Ground-water sampling methods and quality-control data for the Red River of the North basin, Minnesota, North Dakota, and South Dakota, 1993-95

Abstract

Ground-water-quality samples were collected for the intensive data-collection phase of the Red River of the P Torth Basin study unit, one of 60 study units of the National Water Quality Assessment (NAWQA) Program throughout the United States. The sampling protocols used were designed for the NAWQA Program. The protocols include sampling equipment, cleaning procedures, sample-collection methods, and quality-control plans to monitor the accuracy of the data collected. One of the goals of the NAWQA Program was to collect data using similar methcds to build a nationally consistent water-quality data base. Quality-control data demonstrated that most constituents measured for this study yielded reproducible data, with low to undetectable contamination from the sampling and analytical procedures. Several constituents were occasionally or frequently detected in blank samples at levels similar to low-concentration ground-water-quality samples. For example, iron was detected in 75 percent of the blank samples, with a maximum concentration of 27 [ig/L, indicating that iron contamination may interfere with its determination at low levels in ground waters. Copper, aluminum, and dissolved organic carbon concentrations in blank samples overlap those determined in ground-waterquality samples, thereby precluding quantitative reporting of those constituents. Most pesticide data are reproducible, with minimal bias. Some pesticides had low but consistent recoveries; these data may be useful if spike and surrogate data are carefully considered. Data for some pesticides measured in this study should not be quantitatively reported or used, because they may underestimate the concentrations of those pesticides in ground waters. Introduction The USGS began full implementation of the NAWQA Program in 1991. The goal of this program is to collect reliable and nationally consistent information on the status of and trends in the quality of the Nation's water resources, and to provide scientifically valid explanations of these conditions and trends (Cohen and others, 1988, p. 1147). Much of the data collected will come from 60 hydrologic regions called study units. The part of the Red River of the North drainage basin in the United States (hereinafter referred to as the Red River Basin) is one of these 60 study units. An intensive ground-water data collection phase for the Red River Basin study unit began in 1993 and continued through 1995. Figure 1 shows the location of the study unit and of the wells sampled. Data from the study units will be compiled in a national data base. National synthesis teams will review and make larger-scale assessments and interpretations of the data. Purpose and Scope The purpose of this report is to describe the groundwater sampling protocols, sampling equipment, field data-collection techniques, and quality-control data used during the intensive data-collection phase of the Red River Basin NAWQA study. This report describes (1) methods used to prepare wells for sampling, (2) equipment used, (3) sample collection procedures, (4) shipping and storage of the samples, (5) equipment cleaning procedures, (6) and types of quality-control samples collected, with a summary of the qualitycontrol data. Acknowledgments Special appreciation is given to the numerous property owners in the Red River Basin study unit for allowing observation wells to be installed on their property or water-quality samples to be collected from their wells, and to Tim Cowdery, U.S. Geological Survey, for his guidance in the collection of the fieH samples.