Manatee Power Plant: Chlorinated Solvent Leak Presentation Tom Miles Oliver Read

Manatee Power Plant – Chlorinated Solvent Leak Case study overview Manatee county, Florida, USA Isolated chlorinated solvent leak (trichloroethylene and dichloroethane) Point source (time period unknown) Leak discovered in 1988 First phase of containment and remediation in 1988 (SVE) Remedial action plan implemented in 1993 (Pump and Treat) Enhanced options considered in 1995

Manatee Power Plant – Chlorinated Solvent Leak Chlorinated solvents Synthetic industrial chemicals used for many industrial applications Dense Non Aqueous Phase Liquid (DNAPL)->Density = 1.5 x water Moderately volatile Slow to naturally degrade Very low concentrations make drinking water unsafe Cancer causing Very tough to remove from below ground level Trichloroethylene Dichloroethane

Manatee Power Plant – Chlorinated Solvent Leak Groundwater contamination Ground profile: 13m silty sand (aquifer), “Hawthorne Formation” (aquiclude), heterogeneous clay layers in aquifer, water table 1.3-2m below surface Point source plume Transportation by advection, spreading by Diffusion, dispersion and Miscification. DNAPL sinks to the bottom of the aquifer due to its density

Manatee Power Plant – Chlorinated Solvent Leak Remediation options Soil Vapour Extraction Pump and Treat Air Sparging Bioremediation Digging out of Soil

Manatee Power Plant – Chlorinated Solvent Leak Implemented remediation option – soil vapour extraction Objective: plume containment 13x5cm PVC vapour extraction wells 1.5m depth Connected to a regenerative blower Was only effective in the short-term

Manatee Power Plant – Chlorinated Solvent Leak Implemented remedial option – pump and treat Objective: plume containment and recovery of contaminated groundwater 2 recovery wells Extracted water treatment plant Treated effluent to Public-Owned Treatment Works Possible re-use of chlorinated solvent

Manatee Power Plant – Chlorinated Solvent Leak Long time period (20+years) Enhancement option considered Combine pump and treat with SVE/AS system Reduction of project life by 4 years Not economically viable Continue with pump and treat operations Conclusions