Cap at DOE's Lawrence Livermore National Laboratory, Site 300, Pit 6 Landfill OU

Site Name:

Lawrence Livermore National Laboratory

Location:

Livermore, CA

Period of
Operation:

Installed Summer 1997; groundwater monitoring scheduled for 30 years (post-closure care)

Cleanup
Type:

Full-scale cleanup

Vendor:

Lockheed-Martin Energy Systems Inc.
Oakridge, TN

Weiss Associates
Emeryville, CA

Technology:
Multilayer cap that consists of (top to bottom):

- Topsoil and vegetative layer (2-feet)
- Geocomposite drainage layer/biotic barrier (high-density polyethylene (HPDE) netting between synthetic filter fabric)
- HDPE/geosyntheic clay layer (60-mil HDPE liner over bonded bentonite clay layer)
- General fill (compacted native soil; 2-feet thick)
- Georigid reinforcement (HDPE flexible grid material; two to three layers separated by 6-inches of general fill)

Cleanup Authority:
CERCLA
- Removal Action Federal Facility Agreement

Regulatory Contact:
Information Not Provided
Additional Contacts:
Michael G. Brown
Deputy Director
DOE/OAK Operations Office
L-574
Lawrence Livermore National Laboratory
Lawrence, CA 94551
(510) 423-7061

John P. Ziagos
Site 300 Program Leader
L-544
Lawrence Livermore National Laboratory
Lawrence, CA 94551
(510) 422-5479

Contaminants:
Volatile Organic Compounds:
-Trichloroethene (TCE)

Radionuclides:
- Tritium

Waste Source:
Waste debris and biomedical waste from operations at Site 300

Type/Quantity of Media Treated:
Cap--2.4 acre multilayer cap over a landfill

Purpose/Significance of Application:
Multilayer capping of a landfill

Regulatory Requirements/Cleanup Goals:
The CERCLA compliance criteria analysis for the Pit 6 landfill removal action include overall protection of human health and the environment; compliance with the Applicable or Relevant and Appropriate Requirement (ARARs), long-term effectiveness and permanence; reduction in toxicity, mobility, and volume; short-term effectiveness; and implementability.

Results:
- A summary is included in the report comparing the CERCLA objectives to the performance of the landfill. The cap is meeting the objectives for protection of human health and the environment, reduction of mobility of the waste, short-term effectiveness and implementability.
- While the landfill cap construction meets all ARARs, capping alone may not meet State requirements for protection of beneficial uses of groundwater. In addition, a cap does not reduce the toxicity and volume of buried waste and contaminated groundwater. At the time of this report, the post-closure monitoring plan was still being written.

Cost Factors:
- Total cost of constructing the landfill cap was $1,500,000, including design, mobilization and preparatory work and site work.
- Total cost of the removal action was $4,100,000, including costs for preliminary/preconstruction activities, construction activities and projected costs for 30 years of landfill O&M and groundwater monitoring.

Description:
Lawrence Livermore National Laboratory Site 300 is a DOE experimental test facility located near Livermore California. Pit 6 Landfill OU was the location of buried waste including laboratory and shop debris and biomedical waste, including radioactive wastes. From 1964 to 1973, approximately 1,900 cubic yards of waste were disposed of in three unlined debris trenches and six animal pits. The trenches, located near the center of the landfill, were each about 100 feet long, 10 feet deep, and 12 to 20 feet wide. The animal pits, located in the northern part of the landfill, were each about 20 to 40 feet long, 16 feet deep, and nine feet wide. VOC and tritium were detected in soil and groundwater at the site. TCE concentrations in the groundwater have declined from levels as high as 250 mcg/L in 1989 to 15 mcg/L in 1997 (slightly above the federal and state MCL of 5 mcg/L). Trace concentrations of chloroform, cis-1,2-dichloroethene, and tetrachloroethene are also present in the groundwater. The maximum activity of tritium currently detected in groundwater is 1,540 pCi/L, below the MCL of 20,000 pCi/L.

In the summer of 1997, a 2.4 acre multilayer cap was placed over the three trenches and six animal pits. The cap extended more than 25 feet beyond the perimeter of the trenches and pits due to uncertainties in the exact location of the waste and to cover areas where VOCs in the subsurface had potential to cause worker inhalation exposure. The cap consists of a vegetative/topsoil layer, a geocomposite drainage layer underlain by a geosynthetic liner over a bonded bentonite clay layer, and compacted general fill which includes georigid reinforcement. A summary is included in the report comparing the CERCLA objectives to the performance of the landfill which indicates that the cap is meeting the objectives for protection of human health and the environment, reduction of mobility of the waste, short-term effectiveness and implementability. While the landfill cap construction meets all ARARs, capping alone may not meet State requirements for protection of beneficial uses of groundwater. In addition, a cap does not reduce the toxicity and volume of buried waste and contaminated groundwater. A Post-Closure Monitoring Plan was being written at the time of the report and will establish a Detection Monitoring Program and a Corrective Action Monitoring Program. Several observations and lessons learned from this application related to implementation are included in the report, along with information on technology advancements.

Total cost of constructing the landfill cap was $1,500,000, including design, mobilization and preparatory work and site work. Total cost of the removal action was $4,100,000, including costs for preliminary/preconstruction activities, construction activities and projected costs for 30 years of landfill O&M and groundwater monitoring.