Where load tests are required, at least one test shall be performed in each area of the foundation site within which the subsurface soil conditions are "substantially similar" in character, as determined by the engineer, and at least one test shall be performed for each pile type for the entire foundation installation of the building or group of buildings on a site occupying a total area of 5,000 square feet (465 m2) or less. Where load tests are required, at least two load tests shall be performed for a site having a footprint between 5,000 square feet (465 m2) and 30,000 square feet (2787 m2), and one additional load test shall be performed for each 20,000 square feet (1860 m2) of added footprint area. For conditions where multiple pile types or capacities are used, refer to Section 1808.2.5.
Where installed pile capacities are in doubt, the piles are considered non-conforming by the engineer, or as required by the commissioner, additional piles shall be load tested to establish the allowable capacity. For friction piles where the actual production pile lengths vary more than 25 percent from that of the test pile, the engineer shall determine if additional load tests are required to establish the allowable pile capacity. The number of additional load tests shall be determined by the engineer or commissioner.