MANHOLES

PART 1 - GENERAL

1.01 SECTION INCLUDES

A. Manholes for sanitary and storm sewers.

B. Adjustment of existing manholes.

C. Connection to existing manholes.

D. Abandonment of manholes.

E. Existing Manhole Rehabilitation

1.02 DESCRIPTION OF WORK

A. Construct sanitary and storm sewer manholes, modify existing manholes, and abandon manholes where shown on the plans.

B. Rehabilitate existing manholes to waterproof and prevent inflow and infiltration, prevent corrosion, or reestablish the structural integrity of the manhole. Includes construction of structural liners, protective liners, and chimney seals.

C. Reference is made to the Iowa Department of Transportation Standard Specifications for Highway and Bridge Construction, Series 2001, and all current General Supplemental Specifications and Materials Instructional Memorandum by the term "Iowa DOT Specifications" and/or " Iowa DOT I.M."

1.03 SUBMITTALS

A. Submit under provisions of Division 1.

B. Shop drawings showing compliance with this Specification.

C. Shop drawing schedule of new manholes showing total depth, relative elevations of all connecting sanitary or storm sewer lines, all drops, and orientation of connecting lines.

D. Catalog cuts of iron castings, chimney seals, and sewer line connection gaskets.

E. Upon requests, the Contractor will provide Material Certifications to the Jurisdictional Engineer.

1.04 SUBSTITUTIONS

A. Use only materials conforming to these specifications unless otherwise allowed by the Jurisdictional Engineer.

B. Obtain written approval of Jurisdictional Engineer for all substitutions prior to use.

1.05 DELIVERY, STORAGE, AND HANDLING

A. Deliver only materials that fully conform to these specifications or for which submittals have been provided to the Jurisdictional Engineer and approved for use.

B. Store and handle materials to avoid damage. Replace any damaged materials. Remove damaged materials from the site.

1.06 SCHEDULING AND CONFLICTS

A. Construction Sequence:

1. Attend a preconstruction meeting if required by the Jurisdictional Engineer.

2. Submit plan for construction sequence and schedule prior to commencing construction.

B. Conflict Avoidance:

1. Expose possible conflicts in advance of construction, such as utility lines and drainage structures. Verify elevations and locations of each and verify clearance for proposed construction.

2. Complete elements of the work that can affect line and grade in advance of other open cut construction unless noted on the plans.

3. Notify the Jurisdictional Engineer of conflicts discovered or changes needed to accommodate unknown or changed conditions.

1.07 SPECIAL REQUIREMENTS

A. Stop work and notify Jurisdictional Engineer immediately if contaminated soils, historical artifacts, or other environmental or historic items are encountered.

B. Conform to local, state, and federal requirements.

1.08 MEASUREMENT FOR PAYMENT

All measurements for payments will be made by the Jurisdictional Engineer or authorized representative.

A. Manhole: One of the following methods will be specified:

1. Manhole by Lump Sum: Count the number of new manholes properly installed. Payment will be at the unit price for each type and size of manhole properly installed. The unit price for manholes will include all excavation, bedding, backfill, compaction, concrete, reinforcing steel, and all appurtenances, including chimney seals, castings, and covers, necessary for proper installation.

2. Manhole by Vertical Feet: For new manholes properly installed, count the number of combined base and casting units for each size and type. In addition, measure the manhole vertical dimension in feet from the flowline to the bottom of the casting. Payment will be at the unit price for each combined base and casting unit properly installed. In addition, payment will be made by the unit price for the vertical dimension of the manhole.

B. Drop Connection: Measurement of the drop will be in vertical feet, from the flowline of the incoming sewer to the flow line of the drop at its entry into the manhole, for each size of sewer line. Payment will be at the unit bid price for vertical feet of the drop per size of sewer line.

C. Casting Extension Rings: Count the number of existing manhole castings raised with casting extension rings to match the elevation of a pavement overlay. Payment will be made at the unit price for each casting extension.

D. Manhole Adjustment, Minor: Removal or addition of manhole adjusting rings are considered an incidental item to manholes, unless otherwise specified as a pay item in the contract documents. If specified as a pay item, it will be at the unit price bid for each adjustment. If so specified, count the number of manholes adjusted to finished grade by raising or lowering an adjustable casting or by addition or removal of manhole adjusting rings. Whether specified as a pay item or not, new casting is included.

E. Manhole Adjustment, Major: Count the number of manholes adjusted to grade by addition or removal of manhole riser, cone or flat top sections, or the exchange of existing sections with sections having different vertical dimensions. Payment will be at the price for each major adjustment. The unit price will include all excavation, bedding, backfill, compaction, concrete, reinforcing steel, and all appurtenances, including the new casting and new chimney seal.

F. Connection to Existing Manhole: Count the number of connections made to existing manholes. Payment will be at the unit bid price for each connection.

G. Abandoned Manhole: Count the number of manholes abandoned in place. Payment will be at the unit bid price for each abandoned manhole.

H. In Situ Manhole Replacement, Formed-In-Place Concrete: Measurement of the vertical dimension of in situ manhole replacement will be from the manhole invert to the bottom of the frame. Payment will be at the unit price per vertical foot. When a plastic liner is specified, the installation will be measured and paid separately from those without a liner. The unit price includes handling of sewer flows as required to properly complete the installation, bench and invert overlay as recommended by the manufacturer, and testing the manhole upon completion. In addition, the unit price for installations with a plastic liner includes sealing at the frame and cover and sealing pipe penetrations as recommended by manufacturer.

I. Manhole Lining with Centrifugally Cast Cementitious Mortar Liner with Epoxy Seal: For each liner thickness specified, measurement of the vertical dimension of manhole lining will be from the bottom of the lining to the top of the lining. Payment will be at the unit price per vertical foot for each thickness of liner properly installed. The unit price includes the handling of sewer flows during lining operations as required to properly complete the installation.

J. Install Chimney Seal on Existing Manhole: Count the number of manhole chimney seals installed on existing manholes. Payment will be made at the unit price for each chimney seal installed.

PART 2 - PRODUCTS

2.01 CONCRETE MANHOLE COMPONENTS

A. Cast Concrete:

1. Precast: Comply with ASTM C 478

2. Cast-in-place: See Section 6010.

B. Riser Sections:

1. Inside Diameter: Use a 48-inch diameter riser or as shown in the contract documents.

2. Wall Thickness: See Figures 6020.1 through 6020.21. For precast, see ASTM C 478.

3. Coating:

a. Exterior:
1) Sanitary Sewer Manholes: When exterior waterproof coating is specified, provide bituminous or coal tar coating.
2) Storm Sewer Manholes: Exterior coating is not required.
b. Interior:
1) Sanitary Sewer Manholes: When manhole lining is specified, line according to lined, reinforced concrete pipe, Section 4010, 2.01.
2) Storm Sewer Manholes: Interior coating is not required.

4. Riser Joints:

a. Male and female ends.
b. Sanitary Sewer Manhole Joint Sealant:
1) Rubber 'O' ring or profile gasket, flexible joint, per ASTM C 443.
2) Bituminous joint compound or butyl sealant wrap per ASTM C 877 to all exterior joints.
c. Storm Sewer Manhole Joint Sealant:
1) Bituminous Jointing Material: use a cold applied mastic sewer joint sealing compound recommended by the manufacturer for the intended use and approved by the Jurisdictional Engineer. Meet the requirements of AASHTO M 198.
2) Rubber Rope Gasket Jointing Material: Conform to ASTM C 990.

5. Lift Holes: Lift holes not to protrude through manhole wall. Provide non-shrink grout to cover lift hole plug and to fill interior joints.

C. Top Configuration:

1. Capable of supporting HS-20 loading.

2. Use eccentric cone, unless otherwise specified or allowed.

D. Base:

1. Sanitary Sewer:

a. Type A (Standard Precast Manhole: Integral base and lower riser section according to ASTM C 478.

b. All Other Manholes: Cast-in-place concrete base.

2. Storm Sewer:

Use precast or cast-in-place base.

E. Pipe Connection:

1. New Sanitary Sewer Manhole:

a. Flexible, watertight gasket per ASTM C 923.

b. Install drop connection where required on the plans. See also Figure 6020.6A.

c. Use non-shrink grout on internal joint space.

2. New Storm Sewer Manhole:

a. Precast Manholes: Fabricated openings.

b. Cast-in-Place Structures: Structure wall placed around pipe stub.

3. Existing Sanitary Manhole:

a. Cored or Drilled Opening: Provide a flexible, watertight connection that meets and/or exceeds ASTM C 923

b. Knock out Opening: See Figure 6020.21

4. Existing Storm Sewer Manhole: See Figure 4020.1A.

F. Manhole Steps:

1. Comply with ASTM C 478.

2. Manufactured of polypropylene encased steel.

3. Uniformly space steps at 12 to 16 inches.

4. Align with vertical side of eccentric top section

5. First step no more than 36 inches from top of casing.

G. Manhole Types:

Sanitary
Sewer		 Figure
No.		 Type Description
6020.1 A 48" minimum diameter riser with eccentric cone and integral precast base
6020.2 E Cast-in-place box
6020.3 F Combination cast-in-place manhole with 48" diameter lower riser and eccentric cone
6020.4 I 48" diameter riser with eccentric cone and castin-place base for manhole placement on existing sewer
6020.5 J 48" diameter riser with eccentric cone and
T-section
Storm
Sewer		 6020.12 M-A 48" minimum diameter short cone or flat top with cast-in-place or precast base
6020.13 M-B Precast or cast-in-place box with precast or cast-in-place base
6020.14 M-C Cast-in-place box with cast-in-place base
6020.15 M-D Combination 48" diameter short cone with
cast-in-place riser and cast-in-place base
6020.16 M-E 48" diameter short cone with T-section

2.02 MANHOLE ADJUSTMENT RINGS (Grade rings)

A. Utilize one of the following methods for grade adjustments of manhole frame and cover assemblies:

1. Reinforced Concrete Grade Adjustment Rings: Comply with ASTM C 478 and be free from cracks, voids, and other defects. Set concrete rings with asphalt mastic in trowelable or rope form.

2. High Density Polyethylene Grade Adjustment Rings:

Property Test Method Acceptable Value
Recycled Plastic ASTM D 1248 N/A
Melt Flow Index ASTM D 1238 0.3 to 30 g / 10 min.
Density ASTM D 792 0.94 to 0.98 g / cm3
Tensile Strength ASTM D 638 2.00 to 5 x 103 lb / in2

a. Tapered adjusting ring thickness ranges from 1/2 inch to 3 inches.

b. Install grade adjustment rings on clean, flat surfaces according to the manufacturer's recommendations with the proper butyl rubber sealant/adhesives.

c. Do not use polyethylene adjusting rings when they are exposed to HMA pavement.

B. Ensure the inside diameter of the adjustment ring is not be less than the inside diameter of the manhole frame.

C. Construct manholes with at least one adjustment ring, totaling 4 inches minimum and 12 inches maximum for new manholes and 4 inches minimum and 16 inches maximum for existing manholes.

2.03 CASTINGS (Ring, Cover, and Extensions)

A. Gray Cast Iron: ASTM A 48, Class 35.

B. Casting Types:

  Figure
No.		 Casting
Type		 Ring
Cover		 Gasket Bolted Cover
(Floodable)		 Typical Surface
Sanitary
Sewer		 6020.7 A STD Yes1 No Non-paved/flexible2
6020.8 B ADJ Yes1 No PCC3
6020.9 C STD Yes1 Yes Non-paved/flexible2
6020.10 D ADJ Yes1 Yes PCC3
Storm
Sewer		 6020.17 E STD No N/A Non-paved/flexible2
6020.18 F ADJ No N/A PCC3
1 Machine bearing surfaces required.
2 Includes HMA, seal coat, gravel, and brick.
3 Includes castings in concrete boxouts.

C. Manhole Casting Extension Ring:

1. Gray cast iron conforming to ASTM A 48, Class 35.

2. Size the extension ring to fit the existing ring and cover.

3. Maximum height of 3 inches.

4. Match the dimensions of the existing ring and cover with an allowable diameter tolerance of -1/4 inch for the frame ridge and +1/4 inch for the cover recess.

5. The height of the extension ring as required to raise the top of the casting to make it level or no more than 1/4 inch below the finished pavement surface.

2.04 CEMENT MORTAR - Comply with Section 6010.

2.05 REINFORCING STEEL - Comply with Section 6010.

2.06 CHIMNEY SEAL (For New Sanitary Sewer Manholes and Sanitary Sewer Manhole Adjustments)

A. External Rubber Seal:

1. Rubber Sleeve and Extension:

a. Corrugated, minimum thickness of 3/16 inches, per ASTM C 923.

b. Minimum allowable vertical expansion of at least 2 inches.

c. See Figure 6020.1, sheet 2, for dimensional requirements.

2. Compression Bands:

a. One piece band assembly to compress sleeve or extension against manhole and casting surfaces.

b. 16 gauge ASTM A 240, Type 304 stainless steel, minimum 1 inch width, minimum adjustment range of 4 inches more than the manhole outside diameter.

c. For standard twopiece castings, top band shaped to lock sleeve to manhole frame's base flange. For three-piece adjustable castings, top band shaped to lock sleeve to upper piece of adjustable frame.

d. Stainless steel fasteners conforming to ASTM F 593 and 594, Type 304.

B. Internal Rubber Seal:

1. Rubber:

a. Double pleated, minimum thickness 3/16 inch thick, per ASTM C 923.

b. Minimum allowable vertical expansion of at least 2 inches.

c. Integrally formed expansion band recess top and bottom with multiple sealing fins.

d. See Figure 6020.1, sheet 2, for dimensional requirements.

2. Expansion Bands:

a. One-piece band assembly to compress sleeve or extension against manhole and casting surfaces.

b. 16 gauge ASTM A 240, Type 304 stainless steel, minimum 1-3/4 inch width, minimum adjustment range of 2 inches more than the manhole inside diameter.

c. Locking mechanism of studs and nuts used to be stainless steel conforming to ASTM F 923 and ASTM F 594, Type 304.

2.07 INVERT

A. Construct manhole invert up to one-half of pipe diameter to produce a smooth half pipe shape between pipe inverts. Slope invert bench toward pipe 1/4 inch per foot perpendicular to flow line.

B. Use a precast invert on all precast base sections, unless otherwise allowed by the Jurisdictional Engineer. See Figure 6020.1

2.08 MANHOLE REHABILITATION

A. Chimney Seals (For Manhole Rehabilitation):

1. Rubber chimney seals as specified in Section 6020, 2.06

2. Brush Applied Urethane Chimney Seal:

Property Test Method Acceptable Value
Elongation ASTM D 412 800%, minimum
Tensile Strength ASTM D 412 1150 psi, minimum
Adhesive Strength ASTM D 903 175 lb/in, minimum
Pressure Resistance ASTM C 1244 2 minutes

B. Manhole Interior:

1. In Situ Manhole Replacement, Formed-In-Place Concrete:

a. Forming System: Provide an internal forming system capable of forming a new and structurally independent manhole wall within the existing manhole, with the specified thickness, and conforming to the general shape of the existing manhole.

b. Concrete: Type I/II portland cement concrete with 5/8 inch minus coarse aggregate with fiber reinforcement and water reducer, 4000-psi minimum 28-day compressive strength.

c. Plastic Liner: When specified, provide a PVC or PE plastic liner resistant to degradation by sulfuric acid. Use a liner capable of being attached to the exterior of the forming system during erection of the forms. Use a plastic liner with a ribbed or studded exterior surface suitable for anchoring to the newly formed interior wall.

2. Centrifugally Cast Cementitious Mortar Liner with Epoxy Seal:

a. Cementitious Lining:

1) Use a high strength, high build, corrosion resistant mortar, based on portland cement fortified with micro silica. Mixed mortar to have a paste-like consistency that may be sprayed, cast, pumped, or gravity-flowed into any area 1/2 inch and larger.

2) Exhibits the following properties:

Property Value
Unit Weight 125 pcf
Set Time at 70°F ASTM C 403
          Initial Set / Final Set
240 minutes / 440 minutes
Modulus of Elasticity ASTM C 469
            24 hours / 28 days
180,000 psi / 1,150,000 psi
Flexural Strength ASTM C 293
          24 hours / 28 days
650 psi / 800 psi
Compressive Strength ASTM C 109
          24 hours / 28 days
3,000 psi / 10,000 psi
Tensile Strength ASTM C 307 600 psi
Shear Bond ASTM C 882 >1,000 psi
Shrinkage ASTM C 157 None
Chloride Permeability ASTM C 1202 <550 Coulombs

3) Contains a liquid admixture for the prevention of micro biologically induced corrosion. The admixture permeates the mortar during the mixing phase and molecularly bonds to the cement particles, creating an environment incompatible to the growth of bacteria that may be harmful to concrete.

b. Corrosion Resistant Epoxy Lining:

1) Consists of a two-component 100% solids epoxy design formulated for use in sewer systems. The epoxy lining forms a protective layer impervious to biological corrosion.

2) Physical Properties:

Property

 Value
Dry Time 4-6 hours @ 75oF
Compressive Strength ASTM D-695 16,800 psi
Flexural Strength ASTM D-790 13,900 psi
Tensile Strength ASTM D-638 12,400 psi
Hardness ASTM D-2240 68-72 Shore D
Heat Distortion ASTM D-648 220oF
Ultimate Elongation ASTM D-638 4.5%
Adhesive Shear ASTM C-882 1,000 psi

PART 3 - EXECUTION

3.01 MANHOLE INSTALLATION

A. Excavation: Excavate according to Section 3010.

B. Subgrade Preparation:

1. Undisturbed Soil: Hand grade to accurate elevation.

2. Disturbed Soil: Machine compact to 95% of maximum Standard Proctor Density and hand grade to accurate elevation or install stabilization material as directed by the Jurisdictional Engineer.

C. Installation of Cast-in-Place Base:

1. Excavate and prepare subgrade to the required elevation to accommodate the cast-in-place base.

2. Plae Class C concrete base as specified.

3. Embed lower riser section in base concrete a minimum of 3 inches.

4. Ensure proper vertical and horizontal alignment of base riser section.

D. Installation of Precast Base with Base Riser Section:

1. Excavate and prepare subgrade to the required elevation to accommodate the aggregate subbase.

2. Place aggregate subbase as specified.

3. Place base with lower riser section and ensure vertical and horizontal alignment.

E. Additional Risers Sections: Install additional riser sections as required.

F. Repairs: Repair any honeycomb areas or damaged areas as directed by the Jurisdictional Engineer.

G. Pipes: Install and bed pipes. Place bedding and pipe embedment material according to Section 3010.

H. Lift Holes: For sanitary sewers, install rubber plug and grout over manhole lift holes.

I. Manhole Invert: Install manhole invert if not precast.If precast, remove any projections and repair any voids to ensure a hydraulically smooth channel between pipe ends.

J. Top Sections: Install manhole cone or flat top section.

K. Manhole Adjustment Ring(s): Bed each concrete ring with cold-applied bituminous jointing compound. Bed each polyethylene ring with manufacturer's approved product. Use a minimum stack height of 4 inches and a maximum adjustment ring stack height of 12 inches. For greater adjustment, modify lower riser section(s).

L. Manhole Ring and Cover: Install manhole ring and cover and accurately adjust to proper grade. Where manhole is to be in a paved area, adjust slope to match finished surface.

M. Chimney Seal: For sanitary sewer manholes, install internal or external rubber chimney seal meeting the requirements of Section 6020, 3.04.

N. Manhole Joint Sealant: Apply bituminous joint compound or butyl sealant wrap to exterior of sanitary sewer manholes joints. If required, apply engineering fabric wrap meeting the requirements of Iowa DOT 4196.01B to storm sewer manhole joints.

O. Backfill and Compaction: Place backfill and compact per Section 3010. Use extra care to ensure proper and uniform compaction of backfill around structure.

3.02 CONCRETE, REINFORCEMENT, AND PLACEMENT - Comply with Section 6010

3.03 MODIFICATION OF EXISTING MANHOLES

A. Casting Extension Rings: Install and adjust for proper alignment.

B. Minor Adjustment (adding or removing adjusting rings):

1. Remove casting.

2. As necessary, add a maximum height of 16 inches of adjustment rings to adjust existing manhole to finished pavement grade or finished topsoil grade. Bed each concrete ring with cold applied bituminous jointing material. Bed each polyethylene ring with manufacturer's approved product.

3. Remove one or more adjustment rings, as appropriate, to reduce casting elevation.

4. Replace casting. Install new frame and cover on modified adjusting ring.

5. Replace chimney seal for sanitary sewer manholes using only new materials.

6. See Sections 7010 and 7020 for additional manhole adjustment requirements in pavement.

C. Major Adjustment (adding or removing riser or cone sections):

1. Remove casting.

2. Remove top.

3. Remove and replace riser section and/or top section, as appropriate.

4. Replace casting. Install new frame and cover.

5. Fasten manholes to castings with bolts.

6. Replace chimney seal for sanitary sewer manholes using only new materials.

D. Connection to Existing Manhole: Unless otherwise specified in the contract documents, or approved by the Jurisdictional Engineer, core all new openings in existing manholes.

1. Excavate as appropriate. Mark manhole riser for point of insertion of added sewer line.

2. Divert flow as necessary. Obtain approval of the diversion plan from the Jurisdictional Engineer. Maintain sewer service at all times unless otherwise permitted by the Jurisdictional Engineer.

3. Carefully core out opening to manhole. Remove existing manhole invert as necessary to install pipe at required elevation and develop hydraulic channel.

4. Cored Opening:

a. Insert flexible watertight connector into new opening.

b. Install and tighten internal expansion sleeve to hold flexible connector in place.

c. Insert pipe through flexible connector and tighten external compression ring.

d. Do not grout opening or pour collar for cored opening with flexible connector.

5. Cut and Chipped Opening (Knockout):

a. When allowed, refer to Figure 6020.21

b. Install waterstop around outside of pipe. Secure in place.

c. Position end of pipe flush with interior wall of manhole and with waterstop located within wall opening.

d. Grout opening between manhole wall and outside of pipe with non-shrink grout.

e. Pour concrete collar around pipe and exterior manhole opening as shown on Figure 6020.21.

6. Reconstruct manhole invert.

7. Bed pipe and place backfill per Section 3010.

3.04 CHIMNEY SEALS

A. Install chimney seals on all sanitary sewer manholes.

B. Rubber Chimney Seals (see Figure 6020.1, sheet 2):

1. Do not install external chimney seal if manhole is exposed to sunlight.

2. Install seals on a smooth sealing surface.

3. All seals extend to 3 inches below the lowest adjusting ring.

4. For standard two-piece castings, seals to extend 2 inches above the flange of the casting. For adjustable three-piece castings, seals to extend 2 inches above the top of the base section of the casting.

5. Use multiple seals, if necessary.

6. Install compression bands (external chimney seal) or expansion bands (internal chimney seal) to lock the rubber sleeve or extension into place and to provide a positive watertight seal. Once tightened, lock the bands into place. Use only manufacturer recommended installation tools and sealants.

C. Flexible Urethane Seal:

1. Use only for manhole rehabilitation, if specified.

2. Prepare the surface according to the manufacturer's recommendations, including sandblasting, pressure washing, sealing leaks or gaps, and drying surface.

3. Apply primer, prepare product, and brush apply a flexible urethane seal to a minimum thickness of 175 mils, covering 2 inches above the bottom of the frame and the entire adjustment ring area to 3 inches below the bottom adjustment ring.

3.05 ABANDONED MANHOLES

A. Unless otherwise specified, remove top and walls of structure to a minimum of 10 feet below subgrade in paved areas or 10 feet below finish grade in other areas.

B. Plug all pipes in structure using 3,000-psi concrete.

C. Fill remaining structure using flowable mortar per Section 3010.

D. Place compacted earth fill over structure as required for embankment or compacted backfill.

3.06 MANHOLE TESTING - Comply with Section 6040.

3.07 MANHOLE REHABILITATION

A. Manhole Chimney: Install manhole chimney seal according to Section 6020, 3.04.

B. Manhole Interior

1. In Situ Manhole Replacement, Formed-In-Place Concrete: Prepare, install, and test according to forming system manufacturer's recommendations including the following items.

a. Preparation:

1) Clean existing surface to remove loose material and debris.
2) Remove existing steps that might interfere with the erection of the forms.
3) Control infiltration that may affect placement of concrete.

b. Installation:

1) Place pipe extensions through structure to maintain flow during installation.
2) Erect forms inside manhole. Include plastic liner when specified.
3) Bolt the assembled internal forms together to prevent shifting and provide sufficient stiffness and strength to prevent collapsing.
4) Seal forms at the bottom of the manhole to ensure the concrete does not enter the sewer.
5) Carefully place concrete between forms and existing manhole walls. Place concrete from bottom up to prevent segregation of concrete.
6) Consolidate concrete as required to fill all pockets, seams, and cracks within the existing manhole wall.
7) Remove forms when the concrete has cured sufficiently.
8) If a plastic liner is installed, weld and test any joints.
9) Apply a sealing strip around circumference of the invert bench where it meets the vertical wall and around all pipe penetrations, to form a waterstop.
10) Overlay the invert bench with concrete or high strength mortar at a thickness of 3 inches at the wall, tapering to 1/2 inch at the edge of the invert.
11) Apply a 100% solid epoxy to the invert bench for corrosion resistance. Apply clean sand to the epoxy to create a non-slip surface.
12) Seal the plastic liner to the manhole casting and existing pipe stubs as recommended by the manufacturer.

2. Centrifugally Cast Cementitious Mortar Liner with Epoxy Seal:

a. Surface Preparation: Prepare the surface according to the manufacturer's recommendations, including washing the interior with a high‑pressure washer and plugging any active leaks with the appropriate sealing material.

b. Mortar Application: Apply according to the manufacturer's recommended procedures including the following items:

1) Apply with a rotating centrifugal casting applicator, beginning at the bottom of the manhole.
2) Retrieve the applicator head at the manufacturer's recommended speed to achieve the desired thickness.
3) Apply to full required thickness utilizing multiple passes as necessary. Minimize the time between passes so subsequent passes are cast against fresh mortar.
4) Verify thickness with a wet gage at several locations to ensure proper depth.
5) Brushing the mortar after application to improve adhesion is optional.
6) Hand apply additional material to the invert bench surface at a thickness of 3 inches, tapering from the wall to the edge of the channel.

c. Epoxy Seal Application: Apply according to the manufacturer's recommended procedures including the following items:

1) Apply with rotating centrifugal casting applicator or airless sprayer onto the fresh mortar liner.
2) If epoxy seal is applied more than 24 hours after application of the mortar lining, or if the mortar lining is exposed to foreign matter, rinse to neutralize its surface and then apply the epoxy.

END OF SECTION