The soil boring and sampling procedures and apparatus shall be in accordance with ASTM D 1586 and ASTM D 1587 and generally accepted engineering practice. The rock coring, sampling procedure and apparatus shall be in accordance with ASTM D 2113 and generally accepted engineering practice. Rock cores shall be obtained with a double-tube core barrel with a minimum outside diameter of 27/8 inches (73 mm). With the approval of the engineer responsible for the geotechnical investigation, smaller-diameter double-tube core barrels may be used under special circumstances such as telescoping casing to penetrate boulders, or space limitations requiring the use of drill rigs incapable of obtaining large-diameter cores.
Where the foundation design relies on rock to support footings, piles or caisson sockets, a sufficient number of rock corings shall extend at least 10 feet (3048 mm) below the lowest level of bearing to provide assurance of the rock soundness. Where foundations are to rest on bedrock and such rock is exposed over a part or all of the area of the building, borings are not required in those areas where rock is exposed, provided the following requirements are met:
- The presence of defects or the inclination of bedding planes in the rock are of such size and location so as not to affect stability of the foundation.
- The foundation is not designed for bearing pressures exceeding those permitted in Table 1802.3.
The engineer responsible for the geotechnical investigation may engage specialized technicians to conduct alternative investigative methods such as cone penetrometer testing. Data from these investigations may be used to (1) supplement soil boring and rock coring information, provided there is a demonstrated correlation between the findings, and (2) determine material properties for static and seismic or liquefaction analyses. Subject to the approval of the commissioner, alternate exploration methods may replace borings on a one and one-half for one basis, but in no case shall there be fewer than half the required standard borings as per Section 1802.4.1, and no less than two standard borings. The boring depth requirements of Section 1802.4.1 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 pressure meter, 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.