14 Apr Anatomy of a Soil Site Investigation
A Three-fold Objective
A successful soil site investigation requires fulfilling the needs of the three main parties involved in the action — the NJDEP, the client, and ESA — all of whom have differing objectives. To ensure public safety, the NJDEP requires strict adherence to environmental regulations. The client, who is mandated by law to comply with NJDEP’s rules, seeks a timely and cost-effective turnaround. And ESA strives to perform the work flawlessly on behalf of the client while making a reasonable profit. With thousands of clients over 35 years, ESA has yet to encounter a single client who is pleased to learn they must spend money on a soil site investigation. So, to achieve the stated objectives and to keep the client happy, ESA must formulate a strategic plan for the investigation that artfully combines adherence to NJDEP regulations with seeking a route that requires the least amount of work possible.
Collecting the Soil Samples
In the NJDEP’s Site Remediation process, the Site Investigation (SI) is the phase of work where environmental samples such as soil, ground water, sediment, soil gas, and indoor air are collected to determine if contamination is present in regulated media at concentrations that exceed NJDEP remediation standards. While the NJDEP does allow contaminants to be present in the subsurface at certain concentrations, if a sample result is reported by a certified laboratory that exceeds an NJDEP remediation standard, further investigation and possibly remediation are required. For the purposes of this article, we will focus solely on standards and strategies for soil samples.
The NJDEP requires that soil samples be biased towards areas suspected of the highest levels of contamination. Examples of common Areas of Concern (AOCs) are underground storage tanks (USTs), manufacturing areas, loading docks, floor drains, drums storage areas, rail lines, and dumpsters. A proposed sampling plan that includes pertinent details to adequately investigate each AOC is typically documented in a Quality Assurance Project Plan (QAPP). This plan provides NJDEP with a blueprint to ensure, in part, that all possible areas where soil may be impacted are investigated.
Soil Sampling Techniques
Often, a soil investigation begins with a Ground Penetrating Radar (GPR) survey to identify the locations and depths of metallic anomalies and other features indicative of AOCs, such as current and former USTs, septic systems, excavations, rail lines, floor drains, and other belowground piping. Aboveground AOCs are typically easier to identify because they are often directly observable. Sample collection locations usually concentrate on areas with apparent visual staining, discharge locations, low lying areas, and areas with evidence of stressed vegetation. AOC locations can also be determined or refined from due diligence studies, site plans, surveys, and interviews with key personnel.
Other Soil Sampling Considerations
Sample depth and frequency parameters must also be set as part of the overall investigation plan.
Sample depth will be determined based on a series of variables. For example, when investigating a UST site, its depth, level of corrosion, presence of groundwater, and historical changes in ground surface elevation must all be taken into consideration. Because each site is unique, it is paramount to have a thorough understanding of the site’s history and the physical characteristics of each specific AOC.
For sample frequency, NJDEP SI guidance documents provide specific direction to assist the investigator with collecting an appropriate number of samples from various types of AOCs. It is important that the sampling plan demonstrate to NJDEP via the QAPP that all potential AOCs are being properly investigated.
Artful Execution
Once a thorough and proper soil site investigation is performed, the data collected is collated and evaluated and ESA’s strategic dexterity and artful creativity comes into full play. Any exceedances in the data are intensely scrutinized for potential opportunities to minimize or even completely eliminate remedial work. While there are no guarantees, and the top priority is compliance with NJDEP regulatory guidelines, ESA’s unrelenting client advocacy ensures that our clients will receive the best possible outcome for their unique circumstances.