Initial U.S. Environmental Protection Agency (USEPA), State of Nevada, and Clark County involvement included examination of potential environmental impacts from operations within the Black Mountain Industrial (BMI) Complex during the 1970s, which included the area then operated by the Kerr-McGee Chemical Corporation (Kerr-McGee), a previous owner of the Nevada Environmental Response Trust (NERT) Site. The agencies’ involvement included review of atmospheric emissions, groundwater and surface water discharges, and soil impacts.
In response to the 1972 Clean Water Act, Kerr-McGee and other operators within the BMI Complex modified their manufacturing processes between 1971 and 1976 to end the practice of discharging process wastewater to the BMI Complex’s unlined ditches. The operators instead constructed lined ponds to recycle and evaporate industrial wastewater.
In 1980, the USEPA requested specific information from the BMI companies regarding their manufacturing processes and their waste management practices. In response to Federal Resource Conservation and Recovery Act (RCRA) standards, Kerr-McGee initiated a groundwater investigation in 1981 to monitor two existing on-site surface impoundments. Groundwater monitoring results collected as part of this monitoring effort indicated elevated levels of hexavalent chromium in groundwater beneath the Site.
In December 1983, the Nevada Division of Environmental Protection (NDEP) requested that Kerr-McGee investigate the extent of hexavalent chromium impacts in the groundwater beneath the Site. A Consent Order between Kerr-McGee and NDEP, prepared in September 1986, required additional groundwater characterization and the implementation of response activities to address hexavalent chromium in the groundwater. Additional information regarding hexavalent chromium remediation activities, which began in 1987, can be found on the Current Groundwater Treatment page.
In April 1991, Kerr-McGee was one of six companies, which also included Chemstar, Montrose, Pioneer, Stauffer, and TIMET, that entered into a Consent Agreement with NDEP to conduct environmental studies to assess site-specific environmental conditions resulting from past and present industrial operations and waste disposal practices. The six companies that entered into the Consent Agreement included past or present entities that conducted business within the BMI Complex. The Consent Agreement required that, among other things, the companies identify, document, and address soil, surface water, groundwater, and air impacts and document measures that have been taken to address environmental impacts from their respective sites.
In April 1993, in compliance with the 1991 Consent Agreement, Kerr-McGee submitted a Phase I Environmental Conditions Assessment (Phase 1 ECA) to NDEP. The purpose of the Phase 1 ECA was to identify and document site-specific environmental impacts resulting from past or present industrial activities. The Phase I ECA included an assessment of the geologic and hydrologic setting, as well as historical manufacturing activities. In 1994, NDEP issued a letter of understanding (LOU) that identified areas of the Kerr-McGee property where additional information was needed, either in the form of additional document research or field sampling of soil and groundwater. These areas were called LOU Areas.
During the mid to late 1990s, Kerr-McGee collected additional data to fill information gaps identified in the LOU. This was done by investigating past operator records, as well as through field sampling. The results of this work are described in a Phase II Written Response to the LOU, a Phase II Environmental Conditions Assessment, and a Supplemental Phase II Environmental Conditions Assessment, the latter two of which were reports describing the results of soil and groundwater sampling. Through this effort, potential environmental impacts associated with 70 identified LOU Areas were evaluated.
In 1997, perchlorate was discovered in the vicinity of the Las Vegas Wash. This finding followed a period of increased governmental and regulatory concern regarding the potential health effects of perchlorate, as well as advances in laboratory analysis that enabled the detection of perchlorate at much lower levels. The investigation of perchlorate in the Las Vegas Wash was placed on a response fast-track. Impact characterization and treatment technology evaluation were on-going in the late 1990s. The 1999 Consent Agreement between Kerr-McGee and NDEP defined investigation and remediation requirements, including the installation of a seep water collection system adjacent to the Las Vegas Wash. For additional information regarding ongoing perchlorate remediation activities, see the Current Groundwater Treatment page.
In 2001, Kerr-McGee and NDEP entered into an Administrative Order on Consent, which required Kerr-McGee to install additional extraction well systems and construct an on-site groundwater treatment facility. This treatment facility, called the groundwater extraction and treatment system (GWETS), began operation in 2002.
In 2005, a Conceptual Site Model (CSM) was prepared for the Site, which consolidated information gathered regarding environmental impacts, both known and potential. The purpose of a CSM is to distill extensive environmental data and knowledge in order to clearly describe where contamination came from (sources), where it has gone or is going (migration pathways), and how it might change over time (transformation pathways), to help ensure that remediation decisions are effective and protective of human health and the environment (receptors). Based on information in the CSM and at the direction of NDEP, Tronox (a spin-off company of Kerr-McGee) implemented two soil sampling programs (known as Phase A and Phase B Source Investigations) that were completed in 2006 and 2009, respectively. These investigations identified a number of constituents in excess of state Basic Comparison Level (BCL) criteria within the upper 10 feet of soil, including dioxin toxic equivalents (TEQ), hexachlorobenzene, other semi-volatile organic compounds (SVOCs), polychlorinated biphenyls (PCBs), asbestos, metals, organochlorine pesticides, and perchlorate. In an Order dated December 14, 2009, NDEP directed Tronox to remove all soil containing contaminants of potential concern (COPCs) in excess of worker BCLs (or modified risk-based goals agreed upon by NDEP) from the Site by the end of 2010.
Tronox’s consultant prepared a work plan describing a strategy for excavating impacted soil within the upper 10 feet of soil to the extent such soils were accessible. Tronox began the soil removal project in August 2010, but it was not completed when the Site was transferred to NERT on February 14, 2011. Although NERT is not regulated under any of the Kerr-McGee/Tronox consent agreements or administrative orders on consent, NERT completed the interim soil removal program in November 2011, consistent with an Interim Consent Agreement between NDEP and NERT effective February 14, 2011. Between the beginning of soil response activities in August 2010 and excavation completion in November 2011, approximately 579,000 cubic yards of contaminated soil were excavated and removed from the Site. An Interim Soil Removal Action Completion Report was prepared in January 2012 and revised in September 2012 (NDEP Approved on December 17, 2012).
Certain impacted soils that could not be excavated due to physical constraints or other access issues were designated as Excavation Control Areas (ECAs) and such potential risks are managed through the current version of the Site Management Plan (SMP), which is updated annually. The SMP describes procedures to safely manage the known remaining environmental conditions at the Site, as well as contingency actions to be taken if previously unknown environmental conditions are encountered.
Last updated: February 2024
