08 Sep Reducing Site Remediation Costs with UCL
When your property has environmental impacts in either the soil, groundwater, or air, it is imperative that you resolve the impacts for the least cost. This only happens when, from the project’s inception, your environmental consultant takes into consideration the various compliance averaging methods accepted by the New Jersey Department of Environmental Protection (NJDEP). Above all, you want a consultant that is fully versed in the latest and best remediation methods and tactics as they undertake your project. If your consultant is not sufficiently experienced, you may spend more than is necessary.
As ESA begins its 37th year in business, one fact remains undisputable: clients want to minimize their environmental costs. Site remediation is normally the most expensive step in the environmental process. That’s why ESA spends so much time discussing, perfecting, and writing about how to minimize remedial costs.
The UCL Method
One remediation strategy, the 95% Upper Confidence Limit (UCL) method, is a compliance averaging approach applicable when contaminant delineation is complete. If your property is contaminated, then you know that your consultant will be taking a fair number of samples during the site investigation phase. It is critical that, during the sampling phase, your consultant understands the UCL method to ensure that it can be used to optimally direct the selected remedial method.
Considerations
Your consultant must be cognizant of compliance averaging from the outset. Some samples will show high concentrations of contamination, but other samples will show low concentrations. In fact, some samples will show no contamination. It begs the question: which set of data best represents the true degree of contamination? Because analytical data is inherently variable, how can ESA use that variability to your advantage?
The NJDEP recommends using the EPA’s ProUCL computer software for calculating the UCL of a data set. This software supports various statistical methods, including parametric and non-parametric approaches, and handles datasets with non-detects. This means that a representative amount of your clean soil is incorporated into the statistical analysis.
But what about those soil samples whose concentrations appear inordinately high? The ProUCL software incorporates statistical rigor that reduces the influence of such outliers. That is, you do not want samples that are highly impacted to exert too much influence on the remedial design. The NJDEP will oversee this process to ensure that the “Goldilocks Principal” applies. This is when the remedial design weighs the highly impacted samples and the clean samples in a “just right” balance between the two extremes.
Why Use UCL?
In utilizing the UCL method, you will not over-remediate your site due to outliers. Nor will you under-remediate your site due to an over-representation of clean samples. As a result, savings could potentially be in the hundreds of thousands of dollars. You might ask, “Why wouldn’t I want to under-remediate?” The answer is simple: because NJDEP won’t allow it. They closely scrutinize every project to fulfill their mandate of protecting human health and the environment.
Ultimately, the UCL software ensures that decisions are based on a statistically sound estimate of the average contaminant level, not just extremes.
These are the sampling requirements for using UCL:
- Minimum of ten distinct samples per functional area
- Sampling must be biased toward the Area of Concern
- Excessive sampling of clean areas does not provide representative data and is discouraged
- Non-detect samples should not exceed 50% of the dataset
Costs and Risks of Using UCL
There are some risks you need to understand:
- Additional sampling may be needed to meet the requirement of at least ten samples per functional area
- If the UCL is improperly calculated or the sampling plan is flawed, NJDEP may reject the compliance demonstration, leading to delays and added costs
- You don’t want to underestimate contamination. If the UCL is lower than actual hotspot concentrations, there may be residual risk to receptors.
Conclusion
Our team has specialized knowledge and expertise in utilizing the ProUCL software to incorporate UCL into your remediation project. In addition, ESA has used this software on several projects without rejection from the NJDEP. When applied correctly, using this compliance averaging software will achieve regulatory sign-off by employing the least expensive remedial method.