CA Gov't Code Section 29441

In addition to any other revolving funds provided for by this chapter, the board of supervisors may establish a revolving fund to be used by the sheriff in paying the expense of transporting persons committed to state institutions. The fund shall be in an amount sufficient to enable the sheriff at all times to meet such expense.

If necessary the fund may be in an amount greater than one thousand dollars ($1,000). The fund shall be used only in transporting persons the cost of whose transportation is a state charge, and shall be replenished by demands made against the State. In all other respects, the provisions of Article 2 shall govern this fund.