﻿Purpose
The U.S. Environmental Protection Agency (EPA) Region 4 is proposing the partial deletion of the Macalloy Corporation Superfund Site (the "Site") from the National Priorities List (NPL). The EPA ID for the Site is SCD003360476. The Site has a total acreage of 140 acres while the partial deletion will address 134 acres. Figure 1 shows the 140-acre Site. Figures 2-A and 2-B show the 6 acres that will remain on the NPL. A Notice of Intent to Partially Delete (NOIPD, the proposed rule-making) is expected to be published in the Federal Register in the near future. This document provides justification for the partial deletion. Other documents which provide support for the partial deletion are located in the deletion dockets in the information repositories that will be noted in the proposed rule-making.

Partial deletion from the NPL does not itself create, alter, or revoke any individual's rights or obligations. Partial deletion from the NPL does not in any way alter the EPA's right to take enforcement actions, as appropriate. The NPL is designed primarily for informational purposes and to assist the EPA's management. Section 300.425(e)(3) of the NCP states that partial deletion from the NPL does not preclude eligibility for future response actions, should future conditions warrant such actions.

Determination that the Site Meets the Criteria for Deletion
The EPA has consulted with the South Carolina Department of Health and Environmental Control (SCDHEC) on this proposed partial deletion of the Macalloy Corporation Site from the NPL. For the 134 acres of the Site being considered for deletion, the EPA has determined that the response actions taken are protective of public health and the environment and, therefore, taking of additional remedial measures is not appropriate.  

For the 134 acres being proposed for partial deletion from the NPL:

the implemented remedies achieve the degree of cleanup or protection specified in the 2002 Record of Decision (2002 ROD);

all selected removal and remedial action objectives and associated cleanup goals are consistent with agency policy and guidance. The proposed partial deletion meets the completion requirements as specified in OSWER Directive 9320.2-22, Close Out Procedures for National Priority List Sites; and,

all response activities are complete, with no unacceptable risk to human health or the environment remaining. Therefore, the EPA and SCDHEC have determined that no further response is necessary.

State and Agency Concurrence
EPA requested concurrence from the SCDHEC to partially delete the Site from the NPL in a letter dated May 13, 2020. SCDHEC issued a concurrence letter on May 18, 2020. The EPA's Headquarters concurred on the Notice of Intent to Partially Delete proposed rule-making, for the Macalloy Corporation Superfund Site, on (date of NOIPD concurrence memo).  
Community Involvement
Public participation activities have been satisfied as required in CERCLA Section 113(k), 42 U.S.C. 9613(k) and CERCLA Section 117, 42 U.S.C. 9617. During the development and implementation of the remedy for the Site, comment periods were offered for the proposed plan, the five-year review, and the EPA conducted public meetings. The documents that the EPA relied on for the partial deletion of 134 acres from the Macalloy Corporation Superfund Site are in the docket and are available to the public in the information repositories. A notice of availability of the Notice of Intent for Partial Deletion will be published in The Post and Courier of Charleston, South Carolina, to satisfy public participation procedures required by 40 CFR 300.425 (e) (4).

The State of South Carolina is supportive of this partial deletion of 134 acres from the Macalloy Corporation Superfund Site.  The State signed a letter of concurrence on May 18, 2020. 

Site Background and History
The Site, located at 1800 Pittsburgh Avenue in North Charleston, Charleston County, South Carolina is situated on 140 acres fronting Shipyard Creek within the Charleston Peninsula which is formed by the Ashley and Cooper Rivers. Shipyard Creek is a tributary of the Cooper River. The Site is directly adjacent to a tidal creek and marsh along Shipyard Creek. See Figure 1.

The Site was proposed for inclusion on the National Priorities List (NPL) on October 22, 1999 (64 FR 56992), then finalized on the NPL on February 4, 2000 (65 FR 5435).

Ferrochromium alloy was manufactured at the Site by the Macalloy Corporation from 1941 to 1998. The manufacturing process at the time operations ceased 1998 involved the conversion of chromium-bearing ore (chromite) to ferrochromium in a single submerged arc electric furnace. The alloy was then shipped off-site for production of high-quality stainless steel. A second furnace on the property had been out of use for several years when manufacturing ceased in 1998. During operation, smelting was conducted in both submerged and open arc furnaces. Open arc (low carbon) furnaces were operated from approximately 1946 to 1967. Submerged arc furnaces were used in subsequent years. Manufacturing and handling operations resulted in the release of hazardous substances to soil, shallow groundwater, storm water, and sediment in the tidal creek. The primary contaminant of concern was hexavalent chromium in soil and groundwater. Other environmental concerns included metals in storm water and sediment. 

During its final years of operation, the plant was regulated by several federal environmental statutes, primarily the Clean Water Act, the Clean Air Act, and the Resource Conservation and
Recovery Act (RCRA). In 1992, the SCDHEC Bureau of Water Pollution Control issued Administrative Order 92-64-W requiring the Macalloy Corporation to remediate contaminated groundwater on the Macalloy property. Pursuant to this order, a groundwater remediation system was installed in 1994-1995 in the area of the unlined surface impoundment. In 1996, Macalloy began the RCRA corrective action process. In January 1997, pursuant to the terms of a consent order with the SCDHEC (No. 96-38-HW), Macalloy initiated off-site disposal of treated ESP dust from the unlined surface impoundment. 
Macalloy also initiated a removal action in June 1998 under a CERCLA consent order with EPA to implement a surface water management system to mitigate transport of contaminants to Shipyard Creek while a final site remedy was being developed.

Under a second CERCLA consent order with EPA, Macalloy Corporation conducted a comprehensive Remedial Investigation/Feasibility Study (RI/FS) from 2000-2002. Based on the RI/FS findings, EPA issued a Record of Decision for the Site on August 21, 2002 (2002 ROD).

Shipyard Creek Associates (SCA) acquired the Site in March 2007 as a bona fide prospective purchaser. 

The RI/FS, Remedial Action Objectives, Selected Remedies, Cleanup Standards, and Operation and Maintenance activities for are discussed below.

Remedial Investigations and Feasibility Study (RI/FS)
In December 2000, the first phase of the RI was completed by Macalloy with oversight by EPA and SCDHEC. The primary focus of Phase I was to assess the nature and extent of soil and groundwater contamination on the Macalloy property and to evaluate the risk to human health and the environment from site media. The Final Phase I RI Report was approved by EPA on May 17, 2001. Several data gaps were identified in the Phase I RI that needed to be filled before an FS could begin. Therefore, a second phase of the RI was conducted in June 2001, primarily to assess risk to human and ecological receptors from potential contamination in Shipyard Creek. The Final Phase II RI Report was approved by EPA on March 21, 2002. Through the RI, it was determined that approximately 60,000 cubic yards of site soil was determined to be impacted by hexavalent chromium. Soil impacted by hexavalent chromium was observed from the ground surface to approximately 15 to 20 feet below ground surface (bgs) and determined to be concentrated in and around the Marsh Lake Fill Area, the former furnace buildings, the former concentrator area, and other isolated locations across the Site. These areas were filled with material from plant operations, including raw materials, slag, sludge, and treated and untreated dust from air pollution control equipment. An additional 55,000 cubic yards of on-site material used as berm material for surface impoundments also contained elevated concentrations of hexavalent chromium.

Approximately 110 cubic yards of soil and debris with gamma radiation levels greater than background levels were identified near the former concentrator area. The radionuclides detected were radium-226, thorium-232, potassium-40, and uranium-235. This material is believed to have been brought to the Site in railcars carrying feedstock for alloy production. The average depth of the radiological debris was determined to be 18 inches.

Five plumes of groundwater contaminated with hexavalent chromium were identified at the Site during the RI. The largest of the plumes, Plume I extended approximately from the former USI to Shipyard Creek. Hexavalent chromium concentrations of 10,000 micrograms per liter (u/L) were measured in Plume I. Plumes II, III, and IV were smaller in size and located immediately adjacent to the eastern edge of Plume I. Plume V was identified at the plant's former concentrator area. Data collected during the RI, indicated that impacted groundwater at each of the plumes was confined to the shallow aquifer and did not penetrate a clay confining layer that exists across the Site, at approximately 20 feet below ground surface.

Surface water samples associated with the Site's storm water management system exceeded the hexavalent chromium limit at several sampling locations. Other metals including arsenic, copper, lead, and zinc were identified as being a concern due to off-site discharge to Shipyard Creek.

As part of the RI/FS, a Baseline Risk Assessment (BRA) was conducted to evaluate current and potential effects of contaminants to human health and the environment. Human health exposure pathways evaluated included ingestion, inhalation, and dermal contact with surface soils and groundwater, and ingestion of shellfish from Shipyard Creek. The EPA based its assessment on an expected future industrial land use exposure scenario for an on-site worker. Groundwater ingestion was not determined to be a likely exposure pathway at the Site, since shallow groundwater is not currently used for consumption, nor will it likely be in the future. Nonetheless, shallow groundwater beneath the Site was conservatively assumed to be a source of drinking water because South Carolina classifies all groundwater as a potential underground source of drinking water.

Remedial Action Objectives
Based on the RI/FS findings, the 2002 ROD set forth the seven remedial action objectives (RAOs) shown below, based on future commercial/industrial land use and restoration of the groundwater for beneficial use. 

Soils
      Remediate soil that leaches hexavalent chromium to groundwater and surface water at concentrations hazardous to human health and the environment; and,
      Remediate soil and debris that produce elevated levels of gamma radiation to mitigate current exposure pathways.

Storm Water/Surface Water
       Mitigate off-site hexavalent chromium discharges in storm water to Shipyard Creek through a combination of multi-media remediation measures and a comprehensive site-wide storm water management plan; and,
      Manage storm water discharges of toxic inorganic compounds in accordance with the comprehensive storm water management plan to protect ambient saltwater  quality in Shipyard Creek.

Sediment
      Mitigate the exposure of benthic organisms to contaminated sediments in the tidal creek.

Groundwater
      Prevent future Site worker exposure to unacceptable hazard levels in groundwater; and,
      Remediate shallow groundwater zones exhibiting the highest concentrations of hexavalent chromium and limit its migration to Shipyard Creek to minimize long-term threats.

In addition to achieving RAOs and mitigating all unacceptable risk to human health and
the environment, the NCP requires the attainment of all Applicable, Relevant and
Appropriate Requirements (ARARs) which were also listed in the 2002 ROD.

Selected Remedies
To accomplish these RAOs, the following remedial components were specified in the 2002 Record of Decision (2002 ROD):

Soil: on-site chemical reduction and stabilization/solidification via ex situ treatment with mechanical mixing;
Groundwater: enhanced in-situ chemical reduction via injection and trenching.
Radiological Material: excavation with off-site disposal;
Sediment: removal, upland disposal, installation of an engineered fabric/sand cap, and restoration of the tidal creek designated as Zone A; and monitoring of that part of Shipyard Creek which was designated as Zone C. 
Surface Water/Storm Water: Comprehensive storm water management system;
Multi-media: Institutional controls and restrictive covenants to limit land use to commercial/industrial purposes, and prohibit the use of groundwater underlying the property;
Infrastructure: Decommission and demolish all site-wide buildings and infrastructure.
Cleanup Levels
The following table includes the cleanup levels established in the 2002 ROD. The EPA based its cleanup goals on an expected future industrial land use exposure scenario for an on-site worker.
Media
Chemical of Concern
Cleanup Level
Basis of Cleanup Level
Soil
Chromium (VI)
23 mg/kg
Calculated using leachability ratios and groundwater MCL
Debris
Gamma radiation
12 micro-Roentgens/hour
2 times background
Groundwater
Chromium (IV)
100 μg/L
ARAR compliance (MCL)
Sediment
Total chromium
219 to 258 mg/kg
Appendix A of 2002 ROD

Nickel
33 to 35.7 mg/kg
Appendix A of 2002 ROD

Zinc
132 to 163 mg/kg
Appendix A of 2002 ROD
Storm Water
Flow
Report
ARAR compliance (Clean Water Act)

Lead
220 μg/L
ARAR compliance (Clean Water Act, Ambient Saltwater Criteria)

Arsenic
69 μg/L
ARAR compliance (Clean Water Act, Ambient Saltwater Criteria)

Chromium (IV)
1,100 μg/L
ARAR compliance (Clean Water Act, Ambient Saltwater Criteria)

Copper
5.8 μg/L
ARAR compliance (Clean Water Act, Ambient Saltwater Criteria)

Zinc
9.5 μg/L
ARAR compliance (Clean Water Act), Ambient Saltwater Criteria)

Acute Whole Effluent Toxicity
Report
ARAR compliance (Clean Water Act)
Notes:mg/kg: milligrams per kilogram
micro-Roentgens/hour: micro-Roentgens per hour
      μg/L: micrograms per liter

Response Actions
Following the Remedial Design, a Consent Decree (CD) was negotiated with the Macalloy Potentially Responsible Parties Group (MPG) for Remedial Action (RA). The CD was entered in federal court on June 14, 2004. Under the terms of the CD, MPG initiated the RA on October 11, 2004. As described below, MPG took site-wide and comprehensive remedial action to address all the RAOs listed in the 2002 ROD. The Remedial Action Report was finalized in September 2006, while the Construction Completion (CC) target for the Site was also achieved in September 2006 when EPA finalized the Preliminary Close Out Report for the Site on September 26, 2006. 

Soils
Remediate soil that leaches hexavalent chromium to groundwater and surface water at concentrations hazardous to human health and the environment.

To meet this RAO, the 2002 ROD specified a hexavalent chromium concentration in soil of 23 milligrams per kilogram (mg/kg). The soil cleanup was achieved through on-site chemical reduction and stabilization/solidification via ex situ treatment with mechanical mixing. Approximately 194,000 cubic yards of soil over 14 acres was excavated up to 20 feet below ground surface, placed in 500 cubic yard stockpiles, mixed with 3% liquid calcium polysulfide, then placed back in the remediation zone once analysis indicated the cleanup level had been achieved. After the excavation/treatment phase was complete, six inches of clean fill was placed on the treated soil footprint. The surface soil concentrations remaining post-cleanup do not pose an unacceptable risk for future commercial/industrial use. 


Remediate soil and debris that produce elevated levels of gamma radiation to
mitigate current exposure pathways.

To meet this RAO, the 2002 ROD specified a radiation level of 12 micro-Roentgens per hour (twice the site-specific background level). The soil/debris radiation RAO was achieved by excavating approximately 200 tons of material from the southwest portion of the Site and transporting it off-site for appropriate disposal.

Storm Water/Surface Water
Mitigate off-site hexavalent chromium discharges in storm water to Shipyard Creek through a combination of multi-media remediation measures and a comprehensive site-wide storm water management plan.
Manage storm water discharges of toxic inorganic compounds in accordance with the comprehensive storm water management plan to protect ambient saltwater quality in Shipyard Creek.

To meet these two RAOs, the 2002 ROD specified a remedy for storm water/surface water focused on mitigating pollutant discharge into Shipyard Creek. This was achieved by construction of a storm water management system that met the requirements of the South Carolina Storm Water Management and Sediment Reduction Act of 1991 (location-specific ARAR). The selected storm water remedy, in conjunction with the selected soil and groundwater remedies, was developed to meet hexavalent chromium cleanup goals in storm water discharges to Shipyard Creek, and to control sediment (total suspended solids) in discharge water, thereby reducing concentrations of arsenic, copper, lead, zinc and other metals in storm water discharge. Key elements included detention basins and conveyances to reduce suspended sediment concentrations; modern peak flow designs; a consolidated outfall; regraded topography; site topography designed for no runoff from off-site watersheds; and sealed underground pipe sections and migration barriers to minimize potential groundwater infiltration and preferential groundwater flow along pipes. Subsequent to the 2004-06 Remedial Action work, EPA and DHEC approved certain modifications to this storm water design as part of the construction of the Port Access Road.

Sediment
Mitigate the exposure of benthic organisms to contaminated sediments in the tidal
creek. 

To meet this RAO, the 2002 ROD specified a remedy for Zone A of the tidal creek that involved excavation and capping to address sediment posing an unacceptable ecological risk due to contamination with chromium, nickel, and zinc. Implementation of the remedy in Zone A of the tidal creek included removal of up to 24 inches of sediment, upland on-site disposal of the sediment following treatment, installation of an engineered fabric/sand cap, and vegetation restoration. Long-term monitoring was required to determine effectiveness of the sediment remedy including annual monitoring for cap thickness, marsh revegetation survival monitoring, and sediment monitoring in Zone C in Shipyard Creek.   
Groundwater
Prevent future Site worker exposure to unacceptable hazard levels in groundwater.
Remediate shallow groundwater zones exhibiting the highest concentrations of hexavalent chromium and limit its migration to Shipyard Creek to minimize long-term threats.

During the Remedial Investigation, the Macalloy Corporation sampled a comprehensive network of monitoring wells across the Site. A deep and a shallow aquifer exist at the Site and are separated by a continuous zone of low permeability sediment at roughly 30 feet below land surface. Samples were collected from both the deep and shallow aquifers. No exceedance of any regulatory limits was found in the deep aquifer (19 samples collected across the Site). 

Chromium contamination in excess of regulatory limits was found in the shallow aquifer. Thirty-seven of 44 samples contained detectable levels of hexavalent chromium with levels ranging as high as 38,600 ug/l. Five chromium plumes were discovered. Plumes 1-4 were clustered in the northeastern portion of the Site in an area extending from the Former Lake Fill area toward Shipyard Creek and Plume 5 was near the former concentrator area. See Figure 3. 

To meet the two groundwater RAOs, the 2002 ROD specified enhanced in-situ chemical reduction to reduce the concentration of hexavalent chromium in groundwater below 100 micro-grams per liter (ug/l). In addition, the Safe Drinking Water Act Maximum Contaminant Limits (MCLs) are ARARs for this Site. The MCL for total chromium, which is the combination of hexavalent and trivalent, is 100 ug/l. 

The initial implementation of the groundwater remedy took place between November of 2004 and March of 2005. Treatment reagent (sodium dithionite/ferrous sulfate and sodium dithionite/potassium chloride) was injected into 203 wells aligned along a series of transects and designed to treat groundwater as it flowed across the transects. In some instances, wells were unable to accept the designed volume, but overall the effort was successful. Following this work, a series of redox trenches were constructed in December 2005 to access areas that had not been effectively addressed with the treatment reagents. Dry forms of the same chemicals were added in the same molar ratio as for the injection wells. Samples collected from the injection wells and redox trenches over the next year showed excellent treatment effectiveness. Following the in- situ treatment, a network of 20 permanent monitoring wells were established to evaluate the effectiveness of the remedy. This network focused on the five plumes delineated in the RI/FS. Samples were collected quarterly for the first year, then annually for the next five years. After one year of post-treatment monitoring, only seven of the 40 monitoring well locations had total chromium concentrations above 100 ug/l and all of these were in one plume (Plume #1), which is centered on MW041 and MW043.

In 2008, a supplemental action was implemented to better define the boundaries of the remaining plume and re-treat areas where necessary. This action involved installation of three new permanent monitoring wells (MW060, MW061, and MW062) and installation of seven temporary monitoring wells. Four of these temporary monitoring wells defined the western boundary of the plume which extended from MW047 to MW060. See Figure 4. In December of 2008, MPG installed four additional redox trenches with a total of 350 linear feet of trench. These redox trenches were oriented perpendicular to the groundwater flow direction and 
intercepted the contaminated groundwater. Following the completion of this supplemental action, semi-annual sampling of the monitoring network resumed. 

Beginning in 2016, additional work was performed at the Site. This work included the replacement of MW061 and installation of additional temporary wells (IW09-01 to IW-0910) to better define the northern boundary of the plume. The results of this investigation confirmed the continued presence of a chromium plume (mostly trivalent) in the area of MW041, MW043, MW047, MW060, MW061, IW09-04, and IW09-06. Based on this work, a supplemental injection action was implemented in 2017. The goal of this action was to establish reducing conditions in the aquifer around MW043 and IW09-06 where significant concentrations of hexavalent chromium remained. At MW043, reducing agent calcium polysulfide (CPS) was injected at 28 points within the 5,000 square foot treatment area. At IW-09-06, two rounds of CPS injections in March and June resulted in 53 injection points over an 8,100 square foot treatment area. 

Operation and Maintenance (O&M)
As documented in the 2010 and 2015 Five Year Review Reports, O&M activities have continued at the Site after the construction activities were completed. 

Long-term monitoring was required to determine effectiveness of the sediment remedy in Zone A of the tidal creek, including annual monitoring for cap thickness, marsh revegetation survival monitoring in Zone A of the tidal creek, in addition to sediment monitoring in Zone C in Shipyard Creek. Cap thickness measurements were collected annually at 100-foot intervals along the centerline of the tidal creek. Measurements were collected by manually pushing a rod through the sand cap to the underlying geotextile barrier. The results were presented in annual monitoring reports until the first Five Year Review was performed in 2010. There have been no costs associated with Operation & Maintenance over the last five years. Any future costs will pertain to groundwater monitoring of the 6-acre area of the Site that will remain on the NPL, and where the groundwater cleanup goal has not been met for total chromium.  

Institutional controls are in place for the Site, with restrictive covenants in place that limit future use to commercial/industrial purposes and prohibit the use of groundwater underlying the property. These covenants were finalized in May 2006 and have been officially recorded with the Charleston County Register of Deeds.

Five-Year Review
Pursuant to CERCLA section 121(c) and the National Contingency Plan, statutory Five-Year Reviews will be conducted at the Site until the groundwater cleanup goal for total chromium has been met in the 6-acre area of the Site that will remain on the NPL. The EPA plans to complete the Third Five-Year Review for the Site before September 16, 2020.

