Phase II Site Assessment: Soil, Soil Gas, And Groundwater Characterization
CATEGORY OF SERVICE, LOCATION:
Vapor intrusion assessment for a commercial building in downtown Oakland, Radon Study
TYPE OF CLIENT:
Nonprofit, Child-Care Center
BACKGROUND:
Alameda County Department of Environmental Health (ACDEH) requested a radon study to determine a Site-specific building slab attenuation factor for assessing vapor intrusion to indoor air
Radon gas is ubiquitous and naturally occurring in the environment
Radon gas is an established tracer compound for the migration of vapor from the sub-slab to indoor air
Comparison of radon measurements from sub-slab vapor and indoor air generated a site-specific attenuation factor
Trinity used the site-specific attenuation factor to calculate site-specific screening levels for volatile organic compounds (VOCs) in sub-slab vapor
CLIENT GOALS FOR PROJECT:
Demonstrate de minimis risk from vapor intrusion to indoor air and obtain permission to occupy the building
PROJECT APPROACH:
RADON SAMPLING
Trinity monitored radon concentrations from three locations throughout the building in sub-slab vapor and indoor air over a period of 24 hours
Trinity performed statistical analysis of the radon data and established a site-specific attenuation factor for vapor intrusion to indoor air based on the 95% upper confidence limit of the mean (95UCL)
RESULTS, RESOLUTION, NEXT STEPS:
The site-specific attenuation factor was ten times lower than the default attenuation factor used by the San Francisco Bay Regional Water Quality Control Board to determine sub-slab vapor contaminant concentrations, which allowed for higher-than-default screening values for sub-slab vapor at the site
The site-specific screening values established by the attenuation factor reduced the number of contaminants of concern identified for the site
Trinity used the attenuation factor to perform a site-specific human health risk assessment to evaluate the cumulative future risk for building occupants
Trinity presented the results to the ACDEH. The ACDEH granted permission to occupy the building with the condition that IQAir filtration units be placed as an interim mitigation measure to protect indoor occupants
Trinity facilitated the placement of IQAir units within the building, established a quarterly Operations & Maintenance plan, and the building was occupied.
CATEGORY OF SERVICE, LOCATION:
Soil, Groundwater, high resolution site characterization (HRSC), and Soil Gas Assessment, Napa, California
TYPE OF CLIENT:
Former Dry Cleaners Property Owner
BACKGROUND:
The former dry cleaner operated for more than 30 years and was previously shown to have impacted groundwater with solvents, but the extent of soils and soil gas impacts were unknown. Onsite and offsite utility lines were identified as potential conduits for solvent migration.
CLIENT GOALS FOR PROJECT:
The property owner seeks to redevelop the property and/or potentially sell, and wants to have the site characterization and remediation completed without adversely affecting redevelopment plans or scheduling.
PROJECT APPROACH:
Trinity developed a workplan and provided project updates for the San Francisco Bay Area Regional Water Quality Control Board (SFBRWQCB) review, addressing request for a site conceptual model, utilities as conduits, and consideration of multiple point sources at former dry cleaning establishment.
All soil borings, monitoring wells, and soil vapor probes have been properly permitted through the County of Napa, and also City of Napa, Public Works-Encroachment.
Investigations incorporated soil gas screening, Hydraulic Profiling Tool (HPT), Membrane-Interface Probe (MIP), cone penetrometer testing (CPT), and shallow and deep well installation utilizing auger drilling, direct push-Geoprobe drilling, and Sonic drilling technologies. Multiple field events were performed with informal reporting to the RWQCB, to optimize the project schedule.
Completed assessment identifying area of soils impact and delineating extent of shallow groundwater and soil vapor impacts.
Soil vapor delineation was performed by sampling all existing soil vapor probes using a mobile laboratory for real time analytical results; followed by “step out” installation and sampling of additional soil vapor probes till the soil vapor plume was defined to the residential environmental screening levels. The additional soil vapor locations were installed using a AMS driven probe assembly, which allows for quick installation and sampling.
Onsite and offsite deep, Unit 2 and Unit 3 groundwater monitoring wells were installed using Sonic drilling technologies to approximate total depths of 65 and 100 feet below ground surface, respectively.
Further offsite characterization was performed using HRSC subsurface profiling technologies, using the MIP which is the only commercially available tool capable of detecting both chlorinated and non-chlorinated volatile contaminants in the soil, and also in the gaseous, absorbed, dissolved, or free phases. A flame ionization detector (FID), halogen specific detector (XSD), electron capture detector (ECD), and photoionization detector (PID) measures the total VOCs in the carrier gas and immediately registers this information profiled with depth. A combined hydraulic profiling tool (HPT) was also used to help identify and evaluate the hydraulic behavior of the unconsolidated materials, as the probe is pushed and/or hammered down water is pumped through a screen and the pressure responses are monitored.
RESULTS, RESOLUTION, NEXT STEPS:
Field investigation is in progress, to complete the vertical and lateral delineation of impacts in groundwater.
CATEGORY OF SERVICE, LOCATION:
Indoor Air Sampling, San Mateo County, California
TYPE OF CLIENT:
Former Dry Cleaners Property Owner
BACKGROUND:
The property is an industrial building which formerly housed a dry cleaners. Sub-slab vapor was found to have elevated concentrations of dry cleaning solvents, exceeding regulatory screening levels. Remediation using soil vapor extraction was conducted to reduce the solvent concentrations in sub-slab vapor. Indoor air sampling was conducted to determine whether regulatory screening levels were exceeded for dry cleaning solvents.
CLIENT GOALS FOR PROJECT:
The property owner is seeking case closure in order to sell the property.
PROJECT APPROACH:
Trinity developed a workplan for San Mateo County review, describing the protocols for indoor air sampling, consistent with guidance from the California Department of Toxic Substances Control, Cal-EPA.
Trinity conducted a pre-sampling inventory of the building, to identify potential sources of solvent vapors that could interfere with the indoor air sampling.
Samples were collected into certified clean Summa canisters over a 24-hour timeframe, and included an ambient air sample.
Following indoor air sample collection, selected sub-slab probes were sampled. Results were used to determine a site-specific attenuation factor, and in turn, a site-specific screening level for concentrations of solvents in sub-slab vapor.
The indoor air sampling was repeated to provide data from wet and dry seasons.
RESULTS, RESOLUTION, NEXT STEPS:
Indoor air concentrations were found to be at acceptable levels.
Post-remediation sub-slab vapor concentrations are below the site-specific screening levels. Therefore, Trinity recommends no further action.
CATEGORY OF SERVICE, LOCATION:
Soil and Groundwater Site Characterization, Hanford, California
TYPE OF CLIENT:
Major Oil Company
BACKGROUND:
Client had previously disposed refinery liquid wastes and sludge in a surface impoundment at a municipal landfill. The impoundment was subsequently covered with soil, and the landfill was closed. The impoundment area was sold to a private landowner. Previous characterization did not evaluate groundwater, and did not establish extent of impacts laterally or vertically. Regional Water Quality Control Board (RWQCB) requested additional characterization.
CLIENT GOALS FOR PROJECT:
Client goal was to determine cost-effective path to closure for this site.
PROJECT APPROACH:
Trinity developed a workplan for RWQCB review.
Characterization utilized Ultraviolet Optical Screening Tool (UVOST), cone penetrometer testing, soil borings to confirm UVOST data, monitoring well installation
Assessment was completed to RWQCB satisfaction. The assessment included pre-profiling of excavated soils if generated, and provided geotechnical and geochemical data for evaluation of remedial approaches including soil remediation via excavation and disposal and risk assessment modeling.
Risk-assessment approach including fate and transport modeling of chemicals of concern is being utilized to demonstrate that leaving residual waste in-place poses no human health or environmental risk.
RISC4 model is being utilized to evaluate human health and environmental risk based on site-specific data, and potential future impacts to groundwater.
RESULTS, RESOLUTION, NEXT STEPS:
Soil and groundwater impacts were shown to be fairly limited in extent. Combined with the site setting, these results suggested risk assessment would be a cost-effective approach in recommending no further action for site.
Negotiations with RWQCB are in progress.
Continued groundwater monitoring and reporting to establish flow direction, gradient and dissolved plume concentration trends.
CATEGORY OF SERVICE, LOCATION:
Soil and Groundwater Site Characterization, Hollister, California
TYPE OF CLIENT:
Industrial Manufacturing Company
BACKGROUND:
Site is location of former ordnance facility, with known perchlorate and solvent impacts to soil and groundwater. Complex hydrogeologic setting is present, with multiple aquifers and extensive faulting. Offsite wells tap two deeper aquifers for water supply. RWQCB requested offsite plume delineation in three successively-deeper aquifers.
CLIENT GOALS FOR PROJECT:
Utilize several consulting firms working together as a project team
Achieve offsite plume delineation with minimum number of wells
Maintain regulatory compliance in a cost-effective manner
PROJECT APPROACH:
Well clusters were located offsite, with one well in each cluster targeting one of the three impacted aquifers. Well installations proceeded iteratively until plumes were delineated.
Deeper wells were installed using mud-rotary drilling with geophysical logging to allow geologic correlations throughout offsite area.
Twenty three wells were installed to depths ranging from 60 to 430 feet. Access agreements were secured with four property owners.
RESULTS, RESOLUTION, NEXT STEPS:
Offsite plumes in the second and third aquifers were shown to be non‑detect or of relatively low concentration; monitored natural attenuation will be recommended. The first aquifer low concentration perchlorate plume was shown to extend 3,000 feet off-site. An on-site property boundary groundwater containment and pump and treat system has been installed to stop the offsite migration of contaminants.
CATEGORY OF SERVICE, LOCATION:
Soil, Groundwater and Soil Vapor Characterization, (Data Gaps Assessment) Santa Cruz, California
TYPE OF CLIENT:
Major Oil Company
BACKGROUND:
Site is an operating retail service station, formerly owned by client. Several iterations of soil and groundwater assessment and remediation had been conducted over 20 years. Low residual hydrocarbon concentrations remain, but local agency and RWQCB would not close site due to data gaps.
CLIENT GOALS FOR PROJECT:
Achieve site closure, utilizing cost-effective remediation approach
PROJECT APPROACH:
Trinity assembled all past site data into a data gaps assessment, and proposed additional soil, groundwater and soil vapor sampling to address regulatory concerns. Onsite and offsite soil and groundwater investigation targeted data gaps, and soil vapor sampling provided data for evaluating this exposure pathway.
RESULTS, RESOLUTION, NEXT STEPS:
Additional assessment identified a limited area of soils and soil vapor impacts. Concentrations of MTBE and TBA in groundwater were low, but not below regulatory closure levels in downgradient wells.
Local agency is requesting additional assessment.
Trinity is proposing limited SVE to reduce residual source in soils and soil vapor, and batch extraction events in downgradient wells.
Continued groundwater monitoring and reporting to establish flow direction, gradient and dissolved plume concentration trends.
CATEGORY OF SERVICE, LOCATION:
Phase II Soil Assessment, San Jose, California
TYPE OF CLIENT:
Commercial Property Tenant
BACKGROUND:
The site is an operating ice cream truck distribution company with approximately 20 trucks servicing the San Jose area. Trinity was hired by the ice cream truck distribution company to perform soil sampling in areas where surface staining, open containers of oil, and stockpiles of used car parts were noted on the property.
CLIENT GOALS FOR PROJECT:
Determine if ice cream truck service operations on the property and the stockpiling of used car parts on the property contaminated surface soils.
PROJECT APPROACH:
Trinity prepared a hand auger and soil sampling work plan. The plan included a grid-pattern soil boring design for the affected areas of concern at the site and developed a sampling and analysis plan to determine if any impacts occurred to site soil based on past petroleum waste and used parts handling practices.
RESULTS, RESOLUTION, NEXT STEPS:
The site was marked with white paint for USA and a health and safety plan was prepared.
A total of 10 shallow, upper 3 feet, hand auger borings were drilled at the site in suspect areas.
Soil samples were collected from the hand auger borings at approximate depth intervals of 6 inches, 1.5 feet and 3 feet below grade.
Soil samples were submitted to a Califorinia-State certified laboratory for analysis for various petroleum hydrocarbon analyses and LUFT Metals; select deeper soil samples were placed on hold pending results from the laboratory for shallow-6 inch soil sample results.
All soil samples came back from the laboratory at concentrations below regulatory action levels for commercial property or non-detect.
No further action was warranted or recommended and the tenant was cleared of all potential contaminant liability associated with their ice cream truck fleet.
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