703Underdrain Systems

703.01 DESCRIPTION. Construct pipe underdrain systems in

accordance with these specifications and in conformity with lines and grades shown on the plans or established.

703.02 MATERIALS. Materials shall comply with the following

sections and subsections: Asphalt Concrete 502 Portland Cement Concrete (Class M) 901 Aggregate Backfill (Size 3) (Crushed or Uncrushed) 1003.07 Granular Material (Backfill) 1003.09 Perforated and Non-perforated Underdrain Plastic Pipe 1006.01 Perforated Bituminous Coated Corrugated Steel Pipe 1007.03 Perforated Corrugated Aluminum Pipe 1007.06 Reinforcing Steel 1009.01 Precast Concrete Headwalls 1016.06 Hardware Cloth Screen 1018.05 Geotextile Fabric 1019.01 Geocomposite Drains 1019.02 Furnish including plastic pipe when an item for “Shoulder Outlet Underdrains” in the contract. When including an item for “Perforated Pipe Underdrains” in the contract, furnish any of the perforated plastic pipe types, unless otherwise specified. When including an item for “Non -perforated Pipe Underdrains” in the contract, furnish any of the non-perforated plastic pipe types, unless otherwise specified. At the Department’s discretion, pipe plants will be inspected periodically for compliance with specified manufacturing methods. Material samples will be obtained for laboratory testing for acceptance of manufacturing lots.

703.03 Construction Requirements.

703.03.1 Plastic Pipe Shoulder Underdrains: Install plastic pipe

underdrains, aggregate backfill, and shoulder base replacement and surfacing immediately following trenching operations. When permitting traffic on the roadway, conduct operations so that no trench will be open at the end of the day. Perform operations in such a manner that existing pavement, shoulder surfacing, and base course outside the limits of underdrain trenches are not damaged.

703.03.1 1 Trenching: When existing surfaced shoulders are not

to be overlaid with asphalt concrete under the current contract, cut existing shoulder surfacing full depth along the edges of the proposed trench prior to beginning trenching operations. Excess excavated materials may be spread on embankment slopes when permitted. Dispose of removed materials considered unacceptable for spreading on slopes in accordance with 202.02.

703.03.1 2 Geotextile Fabric: Line completed trenches for

perforated plastic pipe with geotextile fabric. Splice adjoining sheets of fabric by lapping a minimum of 18 inches and satisfactorily securing. Sewn or heat-bonded splices may be used. Place a sufficient width of fabric in the trench to permit the cloth to lap over the top of the trench for the full width of trench. During placement of geotextile fabric, pipe and backfill, take care to avoid damaging geotextile fabric. Satisfactorily repair or replace any damaged geotextile fabric at no direct pay.

703.03.1 3 Plastic Pipe Installation: Place plastic pipe under-

drain in the trench immediately adjacent to the pavement or shoulder edge as shown on the plans. Fittings and materials necessary to make splices of the plastic pipe under-drain and to make connections of the plastic pipe under-drain to the non-perforated outlet pipe shall be from the same manufacturer as the pipe. Fittings shall be designed to prevent soil or aggregate intrusion into the under-drain or outlet piping. When terminating the under-drain without an outlet, provide a fitting or use other approved methods to prevent soil or aggregate intrusion into the end of the under- drain.

703.03.1 4 Aggregate Backfill: After pipe installation, backfill

the trench without displacement or damage to the pipe. Uniformly compact aggregate backfill for perforated pipe with approved vibratory equipment to the satisfaction of the engineer. Place aggregate backfill in lifts no greater than 10 inches of uncompacted thickness. Leave the backfilled and compacted trench in a condition ready to receive surfacing. Lap the geotextile fabric over the full width of the trench at the top of the final backfill and secure by an approved method.

703.03.1 5 Replacement of Base Course and Surfacing:

Use asphalt concrete for replacement of removed shoulder base course and surfacing as shown on the plans and construct in accordance with Section 510.

703.03.2 Shoulder Outlet Underdrain: Install the non-perforated

plastic pipe, backfill, and replacement of shoulder base and surfacing immediately behind trenching operations. When permitting traffic on the roadway, conduct operations so that no trench will be open at the end of the day. Perform operations in such a manner that the existing pavement, shoulder surfacing, and base course outside the limits of the trenches are not damaged.

703.03.2 1 Trenching: When existing surfaced shoulders are not

to be overlaid with asphalt concrete under the current contract, cut existing shoulder surfacing full depth along the edges of the proposed trench prior to beginning trenching operations. When permitted, spread excess excavated materials on embankment slopes. Dispose of removed materials considered unacceptable for spreading on slopes outside the right-of-way in accordance with 202.02.

703.03.2 2 Non-perforated Plastic Pipe Installation: Place

non-perforated plastic pipe in the trench and connect to plastic pipe in accordance with manufacturer’s recommendations. The pipe shall comply with the requirements of 1006.02.

703.03.2 3 Backfill: After pipe installation, backfill the trench

without displacing or damaging the pipe. Use excavated trench material that meets the requirements for granular material as backfill. When requiring additional material, provide granular material at no direct pay. Place the backfill material in lifts no greater than 6 inches of uncompacted material. Uniformly compact backfill material by approved methods to the satisfaction of the engineer. Leave the backfilled and compacted trench in a condition ready to receive surfacing.

703.03.2 4 Replacement of Base Course and Surfacing:

Use asphalt concrete for replacement of removed shoulder base course and surfacing as shown on the plans and construct in accordance with Section 510.

703.03.2 5 Headwalls: Portland cement concrete headwalls for

non-perforated pipe shall be cast-in-place or precast constructed in accordance with Section 702. Furnish each outlet pipe with a rodent screen as shown on the plans.

703.03.3 Perforated or Non-perforated Pipe Under-drain: Use

perforated or non-perforated pipe under-drain as shown on the plans to drain wet areas. Install the under-drains and backfill immediately following trenching operations.

703.03.3 1 Trenching: Excavate the trenches to the specified

dimensions and grade or as directed. Unless otherwise specified, place the bedding material layer a minimum of 3 inches thick and compact in the bottom of the trench for its full width and length. Dispose of excess excavated material in accordance with 202.02.

703.03.3 2 Under-drain Pipe: Embed under-drain pipe firmly in

the bedding material and join securely with appropriate coupling fittings or bands. When specified, wrap perforated pipe with geotextile fabric in accordance with plan details or as directed. Cap upgrade ends of pipe to prevent soil intrusion.

703.03.3 3 Backfill: Place specified backfill as shown on the

plans or as directed.

703.03.4 Geocomposite Wall Drains: Before structural

backfilling, place geocomposite wall drains against the structure as shown on the plans. Place the drains to accomplish drainage of the backfill without soil intrusion into the drainage product core or outlet piping. Place and compact the backfill in accordance with Section 802 without displacing or damaging the geocomposite wall drain. Use fittings and materials from the same manufacturer to make splices and connections of the drainage product core to the outlet piping. When the sides of the product are terminated, fold the fabric under to prevent soil intrusion into the end of the drainage product. Overlap the fabric a minimum of 6 inches at all seams.

703.04 Measurement.

703.04.1 Shoulder Under-drains: Shoulder under-drains will be

measured by the linear foot along the pavement or shoulder edge. Required excavation, geotextile fabric, restoration of shoulder base course and surfacing, and disposal of excavated materials will not be measured for payment.

703.04.2 Shoulder Outlet Under-drains: Shoulder outlet under-

drains will be measured per each outlet under-drain installation. Required excavation, plastic pipe and fittings, backfill, replacement of shoulder base course and surfacing, concrete headwalls, rodent screens, and disposal of excavated materials will not be measured for payment.

703.04.3 Perforated or Non-perforated Pipe Under-drains:

Perforated and non-perforated pipe under-drains will be measured by the linear foot of under-drain pipe. Required excavation, bedding, backfill, and geotextile fabric will not be measured for payment.

703.04.4 Geocomposite Wall Drains: Geocomposite wall drains

will be measured by the square yard of geocomposite wall drain.

703.05 PAYMENT. Payment for under-drains will be made at the

contract unit prices, which includes all labor, materials, equipment, tools, and incidentals necessary to complete the work. Pay adjustments for portland cement concrete in accordance with Section 901 will not apply. Payment will be made under: Item No. Pay Item Pay Unit 703-01 Shoulder Under-drains Linear Foot 703-02 Shoulder Outlet Under-drains Each 703-03 Perforated Pipe Under-drains Linear Foot 703-04 Non-perforated Pipe Under-drains Linear Foot 703-05 Geocomposite Wall Drains Square Yard