SEWER MANHOLE SEALING
(As provided by Avanti International)
1 Intent: The intent of this section is the elimination of infiltration/inflow into manholes that are otherwise
structurally sound, using various products and methods either singularly or in combination.
2 General: Sewer manhole sealing includes the following ...
(2.1) The sealing of the manhole base, walls, corbel/cone and chimney of brick, block or precast
manholes.
(2.2) The sealing of precast manhole barrel joints, when general structure sealing is not required.
(2.3) The sealing of the manhole frame joint area and the chimney above the cone.
(2.4) The sealing of manhole covers by either replacement, conversion or by installing a manhole
insert.
(2.5) The inspection and testing of the various types of work to insure compliance.
3 Manhole Structure Sealing: Manhole structure sealing includes the sealing of the manhole base, walls,
corbel/cone and chimney. This type of sealing shall be done during high groundwater conditions, unless
the points of leakage have been previously identified.
(3.1) Chemical Grout Sealing: Shall be in accordance with ASTM F2414-04 Standard Practice for
Sealing Sewer MANHOLES Using Chemical Grouting.
A Chemical Sealing (Grouting) Materials: Shall meet the requirements specified in the
chemical sealing materials section with special attention focused on the safety training
requirements as well providing product liability insurance for all materials used.
B Equipment: The basic equipment shall consist of chemical pumps, chemical containers,
injection packers, hoses, valves, and all necessary equipment and tools required to seal
manholes. The chemical injection pumps shall be equipped with pressure meters that will
provide for monitoring pressure during the injection of the chemical sealants. When
necessary, liquid bypass lines equipped with pressure-regulating bypass valves will be
incorporated into the pumping system.
C Sealing Procedures (Precast Manholes): At each point of leakage within the manhole
structure a hole shall be carefully drilled from within the manhole and shall extend through
the entire manhole wall. In cases where there are multiple leaks around the circumference
of the manhole, fewer holes may be drilled, providing all leakage is stopped from these
holes. Grout ports or sealant injection devices shall be placed in these previously drilled
holes in such a way as to provide a watertight seal between the holes and the injection
device. A hose, or hoses, shall be attached to the injection device from an injection pump.
Chemical sealing materials as specified (see CHEMICAL SEALING MATERIALS) shall
then be pumped through the hose until material refusal is recorded on the pressure gage
mounted on the pumping unit or a predetermined quantity of sealant has been injected.
Care shall be taken during the pumping operation to insure that excessive pressures do
not develop and cause damage to the manhole structure. Upon completion of the
injection, the ports shall be removed and the remaining holes filled with mortar and
troweled flush with the surface of the manhole walls or other surfaces. The mortar used
shall be a nonshrink patching mortar (see SEWER MANHOLE REHABILITATION).
D Sealing Procedures (Brick and Block Manholes): When chemical grouting is used to seal
random or isolated leaks or leaking sections of a brick or block manhole, it shall be done in
accordance with 3.1 B, above.
E Grout Curtain Sealing Procedures (Brick and Block Manholes): When a chemical grout
curtain is required around a brick or block manhole, the procedure may involve the use of
chemical grout in combination with a two-coat cementitious coating.
a Surface Preparation: The manhole surface shall be cleaned, patched, and the
infiltration stopped as required (see SEWER MANHOLE REHABILITATION).
b Set Grout Ports or Injectors: Holes shall be drilled and grout ports or chemical
sealant injection devices installed to insure proper grouting of the soil outside of the
manhole. Some additional ports may be placed after the application of the
waterproof coating.
c Coating: Two coats of a cementitious waterproof coating shall be applied as
required (see SEWER MANHOLE REHABILITATION) before any chemical grout
is pumped. These two coats will provide a dam to optimize the grout sealing
application and shall extend from the manhole base to the bottom of the frame
seal.
d Chemical Sealing: Chemical grout shall be injected into the soil surrounding the
manhole as needed for complete sealing, using the same equipment and
procedures as required earlier in this section. Grouts injected into near-surface
and chimney-corbel areas may require the addition of shrink control agents, gel
reinforcing agents and accelerators.
Sealing Material Suggested Additive
AV-100 Acrylamide Gel AV-257 Icoset Latex
AV-118 Acrylic Gel AV-257 Icoset Latex
AV-350 Urethane Gel AV-257 Icoset Latex
AV-202 Polyurethane Resin (foam)
(3.2) Cementitious Sealing: Manhole structure sealing, as well as the sealing of random and isolated
leaks, can also be accomplished by using the cementitious method (see SEWER MANHOLE
REHABILITATION).
4 Precast Manhole Joint Sealing: Precast manhole joint sealing includes the sealing of barrel joints using
one of the following methods and procedures when general structure sealing is not required.
(4.1) Chemical Grout Sealing: Use the same procedures and materials as required in 3.1 B.
(4.2) Cementitious Sealing: Use the same materials as required in SEWER MANHOLE
REHABILITATION.
(4.3) Expanded Gasket: Use the elastomeric polyurethane resin-soaked oakum method, using dry
twisted jute oakum or resin rod with polyurethane resin (water activated).
(4.4) Manufactured Seal: Install a manufactured manhole joint seal that generally conforms to the
requirements of 5.1 with a stainless steel restraining hoop. Detailed installation procedures shall
be in accordance with the manufacturer's instructions.
5 Manhole Frame Sealing: Manhole frame sealing includes the sealing of the frame joint area and the
chimney above the cone of the manhole with either a manufactured or applied internal or external flexible
seal. The seal shall be designed to prevent leakage of water into the manhole through these areas
throughout a 20-year design life. The seal shall remain flexible, allowing repeated vertical movements of
the frame due to frost lift, ground movement, or other causes of up to 2 inches and/or repeated horizontal
movement of the frame due to thermal movement of pavement or other causes of up to 1/2 inch.
(5.1) Manufactured Frame Seal: If the flexible portion of the seal is made of a rubber type product, it
shall have a minimum thickness of 3/16 inch, a minimum unexpanded width of 8 inches, and be
fabricated from a high-grade rubber compound conforming to the applicable requirements of
ASTM C-923. The internal seal shall have a double pleated and the external seal a corrugated,
expandable center section. Any extension used in conjunction with the sleeve to increase
coverage shall be made of the same material and have the same minimum thickness as the
sleeve and be designed to be mechanically attached to the sleeve. The bands used for
compressing the sleeve and extension against the manhole shall be fabricated from minimum 16-
gauge sheet, if channeled, or 5/16-inch diameter, if round, stainless steel conforming to ASTM A-
240, Type 304, for sheet and ASTM A-479, Type 304, for rods. Any screws, bolts or nuts used on
these bands shall be stainless steel conforming to ASTM F-593 and 594, Type 304. The internal
seal or its appurtenances shall not extend far enough into the manhole opening to prevent or
unduly restrict manhole entry. If the seal is constructed of another flexible material, it shall have
both tensile and tear strength equal to or greater than that of the rubber when tested in
accordance with the applicable ASTM procedures.
Installation: The contact surfaces for the sleeve and extensions shall be clean, reasonably
smooth and circular, and free of excessive voids. If the masonry surface is rough or irregular and
will not provide an effective seal, it shall be smoothed with mortar. A bead of butyl rubber caulk
may be applied to the bottom sealing surface of the seal or extension to fill minor irregularities in
the masonry surface. After the rubber sleeve has been placed in the proper position, the bands
are positioned and individually tightened or expanded as required to provide a watertight seal.
When an extension is used, its top shall be positioned in the bottom band recess prior to installing
the bottom band. The bands are then positioned in the extension and tightened or expanded as
required to provide a watertight seal. Installation procedures shall be in accordance with the
manufacturer's instructions.
(5.2) Applied Frame Seal: An applied seal is one that is achieved by applying a product, approved by
the Engineer, either between the precast adjusting rings of the chimney and under the frame or to
either the inside or outside surface of the chimney and frame to provide a seal that meets the
performance criteria contained in this section. If the applied sealing product is a butyl or mastic
type compound, all of the surfaces that are to be sealed shall be clean, dry, and dust free.
If the applied seal utilizes the elastomeric polyurethane resin-soaked oakum method, each joint
shall consist of two concentric rings of 2-inch oakum. The outer ring shall be saturated with the
urethane base foam chemical sealing material. The inner ring, saturated with water, shall be
placed to prevent urethane foam from entering the manhole. The oakum saturated with urethane
shall be sprayed with water. When foaming begins, the frame shall be set in place.
If the applied sealing product is a type of material that is applied to either the inside or outside
surfaces of the frame and chimney and/or corbel/cone, the surface against which it is applied shall
be clean, and free of rust, dust, oil, loose material and other contaminants. The product shall be
applied by trowel, roller, or by spraying to achieve a thickness of not less than 100 mils. The
sealing material shall extend far enough onto the frame to insure bonding and cover enough of the
chimney to insure sealing. If the sealing material is applied to the outside of the manhole, it shall
be allowed to cure a minimum of 24 hours before backfilling when the ambient temperature is
above 70°F and 48 hours when the ambient temperature is below 70°F and falling. Immediately
before backfilling, two layers of 4 mil plastic sheet shall be loosely wrapped over the sealed area
to prevent direct contact between the sealer and the backfill material.
Application procedures shall be in accordance with the manufacturer's instructions.
(5.3) External Sealing System: The manufactured frame seal: It shall be multi-section continuous
bands, with a neoprene rubber top section and all lower sections made of EPDM (Ethylene
Propylene Di Monomer) rubber with a minimum thickness of 60 mils that meets or exceeds the
ASTM specification C-923. Each unit shall consist of a top and a bottom section and shall have
mastic on the top and bottom of the top section and on the bottom of the bottom section. The
mastic shall be non-hardening butyl rubber sealant that meets or exceeds ASTM Specification
0990-94 and shall seal to the cone/top of the manhole/catch basin and over the lip of the casting.
INSTALLATION:
Suggested tools for application: Tape measure, Hand Held broom, Heavy Duty Scissors,
Abrasive Stone (or other object to remove sharp edges).
Product. The frame seal External Sealing System consists of two sections, the bottom section "A"
and top section "B". Additional extension sections "C" are available if necessary.
Excavate dirt from around the structure to depth of 4" below the top of the cone/top slab. Using
an abrasive stone or other object, remove any sharp. protruding edges from the outside surface of
manhole or catch basin adjustment ring area.
Also remove any dirt clumps or mortar chunks from the casting flange where the mastic is
intended to adhere. Brush Frame seal Adhesive Primer onto the casting and structure surfaces
where the mastic is intended to adhere. After the Adhesive Primer has dried (approximately 10
minutes) begin placing the external unit onto the structure. Unfold and stretch bottom section "A"
around the structure. Lower section "A" into position so that its bottom edge is a minimum of 2"
below the top of the cone/top slab. Flip mastic strip up - facing out. Using a heavy duty scissors
or utility knife, cut off the portion of the top band that extends above the casting flange. Pull top
section "B" over the structure (wider mastic towards the top) until its top edge is 1 1/2" above the
bottom edge of the casting. The bottom edge of top section "B" should overlap bottom section "A"
by a minimum of 2" or an extension section "C" will be required. Flip top and bottom mastic strips
up - facing out. Remove the release tape from the mastic strips, flip mastic strips down and hand
press into position. Installation complete.
6 Manhole Cover Sealing: Manhole cover sealing includes either the replacement of or sealing of existing
manhole covers. All of the methods described require the thorough cleaning of the frame rim surface by
wire brushing. Detailed installation procedures shall be in accordance with the manufacturer's
instructions.
(6.1) Cover Replacement: Replace the existing cover with a new approved solid, gasketed cover.
(6.2) Cover Conversion: Reuse the existing cover by making it watertight. This is accomplished by
installing a gasket between the cover and the cover-bearing surface of the frame and plugging the
vent and pick holes. One of the plugs shall be removable to facilitate removal of the cover.
Manhole cover gaskets and plugs shall be molded from a high-quality rubber compound such as
Nitrile, EPDM or a blend thereof. The rubber product shall have a minimum tensile strength of
2,000 psi with a hardness (durometer) of 60 ±5. The cover gasket shall be provided with an
outside rib and have a minimum thickness of 3/32 inch.
(6.3) Installation of Manhole Insert: Use the existing cover in conjunction with a watertight insert that is
installed under the cover and prevents entry of water into the manhole. The manhole insert shall
be designed to prevent inflow through and around manhole covers and manufactured to fit the
manhole frame rim upon which the manhole cover rests.
A The manhole insert shall be manufactured from a corrosion-resistant material able to
withstand the environment of a sanitary sewer system, road salts, oils and fuel that it may
come in contact with. The material shall be freeze-thaw resistant and withstand a
temperature range of -50°F to 245°F. The manhole insert shall have a minimum thickness
of 1/8 inch.
B The insert shall have an approved system of relieving gas and vacuum pressure and shall
be complete with a closed-cell neoprene or polyethylene gasket with adhesive backing
installed on the underside of the insert rim by the manufacturer. The insert shall have a
corrosion-resistant strap installed within the bowl for ease of installation and removal.
C The manhole insert shall be fully seated upon the manhole frame rim and the cover
replaced to complete the installation.
7 Final Acceptance: After the specified sealing work has been completed, the manholes shall be visually
inspected and tested by the Contractor (as required) in the presence of the Engineer and found to be
acceptable.
(7.1) Structure Sealing Test: Manhole structure sealing shall be visually inspected for watertightness
against leakage of water into the manhole. All visible leaks and defects observed during
inspection shall be repaired to the Engineer's satisfaction.
If the groundwater level is not, in the opinion of the Engineer, high enough to give a realistic visual
inspection, the Contractor may, at his option, test a random sampling of the manholes using one
of the following methods.
A Exfiltration Testing: Incoming and outgoing sewer service lines shall be plugged, the plugs
restrained and the manhole filled with water to the top of the manhole frame. A soaking
period of up to 1 hour will be allowed if bypassing of the sewage is not required or has
been provided for. At the end of this optional soaking period, the manhole shall be refilled
with water and the test begun.
If the water loss exceeds that shown in the following table, the manhole will have failed the
test.
Depth of Manhole Maximum Allowable Loss
Under 8 feet deep 1 inch in 5 minutes
Over 8 feet deep 1/8-inch per foot of depth in 5 minutes
B Vacuum Testing: All incoming and outgoing sewer and service lines shall be plugged, the
plugs restrained and the vacuum tester head placed on the manhole frame and sealed. A
vacuum of 10 inches Hg shall then be drawn on the manhole and the time measured for
the vacuum to drop to 9 inches Hg. This time shall not be less than 40, 50, or 60 seconds
for manhole diameters of 48, 60, and 72 inches respectively. For manholes deeper than
20 feet, the test times shall be increased by 2 seconds per foot of additional manhole
depth.
* * *
If exfiltration of vacuum testing is used, a minimum of 10 percent of the sealed manholes as
chosen by the Engineer shall be tested. Manholes that fail shall be reworked and retested by the
Contractor at no additional compensation. If more than 5 percent of the manholes tested fail the
initial test, an additional 10 percent of the sealed manholes shall be tested. This process will
continue until the testing is satisfactory, or until all manholes have been tested.
Limitation and Considerations: It must be recognized that exfiltration and vacuum testing may be
impractical or cost-prohibitive for all manholes; therefore the use of either method is subject to the
following limitations and considerations.
Complete Sealing: These methods shall be used only when the entire manhole has been sealed
or rehabilitated. The lack of sealing or rehabilitation of some portions of the manhole may prevent
passage of either of these tests. Spot repairs and partial sealing or rehabilitation shall therefore
be subject to infiltration and visual testing only.
Coating or Lining: These methods shall not be used on manholes that have had a cementitious
coating applied or lining installed until the coating or lining has been cured according to the
manufacturer’s recommendations.
Inlet and Outlet Sewers: Manholes built over large diameter sewers may be impractical and
uneconomical to test using either of these methods due to bypassing requirements, availability of
plugs, and high forces that are generated on the plugs. Consideration must be given to these
factors when determining the method of acceptance testing to be used.
Structural Condition: The structural condition of some manholes may be such that testing with
these methods is impractical or destructive. Manholes that have not been structurally lined shall
therefore be deemed as structurally sound by the Engineer and Contractor prior to testing using
these methods.
(7.2) Precast Manhole Sealing Test: Acceptance testing shall be done using the method described in
paragraph 7.1 above.
(7.3) Frame Sealing Test: Manufactured frame seals shall be visually inspected to insure that the
sleeve is properly positioned, tight against the manhole surfaces, that no voids or leakage points
exist under the sleeve and that the bands and locking nuts are tight. This inspection shall be
made prior to backfilling when an external seal is used.
Applied seals shall be visually inspected to insure that they have been applied according to the
manufacturer’s instructions.
Manhole frame sealing shall be randomly tested for leakage using a method approved by the
Engineer. A minimum of 10 percent of the sealed manholes shall be tested. Manholes that fail
shall be reworked and retested by the Contractor at no additional compensation. If more than 5
percent of the manholes tested fail the initial test, an additional 10 percent of the sealed manholes
shall be tested. This process will continue until the testing is satisfactory, or until all manholes
have been tested.
(7.4) Cover Sealing Test: The sealed manhole covers shall be visually inspected to insure that the
bearing surface was properly cleaned and that products were properly sized and installed
according to the manufacturer’s instructions.
Any manholes that are leaking, are visually unacceptable, or fail the test shall be reworked and
retested. The Contractor shall be reimbursed for the cost of this additional work if an inspection
by the Contractor and the Engineer shows that the work performed by the Contractor was not the
reason for the failure of the manhole to pass the leakage test. The Engineer reserves the right to
inspect the sealed manholes during the warranty period. Any leakage or defects in the work
found by this inspection shall be corrected by the Contractor within an agreed-upon time at no
additional cost to the Owner.
