Groundwater Monitoring Services for Chevron USA

At the peak of this program, WPI provided quarterly monitoring and sampling for over 1,000 wells at more than 200 locations.  All work in is performed in accordance with requirements of the California Regional Water Quality Control Boards, and other local oversight agencies (e.g., the Counties of Orange, Ventura and San Diego).  Depth to water ranges from 5 to 95 feet at the various sites.


WPI performs the following tasks as part of the monitoring program:

  • Gauge/measure groundwater levels in all the wells by hand, (pressure-transducers that record groundwater levels at pre-determined intervals have been utilized periodically at various locations)
  • Depending on the agency requirements, wells are purged prior to sampling using the traditional or Micro-purge method. No purge sampling is conducted where it is allowed

Collect groundwater samples for the following analyses:

  • Total petroleum hydrocarbons as gasoline, diesel fuel and oil by modified EPA method 8015
  • Volatile organic compounds, including the fuel oxygenates and ethanol by EPA Method 8260B
  • Monitored Natural Attenuation (MNA) parameters dissolved oxygen, Oxygen Reduction Potential, methane, CO2, ferrous iron, nitrate, nitrite, sulfate, sulfite, alkalinity, total organic carbon, total dissolved solids, and pH

WPI responsibilities include the preparation of a Groundwater Monitoring Report for each site that documents field procedures and presents and analyzes analytical results for use by the primary environmental consultant and/or lead regulatory agency.  These reports include a comprehensive tabulation of groundwater data (gauging, elevation and analytical results) that is prepared and maintained by WPI staff. Reports also include scaled plot plans and isconcentration plots based on current analytical data that depict the distribution of dissolved phase of key constituents of concern (e.g., benzene, MTBE, TBA, etc.).  All reports receive a documented peer review as part of WPI’s internal QA/QC process, and are also reviewed, signed and stamped by a California professional geologist or engineer.


WPI also performs routine well maintenance and well development activities on an as-needed basis.  The WPI team is also responsible for coordination of sampling events with other consultants in instances where co-mingled plumes exist, as well as coordination of surveying and waste management subcontractors.  WPI staff up-load finalized Groundwater Monitoring Reports into the client developed database/file repository systems and the State Water Resources Control Board’s Geotracker database.