new hampshire ll 4537 isco evaluation [newsletter]

TABLE OF CONTENTS

SECTION PAGE

1.0 INTRODUCTION .............. ... ....... .... .. .. .. ............................ .. ................................. .................. 1 1.1 PROJECT BACKGROUND .... ... ............... .. .................................................................. 1 1.2 PILOT PROGRAM GOALS .......................................................................................... 1

2.0 SITE AND TECHNOLOGY SELECTION .......................................... ......... ......................... 3 2.1 TECHNOLOGY SELECTION ...................................................................................... 3 2.2 SITE SELECTION ................................................................................................... ...... 4

3.0 PERSULFATE ISCO REMEDIAL FEASIBILITY EVALUATION ..................................... 6 3.1 SHORT-CIRCUITING AND GEOPROBE® INJECTION METHOD .......................... 6

3.1.1 Short-Circuiting ................................................................................................ 6 3.1.2 Geoprobe® Injection Method ........................................................................... 9

3.2 VOC DATA AND REBOUND / CONTAMINANT MASS ESTIMATES ....... .. ....... 13 3.3 FIELD PARAMETERS ................................................................................................ 20 3.4 SODIUM HYDROXIDE ACTIVATION VERSUS CALCIUM PEROXIDE

ACTIVATION ........................................................................................................ ..... . 22

4.0 CONCLUSIONS AND RECOMMENDATIONS ........................................... .... .... ............. 24

5.0 REFERENCES CITED .......................................................................................................... 27

6.0 LIMITATIONS ... .. ...... .. ..... .. .. .... ... .... ..... .... ..... ... .................................................................. .. 28

FIGURE

FIGURE 1

TABLE

TABLE 1

APPENDICES

APPENDIX A APPENDIXB APPENDIXC

Injection Radius ofInfluence

Summary of Expedited Closure (and Other) Persulfate ISCO Projects

Summary of Persulfate Pilot Sites Residual Contaminant Mass and Persulfate Demand Estimates Charts

-1-

EVALUATION OF ACTIVATED PERSULFATE FOR EXPEDITED PETROLEUM SITE REMEDIATION

NHDES OIL REMEDIATION & COMPLIANCE BUREAU EXPEDITED CLOSURE SITES

1.0 INTRODUCTION

1.1 PROJECT BACKGROUND

At the request of the New Hampshire Department of Environmental Services (NHDES) Oil Remediation & Compliance Bureau (ORCB), GeoInsight, Inc. (GeoInsight) identified several petroleum release sites as potential candidates for inclusion in a pilot program to evaluate the feasibility of performing relatively small-scale in-situ chemical oxidation (ISCO) applications to expedite site closure. In addition to identifying an appropriate ISCO chemical/technology for the program, the NHDES also requested an evaluation and identification of a subcontractor with a technical focus in ISCO technologies and applications.

Following a survey of available literature regarding the use of various ISCO technologies applicable specifically at petroleum sites, discussions with several potential subcontractors, and an initial company success in using the technology at a large scale historical gasoline-release site in Wakefield, New Hampshire, base-activated sodium persulfate was selected as the ISCO technology for use during the pilot program. The qualifications, location, and economics of using one of several potential ISCO firms were evaluated. Redox Tech, LLC (Redox Tech) of Attleboro, Massachusetts was ultimately selected as the ISCO subcontractor for the program based upon their experience in New England in general and with at least one recent petroleum ORCB-managed site in New Hampshire, experience using persulfate as an ISCO technology, and their initial cost quotations for the projects selected for the program.

1.2 PILOT PROGRAM GOALS

Based upon discussions with the NHDES during the development of the persulfate ISCO pilot program, the following goals were identified:

• evaluate base-activated sodium persulfate as remedial technology specifically for the purpose of accelerating petroleum sites with relatively isolated plumes of recalcitrant ground water constituent levels to closure using relatively small-scale, short-duration, and low-cost ISCO injections; and

• evaluate the performance of a specialized ISCO subcontractor as part of a team to design and implement a variety ofISCO injections.

Based upon the funding mechanism used for the program (expedited closure [EXPC] monies), an implicit goal was to attain accelerated site closure using the pilot ISCO

June 30, 2011 GeoInsight Project 4537-A-004 Page 1

technology. This report presents a substantial amount of data obtained and presents associated findings and conclusions resulting from the pilot program to address specific questions presented in a May 13,2011 letter from the NHDES. Finally, key factors to consider in the design and implementation of future persulfate ISCO applications at ORCB petroleum remediation sites, whether for expedited site closure or full-scale remediation, are presented and discussed.

June 30, 2011 Geolnsight Project 4537-A-004 Page 2

2.0 SITE AND TECHNOLOGY SELECTION

2.1 TECHNOLOGY SELECTION

Base-activated sodium persulfate was selected for use in the pilot program after reviewing available industry literature regarding ISCO technologies and specifically persulfate, and consulting with several ISCO remedial contractors (including FMC Corporation [FMC], the primary North American supplier of per sulfate). Favorable findings from an initial pilot application performed for the Huckins Oil site in Wakefield, New Hampshire using base-activated persulfate and recent familiarity using the product assisted with the product recommendation.

Sodium persulfate dissociates in water to yield sodium and the persulfate anion (S20{). The persulfate anion is in of itself a strong oxidant; however, it is reportedly kinetically slower in destroying contaminants than the sulfate free radical (S04-). There are several mechanisms to produce or "activate" the sulfate radical, including elevating the pH or introducing heat, ferrous salts, or hydrogen peroxide to the aquifer. Base-activation of persulfate was the selected mechanism for the pilot injections.

Activated persulfate was selected for the following reasons:

• the product is a strong oxidant that is able to destroy a broad range of petroleum constituents, including benzene, methyl tertiary butyl ether (MTBE), and the mid-molecular weight compounds such as naphthalene and alkylbenzenes, which permanganate reportedly has limited effectiveness in treating (Huling & Pivetz, 2006; ITRC, 2005);

• unlike peroxide/Fenton's Reagent, persulfate is relatively safe to handle with fewer health and safety concerns;

• persulfate has less affinity to natural (background) organic demand in the subsurface (Colorado DLE, 2007; Huling & Pivetz, 2006);

• the density of persulfate solution is greater than water and, therefore, density-driven diffusion of persulfate can occur into lower permeability units of a heterogeneous aquifer (Huling & Pivetz, 2006); and

• compared to peroxide or ozone, persulfate exhibits a longer residence time in the subsurface and, therefore, allows for greater distribution in the subsurface due to diffusion and transport with ground water flow (Huling & Pivetz, 2006).

Alkali or base activation using sodium hydroxide was the primary activation method selected for the pilot program. For three of the sites, Redox Tech recommended a proprietary mixture of sodium persulfate coupled with calcium peroxide (Oxygen BioChem [OBC TM]) for the ISCO oxidant. The use of OBC ™ couples the strong oxidative qualities of activated persulfate with the use of electron acceptors (oxygen and sulfate) to stimulate the longer term


biological aerobic biodegradation. The activation relies upon high pH from the introduction of calcium peroxide to activate the persulfate in lieu of application of a caustic solution such as sodium hydroxide used during the base-activated persulfate applications.

Base activation was selected over other facilitation methods because:

• iron activation typically requires expanded site-specific bench-scale and pilot-scale testing to evaluate its applicability and dosing;

• heat activation using steam or soil heating is typically not cost-effective in New England; and

• activation using hydrogen peroxide can be hindered by the relatively short residence time for peroxide in the subsurface and, therefore, comparatively base-activation may result in wider distribution of the activated persulfate solution into the aquifer.

Redox Tech's approach to implementing base-activated ISCO using sodium hydroxide as the catalyzing agent differs from that of FMC and at least one other ISCO contractor consulted by Geolnsight; notably in the recommended use of smaller quantities of base. FMC recommends co-application of sufficient sodium hydroxide to buffer the production of sulfuric acid during the persulfate oxidation process along with an additional dose to overcome the 'typical' background acidity of an aquifer while keeping the aquifer pH in the range of 10 to 11. Citing propriety reasons, Redox Tech was unable to provide significant detail as to how it determines the sodium hydroxide dosing. For comparison, Redox Tech injected 4,464 pounds of per sulfate and 750 pounds of sodium hydroxide during the Former Pynenburg's Service Station (Pynenburg's) pilot. Using FMC's suggested base dosing calculation for the same quantity of persulfate, approximately 1,500 pounds of sodium hydroxide would be required to buffer the production of sulfuric acid (with an additional possible 10 to 20 percent more base required to buffer the aquifer acidity depending on site-specific conditions). It is beyond Geolnsight's current expertise with this technology at this time to provide a recommendation as to which firm's base activation method is more appropriate, however, the difference in the approach appears to be significant enough to warrant further research on the topic.

2.2 SITE SELECTION

Five sites were initially selected for participation in the expedited closure ISCO pilot program with a sixth added at a later date. These six sites included:

1) Kimball's Country Store, Pembroke, NHDES #199004002 (Kimball's); 2) Pynenburg's, Merrimack, NHDES #199904008; 3) Former Manter Oldsmobile, Laconia, NHDES #198605641 (Manter Olds); 4) Former Bud's Country Store, Warren, NHDES #198906030 (Bud's); 5) Getty Station #55268, Seabrook, NHDES #199106013 (Getty-Seabrook); and 6) Hudson Mobil, Hudson, NHDES #199706042 (Hudson Mobil).


In addition to these six sites included in the expedited closure pilot program, persulfate ISCO applications were also completed at several additional sites during this study period. Data from these additional projects was also used to supplement the evaluation ofthe technology. Funding for implementing the persulfate ISCO technology at these other sites was provided from a variety of sources including private insurance (Wickens and Noguera residences), the Oil Discharge and Disposal Cleanup Fund (Huckins Oil and the Exeter and Derry Getty stations), and American Recovery and Reinvestment Act (ARRA; Lido).

Ampet/Huckins Oil, Wakefield, NHDES #198903031 (Huckins Oil). Wickens Residence, Franklin, NHDES #200705048 (Wickens). Noguera Residence, Londonderry, NHDES #200512010. Getty Station #55211, Derry, NHDES #199501007. Getty Station #55259, Exeter, NHDES #199402006 (Getty-Exeter). Former Lido Station, Plaistow, NHDES #198903017 (Lido).

The specific rationale for selecting the original six sites for inclusion in the expedited closure ISCO program is summarized in Appendix A, along with the rationale for recommending implementation of persulfate ISCO at the additional sites. Table 1 also provides a summary of the sites incorporated into this report. The primary basis for selection was to choose sites that were theoretically close to meeting NHDES site closure criteria, had relatively low, and had relatively low, but stable concentrations of petroleum constituents exceeding applicable Ambient Groundwater Quality Standards (AGQSs). In general, potential candidate sites were generally those where conventional remedial technologies such as soil excavation had either already been implemented (and in some cases, may have effectively remediated significant portions of the site); residual dissolved impacts were limited both in magnitude and extent; and the default remedial strategy of monitored natural attenuation (MNA) was not achieving timely site closure. In several instances (Kimball's and Hudson Mobil), previously completed soil delineation programs had identified a discrete remaining source that appeared to be most cost effectively managed by ISCO than soil excavation.

Site plans illustrating monitoring locations and site features, and data summary tables for the study sites and the other ISCO pilot sites discussed in this report are presented in Appendix A. Additional data obtained during the ISCO activities completed at these sites is included in individual reports prepared for each project and is, therefore, not included herein. The information is available on the NHDES OneStop website under the applicable regulatory file for each site. While this report discusses site-specific data, findings, and conclusions for some of these projects in the sections that follow, notably for evaluating the technology as a whole, the reader is encouraged to review the project files for more details regarding site-specific data.


3.0 PERSULFATE ISCO REMEDIAL FEASIBILITY EVALUATION

The May 13, 2011 NHDES letter suggested the inclusion of several key topics for discussion with respect to the results of the ISCO pilot programs. This section provides a summary of those topics and seeks to provide related explanations and discussion, as appropriate, based upon Geolnsight's experience with the application of persulfate specifically and ISCO technologies (including other chemicals, such as peroxideiFenton's and permanganate) in general.

Sections, 3.1 Short-Circuiting and GeoProbe® Injection Method and 3.2 VOC Data and Rebound/Contaminant Mass Estimates, include an expanded discussion related to the distribution/delivery of oxidant to the target treatment area and rationale and key assumptions necessary for sufficiently estimating site oxidant demand and residual contaminant mass. Current literature and vendor information reviewed (FMC website and personal communications, 2009; Huling & Pivetz, 2006; ITRC, 2005; and Regenesis, 2007) and our experience with these projects suggest that these are the two most critical factors contributing to the success of an ISCO program.

3.1 SHORT -CIRCUITING AND GEOPROBE® INJECTION METHOD

3.1.1 Short-Circuiting

Where was it evidenced?

Short-circuiting of injection solution was observed at the following sites: Pynenburg's, Manter Olds, Huckins Oil, and anecdotally at the Getty-Seabrook property. The observations of short-circuiting at these sites are useful in evaluating the questions the NHDES posed on this topic.

Pynenbur~'s - At Pynenburg's, within minutes of initiating the ISCO injection through a Geoprobe point located immediately adjacent to well GEO-IR (injection point IP-I), persulfate solution was observed discharging at the ground surface at well GEO-4R located 35 feet (hydraulically cross gradient) from the injection point (see the site plan in Appendix A for injection and well locations). The possibility for lateral short-circuiting was discussed during the design of the injection and was anticipated (to some degree) because of the highly stratified nature of the native overburden geology and the presence of the sandy backfill material emplaced during the 2002 and 2006 excavations. It was difficult to evaluate if short-circuiting continued throughout the injection pilot, because well GEO-4R was plugged to eliminate further discharge of the injection solution and, consequently, further observations of short-circuiting could not be made at this location.

The increase in pH and oxidation-reduction potential (ORP) observed on the day of the injection at well GEO-II, located 50 feet downgradient from injection point IP-I, may also indicate short-circuiting; however, injection solution did not discharge from this monitoring


well and, therefore, the field parameter increases may be indicative of normal downgradient migration of the injection solution to this location.

Redox Tech reported injection pressures of 20 to 40 pounds per square inch (psi) and injection flow rates of 5.1 to 6.6 gallons per minute (gpm) for the Pynenburg's site.

Manter Olds - The pilot design called for the injection of 900 gallons of 23 weight percent (wt%) persulfate solution. However, due to higher than anticipated ground water levels (particularly at well GEO-2, which was the center ofthe injection target area), only 400 gallons of solution were injected. Within several minutes of initiating the injection at boring IP-1, the persulfate solution discharged from well GEO-2, located 2 feet from injectionpointIP-I. Well GEO-2 was plugged to reduce the loss of solution out ofthe well casing and the injection was then continued at IP-I. Several minutes following the sealing of well GEO-2, short-circuiting of injection solution to the ground surface was observed in a seam between the original asphalt pavement of the parking lot and the newer asphalt patch covering test pit TP-3 located approximately 10 feet downgradient from inject point IP-I.

Redox reduced the injection pressure from 20 to 40 psi to 10 psi to reduce short-circuiting and additional injection boring locations were attempted to reduce mounding at each injection probe location; however, short-circuiting continued throughout the pilot. Redox Tech reported injection flow rates of 1.6 to 5 gpm for the Manter Olds site.

Huckins Oil- The ISCO pilot at Huckins Oil involved the application of oxidant solution by gravity-feed into an existing set of recovery wells installed in a recovery I cut-off trench (backfilled with gravel) and one existing monitoring well (CB-6) located outside of the recovery trench. Even under gravity-feed conditions, towards the end of the first day of application, injection solution was observed discharging from a wooded slope extending from the area of well CB-6 to the wetland located southwest of the site. The design for the pilot application called for well CB-6 (a 2-inch diameter monitoring well) to receive approximately 10 percent (500 gallons) of the 5,500 gallons of solution applied during the pilot. Based upon field observations, the 2-inch diameter CB-6 well accepted injection at approximately the same application rate as did the 8-inch recovery wells (RW-2, RW-3, and R W -4) located in the former recovery trench.

Limited information is available regarding construction details for well CB-6; however, the short-circuiting observed during the injection is believed to have occurred because the well screen for CB-6 likely intersects an isolated area of higher conductivity soil, which was hydraulically connected to the slope. The site is known to contain a dense basal till at depths of approximately 10 feet below grade, which is overlain by sandy fill. Persulfate solution may have migrated to the wooded slope on top of the basal till.

Getty-Seabrook - The injection design prepared by Redox Tech called for the injection of 1,200 gallons of 23 wt% of activated persulfate into four temporary injection points within the immediate vicinity of well MW-1. Although field evidence for short-circuiting of the injection solution was not observed, the relative speed of application (3.25 hours of injection)


and lack of distribution of injection solution (as observed in water quality data obtained from surrounding sentry monitoring wells) suggests that the persulfate mixture perhaps short-circuited within either what is likely a highly permeable utility corridor located within the western shoulder of Lafayette Road /Route 1 or trenching associated with historical remediation infrastructure on the premises. While it is important to note that direct evidence for this phenomenon was not observed, anecdotal evidence suggests this may have occurred.

It is important to note that several ofthe projects (Wickens and Noguera Residences, Lido, Hudson Mobil, Pynenburg's, and Manter Olds) observed the presence of oxidant solution within monitoring welles) located inside the target application areas during the ISCO activities. Given the relatively close spacing of the injection points to those wells in the target area, this phenomenon was not unexpected and for the purpose of this discussion was not considered indicative of short-circuiting per se.

What conditions should elicit concern?

The short-circuiting observed during the pilot tests described above suggest that the following conditions should elicit concern when designing site-specific ISCO applications as they have the potential to either prevent, or significantly limit, the uniform contact/distribution ofthe oxidant with the impacted media:

• the presence of stratified geology;

• localized pockets or layers of fill material exhibiting significantly different characteristics than the surrounding native material;

• high ground water conditions/relatively low depth to ground water; and

• the presence of subsurface utility corridors with presumably more homogeneous and highly permeable backfill than surrounding native soil.

It is imperative upon initiating an injection, that field personnel commence periodic observations and collect select field data indicative of oxidant migration at nearby monitoring wells. Comparison of pilot and post-pilot ground water elevations and water quality data to baseline data will allow meaningful conclusions regarding ground water mounding, relative distribution of the oxidant/radius of influence, and possible short-circuiting. (An expanded discussion oflSCO water quality monitoring parameter data is provided in Section 3.3.) Key field observations should include the possible discharge of solution from seams and cracks in site pavement or pooling/seeps at the bare ground surface.

Also, if conditions are encountered during injections which differ significantly from those expected (refer to the Huckins Oil example and the ability of 2-inch well CB-6 to receive similar flow rates of oxidant solution as 8-inch injection wells installed in a gravel-lined recovery trench), then a decision to alter the pilot to evaluate possible ramifications of the unexpected conditions should be made in the field.


How can short-circuiting be limited or eliminated?

Methods for reducing the potential for short-circuiting are discussed further in Section 3.1.2, below.

3.1.2 Geoprobe® Injection Method

Evaluate the dynamics of the delivery method.

The ISCO projects discussed herein were implemented using a variety of delivery methods including:

• Geoprobe® direct-push technology;

• a permanent well network (injection well, recovery well, and monitoring wells); and

• gravity-feed applications to existing site infrastructure including wells, recovery trenches, or historical remedial piping.

It is difficult to directly evaluate the dynamics of the Geoprobe® injection method used during the expedited pilot program because ISCO-specific observation wells were not installed at any of the pilot sites. Only existing monitoring wells were available for use in evaluating this application technique and often, the existing sentry well spacing was beyond the anticipated injection radii of 5 to 15 feet reported by Redox Tech for many ISCO injection applications.

The benefits of utilizing direct-push technology for an ISCO application include the potential to install multiple application points and the capability to target discrete depth intervals (with limitations on total depth given specific geologic conditions). The installation of permanent or semi-permanent injection wells not only incurs the cost for the both the drilling rig and the injection well material costs but also creates a 'fixed' network that mayor may not be useful for subsequent applications of oxidant. The ability to focus subsequent applications at those portions of a site not directly targeted during initial applications is an attractive option for Geoprobe® injections. Additionally, use of temporary application points allows flexibility to the project approach should subsequent applications occur. As subsurface mass is destroyed, subsequent injections can target specific residual "hot spot" locations that may not have been part of the original application network or were insufficiently remediated during initial applications.

Theoretically, ofthe two methods presented (permanent wells vs. temporary injection points), a more uniform distribution of oxidant to the subsurface may occur using permanent, fixed application points. This is illustrated in the schematic representations presented on Figure 1. In an idealized homogenous aquifer, application of a solution to a well screen should occur under approximately the same pressure and flow rate applied across the entire surface area of the screened interval (Figure 1-1) and, therefore, solution distribution should


travel approximately uniformly in a radial (two dimensions) and cylindrical pattern (three dimensions). Conversely, use of direct-push rod technology is typically conducted using a "bottom-up" injection method (ITRC, 2005). Upon reaching the deepest target depth (after retracting the rod from the sacrificial expandable point), injection is initiated through the open end of the rod. During rod injections (theoretically in a homogenous aquifer) an oxidant solution should also migrate radially away from the injection point. However, once the rods are extracted to shallower depths for additional injection, each subsequent injection depth receives less oxidant solution than the underlying depth interval assuming similar injection duration for each depth interval (Figure 1-2). This occurs because the injection solution can be forced downward through the bore-hole underlying the injection rod, effectively spreading additional solution over each of the previous underlying depth intervals.

The "bottom-up" phenomenon described above, while theoretical, does suggest there may be a limitation to the dynamics of push rod applications, which warrants further study and consideration. A network of several injection observation wells (located at different distances from an application point and completed and at varying depths) would be needed to further evaluate injection rod dynamics. An alternative approach for future applications could be to alter the injection approach to apply progressively more solution to each subsequent (shallower) injection target depth at each rod location. Similarly, additional injection points, only advanced to target the shallower depth intervals, could be performed to reduce the "bottom-up" effect. These approaches may assist in a more even distribution of oxidant solution when implementing the push-technology.

Theoretically, oxidant applications performed under gravity-feed conditions should occur under laminar (Darcy) flow into the aquifer. Injections occurring under pressure will contribute to some degree of turbulent flow in the aquifer (ITRC, 2005). Turbulent flow has the ability to contribute to short-circuiting/uneven oxidant distribution in heterogeneous aquifers. High injection pressures can also lead to soil fracturing along natural planes of weakness in the surrounding soil matrix. Hydraulic pressure is often necessary to increase injection flow rates and complete injection applications in a reasonable timeframe. However, it appears that significantly increasing injection pressures may increase the potential for short-circuiting and, possibly soil fracturing, and contribute to uneven distribution of oxidant solutions in the subsurface.

Did it result in plume displacement?

The potential for displacement of the dissolved plume, and also non-aqueous phase liquid (NAPL), during ISCO injections is discussed in the literature. ISCO applications using persulfate are performed by mixing the persulfate granular solid with water and, for baseactivated methods, typically liquid sodium hydroxide. The resulting solution is generally applied into or near the saturated portion ofthe aquifer. When the solution enters the aquifer, it can mix with contaminated ground water, but can also serve to displace the dissolved plume and effectively causing contaminants to migrate from the injection area. Data collected during the pilot studies indicate that dissolved plumes were not displaced to a noticeable extent at the injection sites.


Redox Tech's designs for the pilot injections generally included one injection point downgradient of the target application area in addition to several target area points. It was their belief that this provided a safeguard against the preferential migration/displacement of contaminants downgradient ofthe application area by positioning oxidant in the area to destroy contaminants that may become displaced downgradient of the target injection area.

The injection of oxidant solutions can also mobilize previously adsorbed and/or entrapped NAPL as evidenced at the Huckins Oil site where NAPL was observed inside injection well RW-3 shortly after injection was initiated. The occurrence ofNAPL during the Huckins Oil injection was inferred to have resulted from the co-application of sodium hydroxide as an activator, which FMC has indicated can contribute a surfactant-type affect in the aquifer. There was no evidence that NAPL was mobilized or displaced beyond the vicinity of injection well RW-3 at the Huckins Oil site (based upon adequate monitoring control with numerous closely spaced wells in close proximity exhibiting a lack ofNAPL). NAPL can, however, be hydraulically displaced by injection solutions and care should be exercised when completing ISCO activities in known or suspected areas of separate-phase NAPL or suspected bound NAPL globules that could be released. Sorbents were used to recover NAPL that collected on the water surface in the RW-3 injection well both during and after the injection was completed and the presence ofNAPL has not been detected at this location since completion of the 2009 ISCO application.

In addition to the possible physical displacement and movement ofNAPL, oxidants can serve to mobilize additional constituents into the dissolved phase from the adsorbed phase. This phenomenon is further discussed in Section 3.2.

What were the geologic formation limitations encountered?

In more general terms, site geology conditions can be a large controlling factor in the effective distribution of an oxidant solution. Achieving theoretical uniform distribution of the solution as described in the previous section discussing injection dynamics for homogeneous aquifers, is theoretically more difficult in heterogeneous aquifers. Figure 1-3 illustrates how aquifer heterogeneity may affect oxidant injection distribution.

In their analysis of242 ISCO sites (where the data from a variety of full-scale ISCO remediation projects were reviewed), Krembs, et al. (2010) described the general finding that sites with homogeneous and permeable geology were ultimately more likely to achieve remedial goals compared to those sites characterized with heterogeneous and/or relatively impermeable geologic materials in the subsurface. In addition, rebound is also more likely to occur at sites with heterogeneous and relatively impermeable geology.

Specific geologic limitations encountered during the pilot programs were described in Section 3.1.1 and included highly stratified soil at Pynenburg's, the presence of fill/backfill material with relatively higher conductivity at Pynenburg's, Huckins Oil, and GettySeabrook, and high water table elevations at Manter Olds. These conditions may have ultimately affected the outcome of each of the injections performed at those sites.


What would be a good indicator of mixing being achieved?

In the simplest terms, if a sufficient amount of oxidant is applied to a target area and the oxidant is effectively distributed to have complete contact with the contaminant, then the contaminant should be destroyed. However, using ground water contaminant data as an indicator of injection success is problematic and this is discussed further in Section 3.2. Water quality indicator parameters and sulfate and persulfate field and laboratory data are instrumental in evaluating injection solution distribution in a site aquifer. Evidence of mixing/distribution in the field parameter data was documented at most of the pilot sites with the exception of Getty-Seabrook, where substantial short-circuiting is thought to have occurred.

As an example of oxidant mixing, a summary of findings from the Pynenburg' s site are presented in the paragraphs that follow. The target zone for Pynenburg's was the area around and immediately up gradient of well GEO-1R. The water quality indicator and persulfate testing data at Pynenburg's indicated that persulfate was present and oxidation was occurring nine months after the injection. This was particularly evident in the persulfate testing data, which indicated persulfate presence at concentrations of 1,700 milligrams per liter (mg/L) nine months after the injection. In addition, pH decreased to acidic conditions at well GEO-1R compared with background (the persulfate oxidation reaction produces sulfuric acid, which would lower aquifer pH).

The presence of per sulfate nine months after the injection was somewhat unexpected at Pynenburg's. As is discussed in Section 3.2, it appears that the amount of oxidant demand needed in response to the levels of residual impacts may have been underestimated at this site. Therefore, in theory, with a relative "surplus" of contaminant mass compared with oxidant, persulfate would be expected to dissipate relatively quickly as the oxidation process proceeded. However, presence of persulfate nine months after application may be due to back -diffusion of persulfate from stratigraphic layers that were 'overloaded' with persulfatfj compared to persulfate distribution into other layers. Another possible factor may be that insufficient sodium hydroxide was used to activate the persulfate, which would lead to slower oxidation rates with the persulfate anion as opposed to the sulfate radical.

Do we need to consider extraction and re-injection to assure proper contact between the sodium persulfate and the formation water?

It may be prudent to evaluate ground water extraction and re-injection to increase oxidant solution distribution; however, ground water extraction and re-injection will potentially add significant costs and may not be applicable to all sites. If a site contains existing infrastructure such as former recovery wells, it may be beneficial to attempt ground water recovery and re-injection (equipment compatibility with persulfate and activators would have to first be evaluated). However, ground water extraction rates at most petroleum remediation sites in New Hampshire are relatively low due to low hydraulic conductivities. This general condition typically dictates completing injections at moderate pressures. Moderate pressure is typically needed to increase hydraulic head and increase fluid flow to the subsurface to


achieve timely injection periods. As previously discussed, high pressure injections may cause short-circuiting.

Ultimately, the underlying question to consider is: what application methodes) will achieve the most cost-effective distribution of ISCO solution? In their analysis of 242 ISCO sites, Krembs, et. al (2010) report that overall project costs were less using injection wells as the delivery mechanism. Interestingly, the authors did not report a significant difference in the overall success of an ISCO application using one delivery method over another. This finding appears to highlight the importance of evaluating the applicability of each application method to each site. Pilot-testing of various injection methods may be warranted before proceeding to full-scale remediation in order to evaluate which method is best-suited to a particular site. For example, it may be more cost-effective to reduce injection pressures and lengthen the application timeframe of an injection over several days to increase the potential for oxidant distribution and reduce the potential for short-circuiting (particularly in heterogeneous aquifers) when compared with costs for installing injection recovery wells and operating a temporary pumping and recirculation system (assuming the injection would still be implemented at relatively high pressure).

3.2 VOC DATA AND REBOUND / CONTAMINANT MASS ESTIMATES

The following three questions posed by the NHDES are interrelated relative to the topic of contaminant mass estimates and, therefore, were grouped for the discussion provided in this report.

What do the VOC sample results indicate about the remedial approach and the status of subsuiface conditions?

Were the injections designed to treat ground water, soil, or both?

Was the amount of lingering soil contamination adequately pre-characterized?

A major factor controlling the success of an ISCO application is associated with determining residual contaminant mass, which requires a thorough understanding of what type of residual contaminant phase is present at a site and which ultimately dictates the quantity of oxidant that will be required for successful remediation. In addition to calculating contaminant mass, determining the most applicable method of delivery and achieving effective distribution/contact of the oxidant to the contaminant mass is also paramount.

In developing the design for the pilot injections associated with the expedited closure program, existing ground water and soil data was gathered for each of the pilot projects and transmitted to Redox Tech for review and use in its design assumptions. For several ofthe pilot sites, suggestions were provided to Redox Tech including which data may be more representative of site conditions; however, in all instances, Redox Tech was relied upon to develop a design for the applications, which included calculating oxidant demand and residual contaminant mass. For the Huckins Oil, Lido and Exeter Getty sites, which were not

June 30, 2011 GeoInsight Project 4S37-A-004 Page 13

part of the expedited closure program, GeoInsight calculated residual contaminant mass and relied upon FMC to assist in calculating oxidant dosing demands.

After completing the expedited closure persulfate pilot studies, it was evident that residual contaminant mass was likely underestimated in several instances, and resulted in dosing estimates that were too low. This was ultimately a significant factor (along with insufficient distribution of the oxidant to the target zone) controlling the success of the pilot injections in attaining permanent impact reductions to meet the expedited site closure goals.

At petroleum remediation sites, residual contaminant mass may be in the form of dissolved-, adsorbed-, or liquid-phase, of which could be pooling, separate-phase (mobile) NAPL, or entrapped (residual saturation, immobilized) NAPL globules (Huling & Pivetz, 2006; ITRC, 2005). The following order illustrates the relative importance that each constituent phase may have on the residual contaminant mass:

separate-phase NAPL > NAPL globules> adsorbed (soil) > dissolved (ground water)

Accordingly, the mass of oxidant required and the number of oxidant applications to achieve contaminant reductions increases from dissolved-phase target contaminants (lowest) to separate-phase NAPL target contaminants (highest) (Huling & Pivetz, 2006).

The majority of a site's residual contaminant mass resides in the adsorbed (soil) and NAPL phases. If these phases are assumed to not be present or are inadequately factored into a residual mass estimate, rebound will most likely occur following an ISCO application. This is because the oxidant will readily destroy the proportionally small contaminant mass present as dissolved-phase ground water impacts (which may manifest as non-detect or significantly reduced ground water impact data in the short-term). If, however, insufficient oxidant has been applied to destroy the mass also present in the adsorbed (or NAPL) phases, then ground water will re-equilibrate with the residual contaminant present in the adsorbed phase and ground water concentrations will rebound to pre-injection concentration levels. In some instances, the application of oxidant could also serve to mobilize additional dissolved-phase impacts into solution from the adsorbed and NAPL phases, which could cause dissolved ground water concentrations to spike higher than pre-injection conditions (Colorado DLE, 2007; ITRC, 2005).

Because dissolved compound ground water data is not a true measure of the presence of residual contaminant mass at a site, it is not, by itself, a particularly useful parameter to use for designing an ISCO injection or for measuring of the ultimate success of an injection. Soil boring and soil analytical data provide a more accurate measure of residual contamination at a site because the samples effectively measure bulk contaminant concentration that include dissolved-, adsorbed-, and NAPL-phases (Huling & Pivetz, 2006; ITRC, 2005; Krembs, et aI., 2010).

In the absence of soil sampling data, an evaluation of residual petroleum mass in soil (adsorbed-phase) can be performed using partitioning coefficients. Soil/ground water


portioning analyses are difficult for petroleum sites because of the number of target and non-target constituents that need to be factored into the analysis. Moreover, the estimates will only yield adsorbed-phase mass values and not that of separate-phase NAPL (or globules) contamination that may inherently be present.

The success of future persulfate injections in New Hampshire could be greatly increased if additional effort is invested into the evaluation of vertical and lateral mass distribution and in what phase(s) the residual contaminant mass exists. This can be achieved in combination with completing a soil delineation program to collect and analyze representative soil samples for estimating bulk contaminant mass.

The specific contaminant mass estimate and persulfate demand calculations completed by GeoInsight and associated supporting documentation are presented in Appendix B. The sections that follow summarize the comparison of independent contaminant mass and persulfate dosing estimates to the quantities of persulfate applied by Redox Tech at three of the pilot sites. Redox Tech did not furnish specific backup information regarding its mass estimates (citing proprietary reasons), so it is difficult to make a direct comparison. However, the comparisons are useful in evaluating the importance of conservatively estimating contaminant mass to assist in a successful ISCO application.

Pynenburg's Contaminant Mass Estimate Evaluation

As was further described in Appendix B.1, Redox Tech proposed an inj ection consisting of 4,464 pounds of sodium persulfate at the Pynenburg's site. Based upon residual contaminant mass estimates completed by GeoInsight, it appears that this quantity of persulfate was likely too small to provide the necessary oxidant to achieve the desired level of mass destruction in source soil in the vicinity of target well GEO-1R. This condition would be further exacerbated by the finding that injection solution migrated outside of the target injection area (refer to Section 3.1.1).

The mass estimate analysis, which used a range of representative total petroleum hydrocarbons (TPH) concentrations in the target area soil, indicates a significant range in possible residual contaminant mass. On the low end, 120 milligrams per kilogram (mg/kg) of gasoline-range organic (GRO-TPH) was used, which was the detected concentration of TPH in 2006 excavation end-point sample "Comp-4." On the high end, 1,400 mg/kg of GRO-TPH was used, which was the detected concentration of TPH in a composite sample collected from stockpiled soil removed during a May 2006.

In light of the estimated range of residual TPH contaminant levels in the target area, the estimated quantity of soil in the injection target area (583 tons), and a 47:1 oxidant to hydrocarbon ratio, 6,575 pounds (for 120 mg/kg GRO-TPH) to 76,749 pounds (1,400 mg/kg GRO-TPH) of persulfate may have been needed to achieve complete destruction of the residual contaminant mass in the target area during the 2010 injection.


Both demand values indicate that more than 4,464 pounds of persulfate was likely needed for the pilot injection to achieve destruction of hydrocarbons to closure levels. Also, the mass estimates completed for Pynenburg's yields a range of estimates in oxidant quantities that exceed an order of magnitude (with a total cost well over $100,000 to complete the injection ofthe high end estimate of76,750 pounds of per sulfate). Because the estimated range of residual contaminant mass cannot be further refined with the current limited dataset, additional investigation is warranted to refine the design to future oxidant applications. A focused soil boring and sampling program in the inferred source area (including sampling for GRO-TPH) would significantly assist in refming the average concentration of residual contaminant in the target area and would also assist in defining the vertical and lateral limits of the inferred source area. Refinement of the volume of the source area will also directly affect the residual mass estimates.

Hudson Mobil Contaminant Mass Evaluation

A similar independent residual contaminant mass estimate analysis was completed by Geoinsight for the Hudson Mobil site (Appendix B.2). Instead of calculating a range of possible representative values for residual GRO-TPH concentration (as was done for Pynenburg's), "average" values were selected based upon soil laboratory TPH sample results and photoionization detector (PID) screening data. Using values of 694 mglkg (south side of source area) and 1,700 mg/kg (north side of source area) TPH, Geolnsight estimated 200 pounds of GRO-TPH remained in source area soil. This mass of residual impacts would require approximately 6,400 pounds of sodium persulfate and calcium peroxide to remediate. Redox Tech applied 1,300 pounds ofOBC™ at the site in December 2010.

Because NAPL was encountered in well MW-108R as recently as 2009, the "average" values of GRO-TPH selected by Geolnsight for the residual mass calculation may in fact be biased-low. A soil sample collected from boring B-4 (located immediately upgradient of well MW-I08R) reported 5,320 mglkg GRO-TPH and was also determined to be ignitable. While soil containing this level of gross impacts may not be representative of the bulk contaminant mass throughout the remaining source area, it does suggest that pockets of significant adsorbed-phase and possible NAPL-phase impacts remain at the site.

Manter Olds Contaminant Mass Evaluation

The independent residual contaminant mass and persulfate demand estimates completed by Geolnsight for the Manter Olds site indicate that the design for the pilot injection appears to have included sufficient oxidant. Evaluation of injection success at this site, however, is more complex. Only approximately half of the design amount of persulfate was applied during the injection due to short-circuiting to the ground surface. However, the contaminant mass and persulfate demand estimates for this project help illustrate the relative importance of demand due to background soil oxidant demand (SOD) at sites containing relatively small quantities of residual contaminant mass.


As is further summarized in Appendix B.3, background SOD at the Manter Olds site accounted for a significant portion of the total oxidant demand (1,400 pounds of persulfate demand to account for inferred levels of background SOD compared with 120 pound of persulfate demand to remediate the residual contaminant mass). This was due to the relatively low concentrations of residual contaminant mass present in the soil of the target area. The majority of residual contaminant mass appears to reside in the dissolved-phase. At similar sites where most of the residual contaminant mass is present as dissolve-phase impacts, it may be beneficial to conduct site-specific testing for SOD. Site-specific SOD testing would assist in evaluating oxidant demand based upon local conditions and could increase the chance for project success if the testing shows that default levels are insufficient presentations of background SOD.

Huckins Oil Contaminant Mass Evaluation

The assumptions and methods used to calculate residual mass and associated persulfate demand for the Huckins Oil project are summarized in Appendix B.4 and are also presented in reports prepared for the site and previously submitted to the NHDES. The residual mass and persulfate demand calculations performed for this site (completed at three different stages) are useful in illustrating the importance of developing a comprehensive conceptual model of residual impacts at a potential ISCO site. The quantity of per sulfate initially estimated for destroying gasoline NAPL (an estimate of 55 gallons ofNAPL was inferred) for the first pilot test indicated over 20,000 pounds was needed. Because of uncertainty associated with the possible over-estimation of separate-phase NAPL quantity, the scope of the first application was reduced to one-quarter of the initial demand estimate (approximately 5,000 pounds of persulfate was applied).

The design of the second pilot application in early 2010 was developed using PID screening data from one boring located in the target area (which suggested that the average smear-zone GRO-TPH concentration was 600 mg/kg). Persulfate demand based upon the "average" residual concentration of GRO-TPH in the smear-zone of the target area indicated that over 18,000 pounds of oxidant was needed. Geolnsight and the NHDES again elected to reduce the scope of the inj ection because of uncertainties in developing the residual mass and persulfate demand estimates using data from only one boring in the target area.

After the second ISCO pilot application was completed at the Huckins Oil site, a soil delineation study was completed in November 2010 to better refine estimates of residual petroleum mass located in the ISCO target area. The results of the soil delineation study indicated that previous estimates of residual petroleum mass were likely underestimated. Moreover, a larger area of residual impacts was delineated based upon the November 2010 soil boring program. The soil delineation study indicated an estimated TPH contaminant concentration of 1,600 parts per million (ppm) in the target area, which equates to 1,882 pounds of residual petroleum mass in the form ofGRO-TPH in source-soil. Keeping the same design criteria suggested by FMC (and used for the first two applications) of using enough sodium persulfate to completely destroy the "average" estimated concentration of 1,600 mg/kg in the revised injection target area (392 cubic yards), approximately


88,000 pounds of sodium persulfate may be needed for future injections. At a current cost of approximately $1.35 per pound for sodium persulfate, the oxidant itself represents over $118,000 in material cost using these revised mass estimates.

Because of the substantial quantity of oxidant that may be required for successive injections as indicated by the November 2010 soil boring program data and also other uncertainties in completing ISCO applications (e.g., sufficient distribution and mixing of oxidant in target areas), the NHDES and GeoInsight are evaluating costs for excavation and off-site disposal of source-soil defmed by the soil delineation study.

When is post-injection VOC data representative?

In the preceding section, the discussion of contaminant mass estimates sheds light on the relative inherent difficulty of relying on ground water VOC data in evaluating injection success. Simply put, ground water VOC data will not be representative of post-injection conditions until after the oxidant has dissipated and, assuming adsorbed- and NAPL-phase contamination are present at a site, the soil, NAPL, and ground water return to equilibrium conditions.

A recent publication (Huling, et al., 2011) discusses the problems inherent with collecting, analyzing, and interpreting binary mixtures of post-application confirmatory ground water samples that contain both VOCs and persulfate collected at ISCO sites. The authors stress the importance of recognizing when ground water sampling is performed prior to the dissipation of per sulfate that there is significant potential for further destruction ofVOCs within the sample vial sent to the laboratory. Adequate preservation (using ascorbic acid) of the dissolved phase samples collected will effectively stop or quench the oxidant reaction and yield ground water VOC data that is more representative of the current VOC concentrations in the period following an ISCO injection.

It is likely that the presence of persulfate in the subsurface is an indication that further contaminant mass destruction is occurring. Therefore, ground water monitoring following a persulfate application should exclude sampling for VOCs in the target area (including samples preserved with the ascorbic acid method) until field parameters and field or laboratory persulfate testing indicate that persulfate has dissipated to negligible l

concentrations. At that point, equilibrium conditions should return and ground water VOC sampling results in the target area can be considered representative of post-IS CO conditions.

Based upon experience with the projects discussed herein, the rapid dispersal of per sulfate was observed at the Getty-Seabrook pilot injection (field parameter testing from the injection event along with persulfate testing one month later indicated that persulfate was not found in the target area wells) and was still present four to nine months following the application (Pynenburg's, Kimball's, and Hudson Mobil). Krembs, et al. (2010) and the ITRC (2005)

1 Based upon discussions with Redox Tech and at least one other ISCO contractor, persulfate concentrations at levels below 10 to 100 mglL appear to represent a range of concentrations at which point residual persulfate will have a relatively negligible effect on remaining contaminant mass.


both cite a minimum recommendation of a one year period following an ISCO/persulfate application to allow re-equilibration before collecting ground water constituent data to evaluate site conditions.

Once the oxidant dissipates, and ground waterINAPLIsoil conditions return to equilibrium, ground water VOC concentrations may remain similar to pre-injection conditions, or can even spike to higher concentrations2 if constituents were released from the adsorbed phase by the initial oxidant application (Huling & Pivetz, 2006; ITCR, 2005; Krembs, et aI., 2010). Assuming adequate contact is made between the oxidant and the contaminant, some level of bulk mass destruction will occur even at sites where insufficient oxidant was applied to achieve complete remediation.

As previously discussed and as cited in the current literature, the evaluation of pre-injection residual contaminant mass estimates to post-injection mass by way of pre- and post-injection soil boring and sampling programs is the only quantitative means of measuring injection success/progress. The exception to this may be for the sites where the majority of the residual mass resides in the dissolved phase (ground water) or when sufficient oxidant was applied and distributed to destroy the contaminant mass (present in each phase). In these instances, the success of the oxidant injections will be evident in permanent reductions in ground water constituent levels.

Were the ISCO applications more effective on some compounds than others?

The activated persulfate or OBC™ products were applied to a variety of fuel types (gasoline and fuel oil), geologic conditions, and residual constituents (benzene, toluene, ethylbenzene, xylenes, alkylbenzenes, naphthalene, and NAPL) as summarized in Table 1. The success (or lack thereof) of the ISCO applications did not appear to be attributable to a particular suite of constituents or be linked to a certain type of release or subsurface conditions. Rather, for reasons stated previously, the success of a given application had a direct bearing on the original mass estimates and the contact of the oxidant to the remaining source material. Huling & Pivetz (2006); the ITRC (2005); and FMC (refer to FMC's on-line persulfate remediation Resource Center) all list general petroleum products and specific constituents that persulfate is effective in oxidizing.

Were the estimates of oxidant demand accurate?

Oxidant demand is comprised of the amount of oxidant needed to destroy the petroleum mass and to overcome SOD; also referred to as natural oxidant demand). The importance of conservatively estimating residual petroleum mass was addressed in a preceding section of this report. However, a discussion was not provided with respect to SOD, except for its affect on the mass estimates performed for the Manter Olds site. As documented in the Manter Olds example, SOD can potentially account for a significant portion oftotal oxidant

2 This condition may be reflected in the post-injection VOC monitoring data for Pyneburg's and Kimball's sites.


demand at a site. However, depending on the site-specific geology and the relative level of contaminant mass, SOD may be relatively negligible with respect to overall oxidant demand.

Soil boring and subsurface data should be carefully viewed for each site to evaluate conditions that could significantly affect SOD, such as the presence of organics in soil or peat layers. If a site was adjacent to or downgradient of a wetland or landfill, there could also be higher levels of dissolved organics or a leachate plume present, which would need to be considered as competing sources of natural/background organics at a remediation site. In the absence of obvious potential sources of background SOD, one needs to consider if using an estimate for background SOD demand is warranted in-place of collecting and analyzing samples for site-specific SOD. Redox Tech and FMC both provide SOD laboratory analysis services. Based upon our understanding of the analysis, samples of un-impacted soil and ground water are collected from a potential ISCO site from areas representative of geologic conditions in the target application zone. Oxidant is applied to these samples in the laboratory in a titration-type method until it is no longer consumed by the background organic demand and, at that point, the amount of oxidant needed to overcome the in situ SOD is able to be quantified.

GeoInsight collected and analyzed samples for SOD at the Huckins Oil site. Representative samples of soil and ground water were collected from an area cross gradient to the contaminant plume and were sent to FMC for analysis. FMC reported a SOD of 0.7 grams per kilogram (g/kg) for on-site soil. Based upon their experience, FMC reported that the 0.7 g/kg concentration was "low to average compared to persulfate SOD for most soils." In the majority of the ISCO projects discussed for this summary, a value of 1 to 2 g/kg was used as a default SOD persulfate demand estimate in-lieu of site-specific data. SOD values in this range provide a rather insignificant contribution toward the total oxidant demand for sites with known adsorbed- and NAPL-phase contaminant sources (refer to the SOD estimates included in the persulfate demand calculation sheets included in Appendix B for Pynenburg's, Hudson Mobil, and Huckins Oil).

3.3 FIELD PARAMETERS

What parameters were the most useful in predicting successful application?

The collection and field measurement of several water quality indicator parameters proved extremely useful in evaluating two components of the injections: distribution and residence time. Based upon a review of the data collected at this suite of per sulfate injection sites, pH, ORP, and specific conductance/conductivity were the most useful field water quality parameters. Most meters that collect pH, ORP, and conductivity also can collect dissolved oxygen (DO) and temperature and those may be useful for comparative analysis as well, and should be collected if available on the meters used.

Colorimetric field test kits were also utilized to evaluate the presence of persulfate in select wells at each site. These kits were useful and are relatively inexpensive (in the range of $2 to $4 per ampoule). However, the test kits are limited to a high-end range of 70 ppm of


persulfate. Also, the kits work by exposing an ampoule of reagent to a water sample and, after allowing for a chemical reaction per the kit instructions, comparing the color of the solution in the ampoule to a colorimetric scale equating to a given persulfate concentration. Similar to limitations encountered with other colorimetric field test kits (e.g., DO), the turbidity and background color of the aquifer and geochemistry can ultimately affect the color of the solution providing potential false positive persulfate results.

In addition to collecting the field persulfate data, a sub-set of ground water samples was also submitted for laboratory confirmation of persulfate concentrations. The laboratory was able to quantify and report a much wider range of persulfate concentrations than the field test kits.

Shouldjlow cells be employed during application programs or only down-hole equipment?

As a matter of standard practice, GeoInsight typically does not employ down-hole water quality monitoring equipment for routine monitoring at remediation sites due to the increased potential for cross-contamination in using down-hole probes. The use of flow-through cells for monitoring water quality parameters at the ISCO persulfate site is not recommended either. While flow-through cells are well-suited for low-flow sampling events, it is inherently more beneficial to be able to collect many different parameter measurements (spatially and temporally) to assess the ISCO work. This is easily accomplished by using disposable bailers to collect grab samples once monitoring wells have been purged (typically performed prior to the injection during the collection of pre-injection, baseline data). Once the ground water samples are extracted, measurements can be made using a suitable field meter. While care must be taken not to over-agitate the samples during hand-bailing and sample transfer, this method is relatively quick to perform and reduces the exposure time of the field meters to the ground water sample. Depending on the sampling location, the water samples may contain high concentrations of oxidant (with extremely elevated pH in some instances) and prolonged exposure to oxidant solution, which may occur in flow-through cells and could damage the instrumentation.

Whatfactors may explain variance within the range of measurements and with anticipated readings? What numbers or ranges for each parameter were good indicators of success?

The available literature reviewed does not indicate specific anticipated ranges for water quality indicator parameters while performing persulfate injections. However, general theoretical responses of several parameters are discussed in detail in the literature. Field-collected water quality indicator parameters are semi-qualitative, but are useful in comparative evaluation (i.e., comparing baseline, pre-injection parameter data to data collected during and at several points after the injection). Charts illustrating water quality field parameter data collected at selected pilot sites are presented in Appendix C.

pH - During base-activated persulfate injections, pH is a good indicator of the distribution of the oxidant solution. The oxidant solution will have a pH in the order of 10 to 11 and once applied to the aquifer, base conditions may dilute in strength. However, pH can be monitored for potential increases from baseline conditions. Persulfate oxidation produces


sulfuric acid. Injections employing base-activated persulfate typically incorporate sufficient base to buffer the production of sulfuric acid, plus an additional dose to buffer the natural acidity ofthe aquifer. In some instances, the pH may ultimately decrease from baseline conditions if the sulfuric acid production exceeds the base's buffering capacity. Several illustrative examples of increasing pH values in monitoring wells as a response to persulfate injections are presented in the charts presented Appendix C.

ORP and Conductivity - ORP and conductivity readings are generally expected to increase following the introduction of persulfate to a monitoring location when compared to baseline conditions. The dissolution of sodium persulfate in an aquifer increases the dissolved solute concentrations and, consequently, conductivity measurements should increase. ORP is a relative measure of the redox environment. Positive ORP readings are expected to correlate to oxidant solution migration (ITRC, 2005).

DO - As oxidation occurs during a persulfate injection, DO concentrations are expected to increase. Also, sites where persulfate and calcium peroxide are injected, DO should be expected to increase and remain sustained as the calcium peroxide slowly releases oxygen to the aquifer. A marked increase in DO was noted in target area wells following the OBC™ applications at the Wickens Residence and Kimball's sites (refer to the water quality parameter summary tables in Appendix B and the chart plotting DO concentrations at the Kimball's site in Appendix C).

Carbon Dioxide - Carbon dioxide data was not collected in conjunction with these applications; however, the end product of the oxidation of petroleum is carbon dioxide and water. Therefore, carbon dioxide readings may ultimately be useful in evaluating the extent of oxidant transport and reactions at persulfate injection sites.

Sulfate - A byproduct of persulfate oxidation is the production of sulfate. In general, sulfate testing was completed during baseline and post-injection monitoring events. Sulfate concentrations were observed to increase from background at several sites both within and downgradient of the target application area. Increased concentrations of sulfate can have a secondary remedial affect at an ISCO site in that the sulfate ion can act as an electron acceptor for sulfate-reducing bacteria. If sulfate-reducing bacteria are present and active at a site, the increased sulfate concentration may enhance anaerobic biodegradation.

3.4 SODIUM HYDROXIDE ACTIVATION VERSUS CALCIUM PEROXIDE ACTIVATION

Compare and contrast sodium hydroxide activation versus calcium peroxide activation?

Both ISCO approaches are technically base activations (see Section 2.1). Longer term increased oxygen levels are theoretically provided by the calcium peroxide (and can act to stimulate aerobic biodegradation) and, also, calcium peroxide is inherently safer to manage from a safety and handling perspective than sodium hydroxide. However, because calcium peroxide is sparingly soluble and a slurry is produced for injection, distribution into the


surrounding aquifer and/or soil matrix will be limited. As a result, loss of the activation affect is typically anticipated once the solution ceases to migrate and the dissolved persulfate continues to migrate into the aquifer (FMC, personal communication, 2010). The ITRC (2005) also indicate that persulfate effectiveness is controlled in part by the co-distribution/transport of the activator into the aquifer with the persulfate in solution. This condition is anticipated to contribute to uneven distribution of the activated oxidant during persulfate applications using calcium peroxide. Limited migration of calcium peroxide into the aquifer can also be expected to limit the distribution of increased oxygen levels.

Another factor worth noting is that persulfate demand (for GRO-TPH impacts) based upon values provided by FMC is 47:1 (persulfate to contaminant) and for Klozur-CR (50 percent calcium peroxide and 50 percent sodium persulfate), the product demand is approximately 32: 1. There is a lower demand for the calcium peroxide-activated product because the demand calculation includes an estimated contaminant reduction due to aerobic biodegradation resulting from theoretical increases in aquifer oxygen levels. However, because chemical oxidation is a more direct contaminant destruction process when compared with biodegradation, which is more of an indirect process, one may wish to evaluate the relative anticipated effectiveness of contaminant destruction that may occur from enhanced biodegradation, as it will be a component of the remedial process with calcium peroxide-activated applications.


4.0 CONCLUSIONS AND RECOMMENDATIONS

Should we continue to utilize this ISCO method or is there a better technology or chemical oxidant available for use at petroleum sites? Are ISCO in general and sodium persulfate in particular appropriate technologies to speed New Hampshire sites to closure with a one-year time period or does post-injection monitoring indicate the need for additional treatment, supplemental technologies, and/or a longer post-injection monitoring period?

As stated in Section 1.2, the goals of the expedited closure pilot program included an evaluation of the success of: 1) base-activated sodium persulfate oxidation applications at petroleum sites with relatively isolated plumes of recalcitrant ground water constituent concentrations using relatively small-scale, short-duration, and low-cost ISCO injections; and 2) the performance of a specialized ISCO subcontractor as part of a team to design and implement a variety of ISCO injections at expedited closure candidate sites. Based upon the funding mechanism used for the program (EXPC monies), an implicit goal of the exercise was to ultimately attain site closure using the pilot ISCO technology.

While site closure has not yet been attained at the six sites included in the expedited closure program, the application of per sulfate at the Noguera Residence reduced ground water constituent concentrations such that a Certificate of No Further Action was issued for the project on April 6, 2011. Also, pending the results of confirmatory ground water sampling in July 2011, the Getty-Exeter site may be eligible for site closure. The lack of attaining additional site closures for more of the projects should not be viewed negatively, as this comprehensive study yielded significant data to refine methods for the future use of this technology. Furthermore, while not expressed in the VOC ground water monitoring data (for the reasons described in this report), the ISCO applications undoubtedly destroyed a portion of residual contaminant mass at most, if not all, of the pilot sites, which should lead to reduced overall remedial/monitoring costs over time.

Based upon the findings of the pilot injections included in this summary and information presented in the literature, a minimum of a one-year period is needed at most sites before ground water conditions return to equilibrium conditions following a persulfate injection. Therefore, this technology may not be appropriate for "expedited" site closures with timeframes of one year or less. In order for small-scale, short-duration persulfate injections to be successful in achieving expedited site closure, several site-specific factors, including relatively simple site geology and isolated and low-concentration residual source areas (containing primarily dissolved-phase impacts), should be present and well understood.

As described in this report, additional pre-injection investigation appears to be warranted for most petroleum sites being considered for persulfate oxidation applications. Supplemental investigation should include reducing the uncertainty with respect to the remaining residual contaminant mass and should at a minimum include supplemental analysis ofTPH analysis in several source area soil samples to determine "average" residual contaminant mass. Future persulfate applications will likely be more successful if the extent and magnitude of the mass at a given site were better understood.


Additional analysis of persulfate application methods appears to be also warranted to increase the success of future injections. Short-circuiting was observed during several of the pilot tests and the body of professional literature describes limitations with implementing the application using direct-push-type injection methodologies (including the potential for incomplete distribution during the "bottom-up" injection method).

Effective distribution of the oxidant to the residual contaminant is also a controlling factor in the success of an ISCO application and additional pilot testing appears to be warranted to evaluate which of the application methods is best-suited for a particular site.

What limitations were encountered by Geolnsight or the ISCO vendor?

While several vendors were considered, it was evident that subcontractor input could range from product purchase with limited technical support on application (e.g., FMC) to full-scale research projects that include bench-scale feasibility studies, and multi-step implementation tasks that are not economically feasible for the size of the projects being considered and included in this study. Ultimately a decision was made to proceed with awarding the majority of the projects to a single vendor who could provide product delivery, technical assistance, and knowledgeable implementation of similar projects in the New England area.

While interaction with Redox Tech was generally favorable, several potential limitations are discussed below.

• Contaminant mass estimate calculations were not supplied by Redox Tech. Therefore, it was difficult to evaluate the underlying assumptions on which the oxidant demand/dose amounts were developed by Redox Tech and to independently determine if sufficient quantities of oxidant were selected for each site.

• Geoprobe® injection utilizing relatively high injection pressures (20 to 60 psi) does not appear to be applicable to all New Hampshire petroleum remediation sites. To a large extent, alteration of the injection approach at the various sites was not observed despite differences in geologic conditions.

• Redox Tech's approach of using relatively lesser quantities of sodium hydroxide to "activate" the persulfate reaction is contrary to that of some of their peers. Specifically, it is our understanding that both FMC and at least one other ISCO contractor in the area utilize a calculated amount of base dictated by the stoichiometry of the quantity of per sulfate used for each project (and the associated amount of sulfuric acid that will be produced), plus an additional 10 to 20 percent of base to buffer natural aquifer acidity.


• Most of the pilot projects had limited datasets with respect to baseline conditions in the target application areas. With the exception of the Hudson Mobil and Kimball's projects, specific target area soil delineation and sampling programs would have helped significantly in evaluating the residual contaminant mass. This data would have likely assisted Redox Tech with developing more appropriate oxidant application quantities; however, Redox Tech did not specifically identify this potential data gap during the design phase of the pilot tests.

June 30, 2011 GeoInsight Project 4S37-A-004 Page 26

5.0 REFERENCES CITED

Colorado Department of Labor and Employment, Division of Oil and Public Safety (Colorado DLE), June 2007. Petroleum Hydrocarbon Remediation by In-Situ Chemical Oxidation at Colorado Sites.

FMC Chemical Corp (FMC), November 2009. Peroxygen Talk: Determination of the Klozur Persulfate Demand (FMC Environmental Solutions on-line Resource Center at http://www.envsolutions.fmc.comlResource Center).

Huling, S. G. and B. E. Pivetz, August 2006. In-Situ Chemical Oxidation. USEPA Office of Research and Development (EPAl6001R-06/072).

Huling, S. G., S. Ko, and B. Pivetz, 2011. "Groundwater Sampling at ISCO Sites: Binary Mixtures of Volatile Organic Compounds and Persulfate," Ground Water Monitoring & Remediation, 31, no. 2: 72-79.

Interstate Technology & Regulatory Council (lTRC), 2005. Technical and Regulatory Guidance for In Situ Chemical Oxidation of Contaminated Soil and Groundwater, Second Edition.

Krembs, F. J., R. L. Sigrist, M. L. Crimi, R. F. Furrer, and B. G. Petri, 2010. "ISCO for Groundwater Remediation: Analysis ofField Applications and Performance," Ground Water Monitoring & Remediation, 30, no. 4: 42-53.

Regenesis, March 2007. Principles of Chemical Oxidation Technology for the Remediation of Groundwater and Soil, RegenOx Design and Application Manual, Version 2.0.


6.0 LIMITATIONS

Geolnsight completed the evaluations and analysis described in this report in a manner consistent with the level of care and skill ordinarily exercised by other environmental consultants engaged for similar services under similar circumstances. Accordingly, the conclusions ofthis report do not constitute scientific certainties, but rather probabilities based upon professional judgment concerning data gathered during the course of the investigations, and the use of engineering and scientific principles. To the extent that the interpretations and findings presented in this report are based in whole or in part upon information and representations in reports prepared by others, they are contingent upon the validity of the information.


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1 INJECTION WELL

_._v_ ._ ._ ._. _ ._ .

FIGURE 1-1 RADIUS OF INFLUENCE OF INJECTION WELL

(HOMOGENOUS AQUIFER) NOT TO SCALE

1 GEOPROBE ROD

_._v_ ._ ._ ._ .

3RD DEPTH INTERVAL

2ND DEPTH INTERVAL

~----""""""----~1-- 1ST DEPTH INTERVAL

~ FIGURE 1-2 ~ RADIUS OF INFLUENCE OF GEOPROBE ROD

1

_ . _ . _ .\L.. . _ .

MEDIUM HYDRAULIC CONDUCTIVITY

HIGH HYDRAULIC CONDUCTIVITY

LOW HYDRAULIC CONDUCTIVITY

FIGURE 1-3 RADIUS OF INFLUENCE IN HETEROGENEOUS AQUIFER

NOT TO SCALE

NOTES: 1. FIGURES WERE DEVELOPED IN PART AFTER FIGURES 5-1, 5-2, AND 5-3 FROM INTERSTATE TECHNOLOGY AND REGULATORY COUNCIL, JANUARY 2005, TECHNICAL AND REGULATORY GUIDANCE FOR IN SITU CHEMICAL OXIDATION OF CONTAMINATED SOIL AND GROUND WATER, SECOND EDITION.

CLIENT:

PROJECT:

TITLE:

DESIGNED:

DLS

NHDES

MULTI-SITE PERSULFATE ISCO EVALUATION

INJECTION RADIUS OF INFLUENCE

DRAWN: CHECKED: APPROVED:

STM AWK MFD

Geolnsight Practical in Nature

~~ (HOMOGENOUS AQUIFER) 2!i':;; SCALE: DATE: FlLE NO.: PROJECT NO. :

9 ~ NOT TO SCALE NTS 06/30/11 4537d021 4537-A-000 FlGURE NO.:

1 ~~~ ________________________________________________________________________________________________________ ~ ________ 6-__ ~~~ ________ ~ ________ 6-______________ ~

II t: " ~ >. .. c ::I .. :s U ..

~ '" .. = .. -= '" E " ~ ::I ::

Funding Source

Release Product Gasoline Gasoline

Original Target Analyte(s) TMBs. naphthalene BTEX, TMBs, naphthalene

Ut:..~'ruy identified residual soil OcSII'Uy identified soil and NAPL Ina,.tS and remediate ground rlltaS,'i. remedlate ground water and

Remedial Pilot Goal WOltC,f" near CEA-4 NAPL near well MW -108R

Injection #1: NaOH-activated

ISCO Product(s) J""Julf,lC persulfate+Ca-peroxide (OBCTM) ~'Joctjon #2: persulfate+Ca' pe:o<lde (OBC"")

Application Method Injection Injection

Treatment Zone Thickness reet (ft) 4-61\ (Injection #1)

4-61\ 4-6 It (Injection #2)

Target Area 700 sf (Injection # I)

600 sf 700 sf (Injection #2)

Redox Tech Estimated Oxidant Quantity 2,590lbs 1,300lbs

FMC/Geolnsight Estimated Oxidant NIA NIA

Quantity

Distribution/Short-Circuiting issues? no yes

Data Gapsllssues Identified Prior to Injection

none none

Conclusions regarding future Inltllll injection likely did notli<:!:ounl remediation are pending ror sufficient oxidant to destroy addiLiona1 ground water ro$Iduai soil and NAPL bnpacts in ",onltoll"~ data $Oun:c area. Supplemental

Conclusions / Recommendations for Future IPPUendons may be warranted using lllkIlli nlil oxidant and a1ternaLive

Remediation appIlC1l1lon methods.

NOTES:

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0 = ::I ..

U

" ;" ::I

=:l ... " e ... .. ""'

TABLE! SUMMARY OF EXPEDITED CLOSURE (AND OTHER) PILOT PERSULFATE ISCO PROJECTS

NUDES OIL REMEDIATION COMPLIANCE BUREAU EXPEDITED CLOSURE SITES

.>= .. .. .. '" ..

-f." ..

" ~ -= a " ::I <II .. -= '1 ... ";l .: i <II ~ € .: " >. <II

~ C>o ~ ~

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EXPC - Funded ODDCF ODDCF

Gasoline Gasoline Gasoline Gasoline Gasoline Gasoline

Naphthalene 124 TMD , naphthalene 124 TMB, naphthalene Benzene and TBA MTBE and benzene NAPL and gasoline constituents

re.tncdhw: ground water near tJe..\tmy identified soil mass, remediale ground waler near remediate ground water near remediate ground water near destroy NAPL at CB-6, remediaLe source soil,

~ .. II' MW-301 and MW-302 remediate ground water near wellMW-1 weIlGEO-2 well RW-l and reduce gw concenlrations in plume center of

weIlGEO-IR mass

NaOH-activated pcrsulfate NaOH-activatcd persulfate NaOH-activated. persulfate NaOH-activated persulfate NaOH-activated persuUatc NaOH-nctivaLed persulfate

Injection Injection Injection Injection Gravity Feed Gravity Feed

7 1\ (Injection # I) 15 ft 6ft 5-7 ft 8ft 4-8 fI

4,000 sf (Injection #1) 700 sf 700 sf 750 sf 1,415 sf 2,025 sf

4,000 sf (Injection #2)

9.769 Ibs (Injection #1) 4,4641bs 4.6291bs (Injection #2)

2,3141bs 1,8181bs NIA NIA

NIA NIA NIA NIA 2,310 Ibs 5,000 Ibs (1st application); 6.000 Ibs (2nd application); >80,000 lbs for future applications

no yes yes yes no no

Highly stratified naLive soil; Active USTs & utilily Shallow depth 10 ground Limited historical data regarding extent and

two nearby impacted soil corridor in vicinity of target water; possible increased levels of source area NAPL and soil impacts

excavation areas with high area levels of background organics

none penneability backfill

none

Cunclu:dcl1$ regarding future Additional investigation of Due to the apparent short- Only one-half of design The site may be eligible for NAPL apparently destroyed during first

I'Onu,dIOlI.n are pending extent and concentration of circuiling of oxidant outside quantity ofISCO was applied closure pending the resulls of application. Second applicaljon was unsuccessful

Ddilltiunal ground water residual impacts warranted of the target zone, future due to short-circuWng. a July 2011 confirmatory in reducing gw concenlrations. Recent soil

monItoring data before proceeding with a ISCO applications are nol Additional injections not ground water sampling event~ delineation sampling indicates the residual source

second injection currently being considered.. recommended due to the area would require over 88,000 lbs of persulfate

observed short-circuiting. to remediate. Other remedial options are currently being considered.

to ~ ~ ~ <II ~

ODDCF

Gasoline

BTEX. naphthalene, 124TMD

remediate ground water near wtn!MW-5 and MW-16

NaOH-activated persuLfate

Injection

4-6 ft

9,000 sf

18,8411bs

NIA

no

none

Due to continued evidence that ISCO application has not run its course, NHDES recently agreed to replace key downgradienl well (MW-6) that was destroyed by plows and further assess effects oflSCO with fall 2011 GMPevenL.

I) Abbreviations: ODDCF = Oil Discharge and Disposal Cleanup Fund; 124 TMB = 1,2,4-trimethylbenzene; BTEX = benzene, toluene, ethylbenzene, xylenes; Ibs = pounds; NAPL = non-aqueous phase liquid; TBA = tertiary butyl alcohol; MTBE = methyl tert-butyl etber; gw = ground water; NaOH = sodium hydroxide.

June 28, 20J I Geoinsighl Project 4537·A-004:ISCO summary tble.xIsx: Sheet!

<II <II ... ... = = " " " ] .~ Q

"C ~ ~ :l " '" ... 5 ... "

<II ::I .>= E .. .!:! ..

~ Q

z ""' PrivaJe Insurance Pri"aJe Insurance ARRA

#2 Fuel Oil #2 F uel Oil Gasoline

BTEX, MTBE, naphthalene. Naphthalene and benzene Naphthalene alleylbenzenes

remediate ground waler near rernediale ground waler at destroy unquantified residual

well MW-l, destroy well MW-2. destroy impacted soil below 2009

unquantified mass left in unquantified impacted soil excavation and remedlale place along house foundation left. in place along house ground water

in release area foundation in release area

NaOH-activated persulfale activated persulfate+OBCTM NaOH-activated persulfate

Injection Injection Gravity Feed

3-5 ft 4-6 ft 5 ft

700 sf 700 sf 3,350 sf

I.9941bs 2,9051bs NIA

NIA NIA 6,2261bs

no no no

Limited understanding of Limited understanding of Limited understanding of

remaining quantity of remaining quantity of remaining quantity of remaining residual soil mass remaining residual soH mass remaining residual soil mass

CFNA issued April 6,2011 Very limited exceedances SHe-specific discussion remaining. Implement a pending with the NHDES second very targeted regarding potentia1 future application remedial activities.

Page I of!

APPENDIX A

SUMMARY OF PERSULFATE PILOT SITES AND

SITE LOCUS, SITE PLAN, AND VOC AND WATER QUALITY PARAMETER SUMMARY TABLES FOR PERSULFATE PILOT SITES

(APPENDICES A.l THROUGH A.12)