SECTION 6020 - REHABILITATION OF EXISTING MANHOLES
Rehabilitation of existing manholes.
Rehabilitate existing manholes to waterproof and to prevent inflow and infiltration, to prevent corrosion, or to reestablish the structural integrity of the manhole. Includes construction of structural liners, protective liners, and infiltration barriers.
Follow the General Provisions (Requirements) and Covenants as well as the following:
A. Concrete mix design, if required by the Engineer.
B. Catalog cuts of all mortar mixes, sealants, and liners.
Follow the General Provisions (Requirements) and Covenants
1.05 DELIVERY, STORAGE, AND HANDLING
Follow the General Provisions (Requirements) and Covenants.
Follow the General Provisions (Requirements) and Covenants.
None.
1. Rubber Chimney Seal:
a. Measurement: Each rubber chimney seal installed on an existing manhole will be counted.
b. Payment: Payment will be made at the unit price for each chimney seal.
c. Includes: Unit price includes, but is not limited to, all necessary compression or expansion bands and extension sleeves as necessary to complete chimney seal.
2. Molded Shield:
a. Measurement: Each molded shield installed on an existing manhole will be counted.
b. Payment: Payment will be made at the unit price for each molded shield.
c. Includes: Unit price includes, but is not limited to, sealant.
3. Urethane Chimney Seal:
a. Measurement: Each urethane chimney seal installed on an existing manhole will be counted.
b. Payment: Payment will be at the unit price for each urethane chimney seal.
B. In-Situ Manhole Replacement, Cast-in-place Concrete:
1. Measurement: The vertical dimension of in-situ manhole replacement will be measured in feet from the lowest flowline to the top of the rim.
2. Payment: Payment will be at the unit price per vertical foot.
3. Includes: Unit price includes, but is not limited to, handling of sewer flows as required to properly complete the installation, invert overlay as recommended by the manufacturer, replacement of existing casting with a new casting, and testing the manhole upon completion.
C. In-Situ Manhole Replacement, Cast-in-place Concrete with Plastic Liner:
1. Measurement: The vertical dimension of in-situ manhole replacement with plastic liner will be measured in feet from the lowest flowline to the top of the rim.
2. Payment: Payment will be at the unit price per vertical foot.
3. Includes: Unit price includes, but is not limited to, handling of sewer flows as required to properly complete the installation, invert overlay as recommended by the manufacturer, replacement of existing casting with a new casting, sealing at the frame and cover, sealing pipe penetrations as recommended by the manufacturer, and testing the manhole upon completion.
D. Manhole Lining with Centrifugally Cast Cementitious Mortar Liner with Epoxy Seal
1. Measurement: The vertical dimension of manhole lining will be measured for depth in feet from the bottom of the lining to the top of the lining for each liner thickness specified.
2. Payment: Payment will be at the unit price per vertical foot for each liner thickness.
3. Includes: Unit price includes, but is not limited to, the handling of sewer flows during lining operations as required to properly complete the installation, and replacement of the existing casting with a new casting.
A. Rubber Chimney Seal: Comply with Section 6010, 2.11 for external and internal rubber chimney seals.
B. Molded Shield: Comply with Section 6010, 2.11 for molded shields.
C. Urethane Chimney Seal: Comply with the following table for the physical properties.
2.02 In-Situ Manhole Replacement, Cast-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 with 5/8 inch minus coarse aggregate with fiber reinforcement and water reducer, 4,000 psi minimum 28 day compressive strength or as approved by the Engineer.
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.
D. Casting: Provide new casting. Comply with Section 6010, 2.10.
2.03 CENTRIFUGALLY CAST CEMENTITIOUS MORTAR LINER WITH EPOXY SEAL
1. Use a high-strength, high-build, corrosion-resistant mortar, based on Portland cement fortified with micro silica. Mixed mortar is to have a paste-like consistency that may be sprayed, cast, pumped, or gravity-flowed into any area 1/2 inch and larger.
2. Comply with the following table for physical properties.
3. Use a lining containing a liquid admixture for the prevention of micro-biologically induced corrosion.
B. Corrosion-Resistant Epoxy Lining:
1. Use a two-component 100% solids epoxy formulated for use in sewer systems.
2. Comply with the following table for physical properties.
C. Casting: Provide new casting. Comply with Section 6010, 2.10.
A. Rubber Chimney Seal: Comply with Section 6010, 3.01.
B. Molded Shield: Comply with Section 6010, 3.01.
C. Urethane Chimney Seal: Use only when specified in the contract documents.
1. Prepare the surface according to the manufacturer’s recommendations, including sandblasting, pressure washing, sealing leaks or gaps, and drying the surface.
2. Apply primer, prepare product, and brush-apply the 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.
3.02 IN-SITU MANHOLE REPLACEMENT, CAST-IN-PLACE CONCRETE
A. Preparation: Prepare according to the forming system manufacturer's recommendations, including the following:
1. Clean the 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: Install and test according to the forming system manufacturer's recommendations, including the following:
1. Place pipe extensions through the structure to maintain flow during installation.
2. Erect forms inside the manhole. Secure the assembled internal forms to prevent shifting and to provide sufficient stiffness and strength to prevent collapse.
3. Install a plastic liner when specified.
4. Seal the forms at the bottom of the manhole to ensure the concrete does not enter the sewer.
5. Carefully place concrete between the forms and the existing manhole walls. Place concrete from the 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 the forms when the concrete has cured sufficiently.
8. Weld and test joints if a plastic liner is installed.
9. Apply a sealing strip around the circumference of the invert top where it meets the vertical wall and around all pipe penetrations to form a waterstop.
10. Overlay the invert top with concrete or high-strength mortar. Vary thickness from 3 inches at the wall to 1/2 inch at the edge of the channel.
11. Apply an epoxy lining to the invert top. 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.
13. Install new casting.
3.03 CENTRIFUGALLY CAST CEMENTITIOUS MORTAR LINER WITH EPOXY SEAL
A. Surface Preparation: Prepare according to the manufacturer’s recommendations, including the following:
1. Wash the interior with a high‑pressure washer.
2. Plug active leaks with the appropriate sealing material.
B. Mortar Application: Apply according to the manufacturer’s recommendations, including the following:
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 the 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 gauge at several locations to ensure proper depth.
5. Hand-apply high-strength mortar to the invert surface. Vary thickness from 3 inches at the wall to 1/2 inch at the edge of the channel.
C. Epoxy Seal Application: Seal according to the manufacturer’s recommendations, including the following:
1. Apply with a rotating centrifugal casting applicator or airless sprayer onto the fresh mortar liner.
2. If the epoxy seal is applied more than 24 hours after application of the mortar liner, or if the mortar liner is contaminated, clean the liner and then apply the epoxy.
D. Finishing: Install a new casting.
3.04 CLEANING, INSPECTION, AND TESTING
Comply with Section 6030 for in-situ manhole replacement and centrifugally cast mortar lined rehabilitation.
END OF SECTION