California Code, Health and Safety Code - HSC § 17953

Each city, county, and city and county shall enact an ordinance which requires a preliminary soil report, prepared by a civil engineer who is registered by the state, based upon adequate test borings or excavations, of every subdivision, where a tentative and final map is required pursuant to Section 66426 of the Government Code.

The preliminary soil report may be waived if the building department of the city, county or city and county, or other enforcement agency charged with the administration and enforcement of the provisions of this part, shall determine that, due to the knowledge such department has as to the soil qualities of the soil of the subdivision or lot, no preliminary analysis is necessary.