The Santa Fe Pacific Pipeline (SFPP) Silvercroft Wash Release (the Site) has been operating under the oversight of the Arizona Department of Environmental Quality (ADEQ) Voluntary Remediation Program (VRP) since 2005. The Site is located west of the I-10 Freeway, north of Grant Road, along Silvercroft Wash, in Tucson, Arizona.
On July 30, 2003, a rupture occurred on a portion of the SFPP pipeline that transports gasoline between Tucson and Phoenix. The rupture occurred approximately 18 feet east of the eastern bank of Silvercroft Wash, in a utility easement on the western side of the Silver Creek II Subdivision. This residential development was under construction when the release occurred. SFPP initially used vacuum trucks to recover gasoline at the release point and in other Site locations where gasoline ponded on the ground. Later remedial actions included additional excavation, free product removal, ongoing soil vapor extraction (SVE), and ongoing monitored natural attenuation (MNA).
The chemicals of concern (COCs) are benzene, toluene, ethylbenzene, and total xylenes (collectively referred to as BTEX) and methyl tertiary butyl ether (MTBE).
The following provides current characterization information about the Site:
- The geology includes coarse sands and gravels to 175 below ground surface (bgs).
- The depth to groundwater is approximately 140 to 160 feet bgs.
- There are no surface water impacts remaining at the Site.
- Most soil impacts at the Site have been addressed, with the exception of the column of soil within an approximate forty foot radius of the release point source area, which is currently being remediated through SVE.
- The site is in the Feasibility Study Phase, following the Water Quality Assurance Revolving Fund requirements found in Arizona Administrative Code Title 18, Chapter 16 (Ref: A.A.C. R18-16-407). A site that is remediated through the VRP must follow WQARF requirements if offsite groundwater impacts exist.