Performance Based System for Determining Post Closure Care (PCC) at Florida MSW Landfills Southwest Landfill, Alachua County, Florida Dr. Debra Reinhart Asawari Kulkarni

Outline Performance based methodology Timeline Project status Groundwater Module  Groundwater monitoring well locations  Statistical comparison  Groundwater data analysis: VOC  Metal analysis and results  Summary Next

Performance Based Methodology Developed by EREF (Geosyntec contractor) Comprised of four modules:  Leachate Module  Groundwater Module  Landfill Gas Module  Cap Module

Operation Began: Constructed and started accepting waste Horizontal Injection for Leachate Recirculation Initiated Recirculation via Infiltration Ponds Started tires separation/ shredding and recycling Final Closure LFGTE initiated Site history and timeline

Performance Based Methodology Leachate Module  Analysis of leachate monitoring data  Data from  For 90% ND, reduce monitoring frequency and then discontinue

Performance Based Methodology: Leachate Module Outcomes Organic contaminants: Reduce and then discontinue monitoring  Declining and approaching MCL (e.g. acetone)  Detected always below MCL ( e.g. styrene or naphthalene)  Following a significant reducing trend and are below MCL ( e.g. toluene, xylene)

Performance Based Methodology: Leachate Module Outcomes Trends followed by metal contaminants:  Reduce and discontinue monitoring for metals always BDL ( only copper)  Continue monitoring for arsenic, iron, chromium: Concentration and mass variations depending on the leachate flows

Project Status Leachate Module Groundwater Module Landfill Gas Module Cap Module

Groundwater Module Analysis of historical groundwater monitoring data Helps in making a decision on optimizing/terminating current groundwater monitoring plan during PCC Data obtained from Southwest Landfill consultants, Jones, Edmunds & Assoc.

EPA Recommended Comparison Options Comparison with historical data from same well : Intra-well comparisons Comparison With background wells : Inter-well Comparison Comparison with MCL Control Charts Confidence Interval Method Tolerance Interval Test of proportions

ND > 50%? Yes No Data Test of proportions Confidence Interval (CI) Are data normal? Yes Are Log data normal? Yes Normal CI Log-normal CI Non-Parametric Approach Non-Para CI Yes

Groundwater Monitoring Data Monitoring data available from Around 200 parameters are monitored every year CHEMSTAT is used for statistical comparisons Minitab 15 for graphical representations

Groundwater monitoring data √ Statistical analysis tools √

Frequently Detected Contaminants: VOCs Number of Detects VOCs detected at SWLF

Frequently Detected VOC: Acetone Found only in well SW-2D Detected before year 2000 May be due to 7 acres Class III disposal area to the south

Location of well SW-2D: Acetone

Frequently detected VOC: 1,4-dichlorobenzene Wells SW-4D, SW- 7D and SW-10D Found in Compliance wells

Frequently detected VOC: 1,4-dichlorobenzene

Frequently detected VOC: Chlorobenzene Second most frequently detected contaminant Detected in SW-4D and SW-10D Probably comes from degradation of dichlorobenzen e in anaerobic conditions Increasing trend

Frequently Detected VOC: Vinyl chloride

Found consistently in well SW-4D MCL – 1 ug/L Vinyl chloride concentration > MCL May come from dechlorination of chlorinated ethenes under anaerobic conditions VC degrades better aerobically as compared with anaerobic conditions Declined after 2001 Significant contamination when compared with MCL and background wells Never detected in leachate ( always BDL)

Less frequently detected VOC 1,2-dichlorobenzene Benzene C-1,2-dichloroethene Chloroethane Chloroform Chloromethane Dichlorodifluoromethane Methylene chloride Tetrachloroethene

Recommendations for VOCs Reduce, then discontinue monitoring frequency:  1,2-dichlorobenzene  Benzene  C-1,2-dichloroethene  Chloroethane  Chloroform  Chloromethane  Dichlorodifluoromethane  Methylene chloride  Tetrachloroethene

Recommendations for VOCs Continue monitoring for vinyl chloride  Consistent detection frequency  Above MCL

Metal Analysis: Metal Detection Frequency

MetalTMELeachate Range GW Range, µg/LMCL, µg/L UpDown Antimony Arsenic Barium Cadmium Chromium Cobalt BDL0.4-40NA Copper Lead Mercury Nickel Zinc NA

Metal Recommendation Reduce, then discontinue metal monitoring frequency: Antimony Chromium Copper Barium Nickel Cobalt Mercury

Metal Recommendation Continue monitoring for:  Arsenic  Cadmium  Lead

Metal Recommendation Reduce, then discontinue monitoring of metals at wells:  SW-9D  SW-7D  Sw-12D  SW-P1  SW-2D

Metal Recommendation Sampling private wells offsite but down-gradient to track potential transport of heavy metals

Summary Analysis of groundwater monitoring data completed Future monitoring limited to few metals and VOCs 5 monitoring wells can be eliminated from metal monitoring Off-site monitoring for metals

Next Landfill gas module Landfill gas quality and quantity Impact on human health and environment

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