1 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION 7901 NORTH 5TH STREET

KANSAS CITY, KANSAS 66101

MAR - 0 2008MEMORANDUM

SUBJECT: Review of Radiological Conditions, West Lake Landfill

FROM: Chuck Hooper, CHPAir Planning and Development Branch

• THRU: Becky Weber, DirectorAir & Waste Management Division

TO: John B. Askew, Regional Administrator

111Superfund

Site History

In April, 1942, the Manhattan Engineer District (MED) contracted with the MallinckrodtChemical Works (MCW) of St. Louis, Missouri for large-scale uranium refining and processingas part of the atomic weapon's development of World War II.

Several processes were used at MCW to extract uranium from the various ores and feedforms that arrived at MCW with the main goal of extracting as much of the uranium from the oreas possible. The MCW was not a facility that "enriches" the fissile isotopes of uranium; itsimply extracted and produced uranium metal. The uranium produced still had a natural ratio ofuranium isotopes (U-238 at 99.2745%, U-235 at 0.720%, and U-234 at 0.0055%), of which onlyuranium-235 is considered fissionable.

Most of the constituents of an ore, even a high-grade pitchblende ore, are non-uraniummetals and elements, because of this several steps are required and many waste residues arecreated that are not of value for uranium production. After the ore was milled and dried it wasdigested in nitric acid, a sulfuric acid step followed and a precipitate was formed that containedhigh levels of radium and lead, this residue was referred to by MCW as K-65. Ownership of K-65 residue was retained by the supplier because potentially valuable elements were retained inthe residue. Because of this the K-65 was always stored separately from other residues and wasplaced in drums. Later the K-65 residues were shipped to the Lake Ontario Ordnance Works.Another residue referred to as AJ-4, barium sulfate residue, was created when barium carbonateslurry was added when the ore had high levels of sulfates. The sulfate precipitates of this stepalso included trace amounts of uranium, radium and thorium. This residue was loaded into dumpbins and transferred to the airport site and dumped on the ground because it was insoluble inwater and regarded as fairly immobile. Later this barium sulfate residue was returned to MCWand an additional sodium carbonate leach process was added to help extract more uranium fromthe residue. This leached barium sulfate residue was then returned to the airport storage site.

In 1966 the airport storage site was sold by the Atomic Energy Commission to theCommercial Discount Corporation of Chicago who in turn transported the leached barium sulfateresidue and other process residues that still retained some uranium to the nearby Latty Avenuesite. In 1969 the Cotter Corporation, with a facility in Carion City, Colorado, bought the LattyAvenue residues and for the next four years shipped residues to Colorado with the principalexception of 8700 tons of leached barium sulfate. In a 1974 investigation the NuclearRegulatory Commission determined that in 1973 Cotter Corporation had disposed of theapproximately 8700 tons of leached barium sulfate residues mixed with 39,000 tons of top soil atthe West Lake Landfill[2].

The West Lake Landfill used the residues and topsoil mixture as a landfill amendmentwhere it was mixed with landfill debris and trash in two distinct areas at West Lake Landfill.This currently makes up Operable Unit 1; Area 1 (-10 acres) and Area 2 (~30 acres)[3]. Area 2generally has higher concentrations of radionuclides, and higher comparative risk estimates, thanArea 1.

Nature of Contamination

References from MCW records indicate that although the leached barium sulfate waslower in radioactivity and radium/radon than the K-65 residue, it still warranted surveys andprecautions such as dosimetry to be worn by workers at the airport storage site.

Thorium-230

Additionally, when the NRC conducted studies at the West Lake Landfill they observedthat although uranium was in relatively low concentrations, the levels of thorium-230 wereelevated from 5 to 50 times higher than radium-226[4]. As a comparison to the RemedialInvestigation (RJ) Report'31, the ratio of thorium-230:radium-226 from all samples abovereference levels in Area 2 resulted in a ratio of 11:1, consistent with NRC investigations.

The increase in thorium-230 is likely a result of the uranium processing as precipitatescame out of the nitric acid solution at different rates. This would have altered the normal secularequilibrium that built up over millions of years. Because thorium-230 levels are elevated withrespect to radjum-226 it will, over time, create an increase in levels of radium-226 that will equalthorium-230'and thus increase the dose (or risk) in the long term, i.e. in thousands of years.

Secular Equilibrium

Equilibrium of a radioactive decay chain occurs when a fixed ratio between the activitiesof the daughter and the parent exists. This indicates that the daughter activity is decreasing withthe half-life characteristic of the parent. On a graph of activity versus time the curves for theparent and daughter will be parallel when equilibrium is reached.

If the half-life of the parent (80,000 years for thorium-230) is much longer than the half-life of the daughter (1,600 years for radium-226) then secular equilibrium is possible. It is calledsecular since the equilibrium is maintained for a long time due to the comparatively large half-life of the parent. For secular equilibrium to be achieved, sufficient time for the in-growth of thedaughter must pass. This is generally considered to be seven half-lives of the daughter.

Radium-226 and Radon-222

Radium-226 and the rest of the eight decay daughters in the uranium decay chain usuallyprovide the bulk of potential risk from an external gamma radiation perspective. Radium-226also adds a unique challenge in that it decays into radon-222, a colorless, odorless, noble gas thatcan escape from the soil matrix and cause an internal dose as an inhalation hazard. Radon-222and its other naturally occurring isotopes produce the majority of our natural radiationbackground exposure. Radon exposure accounts for 200 millirem of the estimated 360 milliremper year of background radiation dose'5'.

Figure 1. Uranium-238 Decay Chain

238U

(4.51x10y)

ai r

234Th(24.1d) K'

?3<W(1.17m)

^

Radonudkies produced Inless Shan one percent of thetransformations ol Ihe parentare no) shown,

(2,47x1 Oy)|

iex

r

230Th ,(8.0x10 y)

\a

r

226Ra(1602y)

T22{

(3.82

i

aiji3:!)

<JCr

718po

(3,05m;

i

Legend

238 y Rsdlorudkle

(4,51x109y) "HalHJo

™PO | j?1°PCS* (ie4MS} J*\ (l3S.4d)

214RI 'a I I 210RI ' nra *mli P ,,a Mm P l«214pb

(26.8m)

/ 210pb ' [286^

(21y) : (stable)

Topsoil and landfill debris/trash mix

Most of the barium sulfate residue was briefly returned to MCW and leached withsodium carbonate in order to remove additional uranium and then returned to the airport site. Atthis point MCW records indicate that there were 7 tons of uranium left within the total of 8700tons of leached barium sulfate residues, and that radium-226 concentrations were approximately3960 picoCurie/gram[1]. If the residues were dumped in the landfill in an unadulterated formthen the soil sampling results should indicate levels at this approximate level. However, theNRC investigation in 1974[2] revealed that the 8700 tons of leached barium sulfate residues weremixed with 39,000 tons of topsoil (a 4.5:1 soil to residue mixture) and then delivered to the WestLake Landfill (this corresponds to a total volume of material of approximately 39,750 cubicyards at 1.2 tons/cubic yards -compacted). At some point this leached barium sulfate residueand topsoil was mixed with landfill waste at the landfill. Investigations from bore hole analysisin the Remedial Investigation (RI) Report^', and the conclusion reached by the NRC'4\ were thatthe residues were additionally mixed with landfill waste (e.g. wood, plastic, paper, wire, rubber,yard waste, shredded tires, glass, etc.) and that when the residue/soil was encountered withoutwaste it was limited to one or two feet thick or less. Both of these reports estimate that the totalvolume of contaminated debris within the landfill now accounts for approximately 150,000 cubicyards. The 39,750 cubic yards of residue/soil from Latty Avenue was in turn mixed with trash atan approximate ratio of 3.8:1. If the original concentration of unadulterated leached bariumsulfate residue of 3960 picoCurie/gram has been diluted with top soil at a rate of 4.5:1 and then asubsequent rate of 3.8:1 with landfill trash debris, then the average expected radium-226 levelwithin the landfill would be approximately 232 picoCurie/gram for a homogenous mixture. Theaverage radium-226 concentration in the larger Area 2 is 189 picoCurie/gram[3], which indicatesthat the original 8700 tons of leached barium sulfate residues were likely mixed with top soil andlandfill debris at the approximate ratios given. A few soil samples show that there are someareas where the concentration of radium-226 approached this original level of 3960picoCurie/gram, indicating that the material is not a completely homogenous mixture (WL-209at 3,720 picoCurie/gram and WL-234 at 3,060 picoCurie/gram). If a limited removal of severaldozen cubic yards were attempted in these high concentration areas it would likely not create alarge change in the Exposure Point Concentrations (EPC) used in the Risk Assessment becausethese calculations are based on the arithmetic mean and not the maximum values found. Becausea partial removal would have limited effect on the EPC, it would in rum have little effect on theoverall risk results.

Some exceptions with high radium-226 levels exist prior to the RI studies, which wereconducted in an earlier investigation by Radiation Management Corporation in 1982(NUREG/CR-2722). This report often derived soil concentration using a field measurementtechnique using in-situ gamma-ray spectroscopy which is subject to larger error than currentEPA protocols for laboratory analysis (e.g. PVC-11 at 13,000 picoCurie/gram and Base 5Surface at 19,000 picoCurie/gram Bi-214/Ra-226).

Exposure Pathways

Table 1 summarizes the cancer risks associated with radioactive material exposure asshown in the Baseline Risk Assessment for the West Lake Landfill. The total risk from AllRoutes is the sum of the Soil Ingestion, Inhalation and Direct Radiation risks. These risk valuesare based on the increased risk over a lifetime. The results indicate that the majority of risk isfrom Direct Radiation, i.e. external gamma exposure, of which over 90% is from radium-226 andits decay daughters for the Future Area 2 scenarios. Additionally, all Future scenarios includethe calculated increase in radium-226 concentrations that will be present in 1,000 years. It'simportant to note that a 3E-4 lifetime risk corresponds to approximately 15 millirem per year ofradiation dose (residential scenario)^, therefore the Storage Yard Worker at a 4E-4 risk has thepotential of an increased radiation dose of approximately 91 millirem per year (corrected forexposure duration) as compared with other exposure levels in Table 2.

Table 1. Summary of Risks for Future Receptor Scenarios Evaluated in the West LakeOperable Unit 1 Baseline Risk Assessment171

Scenario

Area 1Grounds Keeper

Area 2Grounds Keeper

Area 1 Storage YardWorker

Area 2 Storage YardWorker

Soil Ingestion

1E-5

1E-5

NE

NE

Inhalation

2E-6

3E-6

NE

NE

DirectRadiation

5E-5

2E-4

1E-4

4E-4

All Routes

6E-5(1 in 16,700)

2E-4(1 in 5,000)

1E-4(1 in 10,000)

4E-4(1 in 2,500)

"NE" - No exposure anticipated because a complete exposure pathway does not exist

The Grounds Keeper is assumed to be an employee who brush hogs in Areas 1 and 2three days per year, eight hours per day, for 6.6 years of employment.

The Storage Yard Worker is assumed to be a full time employee (250 days per year for6.6 years) that works in an adjacent building but spends 1 hour per day on a paved section ofAreas 1 and 2.

External Gamma

Overland Gamma and Borehole Measurements

An overland gamma radiation survey was conducted by McLaren/Hart based on awalkover scan at one-meter height that generated 56,736 data points. The survey was conductedwith a sodium iodide 2"x2" detector. The maximum reading in Area 1 was 235 microR/hour(0.235 milliR/hour), and the maximum reading in Area 2 was 2,174 microR/hour (2.174milliR/hour)181.

Radiation detectors used for environmental measurements similar to the West LakeLandfill often employ solid crystalline sodium iodide scintillation detectors because of their highefficiency for detecting gamma radiation. Typical background measurements range from 1,000to 10,000 counts per minute depending on the size of the crystal in the detector, for example aLudlum model 44-10 2"x2" sodium iodide detector will have a sensitivity of approximately 900counts per minute for each microR/hour of exposure. A typical background rate of 5-10microR/hour corresponds to a 4,500 to 9,000 counts per minute background range.

The radiological logging of boreholes during the RI investigations used a I"x4" sodiumiodide detector'3'. Because their volumes are equal, the detector used in the boreholemeasurements will have a similar sensitivity as the Ludlum Model 44-10's 2"x2" detector.Therefore a borehole reading of 1,000,000 counts per minute would correspond to 1,100microR/hour, or 1.1 milliR/hour. However, the geometry in a borehole is much different than areading taken at three feet above the surface as the overland gamma survey was performed.Higher readings in a borehole are expected because the detector is physically closer to thecontaminated material and because it is completely surrounded by the contaminated media.

Exposure Comparison

Often the first reaction when dealing with a radiological issue is to compare the externalgamma radiation readings with background or other familiar exposures such as the doseabsorbed by the body from a medical x-ray image. There are two reasons why this is aninappropriate comparison. First, the external gamma dose is just one pathway that could create apotential health risk, ingestion and inhalation are other pathways for exposure to radioactivematerials, and in certain circumstances they can be the primary driver of risk instead of theexternal gamma pathway.

Secondly, the comparison of a gamma radiation level at a radiological site against othercommon radiation exposures does not fully account for the setting (occupational exposure versuspublic dose limits), exposure duration (full time residential occupancy versus the less durationrecreational use), land use, and even potential benefit that certain radiological exposures canhave in nuclear medicine and diagnostic imaging. Medical exposures have a benefit that cannot

be readily compared with occupational or natural background exposures. Nevertheless, Table 2may help the reader have a better perspective of various exposures.

Table 2. Various Exposure LevelsExample

West Lake Landfill,Area 2 Future StorageYard Worker UnderCurrent Conditions

Background

Uranium MiningOverburden/ProtoreRamsar, Iran High

Natural BackgroundX-Ray Exam, Single

Chest to LumbarSpine19]

CT Chest191

Angioplasty (HeartStudy) [9]

NRC OccupationalLimit

NRC Public Limitfrom Licensed

FacilityDOT Limit for

Occupied Cab ofTransport Vehicle

Exposure Rate(microR/hour)

2,174 max.

5-10

100'stolow 1,000's

8-2,000

Na

Na

Na

Na

2,000

2,000

Radium-226(picoCurie/gram)

189 avg. in Area 2, alldepths

~1

Low 100's

1,030 max.

na

na

na

na

na

na

Dose (millirem/year)

91

360

Na

600 avg. in elevatedareas

2-70 per exam

800 per exam

750-5,700 per exam

5,000

100

5,000

A common range of background radiation exposure as read on portable radiation metersis approximately 5-10 microR/hour (at 8760 hours per year this amounts to -66 millirem/year).However, this only includes the cosmic and terrestrial sources of background radiation. Typicalradiation survey instruments don't account for the internal dose from naturally occurringradionuclides present in our bodies (e.g. potassium-40), nor do they fully measure the dose fromthe inhalation of radon and radon decay products that contribute the majority of our backgrounddose.

A summary of sampling results from waste rock and overburden from several abandoneduranium mining sites are presented in US EPA Technologically Enhanced Naturally OccurringRadioactive Materials From Uranium Mining, Volume 1: Mining and Reclamation Background.Uranium and radium concentrations and direct radiation readings of the protore (unreclaimedsubeconomic ores) and overburden, i.e. waste that is left behind when the uranium ore has been

mined, are presented in the report. These measurements vary from levels that are slightlyelevated above background to levels in the hundreds of picoCuries/gram for uranium and radium.These waste materials left behind were not utilized because of their low uranium concentrationand are likely to be lower than the "ore" material that was removed for processing. Gammaradiation readings also vary depending on the concentration of the material left behind but rangefrom slightly elevated to hundreds of microR/hour to several milliR/hour l l°J.

Some areas of the world have higher terrestrial background levels than others. Oneunusual area with naturally high radiation background occurs in Ramsar, Iran. The town ofapproximately 2000 people on the shores of the Caspian Sea has naturally high levels of radiumdue mainly from residues from mineral deposition from the many hot springs in the area.Exposure rates have been measured from 8 to 2,000 microR/hour, and soil sampling indicateslevels of radium-226 as high as 1,030 picoCurie/gram (3.8E4 Bq/kg)mi.

The NRC occupational limit is 5,000 millirem/year. The public dose limit from alicensed facility is 100 millirem/year, with a limit of 2 millirem/hour.

The Department of Transportation (DOT) and NRC set the acceptable levels of radiationfrom packages for commerce. The maximum radiation reading on a labeled Yellow III packageis 200 millirem/hour on contact and ten millirem/hour at one meter. For an exclusive useshipment the occupied position within the driver's cab is limited to 2 millirem/hour.

Conclusions

Although the radioactive material in the form of leached barium sulfate residues is notexactly typical of ore, overburden, or protore of most uranium mining areas, it is consistent withthese from a radiological standpoint, with the exception that over time the radium concentrationwill increase to the levels of thorium-230. For these impacted areas at the landfill the thorium-230 concentrations are elevated approximately 11:1 over radium-226. The Baseline RiskAssessment accounts for this in the Future exposure scenarios by increasing the radium-226concentrations to levels that will be present in 1,000 years.

Sampling results indicate that the vast majority of radiologically impacted Areas 1 and 2are at levels that do not indicate that the original leached barium sulfate residues transported tothe landfill were dumped in one place, and that they were mixed irregularly throughout thelandfilled material. Removing only a portion of the contaminated material, even in areas that areelevated above the average, would have a small impact on the risk because the Exposure PointConcentration used to calculate risk is based on the arithmetic mean and not a maximumconcentration. While elevated count rates were measured in some areas of the landfill materials,limited removal in these areas would not necessarily reduce the overall risk to below acceptablelevels without the need for further action.

Regardless of any other comparisons, the Baseline Risk Assessment provides the bestassessment of a site's human health risk whether the contaminant is radioactive or not. Theresults of that risk assessment exceeded the acceptable risk range for a Future Grounds Keeperand Future Storage Yard Worker, therefore additional response action is necessary. The

enhanced cover/cap system and other actions outlined in the Feasibility Study and Proposed Plancan be designed to reduce radiation levels at the surface of the landfill to acceptable levels forfuture worker scenarios, with the added benefit that radiation exposure for workers during thecover/cap installation are likely to be much less than if a partial removal of the residues wereattempted.

References

[1 ] Oak Ridge Associated Universities, Dose Reconstruction Team for NIOSH, Basis forDevelopment of an Exposure Matrix for the Mallinckrodt Chemical Company St. LouisDowntown Site and the St. Louis Airport Site, St. Louis, Missouri (ORAUT-TKBS-0005,Revision 2, June 14, 2007); 8.6.2 Assumptions for Radioactive Source Terms, and Table A-4

[2] NRC NUREG-1308, Rev 1, Radioactive Material in the West Lake Landfill Summary Report(June 1988)

[3] Engineering Management Support, Inc, Remedial Investigation Report West Lake LandfillOperable Unit 1 (April 2000)

[4] Radiation Management Corporation, NRC NUREG/CR-2722 Radiological Survey of theWest Lake Landfill St. Louis County, Missouri (May 1982)

[5] National Council on Radiation Protection and Measurements, Report No. 93, IonizingRadiation Exposure of the Population of the United States

[6] OSWER No. 9200.4-18; Memorandum: Establishment of Cleanup Levels for CERCLA Siteswith Radioactive Contamination (1997)

[7] Auxier & Associates, me, Baseline Risk Assessment West Lake Landfill Operable Unit 1,(April 2000); Table A.5-13

[8] McLaren/Hart Environmental Engineering Corp., Overland Gamma Survey Report WestLake Landfill Radiological Areas 1 & 2 (April 30, 1996)

[9] Health Physics Society Fact Sheet; Radiation Exposure from Medical Diagnostic ImagingProcedures

[10] US EPA, Technologically Enhanced Naturally Occurring Radioactive Materials FromUranium Mining, Volume 1: Mining and Reclamation Background; Appendix V. RadiochemicalData for Uranium Overburden and Waste Rock, Pit Lakes and Streams, and In Situ LeachOperations (EPA 402R-05-007, January 2006)

[11] Sohrabi, M., Esmaili, A.R.; New Public Dose Assessment of Elevated Natural RadiationAreas of Ramsar (Iran) for Epidemiological Studies (2002)

10