Louisiana Army Ammunition Plant, Shreveport, LA
The Louisiana Army Ammunition Plant (LAAP) is a government-owned and contractor-operated facility in northwestern Louisiana where munitions were loaded and packed. Munitions loading and waste disposal operations have contaminated groundwater with explosive compounds in a number of specific locales. LAAP was added to the National Priorities List (NPL) in March 1989 due to the potential risk to human health and the environment. CCJM, and a predecessor company, Engineering Technologies Associates, Inc., (CCJM) received a series of contracts to assist the remediation of this site.
CCJM developed a numerical groundwater model of contamination fate and transport in 1990 under contract to the U.S. Army Environmental Center (USAEC). Groundwater flow at LAAP was simulated using the U.S. Geological Survey three dimensional finite difference model, MODFLOW. Contaminant fate and transport in the saturated zone was simulated with RAND3D, a three dimensional solute transport model using the random walk algorithm. The random-walk technique is based on the concept that dispersion in porous media is a random process. Aquifer pumping tests were conducted at LAAP to supply data for the modeling. This model was used to support the initial risk assessment work at the installation, which culminated in records of decision at six sites.
In 1994, ETA conducted supplemental investigations at the LAAP Y-Line area. The Y-Line area was where the artillery shell casings were manufactured. A previous Remedial Investigation (RI) of this site detected chlorinated solvents in ground water and recommended additional study of the extent of contamination. ETA:
- prepared a technical workplan, a supplemental quality assurance plan, and a health and safety plan;
- conducted hydraulic push sampling of shallow ground water and analysis of chlorinated volatile hydrocarbons at a mobile laboratory;
- installed and sampled additional monitoring wells;
- sampled and analyzed subsurface soil;
- sampled and analyzed surface water and sediment; and
- prepared an addendum to the RI report, a proposed plan, and the record of decision for approval by the U.S. Environmental Protection Agency.
ETA also assisted the U.S. Army Waterways Experiment Station in their study of natural attenuation of explosive compounds in ground water. Ground water at LAAP Area P, a former disposal site, is contaminated with carcinogenic byproducts of explosive compounds. Thirty wells were sampled by ETA using state-of-the-art sampling methodologies including low flow purging, dedicated Teflon discharge tubing, and continuous monitoring of purge water for dissolved oxygen. Three years of sampling were conducted.
The installation is currently addressing the contaminated groundwater site-wide. CCJM is supporting this effort with a new groundwater model. The new model includes the data collected for the past ten years, and takes advantage of improvements in computer speed and numerical groundwater modeling technology. The groundwater flow model, MODFLOW 2000, is being automatically calibrated. RAND3D was used for initial contaminant transport simulations at sites simulated in 1990 as well as additional sites. Future contaminant transport simulations will be conducted using RANDFOR, a more powerful version of the random walk program.
