This document discusses various aspects of designing and installing subsoil drainage systems. It provides guidance on determining pipe sizing and placement, choosing the proper filter material, and common installation mistakes to avoid. Key points covered include designing the system from the discharge point upward with uniform fall, using washed sand rather than gravel as the filter material to prevent particle migration, and ensuring proper trench grading and slope.

1. Designing subsoil drains

2. Discharge area: Subsoil drainsDecide where to discharge the waterDesign UP from discharge point (minimum 1:70)Have uniform fall on all pipes

3. Discharge area: Subsoil drainsOpen drainCreekBe aware what will happen during floodingDischarge must be above levelDesign the drain FROM the discharge point upwardUniform fall on all pipes

4. Subsoil drain pattern:Favoured design30-45% angleSmall laterals into larger mainFlexible corrugated tileJoints are offset from each other

5. Determining pipe sizingManufacturers supply max flow performanceAs pipe length increases, friction loss increasesMain runs with the slopeLaterals run across slope

6. A fall of .5ft in 49.5 ft is 1:99Efficient and simpleLaterals same distance apartUniform drainage for the whole area

7. Calculating pipe required

8. How to size pipeAssume area of 1ac (43,560ft sq)Uniform slope of 1:70, down 295 ft. no cross fallSubsoil drains spaced at 6.6ft, topsoil at 12” HC 2”/hrRainfall event of 2”/hr

9. Example of racetrack drainage

10. Sizing drainsHigh traffic area with subtle drain coverOff back of greenRealistic sizingNo additional labor for trimming/maintenance

11. Installing subsoil drainsMigrationFilter materialInstallation techniques

12. Choosing the right filter materialFilter material should bemade on the basis of type or sand that will surround itIf the drain is in a fine soil, filter should be a coarse river sand-NOT GRAVEL!

13. Migration of particlesSignificant amount of fines enter the surrounding soilTHIS moves fines into the pipeQuickly collapses the drain, often during first few waterings

14. Particle migration into coarser gravelsCommon mistakes:Surround pipe with coarse gravel or crushPea gravel ¼ - 3/8” often specifiedOverall, these gravels are too large!!

15. Filter material entering pipe We are too worried about filter material entering the drain pipeIf gravel is used, smaller particles will migrate into the large pores

16. When to use gravel filter material

17. Clean filter materialMake sure no fines in the filter materialUse HC of the filter material >100”/hr (sand withought fines)Misconception: Sand will not enter drain pipe except from above. Surface area of slots is less that 1% of pipe surface area.

18. Bridging factorIf gravel is too coarse, bridging factor will be too highUsing finer filter material prevents migration of particles from surrounding soil.

19. Diameter ratingWhen installing subsoil drains, in any situation other than USGA sand, use clean washed sand. NOT pea gravel, or any gravel with a D15 less than 1mm. D15 means 15% of the filler is larger than the specified size, 85% spec.

20. Installing subsoil drainsCut into the area below the soil to be drainedMake sure sides are verticalAvoid subsoil contaminationProvide uniform slope

21. Installing subsoil drainsClean vertical trenches2” of sand at bottom of trenchEven slopeCorrect high/low points Lay slits on BOTTOM of trench*water enters pipe from the bottom

22. Installing subsoil drainsCover the pipe with filter sand 2” surrounding Firm down/light rollingUse commercial joints

23. Geofabrics: Never wrap pipes

24. Types of pipesFlexible slotted (agricultural)2-8” diameterCommonly used is 4” outer diameterSlot size varyThese pipes self-clean, depositing fines though the ridgesThis process will not block pipes

25. Types of drain pipes

26. Common drainage mistakesIncorrect backfill materialIncorrect pipe connectorsMisunderstanding of surface and subsurface drainage

27. Common Drainage mistakesAssumption that more water moves laterallyImproper fall calculationInsufficient fill below pipe*water fills the pipe from below……

28. Drainage installation mistakes“makeshift” connectorsImproper jointsCrushed tileAll restrict flow

29. Common drainage mistakesIncorrect filter material promoting migrationFines of surrounding soil migrate into large poresDrainage lifetime dramatically reduced

30. Smart installationSmall basin marks lateral connectionAdds surface drainage outletEasily accessed for flush, or sub-air vacumn

31. Sizing drainsHigh traffic area with subtle drain coverOff back of greenRealistic sizingNo additional labor for trimming/maintenance

32. Slit Drainagehttp://tdsdrainage.com/articles.html

33. What is Slit drainage?The remedial method of quickly removing surface waterOften done on fairways, or sports fields constructed with heavier soilA means of “fixing” poorly drained sportfields

34. Slit drainageSeries of narrow vertical trenches backfilled with sandSome have pipes in bottomConnected to larger connectors to stormwater outletsMany work for awhile, but then failA method improving surface drainage

35. Spacing

36. Design and planning steps

37. Typical slit and collector

38. Lateral directionTypical installationLaterals across slopeLarger collector drain

39. Slit Drainage: Greens

40. Trenching the surface

41. Perched water table in trenches? unecessaryGrassing trench linesGravel layer installPrevents dryingPerches the table

42. Summary of Slit drainage

43. Summary continued

44. Slit drainage on Fairways

45. ReviewDrainage

46. Name 2 examples of moisture-related diseases that can be avoided with good drainage.Pythium root rot

47. Pythium blight

48. Rhizoctonia brown patchName 3 advantages to good drainage:less compaction to well-drained soilBetter water absorption after a rainfallImprovement of subsoil moisture conditions

49. What is the name of the longest and deepest drains on a golf course?Main Collector Drains

50. Where are the Collector Drains normally installed?In the lowest-lying areas to be drained into irrigation source

51. How can Slit Drainage save an older green from being totally rebuilt?allows excess water to escape before it can freeze and cause damage to the surface on older push-up style greens.

52. What is the limitation of slit drainage?Trenches must remain open Routinely opened, or top dressed

53. What options are possible for this low lying “mogul” drainage repair?French drainLateral to collectorRe-grade and sod

54. What is the slope & run rule of thumb when designing drainage?3% slope, minimum 1%, max run is 1:70

55. Explain the relationship of a lateral, catch basin, and collector in fairway drainage.Lateral is subsurface drainage system to meet the collector underground, a catch basin intercepts surface water and is connected to main collector

56. How do contour maps illustrate the best place for an irrigation pond?Contour maps illustrate the lowest point on the golf course. ideally, natural drainage will occur into this area.

57. Slit drains are often used on greens and fairways. Do they facilitate surface or subsurface drainage? Slit drainage are surface water drainage

58. Following a slit drainage project, we sod the trenches…..True or False? False

59. Hydraway drainage systemhttp://www.hydraway.net/video.php

60. Hydraway states their product is a subsurface drainage system. This statement is only minutely correct. ExplainThis is primarily a surface drainage system.

61. Lateral movement of water in soil is so minute in comparison.Hydraway states their backfill is coarse sand, providing an “additional filter” to remove clay fines in the soil. Although it does not remove fine particles, the design may minimize lateral movement of silt and clay. How? The impermeable PVC one-sided tile may physically reduce lateral movement of fines from soil to the coarse sand.

62. Would the Hydraway system work without the tile? What advantages does the tile really offer?Yes, backfilling with coarse sand will facilitate equivalent surface drainage properties.

63. The strength of the PVC tile will add to trench longevity by preventing collapse by repeated trafficAlthough you have a trencher, trailer and loader, what other considerations may prompt hiring an outside contractor? They are liable for failed systems

64. daily tasks will not suffer

65. poor soils can add unknown expenses to the project-these are assumed by the contractor, paid by the job. (breakdowns, labor, design changes etc) Although the advantages of using slit drainage as effective surface drainage outweight the disadvantages, what additional concerns may you have if performing this project on a putting green?Trench lines should not be sodded unless with washed sod so not to contaminate coarse sand in the trench.

66. Slit drainage is not a permanent solution, and may need to be done every couple of years.How can trees contribute to poor drainage?by blocking sunlight and air circulation, which reduces both evaporation and transpiration of moisture from the turf canopy.

67. What can you do if your drainage problem is severe due to impermeable soil?Aggressive aeration,

68. deep tine and solid tine with sand topdressing will

69. Slit drainage project or reconstruction may be necessary to reduce cost of aggressive aerations. Indicate probable cause, effect, and solution to this putting green issue.The water cannot run off due to depressions or in this case, a high collar. With no subsurface drainage, the water stays on the surfaceRecommend collar renovation to facilitate surface runoff, core aeration to improve subsurface drainage.