1. ENHANCED BIOREMEDIATION PILOT USING iSOC® TECHNOLOGY AT A FORMER MANUFACTURED GAS PLANT
CASE STUDY PREPARED BY:
MR. DAVID WORK, PE
RETEC GROUP

2. The Site
Large former Manufactured Gas Plant Operated from the 1850’s to the 1930’s.
Primary remedial solution – Excavation and In-Situ Solidification (ISS).
In 2002, 66,000 cubic yards of impacted soil were excavated and 35,000 cubic yards of impacted material below the water table were solidified.
Site remediation carried out by the Retec Group.

3. The Site

4. Lithology

5. The Problem
The downgradient off-site alluvial wells meet the risk reduction standards for groundwater.
ISS and excavation was successful.
Small area of onsite residually impacted material.
The COI trend in one onsite alluvial well was upward.
MNA parameter trend was downward in well.
Regulators wanted action.

6. Feasibility Study Excavation – Ruled out due to cost.
ISS – Ruled out due to cost.
Chemical Oxidation – Ruled out due to cost and uncertainty.
Enhanced Bioremediation was determined to be the best alternative for this area.

7. Implementation
Historically two choices: air sparging or Oxygen Release Compound (ORC®).
Interbedded clays and sands prevent air sparging.
ORC® socks have a small radius of influence.
ORC® slurry injected into treatment zone was going to be labor intensive and expensive (i.e. generally requires multiple applications).
iSOC® Technology selected for evaluation in a pilot study.

8. Pilot Design iSOC® Technology selected as economical and effective.
Pilot cell located at historically impacted well.
Pilot duration - 6-months.
Monitor O2 levels in wells and piezometers.
Measure COI change in monitoring well.
Periodically monitor for nutrient depletion.

9. Microbial Activity
Benzene Degraders

10. iSOC® Technology Description
Microporous hollow fiber provides a large surface area for mass transfer— greater than 7000 m2/m3.
Surface oxygen source is applied to unit and diffuses O2 into groundwater, dissolved oxygen (DO) levels are typically PPM depending on depth in groundwater.
Natural convection current fills well with uniform DO, resulting in supersaturated levels, diffuses to groundwater around the well.
Observed radius of influence is +/- 15 feet.

11. Surface Components

12. Pilot Test Layout

13. Pilot Layout

14. Pilot Layout

15. Pilot Cell Results

16. DO Trend

17. O&M Long term O&M is favorable versus ORC and air sparging.
Total 6-month pilot costs: Capital: $7,500, Analysis and Reporting: $7,000.
On a separate site RETEC designed a 24 iSOC® system, O&M with iSOC® is estimate at $30K/year.
Same site, ORC O&M estimated at $60-80K/year and air sparging at $30-50K per year each with significant upfront capital costs.

18. Conclusions
iSOC® Technology has been successful in stimulating enhanced bioremediation to control COI levels in GW.
One of the first MGP site in the nation to use diffusion iSOC® Technology.
Combination of low O&M cost and effectiveness provides many benefits over other forms of O2 delivery.