6. Annular Space & Sealing (this page left intentionally blank) 6. Annular Space & Sealing Chapter Table of Contents Chapter Table of Contents Chapter Description.........................................................................................................................................................................................6 Regulatory Requirements – Annular Space & Sealing of a New Well.....................................................................................................6 Relevant Sections – The Wells Regulation..............................................................................................................................................6 The Requirements – Plainly Stated..........................................................................................................................................................6 Well Record – Relevant Sections............................................................................................................................................................14 Best Management Practice – Report use of Centralizers..........................................................................................................15 Key Concepts..................................................................................................................................................................................................16 The Annular Space...................................................................................................................................................................................16 Best Management Practice – Annular Space Diameter.............................................................................................................16 Purpose of the Seal...................................................................................................................................................................................16 Examples of Improperly Sealed Annular Spaces.................................................................................................................................17 Requirements for Sealing Various Types of Wells....................................................................................................................................18 Comparison of Bentonite and Cement Grouts..........................................................................................................................................27 Calculating Amount of Materials Required................................................................................................................................................30 Mixing Bentonite Grout (Sealant)................................................................................................................................................................33 Best Management Practice – Mixing Bentonite Grout..............................................................................................................33 Techniques for Successful Mixing..........................................................................................................................................................33 Consequences of Poorly Mixed Bentonite Grout...............................................................................................................................33 Mixing Cement or Concrete Grout (Sealant).............................................................................................................................................34 Techniques for Successful Mixing..........................................................................................................................................................34 Best Management Practice – Techniques for Successful Mixing.............................................................................................34 Consequences of Poorly Mixed Cement Grout...................................................................................................................................34 Grout Placement Requirements...................................................................................................................................................................35 Best Management Practice – Sealing the Annular Space...........................................................................................................35 Grout Placement – Inner String Method..............................................................................................................................................36 Best Management Practice – When Bentonite Grout Settles...................................................................................................36 Grout Placement – Tremie Pipe Outside Casing Method.................................................................................................................39 Best Management Practice – Use of a Grout Pump..................................................................................................................39 Best Management Practice – Use of a Larger Diameter Tremie Pipe.....................................................................................39 Best Management Practice – When Bentonite Grout Settles...................................................................................................40 Grout Placement – Pouring Without Tremie Pipe.............................................................................................................................47 Grout Placement – Displacement Method...........................................................................................................................................47 Best Management Practice – When Bentonite Grout Settles...................................................................................................47 Grout Placement – Double Plug Procedure.........................................................................................................................................49 Water Supply Wells – Requirements and Best Management Practices 3 Chapter Figures Chapter Description6. Annular Space & Sealing Best Management Practice – When Bentonite Grout Settles...................................................................................................49 Grout Placement – When an Annular Space is Created by Use of a Driven Point.......................................................................50 Best Management Practice – A Method of Creating and Sealing Annular Space of a Well Constructed with the Use of a Driven Point..................................................................................................................................................................................51 Tools for Annular Space & Sealing..............................................................................................................................................................57 Chapter Figures Figure 6-1: Well Record – Relevant Sections – Annular Space...............................................................................................................14 Figure 6-2: Well Record – Relevant Sections – Construction Record...................................................................................................15 Figure 6-3: Visible Open Annular Space Adjacent to Drilled Well Casing...........................................................................................17 Figure 6-4: Visible Open and Large Annular Space Around Drilled Well............................................................................................17 Figure 6-5: Visible Open Annular Space Below Pitless Adapter and Horizontal Waterline to the Bottom of the Casing...........17 Figure 6-6: Drilled Well in Overburden – Well Screens that are Artificially Packed or Naturally Developed................................19 Figure 6-7: Drilled Well – Without Well Screen........................................................................................................................................20 Figure 6-8: Examples of Drilled Wells in Bedrock..................................................................................................................................21 Figure 6-9: Drilled Well in Overburden – Natural Development, Casing Pulled Back Exposing Screen Method........................22 Figure 6-10: Bored Wells with Concrete Casing........................................................................................................................................23 Figure 6-11: Dug Well....................................................................................................................................................................................24 Figure 6-12: Driven Point Well....................................................................................................................................................................25 Figure 6-13: Jetted Well.................................................................................................................................................................................26 Figure 6-14: Pumping Grout Down Tremie Pipe – Inside Casing.........................................................................................................37 Figure 6-15: Inner String Method of Grout placement............................................................................................................................38 Figure 6-16: Outside Casing Method...........................................................................................................................................................41 Figure 6-17: Installing Tremie Pipe Outside Casing.................................................................................................................................42 Figure 6-18: A Successful Seal......................................................................................................................................................................42 Figure 6-19: Tremie Remains in Hole During Grout Placement............................................................................................................43 Figure 6-20: Hole Excavated Beside Drilled Well.....................................................................................................................................44 Figure 6-21: Bentonite Grout in Annular Space........................................................................................................................................44 Figure 6-22: Grout Displacement Method.................................................................................................................................................48 Figure 6-23: Suggested Method of Creating and Sealing Annular Space in a Driven point Well......................................................53 4 Water Supply Wells – Requirements and Best Management Practices 6. Annular Space & Sealing Chapter Tables Chapter Tables Table 6-1: Annular Space and Sealing Requirements..................................................................................................................................8 Table 6-2: Some General Bentonite and Cement Advantages and Disadvantages..............................................................................27 Table 6-3: Calculating Volume of Bentonite [at 15%, 20% and 23% Solids based on one 23 kg (50 lbs) bag of Sodium Bentonite].........................................................................................................................................................................................................32 Table 6-4: Calculating Volume of Concrete and Cement.........................................................................................................................32 Table 6-5: Calculating Casing and Hole Volume.......................................................................................................................................57 Water Supply Wells – Requirements and Best Management Practices 5 Chapter Description 6. Annular Space & Sealing CHAPTER DESCRIPTION This chapter covers the construction process involved in sealing the well casing into the hole to ensure that there is no movement of water or other materials along the annular space as required by the Wells Regulation. REGULATORY REQUIREMENTS – ANNULAR SPACE & SEALING OF A NEW WELL RELEVANT SECTIONS – THE WELLS REGULATION Casing – Subsections 13(12) and 13(20) Annular Space – Sections 14 and 14.1 to 14.6 THE REQUIREMENTS – PLAINLY STATED The Wells Regulation requires the following regarding the Annular Space and Seal for new well construction: Sealing Casing in Bedrock for New Drilled Wells • If the aquifer is located in a weathered bedrock zone, the new drilled well must be cased to the bedrock, but the casing is not required to be sealed into the bedrock. • If the aquifer is located in a bedrock zone that is not weathered, the casing of a new drilled well must be sealed into the bedrock with suitable sealant to prevent impairment of the quality of the groundwater and the water in the well. Sealing Annular Space between Casings • The annular space between casings of different diameters must be sealed with suitable sealant to prevent the entry of surface water or other foreign materials into the well. Subsurface Movement for New Well Construction • Any annular space, 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. Sealing Annular Space for New Wells • Table 6-1on page 10 of this chapter for a summary of the requirements outlined in the Wells Regulation regarding the annular space and sealing for new well construction other than jetted wells or wells constructed by use of a driven point. 6 Water Supply Wells – Requirements and Best Management Practices 6. Annular Space & Sealing Regulatory Requirements – Annular Space & Sealing of a New Well New Wells Constructed by Use of a Driven Point • A person constructing a well by use of a driven point must ensure that any annular space is filled to the ground surface using a method and material approved by the Director (see “Grout Placement – When an Annular Space is Created by Use of a Driven Point” on page 44 of this chapter). Definitions for sealant, watertight, tremie pipe and other relevant terms are stated in Chapter 2: Definitions & Clarifications. See Figures 6-6 to 6-13 (pages 19 to 26 of this chapter) for illustrations of the sealing requirements described in Table 6-1 for most common wells. The requirement for jetted wells is outlined in the Plainly Stated, “Subsurface Movement for New Well Construction” section above. For wells constructed by use of a driven point, see “Grout Placement – When an Annular Space is Created by Use of a Driven Point” on page 44 of this chapter. Water Supply Wells – Requirements and Best Management Practices 7 Regulatory Requirements – Annular Space & Sealing of a New Well 6. Annular Space & Sealing Table 6-1: Annular Space and Sealing Requirements New Bored Wells With Concrete Casing and Dug (or Excavated) Wells Bored Well with Bored Well with Concrete Casing Concrete Casing Dug (or Excavated) Well ≥ 6 m (19.7′) deep < 6 m (19.7′) deep From ground surface to From ground surface to ≥ ≥2.5 m (8.2′) below 2.5 m (8.2′) below ground ground surface surface Minimum Diameter of Minimum Diameter is Minimum Diameter is ≥ Hole Greater Than ≥15.2 cm (6″) 15.2 cm (6″) Outer Casing Diameter None to Create Annular From ≥2.5 m (8.2′) below From ≥2.5 m (8.2′) below Space the ground surface the ground surface Minimum Diameter is Minimum Diameter is ≥ ≥7.6 cm (3″) 7.6 cm (3″) Minimum Depth of Annular Space below ≥6 m (19.7′) Bottom of well None Ground Surface Bottom of Filter Pack Material around Well Bottom of well screen Bottom of well screen Bottom of well Screen if present Clean, washed gravel, Clean, washed sand or Native materials (soil) excavated from the well Clean, washed gravel or Clean, washed gravel or sand sand Native materials (soil) can only be used if they are not from a Type of Annular Filter Deposited only after Deposited only after contaminated area and the Pack, Granular or placement of well screen placement of well screen major horizons of soil are Native Material and casing and casing excavated and stored Only applies if well Only applies if well screen separately, kept free of screen is present is present contamination and then backfilled within the annular space in the same relative position that the horizon originally occupied. At least the top of well At least the top of well screen but no closer to Maximum Top of screen but no closer to ground surface than 6 m No closer to ground surface Annular Filter Pack ground surface than 2.5 m (19.7′) below ground than 2.5 m (8.2′) below ground Material around Well (8.2′) below ground surface surface surface. Screen and Well Casing Only applies where well Only applies where well screen is present screen is present 8 Water Supply Wells – Requirements and Best Management Practices 6. Annular Space & Sealing Regulatory Requirements – Annular Space & Sealing of a New Well New Bored Wells With Concrete Casing and Dug (or Excavated) Wells Bored Well with Bored Well with Concrete Casing Concrete Casing Dug (or Excavated) Well ≥ 6 m (19.7′) deep < 6 m (19.7′) deep Suitable sealant placed Suitable sealant placed Annular Seal Material using tremie pipe with using tremie pipe with around Casing in bottom end of pipe bottom end of pipe Remaining Open immersed in rising immersed in rising Suitable sealant that has Annular Space from accumulation of sealant accumulation of sealant structural strength to support Filter Pack, Granular If no well screen is used, If no well screen is used, weight of persons and vehicles or Native Material to ≥ suitable sealant must be suitable sealant must be 2.5 m (8.2′) below used to fill the space from used to fill the space from Ground Surface the bottom of the well up the bottom of the well up to this depth to this depth Bentonite granules, pellets or chips that have Bentonite granules, pellets been screened to or chips that have been Annular Seal Material manufacturer’s screened to manufacturer’s around Casing from ≥ Suitable sealant that has specifications and have a specifications and have a 2.5 m (8.2′) below structural strength to support diameter range between 6 diameter range between 6 Ground Surface to weight of persons and vehicles to 20 mm (0.23 to 0.8″) to 20 mm (0.23 to 0.8″) are Ground Surface are placed immediately placed immediately above above the suitable the suitable sealant sealant Allow cement to cure to Allow cement to cure to manufacturer’s Allow cement to cure to manufacturer’s specifications or for 12 manufacturer’s specifications specifications or for 12 Where Cement is used hours whichever is or for 12 hours whichever is hours whichever is longer. in Suitable Sealant longer. If cement longer. If cement mixture If cement mixture settles, Mixture mixture settles, the settles, the suitable sealant the suitable sealant shall suitable sealant shall be shall be topped up to the be topped up to the topped up to the original original level original level level Water Supply Wells – Requirements and Best Management Practices 9 Regulatory Requirements – Annular Space & Sealing of a New Well 6. Annular Space & Sealing New Drilled Wells, Other Wells* and Well Pits (Table 6-1 continued) Drilled Well or any Drilled Well or any other Well ≥6 m (19.7′) other Well < 6 m deep that is not listed (19.7′)deep that is not New Well Pit (see Chapter 9: on Table 6-1 (except listed on Table 6-1 Equipment Installation) jetted and wells (except jetted and wells constructed by the use constructed by the use of a driven point ) of a driven point ) Minimum Diameter is Minimum Diameter is ≥7.6 ≥7.6 cm (3″) cm (3″) Minimum Diameter is ≥ 5.1 cm (2″) Minimum Diameter of If centralizers are Hole Greater Than attached to casing > 6m Minimum Diameter is ≥5.1 Outer Casing Diameter (19.7’) below the ground cm (2″) ≥7.6 cm (3″) to Create Annular surface using rotary If a breakaway guide is Space drilling equipment OR attached 2m (6.3’) above If a breakaway guide is the bottom of any casing attached 2m (6.3’) above using cable tool equipment the bottom of any casing using cable tool equipment Where no well screen is installed: • bottom of well. If well screen installed: Minimum Depth of • bottom of well screen, Annular Space below ≥ 6 m (19.7′) Bottom of well pit and Ground Surface • top of well screen must not be closer to ground surface than 2.5 m (8.2′). Bottom of Filter Pack Material around Well Bottom of well Bottom of well None Screen if present Clean, washed gravel or Clean, washed gravel or Type of Annular Filter sand sand Pack Material around Placed during or after Placed during or after None Well Screen placement of well screen placement of well screen and casing and casing 10 Water Supply Wells – Requirements and Best Management Practices