CA Civ Proc Code Section 1263.410

(a)

Where the property acquired is part of a larger parcel, in addition to the compensation awarded pursuant to Article 4 (commencing with Section 1263.310) for the part taken, compensation shall be awarded for the injury, if any, to the remainder.

(b)

Compensation for injury to the remainder is the amount of the damage to the remainder reduced by the amount of the benefit to the remainder. If the amount of the benefit to the remainder equals or exceeds the amount of the damage to the remainder, no compensation shall be awarded under this article. If the amount of the benefit to the remainder exceeds the amount of damage to the remainder, such excess shall be deducted from the compensation provided in Section 1263.510, if any, but shall not be deducted from the compensation required to be awarded for the property taken or from the other compensation required by this chapter.