Since the long-term prediction presents a vital basis of modern rehabilitation planning, it is indispensable to ensure a corresponding prediction quality.

On the one hand the predictions are to provide similar results with similar data and thus are to be steady. On the other hand the results are to illustrate the real network aging process as precisely as possible.

The prediction quality can be checked with the help of available re-inspections by ex-…

Priority string

At present short-term rehabilitation plannings are carried out on the basis of a priority list, e.g. according to ATV-M 149 [ATVM149a] or KAPRI [Mölleb]. Due to the lacking or marginal consideration of the initially described section substance as well as section-related limiting conditions wrong decisions are likely to develop in the operative planning process.

In "STATUS-Sewer" especially the differentiated constructional evaluation …

The attainment of a functional wastewater removal and thus the maintenance and rehabilitation of the sewer networks is a public duty of continuous upkeep. Also in the variants of the transfer of drainage tasks to private entities, the communities still finally have guarantee duties towards their citizens. In most cases, the costs of wastewater removal via the community exchequer are covered in their full extent by the drainage fees received. In other …

In view of the prognosis of high costs (Abschnitt 5.7.2) and the fact that sewer rehabilitation is no temporary occurrence but rather a network immanent continuous task, there is the requirement of defining

• long-term rehabilitation strategies as well as
• project-referenced economic efficiency testing.

Almost under the cover of long-term rehabilitation strategies, which can be the base of the medium-term financial planning, there follows the economic …

The sector of the economy most strongly influenced by sewer construction measures must be the retail trade. Although the national economy is negligibly affected by the influencing of individual businesses because the demand can be satisfied by neighbouring businesses, it cannot be the factual aim to endanger their existence by means of construction measures. This is valid at least then when there is an expectation that alternative construction processes …

Indirect costs as a result of traffic hindrances burden the traffic participants. For practical purposes, statements are selected that have been developed for traffic planning. The "Richtlinien für die Anlagen von Straßen - RAS" [RAS86a] (Guidelines for building of roads), as well as the Federal instructions for traffic planning "Gesamtwirtschaftliche Bewertung von Verkehrsinvestitionen" [NN88b] (Overall evaluation of investment in traffic) contain …

Noise emission changed by construction measures can be caused by changed traffic conditions as well as the noise of the construction machinery utilised. The monetary method used can be that used in many towns as a representative level of rents. Often characteristic rents can be charged for more or less than the traffic noise for particular habitations.

The traffic noise, insofar as there are no measurements available or possible, can be estimated …

The pollutant emissions are dependent on fuel consumption as they are determined in connection with the costs of the traffic participants. Points of view of the damage in the following statement are persons, vegetation and buildings. The emissions of fuel-burning motors are converted to carbon monoxide equivalents (COE) and evaluated (in Germany) with resulting costs of 12.00 DEM/t COE (6.14 €/t COE) for damage to health and buildings and 3.50 DEM/…

As sewer rehabilitation measures are, of necessity, mostly carried out in existing roads, there is the question of the influence on the road surface by the open cut method. Several instances can be found in the literature that mention a shortening of the residual utility of road structures of up to 60 % [Beros92] [Thoms95]. Insofar as these are included in the decisions of the indirect costs of the open cut method of construction there must first …

Insofar as excavations, especially for sewer replacement by the open cut method are situated near trees, there is always found damage caused by the cutting of roots or branches or due to the lowering of groundwater or due to consolidating soil (Abschnitt 1.12). If damage is not compensated directly by the carrier of the construction measures, there are often indirect costs, as the affected trees must be replaced early or the trees can no longer fulfil …

The public sewer networks of necessity lie almost exclusively in public areas (Abschnitt 1.11). These areas - mostly in roads dedicated to public traffic - are subject to an extraordinary number of uses. The construction sites required for sewer rehabilitation, depending on the construction process, affect this utilisation to a lesser or greater extent.

The continual rise of individual traffic in the towns, combined with exhaust emissions, development …

In the previous sections, mention was made of the various technical possibilities, the operational tasks of maintenance and cleaning, the inspection including evaluation of the condition of the sewer and the structural maintenance (sewer repairs) that had to be fulfilled and the sewers to be renovated or replaced by means of investment measures.

For this reason, the requirement for economic efficiency can not only refer to the construction measures …