398 SECTION 606 UNDERDRAINS
606.1 -DESCRIPTION : This work shall consist of constructing underdrains and free draining base trenches using pipe and granular material, aggregate filled engineering fabric, and underdrain pipe outlets in accordance with these Specifications and in reasonably close conformity with the lines, grades, dimensions and locations shown on the Plans or established by the Engineer. When Item 606025, “size” Underdrain Pipe, is included as a pay item in the Contract, any of the following pipe types may be furnished for construction of the underdrain: corrugated polyethylene underdrain pipe , or PVC underdrain pipe.
606.1.1 -Free Draining Base Trench: This work shall consist of constructing free draining base trenches and Outlet Pipes in accordance with these specifications and in reasonably close conformity to Standard Details – Volume I with the lines, grades, dimensions, and locations shown on the plans or established by the Engineer.
606.2 -MATERIALS : The materials shall conform to the following requirements:
MATERIAL SUBSECTION TYPE OR GRADATION Concrete for Miscellaneous Uses 715.12 Corrugated Polyethylene Underdrain 714.19 Crushed Aggregate for Free Draining Base Trench 1 703.1, 703.2, 703.3, 703.4 AASHTO 57, 67, 357, or 467 Gravel for Aggregate Filled Fabric Underdrains 1 703.2 & 703.4 or 703.2.3 AASHTO #2 thru #57 or Pea Gravel Gravel for Underdrains 1 703.2 & 703.4 AASHTO Size # 57, 67, 7 or 78 Crushed Stone for Aggregate Filled Fabric Underdrains 1 703.1 & 703.4 AASHTO #2 thru #57 inclusive Crushed Stone for Underdrains 1 703.1 & 703.4 AASHTO Size # 57, 67, 7 or78 Engineering Fabric for Subsurface Drainage 715.11.4 Miscellaneous Concrete 715.12 Outlet Pipe 715.10.1.5 PVC Underdrain Pipe 714.20
1 Only one size may be used at any one installation.
When the locations of manufacturing plants allow, the plants may be inspected periodically for compliance with specified manufacturing methods, and material samples may be obtained for laboratory testing for compliance with material quality requirements. T his may be the basis for acceptance of manufacturing lots as to quality. All materials will be subject to inspection for acceptance as to condition at the latest practicable time the Engineer has the opportunity to check for compliance prior to or during i ncorporation of materials in the work.
399 606.2.1 -Quality Control Testing: Quality control is the responsibility of the Contractor as specified in 106.1. The contractor shall develop a quality control plan in accordance with applicable sections of MP 307 .00.50 excluding the attachment page. Samples will be obtained at a minimum frequency of one sample per day of aggregate placement. Aggregate for underdrain shall be evaluated for specification compliance in accordance with MP 606.03.50. Aggregate for aggregate filled underdrain shall be evaluated for specification compliance in accordance with MP 606.03.50 except Section 6.0 through 6.2 are excluded.
606.2.2 -Acceptance Testing: Acceptance sampling and testing of aggregates used for underdrain is th e responsibility of the Division, Except for furnishing the necessary materials. Quality control sampling and testing performed by the Contractor may be used by the Division for Acceptance.
606.2.3 -Free Draining Base Trench Materials: The perforated p ipe and outlet pipe as detailed in Standard Details – Volume I, or the plans, and shall meet the requirements of this Section.
606.3 -CONSTRUCTION METHODS : 606.3.1 -Pipe Underdrain: Trenches for pipe underdrain shall be excavated to a width of the outside diameter of the pipe plus one ( 1) foot, to a depth of four ( 4) inches below the flow line, and to the grade required by the Plans or as directed. Trench walls shall be as nearly vertical as practicable.
606.3.1.1 -Bedding and Placing Pipe: A minimum four ( 4) inch bedding layer of gravel or crushed stone shall be placed in the bottom of the trench for its full width and length. Subdrainage pipe of the type and size specified shall be embedded firmly in the bedding material. Upgrade ends of all underdrainage pipe installations shall be closed with suitable plugs to prevent entry of soil materials. Perforated pipe shall normally be placed with the perforations down. Flexible pipe sections shall be joined with couplings or bands as recommended by the manufacturer. Non-perforated pipe and rigid pipe shall be firmly set and laid with the bell and groove ends upgrade and with open joints, wrapped with suitable material when specified, t o permit entry of water.
606.3.1.2 -Placing Filter Material: After the pipe installations have been inspected and approved, crushed stone or gravel shall be placed. Care shall be taken not to displace the pipe or the covering at open joints. When there is a heavy percolation of water into the trench at underdrain level, the Engineer may substitute sand for the crushed stone or gravel bedding, cover and filter.
606.3.1.3 -Backfill: When underdrains are not used to drain the base or subbase, the trench shall be filled with suitable random material, as shown on the Plans or as directed by the Engineer, in layers not exceeding four ( 4) inches after compaction. The use of bulldozers or other blade equipment in backfilling is expressly prohibited. The quality control testing and acceptance of suitable soil, soft shale or granular material will be according to applicable sections of 207 and 716, with the following exceptions:
400 1. A lot nor mally consist of the quantity of backfill material required to backfill 100 linear ft. of the installation, or as directed by the Engineer.
the adjacent embankment materia l, the target percentage of dry density for the suitable random backfill will be equal to the X value of the tests in the adjacent lot of embankment material or a minimum value of 95, whichever is greater. For embankments where no tests are on file, the ta rget percentage of dry density will be 95.
606.3.1.4 -Underdrain Outlets: Trenches for underdrain outlets shall be excavated as for underdrains, except that the depth of the trench shall be limited to the flow line. Pipe shall be laid in the trench with all ends firmly joined by the applicable methods and means. No filter material shall be used. After inspection and approval of the pipe installation, the trench shall be backfilled with suitable material in layers and compacted as provided for underdrains.
606.3.2 -Underdrain Structures: 606.3.2.1 -Underdrain Junction Boxes: Underdrain junction boxes shall be constructed to the dimensions in Standard Detail Sheet DR 8 and elevations at locations as shown on the Plans or as directed.
606.3.2.2 -Slope Wa lls for Underdrains: Slope walls for underdrains shall be constructed of concrete conforming to the requirements of subsection 715.12 of the Specifications and shall be constructed in accordance with Standard Details – Volume I and to the dimensions and e levations at locations as shown on the Plans or as directed.
606.3.2.3 -Underdrain Spring Control : Underdrain spring boxes and underdrain for spring control shall be constructed to the dimensions and elevations at locations as shown on the Plans, in acco rdance with Standard Detail Sheet DR -8, or as directed. Any remaining upper portion of the trench shall be filled and compacted as for underdrains.
606.3.3 -Aggregate Filled Fabric Underdrain: Trenches for aggregate filled fabric underdrains shall be ex cavated to the width and depth in Standard Details – Volume I, or as shown on the plans. The trench shall be prepared to a relative smooth state, free of sharp protrusions, depressions, and debris. When fabric is used, it shall be placed with the long d imension parallel to and centered with the alignment of the trench. It shall be placed in the trench in reasonable conformance with the shape of the trench and shall be smooth and free of tension, stress, folds, wrinkles or creases. The fabric shall be ins talled so that any splice joints have a minimum overlap of at least two ( 2) feet in the direction of flow. The overlap of the closure at the top shall be approximately the width of the trench and shall be temporarily used to cover the excavated material on either side of the trench. The aggregate shall be placed by any method which will result in the trench being completely filled to the line shown. The filling process shall not cause the permeability of fabric to be impeded. The fabric, when used, shall be overlapped at the top o f the aggregate. Any portion of the trench not filled with aggregate shall be backfilled in accordance with subsection 606.3.1.3.
401 606.3.4 -Free Draining Base Trench Construction Methods: 606.3.4.1 -Trench: The Free Draining Base (FDB) trench shall be ex cavated to the width and depth as detailed on the plans. Unless otherwise noted, trench walls shall be as nearly vertical as practicable.
606.3.4.2 -Bedding and Placing Perforated Pipe: After excavating the trench, Engineering fabric shall be placed in t he trench in reasonable conformance with the shape of the trench. The Engineering fabric shall be smooth and free of tension, stress, folds, wrinkles, or creases. The Engineering fabric shall be installed so that any splice joints have a minimum overlap of at least two ( 2) feet in any direction. Enough Engineering fabric will be placed in order to properly tie to the mainline placement of Engineering fabric (Item 207034 -*). A two ( 2) inch bedding layer of crushed stone or gravel aggregate shall be placed i n the bottom of the trench for its full width and length. The pipe shall then be placed in the trench. The pipe sections shall be joined with couplings or bands as recommended by the manufacturer. After pipe installation, the remainder of the trench will b e backfilled with crushed stone or gravel aggregate. (refer to table in section 606.2 for material requirements of aggregate)
606.3.4.3 -Outlet Pipe: 606.3.4.3.1 -Connection to Perforated Pipe: At locations designated on the plans or as directed by the E ngineer, rigid outlet pipe will be connected to the perforated pipe. A drop connection utilizing a tee or wye or other means as satisfactory to the Engineer will be used for this connection. This operation may be performed concurrently with the placement o f the perforated pipe or separately.
606.3.4.3.2 -Trenching: The outlet pipe trench shall be excavated to the depth of the flow line of the outlet pipe. Minimum slope of the outlet pipe is to be 3%. Width of the trench will be that width which will allow proper room for pipe placement and backfilling operations.
606.3.4.3.3 -Placing and Backfilling Pipe: The outlet pipe shall be placed in the trench with all ends firmly joined by couplings or bands as recommended by the manufacturer. The outlet pipe sha ll be backfilled with random material in accordance with Subsection 606.3.1.4.
606.3.4.3.4 -Pipe End Treatment: The outlet end of all outlet pipes not tied to drainage structures shall be equipped with a slopewall. Outlet pipes shall be tied to inlets or culverts by the use of pipe saddles, grouting Cementing, or other means satisfactory to the Engineer.
606.4 -METHOD OF MEASUREMENT : The quantity of work done will be measured by the linear foot for pipe, in cluding outlet pipe, for each of the types and sizes as specified, installed, complete, in place and accepted. Length will be determined from actual measurements after the pipe is in place. Angles, tees, and wyes, and other branches which may be required w ill be measured from centerline of main pipe along the centerline of the branch to the end and the length included in the pipe length. Crushed stone, or crushed gravel for underdrains, bedding and spring control will be measured by the volume; the volume w ill be the product of the specified trench width and depth, and the length in place, less