The rating on St. Charles Parish Hospital Service District No. 1, La.'s bonds reflects: A highly concentrated economic and tax base, A moderate debt burden, and Adequate financial performance. The bonds are secured by the unlimited ad valorem tax pledge of the hospital service district, which is coterminous with St. Charles Parish. Assessed valuation (AV) has exhibited strong growth, rising at an annual average of 13.8% from 1993-1998 to an estimated $685.9 million in fiscal 1998. The leading 10 taxpayers account for a concentrated 64% of the $685.9 million AV base. Entergy Waterford Nuclear Power Plant is the largest taxpayer, at $218.3 million, or an estimated 32% of total AV, followed by petrochemical and natural gas companies, which together encompass