Figure
2-1

MEAN ANNUAL PRECIPITATION OF JKSYUS (IN INCHES)
SOURCE: Oregon State Water Resources Board, 1971, Pacific
Northwest River Basin Commission, 1970

Table 2-1

2.2 AIR QUALITY

Under the Clean Air Act Amendments of 1970, Oregon has been divided into five Federal Air Quality Control Regions (AQCRs) on the basis of pollution concentrations, geography, and economics. The JKSYUS lie within the Southwest Oregon AQCR and the Central Oregon AQCR (Figure 2-2).

The airshed in the JKSYUs meets Federal and State Ambient Air Quality Standards, with the exception of the Bear Creek Valley. The topography and climatic conditions of this area restrict ventilation, making it one of the two areas in the continental United States most vulnerable to air pollution episodes.

In 1971-72, national air quality standards for particulates were exceeded at Medford, Grants Pass, and Ashland. By 1975, only the Bear Creek Valley exceeded the standards for particulates. This area was placed in an Air Quality Maintenance Area (AQMA). The Medford-Ashland AQMA has shown significant improvement, especially in particulate air quality, since 1970. Violations of secondary Federal standards (150 micrograms per cubic meter (ug/m3) for a 24-hour sample) dropped from 13 in 1970 to 7 in 1975. In 1976, violations increased to 25, but this increase was due mostly to unusual weather conditions and not to increased emissions (ODEQ 1976b). The number of particulate violations had dropped to nine by 1977, (ODEQ 1977) with the return of more normal weather conditions.

Carbon monoxide standards were violated 178 times in 1977, but insufficient data are available to determine the trend. Despite generally improving air quality, the Medford-Ashland AQMA was designated a non-attainment area by the U.S. EPA in 1978 because it failed to meet ambient air quality standards for suspended particulates and carbon monoxide.

About one-half of the particulates in the JKS YUs originated from the wood processing industries, slash burning, forest fires, and wigwam waste burners. The main sources of excessive hydrocarbons appear to be veneer dryers, motor vehicles, general industry, and activities related to gasoline marketing (ODEQ 1976a).

2.3 GEOLOGY AND TOPOGRAPHY

The JKS YUs encompass the Klamath Mountains, Western Cascades, and High Cascades geographic provinces (Figure 2-3). They are bordered by the Basin and Range province to the east.

Topography in the Klamath Mountain Province consists of rugged and highly dissected terrain with steep, narrow, v-shaped valleys. The geology is very complex due to age and repeated faulting and folding of the rock. The most common rock types are sandstone, siltstone, schist, and serpentine, with

smaller amounts of volcanic rocks such as lava and breccias. Steep sideslopes in this province are often highly unstable, particularly where road