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Fostering the Remediation & Redevelopment of
Manufactured Gas Plant Sites

MGP 2019 Poster presentations

Pilot Study to Evaluate Solar-Powered Automated DNAPL Collection System, Clifton Works Former Manufactured Gas Plant (MGP) Site, Staten Island, NY

Peter Cox, AECOM

Co-Authors:  Sarah Aldridge (National Grid) and Pete Cox, Shail Pandya, Rob Forstner, and Jason Hovis (AECOM)


Abstract:


Background: The remedy for the former MGP includes operation of a DNAPL collection system that includes 20 collection wells. To prevent collected NAPL from overflowing the well sump, DNAPL is manually removed weekly via pumping. Objective: To automate the DNAPL recovery efforts without creating extensive trenches, drum storage areas, and/or power requirements.  Solution: A pilot test is underway to test the efficiency and effectiveness of a solar powered, weather controlled automated system currently installed over a single collection well. The presentation will discuss the design and construction of the standalone solar-powered automated system as well the results of pilot test including: 


•  Components of the standalone self-sufficient system 

•  Efficiency of the system in removal of collected NAPL (to meet remediation goal)  

•  Automated features and maintenance  

•  Performance of solar cells  

•  Effects of harsh winter and summer conditions 

•  Relative Costs compared to manual removal 


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MGP Remediation Through Adaptively Managed Combination of Focus Excavation, Stabilization/Solidification and Off-Site Disposal

Alex Cates, Partner, Global Lead - DDD, Environmental Resources Management (ERM)

Co-Authors: Ben LePage, Seng Sam, and Heather Balfour, Environmental Resources Management (ERM)


Abstract:


Environmental Resources Management (ERM) is a strategic partner with a utility client that operated an MGP in northern California from 1907 through 1947. The former MGP operation was located approximately 600 feet east of Humboldt Bay and occupied a former 200-by-300-foot parcel located within an active industrial facility. The soil, soil vapor, and groundwater at the site was impacted with LNAPL, TPH, BTEX, PAHs, arsenic and lead. The majority of the impacts where within the fill material above a bay mud layer. ERM developed, designed and implemented an adaptively managed remedy to mitigate risks through treatment, reduce potential impacts to Bay and community and not generate substantial waste. The selected remedy used selective excavation and disposal for highly impacted materials (e.g., LNAPL-saturated soil) while using solidification/stabilization (S/S) for the majority of treated soil. In addition, the remedy utilized an engineered cap to prevent direct contact and site restoration with asphalt surface and stormwater management system. The construction team remediated 12,300 cy by excavation, screening, placing, in situ S/S (bucket mixing) and off-site disposal to address lampblack, and impacted soil, soil gas, and groundwater impacts down to Bay Mud. Approximately, 60% of the soil was treated and remained on-site. In addition, 700 cy was remediated below the Bay Mud through in situ S/S (auger mixing).  The team used a tent with a negative air control system over most of the remediation area to control dust, odor, and emissions and limit impacts to community. This project included multiple scopes of work with multiple contractors in a small footprint, which required carefully planned sequencing to safely achieve project objectives. ERM consistently exceeded expectations on scorecard KPIs, including cost savings of $2.2M achieved through schedule efficiencies, hiring local staff, and several value engineering solutions including perimeter slurry wall; pothole program which reduced footprint; pre-profiling waste and site coordination. 


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Suvilahti, Gasholder Renovation and Remediation of Contaminated Soil

Johanna Hytönen, City of Helsinki


Abstract:


The gasholder was founded on early 1900 on filled ground. Front of the building is very bad condition and there is a penalty payment, old structure must repair. There were two important design principles for the repairing. The foundations must be strengthen and the contaminated soil removed safely. There were installed jet grouting piles around the structure. The contaminated soil was excavated away from the pit surrounded by the piles. Then the pit was filled and bored piles were drilled throught the gravel for the foundation of structures inside the gasholder.  Insulating film comes under the floor with volatile compounds collection system. Later next year building will be connect nearest district heat and drain. There is a vision to establish some cultural space inside the gasholder in the future. 


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In-Situ Stabilization/Solidification to Mitigate Migration of Tar-Like Material

Ramzi Khuri, Jacobs

Co-Author:  Dusty R.V. Berggren - Jacobs


Abstract:


In-Situ Stabilization/Solidification (ISS) is a common remediation technology used to mitigate mobility of non-aqueous phase liquids (NAPL), improve the geotechnical properties of soils, and/or reduce leaching of contaminants. ISS was implemented at an industrial site in West Virginia to encapsulate buried tar-like materials that migrate to the surface during warm-weather months, posing direct-contact exposure risk to workers. The tar-like materials exist completely in the unsaturated zone, and temperature fluctuations, measured with subsurface temperature probes, within the top 12 feet of soil significantly changed the tar-like materials’ viscosity throughout the year. A phased bench-scale test evaluated the ability of different ISS reagent blends to immobilize these tar-like materials under Site-representative temperatures. The tendency of tar-like materials to migrate in warmer weather following ISS treatment was evaluated using a unique testing approach. ISS-treated cores were incubated at different temperatures using a heated water bath to observe whether the tar-like materials were likely to migrate and appear on the core surface. Based on the results of this bench-scale test and previous site experience, a 10% Type I/II Portland cement grout (based on moist weight of soil/tar-like material) was selected for the full-scale implementation. Field implementation subdivided the ISS area into smaller cells and utilized an Allu Tool to mix the grout and subsurface material. A portion of the ISS area was within 2 feet of an aboveground chemical piperack supported by shallow footings. Relying on soil arching, smaller “piano key” cells, aligned perpendicular to the piperack alignment, were used for ISS implementation to ensure stability of the piperack footings. Quality control samples collected during construction confirmed achievement of performance objectives and verified swell estimates.  Remedial construction was completed in 2017 (approximately 9000 cubic yards), and no surficial tar-like material migration has been observed since completion.


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Using the Optical Image Profiling Tool with a Green Laser Diode (OIP-G) to Detect Coal Tar at MGP Sites

Tom Koester, Senior Environmental Scientist, S2C2, Inc.

Co-Author: Wesley McCall, PG, Geologist, Geoprobe Systems, Inc.


Abstract:


The Optical Image Profiling Tool with a green laser diode (OIP-G) is a new direct-sensing tool used for the detection of coal tars and other contaminants that contain large PAHs. The OIP-G uses green light focused at the subsurface through a sapphire window. Coal tar PAHs, if present, fluoresce in the red-orange wavelength range when excited by green light. A complementary camera in the probe body captures images of the subsurface and the system software simultaneously analyzes those images for fluorescence. Detections are reported as percent area of the image that exhibits fluorescence in the red-orange wavelength range.  


Additionally, hydraulic and lithologic properties can be simultaneously logged with the integrated Hydraulic Profiling Tool (HPT) (known as OiHPT-G) and Electrical Conductivity (EC) dipole. The HPT injects water into the formation and utilizes a downhole transducer to log the resulting pressure, providing an indication of permeability. The EC uses electrical current to log bulk formation electrical conductivity. These two datasets can greatly assist the site investigator in understanding lithologic control on contaminant migration in the subsurface and advance the development of an accurate CSM. 


Data from two recent subsurface investigations at former MGP sites; the Wellington MGP site in Wellington, Kansas (Site A) and an undisclosed MGP site located in the eastern US (Site B) are presented. The logs collected at both sites defined zones of elevated fluorescence at various depths. At Site A, zones of high concentration/free product coal tars were confirmed by soil sampling and analysis for PAHs.  Sampling also revealed instances of calcite bearing minerals emitting false positive fluorescence. OiHPT-G logs from Site B showed multiple geologic controls over the migration of coal tar PAHs. Data obtained from the OIP-G/OiHPT-G can provide valuable information about coal tar distribution at MGP sites in many geologic settings.


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ISS-in' on the Dock of the Bay

Paul R Lear, Great Lakes E&I

Co-Author:  George Little, Great Lakes E&I


Abstract:


This project involved performing in situ stabilization (ISS) to address coal tar-impacted soil containing continuous dense nonaqueous phase liquid (DNAPL) associated with former manufactured gas plant (MGP) operations at the site. Remedial action objectives for the project included mitigating migration of continuous DNAPL to bay sediments, mitigating exposure to soil and soil gas, and mitigating potential for chemical of potential concern (COPC) in soil to leach into groundwater. ISS involved treatment of two distinct areas within the site to address the DNAPL.  Great Lakes E&I was contracted to perform ISS activities as well as odor control during implementation of the treatment remedy for impacted soils. The scope of work included drilling ISS columns in two distinct treatment areas encompassing approximately 20,000 sf of the site. More than 26,000 cy of ISS was completed using mixing augers ranging from 4 to 8 ft in diameter in order to treat 100 percent of the DNAPL-impacted soils. Work was performed over a six month period utilizing two ISS drill rigs and batch plants to complete treatment on time, and to prevent any impacts and delays of subsequent phases of this remediation.  ISS was completed in the northern and southern continuous DNAPL areas to depths ranging from 20 to 50 ft bgs, and included penetration of approximately 3 ft into the underlying bay mud. The primary performance criteria for the treatment zones was a minimum unconfined compressive strength of 30 psi, maximum hydraulic conductivity of 1 x 10-6 cm/sec, along with a visual observation of soil cores to ensure there was no unmixed soil or observed DNAPL. Additionally, ISS within the bulkhead area of the northern zone was completed through the fill zone and approximately 15 to 20 ft of the underlying bay mud, with a minimum unconfined compressive strength of 100 psi, in order to stabilize the soil mass behind the bulkhead.  The scope of work also included handling of the ISS swell material within the treatment zones and management of obstructions encountered during drilling.  Throughout the project, a number of obstructions such as brick, rocks, concrete, miscellaneous debris, as well as historic (and unidentified) timber piles were encountered. Obstructions in the upper 20 feet bgs were managed with an excavator. For timber piles and wood debris, Great Lakes fabricated and utilized an auger configuration with aggressive cutting teeth to allow advancement of the auger to full treatment depths through the timber piles and wood debris while incorporating the material within the mixed column.  Along the bulkheads, Great Lakes E&I employed an ISS treatment sequence to allow the ISS treatment to be conducted while not destabilizing the bulkhead.  The presentation will discuss auger configuration and the ISS sequencing utilized during the project.  


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Urban Creek Impacted Sediment Removal and Isolation Utilizing a Geosynthetic Clay Liner

Trevor Litwiller, August Mack Environmental, Inc

Co-Author(s):  Joel Ruselink, Principal of Construction Services,  and Tim Dewitt, Senior Technical Engineer,  August Mack Environmental, Inc.


Abstract:


Pleasant Run Creek (PRC) is an urban stream that bisects an 87-acre former Manufactured Gas Plant (MGP) within Indianapolis, Indiana. PRC is considered an impaired waterway with a highly incised channel and more than 50 combined sewer overflow (CSO) discharge locations. Impacts associated with historic MGP plant operations were identified to exist up to 20 feet below the creek bottom. The impacts identified on-site, including free product (coal tar and petroleum), were determined to present potential for ecological risk based upon sediment and pore water sampling. Hydro-geologic data evaluations were conducted by Purdue University to determine upland groundwater contribution to PRC. Results indicated that groundwater up-welling in the areas tested were minimal (~0.8 cm/day). Utilizing results from qualitative and quantitative sampling, a remedial approach was designed to mitigate the potential ecological risk. The remedial approach included sediment removal, sediment isolation, and free product capture from upland groundwater. Multiple capping technologies were reviewed for their ability to isolate the impacted sediment. A geosynthetic clay liner (GCL) was selected due to its isolation ability, constructability, uniform thickness upon application, and long-term viability. Data collection, remedial design, regulatory approval, and remedial construction were completed over a 24 month period.


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The Importance of Versatility of Technology and Field Personnel Know-How when Employing Chemical Oxidation for Treatment of MGP Sites

Eric Lundy, DeepEarth Technologies, Inc.


Abstract:


An in-situ chemical oxidation technology has proven to be effective at emulsifying coal tar and eliminating odors at sites contaminated with MGP artifacts. While the chemistry of the process is proven and contributes to the efficiency and economics of MGP site remediation, proper field application is essential for overall remedial success. Although the majority of environmental cleanup projects are well documented and planned, the popular phrase of, “it’s dark down there,” too often signals confrontation with the unexpected and certainly the unplanned. It is at this juncture where a dynamic, versatile process applied by personnel seasoned in the art of adaptation to the unexpected can make the difference between a successful and failed project. - And, can often cast doubts on the selected technology itself. This paper will provide examples of how experienced field staff, armed with an understanding of the applied technology and mechanical savvy, can muster the know-how to overcome and control unexpected and potentially dangerous situations. These common-sense attributes coupled with a rigorous dedication to safe work and safe living attitudes will profitably apply to a broad spectrum of environmental projects. 


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5 degrees Fahrenheit at the Superior Lakefront - Excavating A Tar Well,  No Heat Added, and the Coal Tar is Still Flowing - Not Magic / Just Science

William Lundy, Sr., Vice President, DeepEarth Technologies, Inc.

Co-Author:  William Gregg, Program Manager, Summit Envirosolutions


Abstract:


An in-situ chemical oxidation technology has proven to be effective at emulsifying coal tar and eliminating odors at sites contaminated with MGP artifacts. While the chemistry of the process is proven and contributes to the efficiency and economics of MGP site remediation, proper field application is essential for overall remedial success. Although the majority of environmental cleanup projects are well documented and planned, the popular phrase of, “it’s dark down there,” too often signals confrontation with the unexpected and certainly the unplanned. It is at this juncture where a dynamic, versatile process applied by personnel seasoned in the art of adaptation to the unexpected can make the difference between a successful and failed project. - And, can often cast doubts on the selected technology itself. This paper will provide examples of how experienced field staff, armed with an understanding of the applied technology and mechanical savvy, can muster the know-how to overcome and control unexpected and potentially dangerous situations. These common-sense attributes coupled with a rigorous dedication to safe work and safe living attitudes will profitably apply to a broad spectrum of environmental projects. 


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Molecular Modification - A New Scientific basis for  Eliminating Odor During MGP Remediation Projects

William Lundy, Sr., Vice President, DeepEarth Technologies, Inc.

Co-Author:  Doug Gray, CGWP, Principal Project Manager / Innovative Remedial Technologies Group Manager, AECOM 


Abstract:


Odors generated by excavation projects, regardless of the target pollutants, have historically been quenched or masked by the application of surfactant foams. Surfactants were the products of choice because they are wetting agents that readily create the bridge between the mostly hydrophobic contaminants and water. And, the fact that they are cheap, easily produced and applied, made them a quick and easy solution to create a barrier between the excavation and the inquiring nose.  Only three items are required to produce a foam; these are soap, water and a gas. When soap is applied to water and the mixture spritzed with a gas (regular air), a foam is produced. However, while it is easy to produce, most foam is easily destroyed by such natural phenomenon as wind or rain. And, aside from a physical barrier, foam makes no contribution to the remediation of the site. There must be a better way.  Investigation of mechanisms that chemically modify contaminant molecules during an in-situ chemical oxidation process has proven to not only convert highly toxic compounds to non-toxic surfactants but, in the process, also produces a heavy foam. In addition to providing an indicator that the process is working, the foam is continuously produced during the remediation project, thereby obviating the need of reapplication. Carbon dioxide, a byproduct of the oxidation reactions, supplies the gas that drives the production of foam. In addition to producing a barrier to volatilization, the technology actually uses the volatile (odor producing) contaminants as feed stock to produce the foam, thus continuously reducing the toxicity of the contaminant mass.  The process, proven by application at several MGP sites, numerous service station closures, and over one-hundred crude oil releases in North Dakota’s Williston Basin, will be discussed in detail. Specifically, the chemical conversion of such MGP bad actors as BTEX, PAHs, creosote, and coal tar will be revealed in an easily understandable manner. And, of course, how all of this works together to take the “stink” out of MGP excavation and soil blending projects.


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The Effectiveness, Need and Challenges of Fenceline Air Monitoring During a Thermal Remediation Project

Melissa McLaughlin, AECOM

Co-Author: Matthew Arvanites, AECOM


Abstract:


AECOM has been designing, installing and operating perimeter ambient air quality and -meteorological programs for over 40 years. AECOM’s more recent experience includes numerous perimeter monitoring programs around hazardous waste sites, landfill excavation projects, former MGP site remediation projects, dredging and sediment processing remediation projects and building demolition projects. This poster will focus on the need for, effectiveness of, and unique challenges of fenceline air monitoring during a thermal remediation project.


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Managing Stakeholders for Remediation of an MGP Site

Brendan Moran, PE, Senior Project Manager, Kleinfelder, Inc.

Co-Author:  Joseph Tarsavage, PE - Principal, Kleinfelder, Inc. and  Peter Farrand, PECO Energy


Abstract:


Managing Stakeholders for Remediation of an MGP Site  The subject site is a former MGP in a suburb of Philadelphia.  Our Client is the Responsible Party for MGP-related impacts but does not own the property.  We have completed soil remediation and the PADEP has issued relief of liability to our Client for MGP constituents in soil.  Groundwater investigation is ongoing.  Prior to soil remediation, the site was comprised of a parking lot and stormwater-driven wetland.  Since remediation, the site has been redeveloped by others with a $20 MM flagship automotive dealership.  Remediation planning, execution and site restoration required involvement of the following stakeholders; often several at a time:  •  Responsible Party and Consultant  •  Previous Owner  •  Current Owner  •  Construction Manager and Subcontractors  •  Local Municipality  •  PADEP  •  Army Corps of Engineers (ACOE)  Remediation project permitting required pre-planning for redevelopment of the property.  In particular, wetland disturbance permitting with the ACOE required the inclusion of specific language to transfer responsibility for maintenance and monitoring of our Client’s restored wetland to the new property owner, once their redevelopment started and hydrology to the wetland was altered.  When that time came, the owner disputed the transfer of responsibility.  However, ACOE sided with our Client and transferred responsibility to the owner. Other considerations:  •  During remedial design, the (now former) property owner changed its redevelopment plan from non-residential use to mixed use that included residential development.  We adjusted our remedial design accordingly, before the Municipality rejected the owner’s zoning application.  However, the remediation was executed with a residential use attainment goal.  •  The Construction Manager has taken issue with the stone screenings and clay-loam backfill materials that were used to restore the site, stating that they incurred delays and additional expense to remove and replace the materials.


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Remediation of contaminants from a manufactured gas plant using bacteria and heat

Dr. Ray Sambrotto, President and Chief Science Officer, Allied Microbiota

Co-Author(s):   Dr. Michael Chin, Director of Technology, Allied Microbiota and Averil Rance, CE; Sr. Vice President, EH&S, Clean Earth, Inc.


Abstract:


Soils from a manufactured gas plant (MGP) containing significant levels of water gas tar were treated with a bacterium and incubated at 150˚F.  The bacteria are unusual in their ability to grow at these elevated temperatures and were shown to break down recalcitrant organics previously.  We present the capabilities of the bacteria for degrading some of the major poly-aromatic hydrocarbons (PaHs) and BTEX (benzene, toluene, ethylbenzene and xylene) in the MGP soils.  In particular, we focus on 7 of the more toxic PaHs on the EPA’s Priority Pollutant List and discuss the approaches that lead to the greatest reduction in overall soil toxicity.  Tests were done ex-situ in heated soil piles.  Oxygen and moisture for optimal microbial degradation was supplied by air forced into the piles.  The impact of peroxide compounds to stimulate enzymatic oxidation and nitrate as an alternative electron acceptor also were evaluated.  The results will be presented in the context of the variation among initial soil types and pH to provide a robust evaluation of the bioremediation approach for MGP sites.  Estimates of cost for this type of treatment also will be presented. 


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Comparative Study for ZVI/Peroxide vs Ferric Iron Oxide Persulfate Activation Followed by Intrinsic Facultative, Biologically Mediated Processes

Michael Scalzi, President, Innovative Environmental Technologies, Inc.


Abstract:


An In-Situ Chemical Oxidation (ISCO) remedial process involves injecting an oxidizing agent, such as activated sodium persulfate (Na2S2O8), or other oxidant into the subsurface to destroy organic compounds.  The persulfate anion (S2O82-) has a high redox potential and can be chemically activated to form the sulfate radical (SO42-•), which is a stronger oxidant. The sulfate free radical is a very potent oxidizing agent roughly equivalent to the hydroxyl radical generated using ozone or peroxide.  The two activation methods presented below have the advantage of utilizing both biotic and abiotic processes that include the use of free radical chemistry, oxidation chemistry and facultative biological attenuation.  The potential combination of these processes extends oxidant and free radical residuals while enhancing the in-situ environment for biologically based attenuation of the constituents of interest (COI).  The abiotic portion of the ZVI/Peroxide activated persulfate method uses a unique blend of peroxyl, hydroxyl, evolved heat and sulfate free radicals which results to the oxidation of the COIs. This mixture allows Fenton-like reactions with long-lived sulfate free radical oxidation to occur, while the presence of zero valent iron acts as a catalyst for both reactions.  The evolved heat is of value in situations where there is a high sorbed mass of the hydrophobic compounds of concern. Furthermore, as mentioned above, the decomposition products of the oxidation process are utilized in the subsurface to stimulate facultative biological degradation of the targeted compounds.  After dissolved oxygen has been depleted in the treatment area following the oxidation process, sulfate (the by-product of the persulfate oxidation) may be used as an electron acceptor for co-metabolic progressions, a process termed sulfanogenesis.  The use of ferric iron to activate persulfate for the purpose of degrading organic compounds presents the additional advantage of quickly generating sulfate and ferrate radicals for ISCO treatment.  Moreover, it also supports long-term, sustained, secondary bioremediation processes to manage residuals and prevent contaminant rebound.  Similar to the ZVI/Peroxide activation method described above, that process is achieved by enhancing the subsequent utilization of sulfate and iron as terminal electron acceptors for facultative redox reactions in order to improve biodegradation of any residual COIs. The ferric activated method, similar in its chemistry to the peroxide, ZVI persulfate, differs in that it is an endothermic process while still providing no extreme pH conditions that can mobilize heavy metals causing secondary impact issues, while the presence of iron will sequester sulfur liberation during sulfate reduction reactions to minimize H2S formation.  Moreover, the remedy combines treatment mechanisms thereby allowing for more cost-efficient dosing of the product.  


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In-Situ Geochemical Stabilization (ISGS) for Non-Aqueous Phase Liquid Treatment – Technical Assessment

Michael Scalzi, President, Innovative Environmental Technologies

Co-Author:  Justin Mariani, Innovative Environmental Technologies, Inc.


Abstract:


ISGS (In-Situ Geochemical Stabilization) technology entails the use of modified permanganate solution that targets mass removal and flux reduction of the NAPL.  The introduction of the permanganate solution results to the migration of the oxidant through the treatment area and consequently to geochemical reactions that destroy the targeted contaminants that are present in the dissolved phase. As a result, the NAPL starts to steadily lose its more labile components and “chemical weathering” or “hardening” occurs.  Subsequently a net increase in viscosity of the organic material is observed, which yields a more stable, recalcitrant residual mass.  Additionally, both the insoluble manganese dioxide precipitate, that results from permanganate oxidation, and other mineral species included in the ISGS formulation accumulate along with the NAPL interface, resulting in the physically coating of the NAPL and thereby reducing the flux of dissolved-phase constituents of interest into the groundwater.  ISGS was implemented at a site located in northern New Jersey in order to decrease the source area NAPL present.  Based on the post remedial data, the ISGS technology was found to be very effective in addressing the groundwater and the free product contamination in all five targeted monitoring wells (MW-11, MW-12, MW-13, MW-14 and MW-15).  In MW-11, the concentrations of almost all SVOC compounds decreased to levels below the laboratory detection limits, total BTEX concentrations decreased by 85%, while the concentrations of total alkanes have also reached non-detect levels. In MW-12 the concentrations of the SVOCs and total alkenes reached levels below the laboratory detection limits, while BTEX compounds overall decreased by 68%.  In MW-13 the concentrations of all targeted SVOC compounds decreased considerably, while naphthalene was the compound that was massively affected with the concentration decreasing from 1,920 μg/L in August 2013 to 1.18 μg/L in January 2014.  In MW-14 the concentrations of all targeted compounds have decreased to levels below the laboratory detection limits except for benzene that decreased by 43%. Finally, in MW-15 the concentrations of almost every SVOC and BTEX compound have decreased to levels below the laboratory detection limits.  The free product that was present in the five wells, disappeared within 30 days of the implementation of the injection event.  


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In Situ Stabilization and Solidification (ISS) Optimized using Sodium Persulfate

Brant Smith, PeroxyChem

Co-Author(s):  Fayaz Lakhwala and Ravi Srigangam, PeroxyChem


Abstract:


Background  In situ stabilization and solidification (ISS) is a well-established remedial technology often used to treat highly contaminated sites.  ISS decreases the contaminant flux by decreasing the hydraulic conductivity and solidifying site soils.  In addition to hydraulic conductivity, ISS is often used to target specific post application unconfined compression strength (UCS) of soils following the application for purposes such as site redevelopment.  Reagent doses can result in displacing 10 to 30 percent of site soils by weight, necessitating treatment or disposal of these excess contaminated soils.  Data has shown that both remedial goals can be accomplished using lower overall mass of reagents when adding alkaline activated sodium persulfate in with the ISS reagents during field events.  Activities The objective of these studies was to demonstrate the effect of adding low levels of alkaline activated persulfate during ISS on hydraulic conductivity, contaminant leachate concentration and post application compressive soil strength.  Various combinations of ISS reagents and alkaline activated sodium persulfate were evaluated on the bench and field scale. In situ soil mixing was utilized in the field and simulated in the laboratory to ensure complete mixing of the contaminated soils with the reagents.  Results  The data show a trend of decreasing hydraulic conductivity and decreasing leachate concentrations with increasing dosages of alkaline activated sodium persulfate. Reagents were balanced to achieve workable post application soils strengths and hydraulic conductivities of 10-6 to 10-9 cm/sec.  Site specific dose response curves demonstrating the effect of varied concentrations will be presented.  


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An Overview of the Historic Massachusetts MGP Industry

Thomas Speight, O'Reilly, Talbot & Okun Associates, Inc.

Co-Authors:  Dr. Allen W.  Hatheway, P.E., P.G. Independent Consulting Geological Engineer


Abstract:


The assessment, remediation, and redevelopment of manufactured gas plant (MGP) sites pose a significant technical and financial challenge to successor property owners, including municipalities and other public entities pursuing revitalization, and to their consulting engineers. Due to the toxicity of many coal tar constituents, sites contaminated as a result of gasworks operations pose a threat to public health.  The presenters are coauthors of Manufactured Gas Plant Remediation: A Case Study, which presents the history of the manufactured gas industry in Massachusetts in the first detailed statewide study of the industry and its modern environmental legacy. Using contemporary primary sources, this research documented the manufactured gas industry’s historical footprint in Massachusetts, and then used MassDEP’s database of Disposal Sites to identify relevant sites and their regulatory status.  This book is intended to be a technical and historical guide for assessment and remediation of gasworks, waste dumps, and other coal-tar sites that threaten public health.  There has previously been no ‘middle ground’ in the professional literature on this topic between individual site assessment reports and macroscopic historical reviews such as USEPA’s 1985 “Radian Report.”  Massachusetts historically had the second-largest statewide MGP industry in the United States, surpassed only by New York. This research identified a ‘core population’ of over 190 confirmed locations in Massachusetts, including 95 former town gasworks; one byproduct coke plant, 18 private fuel gas plants; and numerous district gasholder stations, off-plant dump sites, and other facilities.  The authors offer general observations backed by our research and author Hatheway’s twenty-eight years of experience, including assessment approaches, alternatives for compensating for lack of access to utility archival information, potential remedial approaches, and modern-era cost-recovery litigation. 

 

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Solar Power Development for Site Reuse

Ian A. Webster, Sc.D., Project Navigator, Ltd.

Co-Author: Robert Fritz, B.Sc, Project Navigator, Ltd.


Abstract:


MGP Sites are today's environmental legacy from an earlier era of carbon-based energy production. However, today, as power distribution trends towards a micro-grid configuration, environmentally restricted, single acreage MGP sites can be repurposed as modern era photovoltaic solar power installations. The size of these facilities is small (e.g. 1 to 2 MW), but they have the advantages of being located in urban areas, immediately adjacent to load, with already existing interconnect, thereby further reducing development costs. This presentation will describe this approach to MGP site reuse, by showing project examples our company is working on in California.

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