Facilities-Units

Document Type

Report

Publication Date

1-2024

Abstract

The Department of Energy/National Nuclear Security Administration (DOE/NNSA) and Sandia National Laboratories /New Mexico (SNL/NM) personnel submitted the Mixed Waste Landfill (MWL) Second Five-Year Report for the January 2018 through December 2022 evaluation period to the New Mexico Environment Department (NMED) in accordance with the requirements of the May 2005 Final Order on remedy selection (NMED May 2005) and Section 4.8.2 of the MWL Long-Term Monitoring and Maintenance Plan (LTMMP). The first five-year evaluation period began on January 8, 2014, when NMED approved the LTMMP (Blaine January 2014) and included the first four calendar years under the LTMMP (i.e., January 2014 through December 2017).

The MWL is a 2.6-acre Solid Waste Management Unit (SWMU 76) located in the north-central portion of SNL/NM Technical Area III that has undergone corrective action. As of March 13, 2016, the NMED February 2016 Final Order became effective, granting the Class 3 Permit Modification to reflect that the MWL is Corrective Action Complete with Controls and incorporating the LTMMP in Attachment M of the SNL RCRA Facility Operating Permit. The LTMMP defines all remedy controls, including monitoring, inspection, maintenance/repair, and reporting requirements for the MWL.

This MWL Second Five-Year Report is comprised of seven chapters that include a summary of all monitoring and inspection results for the reporting period, Fate and Transport Model review, an evaluation of remedy effectiveness, a reevaluation of excavation feasibility, summary and conclusions, and references. Other requirements specific to this Second Five-Year Report include evaluation of 13 toxic pollutants added to the New Mexico Administrative Code since January 2014 and evaluation of potential MWL impacts to current and future land use in areas surrounding Kirtland Air Force Base.

The primary purpose of the Five-Year Report is to evaluate the effectiveness of the selected remedy (i.e., the ET Cover) and the likelihood of contaminants reaching groundwater. The 2018 through 2022 monitoring, inspection, and maintenance results provide the empirical data necessary to establish current site conditions, evaluate the effectiveness of the ET Cover and associated controls, and reevaluate the likelihood of contaminants reaching groundwater. The measure of effectiveness is the protection of human health and the environment.

Based upon nine years of monitoring, inspection, and maintenance under the LTMMP, MWL site conditions have improved and continue to be protective of human health and the environment. MWL multi-media monitoring results are consistent with historical data, no trigger levels were exceeded, and there were no indications of new releases or changing conditions that would increase the risk to site workers, the public, or increase the likelihood of contaminants reaching groundwater.

The MWL ET Cover and associated remedy controls are in good condition and performing as designed. The inspection and maintenance results confirm the physical integrity of the ET Cover, remedy controls, and all monitoring networks. Complete excavation of the MWL with offsite disposal is a remedial alternative that could be implemented, if necessary, for the protection of human health and the environment. Considering all available information, the ET Cover with controls continues to be the preferred remedy as it protects human health and the environment without the additional risk to site workers and the public associated with the excavation remedial alternative. 141 pgs.

Language (ISO)

English

Publisher

Sandia National Laboratories/NM

Keywords

LTMM, Long-Term Monitoring and Maintenance, SWMU 76, Solid Waste Management Unit

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