Groundwater Monitoring Services for Regional MTBE Investigation

WPI is presently sampling 55 wells screened in three water bearing zones ranging from 35 to 135 feet below ground surface. Groundwater has been monitored on an on-going basis by WPI since 2006. WPI performs the following tasks as part of the approved monitoring program:


Gauge/measure groundwater levels in all the wells (pressure-transducers programmed to record groundwater levels at 15-minute intervals have been utilized periodically during the project).


Wells are purged prior to sampling using the Micro-purge method.


Groundwater samples are collected 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

Our responsibilities include preparation and distribution of groundwater monitoring reports documenting field procedures and evaluating current groundwater conditions (elevation, gradient and flow direction) and the distribution of dissolved phase contaminants. These reports include a comprehensive tabulation of groundwater data (gauging, elevation and analytical results) that is prepared and maintained by WPI staff. Each quarterly report also includes a trend analysis that compares the most recent report to the four previous quarters. This analysis is automated and uses an algorithm written by WPI. All reports receive a documented peer review as part of WPI’s internal QA/QC process and are signed by a California professional geologist or engineer.


WPI performs routine well maintenance and well development activities as needed.  For example, as part of the remediation efforts at this site, there are numerous oxygen injection wells that require quarterly de-silting to maintain proper performance.