Biosparging Pilot Study Work Plan Hartland 36 Gas Plant SE/NE/NW Section 36, T03N-R06E Hartland Township, Livingston County, Michigan

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1 April 5, 2017 ECT No.: Mr. Sean Craven Regulatory Analyst Merit Energy Company 1510 East Thomas Road PO Box 910 Kalkaska, MI Re: Biosparging Pilot Study Work Plan Hartland 36 Gas Plant SE/NE/NW Section 36, T03N-R06E Hartland Township, Livingston County, Michigan Dear Mr. Craven: Attached please find one copy of the Biosparging Pilot Study Work Plan completed by Environmental Consulting & Technology, Inc. (ECT) for the Hartland 36 Gas Plant (Site). ECT sincerely appreciates the opportunity to provide our consulting services on this important project. Should you have questions or require additional information, please do not hesitate to contact me at or Sincerely, ENVIRONMENTAL CONSULTING & TECHNOLOGY, INC. Jeremy S. Lewandowski Senior Engineer Mark D. Mikesell, PhD Senior Scientist 3399 Veterans Drive Traverse City, MI (231) FAX (231) cc: Mr. Shawn Lehman MDEQ-OOGM (electronic copy) Mr. John Dunleavy Property Owner (electronic copy) Mr. Matthew Germane Consultant to Property Owner (electronic copy) Attachments: Biosparging Pilot Study Work Plan An Equal Opportunity/Affirmative Action Employer

2 Biosparging Pilot Study Work Plan Hartland 36 Gas Plant SE/NE/NW Section 36, T03N-R06E Hartland Township, Livingston County, Michigan Prepared for: 1510 East Thomas Road PO Box 910 Kalkaska, Michigan Prepared by: 3399 Veterans Drive Traverse City, Michigan ECT No April 5, 2017

3 TABLE OF CONTENTS 1.0 INTRODUCTION PROJECT BACKGROUND BIOSPARGING FEASIBILITY (LIMITED) ANALYSIS SUMMARY OF AEROBIC BIODEGRADATION OF SULFOLANE SITE SAFETY PLAN BIOSPARGING PILOT STUDY DETAILS Proposed Pilot Study Area and Equipment Proposed Pilot Study Operating Parameters Pilot Study Monitoring Parameters BIOSPARGING PILOT STUDY REPORT PERMITS AND CORRECTIVE ACTION DISCHARGES... 7 FIGURES Figure 1 Site Location Map Figure 2 Site and Surrounding Properties Map Figure 3 Site Plan Figure 4 Pilot Study Site Plan Figure 5 Biosparge Point Construction Diagram Figure 6 Monitoring Point Construction Diagram TABLES Table 1 Sulfolane Groundwater Analytical Summary & Cleanup Criteria Comparison Table 2 Geochemical/Biological Parameter Analytical Summary April 5, 2017 Biosparging Pilot Study Work Plan i

4 1.0 INTRODUCTION The purpose of this document is to present the procedures to be employed in the operation of a field-scale pilot study to evaluate the effectiveness of biosparging to enhance bioremediation of sulfolane dissolved in groundwater at the Hartland 36 Gas Plant (Site). Refer to the Site Location Map (Figure 1), Site and Surrounding Properties Map (Figure 2), and Site Plan for Site and vicinity characteristics. The majority of published information regarding the environmental fate of sulfolane suggests that oxidation by aerobic microorganisms is the primary degradation pathway. This view appears to be related to the fact that aerobic sulfolane degradation has been observed by all researchers who studied it, while anaerobic sulfolane degradation has been sporadically observed. Sulfolane is expected to have very high mobility in soil and will not adsorb to suspended solids and sediment. Sulfolane is not expected to volatilize from dry soil surfaces given a vapor pressure of mm Hg. Microcosms constructed of groundwater and sediment obtained from natural gas plants suggest that sulfolane degrades readily under aerobic conditions (half-life of 2-3 days), but was shown to be stable under anaerobic conditions. As stated above, the goal of this field-scale pilot study is to evaluate the effectiveness of biosparging to enhance bioremediation of sulfolane dissolved in groundwater at the Site. The final objective of the pilot study is to utilize the data for use in full scale remediation system design. 2.0 PROJECT BACKGROUND Contaminated soil was discovered in September 2015 during facility decommissioning activities at the former sweetening plant/refrigeration building (sulfolane impact from the chemical Sulfinol ). Remediation activities (excavation) completed from September 2015 through December 2015 resulted in disposal of 13,481.4 tons of soil at the Venice Park Landfill in Lennon, Michigan. Verification of soil remediation (VSR) samples collected from the excavations confirmed remediation of impacted soils. Refer to the Soil Closure Report for a detailed summary of soil remediation and sampling activities. Groundwater investigation activities commenced on October 29, 2016 and were completed on March 7, From October 29, 2015 through March 27, 2017 a total of 13 temporary monitor wells, including two vertical aquifer profile (VAP) locations, and 35 permanent monitor wells, including 20 shallow screened monitor wells and 15 deep screened monitor wells, have been installed at the Site. The lateral and vertical extents of groundwater impacted with sulfolane have been delineated to non-detectable concentrations. The maximum sulfolane concentration reported from the most recent sampling event (March 2017) from a permanent monitor well (MW-20D) at the Site was 8,300 micrograms per liter (µg/l). Refer to the attached Site Plan (Figure 3) for monitor well locations. Refer to the attached Table 1 for a summary of groundwater analytical results. April 5, 2017 Biosparging Pilot Study Work Plan 1

5 3.0 BIOSPARGING FEASIBILITY (LIMITED) ANALYSIS Biosparging is an in-situ remediation technology that creates an aerobic environment for indigenous microorganisms to biodegrade organic constituents in the saturated zone. In biosparging, air is injected into the saturated zone to increase contaminant degradation by indigenous microorganisms. Biosparging can be used to reduce concentrations of biodegradable constituents that are dissolved in groundwater, adsorbed to soil below the water table, and within the capillary fringe. Biosparging is similar to air sparging with respect to enhancing the subsurface aerobic environment, but differs in that air sparging also creates a phase transfer of volatile/semi-volatile organic contaminants from a dissolved state to a vapor state, sometimes requiring additional remediation methods (i.e. soil vapor extraction and ex-situ treatment). Biosparging should not be used if the following site conditions exist: Free product is present. Biosparging can create groundwater mounding which could cause free product to migrate and contamination to spread. Basements, sewers, or other subsurface confined spaces are located near the site. Potentially dangerous constituent concentrations could accumulate in basements and other subsurface confined spaces unless a vapor extraction system is used to control vapor migration. Use of vapor extraction may also be warranted if shallow groundwater is present without low permeability vadose zone soils. Contaminated groundwater is located in a confined aquifer system. The effectiveness of biosparging depends primarily on two factors: The porosity of saturated soils which determines the rate at which oxygen can be supplied to the microorganisms that degrade contaminants in the subsurface. The biodegradability of the contaminant(s) which determines both the rate at which and the degree to which the constituents will be degraded by microorganisms. The following considerations establish the potential feasibility of biosparging at the Site: The Site is impacted with sulfolane in groundwater beneath the designated study area. The extent of the impact has been defined. Sulfolane has not migrated beyond the boundary of the Site. The source of sulfolane has been removed from Site (source area soil removal). The Site groundwater aquifer is shallow (±19 feet at pilot study area) and underlain by a clay confining unit which limits vertical contaminant migration at the Site. Off-gassing is not anticipated due to the very low volatility and vapor pressure of sulfolane as well as the clayey soils that are present in the vadose zone. As discussed in Section 4.0, under aerobic conditions, sulfolane is readily biodegradable and resulting breakdown products include carbon dioxide (CO 2 ), water and sulfate. Based on geochemical and biological parameter sampling presented on Table 2, anaerobic conditions and a reduced (oxygen) environment are apparent at the location of MW-13 suggesting that enhanced bioremediation could be a viable treatment alternative. April 5, 2017 Biosparging Pilot Study Work Plan 2

6 4.0 SUMMARY OF AEROBIC BIODEGRADATION OF SULFOLANE As discussed in Section 1.0, the majority of published information regarding the environmental fate of sulfolane suggests that oxidation by aerobic microorganisms is the primary degradation pathway and that sulfolane is readily biodegradable in an aerobic environment. In order to consider biosparging as a viable remedial alternative, an evaluation of potential degradation byproducts of sulfolane is necessary. Published literature, as well as various bench/laboratory studies, indicate the primary biodegradation byproducts of sulfolane include carbon dioxide (CO 2 ), water (H 2 O), and sulfate and that any potential secondary byproducts or intermediates would not accumulate. 5.0 SITE SAEFTY PLAN Prior to the implementation of the field activities described herein, ECT will review and update the current Site-specific Health and Safety Plan (SSHSP). The SSHSP is designed to meet the requirements of the Occupational Safety and Health Administration Standard for Hazardous Waste and Emergency Response Operations (29 CFR ) and establish additional protocols/procedures ECT believes are necessary to preserve the general health and safety of the local public and project personnel, as well as the quality of work performed with regards to this project. A copy of the SSHSP will be on-site during the performance of all environmental field activities and a copy shall be made available upon request. 6.0 BIOSPARGING PILOT STUDY DETAILS The following presents biosparging point (BSP) and monitoring point (MP) locations and construction, and pilot study equipment, methods, and monitoring to complete the field testing. 6.1 Proposed Pilot Study Area and Equipment Three BSPs (BSP-1, BSP-2, and BSP-3) will be installed at the Site in the locations presented on the attached Pilot Study Site Plan (Figure 4). This location was selected based upon sulfolane reported at relatively similar concentrations at the groundwater surface (MW-13: 5,100 micrograms per liter, µg/l) and along the top of the clay confining layer (MW-13D: 5,400 µg/l). Additionally, Table 2 shows that dissolved oxygen is depleted in areas impacted with sulfolane, such as MW-13. Supplying oxygen at this location is expected to stimulate sulfolane biodegradation. Accordingly, the location of the BSPs will provide a means of evaluating the effectives of biosparging throughout the vertical extent of the groundwater unit. BSPs will be constructed of 1-inch diameter galvanized steel casing affixed with air-tight couplings. The BSPs will be installed with the bottom of the 2-foot long, 10-slot stainless steel screen situated approximately 11 feet below the apparent piezometric surface, on top of the clay confining layer, at an approximate depth of feet below ground surface (bgs). Neat cement grout will be added to the annulus of each borehole to minimize/prevent direct April 5, 2017 Biosparging Pilot Study Work Plan 3

7 communication between the underlying sediment formation encompassing the BSP screens and surface atmosphere. BSP construction characteristics are depicted on Figure 5. The BSPs were placed on 10 foot centers in consideration of the generally accepted radius of influence (ROI) of half the distance from the piezometric surface to the bottom of the BSP screen (i.e. ROI of 5 to 6 feet). Additionally, three BSPs were selected as a means to provide a curtain of injected air for monitoring characteristics downgradient of the injection zone. A manifold and above ground plumbing (flexible hose) will be utilized to connect an air compressor/blower (ambient air source) contained in a mobile trailer to the BSPs. Each leg of the manifold will be equipped with a valve to regulate flow, flow meter, and pressure gauge. The blower will be equipped with pressure and temperature gauges. Equipment controls will be located in a control panel within the mobile trailer and will include alarms that, in the event of an alarm condition, trigger equipment shut down. Due to the absence of electrical power at the Site, the mobile trailer will be powered by a generator. Three nested monitoring points (MP-2S/2D, MP-3S/3D, and MP-4S/4D) and an additional deep monitoring point (MP-1D) will be installed at the Site in the locations presented on the attached Figure 4. These locations were selected based on the porosity of saturated soils at the Site with respect to potential radius of influence and sulfolane concentration monitoring. MPs will be constructed of 1-inch diameter schedule 80 PVC pipe with 2-foot long 10-slot PVC screens. The shallow MP will be installed with a screened interval of feet bgs. The deep MP will be installed with the bottom of the well screen situated on the top of the clay confining layer, at an approximate depth of feet bgs. The MPs will be installed within the same borehole and a bentonite seal will be placed between the screened intervals. MP construction characteristics are depicted on Figure 6. ECT anticipates two days to install the BSPs and MPs. Well sealing materials will be provided no less than 72 hours to stabilize/cure prior to initiating pilot study activities. 6.2 Proposed Pilot Study Operating Parameters The following operating parameters and time frames are anticipated for the field testing: Three 10 day tests with individual BSP flow rates of approximately 10 standard cubic feet per minute (scfm), 20 scfm, and 30 scfm. Initial testing at respective flow rates will consist only of operating BSP-2 to determine radius of influence (ROI). Following stabilization of ROI monitoring parameters (discussed below), the three BSPs will be operated for 10 days upon which the system will be shut down for groundwater monitoring (discussed below). Subsequent to determination of ROI, pilot study operations will be continuous (i.e. 24 hours per day) and unmanned. Site visits, field parameter monitoring, and groundwater sampling will generally be completed as follows for each individual flow rate test: o Day 1 ROI determination and commence extended flow rate test. o Day 2, 5, and 8 Site visit and field parameter monitoring. April 5, 2017 Biosparging Pilot Study Work Plan 4

8 o Day 10 Site visit, field parameter monitoring, system shutdown, and groundwater sampling. Site visits will include, at a minimum, recording BSP flow rates and pressures, blower/compressor temperature and pressure, making system operation adjustments, as necessary, and if warranted, recording system alarms and restarting system operations. Field parameter monitoring events will include the use of a calibrated water quality meter to collect temperature, ph, specific conductance, dissolved oxygen (DO), oxidation reduction potential (ORP), and potentiometric surface measurements with the use of an electronic water level meter from the MPs, MW-13, and MW-13D. Groundwater sampling events will include collecting groundwater samples for laboratory analysis from the MPs, MW-13, and MW-13D, as discussed in Section Proposed Pilot Study Monitoring Parameters The following factors will be monitored to evaluate the performance of the biosparging pilot test: The radius of influence (ROI), sometimes referred to as bubble radius, is defined as the greatest distance from a biosparging point at which sufficient injected air pressure and flow can be induced to supply dissolved oxygen to stimulate the biodegradation of contaminants. The ROI will assist with determining the number and spacing of biosparging points (if full scale operations are pursued), and will be established based on the results of this pilot test. The ROI depends primarily on the hydraulic conductivity of the aquifer material in which sparging takes place as well as soil heterogeneities and differences between lateral and vertical porosity of the soils. The design ROI can range from 5 feet for fine-grained soils to >50 feet for coarse-grained soils and is further dependent upon the distance air is injected below the potentiometric surface. Radius of influence will be determined via measuring displacement of the potentiometric surface (i.e. groundwater mounding), subsurface pressure differentials, and DO concentrations. The biosparge injected air flow rate that is sufficient to enhance biological activity is site specific and will be determined by the pilot test. Typical air flow rates range from less than 5 to 30 scfm per injection point. Pulsing of the air flow may provide better distribution and mixing of the air in the contaminated saturated zone, thereby allowing for greater contact with the dissolved phase contaminants. In the event preferred migration pathways of injected air are identified during the biosparge pilot study, the use of pulsing injected air will be further evaluated. Biosparging air pressure is the pressure at which air is injected below the water table. Injection of air below the water table requires pressure greater than the static water pressure (1 psig for every 2.3 feet of hydraulic head) and the head necessary to overcome capillary forces of the water in the soil pores near the injection point. A typical system will be operated at approximately 10 to 15 psig. Excessive pressure may cause fracturing of the soils April 5, 2017 Biosparging Pilot Study Work Plan 5

9 and create preferential pathways that can reduce biosparging effectiveness. Based on depth to the potentiometric surface in the area of the pilot test, approximately 5 psig, plus additional pressure for breakthrough, is the calculated BSP pressure with overall system pressure (considering equipment and pipe losses) expected at less than 10 psig. Sulfolane concentrations will be measured in groundwater samples collected prior to the start and during the pilot testing. They establish a baseline for estimating the constituent mass removal rate and potential full scale system operation time requirements. Measurements and concentrations of biodegradation parameters in groundwater will be monitored during the pilot study. These parameters will be utilized as a means of providing baseline levels of subsurface biological activity and for assessing the effectiveness of enhanced bioremediation processes and resulting biodegradation of sulfolane. For the Site, parameters depicting increased aerobic respiration of sulfolane (e.g. enhanced bioremediation activity resulting from the injection of air) are optimal as oxygen is the preferred electron acceptor for organic-chemical degrading microorganisms (microorganisms gain more energy from aerobic respiration). On the contrary, parameters correlated to anaerobic respiration are less desirable when attempting to remediate a Site via enhanced aerobic bioremediation. In addition to field parameter monitoring discussed in Section 6.2, biodegradation parameter monitoring will include dissolved iron, dissolved manganese, sulfate, nitrate, phosphorus, chemical oxygen demand (COD), carbon dioxide (CO 2 ) and methane. Nitrate and phosphorus further demonstrate macronutrient levels that aid in bioremediation processes. Groundwater samples will be collected from the MPs, MW-13, and MW-13D for laboratory analysis of the biodegradation parameters and sulfolane prior to pilot study startup and at the completion of each of the 10 day tests. Groundwater sample collection and analysis will be completed consistent with current low-flow sampling methods employed at the Site. 7.0 BIOSPARGING PILOT STUDY REPORT At the completion of the pilot study, a Biosparging Pilot Study Report will be prepared and submitted to the MDEQ. The report will present pilot system operations and data and will provide a detailed evaluation of the effectiveness of biosparging as a full scale remedial alternative for sulfolane dissolved in groundwater at the Site. Data and information will be discussed in text and presented on maps, diagrams, tables, and charts, as applicable. Information provided in the report will include, but not be limited to, data pertaining to the determination of BSP ROI (i.e. measurements of displacement of the potentiometric surface and subsurface pressure differentials) at various injected air flow rates and pressures; sulfolane and geochemical/biological parameter tables and charts for use in evaluating the biodegradation of sulfolane and subsurface environment (i.e. aerobic/anaerobic, oxygen reduced, etc.). The report will conclude with a determination of the overall effectiveness of the pilot study and whether additional field testing is warranted for further evaluation of biosparging as a viable remedial alternative for the Site. April 5, 2017 Biosparging Pilot Study Work Plan 6

10 8.0 PERMITS AND CORRECTIVE ACTION DISCHARGES An evaluation of potentially applicable permits and corrective action discharges associated with the pilot test was completed. The findings of the evaluation indicate no permits or corrective action discharges are applicable to the pilot study, as follows. Air sparging systems are exempt from the requirement to obtain a Permit to Install (PTI) from the Michigan Department of Environmental Quality (MDEQ) per R (kk) of the Michigan Administrative Code, which reads as follows: Air sparging systems where the sparged air is emitted back to the atmosphere only by natural diffusion through the contaminated medium and covering soil or other covering medium. The pilot study activities are exempt from the requirement to obtain a groundwater discharge permit from the MDEQ per R (u)(ii) and (iii), which read as follows: (ii) A remedial investigation, feasibility study, or remedial action discharge that is at or below the residential criteria authorized by section 20101a(1)(a) of the act, if applicable, or section 21304(a) of the act, if applicable. (iii) A discharge for a remedial investigation, feasibility study, or remedial action above the residential criteria authorized by section 20101a(1)(a) of the act, if applicable, or section 21304(a) of the act, if applicable, if a remediation investigation, feasibility study, or remediation plan has been approved by the department division that has compliance oversight. The remediation plan shall indicate that the treatment system is designed and will be operated so that contaminated groundwater will eventually meet the appropriate land usebased cleanup criteria authorized by section 20120a(1)(a) to (d) of the act, if applicable, or section 21304(a) of the act, if applicable. April 5, 2017 Biosparging Pilot Study Work Plan 7

11 April 5, 2017 Biosparging Pilot Study Work Plan FIGURES

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18 April 5, 2017 Biosparging Pilot Study Work Plan TABLES

19 Sample Location Screened Interval (ft bgs) TABLE 1 SULFOLANE GROUNDWATER ANALYTICAL SUMMARY & CLEANUP CRITERIA COMPARISON Hartland 36 Gas Plant SE/NE/NW Section 36, T03N-R06E, Hartland Township, Livingston County, Michigan ECT Project # Sulfolane by EPA Method 8270D (µg/l) 10/15/ /4-5/ /13/2015 1/27/2016 6/3/2016 8/3-4/2016 9/21-22/ /12/ /3/ /8/ /21-23/16 2/14/2017 3/14-16/2017 W-Pit , , MW ND --- ND ND --- ND (ND) ND MW ND --- ND ND --- ND ND MW-2D ND MW ND ND --- ND ND --- ND MW-3D ND ND MW ND --- ND ND ND ND ND ND --- ND --- ND MW ND --- ND ND --- ND ND ND --- ND MW ND --- ND ND ND ND ND ND --- ND --- ND MW-6D ND (ND) ND ND ND --- ND --- ND MW (510) ND ND --- ND MW-7D , ,000 MW ND ND ND --- ND MW ND ND ND --- ND MW ND ND ND (ND) --- ND MW ND ND ND --- ND MW-12S ND ND ND ND --- ND --- ND MW-12D ND ND (ND) ND ND --- ND --- ND MW ,600 8, , ,100 MW-13D ,200 (7,800) --- 8, ,400 MW-14S MW-14D , , ,600 MW ND ND ND --- ND MW-15D ,600 (4,500) 3,200 MW ND ND ND --- ND MW-16D ND ND MW-17S , ,100 (3,200) --- 3,000 MW-17D MW , , ,300 MW-19S , , ,300 MW-19D , , ,300 MW-20S MW-20D , ,300 MW-21D ND ND MW-22D ND MW-23D ND MDEQ-OOGM Cleanup Criteria 90 Collection Method Grab LF Grab LF Bailer/PP LF LF LF LF LF LF LF LF Notes 1) ft bgs - Feet below ground surface. 2) Collection method - Grab, peristaltic pump (PP), low flow (LF), Bailer. 3) µg/l - Micrograms per liter, equivalent to parts per billion (ppb). 4) (---) - Not sampled. 5) ND - Concentration not detected above reporting limit. 6) (###) - Concentration is for duplicate sample, only if duplicate sample reported different concentration. 7) Cleanup criteria for sulfolane established by MDEQ-Office of Oil, Gas, and Minerals (MDEQ-OOGM). 8) Concentrations that are shaded and bold exceed cleanup criteria. 9) MW-7 sampled on 8/11/2016 for the 8/3-4/2016 sample event. 10) Screened interval from well installation activities. Actual screened interval to be determined following updated data/survey. Page 1 of 1

20 TABLE 2 GEOCHEMICAL/BIOLOGICAL PARAMETER ANALYTICAL SUMMARY Hartland 36 Gas Plant SE/NE/NW Section 36, T03N-R06E, Hartland Township, Livingston County, Michigan ECT Project # Sample Location MW-12S MW-13 MW-15 Sample Date 8/3/2016 8/4/2016 8/3/2016 Collection Method Sulfolane, µg/l - Method SW D Sulfolane ND LF 6,600 ND Metals, mg/l - Method SW C Manganese Chemical Oxygen Demand, mg/l - Method E410.4 R2.0 Chemical Oxygen Demand Ferrous iron, mg/l - Method A3500-FE B-11 Ferrous iron <0.050 <0.050 <0.050 Nitrogen, nitrate-nitrite, mg/l - E353.2 R2.0 Nitrogen, nitrate-nitrite Sulfate, mg/l - A4500-SO4 E-97 Sulfate Groundwater Stabilization Characteristics Temperature, deg. C Specific conductance, umhos/cm Dissolved oxygen, mg/l ph Oxidation-Reduction Potential, mv Turbidity, NTU Page 1 of 1