Pump and TreatPump and Treat Permeable Reactive BarrierPermeable Reactive Barrier

Former Intersil, Inc. SiteFormer Intersil, Inc. Site

Sunnyvale, CaliforniaSunnyvale, California

Presented by Daniel CheungPresented by Daniel Cheung

Outline of PresentationOutline of Presentation

Site BackgroundSite Background Geotechnology AlternativesGeotechnology Alternatives Science/Principles Involved (PRB)Science/Principles Involved (PRB) Evaluation on RemediationEvaluation on Remediation ConclusionConclusion

Site BackgroundSite Background

Historical ActivitiesHistorical Activities Former Intersil, Inc. (Sunnyvale, California)Former Intersil, Inc. (Sunnyvale, California) 1970s–19831970s–1983 Semiconductor manufacturing Semiconductor manufacturing 19721972 Concrete, epoxy-lined, in-ground neutral Concrete, epoxy-lined, in-ground neutral

ization system installedization system installed 19861986 Identified as potential contaminant Identified as potential contaminant

sourcesource 1987-Present1987-Present Remediation Remediation

Site BackgroundSite Background

Site BackgroundSite Background

Hydrogeology of the Site (2.4 acres)Hydrogeology of the Site (2.4 acres) Semi-confined aquiferSemi-confined aquifer

• Upper silty clay (9-12 feet)Upper silty clay (9-12 feet)• Lower clay and silty clay (~65 feet)Lower clay and silty clay (~65 feet)

Interfingering zonesInterfingering zones of of (~1-8 feet, porosity = 0.3) (~1-8 feet, porosity = 0.3) • Silty fine grained sandSilty fine grained sand• Fine to medium grained sandFine to medium grained sand• Gravelly sandGravelly sand• Average flow rate = 0.8 ft/dayAverage flow rate = 0.8 ft/day

Not usable for consumption Not usable for consumption (high TDS)(high TDS)

Site BackgroundSite Background

ContaminationContamination HalogenatedHalogenated volatile organic compounds volatile organic compounds (VOC(VOC

s)s)

Maximum concentrations in 1986Maximum concentrations in 1986 Halogenated VOCsHalogenated VOCs μμg/Lg/L• Trichlorethene Trichlorethene ((TCETCE)) 13,000 13,000 • cis-1,2-dichloroethene cis-1,2-dichloroethene ((cis-1,2-DCEcis-1,2-DCE)) 19,00019,000• Vinyl chloride Vinyl chloride ((VCVC)) 1,800 1,800• Freon-133Freon-133 16,00016,000

Only detected in the Only detected in the upper aquiferupper aquifer

Geotechnology AlternativesGeotechnology Alternatives

Pump and Treat, P&TPump and Treat, P&T (11/87 – 02/95)(11/87 – 02/95)

4 extraction wells (pump)4 extraction wells (pump) 13 monitoring wells13 monitoring wells 1 Air stripper (treat) 1 Air stripper (treat) →→ Storm sewer (discharge) Storm sewer (discharge) 2 Carbon adsorption (unused)2 Carbon adsorption (unused)

Permeable Reactive Barrier, PRB Permeable Reactive Barrier, PRB (02/95 – Ongoing)(02/95 – Ongoing)

Granular iron treatment zoneGranular iron treatment zone Flow control zoneFlow control zone Hydraulic barrier system (2 slurry walls)Hydraulic barrier system (2 slurry walls)

Science/Principles Involved (PRB)Science/Principles Involved (PRB)

Science/Principles Involved (PRB)Science/Principles Involved (PRB)

Abiotic Reductive Dehalogenation

Evaluation on RemediationEvaluation on Remediation

Pump and TreatPump and Treat HVOCs < MCLs (NPDES)HVOCs < MCLs (NPDES) Inward hydraulic gradient contained the plumeInward hydraulic gradient contained the plume Removal rate Removal rate declined exponentiallydeclined exponentially $1,343,800 (24% capital cost, $1,343,800 (24% capital cost, 76% O/M cost76% O/M cost)) $24,000/kg of total contaminant$24,000/kg of total contaminant

1993 evaluation1993 evaluation Minimise costMinimise cost & & Increase effectivenessIncrease effectiveness Return the site to Return the site to leasableleasable conditions conditions

Evaluation on RemediationEvaluation on Remediation

Permeable Reactive BarrierPermeable Reactive Barrier TCE & Freon-133 < MCLs TCE & Freon-133 < MCLs (California & EPA)(California & EPA)

Cis-1,2-DCE & VC Cis-1,2-DCE & VC >> MCLs>> MCLs (California & EPA)(California & EPA)

Natural attenuationNatural attenuation & Non-migrated & Non-migrated Plume has been Plume has been containedcontained $762,000 (78% capital cost, $762,000 (78% capital cost, 22% O/M cost22% O/M cost)) $108,900/kg of total contaminant$108,900/kg of total contaminant The site was The site was releasedreleased in 1995 in 1995

Evaluation on Remediation Evaluation on Remediation PRB

2M gallons

7kg in 1.5yrs

P&T

36M gallons

56kg in 7.25yrs

98% Total Removal

ConclusionConclusion

Both P&T and PRB were usedBoth P&T and PRB were used Satisfactory overall clean up performanceSatisfactory overall clean up performance Appropriate methods were adoptedAppropriate methods were adopted

HydrogeologyHydrogeology Seriousness of contaminationSeriousness of contamination Cost effectivenessCost effectiveness Legal requirementLegal requirement

Q&AQ&A