Data Quality and Using CEDEN Data
CEDEN accepts data of varying quality and data users must determine if the quality is stringent enough for their intended use. CEDEN provides information to assist data users in evaluating the quality assurance activities of CEDEN data.
Some projects include an evaluation and comparison of the data to measurement quality objectives, which are determined at the beginning of a project to set the level of quality that is required to meet the data quality objectives of the project. The quality assurance and quality control efforts of a project should be documented in a project's Quality Assurance Project Plan (QAPP). CEDEN does not store QAPP documents, but users may find reference to a project's QAPP on the project lookup list along with contact information for the Project.
CEDEN does store results of data quality evaluation. These fields are summarized below.
| Field | Definition | Link to Lookup Values |
|---|---|---|
| Result Level | ||
| Sample Type Code | Refers to the type of sample collected or analyzed. The sample type field indicates the type of sample the record represents including quality control samples that can be evaluated. | Sample Type Lookup |
| QA Code | Applied to the result to describe any special conditions, situations or outliers that occurred during or prior to the analysis to achieve the result. The default code, indicating no special conditions, is 'None'. Default value equals NR if unknown. If more than one code should be applied to a record, the convention is to list them in alphabetical order separated by commas and no spaces. | QA Lookup |
| Compliance Code | Unique code referencing the Compliance with the associated QAPP. Default value equals NR if unknown. | Compliance Lookup |
| Lab Result Comments | The lab results comments field stores information about the result that the laboratory and QA Officer note during data review. | See individual results. |
| Batch Level | ||
| Batch Verification Code | Unique code referring to the Verification of a Batch, particularly for Chemistry or Toxicity results. | Batch Verification Lookup |
| Lab Submission Code | The LabSubmissionCode is a unique batch qualifier code assigned to the LabBatch as a whole by the analyzing laboratory which references the quality of the data in the LabBatch. The LabSubmissionCode should be reviewed by the Project Manager or other appropriate person to ensure that the code has been applied based on project specific data quality objectives and criteria. Default value equals NR if unknown. | Lab Submission Lookup |
| Lab/Tox Batch Comments | The batch comments field stores information about the batch that the laboratory and QA Officer note during data review. | See individual batches. |
If the data were not reviewed for compliance with the project QAPP or meaningful values are not given for these fields in the data set being used, the user may be able to evaluate the data themselves by looking at the results, lab and field replicates, and the associated batch quality assurance data. For example, if a batch's field blank shows a high concentration of the analyte of concern, this may be an indication that samples were contaminated and the results not reliable.
The appendix of each data category guidance document describes how the sample type codes and other fields are used to convey information about the samples analyzed along with the environmental sample to demonstrate the accuracy of the sampling and analysis protocols. Be sure to click the "Include QC Data" checkbox near the bottom of the CEDEN query tool to get these records.
For data providers, it is important to note that for data to be fully considered in the Clean Water Act Section 303(d) listing and delisting process, data shall be of sufficient high quality to make determinations of water quality standards attainment as described in Section 6.1.4 Data Quality Assessment Process of the Water Quality Control Policy for Developing California's Clean Water Act Section 303(d) List.
This section describes that a QAPP, or equivalent, is required for quality data. QAPPs developed and complied with when collecting and analyzing data submitted to CEDEN can be submitted to the Water Board through the Integrated Report Document Upload Portal. If the QAPP is not received or cannot be associated with submitted data, the data will not be used as part of the 303(d)/305(b) assessment process.
For more information about quality assurance and quality control, see: