CA1143182A - Grass sports surfaces and a method for maintaining them - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An apparatus for monitoring the level of liquid in a grass playing field which includes a subsurface liquid reservoir, the apparatus comprising a generally U-shaped tube-like element, said tube-like element being in liquid communication with the liquid in the liquid reservoir, one leg of said tube-like element being positioned within the playing field such that the level of the liquid in the one leg is representative of the level of liquid in the playing field, the other leg being positioned outside of the boundary of the playing field, the liquid in the other leg having a measurable characteristic which is representative of the level of liquid in the playing field; and means for measuring said characteristic.

Description

3iB2 Back-Jround of the Invention As is well known, the construction of a good quality all weather grass playing surface and its maintenance for rec-reational purposes and active sports, such as soccer and foot-ball, has been a problem of long standing.
One of the more recent attempts at: resolving ~his l~roblc has resulted in use of an artificial surface. These sur-faces have recluced the recJular maintel~ ce re~uired but the eost to repair for wear and tear generally exceeds the cost oE mai~tenance of a natural grass field. Further, -the play-ing conditions immediately over a synthetic surface are far less tolerable than over a grass surface since the synthetic and its supp~rting surface retain heat. All synthetic sur-faces have suffered from the inability to provide adequate drainage. In general, these synthetic surfaces arc no~
completely acceptable to player associations since they have a higher incident of injury than that e~xerpienced on a goo(l quality na-tural grass surface.
In general, the factors which must be considered in designing and maintainin-3 a playing surface include the needs of the player utilizing the surface, the requirements of the agrologists in plant growth and maintenclnce and the correct application of acknowledged engineering principles. The finished product will experience variable and sometimes un-predictable environlllental consid~?ra-tions. The total growth ar.d maintenance s~stem must have a f~exibility built into it such that the variables may be accommodated.

The selected grass used must be of a type which has good wear ability characteristics, but also must satis~y the cli-,~

3~82 matic conditions in the locality wherc it is to be uscd. Once the selection has been made as to the seed mixture, the plan-t itself must be established and must be capable of vigorous growth to provide for rapid self-repair following user dama~e. ~he grass mus-t be well anchored in i-ts growing med-ium to minimize tear out by the participant and it should provide a uniform surEace throughout the applicable season.
It is desirable that the quality of the surface be con-stant for the entire g~ras~ed area and that tlle surEace be able to be used extensively even under adverse climatic conditions. This desire obviously requires the surface be free from an accumulation of water and Erost an~ that the watering and fertilization applica-tion do not interrupt use.
Tile ~round conditions should be firm and yet provide a cushion normal for a well established turf which experience has shown to minimize player injuries.
It is further desirable that the playing area should be free from obstructions such as sprinklers or the like and reasonably level throughout its entirety.
~laintenance pcrsonnel require a m-ininlization of the oper-ational function needed to maintain the surface while re-taining a good quality grass condition.

Prior Art In general, grass surfaces heretofore provided can be c3enerally classified as the soil turf Eield, the modified sand field and the mem4rane sand field.
The soil-turf playing surface is a classical method wherein the qrowillg medium is a natural good quality soil ~''13~

placed over a granular material. Drainage is provided by providing a crown to th;e surface and suhsurface drains.
Irrigation is applied to -the surface by conventional methods.
Fertilizer is generally applied to the surface through mech-anical spreading or through sprinkler applied liquid fertilizer.
These soiL-turf fields in general do not stand up to more than minimal use and require heavy maintenance. In wet locations, these fields are consistently muddy due to poor drainage characteristics whereas in dry conditions, ~he grass shows the affect of tile heat and in general are no-t well nourished. In hot loc~tions, surface applied irrigation exp-eriences large evapora~ion losses to atmosphere and a build up of water borne impu~ities at the surface damages the grass.
Surface compaction cau~ed by the natural rainfall, surface irrigation and player use generally renders the drainage system ineffective. The compaction also prevents oxygen from reachillg the roots and inhibits growth. The surface runoff attempted by crowning the field is not rapid enough even under minimal rain-fall. The grass plants are generally surface huggin~ because of the fact tllat tlle water, nutrients alld oxyc~en required are all located there. In this weakened state, the grass may be easily pulled out during normal play, creating bare areas which are not readily self-repairable and require extensive resodding. A weakened grass is more susceptible -to clisease and infestation problems. This method does not lend itself to soil warming techniques since the melted frost and snow a~]gravates the lac~ of drainage and turns the surface to mud.
In cold climates, the surface freezes rapidly due to the high silt content ancl its moisture retaininq characteristics.

,i 3 The inadequ.lc~ vf the soil turf method has led to developmellt of both the modified sand and the memb~ane sand methods. In each of these cases, the primary attempt is -to overcome the drainage and compac~ion problem.
The modified sand method uses two classifica-tions of sand as a growing medium, i.e. a bottom layer Gf natural clear sand while the top surface is a mixture of sand an~ organics.
Drainage is provided by an underlyin(J grid ~nd irrk~ation and fertilizers are surface supplied by tllc s.~ e mealls .1; lor soil turf method.
The modified sand method has essentially uncon-trolled drainage through the sand layer and therefore the modified surface zone is essential to avoid drought conditions at the level of plant growth. Although the addition of organics lS retain the nutified moisture and oxygen relation in the sur-face layer for good plant growth, the oryanics also re-tain water, slow down the drainage rate and result in a soft and slippery surface. The grass is surface hugging for the same reasons as the soil turf field. A major problem in this method is lack of lony term control. The surface zone, although -selected for pro~er liquid retention charac-teris-tics at the time of design, is subject to normal decomposition and leeching of the organics resulting in their loss through the drainage system. Further, the decomposition of the oryanic material consumes nitrogen necessary for strong healthy growth. The eventual replacement of the organics is impossible without entire replacement of the surface layer, an expense similar to resodding for the soil-turf field. The effectiveness of soil warming techniques to remove snow and frost are inhibited by the lack of the systems ability to continuously replace lost 3~2 moisture caused b~ the cold weather drying effect. The surface condition results in freezing condi-tions similar -to .
the soil'turf field.
The membrane sand method is the result of efforts to capitalize on the principles o~ hydroponic growth, which has proven to be totally successful with a controlled propagation of plants in a nursery environinent. Althouc3h variations ex,ist, in c~eneral, the membrane sand method comprises of a natural sand growing medium which is completel~y isolated by ~n imper-vious membrane to ~rovide a contained reservoir of w~-ter and isolate the area. Over the membrane and within -the isolated area is placed the pipe or conduit system which is -tiec~ into a drainage discharge system located outside the field area to allow removal of e~cess water. Over and around the pipes are placed sand and the regulation of the excess drainage discharge is provided by some form of weir like action or ~umps or both.
These systems have not been adec~uately designed to properly handle sub-surface apu:Lied irrigation or fertilizer and gen-erally those installed use surface sprinkler systems and fertilizer applic.ltioll ~y Ille.lnS Sillli]..lr LO tl~o soil turE Ul-1C1 modified sand methods. The majority oE installa-tions have also used a modified surface zone by incLudincJ a layer of organics. This effect minimizes the capillary action (a benefit of the membrane) since capillary rise will no-t readily transfer from the pure sand to the modified sand thus creating a barrier and necessitating supplementary surface applied irrigation and fertilizer. Those with perEorated distribution pipes placed directly on the plastic membrane are impaired since the standard location of the perforation holes 3:~32 and the normally expected onelnchground settlement after construction causes some of the pipes -to indent into the plastic blocking the holes and making them ineffective.
Pumps used to assist in the removal of excess drainage water S are ineffective when the water table is below the entry par-ts of the pipes due to loss of vacuum. Installations using special piping cross joints have shown irregular drainage capabilities due to restricted flow. Systems using only sand exhibit poor lateral liquid movement to or from a pipe sys-tem and require a lar~er head pressure Eor drainage. Vnder certain conditions, the head requirement resul-ts in a sat-uration curve within the sand that will intersect the surface between the pipes and cause surEace puddling. Conversely, liquid attemptin;J subsurface entry into -the field is restricted in uniformity of distribution unless sufEicient pressure is used which could tilen lead to a quick sand condit,ion in the areas of the initial entry ~oints. None of the systems e:~hibit positive and responsive control systems.
Although a search has not been made, U. S. Patent Number 3,~61,675 granted to Izatt on August l~, L9G~ is illustrdtive of the type of systelll de~cribed hereillabove and improved upon by the presellt inve~n~ion.

~resent Invention The imporant criteria of tllis improved membrane sand system is to provi-le and maintain a deep rooted grass surface which e~hibits vigorous growth and which has a level surface throughout ~ithout obstructions and which does not suffer compaction problems. The system is capable of minimizing en-. ,~_ 3~2 .. . .
vironmental problems created by variable climatic conditions of the various locales in which it is installed includes effective surface drainage abilities as well as nutrified liquid replacement to the plants growing zone on a uniform and continuous demand basis as the plant and climatic conditions dictate. Soil warming techniques for frost and snow melting create surface drainage and plant dryin~ out effects and the system is eapable of handlin~ these factors.
The prime eonsideration of this improved membrane sand system is to eontrol the water table within the isolated membrane area and the assurance of uniformity of lateral dis-tribution of the nutrified liquid reservoir such that the surface zone moisture con-tent is main-tained. This control and distribution ensures the proper relationship of nutrified water and oxygen for the particular sand type and within the toleranee limits for the plant. Water and nutrients, whether applied by subsurface means or at the surface, move freely to the membrane reservoir by the excellent vertical d~ainage characteristics of the sand. This reservoir in turn feeds the grass plant by capillary action inherent with the sand.
Excess water occuring during rainfall is discharged out of the system, conservin~ first any rain water that car, be retained for irrigation purposes. Irriclation water make-up is preferably ap~lied throucJh the u-tiliza~ion of a su~surface pipe grid utilized for both the drainaqe and the irricJation or may be applied ~y conventional surface means. Fertilizer is added to the irrigation water using liquid fertilizers and an injection system or may be surface applied.
It has been well demonstrated that depending upon passage or time and as a characteristic of a selected sand, -the sand S'82 absorbs the same amount of liquid whether or not it is applied at the surface or from ~eneath. It can also be easily demonstrated that the absorption of the sand is propor-tional to its depth and the moisture content at any level can be determined as a function of -the depth of a particular gradation of sand.
The capillary rise in the sand, in addition to the drain-age characteristics, is dependent upon the gradation and makeup of the sand and is controllable by proper selection of these materials and the establishment of a water table. The rate of capillary rise is particularly critical in extremely dry climates and the drainage rate is critical in areas of heavy rainfall. It is also required tha-t the selection of the gravel be such that its gradation, in comparison with lS that of the particular sand, be compatible to ensure that the sand will penetrate the gravel layer by a depth of approximately one inch. This penetration places the bot-tom of the sand layer below the minim~n water table -to allow capillary action and yet the lateral flow characteristics of the gravel are not impaired.
It can thus be seen that maintaining a wa-ter table at the bottom of a natural sand layer permi-ts -the more accurate con~
trol of the moisture content at the growing level. Further the natural sand surface extends the playing season by its low moisture retention and thus its ability to hold back freezing for a slightly longer period and to thaw out more rapidly.
The dormant period of the plant is thus reduced. The addition of a uniform heat source, combined with the proper seed selection, may further extend the season by encouraging early cJrowth and resisting die back caused by cold. The inclusion 3~

of an insulation layer under the membrane will minimize frost penetration to the sub~rade at times when the heating system is not in use.
In summary, an accurately controlled, frequently watered, properly fertilized well drained field provides Eor the best quality grass playing surface as well as encouraging rapid regrowth and thus providing maximum utilization. ~lealthy plants are less susceptible to disease and infestation and a natural grass surface provides much lower air tempera-tures immediately over the playin~ surface than the prevailin~ ambient conditions while providing -the immediate air with an enrich-ment of oxygen. Only this improved membrane sand method with automatically operated subsurface drainage and fer~ilization in combination with irriga-tion, i.e. "fertigation,"
provides these requirements on a continuous demand basis as determined by the plant and the environment. The grass itself, in growing, has a deep rooted characteristic as it reaches down to the water table and thus has better wear and tear capabilities, since the plant is more firmly anchored and thus su~fers only leaf dallla~Je durin~l exLollsivc use which is rapidly replaced by vi~orous re~rowth. q'he utilization of "fertigation" by subsurface auplication is a continuous, uniform and steady means which wllen coupled with the membrane isolated area, carefully selec-ted growing medium and liquid transfer medium and system coupled with accurate and responsive control method provides these require-ments.
It is an object of the present invention to provide a playing surface support ma-terial and method which maximizes the utility of a field and minimizes the maintenance require-3~

ments under the most variable and severe climatic conditions.
Still a further object of the present invention is toprovide a system for establishing and maintaininy a grass play surface comprising the steps of: (1) grading the sub-grade at the site of the proposed surface, (2) placing a fluid ..
impermeable membrane adjacent the graded surface with or with-out inclusion of an insulation layer, (3) providing a means of central supply and removal of fluid at the appropriate location in the graded surface, (4) providing a layer of horizontal flow gravel on top of the membrane, ~5) placing a lateral liquid distribution system throughout the desired area on top of the gravel layer, (6) providing a layer of sand with appropriate permeability, capillary and porosity character-istics and having a substantially level upper surface without obstructions into which the grass will be planted, t7) pro-vide a means exterior to the field to direct excess drainage water from the field to the site storm system, (8) providing a responsive control system to control the liquid level within the confines of the membrane beneath the grass, ~9) provide an adequate feltiliz~r injection ancl waL~r make-up sys~elll to sustain optimum ~rowth and replace transpired and evaporated water, (10) provide a drain line -to remove all liquid from -the contained reservoir, (11) when required, installation of a soil warming system to melt snow and remove frost, (12) when required, to provide a means -to sense the nutrified condition or the contained liquid.
Still another object of the present invention is to provide a membrane sand type grassed sports surface including automatic means to provide irrigation as needed, provide fertilizer on a predetermined schedule, and to withdraw ~3 _~ _ liquid from the field in the event that the level within the membrane exceeds the ma~imum desirable for optimal utilization of the field while maintaining the quality and quantity of nutrified liquid to stimulate healthy growth.
It is another object of the present invention to provide a grass playing field which includes a growing medium having predictable capillary action overly:ing a liquid containing material having horizontal flow characteristics assuring uniformity of distribution under low infeed pressure require-ments in which are placed conduits for the addition of water and fertilizer to the liquid reservoir.
A stil] further objec-t of the present invention is to provide a grass supporting medium wherein the upper layer pro-vided a firm noncompacing surface with predictable pe~leability permitting ready drainage and an underlying surface permitting lateral fluid movement such that a minimum head is required to effect the drain~lge.
Still another object of the present invention is to provide a means located within the field beneath the grass sports surfa~e for dctermillin(l the l~vel of liquid within tllC? (JraSS
supporting medium interconnected with a means exterior of the field to provide ready and convenient information as to the liquid level.
It is ano-ther object of the present invention to pro-vide a means and mechanism to sense the system's water level and masnetically transmit this in-to low voltage electrical signals and relays these to a programmable control panel which, in turn, operates, using a low voltage power supply, the irrigation infeed and drainage outflow valves. The system utilizes available irri~ation water pressure to function the _,~ _ main valves throucJh small solenoid valves located on the bleed lines from the irrigation line. 'I'his met!lod thereby minimizes any electrical hazard.
It is another object of the present invention to pro-vide a means and mechanism when electrical energy is notavailable to use float operated devices activated by the systems water table and coupled to -the irrigation bleed line valves to transmit the irriqation pressure into a Eorce to open or close the irrigation and drainage valve.
A further object of the present invention is to provide a means and mechanism for extending the usable seasoll for a playing field through the use of underground hea-ters and pro-tective sub-grade insulation layer combined with a sys~em which accommodates the cJenerated drainage requirements while simultaneously providing a continuous source of liquid to avoid the drying effect normally associated wi-th artificial heating devices.
Yet a further object of the present invention is to provi~e a grass field which may have a chemical inbalance corrected withou~ resort~ J to a restLu(,t:urinc~ or replaeemen~.
A drain and irricJa~ion system is provided such that all chemicals or the like may be easily washed by means of purging from the grass supporting medium ef~ecting a neutral condition.
It is also the object of the drain to allow removal of all liquid from the entire system when necesC;ary.

Brief Description of the Drawings Figure 1 is a plan view of a typical field layout utilizing the present invention.

~3~1L82 :Figure 2 is a sectional view taken alony the line~ 2-2 of Figure 1.
Figure 3 is a plan view of the preferred control room.
Figure 4 is an elevational view of the water supply header as seen alony lines 4-4 of Figure 3.
Figure 5 is a plan view of a valve station.
Figure 6 is an elevational view of a valve statioll.
Fiyure 7 is an elevational view oE the electrically sensed level control unit.
Figure 8 is a flow diac~ram for an automated syst.em.
Figure 9 is an elevational view of an alternate mechanically sensed level control unit.
Fiyure 10 is a sectional view of an alternate construction when heating and sub-grade insulation is incLuded.

Detailed Description of the Drawings As seen in Figure 1, the fieLd generally designated as 2 is divided into three essentially equal sections 4, ~ and 8 and deLined interllally ~y a division al(~ J lines ~2. :I:t is to be understood that the size and shape of the field as well as external conditions such as clima-tic fac-to.rs and dec3ree of use will determille the num~er and shape of t.he sections. Each section has a slope in the sub-grade designated in diagonal lines 3 to a low point at approximately the center of the section where the water level detector 42 will be located as explained hereinafter. l~ithin each section of the field there will e~ist a field section main 10, 12 and 14 interconnectilly with the'required number of horizontal field distribution piping headers 16, 18 and 20. A plurality of perforated field ~,}~ ~ ' 13~2 distribution pipes 22 form a substan~ially equall~ spaced grid work throuc3hout the field assuring rea!ionably equal distribution and/or saturation.
Each of the sloping field sec-tion mains 10, 12 and 14 are connected to a valve station 24, 26, 28 located below grade out-side the playing area and are interc:onnected by means of an irrigation feed system 30 which is interconnected with and controlled from the control room 32 which in turn is connected to the water supply 34~ These field distribution pipes 22 and the headers 16, 18 and 20 as well as the mains 10, 12 and 14 may also be used to discharge excess water by means of the drainage system 36, 38 and 40 which lead to an off site storm system. It is to be no-ted that -the water level detector 42 and its interconnected tube 44 (one for each sec-tion) likewise is interconnected with the valve station and with a storm drain after passiny through the water level sensing unit 110. Also seen in this view is the low voltage electricaL
control system designated generally as 46 from the control room to each one of the valve stations.
Referring llOW to E`igure 2 which, as noted abovc, is a vertical sectional view ta}~en along lines 2-2 of Figure 1 it can be seen that the field inclu-les a subgrade S0 whicll slopes within edch section towards its center and the water level detector 42 which can also act a~ a drainage me~ns. At midpoint Or each section is located the trellch 52 to accolMIodate the piping exitinc3 for each section and includes sand bedding 54 supporting the field section maln 10. The water -t:able le~fel tube 44 is also placed within trench 52 which is ter-minated a-t the center of the section with a vertical perforated ~0 tube designated as the water level detector 42. The remainder _~_ of the trench is filled with onsite m~terial 5h and a men~rane 58 is placed over the sub-grade and sealed at the conduit entry points thus establishing an enclosed dish-like area for the irrigation and grass support pur.poses. As the -trench exits the perimeter of the system a 5 foot long plug using impervious materials is inserted in the trench to ensure a positive seal to the trench itself.
As noted above, the entire Eield is broken into fie1d sections. The field sections are defined by a perimeter berm 60, which extends around the entire periphery of the field, and upwardly extending section divisions 62 extendincJ
across the field and across which the ~embrane 58 is ~olded.
The subgrade 50, AS noted above, is sloped toward the center of each section but the gravel layer 61 which lies thereupo and supports a perforated field distribution pipincJ 22 as well as the piping headers 20 has a horizontal or level upper surface. It is to be noted that tllis surface in general will define the minimum water level through the weir action of the perforations in the event of automatic control shutdown. The gravel layer witllllori~oll~al flow cll.lL~ ris~ics ass~lles evc .. ..
distribution of water or fertilizer.
The perforations of the field distribution piping are placed downwards on top of the gravel and the pipes are then covered with a filter cloth wrapping 66. This cloth is standard to earth work projects and prevents the fines loss from the sand from entering the piping system. The pipe is not entirely wrapped but is covered with the filter cloth which is tilen tucked on each side of the pipe with the edges pro-jectiny outward ~y three or so inches. 'I'his method of wrapping ~5 _~_ 8;Z

is essential since wrapping the pipe on its entire circumference could lead to clogging through salted ou-t fertilizer particles being trapped in the filter material 66. The method employed allows the holes to remain uncovered whi]e the sand is pre-S vented from entering the pipe without first passing throughthe gravel 64. This is not possible because of -the particular selection of the gravel gradation. Tlle sand layer 68 is then placed, overlying the gravel and the distribution piplncJ.
The grass 70 is planted at the top oE the sand layer at the field elevation which is level throughout. The root structure will generally extend vertically downwardl~ to reach the established water table and not bunching toward the pipes.
As seen in Figure 3, the preferred embodiment of the con-trol room is shown. For ease of cleaning, the control room includes a floor drain 80 at the intersection of the various portions of the sloping floor 82. Mounted about the perimeter of the room is fertilizer storage 84 and control panel 86, the required breaker panel and disconnec-t devices 88. Mounted upon the floor of the control room is the fertilizer holding tank 90 which ha~ ounted adjacenL thereto the fertLIizer in-jection pump 92 Eor selectively injectiny the fertiliæer into the irrigation feed 30 as explained in cJrea-ter detail with respect to Figure 4.
Referring now to Figure 4, which is a sectional view taken along lines 4-4 of Figure 3, it is seen that the water suppl~
34 is located beneath grade, is elevated into the water supply header which includes a wash down hose connection 94, back flow preventer set 96, a strainer and clean out 106, a pressure regulator 98, a test pressure gauge connection 108, a fert-ilizer injection valve 100 and a pump pur~e fe~d connection 102, in addition to manual isolating shutoEf valves 104.
In Figure 5, a plan view oE a valve station, there can be - seen that the water level tube 44 extends into the water level sensing unit 110, as described in greater detail hereinafter, and is connected by means of a conduit to the automatic field drain valve 112 which can, as the name implies, be used to remove all liquid from the fiel.d as may be required for purging.
Just befor~ the automatic field drain valve 112 is a vertical water level sight tube 111 complete with a colored ~loat and transparent casing to allow for visual inspection of the water table level within the field section. Also extending into the valve station is the field sec~ion mai.n lO which at its termination has located an automatic draina~e valve 128 which, when open, allows excess water to discharge to the site storm system. The liquid make-up supply -to the field section main 10 is through the irri~ation feed 36 whi.ch ..
includes an irrigation feed line drain 116. Also to be noted in view is a bleed line 118 for pressure assisting the auto-matic valves.
Lookin-l now at Fi~ure 6, which -is a sect:ional view tak~
along lines 6-6 of Figure 5, it can be seen that the valve station lies below the field elevation and as noted in Figure 1, is outside the playing bounda:ries and further, out-side the boundaries of the controlled Eield. The valve station includes a closing cap 120 and is surrounded by means of a ri~id side 122 and a Eloor 124. ~s seen in thi S view, the water level tube 44 e.~ends outwardly generally toward the Eield and within the manhole chamber it terminates with the automatic drain valve 112 which is immediately preceded by the water level sight tube 111. The field section main 10 as seen in p this view, lies immediately in front oL the water level tube 44 and terminates with the automatic discharge valve 128.
Further to be seen in this view, is the irrigation supply to the section mains 10 following the irrigation feed line drain 116, shown in Fiyure 5, is a strainer and clean out 119, bleed line shut-of 118, automatic irrigation supply valve 126, a balancing valve 127 and a test pressure gage connection 12~. rl'he dis-charge to the storm system is designated 3f~.
The water level sensinc~ unit for use in -the totally automatic system is seen in Figure 7 and as seen, this also lies beneath the field elevation and is covered by a removable cap 130 which covers a vertically placed PCV pipe 13:'. A
plurality of reed switches 134 are mounted and sealed in a vertical member 135. A buoyant toroidal shaped float 136 having permanent magnets 137 imbedded therein closes the reed switches 134 by magnetic flux which o~ens and closes the LV=low voltage electrical switches in the terminal base 138 which relays a signal to the main control panel which in turn actuates valves to add or remove liquid from the field. The liquid level within the wa~er level sensing Ullit iS clirectly re.ponsive to the level within the field. This unit in conjunction with the water level detector 42 and the interconn~cting conduit 44 form a U-tube. Tube 44, lying at the lowest por-tion of the section may be used as a drain for purging the field by opening the automatic field drain valve 112 shown in Figure 5 and located within the valve station. Further to ~e seen in this view, is the connection with the low voltage electrical control system 46 and the conductivit~ sensor 139 for relaying the condition of the nutrified liquid.

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~~~

~ 3~

As seen in Figure 8, the flow diacJram is generally divided into two sections (A) which is generally within the valve station and (B) which is generally within -the control room.
As seen in this view, the water enters the control rooms by means of conduit 34, passes through the back flow preventer 36, pressure regulator 98, and then for purging of the pump, an auxillary line is fed to tl~e fer-ti:Li:~er injection ~ump 92 with the main line proceeding after the injection valve 100 directly to the valve station via conduit 38. I'ertilizer from the holding tank 90 is automatically directed to tlle fertilizer pUM
92 and then through line 38 to the valve stations. Also seen in this view, is a means to purge the pump to the sewer or to dump the storage tank. Within a typical valve station the water passes through the irrigation supply ~alve 126, the balance valve 127, and then to the field section main 10. The feed-back demonstrating a need for water is generated by the water level tube 44 and the water level sensing unit 110. Further to be seen in this view, the electrical supply passes through the power panel 88, the master irrigation control 86, and is fed to the various valving, pumps and watcr level sensing uni-ts necessary to perform the functions as described hereinabove.
It is to be remembered that all power except for the pump is low voltage.
A preferred control for a system when electrical power is not available is shown in Figure ~. This installation provides for a mechanically automated system ermployincJ a completely controlled method for subs-lrface drainage and irrigatlon. -l~ith this system, control room is not required and is replaced with a water supply header and an automatic fertilizer application is not contemplated and thus is not included.

"

~ 3~

The control utili~es mechanically functioning float activators 152 linked by parallel linkage 154 to flo~ts 156 all mounted within a manhole 158. A water level tube 44 continues through the control manhole and terminates as for the automatic system in the valve station wi'th a water level sight tube 111 and manual drain valve 162. The float activators utilize the water pressure from the irrigation line through bleed lines 164, 166 and 168 to open and close the pressure operated,irrigation and draina~e discharcJe valves.
Figure 10 illustrates, for full disclosure, and alt~r-nate embodiment of the extreme ri~ht end portion of Fi~ure 2.
Heating ~ables and a sub-grade insulation barrier included as well as a modified periphery of the field. As can be seen, the insulation layer 200 is placed directly under the membrane over the entire field area. At the perimeter this insulation is carried vertically downwards to a location at least 6 inches below the contemplated frost penetration for the locale. The e~terior perimeter is trenched 202 to accommodate the insulation and a standard type perimeter drainage system 2()4. The drain'age pipe 20~ is bedded on sand 206 and the entire excavation is ~ck~ d to will~ (, illCll~?S of tllo surr.lc~ wiLII I L~ r~ iri ill(J
select granular fill 208 to ensure elimination of frost heave problems. Tlle surface of the b~ckfilled trer)c'lis graded .. . .
with 6 inches o- top soil 210 to support grassing. Referrin~;
to the detail within the membrane isolated area, i,t can be seen that the heating cable system 212 is locatecl over the gravel layer and under -the sand layer. The COIl trols -Eor the soil warming system include ground temperature sensor 214 and relay signals back to the main panel in the celltral room to ensure gradual heat elevation and reduction controls using ~?~D
--,;2~--3~8~

solid state devices such that the grass root system is not subjected to the~mal shock. The tleatil-CJ system when combined with the sub-grade insulation may be used intermittently or continuously throughout the winter as user requirements and economics demand.
Although the completely automatic system has been described in detail, it is to be under.Ytood Lhat many of the operations may be handled manually in any one of several combinations. In extremely colcl climates, Lhc installation may be enhanced through the use of an inslJlated~
membrane or heaters, if necessary as pointed out above.
If necessary, the insulation may be used to isolate and keep dry a portion oE the subsoil to prevent frost heaving and the subsequent misalignment of the critical elements.
Thus as can be seen, the present system provides a unique method for establishing and maintaining grass plav fields with superior lonc~ term results and lower overall maintenance and upkeep.

Claims (5)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An apparatus for monitoring the level of liquid in a grass playing field which includes a subsurface liquid reservoir, the apparatus comprising:
a generally U-shaped tube-like element, said tube-like element being in liquid communication with the liquid in the liquid reservoir, one leg of said tube-like element being positioned within the playing field such that the level of the liquid in the one leg is representative of the level of liquid in the playing field, the other leg being positioned outside o-f the boundary of the playing field, the liquid in the other leg having a measurable characteris-tic which is representative of the level of liquid in the playing field; and means for measuring said characteristic.

2. An apparatus of claim 1, wherein the characteristic is liquid pressure.

3. An apparatus of claim 1, wherein the characteristic is liquid level.

4. An apparatus of claim 1, including means responsive to said characteristic for providing electrical signals indicative of said level of liquid in the playing field.

5. An apparatus of claim 4, including means responsive to said electrical signals for adding and deleting liquid to and from the liquid reservoir so as to maintain the liquid in the playing field at a selected level.