UNION PACIFIC TANKER CAR WAS FOUND TO BE LEAKING PERCHLOROETHYLENE (PCE) ONTO THE GROUND. WHEN MOVED TO TO A TURNTABLE IN ORDER TO CONTAIN THE CHEMICAL SPILL UNTIL CONTAINERS COULD BE LOCATED, THE SUMP IN THE TURNTABLE WAS CONNECTED TO THE CHEYENNE BOARD OF UTILITIES-CROW CREEK POTW. THE PCE DISCHARGED TO THE POTW IMPAIRED THE EFFICIENCY OF THE POTW'S WASTEWATER TREATMENT UNITS AND CAUSED THE BIOLOGICAL MASS TO SLOUGH OFF THE ROCK MEDIA OF THE TRICKLING FILTERS, RESULTING IN PASS THROUGH AND INTERFERENCE AT THE POTW.