A Case Study Perspective on Working with ProUCL and a State Environmental Agency in Determining Background Threshold...

Area of Science:

• Environmental Science
• Statistics

Background:

• ProUCL is an EPA-developed software package for environmental statistical analysis, currently in its fifth version.
• Despite its widespread use and advancements, ProUCL faces criticism from statisticians regarding its analytical tools and philosophical approach.
• Some state agencies mandate ProUCL for environmental analyses, limiting the adoption of alternative software and methodologies.

Purpose of the Study:

• To investigate the challenges encountered by state-supervised sites when ProUCL is mandated for environmental analyses.
• To demonstrate the appropriateness of alternative statistical methodologies over ProUCL's standard procedures.
• To address specific statistical issues including outlier detection, Upper Tolerance Limit (UTL) calculations with non-detects, and nonparametric UTL formula usage.

Main Methods:

• Case study analysis of instances where alternative methodologies were proposed against ProUCL standards.
• Statistical demonstration of the appropriateness of alternative methods for outlier detection.
• Evaluation of Upper Tolerance Limit (UTL) calculations, particularly concerning gamma distributions with non-detect data and nonparametric formulas.

Main Results:

• Substantial resources were invested in demonstrating the validity of alternative statistical methods.
• Acceptance of alternative methodologies by state agencies was not always achieved, even with sound statistical evidence.
• Specific statistical deficiencies in ProUCL related to outlier detection and UTL calculations were identified.

Conclusions:

• Mandated use of ProUCL can hinder the implementation of more statistically appropriate environmental analysis methods.
• There is a need for greater flexibility in adopting advanced statistical tools beyond standardized software packages.
• Further research and advocacy are necessary to promote the use of scientifically rigorous statistical approaches in environmental regulation.