AU5195900A - Stormwater dispersing chambers - Google Patents

Description

Our Ref:7518930 P/00/011 Regulation 3:2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): Infiltrator Systems, Inc.

4 Business Park Road PO Box 768 v Old Saybrook Connecticut 06475 o C United States of America DAVIES COLLISON CAVE Patent Trade Mark Attorneys Level 10, 10 Barrack Street SYDNEY NSW 2000 Stormwater dispersing chambers Address for Service: Invention Title: The following statement is a full description of this invention, including the best method of performing it known to me:- 5020 S1NATER DISERIM CHAMBERS

DESCRIPTION

The present invention relates to means for dispersing liquids in gjranular materials'; more particuilarly, to systems for dispersing storm waters within isoiLl of the earth.

In urban and industrial development, engineers often provide 'for fta.,dliung the volumes of rainwater which fall upon the earth from time to =ime. Traditionally, large szorm sewers, with or without surf ace detention bpasins, have been ued. However, there are adverse envirenznental effects rom such. They include the costs of land used for detentiLon basins, l4kce arid stream pollution and erosion due to storm sewer runoff, and lowering of Local vatQr tables when water is diverted from percolating into the earth.

:Consequently, it. in desirable to diLrect storm water into the earth.

Trhis has been done, such as by using large gravel or crushed stone filled tv-rerqches, with ar-d without perforated pipes running through the stone.

Stone filled systems are inefficient in that the stone occupies a ubstantial part of the trench void, thus limiting the ability of the -systemu to handle large surge volumes associated with heavy storms. And bocth the stone and the perforated pipe are susceptible to clogging by 0 cdebris carried by water.

w*oo Arch shaped molded plastic leaching chamsbers, especially those sold under the Infiltrator brand name, and having design features like those !shown in various patents mentioned herein, have met wide commercial success in the USA, especially for dispersing the waters associated with domestic Oft1wage slystems. Such leaching Shambers have also been used in receivin~g smorm waters, detaining themi for regulated flow. and for dispersing themi beineath the surface of the earth. Typically, the chambers are laid side by si~Ae in parallel rows. They rest on and are surrounded by gravel or crushed stone. While such installations provide greater void volume than chas stone trench systems, and have. been in many instances satisfactory, fuxrther Improvementa.arQ desirable as indicated just below.

subsutrface storm weater systems using known technology can take up la~ige surface areas. mince a normal design criterion in that the system be ab2.e to handle and store for gradual dispersal of a large volume of raiLnwater. Thus, where land is expensive it is very desirable to maximize .Va2=ous aims. Among those alms are: First. the volumetric storage capacity of. the system~ an a unit land. surface area basis should be maacimized. Second, the system should be adapted to Tesist the loads; imposed by other uses of the surface of the land, most couwnonly for motor eh'icle parking or driving. Third, the system should be -resistant to clogging and degradation caused by sand, dirt and other debris which may be car,.ried along with the w.ater. And, of course, rho system should be ecawacqnjc, durable and maintainablehn object of the Invention is to provide a subsurface storm -at-er dipersing sysftem which has a high capacity for surge volume relative to the land surface area occupied, but which at the same time is structurally srorng in resisting surf ace weight loadings. Another object is to provide a smormwater 9syostm having improved resistance to clogging from.debris. and toaenable removal. of sueh debris as is carried into the system by *Corgsnwarer. A still, further object is to provide subsurface leaching :haznbere which ace especially resistive to vertical loads, and chambers which have liquid dispersing character especially suited to arid soils.

In accordance with the invention, in a chamber for dispersing liquid when buried beneath soil, of the type wherein the chamber has an arch shaped cross section defining a hollow chamber interior, a base, opposing inward sloping sidewalls having substantially spaced apart sidewall upper ends, each sidewall running from the base to a curving arch shape top which connects said sidewall upper ends, and corrugations comprised of peaks and valleys running up the opposing sidewalls of the chamber and transverse to the length of the chamber, there is provided the improvement which comprises: the chamber having a cross section aspect ratio of at least about 0.8 to 1, where aspect ratio is the ratio between the chamber height and chamber width measured at the base.

Preferably, the chamber has inward sloping sidewalls with a sidewall angle with the vertical plane of less than about 15 degrees, more preferably about 6 to 9 degrees.

Further, preferably, at least one of the peaks and valleys of the 20 sidewall has an arcuate shape, as measured in a plane parallel to the base of the chamber.

f oo* Prefezbly asubsurface storgnwater systemi is comprised of chambers running parallel to one another, wih the sipace between any pair of chambers beizng spanned by a bridge cover res-ting on Lmposts of the chambers. Preferably, the imposts are lower than the elevation of the highest part of the top of the chamber. The system is r-ypically laid on a flat, bed of stone or the Like, and covered over wizh sail. or the like. The gyareo has means for enabling "low of storzwater between a chamber and the space, such as perforations ini a chambe= aidewall. Water Is preferably flowed first into the space bertween any chamber pair, and then into the chambers, to disperse or leach into the stone or soil at the chamber bases.

In preferred practice of the invention: Chambers have a height to width aspect ratio of 0.8:1 or more, and zideWail angles with the "-ertical plaoe of Less than 15 degrees, to provide strength and load *carrying ability to the systemi. Chamber walls are arcuace, or bowed, asL viewed ina a hori~zontal cross section plane, to increase sidewall and system strength. The bridge covers are arched, and the hi.ghest -part of the r-op of the bridge cover arch is. at about the same elevation as the highest *.points of the chambers. And, base flanges of adjacent chambers abut or interlock ra define the pitch of the chambers, thereby defining the centerro-center and impost-to-impos't spapings of the chambers, -hile protecting the material, at the bottom of the space from erosion due to liqguid falling into the space, when the f langes are continuous along the Length of the chamber bases.

The means for enabling flow between the space and the adjacent.chambers is preferably perforations in the sidewalls of the chambers. More pireferably, the perforations are only located at an elevation higher than ac-cauiulate*U in a caviLty at the bottom of' the space, and then f 2ows !into the chambers, thereby inducing some of dirt' and debris in the w'ater to settle out in the cavity.

Further, In the preferred practice of the invention: The ends of *-he chambers, an well as the ends of the spaces between adjacent: =hambers, are clomed by endplates. Pipes fit openings in the endplates o~pf the spaces, to deliver stormwater to the chambeiF assembly. It Lsintnded that debris accusnalate in the space and thus, in another aispect of the invention, means, such as a pipe with perforationso isr laid at the bottom of the space. Water flowed through the pipe in aused to agitate and suspend the debris, which then preferably flows out the same pipe to a discharge point, much as a sumnti.

The invention efficiently receives, stores, and diapersee storm, w.aters; and it in particularly strong. The chambers are economical, idurable, efficiently shipped and easily installed.

mrig. I is a perspective end view of part of a stormwater chambar, with a cover bridge, and with an adjacent chamber shown in phantomlrig. 2 is an end view of a pair of adjacent chambers buried within soil, having a cover bridge spanning the space between them.

Fig. 3 is a perspective view of the ends of an array of parallel lying =hambers having andplates, showing how stormwater io delivered by pipes to the spaces between the chambers.

Fax from 18/88/00 03:04 Pg: Fig. 4 is a horizontal plane cross section of part of the-sidewall of the chamber of Fig. 1, -showing the arcuate shape..of the sidewall.

Fig. 5 shows how the ends of chambers mate with a strong joint, when put together as a string of chambers.

Fig. 6 shows an endplate for one of the spaces between a chamber pair.

Fig. '7 shows in vertical transverse plane section how an impost has a buttress to better retain an arch shape bridge cover in place.

Fig. a shows a non-corrugated chamber with a relatively flat top and a lintel type bridge cover.

Fig. 9 shows in end view a system where a bridge covers is supported on.

the very tops of the adjacent chambers, the chamber base flanges interlock, and there are internal struts to strengthen the cover.

Fig. 10 shows in perspective cross section part of the peak section of chamber 20 of Fig. 1, revealing internal strengthening ribs.

Fig. 11 shows an end 'cross section of the space between-two chambers where debris and a conduit lie at the bottom of the space.

Fig. 12 shows an longitudinal cross section of the space shown in Fig. 11, together with the conduits which enable, water to be introduced into the *space and 'the resultant suspended debris to be removed by gravity flow to a sump.

stormwater chambers of the invention have many structural and material characteristics like molded plastic leaching chambers known in the prior art. Reference should be made to U.S. Patents No. 4,759,661, No.

5,401,116 and No. 5,401,459, having comsmon ownership, and inventorship in part, the disclosures of which are hereby incorporated by reference.

Stormwater chambers of the present invention are preferably fabricated by gas-assisted injection molding of 'predominantly high density polyethylene, and have plastic f low channe1l A which alqo. aid strength, in accord with ]Pat. N~o. 5,401,459 and the general art. Other plastic material and process acambinazions may be employed.

Typi.call~y, an array of chambers, sometimes called a "system", is installed by digging a hole in the earth and creating within it an mosentially planar Surface of gravel or crushed stone- The chambers are mated ead-to-end in--parallel rows and laid on the gravel surface. After.

t-he system is installed in accord with the descrilpticn below, It Is covered w.ith suitable soil. The following preferred eabodinents of the invention mare largely described in terms of two adjacent chambers, being illustrative iof a large system comprised of many parallel rows of chambers.

An end fragment of a preferred chamber 20 is shown in Fig. 1, along

OV.

'vIth a bridge cover 50 and a portion of a like adjacent chamber 20A, in OV. phantom. Fig. 2 shows the chamber 20 in end view .and paired with chamber and part of a larger array, as they appear installed on a gravel, bed .jnd covered aver with gravel or soil. Referring to both Figures, the c:khamber 20 has an arch shape cross section and is corrugated, with aL .ecrnatIng peaks 24 and valleys 26 running up the apposing sidewall. 28 arnd across the top of the arch shape cross Section. peaks and valleys axe connected by webs 35. The highest point of the top has a height h and itkhe base has a nominal width w. Stiffening webs, such an ribs 32. are used o)n the exteriar and interior of the chamber, for additional strengthening, as generally taught by the prLor art. When using the gas assisted injection molding process some of the ribs and other chamber parts will be deszirably hollow. The chamber 20 has a base 22 with flanges 30 extending laterally outward, for supporting the chamber and resisting vertical loads, and for Ithn other purposes described below. Ribs 31 Strengthen the base :Elange.

Pre ferred ch ambers have ad arch shaped. cross section and are about 2 .2 mi long, 86 cm wide and 76 cni high. They are designed to nest, one within ftie other, for easy shipping. Familiar commercial leaching chambers of tche it-ype described in the aforementioned patents and others comlmercially known kijva comparatIvely low aspect ratios in the range 0.36 to 0.65, where mapect ratio of height h to nominal base width v. Width w is measured kbetween the opposing outermost (peak) parts of the'sidewalis, where they intersect the base; and this dimension is nominally; the same an thae width ieamured between the outermost edges of the flanges 30 in most CK2"iers.

!si nce most chambers do not have exceptionally wide flanges- In the invention, the aspect ratio is high, preferably greater than 0-7:1, more preferably about 1:1. Table 1 compares the dimensions and a spect ratios of prior art with the present invention. The high aspect *ratio invention chambers are generally useful for -liaching without using tmhe bridge covers feature, as prior art chambers are. The invention caivbers provide superior strength and improved liquid disperal at the m Ldewall relative to the base. They are especially suited for arid soils, ariG reduce the surface area of land which mnust be utilized for. a given cestic sewage leaching capacity. A~n array of parallel chambers can be b~uried within crushed stone for stormwater dispersal.

The preferred high aspect ratio chamber- has uidewa2.ls 28 running upwardly at a nominal angle, measured from the vertical plane, i~n the range of 6.3 to 83.7 degrees, Because, as described herein, sidewalls are arcuate in the horizontal plane, the nominal sidewall. angle is determined from the kxypothetical inclined plane which rests on the tops of the. peaks, or In the ]barer. of the arcuate valleys, as the case may be, as they run vertically up +thke sidewall. And, while current cozuzercial practice is mostly to make the Midewalls essentially straight when viewed in end cross section. some cc=t1W1Xc;Lal cAbaxber sidewalls -have a curved arch shape when viewed In end cicosp section. For such, tile'sidewall angle plane might be taken as a bear :Cit, or in limiting cases, there in no ascertainable- sidewall angle in the cciontext of -this aspect of the present invention. The mosat preferxed Table I. Typical/ nomuinal parameters of leaching chambers.

Cbamber Producot Sidewall angle (degree) h Aspect. Ratio 9.

*9 9 *9 9 9.

99 9 99* 9 C330 BD I

ODX

zaSI Nlo. S,441,363 No. 5,087,151 11.8 18.3 13 30.5 10- 11 12 7.S' 12 12 is 33 33.3 34 52 201 34 34 1145 34 ~34 74.9 75 84 90 77 76 90 75 75 0-36 0.54 0.39 0-64 0.50 0-32 0.35 0.65 0.35 0.35 0.47 0.99 .9 9 9 99 9 999* 9 9.99.9 9 Typical Invention 30 30 87 Legend: W C width, the zuaxiguzum wall-to-wall spacing at the plane h maximum hoight of a chamber peak measured from plane I1 length arbitrary units from scaling of patent drawing no data, of chamber base of base =vhamber of the present invention has an essentially straight sidewall, vviewed in cross sectional plane, with an angle of 8 degrees from the vrertical- This incline compares to prior art chamber sidewall angles of :f xom 15 to 22 degrees. The sidewalls of t he invention are thus more nearly %rwrtlical. in the generality of the invention chambers wll have a nominal widewall angle of less than iS5 degrees, preferably in the range S-14 lemgrees, more preferably about 7-9 degrees, as measured from the vertical longitudinal plane of the chamber. The combination- of both higher aspect icatio and leasser sidewall angle, compared to leaching chambers hgretofore u~eed in storm water systems, pxovides superior strength and increases the lo<Dad which the bridge cover and thus the system can bear.

The opposing sidewalls 28 of the chaimber 20 have perforations 29 in the form of about 3.2 cm diameter holes. They are located in either or both the *as %ralleoys and peaks of the sidewalls. The lowermost perforation is at- an m levation of about 3S cm from the base for reasons described below. To 1piovida stiffness and buckling resistance, the peak and valley corrugations 4of the sidewalls axe arcuate, preferably bowed outwardly (concave side facing the chamber interior) with radii of about S. 3 Inch, as viewed in the ioprizontal cross setion plane of the chamber, and an illustrat-ed by the mid-elevation hori~zontal plane cross section of chamber sidewall in Fig. 4- ~When chambers are buried in rthe earth, the outermost sidewalls of the mystam will of course not have bridge covers. The perforations in any such midewalls; are either plugged or covered with a fabric to prevent intrusion cof the covering earth.

Referring again to Fig. I. and 2, the top of the chamber 20 has peaks and valleys which are continuations of peaks and valleys of the opposing m.idewalle; the top comprises nominal segments of a circular arch- Imposts 34, in the form of fl~t ledges, are molded into the chamber at the upper exid of the sidewall, where the curved arch segments of the top of the cliajuber starlt, to receive a: bridge cover 50 as detailed below. In other a~bodiments, the imposts may be located higher -up, on the top. or lower dewn the sidewall.

As in the cited prior art patents, chambers have mating ends. and are ccnnected one to the other to form strings; and, the mating ends overlap innd interlock as illustrated by the fragments of mating chambers 20B and 21 iin Fig. 5. (The end joint interlocking features are Omitted from Fig. 1 Ecor clarity.) Fig. S shows how the and of chamber 21 overlaps the f iange pcortion 40 of the end of the chamber 205; and, typical leg 42 overlaps chramber 21 at the joint, to strengmhen the connection, in accord with the :p=inciples taught by U.S. Pat. No. S,40.1,116 and other prior art.

Lkewis, the bridge c overs, which typically axe half the length or the chamber, are preferably provided with ends which overlap to prevent Lifiltration of soil, and they way aleo be interlocked with each other to iLncreass vertical load resistance.

strings of chambers are Installed side by side, running In Fparallel irow., at predeter-mined spacing. Preferably, the chaisber-to-chamiber spacing i-a determined by butting the flanges 30, 30A of adjacent chamber=, as shown &n Figs. 1 and 2- The shape and spacing of the sidewalls of the abutting c=hambere def Ines the width of the space 36 therebetween and the spacing of t-be Imposts. when in place, a corrugated arch shape bridge cover 50 rests %apon and Is supported by the imposts of adjacent parallel chambers. The ]bridge cover fits and laps onto the impost surfaces in a way des igned to prevent passage of soil or gravel into the space between the chambers, from above. Most simply, the bridge cover is molded in one piece without perforations and is imupermeable to soil or water.

Fig. 1 illustratep how the preferred impost in continuous. with a portion running along the top Of typical web 3§ connecting a peak c--orrugatiofl with a valley corrugation.- -In the preferred emb~odiment, the iLmpost is a ledge and the bridge cover outer edge runs continuously -along the ledge. Within the generality of the invention, an Import is a feature of the chamber exterior surface which is adapted to receive and Locate a bridge cover and provide vertical support. Preferably, it provider. registance to lateral motion when cooperating with the bridge cover features where it contacts the Impost. Alternative kinds of Loposta may comprise such integral features as -flats, ridges, pili, bosses, =avJltiau and holes in the chamber wail. For such alternatives the bridge Scover will have appropriate mating feature.

:Fig. 10 shows how the impost 34 and general structure in vicinity of.

he peak corrugatichI 2 4 is strengthened by ribs 80, 82 running lengthwiise.

*along the chamber and smaller gusset ribs *84 under the Impost running kbetween the top of the web and the underside of the impost.

Fig. 9 shows an- unperforated arch shape melded bridge cover resting on Impost surfaces 75 at the tops of adjacent perforated-wall chambers 72.

Vertical fins 74 running lengthwise along the chamber top define the inner *.ebdges of the opposing imposts on the chamber top, and restrain t-he bridge covers from lateral motionl, anm discussed below.

Preferably, a&s hown in Fig. 2, the very top of the archi of the bridge cover in at the same elevation as the very top of the arches of the chambers, to provide a relatively even surf ace anid maximize system storage capacity for a given depth of system. in the generality of the invention, the top of the bridge cover may be either higher or lower than the tops of the chamber arches.

When an arch shape!. bridge cover rests on the imposts anid vertical loads are applied, suph as from a motor vehicle passing across the earth albove, an arch shape coyer bridge will tend to flatten out and expand in w~jdth. Thus, the'edge of th e cover bridge will tend to move' laterally, iti bear against the curved rising part of the chamber top,.so the motion wjLll. be resisted to a degree. Even better resistace to lateral deflection Is obtained when a protrusion, such an buttress. So is molded into the =1hamber adjacent the Impost, ans hown in Fig-.7. See also fins 74 in Fig.

Al ~ternativeS lateral restraint means, such as *crews or pins may also be ewupLoyed; provided there is accomodation. for slight relative motion of the 1parts under changes in vertical load, to avoid local failuire of thie plastic ichamber or bridge cover material. in alternative embodiments, the bridge *ciover may# have molded plastic ta&bs or piars that engage mating features in 'vici~nity of the imposts. In still other embodimenits, additional structural imembers, integral or separate from the bridge cover, may imnproveQ vertical strength of the bridgqe cover. For instance. strut members may extend -vert-Ically from the bottofluosit of the space between the chambers, or struts 76 may angle up from, the chamber wals*, an shownl in Fig. 9.

A chamber embodying the invention principles may have smnooth jrather than corrugated sidewalls and top, as shown for chamber 60 in F ig.

And, bridge covers may have cross section shapes other than -the.

preferred arch shape. For instance, a lintel type bridge cover 62 is shown Ini Fig. 8, where the lintel cross section is molded as a simjple truss.

aind, whIle the bridge cover is ordinarily unperforated and impermeable, in aome instances small perforations may be present to better enable any liquid above the system to percolate into it.

In "he preferred embodiment. the width of the bridge cover the length of span from one Impost to another) is a bit less than the width of the bases of the chambers on which the bridge cover rents, or the cent or-to-center distance between the chambers. In other embodiments, the b3ridge cover may be equal to or wider than either such.

Chambers may have variouls Arch shape cross sections, including those which tre rectangular, trapezoid, triangular, etc. chambers may be molded with integral closed ends, but preferably they have open ends. The .ends of strings of chambers are typically closed by end plates 52 which f it iLnto the chamber end openings as shown In Fig- 3. Endplates are held in place by detentse screws or the like. Bridge cover endplatea 54 having similar construction and function close off the ends of the spaces 36 b~mtwsen adjacent ehankbers. As with' the chambers, the bridge cover er-nIplatea mfay be made integral, but preferably they are separate pieces.

:.Preferably, the bridge cover endplates have ports or openings 5, to =iarceivs pipes 56 carrying atortuwater-from catch basins to the chanber ystam. See 'Figs. 3 and 6. Alternately, the bridge covers may have op openings, so 'the stormwater is delivered vertically downward into the mpaces. Thus, water Ls preferably flowed to the chamber system by entering *-hrough the space endplates and falling to the bottom of spaces 36 between the *chamers. While water is preferably introduced by flowing it directly into t-he spaces, :it may be alternatively delivered into the chambers. or both.

t is not necessary that every space or chamber, as the case may be, have c~irect delivery of storm water.

*As mentioned, perf orations 29 in the chamber sidewall preferably are a distance above the base, to create a cavity or pocket 31 at the bottom of apace 36, near the chamber base where liquid introduced through openings wiLll accumulate bef ore flowing through the perforations into the interior o)f the chambers. See the arrows Indicating liquid flow in Fig. 2. Such construction enables a significant portion of the dirt and ether debris icarried by the water to settle out at the region or cavity 31 at the bottomn cif the space 36 when the water is xtorm water is piped into the space.

13 Preferably, the chamber base flanges 30, 30A abut to Set the centerto-center dimension which fits the bridge covers, and they Are continuous r-o cover the sil at the bottom 'of the space 36 and protect it froa beIng eroded by incoming water, or by Glctioning away of debris if such means is arnplayed. .Abutting chamber flanges may be overlapped or engaged one with.

t2Le arther along their lengths to limit lateral chambher movement and ensure positive locating -as illustrated for the flange connection '78 in Fig. 9.

Generally, flangeo can be diecontinuous, anPd irregular in lazeral dimension while servin'g the chamber spacing! furfction. When flaynges are not const-ructed to set chamber spacing, other built in gaging means, manual measuring, or other f ixturing may be used to achieve the spacing which fits *the bridge covers.

The -chamaber sidew-all perforations preferably have a motal area *sufficient to enable good fluid flow or comunicationl betw.een1 Cho chambers and the spaces. therebetween, relative to the size and capacity of the inlet pipe and chambers. Perforatiens* -other than rounid holes may be used, such as slots. In the generality of the inventionl, other mans for connecting the chamber with the space than sidewall perforations may be used. For e.*xple, the parts of the system may be connected by external pilping; orc, when the settling cavity feature in the space is not required, thes means may comprise cutouts at the base flange.

Fig- 11 and 12 show how. debris removal is conveniently enabled by a perforated pipe 90 laid in the bottom of the space 110 created by Obazabers a2, 84 and bridge cover 86. Settled out debris 99 is shown as i. would accumulate in the cavity at the bottom of the apace. The pipe has a multiplicity of longitudinally spaced apart and downward facing holes 92.

To remove the debris a flexible, hose having a jet nozzle is lowered down -the channel 94, typically another pipe connected to pipe 90, so that it 14 passes along the length of pipe 90 within the cham~ber, to the desired o~ctent. Pressurized water issuIrig fromz the nozzle flows through the holes 9;2, to agritate and temporarily suspend the debris in the water in the avity.- When pressurized water flow is ceased, or moved to a sufficiently diL:stant point along the pipe, debris-laden water flows out the pipe acown the diversion channel 96 and into the sump 98. -Prom there It may be jrencved up access channel. 100, typically a larger diameter pipe or shaf t.

ZXr an alternate e;mbodiment, the line 90 m~ay be used only for agir-ating and a separate pipe or channel may be used for flowing the debris away: 00 :0 Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising"' will be understood to imply the inclusion of a stated integer or step or group **of integers or steps but not the exclusion of any other integer or step or group opf integers or steps.

The reference to any prior art in this specification is not, and should rmot be taken as, an acknowledgment or any form 'of suggestion that that prior art forms part of the 0 common general knowledge in Australia.

Claims (19)

1. In a chamber for dispersing liquid when buried beneath soil, of the type wherein the chamber has an arch shaped cross section defining a hollow chamber interior, a base, opposing inward sloping sidewalls having substantially spaced apart sidewall upper ends, each sidewall running from the base to a curving arch shape top which connects said sidewall upper ends, and corrugations comprised of peaks and valleys running up the opposing sidewalls of the chamber and transverse to the length of the chamber, the improvement which comprises: the chamber having a cross section aspect ratio of at least about 0.8 to 1, where aspect ratio is S 15 the ratio between the chamber height and chamber width measured at the base.

2. The improved chamber of claim 1 wherein the chamber has inward sloping sidewalls with a sidewall angle with the vertical plane of less than about degrees.

3. The improved chamber of claim 2 wherein the sidewall angle is about 6 to 9 degrees.

4. The improved chamber of claim 2 wherein at least one of the peaks and valleys of the sidewall has an arcuate shape, as measured in a plane parallel to the base of the chamber.

An assembly for receiving and dispersing liquid when buried beneath soil, comprising: a pair of moulded chambers, each chamber having an arch shaped cross section defining a hollow chamber interior, a. base, opposing inward sloping sidewalls having substantially spaced apart sidewall upper ends, each sidewall running from the base to a curving arch shape top which connects said sidewall upper ends, corrugations comprised of peaks and valleys running up the opposing sidewalls of the chamber and transverse to the length of the chamber, the chamber having a cross section aspect ratio of at least about 0.8 to 1, where aspect ratio is the ratio between the chamber height and chamber width measured at the base, the chambers lying adjacent and parallel to each other on an essentially flat surface, the adjacent sidewalls of the chamber pair shaped and positioned S. relative to each other to create a space therebetween; 15 means for enabling liquid flow between the interior of at least one chamber and said space; and a bridge cover spanning said space, for preventing soil from locally entering said space from above when the assembly is buried in soil.

6. The assembly of claim 5 wherein the span, or width, of the bridge cover is less than the center-to- center spacing between the pair of chambers. too*.: 25

7. The assembly of claim 5 wherein the bridge cover is arch shaped.

8. The assembly of claim 7 wherein the highest part of the top of the bridge cover is nominally at the same elevation as the highest parts of the tops of the adjacent chambers.

9. The assembly of claim 7 wherein the highest part of the top of the bridge cover is at a lower elevation than the highest part of the tops of the adjacent chambers.

The assembly of claim 5 wherein each chamber has corrugations comprised of peaks and valleys running up the sidewalls and transverse to the chamber length; further comprising an arch shaped bridge cover having corrugations running transverse to the lengths of the chambers.

11. The assembly of claim 10 wherein at least one of the peaks and valleys of the sidewall of at least one of the chambers has an arcuate shape, as measured in a plane parallel to the base of the chamber.

12. The assembly of claim 11 characterized by each chamber having a sidewall sloped inwardly at an angle of less than 15 degrees with the vertical plane.

13. The assembly of claim 12 wherein the sidewall angle is about 6 to 9 degrees.

14. The assembly of claim 5 wherein the means for enabling liquid flow comprises perforations in the 25 sidewall of at least one chamber.

The assembly of claim 14 wherein the sidewall of said at least one chamber has all perforations located at an elevation higher than the elevation of the chamber base, so liquid first introduced into the assembly at said space accumulates in a cavity at the bottom of the space before flowing through one or more perforation into the interior of said at least one chamber.

16. The assembly of claim 5 wherein said space runs lengthwise between said parallel sidewalls, said space having opposed lengthwise ends, further comprising a bridge cover endplate, for closing off an end of said space at an end of the chamber pair.

17. The assembly of claim 16 wherein the bridge cover endplate further comprises means for receiving a liquid-transporting conduit, to enable introducing liquid into said space from an external source.

18. The assembly of claim 5 further comprising a perforated.pipe lying near the bottom of said space, running parallel to the chamber lengths, for introducing or removing liquid from said space.

19. The assembly of claim 18 further comprising: channel means for providing access to the perforated pipe and enabling pressurized water to be flowed into said pipe and through the perforations of the pipe, to agitate any settled out debris near the bottom of said space and to create debris-laden water which is flowable through the perforations of the pipe; and, 25 channel means for receiving debris-laden water flowed from said perforated pipe, to enable removal of the debris-laden water from the assembly. Dated this 11th day of August, 2000 INFILTRATOR SYSTEMS, INC. By Its Patent Attorneys DAVIES COLLISON CAVE