There is hereby created a special trust fund to be known as the "Bear Creek Park Playground Maintenance Trust Fund" into which shall be deposited all bequests and donations designated for the Bear Creek Park Playground Maintenance Trust Fund and all other sums which the City Council directs to be deposited therein. The fund shall be prudently invested and the income therefrom shall be used solely for the maintenance and upkeep of the Children's Community Playground at Bear Creek Park. The fund is intended to provide a permanent endowment for this playground facility, and the principal of the fund shall not be expended. At the end of each fiscal year, the investment income of the fund during such year shall be determined by the finance director and the amount so determined shall then be available for expenditure for the purposes herein specified.