Soil And Groundwater Remediation
CATEGORY OF SERVICE, LOCATION:
Dual-Phase Soil Vapor and Groundwater Extraction (DPE) and Treatment System Operation and Maintenance (O&M), Napa, California
TYPE OF CLIENT:
Commercial Property Owner
BACKGROUND:
The subject property (Site) is a former dry cleaner with a release of the chlorinated volatile organic compound (CVOC) tetrachloroethene (PCE) and it’sits degradation products into the environment. Sub-surface clean-up activities are being performed under oversight of the San Francisco Bay Regional Water Quality Control Board.
CLIENT GOALS:
The goals of the DPE soil vapor and groundwater extraction and treatments system is to: 1) capture CVOCs in the subsurface to remove potential health risks to Site workers and nearby residences and to 2) allow potential redevelopment of the Site property. The radius of soil vapor and groundwater extraction influence and success of the subsurface remediation system is based on a network of groundwater and vapor monitoring points installed to demonstrate remedial success.
PROJECT APPROACH:
Soil vapor extraction is from shallow depths using a skid-mounted blower, control panel (see attached photograph), and moisture separation vessel to extract vapors from an excavation backfill extraction well and two soil vapor extraction wells before carbon treatment and discharge to the atmosphere under permit from the Bay Area Air Quality Management District.
Groundwater extraction is from three successively deeper water-bearing zones to depths of 100 feet using suing dedicated, submersible pumps before carbon treatment and discharged to the publicly owned treatment system under permit from the Napa Sanitary District.
Trinity installed groundwater and soil vapor extraction wells using designs based on the results of pilot studies and feasibility analysis; the pilot studies consisted of groundwater and soil vapor extraction and also the injection of liquefied carbon to assess the effectiveness of in-situ sorption and biodegradiationbiodegradation or injection of other remedial substances.
Trinity performed Site assessment, remediation feasibility studies, remedial system design, remedial system construction, and system O&M operation and maintenance in compliance with regulatory directives and reporting including schedules.
Trinity conducted extraction well and remediation system sampling and laboratory sample analysis in accordance with discharge permitting conditions.
Trinity maintained consistent operation of the DPE soil vapor and groundwater extraction and treatment system by following design specifications and understanding the dynamics of system operation and maintenance.
RESULTS, RESOLUTION, NEXT STEPS:
Trinity created a radius of extraction influence that captured the majority of the CVOC plume in soil vapor and groundwater in order to allow the property owner to have greater options in the disposition of the Site property in the future. The DPE system will and to eventually reduce CVOC concentrations to below clean-up goals to achieve regulatory case closure for on-site areas only.
CATEGORY OF SERVICE, LOCATION:
Active Sub-Slab Vapor Depressurization System (design, construction, O&M), Alameda, CA
TYPE OF CLIENT:
Property Development/Management Company
BACKGROUND:
While reviewing the site for closure, Alameda County requested the collection of sub-slab vapor samples for volatile organic compound (VOC) and Stoddard Solvent analysis to determine if the former dry cleaning operations at the site affected soil beneath the building and resulted in the potential for vapors to migrate into the building. A sampling program was designed and implemented and sub-slab vapor results indicated elevated levels tetrachlorethene, vinyl chloride, carbon tetrachloride and Stoddard solvent were present beneath the building. Mitigation of the vapor intrusion risk to indoor air for the commercial building was warranted. A sub-slab depressurization pilot test was conducted, followed by the design and installation of an active sub-slab depressurization system.
CLIENT GOALS FOR PROJECT:
Mitigate the vapor intrusion risk to indoor air for the commercial building in the most cost-effective manner without significantly disturbing the building tenants or their business operations.
PROJECT APPROACH:
Trinity conducted a sub-slab depressurization pilot test during the weekend after business hours to determine if an active or passive system was needed to mitigate the vapor intrusion concern. Pilot test results indicated that an active sub-slab depressurization system (SSDS) with carbon abatement was needed for the site. The system was designed, permitted, installed and operated and maintained by Trinity.
RESULTS, RESOLUTION, NEXT STEPS:
The SSDS startup and continued operation was successful at mitigating the vapor intrusion pathway beneath the building. The SSDS system influent concentrations reduced significantly enough to cease carbon abatement before discharge to the atmosphere and modify the air permit from monthly to quarterly system monitoring.
The next step is to shut the SSDS down to evaluate rebound effects and determine if sub-slab VOC and Stoddard solvent concentrations are below closure action levels. A component of this phase will be to determine a site-specific attenuation factor to apply to the sub-slab vapor concentrations. Radon gas testing in the sub-slab vapor and inside the building are proposed in order to develop a suitable attenuation factor.
CATEGORY OF SERVICE, LOCATION:
Soil Remediation – Lead Contaminated Soil Removal, Santa Cruz, CA
TYPE OF CLIENT:
City Government – City of Santa Cruz Water Department
Lead Soil Remediation – Excavation
BACKGROUND:
The City of Santa Cruz Water Department had hazardous levels of lead in soil around one of their million plus gallon water tanks. The City needed to remove the lead impacted soil from around the water tank so that work crews could upgrade and retrofit the tank without coming in contact with hazardous levels of lead in soil.
CLIENT GOALS FOR PROJECT:
Remove hazardous levels of lead in soil around the water tank.
Collect confirmation soil samples from excavation limits to document soil cleanup levels have been achieved.
Compact backfill material to 90% relative compaction and document with testing.
Complete all work within 15 days from signing the contract.
Coordinate with the City’s consultant and Santa Cruz County Environmental Health to ensure client goals are met within the project schedule.
PROJECT APPROACH:
Lead Soil Remediation – Disposal
Trinity was awarded a fixed-fee contract with the City under competitive bid to excavate, profile, dispose, confirmation soil sample, backfill and compact, compaction test and regrade the area around the water tank. Pre-excavation soil samples were collected to define the excavation areas with hazardous levels of lead in soil and to pre-profile soils for disposal at either an out-of-state or in state hazardous waste disposal facility. The project had a 15 day window from the date of the signed contract and authorization to proceed so that the City could open the site up for the water tank retrofit contractor.
RESULTS, RESOLUTION, NEXT STEPS:
Pre-profile soil sampling conducted by Trinity defined the area of excavation, identified an additional deeper area to excavate and provided data for profiling the hazardous waste at an appropriate landfill.
Over 100 tons of hazardous waste lead soil was excavated and disposed off site.
Excavation limits and soil cleanup goals were achieved and the project was completed within the clients 15 day window.
Backfilled areas were compacted and tested at or above 90% relative compaction.
Trinity achieved the client and regulatory goals for the soil remediation project.
CATEGORY OF SERVICE, LOCATION:
Soil Remediation – Total Petroleum Hydrocarbons (TPH) and Lead Contaminated Soil Removal, Salinas, CA
TYPE OF CLIENT:
Non-Profit Organization – Monterey Bay Area (Watsonville and Salinas)
TPH and Lead Soil Remediation – Excavation
BACKGROUND:
Trinity conducted Phase I and II Environmental Site Assessments for the property as part of a real estate transaction. Our client was divesting all of their property holdings for transfer of assets to another non-profit organization. While defining a tetrachloroethene (PCE) soil vapor plume with 5 and 15 foot soil vapor probes, TPH and lead impacted soil was found to exist in the parking lot area of the site. The TPH and lead impacted soil area was defined by the drilling of over 20 soil borings. Soil data from the borings was used to pre-profile the soil at a local landfill. The impacted soil was found to run through the site in line with a historic filled in slough.
CLIENT GOALS FOR PROJECT:
Define the area needing soil remediation and provide cost to closure figures in a timely manner so that escrow could close within the client specified time frame and monies could be held in escrow to clean up the site for the new property owner.
Excavate and remove TPH and lead impacted soil to County of Monterey Environmental Health approved action levels.
Perform work on an expedited schedule and coordinate site work with the new owner, tenants, and adjacent private property owners.
Obtain site closure.
PROJECT APPROACH:
TPH and Lead Soil Remediation – Shoring
Trinity prepared a soil remediation work plan and got it approved by the County of Monterey immediately after the property was sold. The approved work plan defined an area of over 1,000 cubic yards needing remediation via soil over-excavation and off-site disposal. Shoring of the deeper parts of the excavation area was needed along the property line with two adjoining private property owners. Existing soils data from numerous soil borings defined most of the excavation limits but additional bottom confirmation soil samples were needed to document TPH and lead closure levels were achieved.
RESULTS, RESOLUTION, NEXT STEPS:
On an expedited schedule, Trinity obtained a grading permit and mobilized to the site to excavate the contaminated soil.
Over 100 feet of sheet pile shoring with whalers was installed along the southern and western property lines.
2,200 tons of TPH and lead impacted soil was removed and disposed off-site.
Eight confirmation soil samples were collected from the excavation bottom and one area was over-excavated deeper to remove lead impacted soil over accepted levels.
Backfilled areas were compacted and tested at or above 90% relative compaction and 95% relative compaction beneath asphalt paved areas.
Site restoration activities were completed promptly and approved by the new owner.
Trinity achieved the client and regulatory goals for the soil remediation project.
Soil excavation report is in progress and site area closure is expected.
CATEGORY OF SERVICE, LOCATION:
Soil Remediation – Total Petroleum Hydrocarbons (TPH) Contaminated Soil Removal, Fremont, CA
TYPE OF CLIENT:
Electric Auto Manufacturer (Tesla Motors)
TPH Soil Remediation
BACKGROUND:
Trinity was contacted by Integrated Engineering Services, Inc. (IES) to provide Tesla Motors with soil remediation services. Tesla was expanding their plan operations to manufacturer the new electric SUV and building expansion was needed for a new metal die cast parts building. The new building was to be built over an area that had historic TPH use and surface soil staining was visible on gravel and pavement areas. Tesla needed this TPH impacted soil removed before the new die cast metal parts building could be constructed.
CLIENT GOALS FOR PROJECT:
Obtain all permits and County and State approval to excavate TPH affected soils.
Collect excavation confirmation soil samples to determine if all TPH affected soils were removed.
Perform all work on a RUSH as soon as possible basis.
Work safely and per Tesla Health and Safety guidelines and have all field crew take required safety training at the plant before starting work.
Dispose of all TPH soils off-site at an appropriate landfill facility
Document work in a letter report.
PROJECT APPROACH:
TPH Soil Remediation
Trinity prepared a soil remediation work plan, health and safety plan, job safety analysis and provided those documents to IES and Tesla Staff for review and approval. a utility locating company,Cruz Brothers Locators out of Scotts Valley, was retained to perform underground utility locating before starting work. The excavation area was marked with white paint and USA North was called 48 hours prior to digging as required by law.
RESULTS, RESOLUTION, NEXT STEPS:
On an expedited schedule, Trinity mobilized to the site to perform soil excavation activities.
Asphalt concrete was removed using a gasoline powered saw and a backhoe.
Excavated soils were placed in 20-cubic yard roll off soil bins.
Approximately 20 cubic yards of TPH affected soils were removed from the proposed die cast metal parts building footprint.
Excavation bottom samples were collected once excavation limits were achieved.
Samples of stockpiled soil in soil bins were collected.
All soil samples were submitted to McCampbell Analytical, Inc. for selected analyses.
Excavation bottom samples were either non-detect for TPH and other potential chemicals of concern or below State and County action levels for a commercial property.
Stockpiled soil sample results indicated that the excavated soil could be disposed of at a non-hazardous local landfill facility.
Tesla was satisfied with the work performed, RUSH work schedules were achieved and the die cast metal parts building in under construction.
A report documenting the above activities was submitted to IES and Tesla for their files. No further corrective action work was necessary.
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