Cal. Rev. & Tax. Code § 401.13

Notwithstanding any other provision of law, on or after January 1, 1998, the assessor shall determine the assessed value of pipelines and related rights-of-way that are located wholly within the county on the basis of a single, countywide parcel per taxpayer, and, to that end, shall combine the assessed value of each component or segment of those pipelines or rights-of-way. However, the assessor shall maintain a separate base year value for each of these components or segments.