Topography at Hunters Point Shipyard (HPS) is dominated by relatively level lowlands that were constructed by excavating portions of surrounding hills and placing nonengineered fill materials along the margin of San Francisco Bay. The remaining land is a moderate to steeply sloping, northwest trending ridge. Ground surface elevations at Parcel C generally range from 8 to 10 feet above mean sea level.
Two aquifers and one water-bearing zone have been identified at HPS: the A-aquifer, the B-aquifer, and the bedrock water-bearing zone. Groundwater flow patterns are complex because of heterogeneity in the hydraulic properties of the fill materials and weathered bedrock, tidal influences, effects of storm drains and sanitary sewers, and variations in topography and drainage.
Remedial Unit C4 (RU-C4) hydrogeology is characterized by shallow bedrock with a rolling and uneven surface overlain predominantly by artificial fill material of variable hydraulic conductivity. In locations where the artificial fill directly overlies the weathered zone at the bedrock interface, both the fill material and the weathered bedrock are considered part of the A-aquifer. The A-aquifer is unconfined and directly overlies the bedrock water-bearing zone. In the western portion of Parcel C where bedrock is present at shallow depths, B-aquifer zones are isolated and mostly absent. At RU-C4, the B-aquifer is present from approximately midway through Building 272 and further to the east. An aquitard separates the A- and B-aquifers in a small area near the eastern edge of the building; however, the two aquifers are in direct contact east of this point, based on lithologic logs of nearby borings and wells. At RU-C4, the A-aquifer predominantly consists of Artificial Fill and weathered bedrock located about 1 to 15 feet below ground surface (bgs). The bedrock water-bearing zone occurs as fractured portions of the Franciscan Complex Bedrock. Groundwater of the bedrock water-bearing zone is primarily within discrete fractures and shear zones.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
Major Contaminants and Maximum Concentrations:
- Trichloroethene (88,000 µg/L)
- Vertical Chemical Profiling
- Other (Pump Tests)
Comments:
Pump test to determine interconnection of fractures.
- Fracturing
- Other (Chemical Reductioon with Zero Valent Iron)
Comments:
This treatability test was conducted to determine whether injections of zero valent iron (ZVI) could remediate chlorinated volatile organic compounds (CVOCs) in groundwater. Ferox, the technology used in the demonstration, involved injection of liquid atomized zero valent iron powder using a packer system to isolate discrete depth intervals within open boreholes. A ZVI slurry is delivered to the subsurface in a liquid atomized form using nitrogen gas as a carrier. Pneumatic fracturing can be performed prior to the injection to promote ZVI movement through the subsurface and its contact with contaminants, leading to the chemical reduction of the CVOCs.
In the 2002 pilot test, the geologic matrix was pneumatically fractured and then a high purity micro scale iron powder was injected into four boreholes to treat groundwater between 7 and 32 ft below ground surface. Each well treated about a 15 foot radius in the fractured rock area. A total of 16,000 pounds of iron was injected during the pilot test. The treatment area covered 1,800 square feet and the treated subsurface volume was 1,700 cubic yards.
Source zone remediation
Results from three rounds of post-injection groundwater monitoring showed reductive dechlorination of all CVOCs. Reduction of TCE to ethane and chloride was rapid and nearly complete with a reduction of 99.2 percent within the treatment zone. No significant increases in TCE degradation intermediates cis-1.2-dichlorethene and vinyl chloride were observed. A statistical analysis of changes in contaminant concentrations outside of the treatment zone further supports the conclusion that TCE and other CVOCs were destroyed rather than displaced as a result of the injections. Monitoring wells outside and below the pilot test area showed little evidence of contaminant migration outside the treatment area. The potential for plume displacement due to injection and mobilization of metals were also evaluated and found to be insignificant.
The total cost of the field scale implementation of the Ferox injection technology was $289,274, or $172 per cubic yard of the treatment zone. Economies of scale for certain cost elements, such as mobilization and demobilization could result in somewhat lower costs for larger-scale applications.
References:
Final Cost and Performance Report: Feroxsm Injection Technology Demonstration Parcel C, Remedial Unit C4, Hunters Point Shipyard San Francisco, California, July 11, 2003. Available at: http:costperformance.orgpdf20040701_352.pdf
http:www.clu-in.orgproductstins: Treatment of Chlorinated VOCs in Groundwater Using Zero-Valent Iron Injection: Hunters Point Shipyard, San Francisco, CA. From Strong Environmental Partners: Our Community, Our Navy, Report for Fiscal Years 2004-2008. Department of the Navy, Environmental Restoration. Chapter 3, p 46-47, July 2004. Available at: http:5yrplan.nfesc.navy.milpreviousjul_2004chapter3.pdf
McCall, John; Greg Swanson; C. Hwakong Cheng; Patrick Brooks; D.B. Chan; Steve Chen; Julie Menack. 2004. Demonstration of Zero-Valent Iron Injection for In Situ Remediation of Chlorinated Solvents at Hunters Point Shipyard. The Fourth International Remediation of Chlorinated and Recalcitrant Compounds Conference, Monterey, California. May 24-27.
Strong Environmental Partners: Our Community, Our Navy, Report for Fiscal Years 2004-2008. Department of the Navy, Environmental Restoration. Chapter 3, p 46-47, July 2004. Available at: http:5yrplan.nfesc.navy.milpreviousjul_2004chapter3.pdf
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