Perform SPT in accordance with AASHTO T 206 or ASTM D1586, within all soil types. Perform SPT every 5-ft interval beginning at 5 ft. from the surface of the boring to the termination depth of the boring, or until the depth bedrock is encountered. Record the blow counts for each 6-inch SPT interval including the seating drive in the boring logs. The sum of the number of blows for the second and third 6-inch drives is termed as the “standard penetration resistance” or the uncorrected SPT “N-value.” Additionally, record the total length of sample recovered during the 18-inch drive within the split-spoon.

Driller shall develop calibration to determine specific hammer system efficiencies in general accordance with ASTM D4633 for dynamic analysis of driven piles. Drilling equipment or hammers shall be tested and calibrated annually and on a project specific basis as needed when questionable results are observed. Indicate calibrated, reported, or suspected efficiencies on the boring logs and geotechnical reports.

Design shall apply corrections to the standard penetration resistance or uncorrected SPT N-values from the geotechnical report boring log, for hammer efficiency and effects of overburden pressure, as applicable to the design method or correlation being used. Use Equations 10.4.6.2.4-1 through 10.4.6.2.4-3 in AASHTO LRFD Bridge Design Specifications for corrections of SPT blow counts.