Human health and ecological risk assessments help determine if there are any health risks to the public or the environment associated with environmental contamination. A health risk assessment (HRA) evaluates potential health risks to on-site or off-site human receptor populations from potential exposures to residual levels of Site-related contaminants present in the environment. An ecological risk assessment (ERA) evaluates potential risks posed by the presence of Site-related contaminants released to the environment on living organisms and the ecosystems in which they live.
NERT's risk assessments in OU-1 and OU-2 concluded that the risks to receptors (e.g., residents, workers, birds, mammals, or plants) are below or within the NDEP and USEPA risk management range. However, groundwater remediation will be required by NDEP because groundwater contamination exceeds NERT’s screening levels and state and federal standards. Using data collected as part of the RI Report for OU-1 and OU-2, HRA and ERA reports have been submitted to and approved by NDEP for OU-1 and OU-2, as described below. Risk assessments for OU-3 will be submitted to NDEP following submittal of the RI report for OU-3.
Risk Assessments in OU-1
· BHRA for OU-1 Soil: The baseline human health risk assessment (BHRA) for OU-1 soils is designed to evaluate potential human health risks for on-site workers from exposures to residual levels of contaminants of potential concern (COPCs) in soils within OU-1. The BHRA for OU-1 Soil was conducted in accordance with the BHRA Work Plan dated February 28, 2014 (NDEP approved on May 20, 2014). Based on initial data evaluations, a preliminary list of COPCs for evaluation in the BHRA and preliminary decision units (areas within OU-1 where health risks will be evaluated) are included in the Interim Report: Identification of COPCs and Decision Units for OU-1 Soils dated November 15, 2017 (NDEP approved on December 27, 2017). The BHRA Report for OU-1 Soil was submitted on January 31, 2020 and NDEP provided comments on June 9, 2020. The BHRA Report for OU-1 Soil was revised (Revision 1) and resubmitted to NDEP on October 15, 2021. NDEP provided comments on December 22, 2021. The BHRA Report for OU-1 Soil, Revision 2 was submitted to NDEP on May 6, 2022 (NDEP approved on June 2, 2022).
· BHRA for OU-1 Soil Gas and Groundwater: The BHRA for OU-1 soil gas and groundwater is designed to evaluate potential human health risks for on-site workers associated with COPCs via the vapor intrusion pathway from soil gas and shallow groundwater in OU-1. This BHRA was conducted in accordance with the BHRA Work Plan for OU-1 and OU-2 Soil Gas and Groundwater, Revision 1 dated December 19, 2018 (NDEP approved on January 24, 2019). The BHRA Report for OU-1 Soil Gas and Groundwater was submitted on September 29, 2021 and NDEP provided comments on March 9, 2022. A response to NDEP’s comments on this report was submitted on June 24, 2022, and NDEP responded to the response to comments on November 3, 2022. The BHRA Report for OU-1 Soil Gas and Groundwater was revised (Revision 1) and resubmitted to NDEP on November 3, 2023 (NDEP approved on January 2, 2024).
· Refined SLERA for OU-1: The refined screening-level ecological risk assessment (SLERA) for OU-1 is designed to assess whether contaminants of potential ecological concern (COPECs) associated with historical manufacturing activities at the NERT Site have the potential to pose risks to plants and animals that inhabit OU-1. The SLERA used data from previous and ongoing evaluations of surface soil at the NERT Site to evaluate whether there are any adverse impacts to plants and wildlife within OU-1. The SLERA for OU-1 was conducted in accordance with the Refined Screening Level Ecological Risk Assessment (SLERA) Work Plan, Revision 2 dated July 6, 2015 (NDEP approved on August 14, 2015). The Refined SLERA Report for OU-1 was submitted on August 6, 2021 and NDEP provided comments on March 2, 2022. A response to NDEP’s comments on this report was submitted on May 19, 2022, and NDEP responded to the response to comments on August 26, 2022. The Refined SLERA Report for OU-1 was revised (Revision 1) and resubmitted to NDEP on April 20, 2023. NDEP provided comments on June 8, 2023. The Refined SLERA Report for OU-1, Revision 2 was submitted to NDEP on December 19, 2023 (NDEP approved on February 1, 2024).
Risk Assessments in OU-2
· BHRA for OU-2 Soil Gas and Groundwater: The BHRA for OU-2 soil gas and groundwater is designed to evaluate potential human health risks associated with COPCs via the vapor intrusion pathway from soil gas and shallow groundwater for off-site residents and workers in the Off-Site Study Area within OU-2. This BHRA was conducted in accordance with the BHRA Work Plan for OU-1 and OU-2 Soil Gas and Groundwater, Revision 1 dated December 19, 2018 (NDEP approved on January 24, 2019). The BHRA Report for OU-2 Soil Gas and Groundwater was submitted on July 23, 2021. A letter from NDEP dated September 8, 2021 required NERT to modify the BHRA Work Plan to include an indoor air investigation of chloroform in the Pittman residential area within OU-2. NERT’s plan to complete the requested work is described in the BHRA Work Plan Modification #1, Revision 1 dated October 29, 2021 (NDEP approved on November 10, 2021). This work was performed out of an abundance of caution and consistent with guidance from USEPA. The limited indoor air investigation for chloroform in the Pittman Neighborhood was performed solely to confirm the results of the vapor intrusion modeling conducted in the OU-2 human health risk assessment as an additional line of evidence confirming NERT’s finding that the risks to residents are below or within the NDEP and USEPA risk management range. The limited indoor air investigation was completed during 2022. The results were reported in the August 29, 2022 OU-1 and OU-2 Soil Gas and Groundwater Modification #1 Technical Memorandum, which demonstrated that chloroform concentrations in indoor air are well below thresholds established by NDEP and USEPA. NDEP provided comments on the BHRA Report for OU-2 Soil Gas and Groundwater and the OU-1 and OU-2 Soil Gas and Groundwater Modification #1 Technical Memorandum on October 13, 2022. The BHRA Report for OU-2 Soil Gas and Groundwater was revised (Revision 1) and resubmitted to NDEP on September 15, 2023 (NDEP approved on November 27, 2023).
· Refined SLERA for OU-2: The refined SLERA for OU-2 is designed to assess whether COPECs released during historical manufacturing activities in and around OU-1 have the potential to pose risks to animals and plants that inhabit OU-2. The SLERA used data from previous investigations where COPECs were measured in soil to evaluate whether there are any adverse impacts to plants and wildlife that currently inhabit OU-2. The SLERA for OU-2 was conducted in accordance with the SLERA Work Plan for OU-2, Revision 1 dated September 28, 2018 (NDEP approved on October 30, 2018). The SLERA Report for OU-2 was submitted on August 5, 2021 and NDEP provided comments on March 2, 2022. A response to NDEP’s comments on this report was submitted on May 13, 2022, and NDEP responded to the response to comments on August 26, 2022. The Refined SLERA Report for OU-2 was revised (Revision 1) and resubmitted to NDEP on May 18, 2023. NDEP provided comments on July 7, 2023. The Refined SLERA Report for OU-2, Revision 2 was submitted to NDEP on December 20, 2023 (NDEP approved on February 1, 2024).
Risk Assessments in OU-3
· BHRA for OU-3: The BHRA for OU-3 is designed to evaluate potential human health risks associated with COPCs that have migrated from the NERT Site to OU-3 for applicable populations in OU-3. Environmental media that will be addressed in the OU-3 BHRA include soil, soil gas, and groundwater. The BHRA Work Plan for OU-3 was submitted on February 28, 2022, and NDEP provided comments on June 29, 2022. The BHRA Work Plan for OU-3, Revision 1 was submitted on December 5, 2022 (NDEP approved on February 1, 2023). The Trust is currently preparing a BHRA Report for OU-3, which is planned for submittal in late 2024.
· BERA for OU-3: The baseline ecological risk assessment (BERA) for OU-3 is designed to assess whether aquatic and terrestrial plants and animals within the Las Vegas Wash are adversely impacted by COPECs released during historical manufacturing activities in and around OU-1 that may have migrated to the Las Vegas Wash via groundwater. The BERA for OU-3 is being conducted in accordance with the BERA Work Plan for OU-3 dated February 1, 2019 (NDEP approved on April 8, 2019), Work Plan Modification No. 1 dated October 15, 2019 (NDEP approved on October 21, 2019), and Work Plan Modification No. 2 dated December 16, 2021 (NDEP approved on December 22, 2021). As part of the BERA for OU-3, a comprehensive field sampling program was conducted in 2019-2020 that included the collection of surface water, sediment, bank soil, benthic invertebrates, and fish tissue. Additional benthic invertebrate sampling was performed during second quarter 2022 in the Las Vegas Wash. The Trust is currently preparing a BERA Report for OU-3, which is planned for submittal in late 2024.
Last updated: February 2024
