This former DOE Pinellas Plant manufactured nuclear weapons components from the mid-1950’s until 1997. The site experienced DNAPL releases from operations as well as soil and groundwater contamination resulting from buried drums that leaked solvents and other wastes. HSW was under contract with a private client to provide site-wide environmental restoration, monitoring, sampling, and analytical services from 1993 to June 1997 when the plant was in operation. Services included sampling groundwater, surface water, soil, and air, water-level monitoring, well maintenance, database management, and monthly and quarterly reporting; RCRA TSD permit modifications and updates, closure of four TSD units, and clean-closure of all permitted RCRA units; and closure assistance of the main manufacturing (non-waste) areas. The plant was closed in mid-1997 and MACTEC-ERS, as DOE’s new contractor, began oversight of ongoing environmental restoration activities as the site began redevelopment jointly by DOE and Pinellas County. HSW was contracted by MACTEC to provide support services for operation and maintenance and engineering support (design, drawings, specifications, installation) of the remediation systems. In 2002, S.M. Stoller, Inc., took over the DOE contract from MACTEC and retained HSW in a continuing engineering and environmental support role. In 2015, the contract was awarded to Navarro Research and Engineering, who continues to rely on HSW for environmental support, including on-going groundwater monitoring activities.
Numerous innovative technologies have been tested at this site and HSW has provided support for many of these. Among the more innovative technologies utilized have been in situ aneraobic bioremediation, dual rotary auger steam stripping, biosparging and in-situ thermally-enhanced NAPL remediation. In situ anaerobic bioremediation, pilot-tested in 1997, involved extraction of groundwater, addition of benzoate, lactate, and methanol, and reinjection of the amended groundwater. The project was one of the most successful, with contaminant reduction rates of 70 to 99%. Full-scale operation was not selected while other possible treatment technologies were under consideration.
A dual rotary auger steam stripping system was operated in early 1997 in a small portion of the area identified as the Northeast Site. The augers were advanced to a depth of 40 feet and compressed air and steam were injected. Off-gas was captured and treated. The system was generally effective, with removal rates of about 70 to 95%, but costs were relatively high at about $400 per cubic yard; thus,full scale operation was not selected.
A biosparging system was installed at what is designated as the 4.5 Acre Site, and operations began in 1999. This system was installed after several years of pump-and-treat and dual-phase extraction system operation.
At the Northeast Site, electro thermal dynamic stripping, a new technology, was pilot-tested for removal of chlorinated DNAPL. System construction began in May 2002, and the system was in operation from late 2002 through spring 2003. This treatment technology employed a combination of in situ electrodes to provide resistive heating, steam injection wells around the outside edge of the contaminant area, and a network of collection wells inside the area. The combination of resistive heating and injected steaming converts the DNAPL to a vapor that is driven to the recovery wells for extraction. The vapor is condensed and recovered for off-site processing. HSW played an integral role during the baseline study and construction phase of the system implementation. During the construction phase, HSW installed the steam injection wells and identified the Hawthorn Formation for proper placement of these wells. The pilot test yielded DNAPL concentrations in groundwater and soil equal to or less than clean-up target levels. Due to the success of the pilot study, this technology was implemented in a second area four times larger than the pilot study area, with HSW continuing to provide support during this supplemental treatment.
Two groundwater contaminant plumes exist under Building 100, the largest building on-site. In 2013-2014, it was concluded that one of these two plumes was not stable and that biodegradation should be implemented to treat both plumes. Injection of emulsified soybean oil was initiated in late 2014 and completed in late 2015.
Throughout our more than two decades-long involvement with this site, HSW has provided continuing operation and maintenance support for other remediation systems at the site, including two horizontal tray air strippers and numerous recovery wells. HSW has performed air emission modeling and permit support for the site’s synthetic-non-Title V air permit since 1998, including permit renewals, modification, certification testing, and insignificant source determination. Air modeling was used to determine potential impacts to neighbors and to demonstrate compliance with permitted emission limits.
DOE’s Office of Legacy Management currently is seeking closure of the Northeast Site and 4.5 Acre Site, as well as another area identified as the Wastewater Neutralization Area, while continuing with long-term groundwater monitoring associated with Building 100. DOE and Navarro continue to rely on HSW’s familiarity and experience with the site, as well as HSW’s high level of professionalism and economic efficiency, with on-going semiannual groundwater monitoring and other as-needed field and technical support.