Presenters' Contact Information

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1 Presenters' Contact Information Paul Ranieri Conestoga-Rovers & Associates 2055 Niagara Falls Blvd. Suite Three, Niagara Falls, New York Phone:

2 CHEMICAL OXIDATION AT OPERATING GAS STATIONS Sophia Dore, Christa Nunn, Donald Pope, Paul Ranieri, and Alan Weston Conestoga-Rovers & Associates

3 Section 1. Introduction 2. Application System Design 3. Case Studies 4. Conclusion

4 ISCO Treatment Review Involves complex processes Requires expertise and suitable site conditions Can save $$$ and accelerate cleanup Can be used as a pretreatment for MNA

5 In Situ Chemical Oxidation An oxidizing agent breaks carbon bonds in organic contaminants and converts them into nonhazardous compounds, primarily carbon dioxide and water Commonly used oxidizing reagents include potassium/sodium permanganate, Fenton s Reagent, ozone, and sodium persulfate A laboratory treatability study is required to select the most effective oxidant, and oxidant dose Successful ISCO treatment depends on the effectiveness of the delivery system

6 Section 1. Introduction 2. Application System Design 3. Case Study 4. Conclusion

7 Active Gas Stations Source of contamination can be spills during filling of tanks or leaky fuel storage tanks Flammable substances -Gasoline and diesel range petroleum hydrocarbons and BTEX compounds in soil and groundwater Remedial activities must accommodate day to day workings of the gas station

8 Steps for Safe ISCO Application at an Operating Gas Station Treatability Study Determination of most efficient oxidant Calculation of dose and application rate Design of application system Design of monitoring system

9 Treatability Study Initial Characterization Microcosm Tests Natural Oxidant Demand (NOD) determination Metals Leaching Tests

10 Delivery Methods Injection wells Direct push Mixing into open excavation Perforated pipe infiltration system Removal of LNAPL is recommended prior to ISCO Application

11 Design of Application System Use of Injection Wells for Injection Advantages Permanent wells can be used multiple times Screened through the relevant depth interval Disadvantages Expensive to install All applications must be made in the same locations May required well permits

12 Design of Application System Use of Direct Push for Injection Advantages Can inject through the relevant depth interval Can offset injections during later events to cover area more effectively Less costly than installing permanent wells Disadvantages Not appropriate for deep applications Not appropriate for bedrock applications Limited pumping rates

13 Design of Application System Mixing of Oxidant into Open Excavation Advantages A large amount of oxidant can be applied therefore the entire dose can be applied at once Can get good distribution of oxidant in tight soils Disadvantages Not appropriate for Fenton s Reagent (H&S); recommended for sodium persulfate Mixing equipment required Depth limitations

14 Design of Application System Perforated Pipe Infiltration System In Excavation Advantages Multiple applications of oxidant can be made Inexpensive to install Gravity vs. pressure injection Can be safer to apply oxidant after backfilling at an active gas station Can locate injection ports away from traffic areas Disadvantages Difficult to get good distribution of oxidant in tight soils

15 Design of Monitoring System Parameters to monitor: Chemicals of concern To determine whether reduction has taken place Metals To determine whether metals have been solubilized by the ISCO reagents; Fe and Mn levels show the oxidation state in the groundwater

16 Design of Monitoring System Parameters to monitor: (cont.) Sulfate If persulfate is used since sulfate can be a breakdown product DO and ORP To verify that oxygen levels have been increased by the oxidant

17 Design of Monitoring System Health and Safety Monitoring: Vapor monitoring for TPH and BTEX To determine whether chemistry has been volatilized Temperature To determine whether a vigorous reaction is taking place Pressure To determine whether the reaction is causing pressure to rise

18 Section 1. Introduction 2. Application System Design 3. Case Study 4. Conclusion

19 Scenario Gasoline spill at an active gas station Gasoline has been detected in soil and groundwater samples No LNAPL is present

20 Treatment Assessment What to do? Consider In Situ Treatment Monitored natural attenuation (MNA) In situ chemical oxidation (ISCO) In situ enhanced biodegradation (ISEB) Permeable Reactive Barrier (PRB) Air Sparge Soil vapor extraction (AS/SVE)

21 Treatment Assessment Monitored Natural Attenuation Gasoline degrades readily under aerobic conditions however: Concentrations in soil and groundwater are high Site is paved therefore oxygen will be depleted quickly Potential for off-site migration if contamination is not addressed quickly Conclusion: This site is not a good candidate for MNA

22 Treatment Assessment ISCO ISCO is effective for treatment of gasoline in soil and groundwater ISCO using sodium persulfate is safe for application at active gas stations ISCO using sodium persulfate is safe for application around underground utilities and around an AST ISCO treatment would be complete in 1-2 years Conclusion: ISCO is retained for consideration

23 Treatment Assessment ISEB Gasoline biodegrades readily under aerobic conditions Oxygen injection would be safe at an active gas station Injection using a technology such as isoc could be applied with most equipment below grade so the day to day activities of the gas station would not be affected ISEB treatment would be complete in 3-4 years Conclusion: ISEB is retained for consideration

24 PRB Treatment Assessment Could intercept and treat contaminated groundwater before it migrates off-site Would not treat soil Would not address on-site contamination Without source treatment PRB would need to be maintained for a long time PRB alone not appropriate for this Site Could be considered in combination with source treatment

25 Treatment Assessment AS/SVE Gasoline is volatile and could be removed by AS/SVE AS/SVE system would need to be installed May not be cost effective for such a small site Once concentrations are reduced to low levels AS/SVE is no longer efficient therefore another technology would be required for polishing Conclusion: AS/SVE is not a good technology for this site

26 Treatment Assessment Technologies Retained for Consideration ISCO ISEB Next Step Conceptual designs and cost estimates

27 Treatment Assessment Conceptual Design 3 injection wells + MW-5 required for either ISCO or ISEB ISCO: reagent injection wells ISEB: air/nutrient injection wells Proposed injection well

28 Treatment Assessment Cost estimates ISCO Assuming 1 year of treatment estimated cost: $75,250 ISEB Assuming 3 years of treatment estimated cost: $96,550 ISCO is more cost effective and faster Recommendation: ISCO

29 Oxidant Application A solution containing a mixture of 15 percent sodium persulfate solution and 25 percent sodium hydroxide solution was injected into MW-5 and each of the three newly installed injection wells Well Volume Injected (gallons) IW MW IW-2 1,330 IW-3 1,830

30 Post Injection Monitoring Monitoring was performed 1 month and 3 months after the first ISCO injection Between 60 and 98 percent removal of petroleum hydrocarbons was observed after treatment Concentrations in some areas remained above criteria

31 Post Injection Monitoring Criteria not exceeded Criteria exceeded

32 Second Injection Event A second injection event was performed focusing on the area that still exceeded criteria After the second injection event, petroleum hydrocarbon concentrations at all monitoring wells were below criteria No further treatment was required

33 Application of Sodium Persulfate at an Operating Gas Station Soil and groundwater at an active gas station are impacted by petroleum hydrocarbons GRO has been detected in Site groundwater at concentrations of up to 100,000 µg/l Benzene has been detected at 2,000 µg/l An area 20 ft x 60 ft was excavated A perforated pipe infiltration system was installed into the open excavation

34 Case Study Cont d The injection consisted of 10% H 2 O 2 mixed with 20% sodium persulfate Mixing of the catalyst and oxidant occurred immediately prior to injection The injection was performed by gravity A bromide tracer was included with the injection

35 Results Monitoring results showed that TPHg and BTEX concentrations in groundwater were reduced below criteria in all but one of the monitoring wells Mobilization of metals did not occur Soil vapor monitoring did not show impacts to air quality A vigorous reaction did not occur

36 Section 1. Introduction 2. Application System Design 3. Case Study 4. Conclusion

37 CONCLUSIONS ISCO can be successfully implemented at active gas station sites Correct dose, application rate, application Correct dose, application rate, application system design, and monitoring must be carefully determined

38 Questions?