National Field Quality Assurance Project
Project Overview and History

The U.S. Geological Survey (USGS) collects water-quality information daily to monitor the Nation's water resources. Water-quality analysts collect water-quality samples for laboratory analysis and make field measurements of alkalinity, pH, and specific conductance. All USGS personnel who make these field measurements are strongly encouraged to participate in the National Field Quality Assurance (NFQA) Project. Contract and cooperator personnel who collect these field measurements to be used in USGS reports or stored in the USGS National Water Information System (NWIS) are also encouraged to participate in the NFQA Project.

In March 1979, U.S. Geological Survey began the NFQA Project. The project is designed to monitor the proficiency of alkalinity, pH and specific conductance measurements performed by USGS water-quality analysts. Initially, the project assessed only the performance of pH and specific conductance measurements; alklinity was added to the project in 1984.

The two specific objectives of the NFQA Project are to provide precision data for the field measurements and to identify water-quality analysts who need additional training. Annual proficiency samples are distributed to individuals who determine alkalinity, pH and specific conductance in the field. The data are summarized and the most probable value (MPV) is determined from all the data. No distinction is made between USGS measurements or data provided by the contract or cooperator personnel when determining the MPV. After the samples are analyzed and the results returned, a proficiency report is prepared by the NFQA manager and submitted to the appropriate USGS offices for review. An annual proficiency report rates values reported by the water-quality analysts as satisfactory, marginal or unsatisfactory.

The criterion used to describe the concentration of the data about the median value is the fourth-spread. The fourth-spread measures the data range of the middle 50 percent of the values (Hoaglin et al., 1983). The median value is the central value in the data set. The bottom 25 percent and the top 25 percent of the values are considered as outliers. The fourth-spread values are presented to NFQA Project customers.

The NFQA Program has gone through several revisions since its inception in 1979. The following describes the changes to the program since 1979.

March 1979

The USGS established a program to provide quality assurance proficiency samples for pH and specific conductance to field analysts. The program was managed by the USGS National Water Quality Laboratory (NWQL) in Arvada, Colorado. Results were sent to the Office of Water Quality, regional office, and then to the participants.


January 1981

The program was discontinued.


February 1982

The program was reinstated to provide proficiency samples for pH and specific conductance, and was managed by the NWQL in Doraville, GA.


August 1984

Alkalinity and chloride proficiency samples were added to the program. After one shipment of proficiency samples was sent to the field analysts in each region, chloride proficiency samples were discontinued in 1985.


October 1985

The responsibility for managing the NFQA Program was transferred from the NWQL in Doraville, GA., to the QWSU in Ocala, FL. The QWSU followed the existing protocol by sending results to the Office of Water Quality and, after review, to the regional offices for distribution to the individual participants.

The program initiated the practice of sending follow-up samples to field-analysts whose proficiency-sample performance ratings were unsatisfactory. Because of this change in practice, the frequency of distribution was changed to 2 initial rounds about every 15 months.

The practice of assigning an unsatisfactory value if a person failed to submit any data was changed to assigning a ranking of "N" (no data reported).

The volume of the proficiency sample was doubled, to 250 milliliters (mL), and sample bottling and labeling procedures were revised to reduce the possibility of error in sample identification.


February 1987

The titration method used for alkalinity, fixed-end point or incremental titration, is recorded and stored with the NFQA data.


October 1989

Frequency of proficiency sample distribution was again changed. It was reduced to once per year to each field analyst with a follow-up sample as needed. Results of the annual proficiency testing are sent to participants two weeks after a summary is sent to the Office of Water Quality, Branch of Quality Assurance (currently the Branch of Quality Systems), and regional offices.


April 1993

The operational NFQA computer programs were written to conform to the Data General (DG) UNIX operating system.


October 1993

Field meter model number and brand names are no longer being stored in the NFQA database located in Ocala, FL. The titration methods used for alkalinity are also no longer being reported or stored.

All transfers of worksheets, and NFQA reports to and from field offices, are made using the USGS electronic mail (E-mail) system. The NFQA Program has evolved into a paperless system.

Participants are given the opportunity to select specific sample ranges.


January 1994

The NFQA database was ported from the PRIME-INFO database located on the PRIME computer (DCOLKA) in Lakewood, CO., to the DG-INGRES database, located in Ocala, FL.

The procedure for evaluating the proficiency-sample results changed from the mean and standard deviation to the fourth-spread and the median value.


October 1996

The NFQA procedure for evaluating the alkalinity proficiency-sample results was modified.


January 2003

The NFQA database moved to a SQL web server in Ocala, FL. Updates to the participant list can be done using the web interface. Participants can enter and view their results via the web.


July 2004

The NFQA project under new management; database and project move to Branch of Quality Systems; Lakewood, CO.


October 2008

The NFQA project under new management; database moved to a new SQL server in Lakewood, CO.


November 2009 - March 2010

The NFQA project application rewritten; database moved to a new MySQL server in Lakewood, CO. Application moved from ASP server side scripting language on Microsoft's Internet Information Server (IIS) web server to the PHP server side scripting language on the Apache web server. The new application was developed from a requirements and design methodology.




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