Perchlorate in Arizona: Occurrence Study of 2004

3.2.3 ComparabilityFor this project, comparability will be defined as the degree to which analyses from previoussampling efforts, at existing sites, corroborate the results obtained from this event. Where resultsare not comparable, standard operating procedures for respective sampling events will bereviewed and compared. Differences in both the sampling methodologies and results will bedocumented. Due to the remedial efforts in Nevada, concentrations of perchlorate are slowlydeclining on the River. However the intensive monitoring at key locations provides a goodrecord of the gradual reduction and will assist in assessing comparability of results from thissampling to earlier sampling efforts.3.2.4 RepresentativenessThis is the degree to which a group of samples is indicative of the population being studied at aparticular site. Representativeness is a qualitative factor which is affected by appropriate samplingand laboratory protocols and will be achieved by using the most environmentally conservativeapproach to sampling. For the objectives of this study, representative samples will be collectedusing grab samples and proper sampling protocols.Excellent quality analytical data, representativeness and comparability are expected.Experienced field monitoring staff from the Hydrologic Support and Assessment Section inWater Quality Division at ADEQ and the Hydrology Division at ADWR will conduct thesampling. Del Mar Analytical Laboratory will perform the analyses. Montgomery Watson willprovide QA/QC analysis on split samples and provide spikes. Both laboratories are certified inthe State of Arizona3.3 Data Review, Validation and Reporting3.3.1 Data reviewData received from the laboratory will be reviewed by the project leads according to theguidelines presented in the Data Reduction and Reporting (section 7.10) and Data Validation,Assessment, and Corrective Action (section 7.11) of the ADEQ Quality Assurance Project Plan(QAPP) to determine whether internal quality control guidelines are met. The followingminimum criteria must be met for the data to be acceptable for unqualified use by all partiesinvolved in this study.3.3.1.1 Split samples: Precision from the split samples submitted to a second laboratory shall beresults within 10% of the average of the two values reported. These criteria will notapply if values are below the practical quantification limit.3.3.1.2 Duplicate samples: Precision from the field duplicate samples submitted to the samelaboratory shall be results within 10% of the average of the two values reported.These criteria will not apply if values are below the practical quantification limit.46