DIAMOND STATE SALVAGE
WILMINGTON, NEW CASTLE COUNTY, DELAWARE
The U.S. Environmental Protection Agency (EPA) Region III requested the Agency for Toxic Substances and Disease Registry (ATSDR) to evaluate the health implications associated with exposure to contaminated (e.g., metal, polychlorinated biphenyls [PCBs]) sediments in Brandywine Creek. Specifically, EPA would like to know if a sediment removal action would be protective of human health.
Brandywine Creek is located in New Castle County, Wilmington, Delaware. Diamond State Salvage Site, a 4.5 acre inactive site located on the northeast bank of Brandywine Creek, is believed to be the source of Brandywine Creek sediment contamination. The site is fenced, but, the fence has holes in it that allows easy access. From 1942 until 1992, the site was used as a scrap metal recovery facility. Operations consisted of cutting various items into sections (e.g., appliances, automobiles, empty tanks, drums), and shipping the copper, iron, brass, and lead from these items to different buyers.
The southeastern border of the site is a mixture of vacant lots, buildings and small scale industries . About 1,469 residents live within 1/4 mile of the site.
Surface water from the site flows down gradient and empties into Brandywine Creek. Marsh wetlands are located along the creek. The Brandywine Creek flows in a south to southeastern direction to Christina River about 1.4 miles away. Christina River eventually flows into the Delaware River about 3.2 miles away from the site. Both rivers are used for recreation and fishing .
EPA contracted with the Delaware Natural Resource and Environmental Conservation (DNREC) Site Investigation Restoration Branch to investigate the magnitude and extent of sediment contamination in Brandywine Creek . In 1996, a Remedial Investigation of sediment and surface water was conducted using field screening methodology . The results revealed the presence of PCBs , lead, copper, mercury, and zinc in areas near the site. Four sediment samples were collected from along each transect across the creek at a depth of 3 - 4 inches. The transects were located at approximately 200 foot intervals beginning about 1,000 feet downstream of the site to about 500 feet upstream of the site .
The sediment samples were analyzed for PCBs, polyaromatic hydrocarbons (PAHs), and various metals. Samples were chosen for PCB homolog analysis on the basis of an immunoassay screening analysis. A total of 40 samples were screened, and 12 samples showing positive results using the screening analysis were further analyzed. The results of homolog analysis for the 12 sediment samples showed PCBs at concentrations ranging from 0.011 to 0.370 parts per million (ppm). The average for the 12 samples was 0.15 ppm.
If the assumption can be made that the screened sample set represent the area of the Brandywine Creek sampled, then the 95% UCL estimate of the mean for the area based on the 12 samples is 0.213 ppm. Given that 28 of the 40 samples did not pass the screening analysis test, it is likely that the true mean PCB concentration for this part of Brandywine Creek is well below 0.213 ppm. For example, if the reported detection limit for the screening method (0.0125 ppm) is used for the 28 remaining samples, then the average for this area of Brandywine Creek is 0.054 with a 95% UCL estimate of mean of 0.081 ppm.
Most of the PAHs analyzed in sediment samples were not detected. The remainder was reported at estimated values. The various metals that were detected in the sediment samples were below their respective background levels for natural soils.