Normatividad / Individuo / Religiosidad

The SVE vacuum blowers will be selected to extract design airflow and vacuum and will be equipped with variable frequency drive (VFD) drive units and motors to allow for

maximum adjustability. The blower motors and associated electrical equipment will be

designed for Class 1 Division 1, Group D hazardous atmosphere. It is anticipated that the SVE off-gas will be near 25 percent of the LEL; therefore, explosion-proof motors and spark-proof blowers will be specified. It is anticipated that multiple vacuum blowers will be necessary to produce the desired design parameters. The use of multiple blowers in conjunction with VFDs will increase the overall operational flexibility of the SVE system.

The SVE system optimization includes a reduction in the total number of SVE wells, which reduces the total design extraction air flow rate. The total number of SVE wells has been reduced to 15 (13 new SVE wells and 2 existing SVE wells) in order to focus vapor capture from the areas where the AAS system is operating, areas where LNAPL persists, and areas where contaminant concentrations exceed the FDEP SCTLs, as presented in Chapter 62-770, FAC. Design air extraction from this system will be 600 scfm at 100 inches H2O vacuum.

This is approximately 1.7 times the proposed maximum AAS injection rate. The vacuum rating for the SVE system is designed to extract the off-gas from each soil vapor extraction well, through the field piping, equipment, instruments, and through the off-gas treatment.

Due to the combined effects of the shallow water table at Site 1159 and suction from the SVE blowers, it is possible that excess moisture could enter the system and collect in the SVE moisture separator(s). Collection and disposal of the unknown quantities of water could present significant problems in maintaining system effectiveness. To minimize any potential adverse effects on treatment system operation, moisture separators will be installed between the SVE lines and the blowers to remove water from the off-gas air stream prior to

processing through the SVE blowers.

The moisture separators will be equipped with effluent pumps, which will operate using high, medium, and low level float switches installed within each moisture separator. Pumps will activate when water levels inside the moisture separators reach the medium-level switch and will automatically turn off when the low-level switch is triggered. The high-level switch will be wired to the control panel to turn the entire system off if triggered by a high water level in the moisture separator.

The SVE moisture separator effluent pump discharge lines will be manifolded together, and the water removed from the soil-gas by the SVE system moisture separators will initially be containerized and tested for lead and petroleum constituents to determine the proper disposal method. Potential disposal methods include onsite discharge, approved disposal at an offsite facility, or discharge to the local publicly-owned treatment works.

Initial influent total petroleum hydrocarbon (TPH) concentrations from the SVE systems are expected to exceed the FDEP limit of 13.7 pounds per day; therefore, off-gas treatment will be provided using a thermal oxidizer with catalytic option. Due to the presence of tetraethyl lead (TEL) in the AVGAS, it is likely that lead-oxide particulates will be generated during the combustion process inside the thermal oxidizer.

Reported TEL values in AVGAS range from 0.56 to 1.12 grams Pb per liter [0.005 to 0.009 pounds TEL (as Pb) per gallon] (Chevron, 2000) to greater than 4 grams TEL (as Pb) per gallon (EPA, 2002). Based on the original volume estimate (TtNUS, September 2002) of 242,000 gallons of AVGAS released at Site 1159, potentially 300 to 2,100 pounds of TEL (as Pb) exists in the treatment zone, and could be entrained in the SVE system off-gas and released to the atmosphere.

The site-specific concentrations at which the TEL will be extracted from the vadose zone are unknown at this time; therefore, lead emissions estimates from an AVGAS-contaminated site at Hickam Air Force Base in Oahu, Hawaii, were used in conjunction with design flow rates to estimate the approximate off-gas treatment system emissions at OLF Bronson. Lead emissions from the Hickam AFB site were observed to be 2.162 milligrams per cubic meter (mg/m³ )(CH2M HILL, 2000). Using this lead concentration, the estimated annual emissions for OLF Bronson Site 1159 would be between 21 and 135 pounds per year, depending on operational flow rates (design flow or maximum flow); this estimate falls below the 500 pounds Pb per year limit established in Chapter 62-210 FAC.

The lead emissions may present a potential risk to human health and the environment. As a precaution, additional influent sampling, off-gas sampling, and ambient air monitoring will be conducted during system startup and routine operations (if startup observations show that it is necessary) to determine the actual mass of lead particulates being generated by the off-gas treatment system and to track TPH emissions. Additionally, air modeling may be conducted to determine the extent of lead particulate dispersion and assess potential effects of lead deposition to areas adjacent to the site. If the concentrations of TEL exceed the Occupational Safety and Health Administration (OSHA) general industry permissible exposure limit of 0.075 mg/m³ as lead, then off-gas treatment system optimization will be performed to reduce the emitted concentrations. If optimization efforts do not successfully reduce the lead concentrations, additional off-gas treatment may be required.

Initial system startup activities will consist of an SVE-only startup during which the SVE and off-gas system operation will be initiated and optimized. Once stable SVE operations have been achieved (i.e., flow rates balanced, TPH off-gas effluent emissions are maintained below 13.7 pounds per day, and lead emissions are below 1.37 pounds per day or up to 500 pounds per year of Pb), the SVE system legs may be cycled based upon field and analytical observations obtained during the initial startup, including off-gas influent concentrations and emissions. Once startup activities are completed (AAS/SVE/off-gas), the SVE system will continue to operate until the cumulative removal curve approaches an asymptotic slope, or lead emissions reach 500 pounds within a 1-year period.

Once soil gas removal rates fall below 13.7 pounds per day as TPH, the off-gas treatment system will be removed and the soil-gas will be vented directly to the atmosphere, with approval from the FDEP. Off-gas sampling and ambient air monitoring (if necessary based on startup observations) will be continued to confirm TPH and lead emissions in order to ensure that human health and the environment are protected and that regulatory emissions criteria are met. The frequency and duration of the continuing off-gas sampling and ambient air monitoring is subject to change (with concurrence from the FDEP), based on the air sampling analytical results.

In order to extend the durability of the system’s mechanical components and minimize the impact of noise pollution on the adjacent campgrounds, the SVE vacuum blowers, moisture separators, and components will be housed inside a structurally reinforced and insulated enclosure wired for explosive atmospheres.