Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
South Indian Bend Wash Area
EPA #: AZD980695969
Congressional District: 00
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Description and History
NPL Listing History
Proposed Date: 12/30/82
Final Date: 09/08/83
The entire area of the Indian Bend Wash Superfund Site (IBW Site) covers approximately 13 square miles in Scottsdale and Tempe, Arizona. EPA divided the Site into two areas known as North Indian Bend Wash (NIBW) and South Indian Bend Wash (SIBW). NIBW and SIBW are on separate cleanup tracks.
This Site Overview focuses on SIBW only. More information on NIBW can be found at: NIBW.
EPA and ADEQ have been involved in investigations and cleanup activities at NIBW and SIBW since the initial discovery of VOCs in the groundwater in 1981. The entire Site, including both NIBW and SIBW, was placed on EPA's National Priorities List (NPL), or Superfund list, in 1983.
Contaminants and Risks
- Soil and Sludges
Groundwater and soils (in certain isolated areas) are contaminated with VOCs, including TCE and PCE.
The primary risk at SIBW was to individuals who may have consumed contaminated groundwater before it was discovered in 1981. Since individuals are currently not drinking the contaminated groundwater, there is no direct human health threat associated with the groundwater contamination. All drinking water in the Tempe area is provided by municipal drinking water suppliers. This water can not be served to customers unless it meets all drinking water standards set by the federal Safe Drinking Water Act.
Wells can not be drilled in the state of Arizona without a permit from the Arizona Department of Water Resources (ADWR). EPA works with ADWR to coordinate the cleanup efforts at SIBW. If someone applied for a well permit, ADWR would inform them of the risks of using the groundwater for drinking, showering, etc.
The greatest risk associated with contaminated soil is its potential to impact the groundwater. If individuals were to come into direct contact with contaminated soil, due to the low concentrations of contaminants present in surface and deep soil, the potential health risks would be minimal or insignificant.
If you have questions about TCE, please review the Agency for Toxic Substances and Disease Registry's (ATSDR's) TCE fact sheet at http://www.atsdr.cdc.gov/tfacts19.html and EPA'sTechnical Factsheet on: TRICHLOROETHYLENE (TCE) under the Documents and Reports section below.
Who is Involved
This site is being addressed through Federal and potentially responsible parties' actions.
Investigation and Cleanup Activities
This site is being addressed in two long-term remedial phases. For the most part, the work has been divided into the following management units: (1) soil; and (2) groundwater. The EPA is addressing SIBW as a separate area of study from NIBW because the contaminants come from different sources and the groundwater plumes are not contiguous.
The Remedial Investigation (RI) for SIBW was conducted over a period of many years and characterized both soil and groundwater conditions. Interim RI Reports were completed in 1991 and 1993. The final RI and the Groundwater Feasibility Study (Groundwater FS) were completed in 1997.
On September 27, 1993, EPA issued a Record of Decision for the Soil Operable Unit entitled, “VOCs in the Vadose Zone” (1993 Soils ROD). This ROD selected Soil Vapor Extraction (SVE) as the cleanup technology for VOCs in soils at SIBW.
Within the SIBW study area there are many facilities at separate locations which are known as subsites. These subsites have the same VOC contamination and very similar types of soils. Traditionally, EPA would investigate and then evaluate cleanup alternatives for each facility or subsite. However, due to the similarities among the SIBW subsites it was likely that the same cleanup would have been selected in each case. Rather than select the same remedy repeatedly for many facilities, EPA selected a remedy in the 1993 Soils ROD that utilized the “Plug-in Approach” in order to save time and resources.
Using this approach, EPA selected a cleanup technology (SVE) that would apply whenever a certain set of conditions existed. This set of conditions was defined in the 1993 Soils ROD. First, investigations are required to be conducted at each subsite. These investigations are known as “Focused Remedial Investigations” or FRIs. After the FRIs have been conducted at each facility, EPA compares the results with the standard criteria. If the facility meets the specified conditions, then soil cleanup is required at that facility.
Once EPA has made a decision regarding whether or not a particular subsite meets the criteria, EPA then issues a “Plug-in Determination Document” and makes the FRI Report available for the public to review. To date, EPA has issued two Plug-in Determinations. The first was in February 1994 for the DCE Circuits Subsite. Soil cleanup was required at DCE Circuits and this cleanup is currently nearing completion. The second Plug-in Determination was issued in January 2002 for the following seven subsites: Circuit Express, Allstate Mine Supply, Desert Sportswear, Cerprobe, Service and Sales, and the City of Tempe Right-of-Way. None of these seven subsites plugged-in to the 1993 Soils ROD and, therefore, soil cleanup was not required.
On September 30, 1998, EPA issued a Record of Decision for VOCs in groundwater (1998 Groundwater ROD). The 1998 Groundwater ROD addressed all three groundwater plumes at the SIBW Site: the western plume, the central plume and the eastern plume. The remedy selected for the western plume was extraction and treatment and the remedy selected for the central and eastern plumes was monitored natural attenuation (MNA).
Currently, work on the central and eastern plumes is being conducted by a potentially responsible party (PRP) under EPA and State oversight. This work includes installation of monitoring wells, groundwater sampling, groundwater modeling and production of a report regarding the status of the MNA remedy. All monitoring wells have been installed. Sampling began in April 2002 and was complete in July 2003. The Remedial Design Report for this work is expected to be submitted in December 2003. Based on current information, the MNA remedy appears to be effectively cleaning up the central and eastern plumes.
Cleanup of the western plume is considered to be a fund-lead action. In other words, EPA is conducting the cleanup and paying for it out of the federal “Superfund”. Following issuance of the 1998 Groundwater ROD, some data gaps needed to be filled before EPA could proceed with design and construction of the extraction and treatment remedy for the western plume. First, additional groundwater data was needed. EPA has continued to collect groundwater monitoring data from the western plume on a quarterly basis to gather this needed information. Also, in order to determine the southernmost boundaries of the western plume three additional monitoring wells were installed early in 2001. EPA is continuing to evaluate this groundwater data.
Cleanup Results to Date
After adding this Site to the NPL, EPA performed preliminary investigations and determined that no immediate actions were required at the Site. Remedies have been selected and cleanup activities in various stages are currently underway at SIBW.
Potentially Responsible Parties
Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.
Online information about the PRPs for the site is not yet available.
Documents and Reports
|02/01/02||EPA Issues Decision for Seven Subsites|
|02/01/04||EPA Proposes Revision to Existing Groundwater Strategy for Western Plume|
|07/27/10||Announcing Start of Five-Year Review|
|05/13/13||Upper Aquifer Cleanup Success|
|12/03/12||SIBW Groundwater Contamination Concentrations / Potentiometric Maps|
|09/27/93||1993 Record of Decision - SIBW for VOCs in Vadose Zone|
|09/30/98||1998 Record of Decision - SIBW for VOCs in Groundwater|
|06/21/04||2004 Record of Decision Amendment - SIBW VOCs in Groundwater Operable Unit|
|09/23/11||First Five-Year Review|
|12/03/12||SIBW Monitored Natural Attenuation Monitoring Report|
|01/10/13||EPA Technical Factsheet on: TRICHLOROETHYLENE (TCE)|
|07/02/13||Indoor Air Sampling, Winter 2013, DCE Circuits Subsite, South Indian Bend Wash |
(SIBW) Superfund Site
Public Meetings: General public meetings have been held since the early 1990s. These have included a meeting on the Proposed Plan for Cleanup in September 1997 and one on a Revision to a portion of the cleanup stategy in March 2004.
Public Information Repositories
The public information repositories for the site are at the following locations:
Tempe Public Library
3500 South Rural Road
Tempe, AZ 85282
Arizona Department of Environmental Quality
1110 West Washington Street
Phoenix, AZ 85007
EPA Site Manager
75 Hawthorne Street
San Francisco, CA 94105
EPA Community Involvement Coordinator
75 Hawthorne Street
San Francisco, CA 94105
EPA Public Information Center
State Project Manager
Wendy Flood, State Community Involvement Coordinator
1110 West Washington Street
Phoenix, AZ 85007
After Hours (Emergency Response)