PRASA OWNS AND OPERATES SIXTY WATER TREATMENT PLANTS ( WTPS ). THE NUEVA PONCE FILTER PLANT, LOCATED AT STATE ROAD IN PONCE, PUERTO RICO IS ONE SUCH PLANT. IT PROVIDES POTABLE WATER IN THE PONCE AREA. A NPDES PERMIT WAS ISSUED TO PRASA FOR THE NUEVA PONCE FACILITY WHICH CONTAINS EFFLUENT DISCHARGE LIMITATIONS. PRASA IS PERMITTED TO DIS- CHARGE FILER BACKWASH WASTEWATER TO THE LA MATILDE RIVER, A WATER OF THE UNITED STATES. AN ADMINISTRATIVE ORDER WAS ISSUED ON 7/18/83. FROM APPROXIMATELY 1983 THROUGH 1988 EPA, EQB, AND PRASA EX- CHANGED CORRESPONDENCE AND TOOK PART IN NEGOTIATIONS REGARD- ING COMPLIANCE SCHEDULES FOR THIS FACILITY AND PRASA'S OTHER WATER FILTRATION FACILITIES. LETTERS OF DEFICIENCY WERE SENT TO PRASA DURING THAT TIME PERIOD. ON 9/28/88 EPA ISSUED AN ADMINISTRATIVE ORDER WHICH CITED FINDINGS OF EFFLUENT VIOLATIONS AT THIS FACILITY AND FAILURE TO COMPLY WITH ITS PERMIT. THE ORDER ALSO CONTAINED INTERIM EFFLUENT LIMITS. ON 3/29/89 EPA ISSUED ANOTHER ORDER TO PRASA REQUIRING COMPLIANCE AND QUARTERLY REPORTING OF COMPLIANCE MEASURES TAKEN. ON 6/15/89 EPA ISSUED A MODIFIED ORDER IN RESPONSE TO REQUESTS MADE BY PRASA. VARIOUS CORRESPONDENCE WAS EXCHANGED WHEN EPA ISSUED ADMIN- ISTRATIVE ORDERS TO SHOW CAUSE. EPA AND PRASA MET ON 8/1/90 TO DISCUSS PRASA'S FAILURE TO COMPLY WITH ITS WATER FILTRATION PLANT PERMITS.