Reference: Enhanced In Situ Biorem ediation (EISB) Implementation Report – 960 Industrial Road, San Carlos, CA
containing volatile organic compounds (VOCs). Investigation and removal of the ENU were summarized in the ENU Removal Report2.
VOC-impacted groundwater in the former ENU area was treated using EISB between 2008 and 2013. Treatment consisted of injecting food-grade carbon substrate and dechlorinating bacteria into the subsurface to create anaerobic conditions and stimulate dechlorination (i.e., degradation) of trichloroethene (TCE) into its progressive breakdown products 1,2-dichloroethene, vinyl chloride, and ethene. As documented in the 2014 Supplemental Site Investigation Report3 and confirmed during groundwater monitoring events, EISB treatment successfully reduced concentrations of TCE and related compounds to below aquatic habitat screening criteria in all wells, except for well MW-16, located hydraulically downgradient of the former ENU. As of February 2022, the concentration of TCE in well MW-16 was 852 micrograms per liter (μg/l). The locations of the former ENU, EISB performance monitoring wells MW-13 through MW-16, and the approximate extent of residual TCE in groundwater in the vicinity of MW-16, are illustrated on Figure 2.
OBJECTIVES AND SCOPE OF WORK
Stantec developed an EISB treatment program to address residual concentrations of TCE present in MW-16. As referenced in previous reports, EISB conducted at the Site between 2008 and 2013 successfully reduced concentrations of TCE sourced from the former ENU to sustained non-detect levels. The objective of additional treatment is to similarly reduce concentrations of TCE in groundwater at MW-16.
Treatment Area
The treatment zone is generally defined as the area immediately upgradient of MW-16 beneath Building 3A. The treatment program consisted of four direct-push injection locations within Building 3A, and injection into existing injection wells IW-6 and IW-7. The extent of the EIST treatment area and injection locations are depicted on Figure 3.
Baseline Monitoring
Prior to injection, Stantec’s subcontractor (Blaine Tech Services, Inc.) collected baseline samples from MW-16 and injection wells IW-1, -3, and -4. Groundwater was monitored in the field for pH, temperature, oxidation reduction potential (ORP), dissolved oxygen (DO), and ferrous iron, and groundwater samples were submitted for laboratory analysis of total organic carbon (TOC), VOCs, and dissolved gases as methane, ethane, and ethene. Groundwater chemical analyses were
2 ENU Removal Report (SECOR International Inc.). November 29, 2000. 3 Supplemental Site Investigation Report (Stantec). December 5, 2014.
January 25, 2024
Katherine Ward
Reference: Enhanced In Situ Biorem ediation (EISB) Implementation Report – 960 Industrial Road, San Carlos, CA
performed by SunStar Laboratories, Inc. in Lake Forest, California. The sample from MW-16 was additionally analyzed for Dehalococcoides bacteria by SiREM in Guelph, Ontario, Canada.
Substrate Injections
Carbon substrate injections were performed on May 24 and 25, 2023, by Cascade working under direction of a Stantec field geologist. Prior to advancing direct-push boreholes, Stantec marked the work areas in white paint, opened a one-call dig ticket, and coordinated with responding utilities. Stantec retained a private utility locator (GPRS, Inc.) to confirm that proposed drilling locations were free of detectable subsurface utilities or obstructions.
The carbon substrate solution consisted of sugar, Lactoil™, water, nutr ient solution, sodium bicarbonate buffer and an inoculant (SiREM microbial inoculant KB-1). Lactoil™ is a proprietary soybean oil emulsification containing approximately 35% ethyl lactate, a readily soluble substrate; 45% soybean oil, with moderate solubility; and 20% water. The treatment solution included 150 pounds of Tersus powdered activated carbon (PAC) per injection point to sequester VOCs and enhance EISB treatment. The injection points each received 100 pounds of sugar, 46 gallons of Lactoil™, 1.5 gallons of nutrient reagent, 1 liter of inoculum, and 150 pounds of PAC mixed with water to a final volume of 600 gallons. Each batch of reagent was prepared using mixing water which was deoxygenated using 0.5 liters of calcium polysulfide.
Carbon substrate was introduced to the subsurface via direct-push injection points DP-1 through DP-4 advanced within Building 3A and existing injection wells IW-6 and IW-7 located outside the building. Direct push injection points received approximately 200 gallons of reagent at each of three intervals: 10 – 13 feet below ground surface (bgs), 14 – 18 feet bgs, and 18 – 20 feet bgs. Each of the four direct push injection points, and each of the two injection wells located outside the building, received 600 gallons of substrate.
All mixing and conveyance equipment was supplied by Cascade. Substrate was injected at approximately 5 gallons per minute (gpm). At each injection point, substrate was bioaugmented with approximately one liter of KB-1 Dehalococcoides bacterial culture. The bacteria was introduced at the approximate mid-point of each injection volume using approximately 20 gallons of anaerobic water, followed by the second half of the substrate material.
Post-Injection Monitoring and Reporting
Following injection, Stantec conducted performance monitoring of wells MW-16 and IW-1 to evaluate EISB effectiveness. Performance monitoring criteria are generally summarized below.
January 25, 2024
Katherine Ward
Reference: Enhanced In Situ Biorem ediation (EISB) Implementation Report – 960 Industrial Road, San Carlos, CA
x Generation and maintenance of anaerobic conditions favorable to reductive dechlorination such as low DO, negative ORP, presence of ferrous iron, and detectable dissolved gases (methane, ethane, and/or ethene gas).
x Reduction and maintenance of VOC concentrations in groundwater to below risk-based screening levels.
Blaine Tech conducted post-treatment monitoring and sampling of wells MW-16 and IW-1 at intervals of one-, three-, and six-months following injection. Purging and sampling was performed using a low-flow bladder pump with dedicated tubing for each well. During purging, groundwater was periodically monitored for pH, temperature, ORP, and DO. At the time of sampling, a representative groundwater sample was analyzed in the field for ferrous iron using a Hach field test kit.
Groundwater samples were collected and submitted to SunStar for analysis of VOCs by USEPA Method 8260B; for dissolved gases as methane, ethene, and ethane by USEPA Method RSK-175; and for total organic carbon (TOC) by wet chemistry methods. The groundwater sample collected from MW-16 during the six-month monitoring event was additionally analyzed by SiREM for Dehalococcoides bacteria during PCR DNA assay.
Waste Management
Soil cuttings and purged groundwater were contained in 55-gallon steel drums and stored onsite at the direction of the Site owner pending characterization and offsite disposal.
EISB PERFORMANCE ASSESMENT
The following sections present baseline and post-injection EISB performance data. Baseline and performance monitoring data are summarized on Table 1 (VOCs in groundwater) and Table 2 (dissolved gases, TOC, field parameters, and Dehalococcoides analyses). Pre- and post-treatment VOC concentrations in EISB performance monitoring wells MW-16 and IW-1 are presented on Figure 4. Laboratory analytical reports are included as Attachment 1.
Selection of Screening Criteria
Because Pulgas Creek forms the southeastern boundary of the Site, groundwater chemical data have historically been compared to groundwater screening criteria protective of aquatic habitat receptors. Table 1, which summarizes VOC groundwater chemical data, includes groundwater Environmental Screening Levels (ESLs) protective of aquatic habitat receptors and of potential vapor intrusion from groundwater under commercial site use.
January 25, 2024
Katherine Ward
Reference: Enhanced In Situ Biorem ediation (EISB) Implementation Report – 960 Industrial Road, San Carlos, CA
Geochemical and Biological Conditions
The goal of injecting fermentable carbon substrate into the subsurface is to create reducing (anaerobic) geochemical conditions favorable to reductive dechlorination of halogenated VOCs by native and introduced bacteria. ORP measurements collected before and following injection confirm that reducing conditions were established at MW-16, as evidenced by negative ORP observed during the 3- and 6-month monitoring events. Similar reducing conditions are observed at IW-1, although only one negative ORP reading has been observed. Overall, ORP measurements (and the presence of ferrous iron) indicate that reducing conditions amenable to reductive dechlorination have been established in the vicinity of MW-16.
Groundwater samples from IW-1 and MW-16 were analyzed for dissolved gases as methane, ethene, and ethane. Ethene is a degradation product of chlorinated ethenes including TCE, and its presence can be used to confirm that TCE degradation is occurring. Ethene was not detected in performance monitoring data, a condition that is not unusual owing to the transient nature of ethene and the relatively low concentrations of TCE and cis-1,2-DCE in MW-16 baseline samples.
The robust concentration of methane (10,400 μg/l) observed during the 6-month sampling event indicates increased methanogenic activity by bacterial populations in response to the substrate injections, which suggests strong reducing conditions supportive of reductive dechlorination. The increase and subsequent decrease in cis-1,2-DCE and small amount of vinyl chloride generates suggest that complete dechlorination has occurred and treatment was successful.
Pre- and post-injection concentrations of Dehalococcoides bacteria were measured in samples from MW-16. The four-fold increase in bacteria populations between baseline and 6-month post- injection samples confirms that a robust population of Dehalococcoides has been established in the treatment zone which further supports the conclusion that complete dechlorination has occurred in the treatment area.
Distribution of Carbon
Baseline and performance monitoring samples were analyzed for total organic carbons (TOC) as a means to measure the distribution of carbon substrate following injection. A notable increase in TOC in MW-16 (from 1.8 milligrams per liter [mg/l] baseline to 230 mg/l after six months) confirms that carbon substrate has migrated from injection points to MW-16. A smaller increase in TOC was observed in IW-1 whereby the reported concentration approximately doubled between the baseline and 1-month sampling event before returning to near-baseline conditions in subsequent monitoring events. The delay in arrival at MW-16 suggests that TOC may increase over time, although VOC concentrations are already below regulatory limits.
January 25, 2024
Katherine Ward
Reference: Enhanced In Situ Biorem ediation (EISB) Implementation Report – 960 Industrial Road, San Carlos, CA
Chemical Concentration Trends
Post-injection monitoring has documented reduced concentrations of TCE and related degradation products in the EISB treatment area. Pre- and post-injection VOC concentrations are illustrated on Figure 4, and time-concentration plots of VOC concentrations in wells IW-1 and MW- 16 are illustrated on Figures 5 and 6, respectively.
Prior to injection, only low concentrations of TCE breakdown products (cis/trans-1,2-DCE and vinyl chloride) and 1,1-dichloroethane (1,1-DCA) were observed at IW-1; during the November 2023 6- month performance monitoring event, all compounds were non-detect. Similarly, pre-treatment concentrations of TCE and related compounds in MW-16 have decreased, most notably TCE, concentrations of which have decreased from 840 ug/l to below the laboratory reporting limit of
1.0 μg/l. Concentrations of cis-1,2-DCE increased an order of magnitude over baseline during the 1- and 3-month performance monitoring events, indicating a significant increase in reductive dechlorination by native and introduced bacteria; similar to TCE, the 6-month cis-1,2-DCE concentration was below the laboratory reporting limit. Vinyl chloride was detected at a low concentration (1.3 μg/l) during the November 2023 monitoring event. This is the only compound exceeding the vapor intrusion screening level, and no compounds exceed the aquatic habitat screening level. Because vinyl chloride degrades both aerobically and anaerobically, the vinyl chloride observed in MW-16 is expected to be transient and will further decrease over time, given the elevated residual TOC, strong reducing conditions and relatively aerobic conditions downgradient.
CONCLUSIONS AND RECOMMENDATIONS
Application of EISB at the Site, consisting of injecting carbon substrate and dechlorinating bacteria, has successfully created geochemical conditions amenable to reductive dechlorination. As documented during post-injection performance monitoring, decreased concentrations of TCE and related daughter compounds indicate that the approach is successfully addressing residual TCE impacts in the vicinity of MW-16. The continued success of the program will be evaluated during future groundwater monitoring events. Stantec recommends completing two additional post-injection monitoring of MW-16 and IW-1 at approximate six-month intervals (approximately May and November 2024). The May 2024 event will be expanded to sample all Site groundwater monitoring wells to provide an updated understanding of VOCs in groundwater across the Site.
January 25, 2024
Katherine Ward
Reference: Enhanced In Situ Biorem ediation (EISB) Implementation Report – 960 Industrial Road, San Carlos, CA
CLOSING
Should you have any questions regarding this proposed scope of work, please contact John Kehs (Northrop Grumman project manager) at 410-765-9143, or the undersigned.
Regards,
Stantec Consulting Services Inc.
Neil Doran, PG
Principal Geologist
Phone: 510-919-0059
[email protected]
Angus McGrath, PhD
Senior Principal
Phone: 510-385-4497
[email protected]
Attachments: Table 1 – EISB Performanc e Monitoring – VOCs in Groundwater Table 2 - EISB Performance Monitoring – Dissolved Gases / TOC / Field Parameters / Dhc Figure 1 – Site Location Map
Figure 2 – Site Plan and EISB Treatment Area
Figure 3 – EISB Treatment Area
Figure 4 – Pre- and Post-EISB Groundwater Chemical Data Figure 5 – Time-Concentration Plots – Well IW-1
Figure 6 – Time-Concentration Plots – Well MW-16
Attachment 1 – Laboratory Analytical Reports
c. John Kehs, Northrop Grumman
1 TABLES
TCE cis - 1,2-DCE trans -1,2-DCE 1,1-DCE 1,1-DCA VC CTC CHFM Other Detected Compounds IW-3 Baseline - 05/05/23 <1.0 <1.0 <1.0 <1.0 <1.0 <0.50 <0.50 <1.0 IW-4 Baseline - 05/05/23 <1.0 2.9 1.8 <1.0 1.2 7.0 <0.50 <1.0 Baseline - 05/05/23 <1.0 2.9 <1.0 <1.0 1.5 6.0 <0.50 <1.0 1 Month - 06/20/23 <1.0 3.1 <1.0 <1.0 <1.0 6.0 <0.50 <1.0 Acetone - 5.0 3 Months - 08/23/23 <1.0 3.9 1.4 <1.0 <1.0 21 <0.50 <1.0 6 Months - 11/20/23 <1.0 <1.0 <1.0 <1.0 <1.0 <0.50 <0.50 <1.0 Baseline - 05/05/23 840 65 <10 27 <10 <5.0 5.3 <10
1 Month - 06/20/23 500 360 5.5 22 <2.0 <1.0 2.5 5.1
3 Months - 08/23/23 13 620 6.5 19 <2.0 <1.0 <1.0 <2.0
6 Months - 11/20/23 <1.0 <1.0 6.1 <1.0 1.0 1.3 <0.50 <1.0 Chloroethane - 1.2; benzene - 2.1; acetone - 17; MEK - 200
200 590 590 25 47 780 240 620
7.5 210 920 280 33 0.14 1.9 3.6
Notes and Abbreviations:
Bold text indicates detections above laboratory reporting limits. 1 - Groundwater Environmental Screening Levels (ESLs), San Francisco Bay Regional Water Quality Control Board (2019). < Constituent not detected at or above specified reporting limit. μg/L = micrograms per liter 1,1-DCE = 1,1-Dichloroethene TCE = Trichloroethene VC = vinyl chloride
cis -1,2-DCE = cis -1,2-Dichloroethene VC = Vinyl chloride trans -1,2-DCE = trans -1,2-Dichloroethene CTC = Carbon tetrachloride 1,1-DCA = 1,1-Dichloroethane CHFM = Chloroform
Groundwater ESLs - Vapor Intrusion 1
IW-1
MW-16
Groundwater ESLs - Aquatic Habitat 1
Table 1
EISB Performance Monitoring - VOCs in Groundwater
Former Litton Electron Devices Facility
960 Industrial Road
San Carlos, California
EISB Performance
Monitoring Well ID Sampling Event
Volatile Organic Compounds (USEPA Method 8260B) - Results in μg/L Stantec Page 1 of 1 1/24/2024
Wet Chem Method Dehalococcoides (Dhc)
Methane Ethene Ethane Total Organic Carbon
(mg/L) ORP (mV) Fe2+ (mg/l) (cells/liter)
IW-3 Baseline - 05/05/23 71.9 <5.74 <6.15 13 122.1 0 -- IW-4 Baseline - 05/05/23 2,540 <5.74 <6.15 14 175.1 1.5 -- Baseline - 05/05/23 395 <5.74 <6.15 10 176.7 2.0 --
1 Month - 06/20/23 238 <5.74 <6.15 19.3 20.4 0.5 --
3 Months - 08/23/23 232 <5.74 <6.15 12.0 -23.0 1.0 --
6 Months - 11/20/23 3.70 <5.74 <6.15 11.5 1.9 1.9 --
Baseline - 05/05/23 <3.28 <5.74 <6.15 1.8 169.7 0 3 x 103 1 Month - 06/20/23 14.4 <5.74 <6.15 89.2 50.3 0 --
3 Months - 08/23/23 35.8 <5.74 <6.15 9.00 -318.2 1.0 -- 6 Months - 11/20/23 10,400 <5.74 <6.15 230 -176.2 0 2 x 107 Notes and Abbreviations:
Bold text indicates detections above laboratory reporting limits. < Constituent not detected at or above specified reporting limit. μg/L = micrograms per liter
mg/l = milligrams per liter
mV = millivolts
-- = not analyzed
Fe2+ = ferrous iron
IW-1
MW-16
Dissolved Gases - RSK 175 - μg/L
EISB Performance
Monitoring Well ID Sampling Event
Field Parameters
Table 2
EISB Performance Monitoring - Dissolved Gases / TOC / Field Parameters / Dhc Former Litton Electron Devices Facility
960 Industrial Road
San Carlos, California
Stantec Page 1 of 1 1/24/2024
FIGURES
960 Industrial Road
(Project Site)
1 Northrop Grumman
Former Litton Electron Devices Facility
EISB Implementation Report
Approximate Site Boundary
185706400
960 Industrial Road
San Carlos, California
Site Location Map
V:\1857\Active\185704828_SanCarlos\gis\mxds\960_industrial_rd\eisb_treatment\fig_01_960_industrial_rd_eisb_proploc_20240119.mxd Revised: 2024-01-19 By: awisher Disclaimer: This document has been prepared based on information provided by others as cited in the Notes section. Stantec has not verified the accuracy and/or completeness of this information and shall not be responsible for any errors or omissions whic h may be incorporated herein as a result. Stantec assumes no responsibility for data supplied in electronic format, and the recipient accepts full responsibility for verifying the accuracy and completeness of the data.
Project Location
Client/Project
Figure No.Title
Notes
1. Coordinate System: NAD 1983 StatePlane California V FIPS 0405 Feet
2. Background: Sources: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), (c) OpenStreetMap contributors, and the GIS User Community
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EISB Implementation Report
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EISB Treatment Area
Approximate Property Boundary
185706400
960 Industrial Road
San Carlos, California
Site Plan and EISB Treatment
Area
V:\1857\Active\185704828_SanCarlos\gis\mxds\960_industrial_rd\eisb_treatment\fig_02_960_industrial_rd_eisb_siteplan_20240119.mxd Revised: 2024-01-19 By: awisher Disclaimer: This document has been prepared based on information provided by others as cited in the Notes section. Stantec has not verified the accuracy and/or completeness of this information and shall not be responsible for any errors or omissions whic h may be incorporated herein as a result. Stantec assumes no responsibility for data supplied in electronic format, and the rec ipient accepts full responsibility for verifying the accuracy and completeness of the data.
Project Location
Client/Project
Figure No.Title
Notes
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EISB Implementation Report
E"J EISB Injection Well
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Approximate Property Boundary
185706164
960 Industrial Road
San Carlos, California
EISB Treatment Area
V:\1857\Active\185704828_SanCarlos\gis\mxds\960_industrial_rd\eisb_treatment\fig_03_960_industrial_rd_eisb_treatarea_20240119.mxd Revised: 2024-01-19 By: awisher Disclaimer: This document has been prepared based on information provided by others as cited in the Notes section. Stantec has not verified the accuracy and/or completeness of this information and shall not be responsible for any errors or omissions whic h may be incorporated herein as a result. Stantec assumes no responsibility for data supplied in electronic format, and the rec ipient accepts full responsibility for verifying the accuracy and completeness of the data.
Project Location
Client/Project
Figure No.Title
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&( Direct Push EISB Injection Points
@A Groundwater Monitoring Well
EISB Treatment Area
Approximate Property Boundary
185706164
960 Industrial Road
San Carlos, California
Pre- and Post-EISB
Groundwater Chemical Data
V:\1857\Active\185704828_SanCarlos\gis\mxds\960_industrial_rd\eisb_treatment\fig_04_960_industrial_rd_eisb_results_20240119.mxd Revised: 2024-01-19 By: awisher Disclaimer: This document has been prepared based on information provided by others as cited in the Notes section. Stantec has not verified the accuracy and/or completeness of this information and shall not be responsible for any errors or omissions whic h may be incorporated herein as a result. Stantec assumes no responsibility for data supplied in electronic format, and the rec ipient accepts full responsibility for verifying the accuracy and completeness of the data.
Project Location
Client/Project
Figure No.Title
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0.0 5.0
10.0 15.0
20.0 25.0
0.0 0.5
1.0 1.5
2.0 2.5
3.0 3.5
4.0 4.5
VC Concentration (ug/L)
VOC Concentrations (ug/L)
Date
Figure 5 - Time-Concentration Plots - Well IW-1
TCE
cis -1,2-DCE
trans-1,2-DCE
1,1-DCE
1,1-DCA
CTC
CHFM
VC
Non-detect values are shown as present at 1/2 laboratory reporting limit.
0 100
200
300
400
500
600
700
800
900
0.0 5.0
10.0 15.0
20.0 25.0
30.0 TCE & cis-1,2-DCE Concentrations (ug/L)
VOC Concentrations (ug/L)
Date
Figure 6 - Time-Concentration Plots - Well MW-16
trans-1,2-DCE
1,1-DCE
1,1-DCA
VC
CTC
CHFM
TCE
cis -1,2-DCE
Non-detect values are shown as present at 1/2 laboratory reporting limit.
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