Cristex RD - Part2 (EK-ISCO) Section 7 .pdf

CRISTEX DRUM SUPERFUND SITE| FINAL REMEDIAL DESIGN – PART 2, REVISION 0

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7.0 EK-ISCO DESIGN

Remediation of the SSZ is focused on protection of human health and groundwater resources from continued migration and dissolution of adsorbed COCs, and possible residual DNAPL, into groundwater. EK-ISCO and biobarrier are the selected remedies for the SSZ at the Site. The EK- ISCO remedy is to target the suspected source area and the most strongly contaminated portion of the SSZ where residual DNAPL and adsorbed phase CVOCs may be present. Based on the CSM summary (Section 4.9), the EK-ISCO remedy (this Part 2 RD) will focus on treating the contaminant mass in the saprolite materials, the most strongly contaminated portion of the SSZ, thus, reducing the contaminant migration into the underlying transition zone. Given the high-flux nature of the transition zone, the treatment of saprolite materials is expected to result in improved groundwater quality in the transition zone beneath and downgradient of the EK-ISCO treatment zone. A remedy performance monitoring program (Section 9) will be implemented to evaluate the effects of the SSZ EK-ISCO. The monitoring results and the contaminant flux trends will be evaluated before determining the timing and extent of subsequent remedial action for the SSZ or DP.

Implementation of the EK-ISCO remedy involves the supply of DC power to electrodes installed in a network of electrode wells located within a target treatment area, thereby creating an electric field in the subsurface between electrodes (Figure 7-1). The electric field will transport the ionic amendment, i.e., the selected chemical oxidant, through the aquifer materials within the target treatment zone. A major mechanism for the EK transport process with the application of an DC electric field is electromigration (or ion migration). Electromigration is the movement of charged dissolved ions through an aqueous medium in response to the applied electric field.

The direction of ion migration is toward the electrode with a polarity opposite of the ion’s charge.

Organic contaminants in contact with the transported chemical oxidant will be oxidized, thereby eliminating contaminant mass in the treatment zone. EK-ISCO is a relatively innovative technology, and implementation of EK-ISCO could be subject to a license agreement from the patent holder of EK-based remediation process.

In addition to supplying DC power from the DC power units located in an EK system enclosure to the electrodes installed in individual electrode wells, remediation amendment solutions, including oxidant solution and buffer solution, will be supplied from the system enclosure to the electrode wells and supply wells located within the target treatment area. Figure 7-2 presents a process flow diagram (PFD) of the overall EK-ISCO remediation system and process. As illustrated in the PFD, oxidant feed to supply wells is a separate, independent component of the overall remediation system. For electrode wells, the remediation system will perform cross-circulation of water between paired cathode and anode wells, in addition to supply buffer solution to individual electrode wells to control pH conditions within the electrode wells. System operations will be controlled by a programmable logic controller (PLC). Additional design details of the remediation system components are provided in Sections 7.2 and 7.3.

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7.1 EK-ISCO REMEDY TARGET ZONES

The EK-ISCO remedy will focus on treating the contaminant mass within the saprolite materials of the SSZ. Based on the CSM and RAOs discussed in Sections 4 and 5, respectively, three separate EK-ISCO target zones are identified (Drawing Sheet C-401):

Target Zone Approximate Area Target Depth Interval* Zone 1 100 ft by 60 ft 20 ft to 50 ft bgs Zone 2 (2A) 100 ft by 60 ft 20 ft to 60 ft bgs Zone 2 (2B) 50 ft by 40 ft 20 ft to 60 ft bgs

* During remedy implementation at each target zone, installation of the first several wells selected from various parts of the target zone should provide field observations of lithology that further confirm the thickness of saprolite unit to be targeted. Groundwater samples can be collected from these first sets of wells and analyzed for target COCs to establish baselines conditions (see Section 12.1). The target depth intervals may be adjusted as needed based on the observed lithology and baseline groundwater quality data.

Drawing Sheet C-401 also shows the approximate boundaries of the soil excavation area that will be implemented as the primary remedy for impacted soil in the UZ. The design for the soil excavation remedy is provided in Part 1 RD report, and the EK-ISCO remedy will be implemented after the completion of UZ soil remedy.

It is noted that a former drum burial area in the general proximity of monitoring wells MW06 and MW06D was previously identified and investigated. While groundwater contamination was detected in this area, the concentrations detected (e.g., 1,300 µg/L PCE at MW06 screened at 13 to 28 ft bgs and 940 µg/L PCE at MW22I screened at 60 and 70 ft bgs; Figures 3-7 and 3-8) do not suggest presence of significant contaminant sources. This former drum burial area is not included as a target zone for the EK-ISCO remedy. Further monitoring of this area after EK-ISCO remedy implementation can better inform if additional remedial actions are needed for this area, and bioremediation may be a remedial alternative for considerations.

Each EK-ISCO target zone is further discussed below.

7.1.1 EK-ISCO Target Zone 1

Target Zone 1 in the general area of former drum storage pad is approximately 100 ft by 60 ft, and the target treatment depth interval is from 20 ft to 50 ft bgs. Solvent was reportedly used as a cleaning and degreasing agent for the fabrics from approximately 1966 to 1986. Solvent was presumably spilled at the former drum storage pad and seeped through the asphalt preferentially at low points. The highest concentration of PCE in soil detected to date was reported in 2010 by NCDENR (180,000 µg/kg) at 3 ft bgs at the eastern edge of the drum storage pad. Based on the soil quality data used to support the soil RD, the former drum storage pad is identified as one of the contaminant source areas for soil remedial actions.

The delineation of EK-ISCO Target Zone 1 in the area of former drum storage pad also considers the following:

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(a) The highest subsurface soil PCE concentration above water table in this area was detected at CDSB37 from 16 to 18 ft bgs (660 µg/kg; Figure 3-5), but the concentration at the same location decreased significantly at 18 to 20 ft bgs (130 µg/kg). A similar pattern was observed at CDSB36, as well as the observations at CDSB07 (PCE concentration at 330 µg/kg at 13 to 15 ft bgs) and the adjacent location MIP05 where PCE concentration was 1.6 µg/kg at 24 to 25 ft bgs (Figure 3-6).

(b) Soil PCE concentration data collected from below 20 ft bgs (i.e., general water table depth) were all fairly low (generally below 6 µg/kg; Figure 3-6).

(c) The highest groundwater PCE concentration detected in the saprolite zone in this area was at MW03 screened at 9 to 24 ft bgs (4,700 µg/L; Figure 3-7). The PCE concentration in the nearby MW03I, screened at 47 to 52 ft bgs, was significantly lower at 820 µg/L suggesting the majority of contaminant mass in this area was likely above the depth of 45 ft bgs. A well located within the footprint of former drum storage pad and screened in the transition zone (60 to 70 ft bgs), MW12I, detected PCE at 160 µg/L, also suggesting the absence of significant contaminant mass at depths in this area.

(d) A well located approximately 80 feet north of the former drum storage pad, MW13S screened at 20 to 30 ft bgs, detected PCE at 1,100 µg/L. This concentration is significantly lower than that at MW03 (4,700 µg/L) which is more representative of the conditions expected for a contaminant source area.

7.1.2 EK-ISCO Target Zone 2 (2A and 2B)

Target Zone 2 is in the general area of existing monitoring wells MW15S, MW21S, MW19S, and MW23S. Target Zone 2 is approximately 100 ft by 60 ft (Zone 2A) plus 50 ft by 40 ft (Zone 2B), and the target treatment depth interval is from 20 ft to 60 ft bgs. The four wells that define the Target Zone 2 are the wells with the highest detected PCE concentrations at the Site. The detected PCE concentrations at these wells (screened between 14.5 and 57.5 ft bgs) ranges from 4,400 to 9,200 µg/L (Figure 3-7), suggesting the presence of significant contaminant mass in the saprolite zone.

Noticeably, two monitoring wells (MW24S and MW25S), screened at 50 to 60 ft bgs, immediately downgradient from Target Zone 2 exhibited significantly lower PCE concentrations at 790 and 410 µg/L (Figure 3-7). Also, a transition zone monitoring well located within Target Zone 2, MW15I, which is adjacent to MW15S and screened at 83 to 93 ft bgs, detected a very low PCE concentration at 16 µg/L (Figure 3-8). A transition zone monitoring well immediately downgradient of Target Zone 2, MW25I, is adjacent to MW25S and screened at 77.5 to 87.5 ft bgs also has a low detected PCE concentration at 58 µg/L. These data suggest that most of the contaminant mass in Target Zone 2 is likely present above the depth of 60 ft.

Given its configuration, Target Zone 2 is presented as Zone 2A and Zone 2B. The EPA has decided to implement the EK-ISCO in Target Zone 1 first. The performance monitoring data and system operation monitoring data related to Zone 1 remedy implementation will be collected to support an evaluation for any potential adjustments needed for the remediation of Target Zone 2. The system designed and built for Zone 1 will have certain built-in flexibility (e.g., modular equipment enclosures, additional manifold connections) so the same system can be expanded as needed to also meet the needs for Zone 2 (Zones 2A and 2B combined) remedy implementation.

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7.1.3 Electrode Well and Supply Well Network

Within each of the EK-ISCO target zones, a network of electrode wells and supply wells will be installed. As presented in Drawing Sheet C-410, a total of 28 electrode wells and 24 supply wells are located within Target Zone 1, 28 electrode wells and 21 supply wells are located in Zone 2A, and 12 electrode wells and 12 supply wells are located in Zone 2B. The spacing between electrode wells is generally at 16 - 18 ft and each individual supply well is located generally at a midpoint between two electrode wells.

The overall orientation of the electrode well-supply well networks and electric field directions align along the general groundwater flow directions in the saprolite formation in the target zones (Figure 3-10). Table 7-1 presents the designation of electrical polarity (cathode or anode) for individual electrode wells. These designations of electrical polarity also result in the overall alignment of electric field orientation in each target zone with the general groundwater flow directions as discussed above. Figure 7-3 provides an illustration of electric field directions established by the arrangements of electrode polarity. As an example, for Target Zone 1, the electrode well-supply well orientation can be represented by the alignment between Z1-EW1, Z1-SW1, and Z1-EW2, and similarly between Z1-EW-8, Z1-SW7, and Z1-EW9. For Target Zone 2A, the orientation is along Z2A-EW1, Z2A-SW1, and Z2A-EW2. For Target Zone 2B, the orientation is along Z2B-EW1, Z2B-SW2, and Z2B-EW2.

As illustrated in Figure 7-3, the polarity of individual electrode wells can be switched to change the electric field orientation. One such change can be a reversal of the designations presented in Table 7-1 (i.e., switch all the designated cathode wells in Table 7-1 to anode wells and vice versa).

As presented in the PFD (Figure 7-2), the system is designed with cross-circulation between cathode wells and anode wells, as well as buffer amendment to electrode wells, for pH control.

The pairing of cathode wells and anode wells for cross-circulation is also presented in Table 7-1.

Additional design details for the cross-circulation are presented in Section 7.2.

7.2 AMENDMENT DELIVERY AND CROSS-CIRCULATION DESIGN

7.2.1 Electrode Well and Supply Well Design

Two types of EK remediation wells will be installed: electrode wells and supply wells. Electrode and supply wells will both be constructed of 4-inch diameter polyvinyl chloride (PVC). The well construction details and wellhead assembly completion are presented in Drawing Sheet C-511.

Each electrode well will have two electrodes (3/4-in diameter and two feet long each) spaced vertically apart in the well. Each electrode is connected by an electrical cable back to a DC power unit located in the system enclosure. Each electrode well is designed with tubing for cross-circulation and buffer supply. The design for cross-circulation flow and buffer supply is further discussed in Sections 7.2.5 and 7.2.6. Each supply well is designed with the tubing to allow oxidant supply. Each supply well is also designed with an additional opening at the wellhead to allow for inserting extraction tubing if needed for contingency purposes.

EK remediation wells will be installed with above-ground wellhead completions as shown in Drawing Sheet C-511. Each wellhead assembly includes a pressure safety valve and will be

7-5 equipped with opening ports for the electrical cable and tubing to go through and into the conduits that will continue back to the remediation system enclosure.

Groundwater monitoring wells will also be installed for the remedy performance monitoring.

Section 9 provides design information related to groundwater monitoring wells and the monitoring program.

7.2.2 Oxidant Dose

Based on the treatability study results (Section 6.1) and the EK-ISCO pilot test results (Section 6.2), the amount of permanganate to be applied in each target zone is:

Target Zone Approximate Dimensions

Estimated Treatment Zone Soil Quantity (kg)

Target Permanganate Dose (kg)

Zone 1 100 ft by 60 ft by 30 ft 6,120,000 19,500 Zone 2A 100 ft by 60 ft by 40 ft 8,160,000 25,000 Zone 2B 50 ft by 40 ft by 40 ft 2,760,000 8,000

These oxidant doses are derived based on NOD of 3 g permanganate per kg soil and assume soil unit weight at 1,200 kg per cubic meter. In addition, the oxidant demand of PCE (the dominant COC for treatment), which is very small compared to soil NOD, is factored in by considering an estimated PCE concentration of 1,100 µg/L in Zone 1 (4,100 µg/L in Zone 2) and an assumed porosity of 0.35 within the target zone.

With the well spacing of approximately 8 ft between a supply well and the corresponding electrode wells (Section 7.1.1) and an estimated net EK transport rate for permanganate at 1.3 -

4.1 ft per month (Section 6.2), the EK-ISCO remediation system is designed to supply the target quantity of oxidant to each target zone over a duration of approximately 8 months (Zone 1) to 10 months (Zone 2A/2B). Given the number of supply wells and the estimated operation duration, the system is designed to supply permanganate solution (457 g/L) at a rate of 2.1 gallons per day to each supply well.

7.2.3 Oxidant Delivery System

To supply the oxidant at the target rate to the target zone, individual 6-channel peristaltic pumps will be used to pump from the oxidant supply tanks located in an enclosure to the supply wells.

Drawing Sheets P-122, P-123, and C-702 present the planned oxidant supply systems for Target Zone 1 and Zone 2. Each peristaltic pump will withdraw concurrently from up to 6 solution tanks by way of a header. The peristaltic pumps will be controlled by a timer programmed in a PLC.

Several times a day, each supply well will receive a small volume of oxidant solution. The operational program, including the run time and frequency of oxidant supply events, is further discussed in Section 7.4.2.

Drawing Sheets C-420, C-601, and C-602 depict the routing of oxidant supply tubing from the amendment supply enclosure to the amendment supply wells. The tubing will be contained

7-6 within a protective PVC conduit that will include heat tracing to prevent freezing in cold temperatures.

With the designed target concentration of the oxidant solution, the system (peristaltic pump) can draw the solution directly from a vendor-supplied 275-gallon tote of 40% (wt.) sodium permanganate and pump to the designated supply wells. The oxidant totes will be equipped with ultrasonic level sensors to monitor the fluid level within the totes. The oxidant solution totes will be positioned within secondary containment inside a temperature-controlled enclosure designed with access to allow for tote replacement by a forklift or other appropriate equipment.

7.2.4 Oxidant Storage and Safety

The oxidant storage totes will be stored in a temperature-controlled, well-ventilated structure located between the well fields of Zone 1 and Zone 2A (Drawing Sheet C-401). Exposure to temperatures <38°F (3°C) may cause sodium permanganate crystals to form. At 5°F (-15°C), 40% (wt.) sodium permanganate product may freeze. Permanganate storage tanks should remain closed and should be properly ventilated locally to the atmosphere. Permanganate storage tanks should be kept away from any combustible materials such as paper or cloth. All storage tanks will be positioned on top of their own secondary containment as a precaution for any unintentional releases.

When handling or working with the permanganate solution in any way, the following personal protective equipment should be worn: chemical-resistant, impervious gloves, safety glasses with side shields or a face shield if there is any risk of splashing, and chemical resistant clothing, such as a rubber or plastic apron. Respirator use should not be necessary so long as adequate ventilation is available within the storage area. An eye-wash station and safety shower should be present in the storage area.

7.2.5 Electrode Wells Cross-Circulation and Buffer Supply Design

Drawing Sheets P-120 & P-121 present the process and instrumentation diagram (P&ID) for the cross-circulation flow and buffer supply flow for the electrode wells in Zone 1 and Zone 2, respectively. As discussed in Section 7.1 that the remedy implementation will be completed in Zone 1 first before the implementation begins in Zone 2. Therefore, the P&ID prepared for this design report reflects the approach of using the same system, with appropriate expansion as needed, for the sequential implementation in Zone 1 followed by Zone 2.

Cross-circulation between the anode and cathode wells will be utilized to mitigate pH changes within the electrode wells due to the application of DC voltage. The cross-circulation system is equipped with two air-operated diaphragm pumps – one pump will facilitate the transfer of well water from anode wells to cathode wells, while the other from cathode wells to anode wells. A manifold equipped with solenoid valves, which are controlled by a PLC to open or close during a given operational step, is used to direct the cross-circulation flows between selected wells. The operational program for controlling these flows is discussed in Section 7.4.2.

For each electrode well, extraction of well water will be achieved using an eductor. Each eductor will be supplied with recirculated well water from the pump (the working fluid) at a specific flow rate and pressure, and water from the well (the extracted fluid) will be drawn into the eductor

7-7 via the venturi effect. This is the same principle behind the operation of a jet pump able to extract well water independent of the water table depth, while avoiding the need for a pump in every well.

Downstream of the eductor, the combined working fluid and extracted fluid will be carried back to the inlet of the pump. A bleed valve upstream of the pump will be utilized to draw off a targeted amount of extracted fluid by adjusting the backpressure in the bleed line. An adjustable constant backpressure valve will be used to maintain a constant backpressure on the extraction manifold to aid in control of the extracted fluid flow rate, and to provide consistent backpressure for eductor operation. The extracted fluid will be routed to the corresponding electrode well, and the remaining flow will become working fluid returned to the inlet of the pump for recirculation back to the eductor in the well.

The wells/eductors will be manifolded together in sets of three wells per manifold. Each manifold will be operated periodically via a user-adjustable timer program managed by a PLC. The control panel will sequentially open and close selected solenoid valves isolating selected manifolds for a specified amount of time to achieve cross-circulation between paired cathode wells/anode wells.

The pairing of cathode wells and anode wells is presented in Table 7-1.

The cross-circulation system will include a pressure tank to dampen pulsations, as well as pressure control valves on the recirculation line to maintain constant pressure upstream and downstream of the eductors. Flow meters will be included on both the outlet and inlet sides of the pumps. These flow meters will report measured flow to the control panel for verification of working fluid and extracted fluid quantities. A pH sensor will also be included on the inlet side of the pump, and will report pH measurements to the control panel to assess effectiveness of pH control within the electrode wells.

Given the configuration of the electrode well network, electrode wells EW7, EW14, EW21, and EW28 in Zone 1, as well as EW3, EW6, EW9, and EW12 in Zone 2B, are not included in the cross-circulation process. Instead, these wells are manifolded together and will receive additional periodic addition of bicarbonate buffer to control pH.

7.2.5.1 Buffer Amendment Supply

A sodium bicarbonate buffer solution will be supplied periodically to the electrode wells based on a user-adjustable timer program supplied by the PLC. A chemical metering pump will transfer sodium bicarbonate solution from a storage tank to the electrode wells via the same manifold system that is used for transfer of the extracted fluid.

The sodium bicarbonate tank will be equipped with an ultrasonic level sensor to track the level of sodium bicarbonate solution in the tank. Sodium bicarbonate solution will be prepared as needed by manually filling the sodium bicarbonate tank with City water via a temporary flexible hose connected to a nearby hydrant. Sodium bicarbonate will be added manually via 50-lb sacks and mixed with a dedicated mixer. Sodium bicarbonate sacks will be stored within the system control enclosure.

The equipment described in this section will be housed with the control enclosure, depicted on Drawing C-701. Drawing Sheets C-420, C-601, and C-602 depict the routing of electrode wires and cross-circulation tubing from the control enclosure to the electrode wells. The wires and

7-8 tubing will be contained within separate protective PVC conduits, and heat tracing will be included to prevent freezing of the cross-circulation tubing.

7.2.6 Material Compatibility

Materials selected for the construction of this system will need to be compatible with a strong oxidizer (sodium permanganate) as well as corrosive liquids such as caustic and acidic cross-circulation water. Material compatibility guides list 316SS, PVC, EPDM and PTFE as most compatible with sodium permanganate. PVC tubing is selected for all sodium permanganate supply tubing in the system design. For strong caustic and acidic cross-circulation water, PVC, Polypropylene, Polyethylene, and EPDM are most compatible. Hard polyethylene tubing is selected for all cross-circulation water tubing. Tubing is required to meet the max 65psi value at the manifold and eductor. Polyethylene tubing is also compatible with the sodium bicarbonate buffer solutions. Verderprene®, Viton™ and Norprene® are all listed as compatible peristaltic pump tubing materials for permanganate from peristaltic pump suppliers. All other system materials that contact the oxidant or cross-circulation water should be made of compatible material. Materials and dimensions are included in the system drawings. The material compatibility lists are included as Appendix D.

7.3 ELECTRICAL DESIGN

A DC power unit will receive alternating current (AC) power input and output DC power to individual electrodes installed in the electrode wells (Figure 7-4). Individual terminal blocks will be connected to the positive or the negative terminal of the DC power unit. Individual, dedicated electrical cables connected to a terminal block will convey the electricity to individual electrodes.

The electrical connection concept illustrated in Figure 7-4 represents a parallel circuit with the subsurface aquifer materials between cathodes and anodes acting as a resistor (electrical conductor). With this type of circuit connection, the voltage across each paired cathode-anode (e.g., Cathode #1-Anode #1 pair or Cathode #2-Anode #2 pair) is the same. Assuming the electrical resistivity between individual paired cathode-anode is relatively the same, which is reasonable given that the subsurface aquifer materials serve as the conductor between electrodes, the overall current output by the DC power unit is generally evenly divided by the paired electrodes.

Table 7-2 presents the designed pairing of cathodes and anodes and the number of DC power units to be used for EK-ISCO implementation in individual target zones. It should be noted that the pairing of cathodes and anodes does not need to involve equal numbers of both. For Target Zone 1, four cathodes are paired with three anodes, and the overall current to be provided by a DC power unit is the sum of current applied to all cathodes (or all anodes) given the parallel circuit connection discussed above. There are two electrodes in each electrode well. Therefore, 8A is the total current provided by DC power unit 1 to a set of four cathode wells (eight electrodes) paired with three anode wells (six electrodes), as shown in Table 7-2. Table 7-2 also presents the electrical design for Zone 2, which is based on the same concept as that for Zone 1.

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7.4 EK-ISCO SYSTEM AND OPERATION

7.4.1 Remediation System Equipment

Table 7-3 presents a list of major system equipment. The list is organized in according to major functional components of the overall remediation system: oxidant supply system, electrode well cross-circulation system, buffer solution supply system, and electrical components. The use and function of individual equipment listed, as well as certain technical requirements of some equipment, are also presented in Table 7-3.

In addition to the system equipment, there will be an enclosure structure (e.g., modified shipping container) to house the system equipment, manifolds, and instruments. A second enclosure with adequate secondary containment and temperature controls will be used to house the amendment solutions.

7.4.2 System Operation and Process Controls

A control panel will control the cross-circulation and chemical amendment processes using a user-defined timer program. Cycling of cross-circulation flow between sets of electrode wells will be accomplished by opening and closing of solenoid valves on a timed program controlled by the control panel, allowing flow of working fluid and extracted water through the corresponding well manifolds. Table 7-4 summarizes the operational program that will be used for control of these processes.

The air diaphragm pumps that operate the cross-circulation system will actuate when the line pressure on the pump inlets falls below the pressure in the air supply. The pressure in the air supply lines will be set manually using a valve and a pressure gauge.

The pressure in the working fluid manifolds will be controlled via mechanical pressure control valves. Mechanical pressure control valves will also control the pressure in the return line that carries the working fluid and extracted well water from the wells. The settings of these valves will be adjusted manually to provide the correct pressure on the upstream and downstream sides of the eductors. Manual valves located at the wellheads will be adjusted manually during startup to fine-tune the pressures and establish good flow distribution to the eductors.

The flow rate of the working fluid pumped to the eductors will be monitored via a flow meter (FS-100, FS-200) and logged at the control panel. The flow rate of the combined working fluid and extracted well water will be monitored using a flow meter in the return line from the wells (FS-101, FS-201). The difference between the flow measurements at FS-101/FS-201 and FS- 100/FS-200 will be the flow rate of the extracted well water. The operator will be able to assess these flow rates remotely to verify that water is being extracted from the wells.

The flow of extracted water to the corresponding electrode wells will be adjusted at startup using a manual valve and by adjusting the setting of the manual backpressure valve. Manual valves at the wellheads receiving the extracted water will be adjusted at startup to establish good flow distribution of extracted water to the wells.

pH sensors (AE-100 and AE-200) will measure pH of the working fluid and extracted water from the wells. The pH measurements will be logged at the control panel. The operator will be able

7-10 to assess trends in pH to evaluate if pH control via the cross-circulation and buffer amendment systems is adequate.

Addition of a buffer amendment will be accomplished by pumping of sodium bicarbonate solution from a storage tank into the same manifolds that carry extraction water to the electrode wells. During this process step, the solenoid valves for the corresponding extraction water transfer manifolds will be open, while the solenoid valves for the working fluid manifolds will be closed. The control panel will open and close the appropriate valves, and activate the sodium bicarbonate metering pump to run for a user-defined amount of time. The flow rate of the metering pump will be adjusted at startup and checked periodically using the calibration column at the sodium bicarbonate supply tank. An ultrasonic level sensor in the sodium bicarbonate storage tank will report the fluid level in the tank to the control panel. The operator will be able to access the tank level readings remotely to verify that the metering pump is transferring sodium bicarbonate solution into the system, and to verify the sodium bicarbonate solution supply. The sodium bicarbonate storage tank will be refilled manually by mixing dry sodium bicarbonate with city water in the storage tank.

Permanganate addition to the oxidant supply wells will be accomplished by pumping permanganate solution from individual supply totes using dedicated six-channel peristaltic pumps. Each peristaltic pump will deliver permanganate solution to six supply wells. The peristaltic pumps will be activated by the control panel, and will run for a user-specified period of time to provide the necessary amount of oxidant to the supply wells. The flow rates of each pump will be set manually at startup using the calibration columns, and the flow to each supply well will be verified by opening a three-way valve in each line and measuring the time required to fill a graduated cylinder. Ultrasonic level sensors will report the permanganate solution level in the totes to the control panel. The operator will be able to monitor the oxidant levels in the totes remotely to verify that permanganate solution is being transferred to the supply wells by the pumps, and to verify the permanganate supply.

7.5 PERMITTING AND NOTIFICATION CONSIDERATIONS

The Site’s Superfund status means that acquisition of specific permits will not be required;

however, the substantive requirements of the following permits (as required by code) will be followed as appropriate:

Compliance with NCG01 Permit with the NCDEQ;

The City of Oxford adopted Tree Ordinance relating to any tree clearing;

Offsite facility disposal permit documentation for non-hazardous or hazardous waste;

Underground Injection Control;

Water use permit; and

Electrical permit.

Additional applicable substantive permit requirements may be identified upon consultation with the City of Oxford or NCDEQ.