Part III. Destruction of Cathodic Protection Wells
Section 16. Requirements for Destroying Cathodic Protection Wells.
General requirements for well destruction are contained in Section 23 of the
Water Well Standards. Special considerations for cathodic protection wells
are as follows:
- Preliminary Work. A cathodic protection well shall be investigated before
it is destroyed to determine its condition, details of its construction and
whether conditions exist that will interfere with filling and sealing.
The well shall be sounded immediately before it is destroyed to make sure
that no obstructions exist that will interfere with filling and sealing. The
well shall be cleaned before destruction, as needed, to ensure that all
undesirable materials, including obstructions to filling and sealing, debris,
and pollutants and contaminants that could interfere with well destruction
are removed for disposal. The enforcing agency shall be notified as soon as
possible if pollutants and contaminants are known or suspected to be in a
well to be destroyed. Well destruction operations may then proceed only at
the approval of the enforcing agency. The enforcing agency should be
contacted to determine requirements for proper disposal of materials removed
from a well to be destroyed.
- Filling and Sealing Conditions. The following minimum requirements shall
be followed when various conditions are encountered.
- Wells that only penetrate unconsolidated material and a single "zone" of
groundwater. At a minimum, the upper 20 feet of the well casing and the
annulus between the well casing and borehole wall (if not already sealed)
shall be completely sealed with suitable material. Sealing material shall
extend to a minimum depth of 50 feet below land surface if the well to be
destroyed is located in an urban area, or is within 100 feet of any potential
source of pollution or contamination. Additional sealing material may be
needed if adverse conditions exist. The remainder of the well below the
minimum surface seal shall be filled with suitable granular fill material,
such as clean sand or pea gravel, or with sealing material.
- Wells that penetrate several water-bearing strata. The upper portion of
the well casing and annular space shall be filled with sealing material as
described in Item 1, above. Strata encountered below the surface seal that
contain poor-quality water, pollutants, or contaminants that could mix with
and degrade water in other strata penetrated by the well, shall be
effectively isolated by sealing the well bore and annulus within intervals
specified in Section 10, above. The remainder of the well shall be filled
with suitable granular fill or sealing material.
- Wells penetrating fractured rock. Sealing material shall be installed as
outlined in Items 1 and 2, above. Cement-based sealing material shall be
used opposite fractured rock. The remainder of the well shall be filled with
fill or sealing material, as appropriate.
- Wells in nonfractured consolidated strata. Sealing material shall be
installed as outlined in Items 1 and 2, above. The remainder of the well
shall be filled with fill or sealing material, as appropriate.
- Wells penetrating water-bearing zones or aquifers of special
significance. The enforcing agency may require that specific water-bearing
zones be sealed off for well destruction.
- Placement of Material. The placement of sealing materials for cathodic
protection well destruction is generally described in Section 23 of the Water Well Standards
and Appendix B (Bulletin 74-81). The following additional requirements shall
be observed in destroying cathodic protection wells.
Casing, cables, anodes, granular backfill, conductive backfill, and sealing
material shall be removed as needed, by redrilling, if necessary, to the
point needed to allow proper placement of sealing materials within required
sealing intervals. Removal of some or all well materials will likely be
required for cathodic protection wells that were not constructed in
accordance with these standards, or standards adopted by the Southern
California Cathodic Protection Committee in December 1969.
Casing that cannot be removed shall be adequately perforated or punctured at
specific intervals to allow pressure injection of sealing materials into
granular backfill and all other voids that require sealing.
The following requirements shall be observed in placing fill and sealing
material in cathodic protection wells to be destroyed.
- Placement Method. The well shall be filled and sealed with appropriate
material upward from the bottom of the well using a tremie pipe or
Sealing material shall be placed by methods (such as by the use of a tremie
pipe or equivalent) that prevent freefall, bridging, or dilution of the
sealing materials, or separation of aggregates from sealants. Sealing
materials shall not be installed by freefall unless the interval to be sealed
is dry and no deeper than 30 feet below ground surface.
- Timing of Placement. Sealing material shall be placed in one continuous
operation (or "pour") from the bottom to the top of the well unless
conditions in the well dictate that sealing operations be conducted in a
staged manner and prior approval is obtained from the enforcing agency.
- Groundwater Flow. Special care shall be used to restrict the flow of
groundwater into a well while fill and sealing material is being placed, if
subsurface pressure causing the flow of water is significant.
- Sealing Pressure. Pressure required for placement of cement-based
sealing material shall be maintained long enough for the cement-based sealing
material to set.
- Verification. Verification shall be made that the volume of sealing and
fill material placed in a well during destruction operations equals or
exceeds the volume to be filled and sealed. This is to help determine that
the well has been properly destroyed and that no jamming or bridging of the
fill or sealing material has occurred.
- Sealing Material. Materials used for sealing cathodic protection wells
for destruction shall have low permeabilities so that the volume of water and
possible pollutants and contaminants passing through them will be of minimal
consequence. Sealing material shall be compatible with the chemical
environment into which it is placed and shall have mechanical properties
compatible with present and future site uses.
Suitable sealing materials include neat cement, sand-cement, concrete, and
bentonite, as described in Section 9 of the Water Well Standards.
Sealing materials used for isolating zones of fractured rock shall be cement-based,
as described in Subsection B, above. Drilling mud or drill cuttings shall
not be used as any part of a sealing material for well destruction. Concrete
may be used as a sealing material at the approval of the enforcing agency.
- Fill Material. Many fill materials are suitable for destruction of
cathodic protection wells. These include clean, washed sand or gravel or
sealing material. Fill material shall be free of pollutants and contaminants
and shall not be subject to decomposition or consolidation after placement.
Fill material shall not contain drilling mud or cuttings.
- Additional Requirements for Destruction of Cathodic Protection Wells in
Urban Areas. The following additional requirements shall be met at each well
site in urban areas, unless otherwise approved by the enforcing agency:
(1) The upper surface of the sealing material shall end at a depth of 5 feet
below ground surface, and,
(2) If the casing was not extracted during destruction and sealing
operations, a hole shall be excavated around the well casing to a depth of 5
feet below ground surface after sealing operations have been completed and
sealing materials have adequately set and cured. The exposed well casing
shall then be removed by cutting the casing at the bottom of the excavation.
The excavation shall then be backfilled with clean, native soil or other
- Temporary Cover. The well borehole and any associated excavations shall
be covered at the surface to prevent the entry of foreign material, water,
pollutants, and contaminants and to ensure public safety whenever work on the
well is interrupted by such events as overnight shutdown, poor weather, and
required waiting periods to allow setting of sealing materials and
performance of tests. The cover shall be held in place or weighted down in
such a manner that it cannot be removed except by equipment or tools.