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CREATIVE THINKINGEXCEPTIONAL SOLUTIONS

Mass Flux as a Tool for Evaluating and Demonstrating Remedial Objectives and

Optimizing a Combined Remedy Hydraulic Containment and Bioremediation System

Jim Langenbach, P.E., BCEE, Joseph Bartlett, P.E., Jason Shye


Today’s Presentation

• Background• Baseline flux evaluations• Hydraulic capture operations and optimization• Bioremediation injection and performance monitoring• Results/flux considerations to support site transition• Summary


Background

• Site: Precision Fabricating & Cleaning (PFC)– Cocoa, Florida– Metals fabricating, cleaning, and maintenance facility– Trichloroethene (TCE) was used for metal parts

cleaning 1964-1977• 1966 – Drum release• 1977 – Rail Car release• Incidental spills from cleaning operations Site


Background

• Groundwater investigation began in 1993

• Detailed investigations and research by University of Waterloo began in 1996–High resolution transect

bundle/monitoring well networks

–Back-diffusion investigations Image Reference: Mass and Flux Distributions from DNAPL Zones in Sandy Aquifers, Ground Water, January-February 2005, Martin Guilbeault, Beth Parker, John Cherry.

Conceptual Mass Flux and Monitoring Transect Downgradient from a DNAPL Source Zone


Baseline Flux Evaluation

• High-resolution transect sampling conducted in 1997/1998

• Property line transect represents 156 discrete groundwater sampling points

• Transect data utilized to assess mass flux leaving site

• Flux data also used to support hydraulic capture system design

Property Line Transect

Property Line SITE

Equivalent TCE Concentrations Property Line Transect – 1998 (G&E Engineering)


Baseline Flux Evaluation

• Mass flux calculated using:– Range of measured gradient– Hydraulic conductivity values– Effective porosity– Cross-sectional

areas/concentrations of transects

• Property line transect mass flux calculated at 72 - 112 lb/yr as Equiv. TCE in 1998

Image Reference: Mass and Flux Distributions from DNAPL Zones in Sandy Aquifers, Ground Water, January-February 2005, Martin Guilbeault, Beth Parker, John Cherry.


Hydraulic Capture Remedy/CSM

• Mass diffused in fine-grained layer and sorbed into sandy clay at ~35 to 38 ft BLS

• Downgradient reinjection to avoid stagnation zones and enhance dissolved plume cleanup


P&T Operations

• Hydraulic Containment (P&T) System started in 2002– Optimization activities implemented

during periods of asymptotic recovery: • Pumping rate configurations • Extraction/injection well screen

modifications– Increased mass flux; however, elevated

concentrations remained• P&T Operating/Reporting costs of

~$60,000/yr ($30,000/yr system related)– Equipment O&M conducted by plant

personnel (not included in costs)– Treatment system approaching end of

useful life


P&T Operations

• 2002-2015 total influent from 12 recovery wells– 30 gpm pumping– Influent TCE ~1,000

µg/L– Modifications resulted

in short-term influent increases

• Time for total influent to decrease to ~100 µg/L or 10 µg/L?

Air Stripper Influent Concentrations vs Time


Mass Removal Data

• Monthly range of TCE mass removal of ~5 –22 lb/month

• Asymptotic mass removal rate of 80 to 130 lb/yr, 106 lb/yraverage (2004 –2014)

• Short-term increases associated with optimizations


Optimization Approach

• Combined remedy for enhanced outcome – Enhanced in situ bioremediation strategy used in conjunction with

existing hydraulic containment system• Inject electron donor and dechlorinating microbial culture in accessible areas• Utilize existing P&T system to draw amendment through target area (source zones

under footprint of active facility)

• Goal: Reduce on site TCE source zone and associated mass flux (as measured via P&T system) to facilitate the accelerated shutdown of the legacy hydraulic containment system


Implementation

• Injection in October 2015– TerraSystem’s SRS®-FRL slow

release large droplet electron donor• 14, 55-gallon drums• Diluted with staged potable water• Total injection volume of 8,480 gallons• Six injection locations each with three,

4-ft lifts – SiREM Laboratories KB-1®

dechlorinating bacteria• 10 L total• 1.7 L per injection point• Injected at ~halfway point of injection

at each lift


Implementation

• Implementation Schedule– P&T system shutdown immediately prior to

injection activities– 2½ day injection event– 5 day shutdown period– 3 day ‘transport’ period – select recovery wells

(RW-4B and RW-5B) restarted– 3 month shutdown– System restarted to maintain hydraulic

containment capabilities– Following ~6 months of system operation,

electron donor observed in system components• Authorized by EPA to shutdown system for an

additional 3 months


Implementation

• Semi-Annual Performance Monitoring– VOCs (EPA 8260B)– TOC (EPA 415.1)– MEEs (RSK-175)– Dhc and vcrA (GeneTrac)– Underground Injection Control

parameters• TRPH• TDS• Sodium


ResultsResults RW-4B – CVOCs

Screen Interval (ft BLS)

TCE (µg/L)

cDCE (µg/L)

VC (µg/L)

10/22/2015 1,400 260 407/5/2016 1,100 270 46

9/15/2016 440 750 1.0 U4/18/2017 660 530 30010/13/2017 670 230 280

Location Date

RW-4B 32 to 60


RW-5B – CVOCsResults

Screen Interval (ft

BLS)TCE (µg/L)

cDCE (µg/L)

VC (µg/L)

10/22/2015 3,200 460 554/29/2016 85 1500 7107/5/2016 18 410 8209/15/2016 .58 U .48 U .40 U4/18/2017 4 88 280

10/13/2017 0.305 2 34

Location Date

32 to 60RW-5B


ResultsS67-9/10 - CVOCs

1/15/2015 200,000 J3 1,600 710 U5/27/2016 610 U 5,300 57,0009/15/2016 0.58 U 1,100 33,000

4/17/2017 .82 I 1,600 55,000

10/10/2017 5.4 4,600 14,000

TCE (µg/L)

cDCE (µg/L)

VC (µg/L)


Location Date

S67-9/10 33.4 to 34.6


ResultsS68-11 - CVOCs

TCE cDCE VC(µg/L) (µg/L) (µg/L)

1/15/2015 71,000 J3 3,300 710 U10/22/2015 3,500 2,100 1504/29/2016 14 15 55

10/26/2016 1.4 13 1604/17/2017 0.68 I 1.1 28

S68-11 34.3 to 34.7


Location Date


ResultsS68-10 – CVOCs

1/15/2015 1,000 1,000 11010/22/2015 680 1,000 984/29/2016 200 200 21010/26/2016 1 200 3804/17/2017 .91 I 52 220

S68-10 36.5 to 37.5

Location Date TCE (µg/L)

cDCE (µg/L)

VC (µg/L)



Results

Dhc vcrA(gene copies/liter) (gene copies/liter)

10/22/2015 52 2.7 13 3 x 103 U NA4/29/2016 3600 200 270 1 x 109 4 x 108

10/26/2016 3900 180 130 3 x 109 2 x 109

4/17/2017 4100 300 90 3 x 109 5 x 108

10/10/2017 6600 510 57 3 x 109 2 x 109

Methane (µg/L)

Ethene (µg/L)

TOC (mg/L)

36 to 37.5S68-10

Location DateScreen Interval (ft BLS)


Results

• >95% sustained reduction in CVOC mass flux (1,487 µg/L to 41 µg/L) since bioremediation implementation

Air Stripper Influent Concentrations vs Time


Results

• Significant post-bioremediation mass flux decrease (>95%)

• Pre-bioremediation 7-12 lb/month flux –asymptotic

• Post-bioremediation 0.1 lb/month flux –continuing to decline

Mass Flux and Cumulative Mass Removed Versus Time


Summary

• 1998 mass flux evaluation was accurate as demonstrated by P&T data!

• Optimization of legacy P&T system provided a significant reduction in P&T life cycle operations/mass flux

• P&T is in process of permanent shutdown• Bioremediation project costs:

– Design - $8,000– Implementation/monitoring - $60,000 – Represents approximately 2 yr of P&T operations related costs

• Implemented strategy/mass flux reduction represents a minimumof 15 yrs of P&T


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Titusville, FL 32780

321.269.5880

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