An Approach to Industrial Stormwater Benchmarks: Establishing and Using Site-Specific Threshold Criteria at Lawrence Livermore National Laboratory Page: 3 of 12
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An Approach to Industrial Stormwater Benchmarks:
Establishing and Using Site-Specific Threshold Criteria at Lawrence
Livermore National Laboratory
Chris G. Campbell, PhD and Sandra Mathews
Current regulatory schemes use generic or industrial sector specific benchmarks to
evaluate the quality of industrial stormwater discharges. While benchmarks can be a
useful tool for facility stormwater managers in evaluating the quality stormwater runoff,
benchmarks typically do not take into account site-specific conditions, such as: soil
chemistry, atmospheric deposition, seasonal changes in water source, and upstream
land use. Failing to account for these factors may lead to unnecessary costs to trace a
source of natural variation, or potentially missing a significant local water quality
problem. Site-specific water quality thresholds, established upon the statistical
evaluation of historic data take into account these factors, are a better tool for the direct
evaluation of runoff quality, and a more cost-effective trigger to investigate anomalous
Lawrence Livermore National Laboratory (LLNL), a federal facility, established
stormwater monitoring programs to comply with the requirements of the industrial
stormwater permit and Department of Energy orders, which require the evaluation of the
impact of effluent discharges on the environment. LLNL recognized the need to create
a tool to evaluate and manage stormwater quality that would allow analysts to identify
trends in stormwater quality and recognize anomalous results so that trace-back and
corrective actions could be initiated.
LLNL created the site-specific water quality threshold tool to better understand the
nature of the stormwater influent and effluent, to establish a technical basis for
determining when facility operations might be impacting the quality of stormwater
discharges, and to provide "action levels" to initiate follow-up to analytical results. The
threshold criteria were based on a statistical analysis of the historic stormwater
monitoring data and a review of relevant water quality objectives.
The site-specific thresholds were established using statistical analyses of historic
stormwater data and were compared to relevant water quality objectives (WQOs). The
procedure includes quality checks of data; calculation of the 95% statistical confidence
limits; comparison of the upper confidence limits (UCL) with applicable WQOs;
re-examination of the UCL exceedence frequency; and periodic readjustment and
recalculation of the confidence intervals. The procedure for calculating the specific
thresholds includes the following five steps:
1. Perform a quality check of the available data;
2. Calculate statistical confidence intervals;
3. Compare the upper confidence interval to available benchmarks;
4. Examine the frequency of exceedence in your data for the upper confidence limit;
5. Adjust the exceedence probability and recalculate step 2 if step 4 is not
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Campbell, C G & Mathews, S. An Approach to Industrial Stormwater Benchmarks: Establishing and Using Site-Specific Threshold Criteria at Lawrence Livermore National Laboratory, article, September 7, 2006; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc886697/m1/3/: accessed December 12, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.