Department of Health Seal

TGM for the Implementation of the Hawai'i State Contingency Plan
Subsection 21.3

21.3 Screening Level Ecological Risk Assessment

Unlike the ERA Scoping Checklist, which can be completed by anyone familiar with the site, the SLERA should be prepared by a person or a team with knowledge of the chemicals, receptors, exposure pathways, and other ERA elements necessary to the investigation.

The purpose of the SLERA is to focus investigation and remediation on sites and chemicals that may pose an unacceptable risk to ecological receptors. The SLERA provides an opportunity for a site to exit the ERA Program with a minimum of effort if the site truly poses very little or no risk to ecological receptors. In cases where the entire site cannot be shown to pose a level of risk below applicable screening levels or alternate (approved) decision level based on a more a detailed evaluation, selected chemicals or receptors may still be identified for possible elimination from further investigation in later steps of the ERA.

21.3.1 Preparing for a SLERA

If the ERA is being conducted as part of a larger site investigation, data collected for other purposes may be available to initiate the SLERA, as shown in Step 1b (Table 21-1). For example, sites where a chemical release happened some time ago may have been investigated for risk to human health. Sites where a discrete release of chemicals occurred may have been subjected to emergency removal actions and/or an investigation of residual risk. In such cases, the risk assessor should gather all available data from the site in preparation for the SLERA. Note that the existence of data from an umbrella investigation does not necessarily mean that no additional samples will be required. Available site-specific data are reviewed for usability during Step 1b and the need for additional data to adequately characterize current site conditions is determined. The risk assessor is encouraged to consult with the HEER Office if unsure about the need for additional data collection. Of special concern is the potential need for additional data collection in cases where existing data were based on a small number of discrete samples, which are not likely to be representative of the decision unit (see TGM Section 4). On the other hand, the risk assessor may have access to additional site-specific data not typically required for a SLERA (such as field-collected tissue samples). In such cases, the additional data can certainly be used in the SLERA to support a decision on the need for further investigation (see Step 2).

If the SLERA is being conducted outside the context of a larger investigation, then some additional steps will be necessary to initiate development of data collection suitable to support a SLERA. (Step 1a, Table 21-1). Guidance on conducting a general site investigation is provided in Sections 3.0, 4.0, and 5.0 of the TGM. Specifically, any field sampling and analysis plan (SAP) should be prepared in accordance with the decision unit (DU) and Multi Increment sampling (MIS) approach described in the TGM. Additional guidance on defining DUs for ERAs is in Appendix 21-C.

The risk assessor should review the pertinent subsections of the TGM, then consult with the HEER Office for assistance in developing a SAP that satisfies the requirements of a SLERA.

Table 21-1. SLERA Framework
Step 1A: Develop and Implement Screening Level Sampling and Analysis Plan (if available data are not adequate to support a SLERA)
Only as Needed: Activities: If site-specific data are not available, prepare a sampling and analysis plan (SAP) in accordance with site investigation guidance in Sections 3, 4, and 5 of the TGM, including clear data quality objectives (DQO). Once data are available, complete the outputs in Step 1B and then proceed to Step 2 below Outputs:
  • DQOs
  • SAP
  • Maps or figures of site, including habitats and proposed sample locations
  • Data tables (if analytical data are available)
  • Preliminary Conceptual Site Model (CSM)

Step 1B: Screening Level Site Characterization Data and Ecological Effects Evaluation

Task 1-1: Describe environmental setting (location, habitats, expected species, sources of chemicals, previous investigations)

Task 1-2: Compile available site-specific and background, ambient, and reference analytical data (from ERA Scoping Checklist or other sources); include a description of ecotoxicity and bioaccumulative potential of target chemicals

Task 1-3: Select assessment and measurement endpoints (see USEPA 1996za; 2016b)

Task 1-4: Identify exposure pathways and ecological receptors

Task 1-5: Develop preliminary CSM

  • Maps or figures of site
  • Data tables
  • Assessment and Measurement Endpoints identified
  • Preliminary CSM
Step 2: Estimate Preliminary Exposure Concentrations and Calculate Hazard Quotients

Task 2-1: Compile screening levels for all media in your dataset. Sediment quality guidelines (SQG) are in Table 21-7. Surface water, groundwater, and sediment pore water should be screened against HEER Office Environmental Action Levels (EALs) for aquatic toxicity (aquatic habitat goals), surface water, and/or groundwater, as applicable and if included in this guidance (see HEER Office EAL Surfer tool). USEPA National Water Quality Criteria (USEPA 2016a, or current reference) can be referenced for chemicals not included in HEER Office EALs (if available). Tissue concentrations may be compared with critical body residues (CBR) reported in the literature). Toxicity reference values (TRV) for receptors evaluated through food chain modeling (e.g. mammals and birds) may be derived from published studies and reports.

Task 2-2: Estimate average exposure concentrations that are representative for sediment and/or water decision units at the site (see TGM Sections 3, 4, and 5).

Task 2-3: Calculate daily dose for higher trophic level receptors (birds and mammals).

Task 2-4: Calculate hazard quotients (HQ) using representative DU-MIS concentrations for sediments/no effect screening levels, representative pore water or surface water concentrations/no effect screening levels, or maximum tissue concentrations to calculate daily doses for comparison with low TRVs.

Task 2-5: Summarize HQs, identify chemicals of potential ecological concern [COPEC], and make a decision about the site. If risk is potentially unacceptable, continue to Step 3A), otherwise the ERA process can stop.

  • List of applicable screening levels (and source) for selected media and receptors
  • Estimated contaminant levels in site decision units/media compared with screening levels
  • Summary of HQs
  • Identification of COPECs
  • Decision Statements
Step 3A: Refine Screening Level Default Assumptions

Task 3-1: Compile available data representing background, ambient, or reference concentrations and submit to the HEER Office for concurrence. Compare the site sediment and/or water concentrations with background, ambient, and reference concentrations, as available.

Task 3-2: Evaluate the magnitude of exceedance, frequency of detection, and distribution of exceedances in sediment (and water, if appropriate) at the site to determine whether any chemicals should be eliminated as COPECs.

Task 3-3: Confirm that the data used are reasonably representative for decision units at the site. Evaluate the reasonableness of default conservative exposure assumptions (100 percent bioavailability of chemicals, 100 percent site use by receptors, maximum chemical concentrations, etc.) and adjust assumptions (if appropriate). Consider the influence of geophysical and geochemical parameters such as grain size, total organic carbon, pH, and other factors on bioavailability of chemicals. If the area is known to be erosional, consider the short-term and long-term fate of contaminated sediments.

Task 3-4: Confirm with HEER Office that the Step 3a refinements are technically defensible based on site conditions.

Task 3-5: Recalculate HQs using more realistic representative exposure concentrations.

Task 3-6: Summarize HQs, evaluate uncertainty, and develop risk characterization to support a decision about the site. If risk is potentially unacceptable, continue to the baseline ERA (BERA); if not, the ERA process can stop.

  • Data tables of background or reference concentrations
  • Technical justification for adjusting exposure assumptions and concentrations
  • Table of adjusted HQs
  • Technical justification for elimination of COPECs, if applicable
  • Decision Statements

21.3.2 Components of a Marine Sediment SLERA

In the interest of streamlining the SLERA process and promoting consistency among SLERAs, the HEER Office provides examples or templates for many of the common components of a SLERA. Additional examples/templates will be added to this TGM as they are developed.

Table 21-2. Components of a Marine Sediment SLERA
Required Information Source of Information
Representative concentrations of chemicals in sediment from the site Risk assessor (representing site owner/regulated community) compiles available site-specific data.
Sediment Quality Guidelines (SQG), HEER Office EALs and background/ambient/reference concentrations HEER Office provides SQGs for most target chemicals (See Table 21-7); HEER Office provides EALs for aquatic toxicity, surface water, and groundwater (see EAL surfer; risk assessor supplements as needed.
Potential receptors (identified by habitat or exposure guild) HEER Office provides species profiles and exposure/effects data (Appendix 21-A, habitat profiles (Appendix 21-D); risk assessor selects and augments as necessary.
Conceptual Site Model (CSM) (identifying pathways and representative receptors) HEER Office provides examples for several habitats (Figures 21-2 through 21-7); risk assessor customizes to site and supplements when necessary.
Sediment dynamics (erosional or depositional) Risk Assessor provides, based on US Geological Survey reports (Fletcher et al. 2012) or site-specific data
Toxicological profiles for COPECs Risk Assessor provides; HEER Office may assist with reference materials.
Exposure factors for assessment endpoint receptors HEER Office provides examples for some common receptors; risk assessor supplements as necessary (Appendix 21-A).

21.3.3 Step 1B: Screening Level Site Characterization Data

The screening-level site characterization, known as preliminary problem formulation, serves as an organizing foundation for the SLERA. It incorporates physical, chemical, and biological elements and features of the site that will guide the ERA process. Although each site is different, Step 1B usually includes five tasks, which are introduced below and discussed in more detail in the subsections below:

  • Describe environmental setting (location, habitats, expected species, sources of chemicals, previous investigations) and summarize results of previous investigations [Step 1B, Task 1]
  • Compile available site-specific, background, ambient, and reference analytical data (from ERA Scoping Checklist or other sources); include a description of ecotoxicity and bioaccumulative potential of target chemicals [Step 1B, Task 2]
  • Select assessment and measurement endpoints [Step 1B, Task 3].
  • Identify exposure pathways and receptors [Step 1B, Task 4]
  • Develop preliminary CSM, [Step 1B, Task 5] Step 1b, Task 1; Describe Environmental Setting

The environmental site setting includes a description of the location, habitats, expected species, sources of chemicals, and other site-specific information pertinent to the SLERA. The site setting should be based on information gathered during a site visit and/or readily available information.

The HEER Office has compiled a list of habitat types (see Table 21-3) and more detailed information on several key habitat types in Hawaiʻi (see Appendix 21-D) to aid in developing the environmental setting and help foster consistency in ERAs across the state. Additional habitat profiles will be provided under subsequent phases of guidance development.

Habitat information in Appendix 21-D should be augmented by the following site-specific information whenever possible:

  • Physical description of the site including:
    • Size (acres)
    • Potentially affected habitats (mudflats, coral reefs, seagrass beds, etc.) [Include map or figure of location and habitat types.]
    • Sediment type or grain size distribution (coral rubble, coarse sand, silt, etc.)
    • Wave environment (high energy, low energy, protected harbor, etc.)
    • Salinity, tidal range (intertidal, subtidal), bathymetry, etc.
    • Erosional/Depositional area (see Fletcher et al. 2012)
  • Current and historical uses of the site (known or suspected)
  • Potential ecological receptors present at the site (per habitat within site)
  • Surrounding land use
  • Any potential sources of contaminants not related to the site activities (storm water outfalls, stream discharge, nearby industries, recreational vessel traffic, etc.)
  • Known or suspected threatened and/or endangered species or other protected species/habitats within or adjacent to the site
  • Maps, photographs, and figures of the site (current and historical)
  • Any site-specific studies conducted at the site or in adjacent habitats

A habitat is considered important if it comprises a substantial portion of the site or provides high-value areas for target receptors. Provide as much detail as is available about the relative distribution of habitats within the site. For example, at a site that is 90 percent soft-bottom and 10 percent coral rubble covered with algae, both soft-bottom and algae-covered rubble would be included as important habitat types. The soft-bottom is spatially dominant and the algae-covered rubble provides sheltering and foraging habitat likely to be used disproportionately by some receptors.

Table 21-3. Unique or Distinct Aquatic Habitat Types and Locations in Hawaiʻi
Habitat Type Description/ Example Locations
Mudflats/Coastal Wetlands/Lagoon (Appendix 21-D) Significant mudflats occur in Mamala Bay, Pearl Harbor, and Kāneʻohe Bay
Rocky Intertidal and Tidepools (Appendix 21-D) Rocky intertidal habitat dominates most shorelines of all islands where constant wave action, currents, steep submarine slopes, and a lack of offshore sand reservoirs limit the accumulation of sand. ʻĪlio Point on Hawaiʻi is a typical high-energy tidepool habitat.
Coastal Fishponds (Appendix 21-D) Mamala Bay, Pearl Harbor, several around Kāneʻohe Bay, and three on the southwestern coast of Kauaʻi.
Seagrass Beds (Appendix 21-D) Significant seagrass beds are known from the inner reef flats of south Molokaʻi; ʻAnini (Kauaʻi); near Mamala Bay and Kāneʻohe Bay; others exist but are not mapped
Mixed Sediment Bays and Harbors (Appendix 21-D) Pearl Harbor; soft sediment overlaid on limestone platform of fossil reef origin; soft sediments often composed of carbonate grains derived from coralline algae, coral, mollusk fragments, foraminiferans, and tests of bryozoans and echinoderms
Young Volcanic Substrate; Little Sediment (profile not yet complete) Big Island
Deep Channels (profile not yet complete) ʻAlenuihāhā Channel, between Hawaiʻi and Maui
Soft Sediment Bays (profile not yet complete) Hanalei Bay, Kauaʻi; no coral rubble
Sandy Beach (profile not yet complete) Along the lagoon reaches of atoll islets and especially along the west and south sides of Kauaʻi, Oʻahu, Molokaʻi, Maui, Lānaʻi, and Hawaiʻi; also along bays and coves on mature islands
Anchialine Pools (profile not yet complete) Rocky shorelines on most islands, up to several hundred meters inland; The Kaloko-Honokohau Park on the western coast of Hawaiʻi contains about 10% of Hawaiʻi's anchialine ponds.
Stream-fed Estuarine Wetlands (profile not yet complete) Mamala Bay and Kāneʻohe Bay, Oʻahu
Mangroves (Introduced) (profile not yet complete) In addition to invading coastal fishponds (see above), mangroves have spread to mud flats and estuarine waters around most of the Islands and to some rocky coastal areas around Hawaiʻi Island.
Subtidal Hardbottom (profile not yet complete) Hardbottom occurs on every island; shallow benthic communities occur in depths of up to 50 meters or more, on basalts, and on consolidated limestone (reef carbonates, beach rock). The distribution of benthic communities is determined by light penetration, temperature, wave action, availability of substrate, and movement and accumulation of sediments.
Coral Reef (profile not yet complete) About 80% of coral reef habitat in Hawaiʻi is in the Northwest Hawaiian Islands (NWHI), including atolls, islands, and banks. The high volcanic islands of the Main Hawaiian Islands (MHI) typically include non-structural reef communities, fringing reefs, and two barrier reefs (Kāneʻohe Bay and Moanalua Bay, Oʻahu).

Species at the Site

Species at the site should be grouped into two categories: (1) typical or common species and (2) threatened, endangered, or specially protected species. A list of typical or common species can be generated using Hawaiʻi-specific publications and websites cited throughout this guidance. Profiles of select species are in Appendix 21-A.

Information on threatened, endangered and otherwise protected species and habitats is widely available on websites published by state and federal resource agencies. The status of species and habitats may change over time. The risk assessor should check the websites below, and other websites, as necessary, to make sure the most current information is used in the ERA:

  • The Hawaiʻi Department of Land and Natural Resources 700-page review, Hawaiʻi's Comprehensive Wildlife Conservation Strategy, describes habitats, species, and threats across the MHI and NWHI (Mitchell et al. 2005). This document lists and describes the distribution and abundance of species of “greatest conservation need,” and provides locations and relative condition of key habitats; threats to species; conservation actions proposed; and plans for monitoring species and their habitats. Fact sheets address larger taxa or groups relevant to the marine ERA program, including waterbirds, seabirds, migratory shorebirds and waterfowl, anchialine pond fauna, marine mammals, marine reptiles, marine fishes, and marine invertebrates.
  • Species Recovery Plans, critical habitat designations, and 5-Year Status Reviews provide extensive information on life history and habitat requirements, as well as current threats to the species protected under the Endangered Species Act (ESA). Recovery plans for species under the jurisdiction of U.S. Fish and Wildlife Service (FWS), such as coastal birds, are available at (USFWS 2018). See (USFWS 2018b) for links to documents proposing and designating critical habitat for FWS species. Links to 5-Year Status Reviews are on the species profile page for each species.
  • The National Oceanic and Atmospheric Administration, Pacific Islands Regional Office of the National Marine Fisheries Service (NOAA 2018) provides information on ecological resources including protected species and unique habitats.
  • The U.S. Navy has compiled data on Hawaiian species in the following documents:
    • U.S. Navy's most recent marine resource assessment for Hawaiʻi (Navy 2005).
    • Hawaiʻi-Southern California Training and Testing Environmental Impact Statement (EIS) and Overseas EIS (Navy 2017)
    • Hawaiʻi Range Complex EIS (Navy 2009)

Identify Potential Sources of Contamination

The site-specific data compilation activities of the SLERA should identify contaminants potentially present at the site and the sources of those contaminants based on the types of activities known or suspected to have taken place at the site. Typical point sources and COPECs are compiled in Table 21-4. While the information in Table 21-4 can be used as a starting point, it should not be assumed that these are the only chemicals associated with site activities. Activities specific to a particular facility may have resulted in different and/or additional chemicals being released into the environment. Also, because operations often change at a site over time, a thorough search of the site history is needed to determine which chemicals may be present at the site.

Table 21-4. Point Sources of Target COPECs in Hawaiʻi
Type of Point Source Chemicals Example Locations Documents
Harbors and marinas Antifouling compounds (Irgarol and other copper-based compounds); polycyclic aromatic hydrocarbons (PAHs) Ala Wai Marina, Kāneʻohe Bay Yacht Club , Kāneʻohe Bay Makani Kai Marina, Sand Island Keʻehi Marina, Waikīkī Yacht Club (Knutson et al. 2012)
Former military installations or disposal sites Metals, polychlorinated biphenyls(PCBs), munitions (energetics), pesticides Waiʻanae, Oʻahu; Mākua Military Reservation, Oʻahu; Midway Atoll, Sand Island (Garcia et al. 2009); (ACOE 2012); (Tetra Tech 2009); (Taylor et al. 2009)
Long Range Navigation (LORAN) stations PCBs, lead Kure Atoll, Cocos Island, Guam; ʻĪlio Point, Molokaʻi; Tern Island, French Frigate Shoals (Element Environmental 2009); (Element Environmental 2010); (ESI 2012); (USCG 2000); Woodward-Clyde Consultants 1994)
Shipyards Tributyltin (TBT), antifouling paints, copper, zinc Pearl Harbor, Oʻahu (Grovhoug 1992) (NAVFAC 2007)
Former shooting ranges on coast Lead shot    
Estuaries Metals, PAHs, pesticides, pharmaceuticals, polybrominated diphenyl ethers (PDBE), pathogens, PCBs   (Grovhoug 1992)(NAVFAC 2007)
Sugar mill or canec manufacture dumping areas arsenic, herbicides Waiākea Mill Pond, Wailoa River (Hallacher et al. 1985) (HDOH 2005c)
Urban/ storm drains PAHs Various streams, Oʻahu (Zheng et al. 2011)
Urban/ storm drains Metals Nuʻuanu watershed, Oʻahu (Andrews and Sutherland 2004)
Urban Run-off Microbial and nutrients Hanalei Bay, Kauaʻi (Boehm et al 2011)
Urban Run-off Pesticides and metals Various locations in Oʻahu and Kauaʻi (Brasher and Wolf 2007)
Agricultural Run-off Pesticides Pineapple fields; Honolua Stream entering Honolua Bay, Maui  
Agricultural Run-off Arsenic, herbicides, pesticides Island of Hawaiʻi sugar cane plantation (Cutler et al. 2013)
Agricultural Run-off Pesticides Taro ponds; run-off to Hanalei River, Kauaʻi (DLNR DAR 2012)
Golf courses Herbicides; pesticides    
Sewage outfalls Metals, PAHs, pharmaceuticals, pathogens    
Sediment disturbance
Coastal marine construction sites All chemicals associated with sediment in given location    
Dredging All chemicals associated with sediment Kūhīo and Hilo Bays, Hilo Commercial Harbor, Hawaiʻi Island (ACOE 2008)
Shoreline erosion (landfill) All chemicals associated with sediment; solid waste in landfills exposed to water and air Step 1b, Task 2; Compile Available Site-Specific and Reference Data on Chemicals and Endpoints

Step 1b, Task 2 requires the risk assessor to compile available site-specific and reference analytical data (from ERA Scoping Checklist or other sources), evaluate ecotoxicity screening levels, and identify bioaccumulative chemicals.

All analytical data collected at the site during current or previous investigations should be compiled and evaluated for use in the SLERA. Analytical data more than five years old may no longer be representative of site conditions and should be discussed with the HEER Office.

A list of site-related chemicals compiled during the scoping phase (see Subsection 21.2 and Appendix 21-B, Table B-1) will be evaluated in the SLERA. Chemicals that act primarily through direct toxicity are evaluated using a hazard quotient (HQ) approach in Step 2. Chemicals that are known or expected to bioaccumulate in living organisms are also evaluated separately because sediment and water screening levels do not typically incorporate risk due to bioaccumulation in tissues (see Appendix 21-E).

Site-specific and reference data compilations for the SLERA should describe the direct toxicity and bioaccumulation potential of COPECs at the site. Direct ecotoxicity of COPECs in sediment is evaluated by comparison of sediment concentrations with SQG designed to be protective of benthic invertebrates in direct contact with sediment (see Subsection 21.3.4 and Table 21-7). In the SLERA, the ecotoxicity evaluation may focus on groups of chemicals such as organochlorine pesticides, as opposed to specific pesticides. The risk assessor may augment the HEER Office SQG in Table 21-7 with data from the published literature to develop ecotoxicity profiles for COPECs whose primary mode of action is direct toxicity. HEER Office EALs (screening levels) for aquatic habitat goals, surface water, and groundwater can be referenced and used for data evaluation, as applicable. See the detailed table links in the EAL surfer tool for breakdown of the aquatic habitat goals and surface water EALs by marine, estuarine, or freshwater categories.

Separate from direct toxicity, some chemicals bioaccumulate in living organisms, meaning that they contain higher concentrations of a chemical in their tissues than in surrounding sediment or water. When bioaccumulated chemicals are transferred from one organism to another through the food web, the concentration may increase even more, in a process called biomagnification. Bioaccumulation of chemicals in tissues provides a pathway for chemicals to transfer to on-site and off-site receptors. The concentration of a bioaccumulating chemical in sediment may be considered safe for receptors in direct contact with sediment but not for receptors higher on the food web. Therefore, bioaccumulative chemicals require additional evaluation in the SLERA to determine whether they pose adverse risks to higher trophic levels that are not addressed by the SQGs. Step 1b, Task 3; Select Assessment and Measurement Endpoints

A key task of the SLERA site characterization process is to identify the ecological resources to be protected at the site (known as assessment endpoints) and the measures used to evaluate risks to those resources (known as measurement endpoints or measures of effect). Assessment endpoints are explicit expressions of the environmental value that is to be protected. The selection of these endpoints is based on the habitats present, migration pathways of probable contaminants, and relevant exposure routes for the receptors. Suitable assessment endpoints species are characterized as follows:

  • ecological relevance;
  • susceptibility to known or potential stressors; and
  • relevance to management goals (USEPA 1998).

For additional discussion of the selection of proper assessment endpoints, see the following:

  • Generic Ecological Assessment Endpoints (GEAEs) for Ecological Risk Assessment: Second Edition with Generic Ecosystem Services Endpoints added. (USEPA 2016b)
  • Guidelines for Ecological Risk Assessment (USEPA 1998i)
  • ECO Update: Identify Candidate Assessment Endpoints Ecological Significance and Selection of Candidate Assessment Endpoints (USEPA 1996za)

Measurement endpoints are estimates of quantifiable biological features or processes (such as mortality, growth, and reproduction) that are believed to be linked to meaningful effects on the assessment endpoints selected at the site.

Assessment endpoints selected for the SLERA are typically carried through to the BERA, unless it is discovered during the SLERA that the species does not fit the requirements of an assessment endpoint (it is not present, not exposed to contaminated media, not valued by the community, or eliminated during earlier steps in the SLERA). Measurement endpoints selected for the SLERA are often augmented in the BERA by endpoints more focused on particular chemicals or pathways of interest at the site.

Example preliminary assessment and measurement endpoints for a coastal marine sediment site in Hawaiʻi are in Table 21-5. Measurement endpoints for the SLERA and the BERA are shown to illustrate the differences between the two phases of an ERA.

Table 21-5. Assessment and Measurement Endpoints: Coastal Marine Sediments
Ecological Guild Assessment Endpoint Typical Species Measurement Endpoint
Seaweed (Limu) Organism Level: Survival, growth, and reproduction

Population/Community Level
: Distribution and abundance within DU
  • Sea lettuce (Ulva fasciata)
  • Limu kohu (Asparagopsis taxiformis)
  • Concentrations of chemicals in site MIS sediment samples compared with SQG protective of marine algae.
  • Estimates of tissue concentrations using biota-to-sediment-accumulation-factors (BSAFs) compared with tissue effect levels for marine algae (Tissue effect levels identified through literature review).
BERA: Concentrations of chemicals in composite samples of tissues collected from the DU or estimates of tissue concentrations from sediment using BSAFs compared with tissue effect levels for marine algae (Tissue effect levels identified through literature review).
  • Comparison of tissue concentrations in site samples to tissue concentrations in reference areas
  • Laboratory toxicity test measuring survival and growth; laboratory bioaccumulation test to provide tissue concentrations (in place of field-collected organisms: see above)
  • Comparison of population metrics in DU (distribution and abundance) with reference area
Soft-bodied benthic invertebrates (macroinfauna) Organism Level: Survival, growth, and reproduction

Population Level/Community Level:
Distribution and abundance within DU
  • Polychaete (Neanthes arenaceodentata)
SLERA: Concentrations of chemicals in site MIS sediment samples compared with SQG protective of polychaetes.
  • Concentrations of chemicals in composite samples of whole body tissues collected from the DU or estimates of whole body tissue concentrations from sediment using BSAFs compared with CBR levels (effect levels) for polychaetes (CBRs identified through literature review).
  • Laboratory toxicity test measuring survival and growth; laboratory bioaccumulation test to provide tissue concentrations (in place of field-collected organisms: see above)
  • Comparison of population/community metrics in DU (distribution and abundance) with metrics at a reference area
Stony Corals Organism Level: Survival, growth, and reproduction (of colony)

Population/Community Level
: Distribution and abundance within DU
  • Lobe coral (Porites lobata)
SLERA: Concentrations of chemicals in site MIS sediment samples compared with SQG protective of corals.
  • Concentrations of chemicals in composite samples of coral tissues from the DU compared with CBR for corals and with reference areas
  • Comparison of tissue concentrations in site samples to tissue concentrations in reference areas
  • Direct toxicity test using coral test organisms
  • Comparison of relative percent cover, growth rates, external signs of health with corals in reference area
Epibenthic Invertebrate (macrofauna ) Organism Level: Survival, growth, and reproduction

Population/Community Level
: Distribution and abundance within DU
  • Samoan crab (Scylla serrata)
  • Kona crab (Ranina ranina)
  • White crab (Portunus sanguinolentus)
  • Helmet urchin (Colobocentrotus atratus)
  • Hawaiian limpet (Cellana exarata)
  • Black sea cucumber (Holothuria atra)
  • Day octopus (Octopus cyanea)
  • Concentrations of chemicals in site MIS sediment samples compared with SQG protective of epibenthic macrofauna
  • Estimates of whole body tissue concentrations from sediment using BSAFs compared with CBR levels (effect levels) for surrogate benthic invertebrates.
BERA (Echinoderm only): Laboratory toxicity test of effect of exposure to sediments and/or sediment pore water on sea urchin survival and development. BERA (Other macrofauna):
  • Concentrations of chemicals in composite samples of whole body tissues representing the DU or estimates of whole body tissue from sediment using BSAFs compared with critical body residues levels (effect levels) for surrogate epibenthic invertebrates.
  • Comparison of population metrics (distribution and abundance) with metrics at a reference area
Benthic Fish (herbivores, corallivores, carnivores) Organism Level: Survival, growth, and reproduction

Population Level:
Distribution and abundance within DU
  • Goatfish (Mulloides vanicolensis)
  • Hawaiian flagtail (Kuhlia sandvicensis)
  • Pacific sergeant (Abudefduf abdominalis)
  • Mozambique tilapia (Oreochromis mossambicus)
  • Spectacled parrotfish (Chlorurus perspicillatus)
  • Yellowbar parrotfish (Calotomus zonarchus)
  • Moray Eel (Muraenidae)
  • Concentrations of chemicals in MIS sediment samples compared with SQG protective of fish.
  • Estimates of tissue concentrations from sediment using BSAFs) derived from field studies on similar fishes compared with CBR (effect levels) for tropical fishes.
  • Concentrations of chemicals in composite samples representing the DU (whole body or organ tissues) or estimates of tissue concentrations from sediment using BSAFs derived from field studies on similar fishes compared with critical body residues levels (effect levels) for tropical fishes.
  • Comparison of population metrics (distribution and abundance) with metrics at a reference area
Pelagic Fish (piscivores) Organism Level: Survival, growth, and reproduction

Population Level
: Distribution and abundance within DU
  • Giant trevally (Caranx ignobilis)
  • Mahi mahi (Coryphaena hippurus)
SLERA: No direct link to sediment. Assume food web link to lower trophic levels in the DU.
  • Concentrations of chemicals in composite samples of tissues from decision unit compared with CBR levels (effect levels) for tropical fishes.
  • Concentrations of chemicals in composite samples of tissues from DU compared with reference area
Sea turtles Organism Level: Survival, growth, and reproduction

Population Level
: Distribution and abundance within DU
  • Green sea turtle (Chelonia mydas)
SLERA: Conservative estimate of daily ingested dose of contaminant within DU compared with no observed adverse effect level (NOAEL) TRVs for sea turtles (or surrogate reptiles). (TRVs identified through literature review).
BERA: Realistic estimate of daily ingested dose of contaminant within DU compared with lowest observed adverse effect level (LOAEL) TRV for sea turtles (or surrogate reptiles). TRVs identified through literature review.
Piscivorous birds Organism Level: Survival, growth, and reproduction

Population Level
: Distribution and abundance within DU
  • Wedge-tailed shearwater (Puffinus pacificus)
  • Black-crowned night heron (Nycticorax nycticorax hoactli)
  • Hawaiian coot (Fulica alai)
SLERA: Conservative estimate of daily ingested dose of contaminant within DU compared with NOAEL TRV for piscivorous seabirds (or surrogate birds). (TRVs identified through literature review).
BERA: Realistic estimate of daily ingested dose of contaminant within DU compared with LOAEL TRV for piscivorous seabirds (or surrogate birds). TRVs identified through literature review.
Marine mammals Organism Level: Survival, growth, and reproduction

Population Level
: Distribution and abundance within DU
  • Spinner dolphin (Stenella longirostris)
  • Hawaiian monk seal (Monachus schauinslandi) [endangered species: assess at the level of individual]
SLERA: Conservative estimate of daily ingested dose of contaminant within DU compared with NOAEL TRV for marine mammals (or surrogate carnivorous mammal). TRVs identified through literature review.
BERA: Realistic estimate of daily ingested dose of contaminant within DU compared with LOAEL TRV for marine mammals (or surrogate carnivorous mammal). Step 1b, Task 4; Identify Complete Exposure Pathways and Potential Routes of Exposure

Complete exposure pathways consist of contaminants, receptors, and routes (such as direct contact, sediment ingestion, and food chain transfer).

  • Receptors: Living organisms present or potentially present at the site are the focus of the SLERA
  • Exposure Medium: This part of the TGM addresses sediment as the primary exposure medium. Organisms in direct contact with the sediment may take up chemicals in their tissues and become sources of contaminants to animals that consume them. Exposure to contaminated food items (and ingested sediment) is evaluated using food chain models (see Subsection 21.3.4: Step 2, Task 3 below).
  • Depth of Sediment Exposure: Benthic invertebrates typically live either on the surface of the sediment or within the top layer where water and oxygen exchange occur (the biotic zone). The default assumption of exposure depth for a SLERA is that benthic and epibenthic receptors are exposed to the top 10 cm of sediment. However, if receptors are known to burrow deeper in the sediment at a particular site, the exposure pathway to deeper sediment layers should be evaluated in the SLERA.
  • Routes of Exposure: The SLERA should focus on routes of exposure most likely to be significant. Receptors living on or in the sediment are exposed primarily through direct contact; they may also be exposed to ingested sediment. Other receptors are indirectly exposed to sediment by consuming organisms that were in direct contact with the sediment.

The preliminary CSM for a SLERA relies on the published literature to predict occurrence of receptors and the trophic relationships among receptors at the site. Reports and publications written for purposes other than contaminant studies can be good sources of information on ecological processes and relationships in a given habitat type or location. For example, NOAA prepared a diagram of trophic linkages on the kaloko reef system for a report on energy flow on the Kona coastline (NOAA 2018b) (Figure 21-1). Although the NOAA project was not focused on contaminants, it provides valuable information on species occurrence and trophic relationships that could be incorporated into a SLERA in that location. Step 1b, Task 5; Develop the Screening Level Preliminary Conceptual Site Model

The CSM presents a description of predicted relationships between receptors and chemicals. It is an integrated model of contaminant sources, transport pathways, and receptors that represents potential contaminant dynamics at the site. CSMs range from simple diagrams to detailed illustrations of habitat emphasizing trophic transfer. To the extent possible, include expected effects of climate change, such as sea level rise, in the CSM.

Elements of a CSM

Regardless of the style, the CSM should depict how contaminants are believed to move across the site (fate and transport) and how receptors might be exposed to contaminants in various media (exposure pathways). The CSM should also identify assessment endpoints, which are the particular functional features of the ecological community to be protected, or representative surrogate species. Table 21-6 presents a list of required elements of the CSM.

Table 21-6. Elements of a Marine Sediment Ecological CSM
Sources of Chemical in Marine Sediments
  • Terrestrial soils (via erosion, stream discharge)
  • Spills into water body
  • Surface water runoff
  • Ground water infiltration
  • Sediment “hot spots” (of unknown origin)
  • Outfalls (combined sewer, storm water, industrial)
  • Atmospheric deposition (including volcanic activity)
Contaminant Transport Pathways
  • Sediment (including resuspension; natural or by human activity)
  • Surface water transport
  • Soil erosion
  • Ground water advection
  • Bioturbation
  • Food chain transfer
Exposure Pathways to Ecological Receptors
  • Direct contact with sediment (algae and invertebrates only)
  • Intentional or incidental ingestion of sediment
  • Direct contact with sediment interstitial water (pore water) (algae and invertebrates only)
  • Direct contact with overlying surface water (primarily algae, invertebrates, bottom-dwelling fish, and pelagic fish)
  • Ingestion of other organisms
Ecological Receptors
  • Algae, seagrasses
  • Benthic/epibenthic invertebrates
  • Bottom-dwelling fish
  • Pelagic fish
  • Seabirds and shorebirds
  • Marine mammals
Modified from (USEPA 2005f): Contaminated Sediment Remediation Guidance for Hazardous Waste Sites

The preliminary CSM developed during the SLERA may include multiple chemicals and receptors to ensure that all potentially complete exposure pathways are included. The CSM is typically updated as more information is learned about the site. For example, if the risk assessor learns that a predicted pathway is incomplete because an expected receptor does not occur at the site, then the CSM is revised to eliminate that pathway and receptor.

Figure 21-1. Food Chain Models Can Support Development of Conceptual Site Model
Graphical representation of the trophic linkages (i.e., who-eats-whom) within the Kaloko reef ecosystem. Each animal group within the system is identified here by an illustration (© M. Bailey); where relevant, an image of a species representative of its group is depicted. Images are not drawn to scale or proportional to the group's biomass. The light grey horizontal lines and associated numbers represent trophic levels (position in the food web); lines connecting individual groups represent trophic links. (NOAA 2018b)

Example CSMs

The HEER Office has prepared several examples to illustrate acceptable preliminary CSMs for a marine sediment SLERA. The risk assessor may adapt one of these CSMs or develop a new CSM incorporating the required elements from Table 21-6.

  • Figures 21-2 and 21-3 present two types of CSM for the same site, a rocky intertidal site such as ʻĪlio Point on Molokaʻi. Figure 21-2 is a simple diagram and Figure 21-3 is a pictorial representation.
  • Figure 21-4 is a CSM for a soft-bottom bay/harbor habitat (such as Hanalei Bay, Kauaʻi or Pearl Harbor) that illustrates both direct exposure to sediment and secondary exposure to contaminated prey. This CSM would be suitable to represent bioaccumulating COPECs (such as PCBs or organochlorine pesticides) that were originally released to soil, then washed into the marine habitat. In this scenario, ingestion of COPECs associated with sediment particles is considered the principal exposure pathway.
  • Figure 21-5 is a CSM prepared for a BERA at Pearl Harbor. Note the multiple sources of COPECs that contribute to the existing load in the sediment.
  • Figure 21-6 presents a focused CSM that illustrates the exposure of a single receptor group (water birds) to a single COPEC (arsenic) in sediments and surface water in Waiākea Pond on Hawaiʻi Island.
  • Figure 21-7 is a CSM focused on a particular class of COPECs (energetic compounds associated with discarded munitions).

Other Features to Consider in CSMs

The following considerations should be taken into account when developing CSMs for marine sediment sites in Hawaiʻi:

  • At intertidal sites, the CSM must capture both high tide and low tide exposure pathways. The intertidal habitat depicted in Figure 21-3 shows the inundated state, during which large pelagic fishes and sea turtles are present. At low tide, the large organisms move off shore and seabirds become the dominant predators. The CSM must account for exposure pathways under the full tidal cycle. See (Harborne 2013) for a discussion of foraging shifts between low and high tides on reef flats.
  • At sites with stream discharge or other terrestrial inputs, the CSM must reflect the seasonal flux of contaminants entering the site. For example, in Hilo Bay, Hawaiʻi, the dominant exposure pathway to marine receptors varied throughout the year. Streams discharged heavy loads of soil/sediment as suspended particulate matter during the rainy season. Contaminants associated with terrestrial sources were transported to the bay along with the fresh water. Exposure of organisms in the bay to terrestrially-derived contaminants fluctuated from station to station, influenced by proximity to stream discharge and the time interval since the last major storm (Atwood et al. 2012). The CSM at a site with substantial terrestrial input must reflect this type of variability.
  • At an anchialine pond site, the CSM must be developed specifically to reflect the relatively simple but unusual food web typical of this habitat. Apart from, or in addition to, effects mediated by contamination, any physical or biological perturbation of the food web can upset the balance of species in the pond, many of which are rare, endemic, or endangered. For background on anchialine ponds (see Dalton et al. 2013).
  • The wave energy at a site must be considered in the CSM because waves are influential in sediment transport, deposition, and particle sorting processes that affect exposure of organisms to contaminants. Also, some receptors thrive in high energy environments while others prefer calmer environments. Many COPECs become bound to fine-grained sediment in the field, which tend to accumulate in areas where wave energy is dissipated by vegetation, such as seagrasses and mangroves, or around coastal protrusions such as jetties and piers. When fine-grained sediments are disturbed, either naturally by storms and erosion or purposefully by dredging or construction, metals can become remobilized from the sediments into the water column (Batley et al. 2013). Organic COPECs can become more bioavailable as fine sediment particles are suspended and ingested by receptors. The U.S. Geological Survey (USGS) has conducted numerous studies of natural processes that affect erosion and deposition in Hawaiʻi. Geophysical processes affect not only where sediments accumulate, but also how receptors are exposed to contaminated sediments. To assist risk assessors in describing the wave environment at a contaminated sediment site, the HEER Office has compiled a database of geophysical information provided in USGS reports, as well as in the primary literature, including descriptions and locations of high and low energy aquatic environments; erosional and depositional areas; and other features. The risk assessor should ensure that the influence of wave action is accurately represented in the CSM.

Figure 21-2. A Simple Diagrammatic Conceptual Site Model for a Rocky Intertidal Habitat with Hardbottom (such as ʻĪlio Point, Molokaʻi)

Figure 21-3. Conceptual Site Model for a Rocky Intertidal Habitat with Hardbottom

Figure 21-4. Conceptual Site Model for a Soft-Bottom Bay/Harbor Habitat (such as Hanalei Bay, Kauaʻi, or Pearl Harbor, Oʻahu)

Figure 21-5. Conceptual Site Model Prepared for a BERA at Pearl Harbor
Source: (NAVFAC 2007), Figure 2-7
(Note the multiple sources of COPECs that contribute to the existing load in the sediment.)

Figure 21-6. Conceptual Site Model Focused on Exposure of a Single Receptor Group (Water Birds) to a Single COPEC (Arsenic) in Sediments and Surface Water at Waiākea Pond on Hawaiʻi Island
Source: (HDOH 2005c), Figure 2-1

Figure 21-7. Conceptual Site Model Focused on a Single Class of COPECs (Energetic Compounds Associated with Discarded Munitions)
Source: (ACOE 2012) Figure 3-2

21.3.4 Step 2: Estimating Exposure and Effects

In Step 2, available site-specific data are used to estimate conservative contaminant concentrations, which are then compared with screening levels to identify (1) chemicals that may pose potential risk and (2) chemicals that may be eliminated from further investigation. Step 2, Task 1; Compile Screening levels

SQGs and other screening levels are compiled as part of the ERA Scoping Checklist following the examples in Tables 21-B-1 through 21B-4. If additional analytical data or screening levels have become available, update the table. The HEER Office has developed screening levels for common COPECs at sediment sites in Hawaiʻi. Each of the screening levels is used to evaluate a different aspect of potential risk to receptors, as described below.

  1. Sediment quality guidelines (SQG) are used to evaluate risks to receptors in direct contact with the sediment, especially benthic invertebrates. The SQGs were derived from large datasets on toxicity to benthic invertebrates under a variety of field conditions. Although the SQGs are not necessarily protective of seagrasses, marine algae, fish, or receptors that are not intimately exposed to sediment, they serve as surrogates during the SLERA. The HEER Office will add SQGs to this guidance as they become available. See Table 21-7 and see Appendix 21-E.
  2. HEER Office Environmental Action Levels (EALs) used to evaluate aquatic toxicity (aquatic habitat goals), surface water, and groundwater are available for screening of chemicals in water (see EAL Surfer). See detailed Tables in the EAL Surfer tool for listings of aquatic toxicity and surface water EALs for marine, estuarine, or freshwater environments, as applicable.
  3. Toxicity reference values (TRV) are daily doses of ingested chemicals used to evaluate risk to birds and mammals that are exposed to contaminants primarily through ingestion of contaminated food items (as well as sediment and water).
  4. Critical body residues (CBR) are used to evaluate risk to receptors from chemicals accumulated by all routes into their tissues. CBRs are available for only a few receptors at this time.

HEER Office Interim Sediment Quality Guidelines

HEER Office SQGs are used to evaluate the potential for sediments to pose a risk to benthic invertebrates through direct exposure. The concentration below which sediments are considered safe for benthic marine organisms is called the interim “No Effect SQG.” The concentration above which adverse effects are indicated on benthic marine organisms may occur is called the interim “Potential Effect SQG.” Chemicals known or expected to bioaccumulate are indicated on Table 21-7 and may require additional evaluation, as described in Appendix 21-E.

The SQGs are considered interim because they are subject to revision as new data become available. The HEER Office anticipates that the HDOH interim SQGs will be revised as warranted by a review of new toxicity data reported from other tropical marine ecosystems, including the ANZEC/ARMCANZ ecotoxicology group. In the future, a range of revised SQGs will represent sediments that vary in percent organic carbon and grain size.

The HEER Office interim SQGs incorporate the Effects-Range Low (ER-L) and Effects-Range Median (ER-M) sediment levels published by (Long and Morgan 1990) and modified by (Long et al. 1995), as well as the ANZECC/ARMCANZ interim SQGs derived from other sources. Interim SQGs for 2,3,7,8-TCDD, which were not available from ANZECC/ARMCANZ or NOAA, were adopted from Canadian Council of Ministers of the Environment (CCME 2001).

The HEER Office considers the chemicals listed in Table 21-7 the most likely to be potential risk drivers at marine sediment sites in Hawaiʻi. Chemicals detected in sediment for which no HEER Office interim SQG is available should be screened using the most recent publicaly available literature available. Suggested sources are listed below:

  • SQGs from (Simpson et al. 2013) and related documents
  • Marine sediment screening levels from sources presented in the U.S. Department of Energy, Risk Assessment Information System - Ecological Benchmark Tool (USDOE 2018).
  • Marine sediment screening levels from sources presented in the NOAA Screening Quick Reference Tables (Buchman 2008)

Table 21-7. HDOH HEER Office Interim Sediment Quality Guidelines for Selected Chemicals
Analyte Recommended Interim Sediment Quality Guidelines for Direct Exposure
No Effect SQG Potential Effect SQG
Inorganic Chemicals (mg/kg dry weight)
Arsenic 20 70
Copper 34a 270
Lead 50 220
Mercury 0.15 1
Tributyltin (µg/kg Sn/kg dry weight) 5 70
Zinc 200 410
Organic Compounds
Pesticides/PCBs/Dioxins (µg/kg dry weight)
4,4'-DDD 2 20
4,4'-DDE 2.2 27
Total DDTs 1.6 46
Total Chlordane 0.5 6
Dieldrin 0.02 8
Endrin 0.02 8
Total PCBs 23 180
TEQ Dioxins and Furans 0.00085 0.0215
Semivolatile Organic Compounds (µg/kg dry weight)
Acenaphthene 16 500
Acenaphthylene 44 640
Anthracene 85 1100
Benzo(a)anthracene 261 1600
Benzo(a)pyrene 430 1600
Chrysene 384 2800
Dibenzo(a,h)anthracene 63 260
Fluoranthene 600 5100
Fluorene 19 540
Naphthalene 160 2100
Phenanthrene 240 1500
Pyrene 665 2600
Sum HMW PAHs 1700 9600
Sum LMW PAHs 552 3160
Total PAHs 4000 45000
High molecular weight
Low molecular weight
Microgram per kilogram
Milligram per kilogram
Polycyclic aromatic hydrocarbon
Polychlorinated biphenyl
Sediment quality guideline
Toxic equivalent
  • The chemicals in Table 21-7 are also considered bioaccumulative and must undergo further evaluation for this hazard (see Appendix 21-E).
  • Some local background/ambient/reference concentrations may exceed No Effect SQG.
  • See Table 21-1, Required, Preferred, or Optional Data for Sediment ERAs, for addressing sediment contaminant levels greater than the No Effect SQGs but less than the Potential Effect SQGs.
  • All organic SQGs are normalized to 1% organic carbon.
  • If data are available for both total organic carbon and grain size fraction, the No Effect SQG for copper is organic carbon (OC)-normalized copper concentration of 3.5 mg Cu/g OC in the < 63 μm sediment fraction. The copper SQG is under review by both ANZECC/ARMCANZ (Simpson et al., 2013) and researchers in Hong Kong (Kwok et al. 2008) and is expected to be revised.
  • The following individual PAHs are typically reported by laboratories using standard EPA analytical methods. This list may change, depending on which specific parameters are requested:
    • LMW PAH = acenaphthene, acenaphthylene, anthracene fluorene, naphthalene, phenanthrene, 1-methylnaphthalene, 2-methylnaphthalene.
    • HMW PAH = benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(g,h,i)perylene, benzo(k)fluoranthene, chrysene, dibenz(a,h)anthracene, fluoranthene, indeno(1,2,3-cd)pyrene, and pyrene.

The chemicals on the HEER Office SQG table (Table 21-7) are also known as common bioaccumulating chemicals, based on a review of technical manuals prepared by USEPA, other states, and international organizations. Therefore, these chemicals should also be considered potential bioaccumulators, and evaluated accordingly using food chain models (see Step 1b, Task 3). The risk assessor should also consider other technical sources of information when determining whether chemicals detected in sediment at a site may be bioaccumulators. The Bioaccumulation Testing and Interpretation for the Purpose of Sediment Quality Assessment, Status, and Needs (USEPA 2000i) provides technical direction on identifying bioaccumulators. More detailed guidance on evaluating risk of bioaccumulating chemicals is in Appendix 21-E.

Toxicity Reference Values

A TRV is an ingested daily dose of a chemical associated with a designated effect level. A low TRV is a conservative value consistent with a chronic no observable adverse effect level (NOAEL). A high TRV is consistent with a lowest observable adverse effect level (LOAEL). When compared to site-specific doses ingested by receptors, the high TRV should be used to identify sites posing potential risk to birds or mammals. Conversely, the low TRV is a dose level below which no adverse effects are expected.

The HEER Office has not compiled a comprehensive list of TRVs for all receptors. The risk assessor may select TRVs based on site-specific receptors and exposure conditions and provide technical rationale for the TRVs selected. TRVs are available from several sources in the literature, including, but not limited, to the following:

  • TRVs developed by the U.S. Navy for 20 chemicals common at San Francisco Bay area naval installations, including 12 metals and metalloids (arsenic, butyltins, cadmium, cobalt, copper, mercury, lead, manganese, nickel, selenium, thallium, and zinc), five pesticides (aldrin, DDT, heptachlor, lindane, and methoxychlor) and three other organic compounds (benzo(a)pyrene, naphthalene, and total polychlorinated biphenyls) (Navy 1998). Several of the Navy TRVs have been updated using more recent toxicological studies (CalDTSC 2009)
  • Toxicological Benchmarks for Wildlife (Sample et al. 1996)
  • FCSAP Supplemental Guidance for Ecological Risk Assessment Selection or Development of Site-specific Toxicity Reference Values (Azimuth 2010). This document does not present specific TRVs but list several sources of TRVs.
  • Recommendations for the Development and Application of Wildlife Toxicity Reference Values (Allard et al. 2010). This document does not present specific TRVs but presents recommendations on the derivation and application of wildlife TRVs.
  • EPA Ecological Soil Screening Level Documents (USEPA 2005g) and supporting documents). Although these documents pertain to soil, some of the toxicological literature cited within them is relevant to birds and mammals exposed to chemicals in surface water and sediment.
  • Los Alamos National Laboratory, ECORISK Database (Release 4.1) (LANL, 2017). This database presents TRVs for several chemicals and receptors.

Note that TRVs used in ERAs in Hawaiʻi are provided in the species profiles, where available (See Appendix 21-A). The HEER Office does not necessarily endorse the use of the particular TRVs presented in earlier ERAs but does recommend that the risk assessor make use of existing literature to select and provide rationale for TRVs suitable to the site.

Critical Body Residues

The CBR can be used to evaluate risk to a receptor based on a chemical concentration in its tissue. However, CBR data are available for only a few chemicals and selected species from a limited number of locations. Few, if any, of the published CBRs cited are for native Hawaiian species. No standard CBR values have been developed by EPA or other national agencies. Limited CBR data are available from the following sources:

  • Linkage of Effects to Tissue Residues: Development of a Comprehensive Database for Aquatic Organisms Exposed to Inorganic and Organic Chemicals (Jarvinen and Ankley 1999). Most of the available data are for freshwater species, although some marine and estuarine species are included.
  • Guidance for Assessing Bioaccumulative Chemicals of Concern in Sediment provides freshwater and marine CBRs for metals, pesticides, PCBs, and 2,3,7,8-TCDD TEQs (ODEQ, 2017).
  • Environmental Residue Effects Database (ERED) is a searchable compendium of CBRs derived by USEAP and the ACOE from literature published in the 1960s to 1990s. (US Army 2018)
  • Dredged Material Evaluation and Disposal Procedures User Manual (DMMP) (ACOE 2016) lists target tissue concentrations for several chemicals.
  • Environmental Contaminants in Biota: Interpreting Tissue Concentrations, Second Edition (Beyer and Meador 2011) summarizes data on CBR for numerous species and contaminants. Step 2, Task 2; Calculating Contaminant Concentration(s) in Sediment and Water

At a minimum, the SLERA requires site-specific sediment concentrations. The preferred approach to estimating exposure concentrations at a sediment site is to use MIS sampling to represent the typical exposure of receptors within a DU. The general guidance in the TGM on developing a sampling plan for a sediment investigation is applicable to an ERA (see TGM Sections 3, 4, and 5). However, the designation of DUs is more complex for an ERA because no single DU is appropriate for all ecological receptors at a site (See Appendix 21-C).

Stationary and relatively immobile species such as algae, benthic infauna, and coral are primarily exposed to chemicals in sediment through direct contact. The MIS concentration detected in a DU is used as the representative contaminant concentration in the SLERA. Assuming laboratory detection limits are lower than the SQGs, non-detects are treated as zero values. If the laboratory detection limit exceeds the SQG, the detection limit is used as the reported value for all nondetects. (In this case, the data should be scrutinized and laboratory methods reviewed so that detection limits appropriate for a SLERA can be achieved.)

If site-specific concentrations are available for surface water, sediment pore water, or groundwater discharging to the site, the MIS detected concentration is used as the contaminant concentration for the SLERA (given the protocol for estimating nondetects in the previous paragraph). Samples should be analyzed for dissolved concentrations for constituents that have WQC based on dissolved concentrations.

The SLERA is purposefully designed to be conservative, evaluating the worst-case exposure scenario and often overestimating contaminant concentrations in early steps. Subsequent steps allow refinement of conservative assumptions to reflect site-specific conditions that may reduce estimated contaminant levels or risk. Step 2, Task 3; Estimating Daily Ingested Dose to Birds and Mammals

The SQG are considered protective of algae, benthic invertebrates, and fish exposed directly to sediment but cannot be used to evaluate risk to birds or mammals feeding on prey at a contaminated sediment site. Risk to birds and mammals ingesting sediment, water, and prey at a site is evaluated using food chain modeling to estimate the dose of a chemical ingested by these animals.

Tissue concentrations are a key component of dose estimates to birds and mammals, but are not always available during a SLERA. If tissue concentrations from organisms collected at the site or from organisms exposed to site-sediment in the laboratory are available, site-specific doses to birds and mammals can be estimated. Site-specific tissue concentrations (also known as CBRs) can also be used to estimate direct effects to the organisms from contaminant body burdens. If no tissue data are available, chemical concentrations in tissue may be estimated using concentrations in sediment, literature BSAFs, and parameter assumptions (see Appendix 21-F).

Ingested doses of bioaccumulative chemicals are estimated using food chain models. The dose estimate represents the mass of chemical ingested per day, indexed to the receptor's body weight (mg/kg-body weight/day). Daily ingested doses are estimated for higher trophic level receptors (birds and mammals) that are exposed to contaminants primarily through their diet rather than through direct contact with sediment. Where appropriate, the dose estimate should include incidental sediment ingestion. For example, the Hawaiian monk seal is reported to consume substantial amount of sediment when it hauls out on beaches. The risk assessor should review the relevant literature on key receptors at the site to determine the need to include sediment ingestion in the dose for a given receptor.

The ingested dose should be estimated using the following generic exposure equation. The equation can be modified, as necessary, based on the specific exposure pathways evaluated in the SLERA:

ED = exposure dose (mg/kg-day)
Cf = chemical concentration in food (mg/kg)
Cs = chemical concentration in sediment (mg/kg)
If = food ingestion rate (kg/day)
Is = incidental sediment ingestion rate (kg/day)
SUF = site use factor (site/species home range – cannot exceed 1.0) (unitless)
BW = body weight (kg)

Chemical concentrations and ingestion rates (for sediment and food) should be reported in dry weight. If tissue concentrations are reported by the analytical laboratory in wet weight, dry weight concentrations can be estimated using either laboratory measures or standard default values for percent moisture.

For the SLERA, the estimated daily dose is intentionally biased high so that any error will be toward indicating greater risk than is present. In later phases of the ERA, biases are relaxed in favor of more realistic assumptions. For example, the estimated dose in the SLERA should be based on the

  • Maximum chemical concentration in sediment and food;
  • Maximum ingestion rates for sediment and food;
  • Lowest body weight;
  • Highest site use factor; and
  • Most sensitive life stage present at the site.

The HEER Office provides species profiles for selected receptors at coastal marine sediment sites (Table 21-8). Species profiles are in Appendix 21-A. Values for exposure parameters required in the food chain model, such as body weight and home range, are included in the species profiles when available. The risk assessor should review the current published literature to obtain additional information where data are not provided.

Table 21-8. Selected Species Profiles
Receptor Group Selected Species*
Marine Algae Sea lettuce (Ulva fasciata)
Invertebrates Samoan crab (Scylla serrata)
Kona crab (Ranina ranina)
White crab (Portunus sanguinolentus)
Helmet urchin (Colobocentrotus atratus)
Hawaiian limpet (Cellana exarata)
Day octopus (Octopus cyanea)
Polychaete (Neanthes arenaceodentata)
Lobe coral (Porites lobata)
Black sea cucumber (Holothuria atra)
Fish Goatfish (Mulloides vanicolensis)
Hawaiian flagtail (Kuhlia sandvicensis)
Convict tang (Acanthurus triostegus)
Pacific sergeant (Abudefduf abdominalis)
Mozambique tilapia (Oreochromis mossambicus)
Spectacled parrotfish (Chlorurus perspicillatus)
Yellowbar parrotfish (Calotomus zonarchus)
Moray eel (Muraenidae)
Birds Wedge-tailed shearwater (Puffinus pacificus)
Black-crowned night heron (Nycticorax nycticorax hoactli)
Hawaiian coot (Fulica alai)
Sea Turtles Green sea turtle (Chelonia mydas)
Marine Mammals Monk seal (Monachus schauinslandi)
* See Appendix 21-A for profiles of these species.

Calculate Critical Body Residues

The HEER Office does not require that tissue concentrations be obtained during the SLERA. However, tissue samples collected to support a human consumption study or other phase of investigation at the site may be available for inclusion in the SLERA. The risk assessor should present the available tissue data in tabular form with details on the sample date, location, species, size of specimen, body part, analytical methods, and results (with data qualifiers). If the tissue samples are composites of more than one individual organism, the details above should be provided for all individuals in the composite. (When possible, tissue concentrations should be measured in single individuals rather than composites for comparison to CBRs.) The maximum detected tissue concentration is used as the exposure concentration in the SLERA. Non-detects are treated as zero values when detection limits are acceptable (see Step 2, Task 2). Step 2, Task 4; Calculate Site-Specific Hazard Quotients

Risk calculations in the SLERA are simple and straightforward for chemicals that are not considered bioaccumulators. The maximum exposure concentration is divided by the no-effect screening level to calculate a hazard quotient (HQ). If the resulting HQ is greater than 1.0, that chemical is designated a chemical of potential ecological concern (COPEC) and should be evaluated further. If the HQ is less than 1.0 for that chemical, it is eliminated as a COPC and dropped from further consideration. Chemicals without screening levels are retained as COPECs at this point in the process. To compensate for the uncertainty inherent in single chemical SQGs, the initial step of the SLERA is purposefully biased toward including chemicals that may not pose a risk rather than eliminating COPECs that may pose a risk, by use of conservative exposure assumptions. This bias toward including COPECs is corrected during later phases of the ERA (i.e., Step 3a or the BERA) in which the COPEC list is refined using more realistic assumptions and site-specific exposure data. The HQs for receptors directly exposed to sediment should be calculated as follows:

HQsediment = maximum sediment concentration/no effect SQG

Risks from chemicals that bioaccumulate can be evaluated using the equation above to assess direct toxicity to organisms. If the resulting HQ is less than 1.0, no direct toxicity is indicated. However, a bioaccumulating chemical cannot be eliminated as a COPEC based on a simple sediment screen because it may be bioaccumulated even when its concentration in sediment is less than the SQG. Risk posed by food chain transfer of contaminants is evaluated using TRVs derived for higher trophic level receptors. The estimated daily dose of a chemical in a given receptor is compared with the no-effect TRV to calculate an HQ:

HQ-TRVlow = estimated daily dose/no-effect TRV

Bioaccumulating chemicals can also pose a direct risk to the receptor in the form of causing neurological, developmental, or other impairment. The concentration of a bioaccumulating chemical in the whole body (or specific tissue type) of a receptor can be compared to the concentration demonstrated to cause an adverse effect on that receptor (or a surrogate species). When tissue effect levels for comparable species and tissue types are available in the literature, risk is estimated by comparing site specific tissue concentrations to CBRs from the literature:

HQtissue = site-specific tissue concentration/CBR Step 2, Task 5; Decision Checkpoint

By this stage of the process, all available sediment, water, and tissue data have been screened against no-effect screening levels and HQs have been calculated. Chemicals for which all HQs are less than 1.0 can be eliminated from further evaluation. Chemicals for which at least one HQ is greater than 1.0 are retained as COPECs. The HEER Office recommends the SLERA include a summary table supporting the decision to eliminate or retain each chemical.

21.3.5 Step 3A: Refine Screening Level Default Assumptions

The COPECs retained at the end of Step 2 were shown to pose potential risk to receptors when conservative assumptions were used. Step 3A is focused on refining the list of COPECs to represent more realistic site-specific conditions. The objective of the COPEC refinement is to identify chemicals that significantly contribute to potentially unacceptable levels of ecological risk and eliminate from further consideration those chemicals that are not likely causing a significant risk. This step consists of refining the conservative exposure assumptions/concentrations used to evaluate potential risks to ecological receptors and re-evaluating the analytical data using screening levels that are more appropriate for the assessment endpoints.

This refinement may result in eliminating chemicals as COPECs for some receptors but retaining them as COPECs for other receptors. For example, a chemical might be retained as a COPEC for benthic invertebrates but eliminated as a COPEC for shorebirds. This is important because if the site proceeds to a BERA, the studies in the BERA should focus only on the chemicals-receptor pairs for which risk is predicted. The following tasks will support a decision regarding the need for further evaluation. Step 3a, Task 1; Conduct Background Screening

The risk assessor should compare site-specific concentrations of COPECs with regionally-appropriate background, ambient, or reference concentrations to ensure that only site-related chemicals are carried through to the BERA. Inorganic chemicals pose unique difficulties for ERAs because of the role of site-specific geology in influencing exposure and effect concentrations. Background evaluations for sediment in Hawaiʻi are complicated by spatial heterogeneity of volcanic and coralline sediment types.

In the absence of CBRs for selected receptors, the risk assessor may compare site-specific tissue concentrations with results from similar habitats or regions considered to be “unimpacted” by chemicals or to represent “background” tissue concentrations. The HEER Office is compiling tissue concentrations reported as “background” or “reference” in various published literature and reports. The values are not considered to represent “no effect” concentrations because the samples were not associated with toxicity testing. At best, the “reference” or “background” tissue concentrations indicate the range of concentrations existing in the area outside of known contaminated sediment sites. The risk assessor may compare site-specific tissue concentrations with the “reference tissue” results for the same species and habitat. Such comparisons are necessarily limited by uncertainty, yet they can provide a useful context for interpreting site-specific data. The relative magnitude of site-specific tissue concentrations compared with reference concentrations may indicate the need for further tissue sampling during the BERA or may strongly suggest that chemicals are not accumulating in tissues at the site to any measurable degree. The identification and interpretation of background, ambient, or reference concentrations should be discussed with the HEER Office before proceeding with the next task. Step 3a, Task 2; Evaluate Magnitude of Screening Level Exceedance and Frequency of Detection

Although the magnitude of risks may not relate directly to the magnitude of a criterion exceedance, the magnitude of the criterion exceedance may be used in a weight-of-evidence approach to determine the need for further site evaluation. The greater the criterion exceedance, the greater the probability and concern that an unacceptable risk exists.

Likewise, the frequency of chemical detection and spatial distribution of concentrations greater than the screening levels may indicate the need for additional investigation. A chemical detected at a low frequency typically is of less concern than a chemical detected at higher frequency if toxicity and concentrations and spatial areas represented by the data are similar. All else being equal, chemicals detected frequently are given greater consideration than those detected relatively infrequently. In addition, the spatial distribution of a chemical may be evaluated to determine the area that a sample represents. The risk assessor should discuss magnitude and frequency distributions with the HEER Office to resolve any issues before continuing with the SLERA. Step 3a, Task 3; Refine Conservative Exposure Assumptions

Initial steps in the SLERA use assumptions of 100 percent bioavailability, high site use by sensitive receptors, representative contamination concentrations, and other factors to ensure that a chemical is not excluded from the SLERA if it poses an unacceptable risk. In Step 3a, more realistic site-specific exposure values replace the default values.

  • Bioavailability: When selecting chemicals as COPECs in the SLERA, it is typically assumed that the chemicals are 100 percent bioavailable. However, in the COPEC refinement, the potential bioavailability of the chemicals can be evaluated by considering total organic carbon (TOC) and grain size data. Typically, this evaluation is more qualitative than quantitative in the SLERA. However, in a BERA, bioavailability can be measured directly through uptake in living organisms. Guidance on adjusting the assumption of 100 percent bioavailability is in Appendix 21-F.
  • Site Use: The conservative default value of 100 percent site use assumes that an organism spends all of its time in contact with contaminants at the site. For some mobile species, this assumption is clearly unrealistic, and a more representative site use factor may be used.
  • Contaminant Concentrations: The most conservative and reasonably representative contaminant concentration for a specific target chemical is used for initial comparison to applicable screening levels, and some potential COPECs may be eliminated from the SLERA using this approach. However, smaller or additional DUs and/or more representative sampling techniques may be used during Step 3a to support further evaluation of the site. Step 3a, Task 4; Obtain HEER Office Concurrence on Refinements

Provide the HEER Office with tables, text, figures, or other defensible rationale for refining the exposure assumptions. After reviewing the submitted materials, the HEER Office may accept the refinements or request a meeting to discuss the rationale and assumptions so that consensus can be reached. Step 3a, Task 5; Recalculate HQs using Refined Exposure Assumptions

Recalculate HQs using more realistic estimate of contaminant concentration and screen against background concentrations. Prepare a summary table of COPECs eliminated and retained and provide rationale for the decisions. If risk is below applicable screening levels (or approved alternative screening level) for all chemicals, the SLERA is complete and the site can move to closure. If COPECs are retained and risk is potentially unacceptable, the site will continue to the BERA (Subsection 21.6). Step 3a, Task 6; Develop SLERA Risk Characterization and Decision

Risk characterization in the SLERA focuses on the summary of HQs prepared in Step 3A, Task 5 and a discussion of uncertainty and data gaps to be addressed in the BERA.

21.3.6 Uncertainty

During the risk characterization phase, the exposure and effects data are interpreted within the context of other site-specific information. Specifically, various sources of uncertainty are evaluated so that the risk assessor can provide a realistic description of risks posed by contaminants at the site. Uncertainty stems from many sources, including the extrapolation of exposure and effects data form one species to another. Efforts to customize the ERA to tropical marine conditions and native Hawaiian species will greatly reduce this source of uncertainty and strengthen the risk characterization. Conversely, modifying existing toxicity tests and adapting protocols to accommodate the environmental conditions that prevail in Hawaiʻi may introduce additional uncertainty in the short term. Such trade-offs are explicitly recognized and addressed in the Sediment Quality Assessment Handbook (Simpson et al. 2005). The following paragraphs present some of the key uncertainties in SLERAs, and where applicable, how the uncertainties relate to sites in Hawaiʻi.

Uncertainty in Ecotoxicity

The HEER Office recommended interim SQGs specifically acknowledge that uncertainty stems from gaps in the science of toxicology, particularly in tropical marine ecosystems. One fundamental source of uncertainty stems from the derivation of single-chemical trigger values from toxicity tests using field-collected sediments containing multiple contaminants. Attributing toxic effects to any one of the many chemicals in such sediments leads to uncertainty that must be addressed in controlled laboratory investigations using single contaminants (Batley and Simpson 2008). The ANZECC/ARMCANZ is actively working to develop bioassays using native Australian or New Zealand species that will better reflect the genetic and ambient environmental conditions in sediments there. Some opportunity exists to adapt the Australian bioassays by substituting native Hawaiian species of similar taxonomic and functional characteristics. Therefore, although toxicity testing is typically not conducted until the BERA, the use of native Hawaiian species as test organisms for toxicity tests is encouraged, when applicable, to reduce uncertainty.

Some ecological risk investigations have been conducted in tropical marine regions, but Australia has developed an organized national program to tailor EPA and ASTM International (ASTM) protocols to tropical marine ecosystems. Although the Australian program is still in a fledgling state, many of the foundational principles are congruent with Hawaiʻi's goal to develop a state-specific ERA program. The Australian program recognizes the EPA framework and the large body of subsequent work on refining questions of metals bioavailability in whole sediments (Batley and Simpson 2008). The Australian group has focused on developing bioassays that reflect reasonable exposure and effects conditions for local habitats (see below). Finally, that group has implemented a regionalized program that incorporates land use, climate, and contaminant source data specific to a watershed so that background conditions can be properly evaluated (Australian Government 2006).

Uncertainty in Exposure

As indicated above, tissue samples can provide a direct measure of the bioavailability of chemicals. However, there is uncertainty in where and how they accumulated the chemicals (i.e., sediment, surface water, food, or a combination). Also, the choice of organisms, portion analyzed (whole body, fillet, liver, etc.), environmental parameters (i.e., pH, TOC, grain size), along with other factors that influence bioaccumulation.

Particulate metal concentrations are nearly always higher in fine-grained sediments (<63 μm) because smaller sediment particles have a higher surface area and more binding sites available for metals (Angel et al. 2012). Although, HDOH does not recommend biasing sediment collection methods to only collect fine-grained sediments, sampling techniques must be appropriate to ensure that the finer-grained fractions are not lost during sample collection. For example, ponar samplers often allow silts to escape as the sampler is being lifted. A coring device may be more appropriate for ensuring that fine-grained sediments are represented in the sample to the extent they are present at the site (see TGM Section 5).