A.66 Shiawassee River, MI

A.66.1 :

Shiawassee River Superfund Site, Howell, Michigan

A.66.2 Contacts

Regulatory Contact: Michigan DEQ & USEPA

Site Contacts: Daria Devantier, Michigan DEQ and James Hannenberg, USEPA Region 5

A.66.3 Summary

Environment:	Plant site on the Shiawassee River
Scale:	Limited removal to facilitate MNR
Contaminants of Concern:	PCB oils
Source Control Achieved Prior to Remedy Selection?	Original remedy: Limited removal at the plant site, subsequently determined high level of PCB in the sediments and fish of the Shiawassee River.
Final Remedy:	Removal and MNR. Hot spot removal and limited excavation; used reduced concentrations using SWAC to justify the decision. Long term monitoring to assess whether reductions are occurring.
Expected Recovery Time:	To be determined (concentrations currently increasing and results ambiguous)
MNR viewed as a success?	No. Poor design, poor characterization. And inappropriate use of the SWAC method appears to be problems at this site. Successive sampling by USEPA after the removal in pre-designated areas have found increasing concentrations of PCB. State of Michigan investigation after the removal found higher levels of PCB in areas not addressed by the removal. Greater areal extent, as well as concentration, were verified overall in the river after the removal had been completed. The limited design assumptions and removal are therefore being questioned. Monitoring of residual contamination and assessment of sediment rates are ongoing.

A.66.4 Site Description

Since 1969, the Cast Forge Company (CFC) and now Western Wheel have manufactured aluminum cast products in Howell, Michigan, at the CFC facility. Until 1973, wastewater contaminated by hydraulic fluids containing polychlorinated biphenyls (PCBs) was discharged by the potentially responsible parties to the South Branch of the Shiawassee River. From 1973 to 1977, wastewater was discharged into a 400,000 gallon on-site lagoon. Discharges from this lagoon as well as periodic overflows have contaminated nearby wetlands and, subsequently, the Shiawassee River. In 1978 and 1979, the state detected high levels of PCBs in soils around the site and in on-site monitoring wells. Concentrations above one part per million (ppm) were found in Shiawassee River sediments fourteen miles downstream of the plant.

The United States Environmental Protection Agency (EPA) proposed the site for the National Priorities List (NPL) in December 1982 and finalized the site on the NPL in September 1983.

A removal action, very strategically designed with the intent of reducing the concentration of PCB in the river to levels that would “eventually” allow the river to naturally recover was the basis for the removal action that was undertaken on a segment of this river.

There were serious questions about the characterization, statistical manipulation of the characterization data to calculate the removal quantities, and the collection and analyses of data to determine whether the limits of excavation were appropriate when the removal action was ongoing. Confirmation data was also questionable when the removal action moved from one segment of the river to the next.

A more thorough analyses and sampling of the river was conducted after the removal in order to evaluate the potential for the removal action to be successful. This led to the discovery of much greater concentrations of PCB and confirmed a more extensive problem when post removal data were interpreted.

Subsequent monitoring of the effectiveness of the removal indicates that natural recovery is not working. In fact, levels appear to be increasing and trends are up. This evaluation process however is ongoing and USEPA has indicated that the removal “may” not have been effective enough to assure natural recovery.

Concentrations of PCB in the Shiawassee River sediment were found to require removal due to fish tissue studies. Natural recovery was postulated as a remedy if selected “hot spots” were removed in order to reduce the influx to the river.

Subsequent independent sampling after the removal uncovered more extensive contamination and far greater concentrations in hot spots than the RI based design and statistical evaluation anticipated.

Post excavation monitoring by USEPA has caused them to acknowledge the success of this remedy is currently questionable. A few more rounds of sampling are anticipated necessary before the agency will further evaluate the meaning of the “currently” increasing trends and the redistribution of PCB contaminant in sediments.

The State of Michigan has authorized this site as a potential case study.

The primary source of contamination at this site was on-site loss of PCB oils and the discharge of PCB oil contaminated waste to the treatment lagoons. Overflow and loss of lagoon contents directly to the Shiawassee River were the primary contamination mechanism.

In November 1977, the State filed suit against Cast Forge for PCB-contamination of the environment. The case was settled through a consent judgment in June 1981. Under that settlement, the company removed the lagoon, cleaned up PCB-contaminated soil and sediment from its property, and provided $750,000 for restoration of the Shiawassee River. Dredging of the South Branch of the Shiawassee River began in June 1982. Only the first mile downstream from the plant was vacuumed, removing approximately 2,600 pounds of PCBs, before the funding was exhausted. Both the site property and river still contain PCBs.

The State began a Remedial Investigation and Feasibility Study (RI/FS) in September 1986. Field sampling activities were started in October 1987 and completed in November 1989. 

The RI report was finalized in January 1992. The FS report, which evaluated various cleanup alternatives, was submitted in December 1997, and a proposed cleanup plan was released to the public in August 1998. Because the data used to develop cost estimates were obtained as long ago as 1986, it was determined that additional data should be obtained to develop more accurate cost estimates for the site. 

Additional sampling of the site began in November 1999 and was completed in April 2000. These sample data were released to the public in a data evaluation report in May 2000. The supplemental FS report was released in early 2001, and USEPA issued a Record of Decision (ROD) on September 28, 2001. The ROD selected the floodplain and contaminated areas near the Cast Forge facility to be remediated to less than 10 ppm PCBs. The river was to be remediated to less than 5 ppm PCBs for the first mile downstream of the facility. Remediation was completed in 2005, meeting all ROD requirements.

USEPA issued the First Five-Year Review Report for the site on August 27, 2009. The review concluded that the remedy is protective of human health in the short term, as exposure pathways that could result in unacceptable risks to humans are currently being controlled. However, in order for the remedy to be protective in the long term, comprehensive monitoring data needs to show that PCB concentrations are decreasing in accordance with the expectations described in the 2001 ROD. The five-year review concluded that additional comprehensive sampling is needed to determine whether the remedy is functioning as intended; comprehensive monitoring is scheduled for 2012 as indicated in the 2001 ROD. Finally, USEPA and the state may evaluate the effectiveness of existing fish advisories.

CSM summary: The Shiawassee River was contaminated by losses of PCB oils directly into the river and through dissolved and waste lagoon discharges. The PCB oils attached to sediments and particulates as well as organics. Once entrained in the river system, they settled with the particles and were bio available in the upper portions of the sediment column. Fish and aquatic organisms became contaminated with PCB, and levels were sufficient to warrant fishing advisories for the river. The wastes are continuously redistributed due to the annual fluctuations in flood stage and fluvial geomorphologyStudy of the evolution and configuration of landforms. dynamics.

A.66.5 Remedial Objectives

The risks posed at the site are to human health through direct contact in some areas and human health and environmental damage through bioaccumulationThe accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost. Thus, the longer the biological half-life of the substance the greater the risk of chronic poisoning, even if environmental levels of the toxin are not very high. of PCB in fish and aquatic life.

RAO(s)/Project objectives: The remedial action objective is to protect human health and the environment from imminent and substantial endangerment due to PCBs attributed to the site. To achieve this remediationThe act or process of abating, cleaning up, containing, or removing a substance (usually hazardous or infectious) from an environment. objective, the ROD called for PCB-contaminated sediment above 5 mg/kg to be removed so that the five-mile reach of the river beginning at M-59 would reach an average PCB sediment concentration of approximately 1 mg/kg (which is equivalent to 1 ppm) immediately after active remediation; the ROD then called for monitored natural recovery over time to achieve the long-term preliminary remediation goals (PRGs). The long-term PCB PRG range for the Shiawassee River sediment, 0.003 to 0.2 mg/kg, is based on protecting mink through dietary consumption of fish. The ROD estimated that it would take 18 years and 7 years, respectively, to attain these long-term goals by natural recovery processes.

A.66.6 Remedial Approach

Final selected remedy: The remedy selected in the 2001 ROD required excavation and off-site disposal of PCB contaminated soils and river and floodplain sediments, and that institutional controlsNon-engineered instruments, such as administrative and legal controls, that help minimize the potential for human exposure to contamination and/or protect the integrity of the remedy. be placed on the CFC property to ensure that it remained zoned for industrial use. Therefore, the following actions were taken from November 1, 2004 to August 15, 2005:

• Excavation of 154 yd³ of PCB-contaminated soils at CFC and disposal off-site.
• Excavation and off-site disposal of 160 yd³ of PCB contaminated floodplain soil at four different locations.
• Removal and off-site disposal of 50 yd³ of PCB-contaminated river sediments.

A total of 364 yd³ of PCB contaminated sediments and soils were excavated.

Removal of contaminated sediments and the volume calculated to excavate were based on SWAC estimates.

Why the remedy was selected: The remedy was selected based upon unacceptable risk to human health and the environment. Multiple completed risk based pathways were confirmed for a multitude of on-site and off-site contaminants. Bioaccumulation of DDT and ongoing losses from the site that included a number of highly toxic aquatic contaminants caused the selection of containment and sediment removal to alleviate exposure threats.

Primary lines of evidencePieces of evidence are organized to show relationships among multiple hypotheses or complex interactions among agent, events, or processes. A weight of evidence approach includes the assignment of a numeric weight to each line of evidence. used to investigate MNR: MNR will take some time to determine whether it is working. Preliminary data do not indicate the removal was successful. Higher concentrations were found in sediment than prior to the excavation.

Expected recovery time: The long-term PCB PRG range for the Shiawassee River sediment, 0.003 to 0.2 mg/kg, is based on protecting mink through dietary consumption of fish. The ROD estimated that it would take 18 years and 7 years, respectively, to attain these long-term goals by natural recovery processes. These estimates were based upon characterization data that may not properly present the volume of contaminant. This dynamic needs further evaluation.

A.66.7 Monitoring

Following completion of the remedial action construction activities in 2005, annual monitoring was conducted in August 2006, July 2007, and August 2008, with each sampling event consisting of 30 samples of PCB contaminated river sediments. These results are presented in a report by ENTACT LLC, entitled Sediment Summary Report for the Shiawassee River Superfund Site, prepared for Johnson Controls, Inc., May 26, 2009 (ENTACT Report). Additionally MDEQ completed sampling and analysis in 2006 and early 2007, with the results presented in a report by Gannett Fleming (for Michigan Department of Environmental Quality, Remediation and Redevelopment Division), entitled Technical Memorandum for the Fourth Phase of the Remedial Investigation Activities at the South Branch of the Shiawassee River, Howell, Michigan, and dated December 2008 (MDEQ Report). The data collected to-date are further discussed below.

Monitoring elements:

Annual monitoring is currently planned to be conducted on an annual basis, with a comprehensive monitoring event currently scheduled for 2012. Monitoring requirements after 2012 will be determined after evaluating the data from the comprehensive monitoring event.

RAOs/project objectives achieved?

Too soon to evaluate, but preliminary data would indicate there may be a problem since data collected after the removal found higher contamination in areas of the river than was considered by the designed removal. Characterization and design assumptions should therefore be questioned and evaluated. The assumptions and spatial variation of samples used to generate the SWAC estimates for removal volumes were also questionable.

Publication Date: August 2014