f * , , _. , ' *- ,f , THE RADIOLOGICAL AND ENGINEERING ASSESSMENT for PROPERTY #ED-00911-RS 1 : March 1984 i .' (Revised May 1984) , , 4 for URANIUM MILL TAILINGS REMEDIAL ACTION PROJECT OFFICE ALBUQUERQUE OPERATIONS OFFICE DEPARTMENT OF ENERGY ' L l , r- I ! by ; | ARIX, A PROFESSIONAL CORPORATION |. Architects Engineers Planners . . i under subcontract to BENDIX FIELD ENGINEERING CORPORATION P. O. Box 1569 i Grand Junction, Colorado 81502 r ! B501070534 841211 PDR WASTE WM-40 .PDR L _
4.1 Exterior Proposed Remedial Action Plan 13.......
List of Tables
Table Page
113.1 Volume Calculations ... 4 ...........
4.1 Estimated Cost of Decontamination and Restoration . . 14
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1.0 EXECUTIVE SUMMARY
The Department of Energy (DOE) has contracted with Bendix Field
Engineering Corporation (BFEC) of Grand Junction, Colorado, to providearchitect-engineering services in assessing the problems resulting fromthe existence of radioactive uranium mill tailings at off-site locationsin Edgemont, South Dakota. The property located at 907 E Street,#ED-03911-RS, has been included for remedial action under Public Law 95-604
because radioactive mill tailings contamination in excess of EPA standards
has been discovered at that location. The property is a private residence.
In this assessment, the extent and severity of contamination fromtailings used as fill material at this property are evaluated. A briefdescription of the remedial action is provided. The quantities of material
- that would be removed and the associated costs are estimated.
1.1 Evaluation and Recommendation
The recommended action for this property is to remove all' identified residual radioactive mill tailings to the maximum evident
depth, and restore the property back to its original condition. Theestimated volume of contaminated material found on this. property is as
The estimated cost to perform the remedial action is $738.00,and the time required to' complete the design work is approximately 1week. After the construction documents are approved, sent out to bid,and the Notice to Proceed is issued, it will take approximately 10
days to perform the remedial action on this property.
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2.0 PROPERTY DESCRIPTION
2.1 General Description
Address: 907 E StreetEdgemont, South Dakota
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Lot Size: Approximately 11,370 square feet
Point of Reference: Subject property is located approximately1/2 mile to the west of the TVA millsite repository. The location ofthis property relative to its surroundings is shown in Figure 2.1.
This is a single story frame house with a full 1,061 squarefoot basement. A 168 square foot enclosed breezeway separates a 4
266 square foot single-car garage from;the east side of the mainstructure. Concrete stoops join the north and east foundations.Concrete walks extend north and south from the breezeway and northeast
from the front stoop. A brick planter is attached to the north sidei of the house.!
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> 3.0 RADIOLOGICAL SURVEYS
3.1 Introduction
Radiological data were collected by ARIX Engineers, Architectsand Planners at location ED-00911-RS on June 6,1980 under contract
with the State of South Dakota Department of Health. The data werecollected as part of a radiological engineering assessment to deter-mine the extent of identified residual radioactive uranian milltailings contamination on the property.
Historical information indicates that this property was origin-ally identified as a probable tailings location during an above groundgamma radiation survey conducted by the U. S. Environmental ProtectionAgency (EPA) in 1971, 1972 and 1978. Subsequent to this survey, theState of South Dakota measured an indoor radon daughter concentration
of 0.041 gross working levels (WL) in the basement based on RadonProgeny Integrating Sampling Unit (RPISU) data collected over a161-hour period during march 1980.
This report section presents the survey data accumulated by ARIXand summarizes the results of this data,
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3.2 Exterior Radiation Surveys and Explorations
3.2.1 Surface Area Gamma Surveys
Portable scintillometers incorporating 1" x 1" sodiumiodide (thallium activated) detector crystals were used to scanthe entire surface area of the property. Resulting data are usedto identify contaminated areas and to assist in defining theperimeter of tailings deposits. Observed meter readings, bothnear contact with the surface and at about 3 feet above thesurf ace, were recorded on an approximate (stepped off) 10-foot
grid basis and additional readings were recorded off the gridwhen survey revealed significant change between grid points.Recorded data is meter readings in " micro-R/hr"; true exposure
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rates can be estimated by applying a scintillometer / gas propor-tional ionization chamber cross-calibration f actor (meter readingx 0.56 + 6 = true exposure rate). Recorded data indicate thatthe true gamma exposure rate background on the property is about13 micro-R/hr and the maximum true gamma exposure rate measured
on the exterior property is about 34 micro-R/hr. Results of .aeexterior gamma radiation survey are shown on Figure 3.1. >
3.2.2 Subsurf ace ExplorationsA total of 11 boreholes, 4" diameter, were drilled at
exterior locations snown on Figure 3.1. These boreholes were
gamma logged using a 1" x 2" sodium iodide (thallium-activated)detector crystal incorporating a recording count rate meter.Relative gross gamma radiation intensities were recorded at2-inch increments down each borehole to determine depth of
tailings contamination. The recorded gamma logs were convertedto equivalent radium-226 (pCi/g) using cross-calibration factorsdetermined through use of the Bendix Technical MeasurenentsLaboratory calibration test wells and experimental data (gannalog count rate compared to representative laboratory analysis ofsoil samples) obtained in and around the Edgemont Uranium Mill
*Site.Data from the exterior borehole logs is shown on Figure 3.1.
I This data shows surf ace layer tailings contamination exceeding EPAcriteria in the extreme southwest corner of the yard. The equi-
|valent radium-226 concentration at the one contaninated borehole
: location is about 9 pCi/g in the top 15 cm soil layer and to6 pCi/g in the subsurface layers.
In addition to borehole gamma logging, surf ace gross gamma|! and delta gamma measurements were recorded at each borehole
! location using a portable scintillometer (micro-R meter). Thedelta scintillometer readings provide a differential gammameasurement by observing the reading with an unshleided detector,and then placing a 1/8 inch lead shield between the detector andsurface of interest and observing the reading; the difference
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between the two measurements is the delta reading representing
radiation emanating from the area directly below the detector.The delta gauna measurements have been cross-calibrated with
laboratory soil analysis to accommodate converting the delta toequivalent pCi Ra-226/g in the surf ace 6" layer of soil. The
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delta gamma measurement is used in conjunction with boreholeganna logging to estimate radium-226 concentrations in the top 6"(15 cm) layer of soil. Delta gamma measurements related to the
11 borehole locations are shown on Figure 3.1.
3.3 Interior Radiation Surveys and Explorations
3.3.1 Surface Area Gamma Surveys
Portable scintillometers (micro-R meters) were used toscan the entire interior surface area. Gross gamma and deltagamma meter readings were recorded in sufficient numbers to
characterize each habitable area of the structure that iscontiguous to the ground, i.e., basement level, slab-on-gradelevel and/or crawl space level. Measurements were taken on floorsurfaces and the foundation walls to assess tailings locationsrelative to these structural components. Figure 3.2 shows theresults of the interior gamma survey.' Data indicate that there
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are no gamma anomalies within the structure.,
Interior gamma measurements were not taken at 3 feet abovethe surface, hence, exposure rate data is not available. How-ever, the maximum interior gamma measurement (converted to true
exposure) observed in contact with floor surfaces is 16 micro-R/hr in the basement which is within the range of normal back-
ground. This data indicates the structure does not exceed EPAcriteria for indoor gamma exposure.
3.3.2 Subsurface ExplorationsOn the basis of negative interior ganma, no interior
The State of South Dakota measured the indoor radondaughter concentration using a RPISU as follows:
Date Location Hours Sanoled Working Level.
3/12-3/19/80 Basement 161 0.041
To confirm the elevated radon daughter concentration measured bythe State, ARIX performed grab sampling using calibrated radonscintillation cells and high volume (251/ min) filter sanples.The 0.5 liter scintillation cells were analyzed by allowing a4-hour decay time after collection and then counting on aphoto-multiplier / scaler. The filter samples were analyzed usingthe modified Kusnetz method. Sanpling locations and resultingdata are shown on Figure 3.2. The grab sampling confirmed
elevated concentrations averaging 8.3 pCi Rn-222/1 and 0.023working levels measured in 2 locations in the basement. Two grabsampling sets, one under closed conditions and one with normalstructure ventilation, were collected from each location toaccommodate condition weighted averaging of data. Accumulateddata indicates the structure probably exceeds the EPA indoorradon daughter concentration criteria.t
3.4 Extent of Contamination
Figure 3.1 shows the apparent deposition of exterior tailingscontanination on the property and there is no . evidence of tailingscontamination within the habitable structure. The extent of apparent
tailings contanination on the property is sunmarized as follows:
Contaminated soil is 12 inches deep in the southwest..
corner of the yard. '
It is interesting to note that the only evidence of contaninatedsoil on the property is that described above. This deposit is. about
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55 feet away from the structure and it covers a surface area of about350 square feet.
This property is located in the southwest section of Ed,gemontwhere naturally elevated indoor radon daughter concentrations have
been, documented by the State and EPA. Several locations in thevicinity of this property have indoor radon daughter concentrationsmeasuring from 0.02 to 0.04 working levels (RPISU data) without anyindication of cultural source material (tailings or other gammaanomalies) on the property. It is apparent that natural geology,i.e., subsurface mineralization, is the source of these elevatedconcentrations. Because of this elevated natural background, allidentified residual radioactive mill tailings should be excavated to
the maximum d,epth of apparent contaninated soil; this would essenti-ally eliminate the possibility of tailings contamination contributingto the indoor radon daughter concentration.
Referencing Figure 3.1, the volume of contaminated material tobe removed from the property is about 13 cubic yards from the exterioryard area (reference Table 3.1 for volume calculations).
@ Sampline Location Basement hg Delta (net) sanma Contact With Surface g13 Gross Ganma Contact With Surf ace 3
- (APfav)-HEASUREMEMT 04 VERTICAL- SURFACE
& AvaD.able On ALL GAWA MEASUREMENTS ARE UNCORRECTED METER;
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MO IMTERIOR BORE HOLES AT THIS LotATION
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TABLE 3.1
Volume Calculations.
Exterior
(Reference Figure 3.1)4
! Area Calculations Cubic Yards
13.0Southwest yard 35' x 10' x l' deep = 350 =
TOTAL EXTERIOR 13.0 CY
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4.0 REMEDIAL ACTION
4.1 Introdyction
As discussed in Chapter 3.0 of this report, contaminated soilexceeding the EPA radium-226 criteria but covering less than 10 squaremeters .is located in the southwest corner of the yard. Additionally,radiological data indicate the structure exceeds the EPA criteria forindoor radon daughter concentration.
4.2 Remedial Action Requirements
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Remedial action would involve removal of tailings identified inthe yard and placement of clean fill and topsoil. Lawn areas damaged
during the removal work will be replaced with grass sod. Figure 4.1shows this remedial action plan.
Dislocation is not reouired at this location during the remedialwork. Safe access in and out of the structure will be provided.
Material would be removed to the maximum depths and boundaries
of all contamination. This would require removal of about 13 cubicyards from the exterior areas.
The estimated costs of implementing this remedial action are
$738.00 (reference Table 4.1).
4.3 Evaluation of Remedial Action
Removal of all identified residual radioactive mill tailings to
the maximum evident depth would completely eliminate the possibility oftailings contaninated soil contributing to the indoor RDC. Implementa-
tion of this action should assure that additiona.1 remedial action willnot be required even if the indoor RDC remained elevated.
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v. ' DEPTH OF TAILINGS$g 9 EXCEEDING EPA CRITERIA [UNSHADEDNUMBER=)
REQUIRED EXCAVATION -
I hMAXIMUMDEPTHOF[; TAILINGS CONTAMINATION (DEPTH j
M TAILINGS (APPROXIMATE LOCATION)'
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EDGEMOMT, S. DAXOTA Jrp FIGURE 4.1
/\ lX OWNER DNN. B(907 E STRttT JTF EXTERIOR PROPOSED
ADDRESS CKD BYREMEDIAL ACFIOM PLAJJA W J ESStONAL OW 00 A T tO*4 ED-OO911 -RS 3-B 7-2-80
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