Offering substantial cost savings in comparison to alternative
systems, Safeticurb is a long established, well proven linear
drainage system with a discrete cross-fall which directs surface
water to drainage entrances for hard landscaped areas and
roadways.
Installation design – units
General principles
All units are unreinforced: protect from stresses caused by
thermal expansion of cementitious paving materials. Leave 1mm gap
between each unit to prevent damage from thermal expansion of the
units themselves.
Expansion joints MUST be installed on each side of drainage runs
in concrete pavements or those incorporating a cement bound/lean
mix concrete roadbase.
DO NOT place these joints directly adjacent to any trafficked
unit as this would allow units to rock under trafficking and may
allow water ingress into the base or sub-grade.
- Recommended position of joints
(minimum distances):
- 600 mm from Clearway/Safeticurb units (see Figs 12-14).
- 125 mm from Highway units (see Figs 5-6).
Note:
As Highway units are not regularly trafficked, expansion joints
could be placed directly against them. However, 125 mm distance is
recommended to avoid ingress of water between the unit and
carriageway construction.
Base foundations
Recommended typical foundations are:
- for Clearway/Safeticurb: minimum 150 mm depth of ST4 concrete
with a 25 mm bed of Class 1 mortar (1:3 cement: sand) to allow easy
adjustment of units to line and level.
- for Highway: minimum 75 mm of concrete.
Note:
Strength, overall depth and width of the base may need to be
increased when laid on low - strength sub-grades.
Haunching
Recommended typical haunches (to within 100 mm of top unit)
are:
- For Clearway/Safeticurb: ST4 concrete.
- For Highway: ST1 concrete minimum 125 mm width.
General principles
Details of outlet units an inspection access differ according to
which linear drainage system is used.
In any system, silt or detritus should normally be prevented from
entering the main drainage sewer. An outfall chamber is required to
enable silt collection before onward connection to a sewer.
Types of outfall chamber
- trapped precast concrete, clay or plastic gully pots. Gully pot
capacity may be insufficient for some largerlinear drainage
installations.
- Purpose-built brick or concrete inspection chamber.
- Precast concrete manhole rings.
- Dedicated sump unit.
Select outfall pipe diameter/gradient
Care should be taken to ensure sufficient capacity.
Highway
Standard outlet formed using two base outlet units (in place of
standard base units) to give full width rectangular outlet 400x275
mm. (shallow and deep base outlet units available). Positioning is
not critical, but should allow access for suction pipe from gully
emptier.
Discharge capacity may be increased by installing more than one
pair of Base Outlet units discharging into the same outfall
chamber.
For larger schemes, chambers to be detailed in accordance with The
Specification for Highway works, clauses 507 and 508. For larger
outfall pipes it may be necessary to incorporate a manhole access
at rear of run.
Clearway/Safeticurb
Select outfall chamber, pipe dimension and pipe gradient to suit
system capacity. Position a silt box top on two courses of
engineering brickwork over the selected outfall chamber/silt trap
to give access (via the silt box lid) for silt removal.
HydroKerb sump unit
With hinged, removable lid for inspection access, is placed over
sump unit in place of standard top units. (See page 143 for
alternative option).
Mini Highway sump unit
With hinged, removable lid for inspection access, is placed over
inflow unit in place of standard top units.
Radii
Highway/Mini Highway:
- To form external radii of 25 metres or less (minimum 6 m),
special radius units should be used (see table below). As these do
not cover all individual radius dimensions, some slight gaps are
required between units as indicated in Highway radii gap widths
table, below.
- For external radii greater than 25 metres, lay straight units
with open joints.
- To form internal radii (minimum 6 metres), use 7/6 internal
radius units.
Clearway/Safeticurb:
- Where necessary, standard (straight) units may be laid to form
radii or bends.
- Safeticurb units: alignment ring within bore acts as a former
for infill mortars to seal joint.
Crossings
Highway/Mini Highway:
- Use crossing base units to carry drainage runs under side
roads/vehicular crossing points. Grid units available.
Safeticurb (DBK unit only):
- To continue linear drainage at road junctions, kerb crossing
points (pedestrian/vehicular), use transition units to reduce kerb
height to road level. These connect with standard grid or slot
units as necessary.
Junctions/sharp bends
Clearway/Safeticurb:
- Use silt box top at outlets or with suitable uPVC pipe fittings
(cut to fit) to form junctions or sharp bends.
Highway radii gaps widths
| Radius (m) |
Radius unit reference |
Top and base gap |
| 6 |
7/6 |
2 |
| 7.5 |
10/8 |
3 |
| 9 |
10/8 |
2 |
| 10.5 |
25/11 |
4 |
| 12 |
25/11 |
1 |
| 15 |
25/11 |
2 |
| 20 |
25/11 |
5 |
| 25 |
25/11 |
7 |
| 26 |
Straight |
7 |
Sitework
Setting out
General principles
Plan for laying to start from an outfall at the lowest point of
the system. This ensures self-draining if wet weather occurs during
installation.
Use level pins and string lines to ensure correct level and
alignment.
HydroKerb:
Excavate trench large enough to allow for concrete bed and
haunching, min. 460 mm wide, depth will vary on choice of HydroKerb
base unit.
Units should be set out such that the top of kerb is at required
level, correct horizontal alignment, radii etc. as shown on setting
out drawing (provided by the Engineer), using string lines and pins
as appropriate. If radii required is larger than available kerb
radius, then use the next size up.
Starting at the outfall, the HydroKerb base units should be laid on
a min. 150 mm thick fresh concrete foundation ST4min. or,
alternatively, on a 25 mm thick mortar bed on a previously laid
foundation of 150 mm thick concrete. Haunching should be to front
and rear of HydroKerb base units 150 mm wide.
Place HydroKerb top unit onto base unit, ensuring that all
seatings are clear of concrete and debris to allow for proper
location, complete haunchings as required and compact. Place
inspection units at required intervals as work proceeds. This would
normally be at the head of the run and at 30 m intervals unless it
would coincide with an outlet. Surfacing can be rolled up to units
but inlets should be examined afterwards and any surfacing removed
from holes.
System should be flushed through after completion.
For optimum laying speed lay a run of base units before laying top
units.
Clearway/Safeticurb:
The surface of these systems’ drainage units should be 3-6 mm
below the level of the surrounding pavement surface. After
completing base foundations, lay units onto a Class 1 mortar (1:3
cement: sand) bed, adjusting to line and level using a pavior’s
maul. Leave 1 mm gap between units to allow for thermal
expansion.
If a watertight joint is required, a gun-applied sealant may be
applied to the end of each unit.
Clearway grid units
Grid fixing bolts should be tightened to a torque of 20 Nm after
installation and whenever grids have been removed for
maintenance.
Safeticurb DBA and DBJ slot units
Protect slots from stones during construction. Slot units
without iron inserts can be damaged when stones are impacted by
vehicle traffic.
Safeticurb DBG and DBJ grid units
Grid fixing bolts should be tightened a minimum of 5 turns after
clamping plate has made contact with the soffit of the bore.
Highway/Mini Highway/Highway Ultra (including Porous
Asphalt units):
Specially designed lifting tools available to enable units to be
placed accurately in position.
Lay units onto a fresh concrete base
(see installation design, page 154), adjusting to line and level
using a pavior’s maul. Apply gun-applied (see note, below) sealant
to the ends of the base outlet unit prior to laying.
Note:
Suitable product would be Evo-Stik roof and gutter sealant.
Alternatively a trowel applied mastic sealant can be used, e.g.
Denso.
Apply gun-applied sealant to the sealant recess in the end of
the first standard base unit – lay the unit against the base outlet
unit with the sealant recess away from the outlet. Lay subsequent
base units, applying sealant to the sealant recess in each,
preferably before laying each unit in position. When a crossfall is
required across the top of Highway units (see Fig 5, page 154), the
base units should be laid to this crossfall. Do NOT rely on varying
the thickness of mortar in the joints between top and base units.
Use Class 1 mortar (1:3 cement:sand) to fill joints between top and
base units (see Fig 5a, page 154). The joint reduces from 20 mm
outside to 15 mm inside the unit to ensure complete filling and
compaction inside the bore and to avoid cavitation from the water
flow.
While laying, the vertical joints between top and bases are
unlikely to be maintained over the full length of the run because
of minor manufacturing and jointing tolerances. A full top unit cut
to suit may be required to complete the run. Use the specially
designed lifting tool to place top units in position, ensuring that
the inlet holes at the ends of each unit are correctly aligned.
Adjust using a pavior’s maul. Remove excess mortar from inside bore
as each unit is laid. Seal the pipe bore at each end of the run,
either by extending the base and haunch concrete (of the Highway
units or any adjacent kerbline), or with engineering bricks
surrounded with concrete or by using the Highway base stop end
units.
Maintenance
Handling equipment
For appropriate handling and lifting equipment, contact Probst
Handling Equipment on 01939 235325.
Maintenance
General
With correct design and installation, maintenance needs for all
linear drainage systems should be minimal. However, it is essential
to continued efficient drainage performance that all channels,
inlets and outlets are kept free from blockage or accumulations of
silt and debris. To that end, regular inspection is
recommended.
Frequency of inspection and maintenance is dependent on local
conditions, the surrounding environment, and on the actual gradient
within the installed system.
Any temporary blockages can be successfully eliminated provided
that:
- sufficient inspection/access points are designed into the
system.
- no hardened material is allowed to choke the bore.
Commissioning and handover
On completion of installation:
- Flush all excess mortar and building debris from the bore.
- Empty silt traps.
- Clean out/clear all inlet holes (including slots or grid
apertures).
For Safeticurb units DBA/DBJ
Slot apertures without cast iron inserts can be damaged when
stones are impacted into the slot by vehicles. Clear all loose
stones. (Slots should also be protected during construction when
stones are present).
For Safeticurb units DBA/DBJ/DBK
Ensure slot apertures are cleared of all loose stones. (This is
especially important when adjacent soft landscaping works are
undertaken). Further advice is available from the Technical
Services Department, Tel 01335 372222.
If necessary, cut back road surfacing adjacent to inlet holes in
order to ensure unimpeded access for surface water (a special
cutting tool is available on request).
Routine maintenance procedures
Inspect system regularly for obstructions, or heavy detritus
build-up.
Empty gully pots/inspection chambers to remove all silt.
Where necessary, cleaning or unblocking can be achieved by:
- high pressure water jetting.
- hand rodding.
For Highway/Mini Highway
If necessary, cut back road surfacing adjacent to inlet holes in
order to ensure unimpeded access for surface water (a special
cutting tool is available on request).
Routine maintenance procedures
Inspect system regularly for obstructions, or heavy detritus
build-up. Empty gully pots/inspection chambers to remove all
silt.
Where necessary, cleaning or unblocking can be achieved by:
- high pressure water jetting.
- hand rodding.
Good practice
The following are general principles of good site practice which
will contribute to successful installations:
Handling
Handle all products with care on site.
Avoid damage to edges and faces.
On-site storage
Prior to installation, stack materials bed on bed on a hard
level surface: protect from rain.
Sitework
Protect channels and gratings from concrete droppings and mortar
splashes during installation. This may be achieved by temporary
covering of openings with hardboard or plywood sheeting.
Protect slot apertures (especially if no iron insert is included)
from stone damage during construction, particularly where site
vehicle trafficking is likely after system installation.
Do not begin construction of adjacent footways and/or surfacing of
carriageways until base and haunch concrete have achieved adequate
strength.