millville site multimedia remediation program

Millville Site Multimedia Remediation Program

Richard Barbour Jeffrey M. Smith Kenneth Wenz

Ricbard Barbour, P.G., CHCM, is a Senior Associate of ERM- Nortbeast and was Project Director of tbe MUXvilc Site Remedidtion Program He bas 15 years of expertence in investi,gating and remediating baxardotrs waste sites and regulatoly negotiations Jeff- M. Smitb, Esq, is special council in tbe Los Angeles omce of Sedgwick Detert, Moran &Arnold Mr. Smitb concentrates bis practice on environmental regulatioa compliance, and corporate transac- tion work Prior to joining SDM&A in 1994 be was amliated for I5 years witb Atrex Industries, Inc, as plant manage?', corporate attorney, andmany as CEO andpresident of tbe company. Kennetb Wen% P. G., is a Senior Hydrogeologist at ERM- Nortbeast and sewed as assistant project managerlbydrogeologist on tbe Mill&&? Remediation Program He bas nine years experience in imrestigat- ing and remediating baxardous waste sites.

Tbe 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 emplo-wd to investigate and mediate multimedia contamination at the site and the unique applications of technologies which were responsible for receiving the AAEE honor award. Unique aspects of thepmject included utilization of variable speed drives to set individual pumping rates for each groundwater recovery well, development ofsophisticated m o t e monitoring and operation capabilities which minimized OGM labor costs, and development of a groundwater treatment system which has consistently achieved nondetect efluent dis- charges. The m o t e monitoring and operation capabilities enables OGM stafl to monitor and change sepints for the groundwater recovery, treatment, and recharge systems.

The site occupant is an aircraft maintenancehepair company located at the Millville Municipal Airport, Millville, New Jersey. The facility, which has been in operation since the mid-l940s, leases the property from the City of Millville. The site investigation under New Jersey's Environmental Cleanup Responsibility Act (ECRA), which has since been superseded by the Industrial Site Recovery Act (ISRA), was triggered when the site occupant company was sold by the client in 1985. The client entered into an Order of Consent with the New Jersey Department of Environmental Protection (NJDEP), which required the investigation and remediation of site-related contamination. The major objective of the remedial program was to adequately characterize site conditions, allowing for an aggressive cleanup program which would operate remotely in order to minimize long- term operation and maintenance (O&M) costs and expedite remediation. Ultimately, there were four entities involved in the investigative and remedial program: the client, the site occupant, NJDEP, and the City of Millville. In addition, to add further complexity, the site is located within the Delaware River basin, so the Delaware River Basin Commission was also involved in the review and approval process. The varied concerns and requirements of each entity had to be coordinated and resolved.

Site geology consists of interbedded silt, silt and clay, and silty sand of the Cohansey and upper Kirkwood Formations. At a depth of between 60

CCC 1051 -5658/95/0504083-21 (0 1995 John Wiley 8 Sons, Inc.

83

RICHARD BARBOUR JEFFREY M. SMITH KENNETH WENZ

and 80 feet below grade, this unit becomes significantly finer and acts as a semi-confining layer for the underlying coarse sand. This semiconfining layer consists of three very fine grained beds, each five- to eight-feet thick. The groundwater contamination at the site is found above this semi-

The site contained various areas of environmental concern (AECs), including contaminated soils, contaminated groundwater, and two areas with free product. Contaminants of concern included chlorinated solvents, petroleum products, polychlorinated biphenyls (PCBs), and toxic metals. Two groundwater plumes were characterized at the site. The major one was found to be emanating from the main productionhepair facilities (known as the Main Plant), and a minor one from a separate engine test cell.

Soil contamination ranged in depth from near-surface (petroleum-related compounds and metals) to the water table (volatile organics), up to 40 feet below grade. The wide range of soil contaminants and depths have required a varied suite of remedial methcds, from excavation and off-site disposal to soil vapor extraction (SVE). Contaminants of concern in groundwater are exclusively volatile organic compound5 WOCs), with significant areal distribution (1,500 feet wide by 3,500 feet long-Exhibit 1) and range of concentrations (up to 55,000 parts per billion). Approximately 90 percent of the dissolved plume consists of tetmchloroethylene (PCE).

The combination of multiparty involvement, multimedia contamination, and a complex hydrogeologic environment resulted in a complex project from both a technical and management viewpoint.

confining unit.

Soil contamination ranged in depth from nw-surface to the water table, up to '' feet below grade*

SOILS INYESTIGATION Initially, a total of 17 AECs related to soils were examined. Investigative

activities related to soils included geophysical studies (downhole, magne- tometry, and ground-penetrating radar), used to characterize site stratigra- phy and to evaluate the reported presence of buried drums, and subsurface sampling during the installation of 70 monitoring wells and numerous soil borings (including several installed to 200 feet), performed to obtain a comprehensive stratigraphic and chemical profile of the site. The locations of the monitoring wells and soil borings were determined based on current and historical site operations, locations of ahoveground and underground storage tanks, location of underground fuel lines, and results of soil gas, geoprobe, and geophysical surveys. In addition, physical testing, including grain size distribution analysis and permeability tests on Shelby tubes, was performed on site soil samples.

A geologic cross-section of the site is shown in Exhibit 2. The site geology consists of interbedded silt, silt and clay, and silty sand of the Cohansey and upper Kirkwood Formations. Significant zones of thin clay laminations are present in the upper 60 to 80 feet. The clay locally impedes the downward migration of both water and contamination. At a depth of between 60 and 80 feet below grade, this unit becomes significantly finer, and acts as a semi-confining layer for the underlying coarsc sand. This semi-confining layer consists of three very fine grained beds, each five to eight feet thick. The groundwater contamination at the site is found above

84 REMEDIATION/AUTUMN 1995

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M.ILLVILLE S m MULTIMEDIA REMEDMTION PROGRAM

In order to evaluate the applicability of the SVE method, a pilot test program was conducted over a three-week period.

this semi-confining unit. The underlying coarse sand is tapped by three large-capacity public water supply wells at the airport, located upgradient and cross-gradient of the site.

The soil characterization program defined eight areas at the Main Plant and the separate engine test cell where remediation was required. Contaminants of concern included VOCs, petroleum products, and/or metals. Most of these were shallow and relatively small in size, so the remediation method chosen was excavation and off-site disposal. In two areas, however, the VOC contamination extended to the water table, located 35 to 40 feet below grade. The great depth involved, in combination with the proximity of these areas to existing and planned structures, eliminated excavation as a remedial alternative. Soil vapor extraction WE) was therefore selected.

In order to evaluate the applicability of the SVE method, a pilot test program was conducted over a three-week period in 1992. This program involved the installation of one SVE extraction well and a series of vacuum observation wells at each AEC. In both cases, existing monitoring wells were also used as vacuum monitoring points. A skid-mounted vapor extraction unit was used for the pilot testing. For each test the vacuum unit was run at several different rates to evaluate a range of potential operating scenarios. The vacuum and air flow rate were adjusted and the SUbSUrfidCC

pneumatic response was measured by periodically recording the change in vacuum at the vapor observation wells, using hand-held vacuum gauges. Extracted vapors were monitored during the testing using several portable instruments including organic vapor analyzers and a combustible gas indicator. In addition, vapor samples were collected before and after emission controls, using adsorption sampling tubes. Thesc tubes were sent for laboratory analysis. Extracted vapors were treated by activated carbon and discharged to the atmosphere. Tempemture and relative humidity measurements were also measured at various locations within the vapor treatment train, to evaluate operational limitations. Thesc data showcd that SVE would be an effective remediation method for both AECs.

Air sparging was also evaluated during the pilot test program. However, while pressure data indicated a large area of influence at cach AEC for this technique, other measured parameters (soil v~pors, dissolvcd oxygen, water table elevation) did not support this conclusion. These data contradictions are explained by the heterogeneous geology in these areas, which includes thin clay laminations that may interfere with air dhpersion. Air sparging was therefore eliminated from the remedial plan for these AECs.

Because SVE was the only feasible remediation method applicable to these two areas, a technology-based criterion for shutoff of the SVE system was proposed. Samples of the extracted vapors have been, and will continue to be, quantitatively and semiquantitatively analyzed. These data, when plotted against time, will be examined for trends. It has been proposed that the systems will be shut down when the respective plots show that asymptotic conditions have been attained. At that time, soil samples will be collected for analysis to detcrmine whether decd rcstric- tions will be required.

~~

REMEDIATION/AUTUMN 1995 87

GROUNDWATER INVESTIGATION The monitoring well network at the site currently consists of a total of

66 wells (refer to Exhibit 1 for well locations). Of this total, 41 are screened across the water table (located approximately 25 to 40 feet below grade), 13 are intermediate in depth (screened in the zone from 55 to 80 feet below grade), and 12 are deep (screened in the zone from 85 to 100 feet below grade). These depth designations were chosen based on the generalized geologic units.

A subset of wells that define the horizontal and vertical extent of the Main Plant plume are sampled on a quarterly basis to ensure that the boundaries of the plume remain defined. Other Main Plant monitoring wells are sampled annually to maintain a database for the evaluation of the efficiency of the groundwater remediation system currently operational. Most wells in the separate engine test cell are sampled only annually, with a few sampled semiannually.

Natural groundwater flow in the shallow and intermediate wells is to the northeast andbecomes more easterly in the northern portion of the site. Within the zone monitored by the deeper weils, groundwater flow is more southerly than in the shallow or intermediate zones, reflecting the regional flow.

The potentiometric surface elevations of nearby shallow and intermediate wells are generally comparable. The potentiometric surface of the deep wells has consistently been lower than that of the nearby shallow/ intermediate wells, indicating a downward component of flow. However, the fine-grained nature of the silt and clay unit acts to impede the downwardmovement of the impacted groundwater. This is shown by the groundwater quality data, which show that total VOC concentrations in the shallow and intermediate wells are generally two to three orders of magnitude higher than in nearby deep wells.

When the extent of the VOC plume had been tentatively defined, it became apparent that a groundwater remediation effort was required at the Main Plant. Therefore, a pump test was performed in 1991 in order to obtain the site-specific hydrologic data necessary to design a recovery system for the site. The pump test program consisted of a step-drawdown test and a constant rate test. Results of the step-drawdown test were used to determine the maximum sustainable rate for the subsequent constant rate test. Analysis of the pump test data yielded values for transmissivity and hydraulic conductivity (both horizontal and vertical) that were utilized in the comprehensive groundwater flow modeling effort for the site.

The objectives of the modeling effort were to (1) locate a network of recovery wells that would effectively extract impacted groundwater from within the portion of the plume targeted for remediation; ( 2 ) determine the pumping rate for the recovery system necessary to contain thc dissolved plume; (3) select recharge areas to provide the hydraulic control required by the closed-loop recovery/recharge system; and (4) verify the capture zones of the recovery wells, using particle tracking. The USGS three- dimensional flow model MODFLOW, which was modified slightly in order to facilitate its use with the required large data sets and to ensure its compatibility with drafting software, was used.

A pump test was performed in order to obtain the site- specific hydrologic data necessary to design a recovery system for the site.

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88 REMEDUTION/AUTUMN 1995

M J L L . ~ E S m MULTIMEDIA REMEDIATION PROGRAM

The treated groundwatet is recharged upgradient of the plume, thus causing flushing and establishment of a near cbsed- loop system.

The modeled domain was extended beyond the site boundaries in order to reach natural flow boundaries. The site is located approximately in the center of the area. Vertically, the modeled area consists of five layers, based on regional and site-specific cross-sections which were constructed from lithologic and geophysical logs of on-site wells and other wells within and adjacent to the modeled area (JZxhibit 3). These layers extend to beneath the coarse sand screened by the public water supply wells.

Aquifer parameters used in the model were determined during the on- site investigation (i.e., pump test program, slug tests, infiltration testing) and from various literature sources. After calibration and sensitivity analysis, the model was used to evaluate different configurations of recovery and recharge wells, including the effects of various well locations and pumping rates. In addition, particle tracking was used to confirm the capture zone of the final recovery network. These modeling results indicated that a recovery system consisting of 13 wells, each pumping at a rate of ten gallons per minute, woiild be sufficient to arrest the off-site migration of the plume and remediate the on-site contamination. Recovery well locations and the modeled capture zone for the final system are shown in Exhibit 4. The capture zone of the recovery system, defined from field measurements, has consistently matched that estimated by the modeling effort (Exhibit 5). The capture zone encompasses a significant area around the site and was designed to capture 95 percent of the contaminant mass. The broad-based nature of the capture zone will also remediate other contaminant sources at the airport.

The treated groundwater is recharged upgradient of the plume, thus causing flushing and establishment of a near closed-loop system (Exhibit 4). The "Random Walk" solute transport modcling data was used to determine chemical removal rates. Particle tracking was performed in order to delineate the capture zone of the proposed recovery system. The modeling results, aggressive groundwater collection .system, and upgradient/closed-lop recharge .system concept were submitted to NJDEP, which conairred with the model results, leading to approval to discharge at existing background levels. However, it should be noted that the treatment systems, which have been in operation for more than a year, have consistently removed all VOCs from the recovered groundwater. A comparison of the influent and effluent concentrations is shown in Exhibit 6.

With regard to the independent groundwater plume associated with the separate engine test cell (Exhibit l), the results of the groundwater flow and mass transport models were utilized to demonstrate to the regihtors that no impact would occur to the nearest downgradient receptor. Consequently, a groundwater monitoring plan, coupled with a natural groundwater remediation program, was approved for this AEC. By achieving this, a significant savings was realized by the client and the environment was protected.

DEVELOPMENT OF RISK-BASED CLEANUP LEVELS Based on the results of the remedial investigation and groundwater

modeling efforts, risk-based cleanup levels were developed for site soil and [conrimed on page 94)

REMEDJATION/AUTUMN 1995 89

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MILLVILLE S m MULTIMEDIA REMEDIATION PROGRAM

Exhibit 4. Flow Net Depicting the Capture Capabilities of the 13 Well Recovery System


RICHARD BAUBOUR JEFFREY M. S r m m KENNETH WENZ

Exhibit 5. Potentiometric Surface Elevation Contour Map for Shallow and Intermediate Wclls

92 REMEDIAITON/AUTUMN 1995

MILLVILLB S m MULTIMEDIA REMEDIATION PROGRAM

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groundwater. Although NJDEP had established cleanup levels under the ISRA/ECRA program for many of the chemicals of concern at the site, there were a number of factors unique to the site which suggested that use of the default cleanup levels would be unnecessarily stringent, resulting in additional remediation time and costs. Therefore, a risk assessment was performed in conformance with NJDEP requirements to i d e n t ~ site-specific cleanup levels which were fully protective of human health and the environment, yet would not result in unnecessarily extensive cleanup activities.

Cleanup levels for chemicals in soil were developed on the basis of three potential exposure pathways: (1) incidental ingestion of soil, (2) dermal absorption of chemicals in soil, and (3) leaching of contaminants in soil to groundwater and subsequent use of groundwater for water supply. Cleanup levels for each exposure pathway were calculated individually, and the lowest calculated level was adopted as the site cleanup level. The resulting cleanup levels were higher than the existing I S W C R A cleanup levels, but yet protective to human health and the environment resulting in a significant cost savings to the client.

Groundwater cleanup levels were also derived for this site using risk assessment methodology. These derived cleanup levels were used to determine the point at which active groundwater remediation at the site can be terminated. The cleanup levels were developed by niodeling contaminant migration in groundwater under a variety of simulated pumping periods.

An integral element of the proposed groundwater cleanup levels is that groundwater quality data will be reviewed on a regular basis during remediation to assess the validity of the original assumptions used in the model, to determine if modifications to the model are required and to evaluate the ability of the remediation system to meet these goals. To date, the original assumptions appear to be correct and the remedial systcms are achieving their goals.

Based on the modeling results, it was estimated that the time necessary for groundwater remediation would be 15 years. This information was utilized to ascertain O&M costs for the life of the project.

PILOTTESTMG In conjunction with the pump test program, full-scale pilot testing of

various groundwater treatment methods was performed. The Full-scale pilot testing program was employed over a 30-day period and treated 78,000 gallons of VOC-contaminated groundwater. Ultraviolet (W) peroxidation and air stripping technologies were tested both in series and parallel to ascertain their effectiveness. The contaminants of concern were VOCs, including PCE, 1,1,l-trichloroethane (TCA), and methylene chloride. The influent concentration of PCE was 2,500 ppb, making up 90 percent of the contaminant mass in groundwater. TCA and methylene chloride were present at much lower concentrations but were important because of the difficulty of removing them with UV peroxidation.

To ascertain the most effective retention time in terms of treatment and

Mu.- SITE MUL-IA REMEDIATION PROGRAM

The result8 of the pilot test demonatrated that a combined technology approach can clearly be applied.

RJMEDIATION/AUTUMN 1995

costs, reaction rates were developed using pilot test data. Site-specific reaction rates showed that a short retention time (38 seconds) would be sufficient to destroy PCE. However, a very long retention time (up to five minutes) was required to destroy the remaining contaminants. By polishing the effluent from the W unit through an air stripper, a discharge of less than 1 ppb of total VOCs could be achieved. The UV reactor destroyed the bulk of the VOCs, allowing the stripper to opeme without the use of emission controls. To date, effluent concentrations have been nondetect (Exhibit 6).

The pilot plant was assembled on-site consisting of a UV peroxidation system, an air stripper, and particulate filters. The groundwater flow path through the pilot plant was modified for three testing scenarios: (1) W peroxidation, (2) air stripping, and (3) both technologies combined in series. Process schematics of each of the three flow paths are presented in Exhibits 7 ,8 , and 9.

General Applicabillty of Results The results of the pilot test demonstrated that a combined technology

approach (W followed by AS) can clearly be applied. If W peroxidation is used in conjunction with air stripping, a 30-second W peroxidation retention time could be used to reduce the PCE concentration to below 10 ppb. A reactor volume of 100 gallons and a power consumption of 75 kw would be required, resulting in an annual energy usage of 657 niwhr. For subsequent air stripping, the packing height required to meet the effluent limits for all compounds is only 17 feet, which could be achieved with a single tower. The total mass of all compounds emitted to the atmosphere would be only 0.4 lbs/day, so emissions controls would not be required. Exhibit 10 summarizes the design requirements of the three alternatives. As indicated by this study, there are three important Factors to consider: amenability to W peroxidation, amenability to air stripping, and air pollution control requirements. The results of the pilot test demonstrated the following:

Alkenes are destroyed quickly by U V peroxidation. Aromatics, phenols, and many base neutral/acid extractable compounds react moderately, whereas alkanes require very long retention times. Air stripping is appropriate for compounds with high Henry’s law constants. These include aromatics, alkenes, and alkanes. Com- pounds with low Henry’s law constants, such as base neutralhcid extractable compounds, are virtually unstrippable. Air pollution control requirements are dictated by federal and state regulation. Many strictly regulated compounds are rapidly destroyed in a UV unit.

Based on these factors and the results of this study, it was concluded that W peroxidation followed by air stripping should be employed to solution while meeting regulatory requirements. (For additional details on the pilot program, refer to the Spring 1994 issue of Remediation.)

(continued on page 991

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MILLVILLE S m MULT~MBDIA REMEDIATION PROGRAM

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Exhibit 10. Comparison of Design Alternatives

UV/oxldatlon Alr Stripping I UV/oxidation: Retention time, min. Volume, gal. Power, kw Annual energy use, mw-hr Annual energy cost (Q $0.1 O/kw-hr)

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INTEGRATED APPROACH RESULTS IN COST SAVINGS The SVE and groundwater remediation systems were designed to

minimize O&M costs over the life of the project. As part of this initiative, a number of features were incorporated into the final design. These include remote operation capabilities for the groundwater recovery and treatment systems, automatic operation of the SVE and product recovery systems, combination of remediation methods for groundwater treatment, the upgradient recharge of the treated water, and the use of variable speed drives for the recovery well pumps.

The on-site computer control system ensures the smooth and efficient operation of the groundwater recovery, treatment, and recharge systems. The computer system was designed to automatically monitor and control all aspects of operation, including pumping rates. The computer system allows the entire process to be monitored remotely on an off-site computer via modem. This allows remote operation from anywhere in the United States and includes the ability to monitor the recovery, treatment, and recharge systems, and make changes to operating setpoints as required.

The heart of the remote operations capability of the design is the utilization of the TransPort System to provide the intelligent interface (VO) between the plant computer and system sensors, allowing for remote monitoring and the ability to make changes in system setpoints. Graphic screens and operator keyboard selections are accomplished through the utilization of the Genesis

REMEDUTION/AUTUMN 1995 99

Rx- BARBOUR JEFFREY M. S m RpJNEnr Wmz

Remote monitoring and operation of the system minimixes the need for on-site labor and reduces the associated O&M costs.

Control software, so that all process monitoring and control are implemented through seven custom gxaphic screens. The graphic screens allow the operator to remotely monitor the recovery well system, treatment system, and groundwater recharge system and make changes to operating setpoints, as required. An opet-dtions computer is located at the offices of ERM-Northeast in W d b u r y , New York, approximately 160 miles from the site.

Another key aspect of the remote operations is the modem hookup between the W systems and the manufacturer’s facilities in Canada. The modem allows the manufacturer’s (Solarchem) representatives to monitor W system operations and to troubleshoot in the event that operators or engineers are unable to resolve a problem. The modem allows Solarchem’s representatives to monitor the following:

process flow rate; lamp voltage, current, and power;

status of the unit’s control program; and history of the unit’s operation.

Remote monitoring and operation of the system minimizes the need for on-site labor and reduces the associated O&M costs.

The remote operations capability also required that the facility be fully automated with control alarms to automatically terminate Operations under specific conditions. The recovery, treatment, and recharge systems have system alarms which receive input signals from instrumentation and equipment. An alarm is signaled when a condition could threaten operating efficiency, operator safety, or the environment. All plant alarm conditions are monitored and enunciated by the plant computer control system. In addition, the most critical alarms directly activate the plant autodialer, which provides automatic callout to designated off-site person- nel. System alarms include the following:

detection of product in recovery wells; high-pressure discharge in recovery well vaults; high turbidity in bag filter system discharge; high differential pressure across bag filter system; moisture detected below W unit; high temperature in UV power supply; UV lamp covers open; high temperature in UV unit; low flow rate in W system; W lamp failure; failure of hydrogen peroxide feed system; low air flow from air stripper; high water level in air stripper sump; high levels in recharge well fields; high level in plant sump; low air temperature in plant building; and high air temperature in plant building.


MILLVIL.LE S m MULTIMEDIA REMEDIATION PROGRAM

Each recovery well is equipped with a submersible pump capable between 5 and 20 gallons per minute (gpm) and a variable speed drive. The pumping rate from each well is set and maintained through the interaction of the pump motors, variable speed drives (VSD) located in the plant building, electromagnetic flow meters located at each well, and the plant computer. The pumping rate is selected by the operator at the plant computer or from the remote computer. The variable speed drives adjust the speeds of the pump motors so that the actual pumping rate matches the operator-selected rates. Variable speed drives were included in the design of the groundwater recovery system for the purpose of automatic selection and control of individual well pumping rates. The unique applications of automatic pumping control rates are as follows:

They allow the pumping rate to be set to match the yield of each recovery well, even as the yield varies over time. Without control of pumping rate, the pumps would be prone to on/off cycling. This would cause the total flow to the plant to vary over a short period of time, making it difficult to optimize treatment. They allow the pumping rate from each individual well to be optimized so that only the amount of water necessary to control and reduce the groundwater plume is recovered. It also allows for shutdown of individual recovery wells over time as conditions improve, thus minimizing O&M costs. They allow the recovery well pumping rates to be readily balanced following automatic or manual shutdowns. They allow the recovery well pumping rates to bc monitored and adjusted from one central location via the plant computer, or from the remote computer location at the Woodbury, New York, office.

To further reduce capital costs, one conduit was utilized for all VSD wiring. Isolation transformers were installed to prevent VSD shutdown from secondary currents. The single conduit application is the first of its kind in the country.

As described above, the combination of UV/oxidation and air stripping has resulted in a significant reduction in O&M costs, compared to either technology alone. The Wloxidation has also destroyed influent PCE, which represents the vast majority of the dissolved plume.

Treated water is recharged upgradient of the plume and recovery wells, in order to establish a closed-loop subsurface flow system, thereby flushing additional contaminants from the aquifer. This further reduces the time and costs required for remediation.

AutomaficpumPink controz .rajes azzow the pumping rate to be set to match the yieM of each recovery well.

SYSTEM EFFECTIVENESS The groundwater recovery, treatment, and recharge system has been

operating for the past 18 months. The predicted capture zone illustrated in Exhibit 1 was based on flow line generated from the three-dimensional groundwater flow modeling as illustrated in Exhibit 4. A groundwater contour map has been developed based on recent groundwater elevation


RICHARD BARBOUR* JEFFREY M. Smm KENNETH WENZ

-bit 11. Site Layout and Monitoring Well Locations

102 REMEDIATION/A~~’UMN 1995

M u m S m MULTIMEDIA REMEDIATION PROGRAM

Site characterization activities were appropriate, and the recovery, treatment, and recharge eystenas designs are meeting the overall owectivea of the remedial program.

data which is illustrated in Exhibit 5. Based on the groundwater contour configuration, a capture zone was superimposed onto Exhibit 5 which matches closely with the predicted capture zone simulated in 1992. Based on field data, the number and placement of the recovery wells were appropriate.

The recovery wells were placed down the spine of the contaminant plume in order to aggressively remediate groundwater contamination. Groundwater flow modeling employed in 1992 simulated flow lines which are depicted in Exhibit 4. The flow lines predicted a “squeezing effect” on the central portion of the plume. An isocon map illustrated in Exhibit 11 has been prepared utilizing recent groundwater quality data. A review of Exhibit 11 and Exhibit 1 demonstrates that significant improvement in groundwater quality has occurred and a “squeezing effect” along the central portion of the plume has occurred as predicted.

Verification of modeling predictions through the ‘use of operational field data demonstrates that site characterization activities were appropriate, and the recovery, treatment, and recharge systems designs are meeting the overall objectives of the remedial program originally established in 1990. W


millville site multimedia remediation program

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