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Contamination from mining activities potentially impacts 37,050 residents of Camden County.
The Camden County Mining area was mined from 1830 to 1910, with lead as the principal product. After 1910, most of the mining was for barite, with galena (lead) as a minor by-product. By 1947, lead production in the Central Mining District had totaled 24,855 short tons. Since 1950, no lead and very little barite have been mined. Mining operations and associated lands in the CMD area have been owned, operated, and managed by various entities and/or private citizens (USGS and Missouri Division of Geological Survey and Water Resources 1967). Hazardous substances typically associated with historic mining sites in Missouri include arsenic, barium, lead, and cadmium. The mining waste products often end up on driveways, in yards, and in children’s play areas.
The CMD–Camden County covers approximately 655 square miles in central Missouri. The climate of the area is characterized by cool winters and hot summers. The average total annual precipitation is about 38–42 inches. Camden County site soils range widely in texture, natural drainage, depth to bedrock, and other characteristics. The predominant soil types are deep to moderately deep, sloping to very steep, very cherty silt that forms on uplands.
Several properties in the CMD–Camden County area were found to exceed the removal action level for lead. Sampling is continuing in this area.
Site assessment activities were conducted July–November 2006. Properties were sampled based on the Geological Survey and Resource Assessment Division's (GSRAD) Inventory of Mines, Operations, and Prospects database which identified more than 900 mining locations in the five-county Central Mining District area. The locations were then mapped out, and door to door sampling began. A total of 646 properties were sampled in the Central Mining District area. Thirty one properties were found to have lead greater than EPA's maximum contaminant level (MCL) of 15 ug/l; one property was found to have cadmium exceeding 5 ug/l, and eight properties were found to exceed the arsenic MCL of 10 ug/l.
A Regional Decision Team (RDT) meeting was held on 27 February 2007 where the proposed future actions of a second phase of sampling would be conducted. The purpose of this second phase was to sample the properties of residents who responded after November 13, 2006, when site assessment activities ended and to expand sampling into the other mining areas where limited sampling was conducted. At this meeting it was also agreed that site assessment would investigate the potential for naturally occurring contamination versus mining contamination. Also EPA’s toxicologist was tasked with completing a site-specific streamlined risk assessment. The naturally occurring contamination project, with associated sampling event and receipt of data, was completed in October 2007. This sampling event included sampling all properties that were found to exceed the MCL of 15 ug/l for lead, 5 ug/l for cadmium, and 10 ug/l for arsenic. At that time both wellhead and tap samples were taken. This information was provided to the removal program.
In June 2007, draft action memos were developed for the Central Mining District to address alternate drinking water sources, soil contamination, and continued drinking water sampling. On September 21, 2007, EPA's toxicologist completed site-specific removal action levels for lead in the Central Mining District memorandum. This memo set the Removal Action Level (RAL) for lead in drinking water at 30 ug/l. This memo is an attachment to the signed action memo.
The action memo for Camden County was signed on September 22, 2008. The response action includes continued sampling of drinking water sources, excavating contaminated soils in yards, and providing alternative drinking water sources to properties which exceed the RAL for this site.
A Regional Decision Team (RDT) meeting was held on July 30, 2009. At this meeting it was agreed that the action memo would be amended to reflect the lower drinking water removal action level (RAL) of 15 ug/l per the September 17, 2008 Memo from Debbie Dietrich, Director, Office of Emergency Management entitled "Revised Superfund Removal Action Levels". Also the Central Mining District Lead sites will not score on the NPL and therefore there is no other planned follow-up remedial action at these sites. It is also anticipated that the Central Mining Lead Sites will not exceed the expenditure of two million dollars in funds(per site).
The RDT also agreed that yards that exceeded 400 ppm of lead in soil would be excavated.
Properties where drinking water filters would be installed would be sampled quarterly for one year (to ensure effectiveness) and after that time, five filters would be left for the residents to change out as appropriate.
All properties which have water softeners, but do not exceed the RAL for lead, arsenic, and cadmium would be referred to the Missouri Department of Natural Resources (MDNR) for follow-up.
During this reporting period, the action memo amendment was signed reducing the removal action level of lead in water to 15 ug/l and the soil cleanup level to 400 ppm for lead.
In the fall of 2009, a drinking water line from a public water supply was extended to a property which exceeded the RAL. This property was hooked up to the public water supply line and the sample at the tap indicates drinking water that does not exceed the RAL. Another property which used water from the private drinking water well was hooked up by the company that owns that property. The private drinking water well was appropriately abandoned by EPA in consultation with the state of Missouri.
Sampling continues on a quarterly basis on a property where a drinking water filter was installed. The filter has been effective during all sampling events.
EPA continues to contact residents who are impacted by the new RALs to obtain access agreements to complete cleanup actions.
Continue contact with residents to obtain access agreements for filter installation and soil excavation.
Contact has failed at several properties where letters have been returned due to residents moving. EPA will travel to the impacted addresses to make contact with residents and explain proposed actions.
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