Monitoring can be defined as the collection and analysis of repeated observations or measurements to evaluate changes in condition and progress toward meeting a management objective. Monitoring is the collection and analysis of data (chemical, physical, and/or biological over a sufficient period of time and frequency to determine the status and/or trend in one or more environmental parameters or characteristics. Monitoring should not produce a "snapshot in time" measurement, but rather should involve repeated sampling over time in order to define the trends in the parameters of interest relative to clearly defined management objectives (OSWER 2004). Monitoring is useful to identify threats and to define removal and remedial actions. Monitoring can be required to verify that no unacceptable exposures to potential hazards posed by site conditions will occur in the futur.
1. Defining of Monitoring Objectives
The monitoring objectives of a Monitoring Plan will depend directly on the specific site activity and associated management objectives. The outcome of the monitoring should be used to support a management decision for the site. Monitoring objectives could address:
- Evaluation of contaminant migration
- Evaluation of remedy effectiveness and protection of human health and the environment
2. Monitoring Plan Development
In order to assist with the development and implementation of a Monitoring Plan, a monitoring team may be formed, this team may include the site manager, supporting technical staff and appropriate stakeholder.
The development of a Monitoring Plan may go through one or more iterations.
3. Formulate Monitoring Decision Rules
A decision rule is an "if... then..." statement that defines the conditions that would cause the decision maker to choose an action. It establishes the criteria for making a choice between taking and not taking an action. A refinement of the preliminary monitoring decision rules may take place.
Generally there are four main elements to a monitoring decision rule:
- the parameter of interest
- the expected outcome of the site activity
- An action level (the basis on which a monitoring decision will be made)
- Alternative actions (the monitoring decision choices for the specified action level)
4. Design the Monitoring Plan
A variety of data (chemical, physical and/or biological) may be necessary to test the monitoring hypotheses to answer the monitoring questions and to support a management decision. Factors to consider when identifying data needs may include:
- anticipated outcome of the site activity
- preliminary monitoring decision rules
- data characteristics
- applicability of data
By determining the monitoring boundaries the following questions have to be answered:
- what data are needed ?
- how should the samples be collected ?
- where should monitoring samples be collected ?
An important step is to define the temporal boundaries. The temporal boundaries should include information on:
(1) when samples should be collected
(2) how often they should be collected
and how long sampling should continue
Analysis of the monitoring data may involve some form of statistical analysis, such as descriptive-, trend-, or uncertainty analysis
The final aspect of developing the monitoring design is the preparation of a Monitoring Quality Assurance Project Plan.
This plan should comprise:
- an overview and general background of the site activity for which the Monitoring Plan has been developed
- a description of the monitoring objectives
- the monitoring hypotheses, questions and monitoring conceptual model
- the data needs and characteristics
- the data collection methods, including sampling location, timing and frequency
- the sampling equipment and procedures
- the data handling requirements
- the data analysis methods
5. Conduct Monitoring Analysis and Characterize Results
The major component of step 5 is the evaluation of the data with regard to the Monitoring Quality Assurance Project Plan. The specific outcome determines whether any modifications or adjustments to the site acitivity or to implementation of the monitoring plan may be appropriate.
6. Management Decisions in the Monitoring Plan
In step 6 the monitoring results are evaluated with respect to the monitoring decision rules. The monitoring results will point toward one of three conclusions:
- the monitoring decision rules have been met
- the data are trending toward meeting the decision rules
- the monitoring decision rules have not been met (monitoring results indicate the site activity has not achieved its stated objectives.
7. Guidelines and Weblinks
OSWER Directive No. 9355. 4-28: Guidance for Monitoring at Hazardous Waste Sites: Framework for Monitoring Plan Development and Implementation.
EPA Report 542-R-04-001a: Demonstration of Two Long-Term Groundwater Monitoring Optimization Approaches
Decision Support Software MAROS: