Department of Health Seal

TGM for the Implementation of the Hawai'i State Contingency Plan
Subsection 3.2


Environmental data must be of the appropriate type, quantity and quality to manage uncertainty and reach a defensible decision on appropriate response actions. The HEER Office recommends that the site investigation be developed using a systematic planning approach to ensure that data obtained during a site investigation are adequate to identify or negate the presence of potential environmental hazards. This approach emphasizes using straightforward, clear questions to design and guide the site investigation.

Systematic planning involves a series of well-thought-out steps that help ensure investigation results are adequate to characterize potential environmental hazards posed by contamination and provide sufficient information to develop response actions (refer to Figure 3-1). For the purposes of this guidance, these steps are summarized as follows (Figure 3-4):

STEP 1 – State the Problem: Draft a Conceptual Site Model (CSM)


  • Assemble, review, and evaluate existing data (e.g. Phase 1 ESA, other)
  • Develop a preliminary CSM


  • Concise description of documented or potential contaminant issues on site
  • Initial CSM

STEP 2 – Identify the Objectives and Chemicals of Potential Concern (COPCs)


  • Identify questions to be answered
  • Identify site characteristics
  • Identify COPCs
  • Identify potential outcomes


  • Questions to be answered
  • General description of the site
  • List of COPCs
  • List of potential outcomes

STEP 3 – Identify Data Information Needs


  • Identify existing valid environmental data
  • Perform a data gaps analysis
  • Identify additional types and sources of information needed
  • Identify media of concern
  • Identify potential environmental hazards posed by COPCs
  • Identify sampling approach and lab methods to be used
  • Specify contaminant(s) to be measured and action level to be used for making the decision


  • List of types of information to be collected, and potential sources
  • Description of media and environmental hazards of concern
  • Sampling approach and analytical methods to be used
  • Table including target contaminants, primary environmental hazard, lab analytical method and reporting limits, and applicable HDOH EALs

STEP 4 – Define Decision Units (DU)


  • Define the geographic boundaries of the area of interest
  • Identify temporal issues/sampling components for groundwater or ecological risk evaluations
  • Specify DU type, size, location, and shape (includes depth of soil DUs)
  • Identify particle size of interest and if surface organic matter will be sampled (for soil investigations)
  • Identify practical constraints (resources, accessibility, etc.)


  • Definition of the project boundaries
  • Description and rationale for selection of Dus
  • Description of soil particle size to be collected and if leaves, roots and other surface organic matter should or should not be included in the samples
  • Description of constraints on selection and investigation of DUs

STEP 5 – Develop Decision Statement(s)


  • Develop a detailed “if… then…if not..” decision statement(s)
  • Determine statistical test and confidence level to be used


  • A detailed “if… then…if not…” decision statement regarding the parameter, based on the action level
  • Description of the statistical test and confidence level for data analyses

STEP 6 – Develop and Implement the Sampling and Analysis Plan


  • Summarize site background
  • Specify investigation objectives
  • Identify scope of work
  • Specify sampling and analysis methods and tools
  • Develop work plan and schedule


  • Sampling and analysis plan
  • Work assignments and schedules
  • Tools / equipment list
  • Quality assurance project plan
  • Safety and health plan
  • Sample collection documentation

STEP 7 – Assess Data Quality


  • Validate and determine adequacy of site data
  • Statistical evaluation of data
  • Interpret data and draw conclusions
  • Identify data gaps


  • Data validation evaluation
  • Determination if data met DQO
  • Data tables, summary, and maps

STEP 8 – Identify Potential Environmental Hazards


  • Compare site data to HDOH Tier 1 EALs (or approved, equivalent action levels)
  • Identify specific, potential environmental hazards if Tier 1 EAL for target contaminant exceeded.


  • Site Investigation Report
  • Environmental Hazard Evaluation report (separate report or included with other reports as appropriate)

STEP 9 – Refine the CSM and Recommend Further Actions


  • Review site conditions, data collected, and environmental hazards
  • Identify additional site investigation actions needed
  • Assess Removal or Remediation alternatives for contaminants above Action Levels
  • Develop engineering or administrative controls for contaminants remaining on site


  • Final CSM
  • Recommend additional site investigation actions (if needed)
  • Recommend advanced evaluation of identified environmental hazards (if needed)
  • Develop Draft Removal or Remediation Action Plans, as appropriate
  • Develop EHMP if contaminants above Action Limits will remain on site

Figure 3-4. Nine Steps of the Systematic Planning Approach

Steps 1 through 3 identify the objectives of the site investigation and establish the type of information needed to determine if contamination at the site poses unacceptable environmental hazards. Site investigation activities are developed and carried out in Steps 4 through 6. Information gained from the investigation is evaluated and summarized in Steps 7 through 9.

The steps above are similar to the concept of Data Quality Objectives (DQOs) published in some guidance documents (Robbat, 1997, USEPA, 2000; USEPA, 2001; Tindall, 2006; USEPA, 2006; Triad, 2007). This term is retained for use in this Manual. Early DQO guidance focused on data quality needs with respect to laboratory analysis performance, however, rather than the quality of the data in terms of field representativeness. The DQO steps are modified and expanded in this guidance in order to incorporate the concepts of "decision units" and the collection of representative samples at the beginning of the process. This more comprehensively reflects the typical progression of environmental investigations at sites with contaminated soil and groundwater.

Preparing DQOs prior to the initiation of field activities should be an essential part of all site investigations. Decision Units and Decision Statements are established up front to reflect the desired end use of the data. The data quality assessment is carried out to determine if the DQOs have been met. This process is essential to ensure that the objectives of the site investigation are well thought out and that all samples to be collected are tied to clear decision statements. This will help avoid debate over interpretation of the resulting data and minimize the collection of data that are unnecessary or unreliable.

The level of detail needed to adequately incorporate the systematic planning approach into a site investigation, as well as formal report preparation and submittal requirements, will vary from site to site. Many of these steps may be combined at relatively simple sites where the risk to public health is low and the extent of environmental impacts well confined. This will allow cleanup actions to be conducted quickly and effectively. A more formal review process with greater regulatory oversight will be required for larger or more complex sites where there is greater public health risk or environmental impact, significant public interest, or where site investigation and response activities will be drawn out over a long time period.

Each of the steps noted above are discussed in more detail in the remainder of this Section.


A systematic planning approach is recommended to ensure that data collected during the site investigation are of the type and quality needed to meet the overall site assessment objectives. The nine-step systematic planning approach recommended by HDOH was summarized in the previous subsection. Additional detail is provided below and in Subsections 3.3 through 3.9 (refer also to Figure 3-1).

Step 1—State the Problem – Draft a Conceptual Site Model (CSM)

Summarize past or ongoing activities at the site that could have led to environmental contamination and will require additional investigation. Phase 1 Environmental Site Assessment documents are a good example of the type and level of detail useful to help summarize past and/or ongoing site activities. Summary information is then framed in terms of a CSM. The CSM is a comprehensive representation of the current understanding of site environmental conditions with respect to recognized or potential environmental hazards and is a necessary part of an Environmental Hazard Evaluation (See Section 13).

The CSM serves to summarize the current understanding of a site and identify gaps where additional data are needed. This then forms the basis of the site investigation. A detailed discussion of CSMs is provided in Subsection 3.3. The CSM is maintained and updated throughout the project as new data and information are obtained. To begin developing the CSM, a concise description of the site and potential problem(s) to be studied is prepared.

Issues to consider in Step 1 include:

  1. What types of past or ongoing activities at the site could have led to environmental contamination?
  2. What environmental conditions are identified in Phase I Environmental Site Assessment Reports (Recognized Environmental Conditions, including identified spill areas, storage areas, underground storage tanks, etc.)?
  3. Can other sources of geologic or hydrologic conditions relevant to the site be identified (e.g. geotechnical reports, borings, etc.)?
  4. Do preliminary data indicate the presence of contaminants in soil, groundwater or other environmental media greater than the HDOH Tier 1 Environmental Action Levels (EALs), and therefore the presence of potential environmental hazards?
  5. Are data available from similar sites that may be useful for evaluating the site?
  6. What are the regulatory requirements for reporting and investigating suspected releases of hazardous substances at the site?

Step 2—Identify the Objectives and Chemicals of Potential Concern (COPCs)

The primary objective of the Site Investigation is to collect data necessary to understand the presence and nature of potential environmental hazards at a site (e.g., direct exposure, vapor intrusion, leaching to groundwater, etc.). The site investigation must be designed to meet this objective, as well as to provide any additional information necessary to develop a response action to mitigate confirmed environmental hazards.

A list of site-specific questions is developed based on the initial CSM. These questions are framed so that their answers will be clear. Examples of typical site investigation questions are:

  • Is soil in the vicinity of the former pesticide storage area contaminated above EALs over an area large enough to pose an environmental hazard?
  • Does lead contamination in soil pose a direct exposure risk to residents?
  • Is the size of the benzene plume in groundwater increasing, stable or shrinking?
  • Does the contamination at the site extend beyond the property boundaries?

At this stage, questions are not specific enough to use in designing the sampling plan, but they roughly outline concerns at the site.

Potential outcomes – actions to be taken based on answers to the questions – should be identified. For example, if the question is "Does the mean concentration of lead in the DU surface soil exceed the action level?", then potential outcomes of the investigation might be: (1) Yes; additional cleanup is needed; (2) No; no further actions are needed.

Issues to review and consider in Step 2 include:

  • What are the important geologic and hydrologic characteristics of the site and adjacent areas?
  • What existing surface and subsurface structures occupy the site?
  • Are there sensitive ecological habitats on the site, or nearby?
  • What areas of the site may require additional investigation?
  • What COPCs may be in each area?
  • What is the appropriate size and location of DUs for the site?

Steps involved in addressing these issues initially include:

  • Identify known or potential sources of chemical releases, including underground and aboveground tanks, piping networks, storage areas, disposal areas, etc.
  • Complete an initial, screening level evaluation of potential environmental hazards and determine the need for additional site data.
  • Develop a description of general surface and subsurface characteristics, including paved versus unpaved areas, soil type, presence of debris or fill material, location of utilities, depth to and use of groundwater, location and types of other manmade structures, etc.
  • Identify nearby water supply wells, bodies of surface water and other potentially sensitive ecological habitats that could be threatened by the contamination.

The following actions may also apply:

  • Collect data necessary to evaluate emergency response actions.
  • Identify short-term containment and/or stabilization issues that may be immediately necessary to prevent exposure of on-site receptors to contaminants and to prevent the off-site migration of contaminants while response actions are being evaluated.
  • Identify data necessary to evaluate the ecological impacts of the contaminants.
  • Identify potential spill areas and/or exposure areas for detailed characterization.

The target COPCs should be identified early in the process based on the known or suspected past history of the site and be specific to the site under investigations. The list of target chemicals will likely be narrowed down substantially prior to investigation based on the Phase I review of the site history and other pertinent information. Testing for lengthy, multiple suites of contaminants is rarely required.

The rationale for including a chemical as a COPC should be clearly stated. A chemical should not be listed as a COPC simply because it is included in a default suite of chemicals reported for a specific laboratory method. For example, if lead and arsenic are target COPCs for a site due to historical operations then they should be specifically referenced, rather than listing the full "RCRA 8" suite of metals typically reported by the laboratory (i.e.., arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver). This helps to ensure that the rationale for the selection of target COPCs is clearly discussed and minimizes the use of resources on unnecessary testing. Section 9 provides supplemental guidance regarding the selection of COPCs for several specific types of releases. Refer also to common contaminants listed in the HDOH Tier 1 EAL lookup tables found in Evaluation of Environmental Hazards at Sites with Contaminated Soil and Groundwater (HDOH, 2016).

Step 3—Identify Data Needs

Understanding and collecting the information needed to answer the questions posed in Steps 1 and 2 is a critical part of the site investigation process. Data gaps are identified by an evaluation of existing site data and a determination of the need for additional data to meet site investigation objectives. Additional data may be needed for site characterization, health and safety planning, advanced evaluation of potential environmental hazards (e.g., need for a detailed, human health risk assessment) and the development of remedial alternatives (refer to Section 13). If additional data are needed, the intended use of the data should be clearly identified. Data needs should be continually re-evaluated and refined as more information about the site is gained and potential environmental hazards are identified.

Step 3 involves considering chemicals of potential concern and pathways that need to be investigated to determine the following:

  • Can some groups of COPCs be eliminated from further consideration and testing based on data from previous investigations?
  • What are the potential environmental hazards posed by targeted COPCs?
  • What types of media should be collected and analyzed (e.g., soil, soil gas, groundwater, surface water, etc.) based on areas and types of potential contamination?
  • For groundwater, how often will sampling need to be repeated, and how will samples for specific contaminants be collected/analyzed (e.g. total and/or dissolved metals)?
  • How can representative concentrations of contaminants be best determined (e.g. Multi Increment sampling)?
  • Will surface soil DU-MIS samples suffice, or will sub-surface DU-MIS soil samples be required as well?
  • Will additional, non-traditional data potentially be needed to support the Environmental Hazard Evaluation or response action based on the results of initial data collected (e.g., bioaccessible arsenic data, batch test leaching data)?

Identify the optimal laboratory analytical method for the target COPCs and the media to be tested. Issues to consider in selecting lab analytical methods include:

  • Is more than one laboratory method available for a target group of chemicals?
  • If more than one lab method is available, is one method considered more accurate for the target COPC?
  • Are reporting limits for each method sufficiently low to meet Tier 1 EALs for the COPC and, if not, are they within the generally acceptable range for commercial laboratories?
  • Is prescreening using field equipment or a less rigorous lab method desirable to help refine the final analytical method? (refer to Section 8)

Samples collected during a site investigation may need to be split and sent to several laboratories for testing, based on the types of analyses required. All laboratories should have adequate internal QA/QC procedures to ensure sufficient data quality to satisfy the requirements of the DQO. Also, consider laboratory certification credentials during the lab selection process.

Less sensitive laboratory analytical methods may be necessary for samples that are known or suspected to be heavily contaminated. For example, Method 8280 (or equivalent) is considered to be adequate for testing of dioxins in soil. Testing of soil using an ultrasensitive, trace analysis test such as Method 8290 is not generally required to achieve reporting limits adequate for comparison to HDOH action levels (refer to Section 9). This will help avoid damage to laboratory equipment due to testing of highly contaminated samples.

Field screening may also be used as a screening tool to guide site investigations, but it is generally not acceptable to document the absence of contaminants. Examples of field screening equipment include photo ionization detectors (PIDs), flame ionization detectors (FIDs), and portable X-Ray Fluorescence (XRF) instruments. Additional information on use of field screening methods is provided in Section 8.

Data collected for targeted COPCs should be compared to action levels specific to the media tested. This is one of the primary uses of the HDOH Tier 1 Environmental Action Levels (Tier 1 EALs, refer also to Step 7). Use of the Tier 1 EALs is discussed in more detail in Section 13. Note that the HDOH EALs, as well as USEPA Regional Screening Levels (USEPA, 2014) and similar criteria, are not intended for comparison to individual, discrete sample data. The EALs instead are to be applied to the mean contaminant concentration within the targeted, decision unit.

In general, contaminants in soil, water, soil gas or indoor air at concentrations below the Tier 1 EALs do not pose a significant threat to human health and the environment. The presence of contaminants above the Tier 1 EALs does not necessarily indicate that significant environmental hazards exist, only that additional evaluation is warranted. Incorporation of the Tier 1 EALs in the site investigation work plan provides a useful endpoint for those tasked to carry out the fieldwork, and can reduce the need for remobilization and additional data collection.

The use of alternative action levels to help define the extent of contamination that may be of potential concern is acceptable but should be approved by the HEER Office in advance of the site investigation, or as part of a follow-up, site-specific Environmental Hazard Evaluation. Site-specific action levels must comprehensively address all potential environmental hazards posed by the chemical. Comparison to action levels that focus on a single potential concern, such as the USEPA Regional Screening Levels (RSLs) for direct-exposure (USEPA, 2014), may not be adequate. The presence of other potential hazards such as leaching, vapor intrusion, gross contamination and ecotoxicity concerns must also be evaluated using additional action levels specific to each hazard. As discussed in Section 13, action levels for each of these environmental hazards are incorporated into the HDOH Tier 1 EALs. Unlike the USEPA RSLs, this allows the HDOH EALs to be used as a stand-alone screening tool at most sites.

Environmental hazards that could be posed by targeted COPCs should ultimately be reflected in the Sampling and Analysis Plan. For example, a potential environmental hazard posed by volatile chemicals is the intrusion of vapors into existing or future buildings. The need to collect soil gas data should be evaluated at sites where releases of volatile contaminants have occurred. If heavy contamination is suspected or has been identified at a site, it may be prudent to include the collection of soil gas samples.

Concurrent collection of groundwater data should be considered at sites where soils are grossly contaminated with highly mobile contaminants (e.g., gasoline) or the type of contaminants present could otherwise pose significant leaching and groundwater contamination hazards (e.g., herbicides, such as atrazine). In other cases, additional laboratory tests may be run on split samples to better evaluate a specific hazard that is identified in initial site data.

Examples include:

  • Collection of soil gas data at sites where initial soil and/or groundwater data indicate potential vapor intrusion hazards.
  • Analysis of soil samples that exceed 24 milligrams per kilogram (mg/kg) total arsenic for bioaccessible arsenic in order to more closely evaluate potential direct-exposure hazards (see Section 9).
  • Use of Synthetic Precipitation Leaching Procedure (SPLP) batch tests to better evaluate contaminant mobility in soil samples with reported concentrations of contaminants above action levels for leaching hazards. The SPLP batch test is used to evaluate the potential leaching of contaminants from soil under natural site conditions (refer to Section 13).
  • Use of Toxicity Characteristic Leaching Procedure (TCLP) batch tests on contaminated soil that is to be disposed of in a landfill. The TCLP batch test uses more acidic conditions to simulate changing conditions over time in a landfill setting. TCLP data are used to determine if contaminated soil can be disposed of in a municipal landfill or instead must be sent to a permitted, hazardous waste landfill. Soil designated for disposal is considered to be a hazardous waste if TCLP data exceed regulatory limits found in HAR §11-261-24 and cannot be disposed of in a municipal landfill. (Note that soil is not generally considered to be a "waste" unless it has been excavated and a decision made for offsite disposal.)

A hazardous waste determination could require a separate sampling and analysis plan in order to address landfill disposal requirements (see Subsection 5.10). Contact the landfill for specific requirements. Consider the inclusion of additional sample collection and analysis in the original SAP in order address disposal needs prior to the initiation of site activities.

Step 4—Define the Decision Units

Steps 1-3 above will help to make a judgment call on how to best establish decision units (DUs) on the investigation site. A DU is a well-defined area of a site where a decision is to be made regarding the potential for contaminants to pose an environmental hazard, as defined in the HDOH Environmental Hazard Evaluation (EHE) guidance (HDOH, 2016). Put simply, a DU is the area and more specifically the volume of the targeted media (e.g., soil, sediment or water) that would be collected and analyzed as a single unit if possible. This is rarely if ever feasible and a representative sample (or samples) of the targeted media must instead be collected and submitted to a laboratory for analysis. In some cases, an entire site can be defined as a single decision unit; however, it is more typical to divide a site into multiple decision units based on known or suspected spill areas or areas where workers or residents are exposed to soil on a regular basis. A more detailed discussion of the selection of decision units is provided in Subsection 3.4.

The size and shape of a decision unit will depend on the specific, potential environmental hazards posed by the target COPCs, the intended use of the site and proposed response actions. Known or suspected spill areas should in general be treated as individual decision units. Spill area DUs are typically very small, ranging from a few hundred square feet to a few thousand square feet in area. This is especially important if the target contaminant is highly leachable from the soil and could pose a threat to groundwater resources or is highly volatile and could pose potential vapor intrusion hazards for buildings (e.g., water-soluble pesticides, solvents, light-end petroleum fuels, etc.). For relatively non-mobile contaminants the driving environmental hazard is often direct exposure, rather than leaching and groundwater protection (e.g., arsenic, lead, PCBs, polychlorinated dibenzodioxins and polychlorinated dibenzofurans "dioxins", etc.). If specific spill areas cannot be identified then the appropriate DU size is the current or anticipated exposure area(s) for the site, such as an entire residential yard or the outdoor work area(s) of a commercial or industrial site. Exposure area DUs typically cover areas of several thousand square feet but could be smaller or larger depending on site-specific circumstances.

Points to consider include:

  • What are the primary environmental hazards posed by the target COPCs?
  • How should the decision units be defined to evaluate these potential hazards and associated risks?
  • Do the selected DUs provide sufficient coverage of targeted spill areas and/or exposure areas on the site?
  • What is the optimal area and depth of the DUs to evaluate potential exposure, leaching, vapor intrusion and/or gross contamination concerns?
  • What is the optimal area and depth of the DUs to optimize potential remedial actions?
  • What soil particle size will be collected for analyses?

As discussed in Section 4, testing of a large number of points within a targeted DU (e.g., >30) is generally required to obtain a representative concentration of targeted COPCs for the DU as a whole.

Establishing DUs early in the investigation will also help integrate the field investigation with the evaluation of potential environmental hazards, as well as the preparation of site remedial action plans and long-term management plans. The designation of DUs and development of clear decision statements prior to the initiation of activities in the field is necessary for all investigations, including cases where discrete samples are collected.

Step 5—Develop decision statement(s)

Develop decision statements using sampling information identified in Step 3 and the decision unit boundaries defined in Step 4. Specify contaminants to be measured and action levels to be used for making the decision.

Decision statements are often phrased in the form:
IF the concentration of [chemical] for the targeted decision unit based on [Multi Increment sampling methods] and analyzed using [analytical method] exceeds [value] THEN [action necessary]. IF NOT, then [outcome]."
Such as:
IF the mean concentration of total lead in soil from DU #1, collected using Multi Increment sampling as per the Sampling and Analysis Plan (SAP) dated (day/month/year), and analyzed using USEPA SW-846 Method 6020, exceeds 200 mg/kg, THEN it will be concluded that the soil in DU #1 could pose a potential direct exposure hazard to residents and additional assessment or cleanup will be needed. IF NOT, then it will be concluded that the soil in DU #1 does not pose a potential hazard and no further action is needed.
If the mean concentration of total arsenic in the soil in DU #1 exceeds the Tier 1 action level of 24 mg/kg, then an arsenic bioaccessibility test will be carried out on the soil. IF NOT, then it will be concluded that the soil in DU #1 does not pose a potential hazard and no further action is needed.

If the data on which the decision will be based consists of multiple values, then the statistic to be used for decision-making must be specified. The most commonly-used statistics are (see Subsection 4.2.5):

  • The arithmetic mean contaminant concentration in the DU or
  • The 95% Upper Confidence Level (UCL) of the mean.

Step 6—Develop and Implement the Sampling and Analysis Plan

The Sampling and Analysis Plan (SAP) should be designed to enable the investigation objectives to be achieved within acceptable uncertainty limits. Additional information on preparing a Sampling and Analysis Plan is provided in Subsection 3.6. A suggested format is provided in Section 18.

As described in Section 4, HDOH strongly encourages the use of Multi Increment and decision unit strategies to enhance sample representativeness in the investigation of contaminated soil (Jenkins et al. 2005; Ramsey and Hewitt, 2005). Field studies have demonstrated that error associated with discrete soil sample data can be significant, including underestimation of both the extent of contamination present and the mean contaminant concentration for a targeted area (e.g., HDOH, 2014). Multi Increment samples can significantly increase the representativeness of contaminant concentrations for targeted areas. Selection of decision units is discussed in Step 4, as well as in Subsection 3.4. A comparison of discrete versus Multi Increment soil sampling approaches is provided in Section 4. Soil sampling tools and techniques are discussed in Section 5.

Issues to consider in developing the SAP for soil, groundwater, soil gas and other targeted media include:

  • How can sample collection be optimized to achieve site investigation objectives in a cost-effective manner?
  • Should resources be focused on an investigation of a specific COPC or environmental hazard?
  • Are adequate maps of the site available and if not what level of surveying or mapping will be required?
  • Will rights of entry be required?
  • Will utility clearance be required?
  • Are geotechnical or other types of testing also necessary and if so can this be combined with the site investigation?
  • How much total sample mass (of the designated maximum particle size, if soil) will be necessary to run all the COPC analyses planned?
  • How many field replicates are required to determine overall representativeness of sample data and precision of estimated mean concentrations, given the targeted DUs and COPCs?
  • Is the lab familiar with, and does it have protocols for representative laboratory sub-sampling of field samples (required for Multi Increment samples)?
  • Should additional lab sub-sampling replicates be included to further examine the precision of the lab sub-sampling/lab analysis compared to the field replicate data?
  • For soil, has the lab taken steps to reduce Fundamental Error by determining and using a digestion/analysis mass that is based on the maximum particle size in the sample (e.g., ten gram minimum subsample mass recommended for metals analyses of <2 mm particle size soil)?
  • Have laboratory quality control criteria been met?
  • How many soil gas samples are required to adequately assess potential vapor intrusion hazards?
  • Is the collection of sorbent tube samples for TO-17 analysis required to test for long-chain hydrocarbons at petroleum release sites?
  • Given the expected subsurface conditions, what is the minimal well size needed to collect the necessary amount of groundwater for sample analyses, given the site geology (e.g., micro-wells may not allow the collection of adequate sample volumes in tight soils)?
  • What are the optimal tools for collecting samples for analyses by the methods identified in Step 3?
  • Will field screening be carried out and if so, how will it be utilized and compared to laboratory data?
  • Are the investigation areas accessible using the proposed tools and drilling equipment?

Soil and sediment sample collection methods are discussed in Sections 4 and 5. The collection of groundwater samples is discussed in Section 6. Soil gas and indoor air sampling is discussed in Section 7.

The reporting limit/practical quantitation limit (RL or PQL) a lab expects to achieve for a particular method generally should be low enough to determine if the analyte is present at or above the Tier 1 EALs or designated alternate value that meets the site investigation objectives. This will be a factor in selecting both the method(s) and the laboratory. If the reporting level achievable using standard laboratory methods is greater than the target action level then the reporting limit can be used for screening purposes (refer to Section 13 and EHE guidance, HDOH, 2016).

If soil/particulate samples are being collected and analyzed, the laboratory should be employing a representative laboratory sub-sampling procedure when processing the samples and preparing lab replicates (see Section 4). Such sub-sampling procedures include use of a sectoral splitter or hand Multi Increment sampling (USEPA, 2003b). Representative sub-sampling in the lab is generally considered the most important factor in reducing overall laboratory error.

After selecting analytical methods based on data needs, the next step is to specify the data quality performance and acceptance criteria the data will need to achieve. Uncertainty limits and performance data are developed in more detail in the Quality Assurance Project Plan (see Subsection 3.7). Both field and laboratory data quality considerations should be included in setting overall data quality and acceptance criteria. Providing limits on decision errors provides limits on the uncertainty in the data (USEPA, 2006b). Uncertainty limits are site-specific, and include considerations such as precision, accuracy, completeness, and comparability parameters.

Exceeding Tier 1 action levels for some contaminants may indicate a need for additional (contingent) analyses. For example, if total arsenic is found to be present in soil above 24 mg/kg then the laboratory should be asked to carry out or subcontract for bioaccessible arsenic tests on the sample or on selected samples if multiple samples were collected (see Section 9). If contaminants are detected in soil above action levels for leaching hazards and the soil is to be left in place, then the laboratory should be instructed to carry out a batch test (i.e. SPLP testing) on the samples to better evaluate contaminant mobility and the threat to groundwater. These possible outcomes should be identified in advance under Step 3 and contingencies made in the project budget to cover additional, potential laboratory costs, as appropriate.

It is important for the team tasked with preparing and carrying out the site investigation to visit the site prior to finalization of the Sampling and Analysis Plan. Final selection of decision units and collection of samples is dependent on a multitude of site-specific factors, including the location of buildings and other structures, the presence or absence of pavement, traffic, access, need for clearing prior to sample collection, suitability of tools to collect media targeted, etc.

An integral part of all SAPs is a site-specific Health and Safety Plan. The Health and Safety plan should be prepared and reviewed with field staff before initiating investigation activities at the site. Although the HEER Office will confirm that a SAP contains a site-specific Health and Safety Plan, workplace safety and health issues are under the jurisdiction of the Hawaiʻi Occupational Safety and Health Division (HIOSH). HIOSH should be contacted regarding any safety and health compliance or consultation matters.

Issues to consider in developing the Health and Safety Plan include:

  • What hazards could the targeted contaminants of potential concern or other chemicals that may be present pose to field staff at the anticipated or potential concentrations in soil, soil gas and groundwater?
  • What physical site conditions could pose hazards to field staff and what type of personal equipment is necessary to protect field staff (e.g., for heavy equipment, confined spaces, trip and fall hazards, etc.)?
  • What other environmental factors could pose hazards to field staff (e.g., heat, sunburn, poisonous plants or insects, wild animals, etc.)

Once the SAP has been finalized and, if required, reviewed and approved by the HEER Office, the site investigation should be implemented. The HEER Office should be notified at least two weeks prior to commencement of field activities.

Issues to consider while implementing the SAP include:

  • Has all necessary sampling equipment been gathered and mobilized?
  • Have field team members been made aware of potential chemical, biological and physical hazards that they may encounter at the investigation site?
  • Can the collection of samples be accomplished in the proposed, allotted time?
  • Do unanticipated field conditions warrant a change in sample collection approaches or sample point locations?
  • What modifications will be required for the SAP if a new spill area is discovered, or a new contaminant of concern is identified?
  • Do reported or field-detected levels of contaminants warrant additional laboratory tests on the samples?
  • Do apparent environmental hazards identified in the field warrant an expansion of the investigation area, the collection of additional types of data, or the use of alternative laboratory analytical tests?

Unforeseen events and conditions are common, so it is important to allow flexibility in fieldwork. Unexpected field conditions such as very hard soils or unexpected rocks, pavement or debris below sample point locations could necessitate the use of heavier equipment or an alternative sampling strategy (see Section 5). Interim findings may indicate a (contingent) need for additional analyses; these should be part of the SAP in case they are needed.

Staff tasked with carrying out the field investigation should have a basic understanding of the Environmental Hazard Evaluation process (Step 8; refer also to Section 13). This helps ensure that DUs appropriate for the targeted COPC are designated and ensure that the appropriate amount and type of sample data are collected during the investigation. Major variations from a HDOH approved SAP should be discussed with the HEER Office project manager prior to implementation.

Step 7—Assess Data Quality

Data Quality Assessment starts with the sampling design (Step 3) and is also closely linked with the follow-up site investigation planning steps (Steps 4 through 6). The key focus of the sampling design is to control heterogeneity. The sampling design must be representative (e.g., Multi Increment sampling for soil) and in most cases will include field replicates in order to determine if the data are adequately representative, as well as determine sample variance from the mean. Good professional judgment is essential when selecting decision units for the site investigation. After the environmental data are collected, the data must be validated in accordance with the Quality Assurance Project Plan (QAPP; see Subsection 3.7) to determine quality (e.g., precision, reliability, etc.) and for comparison to relevant EALs. This assessment will determine if the data are sufficient to answer DQOs and address decision statements (Step 5) with the desired level of confidence.

Issues to consider in data validation and data quality assessment include:

  • Did we follow the SAP? Were there any mistakes?
  • Was the lab able to complete all analyses?
  • How will samples outside lab acceptance criteria be further evaluated or handled?
  • If samples were split and analyzed by multiple labs, how do the results compare?
  • Did the laboratory re-analyze or provide appropriate interpretation data for samples that did not meet the sub-sampling or analysis QC criteria?
  • Do the data come from the right decision unit?
  • Are the sample data acceptable based on the field and laboratory QC data and acceptance criteria?
  • Is there sample bias due to bad sample handling, transport, preparation, etc.?
  • Are field replicate data used to assess precision appropriate for the subject data set?
  • Are lab replicate and other lab QC measures used to assess the precision and accuracy of laboratory samples appropriate for the subject data set?

Figure 3-5. Summary of Environmental Hazards Considered in a Typical Environmental Hazard Evaluation

Additional detail on data validation and data quality assessment is provided in Subsections 3.7 and 3.8.

Step 8—Screen for Potential Environmental Hazards

Once the data assessment is complete, data judged appropriate for decision-making are compared to HDOH EALs to screen for potential environmental hazards or evaluated in a site-specific, Environmental Hazard Evaluation (see Section 13). The latter could include a site-specific, human health risk assessment although other potential environmental concerns must also be evaluated.

A summary of common environmental hazards posed by contaminated soil and groundwater is provided in Figure 3-5. Site investigations and Environmental Hazard Evaluations are iterative processes. Identifying potential hazards early on during site investigation activities, even at a cursory level, will help design and guide the progression of fieldwork and reduce the need for remobilization for additional sampling.

The default Conceptual Site Model used to develop the HDOH Tier 1 EALs assumes that each of these hazards could exist at a site given high enough contaminant concentrations and the absence of engineered or institutional controls. An evaluation of each of these potential environmental hazards must be considered in more site-specific Conceptual Site Models. Additional hazards may need to be considered on a site-by-site basis (e.g., uptake of contaminants in produce, etc.).

Issues to consider when screening for potential environmental hazards include:

  • Do reported concentrations of target COPCS exceed Tier 1 EALs and indicate the presence of potential environmental hazards?
  • Are additional data needed to fully define the horizontal and vertical extent of contamination exceeding Tier 1 EALs?
  • What are the specific, potential environmental hazards posed by contaminants that exceed the Tier 1 EALs?
  • Is additional testing of the samples needed to better evaluate potential environmental hazards (e.g., bioaccessible arsenic data or SPLP batch test data)?
  • Are alternative laboratory analyses needed to better evaluate potential environmental hazards?

Issues to consider when interpreting the data and evaluating hazards include:

  • Do current field conditions indicate an existing environmental hazard (e.g., exposed vs. capped areas of contaminated soil)?
  • Could the removal of existing controls (e.g., pavement, buildings, site use, etc.) lead to actual environmental hazards?
  • Is the collection of additional site data needed?

A basic understanding of the Environmental Hazard Evaluation by those tasked with carrying out the field investigation is critical to the accomplishment of the site investigation objectives. Field staff must ensure that the appropriate amount and type of sample data are collected during the investigation to allow completion of the Environmental Hazard Evaluation and formulate appropriate response actions. Current and anticipated (future) site conditions must be clearly documented and considered.

An overview of the Environmental Hazard Evaluation process and the use of Tier 1 EALs to screen site data for potential hazards is provided in Subsection 3.10 and Section 13. Use of the HDOH EAL Surfer to screen site data is strongly recommended.

Note that HDOH EALs are not intended for direct comparison to individual, discrete sample data. The EALs are intended for comparison to the mean concentration of a COPC in the target media (e.g., soil, air or water) over a specified area and volume of that media. The latter, referred to as the decision unit, is tied in part to the specific environmental hazard under investigation (Subsection 3.4; e.g., soil direct exposure area for evaluation of risk to human health).

Step 9—Refine the CSM and Provide Recommendations for Additional Actions

The CSM should be continually updated as site conditions and potential environmental hazards are better understood (refer to Subsection 3.3). The refined CSM should be used to identify data gaps and determine the scope of work needed to complete the site investigation.

Issues to consider when refining the CSM include:

  • Do site conditions or sample data indicate the presence of previously unanticipated environmental hazards, or the absence of previously suspected hazards?
  • Do reported concentrations of COPCs in soil present potential exposure hazards and warrant further analyses of the soil samples (e.g., direct exposure hazards for total arsenic and follow-up bioaccessible arsenic analysis; see Subsection
  • Do reported concentrations of COPCs in soil present potential leaching hazards, indicating a need for soil leaching tests to evaluate contaminant mobility (HDOH, 2007, 2016) and/or the collection of groundwater data (Section 6)?
  • Do reported concentrations of COPCs in soil or groundwater data present potential vapor intrusion concerns, indicating the need for soil gas or indoor air sampling data (Section 7)?
  • Do reported levels of volatile COPCs in soil gas present potential explosive subsurface conditions, indicating the need for an expansion of the health and safety plan to address subsurface drilling or excavation activities?
  • Do high levels of contaminants in groundwater indicate potential impacts to nearby aquatic habitats, suggesting the need to collect additional groundwater, sediment or surface water data?
  • Do high levels of COPCs in soil and groundwater pose a threat to offsite migration which could lead to contamination of adjacent properties?

The revised CSM is used to make recommendations for additional actions necessary to complete the site investigation and direct appropriate response actions.

Additional site investigation may be necessary to fill identified data gaps, provide enhanced evaluation of specific environmental hazards, and develop clean-up or long-term management options, etc. Subsection 3.3 provides additional information about using CSMs to update and prepare site investigation plans.

Potential issues when considering additional site investigation actions include:

  • Are the existing data adequate to address the objectives of the site investigation, as well as to prepare the Environmental Hazard Evaluation?
  • Are additional data necessary for preparation of removal or remedial alternatives, or potential engineering or administrative controls?
  • Do site conditions warrant emergency response actions to address conditions that pose an immediate endangerment to human or ecological receptors?

As discussed in the previous steps, site investigation is a dynamic and iterative process. Persons carrying out the site investigation should continually consult with those tasked with evaluating potential environmental hazards and those involved in developing response action plans. This will help to ensure that the additional data collected are adequate to fulfill the needs of subsequent stages of the project. Keeping these lines of communication open facilitates quick workplan changes when unexpected site conditions are discovered, reducing the need to remobilize field staff in the future and expediting completion of the project.