The Washington County Lead District Site consists of high concentrations of lead contamination from nearly 285 years of mining activities. The primary problem areas at this site that require action are lead-contaminated soils in yards and lead-contaminated drinking water.
The site is located in a heavily mined region of eastern Missouri known as the Washington County Lead District. The Potosi Area Site primarily includes residential areas within and around the towns of Potosi, Mineral Point, and Cadet, and is only a portion of the larger Washington County Lead Mining District.
Although lead was known to be in southeast Missouri as early as the 1600s, serious mining did not begin until around 1720 when Phillipe Francois Renault established Mine La Motte in present day Madison County, Missouri (part of the Madison County Mines NPL Site). By 1725, Old Mines and Mine Renault were opened in present day Washington County. The smelted lead was molded (lead pigs) and transported to Ste. Genevieve, Missouri, on the Mississippi River where it was shipped to France via New Orleans. Lead mining in southeast Missouri has been continuous until the present day where lead is still mined in the Viburnum Trend, which includes part of Washington County (Doe Run’s Viburnum Mine 29).
In Washington County, Mine Au Breton (current day Potosi) was established in the late 1700s and was eventually taken over by Moses F. Austin (father of Stephen F. Austin of Texas fame) whose mining and reverberatory furnace smelting techniques significantly increased lead production in which, at that time, was shipped to Spain. From 1798-1804, Mine Au Breton produced more lead than all of the other Upper Louisiana mines combined. The Missouri Department of Natural Resources (MDNR) has identified over 1000 lead and barite mining, milling, and smelter sites in Washington County through historic information.
Toward the end of the American Civil War, lead deposits in Washington County ran low and the industry declined. It was soon replaced by the surface mining of barite (barium sulfate) that was used in rubber, paint, soap, drilling fluids, and medical products. Many lead mines were over mined for the barite, which was also associated with galena (lead sulfide). The barite was separated from the clay, initially by hand washing and then by mechanical barite washing plants that were introduced into the area in the 1920s. In 1941, Missouri accounted for 40 percent of United States barite production.
Barite mines in the Potosi area include the following:
Hornsey Brothers Boars Head Lodge Mine
Hornsey Brothers Cadet Mine
Hornsey Brothers Gun Club Mine
Milchem Settle Mine
Milchem Keyes Branch Mine
Dresser Minerals Potosi Mine
Dempsey Mine
Pfizer Mineral Point Mine
Imco Apex Mine
NL Baroid Fountain Farm Mine
NL Baroid Cadet Mine
In June 2005, MDNR began an integrated assessment that included soil and groundwater sampling in the Potosi area. During this sampling event, MDNR sampled the soil at 359 residences located on or near mining or mine waste disposal areas. Based on this data, approximately 65% of these residential properties had soils that exceeded 400 milligrams per kilogram (mg/kg) and roughly 18% had soils that exceeded 1,200 parts per million (ppm) for lead. The MDNR also sampled approximately 172 private drinking water wells in the Potosi area in June 2005. Of these 172 wells sampled, 36 wells exceeded 15 parts per billion (ppb) for lead and one well exceeded 5 ppb cadmium, which are the current Maximum Contaminant Levels for lead and cadmium in drinking water.
In October 2005, EPA began sampling in the Potosi area to support the Potosi Area Site Removal Action. A total of 534 residential properties were sampled by the EPA during this assessment, results of the 2005 assessment and subsequent sampling activities through 2008 are listed in the table below.
| Total Properties Sampled | Lead in Soil > 400 ppm | Lead in Soil > 1,200 ppm | Drinking Water Well Clean | Drinking Water Well > 15 ppb Lead |
|---|
| 2005 Site Assessment | 534 | 150 | 52 | 479 | 55 |
| EPA Assessment to 2008 | 1,685 | 506 | 210 | 655 | 177 |
EPA began cleanup activities on the site in 2006. Between 2005 and 2009 EPA removed approximately 175,444 cubic yards of contaminated materials from high child-use areas and residential properties on site. As of 2009 a total of 205 properties had been remediated.
In June of 2013 EPA identified 30 additional residential properties with lead contamination in soils exceeding the Removal Action Level (RAL). These properties were not previously determined to have children (under 84 months of age) living on the site. Current residents of these properties communicated to the EPA in Spring of 2013 that there were children living there. In accordance with the authority specified in the Potosi Removal Action Memo, these properties were scheduled for the time-critical removal action.
EPA clean up activities were initiated for additional properties on June 17, 2013 and are anticipated to be completed by September 1, 2013. No additional time-critical properties have currently been identified at this time. The Region 7 EPA Remedial Program signed a Record of Decision for the Remedial Action at the Washington County Lead District sites; Potosi, Old Mines and Richwoods in September 2012. Clean up contracts are expected to be in place by September 30, 2013. All remaining clean up activities addressing soil contamination at the Potosi site should addressed under the Remedial Action. Remedial cleanup activities at the Potosi site are anticipated to continue for the next several years.
The completion of Time-Critical Removal Activities will coincide with the start-up the Remedial Cleanup Contract. Ongoing Time-Critical cleanup progress is summarized below.
On July 1, excavation began at property ID 24098. The driveway was the only cell requiring removal. All of the rock material was removed from the driveway at 8-12 inches below ground surface. Excavation was completed on July 1, removing 84 cubic yards of rock.
On 7/2, excavation activities were conducted at EPA property ID 24038. The driveway was the only cell requiring removal. Rock was removed from the driveway to a depth of 6-12” bgs. On 7/3, excavation was completed, with 54 cu. yds. of rock removed and replaced with 64.27 tons of rock.
Excavation began at property ID 20587on July 3. Only the driveway required excavation at this property. The driveway was excavated to 3-6 inches bgs. Excavation was completed on July 8. 24 cy of rock were removed from the property. TABLE border="1"
| WCLD - POTOSI 2013 Task Order D0006
| COST EXTRAMURAL
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| PROPERTIES | CONTAMINATED MATERIALS REMOVED (Cu Yd)
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| CURRENT TOTAL | 9 | 630 |
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| PLANNED SITE TOTAL | 30 | n/a | $400,000.00
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