Site Management Plan — Sunnyvale City Council, March 24, 2026

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Site Management Plan
REPORT DATE: December 23, 2025

SITE INFORMATION
Sunnyvale Park Place
510 De Guigne Drive
Sunnyvale, California 94085

PROJECT INFORMATION
AEI Project No. 500004

PREPARED FOR
TC III SPP North, LLC
351 California Street, Suite 1100
San Francisco, California 94104

PREPARED BY
AEI Consultants
3880 South Bascom Avenue, Suite 104
San Jose, California 95124
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AEI Consultants
3880 South Bascom Avenue, Suite 104
San Jose, California 95124

www.aeiconsultants.com

December 23, 2025

Emma Hoffman-Davies
San Francisco Bay Regional Water Quality Control Board
1515 Clay Street, Suite 1400
Oakland, California

Subject: Site Management Plan
Sunnyvale Park Place
510 De Guigne Drive, Sunnyvale, California
AEI Project No. 500004

Dear Emma Hoffman-Davies,

On behalf of TC III SPP North, LLC, AEI Consultants has prepared this Site Management Plan (SMP) for the proposed Site redevelopment taking place at Sunnyvale Park Place to be located at 510, 920, 930, 950 De Guigne Dr. & 935, 945 Stewart Drive in Sunnyvale, California (the Site). The SMP includes a summary of planned development and earthwork, summary of known and potential environmental conditions, and measures to address environmental impacts that may be encountered. The SMP also includes provisions for health and safety, proper handling of soil, contingency measures, and construction best practices as they relate to potentially impacted soil. Although groundwater is not expected to be encountered as part of the construction activities, groundwater management measures, should groundwater be encountered, are included in the SMP.

AEI appreciates the opportunity to work with the San Francisco Bay Regional Water Board and trust that this report meets with your approval. If you have any questions, please do not hesitate to contact me at (408) 656-1738 or [email protected].

Sincerely,

Trent A. Weise
Senior Vice President

Copies:

TC III SPP North, LLC

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Site Management Plan
Sunnyvale Park Place, Sunnyvale, California 95482

Project No. 500004
December 23, 2025

TABLE OF CONTENTS

1.0 INTRODUCTION ................................ ................................ ................................ .. 1

2.0 BACKGROUND ................................ ................................ ................................ ..... 1

2.1 Current Site Description ................................ ................................ ......................... 1

2.2 Geology and Hydrogeology ................................ ................................ ...................... 2

2.3 Brief Site and Vicinity History ................................ ................................ ................... 2

2.4 Previous Site Investigation Activities ................................ ................................ .......... 3

2.4.1 Soil Sample Results ................................ ................................ ................... 3

2.4.2 Soil Vapor ................................ ................................ ............................... 4

2.4.3 Groundwater ................................ ................................ ........................... 7

3.0 PROPOSED REDEVELOPMENT ................................ ................................ .................. 8

4.0 CONTAMINANTS AND AREAS OF POTENTIAL CONCERN ................................ .................... 8

4.1 Contaminants of Potential Concern ................................ ................................ ............ 8

4.2 Areas of Potential Concern ................................ ................................ ...................... 9

4.3 Planned Management and Mitigation Actions and Goals ................................ .................... 9

5.0 RISK MANAGEMENT MEASURES ................................ ................................ ................. 9

5.1 SMP Applicability................................ ................................ ................................ .. 9

5.2 Pre-Construction Planning and Notification ................................ ................................ .. 10

5.3 Health and Safety ................................ ................................ ................................ 10

5.4 Soil Management ................................ ................................ ................................ . 11

5.4.1 Soil Handling Procedures ................................ ................................ ............ 11

5.4.2 Field Screening ................................ ................................ ........................ 11

5.4.3 Soil Segregation and Stockpile Management ................................ ...................... 12

5.4.4 Off-site Soil Disposal ................................ ................................ ................. 12

5.4.5 Import Criteria ................................ ................................ ........................ 12

5.5 Soil Sampling ................................ ................................ ................................ ..... 13

5.5.1 General Methodology ................................ ................................ ................. 13

5.5.2 Soil Profiling for Off-haul ................................ ................................ ............ 13

5.5.3 Confirmation Sampling ................................ ................................ ............... 13

5.6 Groundwater Management ................................ ................................ ..................... 14

5.7 Removal/Relocation of Existing Monitoring Wells ................................ ........................... 14

5.8 Unknown Conditions ................................ ................................ ............................. 14

5.9 Construction Impact Mitigation Measures ................................ ................................ .... 15

5.9.1 Site Control ................................ ................................ ............................ 15

5.9.2 Equipment Decontamination ................................ ................................ ........ 15

5.9.3 Personal Protective Equipment ................................ ................................ ..... 15

5.9.4 Storm Water Pollution Prevention ................................ ................................ . 15

5.9.5 Dust Control ................................ ................................ ........................... 16

6.0 NEW STRUCTURE VAPOR INTRUSION MITIGATION ................................ ........................ 16

6.1 Additional Characterization ................................ ................................ .................... 17

6.1.1 Sub-Slab Soil Vapor Sampling ................................ ................................ ....... 17

6.1.2 Soil Vapor Sampling ................................ ................................ .................. 17

6.1.3 Data Evaluation ................................ ................................ ....................... 18

6.1.4 Reporting ................................ ................................ .............................. 18

6.2 Vapor Mitigation at Select Structures ................................ ................................ ......... 18

7.0 NOTIFICATIONS ................................ ................................ ................................ ..20 Attachment 15

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Site Management Plan
Sunnyvale Park Place, Sunnyvale, California 95482

Project No. 500004
December 23, 2025

7.1 Notifications ................................ ................................ ................................ ...... 20

7.2 Project Contacts ................................ ................................ ................................ . 20

8.0 COMPLETION REPORTING ................................ ................................ ......................20

9.0 REFERENCES ................................ ................................ ................................ .....21

10.0 REPORT LIMITATIONS AND RELIANCE ................................ ................................ ......22

11.0 SIGNATURES ................................ ................................ ................................ ....23

FIGURES
Figure 1 Site Location Map
Figure 2 Site Plan
Figure 3A VOCs in Soil Vapor and Groundwater (Current Site Configuration) Figure 3B VOCs in Soil Vapor and Groundwater (Proposed New Development Layout) Figure 4A Lead Concentrations in Soil (Current Site Configuration) Figure 4B Lead Concentrations in Soil (Proposed New Development Layout) Figure 5A Soil Sample Data (Current Site Configuration) Figure 5B Soil Sample Data (Proposed New Development Layout)

TABLES
Table 1 Summary of Soil Sample Results - Lead
Table 2 Summary of Soil Sample Results - Pesticides
Table 3 Summary of Soil Vapor Sample Results

APPENDICES
Appendix A Historical Data
Appendix B Conceptual Development Plan
Appendix C Import Criteria
Appendix D Standard Operating Procedures

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Site Management Plan
Sunnyvale Park Place, Sunnyvale, California 95482

Project No. 500004
December 23, 2025

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1.0 INTRODUCTION

On behalf of TC III SPP North, LLC (“the Developer”), AEI Consultants (AEI) has prepared this Site Management Plan (SMP) for the proposed residential development known as Sunnyvale Park Place at 510 DeGuigne Drive in Sunnyvale, California (“the Site”). This SMP applies to subsurface disturbances at the Site during the planned grading and construction activities. The purpose of this SMP is to:
• Assess and communicate the presence of contaminants of potential concern (COPCs) that are known or may potentially exist at the Site.
• Provide protocols for appropriate soil management procedures, as they relate to the COPCs in soil.
• Provide measures to mitigate potential exposure risks to on-site workers, nearby residents, and pedestrians from potential exposure to hazardous substances that may be encountered during on-Site soil intrusive activities such as excavation and grading. • Propose appropriate mitigation measures to address residual volatile organic compounds (VOCs) in groundwater that are affecting soil vapor and pose a potential vapor intrusion risk to new residential buildings proposed for portions of the Site. • Provide for the proper management of previously unknown environmental conditions if identified during redevelopment activities at the Site.

This SMP is not intended to replace federal, state, or local regulations dictating the handling of contaminated media or regulations addressing worker exposure including Federal and California Occupational Safety and Health Administration (OSHA) training and worker protection rules and regulations, Code of Federal Regulations (CFR) Title 29, Part 1910.120 and California Code of Regulations (CCR) Title 8, § 5192.

2.0 BACKGROUND

This section presents the current Site description, historical uses, and a summary of the investigations performed at the Site.

2.1 Current Site Description
The approximately 20.55-acre site is located northeast of the intersection of DeGuigne Drive and Stewart Drive within a mixed commercial and residential area of the City of Sunnyvale. A Site Location Map is provided as Figure 1.

The Site comprises two commercial properties and is currently developed with five commercial office buildings with street addresses 510, 920, 930, 950 DeGuigne Dr ive & 935, 945 Stewart Drive. The remainder of the Site is further improved with asphalt -paved parking areas, dumpster and storage enclosures, and associated landscaping. The current Site configuration is depicted on Figure 2.

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Site Management Plan
Sunnyvale Park Place, Sunnyvale, California 95482

Project No. 500004
December 23, 2025

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2.2 Geology and Hydrogeology
Subsurface conditions observed during prior environmental investigations at the Site (see Section 2.4) indicated that soils underlaying the Site consisted primarily of clay, silty clay, and sand to the maximum depth explored of 10.5 feet bgs.

The Site is graded to relatively level and is situated at an elevation approximately 41 feet above mean sea level with a topographical gradient towards the northeast . The groundwater flow direction beneath the Site is to the northeast as presented in regional plume monitoring reports (see Section 2.3). Groundwater is first encountered between 7 and 8 feet bgs (AEI 2025).

2.3 Brief Site and Vicinity History
Based on information reviewed as part of Phase I Environmental Site Assessments (ESAs) conducted for the Site (AEI, 2024a and 2024b), the Site was agricultural land from at least 1939 to 1956. By the late 1960s, the Site had been developed with several co mmercial structures.

The Site generally appeared to have been developed with its current configuration of buildings by the late 1990s. The Site has historically been used for office, research, and development spaces for various technological companies suc h as Proxim, Vitalone, Trimble, Analog Bits, Advanced Micro Systems, Illumio, etc. Research conducted as part of the Phase I ESAs did not identify use and/or storage of large quantities of halogenated volatile organic compounds (VOCs), such as tetrachloroethene (PCE), trichloroethene (TCE), or cis-1,2-dichloroethene (cis- 1,2-DCE) as part of historic or current land use. Reported use and/or storage of these compounds at the Site appeared consistent with semiconductor laboratory activities and not indicative of mass production of computer equipment which utilizes large quantities of VOCs as part of the fabrication process.

The Site is located within an area of Sunnyvale historically occupied by numerous technology companies. Several contaminated groundwater plumes have been identified in the vicinity of the Site and are attributed to past industrial activities in this region. According to a review of agency records and prior reports (AEI, 2024a and 2024b), the Site is located within Commercial Street Operable Unit (CSOU) Subunit 1 which is a designated VOC groundwater plume associated with a release at the former Mohawk Lab oratories at 932 Kifer Road. The Site is also located immediately west of Stewart Drive Operable Subunit 5 which is a designated VOC groundwater plume associated with a release at 999 East Arques Avenue. These plumes are currently undergoing remedial activities and groundwater monitoring with assigned Responsible Parties.

The predominant contaminants of interest associated with these groundwater plumes include PCE, TCE, cis-1,2-DCE, and total petroleum hydrocarbons (TPH). There are currently multiple groundwater monitoring wells at the Site associated with the Mohawk Laboratories and 999 East Arques Avenue regional plumes, including:
• Mohawk Laboratories: MW-09 (DEGUINE), NMW-12B, 46-S, and 46-D (see Figure 2). • 999 Arques Corporation Wells: MW-2, MW-5, MW-6, MW-7, MW-8, MW-9, 13-S, 13-D S-39A, S-39B, S-38A, and S-38B (see Figure 2).

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Site Management Plan
Sunnyvale Park Place, Sunnyvale, California 95482

Project No. 500004
December 23, 2025

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The Site is located within the Commercial Street Operable Unit (CSOU) of the Mohawk Laboratories Cleanup Site.

2.4 Previous Site Investigation Activities
Between 2010 and 2025, several environmental investigations were conducted at the Site by Cornerstone and AEI (Cornerstone, 2010 and AEI, 2019, 2024c, and 2025 ). As part of these investigations, soil, soil vapor, and groundwater samples were collected at several on -site borings. AEI additionally conducted an indoor air sampling event within the on -site building addressed as 945 Stewart Drive in 2018 (AEI, 2019); notably PCE and related halogenated VOCs were either not detected above laboratory limits or w ere detected at concentrations below applicable ESLs. The previous soil, soil vapor, and groundwater investigation data are included herein as Appendix A, and a summary of the findings are presented below:

2.4.1 Soil Sample Results
Soil samples were collected from 63 boring locations, including 21 previously advanced by Cornerstone in 2010 (EB -1 through EB -10 and SB-1 through SB -11) and 42 by AEI in 2024 and 2025 (SB-1 through SB-19, SB-21 through SB-33, and SB-36 through SB-45), at the approximate locations as depicted on Figure 2. Soil samples collected were analyzed for mercury, arsenic, lead, and organochlorine pesticides (OCPs). The results can be summarized as follows:
• Mercury was not detected above laboratory reporting limits. • Though arsenic was detected above the San Francisco Bay Regional Water Quality Control Board (Regional Water Board) residential Environmental Screening Levels (ESLs) of 0.067 milligrams per kilogram (mg/kg) and/or the construction worker ESL of 2.00 mg/kg , the concentrations detected were consistent with typical background concentrations of up to 11 mg/kg for the Bay Area (Duvergé, 2011). The concentrations of arsenic detected ranged from 2.3 mg/kg to 10.2 mg/kg.
• Elevated concentrations of lead were detected above its residential ESL of 80 mg/lg and construction worker ESL of 160 mg/kg in select soil samples collected during the 2010 investigation event. Elevated concentrations between 110 and 1,900 mg/kg were detected in shallow soils up to 1.5 feet bgs. Subsequent soil samples collected and analyzed during the 2024 and 2025 investigations, including soil samples collected from the previous 2010 sampling locations and composited prior to analysis, did not detect lead above applicable screening levels. Table 1 presents a summary of the soil sample analytical results for lead. • With the exception of elevated concentrations of dieldrin, OCPs were either not detected above laboratory reporting limits or were detected at concentrations below applicable ESLs.

The residential ESL for dieldrin is 0.037 mg/kg, and the ESL for construction worker exposure is 1.1 mg/kg. Elevated concentrations of dieldrin, ranging from 0.0388 mg/kg to

0.0826 mg/kg, were detected in shallow soils at depths of up to 4.5 feet bgs. Table 2 presents a summary of the soil sample analytical results for pesticides.

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Site Management Plan
Sunnyvale Park Place, Sunnyvale, California 95482

Project No. 500004
December 23, 2025

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2.4.2 Soil Vapor
Soil vapor samples were collected from 34 temporary and semi -permanent soil gas probe locations, including 4 previously installed by Cornerstone in 2010 ( temporary probes SV-1 through SV-4) and 30 installed by AEI in 2018, 2024, and 2025 (temporary probes SG-5 through SG-27 and 14 semi-permanent probes SV-1 through SV-10, SV-13, SV-14, SV-19, and SV-22), at the approximate locations as depicted on Figure 2. Soil vapor samples were collected at depths ranging between 4.5 and 9.5 feet bgs and were analyzed for VOCs. Table 3 presents a summary of the soil vapor sample analytical results for select VOCs. The soil vapor sample results can be summarized as follows:
• With the exception of benzene, ethylbenzene, PCE, TCE, cis -1,2-DCE, and chloroform, remaining VOCs analyzed were either not detected above laboratory reporting limits or were detected at concentrations below applicable ESLs.
• Benzene was detected in soil vapor samples analyzed in 25 of the 47 soil gas samples, and detected at elevated concentrations above the residential ESL of 3.2 µg/m3 in 21 of those locations. Elevated concentrations of benzene detected were between 4.2 and 210 µg/m3.

However, the ESLs are based on a conservative attenuation factor of 0.03 to be generically applied to existing building slabs and does not assume bioattenuation. The Supplemental Guidance: Screening and Evaluating Vapor Intrusion, Final Draft (Department of Toxic Substances Control [DTSC] and California State Wat er Resources Board, 2023) presents alternative attenuation factors for petroleum vapor intrusion (PVI) accounting for bioattenuation factors (BAF). The Supplemental Guidance outlines appropriate BAF for oxygen concentrations in the subsurface . Oxygen was detected in soil vapor samples at concentrations between 2.9% and 20%, with most of the concentrations above 4% suggesting a strong bioattenuation zone. Assuming a strong bioattenuation zone, the Supplemental Guidance provides for a BAF of 0.01, which tran slates to a residential screening level of 320 µg/m3. Therefore, the benzene concentrations observed in the samples collected at the Site do not pose an unacceptable risk to future residential users of the Site. • Ethylbenzene was detected in soil vapor samples analyzed from 19 of the 47 soil gas probe locations and detected at elevated concentrations above the residential ESL of 37 µg/m3 in 5 of those locations. Elevated concentrations of ethylbenzene detected were between 61 and 1,700 µg/m3. However, similar to benzene, assuming a strong bioattenuation zone and corresponding BAF of 0.01 calculates a residential screening level of 3,700 µg/m 3.

Therefore, the ethylbenzene concentrations observed in the samples collected at the Site do not pose an unacceptable risk to future residential users of the Site. • PCE was detected in soil vapor samples analyzed from 28 of the 37 soil gas probe locations and detected at slightly elevated concentrations above the residential ESL of 15 µg/m3 in 7 of those locations. Elevated concentrations of PCE detected were between 17 and 66 µg/m3.
• TCE was detected in soil vapor samples analyzed from 13 of the 30 soil gas probe locations, and detected at slightly elevated concentrations above the residential ESL of 16 µg/m3 in seven of those locations. Elevated concentrations of TCE detected were between 18 and 340 µg/m3.

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Sunnyvale Park Place, Sunnyvale, California 95482

Project No. 500004
December 23, 2025

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• Chloroform was detected in soil vapor samples analyzed from 2 of the 27 soil gas probe locations and detected at slightly elevated concentrations above the residential ESL of

4.1 µg/m3 in each of those locations. Elevated concentrations of chloroform detected were

5.9 µg/m3 and 33 µg/m3. Chloroform is commonly found in chlorinated municipal water supplies, and chloroform detected in soil vapor is likely from chlorinated municipal water supply leaks at the Site. It is often detected in groundwater and shallow soil vapor at properties where irrigation provides a pathway for chloroform to enter the subsurface. In general, chloroform should not be considered a risk driver for the vapor intrusion pathway (Eklund, 2024). As such, chloroform is not considered to present an unacceptable risk to future users of the Site through the vapor intrusion pathway and is not considered a COC.

A range of concentrations of PCE and TCE were observed in soil vapor samples collected and analyzed, likely from the presence of these compounds in groundwater beneath the Site from the regional groundwater plume(s). The most elevated concentrations of TCE were observed in soil vapor samples collected from locations SV -4, SV -5, and SV -9. In these areas, a vapor intrusion mitigation system (VIMS) is proposed to control the potential for vapor intrusion as presented in Section 6. Beyond this area, PCE and TCE concentrations are generally low and only slightly exceed the residential ESL.

Evaluation of Soil Vapor Attenuation
The soil vapor ESLs established by the Water Board (January 2019) were developed to be conservative screening levels for use in initially screening sites for potential vapor intrusion concerns. The soil vapor ESLs were developed to be protective of an overlying structure’s indoor air using a default attenuation factor (AF) of 0.03 derived from a nationwide study performed by the United States Environmental Protection Agency (US EPA) . The soil vapor ESLs were calculated by applying the AF of 0.03 to the indoor air direct exposure ESL (ESLIA) as follows:

𝐸𝑆𝐿𝑆𝑉 = 𝐸𝑆𝐿𝐼𝐴
𝐴𝐹
The default AF (0.03) used in developing the 2025 ESLs is based on the US EPA empirical vapor intrusion (VI) database and are 95 th percentile values deemed appropriate for screening evaluations as they provide a high degree of protectiveness (USEPA, 2012) , appropriate for initial screening purposes . The US EPA database include d indoor air data paired with groundwater, exterior soil vapor, sub -slab vapor, or crawlspace measurements from 913 buildings at 74 sites in 15 states. The building types in the database included 85% residential, 10% commercial, and 5% mixed use (residential and non -residential). The buildings were constructed prior to 2006 (latest data collection date) and did not include structures with engineered vapor control measures.

DTSC (2023) and Water Board (2019 and 2022) indicate that the default AF is protective of most building occupancy scenarios and is appropriate for the initial screening of sites in California.

However, as noted in the US EPA database, building construction plays an important role in determining the actual or building-specific attenuation factor. The AFs calculated from the US EPA database ranged across several orders of magnitude from 0.03 (95th percentile or the default AF) to 0.0003 (5th percentile) and are likely due to the differing building construction Attachment 15

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Site Management Plan
Sunnyvale Park Place, Sunnyvale, California 95482

Project No. 500004
December 23, 2025

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types and associated vapor intrusion characteristics . The median (50th percentile) AF was calculated to be 0.003.

Abbasi et al. (2023) and Lahvis and Ettinger (2021) identified challenges with applying the default AFs to sites in California; those included (1) the US EPA database contains few sites in California; (2) most soil vapor data were collected from sites in colder climates (New York, Colorado, Connecticut, and Montana) where building performance is inherently different; and (3) more than 75% of the indoor air samples were collected in residential homes with basements whereas fewer than 5% of homes in Californi a have basements (National Association of Home Builders, 2014) , which also changes vapor intrusion performance . For residential sites in California with no vapor intrusion mitigation (VIM) controls installed, Abbasi et al. (2023) calculated attenuation factors ranging from 0.0025 (50th percentile) to 0.018 (95th percentile) and Lahvis and Ettinger (2021) calculated AFs ranging from 0.00012 (50th percentile) to 0.00081 (95th percentile). The AFs calculated by Abbasi et al. (2022) and Lahvis and Ettinger (2021) are consistent with the average AF of 0.001 for future residential buildings published in the Guidance for the Evaluation and Mitigation of Subsurface Vapor Intrusion to Indoor Air (Vapor Intrusion Guidance) (DTSC, 2011). Abbasi et al. (2022) concluded that the AFs calculated in their study may not be consistent with those in the US EPA’s nation -wide study but are consistent with the Lahvis and Ettinger (2021) California-specific study and that the differences may be due to climatic differences and foundation types specific to California. The range in AFs are attributed to foundation type, sample type (soil vapor vs. sub -slab vapor), soil vapor sample depth, surface cover adjacent to the structure, heating, ventilation, and air conditioning (HVAC) operation during indoor air sample collection, and source concentration.

The 95th percentile represents the upper concentration at which 95% of measurements are expected to be at or below, a nd the 50th percentile represents the median measurement.

Although the use of the 95th percentile AF is appropriate for screening evaluations where limited site -specific data are present and/or where the future land use or building construction/type are un known, its application is overly conservative for well characterized sites and new buildings constructed with modern foundations, building envelopes, and HVAC systems.

The planned development will be new single and multi-family residential buildings with modern foundations, building envelopes, and HVAC systems installed. Based on the Abbasi et al. (2022), Lahvis and Ettinger (2021), and the previous 2011 DTSC guidance, an AF of 0.001 for new residential building construction in California appears to be more appropriate than the overly conservative 0.03 default AF. The reported PCE concentrations are below the residential ESLs when applying the California -specific AFs and the vapor intrusion risk to future occupants appears to be low. Using an AF of 0.001, site -specific PCE and TCE screening levels are calculated as follows:

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Site Management Plan
Sunnyvale Park Place, Sunnyvale, California 95482

Project No. 500004
December 23, 2025

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Table A – Site Specific Screening Levels
Chemical Residential
Indoor Air ESL
(µg/m3)
Residential Soil
Vapor ESL
(µg/m3)
Calculated Site-
Specific Soil
Vapor Screening
Level
(µg/m3)
PCE 0.46 15 460
TCE 0.48 16 480

The following hypothetical excess cancer risk evaluation is presented below:
• Using the maximum PCE concentration detected in soil vapor samples of 66 µg/m3, the estimated risk to a future hypothetical residential user is 4.4 x-10-6, with an AF of 0.03 and

1.4 x 10-7 with an AF of 0.001.
• Using the maximum TCE concentration detected in soil vapor samples (outside of the area of soil vapor probes SV -4, SV -5, and SV -9) of 50 µg/m3, the estimated risk to a future hypothetical residential user using the maximum concentration observed is 3.1 x 10-6 with an attenuation factor of 0.03, and 1.0 x 10-7 with an AF of 0.001.

The United States Environmental Protection Agency (US EPA) recognizes the range of 1x10-4 to 1x10-6 as an acceptable risk management range for carcinogenic risk (US EPA, 2024). With an attenuation factor of 0.001, the calculated excess cancer risk to a future hypothetical residential user of the Site is estimated at 1.0 x10 -7, which is a full order of magnitude below the target excess cancer risk of 1 x 10-6. Therefore, residual PCE and TCE in soil vapor from the regional groundwater plume(s) outside the area of SV-4, SV-5, and SV-6 does not represent an unacceptable risk to the further residential users of the Site and installation of a VIMS or indoor air testing within the future buildings beyond soil vapor probes SV -4, SV-5, and SV -9 is not warranted. Protection for new buildings in the vicinity of probes SV -4, SV -5, and SV -9 is proposed in Section 6.

2.4.3 Groundwater
Four grab groundwater samples (GW -1 through GW -4) were collected during the 2010 investigation. Sample locations are depicted on Figure 2. G rab groundwater data revealed elevated concentrations of cis-1,2-dichloroethene in three of the four groundwater samples at concentrations ranging from 13 micrograms per liter (µg/L) to 390 µg/L, and TCE in one groundwater sample at a concentration of 8.4 µg/L. However, no significant TCE or 1,2 -DCE concentrations were observed in nearby soil vapor samples.

In addition, the most recent four years of groundwater sample results are provided for the Mohawk Laboratories Site wells, including MW-09 (DeGuigne), NMW-09, NMW-12B, and 46-S as shown on Figures 3A and 3B. The most recent sampling event was performed in Attachment 15

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Project No. 500004
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October 24, 2024, and PCE was detected in one of the wells, observed at a concentration of

1.1 µg/L in monitoring well 46-S, TCE was detected in each of the monitoring wells, observed at a maximum concentration of 38 µg/L in monitoring well NMW -09. As presented in the April 9, 2025, Semi-Annual Self -Monitoring Report, Quarter 3 and Quarter 4, 2024 for the Mohawk Laboratories Site, “North of the Central Expressway, the generally stable and declining PCE and TCE concentration trends observed are consistent with ongoing natural attenuation.” On-site groundwater concentrations are anticipated to continue to decline, which will also act as a reduced source to soil vapor. Based on this evidence, PCE and TCE concentrations in soil vapor are anticipated to further decline.

3.0 PROPOSED REDEVELOPMENT

The Site is slated for redevelopment as “Sunnyvale Park Place” a new residential development to include mixed multi- and single-family residential structures. The proposed development will include an estimated 329 units generally comprised of small lot single family homes, attached row homes, attached interlocking townhomes , and 41 attached ADUs . No basements are planned, so planned excavations for the redevelopment are not expected to extend deeper than 5 feet bgs for planned foundational elements, utilities, etc. The estimated depth to groundwater at the Site is 7 to 8 feet bgs (AEI, 2025), therefore groundwater is not expected to be encountered during development activities. The proposed development Site Plan is included in Appendix B.

4.0 CONTAMINANTS AND AREAS OF POTENTIAL CONCERN

This section presents the known contaminants that have been identified at the Site through the investigation activities that may be of potential concern to the new development , including construction worker and/or future residential users of the Site.

4.1 Contaminants of Potential Concern
Based upon historical research and the previous investigation activities performed, the following COPCs have been identified for the Site:
• Elevated lead and dieldrin concentrations in shallow soils, which have been detected above their respective residential ESLs of 80 and 0.037 mg/kg. These contaminants are likely a result of former agricultural activities at the Site.
• Halogenated VOCs, specifically PCE, TCE, and cis-1,2-DCE, are present in groundwater and soil vapor beneath the Site . These compounds are the predominant contaminants of interest associated with the Mohawk Laboratories and 999 East Arques Avenue regional groundwater plumes, and these plumes are understood to be the source of these compounds in on-site groundwater and/or soil vapor. Elevated concentrations of TCE and cis -1,2-DCE have previously been detected in grab-groundwater samples collected on-site and continued to be detected in regional plume monitoring wells.

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Site Management Plan
Sunnyvale Park Place, Sunnyvale, California 95482

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4.2 Areas of Potential Concern
Areas of potential concern can be summarized as follows:
• Figure 3A and Figure 3B present benzene, PCE, and TCE in soil vapor and, where available, groundwater, at the Site. Slightly elevated concentrations of PCE are present in soil gas at central portions of the Site and along the southern portion of the Site. TCE is detected at elevated concentrations in soil gas along the northwestern property boundary and along the southern portion of the Site. PCE, TCE, and cis -1,2-DCE have primarily been detected in groundwater on the southwest portion of the Site; areas of previously detected PCE, TCE, and cis -1,2-DCE detected in groundwater based on grab -groundwater samples collected from the Site and groundwater monitoring of the regional plumes are highlighted in the figures. Figure 3A depicts the Site in its current configuration, and Figure 3B depicts the proposed residential development layout.
• As shown on Figures 4A and 4B, elevated concentrations of lead have been measured in shallow soils to a depth of up to 1.5 feet bgs along the southern property boundary and in the vicinity of SB -11. Additional sampling in that area did not duplicate the elevated concentrations. Figure 4A depicts the Site in its current configuration, and Figure 4B depicts the proposed residential development layout.
• As shown on Figures 5A and 5B, elevated concentrations of dieldrin are present in sporadic shallow soils at depths of up to 3.5 feet bgs. Figure 5A depicts the Site in its current configuration, and Figure 5B depicts the proposed residential development layout.

4.3 Planned Management and Mitigation Actions and Goals Exposure to soil and groundwater during redevelopment activities will be managed under this SMP to mitigate potential health and safety risks associated with the COPCs identified in subsurface media at the Site. Mitigation measures to address potential health and safety risks post-development are outlined in Section 6.0 of this SMP.

Regarding elevated concentrations of lead and dieldrin in shallow soils, it is expected that these soils will be removed or managed during the redevelopment activities (see Section 5.4.1).

Should residual lead and dieldrin remain post -development (see Section 5.4.4), they will be encapsulated on-site under roadways or other hardscape to be determined. The necessity for a Cap Management Plan, based on confirmation sampling results, will be discussed in the SMP Implementation Report (see Section 8.0).

5.0 RISK MANAGEMENT MEASURES
This section presents risk management measures to address the identified COPCs in soil, soil vapor, and groundwater at the Site during redevelopment activities.

5.1 SMP Applicability
This SMP presents protocols for the following construction activities that may encounter COPCs, including the following:

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• Removal of existing foundations, utility lines, and other surfacing; • General earthwork;
• Targeted and mass excavation activities;
• Installation of utility corridors; and
• Rough grading.

Contractors and their subcontractors shall follow the protocols presented in this SMP while performing the above activities at the Site. Contractors and their subcontractors are responsible for the health and safety of their employees.

5.2 Pre-Construction Planning and Notification
Prior to the start of any construction activity that involves below ground work (e.g., foundation removal, subsurface utility removal, or excavating), the Developer shall provide information regarding Site risk management procedures (i.e., a copy of this SMP) to the General Contractor and the General Contractor shall provide this SMP to all relevant subcontractors for their review and acknowledgement, likewise for subsequent tier subcontractors.

5.3 Health and Safety
A written health and safety plan (HSP) may be necessary for Site activities in accordance with California OSHA Construction Safety Orders within Title 8 of the CCR, following a review of this SMP. The General Contractor is to review the information provide d within this SMP and determine whether an HSP is necessary for the proposed construction activities. If deemed necessary, the HSP will be prepared by the General Contractor and/or their subcontractor for their work. At a minimum, the HSP should include:
• A description of proper entry to the Site and all work activities to be conducted at the Site. • A list of project contacts including the Health and Safety Officer. • A list of hazardous materials information.
• Emergency information, including the location of the nearest emergency hospital location. • Identification of on-site health and safety hazards and hazard analysis. • Exposure prevention, safety requirements, hazard exposure guidelines, and safe work practices.
• Safety training procedures and guidelines.
• Levels of personal protective equipment (PPE) needed. • Waste handling procedures.

The purpose of a HSP is to inform all field personnel of proper safety procedures and potential health risks while on-site. All project personnel should familiarize themselves with the HSP and adhere to its established procedures and recommendations. A cop y of the HSP should be kept on-site and made available to all personnel. The HSP should be updated if on -site conditions change. The General Contractor will be responsible for preparing and implementing the safety Attachment 15

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procedures identified in the HSP. Implementing the HSP will minimize potential health risks to on-site construction workers and the general public.

Each contractor shall be responsible for the health and safety of their own workers, as required by CAL-OSHA, including but not limited to preparation of their own HSP and injury and illness prevention plan. The purpose of these documents is to provide general guidance relating to the work hazards that may be encountered during each phase of Site constructi on activities.

Contractors are also required to determine the requirements for worker training, based on the level of expected contact to potentially impacted soil and/or groundwater associated with the contractor’s activities and locations with respect to COPCs described in Section 3.1. The HSP(s) will contain provisions for limiting and monitoring chemical exposure to construction workers, chemical and non-chemical hazards, emergency procedures, and standard safety protocols.

5.4 Soil Management
This section presents the appropriate soil management procedures for soils at the Site during redevelopment activities. Areas of known soil impacts, lead and/or dieldrin, are shown on Figures 4B and 5B. General soil handling procedures are presented below.

5.4.1 Soil Handling Procedures
According to the current plans, the proposed development will encompass the entire Site footprint. The construction activities will involve excavation and mass grading, generating soils that require off -site exportation. Surplus soil excavated from the Sit e, intended for off -site disposal, will be managed as outlined in Section 5.4.4 below.

The previously identified elevated lead and/or dieldrin in shallow soils (i.e., primarily the upper

3.5 feet) will likely be excavated as part of the planned demolition and grading activities needed for the construction. Because elevated lead concentrations could not be confirmed, additional sampling in the elevated lead concentration areas is recommended prior to site grading. Confirmation samples will be collected after the demolition and grading activities to evaluate whether elevated lead and/or dieldr in concentrations remain, post -excavation.

Confirmation sampling would be conducted as described in Section 5.5.3 below. The results of the confirmation samples will be used to evaluate whether additional excavation and or a Cap Management Plan may be required upon completion of the project. If upon completion of the development project soil exceeding the applicable residential ESLs remain on -site, a Cap Management Plan will be prepared and submitted to the Regional Water Board for review. The need for a Cap Management Plan would be discussed in the SMP Implementation Report (see Section 8.0).

5.4.2 Field Screening
Soil may be field screened by the Environmental Consultant in areas of potential environmental impact during demolition and excavation work on an as needed basis to assess whether impacted soil may be present. At this time, field screening is not anticipat ed; however, the Environmental Consultant will be notified if potentially petroleum hydrocarbon impacted soil or other previously unidentified conditions as detailed in Section 5. 8 are identified through visual and olfactory observation. Should any field s creening or inspections performed by the Environmental Consultant identify potentially impacted soil or other previously unidentified conditions, analytical testing will be performed. Significantly impacted soils (i.e., above applicable residential ESLs identified as such by analytical testing performed by the Attachment 15

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Environmental Consultant, shall be handled and managed in conformance with and by OSHA Hazardous Waste Operations and Emergency Response trained personnel.

5.4.3 Soil Segregation and Stockpile Management
Excavated soils from the Site will either be loaded directly into trucks and removed from the Site for off-site disposal based on existing soil analytical data or stockpiled on -site for further testing if required by the appropriately licensed receiving facility . If needed, the Environmental Consultant will perform sampling of stockpiled soil as appropriate for acceptance for off-site disposal.

If stockpiled on -site, all excavated soils will be stockpiled at the Site in a secure location, segregated as appropriate, maintained to prevent excessive dust and to prevent off -site soil migration due to wind and rain erosion, and placed away from storm drains and surface-water drainage courses to prevent potential runoff. Stockpiles will be moistened or covered with 10- mil polyethylene sheeting (e.g., in compliance with Bay Area Air Quality Management District [BAAQMD] Rule 8-40) as needed for purposes of dust mitigation.

Stockpiles of potentially petroleum hydrocarbon impacted soil, or soils with impacts from other previously unidentified conditions as detailed in Section 5.7 identified through visual and olfactory observation, will be segregated from other stockpiled soils and additionally placed on top of as well as covered with 10-mil polyethylene sheeting.

5.4.4 Off-site Soil Disposal
Soil to be disposed off-site will be profiled for waste characterization based on samples already collected and supplemented with additional sampling data as needed by the appropriately licensed receiving facility.

Soil profiled as non-hazardous will be transported and disposed at a licensed Class II/III landfill.

Soil classified as California hazardous waste will be transported either out of state to an appropriate licensed facility or to a Class I facility in Cali fornia. Soil classified as Federal hazardous waste, if any, will be transported to a Class I RCRA facility. Additional segregation of excavated soil may be conducted by the excavation contractor (e.g., “clean” soil), depending upon off -site receiving facil ity acceptance criteria. Soil transporters and specific disposal locations will be identified prior to construction and summarized in the SMP Implementation Report (see Section 7.0).

5.4.5 Import Criteria
If import materials are needed, an evaluation of import materials brought to the Site will be conducted to ensure such fill meets the geotechnical and environmental requirements for the Site. To minimize the potential introduction of impacted fill onto the Site, all selected sources of import fill shall have adequate documentation or certification to verify that the fill source is appropriate for the Site prior to delivery of such soil to the Site. Acceptable documentation would include detailed information on previous land use of the fill source, any Phase I ESAs performed and the findings, and the results of any analytical testing performed. If no documentation is available, the documentation is inadequate, or if no analytical testing has been performed, samples of the potential fill material will be collected and analyzed prior to delivery of such soil to the Site. The analyses will be based on the fill source and knowledge of the previous land use. The sample frequency for potential fill material be condu cted in Attachment 15

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accordance with that outlined in the Information Advisory on Clean Imported Fill Material by the DTSC dated October 2001, included herein as Appendix C. Sampling will be conducted as described in Section 5.5. No fill material will be accepted if contaminant levels exceed applicable residential ESLs, and/or regional background concentrations.

5.5 Soil Sampling

5.5.1 General Methodology
When samples are needed, the Environmental Consultant will collect soil samples utilizing a slide hammer fitted with 2-inch diameter 6-inch stainless steel sleeves to obtain a sample, or alternative industry accepted sampling practices. Soil intervals save d for analysis will be immediately kept in the stainless-steel sampling tubes, with each end covered with polyethylene sheeting and tight-fitting plastic caps, labeled, placed in re-sealable plastic bags.

Samples will be placed in a pre -chilled insulated c ontainer and prepared for transport and analysis using standard chain of custody protocol. Soil samples collected for analysis will be sealed and cooled as soon as feasible to minimize potential volatilization. All samples will be maintained in a locked ve hicle or in direct observation at all times. The Environmental Consultant will generally follow regulatory methods for collecting the soil samples and preparing them for analysis and will submit all soil samples to a California certified laboratory.

5.5.2 Soil Profiling for Off-haul
Soil profiling criteria depends on the proposed receiving facility location. These procedures should be established by the excavation contractor and coordinated with the proposed receiving facility prior to initiating soil excavation. Typical soil profiling requirements are one four-point composite sample per 500 to 750 cubic yards to be disposed.

If needed, the Environmental Consultant will perform sampling of stockpiled soil as appropriate for acceptance at appropriate off-site “fill sites” or for landfill disposal. Soil samples for waste characterization purposes will be collected and analyzed a ccording to the profiling requirements of the fill site or disposal facility. The profiling of the waste and surplus soil is typically required by all facilities considering acceptance of “clean” soil and for impacted soil to determine proper disposal methods, verify that the waste meets all acceptance criteria of the facility, and ensure compliance with all federal, state, and local regulations.

Characterization information will be documented on profile forms provided by the off -site facility. The General Contractor will coordinate with the Environmental Consultant regarding all off-site soil disposal activities.

5.5.3 Confirmation Sampling
Confirmation samples will be collected at the base of the planned excavation at the previous sample locations which detected elevated concentrations of lead or dieldrin. The confirmation samples will be analyzed at a California certified laboratory, as appropriate, for:
• Total Lead using US EPA Test Method 6010B/7471A; or
• Dieldrin using US EPA Test Method 8081A.

The results of the confirmation samples will be used to evaluate if a Cap Management Plan may be required upon completion of the project. If upon completion of the development project, soil exceeding the applicable ESLs remains on -site, a Cap Management Plan will be prepared Attachment 15

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and submitted to the Regional War Board for review. The need for a Cap Management Pla n would be evaluated in the SMP Implementation Report (see Section 8.0).

5.6 Groundwater Management
The planned redevelopment does not include a subterranean component, and therefore no large excavations are proposed. However, grading operations, trenching, and small excavations to depths of up to approximately 5 feet bgs for planned foundational elements such as footings, grade beams, utilities, etc. are expected. The measured depth to groundwater at the Site is first encountered between 7 and 8 feet bgs, and groundwater is not anticipated to be encountered during construction activities. However, if groundwater is encountered in quantities that need to be pumped and removed from excavations, such groundwater would need to be profiled for proper off-site disposal or discharged under permit to the local sanitary sewer system and/or storm sewer in accordance with best practices and applicable regulations.

A settling tank, or other treatment as necessary, may be used to achieve the necessary discharge requirements. All permitting and regulatory requirements shall be followed prior to discharge or off-site disposal.

5.7 Removal/Relocation of Existing Monitoring Wells
There are currently multiple known groundwater monitoring wells at the Site (see Figure 2) associated with regional groundwater plumes in the area, including:
• Mohawk Laboratories: MW-09 (DEGUINE), NMW-12B, 46-S, and 46-D; and • 999 Arques Corporation Wells: MW-2, MW-5, MW-6, MW-7, MW-8, MW-9, 13-S, 13-D S-39A, S-39B, S-38A, and S-38B.

There are existing groundwater wells at the Site used to monitor the regional plumes that will need to be removed or relocated as part of the redevelopment activities. The Developer will work with each Responsible Party to develop a well removal/relocation plan to be submitted to the Regional Water Board for review and approval. Note that a permit from the Santa Clara Valley Water District will be required prior to the destruction of wells.

5.8 Unknown Conditions
If a UST, UST related piping, former previously unidentified wells, significantly impacted soils (indicative by soil staining and suspicious odors), sumps, or underground vaults are discovered during soil excavation the following work shall be conducted:
• Stop all activities in proximity to the subsurface structure or condition of concern. • Cover the area with plastic sheeting and segregate the work area with safety cones or safety tape.
• Notify the superintendent and Environmental Consultant for inspection and follow up procedures.
• Note that a permit from the Santa Clara Valley Water District will be required prior to the destruction of wells.

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5.9 Construction Impact Mitigation Measures
During construction activities, measures will be taken by contractors to minimize construction related impacts. The construction impact mitigation measures are described below.

5.9.1 Site Control
The General Contractor shall implement Site control procedures to prevent unwanted public access and control the flow of personnel, vehicles, and materials in and out of the Site while working with potentially contaminated materials. In addition, Site cont rol measures will help control the spread of COPCs from the Site, if they are present. Site control measures to be implemented by the General Contractor include, but are not limited to:
• Fencing the Site perimeter, including installation of construction fence screen. • Controlling access and egress at selected locations.
• Posting signs at all Site entrances.
• Instructing visitors to sign in at the project support area.

5.9.2 Equipment Decontamination
The General Contractor shall establish and implement decontamination procedures to reduce the potential for construction equipment and vehicles to release potentially impacted soil onto public roadways or other inadvertent off -site transfer. At a minimum, contractors shall place gravel at all Site access points and remove excess soil from construction equipment using dry methods (e.g., brushing or scraping) prior to moving the equipment to off-site locations.

5.9.3 Personal Protective Equipment
Contractors shall use PPE, including appropriate clothing, to isolate workers from COPCs and physical hazards. Each contractor shall evaluate the level of PPE and modify the level of PPE, if warranted, based upon conditions encountered at the Site and/or type of work activity in accordance with their own HSP (see Section 5.3). The minimum level of protection for workers coming into direct contact with potentially contamin ated materials is Level D, as described below:
• Coveralls or similar construction work clothing;
• Reflective safety vests;
• Steel-toed boots;
• Hard hat;
• Work gloves, as necessary;
• Safety glasses, as necessary; and
• Hearing protection, as necessary.

5.9.4 Storm Water Pollution Prevention
A Construction Storm Water Pollution Prevention Plan (SWPPP) will be prepared for the project as required by the City of Sunnyvale . Contractors and their subcontractors shall comply with Attachment 15

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the provisions and protocols of the SWPPP. Storm water pollution prevention procedures may include, but are not limited to the following:
• Constructing temporary berms or erecting silt fences around exposed soil; • Placing straw bale barriers or sediment traps around catch basins or other entrances to storm drains;
• Covering soil stockpiles with plastic sheeting or tarps during rainfall events; and • Implementing other appropriate best management practices (BMPs) as identified in the SWPPP.

Implementation of the SWPPP as required by the City will be sufficient to also protect the potential of off-site migration of affected soils during storm events.

5.9.5 Dust Control
Mitigation measures to minimize the creation and dispersion of dust during soil handling and earthwork activities at the Site will include, but not be limited to, the following measures in accordance with the City of Sunnyvale ordinances:
• Exposed on-site soils to be moistened as needed to prevent visible airborne dust. • Moistening of all soils during truck loading for disposal or off-haul purposes. • Application of water while grading, excavating, and loading, as needed. • If visible dust is present, conducting dust suppression activities such as soil moistening. • Covering stockpiles with 10-mil polyethylene sheeting (or equivalent). • Limiting vehicle speeds on unpaved portions of the Site. • Covering all disposal trucks and/or off haul trucks with a tarpaulin. • Sweeping excess soil off disposal trucks and/or off haul trucks and rinsing of truck tires before leaving the Site.
• Minimizing drop heights while loading/unloading soil. • On-site soil disturbance and/or loading actives will be suspended if winds exceed 20 miles per hour.
• Dust suppression shall not produce excess storm water and runoff. • Dewatered groundwater may not be used for dust control unless previously sampled and analyzed for the Site COPCs, and COPCs are identified as below the applicable screening levels.

Implementation of the City required dust control efforts will be sufficient to also protect the potential of off-site migration of affected soils through airborne migration.

6.0 NEW STRUCTURE VAPOR INTRUSION MITIGATION
This section presents the proposed vapor intrusion mitigation measures for potentially affected structures within the proposed new development.

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6.1 Additional Characterization
To provide additional characterization of VOCs in soil vapor beneath the Site prior to construction, AEI proposes to perform additional soil vapor sampling outside of the area surrounding sampling locations SV -4, SV-5, and SV-9 at the Site. Thirteen (13) additional soil vapor probe locations are shown on Figures 3A and 3B. The proposed locations fill gaps in the current data set that exist primarily due to access issues associated with the presence of the existing commercial buildings at the Site. Soil vapor samples will be collected via sub -slab probes, through the existing commercial building floor slab or in five (5) foot probes outside of existing building locations of if sampling is done following demolition of the buildings. The soil vapor sampling probes will be installed and sampled in general accordance with the guidelines presented in the Advisory: Active Soil Vapor Investigations , prepared by the California Department of Toxic Substances Control (DTSC), et al., dated July 2015. The sampling and data evaluation procedures are presented below.

6.1.1 Sub-Slab Soil Vapor Sampling
At locations within the footprints of the existing commercial buildings sub -slab soil vapor samples may be collected instead of soil vapor probes, as described here. Prior to installation, private utility locating will be performed to identify and located underground utilities in the areas of proposed drilling which were adjusted accordingly when encountered.

Installation of the semi-permanent sub-slab soil gas probes will include coring the concrete slab or tiled surface using a rotary hammer drill with a 1.5-inch diameter drill bit that was advanced to approximately 1.5 inches to create the proper seating for the vapor pin’s protective cover.

A 5/8-inch diameter drill bit will then be used to extend beneath the slab. A Vapor Pin ® will then be installed in each of the drilled locations, with the silicone sleeve of the Vapor Pin ® providing the air-tight vapor seal for the locations. A stainless steel cover will be secured to each Vapor Pin ® at ground surface. The soil gas probes will be allowed to stabilize for approximately 48 hours before sampling.

After waiting a minimum of 48 -hours, the soil vapor sample will be collected from the newly installed soil vapor probes and existing probes using laboratory-supplied 1-liter, batch-certified, evacuated canisters with integrated flow -controllers in accordan ce with AEI’s Standard Operating Procedure (SOP) for soil vapor sampling, included in Appendix D . The collected sample will be analyzed for volatile organic compounds (VOCs) using US EPA Testing Method TO-15 and oxygen and helium using ASTM D-1946-90.

6.1.2 Soil Vapor Sampling
Prior to installation, private utility locating was conducted by Cal -West Concrete Cutting of Union City, California under subcontract to AEI to identify and located underground utilities in the areas of proposed drilling which were adjusted accordingly when encountered.

AEI will contract a State of California-licensed driller to install the proposed seven (7) soil vapor probes using a drill rig equipped with direct push capabilities. If necessary , due to access limitations, select soil vapor probes may be installed in borings advanced with a hand auger.

After drilling each soil boring to a depth of approximately 5.5 feet bgs, semi -permanent soil vapor sampling probes will be constructed in each boring.

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The soil vapor probes will be constructed using a screen -lined probe tip attached to ¼ -inch diameter Teflon™ tubing. The probe tips will be installed at a depth of approximately 5 feet bgs. A 1-foot sand pack will be placed from 5.5 to 4.5 feet bgs followed by an approximately 1- foot layer of dry granular bentonite, followed by an approximately 1 -foot layer of hydrated bentonite. The remaining annular space will be sealed with neat cement to grade. At the soil vapor probe location, a traffic-rated wellbox will be installed for protection and to allow access to the probe if the probe will remain in-place beyond 48-hours.

6.1.3 Data Evaluation
The collected soil vapor sample results will be evaluated to understand whether the VOCs detected in soil vapor would trigger vapor mitigation at additional bu ildings at th e Site. As presented in Section 2.4.2, the current maximum PCE and TCE concentrations outside of where mitigation is proposed are 66 and 50 µg/m3, respectively. The calculated Site-Specific soil vapor screening levels for PCE and TCE are 460 and 480 µg/m3, respectively. Therefore, AEI proposes more protective screening levels of 70 and 55 for PCE and TCE, respectively, to include a factor of safety to account for potential variation from a one -time sampling event. Based upon the soil vapor sample distribution, new residential buildings within a radius of approximately 100- feet from an elevated detection , as defined here, would include a vapor mitigation system , unless additional sampling points demonstrate that additional mitigation is not required.

6.1.4 Reporting
Upon completion of the sampling, a summary report will be prepared that presents the sampling methodology, tables summarizing the sample results, figures presenting the data, and an evaluation of the data. The report may propose additional buildings to have vapor mitigation as described below, based upon the screening levels presented in Section 6.1.3.

6.2 Vapor Mitigation at Select Structures
As discussed in Section 2.4 above, PCE detected in soil vapor does not represent an unacceptable risk to the future residential users of the Site . Elevated TCE concentrations present in soil vapor are limited to a specific area of the northwestern portion of Site as shown on Figure 5B. AEI proposes that only the buildings identified on Figure 5B, within the Proposed Mitigation Area, will be protected with a vapor intrusion mitigation system (VIMS) to include a passive venting system and low-permeability barrier. Prior to construction, a VIMS design and Operation, Maintenance, and Monitoring Plan (OMMP) will be prepared and submitted to the Regional Water Board for review. The design and performance monitoring of the VIMS will be in general accordance with the June 2022 Vapor Intrusion Mitigation Guidance, Technical Resource Document issued by the Regional Water Board, October 2011 Vapor Intrusion Mitigation Advisory, Revision 1, Final (VIMA) issued by the DTSC; June 2015 Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Attachment 15

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Indoor Air issued by the US EPA; and 2010 Methane Mitigation Standards established by the Los Angeles Department of Building and Safety (LADBS).

The passive venting system will be designed to collect soil gas that may migrate towards the building foundation and direct it through piping to the atmosphere to limit the potential for VOC-affected soil gas from entering the indoor air of the building. It will be designed to facilitate conversion to an active system if deemed necessary post -construction. Subslab components of the venting system will generally include:
• Subslab vapor collection piping embedded within a continuous, permeable 4-inch-thick aggregate base layer directly beneath the building slab and low-permeability barrier system.
• The subslab vapor collection piping will be connected to vertical vent risers that trend through the building interior, conveying the collected soil gas to the roof for discharge to the atmosphere. The vent risers will be 3 -inch diameter, solid, ductile i ron pipe (DIP) or cast-iron pipe (CIP) within the building envelope.

The low-permeability barrier engineered barrier system will be a composite membrane system composed of a spray-applied vapor barrier combined with a base layer and protection course.

The barrier system will be installed underneath the building floor slab across the entire building footprint. The typical configuration of the proposed venting and low -permeability barrier system is shown below (from GeoKinetics, June 30, 2025) . The final design will be pre pared appropriate for the building foundation design and then current VIMS design state of practice.

Additionally, utility trenches that pass under the concrete slab of the building s will be sealed at or near the building perimeter via the installation of trench dams. Mechanical and electrical conduits originating from beneath the building slab will also be sealed with a conduit seal to prevent migration of VOC-affected soil gas into the building through open conduits.

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7.0 NOTIFICATIONS

7.1 Notifications
The Developer, the General Contractor, and Environmental Consultant shall be notified immediately of the discovery of COPCs (via field screening, observations, or analytical results) or other conditions of potential environmental concern. If analytical tes ting identifies COPCs above applicable residential screening levels, the Environmental Consultant shall notify the Developer and General Contractor. If such discovery or conditions require notification to other contractors or subcontractors, the General Contractor shall make such notifications.

7.2 Project Contacts
Relevant project contacts for notifications, including in the case of discovery of COPCs or other conditions of potential environmental concern, include the following:

• Developer:

TBD

• Environmental Consultant:

AEI Consultants
3880 South Bascom Avenue, Suite 104
San Jose, California 95124
Phone: (408) 559-7600
Attn: Trent Weise
Phone: (408) 656-1738
Email: [email protected]

• Regulator:

San Francisco Bay Regional Water Quality Control Board
1515 Clay Street, Suite 1400
Oakland, California 94612
Attn: Emma Hoffman-Davies
Phone: (510) 622-2313
Email: [email protected]

• General Contractor:

TBD

8.0 COMPLETION REPORTING
The Environmental Consultant will prepare an SMP Implementation Report upon completion of excavation and earthwork performed per the SMP. The report will include a summary of the work conducted, tables summarizing any analytical data generated as part of the work, and a Site map showing areas of excavation/fill and sample locations, if any. The report will include appendices with copies of permits, including any dewatering permits, manifests or bills of lading for impacted soil and/or groundwater removed, and laboratory reports for soil and water profiling not previously submitted. The report will also include a certification statement that Attachment 15

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indicates the activities were performed in accordance with this SMP. The report will be submitted to the Regional Water Board for review and approval.

9.0 REFERENCES

AEI Consultants (AEI), 2019. Limited Phase II Subsurface Investigation, Oakmead West, 490 and 510 De Guigne Drive; 920, 935, 940, 945, and 960 Stewart Drive, Sunnyvale, California 94085. January 15.

AEI, 2024a. Phase I Environmental Site Assessment, 490, 510 De Guigne Drive; 920, 935, 940, 945, 960 Stewart Drive, Sunnyvale, California 94085. March 14.

AEI, 2024b. Phase I Environmental Site Assessment, 920 -950 De Guigne Drive, Sunnyvale, California 94085. August 22.

AEI, 2024c. Draft Limited Phase II Subsurface Investigation Report, 510 De Guigne Drive & 920, 930, 935, 945, and 950 Stewart Drive, Sunnyvale, California 94085. November 13.

AEI, 2025. Draft Additional Site Investigation Report, 510 De Guigne Drive and 920, 930, 935, 945, and 960 Stewart Drive, Sunnyvale, California 94085. February 28.

AEI, 2025. Additional Soil Vapor Investigation Report, 510 De Guigne Drive and 920, 930, 935, 945, and 960 Stewart Drive, Sunnyvale, California 94085. August 19.

Bradford, G.R., et al., 1996. Background Concentrations of Trace and Major Elements in California Soils. March.

Cornerstone Earth Group, 2010. Phase I Environmental Site Assessment and Preliminary Phase II Investigation, 920, 930 and 950 De Guigne Drive, Sunnyvale, California. May 17.

Department of Toxic Substances Control (DTSC), 2001. Information Advisory on Clean Imported Fill Material. October.

DTSC, 2011. Vapor Intrusion Mitigation Advisory, Revision 1, Final (VIMA). October.

DTSC and California State Water Resources Board, 2023. Supplemental Guidance: Screening and Evaluating Vapor Intrusion, Final Draft. February 2023.

Duvergé, Dylan Jacques, 2011. Establishing Background Arsenic in Soil of the Urbanized San Francisco Bay Region. December.

Eklund, Bart and Rich Rago, 2024. Fate and Transport of Chloroform in VI Evaluations.

August 5.

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Los Angeles Department of Building and Safety (LADBS), 2010. Methane Mitigation Standards.

San Francisco Bay Regional Water Quality Control Board (Regional Water Board), 2019. User’s Guide: Derivation and Application of Environmental Screening Levels (ESLs), Interim Final. dated July 2019, revision 2.

Regional Water Board, 2022. Vapor Intrusion Mitigation Guidance, Technical Resource Document. June.

United States Environmental Protection Agency (US EPA), 2015. Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air. June.

10.0 REPORT LIMITATIONS AND RELIANCE
The General Contractor and subcontractors are responsible for review of this Site Management Plan prior to commencing work at the Site and for the health and safety of their own employees and subcontractors. The Developer is responsible for review of the provisions of this Site Management Plan and for incorporating its guidelines into their project planning and specifications. This document was prepared for the sole use and benefit of TC III SPP North, LLC and their contractors and consultants at the Site . Neither this document, nor any of the information contained herein shall be used or relied upon for any purpose by any person or entities. Where information prepared by others has been provided, AEI cannot be responsible for its accuracy or completeness or for the availability of all information that may be relevant to the preparation of this document.

The completed work includes observations and descriptions of Site conditions encountered by AEI and others. Where appropriate, it includes analytical results for samples taken during the course of the work. This report should not be regarded as a guarant ee that no further contamination beyond that which is reported is present beneath the Site. Undocumented, unauthorized releases of hazardous material, the remains of which are not readily identifiable by visual inspection and are of different chemical con stituents, are difficult and often impossible to detect within the scope of a chemical specific investigation. Any conclusions and/or recommendations are based on these analyses and observations, and the governing regulations. Conclusions beyond those stated and reported herein should not be inferred from this document. Services were performed in accordance with generally accepted practices, in the environmental engineering and construction field, which existed at the time and location of the work. No other warranty, either expressed or implied, has been made.

Attachment 15

Page 26 of 71 ends

Site Management Plan
Sunnyvale Park Place, Sunnyvale, California 95482

Project No. 500004
December 23, 2025

Page 23 ends

11.0 SIGNATURES

This document was prepared by, or under the direction of, the undersigned.

Trent A. Weise, P.E.

Senior Vice President
Attachment 15

Page 27 of 71 ends

FIGURES

Attachment 15

Page 28 of 71 ends

D:\Drawing Files\AEI Consultants\500004\Limited Site Investigation\Fig 1, Site Location Map - 10/23/2024 SITE
LEGEND
N

REFERENCE LOCATION
Map Source:

USGS 7.5 Minute
Topographic Quadrangle Map,
Mountain View, CA - 1997
Site Location
0 APPROXIMATE SCALE.25 .50

IN MILES
SITE
510 De Guigne Drive and 920, 930,
935, 945 & 950 Stewart Drive
Sunnyvale, Caliornia 94085

SITE LOCATION MAP
FIGURE 1
Project No. 500004
Attachment 15

Page 29 of 71 ends

NMW-09
NMW-12B
46-S
MW-09 (DeGeuigne)
SG-5
SG-7
SG-6
IA-4
IA-2
IA-1
IA-3
IA-5
MW-6* MW-9
MW-5
MW-2
MW-7
MW-8*
EB-7
EB-9
EB-6
EB-5EB-2
EB-1
EB-3
EB-4
GW-3
GW-2
GW-1
SV-3/SV-3A
SV-1/SV-1A
SV-2
SV-4/SV-4A
935 STEWART DRIVE
510 DE GUIGNE DRIVE
945 STEWART DRIVE
930 DE GUIGNE DRIVE
920 DE GUIGNE DRIVE
950 DE GUIGNE
DRIVE
SB-18
SB-17
SG-16
SB-16 SB-15
SB-14
SG-15
SB-13SB-12
SB-11
SB-10
SB-9
SG-12 SB-8
SB-7
SG-11
SB-6
SG-10
SB-5
SB-19
SG-17
SB-1
SG-8
SB-2 SB-3 SG-9
SB-4
SG-18
SG-20
SG-19
SG-22
SB-22
SB-20
SG-21
SG-23
SB-21
SB-35
SG-24
SG-25SG-26
13-D
13-S
S-39A
S-39B
46-D
S-38A
S-38B
SG-13
SB-34
SB-33
SB-27
SB-28SB-25
SB-24
SB-23
EB-10
SB-32
SG-27
SB-31
SB-29
SB-30
SB-26
SV-1
SV-2 SV-3
SV-4
SV-5
SV-6
SV-7
SB-43
SB-44
SB-42
SB-45
SB-39
SB-40
SB-37
SB-36
SB-38SB-41
SG-14
GW-4
?
?
SV-8
SV-13
SV-14
SV-9
SV-19
SV-22
SV-10
D:\Drawing Files\AEI Consultants\500004\Work Plan\Fig 2, Site Plan - 08/19/2025 920 and 950 De Guigne Drive
Sunnyvale, California 94085
060 60 120 180

APPROXIMATE SCALE IN FEET
FIGURE 2
Project No. 500004
N NMW-09
SG-5
IA-1
SB-19
MW-2
Regional Plume(s) Monitoring Well Location (Mohawk
Laboratories)
Regional Plume(s) Monitoring Well Location
Soil Gas Sample Location (December 2018)
Indoor Air Sample Location (January 2019)
Soil Boring Location
Soil Boring Location (January 2025)
Soil Gas Probe Location
Semi-Permanent Soil Gas Probe Location
Exploration Boring
Groundwater Grab Sample
Temporary Soil Vapor Well
SG-17
SB-45
EB-1
GW-1
SV-3/SV-3a

EXPLANATION BLOCK
SV-3

SITE PLAN
Attachment 15

Page 30 of 71 ends

NMW-09
MW-09 (DeGeuigne)
SG-5
SG-7
SG-6
IA-4
IA-2
IA-1
IA-3
IA-5
MW-6* MW-9
MW-5
MW-2
MW-7
MW-8*
EB-7
EB-9
EB-6
EB-5EB-2
EB-1
EB-3
EB-4
GW-3
GW-2
GW-1
SV-3/SV-3A
SV-1/SV-1A
SV-2
SV-4/SV-4A
935 STEWART DRIVE
510 DE GUIGNE DRIVE
945 STEWART DRIVE
930 DE GUIGNE DRIVE
920 DE GUIGNE DRIVE
950 DE GUIGNE
DRIVE
SB-18
SB-17
SG-16
SB-16 SB-15
SB-14
SG-15
SB-13SB-12
SB-11
SB-10
SB-9
SG-12 SB-8
SB-7
SG-11
SB-6
SG-10
SB-5
SB-19
SG-17
SB-1
SG-8
SB-2 SB-3 SG-9
SB-4
SG-18
SG-20
SG-19
SG-22
SB-22
SB-20
SG-21
SG-23
SB-21
SB-35
SG-24
SG-25SG-26
13-D
13-S
S-39A
S-39B
46-D
S-38A
S-38B
SG-13
SB-34
SB-33
SB-27
SB-28SB-25
SB-24
SB-23
EB-10
SB-32
SG-27
SB-31
SB-29
SB-30
SB-26
SB-43
SB-44
SB-42
SB-45
SB-39
SB-40
SB-37
SB-36
SB-38
SB-41
SG-14
GW-4
SV-10
SV-7
SV-22
SV-4
SV-5
SV-9
SV-19
SV-6
SV-8
SV-1
SV-2
SV-14
SV-13
46-S
NMW-12B
SV-6
Date Depth Benzene PCE TCE
1/13/2025 5' 5.7 11 <0.81
7/29/2025 5' <0.44 9.8 <0.81
SV-3
Date Depth Benzene PCE TCE
3/11/2010 5' <3.8 ND ND

9.5' <10 ND ND
GW-3
Date cis-1,2-DCE TCE
3/9/2021 <1.1 <1.1
SG-22/SV-22
Date Depth Benzene PCE TCE
10/18/2024 4.5' 10 <4.4 <2.4
7/29/2025 5' <0.44 14 <0.81
SV-4
Date Depth Benzene PCE TCE
1/13/2025 5' 1.6 13 340
7/29/2025 5' <0.44 15 700 E
SG-20/SV-5
Date Depth Benzene PCE TCE
10/18/2024 4.5' 5.9 <4.4 210
1/13/2025 5' 6.7 14 100
7/29/2025 5' <0.44 31 83
MW-09 (DeGuigne)
Groundwater (µg/L)
Date PCE TCE
10/26/2020 ND<0.50 4.7
10/26/2021 ND<0.50 3.3
10/24/2022 ND<1.0 4.72
11/01/2023 ND<1.0 7.30 J4
10/22/2025 ND<1.0 5.10
SG-19/SV-19
Date Depth Benzene PCE TCE
10/18/2024 4.5' 16 <8.7 <4.8
7/29/2025 5' <0.44 6.2 <0.81
SV-9
Date Depth Benzene PCE TCE
7/29/2025 5' 4.2 13 210
SV-2
Date Depth Benzene PCE TCE
3/11/2010 5' 200 ND ND
4/19/2010 5' <69 ND ND
SV-1/SG-18
Date Depth Benzene PCE TCE
3/11/2010 5' 64 ND ND

9.5' <13 ND ND
4/19/2010 5' <40 ND ND
10/18/2024 4.5' 25 <15 <8.1
GW-1
Date TCE
3/9/2010 8.4
SG-17
Date Depth Benzene PCE TCE
10/17/2024 4.5' <13 <44 <24
SG-26
Date Depth Benzene PCE TCE
10/18/2024 4.5' <2.6 <26 <4.8
SV-8
Date Depth Benzene PCE TCE
7/29/2025 5' <0.44 5.6 <0.81
NMW-09 Groundwater (µg/L)
Date PCE TCE
10/26/2021 ND<0.50 38
10/24/2022 0.312 J 19.4
11/01/2023 0.999 J 62.7 J4
10/23/2024 2.55 14.8
SG-8/SV-1
Date Depth Benzene PCE TCE
10/17/2024 4.5' 4.9 17 9
1/13/2025 5' <0.44 20 5.6
7/29/2025 5' <0.44 13 14
SG-9/SV-2
Date Depth Benzene PCE TCE
10/17/2024 4.5' 6.9 13 18
1/13/2025 5' <0.44 13 24
7/29/2025 5' <0.44 8.7 40
NMW-12B Groundwater (µg/L)
Date PCE TCE
10/26/2020 ND<0.50 1.5
10/26/2021 ND<0.50 7.7
10/24/2022 ND<1.0 4.55
11/01/2023 0.682 J 14.8
10/22/2024 ND<1.0 5.63
SV-3
Date Depth Benzene PCE TCE
1/13/2025 5' 13 24 21
7/29/2025 5' 3.1 24 50
46-S Groundwater (µg/L)
Date PCE TCE
10/26/2020 1.8 15
10/26/2021 1.1 11
10/24/2022 28 150
11/01/2023 4.70 18.3
10/23/2024 2.55 14.8
SV-3
SG-11
Date Depth Benzene PCE TCE
10/17/2024 4.5' 2.3 12 <0.81
SG-12
Date Depth Benzene PCE TCE
10/17/2024 4.5' 95 <44 <23
SG-13/SV-13
Date Depth Benzene PCE TCE
10/17/2024 4.5' <13 <44 <24
7/29/2025 5' 15 8.0 2.8
S-38A Groundwater (µg/L)
Date PCE TCE
10/10/2018 ND<0.50 4.11
10/10/2023 ND<0.50 5.57
S-38B Groundwater (µg/L)
Date PCE TCE
10/10/2018 ND<0.5 24.6
10/11/2023 ND<1 123
SG-16
Date Depth Benzene PCE TCE
10/17/2024 4.5' 6.6 5.9 10
SG-15
Date Depth Benzene PCE TCE
10/17/2024 4.5' 10 5.8 11
SG-14/SV-14
Date Depth Benzene PCE TCE
10/17/2024 4.5' <13 <44 <24
7/29/2025 5' 10 10 40
SG-10
Date Depth Benzene PCE TCE
10/17/2024 4.5' 4.2 12 <0.94
SG-25/SV-7
Date Depth Benzene PCE TCE
10/18/2024 4.5' <2.2 22 <4.0
1/13/2025 5' 3.0 22 4.8
7/29/2025 5' <0.44 66 2.7
SG-27
Date Depth Benzene PCE TCE
10/18/2024 4.5' 25 <8.7 <4.8
SG-24
Date Depth Benzene PCE TCE
10/18/2024 4.5' 12 <8.7 <4.8
GW-2
Date TCE
3/9/2010 <0.58
GW-4/SV-4
Date Depth cis-1,2-DCE Benzene PCE TCE
3/9/2010 13 - - <0.63
3/11/3010 5' - <3.7 ND ND
9' - 210 ND ND
4/19/2010 5' - <39 ND ND
9' - <70 ND ND
SG-21
Date Depth Benzene PCE TCE
10/18/2024 4.5' <1.3 <4.4 <2.4
SG-23
Date Depth Benzene PCE TCE
10/18/2024 4.5' 13 <7.3 <4.0
SV-10
Date Depth Benzene PCE TCE
7/29/2025 5' <0.44 9.8 <0.81
?
?
D:\Drawing Files\AEI Consultants\500004\Site Management Plan\Fig 3A, VOCs In Soil Vapor (Current Site Configuration) - 12/22/2025 920 and 950 De Guigne Drive
Sunnyvale, California 94085
VOCs IN SOIL VAPOR
(CURRENT SITE

CONFIGURATION)
060 60 120 180

APPROXIMATE SCALE IN FEET
FIGURE 3A
Project No. 500004
N NMW-09
SG-5
IA-1
SB-19
MW-2
Regional Plume(s) Monitoring Well Location (Mohawk
Laboratories)
Regional Plume(s) Monitoring Well Location
Soil Gas Sample Location (December 2018)
Indoor Air Sample Location (January 2019)
Soil Boring Location
Soil Boring Location (January 2025)
Soil Gas Probe Location
Semi-Permanent Soil Gas Probe Location
Exploration Boring
Groundwater Grab Sample
Temporary Soil Vapor Well
Proposed Additional Soil Vapor Probe
TCE Concentrations in Soil Gas Greater Than the Residential ESL (µg/m3)
PCE in Groundwater (>10 µg/L), A-1 Zone,
Quarters 1 and 2, 2004
TCE in Groundwater (>10 µg/L), A-1 Zone,
Quarters 1 and 2, 2004
cis-1,2-DCE in Groundwater (>10 µg/L), A-1 Zone,
Quarters 1 and 2, 2004
SG-17
SB-45
EB-1
GW-1
SV-3/SV-3a

EXPLANATION BLOCK
SV-3
Notes:
- VOCs US EPA Testing Method TO-15
- Depth in Feet Below Ground Surface (bgs)
- Data displayed in micrograms per cubic meter (µg/m3)
- PCE - Tetrachloroethene
- TCE - Trichloroethene
- cis-1,2-DCE - cis-1,2-Dichloroethene
- E - Indicates that the reportable value is outside the instrument calibration range and the value should be considered as estimated
- Grey - Denotes most recent sampling event
Attachment 15

Page 31 of 71 ends

PARKING
NMW-09
NMW-12B
46-S
MW-09 (DeGeuigne)
SG-5
SG-7
SG-6
IA-4
IA-2
IA-1
IA-3
IA-5
MW-6*
MW-9
MW-5
MW-2
MW-7
MW-8*
EB-7
EB-9
EB-6
EB-5EB-2
EB-1
EB-3
EB-4
GW-3
GW-4
GW-2
GW-1
SV-3/SV-3A
SV-1/SV-1A
SV-2
SV-4/SV-4A
SB-18
SB-17
SG-16
SB-16 SB-15
SB-14
SG-15
SB-13SB-12
SB-11
SB-10
SB-9
SG-12 SB-8
SB-7
SG-11
SB-6
SG-10
SB-5
SB-19
SB-1
SG-8
SB-2 SB-3 SG-9
SB-4
SG-18
SG-20
SG-19
SG-22
SB-22
SB-20
SG-21
SG-23
SB-21
SB-35
SG-24
SG-25SG-26
13-D
13-S
S-39A
S-39B
46-D
S-38A
S-38B
SB-34
SB-33
SB-27
SB-28SB-25
SB-24
SB-23
EB-10
SB-32
SG-27
SB-31
SB-29
SB-30
SB-26
SV-1
SV-2
SV-3
SV-4
SV-5
SV-6
SV-7
SB-43
SB-44
SB-42
SB-45
SB-39
SB-40
SB-37
SB-36
SB-38SB-41
SG-14
SV-2
Date Depth Benzene PCE TCE
3/11/2010 5' 200 ND ND
4/19/2010 5' <69 ND ND
SG-17
SG-13
SV-8
SV-13
SV-14
SV-9
SV-22
SV-19
SV-10
SV-6
Date Depth Benzene PCE TCE
1/13/2025 5' 5.7 11 <0.81
7/29/2025 5' <0.44 9.8 <0.81
SV-4
Date Depth Benzene PCE TCE
1/13/2025 5' 1.6 13 340
7/29/2025 5' <0.44 15 700 E
SG-20/SV-5
Date Depth Benzene PCE TCE
10/18/2024 4.5' 5.9 <4.4 210
1/13/2025 5' 6.7 14 100
7/29/2025 5' <0.44 31 83
SG-19/SV-19
Date Depth Benzene PCE TCE
10/18/2024 4.5' 16 <8.7 <4.8
7/29/2025 5' <0.44 6.2 <0.81
SV-3
Date Depth Benzene PCE TCE
3/11/2010 5' <3.8 ND ND

9.5' <10 ND ND
GW-3
Date cis-1,2-DCE TCE
3/9/2021 <1.1 <1.1
SV-9
Date Depth Benzene PCE TCE
7/29/2025 5' 4.2 13 210
SG-22/SV-22
Date Depth Benzene PCE TCE
10/18/2024 4.5' 10 <4.4 <2.4
7/29/2025 5' <0.44 14 <0.81
SV-3
Date Depth Benzene PCE TCE
1/13/2025 5' 13 24 21
7/29/2025 5' 3.1 24 50
SV-2
Date Depth Benzene PCE TCE
3/11/2010 5' 200 ND ND
4/19/2010 5' <69 ND ND
SV-1/SG-18
Date Depth Benzene PCE TCE
3/11/2010 5' 64 ND ND

9.5' <13 ND ND
4/19/2010 5' <40 ND ND
10/18/2024 4.5' 25 <15 <8.1
SG-8/SV-1
Date Depth Benzene PCE TCE
10/17/2024 4.5' 4.9 17 9
1/13/2025 5' <0.44 20 5.6
7/29/2025 5' <0.44 13 14
SG-17
Date Depth Benzene PCE TCE
10/17/2024 4.5' <13 <44 <24
SG-26
Date Depth Benzene PCE TCE
10/18/2024 4.5' <2.6 <26 <4.8
SG-9/SV-2
Date Depth Benzene PCE TCE
10/17/2024 4.5' 6.9 13 18
1/13/2025 5' <0.44 13 24
7/29/2025 5' <0.44 8.7 40
SV-8
Date Depth Benzene PCE TCE
7/29/2025 5' <0.44 5.6 <0.81
SG-16
Date Depth Benzene PCE TCE
10/17/2024 4.5' 6.6 5.9 10
SG-15
Date Depth Benzene PCE TCE
10/17/2024 4.5' 10 5.8 11
SG-14/SV-14
Date Depth Benzene PCE TCE
10/17/2024 4.5' <13 <44 <24
7/29/2025 5' 10 10 40
SG-10
Date Depth Benzene PCE TCE
10/17/2024 4.5' 4.2 12 <0.94
SG-11
Date Depth Benzene PCE TCE
10/17/2024 4.5' 2.3 12 <0.81
SG-25/SV-7
Date Depth Benzene PCE TCE
10/18/2024 4.5' <2.2 22 <4.0
1/13/2025 5' 3.0 22 4.8
7/29/2025 5' <0.44 66 2.7
SG-12
Date Depth Benzene PCE TCE
10/17/2024 4.5' 95 <44 <23
SG-13/SV-13
Date Depth Benzene PCE TCE
10/17/2024 4.5' <13 <44 <24
7/29/2025 5' 15 8.0 2.8
GW-4/SV-4
Date Depth cis-1,2-DCE Benzene PCE TCE
3/9/2010 13 - - <0.63
3/11/3010 5' - <3.7 ND ND
9' - 210 ND ND
4/19/2010 5' - <39 ND ND
9' - <70 ND ND
SG-27
Date Depth Benzene PCE TCE
10/18/2024 4.5' 25 <8.7 <4.8
SG-24
Date Depth Benzene PCE TCE
10/18/2024 4.5' 12 <8.7 <4.8
SG-21
Date Depth Benzene PCE TCE
10/18/2024 4.5' <1.3 <4.4 <2.4
SG-23
Date Depth Benzene PCE TCE
10/18/2024 4.5' 13 <7.3 <4.0
SV-10
Date Depth Benzene PCE TCE
7/29/2025 5' <0.44 9.8 <0.81
?
?
MW-09 (DeGuigne)
Groundwater (µg/L)
Date PCE TCE
10/26/2020 ND<0.50 4.7
10/26/2021 ND<0.50 3.3
10/24/2022 ND<1.0 4.72
11/01/2023 ND<1.0 7.30 J4
10/22/2025 ND<1.0 5.10
GW-1
Date TCE
3/9/2010 8.4
NMW-09 Groundwater (µg/L)
Date PCE TCE
10/26/2021 ND<0.50 38
10/24/2022 0.312 J 19.4
11/01/2023 0.999 J 62.7 J4
10/23/2024 2.55 14.8
NMW-12B Groundwater (µg/L)
Date PCE TCE
10/26/2020 ND<0.50 1.5
10/26/2021 ND<0.50 7.7
10/24/2022 ND<1.0 4.55
11/01/2023 0.682 J 14.8
10/22/2024 ND<1.0 5.63
46-S Groundwater (µg/L)
Date PCE TCE
10/26/2020 1.8 15
10/26/2021 1.1 11
10/24/2022 28 150
11/01/2023 4.70 18.3
10/23/2024 2.55 14.8
S-38A Groundwater (µg/L)
Date PCE TCE
10/10/2018 ND<0.50 4.11
10/10/2023 ND<0.50 5.57
S-38B Groundwater (µg/L)
Date PCE TCE
10/10/2018 ND<0.5 24.6
10/11/2023 ND<1 123
MW-2 Groundwater (µg/L)
Date PCE TCE
10/10/2018 ND<5 463
10/11/2023 ND<2.5 478
GW-2
Date TCE
3/9/2010 <0.58
D:\Drawing Files\AEI Consultants\500004\Site Management Plan\Fig 3B, VOCs In Soil Vapor (Proposed New Development Layout) - 12/22/2025

EXPLANATION BLOCK
920 and 950 De Guigne Drive
Sunnyvale, California 94085
VOCs IN SOIL VAPOR
(PROPOSED NEW

DEVELOPMENT LAYOUT)
060 60 120 180

APPROXIMATE SCALE IN FEET
FIGURE 3B
Project No. 500004
N
NMW-09
SG-5
IA-1
SB-19
MW-2
Regional Plume(s) Monitoring Well Location (Mohawk
Laboratories)
Regional Plume(s) Monitoring Well Location
Soil Gas Sample Location (December 2018)
Indoor Air Sample Location (January 2019)
Soil Boring Location
Soil Boring Location (January 2025)
Soil Gas Probe Location
Semi-Permanent Soil Gas Probe Location
Exploration Boring
Groundwater Grab Sample
Temporary Soil Vapor Well
Proposed Additional Soil Vapor Probe
TCE Concentrations in Soil Gas Greater Than the Residential ESL (µg/m3)
PCE in Groundwater (>10 µg/L), A-1 Zone,
Quarters 1 and 2, 2004
TCE in Groundwater (>10 µg/L), A-1 Zone,
Quarters 1 and 2, 2004
cis-1,2-DCE in Groundwater (>10 µg/L), A-1 Zone,
Quarters 1 and 2, 2004
Buildings Where VIMS is Required
SG-17
SB-45
Notes:
- VOCs US EPA Testing Method TO-15
- Depth in Feet Below Ground Surface (bgs)
- Data displayed in micrograms per cubic meter (µg/m3)
- PCE - Tetrachloroethene
- TCE - Trichloroethene
- cis-1,2-DCE - cis-1,2-Dichloroethene
- E - Indicates that the reportable value is outside the instrument calibration range and the value should be considered as estimated
- Grey - Denotes most recent sampling event
EB-1
GW-1
SV-3/SV-3a
SV-3
Attachment 15

Page 32 of 71 ends

NMW-09
NMW-12B
46-S
MW-09 (DeGeuigne)
SG-5
SG-7
SG-6
IA-4
IA-2
IA-1
IA-3
IA-5
MW-6* MW-9
MW-5
MW-2
MW-7
MW-8*
EB-7
EB-9
EB-6
EB-5EB-2
EB-1
EB-3
EB-4
GW-3
GW-4
GW-2
GW-1
SV-3/SV-3A
SV-1/SV-1A
SV-2
SV-4/SV-4A
935 STEWART DRIVE
510 DE GUIGNE DRIVE
945 STEWART DRIVE
930 DE GUIGNE DRIVE
920 DE GUIGNE DRIVE
950 DE GUIGNE
DRIVE
SB-18
SB-17
SG-16
SB-16 SB-15
SB-14
SG-15
SB-13SB-12
SG-14
SB-11
SB-10
SB-9
SG-12 SB-8
SB-7
SG-11
SB-6
SG-10
SB-5
SB-19
SG-17
SB-1
SG-8
SB-2 SB-3 SG-9
SB-4
SG-18
SG-20
SG-19
SG-22
SB-22
SB-20
SG-21
SG-23
SB-21
SB-35
SG-24
SG-25SG-26
13-D
13-S
S-39A
S-39B
46-D
S-38A
S-38B
SG-13
SB-34
SB-23
SG-27
SB-31
SB-26
AEI-SV-1
AEI-SV-2 AEI-SV-3
AEI-SV-4
AEI-SV-5
AEI-SV-6
AEI-SV-7
SB-43
SB-44
SB-42
SB-45
SB-39
SB-40
SB-37
SB-36
SB-38
SB-41
EB-9
Date Depth Lead
(mg/kg)
3/11/2010 2.5'-3' 1.4
2/23/2010 1'-1.5' 3.3
EB-7
Date Depth Lead
(mg/kg)
3/11/2010 2.5'-3' 3.5

3.5'-4' <1.0
EB-4
Date Depth Lead
(mg/kg)
3/11/2010 2'-2.5' 7.9
3'-3.5' 8
EB-6
Date Depth Lead
(mg/kg)
2/23/2010 1.5'-2' 9.7
EB-3
Date Depth Lead
(mg/kg)
3/11/2010 1.5'-2' 5.6

2.5'-3' 1.3
EB-1
Date Depth Lead
(mg/kg)
3/11/2010 1'-1.5' 8.6
2'-2.5' 6.6
SB-43
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 14.5
1 4.64
SB-44
Date Depth Lead
(mg/kg)
1/9/2025 0.5' 10.4
1 3.79
SB-42
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 21.4
1' 9.6
EB-2
Date Depth Lead
(mg/kg)
3/11/2010 1'-1.5' 10
2'-2.5' 4.6
SB-41
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 30.1
1' 8.20
EB-5
Date Depth Lead
(mg/kg)
3/11/2010 1.5'-2' 5.4

2.5'-3' <1.0
SB-21
Date Depth Lead
(mg/kg)
10/18/2024 3.5' - - -
SB-39
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 11.6
1 5.15
SB-38
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 23.3
1 <0.12
SB-24
Date Depth Lead
(mg/kg)
10/18/2024 4.5' - - -
EB-10
Date Depth Lead
(mg/kg)
2/23/2010 2.5'-3' 6.9
4'-4.5' 8.8
SB-36
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 7.80
1 11.8
SB-40
Date Depth Lead
(mg/kg)
1/9/2025 0.5' 7.45
1 7.65
SB-45
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 7.10
1 6.60
SB-10
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 33
1'-1.5' 16
3'-3.5' 43
5'-5.5' 4.7
SB-9
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 310
1'-1.5' 5.4
3'-3.5' 7.1
5'-5.5' 7.4SB-8
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 110
1'-1.5' 15
3'-3.5' 8.5
5'-5.5' 6
SB-7
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 61
1'-1.5' 21
3'-3.5' 14
5'-5.5' 9.4
SB-37
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 13.0
1 6.60SB-11
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 1,100
1'-1.5' 5.6
3'-3.5' 35
5'-5.5' 7.3
COMP 4A (8.09)
Date Soil
Boring
Lead
(mg/kg)
5/19/2010
SB-12 2
SB-13 2.5
SB-14 2.45
SB-15 2
SB-6
Date Depth Lead
(mg/kg)
5/19/2010 0'-0.5' 6.5
SB-5
Date Depth Lead
(mg/kg)
5/19/2010 0'-0.5' 30
SB-4
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 880
1'-1.5' 18
3'-3.5' 31
5'-5.5' 7
SB-3
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 6.7
1'-1.5' 1,200
2'-2.5' 11
3'-3.5' 26
5'-5.5' 7.2
SB-2
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 1,900
1'-1.5' 13
3'-3.5' 44
5'-5.5' 6.3
SB-1
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 31
1'-1.5' 41
3'-3.5' 7.5
5'-5.5' 6.9
COMP 5A (12.8)
Date Soil
Boring
Lead
(mg/kg)
5/19/2010
SB-16 4
SB-17 2
SB-18 1.5
SB-19 1.5
D:\Drawing Files\AEI Consultants\500004\Site Management Plan\Fig 4A, Lead Concentrations In Soil (Current Site Configuration) - 10/08/2025

EXPLANATION BLOCK
920 and 950 De Guigne Drive
Sunnyvale, California 94085

LEAD CONCENTRATIONS IN SOIL
(CURRENT SITE CONFIGURATION)
060 60 120 180

APPROXIMATE SCALE IN FEET
FIGURE 4A
Project No. 500004
N
NMW-09
SG-5
IA-1
SB-19
MW-2
Regional Plume(s) Monitoring Well Location (Mohawk
Laboratories)
Regional Plume(s) Monitoring Well Location
Soil Gas Sample Location (December 2018)
Indoor Air Sample Location (January 2019)
Soil Boring Location
Soil Boring Location (January 2025)
Soil Gas Probe Location
Semi-Permanent Soil Gas Probe Location
Exploration Boring
Groundwater Grab Sample
Temporary Soil Vapor Well
SG-17
AEI-SV-3
SB-45
Notes:
- Lead US EPA Testing Method 60108
- Depth in Feet Below Ground Surface (bgs)
- Data displayed in micrograms per kilogram (mg/kg)
EB-1
GW-1
SV-3/SV-3a
Attachment 15

Page 33 of 71 ends

3.5'-4' <1.0
EB-4
Date Depth Lead
(mg/kg)
3/11/2010 2'-2.5' 7.9
3'-3.5' 8
EB-6
Date Depth Lead
(mg/kg)
2/23/2010 1.5'-2' 9.7
EB-3
Date Depth Lead
(mg/kg)
3/11/2010 1.5'-2' 5.6

2.5'-3' <1.0
SB-21
Date Depth Lead
(mg/kg)
10/18/2024 3.5' - - -
SB-39
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 11.6
1 5.15
SB-38
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 23.3
1 <0.12
SB-24
Date Depth Lead
(mg/kg)
10/18/2024 4.5' - - -
EB-10
Date Depth Lead
(mg/kg)
2/23/2010 2.5'-3' 6.9
4'-4.5' 8.8
SB-36
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 7.80
1 11.8
SB-40
Date Depth Lead
(mg/kg)
1/9/2025 0.5' 7.45
1 7.65
SB-45
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 7.10
1 6.60
SB-10
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 33
1'-1.5' 16
3'-3.5' 43
5'-5.5' 4.7
SB-9
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 310
1'-1.5' 5.4
3'-3.5' 7.1
5'-5.5' 7.4SB-8
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 110
1'-1.5' 15
3'-3.5' 8.5
5'-5.5' 6
SB-7
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 61
1'-1.5' 21
3'-3.5' 14
5'-5.5' 9.4
SB-37
Date Depth Lead
(mg/kg)
1/10/2025 0.5' 13.0
1 6.60SB-11
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 1,100
1'-1.5' 5.6
3'-3.5' 35
5'-5.5' 7.3
COMP 4A (8.09)
Date Soil
Boring
Lead
(mg/kg)
5/19/2010
SB-12 2
SB-13 2.5
SB-14 2.45
SB-15 2
SB-6
Date Depth Lead
(mg/kg)
5/19/2010 0'-0.5' 6.5
SB-5
Date Depth Lead
(mg/kg)
5/19/2010 0'-0.5' 30
SB-4
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 880
1'-1.5' 18
3'-3.5' 31
5'-5.5' 7
SB-3
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 6.7
1'-1.5' 1,200
2'-2.5' 11
3'-3.5' 26
5'-5.5' 7.2
SB-2
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 1,900
1'-1.5' 13
3'-3.5' 44
5'-5.5' 6.3
SB-1
Date Depth Lead
(mg/kg)
5/19/2010
0'-0.5' 31
1'-1.5' 41
3'-3.5' 7.5
5'-5.5' 6.9
COMP 5A (12.8)
Date Soil
Boring
Lead
(mg/kg)
5/19/2010
SB-16 4
SB-17 2
SB-18 1.5
SB-19 1.5
D:\Drawing Files\AEI Consultants\500004\Site Management Plan\Fig 4B, Lead Concentrations In Soil (Proposed New Development Layout) - 10/07/2025

EXPLANATION BLOCK
920 and 950 De Guigne Drive
Sunnyvale, California 94085

LEAD CONCENTRATIONS IN SOIL
(PROPOSED NEW DEVELOPMENT

LAYOUT)
060 60 120 180

APPROXIMATE SCALE IN FEET
FIGURE 4B
Project No. 500004
N
NMW-09
SG-5
IA-1
SB-19
MW-2
Regional Plume(s) Monitoring Well Location (Mohawk
Laboratories)
Regional Plume(s) Monitoring Well Location
Soil Gas Sample Location (December 2018)
Indoor Air Sample Location (January 2019)
Soil Boring Location
Soil Boring Location (January 2025)
Soil Gas Probe Location
Semi-Permanent Soil Gas Probe Location
Exploration Boring
Groundwater Grab Sample
Temporary Soil Vapor Well
Proposed Area where Soil Testing is Warranted to
Finalize Soil Management Plan
SG-17
AEI-SV-3
SB-45
Notes:
- Lead US EPA Testing Method 60108
- Depth in Feet Below Ground Surface (bgs)
- Data displayed in micrograms per kilogram (mg/kg)
EB-1
GW-1
SV-3/SV-3a
Attachment 15

Page 34 of 71 ends

NMW-09
NMW-12B
46-S
MW-09 (DeGeuigne)
SG-5
SG-7
SG-6
IA-4
IA-2
IA-1
IA-3
IA-5
MW-6* MW-9
MW-5
MW-2
MW-7
MW-8*
EB-7
EB-9
EB-6
EB-5EB-2
EB-1
EB-3
EB-4
GW-3
GW-4
GW-2
GW-1
SV-3/SV-3A
SV-1/SV-1A
SV-2
SV-4/SV-4A
935 STEWART DRIVE
510 DE GUIGNE DRIVE
945 STEWART DRIVE
930 DE GUIGNE DRIVE
920 DE GUIGNE DRIVE
950 DE GUIGNE
DRIVE
SB-18
SB-17
SG-16
SB-16 SB-15
SB-14
SG-15
SB-13SB-12
SB-11
SB-10
SB-9
SG-12 SB-8
SB-7
SG-11
SB-6
SG-10
SB-5
SB-19
SG-17
SB-1
SG-8
SB-2 SB-3 SG-9 SB-4
SG-18
SG-20
SG-19
SG-22
SB-22
SB-20
SG-21
SG-23
SB-21
SB-35
SG-24
SG-25SG-26
13-D
13-S
S-39A
S-39B
46-D
S-38A
S-38B
SG-13
SB-34SB-33
SB-23
SG-27
SB-31
SB-26
AEI-SV-1
AEI-SV-2 AEI-SV-3
AEI-SV-4
AEI-SV-5
AEI-SV-6
AEI-SV-7
SB-43
SB-44
SB-42
SB-45
SB-39
SB-40
SB-37
SB-36
SB-38
SB-41
SG-14
EB-2
Date Depth p,p-DDE p,p-DDT Dieldrin
3/11/2010 1-1.5' 0.014 <0.016 <0.0085
2-2.5' <0.0022 <0.0032 <0.0017
EB-1
Date Depth p,p-DDE p,p-DDT Dieldrin
3/11/2010 1-1.5' <0.002 <0.002 <0.002
2-2.5' <0.002 <0.002 <0.002
EB-6
Date Depth p,p-DDE p,p-DDT Dieldrin
2/23/2010 1.5-2' 0.16 <0.008 0.012
EB-4
Date Depth p,p-DDE p,p-DDT Dieldrin
3/11/2010 2.5-3' <0.002 <0.002 <0.002

3.5-4' <0.002 <0.002 <0.002
EB-3
Date Depth p,p-DDE p,p-DDT Dieldrin
3/11/2010 1.5-2' 0.0021 <0.0032 <0.0017

2.5-3' <0.002 <0.002 <0.002
EB-7
Date Depth p,p-DDE p,p-DDT Dieldrin
3/11/2010 2.5-3' <0.002 <0.002 <0.002

3.5-4' <0.002 <0.002 <0.002
EB-9
Date Depth p,p-DDE p,p-DDT Dieldrin
2/23/2010 1-1.5' <0.002 <0.002 <0.002
3/11/2010 2.5-3' <0.0095 <0.016 <0.0085
SB-30
Date Depth p,p-DDE p,p-DDT Dieldrin
10/18/2024 4.5' <0.00061 <0.00074 <0.00025
SB-29
Date Depth p,p-DDE p,p-DDT Dieldrin
10/18/2024 4.5' <0.00061 <0.00074 <0.00025
SB-32
Date Depth p,p-DDE p,p-DDT Dieldrin
10/18/2024 4.5' <0.00061 <0.00074 <0.00025
SB-33
Date Depth p,p-DDE p,p-DDT Dieldrin
10/18/2024 4.5' <0.00061 <0.00074 <0.00025
EB-10
Date Depth p,p-DDE p,p-DDT Dieldrin
2/23/2010 2.5-3' 0.66 0.097 0.041
4-4.5' 1.3 0.12 0.077
3/11/2010 5.5-6' <0.008 <0.008 <0.008
SB-28
Date Depth p,p-DDE p,p-DDT Dieldrin
10/18/2024 4.5' <0.00061 <0.00074 <0.00025
SB-27
Date Depth p,p-DDE p,p-DDT Dieldrin
10/18/2024 4.5' <0.00061 <0.00074 <0.00025
SB-25
Date Depth p,p-DDE p,p-DDT Dieldrin
10/18/2024 4.5' <0.00061 <0.00074 <0.00025
SB-25
Date Depth p,p-DDE p,p-DDT Dieldrin
10/18/2024 4.5' <0.00061 <0.00074 <0.00025
SB-32SB-21
Date Depth p,p-DDE p,p-DDT Dieldrin
10/18/2024 3.5' 1.16 0.0338 0.046
EB-5
Date Depth p,p-DDE p,p-DDT Dieldrin
3/11/2010 1.5-2' <0.0095 <0.016 <0.0085

2.5-3' <0.02 <0.02 <0.02
COMP 1A
SB-1-1', SB-2-1', SB-3-1.25', SB-4-1.5'
Date Depth(feet
bgs)
p,p-DDE
(mg/kg)
p,p-DDT
(mg/kg)
Dieldrin
(mg/kg)
Arsenic
(mg/kg)
10/17/2024 1'-1.5' 0.0151 <0.0022 <0.00074 1.37
COMP 2A
SB-5-1.25', SB-6-1.25', SB-7-2'
Date Depth
(feet bgs)
p,p-DDE
(mg/kg)
p,p-DDT
(mg/kg)
Dieldrin
(mg/kg)
Arsenic
(mg/kg)
10/17/2024 1.25'-2' 0.035 <0.0074 <0.0025 1.63
COMP 5A
SB-16-4', SB-17-2', SB-18-1.5', SB-19-1.5'
Date Depth (feet
bgs)
p,p-DDE
(mg/kg)
p,p-DDT
(mg/kg)
Dieldrin
(mg/kg)
Arsenic
(mg/kg)
10/17/2024 1.5'-4' 0.713 0.0375 0.0399 10.2
COMP 4A
SB-12-2', SB-13-2.5', SB-14-2.75', SB-15-2'
Date Depth (feet
bgs)
p,p-DDE
(mg/kg)
p,p-DDT
(mg/kg)
Dieldrin
(mg/kg)
Arsenic
(mg/kg)
10/17/2024 2'-2.75 0.730 <0.0074 0.0389 5.57
COMP 3A
SB-8-3.25', SB-9-1', SB-10-1.5', SB-11-3'
Date Depth (feet
bgs)
p,p-DDE
(mg/kg)
p,p-DDT
(mg/kg)
Dieldrin
(mg/kg)
Arsenic
(mg/kg)
10/17/2024 1'-3.25' 0.110 0.00381 J 0.0145 4.57
D:\Drawing Files\AEI Consultants\500004\Site Management Plan\Fig 5A, OCP Concentrations In Soil (Current Site Configuration) - 10/07/2025

EXPLANATION BLOCK
920 and 950 De Guigne Drive
Sunnyvale, California 94085

OCP CONCENTRATIONS IN SOIL
(CURRENT SITE CONFIGURATION)
060 60 120 180

APPROXIMATE SCALE IN FEET
FIGURE 5A
Project No. 500004
N
NMW-09
SG-5
IA-1
SB-19
MW-2
Regional Plume(s) Monitoring Well Location (Mohawk
Laboratories)
Regional Plume(s) Monitoring Well Location
Soil Gas Sample Location (December 2018)
Indoor Air Sample Location (January 2019)
Soil Boring Location
Soil Boring Location (January 2025)
Soil Gas Probe Location
Semi-Permanent Soil Gas Probe Location
Exploration Boring
Groundwater Grab Sample
Temporary Soil Vapor Well
SG-17
AEI-SV-3
SB-45
Notes:
- Depth in Feet Below Ground Surface (bgs)
- Data displayed in milligrams per kilogram (mg/kg)
- p,p-DDE - Dichlorodiphenyldichloroethylene
- p,p-DDT - Dichlorodiphenyltrichloroethane
* Location may have been destroyed
EB-1
GW-1
SV-3/SV-3a
Attachment 15

Page 35 of 71 ends

PARKING
NMW-09
NMW-12B
46-S
MW-09 (DeGeuigne)
SG-5
SG-7
SG-6
IA-4
IA-2
IA-1
IA-3
IA-5
MW-6* MW-9
MW-5
MW-2
MW-7
MW-8*
EB-7
EB-9
EB-6
EB-5EB-2
EB-1
EB-3
EB-4
GW-3
GW-4
GW-2
GW-1
SV-3/SV-3A
SV-1/SV-1A
SV-2
SV-4/SV-4A
SB-18
SB-17
SG-16
SB-16 SB-15
SB-14
SG-15
SB-13SB-12
SB-11
SB-10
SB-9
SG-12 SB-8
SB-7
SG-11
SB-6
SG-10
SB-5
SB-19
SG-17
SB-1
SG-8
SB-2 SB-3 SG-9 SB-4
SG-18
SG-20
SG-19
SG-22
SB-22
SB-20
SG-21
SG-23
SB-21
SB-35
SG-24
SG-25SG-26
13-D
13-S
S-39A
S-39B
46-D
S-38A
S-38B
SG-13
SB-34SB-33
SB-23
SG-27
SB-31
SB-26
AEI-SV-1
AEI-SV-2 AEI-SV-3
AEI-SV-4
AEI-SV-5
AEI-SV-6
AEI-SV-7
SB-43
SB-44
SB-42
SB-45
SB-39
SB-40
SB-37
SB-36
SB-38SB-41
SG-14
EB-2
Date Depth p,p-DDE p,p-DDT Dieldrin
3/11/2010 1-1.5' 0.014 <0.016 <0.0085
2-2.5' <0.0022 <0.0032 <0.0017
EB-1
Date Depth p,p-DDE p,p-DDT Dieldrin
3/11/2010 1-1.5' <0.002 <0.002 <0.002
2-2.5' <0.002 <0.002 <0.002
EB-6
Date Depth p,p-DDE p,p-DDT Dieldrin
2/23/2010 1.5-2' 0.16 <0.008 0.012
EB-4
Date Depth p,p-DDE p,p-DDT Dieldrin
3/11/2010 2.5-3' <0.002 <0.002 <0.002

3.5-4' <0.002 <0.002 <0.002
EB-3
Date Depth p,p-DDE p,p-DDT Dieldrin
3/11/2010 1.5-2' 0.0021 <0.0032 <0.0017

2.5-3' <0.002 <0.002 <0.002
EB-7
Date Depth p,p-DDE p,p-DDT Dieldrin
3/11/2010 2.5-3' <0.002 <0.002 <0.002

2.5-3' <0.02 <0.02 <0.02
COMP 1A
SB-1-1', SB-2-1', SB-3-1.25', SB-4-1.5'
Date Depth(feet
bgs)
p,p-DDE
(mg/kg)
p,p-DDT
(mg/kg)
Dieldrin
(mg/kg)
Arsenic
(mg/kg)
10/17/2024 1'-1.5' 0.0151 <0.0022 <0.00074 1.37
COMP 2A
SB-5-1.25', SB-6-1.25', SB-7-2'
Date Depth
(feet bgs)
p,p-DDE
(mg/kg)
p,p-DDT
(mg/kg)
Dieldrin
(mg/kg)
Arsenic
(mg/kg)
10/17/2024 1.25'-2' 0.035 <0.0074 <0.0025 1.63
COMP 5A
SB-16-4', SB-17-2', SB-18-1.5', SB-19-1.5'
Date Depth (feet
bgs)
p,p-DDE
(mg/kg)
p,p-DDT
(mg/kg)
Dieldrin
(mg/kg)
Arsenic
(mg/kg)
10/17/2024 1.5'-4' 0.713 0.0375 0.0399 10.2
COMP 4A
SB-12-2', SB-13-2.5', SB-14-2.75', SB-15-2'
Date Depth (feet
bgs)
p,p-DDE
(mg/kg)
p,p-DDT
(mg/kg)
Dieldrin
(mg/kg)
Arsenic
(mg/kg)
10/17/2024 2'-2.75 0.730 <0.0074 0.0389 5.57
COMP 3A
SB-8-3.25', SB-9-1', SB-10-1.5', SB-11-3'
Date Depth (feet
bgs)
p,p-DDE
(mg/kg)
p,p-DDT
(mg/kg)
Dieldrin
(mg/kg)
Arsenic
(mg/kg)
10/17/2024 1'-3.25' 0.110 0.00381 J 0.0145 4.57
D:\Drawing Files\AEI Consultants\500004\Site Management Plan\Fig 5B, OCP Concentrations In Soil (Proposed New Development Layout) - 10/07/2025

EXPLANATION BLOCK
920 and 950 De Guigne Drive
Sunnyvale, California 94085

OCP CONCENTRATIONS IN SOIL
(PROPOSED NEW DEVELOPMENT

LAYOUT)
060 60 120 180

APPROXIMATE SCALE IN FEET
FIGURE 5B
Project No. 500004
N
NMW-09
SG-5
IA-1
SB-19
MW-2
Regional Plume(s) Monitoring Well Location (Mohawk
Laboratories)
Regional Plume(s) Monitoring Well Location
Soil Gas Sample Location (December 2018)
Indoor Air Sample Location (January 2019)
Soil Boring Location
Soil Boring Location (January 2025)
Soil Gas Probe Location
Semi-Permanent Soil Gas Probe Location
Exploration Boring
Groundwater Grab Sample
Temporary Soil Vapor Well
Proposed Area where Soil Testing is Warranted to Finalized Soil Management Plan
SG-17
AEI-SV-3
SB-45
Notes:
- Depth in Feet Below Ground Surface (bgs)
- Data displayed in milligrams per kilogram (mg/kg)
- p,p-DDE - Dichlorodiphenyldichloroethylene
- p,p-DDT - Dichlorodiphenyltrichloroethane
* Location may have been destroyed
EB-1
GW-1
SV-3/SV-3a
Attachment 15

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TABLES

Attachment 15

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TABLE 1: SUMMARY OF SOIL SAMPLE RESULTS - LEAD
Oakmead West, Sunnyvale, California 94085
Location Depth Lead
ID Date (feet bgs) (mg/kg)
Residential ESL 80
Commercial ESL 320
Maximum Background Concentration 97.1
SB-36 1/10/2025 0.5 7.80
SB-36 1/10/2025 1 11.8
SB-37 1/10/2025 0.5 13.0
SB-37 1/10/2025 1 6.60
SB-38 1/10/2025 0.5 23.3
SB-38 1/10/2025 1 <0.12
SB-39 1/10/2025 0.5 11.6
SB-39 1/10/2025 1 5.15
SB-40 1/9/2025 0.5 7.45
SB-40 1/9/2025 1 7.65
SB-41 1/10/2025 0.5 30.1
SB-41 1/10/2025 1 8.20
SB-42 1/10/2025 0.5 21.4
SB-42 1/10/2025 1 9.60
SB-43 1/10/2025 0.5 14.5
SB-43 1/10/2025 1 4.64
SB-44 1/9/2025 0.5 10.4
SB-44 1/9/2025 1 3.79
SB-45 1/10/2025 0.5 7.10
SB-45 1/10/2025 1 6.60
COMP 1A 10/17/2024 1-1.5 2.89
COMP 2A 10/17/2024 1.25-2 4.71
COMP 3A 10/17/2024 1-3.25 7.99
COMP 4A 10/17/2024 2-2.75 8.09
COMP 5A 10/17/2024 1.5-4 12.8
AEI Project No. 500004 Page 1 of 6 AEI Consultants
Attachment 15

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TABLE 1: SUMMARY OF SOIL SAMPLE RESULTS - LEAD
Oakmead West, Sunnyvale, California 94085
Location Depth Lead
ID Date (feet bgs) (mg/kg)
Residential ESL 80
Commercial ESL 320
Maximum Background Concentration 97.1
SB-1 5/19/2010 0-0.5 31
SB-1 5/19/2010 1-1.5 41
SB-1 5/19/2010 3-3.5 7.5
SB-1 5/19/2010 5-5.5 6.9
SB-2 5/19/2010 0-0.5 1,900
SB-2 5/19/2010 1-1.5 13
SB-2 5/19/2010 3-3.5 44
SB-2 5/19/2010 5-5.5 6.3
SB-3 5/19/2010 0-0.5 6.7
SB-3 5/19/2010 2-2.5 11
SB-3 5/19/2010 1-1.5 1,200
SB-3 5/19/2010 3-3.5 26
SB-3 5/19/2010 5.5-6 7.2
SB-4 5/19/2010 0-0.5 880
SB-4 5/19/2010 1-1.5 18
SB-4 5/19/2010 3-3.5 31
SB-4 5/19/2010 5-5.5 7
SB-5 5/19/2010 0-0.5 30
SB-6 5/19/2010 0-0.5 6.5
SB-7 5/19/2010 0-0.5 61
SB-7 5/19/2010 1-1.5 21
SB-7 5/19/2010 3-3.5 14
SB-7 5/19/2010 6-6.5 9.4
SB-8 5/19/2010 0-0.5 110
SB-8 5/19/2010 1-1.5 15
SB-8 5/19/2010 3-3.5 8.5
SB-8 5/19/2010 5-5.5 6
SB-9 5/19/2010 0-0.5 310
SB-9 5/19/2010 1-1.5 5.4
SB-9 5/19/2010 3-3.5 7.1
SB-9 5/19/2010 5-5.5 7.4
SB-10 5/19/2010 0-0.5 33
SB-10 5/19/2010 1-1.5 16
SB-10 5/19/2010 3-3.5 43
SB-10 5/19/2010 5-5.5 4.7
SB-11 5/19/2010 0-0.5 1,100
SB-11 5/19/2010 1-1.5 5.6
SB-11 5/19/2010 3-3.5 35
SB-11 5/19/2010 5-5.5 7.3
AEI Project No. 500004 Page 2 of 6 AEI Consultants
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TABLE 1: SUMMARY OF SOIL SAMPLE RESULTS - LEAD
Oakmead West, Sunnyvale, California 94085
Location Depth Lead
ID Date (feet bgs) (mg/kg)
Residential ESL 80
Commercial ESL 320
Maximum Background Concentration 97.1
EB-1 3/11/2010 1-1.5 8.6
EB-1 3/11/2010 2-2.5 6.6
EB-2 3/11/2010 1-1.5 10
EB-2 3/11/2010 2-2.5 4.6
EB-3 3/11/2010 1.5-2 5.6
EB-3 3/11/2010 2.5-3 1.3
EB-4 3/11/2010 2-2.5 7.9
EB-4 3/11/2010 3-3.5 8
EB-5 3/11/2010 1.5-2 5.4
EB-5 3/11/2010 2.5-3 <1.0
EB-6 2/23/2010 1.5-2 9.7
EB-7 3/11/2010 2.5-3 3.5
EB-7 3/11/2010 3.5-4 <1.0
EB-9 3/11/2010 2.5-3 1.4
EB-9 2/23/2010 1-1.5 3.3
EB-10 2/23/2010 2.5-3 6.9
EB-10 2/23/2010 4-4.5 8.8
EB-10 3/11/2010 5.5-6 --
Notes:
mg/kg Milligrams per kilogram
COMP 1A SB-1-1', SB-2-1', SB-3-1.25', SB-4-1.5'
COMP 2A SB-5-1.25', SB-6-1.25', SB-7-2'
COMP 3A SB-8-3.25', SB-9-1', SB-10-1.5', SB-11-3'
COMP 4A SB-12-2', SB-13-2.5', SB-14-2.75', SB-15-2'
COMP 5A SB-16-4', SB-17-2', SB-18-1.5', SB-19-1.5'
< Less than the stated method detection limit
bgs Below ground surface
Bold Result exceeds a regulatory screening level
ESL
Maximum
Background
Concentration
Typical maximum background concentration provided based on "Background Concentrations of Trace and Major Elements in California Soils" by Bradford, G.R., et. al., dated March 1996.

Environmental Screening Level, based on direct exposure human health risk levels. From San Francisco Bay Regional Water Quality Control Board (Regional Water Board), User’s Guide: Derivation and Application of Environmental
Screening Levels (ESLs), Interim Final, Revision 2, dated July 2019.

AEI Project No. 500004 Page 3 of 6 AEI Consultants
Attachment 15

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TABLE 2: SOIL SAMPLE RESULTS - PESTICIDES
Oakmead West, Sunnyvale, California 94085
Heptachlor Endrin Remaining
Location Depth Epoxide p,p-DDD p,p-DDE p,p-DDT Dieldrin Endrin Ketone OCPs ID Date (feet bgs) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) Residential ESL 0.062 2.7 1.8 1.9 0.037 21 -- Various
Commercial ESL 0.28 12.0 8.3 8.5 0.160 290 -- Various
COMP 1A 10/17/2024 1-1.5 <0.00092 <0.0019 0.0151 <0.0022 <0.00074 <0.0024 <0.0013 <MDL COMP 2A 10/17/2024 1.25-2 <3.1 <0.0064 0.035 <0.0074 <0.0025 <0.0079 <0.0043 <MDL COMP 3A 10/17/2024 1-3.25 <0.00092 <0.0019 0.110 0.00381 J 0.0145 0.00503 J <0.0013 <MDL COMP 4A 10/17/2024 2-2.75 <0.0031 0.0148 J 0.230 <0.0074 0.0389 <0.0079 <0.0043 <MDL SB-12 10/17/2024 2 <0.0030 <0.0063 0.00777 J <0.0073 <0.0024 <0.0078 <0.0043 <MDL SB-13 10/17/2024 2.5 <0.0031 0.0236 0.699 <0.0074 0.0826 <0.0079 <0.0043 <MDL SB-14 10/17/2024 2.75 <0.0030 0.0113 J 0.190 <0.0073 0.0298 <0.0078 <0.0043 <MDL SB-15 10/17/2024 2 <0.0030 <0.0063 <0.0060 <0.0073 <0.0025 <0.0078 <0.0043 <MDL COMP 5A 10/17/2024 1.5-4 <0.0031 <0.0064 0.713 0.0376 0.0399 <0.0079 <0.0043 <MDL SB-16 10/17/2024 4 <0.0030 <0.0063 0.0986 <0.0073 0.00616 J <0.0078 <0.0043 <MDL SB-17 10/17/2024 2 <0.0030 <0.0063 0.0618 <0.0073 <0.0025 <0.0078 <0.0043 <MDL SB-18 10/17/2024 1.5 <0.0030 <0.0063 <0.0060 <0.0073 <0.0025 <0.0078 <0.0043 <MDL SB-19 10/17/2024 1.5 <0.0031 <0.0063 0.209 0.0201 0.00763 J <0.0079 <0.0043 <MDL SB-21 10/18/2024 3.5 0.00254 J 0.0629 1.16 0.0338 0.046 <0.0024 <0.0013 <MDL SB-22 10/18/2024 2.5 0.00512 J 0.0307 0.452 0.0345 0.0246 0.00631 <0.0013 <MDL SB-22 10/18/2024 4.5 0.00498 J 0.0188 0.630 0.0255 0.0155 0.00752 <0.0013 <MDL SB-24 10/18/2024 4.5 <0.00031 <0.00064 <0.00061 <0.00074 <0.00025 <0.00079 <0.00043 <MDL SB-25 10/18/2024 3 <0.00091 0.00750 0.633 0.0939 0.0762 0.0477 0.00594 J <MDL SB-25 10/18/2024 4.5 <0.00031 <0.00064 <0.00061 <0.00074 <0.00025 <0.00079 <0.00043 <MDL SB-27 10/18/2024 3 <0.00091 0.00661 1.48 0.114 0.0644 0.0308 <0.0013 <MDL SB-27 10/18/2024 4.5 <0.00031 <0.00064 <0.00061 <0.00074 <0.00025 <0.00079 <0.00043 <MDL SB-28 10/18/2024 3 <0.00091 <0.0019 0.548 0.0507 0.0388 0.0158 0.00238 J <MDL SB-28 10/18/2024 4.5 0.00247 <0.00064 <0.00061 <0.00074 <0.00025 <0.00079 <0.00043 <MDL SB-29 10/18/2024 4.5 <0.00031 <0.00064 <0.00061 <0.00074 <0.00025 <0.00079 <0.00043 <MDL SB-30 10/18/2024 4.5 <0.00031 <0.00064 <0.00061 <0.00074 <0.00025 <0.00079 <0.00043 <MDL SB-32 10/18/2024 4.5 <0.00031 <0.00064 0.160 0.00781 <0.00025 <0.00079 <0.00043 <MDL SB-33 10/18/2024 4.5 <0.00031 <0.00064 <0.00061 <0.00074 <0.00025 <0.00079 <0.00043 <MDL AEI Project No. 500004 Page 4 of 6 AEI Consultants
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TABLE 2: SOIL SAMPLE RESULTS - PESTICIDES
Oakmead West, Sunnyvale, California 94085
Heptachlor Endrin Remaining
Location Depth Epoxide p,p-DDD p,p-DDE p,p-DDT Dieldrin Endrin Ketone OCPs ID Date (feet bgs) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) Residential ESL 0.062 2.7 1.8 1.9 0.037 21 -- Various
Commercial ESL 0.28 12.0 8.3 8.5 0.160 290 -- Various
EB-1 3/11/2010 1-1.5 -- <0.002 <0.002 <0.002 <0.002 <0.002 -- <MDL EB-1 3/11/2010 2-2.5 -- <0.002 <0.002 <0.002 <0.002 <0.002 -- <MDL EB-2 3/11/2010 1-1.5 -- <0.0094 0.014 <0.016 <0.0085 <0.011 -- <MDL EB-2 3/11/2010 2-2.5 -- <0.0019 0.0022 <0.0032 <0.0017 <0.0023 -- <MDL EB-3 3/11/2010 1.5-2 -- <0.0019 0.0021 <0.0032 <0.0017 <0.0023 -- <MDL EB-3 3/11/2010 2.5-3 -- <0.002 <0.002 <0.002 <0.002 <0.002 -- <MDL EB-4 3/11/2010 2-2.5 -- 0.098 0.56 <0.016 0.05 <0.011 -- <MDL EB-4 3/11/2010 3-3.5 -- <0.0094 0.31 0.06 0.035 <0.011 -- <MDL EB-5 3/11/2010 1.5-2 -- <0.0094 <0.0095 <0.016 <0.0085 <0.011 -- <MDL EB-5 3/11/2010 2.5-3 -- <0.02 <0.02 <0.02 <0.02 <0.02 -- <MDL EB-6 2/23/2010 1.5-2 -- 0.022 0.16 <0.008 0.012 <0.008 -- <MDL EB-7 3/11/2010 2.5-3 -- <0.002 <0.002 <0.002 <0.002 <0.002 -- <MDL EB-7 3/11/2010 3.5-4 -- <0.002 <0.002 <0.002 <0.002 <0.002 -- <MDL EB-9 3/11/2010 2.5-3 -- <0.0094 <0.0095 <0.016 <0.0085 <0.011 -- <MDL EB-9 2/23/2010 1-1.5 -- <0.002 <0.002 <0.002 <0.002 <0.002 -- <MDL EB-10 2/23/2010 2.5-3 -- <0.008 0.66 0.097 0.041 0.02 -- <MDL EB-10 2/23/2010 4-4.5 -- 0.013 1.3 0.12 0.077 0.035 -- <MDL EB-10 3/11/2010 5.5-6 -- <0.008 <0.008 <0.008 <0.008 <0.008 -- <MDL Notes:
mg/kg Milligrams per kilogram
COMP 1A SB-1-1', SB-2-1', SB-3-1.25', SB-4-1.5'
COMP 2A SB-5-1.25', SB-6-1.25', SB-7-2'
COMP 3A SB-8-3.25', SB-9-1', SB-10-1.5', SB-11-3'
COMP 4A SB-12-2', SB-13-2.5', SB-14-2.75', SB-15-2'
COMP 5A SB-16-4', SB-17-2', SB-18-1.5', SB-19-1.5'
<MDL Less than the laboratory method detection limit
bgs Below ground surface
DDE Dichlorodiphenyldichloroethylene
DDT Dichlorodiphenyltrichloroethane
DDD Dichlorodiphenyldichloroethane
OCPs Organochlorine Pesticides
Bold Result exceeds a regulatory screening level
J
-- Not established and/or not analyzed
ESL
Indicates a value between the MDL and practical quantitation limit (PQL); the reported concentration should be considered as estimated rather the quantitative
Environmental Screening Level, based on direct exposure human health risk levels. From San Francisco Bay Regional Water Quality Control Board (Regional Water Board), User’s Guide: Derivation and Application of Environmental Screening Levels (ESLs), Interim Final, Revision 2, dated July 2019.

AEI Project No. 500004 Page 5 of 6 AEI Consultants
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TABLE 3: SUMMARY OF SOIL GAS SAMPLE RESULTS
Sunnyvale Park Place, Sunnyvale, California
Total cis-1,2- trans-1,2- Carbon 1,1- 4- Trichlorofluoro- Location Depth Benzene Toluene Ethylbenzene Xylenes PCE TCE DCE DCE Acetone Disulfide Chloroform Dichloroethane Ethyltoluene Freon 113 methane ID Date (feet bgs) (µg/m3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) Residential ESL 3.2 15,000 37 3,500 15 16 1,400 1,400 1,100,000 -- 4.1 58 -- -- -- Commercial ESL 14 61,000 160 15,000 67 100 5,800 5,800 4,500,000 -- 18 260 -- -- -- SG-8 10/17/2024 4.5 4.9 11 <1.9 13 17 9.0 <2.5 <1.4 86 13 <2.9 <1.6 <1.6 38 <1.7 AEI-SV-1 1/13/2025 5 <0.44 <0.75 3.0 17.7 20 5.6 <0.83 <0.48 <0.40 4.0 <0.97 <0.54 <0.55 28 3.8 AEI-SV-1 7/29/2025 5 <0.44 4.5 <0.63 <1.28 13 14 <0.83 <0.48 <0.40 <0.37 <0.97 <0.83 <0.55 19 5.8 SG-9 10/17/2024 4.5 6.9 11 2.2 11 13 18 <0.83 <0.48 99 2.5 <0.97 <0.54 <0.55 8 4.6 AEI-SV-2 1/13/2025 5 <0.44 2.5 2.4 12.9 13 24 <0.83 2.9 <0.40 10 <0.97 <0.54 <0.55 7.7 3.5 AEI-SV-2 7/29/2025 5 <0.44 2.9 <0.63 <1.28 8.7 40 <0.83 <0.48 17 <0.37 <0.97 <0.83 <0.55 6.0 3.8 AEI-SV-3 1/13/2025 5 13 16 6.5 31 24 21 6.6 3.6 48 130 33 <0.54 <0.55 16 <0.56 AEI-SV-3 7/29/2025 5 3.1 4.1 <0.63 <1.28 24 50 <0.83 <0.48 14 5.2 <0.97 <0.83 <0.55 8.7 <0.56 AEI-SV-4 1/13/2025 5 1.6 3.0 2.2 12 13 340 31 27 12 22 <0.97 4.6 <0.55 82 7.9 AEI-SV-4 7/29/2025 5 <0.44 4.2 <0.63 6.1 15 700 E 34 42 <0.40 <0.37 24 6.9 <0.55 73 7.2 SG-20 10/18/2024 4.5 5.9 10 <1.9 7.9 <4.4 210 <2.5 12 120 60 <2.9 <1.6 <1.6 470 37 AEI-SV-5 1/13/2025 5 6.7 13 4.3 20.9 14 100 8.8 21 <0.40 130 5.9 2.6 <0.55 320 28 AEI-SV-5 7/29/2025 5 <0.44 4.3 5.5 32.1 31 83 <0.83 4.3 40 <0.37 <0.97 <0.83 <0.55 170 <0.56 AEI-SV-6 1/13/2025 5 5.7 13 3.1 14.5 11 <0.81 14 18 24 140 <0.97 3.9 <0.55 <1.0 <0.56 AEI-SV-6 7/29/2025 5 <0.44 3.8 <0.63 3.9 9.8 <0.81 2.0 24 16 <0.37 <0.97 <0.83 <0.55 23 3.3 AEI-SV-7 1/13/2025 5 3.0 8.3 3.1 15.8 22 4.8 3.0 <0.48 33 62 <0.97 <0.54 <0.55 41 <0.56 AEI-SV-7 7/29/2025 5 <0.44 3.7 <0.63 2.8 66 2.7 <0.83 <0.48 17 <0.37 <0.97 <0.83 <0.55 74 3.4 SV-8 7/29/2025 5 <0.44 3.6 <0.63 2.3 5.6 <0.81 <0.83 <0.48 12 6.9 <0.97 <0.83 <0.55 25 4.5 SV-9 7/29/2025 5 4.2 18 5.6 19.4 13 210 <0.83 2.8 <0.40 54 <0.97 <0.83 <0.55 88 7.1 SV-10 7/29/2025 5 <0.44 3.5 <0.63 3.4 9.8 <0.81 <0.83 <0.48 19 15 11 <0.83 <0.55 13 <0.56 SG-13 10/17/2024 4.5 <13 <23 <19 <38.1 <44 <24 <25 <14 <12 <11 <29 <16 <16 <31 <17 SV-13 7/29/2025 5 15 65.0 16 70 8.0 2.8 <0.83 <0.48 <0.40 220 <0.97 <0.83 22 26 3.0 SG-14 10/17/2024 4.5 <13 <23 <19 <38.1 <44 <24 63 <14 <12 <11 <29 <16 <16 <31 <17 SV-14 7/29/2025 5 10 26 6.6 30.2 10 40 <0.83 <0.48 <0.40 9.0 <0.97 <0.83 9.7 19 <0.56 SG-19 10/18/2024 4.5 16 49 <3.8 22 <8.7 <4.8 <5.0 <2.9 110 150 <5.8 <3.3 <3.3 <6.1 <3.3 SV-19 7/29/2025 5 <0.44 29 <0.63 3.3 6.2 <0.81 <0.83 <0.48 15 10 <0.97 <0.83 <0.55 <1.0 <0.56 SG-22 10/18/2024 4.5 10 30 <1.9 33.7 <4.4 <2.4 <2.5 <1.4 150 32 <2.9 <1.6 17 <3.1 <1.7 SV-22 7/29/2025 5 <0.44 5.5 <0.63 4.2 14 <0.81 <0.83 <0.48 13 11 <0.97 <0.83 <0.55 11 60 Notes:
µg/m3
Micrograms per cubic meter
< Less than the stated method detection limit J Indicates a value between the method MDL and practical quantitation limit (PQL) and that the reported concentration should be considered as estimated bgs Below ground surface rather the quantitative
PCE Tetrachloroethylene/Tetrachloroethene E Indicates that the reportable value is outside the instrument calibration range and the value should be considered as estimated TCE Trichloroethylene/ Trichloroethene
cis-1,2-DCE cis-1,2-Dichloroethene
trans-1,2-DCE trans-1,2-Dichloroethene
VOCs Volatile Organic Compounds
Bold Result exceeds a Comparison Value
-- Not analyzed or established
Denotes most recent sampling event
ESL Environmental Screening Level, based on subslab/soil gas vapor intrusion human health risk levels. From San Francisco Bay Regional Water Quality Control Board (Regional Water Board), User’s Guide: Derivation and Application of Environmental Screening Levels (ESLs), Interim Final, dated July 2025.

AEI Project No. 500004 Page 1 of 4 AEI Consultants
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TABLE 3: SUMMARY OF SOIL GAS SAMPLE RESULTS
Sunnyvale Park Place, Sunnyvale, California
Total cis-1,2- trans-1,2- Carbon 1,1- 4- Trichlorofluoro- Location Depth Benzene Toluene Ethylbenzene Xylenes PCE TCE DCE DCE Acetone Disulfide Chloroform Dichloroethane Ethyltoluene Freon 113 methane ID Date (feet bgs) (µg/m3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) Residential ESL 3.2 15,000 37 3,500 15 16 1,400 1,400 1,100,000 -- 4.1 58 -- -- -- Commercial ESL 14 61,000 160 15,000 67 100 5,800 5,800 4,500,000 -- 18 260 -- -- -- SG-10 10/17/2024 4.5 4.2 6.6 <0.74 8.6 12 <0.94 <0.97 <0.56 100 12 <1.1 <0.64 <0.64 7 4.3 SG-11 10/17/2024 4.5 2.3 5.2 <0.63 5.4 12 <0.81 <0.83 <0.48 83 <0.37 <1.3 <0.72 <0.55 130 18 SG-12 10/17/2024 4.5 95 130 <19 94 <44 <23 <25 <14 <12 130 <29 <16 <16 <31 <17 SG-15 10/17/2024 4.5 10 16 <0.63 11.1 5.8 11 <0.83 <0.48 110 <0.37 <0.97 <0.54 2.9 340 3.4 SG-16 10/17/2024 4.5 6.6 10 2.9 14.8 5.9 10 <0.83 <0.48 110 35 <0.97 <0.54 <0.55 75 17 SG-17 10/17/2024 4.5 <13 <23 <19 <38.1 <44 <24 <25 <14 <12 <11 <29 <16 <16 160 <17 SG-18 10/18/2024 4.5 25 55 <6.3 22 <15 <8.1 <8.3 <4.8 250 54 <9.7 <5.4 <5.5 <10 <5.6 SG-20 10/18/2024 4.5 5.9 10 <1.9 7.9 <4.4 210 <2.5 12 120 60 <2.9 <1.6 <1.6 470 37 SG-21 10/18/2024 4.5 <1.3 8.5 <1.9 7.7 <4.4 <2.4 <2.5 <1.4 130 27 <2.9 <1.6 <1.6 <3.1 <1.7 SG-23 10/18/2024 4.5 13 51 15 42 <7.3 <4.0 <4.2 <2.4 170 22 <4.8 <2.7 <2.7 67 <2.8 SG-24 10/18/2024 4.5 12 32 <3.8 16 <8.7 <4.8 <5.0 <2.9 110 62 <5.8 <3.3 <3.3 160 <3.3 SG-25 10/18/2024 4.5 <2.2 13 <3.1 12 22 <4.0 <4.2 <2.4 100 11 <4.8 <2.7 <2.7 72 <2.8 SG-26 10/18/2024 4.5 <2.6 13 <3.8 <7.7 <26 <4.8 <5.0 <2.9 90 20 <5.8 <3.3 <3.3 <6.1 <3.3 SG-27 10/18/2024 4.5 25 55 61 322 <8.7 <4.8 <5.0 <2.9 140 73 <5.8 <3.3 16 <6.1 <3.3 SG-5 12/21/2018 5 -- 3.36 36.3 <1.59 --
SG-6 12/21/2018 5 -- <2.72 172 4,600 --
SG-7 12/21/2018 5 -- 4.99 <2.14 8.84 --
SV-1 3/11/2010 5 64 -- -- -- -- -- <4.7 -- -- -- -- -- -- -- -- SV-1 4/19/2010 5 <40 -- -- -- -- -- <50 -- -- -- -- -- -- -- -- SV-1 3/11/2010 9.5 <13 -- -- -- -- -- <16 -- -- -- -- -- -- -- -- SV-2 3/11/2010 5 200 -- -- -- -- -- <18 -- -- -- -- -- -- -- -- SV-2 4/19/2010 5 <69 -- -- -- -- -- <67 -- -- -- -- -- -- -- -- SV-3 3/11/2010 5 <3.8 -- -- -- -- -- <4.7 -- -- -- -- -- -- -- -- SV-3 3/11/2010 9.5 <10 -- -- -- -- -- <12 -- -- -- -- -- -- -- -- SV-4 3/11/2010 5 <3.7 -- -- -- -- -- <4.6 -- -- -- -- -- -- -- -- SV-4 4/19/2010 5 <39 -- -- -- -- -- <48 -- -- -- -- -- -- -- -- SV-4 3/11/2010 9.5 210 -- -- -- -- -- 13 -- -- -- -- -- -- -- -- SV-4 4/19/2010 9.5 <70 -- -- -- -- -- <87 -- -- -- -- -- -- -- -- Notes:
µg/m3
Micrograms per cubic meter
< Less than the stated method detection limit J Indicates a value between the method MDL and practical quantitation limit (PQL) and that the reported concentration should be considered as estimated bgs Below ground surface rather the quantitative
PCE Tetrachloroethylene/Tetrachloroethene E Indicates that the reportable value is outside the instrument calibration range and the value should be considered as estimated TCE Trichloroethylene/ Trichloroethene
cis-1,2-DCE cis-1,2-Dichloroethene
Bold Result exceeds a Comparison Value
-- Not analyzed or established
Denotes most recent sampling event
ESL Environmental Screening Level, based on subslab/soil gas vapor intrusion human health risk levels. From San Francisco Bay Regional Water Quality Control Board (Regional Water Board), User’s Guide: Derivation and Application of Environmental Screening Levels (ESLs), Interim Final, dated July 2025.

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TABLE 3: SUMMARY OF SOIL GAS SAMPLE RESULTS
Sunnyvale Park Place, Sunnyvale, California
Maximum Allowable
4-Methyl- 1,1,1- 1,2,4- 1,3,5- 1,1- Remaining Helium Detected Field Helium Helium Detection Location Depth 2-Hexanone Hexane 2-Pentanone 2-Butanone Naphthalene 2-Propanol tert-Butanol Trichloroethane Trimethylbenzene Trimethylbenzene Difluoroethane VOCs Oxygen in Sample Shroud in Sample ID Date (feet bgs) (µg/m3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m3) (µg/m3) (µg/m3) (µg/m 3) (%) (%) (%) (%) Residential ESL -- -- 100,000 170,000 2.8 -- -- 35,000 -- -- -- Various -- -- Commercial ESL -- -- 440,000 730,000 12 -- -- 150,000 -- -- -- Various -- -- SG-8 10/17/2024 4.5 <2.0 23 100 90 <3.8 <3.8 <1.9 13 <1.8 <0.90 <1.0 <MDL 6.9 <0.13 24.1 1.21% AEI-SV-1 1/13/2025 5 <0.65 2.5 <0.75 <0.39 <1.3 <1.3 <0.62 15 <0.60 <0.30 <0.35 <MDL 11 <0.072 29.7 1.49% AEI-SV-1 7/29/2025 5 <0.65 <0.46 <0.75 5.9 <1.3 29 2.8 32 <0.60 <0.30 <0.35 <MDL 7.4 <0.19 34.4 1.72% SG-9 10/17/2024 4.5 <0.65 38 38 100 <1.3 17 <0.62 6.5 2.8 <0.30 <0.35 <MDL 2.9 <0.13 24.1 1.21% AEI-SV-2 1/13/2025 5 <0.65 3.7 <0.75 <0.39 <1.3 16 2.2 6.5 <0.60 <0.30 <0.35 <MDL 8.4 <0.050 23.9 1.20% AEI-SV-2 7/29/2025 5 <0.65 <0.46 <0.75 <0.39 <1.3 18 <0.62 7.2 <0.60 <0.30 <0.35 <MDL 11 <0.041 25.5 1.28% AEI-SV-3 1/13/2025 5 <0.65 160 3.4 <0.39 <1.3 <1.3 <0.62 <0.79 <0.60 <0.30 <0.35 <MDL 14 <0.034 27.3 1.37% AEI-SV-3 7/29/2025 5 <0.65 <0.46 <0.75 <0.39 <1.3 43 1.5 <0.79 <0.60 <0.30 <0.35 <MDL 9.8 <0.081 24.9 1.25% AEI-SV-4 1/13/2025 5 <0.65 4.1 <0.75 <0.39 <1.3 <1.3 <0.62 36 <0.60 <0.30 <0.35 <MDL 15 0.38 J 24.2 1.21% AEI-SV-4 7/29/2025 5 <0.65 <0.46 <0.75 <0.39 <1.3 1,700 6.9 43 <0.60 <0.30 <0.35 <MDL 16 <0.027 26.7 1.34% SG-20 10/18/2024 4.5 <2.0 9.3 220 31 <1.3 620 <1.9 75 <1.8 <0.90 <1.0 <MDL 9.8 <0.091 28.5 1.43% AEI-SV-5 1/13/2025 5 <0.65 9.0 <0.75 <0.39 <1.3 620 2.8 53 <0.60 <0.30 <0.35 <MDL 16 <0.092 25.2 1.26% AEI-SV-5 7/29/2025 5 <0.65 <0.46 3.2 <0.39 <1.3 160 <0.62 34 <0.60 <0.30 <0.35 <MDL 18 <0.041 27.8 1.39% AEI-SV-6 1/13/2025 5 <0.65 9.8 2.7 <0.39 <1.3 22 <0.62 <0.79 <0.60 <0.30 <0.35 <MDL 15 <0.086 23.4 1.17% AEI-SV-6 7/29/2025 5 <0.65 <0.46 <0.75 <0.39 <1.3 32 <0.62 <0.79 <0.60 <0.30 <0.35 <MDL 16 <0.027 24.9 1.25% AEI-SV-7 1/13/2025 5 <0.65 15 2.3 <0.39 <1.3 18 <0.62 3.2 <0.60 <0.30 <0.35 <MDL 17 <0.028 25.2 1.26% AEI-SV-7 7/29/2025 5 <0.65 <0.46 <0.75 <0.39 <1.3 21 4.0 7.5 <0.60 <0.30 <0.35 <MDL 9.4 <0.13 25.7 1.29% SV-8 7/29/2025 5 <0.65 <0.46 <0.75 <0.39 <1.3 19 7.0 24 <0.60 <0.30 <0.35 <MDL 17 <0.027 23.0 1.15% SV-9 7/29/2025 5 <0.65 <0.46 2.2 <0.39 <1.3 18 11 31 <0.60 <0.30 <0.35 <MDL 16 <0.12 25.8 1.29% SV-10 7/29/2025 5 <0.65 <0.46 <0.75 <0.39 <1.3 55 8.0 <0.79 <0.60 <0.30 <0.35 <MDL 12 <0.082 23.9 1.20% SG-13 10/17/2024 4.5 <20 <14 <22 <12 <38 <38 <19 <24 <18 <9.0 <10 <MDL 12 <0.045 26.7 1.34% SV-13 7/29/2025 5 <0.65 25 <0.75 <0.39 2.7 24 <0.62 <0.79 24 11 <0.35 <MDL 15 <0.090 23.8 1.19% SG-14 10/17/2024 4.5 <20 1,800 <22 <12 <38 <38 <19 <24 <18 <9.0 <10 <MDL 13 <0.042 27.4 1.37% SV-14 7/29/2025 5 <0.65 50 <0.75 <0.39 <1.3 <1.3 <0.62 <0.79 10 4.9 <0.35 <MDL 15 <0.027 27.0 1.35% SG-19 10/18/2024 4.5 85 25 710 71 <7.6 <7.7 <3.7 <4.8 <3.6 <1.8 <2.1 <MDL 15 <0.072 24.7 1.24% SV-19 7/29/2025 5 4.6 <0.46 <0.75 <0.39 <1.3 23 4.8 <0.79 <0.60 <0.30 <0.35 <MDL 19 <0.12 27.7 1.39% SG-22 10/18/2024 4.5 <2.0 59 430 82 <3.8 <3.8 <1.9 <2.4 32 9.8 <1.0 <MDL 18 <0.059 22.7 1.14% SV-22 7/29/2025 5 <0.65 <0.46 <0.75 <0.39 <1.3 18 7.9 16 <0.60 <0.30 <0.35 <MDL 7.6 <0.16 29.5 1.48% Notes:
µg/m3
Micrograms per cubic meter
< Less than the stated method detection limit J Indicates a value between the method MDL and practical quantitation limit (PQL) and that the reported concentration should be considered as estimated bgs Below ground surface rather the quantitative
PCE Tetrachloroethylene/Tetrachloroethene E Indicates that the reportable value is outside the instrument calibration range and the value should be considered as estimated TCE Trichloroethylene/ Trichloroethene
cis-1,2-DCE cis-1,2-Dichloroethene
trans-1,2-DCE trans-1,2-Dichloroethene
VOCs Volatile Organic Compounds
Bold Result exceeds a Comparison Value
-- Not analyzed or established
Denotes most recent sampling event
ESL Environmental Screening Level, based on subslab/soil gas vapor intrusion human health risk levels. From San Francisco Bay Regional Water Quality Control Board (Regional Water Board), User’s Guide: Derivation and Application of Environmental Screening Levels (ESLs), Interim Final, dated July 2025.

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TABLE 3: SUMMARY OF SOIL GAS SAMPLE RESULTS
Sunnyvale Park Place, Sunnyvale, California
Maximum Allowable
4-Methyl- 1,1,1- 1,2,4- 1,3,5- 1,1- Remaining Helium Detected Field Helium Helium Detection Location Depth 2-Hexanone Hexane 2-Pentanone 2-Butanone Naphthalene 2-Propanol tert-Butanol Trichloroethane Trimethylbenzene Trimethylbenzene Difluoroethane VOCs Oxygen in Sample Shroud in Sample ID Date (feet bgs) (µg/m3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m 3) (µg/m3) (µg/m3) (µg/m3) (µg/m 3) (%) (%) (%) (%) Residential ESL -- -- 100,000 170,000 2.8 -- -- 35,000 -- -- -- Various -- -- Commercial ESL -- -- 440,000 730,000 12 -- -- 150,000 -- -- -- Various -- -- SG-10 10/17/2024 4.5 <0.76 11 52 69 <1.5 16 <0.72 5.5 <0.70 <0.35 <0.40 <MDL 12 <0.21 23.1 1.16% SG-11 10/17/2024 4.5 <0.65 5.1 6.8 60 <1.7 56 <0.82 <0.79 3.2 <0.30 <0.35 <MDL 20 <0.024 22.9 1.15% SG-12 10/17/2024 4.5 <20 1,400 <22 <12 <38 <38 <19 <24 <18 <9.0 <10 <MDL 3.6 <0.047 26.9 1.35% SG-15 10/17/2024 4.5 27 14 35 73 <1.3 19 <0.62 14 4.4 <0.30 <0.35 <MDL 8.7 <0.21 24.4 1.22% SG-16 10/17/2024 4.5 <0.65 38 45 83 <1.3 <1.3 <0.62 37 9.7 4.1 <0.35 <MDL 4.9 <0.12 25.3 1.27% SG-17 10/17/2024 4.5 <20 <14 <22 100 <38 <38 <19 <24 <18 <9.0 5,300 <MDL 5.2 <0.052 29.5 1.48% SG-18 10/18/2024 4.5 110 31 1,200 110 <13 <13 <0.62 <7.9 <6.0 <3.0 <3.5 <MDL 15 <0.056 20.2 1.01% SG-20 10/18/2024 4.5 <2.0 9.3 220 31 <3.8 620 <1.9 75 <1.8 <0.90 <1.0 <MDL 9.8 <0.091 28.5 1.43% SG-21 10/18/2024 4.5 55 13 420 48 <3.8 85 <1.9 15 <1.8 <0.90 <1.0 <MDL 13 <0.077 27.1 1.36% SG-23 10/18/2024 4.5 75 53 500 79 <3.8 <6.4 <3.1 <4.0 <3.0 <1.5 <1.7 <MDL 5.7 <0.074 33.1 1.66% SG-24 10/18/2024 4.5 51 14 770 52 <6.4 <7.7 <3.7 <4.8 <3.6 <1.8 <2.1 <MDL 14 <0.059 25.5 1.28% SG-25 10/18/2024 4.5 48 26 500 54 <7.6 <6.4 <3.1 <4.0 <3.0 <1.5 <1.7 <MDL 13 <0.055 23.4 1.17% SG-26 10/18/2024 4.5 45 13 600 35 <6.4 <7.7 <3.7 <4.8 <3.6 <1.8 <2.1 <MDL 13 <0.059 24.7 1.24% SG-27 10/18/2024 4.5 120 190 1,100 <2.3 <7.6 <7.7 <3.7 <4.8 18 <1.8 <2.1 <MDL 9.1 <0.070 26.0 1.30% SV-1 3/11/2010 5 -- -- -- -- -- <3.7 -- -- -- -- -- -- -- -- -- SV-1 4/19/2010 5 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- SV-1 3/11/2010 9.5 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- SV-2 3/11/2010 5 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- SV-2 4/19/2010 5 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- SV-3 3/11/2010 5 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- SV-3 3/11/2010 9.5 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- SV-4 3/11/2010 5 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- SV-4 4/19/2010 5 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- SV-4 3/11/2010 9.5 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- SV-4 4/19/2010 9.5 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- Notes:
µg/m3
Micrograms per cubic meter
<MDL Less than the laboratory method detection limit J Indicates a value between the method MDL and practical quantitation limit (PQL) and that the reported concentration should be considered as estimated rather the quantitative bgs Below ground surface E Indicates that the reportable value is outside the instrument calibration range and the value should be considered as estimated PCE Tetrachloroethylene/Tetrachloroethene
TCE Trichloroethylene/ Trichloroethene
cis-1,2-DCE Cis-1,2-Dichloroethene
Bold Result exceeds a Comparison Value
-- Not analyzed or established
Denotes most recent sampling event
ESL Environmental Screening Level, based on subslab/soil gas vapor intrusion human health risk levels. From San Francisco Bay Regional Water Quality Control Board (Regional Water Board), User’s Guide: Derivation and Application of Environmental Screening Levels (ESLs), Interim Final, dated July 2025.

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APPENDIX A
Historical Data

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LEGEND AEI Consultants
Oakmead West,
Sunnyvale, California

SITE MAP
FIGURE 2
Project No. 398471
Approximate Property Boundary
Soil Gas Boring
SG-5 SG-6
SG-1 SG-2
SG-3 SG-4
SG-7
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Maximum Allowable
cis-1,2- trans-1,2- Vinyl Helium Detected Field Helium Helium Detection Location De pth Tetrachloroethylene Trichloroeth ylene Dichloroethene Dichloroethene chloride in Sample Shroud in Sample ID Date (feet bgs) (µg/m3) (µg/m3) (µg/m3) (µg/m3) (µg/m 3) (%) (%) (%) SG-1 12/21/2018 5 71.0 168 52.8 16.8 <1.02 <0.10 26.6 1.3 SG-2 12/21/2018 5 33.5 11.3 <6.34 <6.34 <4.09 <0.10 23.3 1.2 SG-3 12/21/2018 5 11.7 41.0 676 <1.59 4.41 <0.10 21.8 1.1 SG-4 12/21/2018 5 24.7 22.5 2.74 <1.59 <1.02 <0.10 21.6 1.1 SG-5 12/21/2018 5 3.36 36.3 <1.59 <1.59 <1.02 <0.10 30.2 1.5 SG-6 12/21/2018 5 <2.72 172 4,600 683 441 <0.10 20.4 1.0 SG-7 12/21/2018 5 4.99 <2.14 8.84 <1.59 <1.02 <0.10 30.7 1.5 Com
parison Values:

ESL-C/I 2,100 3,000 35,000 350,000 160 -- -- --
Notes:
bgs below ground surface
µg/m3
micrograms per cubic meter
< less than the laborator y reporting limit
-- Not a pplicable
Exceeds ESL-C/I
Comparison Values:

ESL-C/I San Francisco Bay Regional Water Quality Control Board Environmental Screening Levels based on vapor intrusion human health, under a commercial/industrial (C/I) land use scenario (RWQCB, February 2016, rev. 3, Table SG-1).

TABLE 1: SOIL GAS SAMPLE DATA SUMMARY
Oakmead West, Sunnyvale,California

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APPENDIX B
Conceptual De
velopment Plan

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APPENDIX C
Information Advisory, Clean Imported Fill
Material
(DTSC, 2001)

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Executive Summary
This fact sheet has been prepared to ensure that inappropriate fill material is not introduced onto sensitive land use properties under the oversight of the DTSC or applicable regulatory authorities. Sensitive land use properties include those that contain facilities such as hospitals, homes, day care centers, and schools. This docu- ment only focuses on human health concerns and ecological issues are not addressed.

It identifies those types of land use activities that may be appropriate when deter- mining whether a site may be used as a fill material source area. It also provides guidelines for the appropriate types of analyses that should be performed relative to the former land use, and for the number of samples that should be collected and analyzed based on the estimated volume of fill material that will need to be used.

The information provided in this fact sheet is not regulatory in nature, rather is to be used as a guide, and in most situations the final decision as to the acceptability of fill material for a sensitive land use property is made on a case-by-case basis by the appropriate regulatory agency.

Introduction
The use of imported fill material has recently come under scrutiny because of the instances where contaminated soil has been brought onto an otherwise clean site. However, there are currently no established standards in the statutes or regulations that address environmental requirements for imported fill material.

Therefore, the California Environmental Protection Agency, Department of T oxic Substances Control (DTSC) has prepared this fact sheet to identify pro- cedures that can be used to minimize the possibility of introducing contami- nated soil onto a site that requires imported fill material. Such sites include those that are undergoing site remediation, corrective action, and closure ac- tivities overseen by DTSC or the appropriate regulatory agency. These proce- dures may also apply to construction projects that will result in sensitive land uses. The intent of this fact sheet is to protect people who live on or otherwise use a sensitive land use property. By using this fact sheet as a guide, the reader will minimize the chance of introducing fill material that may result in poten- tial risk to human health or the environment at some future time.

California
Environmental
Protection Agency
It is DTSC’s
mission to restore,
protect and
enhance the
environment, to
ensure public
health,
environmental
quality and
economic vitality,
by regulating
hazardous waste,
conducting and
overseeing
cleanups, and
developing and
promoting
pollution
prevention.

State of California

DEPARTMENT OF TOXIC SUBSTANCES CONTROL
Information Advisory
Clean Imported Fill Material
The energy challenge facing California is real. Every Californian needs to take immediate action to reduce energy consumption. For a list of simple ways you can reduce demand and cut your energy costs, see our website at www.dtsc.ca.gov.

DEPARTMENT
OF

TOXICSUBSTANCESCONTROL
October 2001
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2 Overview
Both natural and manmade fill materials are used
for a variety of purposes. Fill material properties are commonly controlled to meet the necessary site spe-
cific engineering specifications. Because most sites
requiring fill material are located in or near urban
areas, the fill materials are often obtained from con-
struction projects that generate an excess of soil, and from demolition debris (asphalt, broken concrete,
etc.). However, materials from those types of sites
may or may not be appropriate, depending on the
proposed use of the fill, and the quality of the as-
sessment and/or mitigation measures, if necessary.

Therefore, unless material from construction
projects can be demonstrated to be free of contami-
Potential Contaminants Based on the Fill Source Area
Fill Source:

Land near to an existing freeway
Land near a mining area or rock quarry
Agricultural land
Residential/acceptable commercial land
Target Compounds
Lead (EPA methods 6010B or 7471A), PAHs
(EPA method 8310)
Heavy Metals (EPA methods 6010B and
7471A), asbestos (polarized light
microscopy), pH
Pesticides (Organochlorine Pesticides: EPA
method 8081A or 8080A; Organophospho-
rus Pesticides: EPA method 8141A; Chlori-
nated Herbicides: EPA method 8151A),
heavy metals (EPA methods 6010B and
7471A)
VOCs (EPA method 8021 or 8260B, as
appropriate and combined with collection
by EPA Method 5035), semi-VOCs (EPA
method 8270C), TPH (modified EPA method
8015), PCBs (EPA method 8082 or 8080A),
heavy metals including lead (EPA methods
6010B and 7471A), asbestos (OSHA Method
ID-191)
nation and/or appropriate for the proposed use, the
use of that material as fill should be avoided.

Selecting Fill Material
In general, the fill source area should be located in
nonindustrial areas, and not from sites undergoing
an environmental cleanup. Nonindustrial sites in-
clude those that were previously undeveloped, or
used solely for residential or agricultural purposes.

If the source is from an agricultural area, care should be taken to insure that the fill does not include
former agricultural waste process byproducts such
as manure or other decomposed organic material.

Undesirable sources of fill material include indus-
trial and/or commercial sites where hazardous ma-
*The recommended analyses should be performed in accordance with USEPA SW-846 methods (1996).

Other possible analyses include Hexavalent Chromium: EPA method 7199 Attachment 15

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3 Area of Individual Borrow Area
2 acres or less
2 to 4 acres
4 to 10 acres
Greater than 10 acres
Volume of Borrow Area Stockpile
Up to 1,000 cubic yards
1,000 to 5,000 cubic yards
Greater than 5,000 cubic yards
Sampling Requirements
Minimum of 4 samples
Minimum of 1 sample every 1/2 acre
Minimum of 8 samples
Minimum of 8 locations with 4 subsamples
per location
Samples per Volume
1 sample per 250 cubic yards
4 samples for first 1000 cubic yards +1
sample per each additional 500 cubic yards
12 samples for first 5,000 cubic yards + 1
sample per each additional 1,000 cubic
yards
Recommended Fill Material Sampling Schedule
terials were used, handled or stored as part of the
business operations, or unpaved parking areas where
petroleum hydrocarbons could have been spilled or
leaked into the soil. Undesirable commercial sites
include former gasoline service stations, retail strip
malls that contained dry cleaners or photographic
processing facilities, paint stores, auto repair and/or painting facilities. Undesirable industrial facilities
include metal processing shops, manufacturing fa-
cilities, aerospace facilities, oil refineries, waste treat- ment plants, etc. Alternatives to using fill from con- struction sites include the use of fill material ob-
tained from a commercial supplier of fill material
or from soil pits in rural or suburban areas. How-
ever, care should be taken to ensure that those ma-
terials are also uncontaminated.

Documentation and Analysis
In order to minimize the potential of introducing
contaminated fill material onto a site, it is necessary to verify through documentation that the fill source
is appropriate and/or to have the fill material ana-
lyzed for potential contaminants based on the loca-
tion and history of the source area. Fill documenta-
tion should include detailed information on the pre-
vious use of the land from where the fill is taken,
whether an environmental site assessment was per-
formed and its findings, and the results of any test-
ing performed. It is recommended that any such
documentation should be signed by an appropri-
ately licensed (CA-registered) individual. If such
documentation is not available or is inadequate,
samples of the fill material should be chemically ana-
lyzed. Analysis of the fill material should be based
on the source of the fill and knowledge of the prior
land use.

Detectable amounts of compounds of concern
within the fill material should be evaluated for risk
in accordance with the DTSC Preliminary Endan-
germent Assessment (PEA) Guidance Manual. If
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4 metal analyses are performed, only those metals
(CAM 17 / Title 22) to which risk levels have been
assigned need to be evaluated. At present, the
DTSC is working to establish California Screen-
ing Levels (CSL) to determine whether some com-
pounds of concern pose a risk. Until such time as
these CSL values are established, DTSC recom-
mends that the DTSC PEA Guidance Manual or
an equivalent process be referenced. This guid-
ance may include the Regional Water Quality
Control Board’s (RWQCB) guidelines for reuse
of non-hazardous petroleum hydrocarbon con-
taminated soil as applied to Total Petroleum Hy-
drocarbons (TPH)
only. The RWQCB guidelines
should not be used for volatile organic compounds
(VOCs) or semi-volatile organic compounds
(SVOCS). In addition, a standard laboratory data
package, including a summary of the QA/QC
(Quality Assurance/Quality Control) sample re-
sults should also accompany all analytical reports.

When possible, representative samples should be col-
lected at the borrow area while the potential fill ma-
terial is still in place, and analyzed prior to removal from the borrow area. In addition to performing
the appropriate analyses of the fill material, an ap-
propriate number of samples should also be deter-
mined based on the approximate volume or area of
soil to be used as fill material. The table above can
be used as a guide to determine the number of
samples needed to adequately characterize the fill
material when sampled at the borrow site.

Alternative Sampling
A Phase I or PEA may be conducted prior to sam-
pling to determine whether the borrow area may
have been impacted by previous activities on the
property. After the property has been evaluated, any
sampling that may be required can be determined
during a meeting with DTSC or appropriate regu-
latory agency. However, if it is not possible to ana-
lyze the fill material at the borrow area or deter-
mine that it is appropriate for use via a Phase I or
PEA, it is recommended that one (1) sample per
truckload be collected and analyzed for all com-
pounds of concern to ensure that the imported soil
is uncontaminated and acceptable. (See chart on
Potential Contaminants Based on the Fill Source
Area for appropriate analyses). This sampling fre-
quency may be modified upon consultation with
the DTSC or appropriate regulatory agency if all of
the fill material is derived from a common borrow
area. However, fill material that is not characterized
at the borrow area will need to be stockpiled either
on or off-site until the analyses have been completed.

In addition, should contaminants exceeding accep-
tance criteria be identified in the stockpiled fill
material, that material will be deemed unacceptable
and new fill material will need to be obtained,
sampled and analyzed. Therefore, the DTSC rec-
ommends that all sampling and analyses should be
completed prior to delivery to the site to ensure the
soil is free of contamination, and to eliminate un-
necessary transportation charges for unacceptable
fill material.

Composite sampling for fill material characteriza-
tion may or may not be appropriate, depending on
quality and homogeneity of source/borrow area, and
compounds of concern. Compositing samples for
volatile and semivolatile constituents is
not accept-
able. Composite sampling for heavy metals, pesti-
cides, herbicides or PAH’s from unanalyzed stock-
piled soil is also unacceptable, unless it is stockpiled at the borrow area and originates from the same
source area. In addition, if samples are composited,
they should be from the same soil layer, and not
from different soil layers.

When very large volumes of fill material are antici-
pated, or when larger areas are being considered as
borrow areas, the DTSC recommends that a Phase
I or PEA be conducted on the area to ensure that
the borrow area has not been impacted by previous
activities on the property. After the property has
been evaluated, any sampling that may be required
can be determined during a meeting with the
DTSC.

For further information, call Richard Coffman, Ph.D.,
R.G., at (818) 551-2175.

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APPENDIX D
Standard Operating Procedures

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SOIL VAPOR SAMPLING USING USEPA TO-15

Objective The objective of this standard operating procedure is to provide equipment and procedure walkthrough information in order to complete a soil vapor sample.

Equipment
Fully read the proposal and understand the scope of work required for the proj ect. Order sampling media from a state certified laboratory which includes:
• Evacuated sampling canister(s) – 450-milliliter, 1-liter or 6 - liter • TO-17 sampling absorbent tubes (if part of scope)
• Flow controller(s) – calibrated by the lab to <200 mL/min flow rate • Purge summa canister – 6 - liter (if required), one purge can per three soil vapor points • ¼” O.D. Teflon tubing
• Stainless steel Swagelok bolts and ferrules (see Figure 1) • Shut-in valves (if needed)
• Tee fittings (if needed)
Make sure all sampling media arrives few days before field work begins . If possible, build the sample trains and perform the shut-in test before field work.

Understand the soil vapor well construction details for the project, calculate the purge volume required prior to field work. See attached Purge Volume Calculation below.

Procedure
Field notes should document the following on a Soil Vapor/Sub-Slab Sampling Field Data Form:
• Sample, Summa™ canister, and flow controller IDs
• Pass/fail for shut-in test
• Start/finish purge time and purge canister initial and final vacuum readings • Initial/final vacuums with date/time for sample collection • Helium detector reading after purge

SHUT-IN TEST
Tools needed – 9/16” and 1/2” wrenches (or two adjustable wrenches), scissors/tubing cutter, PPE presented in the site-specific HASP. See Figure 2 for photos of tools and additional Swagelok parts.

ALWAYS use clean gloves when handling sampling tubes and for each new sample . Sampling personnel should not handle permanent markers/sharpies, or smoke cigarettes/cigars before and/or during the sampling event.

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The purpose of the shut-in test is to ensure that all connections for the sample train are properly sealed. To conduct a shut-in test, assemble the above-ground valves, tubing, and fittings with the summa canister (see Figure 3) , create a 100 in-H2O ( ~7.5 in-Hg) vacuum with either a syringe or a purge summa canister. If there is any observable loss of vacuum (vacuum loss should not exceed 5% of vacuum created within one minute), the fittings are adjusted until the vacuum in the sample train does not noticeably dissipate . After the shut -in test is validated, the sample train should not be altered.

LEAK CHECK
To collect a soil vapor sample, connect the assembled sampling media to the soil vapor probe with Swagelok bolts, ferrules, or appropriate connections. The seal around the soil vapor sample port and the sampling train should be evaluated for leaks using ei ther helium or isopropyl alcohol (rubbing alcohol) as a tracer gas. The tracer gas should be introduced AFTER all the connections have been made and throughout sampling (Figure 3).

Leak check using Helium
Supplies/Equipment needed - Helium and Helium Detector (order before sampling event), syringe, tedlar bag, three-way valve, silicone tubing, nitrile gloves Connect purge can, three-way valve with syringe and Tedlar bag, and Summa™ cannister to the soil vapor probe. Once all connections (sample train, Summa™ canister, soil vapor probe) have been made, set up a shroud that covers the sample train, Summa ™ canister, and soil vapor probe. Place the helium detector probe within the shroud. Open the helium flow control valve to add helium inside the shroud. Record helium content within the shroud. Helium content should be greater than 20% in the shroud to simplify the leak check process. Helium should be maintained above 20% throughout sampling.

Purge the required volume from the well and shut the purge canister. DO NOT OPEN THE SAMPLE CANISTER VALVE. Remove the helium detector probe from the shroud to allow the detector to return to a zero reading. If the helium detector does not zero out over time, zero out the detector by pressing the button on the detector.

Use a syringe to pull gas through the sample train and fill a Tedlar bag. Allow sufficient time between each syringe pull to let gas enter the syringe. Once a sufficient volume of gas is in the tedlar bag, remove the Tedlar bag and connect it to the helium detector probe to determine if a significant leak is present.

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For helium in the sample train that is detected in %:

For helium in the sample train that is detected in ppm:

Leak check that are less than 5% are acceptable. If a significant leak is present, check the sample train for potential leaks. Make necessary adjustments to the sample train, re -apply helium to the shroud if needed, and recheck helium levels in the sample train.

Note: Moisture and other gases, such as methane, can give false positives for helium in the sample train.

If no leaks or an acceptable leak is present, close valves to the sample train (Valve 1) and open sample canister valve (see Sample Collection).

Leak check using isopropyl alcohol
Tools needed – Rubbing alcohol, cotton wipes, nitrile gloves.

Once all connections (sample train, Summa™ canister, soil vapor probe) have been made, set up a shroud that cover the sample train, Summa™ canister, and soil vapor probe. Open the isopropyl alcohol bottle and set it inside of the shroud. Do not spill or place isopropyl alcohol on the Summa™ ™ connections. Measure the isopropyl alcohol concentration inside of the shroud using a PID meter and record the value on field note. The isopropyl alcohol shroud should have a PID reading of 5 ppm during the sampling process.

SAMPLE COLLECTION
Open the Summa™ canister valve to initiate sample collection. Record the time when sampling began and the canister pressure on the sample log. If the initial vacuum pressure registers less than -25 in-Hg, the Summa™ canister is not appropriate for sampling and another canister should be used. Once the vacuum pressure reaches -5 in-Hg, record the final vacuum and time, close the valve. Disconnect the flow controller and Summa™ canister from the soil vapor probe, reinstall the brass plug on the canister fitting, and tighten with the appropriate wrench.

Notes: the valve only needs to be finger tight. Do not use a wrench to tighten. For the brass cap, twist the cap on using your fingers, until it is “finger-tight” and then use a 9/16” wrench to ensure it is snug. Do not overtighten.

Upon sample retrieval, the Summa™ canisters should be labeled with the appropriate project information, including the project name, project number, sample location and depth, date and time of sampling, sampler’s name, canister identification number, and the initial and 𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 𝑡𝑡𝑡𝑡𝑠𝑠𝑡𝑡𝑡𝑡 ℎ𝑠𝑠𝑠𝑠𝑡𝑡𝑒𝑒𝑠𝑠 %
helium shroud %
x 100% = Leak Check %
𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠 𝑡𝑡𝑡𝑡𝑠𝑠𝑡𝑡𝑡𝑡 ℎ𝑠𝑠𝑠𝑠𝑡𝑡𝑒𝑒𝑠𝑠 𝑠𝑠𝑠𝑠𝑠𝑠
helium shroud %
x
1%
10,000 ppm
x 100% = Leak Check %
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final canister vacuums. Chain-of-custody documentation was completed and accompanied the Summa™ canisters to the analytical laboratory. The Summa™ canister does not require preservation with ice or refrigeration during shipment.

For field sample collection, samples should be collected with an average flow rate of 200 milliliters per minute into the Tedlar bag using a syringe. Field samples should be analyzed immediately.

Figure 1 – Swagelok connection

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Figure 2: Tools and Additional Swagelok Fittings

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Figure 3 – Sample train set up

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References
California Department of Toxic Substances Control (DTSC), et al. Advisory: Active Soil Gas Investigations, prepared by the, dated July 2015.

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Sunnyvale City CouncilMarch 24, 2026

Sunnyvale City Council
March 24, 2026