Arsenic and Uranium in Arsenic and Uranium in Domestic Water WellsDomestic Water Wells

Cold LakeCold Lake--Beaver River BasinBeaver River BasinCIPHI 10th Annual Fall Educational Workshop

Edmonton, AlbertaSeptember 16, 2009

Brent Welsh, EITRegional HydrogeologistAlberta Environment, Northern Region

Presentation Outline• Introduction

• Arsenic in the Environment

• Arsenic in groundwater in Alberta

• Arsenic in Cold Lake-Beaver River Basin

• Challenges in assessing arsenic in groundwater

• Uranium in the Environment

• Uranium in groundwater in Alberta

• Uranium in the Cold Lake-Beaver River Basin

• Challenges in assessing uranium in groundwater

• Conclusions and Future Considerations

Understanding Groundwater

Groundwater is a key component of Earth’s water cycle

Everything is connected, but over what time scale?

Groundwater Near Surface

Unconfined Aquifer – Higher levels of Dissolved Oxygen

Geological Controls on Groundwater Flow

• Surface Topography

Shallow Groundwater

• Regional Geological Features

Deep Groundwater

U

As

Local and Regional Groundwater Flow Paths

Typical Groundwater Velocities• Un-fractured Clay Till: V << 1 m/yr• Silt (Aquitard): V < 1 to 5 m/yr• Sand and Gravel: V = 5 to > 100 m/yr

Photos from Alberta Geological Survey, ESR 2007-1

Aquifers and Wells

Aquifer Type Typical Depth

(m)

Typical Yield (m3/d)

Surficial < 75 30 to > 150Buried Channel < 150 150 to > 600Bedrock < 100 < 5 to 150

Geochemical Evolution of Groundwater

• Mineralization occurs as rain water infiltrates to the water table and moves along a flow path

• Factors involved:– Age or residence time– Soil or rock chemistry– Recharge water quality– Chemical reactions

• Trace amounts of Arsenic and Uranium dissolve into groundwater this way

• … don’t forget that groundwater travels, so the ratio of what is in the sediment might not be the same as what is in the groundwater!

Arsenic in the Environment

Source: EPA-815-R-00-023, USEPA, 2000

Air and Water Typical Arsenic Concentrations(ppb)

Air [1.5 – 53] x 10-6 or 1.5 – 53 ng/m3

Unpolluted Rain (ocean air) 0.019Rain (terrestrial air) 0.46Rivers 0.20 – 264Lakes 0.38 – 1000Groundwater (well) 1 – 1000Seawater 0.15 – 6.0

Arsenic in the Environment Cont.

Source: EPA-815-R-00-023, USEPA, 2000

Rock and Soil Sediments Typical Arsenic Concentrations(mg/kg)

Soil 0.1 – 1000Stream/river sediment 5.0 – 4000Lake sediment 2.0 – 300Igneous rock 0.3 – 113Metamorphic rock 0 – 143Sedimentary rock 0.1 – 490

Global Arsenic Issue

• Worldwide, Arsenic is recognized as one of the most serious inorganic contaminants in drinking water

• Arsenic was not routinely analyzed until about 20 years ago

• There are several countries at risk• It is estimated that more than 100

million people may be at risk• … yet we do not fully understand the

problem

Arsenic in the Environment Cont.

• Anthropogenic Sources of Arsenic– Various mining activities– Pesticide application– Wood preservation– Combustion of some coal– etc.

• Most sources are naturally occurring• However, some anthropogenic activities can

increase Arsenic dissolution in groundwater– Over pumping– Increased organic loading– Introduction of heat– Localized increased bacteriological activity? UNKNOWN

Behavior of Arsenic in Groundwater

• Highly complex problem– Complex geochemistry and

biogeochemistry• Arsenic speciation dictate behavior

– As (III) and As (V) are the most common inorganic Arsenic species

• Rules of thumb:– Arsenic can mobilize under both oxic and

anoxic conditions so it can be found everywhere

– Arsenic is a sulfide lover• Metal sulfides (like pyrite) are often a source and

potential adsorption site

Mobilization of As in Water1. Competitive anion exchange

– Arsenic oxyanions compete with more abundant anions for adsorption sites (i.e., phosphate)

– This is important to note because phosphate is in some fertilizers

2. Natural Organic Matter (NOM)– NOM can form soluble complexes with As– Also promotes reduction of iron oxides

3. pH– At high pH, As can dissolve in oxic

environments

Mobilization of As in Water Cont.

4. Redox-dependent mobilization– Can be dissolved from sediment both by oxidation

and reduction– Redox environment can be driven by natural

chemical evolution and bacterial activity– Most wide spread occurrence is from reduction of

iron oxides under anoxic conditions

5. Complex and colloid formation– Arsenic forms mobile complexes with sulfide and

fluoride, etc.– Arsenic can sorb to colloids, which are very small

suspended solids that have high mobility (i.e., they are small enough to flow through the pore space of aquifers)

Alberta Agriculture and PFRA initiative in 1997

• ~ 850 wells sampled in the White zone of the province

• At that time, the IMAC for As was 25 ppb

• Only 2.5% of the wells exceeded 25 ppb

• Current in 2006, MAC was reduced to 10 ppb

• How many wells exceed 10 ppb?

Arsenic in Groundwater in Alberta

Arsenic in the Cold Lake- Beaver River Basin

• There has been significant public concern related to Arsenic levels in groundwater in this area for a long time

• In 2000, several government funded studies were initiated by:– Alberta Health and Wellness– Alberta Environment– Alberta Geological Survey / EUB

• Industry and the U of A subsequently launched arsenic studies

• Note that the IMAC was still 25 ppb in 2000• In 2005-06, AGS and AENV conducted a

regional groundwater study in the Cold Lake area

AHW Findings• Concluded that

wells deeper than 50 feet had an increased likelihood of detecting arsenic

• Link to underlying marine shales

• In Lakeland Area, ~ 50% of wells were at or above 10 ppb

AHW Findings Cont.

AENV Findings

• Mobilization of As in relatively shallow wells in this area is most likely due to reductive dissolution of Iron oxides

• Unfortunately the cause of low redox conditions was not identified

AENV Findings Cont.

AENV Findings Cont.

AENV Findings Cont.

AENV Findings Cont.

AGS Findings (ESR 2000-10)

• 7 sediment cores from well distributed test holes from1977 were tested for trace elements

• Arsenic in sediment ranged from 4 to 20 ppm

AGS Findings (GEO 2002-04) NW of CLBRB Basin

1. Adsorption to oxide and clay minerals2. Competition between arsenic species and

phosphorus ions for adsorption sites3. Release of arsenic brought about by

changes in pH4. Proximity to bedrock5. Competition between arsenic species and

phosphorus or bicarbonate ions for adsorption sites

6. Release of arsenic brought about by changes in Eh

7. Dissolution of carbonate or evaporite minerals releasing associated arsenic

AGS Findings from 2005 (SR 73)

Arsenic concentration (mg/L)Arsenic concentration (mg/L)Arsenic concentration (mg/L)0.000 - 0.0100.000 0.000 -- 0.0100.0100.010 - 0.0250.010 0.010 -- 0.0250.0250.025 - 0.0500.025 0.025 -- 0.0500.050> 0.050> 0.050> 0.050

Naturally Occurring Arsenic

Naturally Occurring Naturally Occurring ArsenicArsenic

2008 AENV GOWN Sample Resutls

STATION_DESCRIPTION

ARSENIC III ug/L

ARSENIC V ug/L

ARSENIC DISSO LVED ug/L

HQ OBS WELL #944 - SCREEN 5.8-7.3M 1.09 0.36 1.6HQ OBS WELL # 946? - SCREEN 14.9-16.5M 18.2 2.39 19.4

HQ OBS WELL # 945 - SCREEN 86.9-88.4M 24 2.52 23HQ OBS WELL # 947 - SCREEN 82.9-88.4M 1.36 1.19 2.8

HQ OBS WELL # 948 - SCREEN 111-112.5M 8.77 0.62 10.1

HQ OBS WELL # 949 - SCREEN 14.9-16.5M 27.2 5.18 36.8HQ OBS WELL # 950 - SCREEN 79.9-81.4M 8.46 3.47 9.6

HQ OBS WELL #187 - SCREEN 96 - 101M 9.32 0.45 30.6HQ OBS WELL #188 - SCREEN 52.7 - 57.3M 19.9 8.85 11.3

HQ OBS WELL #242 - SCREEN 187.45 - 194.16M 0.31 0.13 0.8HQ OBS WELL #243 - SCREEN 37.83 - 39M 42 1.95 51.5

HQ OBS WELL #186 - SCREEN 129 - 135M 4.16 2.45 5.1

HQ OBS WELL #200 - SCREEN 74 - 77M 44.4 22.1 52.1

Challenges with Arsenic

• High public concern• Misconception of thermal plumes causing

elevated arsenic at impossible distances from the sources

• Domestic water wells can be difficult to sample• Even for environmental observation wells that

are relatively easy to sample, results can be inconsistent

• The new guideline of 10 ppb is very limiting• Better awareness and communication is

needed• Treatment should almost always be

encouraged if the water wells in this area are to be used for drinking

Uranium in the Environment

• This is not as common as Arsenic• USGS has recently evaluated Uranium

in domestic water wells– Between 1.7 % of wells in the US have

elevated Uranium (N = 1725)– Hot spots have been noted in some regions

with as high as 11% of wells showing signs of elevated Uranium

Behavior of Uranium in Groundwater

• Similar to Arsenic, Uranium also forms complexes (CO3 , OH, PO4 , F, SO4 )

• Uranium also has two predominant species: U (IV) and U (VI)

• Uranium tends to mobilize under oxic conditions– in situ mining of Uranium utilizes this

process

Uranium in Groundwater in Alberta

• The Health Canada IMAC for Uranium was lowered from 100 ppb to 20 ppb in 2001

• As such, the 1997 CAESA study and the 2000 AHW study did not assess domestic wells for Uranium at this level

• Most laboratories did not start adding Uranium to their potable water sampling packages until just recently

• Little is known about Uranium in groundwater in the province

• We are down-ice from the largest Uranium deposit in the world

2007 AENV Inquiry into Uranium

• Matrix Solutions was commissioned to report on Uranium in Groundwater in 2007

• They reported that they had noted uranium exceedances in 650 shallow groundwater observation wells near domestic wells, but not in the domestic water wells themselves

• Unfortunately they were not able to attain permission from their clients to use the data in the study

• It was noted that Uranium daughter products including Radon may also be related to Uranium distributions

Dec. 2007 Cold Lake-Beaver River Basin Elevated Uranium

• AENV’s compliance division received two calls regarding elevated uranium in domestic water wells

• The wells were shallow (< 100 ft) and large diameter (~ 2 ft)

• The wells were also more than 60 years old

AENV’s Response

• Compliance officer sampled domestic water wells within a 1 mile radius of one exceedance– Elevated uranium was found in two more wells

• Literature review was under taken by Approvals staff

• ERCB was notified• GOWN wells were sampled

– No exceedances were detected• CLBRB Groundwater Database was used to

query for Uranium– of ~ 800 samples, there weren’t any repeatable

elevated uranium exceedances in the database

Current Work Being Undertaken by AENV and

AHW• Through the Beaver River Watershed Alliance

(BRWA), AENV has launched an investigation into the elevated uranium in shallow groundwater– ARC has been retained– Study will include geochemical modelling as well as

a thorough field investigation• AHW is taking the lead on a domestic water

well sampling program where ~ 200 samples will be taken– All trace elements will be assessed for health risks

based on today’s standards.

Other Groundwater Initiatives

• Working Well Program– Educational program to enhance

groundwater awareness and resource protection

• Cold Lake Oil Sands Groundwater Management Framework– A Land Use Framework Initiative

Regulation and Monitoring to Protect Groundwater From

Over-pumping

• Water Act licensing:– Pump testing is required to ensure

sustainability and a specified maximum pumping rate

– Ongoing monitoring and water use reporting– Maximum depth of pump intake is specified

as no deeper than the top of the aquifer to prevent oxygenation

• Ongoing monitoring of Water Levels though GOWN

Regulation to Protect Groundwater From Contamination

• EPEA Approval holders in the area are required to monitor shallow groundwater as well as deep groundwater

• A standard approval condition has been installed in all thermal in situ Oil Sands EPEA Approvals requiring operators to assess thermally activated arsenic– Two successful studies are under way– Current results demonstrate that thermal

plumes are attenuating within acceptable distances

– The field tests are long term in nature• Alberta Tier 1/Tier 2 Soil and Groundwater

Remediation Guidelines– Specify actions to be taken in the event that groundwater

contamination is detected– Domestic Use Aquifers are considered receptors,

thereby requiring the highest level of protection

Future Considerations• Routinely testing for trace elements in Domestic

Wells– It is difficult to assess a problem with no data

• Develop fact sheets for specific groundwater contaminants, including As and U– This would need to be an interdepartmental initiative

• Develop data sharing protocols for groundwater from domestic water wells– This is a public resource

• Keep reading As literature– New articles are still being published every month

• Review the 1997 CAESA data and assess it vs. today’s guidelines

• When funding is available, consider retaining an expert to review the 2009 data set– New theories have been developed that might change

the current interpretation for As

Thank you

Questions?

Alberta Environment’s Structure

Northern RegionGroundwater Policy

Oil Sands Policy

Northern Region’s StructureDirector

Regional Approvals

Regional Compliance

Regional Environmental Management

Northeast District

Northwest District

Industrial & Reclamation Approvals

Team

Municipal Approvals

Team

Geo Environmental

Team

Environmental Protection and Enhancement Act (EPEA)

Water Act

Water Team

• Contaminant Hydrogeologists• Geo Environmental Engineers• Soil Scientists

• Hydrogeologists• Hydrologists• Water Administration

Engineers andTechnologists