Between 0900 and 1100 on june 12, 1986, an overflow valve on processing tanks at the general chemical…

Original warning text

General Chemical Corporation; Claymont, Delaware.
Claymont, Delaware.
1. Between 0900 and 1100 on June 12, 1986, an overflow valve on processing tanks at the General Chemical Corporation failed, releasing 12,900 pounds of ammonium sulfite and 11,000 pounds of ammonium bisulfite into the plant water system, which discharges processing effluent into the Delaware River, just north of the Christiana River, approximately 10 miles downstream from Philadelphia. These chemicals were intermediate reducing agents and were being used to make ammonium thiosulfate used in photo processing. The plant had a National Pollution Discharge Elimination System (NPDES) permit, which requires routine composite sampling of discharge water each month; coincidentally, the monthly sampling occurred within 24 hours of the accidental release. Sample results indicated contamination levels of 19.75 ppm, significantly higher than the permit discharge level for both chemicals in composite [...]
2. COMMODITY: AMMONIUM SULFITE, AMMONIUM BISULFITE. MAXIMUM POTENTIAL RELEASE: 24000 GALLONS.
3. POSITION 39.788N 075.491W. NOAA INCIDENTNEWS 6368: https://incidentnews.noaa.gov/incident/6368