St. Louis, MI

A.77 St. Louis, MI

A.77.1 Contacts

Regulatory Contact: Michigan DEQ & USEPA

Site Contacts: Scott Cornelius, Michigan DEQ; Tom Alcamo, USEPA Region 5

A.77.2 Summary

Environment:	River
Scale:	Full
Contaminants of Concern:	PBB, DDT, PCBSa, pesticides, brominated compounds, rare earth/radioactive contaminants, variety of unknown designer chemicals (The list is quite large, this is a short summary.)
Source Control Achieved Prior to Remedy Selection?	Original remedy: Failed slurry wall and capA covering over material (contaminated sediment) used to isolate the contaminants from the surrounding environment.. DDT contaminated sediment removal 2007.
Final Remedy:	Proposed plan not yet completed, however, currently anticipated: On-site treatment, cappingTechnology which covers contaminated sediment with material to isolate the contaminants from the surrounding environment., groundwater pump & treat, slurry wall containment, NAPL/DNAPL removal/treatment, city water supply replacement, 97 million sediment removal (already completed). Downstream Pine River cleanup under evaluation and monitoring. (much more going on)
Expected Recovery Time:	To be determined
MNR viewed as a success?	Yes. Monitoring of residual contamination and assessment of sediment rates are ongoing.

A.77.3 Site Description

The Velsicol Chemical Superfund Site is located in the center of the City of St. Louis Michigan and the 52 acres of plant site is on the shore of a large impoundment on the Pine River that currently produces hydroelectric power for the city. The city water supply is in the regional aquifer system and the water supply wells are located adjacent to the plant site and have been determined to be in hydraulic connection with groundwater recharge from the plant site. The site extends also to the downstream contamination in the Pine River that is below the impoundment. High concentrations of DDT that are accumulating in fish and aquatic organisms need to be addressed due to the high concentrations found in the sediment for a significant distance downstream of the plant site.

The USEPA Record of Decision (ROD) for this operable unit for the Velsicol Superfund Site led to a sediment removal in the Pine River adjacent to the plant site. The Pine River runs through the City of St. Louis and there is an impoundment that forms the boundary for the limits of the excavation. The ROD found that a removal of all the DDT contaminated sediment behind the dam was necessary. Sheet piling was used to control the river while dewatering and “dry” excavation of the sediment was implemented. This was done in successive seasons and the flow of the channel successively managed while sediments were removed from the channel behind the impoundment.

The excavation process uncovered extensive non-aqueous phase liquids (NAPL) moving through the fractured till under the river prior to dewatering. This same NAPL is dense and also mobile. It is now known to have moved to a depth of 100 ft below the plant site and has been found to be present and recoverable in the permeable sand regional aquifer that supplies the cities drinking water.

The design and RI eventually found many more NAPL locations that currently, or at some point in the future have the potential to move off the plant site into the Pine River. This condition therefore has a great potential to recontaminate the river with extremely toxic DDT, other pesticides, and brominated compounds.

The sediments were successfully removed by excavation. The concentrations of bioaccumulative contaminants, DDT, and other pesticides were determined necessary to remove, other treatment options were not protective.

A NAPL collection system is currently installed under the river with a designed containment cap to separate this NAPL from further contact with the river. The NAPL is mobile, contains percentage concentrations of DDT and many other contaminants that will cause damage to the Pine River. This NAPL threatens to recontaminate the section of river already cleaned up.

The cost of the cleanup was approximately 97 million dollars. The monitoring and evaluation of the collection system is ongoing and the evaluation of the success of the excavation and long term monitoring is also currently in effect. The final design and excavation sampling results are also available for evaluation of the success of the removal process.

The primary source of contamination at this site is the 52 acres of the Velsicol Chemical Plant site located adjacent to the Pine River. Years of operational losses, dumping, and spills led to widespread DDT contaminant concentrations and a whole host of hazardous chemicals lost to the Pine River. Pathways for exposure are air born deposition in the community and extensive NAPL and DNAPL contamination that is in groundwater and hydraulic contact with the bed of the Pine River. Recoverable DNAPL is present at 100 ft below the plant site and is in contact with the regional aquifer that supplies the City of St. Louis. This same NAPL is under the river and contains extremely high levels of DDT dissolved in chlorobenzene and other chlorinated solvents.

There is a long and highly complex site history that involves State of Michigan and Velsicol Chemical Company legal agreements, USEPA involvement, bankruptcy negotiations, a failed remedy determination, and the potential for this site to be the most costly fund lead site to date for the USEPA to finance. This history is brief and cannot do justice to the complicated site history due to the number of factors involved.

The Velsicol Chemical Plant site is located adjacent to an impoundment on the Pine River in City of St. Louis, Michigan. This chemical plant site produced a variety of toxic chemicals and was a major producer of DDT and brominated fire retardant chemicals such as PBB that was introduced into feedstock for chickens and cattle. It was then introduced into Michigan’s food supply. Velsicol also produced a fungicide that causes male sterility.

The plant site had been in operation since the 1930’s and dumping of waste into the Pine River both legal and illegal occurred as long as the plant was in operation. The site was dealt with in the 1970’s by razing the plant site, hauling highly contaminated soils back to the plant site from a local illegal dump site, installation of a slurry wall between the plant site and the Pine River and a cap to prevent continued recharge of the waste from rainfall. Water levels inside the slurry wall were to be monitored and if increasing above a certain level were to be pumped out. The conditions required were not properly dealt with by the Velsicol Chemical Company; they went bankrupt and left the State of Michigan and the USEPA with a failed remedy that now appears to be one of the most costly fund lead cleanups by the USEPA to date. The USEPA Record of Decision (ROD) for this operable unit for the Velsicol Superfund site led to a 97 million dollar sediment removal in the Pine River impoundment behind the dam and adjacent to the plant site.

The Pine River runs through the City of St. Louis and the impoundment forms the boundary for the limits of the excavation. The ROD found that a removal of all the DDT contaminated sediment behind the dam was necessary. Sheet piling was used to control the river while dewatering and “dry” excavation of the sediment was implemented. This was done in successive seasons and the flow of the channel successively managed while sediments were removed from the channel behind the impoundment.

During the excavation, extensive NAPL and DNAPL problems were encountered. A seam of sand in the till unit produced over 3,000 gallons of DDT contaminated chlorobenzene and other solvents. The DDT was in percentage concentrations and this sand unit and NAPL was in hydraulic contact with groundwater and the Pine River. Many discreet NAPL/DNAPL were identified on the site during the remedial investigation. Some are known to underlie the river and others are suspected to be in hydraulic contact with groundwater that either vents to the river or finds a path to recharge the regional aquifer system. Hydraulic heads in the groundwater system are both horizontal to the Pine River and downward into the regional aquifer system.

CSM summary: The site was dealt with in the 1970’s by razing the plant site, hauling highly contaminated soils back to the plant site from a local illegal dump site, installation of a slurry wall between the plant site and the Pine River and a cap to prevent continued recharge of the waste from rainfall. Water levels inside the slurry wall were to be monitored and if increasing above a certain level were to be pumped out. Velsicol Chemical did not maintain or operate the remedy properly and the original remedy failed. The slurry wall was assumed to be keyed into a low permeability1) Characteristic of a material or membrane that allows liquids or gases to pass through it; 2) The rate of flow of a liquid or gas through a porous material. clay, when in fact it was a fractured till with sand seams and silt.

This till has been found to be chemically weathered by the solvents and did not serve as a low permeable barrier to the transport of chemicals both vertically and laterally in the groundwater system. NAPL and DNAPL have independently moved through the till fractures and sand seams both horizontally off the plant site and under the Pine River as well as downward to at least 99 ft below the plant site and directly adjacent to the Pine River. Three thousand gallons of NAPL were removed during the excavation of the sediment on top of the till when the backhoe penetrated a sand lens. This same unit continues to produce NAPL from a designed collection trench and piping that now resides below the Pine River with a clay cap over the area where the NAPL originally expressed itself. This NAPL contains percentage concentrations of DDT and, if not managed properly, has the potential to re contaminate the sediments that cost 97 million dollars to remove.

The plant site dumped chemical waste both legally and illegally into the Pine River impoundment since the 1930’s. The 52 acres of plant site had many chemical processing and production facilities that were also subject to spilling, dumping, and pipeline losses as well. Tank farms for raw product as well as final product storage were subject to continued leaks over the years of plant operation. There are several permeable units that underlie the plant site that discharge contaminated groundwater and NAPL and DNAPL DDT and other solvent dissolved phase contaminants directly to the Pine River along with recently discovered old piping that was never dealt with appropriately when the earlier slurry wall was constructed.

These conditions led to the DDT contamination behind the impoundment as well as downstream in the Pine River. Contamination in the impoundment was removed by excavation after dewatering and sheet piling to manage the Pine River flow through the area. The downstream contamination still needs to be addressed and is currently being monitored and evaluated.

The groundwater and contaminants from the site move both laterally into the Pine River and downward into the regional groundwater aquifer system that supplies the drinking water for the City of St. Louis. The hydraulic head is both down and lateral into the Pine River thus complicating the long-term remedy options for protecting the Pine River from becoming contaminated again.

A.77.4 Remedial Objectives

The risks posed at the site are to human health through a variety of exposure routes including drinking water, direct contact, inhalation, and consumption of fish from the Pine River currently contaminated with DDT. Both terrestrial and aquatic life have been found to be impacted with a variety of site specific chemicals that continue to seep into the ecosystem from the plant site.

RAO(s)/Project objectives: This section identifies the site-specific RAOs. These RAOs pertain to “general site cleanup” or are intended to fulfill potential federal and state ARARs and “to be considered “criteria (TBCs). The RAOs proposed for this site, where DDT and its breakdown products are the primary constituents of concern, are as follows:

Reduce DDT concentrations in fish and sediments in the St. Louis.
Impoundment to levels that would not present an unacceptable human- health or ecological risk and would allow eventual elimination of existing fish consumption advisories.
Prevent direct human contact with contaminated sediments.
Prevent significant down river migration of contaminated sediments.
Achieve compliance consistent with federal and state ARARs for the Site.
Comply with risk-based objectives defined by the risk assessment.

The contaminant removal behind the impoundment found that almost all the sediments in the area designated for removal needed to be excavated. The sediment was removed down to the till layer that formed the base of the Pine River, so regardless of the RAO(S), the impoundment was excavated down to the till.

A.77.5 Remedial Approach

Final selected remedy: The operable unit for excavation of sediments in the impoundment was based upon high levels of DDT contamination in the sediment causing risk for aquatic, terrestrial, and human food chains. The containment remedy for the 52 acre plant site has yet to be determined; however, the Feasibility Study focuses on a variety of options that include capping, sheet piling, groundwater pump and treat, NAPL/DNAPL removal and collection, replacement of the City of St. Louis water supply, and on-site treatment of contaminated soils and liquids to reduce the concentrations prior to capping. The glacial till unit below the plant site is permeable therefore resulting in no reliable low permeability base to the final containment remedy. Reduction and destruction of high and mobile contaminant concentrations therefore was deemed necessary.

Removal of the sediments in the impoundment through sheet piling and dewatering of the area to excavate under relatively dry conditions. The main plant site includes capping, sheet piling, groundwater pump and treat, NAPL/DNAPL removal and collection, replacement of the City of St. Louis water supply, and on-site treatment of contaminated soils and liquids to reduce the concentrations prior to capping.

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 is not currently part of this remedy. The downgradient of the impoundment contamination of the Pine River is still being evaluated and data collection is ongoing.

A.77.6 Monitoring

Not yet applicable to this site.

Expected recovery time: Not yet applicable to this site.

Projected monitoring costs: Not yet applicable to this site.

RAOs/project objectives achieved? Not yet applicable to this site.

Publication Date: August 2014

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