Section 34D. There shall be a Christian A. Herter Park Trust Fund, which shall be used for the purposes of advancing recreational, educational and conservation interests including, but not limited to, the construction and maintenance of facilities and infrastructure improvements for Christian A. Herter park within the Charles River Reservation; provided, however, that not less than 50 per cent of the trust shall be used for the Friends of Herter Park, Inc. The trust shall receive, hold and expend all fees generated by permits, licenses and all other agreements not currently being directed to the General Fund relating to the use of the Christian A. Herter Park land as authorized by the commission. The department shall not make expenditures from this fund so as to cause the fund to be deficient.