1 GROUNDWATER REMEDIATION OF A HIGHLY CONTAMINATED BEDROCK SITE - The Oxygen Infusion Phase - J. Morrow D. Side By :

2  Gas station/auto repair 1940s-1999  Heavy residential/commercial area in SE Pennsylvania  Eight USTs removed between  Catastrophic petroleum hydrocarbon release, 1995  Surrounding properties include: Commercial & Industrial sites with water supply wells Residential properties with water supply wells PA Turnpike

3 Location 1273 DeKalb Pike USGS

4  Bedrock Begins 7-10’ below ground surface Sandstone w/interbedded shale  Three saturated zones 15’ to 50’ 60 to 75’ 80’ to 93’?  Groundwater flow, north w/components west and south

5  Hydraulic conductivity - 600’/day, avg.  Water table elevation changes 8 feet  Gradient (average)  Velocity to 2 ft/day  Direction - mixed, complex  Likely multiple source areas of contamination

6  1995-’98 - Site characterization  1995-’02 - LNPL removal  Late ’98 - Install pump/treat remediation w/bioreactor  Early ’02 - Install second bioreactor using on-site WSW  October ’02 - Installed 2 iSOCs in on-site monitoring wells. A third iSOCs added Feb. ‘03  October ’03 - installed 6 infusion wells w/iSOCs upgradient of plume Total of 9 iSOCs

7  iSOC pilot phase was encouraging.  12 months after initiating the pilot phase, 6 new infusion wells were added employing a total of 9 iSOC O 2 infusion points.  Source area contaminant reductions have been excellent both for BTEX and MTBE.  As cleanup has progressed, selective iSOC infusion points have been relocated to optimize contaminant reductions.

8  Initial pump/treat system used extraction wells within the source area. Results were only modestly successful due to low hydraulic conductivity.  Installation of second pump/treat bioreactor used a water supply well (WSW) as the extraction well; pumping rates between 5 and 10 gpm were achieved. Good hydraulic control was obtained and excellent treatment of off-site contamination. Source area contamination was only marginally affected.  Supplemental remediation for onsite contamination was indicated. iSOC was selected initially for a pilot study.

9 Air as source 7-10 mg/l Pure O 2 (when diffused) mg/l O 2 via iSOC 42 5’ head ’ head

10 What it looks like  Hydrophobic, micro porous O 2 delivery system  Extraordinary surface area, 7000 m 2 /m 3  Rugged materials and construction

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12 PA Bedrock Site O 2 Control Systems For 9 iSOCS

13 PA Bedrock Site O 2 Storage

14  Field Tests pH, DO, ORP, NO 3 1-, PO 4 3-  Laboratory BOD 5, TOC, COD Heterotrophic Plate Counts enzymes COCs

15  COCs and field tests - monthly for 18 months  Biochemical parameters BOD, TOC, COD, HPC - quarterly, selective wells  Enzymes - two rounds, selective wells

16  Final installation of iSOC coincided with peak drought in SE Pennsylvania  Subsequently it started raining, groundwater elevations increased 6’ to 10’  Some MWs displayed dramatic increases in COCs

17 PA Bedrock Site with Surrounding Features

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19  Isoconcentration maps  DO plume progression  Selective BTEX, MTBE trends  Selective hydrograph

20 BURTS AUTO REPAIR SHED CAR WASH 1265 DEKALB PIKE 1257 DEKALB PIKE PROPERTY LIMIT SHED WASTE OIL BTEX Maps O2 Infusion Phase 9 months, 3 iSOCs + Baseline Zero iSOCs 20 months, 3 iSOCs + 14 months, 6 iSOCs 800 ppb 5,000 ppb 10,000 ppb 20,000 ppb August 2003 August 2002 July months, 6 iSOCs

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22 BURTS AUTO REPAIR SHED CAR WASH 1265 DEKALB PIKE 1257 DEKALB PIKE PROPERTY LIMIT SHED WASTE OIL FORMER DIESEL DISPENSER FORMER DIESEL UST FORMER KIOSK FORMER PUMP ISLANDS 10 ppm 20 ppm 30 ppm 40 ppm 50 ppm 1 month w/3 iSOCs 16 months, 3 iSOCs + 9 months, 9 iSOCs 23 months, 3 iSOCs + 16 months, 6 iSOCs March 2003 December 2003July 2004

23 PA BEDROCK SITE - MW3 OXYGEN INFUSION PHASE MTBE & BTEX TRENDS, AVERAGE FOR QUARTER

24 PA BEDROCK SITE - MW9 OXYGEN INFUSION PHASE MTBE & BTEX TRENDS, AVERAGE FOR QUARTER

25 PA BEDROCK SITE - MW7 OXYGEN INFUSION PHASE MTBE & BTEX TRENDS, AVERAGE FOR QUARTER

26 PA BEDROCK SITE - IW1 OXYGEN INFUSION PHASE MTBE & BTEX TRENDS, AVERAGE FOR QUARTER

27 PA BEDROCK SITE - IW2 OXYGEN INFUSION PHASE MTBE & BTEX TRENDS, AVERAGE FOR QUARTER

28 PA BEDROCK SITE - IW5 OXYGEN INFUSION PHASE MTBE & BTEX TRENDS, AVERAGE FOR QUARTER

29 PA BEDROCK SITE - IW6 OXYGEN INFUSION PHASE MTBE & BTEX TRENDS, AVERAGE FOR QUARTER

30  Pump and treat system was highly successful in establishing hydraulic control and in treating off site contamination where hydraulic conductivity is high.  On site contamination where hydraulic conductivity is low and initial groundwater contamination was highest have been markedly reduced by iSOC installation. Prior to effective use of oxygen infusion, groundwater contamination on site remained high despite 3 years of pump and treat.  On site oxygen infusion substantially reduced contamination by increasing DO levels and by creating multiple pathways for oxygen diffusion.

31  Free phase petroleum was discovered April 2003 in two of six newly installed infusion wells. Some source contamination evidently is entrapped within fractures of bedrock intersected by the wells.  Recalcitrant areas of on site groundwater contamination appear to result in areas where there is a good hydraulic connection to source areas.