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

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.

Silty Sand

Plastic Clay

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

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

Test Amendments

Benzene Results

Benzene Cost Analysis

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

Benzene Concentration Before Test

Benzene Concentration Before Test

Benzene Concentration Before Test

Benzene Concentration Before Test

Benzene Concentration Before Test

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

Injection Truck

Drilling/Geoprobe Rig

Injection Tips

Former Service Station - Golden

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 2006. 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.

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

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.

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, 2009. 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.

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 0.0044 ppm on 6/14/10. Stay tuned. Seven more monthly injections planned.

Benzene Concentrations at Well MW-L

Former Service Station - Denver

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 2003-2005.

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?

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

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

Benzene Concentrations at Source Area Well

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

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.

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.

Thank You! Contact us for more information John Gould: john.gould@state.co.us Telephone: 303-318-8542 Jesse Taylor: jtaylor@remingtontech.net Telephone: 970-278-1646