For Architects

Important information for architects

The separate listing of the item on “disposal” in the tender serves not least of all to ensure the transparency of offers submitted and helps counter a distortion of competition, which should not be underestimated.

Many of the companies that work on facades ignore the regulations on the utterly necessary treatment of waste water from façade cleaning and disposing of the sludge produced. Should this service not be mentioned in the tender, it follows that it need not be offered – often against the firm’s better judgment. As a result, those firms that do not offer or effect disposal can achieve a price advantage over those that do comply by the legal provisions and regulations – thereby incurring higher costs and being obliged to ask a higher price.

Detailed descriptions of measures should be included in the description of performance – i.e., prior to the actual tender document. The demands made of the company conducting the work may vary considerably depending on the type of work to be executed, the design of the facades, the use of the building and the local conditions regarding condition of the ground around the building. Consequently, it is all the more the task and duty of the architects issuing the tender to accurately describe what disposal entails and articulate relevant requirements in the interests of everyone involved.

In performing the work the executing company must meet the necessary requirements (specialist firm, possibly certified) and proceed with the necessary care. The architect should insist on and monitor compliance with all regulations and conduct random inspections of the building site.

Before providing information on the wording of tenders there follows an outline of the various regulations and necessary measures:

Before work on the facade begins that will generate waste water permission must be secured from the responsible authorities for indirect discharging. Depending on the municipality this may be the Environmental Protection Agency, Waters Protection Agency or even the civil engineering office. In several German states, authority to grant this permission lies with the sewer or purification plant operators. The waste water from façade cleaning may only be fed into a combined waste water or dirty water sewer (even after treatment or purification.
The price charged for securing permission should also include the administrative fees incurred for the discharge permit.

In describing the measures for capturing waste water and sludge the capturing devices to be used must be clearly defined.

The following should be considered:

Is it a building for which a capturing device can be installed at ground level? If so, it is important whether the ground around the building is plastered, has slabs, is tarmacked or only partly so and the rest consists of garden with lawn areas or perhaps beds with flowers, bushes, shrubs, ground-cover plants or even trees.
It is also relevant whether the existing vegetation can be removed or must stay in place. If it is removed care must be taken to remove it entirely and not leave tree stumps, the remains of shrubs, partial stems or the like as they could destroy or at least damage the sheeting tubs installed later. This would result is some of the dirty water seeping into the soil, something that must be avoided at all costs!

That said, likewise where the surface is made up, care must be taken to remove stones, rubble or anything else that could damage the foil before the tubs are installed.

At any rate, the tub must be installed such that the entire scaffolding stands in a tub. The plastic sheeting must fit snug against the facade. On the outer side of the scaffolding the sheeting must be pulled up about 30 cm to form a trough.
The tarpaulin employed for the scaffolding during cleaning work must be long enough to reach down into the tub on the outside of the scaffolding. This is the only way of ensuring that all the waste water is captured.

In some cases it may be necessary to install a so-called gutter trough. An example of this: when a department store is cleaned and the windows on the ground floor must remain accessible during the construction period. From both the façade and scaffolding side plastic sheeting is pulled into the gutter troughs and firmly fastened using adhesive tape. This ensures the sullied water can be properly capture, treated and disposed.

It is totally unacceptable to simply attach a gutter to the façade to capture the dirty water or lay out old carpets or the like to separate out the solid materials.

As regards waste water treatment the procedure also varies depending on a number of factors. If it is planned to clean the façade with cold water and moderate pressure then regardless of the type of facade it can generally be assumed that a two to three stage settling basin will be sufficient to separate out possible solid or suspended matter from the water. But the situation may be different if hot rather than cold water is used. Depending on the temperature and pressure it is possible that certain harmful substances will dissolve and enter into the dirty water.
If there is any doubt the water must be examined for harmful substances, especially heavy metals. If the concentrations are found to be below the limits determined by the authorities then in addition to the settling basin the elimination of the harmful substances is necessary using flocking and filtration. A suitable water treatment system should be used. Once chemicals are used to clean a façade, be it of stone or plaster, in combination with water (high-pressure equipment) or old paint layers are stripped, the water must be properly treated. Here the use of a portable, water treatment system is indispensible (System ETRAS). Both the pH value must be set and the flocking and precipitation of harmful substances (heavy metals) is effected.

After this, the sludge produced has to be filtered off. The cleaned water should at any rate be re-used on the facade via the high-pressure device. This saves a considerable amount of fresh drinking water (ca. 30-50%). An additional water treatment is necessary if chemicals containing chlorinated hydrocarbons are employed. The dirty water is to be treated as explained above: set the pH value, precipitate, flock, filter) and then pumped through an active carbon filter and if necessary ionic exchanger. The nature and size of this filter depends on the concentration of harmful substances in the dirty water. This should be ascertained beforehand by conducting an analysis of a water sample.

The portable dirty water treatment systems should be approved for treating water used to clean facades. It should also be stipulated that this equipment only be operated by trained specialist staff.

An operating log should be maintained which includes the place, date, type of facade work, cleaning or stripping agents used, chemicals used in the water treatment system, duration of the work and documentation of any malfunctions or accidents together with a description of measures taken to eliminate them. This log should be produced for viewing at the request of the responsible authorities. The permanent pH value control should be documented on a test strip.