Site Characterization

What Is Site Characterization?

Site characterization is a process that involves identifying, measuring, and disposing of environmental pollutants, hazards, and liabilities. The site characterization process involves three key phases that serve as a universal roadmap to determine the safest and most efficient way to clean up potential hazards.

The three phases take information from various sources to determine the best steps forward. These sources of information include, but are not limited to:

Historical & Material Records

If available, historical and material records will help environmental consultants understand what activities occurred on the site and which contaminants may be present.

Recorded Chemical Spills

While these records are rarely available for many sites, if available, these records will significantly aid in determining the nature of any present contaminants.

Physical Investigation

The entire site will be searched for the presence of any leaking drums, existing deep wells, injection wells, etc. If any sources of contamination are found, actions will be taken to promptly remove them from the site and dispose of them properly and safely.

Three Phases Of Site Characterization

The three phases of site characterization are summed up by the following words - investigation, confirmation, and remediation. The ultimate goal of each of these phases is to identify, measure, and destroy any present hazards, and each of these phases is crucial to that goal.

Below we're going to go into detail about each phase and what role they play in the process of environmental remediation.

The Three Phases

• Off-site characterization (Investigation)
• On-Site Analysis
• Remediation & Monitoring (Remediation)

What Is The First Step In The Site Characterization Process?

During phase 1 of site characterization, your environmental consultant will focus on off-site efforts, such as analyzing any records available that may aid their investigation. Historical, material, and chemical spill records are all instrumental in this phase of the characterization process.

Historical records are used to understand the various uses businesses have used the site for over the years. The data discovered in historical records will allow remedial teams to understand what chemicals were likely present, giving them an idea of what they might find in later phases of the process.

Material records are a more detailed version of what was held and used on site. These records are beneficial, as it gives your remedial team insights into actual hazards that were present on site. These records can be found through various documents, from storage, delivery, chemical-stock purchasing records, waste disposal records, etc.

Chemical spill records are also helpful, as it tells consultants exactly what was spilled.

Many of these records are only available for some sites and even less for older sites. While these records are instrumental, other methods often need to be used when understanding what contaminants may be found on site.

Once all insights into the property that can be gleamed off-site have been gathered, it's on to on-site investigations, and if it's determined there is a contamination, it's on to phase 2!

What Is The Second Step In The Site Characterization Process?

Phase 2 of site characterization involves gathering information on the contaminant's areal ( x-y plane ) distribution. Once this information is obtained, efforts are made to understand the vertical distribution as well.

In any combination, groundwater, soil, and vapor samples are taken. The most widely tested of these three is groundwater, as groundwater contamination is usually the site's most significant threat. Samples are taken using wells either directly on or near the area.

There are usually several rounds of sampling that are conducted, and the way in which these samples are carried out depends on the type and amount of data gathered in phase 1.

If a lot of information was discovered in phase 1, and consultants are aware of which contaminants they will mainly be dealing with, they can direct their sampling efforts accordingly. However, in situations where the first phase gave little or no information as to which contaminants are potentially on-site, certain priority contaminants are put out by the National Primary Drinking Water Regulations (NPDWR) that will generally be the first ones sought out.

Monitoring wells often may need to be installed as the second phase of a site characterization begins to unfold these wells installed in critical places can greatly arm remedial teams with the information they need to measure and deal with any present contaminants properly.

These monitoring wells can also be used in phase three of this process to help in any remedial efforts in the future as well.

Once confirmed that contaminants are present, the consultants will determine which remediation method will be required to treat the contaminant successfully.

What Is The Third Step In The Site Characterization Process?

Phase 3 site characterization is focused on environmental remediation and continual analysis. Now that the type and extent of contamination have been confirmed, efforts are taken to reduce, destroy or remove any presence that has been identified.

There are many different ways in which contaminants can be either removed, reduced, or destroyed, and which method is chosen depends on many factors. But, once remediation has occurred, consultants continue taking samples until it has been proven that the soil and groundwater have been returned to acceptable levels.

Site Remediation Methods

Ex-Situ Remediation

In ex-situ remediation, machinery is used to haul away contaminated soil. The soil will then be treated off-site in a specialized facility, which can either be replaced with a different medium or brought back after the contamination has been destroyed.

The main benefit of this method is the speed, as the contaminants can be taken off-site within a day or two. However, it is generally also a much more expensive option. In addition to the added expense, it is less effective than in-situ remediation because for it to be effective, all of the contaminated materials need to be removed.

In-Situ Remediation

In-situ remediation generally takes longer than ex-situ. However, it is usually more affordable and more reliable. The reason for in-situ remediation's added reliability is found in the type of remedial reagents used during this process.

In-situ remediation uses various methods and tools to introduce these reagents to any contaminated areas on the surface or subsurface. Usually, these methods include some drilling, such as DPT drilling, sonic drilling, etc.

However, other methods can be used aside from drilling, such as soil mixing, hand lances, etc.

The purpose of these reagents is to introduce chemical reductants, chemical oxidants, or both - in the form of a redox reaction - to reduce contaminant concentrations and ultimately destroy them.