Dense Nonaqueous Phase Liquids (DNAPLs)
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Direct and Multiphase Recovery
American Creosote Works, Inc., Winn Parish, Louisiana
Contact: Michael A. Hebert, U.S. EPA Remedial Project Manager, email@example.com, 214-665-8315
Wood treatment operations have occurred at the site for over 80 years. During this time, spills, runoff, and possibly discharges contaminated areas of the site. Site investigations focused primarily on creosote, PCP, and the contaminated petroleum carrier fluids used in site operations. The contamination includes flowable DNAPL.
The site is underlain by the Prairie Terrace deposits, which are unconsolidated and poorly bedded. They consist of a mixture of gravel, sand, and silt. The Prairie Terrace deposits are up to 25 ft thick at the site, and the deposits exhibit a fining upward grading. Gravels are common at the base, and sandy to clayey silt is common in the upper 10 ft. The Prairie Terrace deposits lie unconformably on the Cockfield Formation forming a wedge that thins to the south. The Cockfield Formation consists of lignitic shales interbedded with silty sands.
The remedy included the installation of 18 vertical extraction wells to capture groundwater and DNAPL and two interception trenches to convey the DNAPL to sumps that pumped to a treatment unit. The fluids recovery system, process liquids treatment system, and in situ bioremediation system have been operational since October 1996. From October 1996 through April 2005, approximately 46,600,000 gallons of groundwater and 138,000 gallons of NAPL have been extracted and treated. Approximately 20,830,000 gallons of treated effluent has been discharged to Creosote Branch Creek in that time, and approximately 23,560,000 gallons have been injected back into the aquifer through the in situ bioremediation system. The remainder of the treated effluent is used by a bio-cell constructed on top of the waste cell as part of the biosolids management program. Approximately 500,000 gallons of groundwater and 1,800 gallons of NAPL are extracted from the aquifer each month.
American Wood, Inc., Richton, Mississippi
U.S. EPA, Region 4 RCRA program
This 26-acre facility uses creosote and pentachlorophenol to treat wood. Operations have resulted in three plumes at the site. Two dissolved-phase plumes (deep and shallow) are migrating to the south/southeast. A DNAPL plume follows the dip of low permeability lenses associated with the Hattiesburg-Citronelle Terrace contact. The DNAPL plume was contained by putting two recovery wells at its leading edge and directly pumping the free-phase creosote.
The Bayou Bonfouca Superfund Site occupies 54 acres near the north shore of Lake Pontchartrain in Slidell, St. Tammany Parish, Louisiana. Commercial operations involving the treatment of wood products with creosote began about 1892. Numerous releases of creosote occurred during the years of operation resulting in eight highly contaminated creosote areas at the site.
Seven stratigraphic layers, including interbedded sands, clays, and silts were encountered in the first 60 ft. Three groundwater systems were encountered, including a surficial aquifer, a shallow artisan aquifer at 30 ft, and a deep artisan aquifer at 60 ft. The elevation of the 100-year floodplain, which would inundate the site, is at 9 ft mean sea level.
Extraction wells were installed as part of the remedy to remove contaminated water and flowable DNAPL. The number and placement of the wells have changed over time but from June 1991 through January 31, 2006, 34,258,255 gallons of groundwater have been extracted and treated, and 71,037gallons of free-phase creosote have been recovered.
Cape Fear Wood Preserving, Fayetteville, North Carolina
Contact: Jon Bornholm, U.S. EPA Remedial Project Manager, firstname.lastname@example.org, 404-562-8820
Cape Fear Wood Preserving began operations at the site in 1953 and continued until 1983. The facility produced creosote-treated wood from 1953 until 1978 when demand for creosote-treated products declined. The site is contaminated with creosote related chemicals. A DNAPL creosote mass exists in the subsurface.
The site is underlain by intermittent beds of sands, clays, and sands in clay matrices. One distinct clay to silty/sandy clay semi-confining unit, however, was identified. This unit divides the subsurface down to a depth of approximately 90 ft into two water producing zones. The upper aquifer consists of unconsolidated sands and clays and is approximately 25 ft thick. The lower aquifer also consists of sands and clays and is approximately 50 ft thick. Separating the aquifers is a clay to silty, sandy clay semi-confining unit, approximately 16 ft thick, which acts as an aquitard. This unit is generally continuous across the site, but was reported missing in one location.
Three extraction wells were installed as part of the remedy to address the DNAPL. The wells contain both water and DNAPL pumps. In addition, a french drain, which also has a dual pump system, was installed. The drain itself is 80 ft long and about 25 ft below grade. Three fingers extend from the main drain—one at each end of the drain and one emanating from the standpipe. These fingers were added to the french drain to increase its influence in the underlying subsurface environment. The two primary goals for installing this drain were to enhance the removal of DNAPL emanating from the west-northwest and the west-southwest side walls of the excavation and allow the elimination of a significant number of extraction wells called for in the 1990 ROD. As of 2006, approximately 12,500 gallons of DNAPL have been removed.
This 12-acre site was used for manufacturing creosote-treated wood products. Prior to 1985, wood preserving wastewater generated by the Garland Creosoting facility was treated and discharged to five surface impoundments for evaporation. The stratigraphy at the site consists of a complex sequence of interbedded clays, silts, and sands that can be laterally discontinuous over relatively short distances. The stratigraphy has been categorized into the Upper Clay, Silt/Sand, and Glauconitic Clay units. Groundwater occurs between seven and 12 ft bgs.
Free-phase product was identified during the site investigation. In addition to other remedial technologies, an interception trench has been placed between the site and an adjacent stream. The interception trench collects contaminated water and flowing DNAPL for on-site treatment and off-site disposal respectively.
The HCC Site is about 23 acres in size and lies predominantly within a wooded area with light industrial, commercial, and recreational land use. The site is underlain by alluvium composed of varying proportions of clay, silt, and sand size material extending to depths up to 220 ft. The subsurface geology was grouped into three low-permeability and three permeable zones. Groundwater occurs 8 to10 ft bgs.
Wood treatment operations, which used a steam preconditioning and pressurized creosote process, began in 1958 and ended in May 1993. Between 1958 and 1977, creosote waste from treatment operations was managed in six unlined surface impoundments (ponds). Around 1977, these ponds were reconfigured into four ponds and used until November 1985. Free product exists in the subsurface. Vertical pumping wells were chosen in the ROD to address the flowable creosote.
Wood treatment operations were performed at the 11-acre site between 1946 and 1986, using a steam preconditioning and pressurized creosote and PCP process. Creosote and PCP (dissolved in a diesel carrier fluid) were stored in the northern part of the facility in aboveground storage tanks (ASTs). Three treatment cylinders, adjacent to the tanks, were employed for creosote or PCP wood treatment. Wood products, typically utility poles and railroad ties, were placed in a cylinder for several hours of pressurized steam preconditioning. The cylinder was then placed under vacuum to remove air, wood sap, and water from the wood. Potential contaminant sources present at the site, following abandonment in 1992, included a drip pad, deteriorating ASTs, contaminated treatment cylinders, wastewater holding tanks (impoundments), filter boxes, cooling towers (heat exchanger), storage containers, an incinerator, and contaminated soil associated with spills and leaks.
The site is underlain by alluvium composed of varying proportions of clay, silt, sand, and gravel-size material extending to depths of 150 ft. The subsurface geology was grouped into three primary strata. Two permeable zones are separated by a low-permeability zone that pinches out near the southeast margins of the former process area. The discontinuous nature of the low permeability layer at this location and potentially elsewhere could facilitate contaminant transport to deeper areas on the site.
Extraction wells were chosen in the ROD to remove flowable DNAPL to the extent practicable.
Koppers Company Inc. Texarkana Plant, Texarkana, Texas
Contact: Charles David Abshire, U.S. EPA Remedial Project Manager, email@example.com, 214-665-7188
The 62-acre Koppers (Texarkana Plant) site is a former wood treatment facility located in Texarkana, Texas. The site consists of a 34-acre residential area and a 28-acre former sand and gravel operation. The entire site lies within a 100-year flood plain. From 1910 to 1961, the Koppers Company treated wood onsite using PCP, creosote, and metallic salts. After on-site operations ceased in 1961, the structures were removed and the property was sold for residential and industrial development.
The subsurface consists of 24 ft of thick coarse sand and gravel graded with fine sand and silt, followed by a 26 ft thick layer of interbedded clay and sand, which is underlain by a 25 ft thick sand and silt unit. The remedy calls for extraction wells fitted with two pumps—one for groundwater and the second only for DNAPL—to remove the flowable DNAPL at the site.
Madisonville Creosote Works, St. Tammany Parish, Louisiana
Contact: Laura Stankosky, U.S. EPA Remedial Project Manager, firstname.lastname@example.org, 214-665-7525
The 29-acre site consists of a former wood treating facility. Wood preserving operations at the site began in 1956 or 1957 under the name of Madisonville Creosote Works, Inc. During its operation, the site facility treated telephone poles, railroad ties, and lumber by impregnating the wood with creosote in retort cylinders under elevated temperature and pressure. The site has extensive subsurface contamination, including flowable DNAPL.
The stratigraphy beneath the site consists of surface soils or fill materials from about ground surface to 2 ft bgs; shallow clayey-silt from about just below surface soils to 25 ft bgs (the first saturated zone is located within this matrix);intermediate clay/peat from approximately 25 to 30 ft bgs; intermediate silt from approximately 32 to 35 ft bgs (the second saturated zone is located within this matrix); and deep silty-clay from approximately 35 to 80 ft bgs (the third saturated zone before the shallow aquifer is located within this matrix).
The remedy selected included the placement of an interceptor trench along the down dip side of the DNAPL plume. The DNAPL collection system was designed to be a passive collection system wherein each pump would not operate until DNAPL had collected to a predefined level in each pump's sump. To date the system has collected over 2,000 gallons of creosote.
McCormick & Baxter Creosoting Company Superfund Site, Portland, Oregon
Contact: Peter Contreras, U.S. EPA Remedial Project Manager, email@example.com, 206-553-6708
Kevin Parrett, Oregon Department of Environmental Quality Project Manager, firstname.lastname@example.org, 503-229-6748
- Record of Decision
- Five-Year Review
- Oregon Department of Environmental Quality McCormick & Baxter website
The McCormick and Baxter site is a former wood treatment facility located on the Willamette River in Portland, Oregon. The site encompasses approximately 43 acres on land and 15 acres in the river. Wood treatment operations were conducted on the site between 1944 and 1991. Wood treating products used at the site include creosote/diesel oil mixtures, PCP/diesel oil mixtures, and a variety of water- and ammonia-based solutions containing arsenic, chromium, copper, and zinc.
Three hydrostratigraphic units are present at the site: the shallow, intermediate, and deep aquifer zones, which are interconnected to varying degrees depending upon the location within the site. The shallow zone consists of poorly-graded dredge-fill sand and wood debris; it ranges in thickness from 5 ft to greater than 30 ft. In parts of the site, the shallow zone consists mostly of sawdust and wood chips up to 20 to 25 ft thick. The shallow zone acts as an unconfined aquifer that is in hydraulic connection with the river. This connection, however, significantly diminishes toward the bluff and within the barrier wall area. Depth to groundwater ranges from approximately 20 to 25 ft bgs. In much of the site, the shallow zone is underlain by a silt aquitard, ranging in thickness from zero near the river to greater than 100 ft closer to the bluff.
Two of the three flowable DNAPL plumes at the site discharge into the Willamette River. A barrier wall was constructed to cut off flow to the river. The site has a number of passive extraction wells that are periodically monitored for the presence of DNAPL. Approximately 6,100 gallons of DNAPL has been recovered.