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Phase I/II Environmental Site Assessments and Site Cleanup
Baseline has performed over 300 Phase I/II ESAs in the Bay Area, including urban redevelopment sites, industrial properties, school sites, former gas stations, auto repair facilities, fire stations, and highway expansion corridors. Our assessments are prepared by experienced professionals who are thoroughly familiar with the potential sources of contamination in urban environments that could affect development and environmental liability. We routinely prepare and oversee implementation of a range of remediation and soil management plans that vary depending on the nature and complexity of contamination. We typically use a risk-based approach to achieve project-specific objectives and site closures from applicable regulatory agencies. Baseline also routinely performs peer reviews of environmental assessments and remedial action plans on behalf of public agencies.
Examples of Environmental Site Investigation and Cleanup Projects
Former Oakland Army Base - RMP Location 167B
In 2021, Baseline oversaw remedial excavation of lead contaminated soil at the Former Oakland Army Base in an area identified as RMP Location 167B. The soil had very high levels of lead which classified much of the soil as federal hazardous waste. The elevated lead in soil appeared to correlate with a red material observed in the soil that was suspected to be related to historical ship maintenance activities in the area.
Baseline performed air monitoring for dust and lead and collected confirmation soil samples during the initial excavation activities. Although the planned excavation area had been horizontally delineated by samples collected prior to the start of excavation, the observation of red material in an excavation sidewall and confirmation sampling results necessitated further investigation and remediation. Multiple rounds of additional investigation and a second round of remedial excavation were performed in 2021 until physical restraints prevented further excavation.
In 2024, Baseline performed additional investigation activities to delineate the extent of lead impacted soil to the west of the previously remediated area. The impacts from lead were found to extend beneath an occupied building that was packed full of equipment and heavy objects that could not be moved, and the presence of other physical constraints (e.g., a wash rack structure and utilities) further complicated the sampling effort. Baseline successfully delineated the extent of lead impacted soil which required strategic selection of sample locations and collection of step-out samples that were placed on hold and analyzed as needed to accurately define the extent of contamination.
Baseline developed proposed excavation limits and performed waste characterization analysis to pre-classify the soil for waste disposal from the various excavation cells. All remediation and investigation activities were performed under the oversight of DTSC, and Baseline completed the project on-time and under budget.
Baseline performed air monitoring for dust and lead and collected confirmation soil samples during the initial excavation activities. Although the planned excavation area had been horizontally delineated by samples collected prior to the start of excavation, the observation of red material in an excavation sidewall and confirmation sampling results necessitated further investigation and remediation. Multiple rounds of additional investigation and a second round of remedial excavation were performed in 2021 until physical restraints prevented further excavation.
In 2024, Baseline performed additional investigation activities to delineate the extent of lead impacted soil to the west of the previously remediated area. The impacts from lead were found to extend beneath an occupied building that was packed full of equipment and heavy objects that could not be moved, and the presence of other physical constraints (e.g., a wash rack structure and utilities) further complicated the sampling effort. Baseline successfully delineated the extent of lead impacted soil which required strategic selection of sample locations and collection of step-out samples that were placed on hold and analyzed as needed to accurately define the extent of contamination.
Baseline developed proposed excavation limits and performed waste characterization analysis to pre-classify the soil for waste disposal from the various excavation cells. All remediation and investigation activities were performed under the oversight of DTSC, and Baseline completed the project on-time and under budget.
CCC Fire Protection District, 1300 Civic Drive, Walnut Creek
In 2025, Baseline performed a Phase I ESA to support the Contra Costa County Fire Protection District’s plan to purchase a vacant commercial building located adjacent to an existing fire station. Prior to development of the commercial building, the site had historically been used as an orchard and subsequently as a gas station and auto service facility in the 1960s and 1970s. No documentation regarding the removal of USTs from the site was identified. The adjacent fire station formerly had fuel USTs which had leaked and potentially contaminated the site. A nearby and directly upgradient property was historically used as a truck repair facility which had leaking USTs. Based on the past land uses identified at the site and surrounding properties, the potential for contamination from agricultural chemicals (e.g., arsenic and pesticides), petroleum hydrocarbons, VOCs, PAHs, heavy metals, and PCBs was identified for the site.
In 2025, Baseline advanced 8 borings and installed five sub-slab vapor probes to collect soil, groundwater, and soil vapor samples for chemical analysis. Physical signs of petroleum contamination were observed beneath the former gas station building/auto repair facility; however, the soil sample analytical results revealed only relatively minor concentrations of petroleum hydrocarbons and VOCs. Other soil and groundwater sampling results identified no detectable concentrations of contaminants. Various VOCs were detected in soil vapor samples at concentrations below applicable Environmental Screening Levels (ESLs) established by the Regional Water Board. Baseline recommended no further investigation and preparation of a Soil Management Plan prior to performing any subsurface construction activities to ensure that contaminated soil would be property managed, if encountered. Baseline completed the project on-time and under budget.
In 2025, Baseline advanced 8 borings and installed five sub-slab vapor probes to collect soil, groundwater, and soil vapor samples for chemical analysis. Physical signs of petroleum contamination were observed beneath the former gas station building/auto repair facility; however, the soil sample analytical results revealed only relatively minor concentrations of petroleum hydrocarbons and VOCs. Other soil and groundwater sampling results identified no detectable concentrations of contaminants. Various VOCs were detected in soil vapor samples at concentrations below applicable Environmental Screening Levels (ESLs) established by the Regional Water Board. Baseline recommended no further investigation and preparation of a Soil Management Plan prior to performing any subsurface construction activities to ensure that contaminated soil would be property managed, if encountered. Baseline completed the project on-time and under budget.
San Francisco Under Ramp Park
In 2018, Baseline performed a Phase I Environmental Site Assessment (ESA) to support the City of San Francisco’s planned development of a public park spanning across several blocks located below a freeway off-ramp and access ramps of the Transbay Terminal. The Phase I ESA found that the proposed park site had historically been used for various industrial purposes that likely involved the use of hazardous materials (e.g., foundries and machine shops) and soil impacted with elevated concentrations of metals was identified beneath the site.
A Phase II ESA Workplan was approved by the SFDPH in December 2018; however, the project was placed on hold due to archeological resource-related issues. In 2024, Baseline prepared a Revised Phase II ESA Workplan and advanced 13 borings to collect soil, soil vapor, and groundwater samples for chemical analysis. Elevated concentrations of petroleum hydrocarbons, heavy metals, cyanide, and polycyclic aromatic hydrocarbons were detected in soil samples collected from the site. Based on the proposed limits of excavation, Baseline delineated areas where soil would require disposal as a hazardous waste. For contaminated soil that would remain onsite, Baseline recommended preparation and implementation of a Cap Management Plan, which is currently being prepared.
Baseline performed an evaluation of vapor intrusion risks based on an elevated concentration of benzene detected in soil vapor near a proposed concessions building. Baseline’s evaluation accounted for the proposed building construction plans and ventilation system and determined that vapor intrusion should not be a concern for the concessions building. An elevated concentration of trichloroethylene (TCE) was identified in one soil vapor sample, and Baseline performed additional investigation activities to evaluate the extent of TCE contamination in soil, groundwater, and soil vapor. SFDPH referred further investigation and remediation of the TCE contamination to the Regional Water Board, and Baseline is currently coordinating with the project stakeholders and Regional Water Board to further investigate the source and extent of TCE contamination.
A Phase II ESA Workplan was approved by the SFDPH in December 2018; however, the project was placed on hold due to archeological resource-related issues. In 2024, Baseline prepared a Revised Phase II ESA Workplan and advanced 13 borings to collect soil, soil vapor, and groundwater samples for chemical analysis. Elevated concentrations of petroleum hydrocarbons, heavy metals, cyanide, and polycyclic aromatic hydrocarbons were detected in soil samples collected from the site. Based on the proposed limits of excavation, Baseline delineated areas where soil would require disposal as a hazardous waste. For contaminated soil that would remain onsite, Baseline recommended preparation and implementation of a Cap Management Plan, which is currently being prepared.
Baseline performed an evaluation of vapor intrusion risks based on an elevated concentration of benzene detected in soil vapor near a proposed concessions building. Baseline’s evaluation accounted for the proposed building construction plans and ventilation system and determined that vapor intrusion should not be a concern for the concessions building. An elevated concentration of trichloroethylene (TCE) was identified in one soil vapor sample, and Baseline performed additional investigation activities to evaluate the extent of TCE contamination in soil, groundwater, and soil vapor. SFDPH referred further investigation and remediation of the TCE contamination to the Regional Water Board, and Baseline is currently coordinating with the project stakeholders and Regional Water Board to further investigate the source and extent of TCE contamination.
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