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    SECTION 02765

    SANITARY SEWER MANHOLE REHABILITATION

   PART 1 - GENERAL

   1.1 SECTION INCLUDES

   A. Sanitary sewer manhole rehabilitation including:

   1. Rehabilitation and leak-proofing of manholes by lining with spray applied or centrifugally cast lightweight structural reinforced concrete, or spray applied urethane or epoxy resin systems - Level B.

   2. The repair and sealing of the manhole base, invert, walls, corbel/cone, and chimney of brick, block, or precast manholes, including the removal of any unsound material.

   3. The inspection and testing of the various types of work to insure compliance.

   B. All existing manholes connected to sewer segments being relined according to Section 02766 shall receive a minimum of Level B rehabilitation.

   1.2 LINING SYSTEMS

   A. The lining system used shall result in a monolithic structure to the shape and contour of the interior of the existing manhole. The lining system shall be completely water tight and free of any joints or openings other than pipe inlets, pipe outlets and the rim opening. The junction of the lining material with the pipe material at the inlets and outlets shall be watertight.

   B. Lining system shall be of the type that allows rehabilitation of a concentric, eccentric or flat top manhole without removing the manhole ring and top section or corbel.

   1.3 SUBMITTALS

   A. Submit the following as required in Section 01340 at least 14 days prior to starting manhole rehabilitation:

   1. Manufacturers’ Certificate of Compliance certifying compliance with the applicable specifications and standards. The certifications shall list all materials furnished under this Section.

   2. Certified copies of test reports of factory tests required by the applicable standards, the manufacturer, and this Section.

   3. Manufacturer's handling, storage, and installation instructions and procedures.

   4. Recommended lining thickness design to withstand groundwater pressure as specified in Part 3 of this Section.

   PART 2 - PRODUCTS

   2.1 MATERIALS

   A. General:

   1. The materials used shall be designed, manufactured and intended for sewer manhole rehabilitation and the specific application in which they are used. The materials shall have a proven history of performance in sewer manhole rehabilitation. The materials shall be delivered to the job site in original unopened packages and clearly labeled with the manufacturer's identification and printed instructions. All materials shall be stored and handled in accordance with recommendations of the manufacturer. All materials shall be mixed and applied in accordance with the manufacturer's written instructions.

   2. The Contractor shall warrant and save harmless the Owner and his Engineer against all claims for patent infringement and any loss thereof.

   3. Handle and store all materials and dispose of all wastes in accordance with applicable regulations.

   4. Each lining system shall be designed for application over wet surfaces (but not active running water) without degradation of the final product and/or the bond between the product and the manhole surfaces.

   B. Stopping active leaks in concrete and masonry manholes:

   1. A premixed fast-setting, volume-stable waterproof cement plug consisting of hydraulic cement, graded silica aggregates, special plasticizing and accelerating agents. It shall not contain chlorides, gypsums, plasters, iron particles, aluminum powder or gas-forming agents, or promote the corrosion of steel it may come in contact with. Set time shall be approximately 1 minute. Ten-minute compressive strength shall be approximately 500 psi.

   2. A siliconate-based liquid accelerator field mixed with neat Portland cement. The set time shall be approximately 1 minute.

   3. The elastomeric polyurethane resin-soaked method, using dry twisted jute oakum, or resin-rod with polyurethane resin (water activated).

   C. Patching, repointing, filling, and repairing nonleaking holes, cracks, and spalls in concrete and masonry manholes:

   1. A premixed nonshrink cement-based patching material consisting of hydraulic cement, graded silica aggregates, special plasticizing and accelerating agents, which has been formulated for vertical or overhead use. It shall not contain chlorides, gypsums, plasters, iron particles, aluminum powder, or gas-forming agents or promote the corrosion of steel it may come into contact with. Set time (ASTM C-191) shall be less than 30 minutes. One-hour compressive strength (ASTM C-109) shall be a minimum of 200 psi and the ultimate compressive strengths (ASTM C-882-Modified) shall be a minimum of 1700 psi.

   D. Spray applied or centrifugally cast lightweight structural reinforced cement manhole lining (Level B):

   The material applied to the surface of the manhole (similar to Strong Seal MS-2, Permacast CR-5000, or Quadex QM-1S) shall be a cementitious blend of acid resistant binders, silicious aggregates, non-metallic fibers and other additives for constructing a liner that is impervious to the flow of water, is resistant to sulfide attack, and restores structural integrity to existing manhole walls.

   2. A monolithic liner shall be formed which covers all interior manhole surfaces and shall have the following minimum requirements at 28 days:

   a. Compressive Strength (ASTM C-579B) 3000 psi

   b. Tensile Strength (ASTM C-496) 300 psi

   c. Flexural Strength (ASTM C-293) (Modified) 600 psi

   d. Shrinkage (ASTM C-596) 0% at 90% R.H.

   e. Bond (ASTM C-321) 130 psi

   f. Density, when applied 105± pcf

   E. Spray applied urethane or epoxy resin system manhole lining (Level B):

   1. The material sprayed onto the surface of the manhole shall be a urethane (similar to Sprayroq) or epoxy resin (similar to Raven 405) system formulated for application within a sanitary sewer environment. The resin will exhibit suitable corrosion resistance and enhance the structural integrity of the existing manhole.

   2. The cured urethane or epoxy resin system shall conform to the following minimum structural standards:

   TEST

   CURED URETHANE METHOD RESULTS

   Tensile Stress ASTM D-638 5,000 psi

   Flexural Stress ASTM D-790 10,000 psi

   Flexural Modulus ASTM D-790 550,000 psi

   PART 3 - EXECUTION

   3.1 REHABILITATION OF MANHOLE STRUCTURE

   A. General Procedures:

   1. Safety: The Contractor shall perform all work in strict accordance with all applicable OSHA, TOSHA, and manufacturer’s safety standards. Each method of manhole rehabilitation in this Section requires some degree of manhole entry by workers. Particular attention is drawn to those safety requirements regarding confined space entry and respiratory protection from airborne particulate materials during cleaning and product mixing and application.

   2. Cleaning: All concrete and masonry surfaces to be rehabilitated shall be clean. All grease, oil, laitance, coatings, loose bricks, mortar, unsound brick or concrete and other foreign materials shall be completely removed. Water blasting utilizing a 210° F steam unit and proper nozzles shall be the primary method of cleaning; however, other methods such as wet or dry sandblasting, acid wash, concrete cleaners, degreasers or mechanical means may be required to properly clean the surface. All surfaces on which these methods are used shall be thoroughly rinsed, scrubbed, and neutralized to remove cleaning agents and their reactant products. Debris resulting from cleaning shall be removed from the manhole and not allowed to be carried downstream.

   3. Stopping Infiltration: After surface preparation and prior to the application of mortars and coatings, infiltration shall be stopped either by plugging with a water stop compound or chemical grout sealing.

   4. Patching: All large holes or voids around steps, joints or pipes, all spalled areas and all holes caused by missing or cracked brick shall be patched and all missing mortar repointed using a nonshrink patching mortar. All cracked or disintegrated material shall be removed from the area to be patched or repointed, exposing a sound subbase. All cracks not subject to movement and greater than 1/16 inch in width shall be routed out to a minimum width and depth of 1/2 inch and patched with nonshrink patching mortar.

   5. Flow Control: The Contractor shall be responsible for plugging or diverting the flow of sewage as needed for repair and lining of manhole inverts and benches. Sewer flow shall be maintained in accordance with Section 02767 of these Specifications.

   6. Remove all loose grout and rubble from existing channel. Rebuild channel if required by reshaping, repairing slope of shelves or benches. Work shall include aligning inflow and outflow ports in such a manner as to prevent the deposition of solids at the transition point. All inverts shall follow the grades of the pipe entering the manhole. Changes in direction of the sewer and entering branch or branches shall have a true curve of as large a radius as the size of the manhole will permit, but will be shaped to allow easy entrance of maintenance equipment including buckets, T.V. camera, etc.

   7. Manhole steps: Inspect all manhole steps prior to rehabilitation. Report to the Engineer any steps which appear loose, deteriorated, broken, or otherwise unsafe. Unless directed otherwise, cut all loose, deteriorated, broken, or otherwise unsafe steps from the manhole.

   8. Each lining system shall be installed in accordance with the manufacturer's recommendation to withstand groundwater pressures. For manholes greater than 12 feet in depth, the lining shall withstand the pressures associated with a groundwater depth equal to the manhole depth. Linings for all other manholes shall withstand the pressures associated with groundwater depth of 12 feet. Measure groundwater depth from manhole bench to top of ground surface.

   9. Application of Level B products shall be by factory certified applicators.

   3.2 SPRAY APPLIED LIGHTWEIGHT STRUCTURAL REINFORCED CEMENT (LEVEL B)

   A. The surface prior to spraying shall be damp without noticeable free water droplets or running water. Materials shall be spray-applied to a minimum uniform thickness to insure that all cracks, crevices, and voids are filled and a somewhat smooth surface remains after light troweling. The light troweling is performed to compact the material into voids and to set the bond.

   B. The first application shall have begun to take an initial set (disappearance of surface sheen which could be 15 minutes to 1 hour depending upon ambient conditions) before the second application to assure a minimum total finished thickness of 1/2 inch. The final finished thickness may need to be greater than 1/2 inch as recommended by the manufacturer to withstand groundwater pressures. A depth gauge shall be used during application, at various locations, to verify the required thickness. The surface then shall be trowelled to smooth finish with care taken not to over trowel so as to bring additional water to the surface and weaken it. Manufacturer's recommendations shall be followed whenever more than 24 hours have elapsed between applications.

   C. The bench covers used to catch debris shall be removed and the bench and invert sprayed such that a gradual slope is produced from the walls to the invert with the thickness at the edge of the invert being no less than 1/2 inch. The wall-bench intersection shall be rounded to a uniform radius the full circumference of the intersection.

   D. No application shall be made to frozen surfaces or if freezing is expected to occur within the manhole for 24 hours after application. If ambient temperatures are in excess of 95° F, precautions shall be taken to keep the mix temperature at time of application below 90° F, using ice if necessary.

   E. The final application shall have a minimum of four (4) hours cure time before being subjected to active flow.

   3.3 CENTRIFUGALLY CAST STRUCTURAL REINFORCED CEMENT (LEVEL B)

   A. The rotating casting applicator shall be positioned to evenly apply the material and be withdrawn at a rate to assure a final minimum thickness of 1/2-inch. The final finished thickness may need to be greater than 1/2-inch as recommended by the manufacturer to withstand groundwater pressures. A depth gauge shall be used during application, at various locations, to verify the required thickness.

   B. The bench covers used to catch debris shall be removed and the bench and invert sprayed or hand applied so that a gradual slope is produced from the walls to the invert with the thickness at the edge of the invert being no less than 1/2-inch. The wall-bench intersection shall be rounded to a uniform radius the full circumference of the intersection.

   C. No application shall be made to frozen surfaces or if freezing is expected to occur within the manhole for 24 hours after application. If ambient temperatures are in excess of 95° F, precautions shall be taken to keep the mix temperature at time of application below 90° F.

   D. The final application shall have a minimum of one (1) hour cure time before being subjected to active flow.

   3.4 SPRAY APPLIED URETHANE RESIN SYSTEM (LEVEL B)

   A. The urethane shall be sprayed onto the surfaces of the manhole walls, the benches, and invert to produce a smooth coating and yield the required structural integrity and corrosion resistance. A depth gauge shall be used during application at various locations to verify the required thickness.

   B. The urethane resin shall be applied to a minimum thickness of 0.25 inches at the top of the manhole and gradually thickened, in accordance with manufacturer's recommendations, to withstand groundwater pressures.

   C. The sloped surface of the manhole bench shall be made non-skid by broadcasting aluminum oxide, or sand into the surface prior to gelatin/set.

   3.5 SPRAYED APPLIED EPOXY RESIN SYSTEM (LEVEL B)

    A. The epoxy resin shall be sprayed onto the surfaces of the manhole walls, the benches, and invert to produce a smooth coating and yield the required structural integrity and corrosion resistance. A depth gauge shall be used during application at various locations to verify the required thickness.

   B. The epoxy resin shall be applied to a minimum thickness of 0.125 inches at the top of the manhole and gradually thickened, in accordance with manufacturer's recommendations, to withstand groundwater pressures. The application shall have a minimum of three hours cure time before being subjected to active flow.

   C. The sloped surface of the manhole bench shall be made non-skid by broadcasting aluminum oxide, or sand into the surface prior to gelatin/set.

   3.6 MANHOLE REHABILITATION ACCEPTANCE

   A. Test all rehabilitated manholes using the vacuum test method, following the manufacturer's recommendations for proper and safe procedures. Vacuum testing of manholes and structures shall be performed after curing of linings. Any visible leakage in the manhole or structure, before, during, or after the test shall be repaired regardless of the test results.

   B. All pipes for vacuum testing entering the manhole shall be installed at the top access point of the manhole. A vacuum of 10 inches of mercury (Hg) (5.0 psi) shall be drawn on the manhole, and the time shall be measured for the vacuum to drop to 9 inches of mercury (Hg) (4.5 psi). Manholes will be considered to have failed the air test if the time to drop 1 inch of mercury is less than what is shown in the following table.

    Vacuum Test Timetable

    Manhole Diameter - Inches

   Depth - feet 48 inches 60 inches 72 inches 96 inches

   4 30 sec. 30 sec. 30 sec. 30 sec.

   8 30 sec. 30 sec. 32 sec. 38 sec.

   12 30 sec. 39 sec. 48 sec. 57 sec.

   16 40 sec. 52 sec. 64 sec. 76 sec.

   20 50 sec. 65 sec. 80 sec. 95 sec.

   24 60 sec. 78 sec. 96 sec. 114 sec.

   + Each 2' +5 sec. +6.5 sec. +8.0 sec. +9.5 sec.

   C. Manhole depths shall be rounded to the nearest foot. Intermediate values shall be interpolated. For depths above 24 feet, add the values listed in the last line of the table for each 2 feet of additional depth.

   D. If the manhole or structure fails the vacuum test, the Contractor shall perform additional repairs and repeat the test procedures until satisfactory results are obtained.

   E. After the manhole rehabilitation work has been completed, the manhole shall be visually inspected by the Contractor in the presence of the Owner's Representative and the work shall be accepted if found satisfactory to the Owner's Representative. The finished surface shall be free of blisters, "runs" or "sags" or other indications of uneven lining thickness. No evidence of visible leaks shall be allowed. In addition, at the Owner's request, the Contractor may be required within two years to visually inspect the manholes that were rehabilitated. Any work that has become defective within the two year period shall be redone by the Contractor at no additional expense to the Owner.

    END OF SECTION

Rembco Geotechnical Contractors specializes in slope stabilization, foundation repair and support, shoring, grouting, soil nails, micropile installations, and sinkholes. We are experienced in these applications: micro piles, sinkhole repair, permeation grouting, pressure grouting, soil nails, chemical grouting, micropiles, compaction grout, rock anchors and compaction piles. Our specialties are rock anchor, chemical and compaction grouting, mini piles, sinkhole repair, micropiles, and soil nailing. We use a problem-solving approach in the geotechnical portions of buildings, bridges, water plants, sewage plants, tunnels, sinkholes, caisson, and roads. Rembco techniques apply when adding new real estate structures: especially rock anchor, microfine grouting, soil nailing, micropile installations for foundation support. Add URL Construction, Drilling and Concrete