1. Jesse Taylor: Remington Technologies
Site Specific Evaluation of Various Oxidizing Compounds for Destruction of BTEX and TPH-G
Jesse Taylor: Remington Technologies
John Gould: Division of Oil & Public Safety, Colorado Department of Labor and Employment

2. Division of Oil and Public Safety (OPS) Study of In-Situ Chemical Oxidation (ISCO) - 2007
Includes evaluation of ISCO application and its effectiveness at 20 petroleum-contaminated sites.
Identified site specific factors and ISCO practices that can affect or contribute to successful remediation.
Factors important to remedial success include adequate site characterization and bench and field-scale pilot testing.
Characterization: Extent and levels of contamination – locations of sources and smear zone, GW concentrations and parameters (ORP, alkalinity, ferrous iron, TDS, and major cations and anions, in addition to DO, pH, temp, and SC). Bench: determine most effective oxidant and TOD. Field: determine injection rates, volume, oxidant concentration, and ROI (injection point spacing). Completion of these activities required prior to CAP approval.

3. Silty Sand

4. Plastic Clay

5. Remediation Strategies
High
© Copyright Regenesis 2008
Biological
Physical
Chemical
Efficiency
High
Concentration

6. Bench Scale Test Controlled Environment Pre and Post Sample Control
Observable Reaction Rate and Type
Contaminant Mass/ Oxidant Mass Ratio Control

7. Test Amendments

8. Benzene Results

9. Benzene Cost Analysis

10. Test Amendments 1 – Sodium Persulfate/Fe-EDTA (80:20)
2 – Sodium Persulfate/H2O2 (80:20)
3 – Sodium Persulfate/Calcium Peroxide (80:20)
4 – RegenOx (Part A:B 80:20)
5 – Calcium Peroxide/Sodium Persulfate (50:50)
6 – Calcium Peroxide/Sodium Persulfate (80:20)
7 – Calcium Peroxide/ Fe-EDTA

11. Benzene Concentration Before Test

12. Benzene Concentration Before Test

13. Benzene Concentration Before Test

14. Benzene Concentration Before Test

15. Benzene Concentration Before Test

16. Pilot Test
Determine if Injection Method Compatible with Subsurface Materials
Determine Radius of Influence
Determine Flow Rate and Down-Hole Pressure

17. Injection Truck

18. Drilling/Geoprobe Rig

19. Injection Tips

20. Former Service Station - Golden

21. History prior to ISCO Application
UST system removed in 1994 along with 1,000 yards of contaminated soil.
Additional excavation of 2,100 yards of contaminated soil performed in ORC spread over base of excavated areas.
Subsequent groundwater monitoring indicated persistent high benzene concentrations in wells downgradient of excavated areas (as high as 11.0 ppm at MW-L).
Proposal for four ISCO injection events submitted.
OPS requested bench-scale and on-site pilot testing.

22. Bench-Scale Testing
In addition to GW samples from well with highest benzene concentration (MW-L), soil samples collected from sandy backfill of former UST basin and native clay-rich material outside of excavated areas.
Two sets of nine batches prepared with sandy or clay-rich soils mixed with GW and four drops of gasoline. After 48 hours, samples collected from each batch were submitted for lab analysis (benzene and TPH-G).
1% solutions of various oxidants prepared. For eight of the clay or sand test vessels, 50 ml of one solution or a combination of two was added. One vessel in each set served as a standard (no oxidant added).
Oxidants included sodium persulfate (Klozur), calcium peroxide (PermeOx), hydrogen peroxide, and Fe-EDTA

23. Bench-Scale Testing (continued)
Seven days later, samples collected from all 18 test vessels and sent for lab analysis.
Final choice of oxidant or oxidant mixture for treating sandy or clay–rich material dependant upon percent reduction in contaminant concentrations as well as relative costs of each oxidant or mixture.
Results suggested most cost-effective approach was to use calcium peroxide in the sandy zones and a 50/50 mixture of calcium peroxide and sodium persulfate in the clay-rich areas.

24. On-Site Pilot Test Injections
To determine allowable flow rates, injection pressures, and injection intervals that would limit surface seepage of solutions.
Conducted May 1, Eight points used to inject solution (5% sodium persulfate/5% calcium peroxide).
Was found best to limit injection volumes to 50 gallons per point, down-hole pressure to 5 psi, and the injection intervals to zone below the water table.

25. ISCO Implementation Approval granted for 12 monthly injection events.
Injection events completed on 2/11/10, 3/23/10, 4/27/10, 5/25/10, and 6/25/10.
Benzene at well MW-L dropped from 8.0 ppm prior to injections to 3.1 ppm on 3/17/10 and to 2.5 ppm on 6/14/10.
Benzene at well MW-A dropped from 2.0 ppm prior to injections to 1.7 ppm on 3/17/10 and ppm on 6/14/10.
Stay tuned. Seven more monthly injections planned.

26. Benzene Concentrations at Well MW-L

27. Former Service Station - Denver

28. History prior to ISCO application
Free product detected at service station in 1989.
Dissolve phase benzene concentrations initially as high as 6,400 ppb.
GW pump and treat system operated between 1991 and 1995.
System shutdown in 1996 after free product was no longer detected.
All USTs removed in 1999.
Several mobile DPE events performed in

29. Pilot Testing In July 2005, bench scale testing performed.
ISCO pilot test injections performed 11/21/05, 1/27/06, and 3/3/ 06.
Sodium persulfate injected, along with chelated iron and hydrogen peroxide.
Due to positive results, approval granted for five full-scale ISCO events.
Same testing as mentioned in 2nd slide?

30. ISCO Implementation
Four three-day ISCO injection events completed on 5/1/08, 6/27/08, 8/7/08, and 6/12/09.
Sodium persulfate used as the primary oxidant.
Chelated iron used as activator/catalyst during first three events, and hydrogen peroxide included during fourth persulfate injection event.
Significant decreases in benzene noted, but BTEX concentrations still exceeded regulatory limits.
Between 2,880 and 5,370 gallons of solution injected (8% persulfate and 12% chelated iron during first three events, and 6% persulfate and 1% hydrogen peroxide during 4th event) into 22 to 24 borings around MW-18, MW-21, and MW-24

31. ISCO Implementation
A fifth ISCO injection event completed on 1/19/10 using calcium peroxide with chelated iron catalyst, focusing on area near three remaining contaminated wells (MW-18, MW-21, and MW-24).
Following this injection event, benzene concentrations dropped by roughly one order of magnitude at these three wells (based on March and June 2010 sampling).
1,500 gallons of solution in 14 borings in vicinity of same three monitoring wells

32. Benzene Concentrations at Source Area Well

33. Additional Source Area Well (maybe include only one of these graphs?)

34. Current status
Benzene concentrations before and after five ISCO treatments: MW-18 went from 1,400 to 36 ppb; MW-21 went from 540 to 79 ppb; and MW-24 went from 170 to 7 ppb.
One additional calcium peroxide injection event has been recommended and this proposal is currently under review.

35. Conclusions
Bench-scale testing important for choosing most effective oxidants and solution concentrations.
Field pilot testing important for determining proper spacing of injection points and ability of subsurface to accept injectate.
Important to note that an oxidant effective at high concentrations may not be as effective as a different oxidant once concentrations have been significantly reduced.

36. Thank You! Contact us for more information
John Gould: Telephone:
Jesse Taylor: Telephone: