Dense Nonaqueous Phase Liquids (DNAPLs)

Combined Remedies

Examples for the Class of Multi-Component Waste

The Avenue Coking Works Remediation
Pensaert, S.
NORDROCS 2012: 4th Nordic Joint Meeting on Remediation of Contaminated Sites, International Conference, September 18-21, 2012, Oslo, Norway. 4 pp paper and 11 slides, 2012

Remediation of the Avenue coking works site in Chesterfield (UK) began in September 2009 and will be finished in late 2013. The nature of the contaminated materials on site—coal tar, creosote, PAHs, BTEX, mercury, and cyanides—requires the implementation of a combination of specially designed on-site treatment techniques: thermal desorption, bioremediation, complex sorting, and soil washing. Paper and Slides

Beazer East, Inc. (formerly Koppers Company, Inc.) (RCRA)
U.S. EPA Region 2
Contact: Alan Straus, 212-637-4160, straus.alan@epa.gov

An EI determination states that arsenic, SVOCs, and VOCs were detected in a shallow fill unit and a deeper glacial sand unit. The units are separated by a continuous layer of organic clay/peat and not hydraulically connected, and accordingly were treated separately. Free-product creosote DNAPL in the shallow fill was treated through soil excavation and stabilization with a 2-foot layer of cement/soil and 4-inch asphalt cover. A pilot study recovery well system was initiated in about 2001 to capture and remove DNAPL in the lower glacial unit, but it is unclear whether the pilot study has expanded or whether additional action was taken to address residuals in the deeper unit.

GCL Tie & Treating (Superfund)
U.S. EPA Region 2, Sep 2006
Contact: Monica Baussan, RPM, 212-637-4271, baussan.monica@epa.gov

This 30-acre sawmill site was used for wood treating, as well as light manufacturing. A 1986 tank failure caused a 30,000-gal release of creosote, which was addressed by excavation of soil and placing it in an on-site mound. Following removal actions, an early 1990s pilot study was conducted on bioremediation of creosote-contaminated soil. The 1994 ROD called for soil excavation and treatment via low-temperature thermal desorption, which went on-line in mid 2000. Treatment concentrations and volumes were discovered to be much higher during treatment, to twice the anticipated volume of soil. Treatment for OU2, addressing soil/sediment on the remainder of the site and surface/groundwater, began in mid 2004 and involves P&T via 8 wells and ex situ thermal desorption. DNAPL pools encountered during OU1 soil excavation were pumped and treated as part of OU1 activities. The site was a pilot SACM project, and underwent optimization evaluation in 2006.

Integrated Mass Recovery and MNA for RCRA Corrective Action
F. Coll, D. Gray, M. King, K. Paschl, and M. Brourman.
In Situ and On-Site Bioremediation 2003: Proceedings of the Seventh International In Situ and On-Site Bioremediation Symposium, 2-5 June 2003, Orlando, Florida.
Battelle Press, Columbus, OH. 2004

Source recovery using modified groundwater recirculation well technology and MNA initiatives were undertaken at an active creosote wood treater where creosote DNAPL is present between 90 and 100 feet below ground. In the early 1990s, source control and recovery interim measures at the site involved a single-phase pump-and-treat recovery system. Since 1998, more innovative source removal efforts were implemented with groundwater recirculation well technology to provide enhanced creosote DNAPL recovery. The enhanced recovery wells were designed for creosote DNAPL mass removal, as well as in situ soil flushing and source containment. Four enhanced creosote DNAPL recovery wells have been operating at the site with a cumulative mass recovery of over 550,000 pounds of creosote since 1998. The creosote DNAPL recovery wells have outperformed the previous pump and treat system at the site by many orders of magnitude in terms of mass recovery. Along with source area control, MNA data collected since 1998 have consistently shown a trend of plume reduction. These data substantiate the viability of DNAPL source management and MNA coupled with institutional controls as a remedial component to corrective action at the site.

A Pilot Study for the Extraction and Treatment of Groundwater from a Manufactured Gas Plant Site [abstract only]

Motco, Inc. (Superfund)
U.S. EPA Region 6, Mar 2007
Contact: Gary Miller, 214-665-8318, miller.gary@epa.gov

The 11-acre (plus off-site areas) former styrene-tar recycling site borders a coastal marsh and slopes toward the Gulf of Mexico at an elevation of 5 to 12 feet. The transmissive zone (TZ) and the Upper Chicot (UC) (clay) Aquifer underlie the site. Groundwater flows in the TZ Zone at 0.2 to 10 feet/yr. The UC Aquifer is located 90 to 230 ft below sea level. DNAPLs were found to 50 feet bgs, with estimated volume of 3 to 4 million gallons. MOTCO site DNAPLs are typically a dark brown-to-black viscous substance that consist of chlorinated aliphatic hydrocarbons, PAHs, aromatics, and ether organic constituents. The volume of contaminated groundwater is approximately 30 to 40 millions gallons. Contamination has migrated 300 feet off the property and is present to a depth of 100 feet. The final remedy includes soil capping and a slurry wall; off-site incineration of oils, sludge, and tar; P&T to restore the 2 aquifers; P&T to prevent lateral migration and maintain hydraulic gradient; recovery of DNAPL to the extent feasible; long-term monitoring; and institutional controls. DNAPL recovery began in 1995. Construction of the slurry wall, and excavation of off-site contaminated materials and consolidation occurred in 1995-1997. By December 31, 2005, 71.3 millions gallons of groundwater and 45,200 gallons of DNAPL were recovered. Progress also includes removal of 7,568 tons of oil, 8,000 tons of tar sludge, 4,699 tons of contaminated soil, and over 3.5 million gallons of contaminated pit water. The next 5-Year Review is due September 2007.

Remediation of a Former MGP Site in Norwich New York: a Case Study
Underhill, S.A., C. Floess, and T. Blazicek.
Proceedings of the 2012 Annual International Conference on Soils, Sediments, Water and Energy, Vol 17 Article 9, 89-93, 2013

MGP operations from the 1860s through the 1950s at a site in Norwich, New York, released contaminants to on-site and off-site soil and groundwater. Site remediation includes four phases of treatment: in situ solidification of on-site source materials; recovery of NAPL from off site; ISCO of off-site areas; and enhanced bioremediation of off-site groundwater. About 52,103 cy of affected sand and gravel were solidified in situ using auger mixing technology, and over 54,000 gal of NAPL were recovered. An ISCO bench-scale study indicated that four applications of hydrogen peroxide will reduce BTEX and naphthalene by 99% and TPH by 50%. Full-scale ISCO application will occur upon completion of NAPL recovery, followed by enhanced bioremediation of dissolved-phase contaminants (benzene and naphthalene).

Southern California Edison Co. (Visalia Poleyard)
Contact (2007): Emmanuel Mensah, State of California, EMensah@dtsc.ca.gov, 916-255-3704

The 20-acre site was operated as a utility pole treatment yard from the 1920s until 1980, and approximately 275,000 poles were treated at the site. Wood preservatives, including 2,500,000 gallons of creosote and 900,000 gallons of pentachlorophenol, were used and stored on site during site operations. In 1977, a slurry wall was built to slow contaminant migration in the shallow aquifer. Southern California Edison, the potentially responsible party, removed all facilities and 2,300 cubic yards of contaminated soil and disposed of it off site at an approved disposal facility. The site has a subsurface barrier wall and a groundwater extraction and on-site treatment system. Starting in 1997, a pre-design pilot-scale steam injection system was installed. It injected over 100,000,000 pounds of steam, which greatly enhanced recovery of pole-treating chemicals. In addition, a full-scale steam injection system was used over a 30-month period to remove and destroy over 150,000 gallons of contamination from the site. Once the subsurface temperature dropped below 70°C, vadose zone bioventing and saturated zone biosparging operated with continued groundwater pump and treat from June 2000 until March 2004. Following the 2005 5-year review, contaminated surface soil to 10 feet below grade was removed in July 2006 and verified with confirmatory sampling to be below the prescribed cleanup standards. The final site closeout report was signed on May 19, 2009. Additional information: In Situ Destruction of Contaminants via Hydrous Pyrolysis/Oxidation: Visalia Field Test (1998); Innovative Technology Summary Report: Hydrous Pyrolysis Oxidation/Dynamic Underground Stripping (2000).