36 



2.4.4 Quality Assurance/Quality Control 



The chemistry data for the Seawolf sediment cores reported here were considered 

 acceptable for the objectives of the NLDS Survey. Data quality was assessed in relation to 

 specified criteria for precision, accuracy, representativeness, comparability, and 

 completeness (PARCC). Sample representativeness was ensured during the sampling survey 

 by collecting a sufficient number of cores and subsamples from the project and surrounding 

 areas. All cores were collected and sampled in a uniform manner and are considered to be 

 representative (see Methods). Comparability is a qualitative parameter expressing the 

 confidence with which one data set can be compared to another. Comparability is limited to 

 the other PARCC parameters because precision and accuracy must be known to compare 

 one data set with another. Data completion was ensured through sample tracking protocols 

 (Section 2.4.4.1). 



One method of assessing analytical accuracy of the laboratory was the quantitative 

 evaluation of the percent recovery of a spiked standard compound added at a known 

 concentration to the sample before the analysis (Section 2.4.4.2). Laboratory accuracy also 

 was evaluated qualitatively by evaluating the laboratory QC information on method blank 

 results, tuning and mass calibration, recovery of internal standards, laboratory quality control 

 samples, and initial and continuing calibration results of analyses of environmental samples. 



Analytical precision was expressed as the percentage of the difference between results 

 of the replicate samples (relative percent difference [RPD] or relative standard difference 

 [RSD]; Section 2.4.4.3). When spiked duplicates are run, the results can be expressed as an 

 RPD to evaluate precision of the analysis of the spiked compounds. By inference, the 

 precision of analysis of other related compounds should be similar. The following sections 

 define the various QA/QC requirements and summarize the data quality objectives for this 

 project. For data to be considered valid, they must have met all acceptance criteria including 

 accuracy and precision, as well as any other criteria specified by the analytical methods used. 



2.4.4.1 Sample Tracking Procedures and Holding Times 



SAIC Standard Operating Procedures for sample tracking and custody were followed, 

 and all samples from the project were analyzed except for one grain size sample (10A, 0.5- 

 0.75) due to laboratory oversight. After placing representative composited material in clean 

 glass jars, the containers were labeled with indelible ink and sealed with waterproof tape. 

 Label information included the date, sample location, station number, replicate number, and 

 type of analysis. Remaining material was placed in double-bagged, gallon-sized plastic bags 

 which were sealed and labeled for grain size analysis. All sediment containers and bags were 

 stored at 0-4° C prior to analysis. Chain-of-custody records were maintained for all samples. 



Monitoring Cruise at the New London Disposal Site, Seawolf Mound 1995 - 1998 



