A Cost-Effective and Practical Remedial Alternative Paul R. Lear, - - PowerPoint PPT Presentation

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A Cost-Effective and Practical Remedial Alternative Paul R. Lear, - - PowerPoint PPT Presentation

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In-situ Stabilization at MGP Sites A Cost-Effective and Practical Remedial Alternative Paul R. Lear, Ph.D. Manufactured Gas Plants Starting in late 1900s, gas was manufactured by heating coal in specialized oven Common in many

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In-situ Stabilization at MGP Sites – A Cost-Effective and Practical Remedial Alternative

Paul R. Lear, Ph.D.

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November 14, 2012 2

Manufactured Gas Plants

  • Starting in late 1900s, gas was

“manufactured” by heating coal in specialized

  • ven
  • Common in many urban areas of the US
  • Manufactured gas was used for residential

and street lighting and cooking

  • An unintended consequence was the release
  • f byproducts including coal tar
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November 14, 2012 3 3

Technology Description

  • “In situ Stabilization/Solidification (ISS) is the

mixing of impacted soils with reagents (such as Portland cement and/or slag) to reduce the leachability of contaminants while decreasing the permeability of the stabilized materials.”

  • ISS can be applied using “auger-based” and

“excavator-based” approaches.

  • “Auger-based” ISS has been practiced for many

years, primarily in the geotechnical and deep foundations arenas.

  • “Excavator-based” ISS has been practiced for

many years, primarily at waste impoundments and sites with subsurface obstructions

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November 14, 2012 4 4

Technology Description

  • To date, approximately 75 MGP sites have been

remediated via ISS

  • Some locally completed WRScompass ISS

projects at former MGP sites include:

  • CHGE MGP Site (Auger-Based) – Poughkeepsie, NY
  • DelDOT/Jutison Landing Redevelopment (Excavator-

based) – Wilmington, DE

  • NYSEG MGP Site (Auger-based) - Norwich, NY
  • Camden MGP Site (Excavator-based) – Camden, NJ
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November 14, 2012 5 5

Typical ISS Criteria for MGP Sites

Parameter Value UCS > 50 psi Permeability < 10-6 cm/sec Leachability UTS or Risk-based Leaching Criterion Free Liquids No free liquids

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November 14, 2012 6 6

Typical “ISS-Auger” Equipment

Crane- Mounted Turn Table or Top Drive Drill Rig Reagent Batch Plant 4-foot to 12-foot Diameter Auger

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November 14, 2012 7 7

Completed ISS Columns

Solidified Columns from Pilot Test

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November 14, 2012 8 8

Auger vs Excavator?

  • Auger-based ISS when:
  • Treatment depths below 20 feet

(can go to 90 ft bgs)

  • Little to no subsurface obstructions
  • Lithologies with blow counts

below 40

  • Vapor capture and containment

required

  • Slurry application of reagents

required

  • Treatment volumes exceeding

15,000 cy

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November 14, 2012 9 9

Auger vs Excavator?

  • Excavator-based ISS when:
  • Treatment depths less than 25

feet

  • Subsurface obstructions
  • Lithologies with greater than 30

blow counts

  • Vapor suppression allowed
  • Dry addition of reagent required
  • Treatment volumes less than

10,000 cy (can do more)

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November 14, 2012 10 10

The “Ideal” ISS Site

  • No overhead restrictions
  • Pre-excavation of underground obstructions
  • Readily available water source (125 gpm)
  • Relatively flat ground surface
  • Sufficient lay down area for batch plant near

work area (50’ x 50’)

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November 14, 2012 11

Leaching Criteria for ISS at MGP Sites

  • No regulatory criteria

typically available contaminants

– PAHs (especially naphthalene and methylnaphthalene) – BTEX

  • Default are typically

Groundwater Quality Standards

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November 14, 2012 12

Leaching Criteria for ISS at MGP Sites – Alternative Approach

  • Utilize Existing Risk-based

Approach to Site Remediation

  • Use Leachate Criterion instead
  • f the GWQS as the leachate

criteria for ISS below the Water Table

– Still protection of human health or the environment – Will allow ISS to be considered for a wider range of sites

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November 14, 2012 13

Health-Based Leachate Criterion

  • Methodologies for risk-based

cleanup standard development allow the use of a Health-Based Leachate Criterion when determining Impact to Groundwater Remediation Standards

  • Represents how much of a

contaminant the soil can leach and still be protective of human health and the environment

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November 14, 2012 14

Leachate Criterion Calculation

  • Site–Specific Leachate Criterion

– The higher of the health-based Groundwater Quality Criterion times site-specific dilution attenuation factor or the aqueous PQL

  • Default Leachate Criterion

– Higher of the health-based Groundwater Quality Criterion times a default dilution attenuation factor of 13 or aqueous PQL

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November 14, 2012 15

ISS Leaching Criterion

  • Can be similar to health-based

Leachate Criterion

– Represent how much of a contaminant the ISS treated material can leach to groundwater and still be protective of human health and the environment – Recognize that the TCLP and SPLP leachates have higher TDS and ionic strength than groundwater typically does (higher PQLs)

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November 14, 2012 16

Suggested ISS Leaching Criterion

  • Example using default DAF for metals

Contaminant Health Based GW Quality Criterion (µg/L) Aqueous PQL (µg/L) Suggested Leaching Criterion (µg/L) Contaminant Health Based GW Quality Criterion (µg/L) Aqueous PQL (µg/L) Suggested Leaching Criterion (µg/L) Aluminum 200 30 43 A Lead 5 5 65 Antimony 6 3 78 Manganese 50 0.4 650 Arsenic 0.02 3 9 B Mercury 2 0.05 26 Barium 6,000 200 78,000 Molybdenum 40 2 520 Beryllium 1 1 13 Nickel 100 4 1,300 Cadmium 4 0.5 52 Selenium 40 4 520 Chromium 70 1 910 Silver 40 1 520 Cobalt 100 0.5 1,300 Thallium 0.5 2 6 B Copper 1,300 4 16,900 Vanadium 60 1 780 Iron 300 20 3,900 Zinc 2,00 10 2,600

A Adjusted so as to not exceed solubility B Adjusted to 3x Aqueous PQL

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November 14, 2012 17

ISS Leaching Criterion Rationale

  • Consistent with the existing use
  • f Leaching Criterion for

calculating site-specific Impact to Groundwater Remediation Standards

  • Recognizes that TCLP and

SPLP leachates are chemically different than groundwater

  • Protective of human health and

the environment

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November 14, 2012 18

ISS Leaching Criterion Rationale

  • Can be determined for most

contaminants using a existing, well-developed regulatory framework

  • Can be easily implemented
  • Can be consistently applied

from site to site

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November 14, 2012 19 19

Camden MGP Site

  • 1st ISS at an MGP site in

New Jersey

  • New electrical substation

needed to support redevelopment of Camden’s waterfront

– Site MGP impacts needed to be addressed first

  • Site contained last gasholder

in New Jersey

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November 14, 2012 20 20

Camden MGP Site

  • Excavation and Off-Site T&D of material to 12

feet bgs

– Depth necessary to accommodate new substation

  • ISS of material from 12 to 30 feet bgs (24,000

cy)

– Leachability to Risk-Based Leaching Criterion – Permeability ≤ 1x10-6 cm/sec (ASTM D5084) – Unconfined compressive strength (UCS) of 50 psi (ASTM D1633)

  • Backfill to grade
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November 14, 2012 21 21

Camden MGP Site

  • Excavator-based ISS selected

– Treatment depth of 18 feet – Presence of cobble layers (>50 blow counts)

  • Batch plant to slurry reagents and

pump slurry to ISS equipment

  • Operated 6 days per week, 10

hours per day for 2 months during winter

  • Average production rate of 800

cy/day

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November 14, 2012 22 22

Camden MGP Site

  • All samples passed for

leachability, permeability, and UCS

  • Remedial work did not impact

substation construction schedule

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November 14, 2012 23 23

Camden MGP Site

  • All samples passed for

leachability, permeability, and UCS

  • Remedial work did not

impact substation construction

– Treatment took place during winter months

  • No lost-time safety incidents
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November 14, 2012 24 24

NYSEG Norwich MGP Site

  • MGP site adjacent to an active shopping center

which remained open during remediation

  • ISS treatment necessary to redevelop the site

– Treatment required to be done in the winter months

  • Extensive work prior to auger-based ISS

treatment

– Removal of asphalt, concrete obstructions – Location of existing gas mains

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November 14, 2012 25 25

NYSEG Norwich MGP Site

  • Auger-based ISS

equipment included

– 4000 series Manitowoc crane – Hain 450T drilling platform

– 10 foot diameter auger tool – Batch plant

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November 14, 2012 26 26

NYSEG Norwich MGP Site

  • Auger-based ISS treatment

– Treatment depth to underlying clay (32-46 feet bgs) – Treated 10 foot wide perimeter first, keyed 4 feet into underlying clay – Treated interior columns, keyed

  • nly 2 feet into underlying clay

– Site was pre-excavated to accommodate swell

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November 14, 2012 27 27

NYSEG Norwich MGP Site

  • ISS Performance

Criteria

– UCS >50 psi – Permeability <1x10-6 cm/s

  • Mix Design

– Initially 8% Portland cement + 1% bentonite – Reduced bentonite addition without adversely affecting UCS and permeability results

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November 14, 2012 28 28

NYSEG Norwich MGP Site

  • Treated 52,000 cy of MGP-

impacted material

– Conducted the treatment during winter months in Upstate NY – All QC samples met the performance criteria – Completed treatment on-time and on budget – Zero safety or environmental incidents

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November 14, 2012 29

Questions or Comments?

plear@wrscompass.com 865-919-5205

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November 14, 2012 30 30

Thank you for your time today.

Visit us at www.WRScompass.com