Construction of an Innovative Permeable Reactive Barrier to Passively Treat TCE within a Storm Sewer System
Construction of an Innovative Permeable Reactive Barrier to Passively Treat TCE within a Storm Sewer System
Client
Lockheed Martin for NASA
Services Provided
Pilot Testing; Remedial Design; Construction Management
Location
New Orleans, Louisiana, USA
Project Practice Areas
Contaminated Sites
Type of Facility
Active Industrial Site
Project Specifics
The Michoud Assembly facility is an active plant operated by Lockheed Martin for NASA. The facility is engaged in the manufacture and assembly of the external tank for the space shuttle. In 1966, about 100 tons of TCE were released from a large tank in the Building 190 Tank Farm Area. Subsurface investigations revealed the presence of chlorinated ethenes, primarily TCE and its degradation products, in soil and groundwater samples. A groundwater extraction and treatment system was installed to address shallow groundwater contamination. However, the storm drainage system within the area has been found to be leaking and therefore acts as a groundwater “sink” in the main area of contamination. This leakage to the storm sewer system resulted in unacceptable concentrations of VOCs in the storm sewer water.
Geosyntec Scope of Services
Geosyntec designed an innovative application of permeable reactive wall technology that takes advantage of the hydraulic gradient resulting from the leaking storm sewer system. We identified an existing manhole within the vicinity of the spill area where there was significant inward leakage of contaminated groundwater. Our design involved the replacement of this manhole with a pre-fabricated structure (sump) that incorporates zero-valent iron backfill in an annulus around the structure. An internal valving arrangement allows control of the hydraulic gradient across the zero-valent iron reaction zone. This allows control of the flow rate and residence time of the groundwater as it flows through the reaction zone. Under highly reducing conditions and in the presence of metallic iron surfaces, certain dissolved chlorinated organic compounds in groundwater will degrade to non-toxic compounds such as ethene, ethane, and chloride. Geosyntec developed this innovative configuration that takes advantage of this process to treat the dissolved-phase TCE and its degradation products. Geosyntec also served as the construction manager and resident engineer for installation of the system described above.
Notable Accomplishments
Geosyntec’s permeable reactive barrier system provides cost-effective, passive treatment of the impacted groundwater that discharges to the sewer, and it significantly reduces the concentration of VOCs in the storm sewer discharge.
Related Projects
Confidential
Denver, Colorado
New Cure, Inc. for Multi-Party PRP Group
Monterey Park, California, USA
Confidential Manufacturing Client
Saranac, Michigan
Bauer Foundation Corp. for the U.S. Army Corps of Engineers
Lake Okeechobee, Florida, USA
COWI A/S
Høfde 42, Jutland, Denmark
