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Groundwater Remediation Design, Operation and Maintenance

Groundwater Remediation Design, Operation and Maintenance 2017-11-03T18:45:49+00:00

Pollution Sources (EPA)Many environmental projects sooner or later will arrive at the remediation or clean-up stage of the project. The previous stage, often referred to as the groundwater characterization (or hydrogeological) stage, should have provided most of the necessary information on the contaminants present to design and implement a remediation solution for the necessary clean-up. Litigation can evolve out of disagreements between joint-venture partners on clean-up approaches and associated costs, and alleged damages resulting from industrial operations.

Source Control

When attempting to clean up such spills, timely and comprehensive source control and associated hydrogeological investigations are needed once a release is detected. This includes:

  • Immediate control and cessation of the release,
  • Repair or removal of the release source (tank, pipe, flange, pump, etc.),
  • Removal / recovery of free product in both the saturated / unsaturated zones, and
  • Removal of residual free product from the subsurface soils.

Any remedial action initiated before the source is controlled is ineffective and has the potential of expanding the scope of the remedial action as uncontrolled sources continue to migrate in the subsurface. Physical action, like excavation, is the usual approach to source control of small releases. Contaminated soils removed by excavation can be treated by disposal (asphalt batching, daily landfill cover), or physical (thermal desorption,) or biological (biopiles) treatment. For larger releases, however, alternatives include free-phase LNAPL recovery, barrier installation, and hydraulic control of the groundwater plume. A variety of single and multi-phase extraction techniques moves both liquid and gas phases to the surface for treatment. At the surface, dewatering and subsequent recycling treats the higher concentrations of recovered material. Direct on-site thermal catalytic processes destroy lower concentrations and absorbents like Granular Activated Charcoal (GAC) polish the air or water before discharge.

Pump-and-Treat Systems

Over the past 20 years, most remediation involved the pump-and-treat solution. Although this type of system is expensive to operate over the many years required to remove the appropriate number of pore volumes of contaminated fluids, there were no alternatives to the approach. The pump-and-treat system has undergone criticism because of its inherent inefficiency, more because of its cost to maintain than because there were alternatives in existence to the problem. These complaints have developed into a chorus of resistance to continuing the approach on the basis that it doesn’t work and it is too costly.

Apparently, state and federal regulators are listening to the industrial complaints because some projects have been halted or terminated as a result, leaving significant contamination in the ground. In recent years, however, EPA has encouraged the development of new remediation technologies in order to reduce the cost and duration of clean-up projects. Many such technologies are showing promise. Field tests and scaled-up tests are under way and are gaining support from regulators. The National Contingency Plan (NCP) encourages the use of new technologies and any reasonable attempt to reduce high concentrations of contaminants present which serve as sources of continuing contributions to plumes of dissolved-phase constituents.

PantSysThe “new” technologies in groundwater remediation more often consist of modifications to the pump-and-treat system than of new technologies. For dealing with the truly difficult contaminants like the DNAPL group, such modifications include: in-situ enhanced bioremediation, solvent flushing, steam flushing, or a combination of all three. The fact remains that the old, inefficient, and costly pump-and-treat system still serves remediation projects as the core technology. The other aspects of the newer technologies are important, but only enhancements to existing technology. Measured against some unknown but anticipated standard, they are still inefficient and costly, and a long-term solution. Incremental improvements will be realized. But, there are no other solutions on the immediate horizon, with the exception of the final solution: “natural attenuation.” This solution may be appropriate for some contaminants but not for recalcitrant contaminants.

For the light hydrocarbons (the LNAPLs and light, dissolved hydrocarbons), natural attenuation has its merits in many cases. Some of the BTEX family, and MTBE is a cousin of it, may not degrade as well as at first believed. So, fluid removal (pump-and-treat), combined with new enhancements, will also probably continue in many cases.

The design of such pump-and-treat systems, even with enhancements, still require a knowledge of subsurface conditions. Hydrogeologic assessments of subsurface conditions are tedious and costly to perform, but they form the foundation of all pump-and-treat, and other remediation systems. In the recent rush to by-pass appropriate characterization of contaminants present in the subsurface, such short cuts may have contributed to the blanket criticism of the pump-and-treat technology. In reality, the approach is all we have to bring to bear on the problems at hand today. Expectations of new technologies will be realized in due course. In the meantime, incremental enhancements of the standard technology will have to suffice until the new technologies can be brought into play.

Optimizing the data from contaminant characterization, combined with realistic approaches toward groundwater modeling and contaminant fate and transport modeling, form the basis of the operation and maintenance of such remediation systems. Improvements in equipment designs and sizing, combined with improved materials lifetimes (pumps, piping, valves, etc.), are also important features in project operation.

The advancement of knowledge in the design and operation of remediation systems depends to a large extent on how effectively the case histories of such systems that are presented in the professional literature are integrated into the engineering and design of the systems. Many case histories are overviews of projects, many others are detailed in some aspects but lacking in detail in other aspects. These features are usually intended to avoid criticism or to avoid implicating the budget numbers for fear of criticism from competitors or clients. The value of the technical literature, however, cannot be understated. It is being ignored by many professionals in the remediation field today. Many professionals prefer to continue re-inventing the wheel, at the expense of industry. However, subsurface clean-up incorporating microbiological processes and wells as delivery and recovery systems have made substantial advances over the past few years.

Bioremediation

The bioremediation discipline is a multidisciplinary field led by microbiologists and supported by a range of other professionals. Working closely with remediation engineers, microbiologists have developed bioremediation to a point now demonstrated to be effective in environmental cleanups throughout the country and overseas. Many such projects have claimed successes, including bioremediation projects, but many successes are a result of volatilization, not to bioremediation per se.

The primary need in bioremediation projects is to address hydrogeology issues, which will characterize the subsurface for use in designing effective bioremediation programs. Laboratory chemical analyses are used to characterize subsurface hydrochemical conditions, and a familiarization with biological processes in hostile, subsurface environments is important to resolve the numerous, complex issues involved in bioremediation.

Gasoline spills (including MTBE, TBA, etc.) are common and can cause water contamination issues as hydrocarbons dissolve in groundwater and travel offsite in the aquifer. Hydrocarbons naturally degrade in the subsurface due to microbial-mediated reactions. However, the reaction rates are slow because electron acceptors, like oxygen, are quickly depleted in contaminated groundwater and are slowly recharged. Contaminated groundwater has significant hydrocarbon concentrations but depleted electron acceptors, whereas the overlying unsaturated zone contains oxygen but lower hydrocarbon concentrations. Early response and intervention is the key to minimizing extent and costs of remedial action for gasoline and its components and is essential to protecting public health and the environment.

From Technology to Techniques

Two major objectives of site remediation include destruction of residual or dissolved gasoline constituents or their removal from the impacted area. Destruction can range from total mineralization/oxidation or reduction to inorganic components or transformation to some unlisted form. Chemical reaction, biological means, or thermal processes accomplish destruction. This is a brief description of the myriad of innovative techniques developed to refine and enhance the implementation of four basic technologies that have evolved for the active remediation of gasoline released to the subsurface:

  • Subsurface ventilation
  • Pump-and-treat technology
  • In-situ chemical oxidation
  • In-situ bioremediation

For example case histories:

Chemical Industry:

Chemical Manufacturing Plant – near Morriston, NC

Situation: This approximately 60-acre chemical site was comprised of four (4) units. DuPont was named as a responsible party subject to pay $160,000,000 to investigate and clean up the property in accordance with the Comprehensive Environmental Response Compensation and Liability Act (CERCLA).

Solution: During 1992, Mr. Schaefer (DuPont) hired one of I2M-Reardon’s Principals, Mr. Richard Bost, P.E., P.G., and his team, to investigate the source and operation of this property with the intent of identifying the operating history, extent of soil contamination and identify remediation measures acceptable by the USEPA for remediation and revitalization reuse.

Results: Mr. Bost and team were more than successful in this project as the team’s work structured suitable evidence, as presented in Court Testimony, to: 1) absolve DuPont from all financial responsibility in this matter, 2) lay foundation for a secondary manufacturing operation to start which continues to operate today.

Lake Charles Chemical Complex – Lake Charles, LA

Situation: This approximately 120-acre chemical plant had contaminated soil with various small and large spills while manufacturing and shipping ethylene. Soil contamination by both organic and metals, was identified both within the manufacturing property and also in the slips at the barge loading facility. A new owner who purchased and operated the plant for a few years managed the manufacturing and barge loading operations. Within the purchase and transfer agreement, DuPont was responsible for paying an increasing amount of money toward soil cleanup costs spent by the new owner.

Solution: During 1994, Mr. Schaefer (DuPont) hired members of the I2M team to investigate the operating conditions of the chemical manufacturing operations. The team applied a unique investigative technique that corroborated traditional investigation approaches to identify non-standard operating conditions.

Results: The team provided important metrics and findings to: 1) show [then] present-day operating practices were the cause of much of the contamination, 2) enable re-negotiation of the Operating Agreements between the two companies, saving DuPont several millions of dollars in operating expenses for these facilities.

Agrico Chemical Co. – Pensacola, FL

Situation: This approximately 35-acre chemical manufacturing site operated for over 90 years contaminating soil and the surrounding environment with heavy metals and organic compounds. The contamination was feared to reach the nearby residential population thus making this a CERCLA cleanup site.

Solution: During 1993, Mr. Schaefer (DuPont) and team investigated the soils beneath the long-closed chemical manufacturing operations and devise a cleanup and revitalization plan.

Results: The team identified and implemented soil cleanup measures including partial soil removal and on-site stabilization, completing their work in 1997. The protective measures remain intact today and enable safe use of the property for solar energy production, warehouse and/or recreational.

Independence, LA – $1.2 MM (Industrial Site):

Situation: Long-term soil and groundwater contamination of chlorinated solvents plagued a facility in Southeastern Louisiana for over two decades. Pump and treat technologies did not achieve required cleanup goals.

Solution: Ozone Injection/Thermal treatment and In-Situ Chemical Oxidation (ISCO) technologies were evaluated and ISCO was selected to bring the facility to a clean state allowing redevelopment. A corrective action report for soils was submitted to the LDEQ after soils injections were completed. The report requested LDEQ to approve no further action for soils.

Results: LDEQ stated in their response letter that, “the soils remedial work has been effective and the remaining constituents in the soil are at levels protective of human health and the environment.” Injection of the powerful oxidant FMC Klosur activated with a caustic solution was the choice chemical treatment in the groundwater zones.

Bryan, TX – $100M (Industrial – Arsenic Site):

Situation: Based on previous bench-scale tests of potential injectates at other sites, an injection of amorphous hydrous ferric oxide (HFO) was the recommended treatment approach for the higher arsenic concentrations in groundwater in affected area.

Solution: This was an onsite pilot-scale test conducted in the Merged Upper/Middle Aquifer over a 30-ft diameter area centered southeast of an existing extraction well. Prior to injection, the HFO suspension was prepared.

Results: The injection criteria were estimated at 16 tons of FeCl3 and 16 tons of sodium hydroxide (NaOH) mixed into 15,000 gallons of water, then injected into 9 injection points. Good response.

Lufkin, TX – $400M (Pipeline):

Situation: The I2M undertook in-situ remediation of soil and groundwater at an East Texas Site. The objective of the project was to use available technology for the enhanced in-situ destruction of Gasoline Range Organics – BETX and MTBE in soil and groundwater found at several areas at the site.

Solution: Soil was treated to a nominal depth of seven (7) feet in the contaminated area with an effective oxidant of 20 percent Hydrogen Peroxide on a gridded injection layout.

Results: BETX Targets were met. Groundwater was treated with a combination of hydrogen peroxide and sodium persulfate for the reduction of MTBE Organics.

National – Corporate Remediation Program (DuPont):

I2M personnel (Campbell and other DERS team members) provided consulting services for the development of a $10 billion Strategic Remediation Program for a “Fortune 10” chemical manufacturing company.

Moundsville, WV – $20M RCRA Closures:

Function: Performed clean closure certification of a surface impoundment and a waste toluene diisocyanate storage facility for a major chemical manufacture. Services included verification sampling and independent engineering certification.

Mobile, AL – $60M RCRA Corrective Action:

Function: A Structural Integrity Test and Assessment was conducted to determine if 14 sumps, basins, and tanks have had releases to the environment which would trigger RCRA Corrective Action. The results were used to negotiate with the state agency that no releases have occurred above risk base action levels, and that RCRA Corrective would not be required for the SWMU’s.

Kinston, NC – $85M Remedial Alternatives for RCRA Corrective Action:

Function: I2M personnel evaluated remedial alternatives for containment of a TCE plume that underlies a major chemical manufacturing facility. Plume containment and aquifer remediation was critical for the protection of a major water supply aquifer in the Kinston Area. Three groundwater containment alternatives and four water treatment systems were evaluated for effectiveness and cost. A Slurry wall containment and pump and treatment system was selected as remedial alternative.

Orange, TX – $600M RCRA RFI, CMS, and CMI:

Function: This project included I2M personnel and included an RFI assessment, CMS Study, and CMI remediation of buried waste caused by releases from a chemical plant waste water treatment system. A diversion ditch system was constructed to maintain plant operations during remediation activities. An RFI was conducted to determine the extent of buried waste and soil contamination. The CMI consisted of excavation, solidification, and disposal of hazardous waste. Final closure was successfully negotiated with the TNRCC.

 

Victoria, TX – $400M Groundwater Remediation:

Function: Project led by I2M (project hydrogeologists) this remediation project was implemented for a major chemical manufacturing plant. A pump-and-treat system was designed and constructed to contain a benzene and chloride contaminant plume. The capture zone design was based on a 400 gpm groundwater flow rate containing 280 ppb benzene and 8,400 ppm chloride from a seven point well system. The treatment system included an air stripper, low-temperature heater, and carbon-polishing units.

To review the technical literature on these technologies and techniques, search “remediation” and related key words in the I2M Web Portal (here).

Feel free to contact us to discuss your project needs or to arrange a speaking engagement by one of our Associates for a professional training session, a technical conference, society meeting, or for a graduation ceremony or other function where the knowledge and experience of our Associates may be of interest to your group.

The I2M Principals responsible for this discipline’s activities are:

Michael D. Campbell, P.G., P.H.

Richard C. Bost, P.E., P.G.

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