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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. Fri . "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 = {Fri Jul 01 00:00:00 EDT 1994},
month = {Fri Jul 01 00:00:00 EDT 1994}
}

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