1803.5 Soil and Rock Sampling

Where the foundation design relies on rock to support footings, deep foundations or caisson sockets, or permanent prestressed rock anchors, a sufficient number of rock corings shall be drilled to sufficient depths to assess the competency of the rock and its load-bearing capacity, but no less than 10 feet (3048 mm) below the lowest level of bearing.

The engineer responsible for the geotechnical investigation may engage specialized technicians to conduct alternative investigative methods such as cone penetrometer testing (CPT) performed in accordance with ASTM D3441 or ASTM D5778. Data from these investigations may be used to (i) supplement soil boring and rock coring information, provided there is a demonstrated correlation between the findings, and  (ii) determine material properties for static and seismic or liquefaction analyses. CPTs may replace borings on a one to one basis, but in no case shall there be fewer than half the required standard borings as per Section 1803.4.1, and no less than two standard borings. The boring depth requirements of Section 1803.4.1 shall be accomplished with borings. The alternative investigative methods must be capable of extending to the depths of the required borings. Other in-situ testing methods, such as geophysical, vane shear, and pressuremeter, may be used to determine engineering design parameters, but may not be used as a substitute for the required number of borings.

Soil and rock samples shall be maintained in an accessible location by the permit holder or owner and made available to the engineer responsible for the geotechnical investigation and to the department, until the foundation work has been completed and accepted, or until 1 year after the investigation is complete, whichever is longer.