The groundwater
and Colorado River water monitoring activities that began in 1997 as part
of the RCRA Facility Investigation/Remedial
Investigation (RFI/RI) groundwater investigations have been incorporated
into an ongoing Groundwater Monitoring Program. Installation and continual
monitoring of additional wells has occurred throughout the program. Five
wells installed in 2007 are "slant" or angled wells, extending underneath
the Colorado River, and allow for groundwater sampling below the river bottom.
Five new vertical wells and three slant wells were installed on the Arizona
shoreline in March and April 2008. In 2009, 13 new wells were installed
at the Topock Site (Site) in the area of the Topock Compressor Station (Station)
known as the East Ravine.
The current Groundwater Monitoring Program includes over 100 monitoring wells. Sampling for hexavalent chromium and dissolved total chromium occurs:
- monthly in 7 wells,
- quarterly in 24 wells, 4 river shoreline, and 12 in-channel river locations (monthly during low river stages)
- semiannually in 33 wells,
- annually in 30 wells, and
- biennially in 16 wells
PG&E also conducts sampling and analysis for other constituents and water
chemistry parameters quarterly in selected wells. Several other wells in
the area are sampled on a less frequent schedule, and private domestic or
agricultural wells are sampled as requested.
PG&E reports monitoring results to the Department
of Toxic Substances Control (DTSC) and submits quarterly sampling
reports summarizing the sampling activities that occurred in that quarter.
DTSC shares these reports with the Consultative
Workgroup (CWG) and places them in the information
repositories and in this website’s Document Library.
To view figures showing groundwater and river sampling locations, or the most recent plume maps based on quarterly groundwater data, please click on the figures and links to the right.
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