Subtitle

Switching it Up: From Long term Pump-and-Treat to In-situ Chemical Oxidation for 1,4-Dioxane in Groundwater Remediation

D. Grant Walsom, B.A.Sc., P.Eng., QP

Partner

XCG Consulting Limited

ESAA Remtech – October 10, 2018

Outline

• Case Study History – how did we start?

• 1,4-Dioxane – What did we know?

• 2002 Technology - Success

• Switching it Up

• Financial Review – Decision Assistance

• Case Study: Switching it Up

• Summary

Case Study History – how did we start?

• Industrial property undergoing property

sale due to bankruptcy.

− 1.3 hectare property developed in 1974

− 6,700 m2 industrial bldg.

− metals fabrication facility – use of solvents

• Environmental Site Assessments to support property sale.

− Original Phase I ESA in 1997

− Successive Phase II ESAs and delineation activities (‘97 to ‘01)

Case Study History – how did we start?

• Identification of Groundwater Impacts … Surprise!

− 1,1,1-trichoroethane (TCA) … up to 480,000 µg/L

− 1,1-dichloroethylene (DCE) … up to 27,000 µg/L

− Other minor chlorinated volatile organic compounds

• Identified to likely migrate off-site – natural flow of

shallow groundwater – no deeper impacts.

• Some minor soil impacts … source location(s).

Case Study History – how did we start?

• Excavated Soil impacts

outside of building

− two hot-spots sent for off-

site disposal

• Installed a passive

vapour diversion system

below building

− (inside hot-spot)

Case Study History – how did we start?

• Designed a groundwater pump-and-treat

system to hydraulically contain any

impacted groundwater to the property.

− 3 sumps on downgradient side of property

− Pumps send water to collection tank

− Air-stripper tower

− Approval to discharge to storm sewer

− Must meet prescribed discharge criteria

• not meant to be a Remediation System

1,4-Dioxane – What did we know?

• Application process with Ontario Ministry of

Environment (MOE)

− Very little known about 1,4-dioxane

→ emerging contaminant

− MOE requested investigations for 1,4-dioxane

• Solvent stabilizer associated with TCA and DCE

• Highly soluble, mobile in groundwater (leading edge)

• Identified as a potential carcinogen

• Very few jurisdictions with Guidelines or Standards

Environmental Science & Engineering, May 2002

1,4-Dioxane – What did we know?

• Found it!

− Groundwater (source area = 10,000 to 13,000 µg/L)

− Migrating?

− Low amount off-site (~140 µg/L)

• Now What?

− Technology review - Proven methods? Very few in 2001.

− Photocatalytic Oxidation … TiO2 and UV energy

1,4-Dioxane – What did we know?

• Photocatalytic Oxidation Unit (Photo-Cat)

− Manufactured by Purifics (London, ON)

− TiO2 activated by UV lamps - destruct

− Add onto previously designed P&T system

− Minor reconfigure

− Approval re-filing

− Start-up Oct. 2002

Switching it Up

• System ran well until circa 2015 –

Remediation did occur

• Discharge met Effluent Limits in C of AContaminant of

Concern

(ppb or µg/L)

MOE

Table 2

Standard

July 2018

Highest

Concentration

Nov 2015

Highest

Concentration

Previous

Highest

Concentration

1,4-Dioxane 50 8000 9100 13600

1,1-Dichloroethane 5 11000 11000 21500

1,2-Dichloroethane 1.6 8.7 9.5 120

1,1-Dichloroethene 1.6 1200 1100 27000

1,1,1-Trichloroethane 200 5500 7600 480000

1,1,2-Trichloroethane 4.7 1.8 1.5 12

Trichloroethene 1.6 14 21 550

Vinyl Chloride 0.5 4 3.5 36

Switching it Up

• Break-downs and issues with replacement parts

− Labour intensive, frequently off-line, compatibility with original

• Evaluation of newer methods/technologies

− New owners in 2018

• Length of time? Another 10+ years? Cost?

• What is out there now that wasn’t in 2001?

• ISCO? Success with other contaminants

• 1,4-dioxane limiting?

Switching it Up

1,4-Dioxane is susceptible to chemical

oxidation, and in groundwater it can

be treated by activated sodium

persulfate, ozone and peroxide, and

modified Fenton's reagent; however,

sodium permanganate is not effective

for 1,4-dioxane treatment

(Chiang et al. 2016): USEPA – CLU-IN.

Financial Review Option DescriptionTime

FrameCost Estimate

i. Continue with Existing Course >15 years > $519,000+

ii.In-situ Chemical Oxidation and Risk

Assessment2 years $444,000

Source Removal and Groundwater

Polishing

(not favoured due to tenant occupancy)

iii. 1 year $425,000

+ indicates that this cost is a net present value and the treatment system replacement of

roughly $250,000 should also be considered in addition to the annual O&M cost.

2002 to 2015

P&T annual Operation

and minor Maintenance

costs were ~$50,000

Break-downs and issues

with replacement parts

Case Study: Switching it Up

• Sodium Persulphate activated with

Sodium Hydroxide

− Delivered in totes at 10% solution

− Ease of use at the site

− Mixed at time of injection (1:1 ratio)

• Remaining Source areas

Case Study: Switching it Up

Staged Remediation

• Injection Wells for

Below Building

• Direct Push in

Zone 1

• Remox SR+ along

downgradient

property

boundaries

• Early Results – below building

Case Study: Switching it Up

Contaminant of

Concern

(ppb or µg/L)

MOE

Table 2

Standard

Pre-Injection

(July 2018)

Post-Injection

(1 month)

1,4-Dioxane 50 8,000 2,700

1,1-Dichloroethane 5 11,000 5700

1,2-Dichloroethane 1.6 8.7 6.5

1,1-Dichloroethene 1.6 1,200 85

1,1,1-Trichloroethane 200 390 340

1,1,2-Trichloroethane 4.7 1.8 0.75

Trichloroethene 1.6 7.7 3.6

Vinyl Chloride 0.5 4.0 2.2

• Successful Trial

• Further injections

below building

• Next Zone

Summary

• 2001 – Limited Abilities/Methods for 1,4-Dioxane with DCE and TCA

• Pump-and-Treat did work well. Served the purpose at the time

− Control of issue for lender to divest, first purchaser to maintain certainty

• New owners with new goals – New Treatment Abilities

− No longer just control … remediate with shorter timelines – cost efficient

Summary

• Seeing success in our trial injections for 1,4-dioxane treatment

through ISCO with activated sodium persulphate

• Continue and provide downgradient property treatment barrier

− ISCO in sources – sodium persulphate activated with sodium hydroxide

− Remox SR+ cylinders along downgradient property boundaries

− Fall 2018 schedule

• Team/support of good suppliers and contractors, tenants/occupants

Thank you for Attending!

Questions?

D. Grant Walsom, B.A.Sc., P.Eng., QP

Partner

XCG Consulting Limited

E: grant@xcg.com

T: 519-741-5774 ext. 7246

www.xcg.com