Cal. Sts. & Hy. Code § 10427.2
If, pursuant to Section 10427, the legislative body determines that any surplus remaining in the improvement fund shall be used as a credit upon the assessment or any supplemental assessment, the legislative body may also determine that such surplus shall be applied as a credit to the city or any local, state or national agency or authority which shall have made a contribution towards the costs and expenses of the improvement. A credit on account of any contribution shall be made in the proportion which such contribution bears to the total amount of the assessment or supplemental assessment prior to the deduction of all such contributions. All such credits shall be returned in cash to the city, local, state or national agency or authority making such contribution. The surplus remaining in the improvement fund after making credits on account of contributions shall then be applied as a credit in the manner provided in Section 10427.1.
Ca. Sts. and High. Code § 10427.2