THIS ORDER IS ISSUED TO RHONE-POULENC AND ITS SUBSIDIARY RHODIA, INC. TO PROTECT HEALTH AND/OR THE ENVIRONMENT. BASED ON INFORMATION RECEIVED, EPA HAS DETERMINED THAT RESPONDENT'S HANDLING OF SOLID WASTE AT THE SILVER BOW FACILITY MAY PRESENT AN IMMINENT AND SUBSTANTIAL ENDANGER- MENT TO HUMAN HEALTH AND THE ENVIRONMENT. AT AN INSPECTION ON 5/1-4/2000, EPA OBSERVED AT 100' DIAMETER, OPEN-TOPPED INGROUND TANK CONTAINING APPROXIMATELY 500,000 GALLONS OF SLUDGE AND A CAP OF SEVERAL FEET OF WATER. RESPONDENTS STATED THAT THE SLUDGE IS A PHOSPHOROUS SLUDGE AND THE WATER CAP IS USED TO PREVENT THE SLUDGE FROM CONTACTING AIR. PHOSPHORUS, WHEN COMBINED WITH WATER, REACTS TO FORM PHOSPHINE GAS, WHICH CAN BE A SEVERE HEALTH HAZARD WHEN INHALED. PHOSPHINE IS ALSO CONSIDERED HIGHLY FLAMMABLE AND MAY SPONTANEOUSLY COMBUST IN THE AIR.