to those areas in which monitoring has been concentrated. Natural Impairment As noted above, impairment caused by natural and manmade sources of air pollution occurs about two-thirds to three-fourths of the time during the summer months in each of the 7 class I areas studied. Sources of the natural impairment include fog, high humidity, rain, wildfire smoke and aerosols associated with vegetative emissions of terpenes. Periods of dense fog and heavy rain are not included. Impairment associated with high relative humidity occurs most frequently at Mt. Hood (19-47$ of the time) and least frequently at Eagle Cap Wilderness (5-17$). These measurements underscore the fact that during the summers of 1982-83, precipitation was about 60$ above the 30 year average while during the summer of 1984, precipitation was about 30$ below the average. Wildfires are not thought to have been a major source contributing to impairment during the 1982-84 period because of the unusually low (1/2 of normal) occurrence of wildfires during this period and the relatively small source of fine particle emissions that wildfires represent. During 1984, wildfires accounted for about 13$ of the statewide fine particle emissions that impair visibility. The true significance of wildfires as a source of impairment is, however, difficult to define with certainty. Naturally formed aerosols from forest terpene emissions are not believed to be significant. E. Sources Impacting Visibility in Oregon's Class I Areas Results from Chemical Mass Balance analysis indicate that during visibility impact periods, agricultural field burning and forest slash burning were the most likely major contributing sources. During the two summers studied, an average of 50$ of the fine particle mass at the Mt. Hood site was from slash burning activity while 20$ was from field burning. For similar periods at the Mt. Washington site, slash burning contributed about 30$ of the mass while field burning contributed about 25-30$ of the mass. Since the light extinction properties of field and slash burning smoke are expected to be very similar, the above proportions should approximate the relative percentages of visibility reduction caused by each source. AD2155.1 Page iv Short-term field and slash burning impacts of approximately 20 ug/m-5 were also documented at the Department's Central Cascade Wilderness Area site. During these periods, visibility was totally obscured in all directions. "Average" impacts for the period July 27-August 23, 1983, indicate results similar to those noted above with 43? of the fine particle mass (and visibility reduction) related to slash burning and 11-14? assigned to field burning. Day-to-day variations in field and slash burning impacts generally make sense when reviewed in relation to burning activity and likely plume transport conditions, although for reasons stated in the text, it is difficult to apply this comparison rigorously. Evaluation of the "clean air" and fall 1983 poor visibility periods shows that these periods were characterized by low sulfate and organic carbon levels with an absence of field burning impacts. Estimated slash burning impacts were about 1/2 of those during the "average" period. The fall 1983 period was dominated by slash burning impacts averaging 11.6 ug/nH (46? of the mass) but reaching levels of 21.3 ug/nr (76?). No field burning impacts were identified by the CMB analysis. This is consistent with the absence of field burning impacts during this fall period. Trajectory Analysis Evaluation of burning activity, transport winds and visibility impact events were used as a means of estimating the likelihood that a source may have caused the impact. Because of the difficulty involved in this work, the results must be considered as qualitative. The findings, however, suggest that within the Mt. Hood and Central Cascade Wilderness Areas, about 1/5 of the impact hours may be related to field burning, 1/5 - 1/4 to Oregon slash burning activity and up to 1/4 from State of Washington slash burning. Fully 1/3 of the impact hours could not be assigned to any specific source or group of sources. These results are quite similar to those obtained from the CMB analysis during impact periods if the State of Oregon and Washington slash burning impacts are combined. Tracer Studies During the fall of 1983, methylchloride, carbon monoxide and freon-11 tracer studies were conducted at the Hickman Butte Lookout site near Mt. Hood to provide an independent method to identify sources that impair visibility near Mt. Hood. Methylchloride is a natural gaseous tracer for vegetative burning. Results from this study identified two specific periods of minor urban haze impact as well as periods of regional and plume impacts from burning activity. Slash burning is the likely cause of these impacts since very little field burning was occuring at the time of the study. Regional haze impacts of 25 to 50 ug/m^ and direct plume impacts of 80-110 ug/nr (10 minute averages) were detected. AD2155.1 Page v F. Regulatory Direction Based on the findings of this study, the Department finds that long term control strategies to remedy visibility impairment within the Mt. Hood, Mt. Jefferson, Mt. Washington and Three Sisters Wilderness Areas will be required as a key element of Oregon's Visibility Protection Program. Control strategies to address visibility impacts associated with Willamette Valley field burning and Western/Central Oregon slash burning may also be required. To insure significant progress toward meeting the national visibility goal established by Congress. The specific level of protection to be established as the initial goal of the plan will be determined by the Department following completion of public opinion surveys and recommendations from the Department's Visibility Advisory Committee. AD2155.1 Page vi
Visibility in Oregon's Wilderness and National Park Lands EXECUTIVE SUMMARY Introduction This Executive Summary presents results obtained from visibility monitoring within Oregon's wilderness areas and Crater Lake National Park during the summer's of 1982-1984• This document has been prepared to assist the Department, Federal Land Managers and public bodies with the management of visibility within Oregon's class I areas. The reader should note that the comments and conclusions found in this document are based on data gathered during the three summer periods of 1982-1984, Insufficient historical data has been gathered to determine if these data are representative of long term visibility conditions, A. Legislative History The Clean Air Act Amendments of 1977, Section 169 (A) established a national visibility protection goal for "Prevention Of Any Future And The Remedying Of Any Existing Impairment Of Visibility In Mandatory Class I Federal Areas Which Impairment Results From Manmade Air Pollution-w This requirement of the Act applies to 11 of Oregon's Wilderness Areas and Crater Lake National Park, Visibility protection has not been afforded to any of the 22 new wilderness areas established under the 1984 Oregon Wilderness Act since these areas have not been redesignated by the Department as class I areas. The regulations promulgated by the Environmental Protection Agency (EPA) required that the Department adopt a Visibility Protection Plan designed to meet the requirement of the Clean Air Act by no later than August, 1986 and approved by EPA no later than December, 1986. A draft of the plan must be submitted to EPA by December, 1985• B. Oregon's Class I Areas Oregon's wilderness lands and Crater Lake National Park are important recreational and economic assets to the State of Oregon. Visitors to these areas purchase recreational equipment and incur travel costs which add about $17.4 million per year to the State's economy. The areas of highest visitation include Crater Lake National Park (210,000 visitor days/year), the Mt. Jefferson Wilderness (110,600), the Three Sisters Wilderness (155,400) and the Eagle Cap Wilderness (99,600). Nearly 96% of the use occurs between mid-June and mid-September. For convenience, the Mt. Jefferson, Mt. Washington and Three Sisters Wilderness Areas are collectively referred to in this report as the Central Cascade Wilderness Areas. c. Visibility Monitoring in Oregon The Department established a visibility monitoring program, in cooperation with the U.S. Forest Service and the National Park Service during the summer of 1982 at locations near Mt. Hood, the Central AD2155.1 Page i Cascade Wilderness Areas and the Eagle Cap Wilderness Areas, A site was also established at Crater Lake, During the summer of 1984, additional sites were established by the U.S. Forest Service near the Kalmiopsis, Diamond Peak and Strawberry Mountain Wilderness Areas. The monitoring systems included measurements of standard visual range (SVR), particle light scattering, fine particle mass and aerosol chemistry; wind direction and speed as well as an extensive program of daily photography of selected visibility targets. The data is intended to provide information on the visual clarity of the atmosphere, the magnitude and duration of impaired visibility, the chemical composition of the particles causing the visibility loss and, through receptor modeling, estimates of specific source impacts on visibility. D. Visibility in Oregon’s Class I Areas Visibility in Oregon's class I areas is often impaired by uniform haze and, to a lesser extent, ground based layered haze. Many of the uniform haze episodes appear to be associated with impacts from dispersed field and forest slash burning activity. Discrete plume blight impairment associated with well defined plumes is uncommon. For purposes of this report, significant visibility impairment is defined as the standard visual range (SVR) which results from a 4$ contrast ratio change at the 90th percentile of the SVR distribution. In terms of light scattering, this definition translates to a threshold value of 0.6 X 10 M . Manmade impairment ranges from an average of 4$ of the daylight hours at Crater Lake to 17? at Mt. Hood and 33$ of the daylight hours within the Central Oregon Wilderness Areas. These data indicate that manmade visibility impairment in Oregon's class I areas may be related to the proximity of the class I lands to sources of manmade air pollution. Periods of impairment have been further subdivided into 3 categories: perceptible, moderate and heavy impairment. The findings reported below are based on these criteria: 1. Mt. Hood Wilderness Median visual range within the Mt. Hood Wilderness Area averages 120 km (74 miles) during the summer months, affording a view of Mt. Jefferson, 80 km (50 miles) to the south. During periods of heavily impaired visibility, minimum visual ranges of 18 km (11 miles) have been recorded. On exceptionally clear days, however, the visual approaches 230 km (138 miles). Visibility is impaired by natural and manmade sources 60-70$ of the July-September daylight hours. About 15-20$ (140 hours) of the daylight hours were impaired to some extent by manmade sources. About 50$ of the manmade impairment was in the "just perceptible" impairment category, while 33$ of the hours were moderate, and 10$ (16 hours) were heavy impairment hours. One-third of these periods occurred on Saturdays or Sundays. About 30$ of the impairment hours are caused by dispersed plume impacts while 70$ are related to regional haze. AD2155.1 Page ii 2. Central Oregon Wilderness Areas Median visual range within the Central Cascade Wilderness Areas was somewhat greater than that found in the Mt. Hood Wilderness, averaging 150 km (92 miles). Minimum visual ranges similar to those found at Mt. Hood were reported, but the visual range on exceptionally clear days was about 250 km (155 miles), or about 20 km greater. As in the Mt. Hood area, visibility in these Central Oregon Wilderness Areas was impaired 60-70% of the time by natural and manmade sources. Manmade sources contributed to impairment an average of 34% of the daylight hours within these three wilderness areas, one-third of which is caused by regional haze. Approximately 160 hours (50%) of the impairment hours are within the moderate and heavy categories. The frequency of weekend impairment is similar to that found for Mt. Hood, about one-third of the total hours. During the summer of 1984, 60% of the periods of heavy impairment occurred on a Saturday or Sunday. 3. Eagle Cap Wilderness Area The visibility within the Eagle Cap Wilderness was among the best in Oregon with a median summer visual range of 165 km (102 miles). Excellent visual range (270 km or nearly 170 miles) occurs about 10% of the time. The visibility was occasionally impaired on the south boundary of the wilderness by agricultural and slash burning. Further monitoring information is required along the northerly boundary of the wilderness to assess impairment conditions before a determination of significant impairment can be made. 4. Diamond Peak, Kalmiopsis and Strawberry Mountain Wilderness Areas One summer of monitoring information within these areas is insufficient to determine if visibility within these wilderness areas is impaired. Preliminary results indicate that the visual range within these wilderness areas is quite good, with median summer visual ranges of from 148-165 km (90-102 miles). Further monitoring is required to identify the extent and sources of impairment, if any. 5. Crater Lake National Park The best visibility within the State of Oregon is found at Crater Lake National Park, averaging 169 km (105 miles) to the north and south. During the clearest 10% of the time, visitors to the Park may experience visual ranges in the order of 280 km or 170 miles. Integral vistas, tentatively identified by the Park Service, south to Mt. Shasta and west toward the Bear Creek Valley are, however, impaired by uniform haze. While visibility within the Park was impaired during the summer of 1984, additional work is required to evaluate the importance of integral vistas and the degree of protection that should be afforded to them. AD2155.1 Page iii 6. Other Oregon Wilderness Areas The other Federal Class I Wilderness Areas within Oregon which are not discussed here (Sky Mountain, Mountain Lakes, Hells Canyon and the Gearhart Mountain Wilderness Areas) have not yet been included in the Department or Forest Service visibility monitoring programs as recreational use of these lands is small in comparison to those areas in which monitoring has been concentrated. Natural Impairment As noted above, impairment caused by natural and manmade sources of air pollution occurs about two-thirds to three-fourths of the time during the summer months in each of the 7 class I areas studied. Sources of the natural impairment include fog, high humidity, rain, wildfire smoke and aerosols associated with vegetative emissions of terpenes. Periods of dense fog and heavy rain are not included. Impairment associated with high relative humidity occurs most frequently at Mt. Hood (19-47$ of the time) and least frequently at Eagle Cap Wilderness (5-17$). These measurements underscore the fact that during the summers of 1982-83, precipitation was about 60$ above the 30 year average while during the summer of 1984, precipitation was about 30$ below the average. Wildfires are not thought to have been a major source contributing to impairment during the 1982-84 period because of the unusually low (1/2 of normal) occurrence of wildfires during this period and the relatively small source of fine particle emissions that wildfires represent. During 1984, wildfires accounted for about 13$ of the statewide fine particle emissions that impair visibility. The true significance of wildfires as a source of impairment is, however, difficult to define with certainty. Naturally formed aerosols from forest terpene emissions are not believed to be significant. E. Sources Impacting Visibility in Oregon's Class I Areas Results from Chemical Mass Balance analysis indicate that during visibility impact periods, agricultural field burning and forest slash burning were the most likely major contributing sources. During the two summers studied, an average of 50$ of the fine particle mass at the Mt. Hood site was from slash burning activity while 20$ was from field burning. For similar periods at the Mt. Washington site, slash burning contributed about 30$ of the mass while field burning contributed about 25-30$ of the mass. Since the light extinction properties of field and slash burning smoke are expected to be very similar, the above proportions should approximate the relative percentages of visibility reduction caused by each source. AD2155.1 Page iv Short-term field and slash burning impacts of approximately 20 ug/m-5 were also documented at the Department's Central Cascade Wilderness Area site. During these periods, visibility was totally obscured in all directions. "Average" impacts for the period July 27-August 23, 1983, indicate results similar to those noted above with 43? of the fine particle mass (and visibility reduction) related to slash burning and 11-14? assigned to field burning. Day-to-day variations in field and slash burning impacts generally make sense when reviewed in relation to burning activity and likely plume transport conditions, although for reasons stated in the text, it is difficult to apply this comparison rigorously. Evaluation of the "clean air" and fall 1983 poor visibility periods shows that these periods were characterized by low sulfate and organic carbon levels with an absence of field burning impacts. Estimated slash burning impacts were about 1/2 of those during the "average" period. The fall 1983 period was dominated by slash burning impacts averaging 11.6 ug/nH (46? of the mass) but reaching levels of 21.3 ug/nr (76?). No field burning impacts were identified by the CMB analysis. This is consistent with the absence of field burning impacts during this fall period. Trajectory Analysis Evaluation of burning activity, transport winds and visibility impact events were used as a means of estimating the likelihood that a source may have caused the impact. Because of the difficulty involved in this work, the results must be considered as qualitative. The findings, however, suggest that within the Mt. Hood and Central Cascade Wilderness Areas, about 1/5 of the impact hours may be related to field burning, 1/5 - 1/4 to Oregon slash burning activity and up to 1/4 from State of Washington slash burning. Fully 1/3 of the impact hours could not be assigned to any specific source or group of sources. These results are quite similar to those obtained from the CMB analysis during impact periods if the State of Oregon and Washington slash burning impacts are combined. Tracer Studies During the fall of 1983, methylchloride, carbon monoxide and freon-11 tracer studies were conducted at the Hickman Butte Lookout site near Mt. Hood to provide an independent method to identify sources that impair visibility near Mt. Hood. Methylchloride is a natural gaseous tracer for vegetative burning. Results from this study identified two specific periods of minor urban haze impact as well as periods of regional and plume impacts from burning activity. Slash burning is the likely cause of these impacts since very little field burning was occuring at the time of the study. Regional haze impacts of 25 to 50 ug/m^ and direct plume impacts of 80-110 ug/nr (10 minute averages) were detected. AD2155.1 Page v F. Regulatory Direction Based on the findings of this study, the Department finds that long term control strategies to remedy visibility impairment within the Mt. Hood, Mt. Jefferson, Mt. Washington and Three Sisters Wilderness Areas will be required as a key element of Oregon's Visibility Protection Program. Control strategies to address visibility impacts associated with Willamette Valley field burning and Western/Central Oregon slash burning may also be required. To insure significant progress toward meeting the national visibility goal established by Congress. The specific level of protection to be established as the initial goal of the plan will be determined by the Department following completion of public opinion surveys and recommendations from the Department's Visibility Advisory Committee. AD2155.1 Page vi