Document Type

Annual Report

Publication Date


GovDoc ID



625 pgs.


The Department of Energy/National Nuclear Security Administration (DOE) and Sandia Corporation are submitting the Mixed Waste Landfill (MWL) Annual Long-Term Monitoring and Maintenance Report for the April 2015 through March 2016 reporting period. This report satisfies the requirements of Section 4.8.1 of the MWL Long-Term Monitoring and Maintenance Plan (LTMMP). The annual reporting period runs from April 1 to March 31.

The MWL is a 2.6-acre Solid Waste Management Unit (SWMU 76) which has undergone corrective action. The MWL is located in the north central portion of Sandia National Laboratories (SNL)/New Mexico (NM) Technical Area III. During the operational period (March 1959 through December 1988), the MWL accepted low-level radioactive waste and minor amounts of mixed waste from SNL/NM research facilities and off-site DOE and U.S. Department of Defense generators.

On May 26, 2005, the New Mexico Environment Department (NMED) issued the Final Order selecting a vegetative soil cover with biointrusion barrier (referred to as the ET Cover) as the final remedy for the MWL. Deployment of the MWL ET Cover. Deployment of the MWL ET Cover was completed in September 2009.

This is the third MWL Annual Long-Term Monitoring and Maintenance Report since approval of the MWL LTMMP on January 8, 2014, and includes information for monitoring, inspection, and maintenance, and repair activities conducted during the reporting period.

This report is comprised of 12 chapters that include monitoring results for radon in air, tritium in surface soil, biota, groundwater, and vadose zone soil-vapor and soil moisture at the MWL. Inspection, maintenance, and repair activities for monitoring well systems and equipment, the storm-water diversion structure, the MWL ET cover system, and perimeter fence are also presented. One chapter is devoted to a summary of regulatory activities pertaining to the MWL that occurred during the reporting period.

The report includes five annexes with supporting field and analytical documentation for monitoring activities. Forms used to document inspection activities are provided in a sixth annex and a seventh contains the annual biology report.

The monitoring and inspection results presented in the report indicate the final remedy, which includes the ET Cover and related physical and institutional controls, is performing as designed. No monitoring trigger levels were exceeded. Site conditions continue to be protective of groundwater, human health, and the environment.

Language (ISO)



Sandia National Laboratories/NM


Annual Long-Term Monitoring and Maintenance Report, LTMMP, Long-Term Monitoring and Maintenance, SWMU 76 Solid Waste Management Unit