2008 Issue

www.utahengineerscouncil.org 40 at Hill AFB, a two-staged hammer mill will be required. In the first stage, the four-inch minus BDU-33 iron will be crushed to a size of approximately 1.5-inch minus. In the second stage, the 1.5-inch minus BDU-33 iron will be crushed to -8 to +50 United States Standard Mesh particle size distribution (Figure 4). A second bench-scale column study was performed using groundwater from OU 5 and granular BDU-33 iron supplied from the crushing demonstration performed by Schutte-Buffalo Hammer Mill. This addi- tional study was performed to determine the reaction rates and design parameters for a proposed PRB field study at OU 5 using the granular BDU-33 iron. Again, results from the bench-scale column study were positive. Bench-scale testing indicated that the granular BDU-33 iron degraded TCE in the OU 5 groundwater to below remediation goals (5 parts per billion [ppb]) with a TCE half-life of 1.6 hours. This is lower than a typical half-life observed from tests using commercial iron sources. Since laboratory studies suggest that the granular BDU-33 iron generated from the hammer mill crushing process is as effective as commercially-obtained granular iron in treating chlorinated solvents in groundwater, Hill AFB is implementing the first stages of an OU 5 field study using granular BDU-33 iron in a PRB. In preparation for the OU 5 field study, Hill AFB has obtained approximately 470 tons of four-inch minus BDU-33 iron from the UTTR and the Barry M. Gold- water Range in Arizona. Hill AFB has also procured a production-scale, two-staged hammer mill fromSchutte- Buffalo Hammer Mill which will be delivered to the Base inApril 2008 after it is fabricated. Four-inchminus BDU-33 iron crushing activities are schedule to begin in July 2008. This will be followed by the first placement of granular practice bomb iron in the OU 5 contaminated groundwater plume in September 2008. Unlike traditional PRB installation methods where a trench is excavated and backfilled with granular iron, Hill AFB intends to install and test the granular BDU-33 iron in a PRB using borehole technology. In this PRB installation method, granular practice bomb iron will be placed in two rows of two-foot diameter boreholes drilled on four-foot centers with the borehole locations staggered across each row (Figure 5). The two rows of boreholes will be placed across the southern OU 5 TCE groundwater plume near its source in the portion of the plume where TCE concentrations are greater than 100 ppb. The borehole PRB installation methodology was chosen over standard trench installation because boreholes allow for placement of iron at greater depths and allow for the option to vary the percent of iron placed at various depths. It also allows for the BDU-33 iron PRB to be implemented in stages that will allow field scale evaluation of treatment capability of the iron. Hill AFB estimates that costs will be reduced by 21% by using granular BDU-33 iron rather than commercially-obtained granular iron for a full-scale PRB treatment system at OU 5. Should BDU-33 granular iron prove to be effective in treating chlori- nated solvent-contaminated groundwater in the field, the implications for the Air Force and the Department of Defense (DOD) as a whole, are far reaching with even greater cost savings realized as greater quantities of BDU-33 iron are crushed for additional PRB groundwater treatment systems DOD-wide. The DBMI project is being managed by the Hill AFB Environ- mental Management Division (75 CEV), which is part of the Base Civil Engineer Group. Hill AFB 75 CEV is being assisted by the engineering consulting firm MWH. Innovation, partnering and a solid government to industry rela- tionship sharing a common goal are inevitably key elements in making this vital environmental project for the Air Force a true success. HILL AFB BOMBS PLUMES — continued Messrs.Roginske, and Stewart, P.G., are Hill Air Force Base En- vironmental Restoration Project Managers. Mr. Mills is a Hill Air Force Base Hazardous Materials Program Manager, Mr. Olsen is a principal hydrogeologist and Ms. Arens is a senior engineer with Montgomery-Watson-Harza, Consulting Engineers. Figure 4. Demilitarized BDU-33 Practice Bomb Iron: Before and After Hammer Mill Crushing Figure 5 Proposed Operable Unit 5 Field Study Location Using Granular BDU-33 Practice Bomb Iron in a Borehole Technology Permeable Reactive Barrier