Welf. & Inst. Code, § 15150

During such time as grants-in-aid are provided or made available by the United States government for public assistance in this state, the State Treasurer shall pay to each county from the sums so granted (1) an amount which shall be used exclusively as public assistance equal to the full amount of any sums received from the United States government as public assistance in respect to recipients within the provisions of this chapter maintained or supported by the county; and (2) an additional amount equal to such county’s proportionate share of any amount so granted or made available to this state by the United States government for the costs of administering such aid, which additional amount shall be used exclusively for paying such administration costs. The department shall determine the portion of the amount so granted or made available for administration costs to be paid to the counties, which portion for each county shall bear the same proportion to the total amount made available to this state for such administrative costs that the administrative costs of that county bear to the total administrative costs of all counties and of the state. The department shall adopt rules and regulations which shall be of uniform application for determining the proportionate shares for such quarter to each county under the provisions of this section and Section 15152.