605PAVEMENT AND SPECIAL UNDERDRAIN

476

605.02Materials

The geotextile filter for aggregate filled underdrain shall be a non-woven material meeting the requirements of AASHTO M 288 for Class 2 Subsurface Drainage Geotextile and Section 810 of these specifications. The geotextile shall be selected from List II-3, of the Department's manual titled "Materials, Sources, and Devices With Special Acceptance Requirements". Information concerning this list is given in Subarticle 106.01(f) and ALDOT-355.

The required types and sizes of pipes will be shown on the plans. The pipe may be of any of the non-corrugated pipe underdrain or smooth lined corrugated pipe underdrain noted in Section 852, perforated or non-perforated as required. Pipe fittings shall be of the same material as the pipe or of a compatible material providing a crush strength equal to, or greater than, that of the type pipe being used.

Aggregate filler shall meet the requirements for Coarse Aggregate, Section 801, for ALDOT size #4, #5, or #57 and the additional requirement that no more that 1% of the aggregate passes the No. 200 {75 m} sieve.

Slope paving for outlet headwalls shall meet the requirements noted in Section 614.

605.03Construction Requirements

The installation of pavement and special underdrain shall be done in coordination with other work to prevent damage to the roadway. Materials from the excavation may be deposited outside the trench work area for reuse in the work. Excess material shall be removed and disposed of as shown on the plan details or as directed by the Engineer.

An aggregate filled underdrain shall be a trench that is lined with a geotextile filter fabric and then filled with aggregate. Pavement median drains and edge drains shall be an aggregate filled underdrain with pipes placed as shown on the plans to collect drainage and provide a connection to the outlets for the drainage. Exposure of geotextiles to the elements between laydown and cover shall be a maximum of 14 days to minimize the potential for damage. The geotextile filter shall be installed in such a manner that all splice joints are provided with a minimum overlap of 3 feet {1 m}. Securing pins shall be installed to anchor the filter fabric if the filter fabric does not remain in place during the construction of the drains. Where seams are required in the geotextile filter in the longitudinal trench direction, they shall be joined by either sewing or overlapping as outlined in Article 608.05 of these specifications. All seams shall be subject to the approval of the Engineer. Overlapped seams shall have a minimum overlap equal to the width of the trench and shall be anchored with securing pins as directed to ensure the required overlap is maintained. Where a filter repair is required, a piece of filter shall be placed over the damaged area and extend 3 feet {1 m} beyond the perimeter of the tear or damage. When an outlet pipe passes through the filter, a separate piece of filter of sufficient size to be wrapped around the pipe and flared against the side of the filled drain filter shall be used. Care shall be taken during the aggregate filler placement operation as well as the pipe installation, when required, to prevent damage to the filter. The aggregate filler shall be placed and compacted by methods acceptable to the Engineer.

Outlets may be classified and paid for as types of "Special Underdrain Outlets" as follows:  Type A - Designated for connecting an aggregate filled or prefabricated drainage mat underdrain line to a roadway front slope and requires a slope paved headwall.  Type B - Designated for connecting an aggregate filled or prefabricated drainage mat underdrain line to a drainage structure (inlet, junction box, etc.). PAVEMENT AND SPECIAL UNDERDRAIN 477

 Type C – Designated for providing an outfall from a drainage plane layer to a front slope and requires a slope paved headwall. Other types may be added as shown on the plans. The width of the outfall trench requiring non-perforated pipe shall be kept to a minimum. The pipe shall be installed with ordinary care and the backfill material placed in layers and compacted to the satisfaction of the Engineer. For Type "A" and "C" outlets, the end of the outfall pipe shall be protected by a slope paved headwall. The end of the outfall pipe shall be modified as necessary to fit the headwall. Should the outlet end of the pipe or the headwall fall within the limits of ditch paving, that portion of the ditch paving within the headwall limits shall be removed to neat lines and the headwall made to blend with the ditch paving. For a Type "B" outlet, the end of the outfall pipe shall be drained into a designated drainage structure. The wall of the structure to which the pipe is to connect shall be modified, adjusted, or replaced as necessary to provide a suitable connection. Any special fitting necessary to accomplish this connection will be considered incidental to the work. For other types of special outlets, the construction requirements will be as noted by plan details. Unless approved otherwise by the Engineer, all special underdrain outlets shall have a rodent protection screen made of galvanized hardware. The screens shall be as detailed on the plans; however, slight modifications to the configurations shown on the plans may be used if approved by the Engineer.

Drainage collection systems and outlets may be classified and paid for as "Special Underdrain Pipe". The details of these collection systems and outlets will be shown on the plans. Special underdrain pipe is usually non-perforated pipe. Trench widths for the unperforated pipe shall be kept to a minimum. The pipe shall be installed with ordinary care, with bells, etc., laid upgrade and all joints sealed. Pipe connections shall be made using appropriate, approved fittings. Backfilling of the pipe trench shall be made by placing the backfill material in layers and compacting each layer as directed by the Engineer. Connections to drainage structures shall be as detailed on the plans or approved by the Engineer.

605.04Method of Measurement

Pavement median and edge drains will be measured in linear feet {meters} along the center of drainage line.

Type A and B Special Underdrain Outlets will be measured in units of 20 feet {6 m} with measurements made along the center of the outfall pipe from the center of the pavement median or edge drain to the centroid of the outfall end. Adjustments will be made for payment purposes when the length of the outfall pipe exceeds 20 feet {6 m}.

Type C Special Underdrain Outlets will be measured individually as one complete unit.

The method of measurement of outlets other than the types of outlets noted above will be as noted by plan details.

Special Underdrain Pipe will be measured in linear feet {meters} along the center of each line or lateral, center to center of fittings.

605.05Basis of Payment

Pavement median and edge drains will be paid for at the contract unit price which shall be full compensation for all materials, equipment, tools, and labor required to construct the drains. The unit price shall include excavation of the trench, disposal of excess material, installation of the geotextile filter, placement of the aggregate, installation of the perforated underdrain pipe, PIPE UNDERDRAIN 478

installation of the elbow at the outlet end of the drain line, any required outlet connections, and for all incidentals necessary to complete this item of work.

A Special Underdrain Outlet, will be paid for at the contract unit price per each, which shall be full compensation for all materials, equipment, tools, and labor required for the construction of the outlet. The unit price shall include excavation of the trench, backfill and compaction of the trench, furnishing and installation of the pipe and fittings, furnishing and placing concrete for headwall or connection of outfall pipe to a structure, the disposal of excess material, and for all incidentals necessary to complete this item of work. Payment for the outfall pipe for Type A and B outlets shall be adjusted as follows: Length of Outfall Pipe % of Unit Price to be Paid Over 6 feet {2 m} but less than 12 feet {4 m} 50 % Over 12 feet {4 m} but less than 19 feet {6 m} 75 % 20 feet ± 1 foot {6 m ± 300 mm} 100 % Over 21 feet {6 m} but less than 27 feet {8 m} 125 % Over 27 feet {8 m} but less than 33 feet {10 m} 150 % Over 33 feet {10 m} but less than 39 feet {12 m} 175 % Over 39 feet {12 m} but less than 45 feet {14 m} 200 %

Special Underdrain Pipe will be paid for at the contract unit price, which shall be full compensation for all materials, equipment, tools, and labor required the installation of the pipe. The unit price shall include the furnishing of all pipe, fittings, and miscellaneous materials, excavation of the trench, installation of all materials, backfilling of the trench, disposal of excess materials, and for all incidentals necessary to complete this item of work.

605-A Pavement * Drain - per linear foot {meter} 605-B Special Underdrain Outlet, Type _____ - per each 605-C Special ____ inch {mm} Diameter Underdrain Pipe - per linear foot {meter} * Median or Edge PIPE UNDERDRAIN

606.01Description

This Section shall cover the work of furnishing pipe underdrain of the type and sizes provided on the plans or in the proposal in accordance with the requirements of these specifications, and installing such pipe at the locations shown on the plans or designated and in substantial conformity with the established lines and grades. The work shall include the furnishing and construction of such joints and connections to other pipes, catch basins, end walls, etc., as may be required to complete the work, as shown on the plans or directed, together with filter material and filter fabric as shown on Standard Drawing – Details of Pipe Underdrain (U.D.) Installation. Designations for the various types of pipe shall be as follows: