Module 4 – Vulnerable Areas

Much of the information here comes from the active learning program created in 2006 and 2007 for local community working groups. We hope you find the activities here useful for teaching or learning about protecting municipal drinking water sources. Information here is provisional, for information and education purposes, and subject to change. For current information please visit ontario.ca and sourcewaterinfo.on.ca. Thank you.

Chapter 4 of the Maitland Valley and Ausable Bayfield Assessment Reports is called Vulnerability, Threats and Risks.

Chapter 4 of the Assessment Reports identifies the sources of drinking water in the area and provides details on defined vulnerable areas.

Source Protection Plan Chapter 3 is called Establishment of Source Protection Policy Areas.

Surface and Groundwater Vulnerability Analysis

A vulnerable area means a:,

a) Significant groundwater recharge area (SGRA),

b) Highly vulnerable aquifer (HVA),

c) Surface water intake protection zone (IPZ), or

d) Wellhead protection area (WHPA).

– from Ontario Clean Water Act, 2006

Learning Expectations

By the end of this module you will be able to:

Understand that some areas are more vulnerable to contamination than others
Understand that the vulnerability of an area – such as the land closest to a municipal well – is a factor that affects whether an activity poses a significant threat to drinking water sources or not
Explain what a vulnerable area is in the context of drinking water source protection planning
Explain the concept of a surface water intake protection zone (IPZ), wellhead protection area (WHPA), highly vulnerable aquifer (HVA) and significant groundwater recharge area (SGRA)
Define and explain the importance of pathways
Know the location of vulnerable areas in the Maitland Valley and Ausable Bayfield source protection areas
Understand the significance of vulnerable areas in local source protection planning
Recognize that vulnerability is a component of risk assessment

Unit 1 – Vulnerable Areas – Appreciating the Potential Risks of Contamination

What is a vulnerable area?

Understanding groundwater and surface water vulnerability

Unit 2 – Groundwater Vulnerability – Understanding the Concepts and the Science

Understanding groundwater and surface water vulnerability

The importance of pathways

What is a wellhead protection area (WHPA)?

Unit 3 – Surface Water Intake Protection Zones

What types of water intake protection zones exist?

What is a surface water intake protection zone (IPZ)?

Unit 4 – Water Vulnerability – Understanding the Concepts and the Science

What and where are our surface water intakes?

What are surface water intake protection zones (IPZ 1, 2 and 3)?

What are differences between river IPZ zones and Great Lakes intakes?

Where do you get your water?

How vulnerable are our wells?

How vulnerable are our surface water intakes?

How is groundwater vulnerability analyzed and calculated?

Unit 5 – Wrapping It Up

Where does vulnerability analysis fit into the source protection planning
process?

Field Learning – ‘How did we do?’

Self-assessment on learning goals

More help

Activity 1 – Introduction Title: How well are my learning goals being met?

Review of Evaluations from Previous Session

1) Did the last module meet your learning goals?

2) Do you need more review?

3) Is the program moving too quickly or too slowly?

Here are other ways to share your assessment of how the program is – or is not – meeting your learning goals:

a) Fill out the survey provided by your facilitator, share with your group if an opportunity is provided, or;

b) Let your facilitator know either in person or through the ‘Parking Lot’ at the front of the room, or:

c) Use your source protection website to find contacts by phone or email.

Activity 2 – Field Learning Review

Field learning activity.

Title: My Personal Field Learning Trip

Take up your findings from last module’s field learning.

1) What did a trip to your local water treatment plant tell you?

2) What challenges do you think are faced by the water treatment operator?

3) What questions would you have for the water treatment operator?

Unit 1 – Vulnerable Areas – What are they?

Activity 3 – Group Dialogue

Title: What is vulnerability?

The foundation for a source protection plan is the assessment report, a science-based delineation of vulnerable areas and analysis of risks to drinking water sources.

1) What does the word ‘vulnerable’ mean to you – not specifically in terms of Source Protection, but just the word ‘vulnerable’ on its own (e.g., what are some words that describe someone one who is, or is feeling, they are ‘vulnerable’ – or, in sports, when is one team or player ‘vulnerable’?)

2) Vulnerability is:

3) What is our definition of a vulnerable area in terms of source protection planning?

Name the four types of vulnerable areas in Ontario drinking water source protection, under the Clean Water Act, 2006:

a)
b)
c)
d)

Activity 4 – Group Dialogue

Title: What land use activities are there in vulnerable areas? (Consult the list of 22 threat activities and conditions at ontario.ca)

Consult an aerial shot of a wellhead protection area (WHPA).

Visit the Province of Ontario Source Protection Map Portal or the region’s Interactive Map Page.

1) What land uses do you find, or think may take place, within 100 metres of the wellhead? (Remember to talk in general terms about classes of activities – not referring to specific properties).

2) Estimate what percentage of land use there is in that zone.

3) What types of land use activities are likely to be present in that area?

Activity 5 – Group Dialogue

Title: Are all areas equal?

Imagine that the Cozy Extra-Long-Break Doughnut Shop has a tanker full of its ‘Stay Awake for Dayz’ Premium High Caffeine coffee product.

What happens if the tanker spills near a storm sewer?
What happens if the tanker spills near a municipal drain?
What happens if the tanker spills in a gravel parking lot within 100 metres of your municipal well head?
Where would the likelihood of contamination be the highest?
Where would it be least?
Without referring to any individual business or property, answer in general terms:

a) Does your local watershed have old corner gas stations that are now closed?

b) Do you know how long their fuel tanks have been there or if they are even there now?

Activity 6 – Small Group Activity

Imagine that your watershed had a hypothetical closed local gas station, ‘Timon’s Gas Bar.’

Timon has retired but his old tanks are still in place.

What if Timon’s old tank was leaking – could the gasoline get into the aquifer?

These are some of the kinds of questions you may have when it comes to determining if your sources of drinking water need further management measures to add protection.

a) Imagine that old gas station was leaking – what kind of area would have a higher chance of carrying that contaminant to your drinking water?

b) What if there was a crack in the bedrock?

c) What if there was an abandoned well nearby?

d) What if there was a sinkhole cluster nearby?

e) What if the leak occurred near sandy beaches?

a) What is a sewage bypass? What impact could a sewage bypass have on water quality? b) What if that bypass takes place near a surface water intake or a municipal wellhead?

Does the potential for reaching drinking water increase?

What impact could highway drainage or runoff from a landfill site, field, or commercial enterprise have on water?
What if that runoff took place near the water table, exposed by a gravel pit?

Does the potential to reach drinking water increase?

Are there abandoned wells in your community?

a) Are they properly capped and sealed off (decommissioned)?

b) Could contaminants potentially enter water sources through those wells?

c) What if the wells are close to a municipal source of drinking water?

Your municipality has to find a location for a snow dump. A snow dump will have potentially contaminating melt water.

a) Describe the kind of area where you would be likely to put a snow dump.

b) What areas would you not put a snow dump?

Activity 7 – Personal Reflection

Title: VA is for Vulnerable Area (or for ‘Very Astute’)

Where do you get your water? (Circle one)

Surface Water Source

Groundwater Source

What percentage of the watersheds population gets its water from a municipal well water supply?

Individual Activity – Personal Reflection

a) 16-35 per cent

b) 36-45 per cent

c) 46-60 per cent

d) 61-80 per cent

e) 81 – 90 per cent

Where are the surface water intakes in the Ausable Bayfield and Maitland Valley Source Protection Region?

Unit 2 – Groundwater Vulnerability – Understanding the Concepts and the Science

Understanding groundwater and surface water vulnerability

Activity 8 – Presentation

Title: Understanding Pathways to Water

Many watershed residents get their water from surface water sources (treated water from Lake Huron). Others get their water from private wells or from municipal wells.

1 What do you think it means when we say an aquifer has intrinsic susceptibility?

What is another word that means the same as pathway?
What are some pathways to aquifers? (How do contaminants get from land to water?)
What are some pathways to surface water?
The ‘intrinsic vulnerability’ of an aquifer is largely determined by ‘natural preferential pathways.’

What is a natural preferential pathway?

What are examples of ‘natural preferential pathways’?
What are examples of ‘constructed preferential pathways’?
When determining the vulnerability of an aquifer, which is the more important consideration, the vulnerability or the pathway? Discuss.
What geographic features are likely to make an area more vulnerable?
What geographic features are likely to make an area less vulnerable?
Review the region’s vulnerable areas.

Activity 9 – Title: What role does vulnerability analysis play in source
protection planning?

We will look at drinking water ‘threats’ and ‘risks’ in source protection planning in later modules but it is important to underline at this time that
vulnerability is one component of drinking water risk assessment. Therefore, we won’t be able to understand the risk assessment process until we understand what vulnerable areas are.

The knowledge we gain today about vulnerable areas will assist you as you learn later in the program about semi-quantitative risk assessment.

These and other terms are located in the glossary at sourcewaterinfo.on.ca and abca.ca and by clicking the Glossary tab above.

Simply put …

… Vulnerability X Threats = Risk.

What is vulnerability analysis?
How does vulnerability analysis fit into the process of developing source protection plans for drinking water sources in the Maitland Valley and Ausable Bayfield source protection areas?

Activity 10 – Presentation

Title: What makes our drinking water vulnerable?

Water Vulnerability – Understanding the Concepts and the Science

When assessing groundwater vulnerability consider the following factors:

Groundwater Vulnerability

Are signficiant groundwater recharge areas present? (Visit keepingwaterclean.ca).

Where?

Is this a highly vulnerable aquifer? (Visit keepingwaterclean.ca and sourcewaterinfo.on.ca ).

How vulnerable is it?

Future Water Supplies

Vulnerable Areas:
Wellhead protection areas (WHPAs)
Highly vulnerable aquifers (HVAs)
Significant groundwater recharge areas (SGRAs)
Surface water intake protection zones (IPZs)

Vulnerability Scores

Mapping of sensitive areas

Other

Unit 3 – Surface Water Intake Protection Zones (IPZ)

What are intake protection zones?

Activity 11 – Group Activity

Title: The Quiz Zone

IPquiZ

Surface Water Intake Protection Zones (IPZs)

What is a surface water intake protection zone (IPZ)?
There are two designated intake protection zones for each of the two Lake Huron intakes. What are they?

3) How far away from shore is the intake at …?

Port Blake (Lake Huron Primary Water Supply System):

a) 10 metres

b) 30 metres

c) 100 metres

d) 500 metres

e) 1000 metres

f) More than 1,000 metres

Goderich:

a) 10 metres

b) 30 metres

c) 100 metres

d) 200 metres

e) 1,000 metres

f) More than 1,000 metres

Activity 12 – Group Activity

Case Study

Title: Shoreline Treasure Hunt

Look throughout your meeting room for recipe cards.

These recipe cards will contain facts about a Great Lakes intake in a town we will call Portville.

An index card listing the surface water intake’s distance from shore could be located behind a framed photo of a shoreline, for instance.

Take two or three minutes to find as many fact cards as you can about this Great Lakes surface water supply of municipal drinking water.

Once you have found a few index cards, and your facilitator has asked you to return to your small break-out group table, find out as a group what you can discover about this water intake.

Share what you have discovered with the larger group. (Although the ‘treasure’ in this game is the information card, the real ‘treasure’ is maintaining a safe source of clean drinking water.)

Shoreline Treasure Hunt

Case Study: Great Lakes Intake at Portville

Situation and Conditions Report

Source

Great Lakes

Intake distance from shore

Water depth at intake, depth of crib

Distance from river outlet

Size (length, diameter) of intake pipe

Activities along nearby lakeshore

Activities along river

Local recreational uses

Municipal activities or facilities near intake

Time required to shut down Water Treatment Plant (WTP)

Prevailing wind directions and intensity

Current and drift patterns

Lake bottom type

Plume movement (of any watercourse outletting in the zone),

Potential spills from transportation routes

Weather and Climate: Long-term and seasonal weather patterns as affecting wave generation

Erosion and scouring patterns

Sediment at intake in probable zone of influence

Existing Water Quality and Sediment Impairments

Watercourses that drain into the lake

Drainage modifications

Location of wastewater treatment plant

Location of municipal landfill sites

Location of gravel pits

Presence of shore cliffs

Shoreline modifications

Historical shoreline and substrate trends

Historical land uses

Atmospheric deposition

Sounding map of intake crib and surrounding area

Engineering and Operations Reports

Raw Water Quality Profile

Incidences where raw water quality maximum permitted levels are exceeded

Other

After developing this Situation and Conditions Report for ‘Portville,’ list your perspectives on the following questions:

1) What further information or investigation is required to address water quality vulnerability?

2) Based on the Situation and Conditions Report that you developed are there situations or conditions that require no more investigation or analysis?

Activity 13 – Group Activity

Title: Beyond the Surface

Looking at the examples of intakes at Goderich and the Lake Huron Primary Water Supply intake north of Grand Bend, at Port Blake, how could contaminants reach an intake or the water that feeds it?

(If you need an example of a pathway, ask your facilitator or source protection region staff member.)

Potential Pathways for Contaminants

Lake Huron Primary Water Supply at Port Blake

Goderich

Take a look at a case study of a surface water intake protection zone, provincially or locally.
What site-specific conditions exist? What do you know about the intake?
What did you find out about the IPZ 1 and the IPZ 2 – how do they differ?

Surface Water Intake Protection Zones (IPZ 1 and IPZ 2)

Characterization of Intake (Depth, lake bottom type, etc.)

Protection zone radius around intake

IPZ 1

IPZ 2

Site-specific conditions (wind, current, etc.)

Refine protection zones (e.g., minimum travel times to intake)

IPZ 1

IPZ 2

Do you think a single intake protection zone will suffice in this case?

Why?

Why not?

What are some of the ways these zones offer a new barrier of drinking water source protection?

What are some of the challenges or questions?

a) Greater protection:

b) Challenges or questions:

What are vulnerability scores?
Your facilitator may provide you with an example of two areas.

What vulnerability scores might be given to them?

Is the vulnerability score enough to make the threat activity a significant threat to drinking water sources?

If the threat is not assessed as significant, how can we reduce risk to the drinking water source? (Please consult source protection plans).

How is the local source protection region using ‘modeling’?
Why is a ‘cautious’ approach to surface water vulnerability analysis
required?

Unit 5 – Wrapping it up

Review concepts from this module and ‘check for understanding’ re: expectations for field learning assignment for next session.

SECTION TWO – Priming the Pump

Notes, Definitions, Fact sheets

Understanding Surface Water and Groundwater Vulnerability

The goal is the same whether we are talking about groundwater or surface water:
we want to know what makes our current and future drinking water supplies vulnerable to contamination.

What is a ‘vulnerable’ area?

In drinking water source protection planning a vulnerable area means a:

(a) Significant groundwater recharge area (SGRA),

(b) Highly vulnerable aquifer (HVA),

(d) Municipal wellhead protection area (WHPA);

We have two main sources of drinking water – groundwater and surface water sources and we have differences in our understanding of the each. This difference in understanding and knowledge requires different approaches.

Secondly, we are more likely to use modeling in Lake Huron assessments: an approach that can effectively compensate for data gaps.

Let’s return to our common aims. It is important to:
Understand the pathways (‘shortcuts’) that contaminants may take in vulnerable areas
Define protection areas around vulnerable sources

Vulnerable Areas in the Maitland Valley and Ausable Bayfield Source Protection Areas

There are four principal categories of vulnerable areas, whether we are considering the Province of Ontario as a whole or we are considering our local region only. One of the categories applies to surface water and three categories apply to groundwater.

Please visit ontario.ca for definitions.

Intake Protection Zones (IPZs)

An intake protection zone is an area, which is not necessarily regular in shape, surrounding municipal drinking water intakes from surface water sources.

The two main surface water intakes in the Ausable Bayfield and Maitland Valley source protection areas are at Port Blake (Lake Huron Primary Water Supply) north of Grand Bend; and at Goderich. Both of these surface supplies source their water from Lake Huron as opposed to inland lakes or river systems within the source protection region.

Significant Groundwater Recharge Areas

Groundwater recharge areas are areas where an aquifer is replenished from:

a) Is replenished through natural processes, such as the infiltration of rainfall and snowmelt and the seepage of surface water from lakes, streams and wetlands; or

b) Is replenished with the aid of human interventions, such as the use of stormwater management systems

Generally, a recharge area will be identified because it has a higher recharge rate than is typical within the watershed.

Source protection guidance documents suggest how to estimate whether an aquifer has recharge rates that exceed thresholds that could be considered typical in a region.

Highly Vulnerable Aquifers

A highly vulnerable aquifer (HVA) is an aquifer that can be easily changed or affected by contamination from both human activities and natural processes as a result of:

a) Its intrinsic susceptibility, as a function of the thickness and permeability of overlaying layers, or

b) The presence of preferential pathways, natural or constructed, to the aquifer.

Wellhead Protection Areas (WHPAs)

A wellhead protection area (WHPA) is the area within which the municipal well’s groundwater sources are vulnerable to surface threats.

The area includes the surface and the sub-surface.

In discussing surface water intake protection, it was mentioned that pathways are more important than threats in the calculation of vulnerability scores. What are these pathways and why are they so important?

There are two types of pathways:
Natural preferential pathways include fractured bedrock and Karst (sinkhole) topography. Such characteristics increase the intrinsic vulnerability of an aquifer.
A constructed preferential pathway may bypass natural protective geologic layers above an aquifer (e.g., improperly constructed well, pits and
quarries). An aquifer’s vulnerability may increase due to an human-made (constructed) feature in an area that disturbs the surface or enhances flow. a feature that disturbs the surface or enhances flow.

A sinkhole – such as the one in the former Tuckersmith Township – are naturally-occurring preferential pathways to groundwater.

Constructed preferential pathways are not accounted for in determining intrinsic susceptibility.

Using the ‘constructed pathway modifier,’ scores are adjusted for two reasons:
The presence of (or plans for) constructed pathways may indicate a need to raise a score.
Risk management activity (e.g., human-made mitigation of a constructed
pathway) may result in a lowering of a score.

The Importance of Pathways

A threat activity (such as storage of fuel) cannot be delivered to a water
source in the absence of a pathway.

Natural contaminants and threats of human causes cannot be completely eliminated. They are difficult to reduce across an entire landscape.
Accordingly, we tend wherever possible to eliminate pathways (decommissioning an abandoned well, for example). Where pathways cannot be closed off, the most efficient action is to eliminate or reduce threats in their vicinity thus controlling the ‘traffic on the pathway.’

Strategically it is very effective to concentrate on ‘pathways.’

Groundwater Vulnerability Analysis

What is the purpose in this kind of analysis?

Groundwater Vulnerability Analysis has a dual purpose:

To map or delineate areas vulnerable to groundwater contamination and;
To assign groundwater vulnerability scores to the areas.

The mapping and scores are used in Water Quality Risk Assessment.

The next sections will help the Working Group and other participants to understand how groundwater’s intrinsic vulnerability to contamination is
assessed.

What are the goals?

Groundwater Vulnerability Analysis provides input to the Water Quality Risk Assessment process.

The goal is to understand the particular vulnerability of (and provide information for the protection of):
Existing municipal ground water supplies wells;
Future municipal ground water supplies.

To achieve those goals it is necessary to:
Map wellhead protection areas (WHPAs);
Map highly vulnerable aquifers outside the WHPAs;
Map groundwater recharge areas, and future municipal water supply areas;
Assign vulnerability scores to each of these vulnerable areas.

How is vulnerability determined?

Simply, the process takes four steps:

Collecting and analyzing data,
Reviewing and selecting the best approach for vulnerability analysis,
Mapping Wellhead Protection Areas, mapping recharge areas, other vulnerable areas,
Assigning a vulnerability score to the vulnerable areas identified that a potential groundwater contaminant, if present, will reach the drinking water
source.

These steps and related analyses are discussed in the regulations posted on the Ontario Ministry of the Environment, Conservation and Park’s Clean Water Act, 2006 website and/or EBR (Environmental Bill of Rights Registry / Environmental Registry).

A more detailed discussion of these four process steps follow.

Collecting and Analyzing Data

Key data includes:

Water well records, other bore hole records, and mapping

Bedrock mapping geology

Geologic cross-sections

Aquifer mapping and aquifer parameters

Depth to water table

Topographic and surface water mapping.

The process begins with reference to municipal groundwater studies and other source water protection studies, e.g. watershed characterization report.

[Data gaps will be identified at this point and decisions will be made on immediate data needs, best approaches for completing the vulnerability analysis and data needs for ‘continuous improvement’ of the vulnerability analysis.]

Groundwater Vulnerability Analysis

There are a number of approaches to Vulnerability Analysis, the selection depending on:
The level and reliability of data in existing studies
Emphases and scale of analysis
The environment and its particular complexities
Land use within the watershed
Extent of water use
Potential for meeting watershed data requirements.

Mapping Vulnerable Areas

Municipal Wellhead Protection Areas

Municipal wellhead protection areas (WHPAs) are identified by at least five zones around each WHPA:
Zone A. 100-metre radius.
Zone B. Two-year time-of-travel (TOT) capture zone.
Zone C. Five-year TOT capture zone.
Zone D. 25-year TOT capture zone.

[The 10 year zone was not a requirement under the Terms of Reference, however, some consultants modeled a 10-year TOT in their analysis.]

These zones and ‘sub-zones’ are used:
To identify the variants in potential risk level to municipal water supplies
from pathogens and chemical contaminants and,
To help prioritize risk management plans addressing specific threats.

Recharge Areas

A significant groundwater recharge area (SGRA) is an area where water enters a saturated zone at the water table surface.

Other Vulnerable Areas

Other vulnerable areas are mapped but they are not designated with zones as are wellhead protection areas (WHPAs).

Other vulnerable areas mapping was completed based on two sets of information:
the first set referred to as “Possible Significant Recharge Areas” are based on the physiograpic categorization of the landscape. Different physiographic areas
have different characteristics with respect to drainage, water movement, infiltration and so on.

Physiographic areas categorized as vulnerable are:
Beaches and shore cliffs
Drumlins
Eskers
Kame Moraines
Sand Plains
Spillways

The second set of vulnerable areas is referred to as potential highly vulnerable aquifers (HVAs) which are those areas that have a calculated ISI (Intrinsic Suceptibility Index) rating of high.

The ISI index is determined based on the type and thickness of overburden overlying the first significant aquifer.

The ISI susceptibility is categorizes into three zones: ‘high’ referring to areas offering little protection to the aquifer, ‘medium’ and ‘low,’ referring
to areas where the aquifer is deeper and protected with a significant thickness of low permeable aquitard material. Only the “high” values form the vulnerable areas.

Applying a Vulnerability Scoring Approach

Reference was made above to various approaches that may be used to assess vulnerability. There are five options for assessing an aquifer’s intrinsic vulnerability to sources of contamination. Frequently, more than one option will be applied.

Simple Hydrogeological Assessment

As implied by the name, the approach is not numerical:

Existing information (e.g. geological maps, cross-sections and groundwater quality data) is assessed by a Professional Hydrogeologist.

Numerical calculations or modeling are not used.

The outcome relies on the professional opinion of the Hydrogeologist

Aquifer Vulnerability Index (AVI)

A score (index or value) is produced to grade the amount of protection provided by the physical features which overlie the aquifer. The calculations are based on:
Available hydrogeological data and
Maps and related products dealing with overburden soil type and thickness and depth to aquifer, etc.

Groundwater Intrinsic Susceptibility Index (ISI)

A score (index) is calculated for wells using the Provincial WWIS [Well Water Inventory System] database. The index factors in:
Overburden soil type and thickness,
Depth to aquifer, and
Static water level in the well.

The index is interpolated for the areas between wells to produce an area-wide assessment (in map form) of the intrinsic vulnerability of the aquifer.

Surface to Aquifer Advection Time (SAAT) or Surface to Well Advection Time (SWAT)

In this case, intrinsic vulnerability is expressed in units of time (i.e., years). An estimate is made of the vertical travel time from the ground to the
top of the aquifer.

Detailed Hydrogeological Assessment

As implied the difference lies in the level of data and evaluation. Methods may include:
Detailed water sampling and assessment and/or
Numerical modeling.

What do we get from these assessment tools?

The products include:
A relative vulnerability (continuous) scale (e.g., 1-5) for each vulnerable area,
A scale breakdown into rankings of low, medium and high vulnerability,
vulnerability maps.

How are these products or findings used?

The maps, scales and rankings reveal:
The intrinsic (the existing or natural) vulnerability of a vulnerable area
The relative susceptibility of the underlying aquifer to contamination.

These indexes (scales) may be used as the basis for preparing vulnerability mapping and developing groundwater protection strategies for areas of greatest risk.

Surface Water Vulnerability Analysis

What is the purpose in this kind of analysis?

Surface Water Vulnerability Analysis has a dual purpose:

To map or delineate intake protection zones (IPZs) and
To assign Vulnerability Scores to these zones.

The mapping and scores are used in Water Quality Risk Assessment.

The Ontario Clean Water Act, 2006 is directed at protection of drinking water sources and one of its primary goals is protecting municipal water intakes that are associated with inland watercourses, Great Lakes connecting channels and inland surface water bodies, (e.g. ponds, lakes). Municipal water sourced from any of the Great Lakes (e.g. Lake Huron), is addressed under other programs as well at the federal, provincial and municipal levels.

The data collected, technical studies undertaken and mapping completed as part of the drinking water source protection work may all provide governments, municipalities, organizations and individuals with a better understanding of the entire watersheds and Great Lakes water sources.

NOTE: There is some cottage use of surface water at sandpoint and some directly from lakes, rivers and springs but there are only two municipal surface water intakes in Ausable Bayfield and Maitland Valley watersheds. They are the Lake Huron Primary Water Supply System intake at Port Blake, north of Grand Bend; and Goderich.

Assessments of the Lake Huron Primary Water Supply intake are undertaken by the City of London on behalf of Lake Huron Primary Water Supply System.

Do we just draw a circle around a lake intake and prevent contamination from entering the circle?

We cannot just focus on the area immediately around these intakes. Currents, wave action and natural and human-made land drainage may indicate a larger and/or an irregular-shaped area of influence affecting (or potentially affecting) the intake. This is addressed through a two-zone approach, the ‘inner zone’ immediately surrounding the intake, the ‘outer zone’ reflecting the extent and seriousness of wider influences.

How is Surface Water (Intake) Vulnerability determined?

Simply, the process takes three steps:

Collecting and analyzing data,
Defining the Surface Water Intake Protection Zone(s),
Assigning a vulnerability score for the IPZs

How are vulnerability scores used in the preparation of source protection plans?

The preparation of source protection plans is very much about Water Quality Risk
Assessment.

Visit sourcewaterinfo.on.ca for locally developed, provincially approved source protection plans (SPPs) for the Maitland Valley and Ausable Bayfield source protection areas.

Vulnerability scores and relative vulnerability ratings are combined with threat identification and assessment to come to a decision on the risk that source of drinking water may become contaminated. Action is then taken to reduce and/or manage the risk. Those actions and risk management decisions are contained in the source protection plans.

These steps and various related analyses are discussed in the sections below:

Collecting and Analyzing Data: What do you know about our Lake Huron Intakes?

Baseline documentation must be compiled for each of the two Lake Huron intakes located within the Region:

Physical description of intake (location, depth of crib, length of intake pipe).

Sounding map of the intake crib and surrounding area.

Engineering and operations reports.

Current and drift patterns.

Prevailing wind directions and intensity.

Long-term and seasonal weather patterns as affecting wave generation, magnitude and direction.

Erosion and scouring patterns.

Sediment at the intake and in a probable zone of influence.

Raw water quality profile.

Local watershed influences.

Local and regional shipping routes and patterns.

Local recreation use.

Historical shoreline and substrate trends.

Shoreline modifications.

Historical land uses.

In the case of our Lake Huron Intakes, the following factors are particularly
important:

High-energy winds,

Waves, strong currents,

Land use activity near the intake,

Existing water quality and sediment impairments,

Atmospheric deposition.

Defining the surface water intake protection zone(s)

Great Lakes Intake Protection Zones

How will we determine what areas need to be protected?

Two zones are identified when defining a Great Lakes intake protection zone.

The first is a one-kilometre circle that surrounds the intake. The second, beyond the one- kilometre circle, is shaped to account for influences such as the currents and contamination from shore or nearby rivers.

Great Lake Intake Protection Zone 1

This first zone surrounds the intake crib and may include adjacent shoreline land uses. This zone is the most vulnerable. The zone will have a radius of not less than one kilometre, where the intake is the zone’s centre.

Great Lakes Intake Protection Zone 2

This zone will be drawn to account for the influence of the shore, streams and rivers that affect or may affect quality of water at the intake. Where the
IPZ-1 zone is entirely within the lake an IPZ-2 may not be required.

Defining the IPZ -2 can be a complicated exercise because analysts need to consider:

All perennial watercourses that directly impact the intake and

All land and stream mixing zones that could directly affect the intake.

There may be other relevant factors: for example, the response time should a spill occur (at an industry or business, agricultural operation, a
sewage/wastewater treatment plant, etc.). A using a two-hour travel time from spill to intake is considered the minimum response time.

We now know what areas need to be protected to safeguard drinking water from a surface (Great Lake) source. What, then, is the level of protection? That depends on the level of vulnerability, which takes us to Assigning Vulnerability.

Assigning Vulnerability to Surface Water Intake Protections Zones

How is vulnerability ‘scored’?

The following formula has been recommended:

V = Vfz x Vfs

V – Vulnerability Score
Vfz – Zone Vulnerability Factor
Vfs – Source Vulnerability Modifying Factor

Daunting at first glance, the formula is readily explained:

The ‘vfz – zone vulnerability factor’ is a preset or standardized vulnerability, associated with the source type, in our case, one of the Great Lakes. The ‘vfs – source vulnerability modifying factor’ is determined locally as the Zone’s particular vulnerability.

What factors affect Zone Vulnerability?

We start with three general factors:

Runoff potential (higher runoff = higher score). Factors include rainfall, land cover, soil permeability, slope.

Transport pathways in the zone (faster and/or numerous pathways = higher score).
This considers urban or rural drainage, for example.

Distance of threat to the watercourse, which influences time of travel to reach the intake.

Determining the impact of preferential pathways

It is important to stress that pathways have a greater effect on the vulnerability score than threats.

Constructed or natural preferential pathways enhance the movement of contaminants.

Constructed preferential pathways include:
Sewer discharge pipes
Rural drains
Urban storm drains
Utility trenches
Natural preferential pathways include:
Small channels or gullies
Sand lenses
Fractured rocks

The presence of any such pathways within a protection zone is of particular interest to the analyst.

What if the data is insufficient to define these Intake Protection Zones and Scores?

The level of uncertainty (or certainty) in arriving at vulnerability zones and scores depends on the strength of the data. A combination of models may be used to improve zone delineation and vulnerability assessment.

Great Lakes Modeling:

In establishing the IPZ-1, the first objective is to map the intake’s zone of influence:

Under extreme conditions and

Under the highest use capacity.

In establishing the IPZ-2, the following effects are considered:
Shoreline,
Plume movement (of any watercourse outletting in the zone),
Potential spills from transportation routes,
Response times for a water treatment plant.

Key Definitions

A wellhead protection area (WHPA) is the area within which the municipal well’s groundwater sources are vulnerable to surface threats. The area includes the surface and the sub-surface.

Intake protection zone (IPZ) – the area of land and water upstream of an intake defined in accordance with a specific response time to an upstream event. (The main purpose is to permit response to spill situations, which result from accident or storm events and which may cause a spike in contamination concentrations.)

Significant groundwater recharge areas – these areas account for the bulk of water flow from surface to aquifer.

To find out more click on the Glossary tab.

Significance:

A decline in the recharge rate can affect those surface water sources, which depend on local groundwater discharge.
Cumulative loadings in recharge areas can impair aquifer water quality.

Other vulnerable areas are areas where the overburden is ineffective at preventing contamination from reaching an aquifer.

Such aquifers are then called ‘highly vulnerable aquifers’ or HVAs. (Visit keepingwaterclean.ca and sourcewaterinfo.on.ca).

In demarking a vulnerable area and taking risk management measures, the goals are:

a) to protect wells and

b) to protect the aquifer for long-term supply.

Intrinsic Vulnerability is the existing or natural vulnerability (of vulnerable areas).

For other definitions consult the Glossary above or visit sourcewaterinfo.on.ca or abca.ca.

SECTION THREE

Handouts, readings, field assignments, findings

Reading, Listening and Viewing Resources:

Read Assessment Report Guidance Technical Modules, Ontario Ministry of the Environment, Conservation and Parks (MECP)

Read Municipal Groundwater Studies

Read Vulnerable Areas brochure, Ausable Bayfield Maitland Valley Drinking Water Source Protection Region, 2007

Evaluation of Group Performance

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