CA1302145C - Diverting ground-borne gases from buildings - Google Patents

Abstract

Abstract of the Disclosure DIVERTING GROUND-BORNE GASES FROM BUILDINGS

The invention provides a system for alleviating smells caused by buried garbage from the basements of buildings.
In the invention, the ground is excavated all round the building down to the footings. Holes are drilled at intervals right through the footing /wall, into the undercore beneath the basement floor. No excavation is required below the footings. Collecting-tubes are inserted into these holes. The tubes are perforated to allow gases to enter. A manifold encircles the building, connecting all the tubes, to convey the gases away, via a stack. The floor and walls of the basement are coated with a sealant. The collecting tubes must be well drained to keep them free of water.

Description

DIVERTING GROUND-BORNE GASES F'ROM BUILDINGS

This invention relates to a system for preventing gases whlch are present in the ground from entering the basement of a building.

Bac~kqround to,~h~ Inven~lon It has long been the practlce of many local authoritles to dump commercial and household xefuse in disposal sites on the outskirts of the city. As a city expands, however~
lnevitably some buildlngs come to be erected on, or near to, the slte of the burled garbage dump~.

Norma~y, thls poses no problem. Sometimes however, and this may not happen until the building has been occupied for a considerable tlme, the occupants begin to notice ob~ectionable ~me~s pervading the bullding, especia~y ln the basement of the building. These sme~s can be traced to the decomposing rubblsh. The gases can ln some cases travel a considerable di~tance underground away from the dump.

Natura~y, lf the smell~ problem had been anticlpated, the bulldlng would elther have been erected elsewhere, or would have been con~tructed ln such a manner as to seal out the gases that cause the smells.

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Once the sme~s develop in a building, the màrket value of the building is drastica~y reduced unless the problem can be cured.

The inventlon provldes a system for rellevlng the basement smells problem ln exlsting building~ that have been erected too near to a buried garbage dump, or other source of qround-borne gase~.

Genera~ E~ snLQ the Inven~lQn The human nose ls extraordlnarlly sensltlve. The alr ln a basement usua~y ls quite stl~ and usually remains unchanqed for long perlods. These are conditions which are not conducive to the di~slpation of smell~. The quantlty of an obnoxlous gas whlch, lf a~owed to leak into the basement, would be detected by the human nose, ls quite tiny. A concentration of gas that would be quite imperceptible if a~owed to escape into the open air, can lead to obnoxious sme~s if allowed to e~cape into a ba~ement.

Basement floors are genera~y made from concrete, and ordinary concrete, belng ~llghtly porous, i~ lnadequate to prevent gases in the ground from percolating through lnto the basement alr. In any case, basement floors usua~y ~302:145 develop ha~rline cracks, through which gases can seep.

When gases are present in the ground, the gases o~ten develop a pressure against the floor and wa~s of the basement, and this pressure can cause tiny movements in the concrete, which can cause cracks to develop, and which can open up any cracks that are already present.

The inventlon lies ln providing a quantity of gas-co~ecting tubes, and in insertlng the tubes into the undercore beneath the basement floor. A manifold is coupled to the co~ection tubes, and conducts the gases away. The gases may be vented through a stack, or led away in some other suitable rnanner.

One of the benefit~, when the system of the lnventlon ls used, is that the various plpes and tubes are physica~y supported very well, by each other and by the basement wa~s and footings. Thls support is needed because lf the pipes and tubes were a~owed to shift and move, leaks might develop~ which would be difficult to locate and expensive to cure. The system of the invention uses the wa~s of the basement, and the layout of the tubes, to ensure that each element of the system is supported securely and firmly and wlthout strain. In the invention, this security is achieved without the need for an exceptional level of care and ski~

on the part of the people who insta~ the system.

In the lnventlon, the wa~s and floor of the basement may be 1302~45 g ~ealed wlth a sultable rubber sealant.

In the lnvention, it is necessary that a suitable drainage n)eans be provided to prevent water entering the co~ection tubes and manlfold. The co~ecting tubes must not be a~owed to fill up wlth water, as this would impalr thelr efflclency ln co~ectlng the ga~es. (The drainage system need not be perfect however, since it would not be too damaglnq lf the smells were to reappear temporarily after heavy rain, providing the smells quickly subsided again.) If the ground around the buildlnq ls well enough drained that the water table always lies we~ below the basement flGor, it may be po~sible, in the invention, to avold addlng a new dralnage system for the co~ecting tubes. Some bulldings already lnclude a dralnage system for conducting rainwater away from the basement wa~s, and if so it wi~
sometlmes be possible for thls already existlng system to be arranged also to draln the co~ectlng tubes.

The problem wlth whlch the inventlon ls concerned is with obnoxlous gases that accumulate ln the undercore beneath the basement of a building. The inventlon makes lt po~sible to gain access to the undercore, and to relieve gas pressure in the undercore, wlthout the need to excavate below the footings. A sme~s-relief system that requlred excavating below the ~ootings would simply be too expenslve to be considered.

In the lnvention, the amount of space that has to be created (by excavation~ to provide room to install the co~ecting tubes is hardly more than the ~pace that is required in any event for the fairly common operation of applying sealant to the outslde of basement wa~s.

e~ iR-tlon--of~ ~referred Embodiments By way of further description of the invention, examples of actual smell-relief systems wi~ now be descr~ed, with reference to the accompanying drawings, in which:-Fig 1 is a plan vlew of a basement of a buSldlng, ln whlch asystem constructed ln accordance with the lnvention has been lnsta~ed;

Fig 2 is a cross-sectlon on line 2-2 of Fig l;

Fig 3 ls a cros~-section, correspondlng to that of Flg 2, of another system which embodies the lnvention;

Fiq 9 ls a pictorlal vlew of some of the components of the system of Fig 3;

Flg 5 ls a cro~s-sectlon, correspondlng to that of Flg 2, of a further ~ystem whlch embodles the lnventlon.

i302i45 Figs 1 and 2 show an example of an apartment bu~ding, of plaln rectangular outllne. The particular buildlng shown is dlvided lnto 4 unlts, and has a floor area of about 25 metres by 10 metre~.

The manner of con~tructlon of the basement of the buildlng ls conventional, as wi~ now be described. First, following excavation of the site, concrete footings 1 are laid around the proposed perimeter of the building, and in line with the proposed divisions between the units. Next, the supporting walls of the building are laid upon the footings. The footings 1 are somewhat wlder than the wa~s, so that lnslde and ouside ledges 2,3 are formed at the foot of the basement walls 4.

An undercore S of gravel is laid on the floor of the excavated hole. Then, a layer of concrete 6 is la~d on the gravel. This layer constitutes the floor of the basement.
The level of the gravel 5 is set ~o that the edges 7 of the floor 6 rest on the inside ledge 2 formed by the footing 1.

The problem with which the invention is concerned is that of gases which may co~ect in the gravel undercore 5, and may penetrate through the concrete floor 6. There is a potentlal leakpath between the edge 7 of the floor, and the correspondlng section of the wall 4. Also, gases may ~eep through any sma~ cracks in the concrete. Furthermore the i302i45 - ? -concrete itself is not completely impermeable to gases.

It can happen that the gases in the undercore 5 bulld up enouqh pressure to force their way through cracks. Even lf there is no appreciable pressure bu~d-up in the gas, enough of a pressure differential can arise, by the mere action of opening the basement door, for example, to draw enough of the gases in, by suction, over a period of t~me, through the concrete.

The procedure for insta~ing the system of the invention wlll now be described. First, soil is removed a~ round the building, deep enough to expose the outside ledge 3 of the footing~ 1, and wlde enough that a man can stand and work ln the excavation. Unfortunately, lt ls often necessary to carry out such excavatlon using only hand tools, slnce powered excavators might cause damage to drains or other bur~ed services.

The second stage is to dri~ a series of holes 8 through the footing 1, starting at the crook of the ~unctlon between the outside ledge 3 and the foot of the wa~ 4. The holes 8 are angled downwards, and pass rlght through the footlng and into the gravel undercore 5 beneath the floor 6.

Into the hole~ 8 are inserted respectlve gas-co~ectlon tubes 9. The tubes are made of PVC and are provided wlth many ~lot~ 10, ln the portlon of the tube that lles wlthln the gravel underco~e 5, to allow ga~ to en~er freely lnto the tube. The tubes 9 are suitably spaced, for example every one and a half or every two metres. The tubes should be long enough to reach we~ towards the centre of the floor 6.

The diameters of the holes 8 and tubes 9 should be such that the tube ls a slldlng flt in the hole. The fit should be such that the tube is firmly located and physica~y supported by the hole. The tube 9 may be sealed into the hole 8 with a suitable adhesive/sealant.

The tube 9 i5 provided with holes, to allow the gases to enter the tubes. As shown, the gas-entry holes are in the form of 3aw-cuts formed chorda~y in the material of the tube, alternately top and bottom, and 3 or 4 cm apart, the tube being 3 or 4 cm in diameter.

The tube 9 may be in sections which fix together as the tube is inserted through the hole 8. This a~ows the space that needs to be excavated in order to insta~ the tubes to be kept to a minimum.

The outer end~ of the tubes 9 protrude out of the holes 8, and are fltted wlth sultable tee-pieces ~. ~engths 12 of PVC tubing run between the tees 11, thus creating a manifold 13. The manifold tublng 13 lies close to the outer ledge 3 of the footing 1, so that the manifold is well-supported.

g It can be seen from the drawings that the tubes ~ and the manifold 13 each provide good lateral support and location for the other.

The good support is necessary, in order to ensure that the various pipes and tubes are not dislodged or dama~ed when the excavation is belng filled in, and in case the fi~ed-in materlal should later settle. In this connection, the real problem is that it is not possible to determine at the time that such damage has taken place, and because to re-excavate to find the damage, and correct it, is very expensive. It ls recognised that it would be worth taking quite expensive steps in order to ensure that the pipes and tubes could not be damaged: lt ls recognlsed in the lnventlon that the amount of physlcal support glven to the components of the system, lnherently in the system of the lnvention, is enough that special, extra, components for protection and support during filling-in are not needed.

Before the excavation ls fi~ed in, ie whilst the outer suraces 14 of the basement wa~s 9 are uncovered, it ls advisable to take the opportunity to fill in any cracks in the wa~s, and to apply sealant 15 to the surfaces 14. In fact, lt wi~ usua~y be economically prudent to seal the surfaces 14 even if the need for doing so has not been flrmly determlned. It would be extremely uneconomlcal to have to re-excavate, in order to apply sealant later, if and when lt i~ found that sme~s are stl~ seeping through the -` 1302i4S

wa~s.

The purpose of sealing the outer surfaces 14 is to prevent gases seeplng through the basement wa~s 4. It is of course well-known to apply sealant to the outer surfaces of ba~ement walls for the purpose of preventing leaks of water through the walls. In the lnventlon, the purpose of the sealant ls more rlgorous, le to hermetica~y seal the basement walls. To achieve this, the coating 15 should be thlcker, and should cover more completely the whole outer surface of the wa~s, than would norma~y be the case ln water-leak sealing. Apart from those dlfference, the sealing of the outer surfaces may be conventlonal, and wl~
not be descrlbed further.

It is necessary to ensure that the gravel undercore 5 is we~ drained. If water were to be present ln the undercore, the water would enter the collectlng tubes 9, through the gas-co~ectlng slots 10, whlch would prevent the gas from enterlng the tubes, and thus defeat the purpose of lnstalling the system of the lnventlon. In some bullding~, however, the land is so well drained that no separate dralnage sytem need be installed to keep the tubes 9 free of water. However, lt is advlsable to carry out thorough testlng of the level of the water table, and preferably at different tlmes of year, before decldlng that extra drainage ls not requlred: again, it would be most uneconomical to re-excavate to install extra drainage later.

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When all the work below ground level is complete, the excavated soil is replaced, and re-landscaped as required.
It wl~ be noted that the installed tubes 9 and manlfold 13, being firmly located, are most resistant to being damaged or dlslodged during the filling operation, even if the operation is carried out without less than the usual care.
This i5 important because of the problem that would be incurred later of determining that damage has in fact occurred, and the expense that would be incurred of finding, and then correcting, the damage.

It ls ~ometlme~ advi~able to fi~ in the excavation, not with the soil that was excavated, but with an aggregate of pebble~ and gravel. ~hi~ may be done either to aid the drainage system, or to prevent a build-up of gas pressure around the footings. It is also advisable, when using pebbles and gravel, to apply a barrier between the soil and the flller aggregate. For this purpose, the barrier may comprise plece~ of polythene sheetlng, which are applied to the exposed surface of the soil, prior to refilllng. Such a barrler acts as a molsture barrier, and to keep the soil from seeplng in and clogging the aggregate.

As mentloned, lt ls advisable to apply sealant 15 to the outer surfaces 14 of the basement wa~s. It is sometimes advisable also to seal the basement floor 6. It is preferred, ln the lnventlon, to ~eal the concrete floor ln - 1302i~

the fo~owlng manner. Flr~t, the floor 1~ cleared of a~
articles resting on the floor. (This may include such items as the heating furnace, and can itself be an expensive operatlon.? Then a rubberised sealant 19 is poured onto the floor 6 and left to cure. Alternatively, the sealant 19 may be ln the form of a mat, whlch ls glued down to the concrete of the floor: in this case, the mat should be large enough that the edges of the mat extend a few cent~metres up the inside of the basement wa~s 4.

Once the sealant, whether in mat form or ln poured-on form, has been set in place on the floor 6, a further layer of concrete 20 should be applled over the sealant 19. This layer will form a dummy floor, and lts purpose is to protect the sealant 19. The layer of concrete should be thick enough to protect the sealant not only against wear, but agalnst being penetrated, even if, for example, a hole ls drl~ed in the concrete of the dummy floor 20. In thls connection, lt should be noted that it is genera~y not possible to guarantee to lnform a~ future occupants of a bullding that there are reasons why the basement floor should not be penetrated.

The building may include a drainage ~ump (not shown) set in the basement floor, for co~ecting any water that may accumulate in the basement, and to some extent in the undercore. It is conventlonal that such a sump be provlded wlth an automatically operated pump, which empties the water ~302145 from the sump. When such a sump ls present, lt is usua~y advisabler lf and when, in the invention, the basement floor is to be sealed and extra drainage insta~ed, that the sump be fi~ed in with aggregate and concrete, and the floor sealant laid over the fi~ed-in sump. If the sump were left open, it might be possible for the sme~s to find their way into the basement through the sump.

It may be noted that it is not so important, economica~y, fo~ the work of sealing of the basement floor to be carried out at the same time as the work that requires the soil to be excavated around the basement wa~s. It can be arranged that the basement floor be left unsealed for a time, and only sealed lf in fact the smells are stl~ percelved.

The possible need, in the invention, for extra drainage has been mentloned. The components however must be lntegrated into a coherent whole system, and the constructlon of various combined drainage and venting systems will now be descrlbed. The important parameters in designing the ~ystem are the lie of the land, and the severity of the s~ells.

In Fig 2, the manifold 13 was enclosed, and the gases were led away. In Figs 3 and 4, the manifold 21 ls provided wlth slots or perforations 22, and the gases are a~owed to dlss~pate up through the backfi~ aggregate. As shown, a secondary pipe 23 may be provided, which runs para~el to the manlfold 21, and lt too 1~ perforated, to increase the area of dl~lpatlon of the gas. The secondary plpe 23 may be set on a slight slope, and may be connected to a sump ~not shown) so that the secondary pipe doubles as a drain plpe to convey water away.

In Flg 3, the outer ~urface 14 of the wa~ 4 ls coated wlth ~ealant 15, and a barrier 24 of plastic sheeting separates the backfi~ agqregate 25 from the surrounding soll 26.

In Flg 5, there is no drainage assistance from the lie of the land, and no convenient main drain to receive the run-off. Also, the sme~s problem ls such that the gases cannot be a~owed to escape at ground level.

In Fig 5, the manifold 27 is enclosed, and connected to a stack. The drain pipe 29 is perforated, and water may weep into the drain pipe. The drain pipe 29 should be at a low enough level that water is led away from the footing 1, and from the undercore 5. The drain pipe 29 connects, via a connecting pipe 30, to a sump 31. (Depending on the size of the bullding and the lie of the land, more than one sump 31 might be needed per building.) The sump 31 includes a soakaway 32. The sump may be fitted with an electric pump 33, which may be arranged to discharge water, through a discharge outlet 34, lnto the storm sewers.

In the system of Fig 5, it is possible for the obnoxious gases to seep into, and co~ect in, the sump 31. For this ~30214S

reason, the sump is provided with an airtight cover 35, and is provlded with a vent pipe 36 which conducts the gases up to the roof of the building, to be exhausted.

It has been described that the co~ected gases can be exhausted through a stack. Alternatively, the collected gases can be piped away, for exhaustion at a remote polnt:
the gases might even be burnt.

It should be noted that the types and quantities of gases with which the invention i5 concerned are not poisonous or corroslve, or dangerous in any way: it is recognised in the invention that the (expensive) degree of reliability that would be, and is, needed for dealing with dangerous gases is not needed when deallng merely wlth unpleasant sme~s.

Claims (9)

1. CLAIM 1. System for relieving the basement of a building from smells contained in ground-borne gases, where the building is of the kind that includes:
   
   a basement wall, which comprises a main wall and a footing, the foot of the main wall being set on the footing;
   
   and, inside the building, a basement floor, and beneath that an undercore;
   
   wherein the system of the invention comprises:
   
   a series of collecting tubes, spaced apart at intervals around the basement;
   
   wherein each tube is set in a corresponding, respective hole in the basement wall;
   
   wherein each tube extends, in its respective hole, right through the basement wall;
   
   wherein the outside end of each tube is outside the basement wall, and the inside end of each tube lies within the said undercore, and lies below the basement floor;
   
   wherein each tube is provided with a means for allowing gases present in the undercore to enter the tube;
   
   a manifold, which lies outside the basement wall;
   
   wherein the manifold is connected to the outside end of each tube, and is adapted to receive gas from the tubes;
   
   and a means for conveying away any gases present in the manifold.
2. CLAIM 2. System of claim 1, wherein:
   
   each of the tubes is a straight length of plastic pipe.
3. CLAIM 3. System of claim 2, wherein:
   
   the footing is wider than the main wall, and is so positioned as to form a ledge outside the main wall;
   
   the hole in the basement wall is positioned, at its outside end, approximately at the crook formed at the function between the main wall and the said outside ledge on the footing;
   
   the hole in the basement wall extends through the footing;
   
   and the hole is angled downwards from the said outside end, such that the inside end of the tube in the hole is at a lower level than the outside end of the tube.
4. CLAIM 4. System of claim 3, further comprising:
   
   a drainage means, for ensuring that the collecting tubes and manifold remain substantially free of water.
5. CLAIM 5. System of claim 4, further comprising:
   
   a drain pipe, located alongside the basement wall, and below the level of the manifold which is provided with means to allow ground-water to enter the drain-pipe;
   
   a water collecting means, connected to the drain pipe;
   
   and a water discharge means, for discharging the collected water.
6. CLAIM 6. System of claim 5, wherein:
   
   the water collecting means is a sump;
   
   the sump is provided with a sealing means for preventing gases within the sump from escaping at ground level into the atmosphere;
   
   and the water discharge means is an electric pump, which is adapted to pump water out of the said sump.
7. CLAIM 7. System of claim 3, further comprising:
   
   a means for venting and dissipating the gases.
8. CLAIM 8. System of claim 7, wherein:
   
   the said means comprises a stack for conducting the gases from the manifold to the roof-level of the building, for discharge into the atmosphere.
9. CLAIM 9. System of claim 7, wherein:
   
   the said means comprises a means for discharging the gas from the manifold directly into the ground.