The goal of erosion and sediment control (ESC) programs is to prevent and minimize sediment loss from construction sites, and field inspection verifies compliance with ESC requirements. Inspectors evaluate whether practices have been installed correctly, identify and document maintenance needs and failures, and determine when corrective action is necessary. These evaluations are essential for construction site management, but they do not necessarily indicate whether the ESC system is achieving the intended water quality objectives.

A recent paper by Cormier et al. (2026) presents a framework for evaluating the effectiveness of ESC best management practices (BMPs) during active construction and explores what evidence is sufficient to conclude that an ESC system is performing as intended.

Inspection approaches can address different questions

Conformity assessment and effectiveness verification are two methods of evaluating an ESC system, but they answer two different questions about the performance of ESC systems. Conformity assessment evaluates whether ESC BMPs have been installed correctly and are being operated and maintained as intended. Common inspection questions that assess conformity include: Was the BMP installed correctly? Is it being operated as intended? Has required maintenance been completed? Are damaged BMPs being repaired?

Effectiveness verification evaluates whether a system of ESC BMPs is achieving performance goals at the time of inspection. For example, an ESC BMP may be properly installed and maintained while still allowing sediment losses under some conditions. Conversely, a poorly maintained BMP may appear to perform adequately during a dry period when little runoff is occurring. Cormier et al. describe how an effectiveness assessment that is conducted during low-rainfall conditions could indicate acceptable turbidity even when BMPs are in disrepair. A conformity inspection would identify those deficiencies even if performance was not obviously affected at the time of inspection. 

For ESC programs, this creates two complementary types of evidence:

• Conformity assessment: Are practices installed, operated, and maintained according to established requirements?
• Effectiveness verification: Is the system producing the environmental outcome those requirements are intended to achieve?

Neither assessment approach fully substitutes for the other (Figure 1).

Figure 1. Conformity assessment and effectiveness verification provide complementary information about erosion and sediment control system performance. Conformity assessment evaluates whether BMPs are installed, maintained, and functioning according to requirements, while effectiveness verification evaluates whether measured water quality conditions meet a defined performance benchmark.

Performance assessment requires a defined benchmark

In order to evaluate ESC system effectiveness, a clearly defined benchmark of performance is needed to distinguish acceptable from unacceptable conditions. Cormier et al. use turbidity as the environmental response. They define an acceptable acute turbidity increase of <8 NTU over 24 hours, with increases above this threshold considered unacceptable. Using this criterion, turbidity measurements can be used to evaluate whether the ESC system is performing within an acceptable range. 

The specific turbidity benchmark used in this study is not necessarily directly transferable to other ESC programs, but it illustrates the structure of the approach. A turbidity measurement represents conditions at a particular place and time, and its meaning depends on when the sample was collected, where it was collected, the flow and rainfall conditions at the time, and the condition of the ESC system. A small number of measurements may therefore provide limited information about overall system performance. 

In order to interpret water quality measurements as evidence of system performance, the assessment requires:

1. A measurable environmental response
2. A defined criterion for acceptable performance
3. A sampling strategy capable of detecting unacceptable conditions
4. A decision rule for determining whether corrective action is needed

How much sampling is enough?

Cormier et al. adapt an approach called acceptance sampling, a method used to determine whether a process meets a standard without measuring every possible observation, to determine the number of samples needed to accurately represent ESC system performance. Their analysis considers two ways a monitoring program can reach the wrong conclusion:

1. An acceptable ESC system may be classified as unacceptable. This could lead to unnecessary corrective action or added costs for the party responsible for the controls. In the study, this is referred to as a Type I error, or the “proponent’s risk.”
2. An unacceptable ESC system may be classified as acceptable. This is the more important environmental concern because poor performance may go undetected and sediment impacts may continue. In the paper, this is referred to as Type II error, or the “environment’s risk.”

Sample size affects how reliably a monitoring program can identify poor performance. More measurements do not simply provide more data, they increase confidence that an unacceptable condition (i.e. poor BMP performance) will be detected. This means that a single water quality measurement does not provide enough information to evaluate overall system performance under.

Cormier et al. show how sample size can be selected based on the performance threshold and level of uncertainty a program is willing to accept. There is no single sample size that applies to every ESC system. The number of measurements needed depends on what is being measured, what is considered unacceptable, and how certain the program needs to be before making a decision. As a result, monitoring intensity should match the decision the data are intended to support. Routine inspections may require relatively limited monitoring, whereas conclusions about overall ESC system effectiveness may require a more structured sampling approach.

ESC system performance changes throughout a construction project as site conditions, BMP condition, maintenance needs, and rainfall vary. A measurement collected during dry weather or low flow may provide different information than one collected during active runoff or after controls have deteriorated. For this reason, water quality measurements should be interpreted alongside rainfall, runoff conditions, construction activity, and maintenance status.

See the forest for the trees (ESC as a system of BMPs)

Cormier et al. emphasize that ESC performance should be evaluated at the system level, not by individual BMPs. Their framework treats ESC as a system of technical measures working together to achieve the goal of water quality protection. Construction site water quality protection depends on how erosion prevention, stabilization, runoff management, conveyance, sediment capture, dewatering, and maintenance work together across the site. An individual BMP can be installed correctly and still fail to protect water quality if other parts of the system are not functioning as intended. 

For example, a sediment basin may be properly constructed but receive excessive sediment because stabilization has been delayed upstream, or a perimeter control may be installed correctly but receive flow from a drainage area larger than anticipated. As a result, performance at the site level depends on how the individual practices function together. Evaluating environmental performance at the system level better reflects the goals of ESC: limiting sediment delivery from the construction site and protecting downstream water quality.

Combining inspection and performance goals

This study does not propose replacing conventional ESC inspection processes with water quality monitoring, but it provides a framework for understanding what different types of assessment can reveal. Visual and structural inspection remain necessary for identifying installation problems, maintenance needs, and deviations from approved plans or specifications. Performance monitoring provides additional information about whether the system of BMPs is achieving its intended environmental objective. 

These approaches answer different and complementary questions: Was the practice installed correctly? Is the practice being maintained and operated correctly? Is the ESC system producing acceptable results? The first two can be evaluated through conformity inspection, while the third requires some measure of environmental performance.

Cormier et al. show that the number and timing of measurements affect how reliably an ESC system can be evaluated. Monitoring should therefore be designed around the decision the data are expected to support: a few turbidity measurements can describe conditions at the time of inspection, but evaluating overall ESC system performance may require a more structured sampling approach.

Reference

Cormier, R., Mallet, M., & Goguen, G. (2026). Developing sampling plans for the verification of the effectiveness of technical measures: An erosion and sediment control case study to protect water quality. Environmental Management, 76, Article 301. https://doi.org/10.1007/s00267-026-02580-4