Upon the establishment of a public improvement benefit district as set out in this chapter, the city finance director shall establish a separate fund or in the case of city or Petaluma community development commission’s constructed improvements, reimburse the existing fund from which resources were drawn into which all such charges received are paid. Said funds shall be for the exclusive payment of costs and charges associated with the construction of the improvements identified as the subject of the district. If any funds remain at such time as the improvements for which the district was formed are completed and said funds are not necessary for future maintenance of the facility, such funds, without interest, shall be returned to the then owners of the private property within the district by applying the apportionment formula for the district to the real property of each owner. In the future event that the improvements are not constructed within a period of ten years from the date of the establishment of the district, funds without interest shall be returned to the then owners of the properties which were required to contribute to said funds pursuant to the apportionment formula adopted for the district, unless the council by resolution extends the terms of the benefit district as provided in Section 13.34.050. (Ord. 1977 NCS §5, 1995; Ord. 1303 NCS §1 (part), 1978.)