70 ILCS 1205/9-1c
Whenever revenue bonds are issued under Section 9-1 hereof, all revenue derived from the operation of the swimming pool, or the artificial ice skating rink, shall be deposited in a separate fund designated as the "Swimming Pool Fund", or the "Artificial Ice Skating Rink Fund", of the park district. These funds, or either of them as designated, shall be used only in paying the cost of operation and maintenance of the swimming pool, or the artificial ice skating rink, in providing an adequate depreciation fund, and in paying the principal of and interest upon the revenue bonds of the district issued under Section 9--1 hereof.
A depreciation fund is a fund for such replacements as may be necessary from time to time for the continued effective and efficient operation of the system. Such a fund shall not be allowed to accumulate beyond a reasonable amount necessary for the purpose and shall not be used for extensions to the swimming pool, or the artificial ice skating rink.
70 ILCS 1205/9-1c