68 SUBSURFACE DRAINS
68-1 General
68-1.01 General
68-1.01A Summary
Section 68 -1 includes general specifications for constructing subsurface drains .
68-1.01B Definitions
Reserved
68-1.01C Submittals
Submit a certificate of comp liance for each type of subsurface drain involved.
68-1.01D Quality Assurance
Reserved
68-1.02 Materials
68-1.02A General
Reserved
68-1.02B Protective Coating
If described as coated, subsurface drains must be protected with a coating under section 66 -1.02C.
68-1.03 Construction
68-1.03A General
Repair damaged coatings under section 66 -1.02C.
68-1.03B Filter Fabric
Remove loose or extraneous material and sharp objects immediately before placing filter fabric. The subgrade and trench to receive the filter fabric must comply with the compaction and elevation tolerance specified for the material involved. Handle and place filter fabric under the manufacturer's instructions. Align and place filter fabric without wrinkles. Overlap adjacent roll ends of f ilter fabric at least 18 inches. The preceding roll must overlap the following roll in the direction that the permeable material is being spread. Completely replace torn or punctured sections damaged during placement or repair by placing a piece of filter fabric that is large enough to cover the damaged area and comply with the overlap specified. Cover filter fabric with the thickness of overlying material within 72 hours of placing the fabric.
68-1.04 Payment
Not Used
68-2 Underdrains
68-2.01 General
68-2.01A Summary
Excavation and backfill must comply with section 19 -3.
68-2.01B Definitions
Reserved
68-2.01C Submittals
Submit a certificate of compliance for each ty pe of pipe, tubing, and fitting. SECTION 68 SUBSURFACE DRAINS
68-2.01D Quality Assurance
Reserved
68-2.02 Materials
68-2.02A General
For alternative pipe underdrain, do not mix types of pipe in the same installation.
68-2.02B Perforated Steel Pipe
Perforated steel pipe and coupling bands must comply with AASHTO M 36 and AASHTO M 218 with the following modifications:
1.Pipe must comply with any one of the full circle types specified in AASHTO M 36.
2.Pipe perforations must be drilled or punched.
3.Perforations must be located in the inside of crests or in the flat tangent portion of all corrugations but not in both locations in a given length of pipe. The weight of galvanizing must comply with ASTM A123/A123M and ASTM A153/A153M. You may substitute sleeve type couplings for the band couplers required under AASHTO M 36. The couplings must be plastic or galva nized steel, suitable for holding the pipe firmly in alignment without the use of sealing compound or gaskets. The couplings must have mechanical properties that will prevent distortion under normal conditions of use.
68-2.02C Perforated Aluminum Pipe
Aluminum underdrain pipe and fittings must comply with AASHTO M 196 and the following modifications:
1.Pipe must comply with Type III specified in AASHTO M 196.
2.Pipe perforations must be either drilled or punched.
3.Minimum thickness of sheet must be 0.060 inch. You may substitute sleeve type couplings for band couplers required under AASHTO M 196. The couplings must b e plastic or aluminum, suitable for holding the pipe firmly in alignment without the use of sealing compound or gaskets. The couplings must have mechanical properties that will prevent distortion under normal conditions of use.
68-2.02D Perforated Plastic Pipe
Perforated plastic pipe must be smooth -wall PVC plastic pipe, corrugated PVC plastic pipe with a smooth interior surface, or corrugated polyethylene plastic tubing. Smooth -wall PVC plastic pipe must comply with AASHTO M 278. Corrugated PVC plastic pipe with a smooth interior surface must comply with material and structural requirements in AASHTO M 278. Pipe must have perforation s located in the bottom half of the pipe; the perforations must be slots complying with the size and opening area requirements in AASHTO M 252. Inside diameter and diameter tolerances must comply with AASHTO M 252 or M 278. Corrugated polyethylene plastic tubing must comply with AASHTO M 252 or M 294. PVC plastic pipe must be connected with belled ends, or with sleeve -type or stop -type couplings under AASHTO M 278. Polyethylene tubing must be connected with snap -on, scre w-on, or wrap -around fittings and couplings under AASHTO M 252 or AASHTO M 294.
68-2.02E Underdrain Outlets and Risers
Underdrain outlets and risers must be fabricated from the same material as the underdrain pipe or from corrugated metal pipe. Do not mix aluminum and steel in the same installation except for covers and coupling band fastening hardware. Outlet and riser pipe and fittings must not b e perforated. Welded steel covers must be galvanized under section 75 -1.02B after fabrication. Welding workmanship and technique must be equal to the best practice in modern commercial shops. SECTION 68 SUBSURFACE DRAINS Covers must be fitted and bolted onto the riser pipe or elbow.
68-2.02F Permeable Material
68-2.02F(1) General
Permeable material for use in backfilling trenches under, around, and over underdrains must consist of hard, durable, clean sand, gravel, or crushed stone and must be free from organic material, clay balls, or other deleterious substances. Permeable material must have a dur ability index of not less than 40. Use Class 1 permeable material for underdrains unless the class or type of permeable material is specified in the special provisions. At bridge abutments and wingwalls, use either Class 1 or Class 2 permeable material. Pl ace filter fabric between Class 1 permeable material and backfill. No filter fabric is required with Class 2 permeable material.
68-2.02F(2) Class 1 Permeable Material
Alternative gradations within Class 1 permeable material are identified by types. Place one of the types specified for Class 1 permeable material. The percentage composition by weight of Class 1 permeable material in place must comply with the gradation requirements shown in the following table: Class 1 Permeable Material Gradation Requireme nts Sieve size Percentage passing Type A Type B 2" -- 100 1-1/2" -- 95–100 3/4" 100 50–100 1/2" 95–100 -- 3/8" 70–100 15–55 No. 4 0–55 0–25 No. 8 0–10 0–5 No. 200 0–3 0–3
68-2.02F(3) Class 2 Permeable Material
The percentage composition by weight of Class 2 permeable material in place must comply with the gradation requirements shown in the following table: Class 2 Permeable Material Gradation Requirements Sieve size Percentage passing 1" 100 3/4" 90–100 3/8" 40–100 No. 4 25–40 No. 8 18–33 No. 30 5–15 No. 50 0–7 No. 200 0–3 Class 2 permeable material must have a sand equivalent value of not less than 75.
68-2.02F(4) Class 3 Permeable Material
The percentage composition by weight of Class 3 permeable material in place must comply with the gradation requirements shown in the following table: SECTION 68 SUBSURFACE DRAINS Class 3 Permeable Material Gradation Requirements Sieve size Percentage passing 1-1/2" 100 1" 88–100 3/4" 52–85 3/8" 15–38 No. 4 0–16 No. 8 0–6 At least 90 percent by weight of Class 3 permeable material must be crushed particles as determined by California Test 205.
68-2.02G Filter Fabric
Filter fabric for use with underdrains must comply with section 96 -1.02B. At bridge abutments and wingwalls, fi lter fabric for underdrains must be Class A.
68-2.02H 68-2.02N Reserved
68-2.03 Construction
Excavate trenches for underdrains, place filter fabric, install pipe, and backfill trenches with permeable material as shown. Where underdrains are installed in trenches outside the subgrade area, backfill the top 6 inches of the trench with structure backfill complying with section 19 -3. Join lengths of perforated steel pipe and perforated aluminum pipe with couplers. Lay perforated pipe with the perforations down. Solvent cementing of joints on perforated plastic pipe is not required. Repair damaged galvanized surfaces under section 75 -1.02B. Underdrain outlets and riser covers must seat uniformly and not be subject to rocking. Place perforated po lyethylene tubing to line and grade in a close -fitting semicircular bedding groove formed in the bottom of the trench. At bridge abutments and wingwalls:
1.Install welded steel covers on underdrains terminating underground.
2.Place permeable material in horizontal layers. Thoroughly consolidate permeable material along with and by the same methods specified for structure backfill in section 19 -3. Ponding and jetting of permeable material or structure backfill adjacent to permeable material is not allowed.
3.You may substitute permeable material for structure backfill material where the required width of backfill material adjacent to the neat lines of the permeable material as shown is approximately 1 foot or less.
68-2.04 Payment
The payment quantity fo r pipe underdrain is the length measured parallel with the slope line. The payment quantity includes the length measured along the centerline of elbows, outlets and risers and the length of wyes, tees, and other branches to the point of intersection.
68-3 Horizontal Drains
68-3.01 General
Section 68 -3 includes specifications for constructing horizontal drains . Section 61 -2 does not apply. SECTION 68 SUBSURFACE DRAINS
68-3.02 Materials
Horizontal drains must consist of nominal 1 -1/2-inch, schedule 80 PVC plastic pipe complying with ASTM D1785. At your option, the type, grade, and design stress designation of the pipe must be 1120, 1220, 2110, 2112, 2116, or 2120 as specified in ASTM D1785. The plastic pipe must comply with the National Sanitation Foundation Standard No. 14 if the plastic pipe is used to conduct water for human consumption. Slotted pipe must have 2 rows of slots. The rows must be in the longitudinal direction of the pipe and the slots must be cut in the circumferential direction of the pipe. The rows must be centered on 2 of the 3rd points, 120 degrees apart, of the pipe circumference. Each row of slots must comply with one of the configurations shown in the following table. The Engineer determines the configuration to be used. Number of slots (±1 per linear foot) Width of slot (in) Minimum opening per linear foot (square inches) 22 0.050 1.00 23 0.020 0.46 46 0.010 0.46 Slots must be spaced uniformly along the pipe. The minimum opening is measured on the inner surface of the pipe. Perforated pipe must have 3 rows of perforations with 1 row on each side of the pipe and the 3rd row on the top. The perforations must be 3/8 inch in diameter spaced at 3 -inch centers with the top perforations staggered in relation to the holes on either side. Fittings for the PVC plastic pipe must be schedule 80 Type II PVC solvent weld type fittings and must comply with ASTM D2467. You may use machined male and female ends instead of couplings. Unslotted or unperforated PVC plastic pipe, approximately 3 to 30 feet in length, must be provided at the outlet of the drain. The Engineer determines the exa ct length of pipe.
68-3.03 Construction
The locations shown for horizontal drains are approximate. The Engineer determines the exact locations and placement sequence. Any ordered exploratory work is change order work. Complete the installation of horizontal drains at a bench in an excavation slope before excavating more than 40 feet below the bench. Furnish water required for drilling. Drill horizontal holes to the designated lines and grades with rotary equipmen t capable of drilling 3 to 6 - inch-diameter holes 600 feet long through soil and rock formations. Install plastic pipe with pipe slots or perforations on top by pushing it into the hole or inserting it inside the drill rod then retracting the drill rod so t hat the drilled hole is cased for the full depth. Tightly plug the entrance end with a rounded or pointed extension that does not extend more than 0.5 foot beyond the end of the pipe. During casing activity, cement plastic pipe together to form a continuou s tube. Prevent telescoping and damage to plastic pipe during installation. Identify each drain by securely attaching a permanent brass plate with a number assigned by the Engineer to the outlet end of the nonperforated pipe drain or by other permanent mar king designated by the Engineer. Tightly plug the annular space between the hole and the pipe with earth for a length of at least 2 feet at the outlet end of the drilled hole. Connect the outlet end of the drain to the collector system by installing a pipe tee, pipe plug, street ell, and galvanized steel pipe or plastic pipe. The Engineer determines the length of the pipe. SECTION 68 SUBSURFACE DRAINS Furnishing and installing a collector system is change order work. During drilling activities, determine the drilled ho le elevation at 100 -foot intervals and the elevation at the upper end of the completed drain hole. You may take measurements by inserting tubes or pipes and measuring liquid levels or by other authorized methods. Dispose of water used for drilling and wate r developed during drilling activities under section 13. Comply with the requirements of the RWQCB for nonstormwater discharges and the Department's Construction Site Best Management Practices (BMP) Manual for dewatering.
68-3.04 Payment
The payment quant ity for furnish and install drain pipe (horizontal drain) is the length measured (1) along the centerline of the pipe and (2) from the outlet end to the collector system. The payment quantity for drill hole is the length measured along the centerline of th e pipe for the length of the hole drilled, except the Department does not measure or pay for any hole drilled where the drain pipe cannot be installed for the full length of the drilled hole.
68-4 Edge Drains
68-4.01 General
Section 68 -4 includes specifi cations for constructing plastic pipe edge drains and edge drain outlets . Edge drain outlets include:
1.Outlet pipes, vent pipes, cleanouts, and Y -fittings at cleanout pipes
2.Intermediate outlet connection s between the couplings at each end of the curved section of the Y - fitting Edge drains include cross drain interceptors at structure approaches, at end anchors or pressure relief joints, and at pavement te rminals joining existing pavements. Section 61 -2 does not apply.
68-4.02 Materials
68-4.02A General
Reserved
68-4.02B Pipe and Pipe Fittings
Pipe installed in trenches to be backfilled with asphalt treated permeable material must be PVC 90 degree C electric plastic conduit, EPC -40 or EPC -80, and must c omply with NEMA TC 2. All other edge drain pipe and edge drain outlets, vents, and cleanouts must be one of the following:
1.PVC 90 degree C electric plastic conduit, EPC -40 or EPC -80, and must comply with NEMA TC 2.
2.PVC plastic pipe, schedule 40 or sc hedule 80, and must comply with ASTM D1785. At your option, the type, grade, and design stress designation of the pipe may be 1120, 1220, 2120, 2116, 2112, or 2110 as specified in ASTM D1785. Pipe must be straight end or bell end. Bell end sockets must comply with ASTM D2672 except for marking. Pipe shown as slotted must have 3 rows of slots in the pipe. The rows must be in the longitudinal direction of the pipe and the slots must be cut in the circumferential direction of the pipe. The 3 rows must be spaced equally around the circumference of the pipe. Each row must have 22 ± 1 uniformly spaced slots per linear foot of pipe. The slots must be 0.045 –0.065 inch wide and of a le ngth to provide at least 2.00 square inches of slot opening per linear foot of pipe. Other suitable configurations of slots that provide drainage equal to or better than the above slot requirements may be used if authorized. Fittings for PVC 90 degree C el ectric plastic conduit must comply with NEMA TC 3, and fittings for PVC plastic pipe must be socket -type fittings under ASTM D2467 for schedule 80 pipe and ASTM D2466 for schedule 40 pipe. Y -fittings must be shop fabricated from pipe as specified for the t ype of edge drain pipe installed. The fitting must provide an unobstructed passageway through both legs of the Y -fitting. SECTION 68 SUBSURFACE DRAINS
68-4.02C Treated Permeable Material
At your option, permeable material for edge drains must be asphalt treated permeable material or cement treated permeable material complying with section 29 for treated permeable bases.
68-4.02D Filter Fabric
Filter fabric must comply with section 96 -1.02B.
68-4.02E Miscellaneous
Concrete for splash pads must be constructed of minor concrete, except the concrete must contain at least 470 pounds of cementitious material per cubic yard. Mortar placed where edge drain outlets and vents connect to drainage pipe and existing drainage inlets must comply with section 51 -1. Expansion type pressure plugs for cleano uts must seat firmly against the pipe lip and be one of the following:
1.Expandable plugs manufactured from neoprene under section 51 -2.04B with commercial quality stainless steel bolts and 2 hex nuts
2.Commercial quality expandable duct plugs consisting of reinforced polypropylene rigid threaded plug with a commercial quality thermoplastic rubber sealing ring Aggregate base for backfilling trenches in existing paved areas must comply with the materials specifications for Class 2 aggregate base, 3/4 -inch-maximum gradation, under section 26 -1.02B. Use minor HMA to backfill trenches in existing asphalt shoulders . The 1/2 -inch screen or grate must be made of commercial quality galvanized metal with nominal 1/2 -inch square openings.
68-4.02F 68-4.02H Reserve d
68-4.03 Construction
Before excavating trenches for the installation of edge drains, outlets, vents, and cleanouts in existing paved areas, cut the outline of the paved areas to be removed to a neat line to a minimum depth of 2 inches with a power -drive n saw or a wheel type rock cutting excavator. Cuts along the joint between existing asphalt concrete and existing concrete pavement are not required. Remove concrete deposits that could occur along the lower edge of the concrete pavement in Type 1 installa tions. Join pipe and fittings with commercial quality solvent cement and primer specifically manufactured for use with rigid PVC plastic pipe and fittings. The solvent cement and primer must be made by the same manufacturer. The color of the primer must co ntrast with the color of the pipe and fittings. Apply the solvent cement and primer under the manufacturer's instructions. Spread treated permeable material when the atmospheric temperature is above 40 degrees F. You may spread the treated permeable materi al in 1 or more layers. Where edge drains are to be installed adjacent to asphalt treated permeable base, you may spread the lower 6 inches of asphalt treated permeable material in a separate operation, then spread the upper portion of the asphalt treated permeable material with the adjacent asphalt treated permeable base. Place asphalt treated permeable material at a temperature of not less than 180 degrees F or more than 230 degrees F, except the temperature of asphalt treated permeable material spread wi th asphalt treated permeable base must comply with section 29 for spreading asphalt treated permeable base. Compact asphalt treated permeable material spread with adjacent asphalt treated permeable base with the adjacent base and in the same way specified in section 29 for compacting the base. Compact all other layers of treated permeable material with a vibrating shoe -type compactor connected to the spreading device. The vibrating shoe -type compactor must be in operation when the material is being spread i n the trench and must be turned off when the material is not being spread. SECTION 68 SUBSURFACE DRAINS Cure cement treated permeable material that is not covered with HMA within 12 hours after compacting the permeable material by sprinkling the material with a fine spray of water every 4 hours during daylight hours or by covering the material with a white polyethylene sheet not less than 6 mils thick. Start the curing requirements at 7:00 a.m. on the morning following compaction of the cement treated permeable material and co ntinue for the next 72 hours or until the material is covered with HMA, whichever is less. Do not spray the cement treated permeable material with water during the first 12 hours after compacting. You may cover the cement treated permeable material with th e polyethylene sheet during the first 12 hours or before the start of the curing period. Backfill and compact trenches in existing embankment areas with native material. Aggregate base backfill must be spread and compacted by methods that produce a uniform base, firmly compacted and free from pockets of coarse or fine material. Place Type G pavement markers with retroreflective face facing away from the oncoming traffic under section 81 -3.02C on paved shoulders or dikes at outlet, vent, and cleanout locatio ns where authorized. The waiting period for placing pavement markers on new HMA surfacing does not apply. Clean edge drain outlets, vents, and cleanout pipes during installation and remove obstructions after installation. Use a high -pressure, flexible hose with a nominal 1 -inch-diameter nozzle containing flushing and propelling jets. Insert the hose into each edge drain outlet, vent, and cleanout pipe and push it through the pipe with a minimum 1,000 psig water pressure so that the entire edge drain system is penetrated by the flushing nozzle. At your expense, replace pipes found to be plugged, including replacement of treated permeable material, surfacing, and backfill materials. Install outlet and vent covers at the end of each outlet pipe and vent pipe. Dispose of surplus excavated material.
68-4.04 Payment
The payment quantity for edge drain is the length measured along the centerline of the pipe with no deductions for gaps in edge drain pipe at outlets and vents. The payment quantity for edge drain outl et is the length measured along the centerline of the pipe.
68-5 Permeable Material Blanket
Reserved
68-6 Reserved
68-7 Geocomposite Drain Systems
68-7.01 General
68-7.01A Summary
Section 68 -7 includes specifications for constructing geocomposite drai n systems . Geocomposite drain includes filter fabric and plastic pipe.
68-7.01B Definitions
Reserved
68-7.01C Submittals
Submit a certificate of compliance for the geocomposite drain certifying that the drain produces t he specified flow rate. The certificate must be accompanied by a flow capability graph for the geocomposite drain showing flow rates and the externally applied pressures and hydraulic gradients. Include verification by an authorized laboratory for the flow capability graph.
68-7.01D Quality Assurance
Reserved
68-7.02 Materials
68-7.02A General
Filter fabric must be Class A. SECTION 68 SUBSURFACE DRAINS
68-7.02B Geocomposite Drain
Geocomposite drain must comply with the specifications for geocomposite wall drain.
68-7.02C Plastic Pipe
Plastic pipe must comply with the specifications for pipe for edge drains and edge drain outlets in section 68-4.
68-7.02D Drainage Pads
Drainage pads must be constructed of minor concrete.
68-7.02E Treated Permeable Base
Treated permeable b ase to be placed around slotted plastic pipe at the bottom of geocomposite drains must comply with section 29. If asphalt treated permeable base is used, place the base material at a temperature of not less than 180 degrees F or more than 230 degrees F.
68-7.03 Construction
Install the geocomposite drain with the drainage void and the filter fabric facing the embankment. The fabric facing the embankment side must overlap at least 3 inches at all joints and wrap around the exterior edges at least 3 inches b eyond the exterior edge. If additional fabric is needed to provide overlap at joints and wraparound at edges, the added fabric must overlap at least 6 inches and be attached to the fabric on the geocomposite drain. Place core material manufactured from imp ermeable plastic sheeting having nonconnecting corrugations with the corrugations approximately perpendicular to the drainage collection system. If the fabric on the geocomposite drain is torn or punctured, replace the damaged section completely or repair it by placing a piece of fabric that is large enough to cover the damaged area and provide at least a 6-inch overlap.
68-7.04 Payment
Not Used
68-8 Prefabricated Vertical Drain S
68-8.01 General
68-8.01A Summary
Section 68-8 includes specifications for installing prefabricated vertical drains.
68-8.01B Definitions
refusal: Drive sleeve or mandrel advancing rate less than 3 inches per second with full applied force.
68-8.01C Submittals
68-8.01C(1) General
Submit:
1.Certificate of compliance
2.Test sample s representing every 8,000 linear ft
3.Minimum average roll value s as defined under ASTM D4 759 Label submittals with the manufacturer's name and product information.
68-8.01C(2) Shop Drawings
Submit 5 copies of shop drawings. Upon review completion , submit from 6 to 12 copies, as requested, for authorization and use during construction. Shop drawings and calculations must be stamped and signed by an engineer who is registered as a civil enginee r in the State. Shop drawings must include: SECTION 68 SUBSURFACE DRAINS
1.Your name, address, telephone number, and email address
2.Plans showing the layout , identification, and working surface and bottom elevations of prefabricated vertical drains
3.Proposed installation sequence
4.Proposed method to loosen and penetrate stiff upper soil layers before installing prefabricated vertical drains and method to backfill the loosen holes, if needed
5.Manufacturer, model number, description and specifications of installation equipment
6.Manufacturer, model number, description and s pecifications of device s for measur ing and recor ding plumbness, installation length , and depth
68-8.01C(3) Construction Record
Submit daily construction record within 24 hours . Includ e identification , locati on, and depth of installed prefabricated vertical drains.
68-8.01D Quality Assurance
68-8.01D(1) General
Reserved
68-8.01D(2) Quality Control
Reserved
68-8.01D(3) Department Acceptance
68-8.01D(3)(a) General
Reserved
68-8.01D(3)(b) Verification Testi ng
Do not start installation until the verification test is accepted. Install 2 prefabricated vertical drains at locations determined by the Engineer. Use the same equipment and method to be used for installation. Perform verification tests in the Engineer's presence. The verification test must demonstrate that the proposed equipment and method can install prefabricated vertical drains to the depth shown. The Department rejects verification tests that fail to install prefabricated vertical drains to the depth shown . Submit revised shop drawings for additional verification tests. Repeat verification testing until the results demonstrate that the proposed equipment and method can install prefabricated vertical drains to the depth s shown .
68-8.01D(3)(c) Acceptance Testing
Reserved
68-8.02 Materials
Prefabricated vertical drain s must consist of a polymeric core with filter fabric integrally bonded to both sides of the core creating a stable drainage void. Prefabricated vertical drain s must be f ree of defects, rips, or holes. Identify prefabricated vertical drain rolls under ASTM D4873 . Label or tag must include lot or control numbers, individual roll number, date of manufacture, manufacturer, and product identification. Prefabricated vertical dr ains must comply with the requirements shown in the following table: SECTION 68 SUBSURFACE DRAINS Prefabricated Vertical Drains Quality characteristic Test method Requirement Total discharge capacity @ 72 psi and unit hydraulic gradient (min, g allon per minute ) ASTM D4716 1.6 Tensile strength (min, lb) ASTM D4 595 225 Nonwoven geotextile of prefabricated vertical drain s Apparent opening size, average roll value (max, µm (US Sieve)) ASTM D4751 212(70) Permittivity (min, sec -1) ASTM D4491 0.3 Grab tensile strength (min, lb) ASTM D4632 112 Puncture strength (min, lb) ASTM D 6241 125 Trapezoidal tear (min, lb) ASTM D 4533 55
68-8.03 Construction
Handle and store prefabricated vertical drain s under the manufacturer 's instructions and ASTM D4873 . During shipment and storage, the prefabricated vertical drain s must be wrapped in a heavy -duty protective covering. Store and protect prefabricated vertical drain s from sunlight, mud, dirt, dust, debris, and detrimental substances. Before installation, survey, mark, and label the prefabricated vertical drain locations as shown. Install prefabricated vertical drains within 6 inches from the locations shown. Install prefabricated vertical drains fro m the working surface and to the tip elevation shown. Equipment for installing prefabricated vertical drains must :
1.Be plumbed with d eviation from vertical less than 1 in 50 during installation of the prefabricated vertical drain s
2.Be able to advance t hrough the soil at the job site to the design tip elevatio n
3.Have a cross -sectional area of the driving sleeve or mandrel combined with the anchor less than 10 square inches
4.Have a driving sleeve or mandrel that can protect the prefabricated vertical drain material from tears, cuts, and abrasions during installation Advance the driving sleeve or mandrel at a constant force or constant rate. Protect prefabricated vertical drain s from tears, cuts, and abrasions during installation. Anchor the tip of each prefabricated vertical drain s with a rod or anchor plate. You may end the prefabricated vertical drain at an elevation within 8 feet of the design tip elevation. Do not use jetting or impact method. If authorized, you may use aug er or vibrator to loosen and penetrate stiff upper soil layers before installing prefabricated vertical drains. Auger holes must be 6 inches or less in diameter and extend less than 12 inches past the obstruction. Backfill the auger hole with sands immediately after install ation of each prefabricated vertical drain. Cut installed prefabricated vertical drains neatly with at least 12 inches protruding above the working surface. Do not damage previously installed prefabricated vertical drains. You may splice prefabricated vertical drains. Spliced section of prefabricated vertical drain s must have the same or better structural and hydraulic properties than prefabricated vertical drain s without splice . Place the end of the trailing roll of prefabr icated vertical drain s inside the geotextile covering of the existing roll. Overlap each end of prefabricated vertical drains with geotextile covering at least 8 inches. Prefabricated vertical drains that are out of plum b, out of location, damaged, or impr operly installed are rejected. Install 2 additional prefabricated vertical drains for each rejected prefabricated vertical drain 2 feet away from the rejected prefabricated vertical drain and at locations determined by the Engineer. SECTION 68 SUBSURFACE DRAINS
68-8.04 Payment
Not Used
68-9 68-15 Reserved
Source: California Standard Specifications, 2024 Edition. Pages 995–1006 of 1,372.