Alternatives to Long-Term Monitoring of Recalcitrant Compounds; What can be done?

Transcription

1 Alternatives to Long-Term Monitoring of Recalcitrant Compounds; What can be done? October 30, 2012 Florida Brownfields Association Conference, St. Petersburg Andrew Lawn, P.G. & William Lais, P.E. HSW Engineering, Inc.

2 Alternatives and Case Studies Background determinations soil/ groundwater Recalcitrant 1,4-Dioxane Institutional Controls/Alternatives Low yield poor quality criteria

3 FDEP Guidance Documents Comparing Background and Site Chemical Concentrations Soil (March 2008 and January 2012) Groundwater (March 2009) Recent guidance and following case study include a Weight of Evidence approach

4 Case Study: 1958 Predevelopment Wetland Topography Future Site

5 Lines of Evidence Used for Closure historic chemical & equipment use; surrounding land use; surface features & subsurface lithology; groundwater flow direction; filtered vs. unfiltered results; metal concentrations in soil; concentration distribution patterns; consistency of concentrations; statistical analyses; metal concentrations in groundwater.

6 Conclusions Lead to NFA Approval Concentrations of Al, Fe and Mn in groundwater above GCTLs are representative of background conditions at the site. Institutional Controls were not applicable to background metals in groundwater at the site. No further action was warranted or required by FDEP.

7 Recalcitrant Compound Example: 1,4-Dioxane Should you sample groundwater for 1,4-Dioxane? If it s present, how will the issue be resolved?

8 What is I,4-Dioxane? Stabilizer and corrosion inhibitor in chlorinated solvents; e.g., 1,1,1- trichloroethane (TCA); also paints, inks, solvents, cosmetics and detergents FDEP Cleanup Target Levels: GCTL ug/l (carcinogen) Low yield/poor quality 32 µg/l SCTL (leachability) 0.01 mg/kg

9 I,4-Dioxane Characteristics 1,4-dioxane physical/chemical characteristics challenging to responsible parties: Highly mobile in the environment Difficult to characterize; historically under-reported past Difficult and costly to treat

10 Challenging Characteristic No. 1 Really Mobile in the Environment Low sorption to soils (leaches easily) Highly soluble in groundwater Migrates ahead of other solvents in groundwater 1,1,1-TCA 1,1-DCA 1, 4-Dioxane

11 Challenging Characteristic No. 2 Hard to Characterize Historical methods (8260) did not detect < 100 ug/l Lab Methods 8260 SIM and 522 have better detection Example premature remediation before 1,4-dioxane discovered Recovery wells installed to remediate known TCA plume 1,1,1-TCA 1, 4-Dioxane unknown when remedial system installed

12 Challenging Characteristic No. 3 Hard to Treat Not treated by conventional methods; e.g., air stripping, activated carbon (not volatile or sorptive) Expen$ive $econdary treatment required

13 Analytical Methods DEP allows EPA Methods 8260 SIM but prefers EPA Method 522 (drinking water method) Method 522 less subject to interference and false positives but expensive and few labs certified Consideration use Method 522 as check against positive results found by another method We found 8260 SIM overestimates the 1,4-D concentrations relative to 522.

14 FDEP Approach to I,4-Dioxane Case-by-case approach across cleanup programs May revisit sites in remediation for additional testing (estimated 10% sites show presence) Likely sites: 1,1,1-TCA 1,1-DCA Chloroethane

15 1,4 Dioxane Treatment Technologies High solubility compared to other VOCs Not Volatile Engineered to be stable Solution: Ex-Situ Advanced Oxidation Process (AOP) Hydrogen peroxide/ozone Photo-oxidation (UV and catalyst)

16 1,4-Dioxane, ug/l Bromate, ug/l AOP Challenges Water clarity Presence of iron, TOC Bromate formation Effluent standards, dosing rates ,4- Bromate ,4-D GCTL = 3.2 ug/l BrO3 GCTL = 10 ug/l Ozone Dose, mg/l 2.8 mole ratio, O 3 - H 2 O 2 0

17 AOP Challenges Chemical handling Capital Costs Lease vs. Purchase Operating Costs: PPE System Operation and Maintenance Effluent Standards

18 Lessons Learned Screen using Method 8260 If I,I,I-TCA or 1,2-DCA present use 8260 SIM or Method 522 Consider multitude of potential sources (offsite sources) Possible area-wide control for low concentrations?