In-Situ Remediation at Silver Lake Region 4 Hazardous Materials Geo/Bridge/Environmental Unit

LUSTs and Sustainability Limited groundwater resources Once impacted from petroleum hydrocarbons, subsurface ecosystem can take decades to recover Limited financial resources

LUSTs – Why So Bad? Petroleum Fuel – contains known or suspected carcinogens Released fuel doesnt stay put – migrates Travels with groundwater Difficult to see Difficult to cleanup = $$$!

What is In-Situ Remediation? In-Situ means in place. Remediation – providing remedy. Treatment or removal contaminants in soil and groundwater. In Situ – in place remedy. Remove, treat, change, transform contaminants in subsurface.

Silver Lake Maintenance Facility

Late 1980s –6,000 gallons of diesel spilled from newly installed AST 1992 –5 USTs decommissioned –Unknown amount of fuel spilled from USTs –3,500 yd 3 of Petroleum Contaminated Soil excavated 1993 –Subsurface investigation, Corrective Action Plan

1995 –Groundwater extraction (pump and treat) –Operated for total of 6 weeks –No measurable hydrocarbon recovery –Soil Vapor Extraction (SVE) system installed –Horizontal trenches –Operated for 21 months –Only recovered total of 25 lbs of petroleum hydrocarbons Silver Lake In-Situ Cleanup What went wrong?

Restoring Aquifers Enhanced Naturally Occurring Biological Degradation Use natural healing forces of nature Microbes dismantle petroleum hydrocarbons (HC) deriving energy from that process Give nature a helping hand What does the system lack? O 2 ? Nutrients? Use mechanical technology to distribute electron receptors and nutrients. What is occurring now under the Do Nothing Technology?

Fresh Start Delineate full extent of diesel contamination Chemistry Evaluate in-situ remedial options Pilot Test Final Design Construction Operation

Drilling – Expanded Subsurface Investigation

Groundwater Sampling

Groundwater Contours

Extent of Contamination

Anaerobic Conditions Aerobic Conditions

HC Molecule (electron donor) e - Oxygen (electron receptor) Secondary receptors => Fe, SO 4, NO 3 Energy Released Aerobic Biodegredation oxidized reduced HC + O 2 -> CO 2 + H 2 O

HC Molecule (electron donor) e - Carbon (electron receptor) Energy Released Anaerobic Biodegradation oxidized reduced HC + CO 2 -> CH 4 + H 2 O Methanogenesis

Remedial Alternatives No Action –doesnt remove risk or future liability Air Sparging –uncertainty of uniformity of air injection Dissolved Oxygen Injection –enhancement of natural attenuation Dual Phase Extraction –removes groundwater and vapors Ozone Injection –uncertainty of uniformity of air injection

O 2 as an electron receptor is primary limiting factor in bioremediation. To promote faster bioremediation, dissolved O 2 must be supplied in large quantities. Solution – Provide dissolved O 2 and lots of it!

Groundwater Recovery Wells DO Injection Wells

In-Situ DO Remediation Installation Install injection points Gnd wtr recovery wells Trenching and piping Super-Ox TM system

Injection Well Installation

Trenches and Piping

Questions?

Beer Molecule e - O 2 Energy Released oxidized reduced Beer + O 2 -> CO 2 + H 2 O