CA Gov't Code Section 4201

Any local agency that undertakes or contracts for an excavation for the installation, removal, maintenance, or repair of underground facilities may backfill that excavation in any local agency public road or highway with native spoil if the conditions in subdivisions (a), (b), and (c) are met. Where the excavation is performed by contract, use of native spoil shall be permitted unless otherwise specified in the contract documents.

(a)

The native spoil is competent spoil.

(b)

Compaction meets the local agency’s requirements, using industry standards for testing compaction.

(c)

The local agency or its contractor has no physical evidence of, or substantial reason to believe that there has been, contamination of the soil from hazardous waste.