Rehabilitation and Maintenance of Drains and Sewers / Publisher: Prof. Dr.-Ing. D. Stein & Partner GmbH, Editorial: D. Stein, R. Stein (2004)

General Requirements

According to EN 752-5 [DINEN752-5:1997], after rehabilitation, the nominal condition of a structure, a sewer sector, a section of the sewer, a network region or drain and sewer system must conform at least to the same standards that apply to a new sewer. Naturally, this also applies to the materials and components used [Rothe83].

The loading that is possible and the corresponding characteristics required are given in very general form in (Table 5.1-1).

 
Table 5.1-1: 

Materials stressing in sewer systems and corresponding properties of materials [DINEN752-2]

Materials stressing Materials properties





Mechanical by means of
Transport Impact and shock resistant
Installation Impact and shock resistant
Soil load, soil material, compaction, Traffic loading Shape stability, bearing strength,
Compressive strength
Settling Flexibility in the pipe joint
Water pressure, buoyancy Weight, compressive strength
Internal pressure Material tensile strength
High flow velocity
Conveyed solids
Cleaning apparatus
Hard pipe surface, wear resistance


Chemical by means of
Inorganic acid, alkali, salts

Corrosion resistant surface of the pipe and
pipe joints
Organic substances, solutions
Changing composition of the sewage
Condensate, steam
Biological reactions
Other by means of Root growth Root−proof pipe joints
Temperature Temperature resistance

More details of the application-specific requirements and regulations are given in the appropriate sections.

According to EN 752-5 [DINEN752-5:1997], the following points must be given special consideration during rehabilitation:

  • Hydraulic capabilities;
  • Operation and maintenance ( (Abschnitt 3.1), EN 752-3 [DINEN752-2] and 752-7 [DINEN752-7]);
  • Selection of the materials;
  • Limitations as regards accessibility and installation conditions;
  • Handling the connections;
  • Maintaining the value

Further general requirements are contained in the following standards:

  • EN 752: Drain and sewer systems outside buildings, Part 1 Generalities and definitions [DINEN752-1], Part 2: Performance requirements [DINEN752-2], Part 3: Planning [DINEN752-3], Part 4, Hydraulic design and environmental considerations [DINEN752-4] ;
  • prEN 13380: General requirements for components used for renovation and repair of drain and sewer systems outside buildings [DINEN13380] ;
  • EN 1610: Construction and testing of drains and sewers [DINEN1610:1997] ;
  • EN 476: General requirements for components used in discharge pipes, drains and sewers for gravity systems [DINEN476:1997] ;
  • prEN 12889: Trenchless construction and testing of drains and sewers [DINEN12889:1997] ;
  • ATV-A 125 E: Pipe driving [ATVA125:1996].

Besides these primary standards and working sheets, there must also be considered the current standards for pipe materials as well as for sealing materials and gaskets ( (Abschnitt 1.7.1) and appendix: European standards).

For the case that in the Federal Republic of Germany materials and components, thus also pipes and materials, are to be used that are not in common use and that have not proven themselves, but that require testing or permission within the scope of the building regulations, then a permission or a test certificate must be obtained from the Deutschen Institut für Bautechnik in Berlin (German Institute of Construction Technology). Permissions and test certificates obtained from this institute have only a limited period of validity and must be applied for again from time to time. Other particulars are regulated by the test certificate regulations of the Länder.

It is often not known that standards, certificates of permission and test certificates are not automatically parts of the manufacturing or supply contracts. It is always necessary to specifically mention these as being part of the contract conditions. If required, it can be an advantage to specifically mention sections of the respective standards. An exact knowledge of the standard is obligatory in individual cases.

In the application of measures for structural rehabilitation there exists the danger that the special conditions of the sewage flow are not sufficiently taken into account and the possibilities of application of processes are incorrectly estimated. For this reason, the processes should be described in accordance with the classification in (Table 5.1-2). In this way one obtains the possibility of evaluating them for their usability and to compare them with each other [ATVM143-1:1989].

 
Table 5.1-2: 

Classification for the description of structural rehabilitation processes to ATV-M 143 Part 1 [ATVM143-1:1989]

1 Brief description
2 Description of the short term and long term behaviour of the materials used
Information, for instance on
  • Mechanical properties
  • Tightness
  • Bearing behaviour
  • Resistance to physical, chemical, chemical- biological and biological attack
  • Temperature stability
  • Fire resistance
  • Environmental friendliness
  • Working and laying conditions
  • Standards, guidelines and testing regulations, class monitoring, test certificates
3 Areas of application
3.1 Description of damage
Information on applicability, for instance to
  • Leaktightness with or without groundwater infiltration, e.g. of pipe joints, components or structural joints, walling,
    connection and transition regions
  • Cavities in the embedment
  • Positional deviations, e.g. angular changes, displacement
  • Mechanical wear, e.g. abrasion
  • Corrosion (internal and⁄or external corrosion)
  • Deformation
  • Cracks, e.g. longitudinal or circumferential, cracks originating at a point
  • Pipe fracture
  • Pipe break (missing pipe wall pieces)
  • Collapse
3.2 Object of damage repair
Information on applicability in view of, for instance
  • Materials
  • Pipe wall characteristics
  • Cross sectional shape
  • Minimum and maximum dimensions
  • Bends and angular changes
  • Lengths of sections of the sewer
  • Structures
  • Side inlets
  • Type of soil and level of groundwater
  • Bedding conditions
  • Gravity system or pressure pipe
3.3 Operating condition
Information, for instance on
  • Type of sewage
  • Composition of sewage
  • Sewage flow
  • Temperature of the sewage
  • Sewer atmosphere
4 Execution
4.1 Preparatory work
Information, for instance on
  • Construction site installation
  • Drainage capability including side inlets
  • Groundwater retention or sinking
  • Inspection and cleaning
  • Removal of obstacles
4.2 Sequence of work
Detailed description of the sequence of the work with information, for instance on
  • Work at construction site
  • Amount of personnel
  • Use of machines and apparatus
  • Emission ⁄ Imission
  • Progress of work
  • Limitation of the sewer operation
  • Linking side inlets
  • Connection to structures
  • Transfer to existing sewers
  • Reduction of the existing cross section
  • Disposal of waste caused by the process
  • Intermediate controls and test control
4.3 Finishing works
Information, for instance on
  • After−work handling
  • Cleaning
  • Control
  • Replacing the drainage capability
  • Work at construction site
5 Acceptance and guarantee
6 Experience and references

The descriptions of the processes in the following sections do not contain all the information mentioned above. Reasons for this are, above all, the newness, insufficient investigation or conscious retention of information on the part of the suppliers.

Standardisation, permission, test certificates and careful production of pipes, fittings, etc. are not alone sufficient for preventing future damage. When errors in transport are excluded, then the professional installation is of decisive importance.

Besides the utilisation of qualified personnel, it is also recommended to have expert supervision and acceptance for the rehabilitation measures including the preparatory work as experience has shown that these bring about larger technical and production problems than new laying [Haend84].

"Work on the sewage system is always associated with risks in the investigation, creation, rehabilitation and also in the maintenance. It is never enough to first think of safety precautions during construction. Safety matters must be considered in all phases from planning, and drafting. These safety aspects must be taken into consideration already in the pre-investigations, as well as in the planning of the laying and the maintenance" [DINEN752-5:1997] (Abschnitt 3.1).

The use in rehabilitation works in the sewers of materials and chemicals that are poisonous and highly flammable, that produce irritation on human skin or in the internal organs or that are otherwise damaging should be kept to a minimum.

The working sequence with handling, storing or utilisation of dangerous materials must call for special measures of care, especially also in confined spaces. In their use it is also possible that dust and vapour can occur.

In damaging and contaminated ambient surroundings, careful controls on their extent must be carried out and, if required, appropriate countermeasures must be taken [DINEN752-7].

Criteria for evaluation and estimation of the work safety in the handling of the chemicals used in rehabilitation measures in all phases and the corresponding instructions for their handling for the prevention of health influences for their user are not yet available.

A survey of the conditions and the development of attempts at solving this last named problem was the aim of a contract granted for an investigation by the Bundestanstalt für Arbeitsschutz und Arbeitsmedizin (Federal Institution for Occupational Safety and Occupational medicine) in Dortmund in the years 1995/96. The most important results are presented in [Lühr97] [Stein97i] and will be partly dealt with in the following presentations of processes.

Rehabilitation and Maintenance of Drains and Sewers / Publisher: Prof. Dr.-Ing. D. Stein & Partner GmbH, Editorial: D. Stein, R. Stein (2004)