7. Annular Space & Sealing

Chapter Description

This chapter covers the construction process involved in sealing the new test hole or dewatering well casing into the hole to reduce the risk of surface water, mineralized groundwater, contaminants or other materials moving along the annular space and impairing groundwater.

The annular space sealing requirements in this chapter do not apply to test holes or dewatering wells that are constructed without casing. The requirements listed in this chapter do not apply to shallow works or other exempted wells discussed in Chapter 3: Exemptions: Wells, Activities & Experienced Professionals.

Regulatory Requirements - Annular Space & Sealing

Relevant Sections - The Wells Regulation

The Wells Regulation - Casing – Subsections 13(11.1), 13(13), 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

Reminder - Definitions for sealant, bentonite, watertight, tremie pipe and other relevant terms are provided in Chapter 2: Definitions & Clarifications.

Reminder - Detailed information, other construction requirements and annular space filling requirements for new multi-level monitoring test hole installations are covered in Chapter 8: Multi-level Monitoring Test Holes.

Reminder - For information on exemptions and special cases see the “Annular Space Sealing Exemptions and Special Cases,” section of this chapter.

Reminder - The regulatory exemptions described in the "Plainly Stated" section regarding test holes and dewatering wells allow for well technicians, engineers and geoscientists to use their professional expertise to design and install test holes and dewatering wells on a case by case basis.

Implications for Annular Space Filling

Records of Site Condition Regulation - Monitoring wells as defined under O. Reg. 153/04 that are scheduled to be abandoned not later than 180 days after completion of the structural stage are not exempt from the annular space sealing requirements in Table 7-1A and Table 7-1B. Further details on O. Reg. 153/04 requirements are found in “Test Holes and Dewatering Wells Scheduled to be Abandoned Not Later than 180 Days” in the “Annular Space Sealing Exemptions and Special Cases” section of this chapter.

Reminder - When mixing, handling or placing any grout material (wet or dry) it is important to always follow manufacturer’s specifications and recommended procedures. It is also important to consult the Material Safety Data Sheet (MSDS) for additional information on safe handling and usage.

Definition - A tremie pipe is a pipe or tube with an inner diameter that is at least three times the diameter of the largest particle of material to pass through it and that is used to conduct material to the bottom of a hole, including a hole containing standing water. For clarification with respect to a tremie pipe, a pipe or tube means a long, hollow (empty space) cylinder.

Relevant Sections - Additional Regulations or Legislation

Ontario Water Resources Act, R.S.O. 1990, chapter O 40. subsection 30(1)

Ontario Regulation 153/04 (Records of Site Condition) as amended made under Environmental Protection Act, R.S.O. 1990, chapter E. 17

Relevant Standards

ASTM D 5092-04 – Standard Practice for Design and Installation of Ground Water Monitoring Wells. DOI: 10.1520/D5092-04E0^{footnote 1[1]}.

ASTM D 6724-04 – Standard Guide for Selection and Installation of Direct-Push Ground Water Monitoring Wells. DOI: 10.1520/D6724-04^{footnote 1[1]}.

ASTM D 6725-04 – Standard Practice for Direct-Push Installation of Pre-pack Screen Monitoring Wells in Unconsolidated Aquifers. DOI: 10.1520/D6725-04^{footnote 1[1]}

Key Concepts

What to Consider When Sealing the Annular Space

The Annular Space

During construction of a well, an annular space is created when the size of the hole in the ground is larger than the casing and well screen diameter.

Purpose of the Seal

If a casing is placed into the ground without an annular space, the formation material along the casing becomes loosened and disturbed. The disturbed section along the casing can become a pathway for the migration of contaminants, gas and groundwater.

A properly created and filled annular space around a casing will:

• isolate a discrete zone,
• prevent migration of surface water and other foreign materials into the well and aquifers,
• prevent migration of groundwater or contaminants between water bearing formations and subsurface formations,
• prevent migration of groundwater or contaminants between water bearing formations and the ground surface,
• prevent aquifer depressurization by stopping the upward migration of water along the casing, or
• prevent gas migration.

Examples of Improperly Sealed Annular Space

Figure 7-1: Visible Open Annular Space Adjacent to a Test Hole

Figure 7-1 shows a white plastic well casing of a test hole extending out of the ground surface. An open space adjacent to the casing (i.e., annular space) is visible at the ground surface and extends to the bottom of the casing (not visible in photograph). The ground surface also slopes towards the well. Any surface water or other foreign materials can flow along the ground surface towards the well and discharge into the open space beside the well casing. The open space acts as a direct pathway for foreign materials to enter and impair groundwater resources and creates quality assurance problems with samples.

Figure 7-2: Visible Open Annular Space Below Pitless Adapter and Horizontal Waterline to the Bottom of the Casing

Figure 7-2 shows a visible open space (i.e., annular space) below the pitless adapter and horizontal waterline. The open space extends to the bottom of the casing (not shown in photograph). Above the waterline, the person constructing the well installed a bluish-grey coloured bentonite grout in the annular space from above the pitless adapter to the ground surface (within blue oval dotted line). When the area beside the well was excavated, it became evident that the annular space was improperly filled (or left open) below the pitless adapter until the exterior of the well was excavated. The open space acts as a direct pathway for foreign materials to enter and impair groundwater resources.

Annular Space Sealing Exemptions and Special Cases

The Ontario Water Resources Act prohibits any person from impairing the quality of any waters in Ontario. This section describes regulatory exemptions to the annular space sealing requirements listed in Table 7-1A and Table 7-1B for test holes and dewatering wells.

These annular space sealing exemptions do not release anyone from complying with the Ontario Water Resources Act general provision regarding the impairment of waters.

The exemptions discussed in this section are: uncased wells, shallow works, wells shallower than 2.5 m with well screens, test holes and dewatering wells scheduled to be abandoned not later than 180 days and new test hole or dewatering well completed with a permanent outer casing - double walled casing.

Uncased Wells

The Wells Regulation - Where a test hole or dewatering well needs to be constructed without casing (and thus no annular space) for testing or dewatering purposes, wells must be scheduled to be abandoned not later than 30 days after completion of the well’s structural stage, and the person constructing the well must cover the upper open end of the well securely in a manner sufficient to prevent the entry of surface water and other foreign materials whenever the well is left unattended during the 30 day (or less) period.

An example for an uncased well could include an open test pit that is considered a test hole and is not an exempted well (e.g., trench, ditch). In this case, it may not be appropriate to insert well casing and seal an annular space to allow for the person to:

• make appropriate field observations of formations in the case of a test hole, or
• lower the water table around an excavation in the case of a dewatering well.

These excavations can be properly filled after observations or dewatering has been completed.

Reminder - Further information, including best management practices, and examples of uncased test holes is found in the “Exemption from the Requirement to Case the Test Hole or Dewatering Well” section of Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well.

Shallow Works

If a test hole or dewatering well is no more than 3.0 m (9.8 ft) deep, the shallow works exemption and requirements can apply to the construction, maintenance and abandonment of the well as long as the well:

• is not constructed in a contaminated area,
• does not penetrate through an entire formation that is not an aquifer, and
• is not constructed in an area known for flowing wells.

Reminder - For further information on shallow works please refer to Chapter 3: Exemptions: Wells, Activities & Experienced Professionals.

Definition - A shallow works is a test hole or dewatering well that is made to a depth of not more than 3.0 m (10 ft) below the ground surface and that meets the other conditions described in Chapter 3: Exemptions: Wells, Activities & Experienced Professionals.

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 requirements stated above.

Implications for Annular Space Size and Filling for New Test Holes

The above requirement means that, if a new test hole qualifies as a shallow works 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 under shallow works do not apply, and
• the annular space size and filling requirements for a test hole stated in Table 7-1A and Table 7-1B and the “Plainly Stated” section do apply.

Reminder - The above requirement in O. Reg. 153/04 also affects obligations relating to casing material, well screen material and shallow works for monitoring wells. See Chapter 3: Exemptions: Wells, Activities & Experienced Professionals and Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well for further information.

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

Reminder - For clarification on the term “monitoring well” and “qualified person” in the Records of Site Condition regulation see Chapter 2: Definitions & Clarifications, Table 2-2.

Wells Shallower Than 2.5 Metres with Well Screens

The person constructing the well must ensure that the top of the gravel or sand material placed in the annular space to at least the top of the well screen is no closer than 2.5 metres to the ground surface for many new wells. Where a new test hole that is less than 2.5 m (8.2 ft) deep and a well screen is needed, the well must be:

• constructed by digging or by the use of a driven or jetted point,
• scheduled to be abandoned not later than 180 days after completion of the structural stage of the test hole or dewatering well, or
• constructed with a casing surrounded by a larger permanent outer casing (sometimes referred to as a double walled casing).

The depth requirement for the top of the sand and gravel layer does not apply to shallow works.

Reminder - For further information on the minimum depth of a test hole and dewatering well with and without a well screen, see the “Minimum Depth of Annular Space below Ground Surface” row in Table 7-1A and Table 7-1B and the “Plainly Stated” section of Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well.

Test Holes and Dewatering Wells Scheduled to be Abandoned Not Later Than 180 Days

The Wells Regulation - A person constructing a test hole or dewatering well that is scheduled to be abandoned not later than 180 days after the completion of its structural stage must seal any annular space, other than annular space surrounding the well screen, to prevent any movement of water, natural gas, contaminants or other material between subsurface formations or between subsurface formations and the ground surface.

The methods to create and seal an annular space specified in the Wells Regulation and Table 7-1 A and Table 7-1 B to achieve a proper seal are not mandatory, but would be a good practice. This allows well technicians, engineers and geoscientists to use their professional expertise to design and install test holes and dewatering wells on a case by case basis, thereby enabling the testing, sampling or dewatering of various groundwater intervals.

This annular space requirement does not apply where a person constructing a test hole or dewatering well is not required to create an annular space and where no annular space is created.

When a test hole or dewatering well is constructed with an inner casing and permanent outer casing (double walled casing), different requirements apply. The specific requirements for this type of construction are found in the “New Test Hole or Dewatering Well Completed with a Permanent Outer Casing – Double Walled Casing” section below.

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 requirements stated above.

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 a new test hole is constructed, 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 Table 7-1A and Table 7-1B and the “Plainly Stated” section do apply.

Reminder - The above requirement in O. Reg. 153/04 also affects obligations relating to casing material, well screen material and shallow works for monitoring wells. See Chapter 3: Exemptions: Wells, Activities & Experienced Professionals and Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well for further information.

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

Reminder - For clarification on the term “monitoring well” and “qualified person” in the Records of Site Condition regulation see Chapter 2: Definitions & Clarifications, Table 2-2.

Wells Shallower Than 2.5 Metres with Well Screens

The person constructing the well must ensure that the top of the gravel or sand material placed in the annular space to at least the top of the well screen is no closer than 2.5 metres to the ground surface for many new wells. Where a new test hole that is less than 2.5 m (8.2 ft) deep and a well screen is needed, the well must be:

• constructed by digging or by the use of a driven or jetted point,
• scheduled to be abandoned not later than 180 days after completion of the structural stage of the test hole or dewatering well, or
• constructed with a casing surrounded by a larger permanent outer casing (sometimes referred to as a double walled casing).

The depth requirement for the top of the sand and gravel layer does not apply to shallow works.

Reminder - For further information on the minimum depth of a test hole and dewatering well with and without a well screen, see the “Minimum Depth of Annular Space below Ground Surface” row in Table 7-1A and Table 7-1B and the “Plainly Stated” section of Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well.

Test Holes and Dewatering Wells Scheduled to be Abandoned Not Later Than 180 Days

The Wells Regulation - A person constructing a test hole or dewatering well that is scheduled to be abandoned not later than 180 days after the completion of its structural stage must seal any annular space, other than annular space surrounding the well screen, to prevent any movement of water, natural gas, contaminants or other material between subsurface formations or between subsurface formations and the ground surface.

The methods to create and seal an annular space specified in the Wells Regulation and Table 7-1 A and Table 7-1 B to achieve a proper seal are not mandatory, but would be a good practice. This allows well technicians, engineers and geoscientists to use their professional expertise to design and install test holes and dewatering wells on a case by case basis, thereby enabling the testing, sampling or dewatering of various groundwater intervals.

This annular space requirement does not apply where a person constructing a test hole or dewatering well is not required to create an annular space and where no annular space is created.

When a test hole or dewatering well is constructed with an inner casing and permanent outer casing (double walled casing), different requirements apply. The specific requirements for this type of construction are found in the “New Test Hole or Dewatering Well Completed with a Permanent Outer Casing – Double Walled Casing” section below.

Records of Site Condition Regulation - The person constructing a test hole or dewatering well should have a signed written contract with the well purchaser and, if not the same, the land owner, that indicates the well owner(s) has agreed to abandon the well in accordance with the Wells Regulation not later than 180 days after the completion of the structural stage of the test hole or dewatering well. The written contract will help protect the interests of the person constructing the well if the completed test hole or dewatering well is not abandoned within 180 days and the contract will advise the well owner(s) of this scheduling requirement.

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 requirements stated above.

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 a new test hole is constructed, 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 Table 7-1A and Table 7-1B and the “Plainly Stated” section do apply.

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

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

New Test Holes or Dewatering Well Completed with a Permanent Outer Casing - Double Walled Casing

In some cases, multiple casings of different diameters are installed in new wells to reach a groundwater zone. This type of installation is common in multi-level monitoring test holes and flowing wells. The annular space around and between the inner casing(s) and the permanent outer casing for a new well that will be in operation for more than 180 days must be sealed as follows:

• All construction and sealing requirements for the corresponding well construction method in Table 7-1A and Table 7-1B apply with necessary modifications to the test hole or dewatering well’s annular space on the outside of the outer casing. As a necessary modification, 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 ft), whichever is less.
• If any groundwater is entering the annular space between the inner casing(s) and the permanent outer casing, the entire annular space between the casings must be sealed, with necessary modifications, in accordance to the minimum requirements of Table 7-1A and Table 7-1B. This requirement does not apply to a well pit or to a test hole or dewatering well constructed by the use of a driven point.
• In all cases, the annular space between casings of different diameters must be sealed with suitable sealant to prevent the entry of surface water and other foreign materials into the well.

Although the person constructing a well is not specifically required to seal the casing 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.

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

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

• natural gas,
• contaminants, or
• other material

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

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

Reminder - See 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 for further information on well abandonment.

Reminder - See Chapter 8: Multi-level Monitoring Test Holes for best management practices on sealing the annular space around the inner casing below the permanent outer casing.

Reminder - Detailed information, other construction requirements and annular space sealing requirements and best management practices for new multi-level monitoring test hole installations are covered in Chapter 8: Multi-Level Monitoring Test Holes.

Requirements for Sealing Various Types of Cased Test Holes or Dewatering Wells

Figures 7-3 to 7-9 show cross sectional illustrations and relevant graphics for the construction of various new test holes or dewatering wells. The figures show the Wells Regulation requirements for minimum hole size, annular space filling products around well screens and suitable sealant in the annular space around the casings.

Reminder - The requirements shown in Figures 7-3 to 7-9 do not apply to test holes and dewatering wells that are scheduled for abandonment (plugged and sealed) not later than 180 days after completion of the well’s structural stage.

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

Reminder - During and after construction the person constructing the test hole or dewatering well must ensure surface drainage is such that water will not collect or pond in the vicinity of the well.

Reminder - The person constructing the test hole or dewatering well must also cover the upper open end of the well securely to prevent entry of surface water and other foreign materials into the well during well construction.

Reminder - For details on the hole, casing and other construction requirements not shown in Figure 7-3 to Figure 7-9 refer to the following chapters in this manual:

• Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well, and
• Chapter 9: Completing the Test Hole or Dewatering Well Structure.

Reminder - Each of the test holes or dewatering wells shown in Figures 7-3 to 7-9 may encounter conditions that may require specialized design or construction. For example:

• flowing artesian conditions,
• presence of gas, or
• breathing (sucking and blowing) conditions where the well and aquifer formation are significantly affected by the changes in atmospheric pressure.

Therefore the illustrations and graphics may not depict every circumstance.

Figure 7-3: Examples Of Wells Constructed By Drilling Or Direct Push Without Using A Driven Point (Not Scheduled To Be Abandoned Within 180 Days After Completing Structural Stage)

Figure 7-3 shows a cross-sectional diagram of three drilled wells (A, B and C) placed into the subsurface. The subsurface consists of a clay deposit underlain by a sand deposit. The sand deposit is underlain by a clay deposit. The clay deposit is underlain by a gravel deposit. The gravel deposit is underlain by a limestone bedrock with water bearing fractures.

The well on the left of the diagram is example “A”. The well is completed with a casing that extends vertically from above the ground surface through the clay and into the sand overburden. A well screen is attached to the bottom of the casing. A plug is attached to the bottom of the well screen. A filter pack has been placed around the well screen to the side of the hole. A secondary filter pack has been placed on top of the filer pack. The top of the secondary filter pack extends just above the sand deposit. Suitable sealant has been placed in the annular space above the secondary filter pack. A vermin-proof well cap has been affixed to the top of the casing. The ground surface has been mounded around the casing to prevent surface water from ponding beside the well.

The well in the middle of the diagram is example “B”. The well is completed with a casing that extends vertically from above the ground surface to the gravel deposit. A well screen is attached to the bottom of the casing. A plug is attached to the bottom of the well screen. A filter pack has been placed around the well screen to the side of the hole. A secondary filter pack has been placed on top of the fitler pack. The top of the secondary filter pack extends just above the gravel deposit. Suitable sealant has been placed in the annular space above the secondary filter pack. A vermin-proof well cap has been affixed to the top of the casing. The ground surface has been mounded around the casing to prevent surface water from ponding beside the well.

The well on the right side of the diagram is example “C”. The well is completed with a casing that extends vertically from above the ground surface through overburden to the limestone bedrock. As a best management practice (BMP), centralizers have been placed from the outside of the casing to the side of the hole to centre the casing in the hole. A well screen is attached to the bottom of the casing and is located at the water bearing zone in the bedrock. A plug is attached to the bottom of the well screen. A filter pack has been placed around the well screen to the side of the hole. A secondary filter pack has been placed on top of the filter pack. The top of the secondary filter pack is located in the bedrock. Suitable sealant has been placed in the annular space above the secondary filter pack. A vermin-proof well cap has been affixed to the top of the casing. The ground surface has been mounded around the casing to prevent surface water from ponding beside the well.

Note 1 states BMP = Best management practice

Note 2 states the top of the filter pack around the well screen must be no closer than 2.5 metres (8.2 feet) below the ground surface.

Note 3 states the hole diameter must be at least 7.6 centimetres (3 inches) greater than the final outer casing (see A or B) for at least 6 metres (19.7 feet) from the ground surface or the full depth of the well (whichever is less).

Note 4 states the hole must be large enough to allow for the installation of a tremie pipe in the annular space. The tremie pipe must be immersed in the rising accumulation of sealant in the annular space.

Reminder - See the “Filter Packs around Well Screens for Drilled Test Holes or Dewatering Wells” section in Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well for filter pack material information and best management practices about filter packs.

Reminder - If centralizers are used with rotary equipment or a breakaway guide is used with cable tool equipment, the hole diameter must be at least 5.1 cm (2 inches) greater than the final outer casing (see C) for at least 6 m (19.7 ft) from the ground surface or the full depth of the well (whichever is less). For additional information, see the “Centering the Casing” section in Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well.

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

Figure 7-4: Example Of Multi-Cased Bedrock Well Constructed By Drilling Or Direct Push Without Using A Driven Point (Not Scheduled To Be Abandoned Within 180 Days After Completing Structural Stage)

Figure 7-4 shows a cross-sectional diagram of multi-cased bedrock well placed into the subsurface. The subsurface consists of a silt deposit underlain by a clay deposit. The clay deposit is underlain by sandstone bedrock. The sandstone is underlain by a limestone bedrock with water bearing fractures.

The well is completed with an inner casing that extends vertically from above the ground surface through overburden to the limestone bedrock. The joints between the sections of inner casing have been made watertight. An outer casing has been placed in the well that extends vertically from above the ground surface through overburden to the sandstone bedrock. A drive shoe has been placed on the outer casing. As a best management practice (BMP), centralizers have been placed from the outside of the outer casing to the side of the hole to centre the outer casing in the hole. As a best management practice (BMP), centralizers have been placed from the outside of the inner casing to the side of the outer casing to centre the inner casing in the hole. A well screen is attached to the bottom of the inner casing and is located at the water bearing zone in the bedrock. A plug is attached to the bottom of the well screen. A filter pack has been placed around the well screen to the side of the hole. A secondary filter pack has been placed on top of the filter pack. The top of the secondary filter pack is located in the bedrock. Suitable sealant has been placed in the annular space above the secondary filter pack around the inner casing and around the outer casing. A vermin-proof well cap has been affixed to the top of the casing. The ground surface has been mounded around the casing to prevent surface water from ponding beside the well.

Note 1 states BMP = Best management practice

Note 2 states See Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well for information on the hole diameter.

Note 3 states the annular space around the permanent outer casing must be filled with suitable sealant as described in Chapter 7: Annular Space & Sealing. The annular space between the casings must be sealed as described in Chapter 7. As a best management practice, the annular space below the permanent outer casing should be filled as described in the best management practice in this chapter, Chapter 7 and, if applicable, Chapter 8: Multi-level Monitoring Test Holes.

Reminder - See the “Filter Packs around Well Screens for Drilled Test Holes or Dewatering Wells,” section in Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well for filter pack material information and best management practices about filter packs.

Reminder - The sealing requirements found in Table 7-1A and Table 7-1B apply with necessary modifications to the well’s annular space between the casings. This requirement applies if any groundwater is leaking into the annular space between the casings. In all cases, the annular space between casings of different diameters must be sealed with suitable sealant to prevent the entry of surface water and other foreign materials into the well.

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

Figure 7-5: Examples Of Directional Well Constructed By Drilling Or Direct Push Without Using A Driven Point (Not Scheduled To Be Abandoned Within 180 Days After Completing Structural Stage)

Figure 7-5 shows a cross-sectional diagram of two drilled wells (A and b) placed into the subsurface.

The well on the left of the diagram is example “A”. The well is completed with a casing that extends at a 45 degree angle downward from left to right into the subsurface. The joints between the sections of inner casing have been made watertight. A well screen is attached to the bottom of the casing. The casing and well screen are adjacent to the left side of the hole. A filter pack has been placed around the well screen to the side of the hole. A secondary filter pack has been placed on top of the filer pack. The top of the secondary filter pack extends just above the sand deposit. Suitable sealant has been placed in the annular space above the secondary filter pack and where the casing and well screen are not against the side of the hole. An air tight locking cap (e.g., J-plug) has been affixed to the top of the casing and a well tag has been affixed to the casing. The ground surface has been mounded around the casing to prevent surface water from ponding beside the well.

The well in the right of the diagram is example “B”. The well is completed with a casing that extends at a 45 degree angle downward from left to right into the subsurface. The sections of the casing have been attached to one another with watertight joints. A well screen is attached to the bottom of the casing. Centralizers have been placed on the casing to centre the casing and well screen in the hole. A filter pack has been placed around the well screen to the side of the hole. A secondary filter pack has been placed on top of the filer pack. The top of the secondary filter pack extends just above the sand deposit. Suitable sealant has been placed in the annular space above the secondary filter pack. An air tight locking cap (e.g., J-plug) has been affixed to the top of the casing and a well tag has been affixed to the casing. The ground surface has been mounded around the casing to prevent surface water from ponding beside the well.

Note 1 states BMP = Best management practice

Note 2 states it is important to use centralizers to centre the casing into the hole (see B). A centred casing allows for the proper distribution of filter pack around the well screen and sealant around the casing. The absence of centralizers forces the casing and well screen to move to one side of the hole (see A). This prevents the installation of filter pack around the well screen and the even placement of sealant around the casing. This can allow formation materials to plug the well screen and increases the risk of contaminant and foreign material migration along the side of the casing.

Note 3 states the top of the filter pack around the well screen must be no closer than 2.5 metres (8.2 feet) below the ground surface.

Note 4 states the hole diameter must be at least 7.6 centimetres (3 inches) greater than the final outer casing (see A or B) for at least 6 metres (19.7 feet) from the ground surface or the full depth of the well (whichever is less).

Note 5 states the hole must be large enough to allow for the installation of a tremie pipe in the annular space.

Reminder - See the “Filter Packs around Well Screens for Drilled Test Holes or Dewatering Wells,” section in Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well for filter pack material information and best management practices about filter packs.

Reminder - If centralizers are used with rotary equipment or a breakaway guide is used with cable tool equipment, the hole diameter must be at least 5.1 cm (2 inches) greater than the final outer casing for at least 6 m (19.7 ft) from the ground surface or the full depth of the well (whichever is less). For additional information, see the “Centering the Casing” section in Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well.

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

Figure 7-6: Drilled Well In Overburden - Natural Development, Casing Pulled Back Exposing Screen Method (Not Scheduled To Be Abandoned Within 180 Days After Completing Structural Stage)

Figure 7-6 shows a cross-sectional diagram of a drilled well in the overburden using natural development, casing pulled back method.

The diagram shows a hole extending vertically into an overburden subsurface. A casing extends from above the ground surface into the hole. The annular space between the outside of the casing and the side of the hole is filled with suitable sealant. A well screen is shown within the bottom of the casing and extends out of the bottom of the casing into the bottom of the hole in the subsurface. The well screen is located in a water bearing sand and gravel. The well screen is made up of a K packer, riser pipe, screen, coupling and plug. The K-packer is located at the top of the well screen and seals the inner casing and to the outside of the well screen. The riser pipe extends from the K-packer to below the bottom of the casing in the subsurface. The screen is located below the riser pipe in the subsurface. The coupling and plug are located below the screen.

Note 1 states the hole diameter must be at least 7.6 cm (3 inches) greater than the final outer casing for at least 6 metres (19.7 feet) from the ground surface or the full depth of the well (whichever is less).

Note 2 states if centralizers are used with rotary equipment or a breakaway guide is used with cable tool equipment the hole diameter must be at least 5.1 cm (2 inches) greater than the final outer casing for at least 6 m (19.7 ft) from the ground surface or the full depth of the well (whichever is less).

Reminder - For additional information, see the “Centering the Casing” section in Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well.

Reminder - See Figure 6-17 of Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well that shows how the well’s casing was pulled back and the annular space was created.

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

Figure 7-7: Example Of Dug Test Hole (Not Scheduled To Be Abandoned Within 180 Days After Completing Structural Stage)

Figure 7-7 shows a cross-sectional diagram of a dug well placed a sand deposit.

The dug well consists of a large open hole. A layer of filter pack has been placed at the bottom of the hole. A casing extends vertically from above the ground surface to the filter pack. The joints between the sections of casing have been made watertight. A well screen is attached to the bottom of the casing. A plug is attached to the bottom of the well screen. A filter pack has been placed around the well screen to the side of the hole. As a best management practice, a secondary filter pack has been placed on top of the filer pack. The top of the secondary filter pack extends above the top of the well screen. Suitable sealant has been placed in the annular space above the secondary filter pack. A solid watertight well cover (e.g., J-plug) has been affixed to the top of the casing. The ground surface has been mounded around the casing to prevent surface water from ponding beside the well.

Note 1 states best management practice.

Note 2 states the top of the sand, gravel, or native materials around well screen and casing must not be closer than 2.5 m (8.2 ft) below the ground surface.

Note 3 states the suitable sealant must be able to provide the sufficient structural strength to support the weight of persons and vehicles that may move over the area.

Reminder - The filling material around and above the well screen must be clean washed gravel or sand. Native materials can also be used in the annular space instead of sand or gravel if the well is not constructed in a contaminated area and the materials are excavated separately, stored separately, kept free from contamination and backfilled in the same relative position they originally occupied. See the “Filter Packs around Well Screens for Drilled Test Hole or Dewatering Wells” section and the best management practices about filter pack in Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well.

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

Figure 7-8: Example Of Dewatering Well Constructed By Jetting With The Use Of A Driven Point (Not Scheduled To Be Abandoned Within 180 Days After Completing Structural Stage)

Figure 7-8 shows a cross-sectional diagram of a dewatering well constructed by jetting.

The diagram shows the casing extending from above the ground surface into the subsurface. The casing is high enough to permit the attachment of a well tag. The joints between the sections of casing have been made watertight. A well screen is attached to the bottom of the casing. A driven point has been attached to the bottom of the well screen. A horizontal dotted line above the well screen represents the water table. Suitable sealant has been placed in the irregular annular space above the well screen. A vermin proof well cap has been affixed to the top of the casing. The top of the casing is high enough to permit the attachment of a well tag. The ground surface has been mounded around the casing to prevent surface water from ponding beside the well.

Note 1 states in this example, the hole is constructed by a jetting tool. After the hole is completed, a drive point well screen with casing is placed into the hole. The person constructing the well by jetting must ensure that any annular space around the well casing is sealed to prevent any movement of water, natural gas, contaminants, or other materials between subsurface formations (e.g., aquifers) or between a subsurface formation and the ground surface.

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

Figure 7-9: Example Of Dewatering Well Constructed By Direct Push Equipment Using A Driven Point (Not Scheduled To Be Abandoned Within 180 Days After Completing Structural Stage)

Figure 7-9 shows a cross-sectional diagram of a dewatering well constructed by direct push using a driven point.

The diagram shows a casing that extends from above the ground surface into the subsurface. The casing is high enough to permit the attachment of a well tag. The joints between the sections of casing have been made watertight. A prepacked well screen is attached to the bottom of the casing. A plug is located at the bottom of the well screen. Suitable sealant has been placed in the irregular annular space above the well screen. An expendable driven point is located below the well screen and plug. A horizontal dotted line above the well screen represents the water table.

Another horizontal dotted line with the text: A – A’, is shown extending through the prepacked well screen.

To the right of the cross sectional diagram there is another diagram that states “Cross-section A – A’”. This diagram shows a circle that represents a stainless steel mesh or “v-wire”. Within the mesh/v-wire is slotted well screen tube. Filter material (typically silica sand) is located between the well screen tube and the mesh/v-wire. A horizontal dotted line with the text: A – A’, is shown extending through the mesh/v-wire, filter material and well screen tube.

Note 1 states in this example, drive rod with a detachable (expendable) driven point were driven into the ground. A prepacked well screen with casing was installed into the drive rods. An annular space was created between the drive rods and the casing. The annular space was filled with suitable sealant and the drive rods were removed.

Note 2 states since a driven point was used during the construction, materials and methods approved by the director must be used to fill the annular space.

Since a driven point was used in the construction, materials and methods approved by the Director must be used to fill the annular space.

Reminder - For information about Director’s approval for sealing methods see the: “Grout Placement – Annular Space for Driven Points” section of this chapter.

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

Comparison Of Bentonite And Cement Grouts

The most common materials used to seal annular spaces are bentonite and neat cement products. Each has specific, unique and desirable properties. Table 7-2 summarizes the advantages and disadvantages of bentonite based sealants (grouts) versus cement based sealants (grouts).

Notes For Table 7-2:

Reminder - Suitable sealant must be compatible with the quality of the water found in the well. Suitable sealant must be used to seal the annular space of a new test hole or dewatering well that will be in operation for more than 180 days or between casings of a new well.

Reminder - Sealant must be a bentonite mixture of clean water and at least 20% solids by weight or a product that will be equivalent with respect to the ability to form a permanent watertight barrier. For example, a mixture of water with cement, concrete or cement with no more than 5% bentonite solids by weight may be an equivalent sealant in some environments.

Reminder - When evaluating bentonite as a suitable sealant to fill an annular space, the following should be considered:

• the position of the static water level and its seasonal fluctuations,
• the ambient groundwater and mixing water quality, and
• the types and potential concentrations of contaminants (i.e., NAPLs) expected to be encountered.

In some cases three to 8% of bentonite is used as an additive to cement or concrete to improve the workability, slurry weight and density of the cement slurry. This may make it easier to pump or pour the material down a narrow tremie pipe or space. However, bentonite is chemically incompatible with cement and will not swell when mixed with cement. The bentonite additive also reduces the set strength of the seal and lengthens set time^{footnote 4[4]}.

Reminder - Definitions for sealant, bentonite, watertight, tremie pipe and other relevant terms are provided in Chapter 2: Definitions & Clarifications.

Dry Bentonite Products

Bentonite is manufactured in various forms such as powder, granules, pellets and chips. In some cases, bentonite granules, pellets or chips can be used as a suitable sealant to fill the well’s annular space. See the “Grout Placement – Pouring Bentonite Chips and Pellets from Surface” section of this chapter for further information on the placement of dry bentonite into a well’s annular space. Table 7-3 provides information on the forms of manufactured bentonite.

Reminder - Some literature indicates that coated bentonite pellets hydrate more slowly than bentonite chips. Other literature indicates that bentonite chips hydrate more slowly than coated bentonite pellets. A person using a bentonite product should always follow the manufacturer’s specifications for the use and placement of the bentonite product.

Calculating Amount Of Materials Required

Before beginning well construction, the amount of materials (sand, gravel and bentonite and/or cement) required to properly seal the annular space should be calculated. Regardless of the base materials or type of grout, it is the measured amount of water and the consistent use of that ratio of water to the dry product that is the key element to achieving the appropriate grout properties.

The amount of material needed will depend on the volume of annular space that needs to be filled (i.e. width and depth of the annular space).

Some things to remember when calculating the amount of materials required:

• The person constructing the test hole or dewatering well should allow for possible hole increases due to drilling actions, geology and flushing media. Adding 10% to 15% more material to the calculated amount should be considered.
• The volume of the hole that the casing will occupy should be accounted for.

The following formulae can be used to calculate the volume of the annular space.

Method 1

Annular Space Volume = Volume Of Hole − Volume of Casing, Where:

Volume of Hole = 3.14 × (Diameter of Hole ⁄ 2)² × Depth
And
Volume of Casing = 3.14 × (Outer Diameter of Casing ⁄ 2)² × Depth

Or

Volume of Hole = 0.785 × Diameter² × Depth of Hole
And
Volume of Casing = 0.785 × Outer Diameter of Casing² × Depth of Hole

Method 2

Where:

D_h

Diameter of Hole (mm or inches)

d_c

Outer diameter of casing (e.g. pipe)(mm or inches)

{[D_h(mm)² − d_c(mm)²] ⁄ 1273} × Depth (metres) = Annular Space Volume (Litres)

Or

{[D_h(inches)² − d_c(inches)²] ⁄ 29.45} × Depth (feet) = Annular Space Volume (Imperial Gallons)

Reminder - The exact amount of grout (sealant) required cannot always be determined due to irregularities in the size of the hole and losses into fractured rock. Extra material should be available on site to add to the initial estimate if needed.

Reminder - See the “Tools for Annular Space and Sealing” section of this chapter for a grouts (sealants) application matrix to help calculate the amount of grout required to fill the annular space.

The following tables can be used to calculate the volume of sealant (i.e., bentonite, cement, concrete) yielded per bag of product.

Remidner - The volumes are calculated using the instructions and information on the package or provided by the manufacturer. Different percentages of bentonite slurry are used for various applications when drilling or sealing.

Reminder - Table 7-5 is based on one, 43 kilogram (94 pound) bag of cement. The volume of concrete is based on one, 43 kilogram (94 pound) bag of cement mixed with 0.027 cubic metres (1 cubic foot) of sand or gravel. The volumes are calculated by using the instructions and information on the package or directly from the manufacturer.

Reminder - One litre of water weighs one kilogram and Portland cement produces a slurry weight of 1.87 kg/L. The volumes are calculated using the instructions and information on the package or provided by the manufacturer.

Mixing Bentonite Grout (Sealant)

When mixing grout, it is important to follow the manufacturer’s specifications provided on the packaging or with the product.

Inhibited bentonite grouts are a powdered type material that are designed to slow the rate of hydration just long enough to allow the bentonite to be placed into the annular space.

Techniques For Successful Mixing

To ensure that the bentonite sealant will last the life of the test hole or dewatering well, bentonite must be mixed with clean water. “Clean,” in this context, means water that will not interfere with the reaction to make a bentonite slurry as recommended by the manufacturer and will not impair the water in and around the well.

Consequences Of Poorly Mixed Bentonite Grout

Mixing water that is not clean (e.g., highly mineralized water), may inhibit the hydration process of the bentonite grout and its effectiveness as a sealant.

If excess “hardness” is present in the mixing water, the polymers and/or bentonite may clump and adhere to the paddles during the mixing phase. In severe cases it can result in plugging of tremie lines and disruption of the grouting process.

Grout that is mixed or sheared too much will start to hydrate too rapidly. This will result in difficulty pumping the grout, plugging up of the tremie line, and wasting a batch.

Reminder - The person constructing the well should follow the manufacturer’s specifications for pH, hardness, chloride, total dissolved solids and other water quality issues (see Table 7-2 for further information on water chemistry and its potential effect on bentonite).

Mixing Cement or Concrete Grout (Sealant)

Cement grout (sealant) must be made using carefully measured quantities of water and Portland cement (see Table 7-5). In concrete grout, aggregate and other materials (e.g., plasticizers) are added to cement and water. For more information on cement, see How Cement is Made.

A paddle mixer in a mixing drum with either a progressive cavity or gear pump is a common choice for mixing and pumping cement or concrete grout (sealant). Small portable grouting machines that combine both the mixing and the pumping operations are also often used. These machines typically have a positive displacement pump because it can work efficiently against much greater head pressures with low loss of grout volume.

Techniques For Successful Mixing^{footnote 6[6]}

Consequences Of Poorly Mixed Cement Grout

Mixing water that is has a high pH or high level of total dissolved solids may result in increased setting times (i.e. slow hydration) and/or failure to set. See Table 7-2 for further information on water chemistry and its potential affect on cement.

If the grout is not thoroughly mixed and free of lumps then partial setting may occur and the effectiveness of the seal will be compromised.

Premature setting may occur due to an incorrect estimate of the hole temperature, the use of hot mixing water, improper water to cement ratios, contaminants in the mixing water, mechanical failures, and interruptions to pumping operations.

Improper water to cement ratios may also cause excessive shrinkage of the grout.

Grout Placement Requirements

The Wells Regulation has specific requirements for the placement of materials in the annular space for new cased test holes and dewatering wells that are not scheduled to be abandoned within 180 days of completion (see Table 7-1A and Table 7-1B in “Plainly Stated”).

The Wells Regulation requires that any annular space of any new cased well, other than the annular space surrounding the well screen, must be sealed to prevent any movement of water, natural gas, contaminants or other material between subsurface formations or between subsurface formations and the ground surface by means of the annular space. This requirement does not apply to the annular space around an inner casing where a new well has been constructed with a permanent outer casing (see the “New Test Hole or Dewatering Well Completed with a Permanent Outer Casing – Double Walled Casing” section of this chapter).

For new cased test holes and dewatering wells, the Wells Regulation requires that

• a tremie pipe be used to install the suitable sealant.
• the bottom of the tremie pipe remain immersed in the rising accumulation of sea

This tremie pipe requirement does not apply for new dug wells, wells constructed with the use of a driven point, wells constructed by jetting and to test holes and dewatering wells that are scheduled to be abandoned within 180 days of completion.

Successful placement of the grout will depend on the temperature, stability, size of the annular space and pressure in the hole, and how well the casing is centered. The following best management practice on sealing the annular space provides suggestions to help achieve a successful seal.

Sealant (Grout) Placement Techniques

The following sections provide different techniques used to place suitable sealant into an annular space. The Wells Regulation requirements found in the following sections do not apply to test holes or dewatering wells that are scheduled to be abandoned within 180 days of completion of the well’s structural stage.

Group Placement - Inner String Method

In the inner string method of placing grout, the tremie pipe is suspended in the casing. A cementing (float) shoe is attached to the bottom of the casing before the casing is placed in the hole. The tremie pipe is lowered until it engages the shoe.

Placing Grout Using the Inner String Method

To place grout using the inner string method:

1. A float shoe or other similar device is attached to the bottom of the casing before the casing is placed in the hole.
2. The casing is placed in the hole to the bottom of the well. Then the tremie pipe is lowered inside the casing until it engages the shoe. This permits the grout to pass into the annular space but prevents it from leaking back into the casing while pumping the grout.
3. Water or drilling fluid is placed into the casing to prevent the grout from coming back up the casing.

Reminder - For shorter strings of casing [i.e., 6 to 30 metres (20 ft to 100 ft)], the tremie pipe is sealed at the top of the casing using one or two stacked top well seals. The barrier created by the well seals along with the weight of the drilling fluid or water will minimize the amount of grout that can travel back up the inside of the casing string during and after the pumping process.

4. The grout is pumped through the tremie pipe and float shoe and is forced upward around the casing.
5. The tremie pipe is disconnected and removed.
6. All grouting equipment is cleaned.
7. 1. Where bentonite grout is used and before further well construction proceeds, the bentonite should be allowed time to achieve gel strength. Bentonite takes 8 to 48 hours to achieve full gel strength.

   Best Management Practice – Topping Up Settled Bentonite Grout

   The bentonite grout should be topped up to the original level before drilling continues if there has been settling or subsidence in the annular space.

   2. Where cement grout is used, cement must be allowed to set according to manufacturer’s specifications, or 12 hours, whichever is longer. If there has been settling or subsidence in the annular space, the cement grout must be topped up to the original level before drilling continues.
8. The float shoe or other device is drilled out or removed from the bottom of the casing.

Reminder - The sealant at the bottom of the casing is susceptible to damage when drilling restarts. The sealant must be physically and structurally sound and capable of withstanding the initial pressures of drilling. After the placement of grout, it is important to prevent flushing media from pushing up and exerting pressure on the grout column when drilling resumes. This upward pressure can be caused by the displacement of water in the casing when using percussion drilling action or when using air or water based flushing media.

Figure 7-10: Pumping Grout (Sealant) Using The Inner String Method

Figure 7-10 shows a steel casing extending out of the ground behind a drill rig. A clamp has been placed around the casing and above a wooden stump to hold the casing in place. A hose from a grout pump (not shown) is attached to a tremie line above the well casing and hidden behind a steel plate. A bentonite grout (suitable sealant) is being forced down the tremie pipe inside the well casing. The grout is being pushed out below the casing and is being forced up the annular space. The benontite grout is seen coming out of the annular space onto the ground surface around the casing.

Figure 7-11: Inner String Method Of Grout Placement

Figure 7-11 shows a cross-sectional diagram of the inner string method to place grout (sealant) into a well.

Figure 7-11 shows a cross-sectional diagram of the inner string method to place grout (sealant) into a well.

The diagram shows a vertical hole that extends into the subsurface. A suspended casing has been placed into the hole from above the ground surface to just above the bottom of the hole. A float shoe has been installed at the bottom portion of the casing. A tremie pipe is inserted within the casing and through the float shoe. Centralizers have been installed between the outside of the tremie pipe and the inside of the casing.

An annular space is located between the outside of the casing to the side of the hole. Above the ground surface, a horizontal tremie pipe is attached to the vertical tremie pipe. The horizontal tremie pipe is attached to a grout pump. Another horizontal pipe is attached to the grout pump and a vertical pipe. The vertical pipe is attached to a hopper that contains sealant.

There are arrows and small circles in the diagram demonstrating the flow of sealant through the hopper, horizontal tremie pipe, grout pump and vertical tremie pipe and discharging out of the bottom of the tremie pipe into the bottom of the hole. The arrows are also demonstrating the sealant is being forced upward in the annular space from the bottom of the hole to the ground surface.

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

Grout Placement - Tremie Pipe Outside Casing Method

When using this placement method, the grout material is pumped or placed using a tremie pipe that is installed in the annular space.

Reminder - The annular space must meet regulatory requirements (see Table 6-2 of Chapter 6: Constructing the Hole, Casing & Covering the Well and Table 7-1A and Table 7-1B in this chapter) and be large enough to accommodate the tremie pipe (see Chapter 6: Constructing the Hole, Casing & Covering the Test Hole or Dewatering Well; “Best Management Practice - Size of Test Hole or Dewatering Well”).

Placing Grout Using the Outside Casing Method

To place grout using the tremie pipe outside the casing:

1. The lower end of the casing is closed with a drillable plug to ensure the grout that is placed in the annular space cannot enter the casing.
   Another option is to drive the casing into the undisturbed formation below the hole.
2. The tremie pipe is installed into the annular space. The person constructing the well must ensure that the tremie pipe reaches the bottom of the annular space.
3. 1. If a pump is used, the grout is pumped down the tremie pipe discharging into the bottom annular space. Continued discharge of grout into the bottom of the annular space causes the rising accumulation of grout to reach the ground surface.

      The pump must be capable of developing enough pressure to overcome the friction caused by moving the grout through the tremie pipe and up the annular space.

      Issues with a grout pressure head that may prevent the upward placement of grout with a pump are not usually a concern since the grout that is rising to the ground surface is at or below the grout pump elevation.

      In some circumstances, it may be advisable to pull the tremie pipe up at about the same rate that grout is filling the annular space after the first mixed batch of grout is pumped into the annular space. This will minimize the grout pressure head on the tremie pipe outlet and reduce any chances of the tremie pipe being stuck in the hole due to hydration of the grout.

   2. If a pump is not used, the grout is poured down a tremie pipe above the ground surface. The grout flows from the tremie pipe into the bottom of the annular space by the force of gravity. The tremie pipe is raised slowly and the bottom of the tremie pipe remains in the rising accumulation of the grout until the grout reaches the ground surface.

      The bottom of the tremie pipe must remain submerged in the rising accumulation of grout until placement of the grout is complete.

4. Grouting may be complete when the grout leaving the annular space at the ground surface is of the same consistency as the grout being introduced into the bottom of the annular space.
5. The tremie pipe is disconnected and removed.
6. All grouting equipment is cleaned.
7. 1. Where bentonite grout is used and before further well construction proceeds, the bentonite should be allowed time to achieve gel strength. Bentonite takes 8 to 48 hours to achieve full gel strength.

   Best Management Practice – Topping Up Settled Bentonite Grout

   The bentonite grout should be topped up to the original level before drilling continues if there has been settling or subsidence in the annular space.

   2. Where cement grout is used, cement must be allowed to set according to manufacturer’s specifications, or 12 hours, whichever is longer. If there has been settling or subsidence in the annular space, the cement grout must be topped up to the original level before drilling continues.
8. The plug is drilled out or removed from the bottom of the casing.

Reminder - The sealant at the bottom of the casing is susceptible to damage when drilling restarts. The sealant must be physically and structurally sound and capable of withstanding the initial pressures of drilling. After the placement of grout, it is important to prevent flushing media from pushing up and exerting pressure on the grout column when drilling resumes. This upward pressure can be caused by the displacement of water in the casing when using percussion drilling action or when using air or water based flushing media.

Figure 7-12: Outside Casing Method Of Grout Placement

Figure 7-12 shows a cross-sectional diagram of the outside casing method to place grout (sealant) into a well.

Figure 7-12 shows a cross-sectional diagram of the outside casing method to place grout (sealant) into a well.

The diagram shows a vertical hole that extends into the subsurface. A suspended casing has been placed into the hole from above the ground surface to just above the bottom of the hole. A plug has been placed at the bottom of the casing. An annular space is located from the outside of the casing to the side of the hole. A vertical tremie pipe has been installed inside the annular space, located to the left of the casing, from above the ground surface to the bottom of the casing.

Above the ground surface, a horizontal tremie pipe is attached to the vertical tremie pipe. The horizontal tremie pipe is attached to a grout pump. Another horizontal pipe is attached to the grout pump and a vertical pipe. The vertical pipe is attached to a hopper that contains sealant.

There are arrows and small circles in the diagram demonstrating the flow of sealant through the hopper, horizontal tremie pipe, grout pump and vertical tremie pipe and discharging out of the bottom of the tremie pipe into the bottom of the hole. The arrows are also demonstrating the sealant is being forced upward in the annular space from the bottom of the hole to the ground surface.

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

Figure 7-13: Installing Tremie Pipe Outside Casing

Figure 7-13 shows a tremie pipe being installed in the annular space of a drilled well. The permanent steel casing is being held in place by the drilling rig. A larger diameter starter (or temporary) casing has been installed during the drilling of the hole. The difference in diameter between the two casings has created an annular space large enough to allow for the placement of the tremie pipe.

Figure 7-14: Tremie Pipe Remains In Hole During Grout Placement

Figure 7-14 shows the tremie pipe remaining in the annular space while grout is being pumped through it to fill the entire annular space. In some cases, the tremie pipe may need to be raised during pumping to ensure the tremie pipe does not get stuck in the curing sealant.

Figure 7-15: A Successful Seal

Figure 7-15 shows a suitable sealant that has been placed in the annular space along the casing and up to the ground surface.

Figure 7-16: Example Of A Properly Sealed Annular Space

Figure 7-16 shows a hole excavated beside a drilled well. The photograph shows the bluish-grey coloured bentonite grout that has filled the annular space of the drilled well adjacent to the black drilled well casing. The bentonite has also adhered to the sand and gravel overburden. The pop can adjacent to the casing near the bottom of the excavation provides the approximate thickness of the grout.

Figure 7-17: Example Of A Properly Sealed Annular Space - Close Up

Figure 7-17 shows a close-up of the same drilled well. The photograph shows the bluish-grey bentonite grout that has filled the annular space of the well adjacent to the black drilled well casing and which has adhered to the sand and gravel overburden.

Grout Placement - Pouring Without Tremie Pipe

A tremie pipe is not required when filling the annular space of:

• a new dug well,
• the upper 2.5 m (8.2 ft) of a new bored well with approved concrete casing, or
• a new well pit.

The Wells Regulation - The grout (sealant) must provide appropriate structural strength to support the weight of persons and vehicles that may move over the filled annular space of a new dug well or well pit.

Reminder - Care is needed when filling the annular space around a large diameter casing that is thin-walled (e.g., fibreglass or corrugated steel), to reduce the risk of distorting the casing wall or casing joints. Care is also needed when pouring suitable sealant to ensure that bridging will not occur.

Grout Placement - Pouring Bentonite Chips And Pellets From Surface

A dry, manufactured bentonite product, such as chips and pellets, can be placed into the hole’s annular space by a gravity method (i.e. pouring the material from the ground surface) where there is a larger diameter starter (or temporary) casing surrounding a smaller diameter permanent casing. In this case, the starter (or temporary) casing is a pipe that acts as a tremie pipe.

Tremie Pipe

A pipe or tube with an inner diameter that is at least three times the diameter of the largest particle of material to pass through it, and that is used to conduct material to the bottom of a hole, including a hole containing standing water.

In this case, the annular space between the starter casing and permanent outer casing must meet the definition of a tremie pipe for this method to be used.

Upon proper placement of the dry bentonite product into the annular space, the starter (or temporary) casing is removed.

If this method of placement of dry bentonite is used, certain precautions should be taken for the reasons discussed below. When pouring dry bentonite from the surface, there is an increased risk of bridging. A high rate of pouring causes the bentonite to clog at an elevation above the bottom of the annular space. In other cases, the bentonite encounters groundwater and hydrates before it settles to the bottom of the annular space. Open gaps, due to bridging, can allow contaminants to travel vertically in the open portion of the well, destabilize the structure of the well and decrease the effectiveness of the plugging materials.

This method may also lead to uneven hydration of dry bentonite in certain situations. As such, improperly hydrated bentonite may not hold the weight of the well column and may cause serious structural problems with the well.

See the best management practice titled "Taking Precautions when Using and Pouring Dry Bentonite Products" in this chapter.

Grout Placement - Displacement Method

The displacement method involves calculating a volume of grout (sealant) material needed to fill the annular space.

Placing Grout Using the Displacement Method

To place grout using the displacement method:

1. In many cases, a starter (or temporary) casing is placed into the hole to support the sides of the well. The sealant is typically installed into the drilled hole by a gravity method such as pouring the material from the ground surface. In this case the starter casing acts as a tremie pipe. In other cases, a tremie pipe is lowered into the open hole and the grout is placed into the open hole through a tremie pipe.

   Reminder - For further clarification of the definition of Tremie Pipe see Chapter 2: Definitions & Clarifications, Table 2-1 or the “Grout Placement – Pouring Bentonite Chips and Pellets from Surface” section in this chapter.

2. A well casing with a plug located on the bottom of the casing is installed into the hole. The grout (sealant) is displaced by the casing and pushed up into the annular space.

   Reminder - Plugs should be made of material that is easily drilled through (e.g. wood or cement).

3. If the sealant does not fill the entire annular space beside the well casing, then the sealant must be topped up using a tremie pipe to fill the entire annular space to the land surface.
4. 1. Where bentonite grout is used, and before further well construction proceeds, the bentonite should be allowed time to achieve full gel strength. Bentonite takes between 8 and 48 hours to achieve full gel strength.

   Best Management Practice – Topping Up Settled Bentonite Grout

   The bentonite grout should be topped up to the original level before drilling continues if there has been settling or subsidence in the annular space.

   2. Where cement grout is used, cement must be allowed to set according to manufacturer’s specifications, or 12 hours, whichever is longer. If there has been settling or subsidence in the annular space, the cement grout must be topped up to the original level before drilling continues.
5. The plug is drilled out or removed from the bottom of the casing.

Reminder - The displacement method using a tremie pipe allows for the sealant to be continuously deposited into the hole. The casing with plug can then be installed into the well and meets the requirements of the Wells Regulation. The volume of sealant placed in the hole must be able to rise from the bottom of the annular space to the land surface.

Figure 7-18: Grout Displacement Method

Figure 7-18 shows a cross-sectional diagram of the grout displacement method to place grout (sealant) into a well.

The diagram shows a vertical initial outer drill hole that extends into the subsurface. The subsurface consists of an upper layer of top soil underlain by a consolidated bedrock formation.

A suspended casing has been placed into the hole from above the ground surface to about three quarters of the depth of the hole. The bottom of the casing will eventually rest at the bottom of the initial drill hole. A drillable plug has been placed at the bottom of the casing. Centring guides have been placed on the upper and lower portion of the casing. The centring guides extend from the outside of the casing to the side of the hole. An annular space is located from the outside of the casing to the side of the hole. Suitable sealant (grout) has been placed into the hole with a tremie pipe (not shown) below the casing and around the casing from about half of the depth of the hole to the bottom of the hole.

1. Grout measured and placed in hole through a tremie pipe.
2. Well casing with bottom drillable plug and centralizers (centering guides) are placed into the well. The bottom of the well casing is placed at the bottom of the inital drill hole in the well.
3. Well casing filled with water or pressure applied to hold casing in place until suitable sealant (grout) properly sets.

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

Grout Placement - Double Plug Method^{footnote 8[8]}

This method is more common in the construction of oil and gas wells than test holes and dewatering wells. It involves calculating a volume of grout (sealant) material needed to fill the annular space. As this method involves installing the predetermined batch inside the well casing and pushing it into the annular space from below the well casing, care is needed to determine if the volume of grout (sealant) within the well casing exceeds the volume of the entire annular space.

Reminder - When determining the volume of grout needed, it is important to include an amount of grout that will leave 3 m to 4.6 m (10 ft to 15 ft) of grout (sealant) in the casing after the annular space has been filled.

Placing Grout Using the Double Plug Method

To place grout using the double plug method:

1. A casing with a plug is installed in the hole. The casing is held above the bottom of the well. A pump and pipe are hooked onto the casing above the ground surface.

   Reminder - Plugs should be made of material that is easily drilled through (e.g., wood or cement).

2. Grout (sealant) is pumped into the casing above the plug. In this case, the casing acts as the tremie pipe.
3. A second plug is installed above the grout. The use of a plug helps ensure slurry and water separation, resulting in a proper grout seal at the lower end of the casing.
4. Clean water or drilling fluid is then pumped into the casing causing the plugs and grout to move down the casing. As the plugs move down the casing, water or drilling fluid inside the casing is displaced. The process allows the lower plug to fall below the bottom of the casing and the grout moves up and into the annular space.
5. 1. Where bentonite grout is used, and before further well construction proceeds, the bentonite should be allowed time to achieve full gel strength. Bentonite takes between 8 and 48 hours to achieve full gel strength.

   Best Management Practice – Topping Up Settled Bentonite Grout

   The bentonite grout should be topped up to the original level before drilling continues if there has been settling or subsidence in the annular space.

   2. Where cement grout is used, cement must be allowed to set according to manufacturer’s specifications, or 12 hours, whichever is longer. If there has been settling or subsidence in the annular space, the cement grout must be topped up to the original level before drilling continues.
6. The plugs are drilled out or removed from the bottom of the casing.

Reminder - Landing collars below the lower plug can be used to reduce the potential for over or under displacement of the grout (sealant). Wire lines attached to the upper plug can also be used to assist in accurately measuring depths when the plugs come together and reduce the risk of damage to the well casing.

Grout Placement - Annular Space For Driven Points

Definition - Construction by the use of a driven point means a method of well construction that uses a solid point or cone that is driven into the ground. This does not include a cutting shoe unless a solid point is installed on an inner rod. This method is not machinery specific.

For example, the type of machinery that can be used to drive the solid point or cone into the ground can include direct push technology, rotary, percussion, pneumatic hammers, sonic, non-powered manual methods, and cone penetration testing equipment.

The Wells Regulation - If a new test hole or dewatering well is constructed by the use of a driven point, the person constructing the well must ensure that any annular space created is filled to the ground surface using a material and a method approved in writing by the Director. An application must be made to the Director to obtain the written approval.

The request for an approved material and method to seal the annular space of a driven point test hole or dewatering well must be made and approved prior to constructing the new well. See the following sections in this chapter for details on the written consent process.

Reminder - The written approval requirement for a well that is constructed by the use of a driven point does not apply to a test hole or dewatering well that is scheduled to be abandoned not later than 180 days after 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 the requirements stated above.

Implications for Filling Annular Space Size for a New Test Hole Constructed by the Use of a Driven Point

With respect to annular space filling, the above requirement in O. Reg. 153/04 means that, if a new test hole is constructed by the use of a driven point, 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 filling exemptions for a test hole stated in this section do not apply, and
• the requirement to ensure that the material and method used to fill any annular space are approved in writing by the Director.

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

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

Where Does The Person Constructing The New Well Have To Go To Seek A Written Consent From The Director?

If the person constructing a new well is required to seek the written consent of the Director to use an alternate method to fill the annular space of a well constructed by the use of a driven point, the person may contact the Wells Help Desk:

• In writing to Wells Help Desk, Environmental Monitoring and Reporting Branch of the Ministry of the Environment and Climate Change, 125 Resources Road, Etobicoke ON M8P 3V6;
• By fax at: 416-235-5960 or
• By e–mail

For further information, the person constructing the well can contact the Wells Help Desk by telephone at 1-888-396-9355 (for Ontario residents only).

What Information Is Needed For A Written Consent?

The Ministry assesses each case individually and on its merits. As a minimum, applicant’s contacting the Ministry for a written approval should provide a written request that includes but is not limited to the following information:

• The name of the individual(s)/entity that owns the test hole(s) or dewatering well(s)
• The location of the test hole(s) or dewatering well(s)
• The number of test hole(s) or dewatering well(s)
• The purpose and use of the test hole(s) or dewatering well(s)
• The type of casing and well screen that will be used
• The type of sealant material and method being proposed to fill the annular space
• The reason for the proposed sealant material and methods
• If applicable, written certification by the manufacturer/installer/professional engineer that the material and method will properly fill the annular space
• Details on how the person will verify that the placement of the sealant materials in the annular space is uniform and does not bridge
• Details on any flowing well conditions and how the proposed material and method will prevent the vertical movement of groundwater in the annular space and near the well site
• Details on any identified or expected contaminant or mineralized condition and how the proposed material and method will effectively seal the annular space to the ground surface
• Other potential permits or approvals that are being applied for in relation to the construction or use of the well. For example, the need for a Permit To Take Water if the water from the well is being taken at a rate of more than 50,000 litres one any one day for well development purposes.

The person constructing the well may be required to retain a Professional Engineer or Professional Geoscientist who would have to prepare a scientific report showing the appropriate scientific rationale to support the application. The person constructing the well would have to submit the report along with the request for written approval to the Ministry for its consideration.

The Director has reviewed the following standards for test holes and dewatering wells:

• ASTM D5092-04 – Standard Practice for Design and Installation of Ground Water Monitoring Wells; sections 6 to 8,
• ASTM D6724-04 – Standard Guide for Selection and Installation of Direct-Push Ground Water Monitoring Wells, and
• ASTM D6725-04 – Standard Practice for Direct-Push Installation of Pre-pack Screen Monitoring Wells in Unconsolidated Aquifers.

In many environments the Director will likely support a material and method for sealing the annular space that is consistent with these ASTM standards. As such, the person constructing the well is encouraged to review these ASTM standards and should indicate on the application, whether and how the standards listed above will be met.

How Does The Director’s Decision Process Work?

The request for written approval should be submitted to the Ministry along with any and all supporting documents such as a hydrogeological and/or a well design report. The person constructing the well and others should be cautioned that obtaining a written approval will not be an automatic process. The Ministry has to provide for the conservation, protection and management of Ontario’s waters and for their efficient and sustainable use, to promote Ontario’s long–term environmental, social and economic well–being.

The Ministry will review the request, supporting information and other information generated from internal and external parties with an interest in the application.

Based on the information, the Ministry will contact the person constructing the well in writing indicating the Director’s decision.

Tools For Annular Space & Sealing

Table 7-6 provides an example of the types of reference charts and tables that can be used to calculate volumes of holes and casing and determine the approximate amount of suitable sealant needed to fill the annular space.