00490.00 402 Secti on 00490 - Work on Existing Sewers and Structures
Description
00490.00Scope - This Work consists of joining new Work to existing work, repairing or abandoning
of sewer lines and Structures, and adjusting existing manholes, inlets, boxes and other similar Structures. Remove and dispose of pipe, manholes and catch basins that are scheduled for removal according to Section 00310.
00490.01Descriptive Terms :
Adjust - To raise, lower or reconstruct Structures to a new top elevation flush with the surrounding surface.
Box - Valve box, meter box, monument box or other similar Structure with a removable cover. Bypass Pumping - The process of pumping sanitary sewer or storm flows around a manhole or pipeline during the construction or rehabilitation of those facilities.
Inlet - Structure designed to receive surface water through a grate or orifice and to discharge water through pipes.
Manhole - Manhole or similar Structure designed to permit entry and working space, usually at intersections of sewer pipes.
Manhole Neck - The upper portion of a manhole, having vertical walls and a uniform diameter or dimension just sufficient to receive and support the metal frame.
Materials
00490.10Materials - Furnish Materials of either existing materials in a condition suitable for r euse
and meeting current design, or new Materials meeting the following requirements:
Joint Materials ..................................................... 02440.40, 02440.50, 02440.60 Metal Frames, Covers, Grates, and Steps ............................................ 02450.30 Reinforcement ....................................................................................... 02510.10
00490.11High Early Strength Concrete - Furnish high early strength concrete meeting the
requirements of C ommercial Grade Concrete, except it shall contain a minimum of 705 pounds per cubic yard of Type III or Type IIIA cement or an approved Type C or Type E admixture with a minimum of 592 pounds per cubic yard of Type I or Type II cement.
Construction
00490.40General - Excavate and backfill according to Section 00405. Remove and dispose of old
concrete and other materials ac cording to Section 00310.
Obtain approval before reusing salvaged metal frames, covers, grates and fittings on Structures to be adjusted.
When concrete is poured around frames, paint the portion of the frame that will contact the concrete with hot asphal t before the concrete is poured.
00490.41 403 Provide high early strength concrete when shown, or when traffic is required to traverse the Structure due to staging requirements. The Engineer will determine the length of curing time.
New construction shall conform to Section 00470.
Repair, replace or restore to existing condition any manhole or similar structure backfill, inlet base drain, Aggregate Base or Pavement disturbed or fouled by the adjustment Work as directed. Bypass pump sanitary sewer and stormwater flows around the pipe section or manhole being repaired or replaced by plugging an existing upstream manhole and pumping the flow around the Work to a downstream manhole. Submit a bypass pumping plan to the Engineer at least 48 hours before beginning bypass pumping. Use a pump with adequate capacity to handle existing flows and additional flow due to rain. Pumps shall not exceed a noise level of 86 dB at a distance of 50 feet. Do not operate bypass pumps at night except in an emergency. Do not discharge raw sewage onto private property or city streets, or into storm drain systems.
00490.41Manholes over Existing Sewers:
according to Section 00470.
Prevent material or debris from entering the line.
When required, provide all diversion facilities and perform all Work necessary to maintain flow in existing lines. Obtain the Engineer's approval prior to diverting flows.
after first cleaning and applying an approved commercial concrete bonding agent to all surfaces of the pipe that w ill be in contact with the manhole.
If the top of the existing rigid pipe is to be cut out, cut it to the springline for the full width of the manhole. Smooth and point the exposed edge of pipe with mortar.
Make rigid sewer pipe connections using an acc eptable pipe connection according to
sewers systems with approved water stops, watertight fittings or boots at connections with the existing flexible sewer.
If approved, manholes may be constructed over existing PVC sewers and sealed at the manhole wall using the following method:
• Apply a coating of PVC solvent to the pipe that will be in contact with the manhole. Apply a dense coating of clean mor tar sand over the PVC solvent cement. After the cement has cured, apply a commercial concrete bonding agent to the sand prior to placement of concrete.
required. Construct connections that are watertight and that will provide a smooth flow into and through the manhole. All sanitary sewer pipe connections, including those at invert level as well as penetrations for drop connectors, conduits and carry -throughs, sha ll conform to the requirements of Section 00470.
00490.42 404 00490.42 Service Line Connections to Existing Sanitary Sewers - Make connections of service lines to existing sewers watertight. Make connections, where possible, to exis ting tees or wyes that have been previously installed and plugged. Remove the plug and make the connection according to Section 00445. Make transition couplings between dissimilar pipe materials using approved commercial adapters with stainless steel bands.
Where tees or wyes for connection are absent or unusable, connect service lines with approved commercial taps. Do not backfill any tap until it is inspected and approved by the Engineer.
Install taps by coring without protrusion into, or damage to, the existing sewer. Support the sewer and replace bedding material , as necessary, to prevent settlement of the sewer grade.
00490.43Abandoning Pipe in Place - Drain abandoned pipes and plug watertight. Plug abandoned
pipes with gasketed mechanical plugs or grout seals, as directed. Where abandoned pipes connect to sewer manholes, install the plugs or seals from the inside of the manhole and reshape the channel to conform to the Standard Drawings.
Fill abandoned pipes greater than 12 inches diameter with Sand, controlled low -strength material meeting the requirements of 00442, or other approved M aterial .
00490.44Filling Abandoned Pipes, Manholes and Catch Basins - Cap or plug all connecting
pipes to manholes and catch basins that are scheduled to be abandoned. Remove the manhole cone or flat top and manhole sections, or the catch basin frame, to a minimum depth of 3 feet below finish grade and fill the r emaining manhole barrel or catch basin with Granular Material meeting the requirements of Section 02630. Compact the Granular Material to 90 percent of maximum density according to AASHTO T 99. When in landscaped or unimproved roadway sections, backfill with approved Materials meeting the requirements of 00330.13. Place Topsoil meeting the requirements of 00330.11 for the last 1 foot of backfill.
00490.45Salvaging Manhole Frames, Covers and Grates - Remove manhole frames, covers and
grates scheduled for salvage and store in an approved location. Frames, grates and covers meeting Specifications may be salvaged from Structures to be adjusted and may be reused in the Work if of suitable size and condition. Replace, at no additional cost to the Agency, all items damaged or lost by the Contractor with similar items that are comparable in all respects with those they are to replace, and which are adequate for the intended purpose.
Clean salvaged components to be reused of foreign material by methods that will not harm the components.
00490.46Adjusting Manholes :
in the adjusted Structure , in kind. Construct according to the Standard Drawings.
or as shown.
to attai n desired grade.
00490.46 405 Precast sectio ns removed in the adjusting Work may be reused in other adjusting Work or in new construction p rovided they are in good condition and otherwise conform to the Specifications. Dispose of precast items, not reused on the Project, according to 00290.20.
or by reconstructing the neck. Fabricated metal rings and plates may be furnished and used in the adjustment Work , provided that:
The metal and its fabrication provide at least the strength and support required for covers or grates. Uniform bearing of bearing surfaces is assured. Positive safeguards are made against displacement when in service.
Do not exceed 24 inches total dis tance from the top of the metal frame at its new adjusted grade to the top of the cone. Riser rings and repairs shall conform with the requirements of Section 00470. Extend manhole barrels of brick, block or concrete in kind.
• Remove existing frames, covers and grates. • Chip away the exposed top surface on which new mortar or concrete is to be placed, to a depth of 1 1/2 inches or until firm concrete is exposed. • Clean the new surface by brushing, and moisten with water at the time of placing new concrete. • Place new concrete to the required grade and cure at least 3 Days when using C ommercial Grade Concrete, and as directed when using high early strength concrete. • Seat the frame in f resh mortar and bring to the proper grade.
follows:
• Raise with new bricks, blocks, precast components, mortar or combinations thereof, or with concrete, as conditions warrant. • Do not place mortar for building up existing masonry to a depth of more than 3 inches. • Do not place concrete to a depth of less than 3 inches. • To conform to these requirements, cut down as necessary the existing shells or walls of Structures to be adjusted to provide space for the new construction.
removal of the cone or flat top, proceed as follows:
• Expose the top of the Structure to the required depth. • Cut off or remove elements of the Structure to an elevation below that established for the bottom of the metal frame or cover. • Build up with mortar, concrete, brick or concrete blocks to the required elevation. • Join new Material to old as specified in above under (a) through (c).
foundation, by adding extensions of like design and material, or by severing the barrel in an acceptable m anner. Dispose of salvaged Structures, not reused on the Project, according to
00290.20
00490.47 406
00490.47Adjusting Catch Basins and Inlets:
• After existing frames and grates or covers have been removed, chip away the exposed top surface to expose firm concrete. Provide at least 1 inch clearance below the frame to be placed. • Clean the new surface by brushing and moistening with water at the time of placing new concrete. • Provide the necessary forms to maintain existing Structure dimensions in the new Work . • Place new concrete according to Section 00440 to the required grades. The frame may either be preset in the form or placed in the fresh concrete to the required grades. • Finish the concrete top surfaces as required to match the grades required. • Grout existing and new inside surfaces as required to attain a uniform surface tr ansition.
new grade when the nature of the Structure and conditions permit.
Precast concrete sections may be added or removed as required to obtain proper grade.
Precast Structures may be raised by using precast sections provided that:
• The material conforms to the general requirements of the existing Structure . • Sections are set and joined to each other and to existing sections. • Uniform bearing of bearing surfaces is assured. • Positive safeguards are made against displacement when in service.
• Place connecting pipe at the required line and grade. • Set the connecting pipe through the full thickness of the wall flush with the inner face of the wall. • Connect to the Structure with a watertight joint.
Structures as shown and by:
Removing existing frame and grate. Chipping away existing concrete to an elevation below finished grade. Reconstructing Structure to accept reinforced concrete cap. Installing cap on existing inlet, box, or Structure .
00490.48Adjusting Boxes, Cleanout Lids and Similar Structures - Raise or lower boxes, lids and
similar Structures by one of the following methods:
• Resetting the entire Structure on a firm foundation. • Adding extensions of like material below the original Structure if raising the Structure to a point where it would not enclose or protect its contents. 00490.90 407 • Placing precast box extensions, or cast -in-place concrete. • Complete replacement of the Structure with a new Structure of adequate design approved by the Engineer.
00490.49Finish Grade - Center a 12- foot straightedge, as nearly as practica ble, over the center of
the cover of manholes and boxes. The final grade of the Pavement surface and adjusted manholes and boxes shall not vary more than 1/4 inch from the finish grade and Cross Section at any point along the straightedge.
Measurement
00490.80Measurement - The quantities of adjusted and reconstructed manholes inlets, boxes, and
other similar Structu res will be measured on the unit basis.
The quantities of manholes over existing sewers, connections to existing Structures, filling abandoned Structures, and capping existing concrete Structures will be measured on the unit basis.
Payment
00490.90Payment - The accepted quantities of Work performed under this Section will be paid for
at the Contract unit price, per unit of measurement, for the following items:
Pay Item Unit of Measurement
Item (a) applies to manholes adjusted by adding or removing precast or metal grade rings.
Item (b) applies to manholes adjusted by:
• removing and reconstructing part or all of the cone or flat top • removing and replacing the entire cone or flat top • adding precast risers below the cone of precast manholes Item (f) includes all extra or additional costs associated with installing the manholes over existing sewers. These costs are in addition to those which are included in payment for the manholes.
Manholes will be paid for according to 00470.90.
Item (h) applies to filling abandoned pipes, manholes, inlets, boxes and other similar Structures.
Payment will be payment in full for furnishing and placing all Materials, and for furnishing all Equipment , labor, and Incidentals necessary to complete the Work as specified.
00490.90 408 No separate or additional payment will be made for:
• earthwork • backfill • protective coatings • replacement of manhole or similar structure backfill • base drains • Aggregate bases • Pavements • connections • Structure abandonment • removing and disposing of existing Structures and pipe • bypass pumping