December 11, 1996
Field Trip to Denver Federal Center
Meeting participants were provided an opportunity to visit the Denver Federal Center, CO. Rick Cushing (Federal Highway Administration [FHA] ) led a tour to see the funnel and gate (F&G) system installed at the Denver Federal Center. The F&G system was also discussed during the second day of the meeting.
December 12, 1996
Welcome and Introductions
Dale Schultz (DuPont), co-chair of the Action Team, welcomed participants to today's meeting and thanked Bob Stone (EPA/Region 8) for hosting the meeting. Dale noted that there was a significant number of newcomers to the Action Team meeting. He also thanked Rick Cushing for providing the tour of the Denver Federal Center F&G system and noted that he, and a few other persons involved with the site, will provide an overview for those who were unable to attend yesterday's field trip.
Overview of the Denver Federal Center
Rick Cushing provided an overview of the Denver Federal Center, focusing on the portion of the Federal Center affected by the installation of the F&G system. The Denver Federal Center is located in Denver, CO, approximately 10 miles from downtown Denver. A site assessment indicated that elevated levels of chlorinated solvents are present in the groundwater. The compounds of concern are trichloroethane (TCA), trichloroethene (TCE), and dichloroethene (DCE). The remediation efforts are targeted to reduce the contaminant levels in the groundwater and to minimize the likelihood of off-gassing. A leak in an underground storage tank (UST) is believed to be responsible for the elevated solvent levels. Rick did note, however, that additional probable source areas have been located since the leaking UST was discovered.
The General Services Administration (GSA), the managing body of the Federal Center, is performing a site-wide investigation to identify any additional areas of concern. The depth to groundwater is 16-25 feet and an impermeable blue/gray groundstone layer (Denver formation) is located 23-30 feet below the surface. Rick indicated that TCA is present at 200 ppm and also noted that TCE contaminant levels are higher downgradient of the identified source area than at the source area itself, suggesting that there are additional sources of TCE. Rick indicated that there are anomalies in the DCE data collected that also suggest additional sources; possibly the same sources supplying additional TCE. Rick indicated that the Colorado Department of Health and Environment (CDHE) was concerned with offsite migration of contaminants, especially TCA. There are 5 domestic drinking wells and 17 irrigation wells that could be affected by offsite migration of contaminants. Rick indicated that monitoring wells have been installed to identify any offsite migration- monitoring wells near the drinking wells are monitored monthly; and monitoring wells near the irrigation wells arc monitored quarterly.
Selection of the F&G System. A pump and treat
(P&T) system was initially proposed to remediate the TCA plume. However,
the pump test that was performed, achieved only a 12.5 foot radius of
influence. Due to the width of the plume, a significant number of extraction
wells would be required, which would have been costly. The CDHE indicated that
the plume must be contained, but agreed to consider any remediation technique
that would meet that end. The USACE's Rapid Response Division, IT Corporation,
GSA, FHA, and other interested parties identified the following list of
potential remediation techniques for consideration:
Each option under consideration was evaluated by the following parameters:
A F&G system was selected, and it was determined that the F&G system would need to be 1,100 feet long to contain the plume. Construction on the F&G system was completed in October 1996, and was overseen by the USACE.
Installation. Dan Gravelding (IT Corporation) provided commentary on the site characterization and installation of the field system. Dan indicated thee the implementation of the F&G system proceeded in three stages: (1) data gathering, (2) data analysis, and (3) construction. The data gathering included emplacement and subsequent monitoring of wells, piezometers, cone penetrometers (CPTs), and aquifer testing. The CPT efforts were performed to obtain more detailed information on the lithology and to determine an estimated depth of refusal from the CPT tip pressure. The placement of gates was determined by groundwater flow paths- four gates, each approximately 40 feet wide, were installed over the length of the wall. Dan indicated that determination of the groundwater flow velocities proved problematic and also noted that hydraulic conductivities determined from pump tests exceeded estimates from slug tests by factors of two to six. The residence time, which was used to aid determination of the gate thickness, was based on bench-scale column tests performed by EnviroMetal Technologies Inc. (ETI) . Four gates were emplaced, and their associated thicknesses are depicted in the table below.
| Gate | Gate Thickness (Ft) |
|---|---|
| 1 |
6 |
| 2 |
4 |
| 3 |
2 |
| 4 |
2 |
Dan noted that, due to the lithography, the trench was excavated to 2 feet below target depth. The funnel walls, composed of sheet pilings, were then installed and the trench was backfilled to secure the funnels. A 60,000-lb vibratory hammer was used to set the sheet piling and a 100,000-lb vibratory hammer was used to drive the sheet piling to depth. Dan indicated that there were some difficulties flushing the joints of the sheet pilings. They used the lighter vibratory hammer to shake the sheet piling/joint slightly, in conjunction with the flushing system to expedite flushing of the joint. Dan indicated that a gate template. 40 ft x 10 ft x 25 ft, was tack-welded to the sheet piling to ensure that the gate retained its shape. The gate area was excavated to a depth of 47 ft by use of a backhoe- Dan indicated that other excavation techniques were considered, such as a clamshell, but that the chosen method was the most suited tothe lithography.
Compliance and Performance Monitoring Peter McMahon (USGS) provided a brief synopsis of the compliance and performance monitoring efforts in support of the F&G system. Peter indicated that monitoring wells were emplaced up- and downgradient of the F&G system. as well as in each of the four gates. Monitoring wells are sampled either biweekly, monthly, or quarterly, dependent upon their location. Peter indicated that volatile organic compounds (VOCs), field parameters, iron in groundwater. hydrogen gas. and other parameters are being measured. Some of these activities are not in direct support of compliance or performance monitoring, but have been undertaken for research purposes. Four wells were emplaced within each of the gates. Peter indicated that efforts will be undertaken to achieve mass balance. Monitoring data collected since the F&G was installed suggest that the plume is being both contained and remediated as designed. Peter did note, however, that contaminant levels do rebound downgradient due to desorption from the aquitard.
Update on Elizabeth City, NC Study
Bob Puls (EPA/NRMRL), co-chair of the Action Team, provided an update of ongoing studies at the United States Coast Guard Support Center (USCG) in Elizabeth City, NC. Bob acknowledged the participation of the University of Waterloo. the U.S. Coast Guard, and the State of North Carolina in the efforts at USCG. Bob reminded participants that the USCG is located on the southern bank of the Pasquotank River. The demonstration site, outside of Hanger 79 at USCG, is approximately 60 meters from the river and was used for more than 30 years as a chrome plating shop. Acidic chromium wastes and associated solvents were discharged through a hole in the concrete floor A pilot test was begun in 1994 and has been monitored over the past 2 years. Based upon the success of the pilot study, a full-scale effort was emplaced in June 1996. Two major plumes have been targeted in the full-scale effort- a chromate plume and a smaller chlorinated solvents plume. The objective is to reach regulatory limits for Cr(VI), TCE, cis-DCE, and vinyl chloride (VC) (see table below).
| Contaminant | Regulatory Target (ppb) |
|---|---|
| Cr(VI) |
50 |
| TCE |
5 |
| DCE |
20 |
| VC |
2 |
The emplaced iron wall was 50m x 8m x 0.6m, required approximately 500 tons of Peerless iron, and cost about $300-350K to install. Bob provided a video of the continuous trench installation. Two days were required for installation, but Bob noted that much of this was for preparation. The width of the trench was based upon column studies by ETI and is wider than necessary to provide a safety factor. Bob noted that a 4 foot-deep channel was cur into the subsurface, through the concrete parking lot, before the trench was dug. In hindsight, Bob believes that the channel may have been problematic as it may have contributed to failure of the concrete under the weight of the trencher, approximately 60-80 tons, which added to site restoration costs. A continuous trench was chosen because it was the least expensive configuration, one-third the cost of a F&G system, expected to remediate the plume. John Vogan (ETI) added that modeling suggested that underflow would occur in a F&G configuration. Bob concurred. and mentioned that there were concerns regarding the effect upon nearby buildings if a vibratory hammer were to be used to emplace sheet pilings. Bob noted that although the trench and many of the monitoring wells were installed in June 1996, the installation of the monitoring system was completed only recently due to logistical complications. Data collected to date have not indicated the presence of chromate downgradient of the trench or in any of the multi-level samplers in the wall, the first of which is a few inches into the wall. This suggests that the chromate is rapidly remediated by the iron. Boo believes that these results are encouraging and also noted that the thickness of the wall was dictated by the chlorinated solvents; therefore, chromate would not be expected to be detected very far into the wall. Bob also noted that scanning electron microscopy (SEM) has been performed on iron samples taken from the wall, and that chromate oxide precipitation is not detectable on the surface of the iron samples, which is also encouraging.
Emplacement Alternative for Permeable Barrier Systems
James Cramer (Nilex) provided an overview of alternative emplacement techniques that may be suitable for emplacement of a permeable barrier system. James indicated that Nilex is involved in a number of emplacement projects, many of which stemmed from wick-drain technology. Wick drains have been traditionally employed by civil engineers to consolidate subsurfaces with an undesirably high-water content. Wick drains may be emplaced as deep as 190 feet and are installed with heavy machinery. James indicated that a large number of wick drains may be installed quickly, and that three emplacement rigs are often used at a site for expediency. The drains are emplaced in a steel casing when driven into the subsurface. The casing is then removed leaving the drain in place.
James indicated that wick drains were emplaced in support of the RTDF
Lasagna™ Partnership's Phase l field study at DOE's Paducah Gaseous
Diffusion Plant (DOE's PGDP). in Paducah, KY. In support of Phase 2a, a mandril
was employed to emplace a treatment zone- the mandril is a hollow tube with a
sacrificial drive shoe that is pushed to depth. Once pushed to depth, the
hollow tube is then filled with the reactive media and removed, leaving the
reactive media in the subsurface. In Phase 2a, the treatment zones were
emplaced to a depth of 45 feet, necessitating a modification of the equipment
used for Phase l a, which emplaced materiels to a shallower depth.
Approximately 9 minutes were required to push the mandril to the 45-foot depth.
He noted that the mandril technology has a number of advantages, including:
In response to a participant's, question, lames indicated that a mandril may be driven through many subsurfaces. As a rule of thumb, he suggested that a mandril could be emplaced so long as a CPT could be emplaced in the same area. He noted that the mandril was driven through clay at DOE's PGDP. James indicated that the permeability of the surrounding subsurface is typically lowered due to densification. In response to a participant's question, James stated that the seismic energy of the vibratory hammer used to drive the mandril is dispersed quickly, such that they have emplaced mandrill near buildings and other surface structures. It typically costs approximately $150K for mobilization and $15-45K/ft² for emplacement.
Update on Studies at Somersworth Sanitary Landfill
John Vogan (ETI) provided a brief update on the studies at the Somersworth
Sanitary Landfill in Somersworth, NH. John reminded participants that elevated
levels of VOCs are found in the groundwater. Modeling studies suggest that a
low ratio of funnel to gate would be desirable. John noted that the groundwater
flow rate is relatively high (2 feet/day). Based, in part, on the flow rate, a
residence time of 1 day was identified. A number of different materials were
considered to compose the funnel and gate, including:
In view of the cost-savings, the third configuration was chosen and installation began during the middle of November 1996. The target depth of the system was 40-45 feet; John indicated that emplacement of the caisson, 8 feet in diameter, has proved problematic. The caisson was temporarily refused at a depth of 35 feet; however, the caisson was able to be pushed to depth successfully. There have been complications removing the caisson- John indicated that 13.5 tons of iron were put into the hole created by the caisson, but that the caisson was subsequently unable to be removed. A number of alternatives have been considered, including using equipment with greater power (which would increase the cost by an additional $30-40K) and cutting off the bottom section of the caisson. Removal of the caisson is still in progress and John will provide an update on progress at the next Action Team meeting.
[Since the time of the meeting, John reported that concrete was added to seal off the bottom of the caisson, and the caisson was then cut dust above the top of the materials (concrete, iron, and gravel) already placed in the caisson (i.e., approximately 12 ft from the bottom of the caisson). The metal frame supporting the monitoring devices was removed and reinstalled after modifying the monitoring well intervals to account for design modification. Iron was added to the caisson, and the caisson was successfully removed using a vibratory hammer.]
Hydraulic Fracturing as Emplacement Technique for Permeable Iron Reaction Barriers
Grant Hocking (Golder) provided an overview of hydraulic fracturing techniques used to emplace permeable iron reaction barriers. Hydraulic fracturing was originally developed by the petroleum industry to maximize collection of petroleum products from the subsurface. Grant indicated thee hydraulic soil fracturing may create either horizontal or vertical fractures, dependent upon the application. Fracturing techniques now allow for "frac and pack" applications whereby a fracture is created and then subsequentlyfilled with a proppant, such as an iron-based material, to fill the fracture and create a permeable wall. The hydraulic fracturing technology is able to make permeable walls of limited thickness, but is not limited in depth.
Grant indicated that the fracture typically follows the principal stress
direction. He noted that the principal stress direction can be
overridden in some geologies, such as those composed of brittle rock. The
initiation of the fracture is critical to the placement and integrity of the
fracture-emplaced wall. Grant indicated that it is easier to control vertical
fractures than horizontal ones. Fractured walls are typically 0.5 - 0.75 inches
in width, but may be emplaced up to 8 inches in width. Grant indicated that a
uniform thickness is achieved over 80% of the wall. The fracking fluid is
typically composed of the following:
Reactive materials such as iron can then be added as desired. Grant indicated that a pilot study will be performed at Otis AFB, MA, with the University of Waterloo. Rich Steimle (EPA) expressed some concern regarding the integrity of the wall. Grant acknowledged that this in an important consideration. and indicated that geophysical verification is needed. He indicated that multilevel sensors will be emplaced every 10 fee: along the length of the wall at Otis AFB. Grant also indicated that electrical verification methods are an option.
Funnel and Gate Cost Analysis
Ken Quinn (Montgomery and Watson) discussed costs associated with funnel and gate systems. Ken focused upon the costs associated with the gate, and suggested that a "partially penetrating" gate may be more cost-effective in many situations. A partially-penetrating gate is one which does nor cover the entire height of an aquifer, but, typically addresses the portion of the aquifer with the highest conductivity. Ken indicated that partially penetrating gates may be preferable in a stratified system where low and high conductivity regions exist. The lower region may be sealed from the higher conductivity region, where the partially-penetrating gate is emplaced. Ken indicated that bentonite or cement grout may be used as the lower sealing material. The partially-penetrating gate will be of smaller volume than a fully-penetrating gate and will, therefore require less reactive media. Ken indicated that the gate becomes more of a "window," in that groundwater is funneled into it both horizontally and vertically. Ken noted that the partially-penetrating gate may be thicker than a corresponding fully-penetrating gate, but the former is expected to be of appreciably smaller volume than the latter.
The figure below illustrates the estimated cost savings of using a partially-penetrating gate. The costs presented are based upon a $450/ton of iron, iron density of 3.18 ton/m³, gate width of 4 meters, height of 12 meters for the fully-penetrating gate, and 3 meters for the partially-penetrating gate.
Ken noted that the cost savings may be expected to be higher than those depicted in the figure, if either larger gates are be used or multiple-gates are used. both of which would increase the cost savings. Ken did note that the savings will vary dependent upon the geologic conditions, hydraulic conductivity contrasts, groundwater velocities. and concentrations at each site.
Nickel-Iron as Reactive Material
Tim Sivavec (GE) and Bob Gillham (University of Waterloo) provided overviews of column studies they have, independently, performed to investigate nickel-iron as an enhanced reactive material for the degradation of chlorinated solvents. Tim indicated that GE's column studies focused on the degradation of TCE, and he provided the following data on enhanced reaction media:
| Reactive Media | Relative Reaction Rate | Cost ($/ton) |
|---|---|---|
| Iron (control) |
1.0 |
325 |
| 0.5 mol % Cu |
1.9 |
350 |
| 0.5 mol % Ni |
5.6 |
380 |
| 0.5 mol % Pd |
45.0 |
65,000 |
Tim suggested that the enhanced reactive media follow a different mechanism than straight iron, which accounts for the increased degradation rate and also suggested that these enhanced rates are not sustained over the life of the reaction media. The straight iron appears to degrade chlorinated solvent in a step-wise progression. i.e., TCE- DCE- VC- ethene- ethane. Tim suggested that, in the presence of the enhanced media, TCE degrades by way of a different mechanism, which does not generate the daughter products, i.e., TCE- chloroacetylene- acetylene- ethene- ethane. Tim believes that this is a preferred pathway as DCE and VC are not generated during the degradation.
Tim indicated that GE recently performed column studies investigating nickel-iron as an enhanced media He indicated that a loss of reactivity was seen over the duration of the study, such that, at the end of the study, the reaction rate was similar to that of straight iron (see table below):
| Pore Volumes | Half-Life (min) | Relative Rate |
|---|---|---|
| 0-76 |
16 |
1.0 |
| 77-108 |
28 |
0.57 |
| 109-148 |
40 |
0.4 |
| 149-206 |
71 |
0.29 |
| 207-250 |
106 |
0.16 |
Tim noted that DCE and VC were not detected in the early stages of the
column study, but were detected in the later stages, suggesting that a shift in
the dominant reaction pathway occurs. Tim indicated that leaching of the nickel
is not observed, but that precipitates are observed on the iron surface. He
speculated that this may be causing the reduced reaction rate. Tim provided the
following summary comments regarding nickel-iron as an enhanced reactive
material:
Bob Gillham indicated that the University of Waterloo also performed column studies investigating nickel-iron as an enhanced reactive media. and used an experimental design similar to GE's. However, Bob indicated that a loss in reactivity was not seen in these column studies. He indicated that the reactivity, which was observed to be 30x faster than that of iron, was maintained over 2,400 pore volumes. Bob did note, however, that no daughter products were detected, which is in agreement with Tim's conclusion regarding reaction mechanisms.
Bob also briefly discussed an above-ground canister remediation study that
has been in operation since October 1994, which uses nickel-iron as the
reactive media. Perchloroethene (PCE; 10,000 µg/L) and TCE (400
µg/L) are the primary contaminants of concern. Bob indicated that the
laboratory tests using nickel-iron were encouraging. Two tons of nickel-iron
were used at $2,600/ton. Bob indicated that the system has not been performing
at design expectations, and suggested that this may be due to:
Bob indicated that he is jointly investigating nickel-iron with the Idaho National Engineering Laboratory (INEL). A column study using nickel-iron is underway, and that after 280 pore volumes, no enhanced rate has been observed. However, Bob believes that this system is still preferable to that of straight iron because daughter products are not observed. In summary, Bob suggested that it is premature to form any definitive conclusions on the utility of nickel-iron as an enhanced reactive media.
Hydraulic Modeling of Funnel and Gate Systems
George Korfiatis (Stevens Institute of Technology) provided a brief overview of efforts at the Stevens Institute of Technology to model F&G systems. George stepped through a funnel modeling effort, and provided comments on the methods employed and parameters typically investigated to model a F&G system. He indicated that the ratio of the maximum velocity (Vmax) to the minimum velocity (Vmin) traveling through the gate should equal one, which indicates a uniform flow through the gate. Modeling suggests that extending the gates up- and downgradient of the reactive zone will drive Vmax:Vmin towards one. Modeling also suggested a wing-wall angle of 60° provided the greatest ration of Vmax versus Vmin.
George indicated that modeling efforts were used in conjunction with a field effort to remediate BTEX compounds in a creek. The site has soil with low permeability and the depth to the aquifer is 10-25 feet. Preliminary experimental results suggested a residence time of 2 days. A 4 foot long reactor was designed to determine the efficacy of the permeable barrier design to be used in the field. George indicated that 95% of the BTEX compounds were reduced in the first 4 inches of the reactor, which was encouraging. Field efforts began two weeks ago, and results from the field effort are not yet available.
Overview of Cape Canaveral, FL Pilot Study
Ed Marchand (AFCEE) provided a brief overview of a permeable barrier system to be installed in the vicinity of Hanger K at the Cape Canaveral Air Station. FL. The system is expected to be installed in 1997 and Ed indicated that a number of design parameters have not been finalized. The system will remediate a chlorinated solvents plume containing TCE (90 mg/L) and DCE (170 mg/L). A continuous wall is expected to be installed by use of a mandril and will be 50-feet long, 4-inches wide, and 60-feet deep. Ed indicated that the depth to groundwater is 5 feet and that the seasonal groundwater flow direction varies such that the wall orientation has not vet been established. Ed hoped that he would be able to provide additional details on the study at a future Action Team meeting.
Update on Dover AFB, DE Demonstration
Dennis O'Sullivan (Air Force) provided a brief status update on the
Strategic Environmental Research and Development Program (SERDP) demonstration.
to be conducted at Dover AFB, DE. He noted that the RTDF Permeable Barriers
Chlorinated Solvents Design Team met yesterday, December 11,1996, and further
discussed the draft Permeable Barriers Design Protocol, and the demonstration
design. Dennis identified the following steps in the development of the
protocol:
An objective of the SERDP demonstration is to compare reactive media- Dennis noted that the selection of reactive media to be compared has been discussed at length, and that consensus has not yet been reached. He also indicated that an innovative emplacement technique, jetting, is expected to be used to emplace the funnel walls and one of the gates. Additional site characterization is expected to be completed by March 1997, and construction should begin by July/August 1997. Dennis noted that monitoring efforts are only expected to continue for 18 months after the system is in place. He indicated that there is interest among the Design Team to obtain funding to extend the monitoring efforts beyond this period. The lessons learned from the SERDP demonstration are expected to be incorporated into the design protocol.
Interaction Between Iron and Microbial Communities
Tony Palumbo (ORNL) briefly discussed interactions between iron and
microbial communities. He acknowledged Tom Phelps (ORNL), a colleague, who was
involved in the efforts to be discussed. The ORNL efforts endeavored to
determine the role of microorganisms in iron reactive zones, especially their
role in precipitation/clogging of reactive zones. He indicated that column
studies were performed using iron as the reactive media. Microbial populations
were seen to increase in the column study, as did pH and hydrogen gas. Clogging
was also seen in the columns and Tony indicated that the formation of a 2 inch
crust clogged the system. Clogging due to precipitation is one of the limiting
factors of the longevity of a permeable barrier system. Tony suggested the
following potential solutions to increase the longevity of a permeable barrier
system:
Collaborations Between the RTDF and the ITRC
Matt Turner (NJ-DEP) provided an overview of the Interstate Technology and Regulatory Cooperation (ITRC) Work Group. He indicated that the ITRC is a state-lead organization that fosters interstate acceptance of demonstration projects. provides guidance technology development and encourages dialog on interstate development of innovative technologies. Stakeholder, tribal, and industry representatives participate in the ITRC, which was formed in February 1995. Industrial participants are not ITRC members per se, but they are involved in most facets of the ITRC. There is participation from the 27 states listed below, and Matt indicated that additional states are being encouraged to join:
| Arizona |
Kansas |
Nevada |
South Dakota |
Six states (indicated by an asterisk above) have entered into a Memorandum
of Understanding (MOU) to accept field data generated within any one of the
other five states to promote technology transfer. The ITRC works actively with
a number of federal agencies, including the Department of Energy (DOE),
Department of Defense (DOD), and EPA. Several task groups have been formed
since the inception of the ITRC. with the following focus areas- low
temperature thermal desorption, in-situ bioremediation, plasma
technology, site characterization, permeable barriers, and site
characterization and analysis penetrometer system (SCAPS). Matt identified the
following outputs of the existing focus groups:
Seven states- New Jersey, New Mexico, California, Nebraska, Utah, Louisiana, and Idaho- co-signed the SCAPS report.
The ITRC Permeable Barriers Work Group, formed in October 1996, currency has the following participants:
| Colorado |
New Jersey |
The ITRC Permeable Barriers Work Group will: (1) develop regulatory requirements for permeable barrier systems, (2) participate in the development of the Design Protocol for Permeable Barriers to Remediate Chlorinated Solvents, under development by the RTDF Permeable Barriers Chlorinated Solvents Design Team. and (3) study/observe the stare of the technology. Matt indicated that ITRC members have participated in past Design Team meetings and have provided initial feedback on the protocol. They will soon begin work in the development of regulatory requirements for permeable barrier systems. He speculated that a draft of the regulatory requirements will be available by May 15, 1997. The draft will be provided to parties outside of the ITRC, such as the RTDF, for comment. Mart suggested that the regulatory requirements could be incorporated into the Design Protocol as appropriate.
In addition to the newly formed Permeable Barriers Work Group, additional ITRC groups will be formed to facilitate the integration of state efforts across working groups review innovative state programs, and increase electronic transfer of information. The next meeting of the ITRC will be held in Albuquerque, NM, on January 22-23, 1997.
Update on Dithionite Field Studies at Hanford, WA
John Fruchter (PNNL) provided an update of studies at Hanford, WA, which are investigating the use of dithionite to manipulate in-situ redox conditions. Aquifers are often oxidizing environments and many contaminants are mobile only under these conditions. An objective of in-situ redox manipulation (ISRM) is to immobilize or destroy contaminants that migrate into the manipulated zone. John indicated that sodium dithionite (Na2S2O4), which dissociates into sulfoxyl radicals, interacts with the iron in the subsurface:
SO2 - + Fe(III) + H2O=SO32- + Fe(II) + H+
By changing the oxidation state of the native iron. a reactive zone analogous to a zero-valent iron wall, may be created. John indicated that chromate and carbon tetrachloride are the primary contaminants of concern are Hanford, WA. As part of a proof-of-concept study, 21.000 gallons of buffered sodium dithionite solution were injected into the subsurface near 100-H Area in September 1995. Dissolved oxygen levels were seen to lower significantly; Cr(VI) levels lowered to non-detect in the influenced area. Based upon the success of the proof-of-concept field test, 100-D Area has been chosen to perform a treatability study.
John estimated. based upon laboratory studies, that the in-situ reactive area will last 15-30 years. In response to a participant's question, John indicated that dithionite costs approximately 50¢/lb.
Dissemination of Action Team Materials
Rich Steimle (EPA/TIO) noted that e:<change of information is one the primary goals of the RTDF. An RTDF webpage, <www.rtdf.org>, has been established and Rich indicated that a subpage has been created for the Permeable Barriers Action Team. He asked participants if they are interested in development of the webpage to include meeting summaries, project updates. etc. Rich also noted that a password encrypted section could be established for use by Action Team members only. Matt Turner believes that the Action Team webpage would be beneficial and suggested that it be fully developed. He noted that the ITRC has a Communications Work Group and suggested that the Permeable Barriers Action Team coordinate with this Work Group. A meeting participant observed that not all parties have access to the Web, but suggested that more and more people will have access in the future so that if should not delay the development efforts. In response to a participant's question, Rich indicated that EPA. sponsor of the RTDF, may be able to provide the initial funding for maintenance of the website. but reminded participants that the RTDF is a joint public/private effort, and hoped that Action Team members would be able to support the website as well. Rich noted that the RTDF Bioremediation Consortium is following a similar path. He agreed to determine if EPA would be able to provide funding for maintenance of the Action Team website.
Roundtable Discussion
Alvin Yorke (Foremost Solutions) provided participants with a brief overview of an study investigating in-situ bioremediation of petroleum in soils using hydraulic fracturing, which is being performed at the Denver Federal Center. He indicated that the average soil petroleum hydrocarbon concentrations decreased from 5,700 mg/kg to 475 mg/kg within 9 months of hydraulic fracturing. He asked that participants contact him (contact information is found in the attached Participant's List) for additional information.
Bob Spangler (Spangler Environmental Technologies) mentioned the Fry Canyon field study, which will demonstrate the use of chemical barriers to remediate uranium contamination in groundwater. Site characterization was performed during Fall 1996. the demonstration design is underway, and installation should begin in Spring 1996.
Don Marcus (EMCON) indicated that EMCON has been investigating the remediation of TCE using a Cercona-foam product. Column studies have shownremoval of up to 99% TCE and Don indicated that the investigation will continue in the field. He estimated that additional results would be available in 4-5 months.
Concluding Remarks
Dale Schultz thanked participants for attending and encouraged interested
Action Team members to attend the February 9-12, 1997, International
Containment Technology Conference. to be held in St. Petersburg, FL. He
indicated that there will be a number of sessions on aspects pertaining to
permeable barriers, such as performance monitoring, site characterization, and
emplacement techniques. Given the date of the conference, the next Action Team
meeting will be held in Spring 1996. He asked that participants provide any
comments regarding today's meeting or future topics of discussion to Mark
Searles (SCG) or to him. Dale also thanked Bob Stone for hosting the meeting.
| Mr. Jim Beran Mr. Jeff Breckenridge Mr. Randall Breeden Ms. Darcy Campbell Ms. Margaret Carrillo-Sheridan Mr. Alex Caruana Dr. Stephen Chao Mr. Rick Cushing Dr. Jim Davis Mr. Michael Day Dr. Joe Devary Mr. George Duba Ms. Lynn Fossum Mr. Tad Fox Dr. John Fruchter Ms. Annette Gatchett Dr. Arun Gavaskar Dr. Bob Gillham Mr. Will Goldberg Mr. Bashua Gu Mr. Dan Gravelding Mr. Robert Hanson Ms. Christine Hanton-Fong Mr. Frank Harrison Mr. Joseph J. Hayes Mr. Rich Helferich Mr. Grant Hocking Mr. Bob Janosy Mr. Harry R. Johnson |
Dr. Jerry Jones Mr. Gary Kleeman Mr. Stephen Koenigsberg Dr. George P. Korfiatis Mr. Andy Koulermos Mr. David Kruchek Mr. Larry Kwicinski Dr. Rich Landis Mr. David LaPusata Ms. Bonnie Lavelle Mr. Joshua Lieberman Mr. Tom M. Malloy Major Ed Marchand Mr. Donald Marcus Dr. Dianne Marozas Dr. Peter McMahon Dr. Ted Meiggs Mr. Al Meyers Dr. Stan Morrison Mr. Brian Myller Ms. Mary North-Abbott Ms. Deirdre O'Dwyer Dr. Bob Olffenbuttel Dr. Robert Orth Second Lieutenant Dennis O'Sullivan Dr. Ian T. Osgerby Mr. Anthony V. Palumbo Mr. Jim Paulson Ms. Carey Peabody |
Ms. Brenda Pohlmann Ms. Elizabeth Pottorff Mr. Robert M. Powell Dr. Robert Puls Dr. Kenneth Quinn Mr. Chuck Reeter Mr. William Rothenmeyer Mr. Mark Sandstrom Ms. Theresa Santangelo Ms. Cindy Schreier Dr. Dale Schultz Ms. Debbie Sherer Dr. Timothy Sivavec Mr. Gregg Somermeyer Mr. Robert Spangler Mr. Carl Spreng Mr. Bob Starr Mr. Richard Steimle Mr. Robert Stone Mr. Jeff Swanson Ms. Anna G. Symington Mr. Matthew Turner Mr. John Vogan Mr. Tom Westenberg Mr. Stephen White Mr. Randy Wolf Mr. Alvin Yorke |
| Dr. Jim Anderson Mr. Frank Anderson Mr. William Baughman Dr. Martin Bell Dr. David Blowes Dr. Robert Bowman Dr. David Burris Ms. Darcy Byrne Ms. Beverly Campbell Mr. Kirk Cantrell Mr. Cliff Casey Mr. Skip Chamberlain Mr. Dean Chartrand Dr. Chien Chen Mr. Mark Cipollone Ms. Sandy Clavell Mr. Richard Conway, P.E. Dr. Tom Early Mr. Bob Edwards Dr. David Ellis Dr. Steven Fann Ms. Stephanie Fiorenza |
Dr. Neil Gray Dr. Neeraj Gupta Dr. Johnson Haas Mr. Joseph Hailer Dr. Kirk Hatfield Dr. Ron Holser Mr. Conrad Ingram Mr. Peter Jeffers Mr. Brad Job Dr. Erica Jonlin Mr. Mark Kaminski Mr. Joe King Dr. Gary Klecka Mr. John Koutsandreas Ms. Liyuan Liang Mr. Gus Lo Dr. Patricia MacKenzie Mr. Steve Mangion Mr. Jeff Marqusee Dr. Steven McCutcheon Ms. Lynn McCloskey Ms. Alanna Mitchell Ms. Jennifer Nelson |
Mr. Mark Noll Major Jeff Ogden Ms. Stephanie O'Hannesin Mr. Philip Palmer, P.E. Mr. Greg Penland Mr. Edward Pesce Mr. Gene Peters Mr. Mark Phifer Mr. Alan Rabideau Dr. Will Robertson Mr. Michael Royer Mr. Peter Russell Mr. H.G. Sanjay Dr. Bruce Sass Mr. Bob Schenck Mr. Richard Scheper Mr. Michael Schnarr Mr. Brad A. Schwartzman Mr. Mark Searles Mr. Steve Shikaze Mr. Stephen Shoemaker |