As demand for housing, infra structure, and commercial and industrial buildings continues, there is increasing pressure on developers (imposed sometimes by economic considerations and sometimes by governmental or quasi-governmental regulation) to develop so-called"brownfield"sites. A brownfield site may conveniently be defined as land which has previously been used, often in a commercial or industrial application, but which is no longer used in that way, or is no longer used at all. Often, particularly when the previous use has been industrial, the site may contain contaminated land. Contaminated land has been defined in the past as land which is contaminated by any substance or substances in quantities sufficient to cause significant harm or damage to humans, animals or environment.

However, regulatory definitions of contaminated land may change from time to time.

The problem of clearing contaminated land is substantial and costly for the developer of a brownfield site. Contaminated brownfield sites are very often produced by industries producing, storing or handling chemicals on the site in its previous use. Even under best practice conditions, spillages do occur and the contamination provided by such spillages spreads into the site soil by ground water movement, and by rain water transportation. Because environmental and health and safety regulations were less stringent in the past than they are today, older brownfield sites are particularly likely to be contaminated in this way. The resulting contamination can sometimes be treated on site (i. e decontaminated) by the application of chemicals which react with the chemical contaminant to produce a harmless product, for example. However, very often the only solution to contamination on a brownfield site is the physical removal of the contaminated soil, its transportation away from the site and its storage in a designated location. Prior art in this respect includes WO-A-96/37664 and WO-A-98/53928.

However, the cost of removing and storing contaminated land has continued to be a problem which has a negative impact upon the availability of brownfield sites for redevelopment. One solution has been proposed in EP-A-1254727, which describes a method of storing contaminated material such as contaminated soil in a containment cell which is buried underneath the ground and surrounded by non- contaminated soil.

It is an object of the present invention to overcome or ameliorate at least some of the problems associated with the prior art and to provide an altogether novel solution to the problem of what to do with contaminated soil.

According to the present invention there is provided the use as a construction element of a sealed container at least partially filled with contaminated soil.

Preferably, the container is a flexible intermediate bulk container of the type commonly used to transport various types of powder or granular material, such as chemicals, food and pharmaceutical products. Flexible intermediate bulk containers have advantages over more rigid containers in that they are, when empty, very easily transportable and can therefore be moved to the site in large quantities at relatively low cost, and then transported around the site conveniently. Flexible intermediate bulk containers are generally made from woven polypropylene or high density polyethylene but other materials, such as welded PVC may alternatively be used.

"Flexible intermediate bulk container"is a term of art which will be readily understood by the skilled person, and they are sometimes known in the trade as"big bags"or"bulk bags". The flexible intermediate bulk container association (EFIBCA) is a useful source of further information in connection with flexible intermediate containers, accessible via their website www. FIBCA. com.

When the container is a flexible intermediate bulk container it is desirable that the container be lined with an impermeable liner which can then be filled with contaminated land and sealed within the flexible intermediate bulk container. The resulting construction element can be moved to its construction position using the lifting loops of the flexible intermediate bulk container. In this case, the impermeable liner, which may be constructed for example of low density polyethylene or other suitable material, is preferably provided with a one way valve which will allow gas contained within or generated within the sealed liner to escape."Contaminated land"in the context of this application is any land which is in such a condition, by reason of substances in, on or under the land, that: a) significant harm is being caused or there is a significant possibility of such harm being caused; or b) pollution of controlled waters is being or is likely to be caused.

"Harm"in the last context means harm to the health of living organisms or other interference with the ecological systems of which they form part and, in the case in of man, includes harm to his property.

One of the advantages of the construction element of the invention is that the pathway of pollutants contained within the element is blocked from transmission to the surrounding environment by the flexible intermediate bulk container.

Also provided in accordance with the invention is a construction element comprising a flexible intermediate bulk container lined with an impermeable liner, at least partially filled with contaminated soil and sealed, the sealed liner being provided with a one way valve to allow gas generated or contained within the liner to escape, the flexible intermediate bulk container being of a gas permeable material.

The invention further provides a process for decontaminating a brownfield site comprising transferring contaminated land on the site into a plurality of containers, sealing the containers and using the sealed containers as construction elements. Preferably the sealed containers are used as construction elements on the site.

Also provided in accordance with the invention is a building structure comprising a plurality of sealed containers at least partially filled with contaminated land. The building structure may, for example, be a wall or insulating membrane inside a wall cavity, or a road underlay, but various other building structure types will be apparent to the skilled person. Preferably the sealed containers are tessalated in the building structure and nearest neighbour sealed containers may contact each other or be affixed to each other by means of a suitable fixative, such as cement, mortar or concrete. T he s ealed c ontainers m ay b e 1 aid s ide-by-side and/or o n t op o f o ne another.

The sealed container useful in the invention may be of any suitable size and/or shape. Preferably the volume of the filled container is greater than about 0. 5m3, for example greater than about lm3. Most preferably the volume of the filled container is from about 0. 5m3 to about 25m3, for example from about 0. 75m3 to about 20m3, most preferably from about lm3 to about 15m3 or from about lm3 to about l Om3, still more preferably form about lm3 to about Sm3. The container, when filled, conveniently has a square or rectangular horizontal cross section. Other shapes may be used but in this case are preferably selected for ease of tessalation when used as construction elements. Preferably, the construction element of the invention is able to fit together with other similar construction elements without leaving any substantial void space therebetween.

Preferably the sealed container useful in the invention is at least substantially filled with contaminated land.

The container preferably comprises an exterior shell formed from a material selected for strength in transporting or moving the container when filled. Particularly suitable materials include woven polypropylene, HDPE and PVC, which may suitably be welded at the seams of the container, if the container is provided with seams. The exterior shell is preferably provided with one or more handles suitable for attachment or securement to a mechanical lifting device such as a crane. The exterior shell is preferably made from a flexible material. The exterior shell is preferably lined with an impermeable liner, which may conform shape-wise with the exterior shell. The liner material need not be as strong as the exterior shell (since lifting of the sealed container would be through the exterior shell) but is preferably formed from an impermeable material, LDPE or another suitable plastic for example, and is preferably in this case provided with at least one one-way valve to allow gas inside the sealed container to escape. The liner, once filled with contaminated land may be sealed by any suitable closure means, for example by providing a sufficient length of liner material in the region of the liner inlet to"goose-neck"the extraneous length of material, the resulting closure being secured by means of a suitable restraining clip or adhesive, for example.

Also p rovided i n a ccordance w ith t he p resent i nvention i s a m ethod for storing contaminated land comprising providing a plurality of flexible intermediate bulk containers which, when at least partially filled, are capable of being stacked or aligned together leaving substantially no void space between neighbouring containers, at least partially filling the containers with contaminated land, sealing the containers and storing the at least partially filled, sealed containers in a stacked or aligned configuration leaving substantially no void space between neighbouring containers in the configuration.

The invention therefore additionally provides a method for storing contaminated land using flexible intermediate bulk containers which minimises the storage space required by the stored contaminated land. The method of the invention may include storing the containers in a location accessible for subsequent access and removal of the contaminated land therein should it become necessary, or desirable, to access the land.