Guidelines for Tennis Court Construction

Section 1.E. – Subsurface and Surface Drainage for Recreational Areas

1.0	Introduction The greatest single factor in the deterioration of recreational surfaces is the presence of standing water on or free water beneath the surface.Surface drainage (above ground) and subsurface drainage (below ground) are both essential components of properly constructed recreational surfaces. There are three basic tasks of water drainage: 1. Collect; 2. Conduct; and 3. Dispose of excess water.
2.0	Purpose The intention of this guideline is to equip the reader with a basic understanding of systems in order to plan properly for new construction or to recognize and correct existing problems.
3.0	General Requirements
	A.	Subsurface Drainage A peripheral subsurface drainage system is installed where needed to intercept and redirect the flow of subsurface water that might otherwise accumulate beneath recreational areas.Where it is necessary to lower the water table at a given site, a subsurface lateral or parallel drainage system may be required to direct free water from the subsurface to other areas.
	B.	Surface Drainage Surface drainage usually consists of a series of swales or a fabricated system designed to redirect surface water that might otherwise flow over the recreational surface, and to prevent seepage of water beneath the surface.
4.0	Procedures
	A.	Subsurface Drainage There are three types of subsurface drainage systems used to redirect subsurface water:
	Conventional Vertical Stone Drains
	1.	This type of drain is classified as an interceptor drain. It intercepts subsurface water in a stone “wall” and causes it to drain downward into a perforated pipe which carries the water to an outlet.
	2.	A trench is dug 1’-2′ wide on the full or partial perimeter of the facility as directed by local conditions. The depth of the trench will depend on the predetermined water level, but should have a minimum depth of 18″. Since the trench must be sloped a minimum of 0.28% (1:360), the depth of the trench will also be determined by the length of the trench before the water outlet. Multiple water outlets or catch basins may be necessary to minimize trench depths. Place 2″ to 4″ of permeable aggregate in the base of the trench. Note: Non-woven geotextiles are usually used as a filter fabric to protect either the entire stone trench or the pipe only. Corrugated, perforated pipe is available with a “sock” over it. In either case, filter fabrics tend to clog when used in clay or silty soils.
	3.	A porous or perforated pipe with a minimum diameter of 4″ should be placed on the aggregate in such a way as to have not less than 0.28% (1:360) of pitch and not more than 0.83% (1:120) of pitch. A larger pipe may be required as dictated by the amount of free water to be conveyed, the surface area to be drained, or available pitch on the pipe.
	4.	Back fill of the trenches should be of permeable aggregate of no larger than 1 1/2″ placed in 6″ lifts, each of which should be compacted to minimize the risk of subsequent settlement. Note: It is generally recommended when using a filter fabric around the stone to use 1 1/2″ stone size and when not using a filter fabric, to use smaller aggregate to act as a natural filter.
	5.	The trench is then filled to the surface with smaller washed stone where an open drain is desirable.
	6.	Where a closed drain is desired, the trench is filled to 8″ below the surface, after which a porous type membrane is placed over the stone, and a sod or an impervious type swale formed over this.
	Subsurface Horizontal Stone Drain Layer
	This drainage layer is a “capillary breaker” used in areas with ground water problems or heavy clay soils. When installed properly, it prevents vertical movement of ground water under a surfaced area. It is highly recommended that this system be used in conjunction with a perimeter interceptor drain system.
	1.	Installation includes excavation of all vegetation and topsoils under the surfaced area and to a minimum of 5′ beyond. The soil subgrade must be sloped. The slope of the stone drainage layer is then graded to match the proposed finish slope requirements of the surfaced area. Installation includes a 6″ to 12″ stone layer of two inch (2″) minimum washed aggregate installed and compacted in 6″ lifts. Compaction should be 95% of the maximum density determined by ASTM Method D1557.
	2.	On the low end of the drainage layer, a perforated pipe should be installed with a proper slope to collect and dispose of water at the outlet area.
	3.	The horizontal drain layer does not necessarily take the place of subgrade gravel materials.
	4.	Design of this system should be done by a geotechnical engineer.
	“Prefabricated Rockless” or “Geocomposite Drain”
	This system is also classified as an interceptor or curtain drain.
	1.	The system consists of a plastic dimpled or waffle sheet that forms a channel to permit the vertical and horizontal flow of water on each side covered by a non-woven geotextile fabric. Curtain drains usually have a corrugated pipe inserted along the bottom to carry the accumulated ground water to the outlet area.
	2.	Geocomposites are available in various heights ranging, depending on the manufacturer, from 2″ to 60′. The installation requirements may differ from manufacturer to manufacturer but, in general, the installation requires excavation of a trench wide enough to install the geocomposite (usually 4″ to 8″). The trench is backfilled with the excavated material. Some clay type soils may require backfilling with a coarse sand. Consult with your local contractor, geotechnical engineer or architect for design and installation specifications.
	B.	Surface Drainage – Tennis Courts
		There are several types of systems. Open Drain System Open drains are shallow swales using gravity to move water around the recreational area. Swales used to collect and conduct surface water should be a minimum of 5′ wide and 6″ to 8″ deep in the center. Slope requirement should be a minimum of 2% (1:50) on grass and 0.56% (1:180) on pavement. Swales can be located on the ends or sides of a facility and carry water to the outlet area.Closed Drain System A closed drain system utilizes the swale design to collect and conduct water to inlets located (at a minimum of every 200′) in the center of the swales. The water inlets are connected below ground to pipe (size is determined by volume of water being collected) which carries water to catch basins or other outlet areas. Combination Systems Combination systems utilize swales and/or conventional open or closed vertical stone drains or “prefabricated rockless” geocomposite drains as discussed in the above section on subsurface drainage. Prefabricated Channel Drain Systems Another functional system being used for surface drainage is the prefabricated channel drain. These vertical lineal drains have been used for years in the track industry to drain both the field and the track surface. Their application with tennis courts and other related surfaces are also being used successfully. They require shallow excavation and some manufacturers offer sections with “built in slopes”. Channel drains are available in radius, angles and straight lengths. They also have removable grates to allow for easy cleaning. To obtain the correct system for your facility, you should consult with an experienced contractor, qualified architect and/or engineer.
	C.	Surface Drainage – Tracks
		Calculations should be done to determine the amount of subsurface and surface drainage that must be handled. Following are several systems that have worked effectively for running track construction.
	1.	A perimeter drain tile system is an effective way of intercepting and redirecting the flow of surface and subsurface water that would otherwise accumulate beneath the track surface. Such a system normally terminates either in a storm sewer connection or through an end wall to direct water to an area of the site that is lower in elevation. It has proven to be an effective and economical system for providing subsurface drainage and also providing some residual surface drainage. Normally this would form a perimeter drain around the inside of the running track.
	2.	Four to eight catch basins can be located around the inside of the track to intercept surface water and direct it into a storm sewer, drain pit, or end wall outlet. The swale in this area should be graded to allow track and infield water to flow to the catch basins.
	3.	Curb and gutter drainage consists typically of a 6” x 18” interior curb with a 12” wide gutter pan. In most applications, the track is sloped 6” (maximum of 8”) toward the lower end of the existing exterior terrain. Water from the track surface, as well as the infield, flows on the gutter pan to the low end, where it enters multiple catch basins located in the gutter pan. Catch basins are connected to a concrete or PVCpipe installed under the radius of the track.
	4.	A permeable system allows surface water to flow through the track surface, asphalt, and aggregate base to a collector system that directs it to a storm drainage outlet.
	5.	Continuous trench drains can be used around the inside edge of the track surface. This system allows for rapid movement of water. It typically has several outlets to a storm drainage system. This drain can also serve as a termination point for artificial turf on the infield.
	D.	Storm Water Detention
		The free water “spill off” from the drainage system should be directed to avoid complications to surrounding areas. Local building and/or zoning codes may require detention basins or dry wells large enough to retain approximately 1/2″ to 1″ of rain water falling on the surface area in one hour. Consult with local authorities having jurisdiction. A pipe having an open discharge should be protected with a head wall for easy identification, and covered with screening to prevent small animals from entering and clogging the drainage system.
5.0	Conclusion
	A.	The greatest single factor in the deterioration of recreational surfaces is the presence of standing water on or free water beneath the surface.
	B.	Addition of more base or placement of overlays does not eliminate the basic problems of surface failures due to poorly designed facilities or improper drainage systems.
	C.	Proper pitch and consistency of grade in the subsurface drainage system are essential.
	D.	Proper and consistent pitch to the subgrade and in the subbase are frequently underestimated. Correct pitch is essential to avoid “pockets” that might hold free water, thereby negating an otherwise functional drainage system.

Drawings:
Typical Drainage Patterns for one Tennis Court
Surface Drainage at Court Edges
Subsurface Drainage at Court Edges
Rockless or Geocomposite Drain at Court Edge
Surface Drainage Tracks

ASTM specifications are available from
American Society of Testing Materials (ASTM)
100 Barr Harbor Drive
West Conshohocken, PA 19428
610-832-950

NOTICE: These Construction Guidelines are for use by architects, engineers, contractors, tennis court and running track owners. Parties not experienced in tennis court or running track construction are advised to consult a qualified contractor, consultant and/or design professional. Experienced contractors, consultants and/or design professionals can be identified through the U. S. Tennis Court and Track Builders Association. Due to changing construction technology and techniques, only the most recent version of these Guidelines should be used. Variances in climate, soil conditions, topography and other factors may make these Guidelines unsuitable for certain projects.