Designing and implementing an urban river remediation

In 2017, Consumers Energy completed a sediment response action in the Flint River to address manufactured gas plant‐related impacts in sediments and at the groundwater‐surface water interface. The project site is located in an urban, channelized, developed reach of the river. Multiple property owners and site constraints presented unique challenges for the remedial design, including the presence of Hamilton Dam at the downstream edge of the site which was considered a high‐hazard dam in “very poor condition.” An additional consideration was the City of Flint water crisis which was initially exposed in 2014. The sediment response action was not related to the water crisis because the site is located approximately two miles downstream of the City's water intake, but design, permitting, and construction began after 2014, so the timing added a heightened sense of awareness from the public stakeholders. The successful completion of the sediment response action was the result of deliberate planning, iterative engineering, and open communication with stakeholders that enabled a careful balancing of objectives with sometimes competing interests.     

Applied geologic,microbiological, and engineering constraints of in-situ BTEX bioremediation

An in-situ bioremediation project has been designed and constructed for a site in south-central Kansas just north of Wichita. A pipeline leaked an unknown quantity of refinedfuels in the 1970s. The spill was undetected until hydrocarbons were found in a nearby municipal water supply well. Of concern, from a regulatory perspective, are the alkylbenzene components found in the groundwater, including benzene, toluene, ethylbenzene, and xylene (BTEX). Initial abatement procedures, including free product removal and pumping, had become ineffective. In-situ bioremediation was selected to complete the restoration process. The project emphasizes the need for a strong understanding of the geologic and hydrogeologic conditions prevalent under the site. Site studies were conducted to determine the distribution and mass of the contaminant and the hydraulic regime. Laboratory microbial studies were used to determine the efficacy of nitrate as a primary electron acceptor. Information from site studies was used to design a treatment system tailored to the requirements of the site. The treatment system is designed to deliver the maximum amount of nutrient-enriched water to the contaminated zone while maintaining hydraulic control of the site.     

Use of mixed technologies to remediate chlorinated DNAPL at a Brownfields site

A former chlorofluorocarbon manufacturing facility in northern New Jersey was purchased for redevelopment as a warehousing/distribution center as part of the New Jersey Department of Environmental Protection's Brownfields redevelopment initiative. Soil and groundwater at the site were impacted with dense nonaqueous‐phase liquids (chlorinated organic compounds) and light nonaqueous‐phase liquids (petroleum hydrocarbons). The initial remedial strategy (excavation and offsite disposal) developed by prior site owners would have been cost‐prohibitive to the new site owners and made redevelopment infeasible. Mixed remedial technologies were employed to reduce the cost of remediation while meeting regulatory contaminant levels that are protective of human health and the environment. The most heavily impacted soils (containing greater than 95 percent of the contaminant mass) were excavated and treated onsite by the addition of calcium oxide and lime kiln dust coupled with physical mixing. Treated soils were reused onsite as part of the redevelopment. Residual soil and groundwater contamination was treated via in situ injections of emulsified oil to enhance anaerobic biodegradation, and emulsified oil/zero‐valent iron to chemically reduce residual contaminants. Engineering (cap) and administrative (deed restriction) controls were used as part of the final remedy. The remedial strategy presented in this article resulted in a cost reduction of 50 percent of the initial remedial cost estimate. © 2008 Wiley Periodicals, Inc.     

Best Available Treatment Technologies Applied to Groundwater Circulation Wells

Groundwater circulation wells (GCWs) are a quasi‐in‐situ method for remediating groundwater in areas where remediation techniques that limit the water available for municipal, domestic, industrial, or agricultural purposes are inappropriate. The inherently resource‐conservative nature of groundwater circulation wells is also philosophically appealing in today's culture, which is supportive of green technologies. Groundwater circulation wells involve the circulation of groundwater through a dual‐screen well, with treatment occurring between the screens. The wells are specifically designed so that one well screen draws in groundwater and the second returns the groundwater after it has been treated within the well. Historically, the treatment has been performed with specialized equipment proprietary to GCW vendors. Two full‐scale pilot systems at a formerly used Defense Superfund site in Nebraska used best available technologies for treatment components. A multiple‐tray, low‐profile air stripper typically used for pump‐and‐treat remediation systems was successfully adapted for the GCW pilot system located in a trichloroethylene (TCE) hot spot. An ultraviolet water disinfection system was successfully adapted for the GCW pilot system located in a hot spot contaminated with the explosive compound hexhydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX). The pilot systems showed that GCW technology is competitive with a previously considered pump‐and‐treat alternative for focused extraction, and the regulatory community was supportive of additional GCW applications. A remedial design for the site includes 12 more GCW systems to complete focused remediation requirements. © 2002 Wiley Periodicals, Inc.     

Case study: On-site remediation of soil and groundwater for a michigan town's water supply

In 1993 environmental consultants, working in concert with the State of Michigan, discovered groundwater contamination that threatened the drinking water supply of the town of Big Rapids. The contamination originated from leaking underground storage tanks and gasoline lines, which were removed. A pilot study indicated the contaminated area extended to 240′ x 180′ and affected soil as well as groundwater. A remediation plan was designed by and implemented by Continental Remediation Systems, Inc., a Natick, Massachusetts, firm. The remediation plan is ongoing and includes an interceptor trench to stop gasoline from flowing into the creek, as well as air sparging to vent and treat the contaminated soil. It is anticipated that the remediation project will take six months to complete. The chief advantage of on-site remediation is that it avoids the costs and liabilities associated with landfill disposal and no materials need leave the site.     

Using wind to power a groundwater circulation well—preliminary results

In areas of the country where the U.S. Department of Energy has classified the available wind resources as Class 3 or greater, the use of wind turbines to provide power to relatively small remediation systems such as groundwater circulation wells may be technically and economically feasible. Groundwater circulation wells are a good candidate technology to couple with renewable energy, because the remediation system removes contamination from the subject aquifer with no net loss of the groundwater resource, while the wind turbine does not create potentially harmful air emissions. Wind data collected in the vicinity of the former Nebraska Ordnance Plant Superfund site were used to select a wind turbine system to provide a portion of the energy necessary to power a groundwater circulation well located in an area of high trichloroethylene groundwater contamination. Because utility power was already installed at the remediation system, a 10 kW grid inter‐tie wind turbine system supplements the utility system without requiring batteries for energy storage. The historical data from the site indicate that the quantity of energy purchased correlates poorly with the quantity of groundwater treated. Preliminary data from the wind turbine system indicate that the wind turbine provides more energy than the remediation system treatment components and the well submersible pump require on a monthly average. The preliminary results indicate that the coupling of wind turbines and groundwater circulation wells may be an attractive alternative in terms of the system operation time, cost savings, and contaminant mass removal. © 2004 Wiley Periodicals, Inc.     

Millville site multimedia remediation program

The Millville Remediation Program recently received the 1995 Honor Award for national excellence in environmental engineering from the prestigious American Academy of Environmental Engineers (AAEE). This article discusses various aspects employed to investigate and remediate multimedia contamination at the site and the unique applications of technologies which were responsible for receiving the AAEE honor award. Unique aspects of the project included utilization of variable speed drives to set individual pumping rates for each groundwater recovery well, development of sophisticated remote monitoring and operation capabilities which minimized O&M labor costs, and development of a groundwater treatment system which has consistently achieved nondetect effluent discharges. The remote monitoring and operation capabilities enables O&M staff to monitor and change setpoints for the groundwater recovery, treatment, and recharge systems.     

Insufficient source area remediation results in the rebound of TCE breakdown products in groundwater

In the early 1990s, a soil removal action was completed at a former disposal pit site located in southern Michigan. This action removed waste oil, cutting oil, and chlorinated solvents from the unsaturated zone. To contain groundwater contaminant migration at the site, a groundwater pump‐and‐treat system comprised of two extraction wells operating at a combined flow of 50 gallons per minute, carbon treatment, and a permitted effluent discharge was designed, installed, and operated for over 10 years. Groundwater monitoring for natural attenuation parameters and contaminant attenuation modeling demonstrated natural attenuation of the contaminant plume was adequate to attain site closure. As a result of incomplete contaminant source removal, a rebound of contaminants above the levels established in the remedial action plan (RAP) has occurred in the years following system shutdown and site closure. Groundwater concentrations have raised concerns regarding potential indoor air quality at adjacent residential properties constructed in the past 9 to 10 years. The only remedial option available in the original RAP is to resume groundwater pump‐and‐treat. To remediate the source area, an alternate remediation strategy using an ozone sparge system was developed. The ozone sparge remediation strategy addresses the residual saturated zone contaminants beneath the former disposal pit and reestablishes site closure requirements without resumption of the pump‐and‐treat system. A pilot study was completed successfully; and the final system design was subsequently approved by the Michigan Department of Environmental Quality. The system was installed and began operations in July 2010. As of the January 2011 monitoring event, the system has shown dramatic improvement in site contaminant concentrations. The system will continue to operate until monitoring results indicate that complete treatment has been obtained. The site will have achieved the RAP objectives when the system has been shut down and meets groundwater residential criteria for four consecutive quarters. © 2011 Wiley Periodicals, Inc.     

Case study of ex situ remediation and conversion to a combined in situ/ex situ bioremediation approach at an oxygenated gasoline release site

In response to an oxygenated gasoline release at a gas station site in New Hampshire, a temporary treatment system consisting of a single bedrock extraction well, a product recovery pump, an air stripper, and carbon polishing units was installed. However, this system was ineffective at removing tertiary butyl alcohol from groundwater. The subsequent remedial system design featured multiple bedrock extraction wells and an ex situ treatment system that included an air stripper, a fluidized bed bioreactor, and carbon polishing units. Treated effluent was initially discharged to surface water. Periodic evaluation of the remediation system performance led to system modifications, which included installing an additional extraction well to draw contaminated groundwater away from an on‐site water supply well, adding an iron and manganese pretreatment system, and discharge of treated effluent to an on‐site drywell. Later, the air stripper and carbon units were eliminated, and an infiltration gallery was installed to receive treated, oxygenated effluent in order to promote flushing of the smear zone and in situ bioremediation in the source area. This article discusses the design, operation, performance, and modifications to the remediation system over time, and provides recommendations for similar sites. © 2007 Wiley Periodicals, Inc.     

Limitations on infiltration and reinjection of treated groundwater to remove trace amounts of pesticides in groundwater and soil

Infiltration and reinjection of treated groundwater have been used to increase the recovery of pesticide-related constituents at a pesticide formulation plant that produces consumer pesticide products. The stratigraphy at the site consists of silty and sandy clay deposits overlying a shallow silt, sand, and gravel aquifer. The groundwater and soils in two areas in the northwest portion of the property have been identified as being significantly affected by pesticide and pesticide-related compounds. An integrated system of soil removal, recovery wells, injection wells, an infiltration gallery, and a cut-off wall was selected as the best remedial alternative. Groundwater modeling, column tests, biological jar tests, and a pilot test demonstrated the feasibility of the system. The affected groundwater is treated to drinking-water quality by a system of filtering and carbon adsorption. Approximately 75 percent of the treated water is reinjected or allowed to infiltrate through the vadose zone, and the remainder is discharged to the local sewer system. Initially, the system was effective in removing the dissolved, suspended, and weakly adsorbed constituents. Subsequently, the recovery rate of the chemical constituents became dependent on chemical and physical processes related to the presence of residual amounts of dense, nonaqueous phase liquids and the clay content of the strata. The rate of pesticide recovery has decreased because of the retarding effect of the clay and the low solubility of the pesticides.     

Remediating groundwater using a hydraulic containment system for pump and treat

Twenty years of waste disposal operations at the Conservation Chemical Company (CCC) site in Kansas City, Missouri, led to contamination of soils and groundwater on a six-acre site. As a result of this contamination, the site was listed on the federal government's National Priorities List. Following extensive litigation initiated in 1982, more than 200 contributors to the site (Potentially Responsive Parties or PRPs), CCC's insurance companies, and the government ultimately reached a settlement to fund the remedial action. The remedy that was agreed upon included: (1) a permeable cap to allow water intrusion to assist groundwater cleanup; (2) a with drawal well system to achieve an inward groundwater gradient; and (3) a groundwater treatment system employing several unit operations. Containment of the contaminated plume relied on hydraulic, rather than structural, containment to prevent mitigation of contaminants from the site. ABB Environmental Services, Inc. (ABB-ES) was retained to perform treatability tests and to design, construct, and start up the groundwater treatment plant after the installation of the permeable cap by others.     

GIS-based approach for optimized siting of municipal solid waste landfill

The exponential rise in the urban population of the developing countries in the past few decades and the resulting accelerated urbanization phenomenon has brought to the fore the necessity to develop environmentally sustainable and efficient waste management systems. Sanitary landfill constitutes one of the primary methods of municipal solid waste disposal. Optimized siting decisions have gained considerable importance in order to ensure minimum damage to the various environmental sub-components as well as reduce the stigma associated with the residents living in its vicinity, thereby enhancing the overall sustainability associated with the life cycle of a landfill. This paper addresses the siting of a new landfill using a multi-criteria decision analysis (MCDA) and overlay analysis using a geographic information system (GIS). The proposed system can accommodate new information on the landfill site selection by updating its knowledge base. Several factors are considered in the siting process including geology, water supply resources, land use, sensitive sites, air quality and groundwater quality. Weightings were assigned to each criterion depending upon their relative importance and ratings in accordance with the relative magnitude of impact. The results from testing the system using different sites show the effectiveness of the system in the selection process.     

Dynamic workplans and field analytics: Metals assessment by inductively coupled plasma/optical emission spectroscopy

Hazardous waste site investigations were carried out at the Marine Corps Air Station (MCAS) in Yuma, Arizona and at Hanscom Air Force Base (HAFB) in Bedford, Massachusetts. The purpose of the first was to determine the location and extent of metals contamination throughout the base. The objective of the second was to evaluate the risk of metals contamination to groundwater from soil at three locations within the airfield. Dynamic workplans were developed and an adaptive sampling and analysis plan carried out with the data produced in the field used to support the goals of each project. An inductively coupled plasma/optical emission spectrometer (ICP/OES) was modified for field operation. A more efficient microwave digestion method and pressurized Teflon filtration system were developed for the HAFB project. Results were comparable to standard Environmental Protection Agency (EPA) methods, which must rely on two digestion procedures to recover EPA-targeted metals within the prescribed recovery range. The MCAS investigation, conducted over a five-month period, advanced the Navy's efforts from 30 months behind schedule to 18 months ahead of schedule, while the data generated at HAFB showed no risk to groundwater from metals.     

U（Ⅵ）在处置场地质环境中迁移规律的模拟研究

以西南某极低放射性废物处置场土壤为研究对象,采用静态吸附和动态吸附实验获取处置场地质特征参数,结合PHREEQC软件和地下水数值模拟系统（GMS）预测U（Ⅵ）在处置场环境中的化学种态和迁移规律。结果表明：U（Ⅵ）在处置场土壤中的吸附平衡时间为20 d,吸附分配系数为358 mL/g;U（Ⅵ）在处置场地下水环境中主要以UO₂（CO₃）₂^2-和UO₂（CO₃）₃^4-形式存在;处置场关闭后安全运行30 a,处置场中心U（Ⅵ）质量浓度下降4.20%,外围50 m与下游河流边界处U（Ⅵ）质量浓度分别为初始给定值的3.40%和1.32%;在12 a时有0.10%的U（Ⅵ）到达河边。     

The treatment of contaminated water at remedial wood preserving sites

Contaminated groundwater and surface water have posed a great challenge in restoring wood preserving sites to beneficial use. Often contaminated groundwater plumes extend far beyond the legal property limits, adversely impacting drinking water supplies and crop lands. To contain, treat, and/or remediate these valuable resources is an important part of restoring these impacted sites. Various options are available for remediating the groundwater and other affected media at these sites. Frequently, pump and treat technologies have been used that can provide well‐head treatment at installed extraction wells. This approach has shown to be costly and excessively time consuming. Some of the technologies used for pump and treat are granular activated carbon (GAC), biotreatment, and chemical oxidation. Other approaches use in‐situ treatment applications that include enhanced bioremediation, monitored natural attenuation (biotic and abiotic), and chemical reduction/fixation. Ultimately, it may only be feasible, economically or practicably, to use hydraulic containment systems. Depending upon site‐specific conditions, these treatment approaches can be used in various combinations to offer the best remedial action. A comparison of water treatment system costs extrapolated from the treatability studies performed on contaminated groundwater from the McCormick/Baxter Superfund site in Stockton, California, yielded operation and maintenance costs of $1.19/1,000 gal. for carbon treatment and $7.53/1,000 gal. for ultraviolet (UV) peroxidation, respectively.     

Treatment of Highly Contaminated Groundwater: A SITE Demonstration Project

From September through November 1994, the U.S. Environmental Protection Agency (EPA) conducted a field demonstration of the remediation of highly contaminated groundwater at the Nascolite Superfund site located in Millville, New Jersey. Besides high concentrations of the major contaminant, methyl methacrylate (MMA), the groundwater also contained small amounts of volatile and semivolatile organic compounds. ZenoGem® technology, an integrated bioreactor and ultrafiltration membrane system, was employed for this demonstration project. Approximately 30,000 gallons of groundwater containing MMA in concentrations of 567 to 9,500 milligrams per liter (mg/L) and chemical oxygen demand (COD) values ranging from 1,490 to 19,600 mg/L was treated. The demonstration focused on the system's ability to remove MMA and reduce COD from the groundwater. Results of the three‐month demonstration showed that average MMA and COD removal efficiencies were greater than 99.9 and 86.9, respectively. The total cost of treatment, depending on the duration of the project, is estimated to vary from $0.22 to $0.55 (in 1994 dollars) per gallon of groundwater treated. © 2001 John Wiley & Sons.     

A Practical Guide to Estimating Cleanup Costs

Cost estimates are frequently developed to evaluate hazardous‐waste‐site cleanup options in support of a site investigation, remedy selection decision, or assessment of environmental liabilities. The accuracy of the cost estimate depends largely on the quality of the information available at the time it is prepared. This article presents a practical guide to developing a cleanup cost estimate. It includes information on how to document assumptions, use the latest technical resources, and perform basic adjustments to account for uncertainty and the time value of money. The content is based upon a recent guidance document issued by the U.S. Environmental Protection Agency and U.S. Army Corps of Engineers entitled A Guide to Developing and Documenting Cost Estimates during the Feasibility Study (USEPA, 2000). © 2001 John Wiley & Sons, Inc.     

Transpiration in Black Willow Phytoremediation Plots as Determined by the Tree‐Trunk Heat Balance Method

Plant transpiration is a critical process that affects the water balance in phytoremediation plots. The desired effect is to remove contaminated water from the soils through the plant metabolism. Thus, the transpiration rate can be a major component in modeling the groundwater flow and solute transport for a phytoremediation project and ultimately can determine the time expected to achieve remedial goals. Two phytoremediation plots of black willows (Salix nigra) were planted during October 1996 over separate,shallow groundwater plumes at a site in southeastern Louisiana. Concentrations of less than 10 mg/l of the herbicide bentazon were present in the shallow groundwater. Field experiments were developed and performed during the 1998 and 1999 growing seasons to measure sap flow as an indicator of plant transpiration. The tree‐trunk heat balance method was used to measure sap flow. Sap flow was indexed to the cross‐sectional area of the stem, and the sum of the available stem area for each plot was used to calculate the monthly water use in each plot. Daily water use in the plots averaged between 6 to 13 l/day/m² during the periods tested in 1998 and 1999. By applying growth‐rate observations with the daily water use, annual water use at tree plot maturity was estimated to be 3.6×10⁶ l/year in Plot 1 and 11.39×10⁶ l/year in Plot 2. Application of these data will allow groundwater modeling to be performed to measure the effectiveness of phytoremediation and to predict closure of remediation at the test site. © 2001 John Wiley & Sons, Inc.     

Using uncertainty analysis to reduce costs at a pump-and-treat site

The former Nebraska Ordnance Plant site in east-central Nebraska was included on the National Priorities List because of explosives and trichloroethene contamination. The preferred groundwater remedy includes hydraulic containment of the contaminated groundwater and focused extraction of the more highly contaminated groundwater as components of the remedial action. The purpose of hydraulic containment is to stop the spread of contamination, while the more aggressive focused extraction will be used to speed up the remediation and reduce total cleanup costs. This case study illustrates how straightforward groundwater models were combined with uncertainty analysis to select a precise definition of the focused extraction areas. The purpose of the analysis was to reduce ultimate remediation costs, given the significant uncertainty associated with the estimated remediation times. The selected definition provides a basis for more sophisticated groundwater modeling, the goal of which was to locate extraction wells and define their flow rates. The batch flushing model provided the governing equations, and Monte Carlo analysis was used for the uncertainty analysis. All of the analysis was performed on a personal computer using commercially available software.     

Interim pump-and-treat remediation of a hydrocarbon-contaminated aquifer

The continuous and discontinuous release of petroleum hydrocarbons from an oil refinery in Alaska resulted in the contamination of an unconfined glacial outwash aquifer. Geologic conditions at the site allowed for the vertical migration of hydrocarbon product to the water table and subsequent formation of an areally extensive floating product layer. Since the petroleum hydrocarbon phase would provide a major source of BTX (benzene, toluene, xylene) contamination to the groundwater, interim product and groundwater recovery measures were initiated to limit aquifer degradation. Phase I remedial activities involved the operation of nine well pairs, with one well used for groundwater extraction and the other for product recovery. Phases II and III involved expansion of the recovery well network and use of a two-pump system. Petroleum product recovered was reprocessed at the refinery. Contaminated groundwater was initially treated using the refinery's wastewater treatment system, but treatment inefficiencies and continued system expansion necessitated use of a separate treatment unit. Performance evaluations indicate that the remedial phases have been successful in halting further contaminant migration and in recovering a significant volume of the released petroleum hydrocarbons.