skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Analysis of censored data in groundwater monitoring wells at the Savannah River Site

Abstract

It is common in environmental analyses to deal with censored data. Censored data characteristically arise through laboratory analysis of samples with contaminant concentrations less than what the analytical method is able to reliably detect. These data are called ``less than detectable.`` Comparisons between downgradient or monitoring groundwater wells and upgradient or background wells are frequently done to determine if downgradient wells are more contaminated than background or some established maximum concentration limits (MCL`s). In addition, parameter estimates are often desired. The presence of censored data complicates the statistics that can be used as estimators for individual populations or to estimate differences between two populations. This paper describes the current process at Savannah River Site (SRS) to determine constituents of concern (COC`s) for complying with groundwater monitoring and clean-up regulations. COC`s are analytes found in downgradient monitoring wells in concentrations significantly greater than in background wells or significantly greater than the MCL`S. Both parametric and non-parametric statistics are explored. Data plots are examined for outliers, trends, laboratory or sampling contamination, and unusually large detection limits for censored results. Wells are grouped by similar concentration levels to form a ``characteristic`` well, improving the estimation and decision process.

Authors:
Publication Date:
Research Org.:
Westinghouse Savannah River Co., Aiken, SC (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10168354
Report Number(s):
WSRC-MS-94-0113; CONF-940748-15
ON: DE94015568; TRN: 94:014719
DOE Contract Number:
AC09-89SR18035
Resource Type:
Technical Report
Resource Relation:
Conference: 35. annual meeting of the Institute of Nuclear Materials Management (INMM),Naples, FL (United States),17-20 Jul 1994; Other Information: PBD: [1994]
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; GROUND WATER; SAMPLING; STATISTICAL DATA; DATA ANALYSIS; RADIOACTIVE MATERIALS; ECOLOGICAL CONCENTRATION; HAZARDOUS MATERIALS; SAVANNAH RIVER PLANT; CONTAMINATION; 540230; 540220; RADIOACTIVE MATERIALS MONITORING AND TRANSPORT; CHEMICALS MONITORING AND TRANSPORT

Citation Formats

Weber, J.H.. Analysis of censored data in groundwater monitoring wells at the Savannah River Site. United States: N. p., 1994. Web. doi:10.2172/10168354.
Weber, J.H.. Analysis of censored data in groundwater monitoring wells at the Savannah River Site. United States. doi:10.2172/10168354.
Weber, J.H.. 1994. "Analysis of censored data in groundwater monitoring wells at the Savannah River Site". United States. doi:10.2172/10168354. https://www.osti.gov/servlets/purl/10168354.
@article{osti_10168354,
title = {Analysis of censored data in groundwater monitoring wells at the Savannah River Site},
author = {Weber, J.H.},
abstractNote = {It is common in environmental analyses to deal with censored data. Censored data characteristically arise through laboratory analysis of samples with contaminant concentrations less than what the analytical method is able to reliably detect. These data are called ``less than detectable.`` Comparisons between downgradient or monitoring groundwater wells and upgradient or background wells are frequently done to determine if downgradient wells are more contaminated than background or some established maximum concentration limits (MCL`s). In addition, parameter estimates are often desired. The presence of censored data complicates the statistics that can be used as estimators for individual populations or to estimate differences between two populations. This paper describes the current process at Savannah River Site (SRS) to determine constituents of concern (COC`s) for complying with groundwater monitoring and clean-up regulations. COC`s are analytes found in downgradient monitoring wells in concentrations significantly greater than in background wells or significantly greater than the MCL`S. Both parametric and non-parametric statistics are explored. Data plots are examined for outliers, trends, laboratory or sampling contamination, and unusually large detection limits for censored results. Wells are grouped by similar concentration levels to form a ``characteristic`` well, improving the estimation and decision process.},
doi = {10.2172/10168354},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1994,
month = 7
}

Technical Report:

Save / Share:
  • Data is presented regarding ground water monitoring results from the Savannah River Plant for the years of 1952-1986. (CBS)
  • This report summarizes the Groundwater Monitoring Program conducted by SRS during second quarter 1998. It includes the analytical data, field data, data review, quality control, and other documentation for the program; provides a record of the program's activities; and serves as an official record of the analytical results.
  • This schedule provides a final record of the 1990 sampling schedule for the SRS groundwater monitoring program conducted by the Environmental Protection Department/Environmental Section (EPD/EMS). It includes all the wells monitored by EPD/EMS at SRS during 1990 and identifies the constituents sampled, the sampling frequency, and the reasons for sampling. Sampling requests are incorporated into the schedule throughout the year. Drafts of the schedule are produced and revised quarterly.
  • This report summarizes the Savanna River Site (SRS) Groundwater Monitoring Program conducted by EPD/EMS during the first quarter 1996. It includes the analytical data, field data, data review, quality control, and other documentation for this program. It also provides a record of the program`s activities and serves as an official record of the analytical results.
  • This investigation was undertaken with the primary purpose of assessing the groundwater monitoring program within the A/M Area to identify ways in which the monitoring program could be improved. The task was difficult due to the large number of wells located within the A/M Area and the huge database of analytical data. It was recognized early in this investigation that one of the key tasks was to develop a way to gain access to the groundwater databases so that recommendations could be made. To achieve this, geographic information systems (GIS) technology was used to extract pertinent groundwater quality information frommore » the Geochemical Information Management System (GIMS) groundwater database and display the extracted information spatially. GIS technology was also used to determine the location of well screen and annular material zones within the A/M Area hydrostratigraphy and to identify wells that may breach confining units. Recommendations developed from this study address: (1) wells that may not be providing reliable data but continue to be routinely sampled (2) wells that may be inappropriately located but continue to be routinely sampled and (3) further work that should be undertaken, including well development, evaluation of wells that may be breaching confining units, and development of an automated link to GIMS using GIS so that GIMS data can easily be accessed and displayed geographically.« less