Kent Design - Technical Appendix - Kent County Council

design
In Residential Shared Surfaces ground cover planting will usually be
required in service strips.
Where a lay-by is provided on a Residential Shared Surface, the
adjacent service strip shall be hard paved, so as to provide a paved
surface for persons alighting from vehicles.
Where it is agreed trees can be planted within a service strip, such planting
shall be agreed with the Engineer and conform with Section 2.9.4.
The highway boundary associated with a service strip shall be defined
by continuous 50mm x 150mm edging type EF to BS7263.
2.9.4 TREES
When siting new trees within a verge, visibility splay or service strip,
considerable care needs to be taken regarding:-
• Obstruction of visibility.
• Lighting
• Possible root damage to paved surfaces, pipes, services etc.
• Proximity to carriageway.
No new trees shall be planted within the 2.0 metre 'x' distance by 'y'
distance visibility splay area at a junction. Behind this splay but within
the general junction visibility splay area the limited planting of suitable
species of trees may be acceptable after careful consideration of the
affect of the trees on junction visibility.
In forward visibility splays, the limited planting of suitable species of
trees may be acceptable after careful consideration of the affect of
the presence of the trees on forward visibility.
Where it is agreed that trees are acceptable within visibility splays,
they shall be clear stemmed for up to 2.0 metres above ground level.
Trees within verges and service strips shall be set back at least 1.5
metres from the carriageway adjacent to Local Distributor Roads and
Industrial and Commercial Roads, and at least 1.0 metre from the
carriageway. adjacent to Residential Access Roads.
Trees can be underplanted with low shrubs if within the highway area.
Those trees which are known to be surface rooting i.e. cherries
should not be used near services or footways. Trees with large slow
decomposing leaves should also be avoided at sensitive locations.
The eventual branch-spread should allow for a 5.3 metres clearance
between the carriageway and the lowest branches. Upright growing
trees should be used where there are space problems.
It is essential that tree species conform to the very vigorous requirements
of the Highway Authority. Such requirements include the following:
• Root Systems - Must not be surface rooting.
• Stability - Must have good stability and not be prone to
branch drop.
• Fruits - Must not have large or messy fruits, or be
copious seeders. Species that encourage aphids i.e. limes
should also be avoided.
• Leaf Problems - Should not have large leaves that are
slow to rot.
• Growth Characteristics - Need to be compatible with the
highway location. Light or dappled shade is preferable.
• Robust - Tolerant of disturbed ground conditions and
road salt.
• In Keeping - With the local character of the area, and
appropriate for the soil type
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Kent
Design
2.9.5 SOIL PREPARATION
Subsoil in the base of tree pits shall be thoroughly broken up to a
minimum depth of 150mm below the base of the pit. In tree pits trees
shall be planted in an open and friable soil complying with BS 3882
Premium Grade. If this is not available topsoil to BS 3882 General
Purpose Grade, improved by addition three parts of non-peat based
tree compost to seven parts of topsoil. Approximately 200g of slow
release fertiliser per tree shall be worked into the backfill mixture.
The tree pit shall be excavated to allow adequate clearance between
the root ends (when fully spread) or the perimeter of the ball and the
side of the pit. The size of the pit must be such as to allow for the
provision of not less than 0.5m 3 of good topsoil for planting. The depth
must be at least 75mm greater than the depth of the root system.
In shrub areas, Premium quality topsoil to BS3882 must be spread
in planting areas to a minimum depth, after settlement, of 300mm
over a minimum depth of 150mm of previously loosened subsoil.
This will necessitate restricting concrete haunching to kerb edgings in
order that the soil space is not unnecessarily reduced.
In grass seeding and turfing areas, topsoil to BS3882 shall be spread
to a thickness of 100mm. The subsoil layer must be loosened to a
further 150mm depth prior to the spreading of topsoil. Topsoil shall
be spread to give a finished level after light consolidation 25mm
above adjacent edges, hard surfaces or manhole covers.
2.9.6 SHRUBS
For the successful establishment of ground cover shrubs in service
strips and visibility splays it is essential that the species selected
conforms to the very vigorous requirements of the Highway
Authority. Such requirements include the following:
• Availability - Readily available in the trade to allow for
planting in bulk and for replacements following
disturbance by Statutory Undertakers or the Highway
Authority.
• Establishment - Quick establishment to provide
immediate effect and reduce maintenance costs.
• Root Systems - That does not interfere with underground
services or adjoining surfaces.
• Restricted Growth - Growth characteristics which
restrict themselves to the planted area and below a
height of 600mm, and with minimal pruning needs.
• Wear Resistance - Tolerant of the occasional trampling.
• Hardiness - Resistant to frost damage, diseases and pests
and long lived.
• Chemical Tolerance - To avoid damage from common
chemicals used in the initial stages of establishment to
control weed growth.
• Non Injurious - No toxic fruit or sap, no thorns.
• Visual Qualities - Neat appearance and providing an all
year round effect, preferably with seasonal variations.
2.9.7 SUSTAINABILITY ISSUES
These should be considered when specifying planting schemes. In
particular:
Tree stakes should be from local renewable resources. Sweet
Chestnut is ideal, as it lasts long enough to do its job with minimal
preservative treatment and is also a traditional Kent product.
Soil Ameliorants must be peat free.
Where native species are used, stock of local provenance is desirable.