Department of Health Seal

TGM for the Implementation of the Hawai'i State Contingency Plan
Section 13.3
TIER 1 ENVIRONMENTAL ACTION LEVELS

13.3 TIER 1 ENVIRONMENTAL ACTION LEVELS

Tier 1 Environmental Action Levels (Tier 1 EALs) are concentrations of contaminants in soil, soil gas and groundwater below which the contaminants are assumed to not pose a significant threat to human health or the environment. Exceeding the Tier 1 EAL does not necessarily indicate that contamination at the site poses environmental hazards. It does, however, indicate that additional evaluation is warranted. This can include additional site investigation and a more detailed evaluation of the tentatively identified environmental hazards. For example, the Tier 1 EALs incorporate conservative, risk-based exposure assumptions that may not be applicable under current site conditions and warrant a more site-specific risk assessment (see also Section 13.5.3 ). The action levels, or approved alternatives, can be used to delineate specific areas of the site that require response actions. These actions can vary, depending on the hazard present and site conditions.

A detailed discussion of the development of the Tier 1 EALs is provided in the HDOH HEER Office document Screening for Environmental Hazards at Sites with Contaminated Soil and Groundwater (HDOH, 2016). The EALs described in the EHE document are not intended to establish policy or regulation. Use of the document and associated EALs is optional on the part of the party responsible for investigation and cleanup of a contaminated site. Reference to updated EALs will generally not be needed at sites where final cleanup levels have already been reviewed and approved by the HEER office, including sites that have already been closed. For sites where investigation is currently underway, referral to updated EALs is recommended.

13.3.1 DEFAULT CONCEPTUAL SITE MODELS

A conceptual site model (CSM) is a comprehensive representation of site environmental conditions with respect to contaminated soil and groundwater and related environmental hazards (see Section 3.4.3). Four default CSMs were used to develop The Tier 1 EALs (HDOH, 2016):

  1. Groundwater affected or potentially affected by the release is a current or potential drinking water resource; site located within 150m of a surface water body.
  2. Groundwater affected or potentially affected by the release is a current or potential drinking water resource; site not located within 150m of a surface water body.
  3. Groundwater affected or potentially affected by the release is not a current or potential drinking water resource; site located within 150m of a surface water body.
  4. Groundwater affected or potentially affected by the release is not a current or potential drinking water resource; site not located within 150m of a surface water body.

Only surface water bodies that are hydraulically connected to groundwater are considered to be potentially threatened by contaminated groundwater. For the purposes of the Tier 1 EALs, it is further assumed under each default CSM that contaminated soil is exposed at the ground surface or could otherwise become exposed in the future. Using this approach to initially screen site data clears the site for unrestricted land use if Tier 1 EALs are not exceeded and avoids the need for additional investigations if site conditions change. Refer to the HDOH document Evaluation of Environmental Hazards at Sites with Contaminated Soil and Groundwater for additional information on site conditions assumed for development of the Tier 1 EALs (HDOH, 2016).

The default CSMs can be modified and alternative action levels developed if necessary. Alternative soil action levels for direct exposure and gross contamination hazards at commercial/industrial sites are included in Appendix 1 of the detailed EHE document (HDOH, 2016). As discussed below in Section 13.3.3, the EAL Surfer has been modified to allow selection of land use on a site-by-site basis. Alternative action levels for deeper soils are also provided in the guidance (e.g., >3 meters below ground surface). Be aware, however, that the use of alternative CSMs and action levels could require that formal institutional or engineered controls be imposed on the property, especially for nonpetroleum-related contamination (see Section 19). Site data should always be initially screened using the Tier 1 EALs (or approved, alternative action level) for unrestricted (e.g., residential) land use. If the site passes this screen then there is no need to screen the data using an alternative CSM and assumed land use.

13.3.2 COMPILATION OF ENVIRONMENTAL ACTION LEVELS

Figure 13-3 summarizes the general use of the Tier 1 EALs. Approximately 150 chemicals are listed in the EAL lookup tables (HDOH, 2016). For each chemical, an action level was compiled to address each specific environmental hazard discussed above and noted in Figure 13-2, as applicable and available.

The lowest of the individual action levels for each hazard was selected for inclusion in the summary Tier 1 EAL lookup tables. This ensures that the EALs presented in these tables are protective of all potential environmental hazards. The detailed tables used to develop the Tier 1 EALs can be used to identify the specific environmental hazards that are potentially present at the site. The EAL Surfer makes this process relatively quick and easy (see Subsection 13.3.3).

An example of the selection of Tier 1 EALs for benzene is presented in Figure 13-4 (surface soils, drinking water resource threatened, unrestricted land use desired).

For soil, the action level for leaching hazards (0.22 mg/kg) is lower than the action levels for each of the other environmental hazards. This action level is therefore selected as the Tier 1 EAL [refer to lookup tables in HDOH EAL document (HDOH, 2016)]. For groundwater, the action level for drinking water toxicity concerns drives environmental hazards and is selected as the Tier 1 EAL (5 ug/L, the primary drinking water standard).

Figure-13-3

Figure 13-3 Summary of Steps for Use of Tier 1 EAL Lookup Tables.



Figure-13-4

Figure 13-4. Summary of Action Levels Used to Select Tier 1 Soil and Groundwater EALs for Benzene. CSM A based on (1) groundwater is a drinking water resource, and (2) site within 150m of a surface water body. For soil and groundwater, the lowest action level for environmental hazards is selected as the final Tier 1 EAL.

13.3.3 USE OF THE EAL SURFER

The EAL Surfer, an Excel-based version of the lookup up tables, makes use of the EALs and the identification of potential environmental hazards at contaminated sites especially easy. The EAL Surfer is available for download from the HEER Office web page:

Use of the EAL Surfer in Environmental Hazard Evaluation reports is highly recommended. To use the Surfer, simply select the appropriate site scenario information from the pull-down list (groundwater utility, distance to nearest surface water body, land use, etc.), select the target contaminant, and (optional) input the representative concentration of the contaminant in soil and/or groundwater. If included, the input concentration is compared to action levels for specific environmental hazards and the Surfer flags hazards where the action level is exceeded. A separate, summary report is generated that can be printed and included in the Environmental Hazard Evaluation report.

The 2008 version of the EAL Surfer is modified from previous versions to allow selection of commercial/industrial land use, rather than residential/unrestricted land use as assumed in the default, Tier 1 CSMs and EALs. Soil action levels for direct exposure, vapor intrusion and gross contamination hazards are higher (i.e., less stringent) than correlative action levels for residential/unrestricted land use. Soil action levels for leaching hazards are unchanged because land use does not alter the threat to groundwater. Groundwater action levels for vapor intrusion hazards are also higher for a commercial/industrial land use scenario. Action levels for other hazards are unchanged.

Example printouts of the Surfer are provided in Figures 13-5a (data input form), 13-5b (detailed environmental hazards) and 13-5c (EHE summary report). The example is based on an assumed residential land use scenario. Contaminated soil is located within three meters of the ground surface ("shallow") and overlies groundwater that is a current or potential source of drinking water. The site is within 150 meters of a surface water body.

In the example (i.e., Figures 13-5a, 13-5b, and 13-5c), the input concentration of benzene in soil (5.1 mg/kg) causes direct exposure, vapor intrusion and leaching hazards to be flagged. Potential impacts to terrestrial ecological receptors and gross contamination are not flagged as potential hazards. The input concentration of 150 ug/L benzene in groundwater flags drinking water toxicity concerns and aquatic ecotoxicity concerns, but no other potential hazards.

Figure-13-5a

Figure 13-5a. Printout of EAL Surfer Input Page. Data used for this example was 5.1 mg/kg benzene in soil, and 150ug/L benzene in groundwater. Also, check for updates. The EAL Surfer is updated periodically and the page configurations may change.



Figure-13-5b

Figure 13-5b. Printout of EAL Surfer Detailed Environmental Hazard Identification Page, Using Benzene at Noted Concentration in Soil and Groundwater as an Example. Refer also to Figure13-5a.



Figure-13-5c

Figure 13-5c. Printout of EAL Surfer EHE Summary Report, Using Benzene at Noted Concentration in Soil and Groundwater as an Example. Refer also to Figure13-5a. This page can be printed and included in the Environmental Hazard Evaluation report. Referenced tables are from Appendix 1 of the EHE guidance (HDOH, 2016).

13.3.4 USE OF EALS IN SITE INVESTIGATIONS

One of the most basic uses of the EALs is to determine the extent of investigation needed at a site where contaminated soil or groundwater is identified. The list of Chemicals of Potential Concern (COPCs) can be quickly narrowed down by direct comparison of soil and groundwater data to the Tier 1 EALs (HDOH, 2016). Further consideration of contaminants that do not exceed Tier 1 EALs is not necessary. This assumes that existing data are representative of overall site conditions.

Delineation of the narrowed list of target COPCs to non-detect levels is often impracticable and, from a hazard evaluation standpoint, unnecessary. The investigation can be considered complete once the extent of contamination is delineated to Tier 1 EALs (or approved alternatives). As data are received during the site investigation, the EALs can be used to determine areas where the extent of contamination has been adequately identified as well as areas where additional sampling is needed. The use of field screening methods, onsite mobile labs, and/or quick turnarounds in laboratory analyses will help reduce the need for remobilizations and expedite the completion of site investigation activities.

As the site investigation is underway, a comparison of site data to action levels for specific environmental hazards can also help identify the need for alternative types of site data that will help evaluate appropriate response actions to address the contamination. For example, if arsenic is reported in soil at concentrations above the Tier 1 EAL of 20 mg/kg, then laboratory arsenic bioaccessibility tests can be used to more accurately evaluate potential direct-exposure hazards (refer to Sections 3 and Section 9 ). If the reported concentration of volatile contaminants in soil or groundwater exceed action levels for vapor intrusion concerns, then soil gas data can be collected to more closely evaluate this potential hazard. Incorporating these decisions in the sampling and analysis plan for the site will help expedite completion of the site investigation as well as alert responsible parties to potentially significant environmental conditions at the site.

13.3.5 USE OF EALS IN ENVIRONMENTAL HAZARD EVALUATIONS

The most important use of the HDOH Tier 1 EALs is the rapid identification of potential environmental hazards associated with contaminated soil and groundwater (refer to Section 3.4). With the exception of gross contamination, most of the environmental hazards noted above are not obvious in the field. An initial comparison of site data to the Tier 1 EALs will only indicate if a potential hazard is present (i.e., "yes" or "no"). If the Tier 1 EAL is exceeded, site data should be compared to the detailed action levels used to develop the Tier 1 EALs to identify the specific potential environmental hazards present. As discussed above, use of the EAL Surfer will significantly expedite this process (see Subsection 13.3.3).

Potential environmental hazards identified in a basic screening level Environmental Hazard Evaluation can be evaluated on a more site-specific basis as needed. The information gained can be used to better define the need for additional site investigation as well as develop appropriate remedial options. Approaches for more advanced or site-specific evaluation of specific environmental hazards are briefly discussed in Subsection 13.5.4.

The level of effort required for advanced evaluations can vary greatly. For example, qualitatively discounting potential hazards posed to terrestrial ecological habitats will be relatively simple at highly developed commercial or industrial sites, based on the lack of significant habitat. The collection of additional soil gas data is very useful (and strongly recommended) for more detailed evaluations of vapor intrusion concerns. The inclusion of soil gas action levels in this guidance helps expedite this evaluation. A detailed review of groundwater data can sometimes be used in place of soil action levels to better evaluate leaching and groundwater contamination concerns. In other cases, additional laboratory tests and/or use of environmental models may be required (see Subsection 13.5.4 ).

13.3.6 USE OF EALS IN RESPONSE ACTIONS

The Tier 1 EALs are not strict cleanup standards. In cases where the extent of contamination is minimal and time is of the essence, however, it may be more cost-effective to simply remediate soil contaminated above the Tier 1 EALs (or acceptable, alternative action levels) without further evaluation. In other cases, use of the detailed action levels to identify site-specific environmental hazards posed by the contamination will play an important role in final response actions.

For example, placing a soil cap on contaminated soil may be acceptable in some cases (e.g., direct exposure to non-volatile contaminants) and not in others (e.g., vapor intrusion or leaching hazards). Using the detailed action levels to understand the specific environmental hazards posed by contaminated groundwater is especially important. Identifying toxicity hazards and taste and odor hazards in groundwater that is currently used as a source of drinking water is obviously important. Expeditious actions to address vapor intrusion hazards posed by contaminated soil are usually warranted. In contrast, long-term monitoring may be acceptable for groundwater that poses only gross contamination hazards (e.g., toxicity-based action levels for currently unused drinking water resources not exceeded) or potential aquatic toxicity hazards if it were to migrate offsite and discharge into a body of surface water.

Long-term management will be required for sites where soil and groundwater contaminated above levels of potential concern cannot be remediated in a relatively short time frame. In such cases, the detailed action levels presented in this guidance (or acceptable alternatives) should be used to delineate areas of contaminated soil and groundwater that will require long-term management as well as the specific environmental hazards posed by the contamination under uncontrolled site conditions. Specific actions required to address these hazards should then be described in an Environmental Hazard Management Plan (EHMP). Refer to Sections 18 and Section 19 for additional details on EHMPs.

13.3.7 CHEMICALS WITH MRL THAT EXCEED EALS

Environmental Action Levels (EALs) for a number of chemicals can be below commercial laboratory Method Reporting Limits (MRLs) for a number of chemicals in groundwater. This is not generally the case for soil. As discussed in the EHE guidance, the laboratory MRL, or equivalent, should be used to screen site data (see HDOH 2016).

Chemicals with laboratory MRLs that could exceed the HDOH EALs for groundwater are given in Table 13-2.

If the reported concentration of a chemical exceeds the MRL then the need for additional action should be discussed with the HEER office.

Table 13-2 Chemicals with laboratory reporting limits that could be higher than HDOH Environmental Action Levels.

Groundwater

Soil

Aldrin

Bis(2-chloroethyl)ether

Benzo(a)anthracene

Bromodichloromethane

Benzo(a)pyrne

Bis(2-chloroisopropyl)ether

Benzo(b)fluorene

p-Chloroaniline

Bis(2-chloroethyl)ether

Chloroform

Bis(2-chloroisopropyl)ether

2-Chlorophenol

Boron

3-Dibromo, 1,2-chloropropane

Bromodichloromethane

Dibromochloromethane

Chlordane(Technical)

1,2-Dibromomethane

2-Chlorophenol

3,3-Dichlorobenzidine

Cobalt

1,2-Dichloroethane

Cyanide(Free)

1,4-Dioxane

Dibenzo(a,h)anthracene

Methyl tert-Butyl Ether

3-Dibromo,1,2-chloropropane

Perchlorate

Dibromochloromethane

Phenol

1,2-Dibromoethane

tert-Butyl Alcohol

3,3-Dichlorobenzidine

1,1,1,2-Tetrachloroethane

Dichlorodiphenyldichloroethane (DDD)

1,1,2,2-Tetrachloroethane

Dichlorodiphenyldichloroethylene (DDE)

 

Dichlorodiphenyltrichloroethane (DDT)

 

1,2-Dichloroethane

 

2,4-Dichlorophenol

 

1,3-Dichloropropene

 

Dieldrin

 

Diethylphthalate

 

Dimethylphthalate

 

Endosulfan

 

Endrin

 

Heptachlor

 

Heptachlor Epoxide

 

Indeno(1,2,3-cd)pyrene

 

Methoxychlor

 

1-Methylnaphthalene

 

2-Methylnaphthalene

 

Polychlorinated Biphenyls (PCBs)

 

1,1,1,2-Tetrachloroethane

 

1,1,2,2-Tetrachloroethane

 

Toxaphene