Category:732 Flared End Sections
Proper installation is important to the long term stability of the flared end section (FES) and they should be installed and backfilled it the same manner required for the pipe. The inspector should ensure the installed FES is properly matched to the surrounding soil grading. Grading around all FES should slope away from the side of the end section. When the surrounding soil slopes towards the sides of the end section, it concentrates run off water along the FES which leads to erosion and future maintenance.
For concrete FES, the same mastic used to join pipe sections should also be used to join the FES to the pipe.
For FES made of flexible pipe materials such as metal and thermoplastic, care should be taken to ensure the sides of the FES are well compacted. The sides of metal and plastic end sections that are not properly supported are likely to be flimsy and prone to movement that will need future maintenance.
Metal FES must be aluminized for Group A pipes. For Group B and C pipes, either zinc or aluminized is acceptable.
For metal end sections, care should be taken to ensure the end section has an appropriate connection type per Std. Plan 732.00 that is tight.
When jointing a metal FES to thermoplastic pipe, any connection rod or strap used should be placed behind at least one full corrugation. The female bell section does not count as a corrugation. Thermoplastic pipe is flexible and failure to secure the rod or strap behind at least one full corrugation may allow the FES to come loose. Proper installation is essential to ensure that the metal end section stays connected to the pipe and can resist the forces placed on it by flowing water.
The toe strip staying embedded is important to the long term performance of the MES. The fill material used around the toe should be well graded and compacted well enough to protect the toe. If scour is observed after installation, corrective measures should be taken. The toe wall is especially important on the outlet end of safety slopes to do the extra force exerted on the bars by the flowing water.
Included in Std. Plan 732.00 are details for dimensions including closure gaps for installed MES. There may be some variance from those details with thermoplastic pipes due to the thicker wall differences. The standard plan allows for some deviation from the details and judgment should be used to ensure the MES is suitable.
732.2 Safety Slope FES
Safety slope FES are used in cases where a FES is within the recovery area and could pose a hazard to the traveling public. Any possible change or substitution during construction involving a safety slope FES should involve the design engineer.
732.3 Tapered Sleeve
A tapered sleeve is used in some cases to adapt a FES to a type of pipe. The tapered sleeves are essentially a metal cone with corrugations on one end to allow the secure attachment of a metal FES. The cone portion must be friction fit into the end piece of pipe, usually using a piece of equipment to secure it. The inspector should check each tapered sleeve to ensure it is not loose.
These items are paid for on a unit basis. Payment for any tapered sleeves or other short runs of pipe used as adaptors or for UV protection at an FES are NOT paid for with the FES. Payment for those items is included in the pipe run.
FES may be different lengths depending on material type (metal vs. concrete). This different does not affect the pay for either the FES or the pipe run.
The contractor may choose to adjust the length of the pipe run to aid in the fitment or grading operations. Approval and payment for this change may be considered at the discretion of the engineer.
If the contractor chooses to use a larger size pipe than shown on the plans, any FES used for that pipe should be paid for at the bid price for the smaller size FES originally shown on the plans.
732.5 Construction Records
The inspector should record in a diary when FES were installed and which type of toe wall was used.
732.6 Materials Inspection and Laboratory Testing
These items will be inspected by Construction and Materials and an inspection report will be issued in AASHTOWARE Project (AWP). See Sec 1020 for metal and Sec 1032 for concrete.