Expanded Preliminary Assessment Report Guidance

SAMPLING

Objectives

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:

Soil
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.

Groundwater
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.

Air
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.

Results

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.

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