8. Multi-level Monitoring Test Holes

Chapter Description

This chapter provides detailed information, construction requirements and annular space sealing requirements for new multi-level monitoring test hole installations. For hole, casing and well screen requirements the reader will generally be referred back to Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well. The reader will also be referred back to Chapter 7: Annular Space & Sealing for some annular space filling requirements. For further information on requirements and best management practices for dewatering wells and test holes other than multi-level monitoring test holes, the reader is referred to the other chapters in this manual.

Regulatory Requirements – Equipment Installation

Relevant Sections – The Wells Regulation

Casing and Well Screen – Section 13 including Subsection 13(20)
Annular Space – Sections/Subsections 14, 14.1, 14.1(2), 14.2, 14.2(3), 14.3, 14.3(2), 14.4, 14.4(4), 14.5, 14.5(3), 14.6

The Requirements – Plainly Stated – Installing the Equipment

Reminder: Further information on abandonment requirements is provided in Chapter 16: Abandonment: When to Plug & Seal Test Holes & Dewatering Wells and Chapter 17: Abandonment: How to Plug & Seal Test Holes & Dewatering Wells of this manual.

Reminder: The regulatory exemptions regarding sealing the annular space below the permanent outer casing allow for well technicians, engineers and geoscientists to use their professional expertise to design and install multi-level wells on a case by case basis, thereby enabling the testing and sampling of various groundwater intervals while preventing contamination.

Key Concepts

Multi-Level Monitoring Test Holes

There are many hydrogeological and chemical complexities when determining the location of dissolved contaminants in groundwater. Hydrogeologists need to think and model in three dimensions when attempting to characterize contaminant plumes that may impact groundwater resources.

A single sampling port (e.g., one well screen per well) position in the ground and aquifer:

• can locate the port at the wrong depth or
• can be constructed with a well screen that is too long

The position of the sampling port could create a number of problems, some of which include:

• a failure to detect the presence of a contaminant plume,
• a potential for a bias in sample results because fresh groundwater above or below a plume can mix with the plume’s contaminated groundwater in the well,
• a risk of non-representative data because single zones are either too short and do not represent (miss) critical hydraulic or hydrogeochemical features, or are too long, and provide measurements (hydraulic head, chemistry) of a non-representative unknown blended fluid mixture,
• a lack of understanding of potentially significant flow paths and/or barriers to flow in the groundwater system,
• the development of a two dimensional model instead of a three dimensional model of the contaminated plume, or
• improper location of remediation wells.

Because of the potential problems listed in the bullets above, the vertical extent of the aquifer and plume may not be properly characterized in 3 dimensions. This can result in a potential to underestimate the health and environmental concern to down-gradient receptors such as wells and surface water bodies.

To overcome the problem, groups of test holes completed at different depths can be installed at one location. Another option is to install multiple discrete sampling well screens or devices at several depths in a test hole to accurately locate the contamination plume in the groundwater and identify changes in hydraulic head. The second option is commonly called a multi-level monitoring system.

The screens or ports should be properly constructed and sealed to reduce the risk of cross-flow of groundwater and contaminants between screens or ports within the multi-level well. Reducing the risk of intermingling:

• provides quality assurance that samples from each discrete port or well screen are representative of the discrete zone in the groundwater, and
• reduces the risk of contaminants intermingling with and impairing fresh groundwater in the same or a different formation.

Reminder: When designing and constructing multi-level monitoring systems, it is important for a person involved in well design or construction to take a “cradle to grave” approach. See the Best Management Practice - “Cradle to Grave” Approach for Test Holes and Dewatering Wells in Chapter 5: Siting Considerations and Initial Planning.

Multi-Level Monitoring Systems

Various nested and dedicated multi-level monitoring wells (test holes) are used to accurately locate and monitor the vertical extent of plumes of contamination in groundwater.

The type and installation of the various multi-level monitoring wells are described below. Figure 8-1 to Figure 8-21 illustrate various systems and the components that are presently in use.

Bundled Multi-Level Monitoring Test Hole

Bundled multi-level monitoring test holes are designed to study groundwater in unconsolidated collapsing overburden formations such as sand.

Typically, a hole is constructed into the collapsing formation using direct push, auger or rotary drilling equipment. Measurements and observations are made about the location of the groundwater level and aquifer as the well construction equipment is being advanced into the ground. A temporary drill rod, auger flight or pipe is installed during the construction of the hole to hold the hole open.

A bundle of tubing is installed into the temporary rod or pipe. The temporary rod or pipe is removed allowing the unconsolidated overburden to collapse around the bundle of tubing.

A commonly used bundle design will consist of a number of flexible or rigid tubes of different lengths affixed together using a binding tape. In another bundle design, up to 20 tubes are affixed to a larger diameter rigid PVC casing core. The tubing’s inside diameter typically ranges from 0.8 to 1.25 cm (0.3 to 0.5 inches). The bottom of each tube is plugged with a sealing product such as epoxy cement. The bottom 10 cm (4 inches) of each tube is slotted or perforated and covered with a fine nylon mesh. The length of each tube is designed to allow the slots or perforations to be set to a discrete depth in the ground. Each tube allows for the collection of a groundwater sample from a discrete zone in the formation. In some cases, a measurement of the groundwater level can be performed in the tube. Based on sample results, a vertical image of a contaminant plume can be generated. As there is no sealant between the different tubes in the bundle, the application of these systems is dependent on the environment. See the section titled “Recommended Environments for a Bundled Multi-Level System” on page 20 of this chapter.

Figure 8-1: Example of a Bundled Multi-Level Test Hole

Figure 8-1 shows an example of how the bundled tubes (small brown tubes surrounding a larger diameter tube) are attached to a rigid core tube (larger diameter white tube). The bottoms of the tubes are slotted or perforated and typically surrounded by a fine nylon mesh.

Reminder: Figure 8-1 is for illustrative purposes only and does not necessarily represent full compliance with requirements found in the Wells Regulation.

Casing and Well Screen Requirements

The flexible or rigid tubes support the sides of the well. As such, each tube is considered “casing” under the Wells Regulation. The slotted or perforated end of each tube filter out particulate matter and form the water intake zone. As such, each slotted or perforated end of each tube is considered “well screen” under the Wells Regulation.

The casing requirements and exemptions of the Wells Regulation that are outlined in the “Plainly Stated” section of Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well apply to the flexible or rigid plastic tubing (casing) and a permanent outer casing that is placed around the bundle of tubes.

The well screen requirements and exemptions of the Wells Regulation that are outlined in the “Plainly Stated” section of Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well apply to the perforated or slotted area of each tube (well screen).

Reminder: The exemptions in the Wells Regulation allow a person to construct a bundled multi-level system to obtain groundwater samples.

The Wells Regulation - If the new bundled multi-level test hole is finished above the ground surface, the minimum casing extent and casing height requirements in the Wells Regulation that are outlined in Chapter 9: Completing the Test Hole or Dewatering Well Structure apply to each flexible or rigid tube (casing).

For example, if the hole was constructed using sonic equipment, the person constructing the well must ensure each flexible or rigid tube (casing) extends:

• from the water intake zone,
• to at least 40 cm (16 inches) above the highest point on the ground surface within 3 m (10 feet) radially from the outside of the casing after the ground surface (surface drainage) so that water will not collect or pond near the well, as measured on completion of the well’s structural stage.

The Wells Regulation - If the new bundled multi-level system test hole is located in an area where there is a likelihood for pedestrian or vehicular traffic, the Wells Regulation allows for the top of the tubes (casings) to be finished below the ground surface as long as the person constructing the well completes the well with a flush- mounted well cover and meets the Wells Regulation. See Chapter 9: Completing the Test Hole or Dewatering Well Structure for further information on flush-mounted well covers. See Chapter 12: Equipment Installation for further information on flush-mounted well pit (vault) construction requirements.

The Wells Regulation - The top of the tubes (casings) must be covered or capped in accordance with the Wells Regulation requirements. See the “Plainly Stated” section in Chapter 12: Equipment Installation for further information.

Records of Site Condition Regulation - Starting on July 1, 2011, amendments to O. Reg. 153/04 came into force and apply to phase two environmental site assessments (ESAs) conducted in support of records of site conditions (RSCs). For any such RSC submitted on or after this date, where a groundwater sampling method is to be used to characterize contamination or determine if the concentration of a contaminant is above, at or below and applicable site condition standard or standard specified in a risk assessment for the contaminant, the following requirements apply to construction of a well:

• where a monitoring well is being used, well screens shall not exceed 3.1 m (10 feet) in length, based on the saturated length of the screen, and
• where petroleum hydrocarbons or light non-aqueous phase liquids may be present on, in or under a phase two property, sampling depth intervals, including screened intervals of monitoring wells, shall be positioned to intersect the water table.

Implications for the Qualified Person

The qualified person shall ensure that the phase two ESA is conducted in accordance with requirements stated above.

Records of Site Condition Regulation - Please refer to O. Reg. 153/04 for RSC requirements.

Reminder: For clarification of the term “monitoring well” and “qualified person” as they relate to O. Reg. 153/04, see Chapter 2: Definitions & Clarifications, Table 2-2.

Reminder: There are many factors that affect the casing selection including depth of the well and water quality.

Reminder: Some materials such as ABS, polytetrafluoroethylene (PTFE) (e.g., Teflon), fiberglass and glass are not typically used for casing for test holes. It is important to refer to manufacturer’s specifications and other information to determine if the material is appropriate for use in the test hole at a specific site.

Reminder: A downhole video camera should be used to visually observe the casing, casing joints and the sealing of the bottom of the casing into competent bedrock as long as a contaminant will not interfere with the device.

Annular Space Requirements - Operating Not Later Than 180 Days

This section applies to a new test hole that is scheduled to be abandoned not later than 180 days after the completion of the structural stage of the test hole, and where an outer permanent casing is not placed around the bundle of tubes.

The Wells Regulation - Instead of following the annular space requirements listed in Chapter 7: Annular Space and Sealing, the person constructing a new multi-level monitoring test hole without a permanent outer casing must ensure that:

• there is no movement of water, natural gas, contaminants or other material between subsurface formations or between a subsurface formation and the ground surface in any annular space along a well casing or between overlapping casings, and
• the test hole is scheduled to be abandoned within 180 days of the completion of its structural stage.

Records of Site Condition Regulation - Starting on July 1, 2011, O. Reg. 153/04 prescribes that the provisions of the Ontario Water Resources Act and of Regulation 903 of the Revised Regulations of Ontario, 1990 (Wells) made under that Act, that would apply to a test hole but for section 1.1, and subsections 13 (2), 14.1 (2), 14.2 (3), 14.3 (2), 14.4 (4) and 14.5 (3) of that regulation, apply to a monitoring well installed for the purpose of,

1. a phase one environmental site assessment; and
2. a phase two environmental site assessment.

Implications for the Qualified Person

The qualified person shall ensure that phase one and phase two environmental site assessments (ESAs) are conducted in accordance with O. Reg. 153/04.

Implications for Annular Space Size and Filling for New Test Holes

With respect to annular space size and filling, the above requirement in O. Reg. 153/04 means that, if the new bundled multi-level monitoring test hole is constructed and is scheduled to be abandoned not later than 180 days after the completion of its structural stage, and is to be used as a monitoring well in an ESA for a record of site condition, then:

• the annular space size and filling exemptions for a test hole stated in this section do not apply, and
• the annular space size and filling requirements for a test hole stated in the section titled “Annular Space – Operating Longer than 180 Days” section do apply regardless of the amount of time that the monitoring well will be in operation.

Reminder: The above requirements in the O. Reg. 153/04 also affect other obligations such as shallow works, casing material and annular space filling for monitoring wells. See Chapter 3: Exemptions: Wells, Activities & Experienced Professionals, Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well and Chapter 7: Annular Space & Sealing for further information.

Reminder: Please refer to O. Reg. 153/04 for RSC requirements.

Annular Space - Operating Later Than 180 Days

The Wells Regulation allows for the construction of a new bundled multi-level monitoring test hole that will be in operation for more than 180 days after the completion of the well’s structural stage, if the following casing and annular space requirements are met:

The Wells Regulation - The person constructing the well must install a permanent outer casing around the bundle of tubes, which are considered inner casings.

The Wells Regulation - Depending on the type of well construction method used, the person constructing the well must follow the Wells Regulation requirements listed in Chapter 7: Annular Space & Sealing, Table 7-1 A and Table 7-1B to create and seal an annular space on the outside of the outer permanent casing.

Reminder: As a necessary modification for systems installed using drilling, augering or sonic equipment, the depth of the annular space must extend from the ground surface to at least the bottom of the permanent outer casing or 6 m (19.7′), whichever is less.

The Wells Regulation - When the bundle of smaller diameter casings (e.g., flexible or rigid plastic tubing) is installed into the permanent outer casing, the annular space between the permanent outer casing and the inner casings (or tubes) must be sealed with a suitable sealant to prevent the entry of surface water and other foreign materials into the well. Depending on the environment, a suitable sealant could include a bentonite product, cement product or a mechanical device such as a packer.

The Wells Regulation - If any groundwater is entering the annular space between the bundle of tubes (casings) and the permanent outer casing, the entire annular space from the tubes to the permanent outer casing must be sealed, with necessary modifications, in accordance to the minimum requirements of Chapter 7: Annular Space & Sealing, Table 7-1 A and Table 7-1B. The annular space between casings of a well constructed by the use of a driven point is not required to be sealed in accordance with Chapter 7: Annular Space & Sealing, but is required to be sealed with a suitable sealant.

The installation of an inner and a permanent outer casing is referred to as a double walled casing in the Wells Regulation.

Although a person constructing a well is not specifically required to seal around the casings or tubes between wells screens in a bundled multi-level monitoring test hole below the permanent outer casing, the person must do what is necessary as the Ontario Water Resources Act prohibits every person from discharging or causing or permitting the discharge of any material of any kind into any waters that may impair the quality of any waters. This includes prohibiting contaminated groundwater from impairing the quality of other groundwater zones when constructing a well.

The regulatory exemptions regarding sealing the annular space below the permanent outer casing allow for well technicians, engineers and geoscientists to use their professional expertise to design and install a bundled system on a case by case basis, thereby enabling the testing and sampling of various groundwater intervals while preventing (further) contamination.

Persons using the above professional judgement and the well owner should be aware of the following requirement.

The Wells Regulation - If the test hole or dewatering well acts as a pathway for the movement of:

• natural gas,
• contaminants, or
• other materials

between subsurface formations (including aquifers) or between the ground surface and a subsurface formation and where the movement may impair the quality of the any waters, the person abandoning the well, often the well owner, must do one of the following:

• take measures to prevent the movement of the above materials and ensure the measures are functional at all times, or
• immediately abandon the well.

This Wells Regulation requirement ensures that, at all times, steps must be taken by the well owner to prevent the well from acting as a pathway for contaminants that may impair groundwater resources.

Reminder - Further information on abandonment requirements is provided in Chapter 16: Abandonment: When to Plug & Seal Test Holes and Dewatering Wells and Chapter 17: Abandonment: How to Plug & Seal Test Holes & Dewatering Wells of this manual.

Examples

The following provides two examples of the annular space requirements for new bundled multi-level monitoring test holes that will be in operation more than 180 days:

Example A: Constructing a Bundled Multi-level Monitoring Test Hole with Seals using Direct Push Equipment

A person constructing a bundled multi-level monitoring test hole uses direct push equipment to advance a hole in the ground by the use of a driven point. The person constructing the test hole completes the well in the following manner:

1. A permanent outer casing is driven with a driven point to the full depth of the hole to create the hole and keep it open.
2. The bundle of flexible or rigid plastic tubes is installed into the hole to the designed depths.
3. The permanent outer casing, used to hold the hole open, is lifted up exposing all well screens (or slots) in the bundle. The driven point used during the construction of the hole is left in the ground below the bundle of tubes. The formation should collapse around the bundle below the outer casing.
4. As required by the Wells Regulation, the permanent outer casing remains in the test hole. As a best management practice, the permanent outer casing is installed to a depth above the top of the upper well screen (see best management practice following the examples in this section).
5. As required by the Wells Regulation, any annular space around the permanent outer casing is sealed to prevent the movement of water, natural gas, contaminants or other material between subsurface formations or between a subsurface formation and the ground surface.
6. As required by the Wells Regulation, the annular space between the bundle of flexible or rigid tubes and the permanent outer casing is sealed with a suitable sealant, such as a bentonite product, a cement product or a mechanical device (e.g., packer), to prevent the entry of surface water and other foreign materials into the well (see the second best management practice on page 19 of this chapter).

Example B: Constructing a Bundled Multi-level Monitoring Test Hole using Dual Roatary Equipment

A person constructing a bundled multi-level monitoring test hole uses dual rotary (barber) equipment to advance a hole in the ground. The person constructing the test hole completes the well in the following manner:

1. As required by the Wells Regulation, a hole that is at least 5.1 cm (2″) larger than the outside diameter of the permanent outer casing is advanced from the ground surface to at least the designed bottom of the permanent outer casing. A temporary outer casing that is the same size as the hole is advanced during the drilling process.
2. As required by the Wells Regulation, a permanent outer casing with centralizers is installed into the hole and positioned to be located above all well screens in the bundle.
3. A hole is drilled below the permanent outer casing to the designed depth of the hole. A temporary inner casing is installed during drilling to the full depth of the hole to keep the hole open. The drilling tools are removed from the hole.
4. A bundle of flexible or rigid plastic tubes is installed into the hole to the designed depths.
5. The temporary inner casing, used to hold the hole open, is lifted up and out of the hole allowing all of the well screens in the bundle to be exposed to the formation. The formation should collapse around the bundle below the permanent outer casing.
6. As required by the Wells Regulation, the annular space between the permanent outer casing and temporary outer casing is filled with suitable sealant using a tremie pipe. The temporary casing is used as the tremie pipe. As an alternative, a small diameter tremie pipe can be installed in the annular space to place the suitable sealant (see Chapter 7: Annular Space & Sealing for further information). As required by the Wells Regulation, the tremie pipe is immersed in the rising accumulation of the suitable sealant. The suitable sealant must prevent the movement of water, natural gas, contaminants or other material between a subsurface formation and the ground surface. The temporary outer casing is then removed.
7. As required by the Wells Regulation, the annular space between the permanent outer casing and temporary outer casing is filled with suitable sealant using a tremie pipe. The temporary casing is used as the tremie pipe. As an alternative, a small diameter tremie pipe can be installed in the annular space to place the suitable sealant (see Chapter 7: Annular Space & Sealing for further information). As required by the Wells Regulation, the tremie pipe is immersed in the rising accumulation of the suitable sealant. The suitable sealant must prevent the movement of water, natural gas, contaminants or other material between a subsurface formation and the ground surface. The temporary outer casing is then removed.

Recommended Environment For A Bundled Multi-Level System

The bundled system’s tubes of varying lengths can work well in identifying the vertical extent of a contaminant plume in a collapsing formation (e.g. a sand formation) that has a small vertical hydraulic gradient.

These systems, however, are not suitable in some environments and for certain activities. For example, the bundled multi-level test hole system’s small diameter tubing makes measuring the hydraulic head difficult or in some cases impossible. In some environments, a suitable sealant (e.g. cement, bentonite, packer) is needed around casings and between the depths of individual well screens to prevent intermingling of the groundwater and contaminants in the groundwater. As such, it is not advisable to use a bundled multi-level monitoring test hole to determine the vertical extent of the plume in a number of environments including formations that:

• do not collapse, or
• have vertical hydraulic gradients between formations or within the groundwater zone that could cause intermingling or sample bias.

Nested Multi-Level Monitoring Test Holes With Seals

Nested multi-level monitoring test holes with seals are designed to study groundwater at different depths in a formation or in various formations.

A common design will have three or four PVC plastic or stainless steel casings (risers) installed into a hole. A manufactured PVC plastic or stainless steel well screen is attached to the bottom of each casing. A typical riser has an inside diameter range from 2.5 cm (1″) to 5 cm (2″). The length of each casing is designed to allow the well screen to be set to a discrete depth in the ground. Well screens are usually no longer than 0.3 m (1′) to 0.6 m (2′).

Installation commonly occurs as follows:

• A hole is constructed into a formation or formations using auger, sonic or rotary drilling equipment. The hole should be large enough to install the number of casings needed. Measurements and observations should be made about the location of the formation, location of groundwater levels and aquifer sampling zones when the well construction equipment is being advanced into the ground.
• A temporary drill rod or starter casing may be installed during the construction of the hole in case a portion of the formation is prone to collapse or to prevent the vertical movement of groundwater and contaminants.
• Based on observations, the longest casing and well screen are installed into the hole to the deepest identified sampling location.
• Inert sand is placed in the annular space of the hole, typically using a tremie pipe, to create a filter pack around the deepest well screen.
• A bentonite or cement based sealant is placed in the annular space from the filter pack up to almost the next sampling interval.
• The next casing and well screen are installed into the hole, and the filter pack and sealing process is repeated.
• The process is continued until the hole is completely filled.

Each well screen allows for collection of a groundwater sample from a discrete zone in the formation and allows for the measurement of groundwater levels and for hydraulic conductivity testing. If enough screen points are installed at the correct locations, the vertical delineation of a contaminant plume can then be determined.

Figure 8-2 below shows an illustration of the steps involved in creating a nested multi-level test hole with seals

The three steps shown in Figure 8-2 illustrate a common way to install the components of a nested multi-level test hole with seals. Step 1 shows a well screen and casing placed into the test hole. Inert sand is placed around the well screen to create a filter pack. Suitable sealant is placed above the filter pack. The process is repeated until the hole is completely filled as shown in Step 3.

Reminder - Figure 8-2 is for illustrative purposes only and does not necessarily represent full compliance with requirements found in the Wells Regulation.

Casing And Well Screen Requirements

Casing material may be plastic, stainless steel, polytetrafluoroethylene or fiberglass. The multiple casings (risers) that are installed support the sides of the well. As such, each casing is considered “casing” under the Wells Regulation. The manufactured well screens attached to the bottom of the casings meet the definition of the term “well screen” under the Wells Regulation.

The casing and well screen requirements and exemptions discussed in the “Casing and Well Screen Requirements” section for a bundled multi-level monitoring test hole on page 10 of this chapter apply to a nested multi-level test hole with seals.

Reminder: There are many factors that affect the casing selection including depth of the well and water quality.

Reminder: Some materials such as acrylonitrile-butadiene-styrene (ABS), polytetrafluoroethylene (PTFE) (e.g. Teflon), fiberglass and glass are not typically used for casing for test holes. It is important to refer to manufacturer’s specifications and other information to determine if the material is appropriate for use in test holes at a specific site.

Reminder: A downhole video camera should be used to visually observe the casing, casing joints, the seal between the screen and casing as long as a contaminant will not interfere with the device.

Annular Space - Operating Not Later Than 180 Days

For this circumstance, the requirements for the size and filling of the annular space in the Wells Regulation and in the Records of Site Condition regulation for a nested multi-level monitoring test hole with seals are outlined in the “Annular Space Requirements - Operating not Later than 180 Days” section for a bundled multi-level monitoring test hole on page 13. Relevant best management practices are also found in this section starting on page 13.

Annular Space - Operating Later Than 180 Days

The Wells Regulation allows for the construction of a new nested multi-level monitoring test hole with seals that will be in operation for more than 180 days after the completion of the well’s structural stage, if the following casing and annular space requirements are met:

The Wells Regulation - The person constructing the test hole must install a permanent outer casing around the inner casings.

The Wells Regulation - Depending on the type of well construction method used, the person constructing the well must follow the Wells Regulation requirements listed in Chapter 7: Annular Space & Sealing, Table 7-1 A and Table 7-1B to create and seal an annular space on the outside of the permanent outer casing.

Reminder: As a necessary modification for systems installed using drilling, augering or sonic equipment, the depth of the annular space must extend from the ground surface to at least the bottom of the permanent outer casing or 6 m (19.7′), whichever is less.

The Wells Regulation - When the smaller diameter casings (e.g., PVC plastic) are installed into the permanent outer casing, the annular space between the permanent outer casing and inner casings must be sealed with a suitable sealant to prevent the entry of surface water and other foreign materials into the well. Depending on the environment, a suitable sealant could include a bentonite product, a cement product or a mechanical device such as a packer.

The Wells Regulation - If any groundwater is entering the annular space between the permanent outer casing and the inner casings, the entire annular space between the inner casings and permanent outer casing must be sealed, with necessary modifications, in accordance to the minimum requirements of Chapter 7: Annular Space & Sealing, Table 7-1 A and Table 7-1B. The annular space between casings of a well constructed by the use of a driven point is not required to be sealed in accordance with Chapter 7: Annular Space & Sealing, but is required to be sealed with a suitable sealant.

The installation of an inner and permanent outer casing is referred to as a double walled casing in the Wells Regulation.

Although a person constructing a well is not specifically required to seal around the inner casings between well screens in a nested multi-level monitoring test hole below the permanent outer casing; the person must do what is necessary as the Ontario Water Resources Act prohibits every person from discharging or causing or permitting the discharge of any material of any kind into any waters that may impair the quality of any waters. This includes prohibiting contaminated groundwater from impairing the quality of other groundwater zones when constructing a well.

The regulatory exemptions regarding sealing the annular space below the permanent outer casing allow for well technicians, engineers and geoscientists to use their professional expertise to design and install a bundled system on a case by case basis, thereby enabling the testing and sampling of various groundwater intervals while preventing (further) contamination.

Persons using the above professional judgement and the well owner should be aware of the following requirement.

The Wells Regulation - If the test hole or dewatering well acts as a pathway for the movement of:

• natural gas,
• contaminants, or
• other materials

between subsurface formations (including aquifers) or between the ground surface and a subsurface formation and where the movement may impair the quality of the any waters, the person abandoning the well, often the well owner, must do one of the following:

• take measures to prevent the movement of the above materials and ensure the measures are functional at all times, or
• immediately abandon the well.

This Wells Regulation requirement ensures that, at all times, steps must be taken by the well owner to prevent the well from acting as a pathway for contaminants that may impair groundwater resources.

Reminder: Further information on abandonment requirements is provided in Chapter 16: Abandonment: When to Plug & Seal Test Holes & Dewatering Wells and Chapter 17: Abandonment: How to Plug & Seal Test Holes & Dewatering Wells of this manual.

Examples

The following provides two examples of the well construction requirements for new nested multi-level monitoring test holes with seals that will be in operation more than 180 days.

Example A: Constructing a Nested Multi-level Monitoring Test Hole with Seals using Auger Equipment

A person constructing a nested multi-level monitoring test hole with seals uses auger equipment to advance a hole in the ground. The person constructing the test hole completes the well in the following manner:

1. A hole, that must be at least 7.6 cm (3″) larger than the outside diameter of the permanent outer casing, is advanced to a predetermined depth using hollow stem auger flights. The auger flights act as a temporary casing during the construction process.
2. The longest casing and well screen are installed into the hole to the deepest identified sampling zone. Using the best management practices outlined in Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well, inert sand is carefully placed in the annular space of the hole to create a filter pack around the well screen. Using the best management practices found in Chapter 7: Annular Space & Sealing, bentonite or a cement based suitable sealant is placed in the annular space from the filter pack up to almost the next sampling interval.
3. The auger flights, temporarily used to hold the hole open, are lifted up exposing the well screen and filled annular space to almost the next interval. Measurements are performed to verify that the annular space materials have filled any annular space occupied by the auger flights. The next casing and well screen are installed into the hole and the best management practices of placing the filter pack and suitable sealant are repeated.
4. The shortest casing and final well screen are installed in the hole and the best management practices of placing the filter pack around the shallowest well screen are repeated.
5. A permanent outer casing is installed into the test hole. The permanent outer casing should be installed to a depth above the top of the shallowest well screen.
6. As required by the Wells Regulation, the annular space around the permanent outer casing and auger flights is filled with suitable sealant using a tremie pipe. The auger flights are used as the tremie pipe to place the suitable sealant. As an alternative, a small diameter tremie pipe can be installed in the annular space to place the suitable sealant (see Chapter 7: Annular Space & Sealing for further information). As required by the Wells Regulation, the tremie pipe is immersed in the rising accumulation of the suitable sealant. The suitable sealant must prevent the movement of water, natural gas, contaminants or other material between a subsurface formation and the ground surface. The temporary auger flights (temporary outer casing) are then removed.
7. As required by the Wells Regulation, the annular space between the permanent outer casing and the inner casings is sealed with a suitable sealant such as a bentonite product, a cement product or a mechanical device such as a packer to prevent the entry of surface water and other foreign materials into the well. In addition, if groundwater is leaking into the annular space between the inner casings and the permanent outer casing, a suitable sealant must be installed in the same manner as step 6 of this example.

Example B: Constructing a Nested Multi-level Monitoring Test Hole with Seals using Sonic Drilling Equipment

A person constructing a nested multi-level monitoring test hole with seals uses sonic drilling equipment to advance a hole in the ground. The person constructing the test hole completes the well in the following manner:

1. As required by the Wells Regulation, a hole, that is at least 7.6 cm (3″) larger than the outside diameter of the permanent outer casing, is advanced from ground surface to at least the predetermined bottom of the permanent outer casing. A temporary outer casing that is the same size as the hole is advanced during the drilling process.
2. A smaller diameter hole is drilled below the temporary outer casing to the predetermined depth of the hole. A permanent outer casing that is the same size as the smaller hole is temporarily advanced during the drilling process to the full depth of the hole. The permanent outer casing temporarily keeps the hole open. The drilling tools are removed from the hole.
3. The longest casing and well screen are installed into the hole to the deepest identified sampling zone. Using the best management practices outlined in Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well, inert sand is carefully placed in the annular space of the hole to create a filter pack around the well screen. Using the best management practices found in Chapter 7: Annular Space & Sealing, a bentonite or a cement based suitable sealant is placed in the annular space from the filter pack up to almost the next sampling interval.
4. The permanent outer casing, temporarily used to hold the hole open, is lifted up exposing the well screen and filled annular space to almost the next interval. The next casing and well screen are installed into the hole and the best management practices to place filter pack and suitable sealant are repeated.
5. The shortest casing and final well screen are installed in the hole and the best management practices of placing the filter pack around the shallowest well screen are repeated. The permanent outer casing is raised to a pre-determined depth above the shallowest well screen but below the top of the filter pack.
6. As required by the Wells Regulation, the annular space around the permanent outer casing and temporary outer casing is filled with suitable sealant using a tremie pipe. The temporary casing is used as the tremie pipe to place the suitable sealant. As an alternative, a small diameter tremie pipe can be installed in the annular space to place the suitable sealant (see Chapter 7: Annular Space & Sealing for further information). As required by the Wells Regulation, the tremie pipe is immersed in the rising accumulation of the suitable sealant. The suitable sealant must prevent the movement of water, natural gas, contaminants or other material between a subsurface formation and the ground surface. The temporary outer casing is then removed.
7. As required by the Wells Regulation, the annular space between the permanent outer casing and the inner casings is sealed with a suitable sealant, such as a bentonite product, a cement product or a mechanical device such as a packer, to prevent the entry of surface water and other foreign materials into the well. In addition, if groundwater is leaking into the annular space between the inner casings and the permanent outer casing, a suitable sealant must be installed in the same manner as Step 6 of this example.

Annular Space - Best Management Practices

Figure 8-3: Lantern Style Centralizer With Discs^{footnote 3[3]}

The left side of Figure 8-3 shows a cross section of the drill hole with a lantern style centralizer placed inside the hole. The centralizer is centering the casing in the hole so that is does not touch the side of the hole or other casing inside the hole by using a spacer disc that each casing runs through.

The right side of Figure 8-3 shows a top down view of the centralizer inside the hole with the holes in the spacer disc that casing pipes go in to separate the casing from each other and the side of the hole.

Dedicated Multi-Level Monitoring Test Holes

Dedicated multi-level monitoring test holes are designed to study groundwater at different depths in a formation or various formations. Where feasible, monitoring at different levels from one well location enhances the understanding of the vertical distribution of contaminants and aquifer hydraulic characteristics.

A typical installation consists of one dedicated multi-level casing system that spans the length of the test hole. Ports (or well screens) are placed at predetermined intervals on the dedicated multi-level casing system. The ports connect to tubes, channels or cables or the interior of the multi-level casing system. Within the dedicated multi-level casing system, the sampling devices, tubing, channels or cables extend from the ports to the ground surface and attach to various sampling pumps or monitoring devices.

For some installations, the annular space along the casing and between the ports of the dedicated multi-level casing system may be sealed with inflatable packers or suitable sealant between the outside of the casing and the side of the well. Depending on the installation, a filter pack may be installed in an annular space beside the ports to the side of the well.

For other installations, multiple outer casing sections and well screens of the same diameter are sealed together (sometimes called a casing and screen string) based on a predetermined design for the hole. The casing and screen string is placed into the well. The annular space intervals along the casing sections and between the well screens are sealed with sealant. A filter pack is placed in the annular space beside the well screens to the side of the well. A smaller diameter dedicated multi-level casing system with ports is placed into the casing and screen string. The depths of the ports will match the elevation of the well screens. Between the ports, the annular space intervals between the system’s casing and outer casing may be sealed with inflatable packers or sealant. Depending on the installation, a filter pack may be installed in an annular space beside the ports to the inner portion of the well screen.

Once packers or suitable sealant are placed, the sampling intervals are typically purged through ports, monitored for stabilization criteria and sampled. The person conducting the monitoring should carefully evaluate geophysical and hydraulic information previously collected from the hole to determine the potential of groundwater and contaminants moving vertically between ports.

See the best management practices starting on page 61 regarding construction and siting of dedicated multi-level monitoring test holes.

Advantages of dedicated multi-level monitoring test holes, compared to other test holes, include:

• Groundwater samples and hydraulic head measurements can be obtained from many more zones than a nested multi-level test hole with seals or a well cluster. More sampling points can provide a more accurate representation of the aquifer and the contaminant plume in the groundwater.
• In many cases, a dedicated multi-level casing system can be placed into the hole instead of a nested multi-level test hole or a series of single-level test holes. A system consisting of one pipe or liner with multiple ports simplifies the process of installing packers or suitable sealant in the hole. As long as the dedicated multi-level casing system is properly centered in the hole, suitable sealant should create a proper seal between sampling ports. If casings are touching the side of the hole or each other in a nested multi-level test hole, sections of the hole may not be properly sealed creating void spaces once the suitable sealant or filter pack has been placed into the test hole.
• Fewer holes need to be advanced into the ground to delineate vertical groundwater characteristics which lowers well construction costs and reduces the footprint on the property. For example, one dedicated multi-level monitoring test hole can do the job of five nested multi-level test holes with seals or 20 single test holes in a well cluster.
• The volume of purged water for sampling is reduced resulting in lower water storage and disposal costs.
• The small diameters of the tubes and channels used in a dedicated system allow groundwater head pressures to equalize more quickly with a result that hydraulic heads (i.e., static water levels) can be measured rapidly.
• Some designs eliminate the need for suitable sealant or backfill material around ports that can impact the sample water quality.

Disadvantages of dedicated multi-level monitoring test holes, compared to other test holes, include:

• The drilling options for installing these systems can be limited.
• The hole may require a temporary (starter) casing to be placed into the hole to reduce the risk of the vertical migration of contaminants and hole collapse.
• Qualified well technicians who are familiar with the type of dedicated system are needed to install the casing, ports and other equipment correctly.
• The installation of vertical isolation packers or suitable sealant in wells requires very reliable material and installation equipment due to the highly complex system.
• If the system fails during or after installation, parts such as specialized packers or ports may not be readily repairable or replaceable.
• Due to their design, certain systems may be difficult to remove making repairs complicated.
• Some dedicated systems can be more difficult to properly abandon (plug and seal).
• If packers are used, the well owner should have a contingency plan in place in case there is a partial or complete failure of a packer.
• Freezing problems can cause inflation line blockages when attempting to re-inflate packers in certain dedicated systems.
• In certain dedicated systems, inflatable packers become unsealed increasing the risk of the vertical migration of contaminants along the well casing or open hole.
• Flowing artesian conditions may create high enough water pressures to prevent the installation of some dedicated systems.
• As with single well installations, improper assembly of electronics may cause pressure transducers and dataloggers to act as sacrificial anodes, and increase the risk of lightening strikes.
• If a liner dedicated system is used (e.g. Water FLUTe™), contaminants can leach from the liner into groundwater that could cause a bias in some samples. For example, Water FLUTe™ liners leach trace levels of toluene for several months.
• Continuous Multi-Channel Tubing (CMT™) tubing could allow for a bias in sample results. Bias can be minimized by purging, using specialized tubing or using systems that take samples from areas of the channel near the ports.
• There is an increased potential for vertical migration of contaminants if packer locations or bentonite seals are not chosen or installed carefully.

There are four dedicated multi-level monitoring systems that are known to be commonly used in Canada at the time of publication. These systems are:

• Schlumberger Westbay© System,
• Solinst Waterloo™ System (since, 1984),
• Solinst CMT™ (Continuous Multi-Channel Tubing™) System (since, 1999), and
• Water FLUTe™ (Flexible Liner Underground Technology) System.

Table 8-1 outlines common characteristics of the systems. Figures 8-4 to 8-21 (pages 41 to 51) show various components of the systems.

Reminder: The use of brand names in this manual is for identification purposes only and does not constitute an endorsement by the Ministry of the Environment.

Reminder: The information and illustrations of these systems do not constitute a recommendation of any or all of the systems. The table and illustrations are presented solely to provide information on the systems that are currently available and how these systems could be installed to meet the requirements of the Wells Regulation.

Figure 8-4 and Figure 8-5 on page 41 and Figure 8-6 on page 42 provide examples of two completions of the Westbay ® System.

Figure 8-4: Cross-Section of A Westbay ® System in an Open Hole^{footnote 4[4]}

The left side diagram in Figure 8-4 shows a cross-section of a Westbay dedicated multi-level monitoring system in a vertical open hole. A permanent outer casing is located in the upper portion of the hole around the Westbay system. An annular seal is located around the outside of the permanent outer casing.

To the right of the Westbay system cross-section is an expanded view of the centre of the Westbay system in the hole. The upper portion of the expanded view shows the Westbay system’s casing extending vertically down to a Westbay packer. The packer has been expanded to the side of the hole. A casing is attached from the bottom of the packer to a measurement port. A casing is attached from the measurement port to a pumping port. A casing is attached from the pumping port to a lower packer. The lower packer has been expanded to the side of the hole.

Figure 8-5: Cross-Section of A Westbay ® System Completion in A Cased Well^{footnote 5[5]}

The left side diagram in Figure 8-5 shows a cross-section of a Westbay dedicated multi-level monitoring system in a vertical open hole. A vertical string of altering permanent outer casing and well screens are located in the hole around the Westbay system. The well screens are located in monitoring zones. An annular seal is located around the outside of the permanent outer casing and filter pack is located around the outside of the well screens in the hole.

To the right of the Westbay system cross-section is an expanded view of the centre of the Westbay system in the hole. The upper portion of the expanded view shows the Westbay system’s casing extending vertically down to a Westbay packer. The Westbay packer has been expanded to the side of a permanent casing in the hole. A Westbay casing is attached from the bottom of the packer to a measurement port. A casing is attached from the measurement port to a pumping port. A Westbay casing is attached from the pumping port to a lower packer. The lower packer has been expanded to a permanent outer casing. The zone between the two packers is called a Monitoring zone. In the monitoring zone, a well screen is attached between the two permanent outer casings. A filter pack material has been placed between the well screen and the side of the hole. A suitable sealant has been placed between the permanent outer casings and the side of the hole.

Reminder: These figures are not to scale, are for illustrative purposes only and do not necessarily represent full compliance with the requirements found in the Wells Regulation.

Figure 8-6: Cross-Section of A Westbay ® System in A Backfilled Hole^{footnote 6[6]}

The left side diagram in Figure 8-6 shows a cross-section of a Westbay dedicated multi-level monitoring system in a vertical open hole. A permanent outer casing is located in the upper portion of the hole around the Westbay system. An annular seal is located around the outside of the permanent outer casing.

To the right of the Westbay system cross-section is an expanded view of the centre of the Westbay system in the hole. The upper portion of the expanded view shows the Westbay system’s casing extending vertically down to a measurement port. A casing is attached from the measurement port to a pumping port. A casing is attached from the pumping port and extends down into the hole. Above and below the pumping port and measurement port zone, a suitable sealant has been placed around the casing to the side of the hole. In the pumping port and measuring port zone, a filter pack has been placed from the ports to the side of the hole.

Reminder: This figure is not to scale, it is for illustrative purposes only and does not necessarily represent full compliance with the requirements found in the Wells Regulation. For example, an outer casing is required to allow a new system to be used for more than 180 days.

Figure 8-7: Sampler Probe For The Westbay ® System^{footnote 7[7]}

The diagram is a cross-section illustration that shows the 5 stages of a sampler probe in the Westbay System. The first two illustrations show the sampler probe locating a sampling port, the third illustration shows the system connecting to the port, the 4^th shows that is collecting a sample and the fifth one shows the closing of the sample passage and storing of the sample.

The above cross-section illustrations show the various stages of a sampler probe in the Westbay ® System, locating a port (a) and (b), connecting to the port and monitoring (c), collecting a sample (d), and closing the sample passage (e).

Reminder: This figure is not to scale, it is for illustrative purposes only and does not necessarily represent full compliance with the requirements found in the Wells Regulation.

Figure 8-8: Stainless Steel Ports^{footnote 8[8]}

Figure 8-9: Permanent Waterloo Packer^{footnote 8[8]}

Figure 8-10: Manifold^{footnote 8[8]}

Figure 8-11: O-Ring With Shear Wire^{footnote 8[8]}

Figures 8-8 to 8-11, show various components for a Solinst Waterloo™ system. The ports (Figure 8-8) connect monitoring equipment with a groundwater zone. Packers (Figure 8-9) can be expanded to seal the system to the side of the well. A manifold (Figure 8-10) seals the top of the system. Connections using O-rings and shear wires (Figure 8-11) provide a watertight connection between casing, packers and ports. The figure shows the components assembled and placed into the ground.

Reminder: Figure 8-8 to Figure 8-11 are for illustrative purposes only and do not necessarily represent full compliance with requirements found in the Wells Regulation.

Figure 8-12: Examples of Three Completions of the Solinst Waterloo™ System^{footnote 9[9]}

The first example on the left shows a cored hole in bedrock with no casing. Permanent packers are placed in the cored hole above and below the monitoring port. The 2^nd example in the middle shows a cored hole that can either be in bedrock or the overburden. In this example, well casing is placed inside the cored hole and permanent packers are in the casing or well screen. The third example on the right side of the figure shows a cored hole that can either be in bedrock and/or overburden. In this case sand and bentonite is placed directly around screen monitoring ports.

Reminder: This figure is not to scale, it is for illustrative purposes only and does not necessarily represent full compliance with the requirements found in the Wells Regulation. For example, a permanent outer casing is required to allow a new multi-level monitoring system to be used for more than 180 days.

Figure 8-13: Details of A Sampling Port Construction in A Solinst CMT™ (Continuous Multi-Channel Tubing™) System^{footnote 10[10]}

This figure shows the components that make up a CMT system. From top to bottom, the system includes a well cap, a CMT wellhead that contains numberd channels within it. Attached below and within the wellhead is polyethylene CMT tubing with a screen wrapped around it. Oetiker Clamps hold the screen on the CMT tubing

.

Reminder: This figure is not to scale, it is for illustrative purposes only and does not necessarily represent full compliance with the requirements found in the Wells Regulation.

Figure 8-14: Seven-Channel MDPE Tubing in A Solinst CMT™ (Continuous Multi-Channel Tubing™) System^{footnote 11[11]}

Figure 8-15: A Person Laying Out The MDPE Tubing Prior To Installation In The Hole^{footnote 11[11]}

Reminder: To prevent contamination to the groundwater and to meet the Wells Regulation, persons should lay out MDPE tubing on clean plastic sheets rather than directly onto the ground as shown in Figure 8-15.

Reminder: These figures are for illustrative purposes only and do not necessarily represent full compliance with the requirements found in the Wells Regulation.

Figure 8-16: Screened Port Completion^{footnote 12[12]}

Figure 8-16 shows a screened port completion for the centre channel of a Solinst CMT™ (Continuous Multi-channel TubingTM) system. The port is called a guide point port assembly and is attached to the bottom of the MDPE tubing.

Figure 8-17: Guide Port Assembly Anchor^{footnote 13[13]}

Figure 8-18: Centralizer On MDPE Tubing^{footnote 14[14]}

Figure 8-18 shows a three half circle centralizer clamped onto the MDPE tubing. The centralizer helps centre the MDPE tubing in the hole.

Reminder: These figures are for illustrative purposes only and do not necessarily represent full compliance with the requirements found in the Wells Regulation.

Figure 8-19: Example Of Solinst CMT System Completion^{footnote 15[15]}

Reminder: These figures are not to scale, are for illustrative purposes only and do not necessarily represent full compliance with the requirements found in the Wells Regulation. For example, a permanent outer casing is required to allow a new system to be used for more than 180 days.

Figure 8-20: Cross-Section Of A Water Flute™ System^{footnote 16[16]}

Reminder: These figures are not to scale, are for illustrative purposes only and do not necessarily represent full compliance with the requirements found in the Wells Regulation.

Figure 8-21: Installation of A Water FLUTe™ Into A Test Hole^{footnote 17[17]}

Figure 8-21 shows the factory-made installation of a Water FLUTe™ into a test hole, using the eversion process. The liner was shipped to the site fully fabricated on the shipping reel in the background. The bottom end of the liner is entering the hole and the pump systems for the ports will follow it to the bottom of the hole. The pump tubing is sheathed in a diagonally woven white cover containing the pumps, the 15 transducers and cables, the supporting tether and the tag line.

Reminder: This figure is for illustrative purposes only and does not necessarily represent full compliance with the requirements found in the Wells Regulation.

Casing And Well Screen Requirements

The material used in a dedicated multi-level monitoring system may be plastic, stainless steel, polytetrafluoroethylene, fiberglass or polyurethane-coated nylon fabric (sometimes called a sock or liner).

The materials used to make casing should be designed to support the sides of a well to prevent the present and future collapse of overburden and bedrock formations into the well.

Where a pipe, tube or other material (e.g., liner) in a dedicated multi-level monitoring system is used to support the sides of a well, the material is considered “casing” under the Wells Regulation. In some cases, such as the Solinst Waterloo™ system, a manifold is used to house all of the monitoring tubes and cables at the top of the system. Where a portion of the manifold is being used to support the sides of the test hole, the manifold is considered “casing”.

The Wells Regulation - The casing requirements and exemptions of the Wells Regulation that are outlined in the “The Requirements – Plainly Stated” section of Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well apply to the lengths of casing in a dedicated multi-level casing system. Also, any permanent outer casing that is placed around the dedicated multi-level casing system must meet casing requirements and exemptions of the Wells Regulation.

Where the pipe, tube or other material is part of a port to sample or monitor groundwater, the pipe, tube or other material is considered a “well screen” under the Wells Regulation. This includes port areas that are wrapped in a screen mesh or part of a spacer area in a liner (see Figure 8-16, Figure 8-17, and Figure 8-20).

The Wells Regulation - The well screen requirements and exemptions of the Wells Regulation that are outlined in the “Plainly Stated” section of Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well apply to the port areas, including spacer areas, in a dedicated multi-level casing system.

The exemptions in the Wells Regulation allow for the use of unique casing and port designs in a dedicated multi-level casing system to obtain groundwater samples and to determine groundwater characteristics that are representative of the study area.

The Wells Regulation - If a new dedicated multi-level casing system is finished above the ground surface, the minimum casing extent and casing height requirements in the Wells Regulation that are outlined in Chapter 9: Completing the Test Hole or Dewatering Wells Structure apply as long as the upper part of the system is using a length of material that is defined as “casing”.

For example, if a new Solinst Waterloo CMT™ system is installed in an overburden hole, the person constructing the well must ensure the HDPE casing extends:

• from the water intake zone,
• to at least 40 cm (16″) above the highest point on the ground surface within 3 m (10′) radially from the outside of the casing after the ground surface (surface drainage) has been mounded so that water will not collect or pond near the well as measured on completion of the well’s structural stage.

The Wells Regulation - If the new dedicated multi-level casing system is located in an area where there is a likelihood of pedestrian or vehicular traffic, the Wells Regulation allows for the top of the casing to be finished below the ground surface as long as the person constructing the well completes the well with a flush-mounted well cover and meets the Wells Regulation requirements. See Chapter 9: Completing the Test Hole or Dewatering Well Structure for more information on flush-mounted well covers. See Chapter 12: Equipment Installation for further information on flush-mounted well pit (vault) construction requirements.

The Wells Regulation - The top of the dedicated multi-level casing system must be covered or capped in accordance with the Wells Regulation requirements. See “Plainly Stated” section in Chapter 12: Equipment Installation for further information.

Records of Site Condition Regulation - Starting on July 1, 2011, amendments to O. Reg. 153/04 came into force and apply to phase two environmental site assessments (ESAs) conducted in support of records of site conditions (RSCs). For any such RSC submitted on or after this date, where a groundwater sampling method is to be used to characterize contamination or determine if the concentration of a contaminant is above, at or below and applicable site condition standard or standard specified in a risk assessment for the contaminant, the following requirements apply to the construction of a well:

• where a monitoring well is being used, well screens shall not exceed 3.1 m (10′) in length, based on the saturated length of the screen, and
• where petroleum hydrocarbons or light non-aqueous phase liquids may be present on, in or under a phase two property, sampling depth intervals, including screened intervals of monitoring wells, shall be positioned to intersect the water table.

Implications for the Qualified Person

The qualified person shall ensure that the phase two ESA is conducted in accordance with requirements stated above.

Records of Site Condition Regulation - Please refer to O. Reg. 153/04 for RSC requirements.

Reminder: For clarification of the term “monitoring well” and “qualified person” as they relate to the O. Reg. 153/04, see Chapter 2: Definitions & Clarifications, Table 2-2.

Annular Space Requirements - Operating Not Later Than 180 Days

This section applies to a new test hole that is scheduled to be abandoned not later than 180 days after the completion of the structural stage of the test hole, and where an outer permanent casing is not placed around the new dedicated multi-level casing system.

The Wells Regulation - Instead of following the annular space requirements listed in Chapter 7: Annular Space and Sealing, the person constructing a new dedicated multi-level casing system new multi-level monitoring without a permanent outer casing must ensure that:

• any annular space created beside a casing or between casings is sealed to prevent the movement of water, natural gas, contaminants or other material between a subsurface formations or between a subsurface formation and the ground surface, and
• the test hole is scheduled to be abandoned not later than 180 days after the completion of the structural stage of the test hole.

Reminder: See the “Best Management Practice –Written Contract for Wells Scheduled to be Abandoned” in the “Bundled Multi-level Monitoring Test Hole” section in this chapter.

Records of Site Condition Regulation - Starting on July 1, 2011, O. Reg. 153/04 prescribes that the provisions of the Ontario Water Resources Act and of Regulation 903 of the Revised Regulations of Ontario, 1990 (Wells) made under that Act, that would apply to a test hole but for section 1.1, and subsections 13 (2), 14.1 (2), 14.2 (3), 14.3 (2), 14.4 (4) and 14.5 (3) of that regulation, apply to a monitoring well installed for the purpose of,

1. a phase one environmental site assessment; and
2. a phase two environmental site assessment.

Implications for the Qualified Person

The qualified person shall ensure that phase one and phase two environmental site assessments (ESAs) are conducted in accordance with the requirement stated above.

Implications for Annular Space for New Test Holes

With respect to annular space size and filling, the above requirement in the O. Reg. 153/04 means that, if the new dedicated multi-level monitoring test hole is constructed and is scheduled to be abandoned not later than 180 days after the completion of its structural stage, and is to be used as a monitoring well in an ESA for a record of site condition, then:

• the annular space size and filling exemptions for a test hole stated in this section do not apply and
• the annular space size and filling requirements for a test hole stated in the “Annular Space – Operating Longer than 180 Days” section do apply regardless of the amount of time that the monitoring well will be in operation.

Reminder: The above requirement in O. Reg. 153/04 also affects obligations such as shallow works, casing material and annular space filling for monitoring wells. See Chapter 3: Exemptions: Wells, Activities & Experienced Professionals, Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well and Chapter 7: Annular Space & Sealing for further information.

Reminder: Please refer to O. Reg. 153/04 for RSC requirements.

Annular Space - Operating Later Than 180 Days

The Wells Regulation allows for a new dedicated multi-level casing system that will be in operation for more than 180 days after the completion of the well’s structural stage, if the following casing and annular space requirements are met:

The Wells Regulation - The person constructing the test hole must install a permanent outer casing around the dedicated multi-level casing system.

In situations where a casing and screen string is employed in the construction of the new dedicated multi-level casing test hole, the person constructing the test hole must install a permanent outer casing around the casing and screen string.

The Wells Regulation Depending on the type of well construction method used, the person constructing the new dedicated multi-level casing test hole must follow the Wells Regulation requirements listed in Chapter 7: Annular Space & Sealing, Table 7-1 A and Table 7-1B to create and seal any annular space on the outside of the permanent outer casing.

Reminder: As a necessary modification for systems installed using drilling, augering or sonic equipment, the depth of the annular space must extend from the ground surface to at least the bottom of the permanent outer casing or 6 m (19.7′), whichever is less.

The Wells Regulation The person constructing the new dedicated multi-level test hole must seal the annular space between casings with a suitable sealant to prevent the entry of surface water and other foreign materials into the well. Depending on the environment, a suitable sealant could include a bentonite product, a cement product or a mechanical device such as a packer.

The Wells Regulation If any groundwater is entering the annular space between casings, the entire annular space between the casings must be sealed, with necessary modifications, in accordance to the minimum requirements of Chapter 7: Annular Space & Sealing, Table 7-1 A and Table 7-1B. The annular space between casings of a well constructed by the use of a driven point is not required to be sealed in accordance with Chapter 7: Annular Space & Sealing, but is required to be sealed with a suitable sealant.

Reminder: The annular space creation and filling method requirements in the Wells Regulation do not apply to any annular space located below the bottom of the permanent outer casing. The regulatory exemptions regarding sealing the annular space below the permanent outer casing allow for well technicians, engineers and geoscientists to use their professional expertise to design and install multi-level wells on a case by case basis, thereby enabling the testing and sampling of various groundwater intervals while preventing contamination.

Reminder: For further information on creating and filling an annular space for multi-level systems, see the Best Management Practice – Designing and Placing Sealant in Dedicated Multi-Level Systems on page 64 of this chapter.

The installation of an inner and permanent outer casing is referred to as a double walled casing in the Wells Regulation.

Although a person constructing a well is not specifically required to seal around casings between well screens or ports in a dedicated multi-level monitoring test hole below the permanent outer casing; the person must do what is necessary as the Ontario Water Resources Act prohibits every person from discharging or causing or permitting the discharge of any material of any kind into any waters that may impair the quality of any waters. This includes prohibiting contaminated groundwater from impairing the quality of other groundwater zones when constructing a well.

The regulatory exemptions regarding sealing the annular space below the permanent outer casing allow for well technicians, engineers and geoscientists to use their professional expertise to design and install a bundled system on a case by case basis, thereby enabling the testing and sampling of various groundwater intervals while preventing (further) contamination.

Persons using such professional judgement and the well owner should be aware of the following requirement:

The Wells Regulation - If the test hole or dewatering well acts as a pathway for the movement of:

• natural gas,
• contaminants, or
• other materials

between subsurface formations (including aquifers) or between the ground surface and a subsurface formation and where the movement may impair the quality of the any waters, the person abandoning the well, often the well owner, must do one of the following:

• take measures to prevent the movement of the above materials and ensure the measures are functional at all times, or
• immediately abandon the well.

The Wells Regulation requires that, at all times, steps must be taken by the well owner to prevent the well from acting as a pathway for contaminants that may impair groundwater resources.

Reminder: Further information on abandonment requirements is provided in Chapter 16: Abandonment: When to Plug & Seal Test Holes & Dewatering Wells and Chapter 17: Abandonment: How to Plug & Seal Test Holes & Dewatering Wells of this manual.

Examples

The following provides four examples of the well construction requirements for new dedicated multi-level monitoring test holes that will be in operation more than 180 days.

Example A: Installing the Westbay® System using Dual Rotary Equipment
Example B: Installing a Continuous Multi-Channel Tubing™ (CMT™) using Sonic Equipment
Example C: Installing a water FLUTe™ liner using Dual Rotary Equipment
Example D: Installing a casing and screen string and Waterloo™ system using Sonic Equipment

Example A: Installing the Westbay® System using Dual Rotary Equipment

A person constructing a dedicated multi-level monitoring test hole uses dual rotary equipment to advance a hole in the ground. The person constructing the test hole completes the well in the following manner:

1. A hole, that must be at least 7.6 cm (3″) larger than the outside diameter of a permanent outer casing, is advanced to 4 m (13′) below the ground surface. The hole is drilled through 3 m (10′) of overburden and 1 m (3.3′) of competent bedrock. A temporary outer casing that is the same size as the hole is advanced during the drilling process.

   A permanent outer casing is installed into the test hole to 4 m (13’) below the ground surface.

2. As required by the Wells Regulation, the annular space between the permanent outer casing and temporary outer casing is filled with suitable sealant using a tremie pipe. The temporary outer casing is used as the tremie pipe to place the suitable sealant into the annular space. As an alternative, a small diameter tremie pipe can be installed in the annular space to place the sealant (see Chapter 7: Annular Space & Sealing for further information). As required by the Wells Regulation, the tremie pipe is immersed in the rising accumulation of the suitable sealant. The suitable sealant must prevent the movement of water, natural gas, contaminants or other materials between subsurface formations or between a subsurface formation and the ground surface. The temporary outer casing is then removed.
3. A smaller diameter hole is drilled below the permanent outer casing to the predetermined depth. The hole is advanced through competent bedrock. A temporary inner casing is advanced during the drilling process to the full depth of the hole. The temporary inner casing acts to hold the hole open and to reduce the risk of contaminants and groundwater moving along the well column. The drilling tools are removed from the hole.
4. After assessing geophysical and hydrogeological information taken during or shortly after drilling, the intervals for monitoring and sampling groundwater are determined to design the Westbay® System. Based on the information, casing, inflatable packers and port components of the Westbay® System are assembled on site and placed into the hole.
5. The small diameter temporary inner casing is raised to expose each port and packer.
6. Using the best management practices outlined in this chapter, each packer is inflated to seal the system to the sides of the Westbay® System’s casing. The process is repeated until all ports are installed and all packers are expanded.
7. As required by the Wells Regulation, the annular space between the dedicated multi-level casing and the permanent outer casing is sealed with suitable sealant, such as a bentonite product, a cement product or an inflatable packer, to prevent the entry of surface water and other foreign materials into the well. In addition, if groundwater is leaking into the annular space between the casing of the sampling system and the permanent outer casing, a suitable sealant must be installed in the same manner as Step 3 of this example.
8. As required by the Wells Regulation, the annular space between the dedicated multi-level casing and the permanent outer casing is sealed with a suitable sealant, such as a bentonite product, a cement product or an inflatable packer, to prevent the entry of surface water and other foreign materials into the well. In addition, if groundwater is leaking into the annular space between the casing of the sampling system and the permanent outer casing, a suitable sealant must be installed in the same manner as Step 7 of this example.

Example B: Installing a Continuous Multi-Channel TubingTM (CMT™) using Sonic Equipment

A person constructing a dedicated multi-level monitoring test hole uses sonic drilling equipment to advance a hole in the ground. The person constructing the test hole completes the well in the following manner:

1. A hole, that must be at least 7.6 cm (3”) larger than the outside diameter of the permanent outer casing, is advanced from ground surface to at least the predetermined bottom of the permanent outer casing. A temporary outer casing that is the same size as the hole is advanced during the drilling process.
2. A smaller diameter hole is drilled below the temporary outer casing to the predetermined depth. A temporary inner casing is advanced during the drilling process to the full depth of the hole. The temporary inner casing acts to keep the hole open and reduces the risk of contaminants and groundwater moving along the well column. The drilling tools are removed from the hole.
3. Based on hydrogeological information obtained during the drilling process and using the installation recommendations of the manufacturer, seven ports are created on a length of MDPE tubing of a Continuous Multi-Channel Tubing™ (CMT™) system. One of the ports is located at the bottom of the MDPE tubing. As a best management practice, centralizers are placed around the MDPE tubing at various intervals to ensure the CMT™ will be centered in the hole. The CMT™ is installed into the hole.
4. Using the best management practices outlined in Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well for filter pack installation, inert sand is carefully poured down the annular space around the MDPE tubing to create a filter pack around the deepest well screen. Using the best management practices found in Chapter 7: Annular Space & Sealing, a suitable sealant is installed in the annular space from the top of the filter pack up to almost the next port. The best management practices of placing sand and suitable sealant are repeated until the process reaches the bottom of the temporary outer casing.
5. The temporary inner casing, used to hold the hole open, is lifted up and out of the well exposing all ports with filter packs to the formations.
6. A permanent outer casing is installed into the test hole between the MDPE tubing and temporary outer casing. The permanent outer casing should be installed to a depth above the top of the upper port.
7. As required by the Wells Regulation, the annular space between the permanent outer casing and temporary outer casing is filled with suitable sealant using a tremie pipe. The temporary outer casing is used as the tremie pipe to place the suitable sealant into the annular space. As an alternative, a small diameter tremie pipe can be installed in the annular space to place the sealant (see Chapter 7: Annular Space & Sealing for further information). As required by the Wells Regulation, the tremie pipe is immersed in the rising accumulation of the suitable sealant. The suitable sealant must prevent the movement of water, natural gas, contaminants or other materials between subsurface formations or between a subsurface formation and the ground surface. The temporary outer casing is then removed.
8. As required by the Wells Regulation, the annular space between the permanent outer casing and the inner casing of the CMT™ is sealed with a suitable sealant such as a bentonite product, a cement product or a mechanical device such as a packer, to prevent the entry of surface water and other foreign materials into the well. In addition, if groundwater is leaking into the annular space between the CMT™ and the permanent outer casing, a suitable sealant must be installed in the same manner as Step 7 of this example.

Example C: Installing a water FLUTe™ liner using Dual Rotary Equipment

A person constructing a dedicated multi-level monitoring test hole uses dual rotary equipment to advance a hole in the ground. The person constructing the test hole completes the well in the following manner:

• A hole, that must be at least 7.6 cm (3″) larger than the outside diameter of the permanent outer casing, is advanced from ground surface to at least the predetermined bottom of the permanent outer casing. A temporary outer casing that is the same size as the hole is advanced during the drilling process.
• A permanent outer casing is installed into the test hole. As a best management practice, the permanent outer casing is installed to a depth just above the top of the upper port. This location represents a highly fractured bedrock zone below competent bedrock.
• As required by the Wells Regulation, the annular space between the permanent outer casing and temporary outer casing is filled with suitable sealant using a tremie pipe. The temporary outer casing is used as the tremie pipe to place the suitable sealant. As an alternative, a small diameter tremie pipe can be installed in the annular space to place the suitable sealant (see Chapter 7: Annular Space & Sealing for further information). As required by the Wells Regulation, the tremie pipe is immersed in the rising accumulation of the suitable sealant. The suitable sealant must prevent the movement of water, natural gas, contaminants or other materials between subsurface formations or between a subsurface formation and the ground surface. The temporary outer casing is then removed.
• A smaller diameter hole is drilled below the permanent outer casing to the pre-determined depth. The hole is advanced through competent bedrock. A temporary inner casing is advanced during the drilling process to the full depth of the hole. The temporary inner casing acts to hold the hole open and to reduce the risk of contaminants and groundwater moving along the well column. The drilling tools are removed from the hole.
• The temporary inner casing is removed from the hole. A factory-made water FLUTe™ liner with no ports is installed into the hole using an eversion technique with water. The water inside the liner holds the hole open in the highly fractured bedrock zone and reduces the risk of contaminants and groundwater moving along the well column.
• Based on hydrogeological information obtained during the drilling process and all other available information from geophysical measurements and transmissivity measurements during the blank liner installation in this hole, a factory-made water FLUTe™ liner with specially made ports, tubing and cables is made and arrives at the well site. The water FLUTe™ liner with no ports is removed and the water FLUTe™ liner with ports is placed into the hole under the supervision of persons properly trained to install the liner using an eversion process.
• The liner seals to the permanent outer casing, fractured bedrock zone and deeper competent bedrock. The liner is considered casing because it is supporting the sides of the well including the portion of the highly fractured bedrock zone. However, as there is no annular space between the liner and the permanent outer casing, suitable sealant is not required to be placed between the liner and outer casing.

Example D: Installing a casing and screen string and Waterloo™ system using Sonic Equipment

A person constructing a dedicated multi-level monitoring test hole uses sonic drilling equipment to advance a hole in the ground. The person constructing the test hole completes the well in the following manner:

1. A hole, that must be at least 7.6 cm (3″) larger than the outside diameter of the permanent outer casing, is advanced through overburden and a highly fractured bedrock formation to at least the predetermined bottom of the permanent outer casing. A temporary outer casing that is the same size as the hole is advanced during the drilling process.
2. A permanent outer casing is installed into the test hole to a depth just above the top of the upper port.
3. As required by the Wells Regulation, the annular space between the permanent outer casing and temporary outer casing is filled with suitable sealant using a tremie pipe. The temporary outer casing is used as the tremie pipe to place the suitable sealant. As an alternative, a small diameter tremie pipe can be installed in the annular space to place the suitable sealant (see Chapter 7: Annular Space & Sealing for further information). As required by the Wells Regulation, the tremie pipe is immersed in the rising accumulation of the suitable sealant. The suitable sealant must prevent the movement of water, natural gas, contaminants or other material between subsurface formations or between a subsurface formation and the ground surface. The temporary outer casing is then removed.
4. A smaller diameter hole is drilled below the permanent outer casing to the predetermined depth. A temporary inner casing is advanced during the drilling process to the full depth of the hole. The temporary inner casing acts to keep the hole open and to reduce the risk of contaminants and groundwater moving along the well column. The drilling tools are removed from the hole.
5. After assessing geophysical and hydrogeological information taken during or shortly after drilling, the intervals for a casing and screen string are determined. The stainless steel casing sections and well screen lengths are joined together to form a casing and screen string. The string is placed into the hole. The well screens are designed to match sampling depths and intervals that are to be sampled or monitored.
6. Using the best management practices in the “Filter Packs around Well Screens for Test Holes or Dewatering Wells” and “Artificial Filter Packs” sections of Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well, inert sand is carefully poured down the annular space of the hole to create a filter pack around the deepest well screen. Using the best management practices found in Chapter 7: Annular Space & Sealing, a suitable sealant is installed in the annular space from the top of the filter pack up to almost the next sampling interval. The best management practices of placing sand and suitable sealant are repeated until the process reaches the bottom of the temporary outer casing.
7. The temporary inner casing, used to hold the hole open, is lifted up and out of the well exposing all well screens with filter packs to the formations. During this process the well screen areas should be developed to remove any drilling mud and to repair damage done to the formation.
8. Ports, tubing, cables, casing, inflatable packers and a manifold are assembled to create a Waterloo™ system based on the geophysical and hydrogeological information taken during, or shortly after, drilling and the present location of well screens in the casing and screen string. The system is placed in the hole with individual ports matching the depths of individual well screens.
9. Using the best management practices outlined in this chapter, the packers are inflated to seal the system to the sides of the steel casing.
10. As required by the Wells Regulation, the annular space between the shallowest casing of the Waterloo™ system and the shallowest section of the casing and well string is sealed with a suitable sealant such as a bentonite product, cement product or a mechanical device such as a packer to prevent the entry of surface water and other foreign materials into the well. In addition, if groundwater is leaking into the annular space between the shallowest casing of the Waterloo™ system and the shallowest section of the casing and well string, a suitable sealant must be installed in the same manner as Step 3 of this example.

Decicated Multi-Level System - Best Management Practices

Reminder: There are many factors that affect the casing selection including depth of the well and water quality.

Reminder: Some materials such as ABS, polytetrafluoroethylene (PTFE) (e.g. Teflon), fiberglass and glass are not typically used for casing for test holes. It is important to refer to manufacturer’s specifications and other information to determine if the material is appropriate for use in test holes at a specific site.

Reminder: A downhole video camera should be used to visually observe the casing, casing joints, the seal between the screen and casing as long as a contaminant will not interfere with the device.

Reminder: All individuals working on the installation of the system must have the proper well contractor and well technician licences unless exempt under the Ontario Water Resources Act or the Wells Regulation. For further information on licensing and exemptions see: Chapter 3: Exemptions: Wells, Activities & Experienced Professionals and Chapter 4: Well Contractors & Well Technicians – Licences, Responsibilities & Exemptions.

Diagrams Of Multi-Level Monitoring Systems

Figures 8-22 and 8-23 show cross-sectional illustrations and relevant graphics for various types of test holes that have been discussed in this chapter. The illustrations include the minimum size of the hole, the length of well casing, the type of well screen and the annular space filling materials around the well screen.

Reminder: All figures and diagrams are for illustrative purposes only and do not necessarily represent full compliance with the requirements found in the Wells Regulation (e.g. well covering during construction).

For details on the requirements involved in constructing the hole, sealing the annular space and completing the well, refer to the following chapters in this manual:

• Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well
• Chapter 7: Annular Space & Sealing
• Chapter 9: Completing the Test Hole or Dewatering Well Structure

Reminder: Each of the wells shown in Figure 8-22 and Figure 8-23 may encounter conditions that require specialized design or construction. For example:

• Flowing artesian conditions
• Presence of gas
• Sucking and blowing (breathing) conditions where the well and aquifer formation are significantly affected by changes in atmospheric pressure

Reminder: The illustrations and graphics may not depict every circumstance.

Figure 8-22: Examples Of Multi-Level Monitoring Systems (Must Be Scheduled To Be Abandoned Within 180 Days After Completing Structural Stage)

Figure 8-22 shows a cross-sectional diagram of two examples of multi-level monitoring systems that must be abandoned not later than 180 days after completing the well’s structural stage.

The diagram shows a nested multi-level test hole with seals on the left side of the diagram and a dedicated multi-level monitoring test hole on the right side of the diagram.

On the left side of the diagram, a nested multi-level test hole with seals is constructed through an upper silt, upper sand, clay, lower sand, lower silt and gravel deposits. The nest consists of three casings with well screens attached to the bottom of the casings. The joints on all of the casings have been sealed.

On the left side of the hole in the diagram, a casing and well screen extend from above the ground surface to the gravel deposit. As a best management practice, filter pack material is placed around the well screen and the lower portions of the casing. As a best management practice, a layer of sealant is placed above the filter pack to the top of the lower silt deposit.

In the centre of the hole in the diagram, a casing and well screen extend from above the ground surface to the lower sand deposit. As a best management practice, filter pack material is placed around the well screen and the lower portions of the centre casing in the lower sand deposit. The filter pack material also fills around the casing on the left side of the diagram. As a best management practice, a layer of sealant is placed around the casings from above the filter pack to the top of the clay deposit.

On the right side of the hole in the diagram, a casing and well screen extend from above the ground surface to the upper sand deposit. As a best management practice, filter pack material is placed around the well screen and the lower portions of the right casing in the upper sand deposit. The filter pack material also fills around the casings on the left side and centre area of the diagram. A suitable sealant is placed around the casings from the ground surface to the top of the upper sand deposit.

On the right side of the diagram, a dedicated multi-level monitoring test hole is constructed through overburden and into the bedrock. The upper portion of the dedicated system consists of a casing that extends vertically above the ground surface, through the overburden and into the bedrock. A suitable sealant is placed in the annular space adjacent to the casing from the ground surface to the bottom of the casing. An isolated sampling port is attached to the bottom of the casing in the bedrock. As a best management practice, an inflatable packer is attached to the bottom of the sampling port. Five additional sampling ports and four packers have been attached below the upper packer in the same sequence as with the upper sampling port and packer. The diagram also shows the dedicated multi-level system intersecting water producing bedrock fractures.

This diagram shows two examples of the many types of multi-level monitoring systems. For test holes and dewatering wells that are not scheduled to be abandoned within 180 days, the Wells Regulation requires that a continuous column of suitable sealant be placed above the filter pack material (see subparagraph ii, paragraph 1 of subsection 14.4 (2) of the Well Regulation). The two systems depicted above require separate zones of sealant materials to separate the different well screens and filter packs or ports. As such, these systems cannot meet the regulatory requirements for a test hole that will be in operation for more than 180 days and must be scheduled to be abandoned within that time. See Figure 8-24 for a multi-level monitoring system installed with a permanent outer casing.

Reminder: This figure is not to scale, it is for illustrative purposes for this chapter only and does not necessarily represent full compliance with the requirements found in the Wells Regulation.

Figure 8-23: Examples of Multi-Level Monitoring Systems (Not Scheduled To Be Abandoned Within 180 Days After Completing Structural Stage)

Figure 8-23 shows a cross-sectional diagram of two examples of multi-level monitoring systems that are not scheduled to be abandoned within 180 days after completing the well’s structural stage.

The diagram shows a nested multi-level test hole with seals on the left side of the diagram and a dedicated multi-level monitoring test hole on the right side of the diagram.

On the left side of the diagram, a nested multi-level test hole with seals is constructed through an upper silt, upper sand, clay, lower sand, lower silt and gravel deposits. The nest consists of three casings with well screens attached to the bottom of the casings. The joints on all of the casings have been sealed.

On the left side of the nested multi-level test hole diagram, a casing and well screen extend from above the ground surface to the gravel deposit. As a best management practice, filter pack material is placed around the well screen and the lower portions of the casing. As a best management practice, a layer of sealant is placed above the filter pack to the top of the lower silt deposit.

In the centre of the nested multi-level test hole diagram, a casing and well screen extend from above the ground surface to the lower sand deposit. As a best management practice, filter pack material is placed around the well screen and the lower portions of the centre casing in the lower sand deposit. The filter pack material also fills around the casing on the left side of the diagram. As a best management practice, a layer of sealant is placed around the casings from above the filter pack to the top of the clay deposit.

On the right side of the nested multi-level test hole diagram, a casing and well screen extend from above the ground surface to the upper sand deposit. As a best management practice, filter pack material is placed around the well screen and the lower portions of the right casing in the upper sand deposit. The filter pack material also fills around the casings on the left side and centre area of the diagram. A suitable sealant is placed around the casings from the ground surface to the top of the upper sand deposit.

A permanent outer casing is placed outside of the three casings from above the ground surface to the top of the upper sand in the nested multi-level test hole diagram. The annular space from the top of the permanent outer casing to the bottom of the permanent outer casing is filled with a suitable sealant.

On the right side of the diagram, a dedicated multi-level monitoring test hole is constructed through overburden and into the bedrock. The upper portion of the dedicated system consists of a casing that extends vertically from above the ground surface, through the overburden and into the bedrock. A suitable sealant is placed in the annular space adjacent to the casing from the ground surface to the bottom of the casing. An isolated sampling port is attached to the bottom of the casing in the bedrock. As a best management practice, an inflatable packer is attached to the bottom of the sampling port. Five additional sampling ports and four packers have been attached below the upper packer in the same sequence as with the upper sampling port and packer. The diagram also shows the dedicated multi-level system intersecting water producing bedrock fractures.

A permanent outer casing is placed outside of the dedicated system’s inner casing from above the ground surface, through the overburden and into the bedrock. The annular space from the top of the permanent outer casing to the bottom of the permanent outer casing is filled with a suitable sealant.

• This diagram shows two examples of the many types of multi-level monitoring systems. To operate a new multi-level monitoring test hole longer than 180 days a person must install a permanent outer casing around the dedicated system or inner casings.
• As a best practice, the permanent outer casing should be extend to at least 6 m (19.7') from the ground surface or as close to the top of the upper screen or port internal as possible.
• An annular space must be created around the permanent outer casing and then filled with a suitable sealant as described in this section and in Chapter 7: Annular Space & Sealing.
• A suitable sealant, such as a bentonite product, a cement product or an inflatable packer should be properly placed between ports or well screens, except in the case of a dedicated system that employs a liner.
• If groundwater is entering between the inner casing(s) and the permanent outer casing, the entire annular space from the inner casing(s) to the permanent out casing must be sealed (with necessary modifications). The proper sealing process is described in Chapter 7: Annular Space & Sealing and must be followed unless the new test hole was constructed by the use of a driven point. In all cases, the annular space between the inner casing(s) and permanent outer casing must be sealed with suitable sealant to prevent the entry of surface water and other foreign materials.

Reminder: This figure is not to scale, it is for illustrative purposes for this chapter only and does not necessarily represent full compliance with the requirements found in the Wells Regulation.

Disclaimers

Reminder: The use of brand names in this manual is for identification purposes only and does not constitute an endorsement by the Ministry of the Environment.

Reminder: The information and illustrations of these systems do not constitute a recommendation of any or all of the systems. The table and illustrations are presented solely to provide information on the systems that are currently available and how these systems could be installed to meet the requirements of the Wells Regulation.