The project is a redevelopment property within the Teledyne-Spectraphysics (T-S) plume with underlying groundwater probably impacted by the upgradient T-S source properties. The developer plans to construct the building wiht a vapor intrusion mitigation system (VIMS) and water barrier. Indoor air testing will be conducted to verify that the VIMS is working as designed.
The Teledyne property is part of a two-property Superfund site along with the adjacent Spectra-Physics property.
The responsible parties (RPs) for the Teledyne/Spectra-Physics site completed a Monitored Natural Attenuation (MNA) study in the off-property area north of and downgradient of the site. The MNA study concluded that natural breakdown of the chlorinated volatile organic compounds of concern is occuring naturally and at the same rate as groundwater extraction. As a result, only a few of the off-property downgradient extraction wells were operating mainly to maintain hydraulic control of the plume. The RPs completed a pilot study to test the feasibility of enhanced reductive dechlorination (ERD) and concluded that ERD is feasible with bioaugmentation of the Shallow Zone.
Within the last five years, the RPs detected elevated source areas at the Teledyne property using high resolution technology and continuously logged and screened ERD injection well boreholes. Implementing a full-scale ERD treatability study, they have been and are currently remediating the property with groundwater-CVOC levels dropping from as much as over 80,000 ug/l to low multiples of MCLs. Several rounds of ERD injections successfully cleaned up most of the Shallow Zone at the Teledyne property and the adjacent Spring Street residential area to drinking water standards and the treatability study was even more successful in the underlying Upper and Lower Intermediate Zones.
An on-property IA VI evaluation at a SpectraPhysics property in 2004 indicated no IA-CVOC contamination above the Regional Water Board’s 2008 ESLs. More recently, the RPs also assertively evaluated potential IA VI in the off-property commercial North Bayshore and residential Spring Street areas to conclude that IA VI is not occurring in most of the commercial area and is occasionally occurring in several homes in the residential area. The RPs installed sub-slab depressurization systems in the impacted on-property commercial buildings and offered the affected residents crawl space fans to address the issue.
Nine indicator chemicals were identified from approximately 30 chemicals detected in the Study Area. The nine indicator chemicals are as follows: 1,1-dichloroethane (1,1-DCA) 1.1-dichloroethylene (1,1-DCE) 1.2-dichloroethylene (1,2-DCE) tetrachloroethylene (PCE) toluene 1,2,4-trichlorobenzene (1,2,4-TCB) 1,1,1-trichloroethane (1,1,1-TCA) trichloroethylene (TCE) vinyl chloride (VC
RECORD OF DECISION, TELEDYNE SEMICONDUCTOR AND SPECTRA-PHYSICS, INC. JOINT SUPERFUND SITES MOUNTAIN VIEW, CALIFORNIA MARCH 22, 1991 U.S. ENVIRONMENTAL PROTECTION AGENCY REGION 9 p. 26 https://semspub.epa.gov/work/09/46745.pdf
You must be logged in to post a comment.