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Dr Ian Plummer

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Lawn Care
Sportsfield Drainage

These are anonymous notes from a groundsmans course.  They deal with general principles of drainage for sports fields, not specifically targetted at croquet lawn production.

Contents

The Benefits Of Good Drainage
Kinds Of Drainage Systems
Drainage
  Types Of Drain For Sports Fields
  Mole Plough Draining
  Drains - Clay, Porous Concrete, Perforated Plastic
  Clay Tiles
  Porous Concrete
  Perforated Plastic
  Natural Drainage

Drainage Systems 
  Depth Of Drains
  The Fall
  The Trench
  Laying The Pipes
  Backfilling
  New Ideas
Hydraulic Conductivity
Hooghoudt's Drain Spacing Equation
Conclusions

For turf used in sports the aim is not merely to remove surplus water, but to remove it quickly enough to allow play as soon as possible. This involves:

  • The provision of a drainage system.
  • Ensuring the water gets through the soil to the drainage system.

The Benefits of Good Drainage

  1. Removal of excess water and lowering the water table.
  2. Improves the quality, firmness and durability of the turf, especially for winter games.
  3. Quick drying of the soil extending possible playing time.
  4. Prevention of erosion.
  5. Prevention of heaving.
  6. Improved air movement in soils.
  7. Increased root development.
  8. Increased capillary moisture in dry weather.
  9. Improved drought resistance.
  10. Better soil structure.
  11. Higher soil temperature and longer growing season.
  12. Improved bacterial action.

Kinds of Drainage Systems

  1. Open drains or ditches.
  2. Pipe drains.
  3. Mole drains.
  4. French drains.

Drainage

The cause of the cancelled match or the playing of a match in bad ground conditions is usually because of the water on the surface or in the surface layer of top soil. It takes time for water to penetrate the soil surface and enter drains that are several feet down, so at this point sports field drainage requirements differ from that of the farmer and agriculture, although the basic points are still applicable, such as the laying of pipes, junctions, falls etc.

Types of Drain for Sportsfields

MOLE PLOUGH DRAINING: effective but limited life and the mole cuts must be lined to either a ditch or a drain of some sort - pull mole uphill - clay type soil required: winch pulled mole and/or mole plough fitted direct to tractor on three point linkage. Plough follows ground levels - time of year to carry out work and when not to!

DRAINS - CLAY, POROUS CONCRETE, PERFORATED PLASTIC: I prefer to use clay - up to now I have not been impressed with the results of plastic pipes that I have seen laid. Although I personally have never supervised any drainage using plastic pipes.

Clay Tiles: For normal work: 3" dia. 4" dia. 6" dia. Plus necessary junction: always use a salt-glazed pipe or similar 3' long at outlet into water course or if connected to storm water system. You have no right of discharge into a surface water sewer. If you get permission to do this you will have to fit a silt trap prior to entry into the sewer, also concrete the face of your outlet into a water course to prevent water undermining it.
Porous Concrete: These drainage pipes can be used except in sulphate-bearing clays such as Gault and London clay. Both contain sulphate and the use of porous concrete drains in these areas is not recommended.
Perforated Plastic: These are now the most widely used pipes for land drainage work. They come in a wide range of sizes - 1 1/2" to 4" - and in lengths of 12 to 20 feet or in large coils. The lengths have a male and female end so that they are easily fitted together. The coils have a sleeve fitting for linking sections together. Because they conduct water more 'smoothly' than clay pipes, a smaller diameter pipe - i.e. 1 1/2" dia. can carry as much drainage water as a 3' clay pipe set at the small rate of fall. This also means that drainage trenches can be narrow, resulting in the removal of backfilling material. They are also lighter to handle and transport than clay and concrete tiles.

NATURAL DRAINAGE: Some soils are well-drained, others easily waterlogged. As rain falls on the turf some evaporates, some may run off and the rest passes into the ground to become soil water. Some of this is absorbed by the plants' roots and is passed back into the atmosphere by transpiration. The rest passes on down until it reaches the level of the water table or an impermeable layer of soil or rock strata. It then commences to form a water table. Water table rises during the winter and falls during the summer. Sandstone is porous and these types or soil are naturally well-drained. Clay-type soils when dry can absorb up to 50% of their bulk in water (like blotting paper), but once this water has been absorbed the clay becomes impermeable and water cannot pass through it.
 

Excess Water. This means inadequate aeration, lower soil temperature - as much as 12°F degrees between drained and undrained soils. A high water table limits the range of roots. Insufficient air and low temperature slows down the decomposition of organic matter in the soil; and to the groundsman cancelled matches or the destruction of the soil structure if play is allowed to take place, this in turn means difficulty in renovating and establishing new turf during the close season. Can show drought conditions quicker in the summer. Can these undesirable points be corrected? The reduction of the height of the water table if closer than 2 feet to the soil surface will enable grass roots to reach their maximum depth. In turn, this improves aeration and mechanical equipment can be used to assist this. Also raises the soil temperature. The ground and turf are less likely to suffer drought conditions in the summer for it is a fact that in wet weather the driest soil is to be found around the drain, yet in dry weather the soil around the drain has the greatest moisture content.

Drainage Systems

Natural: where drains follow natural contours, not usually of use in large sports ground work, possibly of use in light soils or on small areas.
Herringbone: gives short lengths to the lateral drains. More complicated for machine working and the many junctions increase the danger of silting.
Grid system: easy for machine working. Long laterals. Size of clay drain up to half to half an acre at a fall of 1-300-3". If fall increased the larger areas can be dealt with. After this 4" pipes then use 6" mains unless rate of fall of the main is increased. In laying out a system the aim should be to set the laterals at an angle to the slope so acting as interceptors to the flow of water. Also cut off interceptor drains at banks etc.

DEPTH OF DRAINS: The outfall - this is usually the governing factor. It should be as deep as possible subject to reason. It should be above the normal level of a watercourse, so as to give unimpeded flow, but deep enough to allow for drains to reach the farthest part of the system at a depth of at least 12" (preferably 18"). In allowing for this, also allow for a fall from lateral drains into main drains. Also, it is generally accepted that the main should fall quicker than the lateral drains to prevent silting and this is also necessary if the same size dia. pipes are used. However, if it is difficult to get sufficient fall then the mains should be of larger size and silt traps built. These can be cleaned out when necessary. There is a rough rule of thumb that for every 1" of depth, the drain will pull for 1 foot on each side: more in light soil, less in heavy. This gives a rough guide to the distance apart of the laterals.

THE FALL: This can be as steep as 1-50 if necessary. However, 1-75 is normally regarded as ideal although it can be 1-300, or if dealing with very large areas then 1-600. The important points to bear in mind are that the drain runs are straight and constant in their fall.

THE TRENCH: Nothing is gained in taking out a trench wider than is necessary, i.e. a 4" trench for a 3" pipe. It is a fallacy that more water will enter the pipe by having a trench wider than is necessary to get the pipe into it. The base of the trench should be 'boned' to ensure that there is a constant even fall.

LAYING THE PIPES: There are two schools of thought:

  • Lay the pipes with a slight gap between each pipe not more than 1/8".
  • Lay the pipes as close together as possible, i.e. butt the ends tightly to each other.

I prefer the second method and quote Kendall, p. 54(4). Laterals should be laid to fall into the top of the main drain.

BACKFILLING: Size of backfilling: should be not more than 1 1/2" and smaller if possible. Backfilling should go to within 3-4" of the surface and a binding of fine ash or pea shingle over the top. Then fill with good top soil and either turf or sand.

NEW IDEA: Above the pipe put a 2-3" layer of 3/8" shingle, fill trench with dune sand to within a few inches of the surface, then use light top soil. The idea is that the shingle acts as a valve and once water falls on the surface, so that the dune sand is at field- capacity, then the excess immediately passes from the dune sand into the shingle and then to the drain. The idea is to provide instant drainage yet enable sufficient water to be held in the sand to provide against drought conditions in summer.

The soil around the drain is the driest point in winter and wettest point in summer - hence the dark green colour in the turf.

Hydraulic Conductivity

This can be calculated by setting up a small experiment using a long glass tube having a bung with a glass tube set in it at the lower end with a small amount of porous material topped by a set amount of top soil from the area to be drained. The tube is then filled with water and the time taken for the water level to drop a given amount is recorded. The following calculation is then made:

formula

F = fall in inches
D = depth of soil layer
H = Average between starting and finishing head of water
T = time taken in seconds

Hooghout's Drain Spacing Equation

formula

S = drain spacing (CMS)
h = depth to impermeaable layer
K = hydraulic conductivity of permeable layer
V = design rate (CM/hr) at which rain is to be cleared from surface.

Example

Soil has a 30cm layer of top soil: hydraulic conductivity is 40 cm per hour. Rain to be cleared from surface at 0.125cm per hour (i.e. 3cm per day).

formula

formula

S = 10.72m distance apart from laterals

CONCLUSIONS: See KENDALL, pages 92/93, nos 3, 5, 6, 7, 8, 9, 10, 11, 12 , 13, 14, 15 & 21. Not 17 & b18.

Conclusions

  • Barring exceptional circumstances all land pays for draining.
  • High back lands, water furrows etc, are a visual proof that something is wrong or the farmer fails to understand the principles of draining with a view to growing maximum crops.
  • A field is as dry as its wettest place.
  • All draining is undertaken two years or more too late, as no-one ever drains until the damage is done and he sees the water.
  • Water on the surface proves that rain has fallen somewhere, but it is f or the drainer to find out how it got there and by what route.
  • The best method to attach a field needing a pipe system is to find the water in the subsoil, trace it to its source and intercept it.
  • A survey should be made before any scheme is undertaken.
  • Where a comprehensive survey is necessary, the levels should be taken 'on the squarer (see appx. two).
  • Where the fall is more that 1 in 66 (or 1 foot per chain), every endeavour should be made to reduce it.
  • Where the fall is less than 1 in 264 (or 3" per chain), every endeavour should be made to increase it.
  • Shallow pipe draining is the most expensive form of draining in the long run.
  • In heavy clay soils the minors of any tile system should not be more than 7 1/3 yards apart and should be between 3 & 4 feet deep. (Advise 1 1/2 feet to 3 feet for sportsgrounds)
  • All minors in any system should be spaced with this in view, ie 7 yards, 14 yards, 28 yards, 56 yards etc, so that if an original spacing is not found sufficient minors can be addedd at regular intervals.
  • All draining undertaken on clay soils needs periodic surface cultivations to enable it to function properly. (Aeration)
  • 95% of all blockages in pipe draining are caused by a faulty scheme or badly laid pipes.
  • With the exception of IUI drains, I have never seen a pipe system fail because it was 'worn out'.
  • Unless there is over 13.5% moisture in the subsoil, mole draining is liable to collapse.
  • Where over 30% moisture is found in the subsoil, mole drains are liable to close in.
  • Draining is the only department in agriculture in which farmers as a whole consider it beneath their dignity to seek or accept advice.

Author: Kendall, R. G.
Title: Land drainage.
Publisher: London : Faber and Faber, 1950.
Description: 133 p. : ill., maps ; 23 cm.
Subjects:  Drainage.
Radcl.Science RSL Stack: 18647 e. 55

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Updated 28.i.16
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