Drainage
Installation Advice for Athletic Fields
A. Natural turf
Intensively
used surfaces require intensive drainage to maximize usage time
and reduce compaction. 
1.
Trenching
In most natural turf situations, it is best to install MultiFlow
vertically. A 4 inch wide trench is ideal both for performance
and ease of installation. It produces little spoil and results
in excellent drainage because it takes advantage of MultiFlow's
significant vertical footprint. Installations that use a combination
trencher/conveyor can trench and remove spoil in one efficient
operation.
2.
Layout pattern
a.
Crowned or sloped fields
If the surface of the field has a consistent slope (greater
than .5%), it is advised that the collector lines be placed
such that they intersect the water flow direction. Placing
the lines at a 90 degree angle to the flow direction and running
toward the end zone is usually not the best policy. The resulting
lines would be too long and, in order to maintain fall, excessively
deep. A 45 degree angle running toward the sidelines works
well because it allows the lines to maintain grade while also
intercepting the direction of surface water flow. The resulting
herringbone pattern complements the existing field contour,
providing effective drainage as well as an uncomplicated installation.

Lines
laid out in a herringbone pattern on a crowned field intercept water
moving toward the side of the field. 
b. Flat or irregular fields
If the field is flat, or has less than a .5% slope from the
center, then a parallel drainage pattern may be appropriate.
Since the water will basically stand on the surface of a flat
field, there is no advantage in attempting to place drainage
lines in the flow path. Collectors could run toward the sidelines
or the center of the field. On flat fields, proper grade needs
to be maintained by increasing the depth of the trench.
3.
Coverage
The drainage pattern should extend 10 to 15 feet beyond the
field to include the intensively used sideline area. 6inch
MultiFlow is ideal for these onfield collectors. It is also
advisable to run 18inch MultiFlow lines along the sides of
the field or all around the field. These lines will collect
water that might run toward the field from the outside and provides
supplemental drainage to the sidelines. It also cuts down on
the number of connections that are needed to the transport system.
If 18inch MultiFlow is run parallel to the sidelines, or sidelines
and end zones, then the 6inch collectors used in the playing
area can empty into the 18inch lines using an 1800P (Y left)
or an 1800Q (Y right).

A 4inch
trench produces only a moderate quantity of spoil but allows ample
room to encase MultiFlow in filtersand. 
4.
Collector line spacing
Placing collector lines 10 feet apart, outlet to outlet, provides
excellent reaction time and uniform drainage performance. 15
feet apart provides an adequate system. A field employing 20
foot spacings will require a longer waiting period before use
after a rainfall event.
An
example will illustrate the consequences of line spacings. Assume
40 lines of 6inch MultiFlow in an area 210 feet by 400 feet
(10 foot spacings). This will provide capacity to handle a maximum
of 1.56 inches an hour, assuming:
•
17 gpm x 40 lines = 680 gallons per minute each side of the
field.
• 680 gpm x 2 sides = 1,360 gallons per minute.
• 1360 gpm x 60 minutes = 81,600 gallons per hour.
• 210 feet by 400 feet = 84,000 ft2
• 81,600 gph / 84,000 sq./ft. = .971 gallons per sq./ft.
per hr.
• .971 gal./sq. ft./hr. = 1.56 inches of rainfall per
hour (.971/.623)
Capacity
could be increased by adding more MultiFlow drainage lines.
Three
factors will determine the line spacing decision:
1) anticipated schedule 2) local rainfall events 3) project
budget

A standard
PVC elbow can be slipped over any MultiFlow connector. 
5. Transport system
Due to strength and flow rate requirements, a smooth wall pipe
makes for the best transport system. PVC pipe is commonly used.
A standard PVC elbow or tee can be slipped over a MultiFlow
connector.
To
design a transport system it is necessary to calculate the total
drainage system capacity. For an example, let's again assume
forty lines of 6inch MultiFlow in an area 210 feet by 400
feet. If the field is crowned and laid out in a herringbone
pattern, these lines will empty into the transport system on
both sides of the field. So effectively, there are eighty collector
lines. If each carried 17 gallons per minute, these eighty lines
could deliver 1,360 gallons a minute or 81,600 gallons an hour.
Sideline drains could increase that amount. Leaving the site,
this would require a minimum of one 12inch or two 8inch PVC
pipes.
If
an 18inch MultiFlow is used as a collector line along the
two side lines, and the 6inch collectors empty into these 18inch
lines (using 1800P or 1800Q connectors), then it will be necessary
to tap into the 18inch line at calculated intervals in order
to accommodate the volume of water. To calculate that interval,
assume the following:
•
6inch MultiFlow = 17 gallons per minute.
• 18inch MultiFlow = 47 gallons per minute.
• 1800P or 1800Q = 112 gallons per minute.
• 4inch PVC = 112 gallons per minute

If 18inch
MultiFlow is used as a collector line along each side line, and
the 6inch collectors empty into these 18inch lines, then it will
be necessary to tap into the 18inch lines at calculated intervals
in order to accommodate the volume of water. 
Based
on the above assumptions the 18inch line should be emptied
into the transport system once for every six or seven lines
of 6inch MultiFlow. This is accomplished by attaching an elbow
or a tee to the bottom of every sixth or seventh 1800P or 1800Q.
The 18inch perimeter drain is installed without a slope so
the outlet to the transport line will be accepting water from
both directions. Keep in mind that when the system is at full
capacity there will be substantial head pressure on the system
which will increase the flow rates of all components.
It
is common to step up the size of the transport pipes as they
proceed down the field, thus avoiding the cost of unnecessary
large PVC connectors. A 4inch PVC can carry 112 gallons of
water a minute (1% slope, no head pressure) so it would be adequate
for handling water from the first six collector lines. A 6inch
PVC would be suitable for carrying the previously collected
water plus the water from the next thirteen collector lines.
An 8inch PVC could do the job the rest of the way down the
field.
Assuming
the 210 X 400 foot field from the example, if the 18inch collectors
are employed, it will empty into the collector system from an
1800P at six to seven locations along the left side of the field
and from an 1800Q at six to seven locations along the left side
of the field. Without the 18inch collectors, each of the forty
collector lines would empty directly into the collector lines
on both sides of the field.

Centering
devices are convenient for holding MultiFlow in the center of the
trench while backfilling. 
Transport
pipes can be located beneath the sideline drain or in a separate
trench beyond the sideline drain. The second option is generally
more efficient and cost effective
6.
Backfilling
Backfill material may be the single most important factor affecting
the longevity of a drainage system. Sand can function as a filtration
device, removing silt and clay particles, while allowing water
to pass through. Clay or silt spoil excavated from the trenches
should be removed from the site. Trenches should then be backfilled
with a clean very coarse sand, nearly to the surface. To eliminate
voids in the backfill, trenches can be jetted with water or
settled with a vibratory compactor after all connections have
been made.

B. Synthetic turf
Placing
collector lines 15 feet apart, outlet to outlet, provides excellent
reaction time and uniform drainage performance. 
1.
No trenching required
In most synthetic turf situations, it is best to install MultiFlow
flat. Collector lines can be positioned horizontally directly
on the compacted base, or on top of the geotextile soil separator
if one is used. No costly and time consuming trenching is necessary.
2.
Layout pattern
Synthetic turf fields typically have a consistent center to
sideline slope. Collector lines should be placed such that they
intersect the water flow direction. Placing the lines at a 90
degree angle to the flow direction and running them toward the
end zone is not the best policy because the resulting lines
would be too long. A 45 degree angle running toward the sidelines
works well because it allows the lines to maintain grade while
also intercepting the direction of surface water flow. The resulting
herringbone pattern complements the existing field contour providing
effective drainage as well as uncomplicated installation. This
drainage pattern should extend all the way to the edge of the
synthetic turf so it will include the intensively used sideline
area. Transport lines should be located at the edges of the
field.

MultiFlow
requires no trenching because of its' flat profile and strength.

3. Collector line spacing
The coarse sand and rock used in synthetic turf fields is capable
of absorbing substantial amounts of water. Consequently, it
is acceptable to allow more time for desaturating the base of
a synthetic field than a natural turf field and as a result,
collectors can be spaced farther apart. Placing collector lines
15 feet apart, outlet to outlet, provides excellent reaction
time and uniform drainage performance. Twenty feet apart provides
an adequate system. A field employing 25 foot spacings will
require significantly longer to drain after a rainfall event.
It would be unwise to space them farther apart because allowing
water to set on the compacted base for prolonged periods of
time will soften the subgrade and destabilize the base.
An
example will illustrate the consequences of line spacings. Assume
twentyseven lines of 6inch MultiFlow in an area 210 feet
by 400 feet (15 foot spacings). This will provide the capacity
to handle a maximum of 1.05 inches an hour, assuming:
•
One 6inch Multi Flow can carry 17 gallons per minute.
• 17 gpm x 27 lines = 459 gallons per minute each side
of the field.

Welldrained
synthetic turf provides for more available use hours, good playing
conditions, and a longer lasting field. 
•
459 gpm x 2 sides = 918 gallons per minute.
•
918 gpm x 60 minutes = 55,080 gallons per hour.
• 210 feet by 400 feet = 84,000 ft 2
• 55,080 gph / 84,000 sq./ft. = .656 gallons per sq./ft.
per hr.
• .656 gal./sq. ft./hr. = 1.05 inches of rainfall per
hour (.656/.623)
System
capacity can be increased by adding more MultiFlow drainage
lines.
Five
factors will contribute to the spacing decision:
1) anticipated intensity of field use
2) local rainfall events
3) project budget
4) stability of the subgrade
5) particle size of the select aggregate base

In some
systems the MultiFlow collectors empty into a drained perimeter
trench. 
4.
Transport system
Many synthetic turf installers and designers call for a perimeter
trench containing a perforated transport pipe. MultiFlow collector
lines either empty into this drained perimeter trench or are
connected directly to the transport pipe at perhaps 15 or 20
foot intervals. This method has worked well on many fields.
A
more efficient system employs an 18inch MultiFlow line installed
vertically along each side of the field. The 6inch collector
lines connect directly to these 18inch sideline collectors.
Accumulated water is then emptied directly into a parallel collector
line after each six or seven inlets as in a natural turf system.

In some
systems the MultiFlow collectors empty directly into a perforated
perimeter drain pipe.
The
best systems employ an 18inch MultiFlow line installed vertically
along each side of the field. The 6inch collector lines connect
directly to these 18inch sideline collectors which periodically
empty into solid PVC transport pipes. Sideline catch basins add
additional drainage capacity. 
Because
of strength and flow rate requirements, a smooth wall pipe makes
for the best transport pipe. To design an adequate transport
system it is necessary to first calculate the total drainage
system capacity. For example, let's again assume twentyseven
lines of 6inch MultiFlow in an area 210 feet by 400 feet.
If the field is crowned, these lines will empty into the transport
system on both sides of the field. So effectively, there are
fiftyfour collector lines. If each is capable of carrying 17
gallons per minute, these fiftyfour lines could deliver 918
gallons a minute or 55,080 gallons an hour. Leaving the site,
this would require a minimum of one 10inch or two 8inch smooth
wall transport pipes. It may be advisable to build in additional
capacity for water that enters the perimeter trench through
other means such as catch basins.
•
It is acceptable to step up the size of the transport pipes
as they proceed along the perimeter trench.
• A 4inch PVC can carry 112 gallons of water a minute
(1% slope, no head pressure) so it would be adequate for handling
water from the first six or seven collector lines.
• A 6inch PVC can carry 327 gallons of water a minute
(1% slope, no head pressure) so it would be suitable for carrying
the previously collected water plus the water from the next
thirteen collector lines.
• An 8inch PVC can carry 704 gallons of water a minute
( 1% slope, no head pressure) so it could do the job the rest
of the way down the field.

Clean, very coarse sand acts as an excellent filter,
dramatically extending the life expectancy of the system. 
5.
Backfilling
Backfill material may be the single most important factor affecting
the longevity of a drainage system. Sand functions as a filtration
tool, removing silt and clay particles, while allowing water
to pass through. A 2inch band of very coarse sand should be
installed covering the top and sides of each collector line.
This
sand backfill could be eliminated if the select aggregate is
free from silt and clay, but this is seldom the case. See Selecting
Backfill Material for more information on this topic.

A
more extensive version of this Athletic
Field Drainage Guide can be opened in a printable PDF format.”
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Varicore Technologies is qualified and always ready to assist customers
in designing and drawing drainage systems for their specific athletic
fields.
