Pilot Testing a Sorptive Biomatrix as an MTBE Barrier

Jack SheldonAEHS ConferenceSan Diego, CAMarch 22, 2017

Carbon-based amendments are making a difference!!

• The Site• Microbial Profile• Field Application &

Performance

The Site

From the Sky – 76 Station, Daly City, CA

The Treatment Area

• Soil and groundwater impacts in source areas (former USTs and dispensers)

• Varying degrees of LNAPL – apparent or ganglia

• Plumes migrate off-site and may have BTEX, MTBE and/or TBA constituents

Typical Service Station Scenario

• Operating gas station with prior leaking UST.• Prior remedial efforts to clean up BTEX and TPH-

GRO.• Minimal impacts remain on-site. Off-site

groundwater is the current focus. Minimal soil impact off-site and only 7 lbs. of MTBE mass in groundwater.

• Groundwater at 32 ft. bgs.• San Mateo County Groundwater Protection

Program.

The History

• AS/SVE and MNA important remedies on-site.• Site responded well to increased dissolved

oxygen.• Plume migration through narrow channel and

limited 5 ft. vertical horizon.• Expansion of AS/SVE or switch to P&T for off-

site riddled with logistical issues and costly.

The History – Part 2

Site Geology• ~12’ to 37-38 feet bgs: poorly sorted primarily sand (SP) with some interbedded silt and clay• ~38’ to 45 feet bgs: continuous clay layer (aquitard) found in all borings south of most downgradient well

Microbial Profile

BioTraps® and Geochemistry

Unit SamplersGEO

COC

MICRO

Supplier

Assembly

MNA

BioStim

BioAug

• MW-8, 10, 11, and 14 used for testing• Water column height dictated specific approach

per well • Sulfate and ORC-A® compared to control• PM-1 organism (MTBE degrader) and MTBE/TBA

gene functions analyzed• 13C labeled MTBE used to show microbial

growth versus actual degradation

Microbial Results

Field Application and Performance

• Fine particle activated carbon (1-2 microns)

• Combined with unique polymer for distribution enhancement

• Binds to aquifer solids• Establishes biodegradation

site• Regeneration occurs

The Chemistry -

PlumeStop® Bench Test

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Bench test water from MW-24 showed 92% reduction with PlumeStop®.

• Direct push PlumeStop® at MW-14 and MW-24.• Direct push ORC-A® to enhance biodegradation

30 days later.• Three injection points per well per amendment• Monitor every two weeks for MTBE/TBA and

secondary parameters – geochem/field parameters/microbial (RNA vs DNA)

• Remedial goal – 1 mg/L MTBE

Pilot Test Approach

• Target interval – 32 -37 ft. bgs MW-14/34 – 39 ft. bgs MW-24 with bottom up approach

• 4 total injection events - several challenges with refusal using direct push and HSA

• Communication/information issues.• Hydropunch and injection tooling used to overcome friction issues• Injection volume – 1047 gal per event at 5,500 mg/L PS + 17 gallons

30% ORC-A® at MW-14• Injection volume – 1438 gal per event at 20,000 mg/L PS + 51

gallons 30% ORC-A® at MW-24• Spacing – 8-10 ft.• Flow/Pressure – 1 -2 gpm/30 - 100 psi (higher observed)

Injection Highlights

Photos from the Field

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Critical to Success

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The Results – MW-14

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1/31/2016 3/21/2016 5/10/2016 6/29/2016 8/18/2016 10/7/2016 11/26/2016

Conc

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TBE,

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MW-14MTBE, TBA, versus Time

Former 76 Service Station 11202Daly City, California

MTBE(ug/L)

Plume Stop Injection ORC-A Injection Plume Stop Injection TBA(ug/L)

The Results – MW-24

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4/20/2016 5/10/2016 5/30/2016 6/19/2016 7/9/2016 7/29/2016 8/18/2016 9/7/2016 9/27/201610/17/201611/6/201611/26/2016

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BA, u

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TBE,

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MW-24MTBE, TBA versus Time

Former 76 Service Station 11202Daly City, California

MTBE(ug/L)

Plume Stop Injection ORC-A Injection TBA(ug/L)

Secondary Results – MW-14

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1/31/2016 3/21/2016 5/10/2016 6/29/2016 8/18/2016 10/7/2016 11/26/2016

ORP

, mV

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O, m

g/L)

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MW-14DO, ORP, versus Time

Former 76 Service Station 11202Daly City, California

Oxygen, Dissolved(mg/L)

Plume Stop Injection ORC-A Injection Plume Stop Injection Oxidation Reduction Potential(mV)

Secondary Results – MW-24

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5/15/2016 6/4/2016 6/24/2016 7/14/2016 8/3/2016 8/23/2016 9/12/2016 10/2/2016 10/22/2016

Oxi

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MW-24DO, ORP versus Time

Former 76 Service Station 11202Daly City, California

Oxygen, Dissolved(mg/L)

Plume Stop Injection ORC-A Injection Oxidation Reduction Potential(mV)

• Direct push injection into sand isn’t always what it appears

• A bioamendment is an important addition to the carbon-based amendment

• With the right microbiology and conditions, substantial reduction in MTBE/TBA concentrations is possible

• 6 ORC-A® and 5 PS points per day is possible• Communicate

Lessons Learned

• Full-scale biobarrier planned.• Dual rows of PlumeStop® with ORC-A®

upgradient side to move oxygen to barrier.• Target MW-14 and MW-24, but add “wing” to

barrier to address well in the street.• Take lessons learned and apply.

Path Forward

Full-scale – 19,000 lbs. PS/4800 lbs. ORC-A®

Jack Sheldonjacks.heldon@anteagroup.com

AnteaGroup @AnteaGroup

Acknowledgements:Dacre Bush, PG, Antea Group (Long Beach)

Craig Sandefur, Dan Nunez - Regenesis (San Clemente)Gregg Drilling

Regenesis Remediation Services (RRS)Microbial Insights

Thank You/Q&A