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Expanded Preliminary Assessment Report Guidance

The purpose of a Preliminary Assessment or PA Equivalent is to determine whether a site is releasing, has released, or could release hazardous substances to the environment, and whether a response action is required. Occasionally, however, following the completion of a PA or PAE there is insufficient information available to make such determinations about a site. In such cases, an Expanded Preliminary Assessment can be a useful means to gather the additional data needed to formulate the further-action conclusions that are expected from PA-level investigations. While XPAs typically involve the collection of samples to obtain information about the presence, type, or magnitude of contamination at a site, they are not remedial investigations, and are not designed to fully characterize site contamination.

There are two parts to an XPA investigation: preparing a sampling plan and producing the XPA report. DEQ has developed two guidance documents to explain these two parts: the XPA Sampling Plan Guidance, and this document, which addresses XPA reports.

The XPA report should discuss: 1) the reasoning behind and procedures used to carry out the sampling portion of the investigation; 2) the results of all sampling and analyses outlined in the XPA sample plan; and 3) any additional site information obtained during the XPA investigation. In the XPA report, it is important to include information on sampling objectives, field procedures, analytical QA/QC, etc., to permit an assessment of the validity of sampling data. The XPA report should also discuss any changes to the sampling plan due to unexpected field conditions.

The XPA report should include at least the elements listed below; sometimes, additional information may also be needed, on a site-by-site basis.

The links below explain the structure and content of a DEQ XPA report.


Provide the site name and location. Discuss who performed the XPA work, for whom the work was performed, under what authority or type of agreement, and for what purpose. An example of how this section might be written appears below.

  • This Expanded Preliminary Assessment (XPA) report has been completed by [Preparer's Name] for the [Site Name] site, located in [City, State]. The purpose of conducting the XPA and its associated sampling was to collect information beyond that gathered in the Preliminary Assessment (PA) or PA equivalent so that DEQ could better evaluate any threat(s) the site may pose to the surrounding population and environment.
  • An XPA typically consists of a field investigation with limited sampling; and may also include investigative work involving interviews with site owner/operators, or file research. The XPA is limited in scope and is not intended as a full characterization of the site. Field sampling was conducted under protocols accepted by DEQ and the U. S. Environmental Protection Agency.
  • Authority for conducting the XPA is provided in Oregon Revised Statute (ORS) 465.245.

Describe the physical characteristics of the site and the area immediately surrounding it. Include information on location, size, and current and former operational and ownership history. Include after this section, or at the end of the report, a legible, scaled site location map.

Discuss the apparent problem(s) at the site. Identify all areas at the site where hazardous substances are known or suspected to have been released, or may be released in the future. [Much of the information in this section can be lifted from Section 2 of the XPA sample plan.]


Summarize the objectives of the sampling event. Describe what media were sampled and for what purpose. Identify what data gaps were to be eliminated by the sampling, what information was to be clarified, etc. Again, as applicable, use information presented in the XPA sample plan.

Activities Performed

Describe all sampling activities performed during the XPA. Identify any deviations from the XPA sample plan. Include after this section, or at the end of the report, a legible, scaled map showing sample locations with sample numbers noted. Include on this map any features such as site buildings, roads, fences, etc. that can help pinpoint sampling locations. At a minimum, supply the following information for each media sampled:

Sample locations and numbers.

  1. Depth of samples
  2. Physical description - soil type, appearance, moisture content, any unusual features
  3. Sampling procedures and tools used
  4. Deviations, if any, from the XPA sample plan

Include soil boring logs or soil descriptions generated in the investigation as attachments at the end of the XPA report.

Sample locations and numbers.

  1. Sample type - monitoring or domestic well, test pit, other
  2. Depth of samples - screened interval of well, or distance to water
  3. Physical description of samples - pH, EC, color, clarity, any unusual features
  4. Sampling procedures - type of sampler, well purging procedures, etc.
  5. Well construction details - diameter, depth, water level, etc.
  6. Deviations, if any, from the XPA sample plan

Include groundwater sampling data sheets, monitor well construction diagrams, etc. that may have been generated in the investigation as attachments to the XPA report.

Surface Water
Sample locations and numbers.

  1. Sample type - pond, stream, leachate, sediment, etc.
  2. Depth of samples - at surface, near bottom, etc.
  3. Physical description of samples - pH, turbidity, clarity, color, any unusual features
  4. Sampling procedures - type of sampler, etc.
  5. Deviations, if any, from the XPA sample plan

Include surface water sampling data sheets or related information generated in the investigation as attachments to the XPA report.

Sample locations and numbers.

  1. Sample type - vapor, particulate
  2. Elevation of sampling point
  3. Physical description of samples - odors, particulate, color or other features
  4. Sampling procedures - type of equipment used, duration of sampling events, etc.
  5. Weather during sampling
  6. Deviations, if any, from the XPA sample plan

Include air sampling data sheets, meteorological readings or plots, etc. as attachments to the XPA.


Provide a brief narrative summarizing the results of all chemical and physical analyses, including relevant on-site data collection from direct-reading instruments. Where applicable, compare concentrations of hazardous substances in background and on-site samples, and discuss the implications. Organize discussions of sample results by media, and include the results of contaminant screening (see below). Provide sample data in tabular form, include screening criteria for comparison, and identify screening criteria and qualified data as needed. Include laboratory data sheets as attachments at the end of the XPA report. The sampling results section should include a QA/QC evaluation of data generated during field work. Some lab data may be of limited use because of issues such as inadequate matrix spike returns, compounds being detected at or below instrument or method detection limits, or holding times that exceed standards. Describe these or other problems that may affect data quality.

Contaminant Screening. An initial data evaluation step in the XPA is to screen environmental concentrations against appropriate risk-based concentrations to identify a preliminary list of contaminants of potential concern (COPCs). Sources for appropriate screening levels include:

  • EPA Region 9 Preliminary Remediation Goals (PRGs);
  • DEQ’s Risk-Based Concentrations for petroleum sites (RBCs);
  • DEQ’s Screening Level Values (SLVs) for potential ecological receptors; or
  • Oregon’s Default Background Metals - to use if it is suspected that naturally occurring concentrations of metals exceed PRGs.

Depending on the nature of contaminants and on site-specific issues, it may be appropriate to use other screening tools or generic remedies to evaluate the significance of XPA sampling results.


Discuss site information gathered during any non-sampling portion of the XPA investigation, such as interviews with site personnel, file reviews, etc. Comment on the significance of this new information and how it sheds light on any threat(s) that the site may pose to the surrounding population or environment.


Summarize the results of sampling and information-gathering activities associated with the XPA. Focus on new information the XPA generated, and how this information affects the site’s further-action needs and priority. Discuss what questions or data gaps, if any, remain for the site.


Reference all data from outside sources cited in the report. Include the body of major references in the back of the report as attachments. In addition to the materials cited as references, include at least the following materials in the XPA report as attachments (as applicable):

  • Site location map(s)
  • Sample location map(s)
  • Health and Safety Plan from the XPA sample plan
  • Laboratory data sheets
  • Well or boring logs
  • Well construction diagrams.


For more information, contact 
the Environmental Cleanup Program 
or call 1-800-452-4011

To submit a report to DEQ, use Your DEQ Online.