The site is located in a region characterized by a generally high frequency of low wind speeds and calms, i.e., of poor dispersion conditions (Fig. II-7).(4)The duration and frequency of calm and near-calm conditions for three nearby locations are tabulated by season in Table II-1.

To avoid any uncertainty about onsite conditions, the applicant conducted a series of diffusion experiments at the site, in order to verify estimates of the atmospheric dispersion under the worst dispersion conditions. Results from these experiments are the basis for Tables A-II-2 through A-II-7 in Appendix II-2.

The site is subject to severe weather events but is in this respect not unusual for the area. High winds (over 50 miles per hour) can occur in any month of the year, but damaging extremes are rare. The site is sufficiently far inland so that tropical storms, which affect the area several times per year, have winds that are reduced well below hurricane level by passage over land. Associated rainfall amounts, however, may be large. Stations within a 50-mile radius of the site have reported rainfall of up to 20 inches in a 24-hour period.

Tornadoes are comparatively rare in this area but have been observed. The PSAR notes that five tornadoes with tracks long enough to plot occurred in Oconee County in the 50-year period ending in 1965. The mean number of thunderstorm days per year is approximately 60.

In summary, the meteorology is governed mainly by proximity to the Appalachians. This channels the low-level winds and contributes to a generally slow surface air movement. Special meterological studies have verified the atmospheric dispersion for these conditions at the site. Severe weather events occur with the expected frequency for the general

The bedrock at the site consists of a banded biotite hornblende gneiss and granite gneiss. The surface of the gneiss has weathered unevenly, and the residual soils found at the surface grade down irregularly. Partly weathered but sound rock is found at depths of from 5 to 40 feet. Enough of this weathered material was excavated so that the foundations of the plant are on firm rock.

The site is in the southeastern Piedmont physiographic province. This northeastward-trending belt of ancient metamorphic rocks extends northward from Alabama east of the Appalachians, and in South Carolina it crosses the state from the fall line on the east to the Blue Ridge and Appalachian

DURATION AND FREQUENCY (IN HOURS) OF CALM AND NEAR-CALM WINDS

*

The three locations were Charlotte WBAS, Winston-Salem WBAS, North Carolina; and Greenville WBAS and Greenville-Spartanburg WBAS, South Carolina.

**

Hours per season or hours per year as appropriate.

Mountains on the west. These rocks are generally recognized as being divided into four parallel northeast-southwest-trending belts in the Carolinas. From southeast to northwest these are the Carolina slate belt, the Charlotte belt, the Kings Mountain belt, and the Inner Piedmont belt. The site is in the northwestern (Inner Piedmont) belt.

zone.

The rocks of the site are geologically ancient and complex. Forces that folded and metamorphosed these rocks were associated with the formation of the Appalachian Mountains during the Appalachian Revolution, some 270 million years ago. These forces long since have died away and are no longer possible sources of earthquakes in this area. Faults and other lines of weakness dating from this Revolution may serve to locate present-day minor crustal movements which produce small earthquakes, and their location is of some importance. The most important is the Brevard fault zone that passes 11 miles northwest of the site. The design criteria for the Station, based upon earth shock considerations, took into account the nearest fault Small earthquakes have been detected along this zone with intensities of IV to VI. On this scale of intensities, V and VI represent disturbances that can dislodge loose plaster, etc.; X, XI, and XII represent disturbances that are severely damaging. Epicenters for quakes (positions on the earth's surface directly above the maximum disturbance) are generally in fault zone areas. Besides the Brevard fault there are fault zones 30 to 200 miles southeast where quake intensities of VII or VIII have been recorded; because of their distance, these zones are of slight importance for the Station. By far the largest quake in this general area was the Charleston, South Carolina, earthquake of 1886, that had an intensity at the epicenter of X. This quake was felt over a wide area but was destructive only in the vicinity of the epicenter, 200 miles from the plant. No faulting was observed in connection with this shock; although the bedrock at Charleston is covered with a thick deposit of coastal plain sediment, and faulting might not show.

F. ECOLOGY OF THE SITE AND ENVIRONS

The biota of that part of the Keowee-Toxaway project inundated by Lake Keowee was similar to the biota that at present dominates the area surrounding the lake, except that previously more stream-side communities were presents) No species listed as endangered species by the Department of Interior inhabit the project area. Two forest types constitute the dominant vegetation of the Keowee-Toxaway area: (1) the intermediate deciduous forest which occupies the upland and mountain slopes and (2) the intermediate hemlock-hardwood forest found principally along the upper river banks and sheltered coves. A relatively detailed listing of trees (6) and understory plants of the area was available. Some unusual plants known to occur locally include (1) a pennywort (Hydrocotyle americana), (2) a sundew (Drosera Rotundifolia), (3) mountain camellia (Stewartia ovata), (4) a milkwort (Polygala incarnata) which is rare outside the coastal plain, and (5) a filmy fern (Hymenophyllum tunbridgensa) which