Brownfield Site Contamination Investigation

Several steps are involved in determining the potential for and extent of contamination of a site.  These include: coordinating with the pertinent regulatory agencies, retaining the services of a consultant to carry out the site investigations, and conducting the necessary investigations.

Environmental Regulations and Compliance

The redevelopment of Brownfield sites is subject to a variety of federal, state, and local laws, regulations, policies, and guidelines with respect to the identification of site contamination and site cleanup. Such sites also may be governed by the standard practices of other government, nongovernment, and private institutions.

The applicable laws, regulations, policies, and guidelines will vary by site, depending on the regulatory authority that manages the cleanup.  Therefore, it is important to identify the appropriate regulatory agency(s), have them determine the site specific requirements and approvals/permits needed for site investigations, and work closely with the appropriate regulatory authority throughout the cleanup process.  EPA also can be a valuable resource for brownfields stakeholders by providing regulatory and policy support to facilitate selection of technologies.

Consultant Procurement

Procuring the services of a qualified consultant is an important step in determining the existence and extent of contamination, if any on a Brownfield site.  The organization interested in hiring a consultant will have specific procurement procedures which must be adhered to.  A sample Request for Proposal for the performance of Brownfield assessment services is provided.

In CT, MA, and now, NJ, some remedial sites require the use of a private Licensed Site Remediation/Environmental Professional (commonly referred to as an LEP in CT, LSP in MA, and LSRP in NJ).  These professionals guide the remedial process for a site through to completion, usually with little oversight from the state environmental regulatory agency.  The activities of the professionals are overseen by licensing boards and strict codes of ethics.  A list of the professionals who are licensed to perform site remediation work can be found at each respective state’s environmental regulatory agency websites.  In addition, each of the three states have Licensed Site Remediation/Environmental Professional Associations that have web sites that provide valuable information: for CT, for MA, and for NJ.

Phase I Environmental Assessment

Phase 1 Environmental due diligence is the systematic practice of determining the potential for environmental conditions, issues, and liabilities at a Brownfield site. Since by nature, Brownfield sites are considered to be impacted in some degree by past uses and therefore the potential does exist for the presence of contamination, environmental due diligence is essential to successful Brownfield site transaction and redevelopment. These activities support two basic objectives:

  • Transactional: In order to provide assurance for lenders, investors and other stakeholders involved with the property transaction.
  • Legal: To meet liability protection and regulatory obligations under federal and state environmental laws (CERCLA; N.J.A.C. 7:26E)

A Phase I Environmental Assessment is the first step in evaluating the potential environmental issues with a Brownfield site. It generally involves a review of readily available information on the potential presence of contamination; the potential, existing or past contaminant releases; and the possible paths of exposure that would be of concern. Interviews with community members and others can also be conducted to determine past practices associated with a particular site. This initial effort could be combined with developmental data gathering, particularly in regard to the potential land use for the site.  A Phase I can provide information to developers, municipal planners and the community early in the assessment process on potential environmental concerns which would be helpful in initial planning regarding land use and the viability of the property for redevelopment.

All Appropriate Inquiry (AAI)

A component of the Phase 1 process is All Appropriate Inquiry (AAI). EPA defines All Appropriate Inquiry as the requirements for assessing the environmental conditions of a property prior to its acquisition. AAI is the Phase 1 process identified in the Brownfield Law and as such, EPA Brownfield Grantees are required to assess and characterize properties in accordance with All Appropriate Inquiry standards. Such inquiries must be conducted or updated within one year prior to the date of acquisition of a property. If all appropriate inquiries are conducted more than 180 days prior to the acquisition date, certain aspects of the inquiries must be updated.

The inquiries must be conducted by a Qualified Environmental Professional (QEP) which is defined as “someone who possesses sufficient specific education, training, and experience necessary to exercise professional judgment to develop opinions and conclusions regarding conditions indicative of releases or threatened releases of hazardous substances on, at, in, or to a property, sufficient to meet the objectives and performance factors of the rule”.  See the All Appropriate Inquiries Rule: Definition of Environmental Professional (pdf) for more information.  ASTM International’s E1527-00 standard, "Standard Practice for Environmental Site Assessments: Phase I Environmental Site Assessment Process" may be used to comply with the AAI requirements.

The AAI generally includes:

  • interviews with past and present owners, operators and occupants;
  • reviews of historical sources of information;
  • reviews of federal, state, tribal and local government records;
  • visual inspections of the facility and adjoining properties;
  • commonly known or reasonably ascertainable information; 
  • degree of obviousness of the presence or likely presence of contamination at the property and the ability to detect the contamination.
  • searches for environmental cleanup liens;
  • assessments of any specialized knowledge or experience of the prospective landowner (or grantee);
  • an assessment of the relationship of the purchase price to the fair market value of the property, if the property was not contaminated; and commonly known or reasonably ascertainable information.

Users of the Environmental Due Diligence

  • Buyers & Sellers
  • Developers
  • Tenants
  • Lenders (Banks)
  • Lawyers
  • Insurance Companies
  • Regulators

Site Reconnaissance

A site reconnaissance supplements the Phase I Assessment by visually observing the site and its surrounding areas. This reconnaissance should expand the understanding of site conditions.  Specific objectives of the reconnaissance include: documenting the physical features of the site (i.e. dimensions, buildings etc.) and the surrounding area; recording any differences from the information gathered in the Phase I; identifying any sources of hazardous substances and pathways that may be of concern; and, identifying any new features that may have an impact in the assessment and decision regarding the site. Preparation for the reconnaissance will include: reviewing all information garnered from the Phase I, arranging for site access, and identifying any health and safety concerns.

Phase II Environmental Assessment

If a Phase I Environmental Assessment indicates that there is the potential for environmental impacts from past uses, then the environmental due diligence process continues with the Phase II Environmental Assessment. The primary objectives of conducting a Phase II EA are to evaluate the recognized environmental conditions identified in the Phase I EA or transaction screen process for the purpose of providing sufficient information regarding the nature and extent of contamination to assist in making informed business decisions about the property; and where applicable, providing the level of knowledge necessary to satisfy the innocent purchaser defense under CERCLA.

At the completion of a Phase II EA, the environmental professional should be able to conclude, at a minimum, that either (a) the EA has provided sufficient information to render a professional opinion that there is no reasonable basis to suspect the presence of hazardous substances or petroleum products at the property associated with the recognized environmental conditions under assessment, or (b) the EA has confirmed the presence of hazardous substances or petroleum products at the property under conditions that indicate disposal or release. If the information developed in the EA is insufficient for the environmental professional to reach either of these conclusions, the environmental professional may recommend additional iterations of assessment if warranted to meet the objectives of the user. If the environmental professional reasonably suspects that unconfirmed hazardous substance or petroleum releases remain but concludes that further reasonable assessment is not expected to provide additional information of significant value, he/she may recommend that further assessment is not warranted. In such circumstances, the recommendation for no further assessment should be accompanied by an explanation why a reasonable suspicion of releases remains and why further reasonable assessment is not warranted.

Quality Assurance for Site Assessments

Quality assurance is an integrated system of management activities involving planning, implementation, assessment, reporting, and quality improvement to ensure that a process, item, or service is of the type and quality needed and expected. Quality control is the overall system of technical activities (including checks on sampling and analysis) that measure the performance of a process against defined standards to verify that they meet predefined requirements. Since errors can occur in the field, laboratory, or office, QC must be part of each of these functions.

Additional information regarding quality assurance for site assessments can be found at the EPA website.

Site Investigation Methods

Phase II Environmental Assessments involve the collection of media samples, the testing of the samples in an appropriately accredited laboratory and then comparing the results to environmental media standards established by the state and/or Federal government. The sampling can include:

  • Building interiors.
  • Soil samples from suspected impacted areas.
  • Ground water samples and water level measurements.
  • Surface water and sediment samples.
  • Soil gas samples to evaluate for the potential for vapor intrusion.
  • Background soil samples to establish base line conditions.
  • Ecological conditions evaluation.
  • Presence of historic fill.

Watch The Basics of Environmental Investigations (8:01)

by the New York City Office of Environmental Remediation. This video describes the basics of environmental investigations in a non-technical manner.

Soil Investigation

A significant portion of the Phase II Environmental Assessment sampling will be oriented toward evaluating if soil contamination exists and to what degree. Most states within Geographic Zone 1 (EPA Regions 1, 2 and 3) have soil clean up standards. In many states the standards recognize two different reuse scenarios, residential or commercial/industrial. Initially surface and subsurface soil samples are collected to confirm or deny that an impact has occurred above the appropriate standard. The location of the soil sampling is based upon information developed during the Preliminary Assessment process, in which certain areas that may have received a release are designated areas of potential concern. By performing a first round of simple soil sampling at key locations, the areas of potential concern can be either removed from further consideration or, if impacts are present above standards, then additional soil sampling can be performed to delineate the extent of impacts.

Many states have guidance manuals on methodologies and procedures for collecting soil samples. For example, the New Jersey Department of Environmental Protection (NJDEP) has prepared an extensive Field Sampling Procedures Manual ( that provides detailed discussions on a wide variety of activities associated with soil sampling. Discussions include quality assurance procedures, sampling equipment handing and decontamination, sample collection, sample handling and labeling, analytical methods and data reporting. Other states and the EPA also have published guidance manuals, but essentially the methods for soil sampling are generally consistent throughout.

Groundwater Investigation

Perhaps the most discussed and written about aspect of site investigations is groundwater impact evaluation and understanding site hydrogeology. The EPA and states within Geographic Zone 1 have groundwater quality standards that define specific concentrations for a wide range of chemicals. Exceeding the allowable groundwater quality standard defines an impact to groundwater and requires further investigation to delineate the extent of impact and determine the risk of that impact to human health and the environment. Usually groundwater is considered a resource of the state and while the specific water bearing unit impacted may not be used for drinking water purposes in the area of the Brownfield site, the simple fact that groundwater is impacted will trigger the need for further studies.

A typical Phase II Environmental Assessment groundwater investigation consists or two parts:

  • Identification of the subsurface water bearing units or aquifers underlying the site.
  • Determination that a groundwater impact from site operations has occurred through groundwater sampling.

Determination of the water bearing units or aquifers underlying a site can usually be accomplished through publicly available information sources, such as maps and studies performed by the United States Geologic Survey (USGS) or the state geologic survey or environmental agency. Many states have performed water supply studies that identify primary groundwater supply sources and have mapped aquifers. These studies are usually posted on web sites or are available from the federal or state map distribution outlet. Additionally, states within Geographic Zone 1 also have water supply bureaus or departments which routinely publish reports on groundwater resources.

One important aspect of collecting regional groundwater information is identifying the location of public and private supply wells. This is critical information for risk analysis if groundwater impacts are discovered at the Brownfield site. To the degree possible, private or public groundwater supply wells with a half mile radius of the Brownfield site should be located and plotted on a map.

Regarding site specific groundwater impacts, two issues are critical. One is collecting a groundwater sample from the first principle water bearing zone adjacent to the area of concern or possible impact. The other is determining groundwater flow direction in order to establish upgradient and downgradient groundwater directions. Since many Brownfield sites are located in industrial areas, at least one groundwater sample should be collected on the upgradient side of the Brownfield site to establish background conditions and determine if groundwater impacts are flowing on to the site. Additionally, at least one groundwater sample should be collected with 10 feet downgradient of areas of the Brownfield site where the Phase I EA indicated possible contamination from past operations could exist. 

There are many guidance manuals available on monitoring well installation procedures, groundwater sampling methods and sampling handling procedures. Listed below are web addresses for several manuals:

Soil Gas and Vapor Intrusion

Vapor intrusion is the migration of volatile chemicals from the subsurface into overlying buildings. Volatile chemicals in buried wastes and/or contaminated groundwater can emit vapors that may migrate through subsurface solid and into air spaces of overlying buildings.  In extreme cases, the vapors may accumulate in dwellings or occupied buildings to levels that may pose near-term safety hazards, acute health effects or aesthetic problems. 

These air quality and vapor intrusion issues are a growing concern associated with Brownfield redevelopment. If volatile organic compounds (VOCs) are discovered in the groundwater or soil, then a vapor intrusion (VI) study is required. One approach to evaluating if VI is an issue at the Brownfield site is to collect soil gas samples from the unsaturated zone beneath the site. EPA has developed procedures for collecting soil gas samples and evaluating if VI could be an issue. Please visit the EPA website for more information regarding vapor intrusion and soil gas sampling.

Surface Water and Sediment Sampling

Sometimes a Brownfield site is adjacent to a pond, wetland, stream or other waterway. Under these circumstances, many environmental regulators require that sampling be performed to evaluate if chemicals related to the Brownfield site have migrated off-site and impacted the adjacent water body or wetlands. This requires surface water and sediment sampling.

Since surface water is transient, sampling is usually performed at either low flow periods or storm events.  Under low flow conditions impacts that may be leaking from the site into the water body through a groundwater pathway can be identified.  During storm events, overland flow increases and impacts that may be imbedded in surface soil could be transported to the nearby water body. Prior to sampling, the shoreline on the Brownfield site should be surveyed for discharge pipes, erosion channels or leachate seeps.  The sampling locations should be focused to these features.  Also, simultaneous to collecting site related samples, surface water samples should be collected upgradient of the site and downgradient to place any site related impacts in context to regional impacts that originate from urban storm water runoff.  Finally, the testing parameters should be chosen based on the specific contamination found at the Brownfield site. Since urban runoff contains PAHs, metals and petroleum hydrocarbons, it is important to be able to distinguish site related impacts from urban background.

Sediments will accumulate impacts, particularly at low points in the hydrologic system (ponds/lakes) or at low flow points in the stream flow requiem (stream depositional areas).  Sample locations should be biased toward these points in order to maximize the effectiveness of the sampling.  Additionally, as with the surface water samples, sediment samples should be collected adjacent to discharge points (storm water or process discharge outfall pipes) and/or runoff channels or seeps. At each sediment sampling location, two samples should be collected, one from the upper six inches of the sediment core and one from the 6 to 12 inch interval.  Since many Brownfield sites have been either underutilized or abandoned for years, the impacted sediment may have been covered over with newly deposited relatively cleaner sediment.  Again, as with surface water sampling, upgradient and downgradient sediment samples should be collected to place the results of site related sediment sampling in context with the regional impacts. Also, since urban runoff accumulates in sediment, PAHs, metals, petroleum hydrocarbons are common sediment impacts from urban runoff and site related impacts need to be distinguished from urban background.

Remedial Investigation

If the Phase II Environmental Assessment identifies impacts over applicable standards, then further study is needed to delineate the impact and determine the risk associated with the impact. The Remedial Investigation (RI) includes the activities needed to collect data to characterize the horizontal and vertical extent of contamination; identify potential sources of continued contamination including the presence of “hot spots”; determine the surface and subsurface characteristics of the site including soil characteristics and depth to groundwater; and assess risk to human health and environment through the identification of paths of exposure and actual or potential receptors. 

 In the last five years advances have been made in the tools available to conduct RIs, which can make them more robust and cost effective. The EPA Web site provides detailed information on many of these investigative methods. See

When combined with the correct QA/QC program, advanced site investigation methods can increase confidence in the design of the remedy thorough increased data density.

In addition to assisting in the development of investigation technology and the education of professionals in the use of advanced site investigation methods, EPA has also developed a system for expediting the remedial investigation process called the Triad approach. The Triad approach consists of three integrated parts: (1) systematic planning, (2) dynamic work strategies and (3) real time measurement technologies. The systematic planning forces all parties to articulate the goals and objectives clearly and within the context of the Brownfield project. The dynamic work strategies which use real time measurement devices reduce uncertainty associated with sampling and site characterization by increasing sample density and sample accuracy. The Triad approach is useful for Brownfield sites because it considers the whole site (not just Area of Concern focuses), is flexible (can be adjusted to unexpected conditions) and integrates all stakeholders into the site decision making process (no surprises).  More information on the Triad approach can be found at the Triad Resources Center (; the EPA Innovative Technology Program web site ( and Interstate Technology & Regulatory Council (

Examples of advanced site characterization methods include:

  • Using the membrane interface probes (MIP) to delineate the extent of a chlorinated volatile organic compound (VOC) plume in groundwater, and then developing a collaborative data set using interval specific groundwater sampling.
  • Using an XRF instrument to obtain real time measurements of lead concentrations in soil and, using this information, making field decisions on the next sampling locations.
  • Using GIS software to imaging electronic logs from direct sensing probes to create three dimensional depictions of subsurface VOC or petroleum products impacts and then using these images to design remedial applications.
  • Using direct push electronically conductivity probe (DPECP) to map the thickness and horizontal extent of historic fill and then select soil samples for characterization of fill contents.

Feasibility Study

The Feasibility Study, which culminates in the selection of a Remedial Action, includes the identification and engineering analysis of remedial action alternatives for the site which are cost-effective and consistent with the development requirements (i.e. proposed use, critical time schedule, funding goals).  During this phase, remedial action objectives are identified, technologies or approaches that meet those objectives are screened, and detailed engineering analysis is conducted.

This is the process of identifying possible remedial alternatives and developing the engineering data to evaluate their effectiveness. There are a wide range of remedial options available for cleaning up impacted sites. These range from simple excavation of impacted soil from a tank leak to complex multiple phases of injection of treatment liquids to remove concentrated VOCs. Various web sites are available that list remedial technologies and describe their application, cost and effectiveness. Several are:

Another aspect of the feasibility study is to perform small tests of potential remedial treatment options on site specific samples. This is called bench scale treatability studies and involves exposing contaminated soil from the site to various types of treatment liquids and concentrations. This is most appropriate when considering an in situ remedial technology such as enhanced biodegradation, chemical oxidation or thermal desorption.

Remedial Action Selection 

In general this evaluation shall include (1) a narrative description of appropriate remedial action objectives (RAOs) that would be consistent with the future intended use of the site, (2) identification and evaluation of an applicable and focused list of the remediation alternatives that satisfy the RAOs (The remedial alternatives may be presented as broadly defined measures that by themselves or in combination with other measures will satisfy the applicable RAOs for the site); and, (3) an analysis of the applicable evaluation criteria - effectiveness, implementability, cost and consistency with applicable laws and regulations. Other factors including potential impacts of the remediation to the local community, the degree of permanence of the remedial action, and potential injury to natural resources may also be considered. 

Effectiveness: The effectiveness evaluation focuses on three factors: (1) the overall protection of human health and the environment; (2) the potential short-term and long-term effectiveness in treating impacted media and mitigating direct and indirect receptors; and, (3) the proven performance and reliability with respect to the reduction of toxicity, mobility, and volume of contaminants and conditions at the site.

Implementability: This criterion encompasses the technical and logistical, and administrative feasibility of implementing the remedial action.  The site-related aspects of implementability may include, but are not limited to: site work accessibility; final structural integrity of the site during and after remediation; ability to obtain the necessary permits for remedial actions; and availability of necessary resources, equipment, and skilled workers to implement the remedy.

Cost: Estimates of capital and operation and maintenance (O&M) costs associated with each alternative are developed. The cost estimates used in the alternative screening process may originate from several sources of information: commercial cost estimating guides, such as Means Site Work Cost Data; generic unit costs derived from other publications; vendor contacts; and, actual cost data from similar sites.

Consistency with Applicable Laws and Regulations: This criterion encompasses the regulatory feasibility of implementing the remedial action.  The selected remedial alternative must be consistent with applicable laws and regulations (federal, state and local). In addition the feasibility of acquiring stream encroachment permits, soil erosion and sediment control permits, local construction permits, and general stormwater permits should be considered.

A table of contents for such a Feasibility Study and Remedial Action Selection analysis should include:

  1. Introduction
    1. Purpose and Scope
    2. Brief Site Description
    3. Content of Report
  2. Appropriate and Relevant Remedial Action Objectives
    1. Soil
    2. Groundwater
    3. Identification of Constituents of Concern
    4. Applicable Remediation Criteria
  3. Identification of Potential Remedial Actions
  4. Evaluation of Remedial Alternatives
    1. Applicable Evaluation Criteria
      1. Effectiveness
      2. Implementability and Consistency with Project Schedule
      3. Consistency with Applicable Laws and Regulations
      4. Potential impacts to the Local Community
      5. Potential for Natural Resource Injury
      6. Cost
    2. Identification, Evaluation, and Selection of Remedial Alternatives
      1. Screening of Site Specific Remedial Alternatives
      2. Identification of Selected Remedial Action(s)
  5. Preliminary Engineering Evaluation
  6. Remedial Action Work Plan