The standard recovery of Brownfield land involves three phases: the “cleaning-up” of the site, involving removal of debris and a check for contaminants (and their removal if found), followed by levelling of the site and restoring to a new level if a required height about mean high water mark is needed (as it is for riverside dwellings). Finally there is establishment of services provision (drainage, water, electricity). Housebuilding follows, but these are “standard” houses, other than having a small ‘attractiveness’ premium by virtue of their proximity to a river.
Our alternative idea for housebuilding recovery goes as follows. The land is first secured from the river by a stout and strong concrete wall. Then the clearance still happens but the land is now dug out to at least 3 or 4 metres below the low tide level. The subsoil so excavated can be moved by barges; the concrete wall is made strong enough to moor these alongside. The recovered subsoil has value as building material and is sold, recovering some of the site’s construction costs.
Next, this basin is build up from a strong base layer (concrete and steel foundations) with internal walls to subdivide the construction into individual chambers. The “technical fitting out” now happens, where turbines, generators, heat pumps and the like are placed in various of the walls and of course between the basin and river, with outer doors that can be fully closed.
The roof is added. Checks with planning law have revealed there is no legal issue preventing the building of dwellings on this roof. Figures on housing density from The Royal Institute of Chartered Surveyors (www.https://www.rics.org/uk/) indicate that for the typical sizes of basins under consideration there is space for between 250 to 1,000 houses and flats (more on some but never less than 250).
Obviously this varies from countryside to city centres; we have worked on 800 dwellings with a higher proportion of flats.
What we can do here is to use the circumstances as follows. In the underlying basin some of the electricity is tapped to provide a supply to the houses built above and the heat pumps are so arranged to provide a constant supply of warm water (in winter) or cold water (in summer) to provide heating or cooling (or air conditioning) making these houses probably the most “environmentally friendly” in the world, with all power and heating provided purely by the rise and fall of the tide.
Nothing else. Just the rise and fall of the tide.
There could easily be spare capacity built in so that buildings off – site but in the same locality could be included in a wider heating loop.
Cost estimates, discussed with professional construction companies, show that selling these houses for a typical 20% premium covers all the outlay of site construction to beyond break-even and on most sites will realise a profitable return on the capital investment required.
When this is the case, the surplus electricity generated (which is most of it) is basically “free” and can be sold into the grid at the ruling strike price (the housing requirement for power is relatively small). The total output is between 20 to 150 megawatts per site (this depends on location, size, and on the range of tide) but the flooding and emptying of the tidal basin is predictable and completely controllable so the electricity supply as well as the air conditioning are permanent and independent of external factors such as power cuts.
The cost difference between (recovery + housebuilding) and (recovery + tidal basin + environmentally friendly housebuilding) has been calculated to be relatively small. The time to completion will be longer but cost recovery is now in three sectors; the sale of the building spoil, housing sale, then electricity sale. The development of tidal basins recovers otherwise derelict land, provides a new and environmentally aligned power source that broadens the national energy mix and allows the building of a new style of housing that takes the dwellings “off grid” as far as power and heating are concerned.