Cal. Lab. Code § 6707
Whenever the state, a county, city and county, or city issues a call for bids for the construction of a pipeline, sewer, sewage disposal system, boring and jacking pits, or similar trenches or open excavations, which are five feet or deeper, such call shall specify that each bid submitted in response thereto shall contain, as a bid item, adequate sheeting, shoring, and bracing, or equivalent method, for the protection of life or limb, which shall conform to applicable safety orders. Nothing in this section shall be construed to impose tort liability on the body awarding the contract or any of its employees. This section shall not apply to contracts awarded pursuant to the provisions of Chapter 3 (commencing with Section 14250) of Part 5 of Division 3 of Title 2 of the Government Code.
Ca. Lab. Code § 6707