There is hereby created a special trust fund to be known as the "Bear Creek Park Playground Reconstruction Trust Fund" into which shall be deposited all bequests and donations designated for the Bear Creek Park Playground Reconstruction Trust Fund and all other sums which the City Council directs to be deposited therein. The fund shall be prudently invested and the investment income of the fund shall be added to the principal. No expenditure shall be made from this fund until after June 30, 1999; thereafter, the principal and income of the fund may be used only for the reconstruction of the Children's Community Playground at Bear Creek Park.