Groundwater Monitoring And Reporting

 

 

CATEGORY OF SERVICE, LOCATION:

Soil, Groundwater 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 not known. 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 wants to have the site characterization and remediation completed without adversely affecting redevelopment plans or scheduling.

PROJECT APPROACH:

  • Trinity developed a work plan for Regional Water Quality Control Board (RWQCB) review, addressing request for a site conceptual model, utilities as conduits, and consideration of multiple point sources at former dry cleaning establishment.
  • Investigation incorporated soil gas screening, Membrane-Interface Probe, cone penetrometer testing, and shallow and deep well installation utilizing auger drilling. Multiple field events were performed with informal reporting to the RWQCB, to avoid multiple iterations of reporting and workplan preparation.
  • Completed assessment identifying area of soils impact for potential excavation, and delineating extent of shallow groundwater and soil vapor impacts. Deeper water impacts to be addressed separately.

RESULTS, RESOLUTION, NEXT STEPS:

  • Field investigation is 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, 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 Remediation, Sunnyvale, California

TYPE OF CLIENT:

Major Oil Company

BACKGROUND:

  • Site is a former service station, redeveloped as a strip mall.
  • Soil and groundwater impacts have been defined.
  • Residual impacts in shallow water and capillary fringe remain
  • CAP recommended dual-phase extraction/air sparging (DPE/AS) utilizing three extraction and 30 sparge wells, but at an estimated cost of $750,000 to implement to achieve closure

CLIENT GOALS FOR PROJECT:

Cost-effective remediation, maintaining regulatory compliance.

PROJECT APPROACH:

  • Conducted 11-day DPE/AS pilot test to gain design parameters for SVE/AS system
  • Evaluate additional alternatives including risk assessment to achieve closure.

RESULTS, RESOLUTION, NEXT STEPS:

  • DPE/AS shown to be an effective remedial option based on pilot test results.  However, full-scale implementation may not be cost-effective, because most residual mass is in fine-grained soils.
  • Continued groundwater monitoring is underway to evaluate the longer-term effect of the DPE/AS test.
  • Site may be suitable for risk-based closure in view of low residual concentrations and lack of nearby receptors.
 

 

CATEGORY OF SERVICE, LOCATION:

Groundwater Monitoring Program Reduction, Santa Cruz, California

TYPE OF CLIENT:

Former Retail Service Station Owner/Operator

BACKGROUND:

The former station is currently an automobile repair business and was utilized as a gasoline station from 1950 until approximately 1987.  The waste oil tank and three underground storage tanks (USTs) and product islands were removed in 1992.  No USTs remain at the site.  A total of 29 groundwater monitoring wells define a commingled petroleum hydrocarbon plume which is approximately 800 feet long and 360 feet wide in an area of mixed residential, retail and commercial property uses.  The Central Coast Regional Water Quality Control Board (CCRWQCB) issued a Monitoring and Reporting Plan (MRP) for the site in August 2006.

CLIENT GOALS FOR PROJECT:

Reduce the MRP requirements for the 29 wells to reduce costs.

PROJECT APPROACH:

Prepare a detailed proposal for groundwater monitoring reduction including discussions on background and local land use, summary of well installations and plume definition, summary of site conditions, review of site Constituents of Concern (COCs) and propose a revised MRP.

RESULTS, RESOLUTION, NEXT STEPS:

  • Sampling frequency and laboratory analyte reductions were proposed and accepted.  Inter-plume and redundant data collection wells were placed on standby.  A revised and more cost effective MRP was prepared for the site by the CCRWQCB.

  • As a result of the monitoring reduction, costs for monitoring were reduced by approximately 50%.  Further monitoring reductions have reduced costs by an additional 10%.
 

 

CATEGORY OF SERVICE, LOCATION:

Soil Vapor Extraction System Operation and Maintenance, Monterey, California

TYPE OF CLIENT:

Underground Storage Tank (UST) Fund

BACKGROUND:

The site was formerly operated as a dry cleaner, with four USTs beneath the site from 1940s until 1963, when the property was purchased by our client.  Based on former employee indications, the dry cleaning facility contained equipment commonly used with Stoddard solvent cleaning processes, and chlorinated solvents such as tetrachloroethene (PCE) were not used during the time of operation.  The USTs were removed in 2000, a series of soil and groundwater investigations were conducted between 2000 and 2003 and a soil vapor extraction system was installed in 2004 under an approved Corrective Action Plan.

CLIENT GOALS FOR PROJECT:

Provide cost effective and responsive remedial system O&M for an occupied residential property.

PROJECT APPROACH:

As a cost savings measure, operate and maintain the SVE system during the low groundwater summer months and shut down the system during the higher groundwater winter months.  Collect monthly depth‑to‑groundwater level readings to optimize system operation and shut down periods based on water levels in SVE wells.

RESULTS, RESOLUTION, NEXT STEPS:

  • SVE mass removal rates are maximized during summer lower groundwater level months.  Additional shallow SVE wells installed and connected to the system to increase radius of influence in petroleum hydrocarbon-affected areas.  System expansion is planned to include dual‑phase extraction to address impacted groundwater in plume core.
  • Trinity identified a sewer line leak in the plume area.  The leak is a source of shallow groundwater in the affected area, and should be repaired to prevent further shallow groundwater impact.
  • Annual groundwater monitoring to evaluate system performance.