Streets and Highways Code § 27248
CHAPTER 13. Issuance of District Bonds and Disposition of Surplus Proceeds
The money in the reserve interest fund shall be deposited in the same manner as other funds of the district or invested in securities which are legal investments for public funds, and the fund shall be used solely for the payment of interest on such bonds whenever there shall be a deficit in the revenues of the works and only to the extent of such deficit.