605 Underdrains
Description (605.01)
Materials (605.02)
Pipe Underdrains Construction (605.03)
Construction Underdrains (605.04)
Prefabricated Edge Underdrains (605.05)
Underdrain Outlets (605.06)
Aggregate Drains (605.07)
Method of Measurement (605.08)
Basis of Payment (605.09)
Documentation Requirements – 605 Underdrains
Description (605.01)
The types of underdrains are specified in accordance with their application and intended usage. For a brief description of typical
applications see section 605.02. If you need a more detailed description, see the ODOT Drainage Design Manual and the plans.
Materials (605.02)
Use approved granular material consisting of No. 8, 9, or 89 size air-cooled blast furnace slag, limestone, or gravel for underdrain
backfill only but not for underdrain outlet pipes.
Pipe for 605 Rock-Cut Underdrains.
When the pay item description says Rock Cut Underdrains and the kind of pipe is not specifically itemized in the Proposal, then
use one of the following:
1.
2.
3.
4.
Corrugated Polyethylene Drainage Tubing (Perforated) 707.31
Polyvinyl Chloride plastic Pipe 707.41
Polyvinyl Chloride Corrugated Smooth Interior Pipe (Perforated Per 707.31) 707.42
Polyvinyl Chloride Solid Wall Pipe (Perforated Per 707.31) 707.45
Provide the pipe type on the 605 CA-P-2 Structure Underdrain Form.
Pipe for 605 Pipe Underdrains
When the pay item description says Shallow Pipe Underdrains or Deep Pipe Underdrains and the kind of pipe is not specifically
itemized in the Proposal, then use one of the following:
1.
2.
3.
4.
5.
6.
7.
8.
Perforated Concrete Pipe 706.06
Concrete Drain Pipe Extra Quality 706.07
Perforated Vitrified Clay Pipe 706.08
Clay Drain Tile Extra Quality 706.09
Corrugated Steel Underdrains, Type III 707.01
Corrugated Polyethylene Drainage Tubing (Perforated) 707.31
Polyvinyl Chloride plastic Pipe 707.41
Corrugated Aluminum Alloy Pipe and Underdrains, Type III 707.21
If the size and type of the underdrains required is a 6-inch (150 mm) shallow pipe underdrain, and the kind of pipe material is not
specifically itemized, then use 4-inch (100 mm) 707.31 perforated corrugated polyethylene drainage tubing. An example would
be “6-inch shallow pipe underdrains” listed in the description, then the contractor can furnish 4-inch 707.31 underdrains placed at
the same location as the “6-inch shallow pipe underdrains”. Provide the pipe type on the 605 CA-P-2 Structure Underdrain Form.
Pipe for 603 Type F Conduit Underdrain Outlets.
The backfill requirements are as per 603. When the pay item description says “603 Type F Conduit Underdrain Outlets” and the
kind of pipe is not specifically itemized in the Proposal, then use one of the following:
1.
2.
3.
4.
Corrugated Polyethylene smooth lined pipe 707.33
Polyvinyl Chloride plastic Pipe (non-perforated) 707.41
Polyvinyl Chloride corrugated smooth interior pipe 707.41
Polyvinyl Chloride solid wall pipe 707.45
Provide the pipe type on the 605 CA-P-2 Structure Underdrain Form.
Pipe for 605 Construction Underdrains
Corrugated Polyethylene Drainage Tubing (Perforated) 707.31 is the only pipe type permitted.
Provide the pipe type on the 605 CA-P-2 Structure Underdrain Form.
Pipe for 605 Prefabricated Edge Underdrains
Prefabricated Edge Underdrains 712.10 is the only pipe type permitted.
Provide the pipe type on the 605 CA-P-2 Structure Underdrain Form.
Pipe Underdrains Construction (605.03)
Construct underdrains as follows:
Excavation
UNDERDRAIN ID
6inches (150mm)
4 inches (100mm)
TRENCH WIDTH
14 inches (350mm)
10 inches (250mm)
Provide the trench width on the 605 CA-P-2 Structure Underdrain Form.
If filter fabric is specified, note this on the 605 CA-P-2 Structure Underdrain Form along with a sketch of how the fabric was
placed and overlapped at the top of the trench.
Laying Underdrain
Lay the underdrain true to line and grade with close fitting joints. Use locking bands or smooth sleeve type couplers matching
the underdrain material type to join 707.01, 707.31, 707.41, and 707.21. When bell and spigot underdrain is used, lay it with the
bell end facing up grade. Set the underdrain on a solid bed shaped to fit the underdrain throughout its entire length. Make all
necessary connections with branches, wyes, tees, transitions, and bends that match the underdrain material type. Close the upper
ends of underdrains with suitable plugs.
Lay perforated underdrain so that the perforations are in the bottom half of the underdrain.
Provide the pipe joint type on the 605 CA-P-2 Structure Underdrain Form.
Backfilling
Inspect the underdrains before placing any granular material. Place the granular material for the full width of the trench around
the underdrain, and extend it to the bottom of the pavement or base as shown on the plans. If underdrains are placed outside of
the pavement or base area, extend the granular material to within 4 inches (100 mm) of the finished grade. Fill the remaining
depth of the trench with 203 Embankment material. Provide the pipe backfill material type on the 605 CA-P-2 Structure
Underdrain Form.
Protection
Place the pavement over the underdrain trench within 90 days after placing the trench backfill. If the trench remains open for
longer than 90 days, remove and replace backfill contaminated by soil. Provide the dates when the underdrains were placed and
the date the pavement was placed over the underdrain trench on the 605 CA-P-2 Structure Underdrain Form.
Construction Underdrains (605.04)
Excavation
CONSTRUCTION UNDERDRAIN
4 inches (100mm)
TRENCH WIDTH
10 inches (250mm)
Provide the trench width on the 605 CA-P-2 Structure Underdrain Form.
Trench depth and backfill
Construct the trench depth to that shown on the plans or 30 inches (750 mm). Backfill the full width and height of the trench
with granular material. Provide the pipe backfill material type and trench depth on the 605 CA-P-2 Structure Underdrain Form.
Outlet
Outlet the construction underdrains as possible into the ditch or drainage structures. There is no change in pipe types for the
outlet. Provide the trench outlet location on the 605 CA-P-2 Structure Underdrain Form.
Removal
Do not removed Construction underdrains at any time. If a construction practice requires the construction underdrains to be
removed, then install replacements as soon as possible. Example would be if trenching for a culvert would cut the construction
underdrains.
Provide the dates when the construction underdrains were placed on the CA-P-2 605 Structure Underdrain Form.
Prefabricated Edge Underdrains (605.05)
Install the prefabricated edge underdrains against the outside wall of a 4-inch (100 mm) trench, and backfill the trench adjacent to
the pavement with granular material. Place the granular material in one or more lifts with a vibratory compactor run over the
final lift to compact the granular material before placing the asphalt plug. Place the first layer of the granular material
simultaneously with the trenching operation to hold the edge underdrains flush against the trench wall.
Splice the prefabricated edge underdrains as required before placing in the trench, using material furnished by the manufacturer
and according to the manufacturer’s directions. Require the manufacturer to furnish all material required for the splices, and
furnish any equipment required for splicing. Construct splices to prevent separation of adjoining sections of the prefabricated
edge underdrain panels. Provide the dates when the prefabricated edge underdrains were placed on the 605 CA-P-2 Structure
Underdrain Form.
Underdrain Outlets (605.06)
Construct outlets per 603 and document this work as required in 603. The manufacturer must supply outlet fittings that transition
between the underdrains and the outlet pipe. These are included in the 605 pay items. Place underdrains and outlets on fractured
slab projects, such as crack and seat, rubblized, or break and seat projects before fracturing the existing pavement.
Mark all underdrain outlets with a wooden lath prior to final seeding. Clean all debris from the outlets after final seeding. These
are included in the 605 pay items.
Aggregate Drains (605.07)
Construct the aggregate drains after the completion of pavement.
Excavation
Excavate trenches for aggregate drains to a minimum width of 12 inches (0.3 m) and to the depth shown on the plans. Slope the
bottom of the trench to drain and keep it free from loose particles of soil. Excavate the trench to provide a clean exposure of the
granular pavement courses to be drained. Provide the dates when the aggregate drains were placed on the 605 CA-P-2 Structure
Underdrain Form along with a sketch.
Placing and Backfilling
Use granular material for the drains. Place the aggregate to a minimum depth of 8 inches (200 mm) above the bottom of the
trench. Backfill the remaining depth of the trench with suitable embankment material according to Item 203. Provide how the
aggregate drains were backfilled on the 605 CA-P-2 Structure Underdrain Form.
Method of Measurement (605.08)
How were the underdrains measured? Example: station to station or by wheel or other. Provide this on the 605 CA-P-2 Structure
Underdrain Form.
Basis of Payment (605.09)
Note the length paid per day. Provide this on the 605 CA-P-2 Structure Underdrain Form.
Documentation Requirements - 605 Underdrains
1.
2.
Edge drains
a. Document on form CA-P-2
b. Trench backfilled with granular material, document type of aggregate
c. Measure as per 605.08
d. Provide precast reinforced concrete outlet per 605.06 as required
Aggregate drains
a. Width and depth of trench
b. Trench backfilled filled with granular material, document type of aggregate
c. Measure as per 605.08
d. Ends re-opened after final seeding