Data Quality Assurance

H-GAC staff obtained data for this review from TCEQ Surface Water Quality Monitoring Information System (SWQMIS) database. These data are quality assured at multiple levels from collection through submittal to the database. Most of the data selected by H-GAC for analysis were collected under a Quality Assurance Project Plan (QAPP), which establishes acceptable collection and analysis methods as well as parameter-specific measurement performance specifications (MPS). Data not collected in accordance with the QAPP, or not meeting the applicable MPS, are not accepted for the SWQMIS database. While there are some data marked as "qualified" in the database, because a protocol was not followed or MPS were not met, H-GAC did not incorporate qualified data in the analysis.

An additional level of quality assurance was created by the passage of House Bill 2912 (2001), which required TCEQ to accept data to be used for the purposes of decision making only from laboratories conforming to standards established by the National Environmental Laboratory Accreditation Conference (NELAC). The NELAC standards establish requirements for environmental laboratory quality and technical systems and are intended to ensure that data "of known and documented quality" are produced by laboratories conforming to the standard. Beginning July 1, 2008, only data from accredited laboratories were accepted by the Clean Rivers Program. H-GAC provided financial and technical support for regional laboratories that participate in the Clean Rivers Program in order to facilitate initial accreditation and continues to provide financial and technical support for maintenance of accreditation. In July 2010, H-GAC sponsored a workshop by The NELAC Institute on the details of the revised NELAC standards that take effect July 1, 2011.

H-GAC has an intensive data management process that is designed to ensure the data collected by regional partners and submitted to the TCEQ are of known and documented quality. Data are evaluated against a variety of data quality indicators, including, but not limited to, evaluation of inter-parameter relationships, parameter minima and maxima, reporting limits required by the QAPP and criteria of reasonableness established on the basis of professional judgment. Reviewing and processing data prior to submission to TCEQ is an iterative process, involving communication between H-GAC staff, regional partners and TCEQ staff. Data is uploaded to a SWQMIS validation module to identify other problems not discovered previously and is subject to further review by TCEQ staff before it is loaded into the database and made available to the public.

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