ML100070117

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Oak Ridge Institute for Science and Education, Final Report - Radiological Survey for New Generation Footprint Area Plant Soils at Humboldt Bay Unit 3
ML100070117
Person / Time
Site: Humboldt Bay
Issue date: 11/19/2009
From: Adams W
Oak Ridge Institute for Science & Education
To: John Hickman
NRC/FSME
References
Download: ML100070117 (51)
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INDEPENDENT IRADOLOGCALL SURVEY REPORT FOR THE UNIT 3' NEW GENERATION FOOTPRINT.AkEA PLA.NT SOILS AT THE HUBOLDT BAY POWER PIANT EUREKA', CALIFORNIA S I f* _______

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RADIOLOGICAL SURVEY REPORT FOR UNIT 3 NEW GENERATION FOOTPRINT AREA PLANT SOILS AT THE HUMBOLDT BAY POWER PLANT EUREKA, CALIFORNIA Prepared by W. C. Adams ORISE Prepared for the U.S. Nuclear Regulatory Commission FINAL REPORT November 2009 This report is based on work performed by the Oak Ridge Institute for Science and Education under contract number DE-AC05-06OR23100 with the Department of Energy.

Prepared by the Oak Ridge Institute for Science and Education, under interagency agreement (NRC FIN No. f1008) between the U.S. Nuclear Regulatory Commission and the U.S. Department of Energy.

Humboldt Bay Power Plant 1759-SR-01-0

FOR. UNT E GNRTONFOPI-N'-T AR-,E-"AP1AN N:SOILAT TU{E HIU,.MBOLDT BA-Y POWER PLANT EUREK-A-,-ILiFORNIfA Prepareff by:~ Oate  :

W.C Adams, Piojct'Leader

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ACKNOWLEDGMENTS The author would like to acknowledge the significant contributions of the following staff members:

FIELD STAFF T. D. Herrera LABORATORY STAFF R. D. Condra J. S. Cox W. P. Ivey W. F. Smith CLERICAL STAFF R. M. Fink

  • K. M. Moore A. Ramsey J. L. Clary ILLUSTRATORS T. L. Brown J. A. Viars Humboldt Bay Power Plant 1759-SR-01-0

TABLE OF CONTENTS PAGE List of Figures ..................................................................................................................................................... ii List of Tables .................................................................................................................................................... iii A bbreviations and Acronym s.......................................................................................................................... iv Introduction and Site H istory.................. 7........................................................................................................ 1 Site D escription .................................................................................................................................................. 2 C ontam inants of C oncern ................................................................................................................................ 3 Radiological Survey O bjectives ............................................................................................................... 4 D ocum ent Review ............................................................................................................................................. 4 Field Sam pling and M easurem ent Plan ..................................................................................................... 4 Survey Unit Classification ....................................................................................................... ..................... 5 Radiological Survey Procedures ............................................................................................................. 6 Reference System ........................................................................................................................................... 6 Surface Scans .................................................................................................................................................. 6 G am m a D irect M easurem ents ........................................................................................................... 7 Soil Sam pling .................................................................................................................................................. 7 In-Process Inspection ................................................................................................................................... 8 Sample Analysis and D ata Interpretation ................................................................................................... 8 Findings and Results .......................................................................................................................................... 9 D ocum ent Review ......................................................................................................................................... 9 Surface Scans ................................................................................................................................................. 9 G am m a A ctivity C ount R ates ............................................................................................................. 9 Soil Samples .................................................................................................................................................. 10 In-Process Inspection ...................................................................................................................................... 10 G am m a Scan O bservations ....................................................................................................................... 10 G am m a Soil Sample Analyses O bservations .................................................................................... 11 Com parison of Results with Site Release Criteria .................................................................................. 11 Conclusion ........................................................................................................................................................ 12 References ......................................................................................................................................................... 13 Appendices:

Appendix A: Figures Appendix B: Tables Appendix C: Major Instrumentation Appendix D: Survey and Analytical Procedures Appendix E: ORISE Statistical Survey Design for the New Generation Footprint Area Humboldt Bay Power Plant i 1759-SR-01-0

LIST OF FIGURES PAGE Figure A-i: Plot Plan of Humboldt Bay Power Plant ........................................................................ A-1 Figure A-2: Plot Plan of the Humboldt Bay Power Plant Indicating New Generation Fo o tprin t A rea ......................................................................................................................... A -2 Figure A-3: New Generation Area Final Status Survey Plan Sampling Locations .............................. A-3 Figure A-4: New Generation Footprint Area, East - Gamma Surface Scans ...................................... A-4 Figure A-5: New Generation Footprint Area, West - Gamma Surface Scans ..................................... A-5 Figure A-6: ORISE Ranked Set Sampling Gamma Measurement Locations ...................................... A-6 Figure A-7: ORISE Ranked Set Sampling Soil Sample Locations ........................................................ A-7 Figure A-8: ORISE Judgm ental Soil Sample Locations .......................................................................... A-8 Figure A-9: ORISE New Generation Footprint Area Final Status Survey Split Soil Samples .......... A-9 Figure A-10: Gamma Count Rate Distribution in NGFA-East ..................................................... A-10 Figure A-11: Gamma Count Rate Distribution in NGFA-West ................................................... A-10 Humboldt Bay Power Plant ii 1759-SR-01-0

LIST OF TABLES PAGE Table 1: D ecay Corrected Radionuclide Inventory ................................................................................. 3 Table 2: NRC Screening Values For Surface Soil Contaminants Of Concern .................................... 11 Table B-I: ORISE Ranked Set Sampling Locations Data .............................................................. B-1 Table B-2: Radionuclide Concentrations In Soil By Gamma Spectroscopy ................. B -2 Table B-3: Interlaboratory Com parison A nalyses ................................................................................... B-3 Humboldt Bay Power Plant iii 1759-SR-01-0

ABBREVIATIONS AND ACRONYMS AEC Atomic Energy Commission BKG background CCPMP Cross Contamination Prevention and Monitoring Plan CFR Code of Federal Regulations cm centimeter Co-60 cobalt-60 COC contaminants of concern CP characterization plan cpm counts per minute Cs-137 cesium-137 DCGL derived concentration guideline level DP decommissioning plan DQOs data quality objectives EPA U.S. Environmental Protection Agency ESI Enercon Services, Incorporated FSS final status survey FSSP final status survey plan FSSR final status survey report GPS global positioning system HBPP Humboldt Bay Power Plant HBRP Humboldt Bay Repowering Project HSA historical site assessment IEAV Independent Environmental Assessment and Verification ISFSI Independent Spent Fuel Storage Installation ISM Integrated Safety Management ITP Intercomparison Testing Program JHA job hazard analysis kg kilogram m2 square meters MAPEP Mixed Analyte Performance Evaluation Program MARSSIM Multi-Agency Radiation Survey and Site Investigation Manual MDC minimum detectable concentration MDCR minimum detectable count rate MeV million electron volts NaI(1l) sodium iodide (thallium-activated)

NGFA New Generation Footprint Area NIST National Institute of Standards and Technology Ni-63 nickel-63 NRC U.S. Nuclear Regulatory Commission NRIP NIST Radiochemistry Intercomparison Program ORAU Oak Ridge Associated Universities ORISE Oak Ridge Institute for Science and Education Humboldt Bay Power Plant iv 1759-SR-01-0

ABBREVIATIONS AND ACRONYMS (continued) pCi/g picocurie per gram PG&E Pacific Gas and Electric Company PNL Pacific Northwest Laboratories RSS rank set sampling s second SAFSTOR safe storage SPCS State Plane Coordinate System Sr-90 strontium-90 SU survey unit TAP total absorption peak VSP Visual Sample Plan v. 4.6 Humboldt Bay Power Plant V 1759-SR-01-0

RADIOLOGICAL SURVEY REPORT FOR UNIT 3 NEW GENERATION FOOTPRINT AREA PLANT SOILS AT THE HUMBOLDT BAY POWER PLANT EUREKA, CALIFORNIA INTRODUCTION AND SITE HISTORY The Pacific Gas and Electric Company (PG&E) operated the Humboldt Bay Power Plant (HBPP)

Unit 3 nuclear reactor near Eureka, California under Atomic Energy Commission (AEC) provisional license number DPR-7. HBPP Unit 3 achieved initial criticality in February 1963 and began commercial operations in August 1963. Unit 3 was a natural circulation boiling water reactor with a direct cycle design. This design eliminated the need for heat transfer loops and large containment structures. Also, the pressure suppression containment design permitted below-ground construction.

Stainless steel fuel claddings were used from startup until cladding failures resulted in plant system contamination-zircaloy-clad fuel was used exclusively starting in 1965 eliminating cladding-related contamination. A number of spills and gaseous releases were reported during operations resulting in a range of mitigative activities (see ESI 2008a for details).

In July 1976, Unit 3 was shut down for annual refueling and seismic modifications. However, by December 1980 it was concluded that completing the required upgrades and restarting Unit 3 would be cost prohibitive. PG&E decided in June 1983 to decommission Unit 3, received a possession only license amendment, and placed the unit into cold shutdown and safe storage (SAFSTOR).

Unit 3 is currently undergoing decommissioning. PG&E also intends to build a new fossil fuel unit on the site in the vicinity of Unit 3 as part of the Humboldt Bay Repowering Project (HBRP).

For the site characterization, PG&E has contracted with Enercon Services, Incorporated (ESI). ESI has provided a site characterization plan (CP) for radiological surveys and a cross contamination prevention and monitoring plan (CCPMP). PG&E will decommission Unit 3 at a later date and provide a decommissioning plan (DP) when appropriate. Currently, PG&E is preparing an area in the vicinity of Unit 3 for the new generation fossil fuel facility. It is PG&E's intent to prepare this area for the new facility, to perform radiological surveys in the area consistent with a final status survey (FSS), and to document the baseline radiological condition of this new area prior to the decommissioning of Unit 3 (ESI 2008b). The CCPMP will be employed to prevent contamination of the new facility area and the remainder of the facility during decommissioning of Unit 3.

Humboldt Bay Power Plant 1759-SR-01-0

Amendment 40 to the license dated September 11, 2007, authorized the licensee to release the area for construction of the HBRP.

The U.S. Nuclear Regulatory Commission's (NRC's) Headquarters and Region IV Offices requested that the Oak Ridge Institute for Science and Education (ORISE) perform radiological surveys of the new fossil fuel plant area site soils. The survey was coincident with the licensee's FSS soil sampling activities. The NRC also tasked ORISE with reviewing the licensee's CP and CCPMP. The radiological surveys were performed during the period of January 12 through 15, 2009.

SITE DESCRIPTION The HBPP site, owned by PG&E, consists of 143 acres on the southern edge of Humboldt Bay four miles southwest of the town of Eureka, in Humboldt County, in the state of California (Figure A-I).

PG&E maintains four operating electric generating units at the HBPP site that run on fossil fuels and one non-operational nuclear unit (Unit 3). The controlled land that includes Unit 3 encompasses approximately 13 acres and the area targeted for the new fossil fuel unit is located immediately adjacent to and south-southeast of Unit 3. This controlled area, referred to as the New Generation Footprint Area (NGFA), consists of approximately 50% open grassy and otherwise naturally vegetated areas and 50% covered with asphalt and/or rock (Figure A-2). Large portions of the area were covered with fill material both prior to and after Unit 3 operational startup (ESI 2008a). The balance of the property includes mostly open areas and protected wetlands.

The new fossil fuel electric generating units in the NGFA will replace the existing fossil fuel units (Units 1 & 2). An Independent Spent Fuel Storage Installation (ISFSI) was constructed on-site for dry cask storage of the spent nuclear fuel and greater than Class C wastes. After the new electric generating units are operating, decommissioning may start on Units 1 & 2 to be followed by the decommissioning of Unit 3.

PG&E has demolished buildings, excavated, and redirected major utilities within the NGFA. ESI performed radiological surveys of the whole area to include the excavated pipe and utility trenches.

ESI also performed FSS type radiological surveys within the excavations prior to backfilling the area.

After backfilling, ESI prepared an FSS type approach sampling plan for the NGFA which included 100% gamma scans and a systematic soil sampling pattern; these survey activities were in progress during ORISE's radiological survey activities.

Humboldt Bay Power Plant 2 1759-SR-01i-0

CONTAMINANTS OF CONCERN The radiological contaminants of concern (COC) for the HBRP are consistent with other nuclear reactors that have had fuel cladding failures. Since the reactor has not been in operation for the last 30 plus years, many of the isotopes have decayed to less than 99% of their original activities, i.e.

reached seven or more half-lives. Table 1 lists the primary COC for the site, noting the 1981 quantities are from Pacific Northwest Laboratories (PNL)-4628, ResidualRadionuclide Distributionand Inventoy at the Humboldt Bay Nuclear Plant (PNL 1983). The values were then corrected to projected 2008 levels based onradiological decay alone. The overall inventory focuses on the systems and surfaces in Unit 3 and associated buildings and does not focus on quantities in the reactor vessel and environs surrounding the power plant. Site-wide COCs are therefore condensed in Table 1 into surface-soil-specific COCs subject to this confirmatory survey plan. Surface-soil-specific COCs are noted with a bold Y (for yes) under the "Soil COG" column.

Haft- 1981 .2008 Soils Nuclide Life Inventory Inventory COCb Commentc ,

(years): (millicuries) (millicuries),

H-3 12.3 unknown unknown N Not a surface soils COC Fe-55 2.7 149,000 157 N Reactor systems COC only Co-60 5.27 18,000 517 Y Surface soil COC Cs-137 30.2 2,200 1,180 Y Surface soil COC Ni-63 100 1,400 1,160 Y Surface soil COC Mn-54' 0.855 337 1.IE-07 N Decayed to de minimis levels Sr-90 28.5 17.9 9.28 Y Surface soil COC Am-241 432 12.1 11.6d N Not a surface soils COC Pu-238 87.7 7.0 5.7 N Not a surface soils COC Pu-23 9/240 24,110 6.1 6.1 N Not a surface soils COC Cm-244+ 18.1 4.9 1.7 N Reactor systems COC only

-Table derived from information within Tables 2-1 and 2-2 of the HBPP Site Characterization Survey Plan (ESI 2007); 2008 inventory calculated by ORISE.

bCOC = contaminants of concern.

cMedium/systems-specific comment based on input from Table 2-2 (ESI 2007).

dThe inventory of Am-241 does not account for the decay of Pu-241 to Am-241 (ESI 2007).

The surface-soil-specific COCs for the HBRP surface soils are beta/beta-gamma emitting fission and activation products resulting from reactor operation. Of eleven potential radionuclides that could be present based on site operations, only four are designated as surface soil contaminants:

Co-60, Cs-137, Ni-63, and Sr-90. Cesium-137 and Co-60 were specifically identified during Humboldt Bay Power Plant 3 1759-SR-01-0

characterization as the predominant radionuclides present in surface soils (ESI 2008b). Note that site-specific derived concentration guideline levels (DCGLs) have not been established for site soils, thus the licensee will use the NRC screening value DCGLs from NUREG/CR-5512 for guidance (NRC 1999). ESI also established a site wide Cs-137 background of 0.5 picocuries per gram (pCi/g).

RADIOLOGICAL SURVEY OBJECTIVES The objective of the ORISE side-by-side survey activities was to generate independent radiological data for use by the NRC in evaluating the adequacy and accuracy of the licensee's radiological soil sampling results from the NGFA. Data collected by ORISE and the licensee were to be reviewed to assess whether classifications based on the Multi-Ageny Radialion Survey and Site InvesligationManual (MARSSIM) were appropriate (NRC 2000), whether COCs were detected above historically low levels in the HBRP footprint [i.e., less than about 0.65 pCi/g for Cs-137 and non-detected for all -

other COCs], and whether data quality is sufficient for comparison to NRC screening value DCGLs.

The objective of the document review of the licensee's proposed CCPMP and the site CP was to evaluate the technical processes and radiological survey techniques that were used to identify radiological contamination and/or prevent cross contamination of the HBPP site.

DOCUMENT REVIEW ORISE has reviewed and evaluated the site CP and the CCPMP for adequacy and appropriateness, considering the data quality objectives (DQOs) established in those documents and to ensure that radiological procedures and results adequately met site CP commitments and MARSSIM considerations (ESI 2007, ESI 2008b and NRC 2000). The review of the CCPMP was documented in a letter report submitted to the NRC on February 5, 2009 (ORISE 2009a).

ORISE was also to review and evaluate ESI's final status survey data documenting the FSS survey activities for the NGFA. At the time of the issuance of this draft report, ORISE has not received a copy of the licensee's preliminary FSS soil sample results for the NGFA.

FIELD SAMPLING AND MEASUREMENT PLAN To expedite the survey process, ORISE coordinated with the NRC site representative to perform radiological survey activities coincident with ESI's survey activities in the NGFA. It was ORISE's intent to complete side-by-side radiological surveys so that a direct comparison of survey data could Humboldt Bay Power Plant 4 1759-SR-01-0

be performed in order to ensure that the probability of satisfying ESI's FSS DQOs was high.

ORISE has not received the ESI soil sample results for the split soil samples collected during the ORISE radiological survey activities and therefore cannot provide a comparison of the split soil sample results.

SURVEY UNIT CLASSIFICATION The MARSSIM FSS process relies upon the use of characterization surveys and site history to divide the site into properly classified survey units (SUs) of appropriate physical area. Modifications to the SU classification can be made based on new survey findings or information. SUs are limited in size based on their classification, exposure pathway modeling assumptions and site-specific conditions.

The remediation contractor should, in the forthcoming final status survey plan (FSSP), assign land area SUs with an initial classification based on past surveys and the historical site assessment (HSA).

Under MARSSIM, the level of survey effort required for a given SU is determined by the potential for residual contamination as indicated by the classification; therefore, SUs with a higher classification receive a higher degree of survey effort. The remediation contractor is using the following MARSSIM classifications:

" Non-impacted: Areas that have no reasonable potential for residual contamination from site operations.

" Impacted Areas: Areas that may contain residual contamination from licensed operations.

Impacted areas include Class 1, 2, and 3 areas.

" Class 1: Areas with the highest probability of contamination, with potential for containing concentrations of residual radioactivity that exceed the DCGLs.

" Class 2: Areas with low potential for containing concentrations of residual radioactivity that exceed the DCGLs.

" Class 3: Areas with little or no potential for containing concentrations of residual radioactivity that exceed the DCGLs.

The NGFA was designated as a Class 3 SU. MARSSIM classifications for the site are presented in Figure A-1.

Humboldt Bay Power Plant 5 1759-SR-01-0 3

RADIOLOGICAL SURVEY PROCEDURES ORISE personnel visited the HBPP site from January 12 through 15, 2009 to perform visual inspections and independent measurements and sampling. The survey activities were to be conducted in accordance with a site-specific survey plan and the ORISE Survey Procedures Manual and Oak Ridge Associated Universities (ORAU) Quality Program Manual (ORISE 2008a and b and ORAU 2009).

After the initial walkover tour of the areas to be surveyed, it was determined that the entire excavation area had already been backfilled with a minimum of two feet of clean soil. ORISE had expected that the licensee would be collecting soil samples from three separate sub-units within the new plant area and that ORISE would perform side-by-side sampling from the excavations. Since the area was already backfilled, with NRC approval, ORISE changed the confirmatory survey plan to incorporate gamma scan coverage over approximately 50% of the NGFA and to perform a ranked set sampling (RSS) approach in collecting soil samples (EPA 2002). For the RSS approach, ORISE decided to combine the two ESI SUs (Figure A-3) into one SU. The revised survey approach, which was approved by the NRC site representative, required 18 randomly selected locations for gamma direct measurements from which six locations would be sampled for radionuclide concentrations in soil. The revised approach also incorporated collecting four split samples from ESI FSS soil sample locations and six soil samples from judgmental locations at the original excavation depths. Deviations to the survey plan were documented in the site logbook.

REFERENCE SYSTEM Global positioning system (GPS) coordinates were used for referencing measurement and sampling locations. The specific reference system used was the California State Plane Coordinate System (SPCS Zone 4202 US Survey Feet).

SURFACE SCANS ORISE performed gamma radiation scans over approximately 5 0% of the accessible soil surface concentrating on areas where contamination may have c6ncentrated during operations (e.g.,

transport routes, drainage areas, areas of known radiological releases, etc.) as well as other judgmentally selected locations based on site observations. Particular attention was given to areas Humboldt Bay Power Plant 6 1759-SR-01-0

within the NGFA which had not been backfilled and other locations where material may have accumulated (though no such surface/areas were thought to exist in this Class 3 SU). Scans for gamma radiation were performed using sodium iodide (thallium-activated) [NaI(Tl)] scintillation detectors coupled to ratemeters with audible indicators and a GPS system. The use of the GPS enabled real-time gamma count rate and position data capture. Gamma scan GPS walkover paths are presented in Figures A-4 and A-5.

GAMMA DIRECT MEASUREMENTS A one minute gamma direct measurement was performed at each of the 18 randomly selected locations determined for the RSS plan (Figure A-6). Gamma direct measurements were also performed at each soil sample location, either for the RSS plan soil samples, for the judgmental soil samples and for the split PG&E FSS soil sample locations (Figures A-7 through A-9).

SOIL SAMPLING A random sampling approach was used to design the revised confirmatory soil sampling plan for the NGFA SUs (EPA 2002). The ESI preliminary characterization survey data provided the information for determining the number of random soil samples necessary to verify the mean concentrations. Specifically, the inputs used were the respective DCGLs for the primary radionuclides--Cs-137 and Co-60 and the observed maximum variability (standard deviation) for the area.

Random surface (0 to 15 cm) soil samples were collected from six locations within the combined SUs. The number of samples collected was adequate to estimate the mean activity concentration level across these impacted site areas. A one-minute static gamma count rate measurement was also performed at each soil sample location. The software Visual Sample Plan v.4.6 (VSP) was used to generate the random locations (Figure A-7).

Based on characterization sample data, ORISE judgmentally collected seven subsurface soil samples from the original excavation soil surface. ORISE also collected four side-by-side soil samples in conjunction with the licensee for confirmatory sample analysis. Additionally, at the request of the NRC site representative, ORISE collected two soil samples from a soil pile in the northwest corner of the site (Figure A-8).

Humboldt Bay Power Plant 7 1759-SR-01-0

With the exception of Cs-137, surface soil COCs are not found in background. Preliminary data suggests Cs-I 37 concentrations are no greater than 0.65 pCi/g as compared to the NRC screening value of 11 pCi/g (NRC 1999). A background investigation was not required because the gamma emitting COCs within the on-site soil samples were at background levels.

Since the ESI soil samples from the characterization survey were from the excavation prior to backfilling, ORISE made a formal request for soil samples from these areas and/or from other site areas in order to perform interlaboratory comparison of the soil samples with the onsite ESI laboratory. According to ESI, all soil samples with noted elevated activity had been disposed; therefore, a direct interlaboratory comparison for a wide range of COC concentrations was not possible. ORISE did receive from ESI, ten low-level concentration soil samples and performed radiological analyses for gamma emitting radionuclides.

IN-PROCESS INSPECTION While on-site, ORISE personnel observed ESI radiological technicians performing FSS survey activities (gamma scans and soil sampling) and on-site gamma soil sample analyses.

SAMPLE ANALYSIS AND DATA INTERPRETATION Samples and data were returned to the ORISE laboratory in Oak Ridge, Tennessee for analysis and interpretation. Gamma scan data were evaluated and gamma scan rates and scan paths were reported in detailed figures. Gamma scan data and gamma direct measurements were reported in units of counts per minute (cpm).

Samples were analyzed in accordance with the ORISE Laboratory Procedures Manual (ORISE 2009b). Soil samples were analyzed by gamma spectroscopy for Co-60 and Cs-137. The spectra were also reviewed for other gamma-emitting radionuclides (i.e., fission and activation products) associated with the HBPP. After reviewing the gamma spectroscopy results for these samples, wet chemistry analyses for additional radionuclides, such as Ni-63, Sr-90 and transuranics were deemed unnecessary since sample concentrations for the gamma emitters (Co-60 and Cs-1 37) were at background levels. Soil sample results were reported in units of pCi/g.

The data generated were compared with the applicable NRC screening value DCGLs for Co-60 and Cs-137. Additional information regarding instrumentation and procedures may be found in Appendices C, D, and E.

Humboldt Bay Power Plant 8 1759-SR-01-0

FINDINGS AND RESULTS The results for the radiological surveys are provided below.

DOCUMENT REVIEW ORISE's review of ESI's CCPMP was submitted to the NRC on January 9, 2009 (ORISE 2009a). It is ORISE's understanding that the licensee's FSS results for this area will not be submitted to the NRC until the results for the rest of the site have been completed. Therefore, ORISE is not able to determine if the procedures and methods implemented for the FSS were appropriate and that the resultant data were acceptable.

SURFACE SCANS Gamma surface scans, on the NGFA backfill soil, did not identify any areas of residual elevated gamma radiation. Soil surface gamma scan count rates generally ranged from approximately 2,500 to 5,100 counts per minute (cpm) with the variability in the ambient gamma radiation levels consistent with the localized soil surface material type and the respective gamma detectors that were used during the survey activities. Typical background count rates ranged from approximately 2,900 to 3,500 cpm. Gamma scan results are illustrated in Figures A-4 and A-5. Gamma scan rate data are provided as the gross, observed count rates. The distribution of counts obtained during the walkover scans for both the NGFA-East and NGFA-West survey units were identical (refer to Figures A-1 and A-i 1), indicated a normal distribution, and provided a strong indication that the backfill for both survey units was from the same location.

GAMMA ACTIVITY COUNT RATES The one minute static gamma count rates at each RSS location are provided in Table B-1. Count rates for the RSS gamma activity measurement locations ranged from 2,941 to 3,522 cpm and are consistent with the gamma surface scan results. Gamma count rates for the RSS soil samples collected by ORISE ranged from 3,196 to 3,434 cpm. Gamma count rates for the NGFA judgmental soil samples and the soil pile soil samples ranged from 2,926 to 4,336 cpm. The average background count rate was approximately 3,200 cpm.

Humboldt Bay Power Plant 9 1759-SR-01-0

SOIL SAMPLES Soil sample concentrations from the ORISE collected soil samples from within the NGFA (the ORISE RSS and split soil samples) and the soil pile ranged from -0.02 to 0.02 pCi/g for Co-60 and 0.00 to 0.15 pCi/g for Cs-137. Subsurface soil sample concentrations, for samples collected at the original soil excavation depths within the NGFA (Soil Samples S0009 to S001 5), ranged from

-0.04 to 0.03 pCi/g for Co-60 and 0.00 to 0.20 pCi/g for Cs-137. The soil concentrations for each soil sample are provided in Table B-2.

Ten soil samples, collected by ESI and analyzed by GEL Laboratories, were shipped to the ORISE laboratory for interlaboratory comparison analyses. The' samples did not have a wide range of COCs as requested and were basically at background levels (Table B-3). Also, ORISE had requested to perform an interlaboratory comparison with the on-site ESI radiological laboratory since ORISE had concerns regarding the validity of the on-site measurement results. ORISE has not received data for the FSS side-by-side soil sampling effort; therefore, this task has not been completed.

IN-PROCESS INSPECTION GAMMA SCAN OBSERVATIONS ORISE observed two radiological technicians performing gamma soil scans in the NGFA. One technician carried the GPS unit and the other carried the radiological instrument that was coupled to a lead shielded Nal detector. The GPS unit was not attached to an external antenna and the GPS technician was two to three feet away from the other technician who was performing the gamma scan. A moving GPS unit will have some location inaccuracies (with the internal antenna) which would be further enhanced by the unit being three feet away from the actual scan path. ORISE recommends that one technician perform the scans with an attached external antenna to decrease the scan path inaccuracies. It was ORISE's understanding that PG&E intended to use the gamma scan system mounted on a motorized cart (PG&E 2008); however, the motorized carts were getting stuck in the mud, therefore PG&E decided to perform the scan manually. ORISE did not review the licensee's procedure for performing the gamma scans manually; therefore, ORISE was unable to verify that the manual scan process was adequate.

ORISE observations of the FSS soil sample collection deemed the process appropriate.

Humboldt Bay Power Plant 10 1759-SR-01-0

GAMMA SOIL SAMPLE ANALYSES OBSERVATIONS ORISE personnel toured the PG&E on-site radiological laboratory which was within a small Connex Box. The laboratory was heated with a portable heating unit with no humidity control.

PG&E placed the samples in a 1 liter (L) Marinelli jar for counting. The samples are counted as collected (wet, rocks, vegetation, etc.); there was no equipment available to dry the samples.

The counting equipment consisted of a Ludlum Model 2221 ratemeter/scalar coupled to a Thermo Scientific Model SPA3 Nal scintillation detector with the detector located within lead shielding. The counting system was windowed for Cs-137 only. A 1 L gamma source was used to calibrate the counting system which has a 1% efficiency for Cs-137; ESI personnel stated that the calibration source standard contains moisture equivalent to a wet sample. ESI personnel also stated that they send 5% of the samples to an outside lab for Quality Control (QC) checks.

ORISE recommends that ESI use a more stable counting system with a higher efficiency for sample analyses. Since ESI has not established a surrogate ratio for the contaminants, ORISE recommends a system that will identify all associated COC photopeaks, e.g., Co-60.

COMPARISON OF RESULTS WITH SITE RELEASE CRITERIA Confirmatory survey data for soil samples were compared with the NRC Screening Values for Surface Soils as presented in Table 2.

SI NRC Screenig value DCGLsa

  • ,..CQ-60?,, ", [3.79 E ECs-137 C 11.0 Ni-63b: 2,110 Sr-ý90 ' . 1.72

-Derived concentration guideline levels from NUREG/CR-5512, Volume 3, Table 6.91.

bCobalt-60 and cesium-137 concentrations were at background levels; hence, Ni-63 and Sr-90 radiological analyses were not performed.

Humboldt Bay Power Plant 11 1759-SR-01-0

None of the 19 soil sample results for the NGFA and the soil pile had soil concentrations that exceeded the NRC Screening Values for Cs-137 or Co-60. The ten soil samples collected by ESI

  • and provided to ORISE for interlaboratory comparison analyses were also well within the NRC Screening Values for Co-60 and Cs-137.

CONCLUSION During the period of January 12 through 15, 2009, ORISE performed radiological survey activities which included gamma soil surface scans and soil sampling within the New Generation Footprint Area (Figure A-2) at the Humboldt Bay Power Plant in Eureka, California.

Gamma soil surface scans did not identify any locations of elevated gamma radiation on the evaluated soil surfaces. The radiological analyses of the soil samples, including the interlaboratory comparison samples, were all well within the Cs-137 and Co-60 NRC Screening Values.

It is ORISE's opinion that final status survey activities should have been performed at the bottom of the excavated areas. It is not reasonable to perform FSS of backfill soil as was done in this instance.

ORISE recommends that PG&E/ESI perform a baseline radiological survey of the New Generation Footprint Area concurrently with the implementation of the Cross ContaminationPrevention and MonitoringPlan (ESI 2008c), after the area has been backfilled and the new plant facilities are in place. The result for this recommended baseline survey would provide radiological data that would be used to determine if the new facility grounds become contaminated during the decommissioning of the remainder of the plant (to include Unit 3).

ORISE also recommends that further evaluations of the on-site radiological laboratory be performed as well as the implementation of the gamma scan procedure.

Humboldt Bay Power Plant 12 1759-SR-01-0

REFERENCES Enercon Services, Inc. (ESI). Site CharacterizationPlan - Humboldt Bay Power Plant. HBPP-PP-003, Rev. 0; July 16, 2007.

Enercon Services, Inc. HistoricalSite Assessment. Prepared for the Humboldt Bay Power Plant Pacific Gas & Electric Company, Eureka, California, Draft; September 2008a.

Enercon Services, Inc. RadiologicalStatus of the Humboldt Bay Repowering ProjectSoils. Prepared for the Humboldt Bay Power Plant, Pacific Gas & Electric Company, Eureka, California, Drift; September 2008b.

Enercon Services, Inc. Cross ContaminationPrevention and MonitoringPlan. Prepared for the Humboldt Bay Power Plant, Pacific Gas & Electric Company, Eureka, California, Draft; September 30, 2008c.

Oak Ridge Associated Universities (ORAU). Quality ProgramManualforthe Independent Environmental Assessment and Verification Program. Oak Ridge, Tennessee; June 30, 2009.

Oak Ridge Institute for Science and Education (ORISE). Draft-Conflrmatoy Survey Planfor Unit 3 PlantSoils at the Humboldt Bay Power Plant,Eureka, California[Docket No. 50-133; RFTA No. 09-003]. Oak Ridge, Tennessee; December 17, 2008a.

Oak Ridge Institute for Science and Education. Survey ProceduresManualfor the Independent EnvironmentalAssessmentand Verification Program. Oak Ridge, Tennessee; May 1, 2008b.

Oak Ridge Institute for Science and Education. Document Review. Cross ContaminationPrevention and MonitoringPlan. Humboldt Bay Power Plant. Eureka, California. Oak Ridge, Tennessee; January 9, 2009a.

Oak Ridge Institute for Science and Education. Laboratory ProceduresManualforthe Independent EnvironmentalAssessment and Verification Program. Oak Ridge, Tennessee; June 30, 2009b.

Pacific Gas & Electric Company (PG&E). Humboldt Bay Power Plant Technical Basis Document:

Gamma Scan Detection Capabilities. TBD-006, vol. 12, Rev. 0. Eureka, California; October 2, 2008.

Pacific Northwest Laboratory (PNL). Residual Radionuclide Distributionand Inventory at the Humboldt Bay NuclearPlant, (PNL-4628); May 1983.

U. S. Environmental Protection Agency (EPA). Guidance on Choosing a Sampling Designfor EnvironmentalData Collectionfor Use in Developing a Quality Assurance Project Plan, EPA QA/G-5S.

Washington, DC; December 2002.

U.S. Nuclear Regulatory Commission (NRC). Residual Radioactive Contaminationfrom Decommissioning:

ParameterAna~ysis.NUREG/CR-5512; Volume 3. Washington, DC; October 1999.

U.S. Nuclear Regulatory Commission. Multi-Agengc Radiation Survey and Site InvestigationManual (MARSSIM), NUREG-1 575; Revision 1. Washington, DC; August 2000.

Humboldt Bay Power Plant 13 1759-SR-01-0

APPENDIX A FIGURES Humboldt Bay Power Plant 1759-SR-01-0

0 CD 0 CL4ASS I LAW AWA

-. r~UCLAMS 3LANCAMA 0 W*4WAGMH *0INAREA 0 F-D UJMWLtflA* POWER PLMT?

0

0. NOT TO SCALE tNELAlFCTO4

>dV~

L____m

I dI Li I

I,

i ,"i I 32~

N N

-1 L Figure provided by Enercon NOT TO SCALE Figure A-2: Plot Plan of the Humboldt Bay Power Plant Indicating New Generation Footprint Area Humboldt Bay Power Plant A-2 1759-SR-01-0 J

NOT TO SCALE NGFA-WST-# I ESI Sample provided by Enercon.

Figure A-3: New Generation Area Final Status Survey Plan Sampling Locations Humboldt Bay Power Plant A-3 1759-SR-01 0

)oipflfT tirea, r-asi - "xamina 3ui Humboldt Bay Power Plant A-4 1759 SR 01 0

rigure v-D:) iNew %ueneraxion rootpnrnitire, WeST - %Jramma 3U]

Humboldt Bay Power Plant A-5 I759-SR-01-0

g Uamma Measurement Locations Humboldt Bay Power Plant A-6 1759-SR-01-0

N>

0 Ii.sol

-i

/

.. Survey Units n # Sample ID N

f 0 25 50 rigure uA- /: an~ea Dey 3ampi-ng z~ou 3ampie i~ocations Humboldt Bay Power Plant A-7 1759-SR-01 0

Figure A-8: ORISE Judgmental Soil Sample Locations Humboldt Bay Power Plant A-8 1759-SR-01 -0

Survey Units ORISE/4NGFA Samples 0 25 so Meters Figure A-9: ORISE New Generation Footprint Area Final Status Survey Split Soil Samples Humboldt Bay Power Plant A-9 1759-SR-01-0

NGFA-East Histogram 2000 1800 1600 1400 1200 4 1000 0

800 600 400 200 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400 4600 4800 5000 5200 More Counts per minute (cpm)

Figure A-10: Gamma Count Rate Distribution in NGFA-East NGFA-West Histogram 1600 1400 1200 E 1000 800 o" 600 400 600 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400 4600 4800 5000 5200 More Counts per minute (cpm)

Figure A-11: Gamma Count Rate Distribution in NGFA-West Humboldt Bay Power Plant A-10 1759-SR-01-0

APPENDIX B TABLES Humboldt Bay Power Plant 1759-SR-01 0

TAL B-1 NE GEEATO FOTPIN AREA H *UMOD BAYN.¶l PO5WER PLANT~

EUEA CALIFRNA Coordinates ORISE Rank Set Sample Locationsa

[k~e

  • Low R

..:RSSam Gamma Medium Counts North 2160845 I East 5949889

} Label. -

RSS Rank 1

Set 1

Sample High (cpm) 1 3,196 1 2161130 5949756 RSS 1 1 2 L 3,311 2160768 5949823 RSS 1 1 3 L 3,522 2161034 5949870 RSS 1 2 1 2161082 5949955 RSS 1 2 2 M 3,277 2161222 5949840 RSS 1 2 3 M 2,941 2161003 5949784 RSS 1 3 1 2160781 5949724 RSS 1 3 2 H 3,290 2160819 5499773 RSS 1 3 3 H 3,099 2161098 5949827 RSS 2 1 1 2160835 5949841 RSS 2 1 2 L 3,415 2160941 5949707 RSS 2 1 3 L 3,421 2160864 5949542 RSS 2 2 1 M 3,508 2161153 5949970 RSS 2 2 2 M 3,091 2160978 5949913 RSS 2 2 3 2160876 5949746 RSS 2 3 1 H 3,177 2161168 5949804 RSS 2 3 2 H 3,179 2160799 J 5949879 j RSS J 2 3 3 1 3,260 1 aRefer to Figure A-6.

bShaded areas indicate RSS soil sample locations based on gamma measurement results. Refer to Appendix E for RSS procedure.

Humboldt Bay Power Plant B-1 1759-SR-01-0

TAL B-2 RADINUCID COCNRAIN IN SOI

. amma G RadionucideConcentration in Soil Samples Sample Sample Grid Activity (tCi/g)

ID/Location Coordinates (cpm) Co,60 Cs-137 ORISE Ranked Set Samples - New Generation Footprint Areab S0003 5949889E, 2160845N 3,196 0.00c +/- 0.03d 0.00 + 0.02 S0004 5949870E, 2161034N 3,226 -0.01 +/- 0.03 0.04 + 0.02 S0005 5949784E, 2161003N 3,434 0.00 +/- 0.03 0.04 + 0.03 S0006 5949827E, 2161098N 3,374 -0.01 +/- 0.04 0.04 + 0.01 S0007 5949913E, 2160978N 3,197 0.01 + 0.03 0.00 + 0.02 S0008 5949879E, 2160799N 3,260 0.01 +/- 0.03 0.01 + 0.02 Mean Activity/Concentration 3,281 0.00 0.02 ORISE Judgmental Soil Samples - Soil Pilee S0001 5949417E, 2161496N 3,626 0.02 + 0.03 0.15 + 0.02 S0002 5949387E, 2161482N 4,336 0.00 +/- 0.05 0.10 + 0.02 ORISE Judgmental Soil Samples - New Generation Footprint Areae S0009 5949769E, 2161119N 3,333 -0.02 +/- 0.04 0.15 + 0.03 S0010 5949827E, 2161095N 3,314 -0.01 +/- 0.03 0.00 + 0.03 S0011 5949760E, 2161092N 3,386 -0.01 +/- 0.04 0.07 + 0.02 S0012 5950032E, 2161093N 2,926 -0.01 +/- 0.04 0.07 + 0.02 S0013 5949966E, 2160780N 2,937 0.03 +/- 0.04 0.20 + 0.03 S0014 5949799E, 2160836N 3,085 -0.04 +/- 0.05 0.09 + 0.02 S0015 5949781E, 2160797N 3,056 0.02 +/- 0.03 0.02 + 0.01 ESI Final Status Survey Split Soil Samples - New Generation Footprint Area' S0016 NGFA-WST-7 ---g 0.02 + 0.03 0.01 + 0.02 S0017 NGFA-WST-5 --- 0.02 +/- 0.04 0.02 + 0.02 S0018 NGFA-EST-4 --- 0.01 +/- 0.03 0.01 + 0.02 S0019 NGFA-EST-13 .- 0.02 +/- 0.06 0.11 + 0.03 aORISE Laboratory Procedure, CP1, Revision 16.

bRefer to Figure A-7.

cZero values due to rounding.

dUncertainties are total propagated uncertainties, based on the 95% confidence interval.

eRefer to Figure A-8.

fRefer to Figure A-9. Sample grid coordinates are those provided by ESI for their FSS split samples.

gORISE did not collect gamma surface activity measurements at the ESI FSS split soil sample locations.

Humboldt Bay Power Plant B-2 1759-SR-01-0

EUEA CALIFORNIA*'

Sample Sample Grid Cs-137 Concentration in Soil Samples (pCi/g)

ID/Location Coordinates, ORISEC I GEL-S0020 B-15-1.0 0.03 +/- 0.02c 0.02 + 0.03 S0021 B-33-4.5 0.01 + 0.04 -0.04 +/- 0.04 S0022 PS-02C0.3 0.07 + 0.03 0.01 +/- 0.04 S0023 PS-06C-2.0 -0.07 +/- 0.07 0.01 + 0.02 S0024 B-12-4.0 0.01 + 0.04 0.01 +/- 0.03 S0025 B-11-1.0 0.001 + 0.05 0.00 +/- 0.02 S0026 B-6-4.0 0.05 + 0.06 -0.02 +/- 0.04 S0027 B-24-0.5 0.08 + 0.02 0.09 +/- 0.05 S0028 B-4-1.0 0.06 + 0.03 0.00 +/- 0.05 S0029 B-23-4.0 0.06 +/- 0.07 -0.04 +/- 0.06 aThe laboratories are ORISE and GEL.

bSample grid coordinates provided by ESI.

CORISE Laboratory Procedure, CP1, Revision 16.

dGEL analytical results provided to ORISE by ESI.

ýORISE uncertainties are total propagated uncertainties, based on the 95% confidence interval.

fZero values due to rounding or the result of equal sample and background counts in the region of interest.

Humboldt Bay Power Plant B-3 1759-SR-01-0

APPENDIX C MAJOR INSTRUMENTATION Humboldt Bay Power Plant 1759-SR-01-0

APPENDIX C MAJOR INSTRUMENTATION The display of a specific product is not to be construed as an endorsement of the product or its manufacturer by the author or his employer. Each instrument/detector combination was within the required calibration intervals as per the ORISE Survey Procedures and Laboratory Procedures manuals.

SCANNING INSTRUMENT/DETECTOR COMBINATIONS Gamma Ludlum Ratemeter-Scaler Model 2221 (Ludlum Measurements, Inc., Sweetwater, TX) coupled to Fluke Miomedical NaI(T1) Scintillation Detector Model 489-55, Crystal:,3.2 cm x 3.8 cm (Fluke Biomedical, Cleveland, OH) coupled to:

Trimble GeoXH Receiver and Data Logger (Trimble Navigation Limited, Sunnyvale, CA)

DIRECT MEASUREMENT INSTRUMENT/DETECTOR COMBINATIONS Gamma Victoreen Nal Scintillation Detector Model 489-55, Crystal: 3.2 cm x 3.8 cm (Victoreen, Cleveland, OH) coupled to:

Ludlum Ratemeter-scaler Model 2221 (Ludlum Measurements, Inc., Sweetwater, TX) coupled to:

Trimble GeoXH Receiver and Data Logger (Trimble Navigation Limited, Sunnyvale, CA)

LABORATORY ANALYTICAL INSTRUMENTATION High Purity Extended Range Intrinsic Detector CANBERRA/Tennelec Model No: ERVDS30-25195 (Canberra, Meriden, CT)

Used in conjunction with:

Lead Shield Model G-1 1 (Nuclear Lead, Oak Ridge, TN) and Multichannel Analyzer Canberra's Apex Gamma Software Dell Workstation (Canberra, Meriden, CT)

Humboldt Bay Power Plant C-1 1759-SR-01-0

LABORATORY ANALYTICAL INSTRUMENTATION - CONTINUED High Purity Extended Range Intrinsic Detector Model No. GMX-45200-5 (AMETEK/ORTEC, Oak Ridge, TN) used in conjunction with:

Lead Shield Model SPG-16-K8 (Nuclear Data)

Multichannel Analyzer Canberra's Apex Gamma Software Dell Workstation (Canberra, Meriden, CT)

High-Purity Germanium Detector Model GMX-30-P4, 30% Eff.

(AMETEK/ORTEC, Oak Ridge, TN)

Used in conjunction with:

Lead Shield Model G- 16 (Gamma Products, Palos Hills, IL) and Multichannel Analyzer Canberra's Apex Gamma Software Dell Workstation (Canberra, Meriden, CT)

Humboldt Bay Power Plant C-2 1759-SR-01-0

APPENDIX D SURVEY AND ANALYTICAL PROCEDURES Humboldt Bay Power Plant 1759-SR-01-0

APPENDIX D SURVEY AND ANALYTICAL PROCEDURES PROJECT HEALTH AND SAFETY The proposed survey and sampling procedures were evaluated to ensure that any hazards inherent to the procedures themselves were addressed in current job hazard analyses (JHA). All survey and laboratory activities were conducted in accordance with ORISE health and safety and radiation protection procedures.

Pre-survey activities included the evaluation and identification of potential health and safety issues.

Survey work was performed per the ORISE generic health and safety plans and a site-specific integrated safety management (ISM) pre-job hazard checklist. PG&E also provided site-specific safety awareness training.

CALIBRATION AND QUALITY ASSURANCE Calibration of all field and laboratory instrumentation was based on standards/sources, traceable to the National Institute of Standards and Technology (NIST).

Analytical and field survey activities were conducted in accordance with procedures from the following Oak Ridge Associated Universities (ORAU) and ORISE documents:

- Survey Procedures Manual (May 2008)

- Laboratory Procedures Manual (June 2009)

- Quality Program Manual (June 2009)

The procedures contained in these manuals were developed to meet the requirements of 10 CFR 830 Subpart A, Quality Assurance Requirements, Department of Energy Order 414.1 C Qualiy Assurance, and the U.S. Nuclear Regulatory Commission Quality Assurance Manualforthe Ofice of NuclearMaterial Safety and Safeguards and contain measures to assess processes during their performance.

Quality control procedures include:

Daily instrument background and check-source measurements to confirm that equipment operation is within acceptable statistical fluctuations.

Humboldt Bay Power Plant D-1 1759-SR-01-0

" Participation in Mixed-Analyte Performance Evaluation Program (MAPEP), NIST Radiochemistry Intercomparison Testing Program (NRIP), and Intercomparison Testing Program (ITP) Laboratory Quality Assurance Programs.

" Training and certification of all individuals performing procedures.

" Periodic internal and external audits.

CALIBRATION PROCEDURES Calibration of all laboratory instrumentation was based on standards/sources, traceable to NIST, when such standards/sources were available. In cases where they were not available, standards of an industry-recognized organization were used.

SURVEY PROCEDURES Surface Scans A Nal scintillation detector was used to scan for elevated gamma radiation. Identification of elevated radiation levels was based on increases in the audible signal from the recording and/or indicating instrument. Additionally, the detectors were coupled to GPS units with data loggers enabling real-time recording in one-second intervals of both geographic position and the gamma count rate. Positioning data files were downloaded from field data loggers for plotting using commercially available software (http://trl.trimble.com/docushare/dsweb/Get/Document-261826/GeoExp12005 100A GSG ENG.pdf>. Position and gamma count rate data files were transferred to a computer system, positions differentially corrected, and the results plotted on geo-referenced aerial photographs. Positional accuracy was within 0.5 meters at the 9 5 th percentile.

The scan minimum detectable concentrations (MDC) for the Nal scintillation detectors were 10.4 pCi/g for Cs-137 and 5.8 pCi/g for Co-60 as provided in NUREG-1507. An audible increase in the activity rate was investigated by ORISE. It is standard procedure for the ORISE staff to pause and investigate any locations where gamma radiation is distinguishable from background levels.

Soil Sampling Approximately 0.5 to 1 kilogram (kg) of soil was collected at each sample location. Collected Humboldt Bay Power Plant D-2 1759-SR-01-0

samples were placed in a plastic bag, sealed, and labeled in accordance with ORISE survey procedures.

RADIOLOGICAL ANALYSIS Gamma Spectroscopy Samples of soil were dried, mixed, crushed, and/or homogenized as necessary, and a portion sealed in a 0.5-liter Marinelli beaker or other appropriate container. The quantity placed in the beaker was chosen to reproduce the calibrated counting geometry. Net material weights and volumes were determined and the samples counted using intrinsic germanium detectors coupled to a pulse height analyzer system. Background and Compton stripping, peak search, peak identification, and concentration calculations were performed using the computer capabilities inherent in the analyzer system. All total absorption peaks (TAP) associated with the gamma emitting COC were reviewed for consistency of activity. TAPs used for determining the activities of COC and the typical associated MDCs for a one-hour soil gamma spectroscopy count time and a 16-hour water gamma spectroscopy count time were:

Co-60 1.173 0.06 Cs-137 0.661 0.11 Uncertainties The uncertainties associated with the analytical data presented in the tables of this report represent the total propagated uncertainties for that data. These uncertainties were calculated based on both the gross sample count levels and the associated background count levels.

DETECTION LIMITS Detection limits, referred to as minimum detectable concentrations, were based on 3 plus 4.65 times the standard deviation of the background count [3 + (4.65 (BKG)'"2 )]. Because of variations in background levels, measurement efficiencies, and contributions from other radionuclides in samples, the detection limits differ from sample to sample and instrument to instrument.

Humboldt Bay Power Plant D-3 1759-SR-01-0

APPENDIX E ORISE STATISTICAL SURVEY DESIGN FOR THE NEW GENERATION FOOTPRINT AREA HUMBOLDT BAY POWER PLANT EUREKA, CALIFORNIA Humboldt Bay Power Plant 1759-SR-01-0

APPENDIX E ORISE STATISTICAL SURVEY DESIGN FOR THE NEW GENERATION FOOTPRINT AREA HUMBOLDT BAY POWER PLANT EUREKA, CALIFORNIA SURVEY DESIGN

SUMMARY

ORISE used available pre-final status survey data to develop a defensible statistical sampling and survey design for the New Generation Area Footprint. The selected VSP statistical approach, as set forth in EPA QA/G-5S, calculates the number of samples required to determine a confidence interval for the mean that meets the boundaries provided by the user. A ranked set sampling (RSS) design was selected using associated statistical assumptions as well as general guidelines for conducting post-sampling data analysis. The sampling plan components included how many sampling locations to choose and where within the sampling area to collect those samples.

The following table summarizes the balanced ranked set sampling design developed. Figure A-6 shows the VSP measurement locations in the field. Table B-1 lists the sampling coordinates generated by VSP that were identified in the field.

'Prtm-ary.Objrtive, f Design Sample Placement (Location)

ISimpleEsiimaýtet4-random sampling popltheen,  :,

in the Field Formula for calculating Balanced ranked set sampling equations number of sampling locations in EPA QA/G-5S (EPA, 2001)

Number of Ranks (m) 3 (Chosen Set Size)

Calculated Number of Cycles (r) 2 Number of Samples to Analyze 6 (m x r)

Number of Field Locations to Rank 18 (m x m x r)

Number of selected sample areas 2 Specified sampling area b 202,754 ft2 The number of selected sample areas is the number of colored areas on the map of the site. These sample areas contain the locations where samples are collected.

The sampling area is the total surface area of the selected colored sample areas on the map of the site.

The following VSP report was generated using site inputs and is as follows: RSS involves selecting a set of field locations using simple random sampling, then dividing the locations into subsets (called "sets"). Then either professional judgment (expert opinion) or a quantitative inexpensive field measurement method is used in the field to rank (order) the locations within each set with respect to the variable being measured. Then, within each set, only one location among the ranked locations is selected to be sampled for laboratory analysis. The method used to determine the number of Humboldt Bay Power Plant E-1 1759-SR-01-0

locations that need to be ranked and the number of locations that need to be sampled for measurement in the laboratory is described in EPA QA/G-5S (EPA 2006).

RSS was chosen because that design was found to be more cost effective for estimating the mean than simple random sampling. It is expected to yield a narrower confidence interval for the mean than a. simple random sampling design with the same number of laboratory analyzed samples. RSS sampling design can achieve cost savings by implementing relatively inexpensive qualitative (expert opinion and/or professional judgment) or quantitative field screening techniques in association with more expensive laboratory analytical measurements of samples. Additionally, RSS provides an unbiased estimate of the mean and can yield an increased ability to detect differences in the parameters of different populations (e.g., site and background areas).

The assumptions that underlie RSS are expected to be valid and will be examined in post-sampling data analysis. There are some limitations associated with ranked set sampling. The increased precision of the estimated mean obtained using ranked set sampling compared to simple random sampling is reduced if errors are made in ranking field locations. However, even when ranking errors occur, RSS is never expected to be less precise than if simple random sampling with the same number of measurements is used. Another limitation is that ranked set sampling may not be more cost effective than simple random sampling if field locations are clustered in space rather than selected randomly. In addition, computations needed to conduct some statistical analyses such as tests of hypotheses using data obtained from RSS are different that the standard computations used when sample locations are selected using simple random sampling. Hence, statistical expertise may be needed to determine the appropriate calculations. Finally, information collected from the ranking process, including any quantitative measurements that are used to conduct the ranking, is not used to calculate the mean (EPA 2006).

DETERMINATION OF NUMBER OF DATA POINTS Number of Total Samples: Calculation Equation and Inputs The number of samples is calculated by following the process for RSS outlined in EPA QA/G-5S.

This process has been detailed in the following discussions of the points. The following steps outline the user inputs and calculations conducted within VSP to determine the RSS design.

1. Determine the number of samples required under simple random sampling, n,
2. Select the "set size", m
3. Determine the relative precision (RP) of simple random sampling compared to ranked set sampling
4. Compute the number of cycles, r, of RSS that are required
5. Compute the total number of ranked set samples, n, that should be collected and measured to estimate the mean
1. Determine the number of samples required under simple random sampling, n,;

In order to determine the number of samples to collect if simple random sampling were used, n0, VSP requires the user to specify whether the distribution of measurements resulting from laboratory samples is expected to be symmetric or skewed to the right (a long right tail). If the expected distribution is symmetric, then a balanced ranked set sampling design will be used and the number of samples is calculated by VSP using either a one-sided or a two-sided confidence interval equation, Humboldt Bay Power Plant E-2 1759-SR-01-0

as selected by the VSP user. If the expected distribution is skewed to the right, then an unbalanced ranked set sampling design will be used and the number of samples is computed using the method outlined by Perez and Lefante (1997).

The equation used to calculate no for the balanced RSS case is the same as VSP uses to compute the number of samples required for computing a two-sided confidence interval for the mean when simple random sampling is used. The calculated number of samples, no, using simple random sampling will result in a confidence interval that has a half-width that does not exceed the maximum acceptable half-width specified by the VSP user.

For a two-sided confidence interval, the equation used to calculate the number of samples under simple random sampling, no, when the expected distribution is symmetric and a balanced ranked set sampling design is used is:

Where, no is the recommended minimum number of samples for the study area if simple random sampling were used, s is the estimated standard deviation of measurements of collected samples, d is the maximum desired half-width of the confidence interval, tl_=/2,df is the value of the Student's t-distribution with n-I degrees of freedom (dJ) such that the proportion of that distribution less than tl-/2,df is 1 -a/2 Because n appears on both sides of the above equation (on the right side it appears in the degrees of freedom of the t distribution), the equation must be solved iteratively. VSP does this automatically using the iteration scheme in Gilbert (1987, pg. 32).
2. Select the "set size", m; The set size, m, is an integer between 2 and 8 selected by the VSP user. When a balanced RSS design is used, m is the number of field locations sampled in each cycle of RSS. The number of cycles is denoted by r. Hence, the total number of locations sampled when balanced ranked set sampling is used is n = m x r. The value of m selected is usually based on practical constraints in ranking locations by professional judgment or quantitative field measurements. If professional judgment is used to rank potential field locations, G-5S recommends setting m <= 5 due to the potential lack of accuracy in ranking by professional judgment. If field quantitative measurements are used to rank potential locations, then the ranking may be accurate for larger values of m.
3. Determine the relative precision (RP) of simple random sampling compared to ranked set sampling; The estimated relative precision (RP) is the estimated variance of the mean if simple random sampling is used divided by the estimated variance of the mean if ranked set sampling is used. When a balanced ranked set sampling design is used, VSP uses the RPs published by Patil et al. (1994, Table 1) for the normal distribution. The RPs depends only on the set size, m, specified by the VSP user. (If an unbalanced ranked set sampling design is used, then VSP uses a more complicated process to determine the RP, as described in EPA QA/G-5S.)

Humboldt Bay Power Plant E-3 1759-SR-01-0

4. Compute the number of cycles, r, of ranked set samples that are required; VSP calculates the number of cycles, r, needed in the ranked set sampling design by using the values of no, m, and RP as follows:

r= x

Where, r is the number of cycles, no is the number of samples required under simple random sampling, m is the set size specified by the VSP user, RP is the relative precision.
5. Compute the total number of ranked set samples, n, that should be collected and measured to estimate the mean; The number of field locations that are sampled and taken to the laboratory for measurement is calculated by VSP as nl -r
where, n is the number of samples that are measured, r is the number of cycles, m is the set size.

The values of these inputs that result in the calculated number of sampling locations are:

i- i-,teV Mý 3 S_ 0.34

_.. _d, 0.23 cc 5%

t-/2,d"f 2.22814a RP 21.914b r 2

'This value is automatically calculated by VSP based upon the user defined value of a.

bThis value is automatically calculated by VSP based upon the set size.

Statistical Assumptions The assumptions used to determine the number of balanced RSS are:

1. The sample mean is normally distributed (used to compute no),
2. The variance estimate, s2, is reasonable and representative of the population being sampled (used to compute n.),
3. The data distribution is symmetric and approximately normally distributed (used to determine the Humboldt Bay Power Plant E-4 1759-SR-01-0
4. The estimate of the sample mean is reasonable and representative of the population being sampled, and,
5. The field locations that will be ranked are selected using simple random sampling.

The first three assumptions will be assessed in a post data collection analysis. The fourth assumption is valid because the estimate of the mean will be an unbiased estimate of the mean.

Sensitivity Analysis The sensitivity of the calculation of number of samples was explored by varying the standard deviation, confidence level (1-a) (%), width of confidence interval and set size. The following table shows the results of this analysis.

m=2 m#3 m 4 s=0.68[s=0.34 s--0.68 [s=0.34~ s=0.68 :s=0.34 CL=99 d=0.115 162 44 126 33 104 28 d=0.23 44 14 33 12 28 12 d=0.345' 22 8 18 6 16 8 CL=97 d=0.115 116 32 90 24 72 20 d=0.23 32 10 24 9 20 8 d=0.345 16 6 12 6 12 4 CL=95 d=0.115 94 26 72 21 60 16 d=0.23 26 8 21 6 16 8 d=0.345 14 6 12 6 8 4 CL=93 d=0.115 80 22 63 18 52 16

_ d=0.23 22 8 18 6 16 8 d=0.345 12 6 9 6 8 4 CL=91 d=0.115 72 20 54 15 44 12 d=0.23 20 8 15 6 12 4 d=0.345 10 4 9 3 8 4 s= Standard Deviation CL = Confidence Level (1-a) (%)

d = Width of Confidence Interval m = Set Size This report was automatically produced* by Visual Sample Plan (VSP) sofrware version 5.3.

Software and documentation available at http://dqo.pni.gov/vsp Software copyright (c) 2009 Battelle Memorial Institute. AD rights reserved.

  • - The report contents may have been modified or reformatted by end-user of software.

Humboldt Bay Power Plant E-5 1759-SR-01-0

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