2502Subsurface Drains

2502.1DESCRIPTION

This Work consists of constructing subsurface drains and installing plant -fabricated pipe and appurtenant Materials:

2502.2MATERIALS

Provide perforated pipe except where unperforated is required. Provide fittings connecting multiple lengths of drain pipe made of the same Material as the pipe.

A Medium Filter Aggregate ................................................................................................3149.2I.1 B Fine Filter Aggregate ......................................................................................................3149.2I.2 C Drain Pipe and Fittings G Precast Concrete Headwall ........................................................................... Standard Plate 3131 H Flexible Transition Couplings .................................................................................... ASTM C1173

2502.3CONSTRUCTION REQUIREMENTS

A General A.1 Excavation, Bedding and Laying Drains General For bituminous Shoulders remaining in-place after drain placement, use a coulter, saw, milling mandrel, or other method approved by the Engineer on the bituminous Shoulder to leave a smooth edge and to prevent disturbance to the bituminous pavement. For new construction, place the Aggregate base before trenching, except for bituminous pavements, place the Aggregate base to the height of the adjacent Layer at the time of trenching. Do not compact greater than 12 inches of backfill in any one Layer. After compaction and leveling, extend the filter Aggregate up onto the adjacent pavement as shown on the Plans. After placing the drain and discharge pipe, do not allow construction E quipment to travel over the drain or discharge pipe until the system is covered. Allow the drain to remain open and operational after installation to prevent water from collecting in the pipe. Excavate the trench to the lines and grades as shown on the Plans. Place drains constructed in conjunction with PCC pavement after pavement placement . Place drains constructed in conjunction with bituminous pavement after placement of the non wearing course(s) and before the wearing course. Construct drains before placing the additional Aggregate base in the Shoulder area. Use cement solvent type joints unless otherwise indicated. Flexible transition couplings are allowed with the Engineer’s approval. Close upgrade ends of subdrain pipe with caps. Use wyes or bends at junctions and turns suitable for cleaning and inspection.

Use 3A grout for connecting to a storm sewer or basin. Remove rock encountered within the excavation to a width of at least the N ominal pipe width plus 2 times the pipe diameter or the Plan width whichever is greater and to a depth of at least 1 pipe diameter below the bottom of the pipe. No stone larger than 1 inch is allowed in the trench. Line the bottom of the drainage trench with geosynthetic as required in the Plan. On the pavement side of the trench, terminate the geosynthetic within the A ggregate base. Do not extend the geotextile up onto the PASB, OGAB, DSB, PASSRC or allow it to fall below the bottom of the Aggregate base. On the side of the trench farthest from the pavement, the Contractor may terminate the geotextile within or above the Aggregate base, but not below it. Place pipe on a minimum 0.2 percent grade or as shown on the Plan. If pipe grades do not follow the Roadway profile at a constant depth, provide and use laser grade control Equipment to place pipe. Follow pavement grades at the depth shown on the Plans when placing pipes in trenches. Properly align the pipe in the cradle before placing the backfill when separate operations are used to place the pipe and backfill. Bed trench with Material as specified in the Plans and compact meeting the requirements 2106.3G.2, “Quality Compaction.” Excess Materials become the property of Contractor. Dispose of excess Materials per 2104.3D.3, “Disposal Outside Right-of-way.” Where a drain connects with a Structure or catch basin, construct a connection that does not leak through the wall of the Structure. Terminate drainage discharge pipe at a precast concrete headwall, per Standard Plate 3131. A.1.a Excavation, Bedding, Laying Drains, and Connecting TP Pipe Place pipe in an open trench. Shape the bedding foundation with the required Material to fit at least the lower 30 percent of the outside circumference of the pipe. Lay drains to line and grade shown on the Plans and with the perforations down. Use a rubber or plastic gasket cast into the headwall. A.1.b Excavation, Bedding, Laying Drains, and Connecting PE pipe Use a trencher capable of cutting the trench to the Plan dimensions, shaping the trench bottom to cradle the lower 1/3 of the pipe, laying the pipe and backfilling with Plan required Aggregate in a simultaneous and continuous operation. Do not plow. If the off-set between the tracks or tires of the trencher is greater than 6 inches, use a self-leveling trenching machine.

Provide trenching Equipment designed and operated to prevent the excavated Material from falling back into the trench. If the trench sides are sloughing or caving in, use a shield to place the backfill. Use couplers for joints unless otherwise indicated. A.2 Geosynthetics Install geosynthetics as shown in the Plans in conformance with 2108, “Geosynthetic Construction Materials.” If required per the Plans, wrap perforated pipe with factory-seamed or factory-produced continuous knit weave geotextile. Place the fabric seam at the top of the pipe, opposite the perforations. For seams at fittings or connectors, mechanically fasten or overlap the adjoining geotextiles at least 6 inches. A.3 Backfill and Compaction For perforated pipe installations, if Plan does not designate Material type, backfill with Material meeting 3149.2I.2, “Fine Filter Aggregate.” Moisten the Aggregate for compaction. Do not use the tire-rolling method to compact the backfill. Do not use stones greater than 1 inch for backfilling. Meet the requirements of 2106.3G.2, “Quality Compaction.” For fine filter Aggregate backfill, meet a DPI of 75 millimeter per hammer blow when using a Dynamic Cone Penetrometer (DCP). A.4 Drain Discharge A.4.a Precast Concrete Headwall Place concrete headwalls on discharge pipes before the end of the construction season. Place precast concrete headwall outlet inverts 12 inches above ditch grades unless otherwise noted in the Plan. Place the uppermost point of the headwall flush with the in-slope at a downward grade of at least 2 percent. Shape the side slopes adjacent to the headwall to conform to the sides and toe of the headwall. Compact the soils around and under the concrete headwall to meet 2106.3G.2, “Quality Compaction.” If headwalls are not required:

A.4.b Discharge Pipe Provide the same diameter of discharge pipe as the pipe. Use connection and coupling methods approved by the Engineer. Construct the discharge pipe to the drain outlet while constructing the drains . Place the discharge pipe and the drains at right angles to the Roadway centerline. Connect the discharge pipe to the headwall. Solvent or gasket joint into a TP coupling cast into the headwall. Connect two drain runs that come together at a low point with a TP “ Y” connection. Use a TP discharge pipe to outlet the “Y” connection to a single headwall. Place discharge pipes at grades no less than the drain pipes and with at least 2 percent fall. The Engineer may approve trench widths greater than 10 inches for the discharge pipes, if the Contractor meets the following requirements:

pipe

Embankments and Backfills” Use compaction Equipment capable of compacting the Material in the drain trench without compacting the adjacent soils. Use backfill Layer uncompacted thicknesses no greater than 6 inches. Correct Shoulder settlement above the discharge pipe as directed by the Engineer and at no additional cost to the Department. Replace crushed or deformed discharge pipes or connections at no additional cost to the Department. If drains discharge to storm sewers, place the drain invert from 6 inches to 12 inches above the sewer invert using a connection method approved by the Engineer at no additional cost to the Department. Establish turf in accordance with specification 2575.3L, “Turf Establishment,” concurrent with drain outlet installation. A.5 Quality Assurance Testing and Clean Out The Engineer will perform inspections using a probe mounted on the end of a flexible fiberglass rod 4 inches long and with a diameter of 1 Nominal pipe size smaller than the drain pipe being inspected. The Engineer will conduct the inspection through the discharge pipe, radius connection, and at least 3 feet into the main drainage line. Clean or repair inoperative discharge pipe and connections as approved by the Engineer. Replace crushed or deformed pipes or connections at no additional cost to the Department.

A.6 Maintenance during Construction Place Aggregate base in the Shoulder area over the compacted drain and backfilled trench, to avoid contamination. Remove and replace contaminated Materials at no additional cost to the Department. Allow the drain to remain open and operative after installation to prevent water from collecting in the pipe. A.7 Marking Outlet Locations Permanently mark the locations of outlets with a 6 inch by 18 inch strip of white marking tape in accordance with 3354, “Preformed Pavement Marking Tape.” Place the tape at the outside edge of the bituminous Shoulder, at right angles to the Roadway, and roll the tape into the Shoulder while the bituminous pavement surface temperature is from 120°F to 150°F. If 2 runs of drain pipe come together at a low point and discharge via a “ Y” to a single outlet, place 2 markings side-by-side with a 6 inch spacing. For locations with no bituminous Shoulder, place the tape on the bituminous pavement or spray a white paint strip on concrete pavements . B Subcut Drain Specific Requirements The Contractor may directly connect subcut drains to permanent drainageS tructures or outlet the drains to the ditch using a discharge pipe and headwall. Maximum spacing of Structures is 800 feet. Make connections to drainage Structures as approved by the Engineer. Place discharge outlets at low points and spaced no greater than 500 feet apart. B.1 Design Option One Place perforated TP pipe in the bottom of the subcut in accordance with the design typical in the Plans. Place 12 inches of backfill above the pipe before compacting. Provide pipe with either bell and spigot or sleeve couplings and either gasket or solvent joints. Mark the fitting insertion line on the ends of the bell or sleeve. Maximum angle is 22 1/2 degrees when connecting to drainage Structures. B.2 Design Option Two Place perforated PE pipe after partially or totally backfilling the subcut. Backfill and compact as shown in the Plan.. Perform the trenching operation after placing and compacting at least 24 inches of subcut backfill. If trenching after completely backfilling the subcut, only backfill the lowermost 24 inches of the trench. Backfill the remaining trench with the same Material used for the subcut. C Pavement Edge Drain Specific Requirements Place edge drain adjacent to new concrete pavements after constructing the pavement. Run the trenching head tight against the pavement to completely excavate adjacent soil. Place the edge drains before pavement cracking when cracking in -place PCC pavement. Place the drains before excavating the widening-trench for edge drains placed in conjunction with pavement widening. Use an approved device on the trenching machine to ensure that the pipe is located at the design distance from the edge of the in-place pavement. After compaction, ensure the backfill in the drain extends at least 4 inches above the bottom of the pavement widening trench. When placing edge drains adjacent to new bituminous pavement, construct the edge drain after placing the non wearing courses, but before placing the wearing course. For new and retrofit bituminous construction, ensure the trenching head continuously intercepts and cuts -off the roll-over portion of at least the lower bituminous pavement course.

D Interceptor Drains Specific Requirements Construct 4 inch to 6 inch Aggregate-filled interceptor drains at the end of each pavement joint and at mid-panel cracks, or at other major cracks as designated by the Engineer. Interceptor drains must be installed before placing a stress relief Layer or any other overlaying Work. Cut trenches normal to the pavement edge centered on the joint or crack. Cut trenches 2 inches deeper than the adjacent pavement and running the full-depth from the in-place pavement edge to at least 4 inches beyond the edge of the unbonded concrete overlay. Clean soil or debris from the exposed pavement crack or joint before backfilling the trench. The Engineer will approve the method and extent of joint/crack cleaning. Backfill any void space to the top of the trench with fine filter Aggregate.

2502.4METHOD OF MEASUREMENT

A Drainage System The Engineer will measure drainage system on a lump sum basis. No measurement will be made of any individual subsurface drain item. B Precast Concrete Headwalls The Engineer will measure Precast concrete headwalls on an each basis. C Interceptor Drains The Engineer will measure Interceptor drains on an each basis. D Subsurface Drains The Engineer will measure subsurface drains by the length of the provided and installed subsurface drain and discharge pipe approved by the Engineer. The Engineer will measure drain and discharge pipes by installed length along the centerline of the pipe. The Engineer will begin and end measurement at the pipe end at free outlets, at the point of junction with in-place pipe, or at the center of Structures, catch basins, or multiple junction points. Where the Contract requires subsurface drains, the Engineer will separately measure the lengths of each size and type of pipe.

2502.5BASIS OF PAYMENT

The Contract Unit Prices for subsurface drains and outlets of each size, type, kind, and strength class includes the cost of pipe, geotextiles, excavation, and backfill. For subcut drains, if the Plan includes both Option 1 and Option 2, the Contractor may select either option and the Pay Item will be 4” Perforated TP pipe drain. Payment for Interceptor drains under the Contract bid item includes cutting the trench, cleaning joint and crack face, furnishing and compacting Aggregate, and other associated Work. The Contract Unit Price for Precast concrete headwall includes the cost of the headwall, connecting the pipe, couplings, rolled erosion prevention product and seed, marking outlet location, inspecting, and other associated Work. For required sodding, the Engineer will include the cost of the sod with relevant Contract Pay Items.

The Department will pay for subsurface drains on the bas is of the following schedule: Item No. Item Unit

2502.501 Drainage System Type (____) lump sum

2 ___” Precast Concrete Headwall each

2 Interceptor Drain each

2 Install * each

3 ___” Perf ǁ Pipe Drain † linear foot

3 Install ___” † linear foot

3 ___” * Pipe Drain † linear foot

* Specify item name. ǁ Specify kind in accordance with 2502.2C, “Drain Pipe and Fittings.” † Specify strength class if other than the minimum requirement.