1. Introduction

This guidance document explains statistical techniques to evaluate and optimize groundwater monitoring for environmental projects. The primary audience for this guidance is environmental practitioners who have technical and project management experience, but who may not have specific expertise in statistics. Public and tribal stakeholders reviewing environmental reports will also find this guidance helpful. Other good sources of information about statistics include the United States Environmental Protection Agency’s (USEPA's) March 2009 Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities (known as the Unified Guidance), Statistical Methods for Groundwater Monitoring (Gibbons, Bhaumik, and Aryal 2009), and several ASTM International (ASTM) publications on statistical methods for environmental monitoring (ASTM 2010a, 2010b, and 2012), as well as a wide variety of tools and software packages for performing statistical calculations and evaluations. Even with these resources, however, practitioners may still feel challenged when reviewing or implementing statistics. This guidance document provides an overview of the Unified Guidance and other resources and shows how to apply statistics specifically to analytical results from groundwater sampling in order to make better decisions in environmental projects.

1.1 Purpose

The purposes of this document and associated Internet-based training include the following:

1.2 Scope and Limitations

This document offers practical tips for using information that is already published in other resources such as USEPA’s Unified Guidance. This document is not a stand-alone tutorial on statistics, but instead addresses the practical applications, challenges, and misapplications associated with the use of groundwater statistics. The study questions, methods, and software packages are not all-inclusive and others may be appropriate. Concepts presented in this document apply to groundwater projects in many regulatory programs such as those under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), the Resource Conservation and Recovery Act (RCRA), voluntary cleanup, and underground storage tank (UST) programs. The document is organized around life cycle stages of typical environmental projects including release detection, site characterization, remediation, monitoring, and closure. The guidance presented here will help users to ask the right questions about data and identify appropriate statistical methods to answer these questions.

1.3 Background

The guidance presented here condenses and simplifies a selection of important methods from the Unified Guidance. The Unified Guidance was developed for the statistical analysis of groundwater data at RCRAResource Conservation and Recovery Act facilities, but the statistical tests and graphical methods it describes are broadly applicable for a variety of other environmental programs.

1.4 Document Audience

Based on the groundwater statistics survey (Appendix E), the target audience for this guidance is a project manager (in industry, government, or consulting) who must review or use statistical calculations to generate a report or demonstrate compliance for a groundwater-monitoring project. This individual typically has technical experience in one or more disciplines related to site compliance or cleanup but does not have specific expertise in statistics. This individual may not have access to in-house statistical expertise, but still must make recommendations or decisions based on statistics. This document guides the project manager in using appropriate statistical methods to address common project objectives and recognizing common misapplications of statistics. A typical application might include evaluating whether a groundwater remedy is functioning effectively or whether there is a downward trend which supports a natural attenuation remedy selection.

1.5 Project Life Cycle Stages

Groundwater statistical methods can apply throughout the life cycle of environmental cleanup projects, including monitoring of active remediation systems. The terminology and regulatory framework for the stages of the project within its life cycle, however, often vary under different regulatory programs. For clarity, this document organizes the discussion of site management around five main technical tasks:

1.6 Study Questions

Each of the project life cycle stages listed above progress through development and refinement of the CSMconceptual site model. This guidance explores some of the commonly identified problem statements that guide decision making throughout environmental projects and poses a list of typical study questions that are intended to connect life-cycle-based issues of concern with relevant statistical methods.

Ten common study questions were selected:

Study questions are discussed in more detail in Appendix C. Life cycle stages and related study questions are discussed in Section 4. Statistical methods are presented in Section 5.

Publication Date: December 2013

Permission is granted to refer to or quote from this publication with the customary acknowledgment of the source (see suggested citation and disclaimer).


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