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This page contains the following technical assistance resources for sample collectors and data users:
Environmental laboratory data validation is accomplished through a series of checks and reviews that are intended to assure that reported results are of a verifiable and acceptable quality. When the accuracy of those results is uncertain (as indicated by deviations from established quality control limits), the laboratory must provide sufficient information to allow for independent interpretation of data validity and usability. This may include additional associated information about a sample that may not necessarily invalidate the data (e.g., reducing agents detected in a BOD sample), but must be taken into account during data assessment. This information is communicated to Departmental personnel on data reports by means of data qualifier codes.
Historically, these Remark Codes were mandated and defined by the Environmental Protection Agency’s Legacy STORET data management system. In March of 2001, the NC Division of Water Resources Chemistry Laboratory implemented a revised suite of data qualifiers. The following table provides a key to the data qualifier codes used for analytical results reported by the NC DENR/DWR Chemistry Laboratories located in Raleigh, Asheville and Washington. The reported value always precedes the data qualifier code. Contact the laboratory any time you have questions about data qualification and interpretation.
NC DWQ Laboratory Section Data Qualifier Codes Table
Cost Per Analysis Fee Schedule (updated 7/18/2011)
The fee schedule provided here relates only to the North Carolina Division of Water Resources Chemistry Laboratory’s cost recovery fees. This fee structure reflects the characteristics of the different types of analyses performed, the different matrices encountered, the regulations to which they are subject, and the level of effort expended by the Laboratory in producing the data. The primary focus of the Laboratory’s fee setting process and structure is to directly link the fees to be charged to the costs of activities required for sample preparation and handling and the issuance of reports and to recover the full costs of these activities.
Determinations were based on an estimate of the number of hours laboratory personnel spend on work necessary for processing a sample and generating a report. It should be noted that the posted fees were determined per average load – a single sample generally demands more resources on a per sample basis. Different sample matrices (e.g., water, soil, fish tissue) are charged differential fees in recognition of the relative complexity of these samples and the frequency of laboratory surveillance. The following items were also considered when these estimates were established:
We hope this information will be useful in your compliance and enforcement activities. You may contact the laboratory with any questions regarding this fee schedule at (919) 733-3908.
The DWR Chemistry Lab requests each VOA vial submitted to be labeled appropriately to prevent misidentification. The VOA Vial Labeling Guidance describes multiple options for accomplishing this.
Trip Blanks are a required, and essential, element of quality control for Volatile Organics sampling and analysis. They serve as a guarantee that the primary samples were not contaminated during transport to the laboratory. A trip blank is a sample of analyte-free media collected in the same type of container that is required for environmental samples for the analytical test(s). Trip Blanks must be taken from the point of origin to the sampling site, then returned (un-opened) to the laboratory along with associated environmental samples.
Click here to read guidance document about trip blanks.
Keep in mind, tap water is generally not acceptable as a volatile organics trip blank source. Trihalomethane, chlorinated compounds and other interfering artifacts are predominant in tap water. Bottled waters may exhibit similar problems. Please keep in mind that even when contaminants are not target analytes, they may contribute to the background noise and miscellaneous unidentified peaks that are present in the chromatograms.
Some bottled waters supplied in clear plastic jugs have proven to be an acceptable trip blank source even without charcoal filtration; however, please stay away from those bottled in the opaque milk jug-type containers. They may contribute phthalate contamination.
The following include acceptable sources of analyte-free media for trip blanks:
The most reliable source is well water or distilled water that has passed through an activated carbon filter. Activated carbon is used to remove free and combined chlorine and organic contaminants from water. The Central Laboratory simply passes well water through a wide bore buret packed with baked, activated charcoal (an approx. 1ft. column of charcoal should provide sufficient contact area). The charcoal is replaced about every three to four months.
Click here for a link to a list of the supplies needed for this filtration setup. This is not meant to be an endorsement of any one product or brand, but simply a list of the supplies used currently at the Central Laboratory. Contact Victor Andrews, Organics Unit, at (919) 733-3908 ext. 260 if you have additional questions.
The Practical Quantitation Limit (PQL) is defined and proposed as "the lowest level achievable among laboratories within specified limits during routine laboratory operation". The PQL is about three to five times the calculated Method Detection Limit (MDL) and represents a practical and routinely achievable detection limit with a relatively good certainty that any reported value is reliable". For a list of laboratory PQLs and method numbers, click on the following links:
Click here for a view of the Central Laboratory Floorplan.