Information compiled from State of Delaware Preassessment Screen Report (10/25/89) Prepared by Diane E. Wehner, DNREC, Division of Air & Waste Management, CERCLA Management Branch, New Castle, Delaware
Brief Summary of Spill Event
On Saturday, June 24, 1989, the Presidente Rivera, a 749 foot Uruguayan tanker, ran aground in the Delaware River on Claymont Shoal, near Naamans Creek. The ship was carrying 18 million gallons of No. 6 fuel oil and was preparing to dock at the Sun Oil Company refinery in Marcus Hook, Pennsylvania. The grounding resulted in the opening of four if its 17 cargo tanks, releasing approximately 306,000 gallons of oil. The tanker was refloated on Sunday, June 25, 1989, and was taken to the Sun Oil Company refinery where the remainder of its cargo was unloaded.
The DNREC 1989 Preassessment Screen Report on the spill reports that 22 miles of riverine and estuarine shoreline was impacted by the oil. The most heavily oiled areas in the Delaware River were immediately south of the Port of Wilmington for a distance of approximately three miles. The oil was observed as far south as New Castle, Delaware. The No. 6 fuel oil spilled by the Presidente Rivera was a highly viscous oil, and formed a thick coating upon contact with the shoreline. The oil tended to stick together in globs rather than form extensive slicks. Vegetation along 22 miles of Delaware River and Bay shoreline were impacted in widths of 5-20 feet, with the heaviest floating oil concentrations observed in the area of the Christina River and New Castle, Delaware. Along impacted shoreline areas huge clumps of oil, some ten feet in diameter, were observed, and some of the oil clumps were embedded in the sediments.
Response and Clean-up Activities
Initial response efforts involved the placement of sorbent boom around the leaking tanker and across tributaries to the Delaware River, Christina River, Naamans Creek and Shellpot Creek. In addition, booms were strategically placed to help reduce impacts to sensitive riverbank areas and Pea Patch Island.
Clean-up efforts were complicated by the tar-like nature of the material spilled. Because the pour-point of the No. 6 fuel oil is 95 degrees farenheit and the sub-surface bay water temperature was approximately 65 degrees farenheit, the oil did not flow or spread readily on the water surface or disperse as small droplets. Rather, the oil was persistent as large masses in the water column, surfacing as “tar balls”. Clean-up crews combed shorelines, using pitchforks, rakes and shovels to remove the “tar balls” that had washed ashore. Floating material was recovered by skimmer vessels, clam shell dredge and by had with small boats.
Clean-up of the shoreline, wetland areas, and riprap was also performed using a snare technique. The snare was reported to be moderately effective in wetlands, but to avoid additional impacts to wetland vegetation, work crews were instructed to avoid traversing wetlands with equipment or on foot, and cutting wetland vegetation was not allowed. High pressure washing of boat ramps and other man-made structures was also performed.