mark blohm blohm consulting llc....
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Introduction
Overall Objectives of Work (OU B-1) Remedial Action (RA) to Identify and Dispose of Munitions and
Explosives of Concern (MEC).
Clear all Munitions to a depth of 4 feet below the top of the mineral layer.
Digital Geophysical Mapping (DGM) is primary method to detect buried MEC.
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IntroductionOverview What is Quality Assurance (QA) in DGM surveys?-In our case, the
basic QA objectives were to assure that the contractor adhered to approved project plans and met project performance criteria while the work was ongoing.
What is Quality Control (QC) in DGM surveys?- In our case, QC is adherence to a defined set of measurement performance criteria.
QA (Battelle function) is not intended to eliminate the need for or interfere with QC (contractor function).
In this project, QC and QA were guided by a comprehensive set of Measurement Performance Criteria (aka Data Quality Objectives or DQO’s) provided in the Munitions and Explosives of Concern-Quality Assurance Project Plan (MEC-QAPP), and other plans.
The specific QA metrics and procedures also were detailed in a Quality Assurance Surveillance Plan (QASP) generated by Battelle.
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Introduction
QA for DGM Surveys on Adak Island, AK. 9
•411 Grids
•~352 Acres
•11 Contractor DGM
Crews
Introduction
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DGM coverage at MM-10-F
•Approximately 1,176
linear miles of DGM.
•36,738 DGM targets
(approximately 104/acre)
•Field DGM and all QA of
Field DGM is 100%
complete.
•Intrusive operations
approximately 25%
complete.
Introduction Review of Digital Geophysical Mapping (DGM)
Methodology: Man-portable EM61-MK2 systems were utilized due to rough terrain.
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Introduction Review of Digital Geophysical Mapping (DGM)
Example DGM data from single profile over target.
Profile Location
EM61-MK2 Response
*Response is typically a single,
symmetric positive peak (anomaly),
centered over target location.
*The goal of QC (contractor) and QA
(Battelle) is to assure repeatability of
and accuracy of this anomaly.
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Introduction Review of Digital Geophysical Mapping (DGM)
Example DGM data coverage over a survey grid.
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Introduction Review of Digital Geophysical Mapping (DGM)DGM Targets from Grid Data.
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Targets to
Target list
and
Intrusive
Teams
QA Procedures and Results
QA of DGM data was performed after Contractor QC approved the DGM and was comprised of the following primary steps:
Complete review of contractor equipment tests.
Complete re-processing (from raw data to final target maps) of the contractor DGM data.
Comparison of Contractor and QA target lists to provide a final target list (Target Concurrence).
Additional QA procedures included:
Field QA Surveillances
QA Blind Seed Program
Post Intrusive QA Confirmation DGM Mapping
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Simplified DGM Data
Process
QA Procedures and ResultsContractor QC tests/procedures and performance criteria pertaining to DGM:
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Data TypeQC Sample and/or Activity to Assess Measurement
PerformanceMeasurement Performance Criteria
Raw Geophysical Sensor
Data
Standardization tests: QC audit of response test recordsResponse above background to standard object will not vary more than 20% for the instrument
used (Geonics EM61-MKII or approved equivalent)
All DGM grid data will be checked by the data
processors to ensure adequate coverage is obtained.
Total positioning holidays or “drop-outs” will not exceed 2% of the accessible area surveyed. If
the total area of the gaps exceeds this percentage, data will be recollected in those gaps if possible.
Operator ensures settings in data logger are set to project
requirements prior to geophysical data collection.Minimum data density of twelve points per second (approximately one point per 0.15 meter)
Noise Error: Referenced amplitude to be determined
during GPO; Standard deviation of background noise in
daily instrument checks to be calculated and assessed
during field activities
Maximum standard deviation of noise not to exceed 20% of the amplitude for the signal for a
horizontal 60mm mortar at 1.5 feet bgs
Raw Positional Data
QC audit of positioning system error test records (Sensor
Positioning Test)
Grid corners will be selected during the data processing of the grid data. Offsets can be measured
from the pick locations. Determined location must be within 2.5 ft of known location.
QC audit of actual grid digital geophysics maps.
Total positioning holidays or “drop-outs” will not exceed 2% of the accessible area surveyed. If
the total area of the gaps exceeds this percentage, data will be recollected in those gaps if
possible.
Processing and
Interpretation
Accuracy of interpreted anomaly locations assessed
during reacquisition of interpreted target anomaly
location
Interpreted location of anomalies within 2.5 ft radius of actual location.
OC review of identification of blind seed item location100 percent of all blind seed items installed by the UXOQCS will be accurately located to within
2.5 foot radius.
Last lane of grid is recollected from opposite direction
and compared (repeat line test and sensor position test)
Accuracy-Positional difference is <1.25ft.
Precision-Relative percent difference (RPD) in anomaly signal strength is less than +/- 20%.
QC audit of “latency” test recordsTotal positional error of merged data set will not exceed 0.5m based on a collection speed of 1.34
m/s (3mph). Collection speed must be less than 1.34 m/s (3 mph).
Comparison of primary target anomaly picks to QC picks
and comparison of combined primary and QC picks to
QA target anomaly picks.
RPD between primary and QC list is less than +/- 20%. RPD between primary /QC picks and QA
picks is less than +/-10%.
QA Procedures and Results
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Static-Standard Set-up
Static-Standard Data
Measurement Performance
Criteria: Raw Geophysical
Sensor Data-Standardization
Test
QA Procedures and Results
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Repeat Line Test
Measurement Performance Criteria:
Processing and Interpretation-
Repeat Line Test
QA Procedures and Results
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Contractor DGM QC Summary Documentation
QA Procedures and Results
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QA DGM Summary
Documentation(Detail of portion of Contractor
Section)
QA Procedures and Results
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QA DGM Summary Documentation(Detail of QA portion)
QA Procedures and Results
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QA Flags and Minor Incidents were handled via weekly QC teleconferences,
and email communications between QA/Navy and Contractor.
This allowed rapid resolution of minor (but potentially problematic) issues.
Minor QA Issues
Intermittent Failures of Equipment Tests
Incomplete Deliverable Packages
Differences in Target Selection methods between Contractor and QA
Documentation of Inaccessible Areas
QA Procedures and Results
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Major QA Incidents were handled by:
1) Initial discussion via weekly QC teleconferences, and email communications
between QA/Navy and Contractor.
2) If Issue was not resolved, a Non-Conformance Report (NCR) was issued.
Major QA Incidents
Method of Mounting GPS antenna on EM61-Resolved via email and other communications
Repeated Failure of Equipment Tests and subsequent rejection of Field Data-Resolved via NCR
Missed QA seed-Resolved via NCR
QA Procedures and Results
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Target Distribution at MM10F-Total Targets per Grid
Conclusions
QA of Contractor DGM Surveys Results:
Resolution of numerous “minor” deviations from project Measurement Performance Criteria in near real time.
Rapid resolution of several “major” deviations via Non Conformance Reports.
Independent evaluation of 100% of Contractor DGM Data and Target selection provides a very high confidence of results of DGM surveys. 36,738 targets identified in MM 10-F.
More than 500 DGM certification packages generated (due to changes in target picking threshold).
QA evaluation of DGM data (Target distribution) provides a “roadmap” for future field QA activities.
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