Do radiologically contaminated materials disposed of in Areas 1 and 2 pose a current public health risk and is it unsafe to manage these materials in place?
“Evaluation of the factual information does not support this claim. For toxic materials to pose a health risk to individuals or populations there must be human exposure. Exposure to toxic pollutants may occur through three primary exposure pathways: ingestion, inhalation, and absorption through the skin. In the case of radionuclides, the external (gamma) radiation pathway must also be considered. Under current conditions and current land uses, there are no complete pathways for significant exposure to the general public. The contamination that could pose an exposure concern is in soils and solid waste buried in the landfill. The Site is fenced and access controlled. There is no opportunity for members of the general public to contact materials that are disposed in the landfill, and there are no contaminated drinking water sources. Radon concentrations are elevated only in the immediate vicinity of the buried materials. There is little opportunity for unplanned earth moving activities in Areas 1 and 2 that might release fugitive dust and cause an inhalation concern. There is no opportunity to take up occupancy of Areas 1 and 2 where long-term exposure to radon and external gamma radiation might occur. As long as the Site is used in ways consistent with it being a landfill, there is no public health concern.”
“To put some perspective on it, risks of this magnitude expressed in annual radiation dose to a residential receptor are in the range of 15 millirem (mrem). The average person in the United States receives about 360 mrem of radiation exposure per year, 82 percent of which is from natural sources like cosmic radiation and radon exposure. In other words, the potential radiation doses being addressed by this remedy are a small fraction of the doses people receive from normal background radiation.”
“The general conclusion is that members of the general public, i.e., people who live and work in the vicinity of the Site, are not at risk under current conditions. There are potential risks to future on-site workers or others who might come in direct contact with the contaminated material. The potential risks are not acute and can be managed by preventing direct contact with the waste materials.”
USEPA Responsiveness Summary West Lake 05-29-08—Pages 2 to 3 (Comment 1)
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Is the Site in a flood plain which could affect the integrity of the remedy and spread contamination or impact water quality in the Missouri River?
“Under current conditions, the Site is not located in a flood plain. The Site is located behind the Earth City Levee. The Earth City Levee District is protected from flooding of the Missouri River by a 500-year earthen levee and supporting flood control system. At the end of 2005, this Levee District contained 450 businesses employing 22,800 people.”
“It is important to understand that the landfill itself has altered the topography such that the surface elevation of the Site is 20 to 30 feet or more above the level of the historic flood plain. After construction of the remedy, surface grade at the landfill will be a minimum of 25 feet above the flood plain. In the event that the levee is breached and 500-year flood waters were to encroach on the business park, it would be expected to result in about two feet of water at the northwestern toe of the landfill. As part of the Selected Remedy, the landfill toe in this area will be regraded through placement of additional clean fill and capped with an engineered landfill cover resulting in approximately 100 lateral feet of additional materials between the current landfill toe and the toe at completion of the remedial action. Only cover material and clean fill material are potentially impacted by flood water. As part of the remedial design process and in response to public comment, flood protection measures will be evaluated during remedial design and appropriate bank protection methods will be used in construction of the toe area. Any encroaching flood water would be expected to recede with no damage to the landfill cover. However, in the event any damage did occur, it will be repaired in accordance with the operation and maintenance (O&M) plan.”
See EPA’s Response to Congressional Inquiry on the levee systems and flood plain issues. (PDF; direct external link to EPA; opens in new window)
See the Site as compared to the 500-year flood plain: Map of 500 Year Flood Plain
See the Site as compared to the extent of the 1993 Flood: 1993 Flood Extent
USEPA Responsiveness Summary West Lake 05-29-08—Page 5 (Comment 3)
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Are radiological contaminants at the Site migrating or have migrated to the groundwater and impact off-site water supply wells and/or water quality in the Missouri River?
“Groundwater samples obtained from a network of on-site monitoring wells over a period of years have been analyzed for a wide range of chemicals including radionuclides, trace metals, petroleum hydrocarbons, volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), pesticides, and polychlorinated biphenyls. … The results are not indicative of on-site contaminant plumes, radial migration, or other forms of contiguous groundwater contamination that might be attributable to the landfill units being investigated.”
“The groundwater results show no evidence of significant leaching and migration of radionuclides from Areas 1 and 2. The vast majority of the results are consistent with background concentrations. Only four wells exhibited a total radium concentration above the MCL of 5 picocuries per liter (pCi/l). These exceedances ranged from 5.74 pCi/l to 6.33 pCi/l. These slight exceedances are isolated spatially. Two of the four wells with total radium exceedances are located in areas that are not downgradient of either Radiological Area 1 or Radiological Area 2. Uranium isotopes (U-238 and U-234) were generally detected in wells at 5 pCi/l or less. For comparison, the background level is about 2 pCi/l and the drinking water standard is about 20 pCi/l (converted from the uranium MCL of 30 micrograms per liter [ug/l]). Moreover, perched water from locations in the waste material contained in Areas 1 and 2 was sampled and analyzed and elevated concentrations of radionuclides were not detected. This is the case even though the waste materials have been in place without a landfill cover for over 30 years. In other words, significant leaching and migration of radionuclides to perched water or groundwater have not occurred despite landfilled waste materials having been exposed to worst-case leaching conditions from surface water infiltration over a period of decades.”
“In conclusion, the results of extensive monitoring over a period of years show that the radiological contaminants have not had significant impacts on shallow groundwater underlying Areas 1 and 2. Without significant impacts to the groundwater underlying and immediately downgradient of the waste material, there can be no significant impact to the alluvial aquifer or the Missouri River. Based on the data, it is reasonable to conclude that no current or potential water supplies have been affected.”
“Also, according to the applied chemistry that is known from the reprocessing of ore residues, the uranium in barium sulfate is insoluble in water. That is, the uranium cannot be leached from the barium sulfate using water. The Mallinckrodt process used sodium carbonate solution to recover trace uranium from barium sulfate cake. Based on this information, one would not expect to find significant levels of uranium in the water at the Site and the groundwater data bear this out.”
“Groundwater protection is a principal objective of the Selected Remedy. The long-term groundwater monitoring program will be designed to verify over time that the remedy is protective of the groundwater. The objectives of the monitoring program are described in section 12 of the OU 1 ROD. The monitoring plan required as part of the remedy will specify sampling locations, sampling frequencies, analytical parameters, procedures, etc. Periodic sampling reports that include data summaries and interpretation will be published. After the baseline is established, trend analysis will be used to verify performance.”
USEPA Responsiveness Summary West Lake 05-29-08—Pages 3 to 5 (Comment 2)
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Are the radioactive wastes at West Lake extremely rare and particularly dangerous?
“Many of the claims made here are not true or are misleading. The radionuclides in the waste material at Areas 1 and 2 are derived from natural uranium ore. Natural uranium ore has both U-235 and U-238. Each of these has a chain of decay products, for a total of 32 separate isotopes including the isotopes identified in this comment. The nuclides in these series are not rare or unusual. Also, the dangers posed by these radionuclides are a function of the concentration, the manner in which someone becomes exposed, and the period of time over which someone is exposed. Judgments regarding health risk cannot be made without considering these factors.”
“Uranium is one of the most abundant elements found in the earth’s crust. ... The measured uranium concentration in the landfill is much lower than the concentration found in uranium ore.”
USEPA Responsiveness Summary West Lake 05-29-08—Page 22 (Comment A)
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What radiological materials are in the landfill?
“It should be clarified that there are actually no feed materials (ore or ore concentrates) in the landfill and there is no raw Belgian Congo pitchblende in the waste materials. The radiologically contaminated material in the landfill is soil blended with residues that were the byproduct of processing the ore for its uranium content. Certainly, the most reliable way to ascertain the composition of the waste material in the landfill is through direct measurement. Therefore, as part of the RI, extensive field study was performed on the landfill and the waste materials including overland gamma surveys, surface and subsurface sampling through an extensive boring program, downhole radiological logging, radon flux measurements, perched water and landfill gas sampling, surface water and sediment investigation, etc. The data provide the primary basis for the technical judgments that have been made in the EPA decision-making process”
USEPA Responsiveness Summary West Lake 05-29-08—Pages 8 to 10 (Comment 7)
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Nearby North St. Louis sites are managed under FUSRAP, and at those sites radiologically contaminated material is being excavated and shipped offsite. Why not this one, too?
“The differences in the remedies selected for each site are a function of the differing site-specific circumstances; the differences cannot be attributed to the fact that one site is FUSRAP and the other is not. The AEC established FUSRAP in March 1974 under the authority of the Atomic Energy Act (AEA) of 1954 to identify, investigate, and take appropriate cleanup action at sites where work was performed in support of MED and early AEC programs. FUSRAP provides for federal funding to designated sites. It is CERCLA, however, that provides the response authority and governs the decision-making process at both North St. Louis County FUSRAP sites and the West Lake Site.
"In the case of the North St. Louis County sites, the contaminated media is generally surface soils. The contaminated soil is or was widely distributed across approximately 80 properties including SLAPS, owned by the city of St. Louis, and a variety of properties used for a variety of purposes, e.g., commercial, light industrial, recreational, open fields, and transportation facilities. The mostly private properties are criss-crossed with public roadways, railroads, and utility right-of-ways. The majority of these soils are accessible to the public. The contaminated soil is located in places where workers or members of the public might reasonably be expected to come into contact with it. Moreover, many of these properties are being used or could be used in ways that are incompatible with leaving the soil in place. These considerations were factored into the remedy which calls for the accessible contaminated soils to be excavated and shipped for commercial disposal.
“A subset of the St. Louis FUSRAP contaminated soils, referred to as the inaccessible soils, are located under roads, active rail lines, buildings, and other permanent structures. There are over 69,000 cubic yards of contaminated soils in this category. The inaccessible soils do not pose an exposure concern as long as the road or other permanent structure remains in place. The Selected Remedy for the inaccessible soils at the North St. Louis County North FUSRAP sites is to manage these in place using institutional controls.
“In contrast to the situation in North St. Louis County, the West Lake Site has been a landfill site since the early 1950s and will remain a dedicated landfill site into the future. The radiological contamination is disposed with other wastes in the landfill. The current use and the reasonably anticipated future use of the Site is as a landfill. In short, waste disposal is consistent with current and future land use at the West Lake Site; such is not the case for the St. Louis sites. Accordingly, land use at the Site is restricted through covenants recorded by the property owners; the restrictions cannot be terminated without the written approval of both the Missouri Department of Natural Resources (MDNR) and EPA. In addition, more comprehensive land-use restrictions are required as part of the Selected Remedy. If there is an analogy to be drawn with the St. Louis FUSRAP, it is with the inaccessible soils that, like the soils in the landfill, do not pose a health concern as long as the barrier to exposure remains in place.”
USEPA Responsiveness Summary West Lake 05-29-08—Pages 13 to 14 (Comment 12)
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The other St. Louis radiologically contaminated sites have been or are being cleaned up by the U.S. Army Corps of Engineers. Why not this one, too?
“Distinctions in cleanup decisions between the St. Louis sites and the West Lake Site have nothing to do with which federal agency is responsible for the cleanup. In both cases, the remedy selection is governed by the Superfund process and the distinctions have to do with the physical setting and the reasonably anticipated land use. In St. Louis, accessible soils are being excavated for commercial disposal because these contaminated soils would present potential exposure concerns. The inaccessible soils in St. Louis, i.e., soils under roads, buildings, and other structures, are being managed in place. Like the soils in the landfill, the inaccessible soils do not present a health concern as long as they remain where they are. At the Site, the contaminated soils are disposed in a landfill that is dedicated to use as a landfill.”
USEPA Responsiveness Summary West Lake 05-29-08—Page 32
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Will capping without a liner be sufficient to isolate the contamination from the environment?
“Capping through the use of engineered covers is a mature and routinely applied technology that forms a barrier between the contaminated media and the surface, thereby shielding humans and the environment from the contaminants and from the effects of radiation. Capping is the approach used at uranium mill tailing sites for example. The cap is designed to be sufficiently thick and impermeable to isolate the waste and restrict surface water infiltration into the subsurface. When the waste is above the water table, as in the case of the radiologically contaminated material at the Site, a properly designed cap can prevent the percolation of water from the surface to the underlying contaminated materials. The cap will be extended beyond the perimeter of the contaminated area and include side slopes to prevent any lateral infiltration. It is important to understand that it is the cover, not a liner, which prevents surface water from contacting the waste material.”
USEPA Responsiveness Summary West Lake 05-29-08—Page 7 (Comment 5)
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Is there cause to be concerned about radon releases and the effectiveness of landfill caps or clay liners in containing radon releases?
“First of all, it should be clarified that any release or potential release of radon from the radiologically contaminated disposal areas (Areas 1 and 2) is only an exposure concern for someone who occupies the surface of Areas 1 and 2 and the immediate vicinity. The average radon flux from the Site under current conditions with no landfill cap in place at Areas 1 and 2 is already less than the standard that is considered safe for tailings piles at uranium mill tailing sites. The net contribution of radon to the ambient air from the Site is very small and would not be detectable at off-site locations. Even if left in its current condition, radon from the Site will not pose any sort of threat to the air in the St. Louis region and beyond as some commenters claim.
“Multi-layer, natural material cover systems are effectively designed and engineered to mitigate the release of radon gas, minimize water infiltration, and remain effective for long periods of time. When caps are used to contain radium-contaminated wastes, they are typically designed to confine gaseous radon until it has essentially decayed. Such systems are used to contain long-lived radionulides at large uranium mill tailing sites where radon generation is a larger problem than at the Site due to the vast amounts of tailings involved. Since radon decays rather rapidly (Ra-222 has a half life of 3.8 days), vertically migrating gas only needs to be detained for a relatively short period of time for the radon to decay. The typical depth of a natural materials cover necessary to accomplish this is about five feet for radon-222. When the remedy is implemented, it will be designed so that radon measurements at the surface of the cap should be indistinguishable from background.”
USEPA Responsiveness Summary West Lake 05-29-08—Pages 12 to 13 (Comment 10)
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