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 a more detailed description is required,
see the ODOT
Drainage Design Manual and the plans.
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.
When the pay item description
says Rock Cut Underdrains and the type of pipe is not
specifically itemized in the Proposal, use one of the following:
1. Corrugated Polyethylene Drainage Tubing (Perforated) 707.31.
2. Polyvinyl Chloride Plastic Pipe 707.41.
3. Polyvinyl Chloride Corrugated Smooth Interior Pipe
(Perforated per 707.31)
707.42.
4. Polyvinyl Chloride Solid Wall Pipe (Perforated per 707.31)
707.45.
Provide the pipe type on the 605
CA-P-2 Structure Underdrain Form.
When the pay item description
says Shallow Pipe Underdrains or Deep Pipe Underdrains, and the type of pipe is not specifically
itemized in the Proposal, use one of the following:
1. Perforated Concrete Pipe 706.06.
2. Concrete Drain Pipe Extra Quality 706.07.
3. Perforated Vitrified Clay Pipe 706.08.
4. Clay Drain Tile Extra Quality 706.09.
5. Corrugated Steel Underdrains,
Type III 707.01.
6. Corrugated Polyethylene Drainage Tubing (Perforated) 707.31.
7. Polyvinyl Chloride Plastic Pipe 707.41.
8. 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 type of pipe material is not specifically itemized, 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,
and the Contractor can then 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.
The backfill requirements are
as per 611.
When the pay item description says, “611 Conduit, Type F for Underdrain
Outlets,” and the type of pipe is not specifically itemized in the Proposal,
use one of the following:
1. Corrugated Polyethylene Smooth Lined Pipe 707.33.
2. Polyvinyl chloride plastic pipe (non-perforated) 707.41.
3. Polyvinyl chloride corrugated smooth interior pipe 707.41.
4. Polyvinyl chloride solid wall pipe 707.45.
Provide the pipe type on the 605
CA-P-2 Structure Underdrain Form.
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.
Prefabricated edge underdrains 712.10
is the only pipe type permitted.
Provide the pipe type on the 605
CA-P-2 Structure Underdrain Form.
Construct underdrains
as follows:
|
Underdrain ID |
6 inches (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.
Lay the underdrain true to
line and grade with close fitting joints.
Use locking bands or smooth sleeve type couplers, which match 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.
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.
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 Underdrain |
4 inches (100mm) |
|
Trench Width |
10 inches (250mm) |
Provide the trench width on
the 605
CA-P-2 Structure Underdrain Form.
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 the construction underdrains 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.
Do not remove construction underdrains at any time.
If a construction practice requires the construction underdrains
to be removed, then install replacements as soon as possible. For example, 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.
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 granular material
simultaneously with the trenching operation to hold the edge underdrains flush against the trench wall.
Before placing into the trench,
splice the prefabricated edge underdrains, as
required, using material furnished by the manufacturer and according to the
manufacturer’s directions. The
manufacturer must furnish all material required for the splices and furnish any
equipment required for splicing.
Construct splices to prevent adjoining sections of the prefabricated
edge underdrain panels from separating. Provide the dates when the
prefabricated edge underdrains were placed on the 605
CA-P-2 Structure Underdrain Form.
Construct outlets per 611
and document this work as required in 611.
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.
Construct the aggregate
drains after the completion of pavement.
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 to 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 of
when the aggregate drains were placed on the 605
CA-P-2 Structure Underdrain Form along with a sketch.
Use granular material for the
drains. Place the aggregate to a minimum
depth of 8 inches (200 mm) above the bottom of the trench. According to Item 203,
backfill the remaining depth of the trench with suitable embankment material.
Provide how the aggregate drains were backfilled on the 605
CA-P-2 Structure Underdrain Form.
Provide the method used to
measure the underdrains on the 605
CA-P-2 Structure Underdrain Form, e.g. station-to-station, by wheel, or
other standard method of field measurement.
Note the length paid per day.
Provide this on the 605
CA-P-2 Structure Underdrain Form.
1. 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.
2. Aggregate drains.
a. Width and depth of trench.
b. Trench backfilled with granular material; document
type of aggregate.
c. Measure as per 605.08.
d. Ends re-opened after final seeding.