ITEM
657 RIPRAP FOR TREE PROTECTION
657.01
Description
657.02
Materials
657.03 Tree
Wells in Fill
657.04 Walls in
Cut
657.05
Hand-Laid Stone Riprap
657.06
Earthwork
657.07 Pipe
Drains
657.08 Method
of Measurement
657.09 Basis of
Payment
657.01 Description. This work consists of
furnishing and placing riprap for protecting selected trees or shrubs by tree
wells and retaining walls.
657.02 Materials. Furnish stone consisting of
sandstone, limestone, or other natural rock with a maximum 30 percent single
slab loss and a maximum 20 percent cumulative loss after testing to ASTM D 5240. Use an
8-inch slab test sample. The Department may waive testing when the stone
source has a known durability history. Furnish embankment according to
Item 203. Unless otherwise specified, use
4-inch (100 mm) pipe conforming to 611 Type E conduits.
657.03 Tree Wells in Fill. Where a
fill around a tree or shrub not marked for removal will be 12 inches (0.3 m) or
more in depth over the feeding root area or ground surface lying within the
periphery of the tree, construct a dry hand-laid stone riprap tree well.
Construct a wall, of the same height as the fill, circling the tree or shrub
and 3 1/2 feet (1 m) from the tree trunk or as specified. Construct
the wall so that the top of the wall follows the contour on the finished grade
in a neat line.
Construct
tree wells before placing the fill over the root area. However, the
Contractor may bring up the fill with the wall after required aggregate for
root aeration is in place according to Item 658.
657.04 Walls in Cut. Where the top of the slope
in cut is within 6 feet (2 m) of the trunk of a tree not marked for removal,
construct a dry hand-laid stone riprap wall. Toe the bottom of the wall
into the ground 2 inches (50 mm) unless otherwise shown on the plans, and make
the top of the wall even with the original ground line at the base of the
tree. Extend the length of the wall far enough from the tree to amply
cover the roots, or according to the shape and size as shown on the
plans. Flare the ends of the wall back, and
taper or fade them out into the finished grade of the slope in a neat line.
657.05 Hand-Laid Stone Riprap. Construct
the earth bed on which riprap is to be placed to a slope of 1 foot (300 mm)
vertical to 2 inches (50 mm) horizontal. Dress the earth bed to a true
plane. Where riprap is to rest against a fill, tamp the embankment
against the back of the stone.
Construct
riprap for walls or wells according to the arrangements and dimensions shown on
the plans. Lay each course with the long dimensions of each stone
perpendicular to the slope or batter.
Use
individual stones that are roughly rectangular in cross-section and are a
minimum of 3 inches (75 mm) in the vertical depth with a horizontal dimension
of not less than 15 inches (0.4 m). Place the individual stones by
hand, one upon the other so that they break joints with the stone in the course
below. Where it is necessary to use more than one stone to provide the
specified thickness or depth of the wall, thereby resulting in joints parallel to
the face of the wall, place such stones to break joints with the adjacent
stones.
Fill
the space between the larger stones with spalls rammed into place. Ensure
that the surface of the finished riprap does not vary more than 3 inches (75
mm) from that shown on the plans, and that it presents an even, tight surface,
pleasing in appearance.
657.06 Earthwork. Perform excavation and
embankment, as necessary, according to Item 203.
657.07 Pipe Drains. Drain tree wells with pipe
starting on the original ground surface and lay to drain beyond the toe of the
fill. Install pipe for drains according to Item 611.
657.08 Method of Measurement. The Department
will measure Riprap for Tree Protection by the number of square yards (square
meters) in place, completed and accepted. The Department will measure
parallel to the face of the wells or walls.
657.09 Basis of Payment. The
Department will pay for embankment and excavation under Item 203 and the pipe for drains under Item 611.
The
Department will pay for accepted quantities at the contract price for as
follows:
Item
Unit
Description
657
Square
Yard
Riprap for Tree Protection
(Square Meter)