Phase II Esa / Investigation

What Types of Phase II Environmental Site Assessment Are There?

So, you have been told you need to do a Phase II Environmental Site Assessment (ESA) and are wondering what this entails. Here are the things you need to know as you move forward.

What is a Phase II ESA, also known as a Phase Two Environmental Site Assessment?

A Phase II ESA is a limited subsurface investigation that is performed when you have reason to believe there may be contamination on the site and need to establish how likely it is that contamination occurs. Typically, this means there was a Recognized Environmental Condition (REC) discovered during the Phase I ESA.

A Phase II ESA, thus, is performed when Phase I has led to some suspicion of a problem with the site. The recommendation for a Phase II does not mean there is contamination, the only reason to suspect its presence. It’s basically a form of due diligence.

Who Performs a Phase II ESA?

Typically, a Phase II ESA is overseen by a professional geologist, who works with a team of environmental professionals and engineers – at Essel, we are your premier phase II ESA providers. They may need to consult with state and tribal brownfield programs, as many states have assessment activities they require in specific circumstances.

The geologist will look at the Phase I report and use that to design a site assessment, taking into account the contaminants most likely to be present based on the property’s history.

What are the Types of Phase II ESA?

It is critical to understand what is a Phase Two Environmental Site Assessment and the types along with it.

Typically, there are three types of Phase II ESA, any or all of which might be performed depending on the results of the Phase I assessment. The geologist will determine which are likely to be necessary. The three types of site assessment are:


Of particular concern on many brownfield sites is the presence of soil vapor, which may intrude into existing or new buildings. Vapor intrusion is often considered in connection with natural radon, which can be carcinogenic and requires mitigation systems. However, certain chemical contaminants can also cause vapor intrusion. The kind of chemicals the geologist will be concerned with is:

  • Volatile organic compounds (VOCs), such as benzene or trichloroethylene. There are a lot of VOCs, and they may also be emitted from sources inside a vacant building, such as paints and even building materials.
  • Semivolatile organic compounds, such as naphthalene. These are commonly found on sites that used to be manufacturing industries or agrochemical plants.
  • Elemental mercury
  • Certain pesticides, which can also be an issue if the site was used for intensive agriculture.
  • Polychlorinated biphenyls.

Mostly, vapor intrusion is a concern after the demolition of prior buildings or in sites used for manufacturing. However, it is something to be aware of. During a Phase II ESA, the team will test for vapor intrusion by taking samples of soil-gas using a probe and, if there are existing buildings, sampling indoor air. They will then come up with a risk model for vapor intrusion. This might include mitigation recommendations to ensure vapors do not build up inside structures.


Soil contamination is common on brownfield sites. Soil testing is thus a key part of a Phase II ESA, and you will need an experience phase II provider to help you test these samples. This requires that permits are obtained to drill into the soil and then take discrete samples. Soil samples can reveal not just the presence of contamination, but its location.

Typically, the geologist will also classify the soil per the unified soil classification system and determine its overall properties. This can be useful information for eventual landscaping of the site, helping choose plants and promote good drainage.

The soil samples will be extracted by boring and then taken to a laboratory for assessment. If contamination is found, further samples may be taken to establish the extent of soil contamination on the site. This can then inform recommendations made for mitigation and cleanup. For example, widespread contamination throughout the site may need a very different approach from an issue that only affects one corner and can be, if needed, “built around” or remediated locally.

All Phase II ESAs will include soil sampling, and in most cases determining the extent of potential soil contamination is a key reason for performing one. However, if you are fortunate, they may discover the contamination is non-existent or minimal. Furthermore, to understand what is a Phase Two Environmental Assessment, it is critical to have a provider who can perform and study all its facets.


Most sites will also require groundwater sampling, although the extent to which this is necessary depends on the underlying geology and the watershed. Groundwater samples are taken by drilling and are also studied in a lab.

This requires first assessing the depth of groundwater on the site so that appropriate sampling can be taken. Groundwater can easily be contaminated with petroleum, metals, etc. Another technique that is sometimes used is to sample soils at about the depth of groundwater, rather than the water itself.

A survey will be done to establish the likely location of groundwater, and the geologist will also take into account the groundwater flows both into and out of the site. Upstream contamination from another site is common in heavily developed areas but also needs to be mitigated.

In a few cases, some other work might be done. For example, an updated site survey might be needed to establish the best sampling locations. For some sites, a radiological survey might also be performed.

Once the required assessments have been done, the geologist will prepare a report. This will take into account your planned use for the land. Standards for residential development are obviously tighter than for commercial, especially for uses such as warehousing, and due to this, it is important you have a diligent Phase II provider perform this assessment.

Phase II Esa / Investigation

When Does Phase II Investigate All Three?

You might be concerned that performing a Phase II ESA will result in delayed construction or worse, the site being ruled unsuitable for your use. This might make it tempting to only perform one or two of the assessments. This comes from a lack of understanding what a Phase Two Site Assessment is, how it can help your project safely progress.

First of all, not all Phase II ESAs find significant contamination. While they are performed only if the Phase I assessment reveals concerns, it’s not uncommon for them to find no problems or ones which can easily be mitigated.

Regardless of the findings, however, there will likely be a recommendation to perform all three tests to ensure any hazards or risks are identified. The CEQA/NEPA process typically requires the subsurface investigations to be performed, and we always suggest going with an experienced Phase II ESA provider.

Significant contamination will require a mitigation plan that might delay your plans. However, it’s worth remembering that ensuring that the site and buildings are safe is always cheaper in the long run. Make sure to choose a company that will do a thorough assessment and not rush them.

Phase II ESAs can also come with business environmental risks that can affect a real estate transaction negatively. This is something you should be concerned with, but it is not necessarily a reason to walk away from a deal. Performing one is necessary for ensuring safety and avoiding liability, and understand what is a Phase Two Environmental Assessment is of paramount importance, so these risks should be considered an inherent part of brownfield development.