Relating to NEHRP earthquake design criteria for classifying subsurface conditions, indicate the Site Classification for each of the following site location descriptions (see Table 5): (a) Area that...

Relating to NEHRP earthquake design criteria for classifying subsurface conditions, indicate the Site Classification for each of the following site location descriptions (see Table 5):

(a) Area that is geologically blanketed with transported soils that overlay bedrock found at great depth. An extensive soil boring investigation indicates the construction site is underlain by sandy soils; results of the standard penetration test (SPT) blow count N recorded for soil samples obtained from the borings show N-values between 25 and 40 for all locations.

(b) Area is geologically blanketed with a thick accumulation of firm fine-grain (silt-clay) soils, and bedrock is very deep. The area’s history indicates the soil deposit has been subject to the weight of overlying glaciers, and an affect is that the soil is highly consolidated and the cohesion shear strength is in excess of 2000 psf (100 kPa).

(c) Area is blanketed by residual soils which grade into bedrock generally located at a depth of 40 ft (12 m). The residual soil below the foundation level planned for new structures (including the deeper zone of weathered rock) is very dense; SPT results from borings indicate N-values between 60 and 90.