Ian Mitchell, SLR Consulting (Canada) Ltd.

IRON AND MANGANESE IN

GROUNDWATER

IMPLICATIONS, OPTIONS AND

RECOMMENDATIONS FOR REGULATING

CONTAMINATED SITES IN BC

Acknowledgements

• Greg Sutherland (CSAP, O’Connor)

• Peggy Evans (BCMOE)

• Robin Jones (CSAP, SLR)

• Raminder Grewal (UDI, CSAP, Keystone)

• Paul Gordon (CPPI, Suncor)

• Phil De Leeuw (BCBC, Imperial Oil)

• Ian Mitchell (CSAP, SLR)

Background

• BCMOE released 2 key technical guidance

documents in 2011 (TG6 and TG8)

• Has resulted in DW applying at most sites

• Has increased uncertainty and delays with

significant economic impacts

• In June 2011, BCMOE engaged CSAP to

hold a stakeholder workshop to identify key

issues and form committees to evaluate

options

Background

• A key issue identified is that TG6/TG8

require Fe & Mn analysis if organic

contamination is present

• Many sites found to exceed for Fe and Mn

resulting in substantial complications

• A TG6 ‘working group’ was formed to

review Fe and Mn issues and to develop

timely options for BCMOE consideration

Issues

• Increased cost, uncertainty associated with

delineation, risk assessment

– Recent increase in Mn and Fe DW standards

from aesthetic-based values to toxicity-based

values has provided little relief

– Difficulty in determining background

concentrations in urban/industrial areas

– Background concentrations highly variable

– Off-site notification issues

– Return of sites to productive use delayed

BCMOE Perspective

• Options must be practical and apply

Province-wide

• Want to avoid orphan liability

• If an option leaves contamination in place,

who will pay for alternate groundwater

resource?

• If Fe & Mn are the drivers, will TG6 work for

other contaminants?

Work Group Objectives

• Review the basis for BCMOE guidance

• Document the economic impacts of the

current Fe and Mn DW standards

• Conduct a technical literature search to

characterize Fe and Mn plumes associated

with PHCs:

– How far they typically extend past PHC plumes

– How long they persist after PHC remediation

Work Group Objectives

• Research what has been done in other

jurisdictions and on what basis

• Review Fe & Mn data from site assessments

to identify where and how often Fe and Mn

background concentrations exceed DW

• Review cost and practicality of Fe and Mn

DW treatment technologies

• Define potential solutions and approaches

in consultation with BCMOE

Economic Impacts

• Presence of Fe & Mn estimated to increase

delineation costs by $25k - 100k per site

• Has affected more than 500 sites in BC

• Estimated that over $100M in site

redevelopment has been deterred in BC

– After PHC remediated, lingering Fe & Mn has

resulted in many sites remaining vacant

– Discourages use of regulatory closure

– Uncertainty has deterred potential purchasers

– Refinancing not approved

Technical Background

• Dissolved Fe and Mn are generated by

reducing conditions that develop under

anaerobic biodegradation of PHCs

• Consultation with natural attenuation

experts in Canada and the US indicated

that the Bemidji site in Minnesota provides

some of the most comprehensive

information available on Fe and Mn

associated with PHC plumes

Literature Review

Figure from US Geological Survey, Fact Sheet 084-98

Literature Review

• Research has shown that the extent of

dissolved Fe and Mn is closely tied to the

leading edge of the PHC plume

PHC Plume Fe, Mn Plume

Literature Review

• At leading edge of PHC plume, transitions

from anaerobic back to aerobic conditions;

causes Fe & Mn to precipitate out and

more rapidly degrades residual PHCs

PHC Plume Fe, Mn Plume

Literature Review

• US studies of >1,000 sites indicate that

most PHC plumes extend <75 m; suggests

that Fe & Mn plumes associated with PHC’s

may be similarly limited in extent

PHC Plume Fe, Mn Plume

Literature Review

Journal of Contaminant Hydrogeology 53 (2001)

Literature Review

• Lack of information in the literature on Fe

and Mn persistence after PHC remediation

• Hydrogeology and geochemistry key factors

PHC Plume Fe, Mn Plume

How long does Fe

and Mn linger?

Literature Review

• Experience of working group participants

that when the PHC source area is removed

in coarse grained soils, dissolved Fe and

Mn concentrations often recover relatively

quickly to background levels (~2 years?)

Other Jurisdictions

• Working group researched how other

regulatory jurisdictions have dealt with Fe

& Mn, and precedents that have been set

• Many jurisdictions do not require Fe/Mn

analysis during contaminated sites

investigations for the protection of DW:

– Ontario - USEPA

– Washington - Denmark

– Oregon

Other Jurisdictions

Background Issues

• Fe and Mn occur above DW standards in

many shallow aquifers due to natural or

wide range of anthropogenic sources

– Makes delineation challenging

– Difficulty in determining source area(s)

• Fe and Mn behave differently in different

groundwater systems

• BCMOE database for groundwater is

primarily from deep water supply aquifers

Background Issues

• Working group reviewed Mn data from site

investigation background wells across BC

• The average Mn concentration was found

to exceed the DW standard in Vancouver

(dataset 103 wells)

• Mn found to exceed the DW standard in 45

municipalities across BC (more than 350

wells)

DW Treatment Technology

• There are common, commercially-available

and economically-feasible treatment

options for homeowners to remove Fe and

Mn from drinking water

– Treatment typically involves oxidation/filtration;

system costs ~$1K for single family dwelling

– Fe and Mn are routinely tested for DW supply

– Several Municipal water supply systems

currently must treat for Fe and Mn

Working Group Conclusions

• Substantial economic impacts associated

with regulating Fe/Mn for DW supply

• Background concentrations of Fe and Mn

found to exceed DW standards at many

sites in BC

• The extent of Fe/Mn is correlated to PHC

plumes and is constrained by associated

redox conditions

Working Group Conclusions

• Fe and Mn treatment is common,

economical and readily available

• Fe and Mn treatment is commonly

implemented for aesthetic issues; aesthetic

standards are 10x less than tox-based

standards

• There are precedents for not regulating Fe

and Mn during contaminated sites

investigations

Options Presented to BCMOE

• Several options considered by the working

group:

– Develop specific exemptions for Fe and Mn

– Simplify the protocols for obtaining a

background release

– Develop regional background concentrations

for Fe and Mn for each region in BC

– Remove Fe and Mn DW standards from the

regulation

Working Group met with

BC MOE on April 2, 2012

for further discussion and

input on options refined

by BC MOE

BC MOE Revised Options

• Repeal Fe/Mn standards

• Revise Fe/Mn standards

• Adjust Fe/Mn standards for Provincial

background levels

• Limit Fe/Mn standards to sites where DW is

being used (rely on treatment for future use)

• Limit delineation for Fe/Mn redox sites

• Limit applicability of Fe/Mn standards to sites

with specific uses

Next Steps

• BC MOE developed a criteria decision

matrix

• All potential options were run through the

decision matrix

– Mandatory Criteria

• Failure of a single criterion = exclusion of option

– Desirable Criteria

Next Steps

• Repeal of Fe/Mn standards no longer considered

• Proposed solution expected within ~ 6 months

• Solution likely tied to exemptions for specific

Fe/Mn sources, with a monitoring commitment

Thank You SLR Consulting (Canada) Ltd.

Questions?