N.Y.C. Admin. Code § 28-105.4.6: § 28-105.4.6 Geotechnical investigations.

A permit shall not be required for excavation performed for a geotechnical investigation required by section 1803.4 of the New York city building code provided such excavation does not exceed 10 feet (3048 mm) in length, width, or diameter and is conducted under the supervision of a registered design professional. All excavation activity, including backfilling of excavations, shall comply with all relevant code provisions, including but not limited to sections 1803 and 3304 of the New York city building code.