6.0 SURVEY DESIGN
6.1 Determining Survey Locations
A scale drawing of each survey unit will be developed that shows the planar reference coordinate system, i.e. the grid system. This will be used to identify the specific location for each measurement within a survey unit such that measurements can be reproduced accurately.
Class 1 survey units will have dimensions as determined in Section 4.1. The number of calculated survey locations, n, determined as specified in Section 4.5, will be used to determine the spacing, L, of the systematic pattern, based on the area, A, of the survey unit. This will be done for a triangular grid system with:
L=Square Root of "A" divided by "0.866n"
The following grids will have a triangular grid spacing:
EZ-5, EZ-6, EZ-7, EZ-8, EZ-9,
EZ-10, EZ-11, EZ-12, EZ-14, EZ-15,
EZ-18, EZ-19, DMP-1, DMP-2, DMP-3,
DMP-4, DMP-5, DMP-6, DMP-7, DMP-8
If approved by the project Certified Health Physicist, project manager and contracting officer's representative the spacing of the grids may be changed to square grid spacing.
For a square grid system:
L=Square Root of "A" divided by "n"
The following grids will have a square grid spacing:
EZ-1, EZ-2, EZ-3, EZ-4, EZ-13,
EZ-16, EZ-17, HWY-1, HWY-2, HWY-3,
HWY-4, HWY-5
When L has been determined a random coordinate location will be identified by picking two random numbers and multiplying them by the appropriate survey unit dimension to provide coordinates, representing the X axis and Y axis, relative to the origin of the survey unit. Beginning at the random starting coordinate, a row of points is identified, parallel to the X axis, at intervals of L.
For a triangular grid, a second row of points is then developed, parallel to the first row, at a distance of 0.866 x L from the first row. Survey points, along the X axis, along the second row are midway between the points on the first row. See Section 5.5.2.5 of Reference 2.1. These survey points are where soil samples shall be taken. If any measurement, either sample gamma analysis or scanning is above the DCGLwor the DCGLEMC they shall be flagged for further investigation.
Structure surfaces for a specific survey unit will be included on a single reference grid system for purposes of identifying survey locations. Judgement locations should be included in addition to the specified survey locations that seem to have an unusual appearance, suspect location, high potential for residual contamination or other objective characteristic as determined by the project radiological team. These points are not to be included in the points selected for statistical evaluation. These judgmental points are evaluated individually with the established DCGLw. If the measurement, either scaler counts, scanning results or smear results, are above the DCGLw they shall be flagged for further investigation. If the measurements are above the DCGLEMC the area will be remediated.
Table 6.1
Final Status Survey Investigation Levels
|
Survey Unit
Classification |
Flag Direct Measurements or Sample Results When: |
Flag Scanning Measurement Results When |
|
Class 1 |
>DCGLEMC> DCGLw and > a statistical parameter based value |
>DCGLEMC |
6.2 Survey Strategy
The objective of the scanning surveys is to identify areas that need additional investigation and determine the concentration, area and extent of the contamination.
Class 1 areas will be scanned over 100% of the surface area during the final status survey. This is to provide reasonable assurance that small areas of elevated activity will not be missed. Parallel survey lines will be developed that cover the field of view of the detector scanning instrument. For example, if the field of view of the detector is 5 cm, parallel paths should be set up 5 cm apart. See Table 6.2.
Table 6.2
Recommended Survey Coverage
|
. |
Structures |
Structures |
Land Areas |
Land Areas |
|
Area Class-
ification |
Surface Scans |
Surface Activity Measurements |
Surface Scans |
Soil Samples |
|
Class 1 |
100% |
Number of data points § 4.5, plus areas of elevated activity |
100% |
Number of data points § 4.5, plus areas of elevated activity |
6.3 Surface Soil
6.3.1 Rationale
Surface soil and near-surface soil will be collected before, during, and after the remedial activities for several different purposes. This subsection is intended to describe the numbers, locations, purpose, and rationale for collecting each type of soil sample.
6.3.1.1 Surface and Near-Surface Soil Sample Locations
Soil samples will be collected and analyzed during the remedial action program for two different purposes.
The first set of soil samples will be collected during the remedial activities and is referred to as the "Soil Characterization Samples." These samples will be collected from the perimeter of the excavation areas, excavation pit floor, and from elsewhere on-site (e.g., haul road, soil storage area, loadout area) where the gamma walkover surveys show gamma radiation levels to be at the threshold values and it is unclear whether the soil materials are >8 or <8 pCi/g. The collection of these samples and rapid analyses in the on-site laboratory will provide a means to quickly assess whether or not soil materials should be sent off-site for disposal.
The second set of soil samples to be collected during the project is the "Final Status Survey samples." These samples will be collected from excavation pit floors and side slopes after all contaminated soils have been removed and a gamma radiation walkover survey of each excavation area has been performed. They will also be collected from other survey units around the Site. The purpose of these samples is to confirm that all contaminated soils exceeding the cleanup criteria have been removed.
6.3.1.2 Sediment Sample Locations
Two different types of sediment samples will be collected during the course of the project. The first type involves sediments that accumulate in the sumps, the water retention pond, and the silt fences that are potentially contaminated. Each of these sediment locations will be sampled and analyzed based on sediment build-up in the field laboratory. When necessary, the sediment that has accumulated at these locations will need to be removed. The laboratory analyses will dictate whether the sediments will be placed in the <8 pCi/g soil storage pile, or whether it will be placed in the pile destined for off-site disposal.
The second type of sediment samples to be collected are those from the drainage swale that is present on-site. This swale drains to a corrugated metal pipe (CMP) that eventually runs underneath Route 539. The samples will be collected at the discharge point of the CMP and analyzed at the field laboratory. The results will help determine whether radiologically-contaminated soils are migrating off-site and whether remedial activities are accelerating the rate of off-site migration. If the data indicate that off-site migration is measurable, then additional steps for controlling soil erosion will be evaluated and implemented to reduce off-site migration of contaminated sediments.
6.3.1.3 Discrete/Composite Soil and Sediment Sampling Requirements
All soil and sediment samples collected during the project will be discrete samples, except for the composite soil samples that will be collected from the >8 pCi/g pile that is destined for off-site disposal. For composite soil samples collected from stockpiles destined for disposal 20 discrete samples will be taken from each 500 cubic yards of soil. These samples will be composited into 5 samples that will be analyzed by the on-site gamma spectroscopy laboratory to determine the Pu concentration.
6.3.1.4 Field and Laboratory Analyses
Table 6.3 lists the field measurements that will be made, the analyses that will be performed in the field laboratory, and the analyses that will be performed in the off-site laboratory for soil samples and sediment samples collected during the field program.
For all samples, gross gamma measurements will be performed using hand-held field instruments and analyses of moisture content and gamma spectroscopy will be performed in the field laboratory.
The on-site laboratory is equipped with a High Purity Germanium (HPGE) gamma spectroscopy system. The HPGE system consists of an EG&G HPGE detector, a multi-channel analyzer, and the EG&G GammaVision ® software. The HPGE system is capable of detecting low energy gamma radiation in soil, soil equivalent material (concrete, vegetation), and water. The HPGE system is setup to analyze the full spectrum of the gamma library using gamma emission calculations and subsequent equilibrium and decay calculations.
Table 6.3
Contaminants of Concern and Corresponding Analytical Methods
for Soil and Sediment Samples
|
On-Site Analyses |
Analytical Method |
|
Am-241 |
On-Site Gamma Spectroscopy Unit |
|
Off-Site Analyses |
. |
|
Am-241 |
EML Am-01-RC/ Alpha Spectroscopy, serial extraction, Reference 2.9 |
|
Pu-239/240 |
EML Pu-02-RC/ Alpha Spectroscopy, serial extraction, Reference 2.9 |
|
Am-241 |
Gamma Spectroscopy |
|
Lead |
SW3050A, 6010B |
Quality Control Requirements for Soil and Sediment Samples
|
On-Site Analytical Method |
Analyte |
Required Precision
(2) |
Required Accuracy(2) |
Required MDA
(3) |
|
Gamma Spectroscopy |
Am-241 |
(1) |
(1) |
0.19 pCi/g |
|
Analytical Method |
Analyte |
Required Precision (2) |
Required Accuracy (2) |
Required MDA (3) |
|
Alpha Spectroscopy |
Isotopic Americium |
35% |
80-120% |
0.19 pCi/g |
|
Alpha Spectroscopy |
Isotopic Plutonium |
35% |
80-120% |
0.19 pCi/g |
|
Gamma Spectroscopy |
Am-241 |
(1) |
(1) |
0.19 pCi/g |
|
Metals |
Lead |
20% |
80-120% |
3 micro g/l |
(1) Required accuracy and precision is accomplished by performing a soil spectrum standard at the beginning of every day. This is the reference check for the on-site gamma spectroscopy unit. The results obtained during the day are compared against this standard. Three radionuclides spectrum are compared against the reference. The results between the two should be within a 90 percent confidence interval. These results should also be recorded such that trending of the spectrum against the reference be accomplished daily. The minimum detectable concentration (MDC) for this instrument is also based on this reference spectrum.
(2) Required accuracy and precision for off-site analyses are determined by the recovery of the tracers and the Relative Percent Difference (RPD) between laboratory duplicates and/or lab control samples. Recovery fractions should be approximately 50% and shall be greater than 15% for Pu and Am. This is tracked by the coefficient of variation on the distribution of ratios of Pu to Am . Counting and system errors are also taken into consideration.
(3) The MDC for a given analyte is determined from the lowest standard in the calibration curve for that analyte. Detection limits for radiological samples are highly variable and must take into consideration daily calibration results of the sources, instrument efficiency, matrix, count time, etc.
6.3.1.5 QA/QC, and Blank Samples and Frequency
Sample replicates (i.e., blind duplicates) will be sent to the field laboratory and the off-site laboratory at a frequency of one replicate per 20 soil and sediment samples analyzed. These samples will be taken during the final status survey. The replicate samples will be analyzed for the same parameters that the primary samples are being analyzed. The replicate sample used for gamma spectroscopy by the off-site laboratory may be the same sample used on-site. Agreement for precision between the on-site analysis and off-site analysis will be considered acceptable if the results and the ranges covered by + or - 3 standard deviations overlap.
Blank samples, samples that represent soil from off-site areas, will be taken during the final status survey and will be analyzed by the on-site laboratory. Agreement for precision between the analysis and the minimum detectable concentration will be considered acceptable if the results and the ranges covered by + or - 3 standard deviations overlap.
6.3.2 Procedures
6.3.2.1 Sampling Methods for Surface Soil and Sediment
Surface soil samples will be collected from a depth of 0 to 6 inches using a decontaminated trowel. Sediment will be collected from the uppermost 6 inches of material. Gross gamma survey measurements will generally be employed to select discrete sampling locations that have the highest gross gamma values. If soil sampling locations are vegetated, the above-ground vegetation and top one inch of soil material will be scraped off and discarded.
For dry soil sampling locations, the soil will be stirred and mixed in-place and then placed directly into sample containers. If the soil sampling location is saturated or contains standing water, then the sample material will be dug up with the trowel, placed into a stainless steel mixing bowl, excess water will be decanted out of the bowl, and the material will be thoroughly mixed using the trowel. The trowel will then be used to place sample material into the sample container.
6.3.2.2 Field Measurement Procedures and Criteria
For each Soil Characterization Sample not submerged beneath standing water, a gross gamma radiation measurement will be made from directly above the sample, and the location and approximate elevation will be determined. For most of the sampling sites, the locations will be determined using the GPS instrument. However, engineer's surveying equipment and methods will be used to get a more accurate fix on sampling location and elevation, if necessary.
6.3.2.3 Sample Containers and Preservation Techniques
All soil samples that are collected for on-site and off-site radiological analyses will be placed in a one-liter, wide-mouth polyethylene bottle or zip-lock plastic bag. Samples for radiological analyses do not require preservation.
6.3.2.4 Field Quality Control Sampling Procedures
For each twenty soil samples collected for the on-site laboratory during the Final Status Survey, one blind duplicate will be submitted to the on-site laboratory and one replicate sample will be sent to the off-site laboratory for gamma spectroscopy. This replicate sample may be the same sample that was counted by the on-site laboratory.
6.3.2.5 Decontamination Procedures
Soil sampling equipment includes stainless steel trowels, spoons, mixing bowls and a hand auger. All soil sampling equipment will be decontaminated after each use as follows:
· scraping off dirt and mud;
· scrubbing with Alconox and potable water solution;
· rinsing with potable water; and
· rinsing with distilled water.
All used decon solutions will be placed in a holding tank, which will be used for dust control on the >8 pCi/g soil to be excavated.
6.4 Storm Water and Surface Water
6.4.1 Rationale
No runoff waters from the disturbed areas or the soil stockpile areas will be allowed to leave the site. Waters from the sumps and excavation pits will be transferred to the temporary holding tank or a water truck and will be used for on-site dust suppression. If present, nearly all Pu present will be sorbed to the suspended solids. By allowing the suspended sediment to settle, the clarified water will be marginally clean and will be used to water the >8 pCi/g soil pile.
6.4.1.1 Surface Water Sample Locations
One grab sample will be collected from the drainage swale upstream of the drainage pipe that leads offsite during storm events, if possible. Samples will be collected based on visual observations of the volume and clarity of the surface water.
6.4.1.2 Sample Collection for On-Site and Off-Site Analysis
The surface water sample will be a discrete sample; compositing of water samples will not be performed. Samples will be analyzed by the on-site laboratory for gamma analysis using the HPGE system. One in 20 samples will be sent off-site for gamma spectroscopy.
6.4.1.3 QA/QC and Blank Samples and Frequency
For every twenty samples of surface water collected, duplicate samples will be submitted to the field and off-site laboratories for analysis by gamma spectroscopy.
6.4.2 Procedures
6.4.2.1 Sampling Methods for Surface Water - General
Water samples will be collected by lowering the sample bottle (one-liter polyethylene) into the water and allowing the bottle to fill. No sampling equipment will be used.
Since nearly all of the radioisotopes are sorbed onto suspended sediment, gross alpha measurements will be performed on filtered and un-filtered water samples. Total gross alpha activity will be measured in each sample.
6.4.2.2 Sample Containers and Preservation Techniques
Water samples will be collected in one-liter polyethylene bottles. Refrigeration or preservation will not be required. It should be noted when these samples are ready for laboratory analysis, the samples will be shaken vigorously to re-suspend the sediment.
6.4.2.3 Field Quality Control Sampling Procedures
For every 20 surface water samples collected, one duplicate sample will be collected. The duplicate samples will be analyzed for gross alpha radiation.
6.4.2.4 Decontamination Procedures
Since no field sampling equipment will be used for the collection of surface water samples, decontamination will not be required.
6.5 Surface Wipes
6.5.1 Rationale
Surface wipe samples will be collected from Shelter 204, the outer surfaces of shipping containers, trucks, automobiles, equipment, sample containers, or other items leaving the exclusion area or loading area that could be potentially contaminated. The sampling and analysis of wipes from these objects is required before they can be released from the Site for unrestricted use. Wipe samples are used to measure the amount of gross alpha, and beta activity that can be removed from a solid surface (i.e., removable activity).
6.5.1.1 Sample Locations
One or more surface wipe samples (100 cm2) will be collected from each object leaving the exclusion areas. The number of wipe samples per object will depend on the size of the object. Each object will be scanned first using hand-held gross alpha meters. The wipe samples will be collected from surface areas that exhibit the highest readings.
6.5.1.2 Sample Collection and Laboratory Analyses
A soft, dry filter paper will be used to wipe a 100 cm2 surface area using moderate pressure. The filter paper may be placed in a properly labeled envelope, and submitted to the on-site laboratory for gross alpha and beta analysis.
On-site gross alpha and beta analysis will be performed using a Protean LB5100 gas proportional detector. The Protean LB5100 unit is primarily setup and calibrated to detect gross alpha and beta contamination levels in surface and air contamination samples.
6.5.1.3 QA/QC and Blank Samples
Since a wipe sample cannot be replicated, no attempt will be made to collect replicate samples. Alpha counting is nondestructive and the same sample may be counted numerous times.
6.5.2 Procedures
6.5.2.1 Sampling Methods
After an object being surveyed is scanned, areas of highest activity will be sampled with a wipe to determine the amount of removable activity. A soft, dry filter paper will be used to wipe a 100 cm2 surface area using moderate pressure. The wipe may be placed in a properly labeled envelope and submitted to the on-site laboratory for gross alpha, beta, and gamma analysis.
6.5.2.2 Field Measurement Procedures and Criteria
Each object being surveyed for Free Release will first be scanned with a hand-held gross alpha meter.
6.5.2.3 Sample Containers and Preservation Techniques
When the wipe sampling procedure is completed, the wipe may be placed in a pre-labeled glassine envelope and submitted to the on-site laboratory. No refrigeration or preservatives are necessary for these samples.
6.5.2.4 Decontamination Procedures
Not applicable. Sampling equipment (i.e., the filter paper) is nonreusable and disposable.
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