PG&E Topock Compressor Station Site: Installation of Conveyance Piping and Power Supply for Extraction Well PE-1
Summary
SCH Number
2005108174
Public Agency
Department of Toxic Substances Control
Document Title
PG&E Topock Compressor Station Site: Installation of Conveyance Piping and Power Supply for Extraction Well PE-1
Document Type
NOE - Notice of Exemption
Received
Posted
10/7/2005
Document Description
Pursuant to Chapter 6.5 of the California Health & Safety Code, the Department of Toxic Substances Control has approved a Corrective Action Work Plan submitted by PG&E that describes actions to be undertaken in a floodplain near the Topock Compressor Station site to prevent groundwater contaminated with hexavalent chromium from entering the waters of the Colorado River.
Contact Information
Name
Norman Shopay
Agency Name
Department of Toxic Substances Control
Contact Types
Lead/Public Agency
Phone
Location
Counties
San Bernardino
Regions
Unincorporated
Notice of Exemption
Exempt Status
Emergency Project
Type, Section or Code
Section 15269(b)(c)
Reasons for Exemption
An Interim Measure (IM) is currently being implementd by PG&E to address hexavalent chromium in groundwater at the site. The IM consists of a groundwater extraction and treatment system that provides hydraulic control of the groundwater plume boundaries located near the Colorado River. Due to the influence of the Colorado river stage on groundwater levels, DTSC determined that extracting groundwater at a rate of approximately 130 gallons per minute (gpm) was necessary to maintain the stated goal of hydraulic control. To achieve this extraction rate, DTSC directed PG&E to install one deep extraction well (TW-2D) with a pumping capacity of 90 gpm, one shallow extraction well (TW-2S) with a pumping capacity of 40 gpm, and a monitoring well (MW-34-100) in the floodplain area of the Colorado River.
Despite preliminary successes achieved by the IM, recent samples collected on September 20, 2005 show that concentrations of hexavalent chromium in MW-34-100 located approximately 65 feet from the Colorado River, increased from 400 ppb to 675 ppb from when the well was installed in February 2005 (the California MCL for total chromium is 50 ppb). This suggests that hydraulic control of the contaminated groundwater is not being maintained. Compounding this problem, beginning in September 2005 and continuing through January 2006, Colorado River levels are expeced to decline, requiring an increase in pumping rates in the deeper, more contaminated portion of the aquifer near MW-34-100 in order to maintain sufficient gradients away from the river. Immediate hook-up and operation of an existing extraction well (PE-1) installed in March 2005 in the floodplain area would provide an additional pumping capacity necessary to regain hydraulic control of the contaminated groundwater.
Disclaimer: The document was originally posted before CEQAnet had the capability to host attachments for the public. To obtain the original attachments for this document, please contact the lead agency at the contact information listed above. You may also contact the OPR via email at state.clearinghouse@opr.ca.gov or via phone at (916) 445-0613.