Design and Layout
Athletic fields should be designed to meet standard dimensions established for the game for which they will be used. Complete diagrams of field dimensions and markings may be found in official rule books of the Pennsylvania Interscholastic Athletic Association, the National Collegiate Athletic Association, or the professional leagues. Football dimensions and markings, for example, differ among high schools, colleges, and professional leagues. Contours and drainage provisions are particularly important from the standpoint of play and to provide for fast removal of surplus water. Surface grades and the design of subsurface tile lines for water removal are shown in Figures 1 through 7.
Soil compaction is a major problem on athletic fields constructed from soil or modified soil mixes. Its primary cause is trampling and the use of heavy equipment either in construction or maintenance, especially if the soil is wet. Compaction seals the surface and prevents normal movement of air and water into and through the soil. This not only interferes with normal plant growth but also causes very unsatisfactory playing conditions. Good contouring will aid substantially in reducing compaction. Contouring allows rapid removal of excess surface water, which is primarily responsible for chronically wet soil.
Compaction is less of a problem on soilless fields but provisions must be made for their drainage. The high infiltration and percolation rates of these fields normally require the installation of internal drainage tile.
Turfgrasses require a quarter to a third of an inch of water per day. This is equal to approximately 150 to 200 gallons per 1,000 square feet. A good quality loam soil will hold about 1,200 gallons of available water per 1,000 square feet, to a 6 inch soil depth. Therefore, an adequate irrigation installation for turf on a loam field should be capable of supplying the turf with a minimum of 1½ inches of water every 7 to 9 days. Sand has a much lower water holding capacity than loam soils. Irrigation systems for sand fields should supply the turf with a minimum of 1½ inches of water about every 4 to 5 days. The proper system is one which will distribute enough water uniformly to meet maximum turf needs.
Irrigation systems vary from padded pop-up types of sprinklers, spaced uniformly over the entire playing area, to occasional outlets on the perimeters. Traveling sprinklers, with hose connections to perimeter outlets, provide very satisfactory and efficient irrigation for athletic fields. They apply water uniformly over an area and are readily adjusted to wind direction and velocity. However, lower initial costs of perimeter outlets may prove more expensive in the end, when consideration is given to the additional labor and equipment required over many years.
The capacity of an irrigation system depends upon many variables such as water pressure, volume, pipe sizes, and sprinkler outlets. Since these vary widely under different local conditions, a competent irrigation engineer or other authority should be consulted when field irrigation is to be installed.
The orientation of fields in relation to the sun must be considered in designing an athletic field. Where daylight use is anticipated, fields should be laid out with the main or long axis north and south.
Football gridiron. Proper crowning of gridirons constructed from natural soil or modified soil is a necessity that will ensure excellent surface drainage without interfering with play. The design should provide a 10- to 18-inch crown (approximately 1 to 1.9 percent) sloping uniformly from the center of the field to the sidelines, without pockets. The parallel sidelines should be level. Tile systems are placed along the sidelines with open catch basins to remove water more rapidly than it will be absorbed through the soil (Fig. 1 and 2). Except for cases of seepage and high water tables, tiles under the entire playing area of soil fields may be of little value because surface compaction impedes water movement to the tile.
Figure 1. Football gridiron showing end section and tile lines for natural soils and modified soil fields
Figure 2. Cross section of tile line along sidelines for fields constructed of natural and modified soils. Open catch basins are not necessary for soilless fields, but other specifications would be similar.
Soccer fields. The design of natural soil or modified soil soccer fields (Fig. 3) should provide grades with a drop of not more than 1 percent from the center crown to the edges. This is much less than the grade permissible on a football gridiron. Since the high center crown on the latter makes side shots in soccer more difficult, it is not advisable to use an area for both football and soccer. A field of minimum width and a 1 percent slope would have an approximate 9-inch crown. A field of maximum width and 1 percent slope would have an approximate 16-inch crown.
Figure 3. Soccer field showing end section and tile lines for natural soil and modified soil fields
Field hockey fields. The drainage crown for natural soil or modified soil field hockey fields should be the same as for soccer. Due to the nature of the game, crowns greater than 1 percent would be a detriment to play.
Figure 4. Field hockey field showing end section and tile lines for natural soil and modified soil fields.
Baseball diamonds. Standard baseball diamonds normally have the pitcher’s mound elevated approximately 15 inches above homeplate and the baselines. The fall from the mound should be turtle-backed and not abrupt to the edge of the mound area. The infield area, from the edge of the mound to the basepaths, should have not more than 1 percent grade. Surface water from the infield can be removed by placing tile lines on the outer edge of the skinned area. These lines should be drained away from the playing area in any manner conforming to local conditions. the outfield should be graded to 1 percent slope, from the center in all directions, with the water carried off at the edges by a catch basin tile system if necessary (Fig. 5). Little League fields are laid out in the same manner but on a reduced scale.
Figure 5. Regulation baseball diamond showing design of tile system.
Soilless (sand) fields for all sports. A false water table normally will develop at the interface of the sand layer and the underlying soil. The underlying soil has very low infiltration and percolation rates in comparison to the sand. Therefore an internal tile drainage system if necessary in a sand field.
Two basic tile systems are used. The most common system (Fig. 6) is to install 4-inch tile lines in the subgrade at a depth equal to the tile size, at 20- to 30-foot intervals across the field. These lines are connected to a perimeter line beyond the field sidelines. A second approach is to grade the subsoil so that sloping channels run the length of the field are are approximately 40 to 50 feet apart (Fig. 7). These channels should have a minimum sllope of 2 percent. Gravel-encased tile lines are placed in the bottom of the channels. Excess water drainage from the sand then flows down the underlying slope to the tile lines which are connected to perimeter lines at the end of the field. This system will require more sand than the cross tiling system because it is desirable to maintain 14 to 18 inches of sand at the most shallow point. Conversely, this system requires considerably less tile line and no trenching.
Figure 6. Overhead drawing of a cross-field tile system (tile lines approximately 20-30 feet apart) for modified soil and soilless (sand) fields. Soilless fields do not require open catch basins. Modified soil fields must be crowned, soilless fields may be level.
Figure 7. Longitudinal tile system for all types of soilless (sand) fields. Tile line laid on bottom of swale and encased in gravel. Minimum of 14 to 18 inches of sand at most shallow point.