########### Drainage Guidelines

A.  **Excavation:**

    1.  Trenches 1.5 meters (5 ft) and greater in depth shall provide
        for worker safety by either laying back the soils to a 1.5:1
        slope or providing shielding with a properly designed \"trench
        box\". This is not required for excavations in stable rock.
        There is no additional payment for laying back slopes beyond the
        trench payment lines. (Spec Ref.) and 29 CFR 1926

    2.  When excavations occur in unstable soils, select granular
        material will be required below the pipe invert (steel pipe) or
        bedding control line (concrete pipe). For steel pipes, the
        sub-excavation limit shall not exceed 0.6 meters (2 ft.) in such
        unstable soil. For concrete pipe, the sub-excavation below the
        bedding control line can vary 0.3 to 0.6 meters (min/max). When
        excavations occur in rock, the sub-excavation will be 0.3 meters
        for steel pipe. For concrete pipe, the sub-excavation will be
        the bedding thickness for the appropriate pipe size. As such,
        the Standard Sheets should be consulted.

    3.  For open trenches in publicly accessible areas, fence or
        barricade no less than 1.2 meters (4 ft) high, having supports
        at no greater than 3 meter (10 ft) spacing, will be provided.
        \"DANGER - KEEP OUT\" signs 400mm high x 600mm wide will be
        mounted thereupon at no less than 30 meter (100 ft) intervals.
        Sheeting box extensions to 1.2 meter above ground surface
        elevation or a substantial covering over the excavation are
        alternate protective measures. (Spec ref.)

    4.  Before conduit and direct burial cable is placed in an
        excavation, the engineer must approve the excavation depth and
        cross-section. NOTE: All excavated material is the property of
        the contractor for either disposal or for use as another pay
        item within the contract. (spec ref.)

    5.  Excavation is typically completed to either the invert elevation
        of the steel pipe, conduit or culvert or for concrete pipe, the
        bottom of bedding. This is the bottom payment line. For pipes,
        conduits or culverts 300 to 3700 mm diameter (1 ft to 12 ft),
        excavation and payment widths will be either the diameter plus
        1.2 meters (4 ft) or 3 times the diameter, whichever is greater.
        For concrete pipe, add 2x the wall thickness. For sizes greater
        than 3700 millimeters diameter, see the Standard Sheets.

    6.  Drainage basin, manhole and other minor structure excavations
        are made to the bottom of footing (base or foundation slab)
        elevation. Excavation width and payment line is 0.6 meters (2
        ft) outwards in all directions from the structure walls. (Spec
        ref.)

    7.  The top of excavation (payment line) varies for cut and fill
        sections. For cuts, it is usually the ground elevation following
        unclassified excavation. In fills, it is the ground surface
        prior to commencing work on the contract. These same parameters
        apply to drainage basins, manholes and other minor structures.
        (Spec ref.)

B.  **Culvert, Storm Drain and Minor Structure Installation:**

    1.  The bottom of trench, which is coincidental with the invert of
        the steel pipe, conduit or culvert, is either carefully shaped
        to fit the pipe or buttressed on both sides by compacted Select
        Granular material (see F1 below for gradation requirements).
        [For concrete pipe, the bedding material is not
        shaped]{.underline}. However, the material directly below the
        center of pipe (1/3 the outside diameter) shall remain
        un-compacted. All pipe shall be laid in close conformity with
        the line and grade having full, firm and even bearing. Spec ref.

    2.  Concrete pipe will be laid with the bell-end upstream. The
        minimum pipe length for a \"run\" which is [open at either
        end]{.underline}, will be 2300mm (7.5 ft) for pipe sizes between
        600mm and 1525mm (24 and 60 inch) diameters. All other sizes
        have a minimum length of 1800mm (6 ft). When necessary to obtain
        an exact length of culvert, a shorter pipe \"run\" can be
        approved by the engineer. For closed drainage runs (connecting
        minor structures), the minimum section length is unspecified.
        Spec ref

    3.  Round corrugated metal and pipe arches (steel or aluminum) shall
        be placed with the longitudinal seams at the sides. The
        circumferential seams are placed so that lapping occurs in the
        downstream direction, directing water flow over versus under the
        succeeding pipe section. For metal pipe, the contractor shall
        supply measuring devices to verify gauge and steel coating
        thickness. Spec ref.

    4.  Polyethylene pipe will be handled, stored and assembled in
        accordance with the approved Materials Details. Joint
        misalignment greater than 6mm (0.25 inches) or joint separations
        greater than 13mm (0.50 inches) between adjoining sections of
        pipe will not be allowed. Field cutting is permitted for the
        terminal end only but the minimum length of pipe will be 1 meter
        (3.30 ft). Spec ref.

C.  **Pipe Repairs:**

    1.  Concrete pipe damage can be repaired with a Materials Bureau
        approved \"Concrete Repair Material\" (such material be found in
        the State\'s Approved List). The repair shall be properly
        finished and cured per the manufacturer\'s specifications or
        normal procedures. Spec ref

    2.  Bituminous coatings and paving damage, when less than a 0.2
        square meter (2 sq. ft.) area, can be repaired with material
        from the State\'s Approved List. Pipes having coating and paving
        damage greater than 0.2 square meters will be rejected. Spec
        ref.

    3.  Polyethylene pipe having damaged ends can be incorporated into
        the work provided the damaged portion is removed by field
        cutting. For other mid section damage, the pipe may be
        incorporated. However, after backfilling, the interior shall be
        checked to assure no more than 5% percent deflection of the
        interior diameter has occurred. Spec ref.

D.  **Pipe Joints:**

    1.  Round concrete pipe uses flexible water-tight elastomeric
        gaskets. Elliptical concrete pipe uses a joint sealing compound
        conforming to AASHTO M198 Type B or ASTM C990 and Spec ref.

    2.  The last three full-length concrete pipe sections shall be
        joined together at the springline on each side with a
        restraining device (minimum length described under B2 above
        shall be considered a \"full length\". Also, an end-section is
        considered as a \"full-length). For circular pipes 1300mm (48
        inches) diameter and smaller, the device will be a 6mm x 57mm
        (0.5 x 2.25 inch) steel strap conforming to ASTM A36. Nuts,
        bolts and washers will be used to secure through the wall and
        the holes shall be no closer than 450mm (1.5 ft) from the pipe
        end or end of flared end-section. For all other concrete pipes,
        the restraining device will be detailed on the plans. Note: the
        device may be placed on the either the inside or outside. Spec
        ref.

    3.  Ductile iron pipe joints are sealed by caulking a gasket of jute
        or oakum into the hub. Caulking can be either equal parts cement
        and sand mortar or a preformed and/or poured caulking compound
        approved by the engineer. Spec ref.

    4.  Corrugated metal pipe is joined by corrugated band connections.
        The band is lapped on equal sections of the corrugated pipe.
        Spec ref.

    5.  Polyethylene pipe joints are the manufactured ends. No field
        cuts are permitted unless approved by the engineer. The pipe may
        protrude 50mm (2 inches) into a basin to allow for a 45-degree
        mortar seal. This seal is placed at both the interior and
        exterior faces of the basin. Spec ref.

E.  **Concrete Drainage Structures and Manholes:**

    1.  Unless specified otherwise, contractors have the option to use
        pre-cast or cast-in-place drainage structures. Cast-in-place
        structures shall be constructed of Class \'A\' concrete meeting
        all the requirements for structural concrete. Drainage structure
        changes from the details shown in the Standard Plans or in the
        Contract Plans will require submittal and approval of working
        drawings and design calculations. Spec ref.

    2.  Pipe entries will be flush with the inside face of the structure
        (except polyethylene pipe). Concrete pipe bell-ends will be cut
        off where the bell enters the drainage structure. Sealing the
        space around the pipe shall be done with concrete mortar, grout
        or repair material. Spec. ref.

    3.  Pre-cast concrete drainage unit sections shall be joined by a
        male-female joint and sealed with a choice of flexible
        elastomeric gaskets, pipe joint sealing compounds or concrete
        mortar, grout or repair material. Elastomeric gasket shape, size
        and placement follows the recommendations of the precast
        manufacturer. Spec ref

    4.  Drainage unit steps may be cast or bolted in place during
        construction and mortared with a concrete grout after completed
        or attached by friction locking into preformed and/or drilled
        holes. The steps shall be placed no further than 400mm (16
        inches) apart to form a continuous ladder and shall project a
        clear distance of 100mm (4 inches) from the face-of-wall. Spec
        ref

    5.  Units containing minor defects caused by mishandling (defined as
        holes or spalls less than 200mm diameter that do not extend
        beyond the reinforcement) shall be repaired using a concrete
        repair material, the same as that described under C1 above. Once
        finished and cured, the repair shall withstand a moderate blow
        with a 450g (1 lb) hammer. Spec ref.

F.  **Backfill and Compaction:**

    1.  All rigid pipe installations, including sub-excavations, shall
        be backfilled with Select Granular Fill having the following
        gradation:

  -------------------- --------------------------------------------------
  **Sieve**            **  Percent Passing  **

  100mm                100

  75µm                 0 to 15

  425µm                0 to 70
  -------------------- --------------------------------------------------

2.  Note: For corrugated aluminum pipe (Type 1R spiral ribbed pipe),
    100% shall also pass the 50mm sieve. For plastic pipe, 100% shall
    also pass the 19mm sieve. Spec ref.

3.  Fill shall be deposited in horizontal layers 150mm (6 inches) in
    thickness before compaction (However, the first 150mm backfill over
    conduit and cable installations will remain un-compacted). A minimum
    95% percent Standard Proctor Maximum Density is required. Material
    will be deposited to progressively bury the pipe to equal depths on
    both sides. Spec ref.

4.  Select Granular Fill will be placed to 300mm (1 ft) above the pipe
    in cut sections. In embankment fill sections and off-road areas, the
    granular material will be placed to a height 0.6 x O.D. alongside
    the pipe. This is the top pay limit for \"Select Granular\". Beyond
    this point, subgrade area material will be used in the fill and
    off-road sections to 0.3 meters above the pipe. Suitable material is
    then used for the remainder of the backfill. Spec ref.

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G.  **Underdrain:**

    1.  Underdrain excavation is completed to 100 mm (4 inches) below
        invert elevation. The excavation width is the diameter plus 300
        millimeters (plus 1ft). Filter material is then placed and
        compacted to a depth of 100 millimeters minimum (4 inches) as
        \"bedding\" for the underdrain.

    2.  Underdrain filter material shall be stockpiled and have the
        following gradations:

+-----------------------------------+-----------------------------------+
|   ---------------- -------------  |   ---------------- -------------  |
|   **Type 1**                      |   **Type 2**                      |
|                                   |                                   |
|   **  Sieve        **% Passing**  |   **  Sieve        **% Passing**  |
|   Size  **                        |   Size  **                        |
|                                   |                                   |
|   25.0mm           100            |   12.5mm           100            |
|                                   |                                   |
|   12.5mm           30 to 100      |   6.3mm            20 to 100      |
|                                   |                                   |
|   6.3mm            0 to 30        |   2.0mm            0 to 15        |
|                                   |                                   |
|   2.0mm            0 to 10        |   850µm            0 to 5         |
|                                   |   ---------------- -------------  |
|   850µm            0 to 5         |                                   |
|   ---------------- -------------  |                                   |
+-----------------------------------+-----------------------------------+

3.  For polyethylene underdrain, the up-gradient end shall be closed
    with a cap. All other underdrain types shall use a suitable plug.
    Unless the plans show otherwise, perforations will always be placed
    down. For semi-circular steel pipe underdrain, the flat surface will
    face upwards.

4.  Filter material is placed to a depth of 150 millimeters (6 inches)
    and shall remain uncompacted. Successive \"lifts\" will be 150
    millimeters thick and compacted by two vibratory passes of a pad or
    drum type compactor. For polyethylene pipe, the depth of filter
    placement shall be such that 300 millimeters will extend over the
    underdrain following three vibratory passes with a pad or drum type
    compactor (i.e. approximately 450 millimeters or 1.5 ft of filter
    material will be placed before compacting).

5.  Polyethylene underdrain outlets are protected from the sun by
    connection to precast \"aprons\" (as detailed in the plans) or the
    placement of a minimum 1m long (3.3 ft) section of corrugated steel
    or aluminum pipe over the outlet end. When using the metal pipe
    option with 100 to 150 mm diameter underdrain, it shall extend 150
    millimeters into the ground and overlap the underdrain a similar
    distance. The joint can be \'sealed\' by using a reducer fitting or
    wrapping roofing felt over the joint. NOTE: For 200 to 300
    millimeter diameter underdrain piping, the burial distance and
    overlap will be 300 millimeters each.