MGP Remediation Using ISCO-A Practical Approach

presentation for

The Third International Symposium And Exhibition On TheRedevelopment of Manufactured Gas Plant Sites (MGP USA 2008)

Mystic, ConnecticutSeptember 23-25, 2008

by:

Will Caldicott

Prasad Kakarla & Mike TempleIn-Situ Oxidative Technologies, Inc.

West Windsor, New Jersey

MGP Treatment-Setting Realistic Goals

In-situ oxidation (ISCO) has been used withvaried degrees of success.

Success or failure of ISCO for MGP treatment islargely dependent on treatment goals set.

Given a reasonable set of treatment goals, ISCOcan be a potent tool for comprehensive siteremediation and closure.

ISCO technology using Modified Fenton’s Reagent(MFR) at two separate MGP sites are discussed.

MFR Technology Overview

Circum-neutral pH chemistry. Chelated iron catalysts. Stabilized hydrogen peroxide. No acids used. Desorption capability.

MFR Reaction Scheme

•• HH22OO22 + Fe + Fe2+2+ →→ OHOH•• + OH + OH-- + Fe + Fe3+3+

•• HH22OO22 + + OHOH•• →→ HOHO22•• + H + H22OO

•• HOHO22•• →→ H H++ + + OO22••--

•• HOHO22•• + + OO22••-- →→ HOHO22-- + O+ O22

pKa = 4.8perhydroxylperhydroxyl

radicalradical

hydroxyl radicalhydroxyl radical

superoxidesuperoxide radical anionradical anion

hydroperoxide anionhydroperoxide anion

WhereWhereHH22OO22 = hydrogen peroxide = hydrogen peroxideFeFe2+2+ = ferrous iron = ferrous ironOHOH•• = hydroxyl radicals = hydroxyl radicalsOHOH-- = hydroxide ion = hydroxide ionFeFe3+3+ = ferric iron = ferric ironHOHO22•• = perhydroxyl radical = perhydroxyl radicalHH22O = waterO = waterHH++ = hydrogen ion = hydrogen ionOO22••-- = superoxide radicals = superoxide radicalsHOHO22

-- = hydroperoxide anion= hydroperoxide anionOO22 = oxygen = oxygen

Site #1-Background

Former MGP site located along the bank of amajor river in New York state.

Location of the site was in the vicinity of the city’sresidential, shopping and restaurant districts.

Remediation of the site was part of a waterfrontrevitalization effort.

Site Contamination

Gas extraction processes used at the site resultedin bedrock, soil, groundwater and soil gascontamination.

COCs included MGP-related: coal tar volatile organic compounds (VOCs) polyaromatic hydrocarbons (PAHs) non-aqueous phase liquids (NAPLs) dense non-aqueous phase liquids (DNAPLs)

Site Contamination

o Dissolved phase:o VOCs > 6 mg/Lo PAHs > 1,200 mg/L

o NAPL:o VOCs >8,500 mg/Lo PAHs >36,000 mg/Lo Total petroleum hydrocarbons >900,000 mg/L

Bench Scale Treatability Study

Performed on overburden soil, tar soil andNAPL to determine effectiveness anddosages required to reach treatmentgoals.

Treatment was effective in reducing COCsto varying degrees: 65% reduction of PAHs. 45% reduction of TPH. >99% reduction of VOCs.

Remedial Strategy

The New York State Department of EnvironmentalConservation (NYSDEC) in consultation with the New YorkState Department of Health (NYSDOH) selected a multi-phased remedy for the site. 1) ISCO to treat the source area bedrock formation. 2) Excavation/removal of the overburden soil in the upper

terrace area. 3) In situ solidification (ISS) in the lower terrace area.

Objective as described in the Record of Decision (ROD) is toeliminate/reduce to the extent practical: 1)the presence ofNAPL and MGP-related COCs as sources of soil, GW and soilgas contamination; and 2)the migration of NAPL and MGP-related COCs that would result in soil, GW, or soil gascontamination.

ISCO-Bedrock Treatment Source of site contamination. ISOTEC’s MFR technology selected. ~ 36,000 cubic yards. Vertical thickness of ~ 20 feet. Total pore volume estimated to be 145,000 gallons. Approximately 24% of pores and fractures contain

NAPL or “sheen” impacts. ISCO treatment program to inject between 50%-

100% of the effective pore volume of the bedrocksystem with concurrent GW extraction fromdowngradient wells, treatment re-injection/disposal.

Field Implementation

90,000 gallons of MFR was injected via 20 IW’s. 17% H2O2 concentration. Treatment program implemented over 39

working days. 35,000 gallons of GW was extracted and treated

over 42 days. Air monitoring was performed around the

perimeter of the site. Only 36 liters of LNAPL and DNAPL had been

recovered prior to ISCO treatment.

Results The bedrock well network was monitored for

several weeks following injections. Impossible to quantify the volume of NAPL

destroyed within the bedrock fractures; butabsence of NAPL in the MWs following injectionsindicated the program was successful in treatinga large proportion of NAPL in the bedrock.

No exceedances were encountered during theperimeter air monitoring.

The project was presented with the “2007 Awardof Merit” by New York Construction Magazine.

Site #2-Background/Geology

Former MGP site located in southern US. Past remedial activities include excavation and

ISS. Fill material from 0.2 ft to 13 ft bgs underlain by

alluvial deposits, which is underlain by saprolite. GW at the site ranges from 6-25 ft bgs.

Site Contamination

GW and alluvial soils impacted with MGP-relatedcontamination. Heavier impacts of by-product-like material (BPLM) have been found in someareas.

COCs included MGP-related VOCs and PAHs;primarily BTEX and naphthalene.

Bench Scale Treatability Study

Treatment was effective in reducing COCsto varying degrees in soil and GW: >99% reduction of BTEX with individual

contaminants treated to ND levels. 87% reduction of PAHs with naphthalene

(primary COC) being treated to >99%.

Site Objectives

The Groundwater Corrective Action PlanAddendum objectives for the site included: 1) Treat residual BPLM, to the extent practical

with ISCO, and 2) Establish suitable geochemical conditions to

allow monitored natural attenuation (MNA).

ISCO-Impacted Alluvium

ISOTEC’s MFR technology selected. Treatment interval varies from 6-36 ft

bgs. IW’s spaced at 15 ft intervals. Screened intervals ranged from 1-15 ft. Nested wells used in some locations

targeting the entire vertical depth ofcontamination.

ISCO-Impacted Alluvium

Two distinct areas; 1) Larger off-site (285 ft x 160 ft) area with

heavier BPLM impacts, and 2) Smaller on-site (50 ft x 50 ft) area with

only residual materials. Total treatment area estimated to be 19,554

yd3.

Bench-scale results estimated 12.9 gallons ofMFR/yd3 required to achieve >95% reduction ofBTEXN.

~ 252,000 gallons of MFR to treat the site.

Field Implementation-Phase I

111,000 gallons of reagent injected via 270IW’s to date.

H2O2 concentration of 16.7% used formajority of site with some sensitive areasreceiving 8.3%.

Treatment program implemented over 68-10 day injection events.

36 liters of LNAPL and DNAPL had beenrecovered from some of the wells prior toISCO treatment.

Treatment Design

Discussions with regulators led to asite-specific four-step operationalperformance criteria.

Treatment Process Flow Chart for ISCO in Alluvium

Inject 25% of the volume of Oxidant calculated during the LTS

Monitor Head Space with PID

If PID is < 50 mg/L

Monitor for H2O2

If H2O2 > 250 mg/L over an 8 hr period

Monitor until H2O2 < 2.5 mg/L

If PID is still < 50 mg/L

Treatment Complete

Inject until the next oxidant decisionpoint (i.e. 50, 75, or 100%)

Is oxidant volume injected ininjection well less than 100%

Yes

Yes

Yes

Yes

No

No

No

Results

Phase I completed with approximately111,000 gallons of MFR being injected.

The majority of IWs installed during PhaseI met remedial requirements and nofurther injections into those wells arenecessary.

Phase II is scheduled to begin soon withmore than 100 IWs to be installed in theoff-site portion of the site.

ISOTECISOTECSMSM

In-Situ Oxidative Technologies, Inc.In-Situ Oxidative Technologies, Inc.www.insituoxidation.comwww.insituoxidation.com

Thank You Questions?

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