New Castle County, Koppers Site, DE

A.33 New Castle County, Koppers Site, DE

A.33.1 Contacts

Regulatory Contact: USEPA (Region III)

EPA ID# DED980552244

Site Contact: Matthew T. Mellon

A.33.2 Summary

Environment:	Tidal and non-tidal freshwater wetlands, tributary, and river system
Scale:	Full
Contaminants of Concern:	NAPL and TPAH
Source Control Achieved Prior to Remedy Selection?	No
Final Remedy:	Source control, excavation, and cappingTechnology which covers contaminated sediment with material to isolate the contaminants from the surrounding environment.
MNR viewed as a success?	Not applicable

A.33.3 Site Description

The entire Koppers Newport Plant is a Superfund site located in the northern part of New Castle County, Delaware, southwest of the town of Newport and northwest of the Route I-95 and route 141 interchange. The site is comprised of over 300 acres and currently consists of old field/grass and shrub uplands (approximately 163 acres), forested areas, forested wetlands, non-tidal and tidal freshwater wetlands (> 137 acres), and bald eagle foraging habitat. The tidal wetlands drain individually into Hershey Run, White Clay Creek, and the Christina River. Hershey Run drains into White Clay Creek, which then flows into the Christina River. White Clay Creek is Delaware’s only “National Wild and Scenic River.”

The site is bordered by high-speed railroad lines. Beyond the rail lines are a former municipal sewage treatment facility, an industrial property, and a residential area. The site is bordered to the east by the former DuPont Holly Run Plant and the Christina River. White Clay Creek and Hershey Run border the site to the south and west, respectively.

The primary sources of contamination at this site are creosote constituents (total PAHs), metals (not site-related), and PCBs (not site-related) present in sediment. PCBs concentrations in sediment have resulted in a fish advisory of Hershey Run marsh that has been in place since 1996. Free product (NAPL) is present in groundwater, and groundwater impacts include creosote, BTEX, PCP, Dioxins, and pesticides.

The Koppers’ Site served as a creosote wood treating operation from 1929 through 1971. Approximately 1,000,000 gallons of creosote were stored on site at any one time. The site has remained largely inactive since operations ceased in 1971.

The primary material used in the wood treatment processes was a creosote/coal tar solution, which was used to preserve railroad ties, telephone poles, and other wood products. Although to a much smaller degree, pentachlorophenol (PCP) was also used to treat wood. Throughout a large area of the site (approximately two-thirds of the operations area), an array of railroad tracks provided for the movement of wood and materials to and from the site with the primary handling occurring in the Process and Drip Track Areas.

The Process Area was used for the application of wood preservatives and contained various wood-treatment equipment and associated structures. This area also provided storage for approximately 1,000,000 gallons of creosote and other process-related materials. The treatment consisted of heating and pressurizing tanks filled with creosote and wood, forcing the creosote into the wood. After treatment, the freshly-treated wood products were temporarily allowed to cure and drip dry in the Drip Track Area prior to transfer to the Wood Storage Area. The Fire Pond was created as a source of water for firefighting purposes.

The site was identified as a potential hazardous waste site in 1979. The site was added to the NPL list on August 30, 1990, and Beazer and DuPont signed an agreement to conduct a RI/FS in 1991.

CSM summary: A human health and ecological risk assessment were completed for the site. The human health risk assessment indicated an unacceptable risk to future industrial workers from ingestion of soil from benzo(a)pyrene and cPAH but did not suggest a risk related to sediment. The ecological risk assessment suggested that sediment concentrations of 197.6 mg/kg were lethal to test organisms (benthos), and sediment concentrations of TPAH <82.3 mg/kg did not cause mortality.

The site areas of concern were determined to have both ecological and human health risks. Geographical comparison of risk indicated that ecological risk cleanup goals were protective of human health risks as well. Therefore, the cleanup goals for the site were based on ecological risk assessment conclusions (sediment: 150 mg/kg TPAH). The 150 mg/kg TPAH value for sediment and seasonally flooded soil was the rounded off geometric mean of the range of no observed adverse effect level (NOAEL) and lowest observed adverse effect level (LOAEL) values (82.8 and 197.6).

A.33.4 Remedial Objectives

RAOs/project objectives include:

Prevent current or future direct contact with contaminated sediments that would result in unacceptable levels of risk to ecological receptors by reducing levels of TPAH concentrations to below 150 mg/kg in sediment. Soil that was to be converted to wetlands required a cleanup goal of 150 mg/kg.
Prevent unacceptable human health risk due to contaminated groundwater.
Minimize the ongoing contamination of groundwater from presence of NAPL through removal and/or containment.
Maximize the area of wetlands available for various re-use options (for example, wetlands banking by Delaware Department of Transportation).

A.33.5 Remedial Approach

Final selected remedy: Complete excavation, consolidation and capping of all contaminated sediment, subsurface groundwater barrier wall around consolidation area (a) with passive NAPL recovery, excavation of NAPL-contaminated aquifer material outside of consolidation areas, re-channelization of Hershey Run, wetlands mitigation, and monitored natural attenuation of groundwater contamination.

The sediment component of the remedy was necessary to protect trespassers and ecological receptors. The remedy involved complete excavation and consolidation of the impacted sediment into an on-site landfill of contaminated sediments containing TPAH concentrations above 150 mg/kg. Areas excavated included what was known as the Fire Pond, South Pond, K Area, West Central Drainage Area, lower Hershey Run, and the marsh adjacent to the upper portion of Hershey Run. The depth of the excavation ranged from 0 to 13 ft with an average of 2 to 4 ft. Restoration activities would take place as appropriate to provide suitable ecological habitat. Only minor backfilling, if at all, would be required, thereby increasing the diversity of the wetland types.

The landfill would be located in an area of the worst NAPL contamination and would include the groundwater barrier wall and collection system to prevent further migration of the NAPL contamination. The upper portion of Hershey Run would be re-channelized to allow for installation of sheet pile and passive NAPL recovery. Any wetland acreage that was lost would be replaced on site. Approximately one and one-half miles of Hershey Run would be dredged along with approximately 4 acres of wetlands. It was estimated that a total of approximately 80,000 yd³ of stabilized sediments would be added to the consolidation area (includes a 15% increase in volume for stabilization to improve soil/sediment properties to support a capA covering over material (contaminated sediment) used to isolate the contaminants from the surrounding environment.).

This remedy was selected based on the following criteria:

addresses risk present in all site media
addresses all source areas, stopping current releases and minimizing potential for future releases
provides for maximum flexibility for future reuse options
provides for overall protection of human health and the environment
balances protectiveness and cost (is over $200 million less costly than other FS alternatives)
minimizes disturbances to surrounding community
has the support of state agencies.

Expected recovery time: NA

A.33.6 Costs

Project capital costs: $45,260,000 (includes soil and groundwater remedy costs)

Projected operation and monitoring costs: $48,155,000 (includes soil and groundwater remedy costs)

A.33.7 References

Mellon, M. 2004. Koppers (Newport, De) Superfund Site - National Remedy Review Board Presentation. USEPA (Region III). Washington, D.C.

USEPA. 1997. Ecological Risk Assessment: Koppers (Newport, DE) Site. USEPA ERT. Edison, NJ (Mark Sprenger - POC).

Publication Date: August 2014

Permission is granted to refer to or quote from this publication with the customary acknowledgment of the source (see suggested citation and disclaimer).