30 September 1999
Table B-1. Site Soil Profile Classification
Hard rock with measured shear wave velocity, v s > 5,000 ft/sec (1,500 m/s)
Rock with 2,500 ft/sec < v s ≤ 5,000 ft/sec (760 m/s < v s ≤ 1,500 m/s)
Very dense soil and soft rock with 1,200 ft/sec < v s ≤ 2,500 ft/sec (360 m/s < v s ≤
760 m/s) or with either N > 50 or s u > 2,000 psf (100 kPa)
Stiff soil with 600 ft/sec ≤ v s ≤ 1,200 ft/sec (180 m/s ≤ v s ≤ 360 m/s) or with
15 ≤ N ≤ 50 or 1,000 psf ≤ s u ≤ 2,000 psf (50 kPa ≤ s u ≤ 100 kPa)
A soil profile with v s < 600 ft/sec (180m/s) or with either
N < 15 s u < 1,000 psf or any profile with more than 10 ft (3 m) of soft clay defined
as soil with
PI > 20, w ≥ 40 percent, and su < 500 psf (25 kPa)
Soils requiring site-specific evaluations:
1. Soils vulnerable to potential failure or collapse under seismic loading
such as liquefiable soils, quick and highly sensitive clays, and
collapsible weakly cemented soils.
2. Peats and/or highly organic clays (H > 10 ft [3 m] of peat and/or highly
organic clay where H = thickness of soil).
3. Very high plasticity clays (H > 25 ft [8 m] with PI > 75).
4. Very thick soft/medium stiff clays (H > 120 ft [36 m]).
Exception: When the soil properties are not known in sufficient detail to determine the Site
Class, Site Class D shall be used. Site Classes E or F need not be assumed unless the
authority having jurisdiction determines that Site Classes E or F could be present at the site, or
in the event that Site Classes E or F are established by geotechnical data.