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here have been major reconstruction works in progress in Berlin since the reunification of Germany including the reneval of the sewer network both with traditional and with No-Dig technologies. Berlin is the city of lakes and lagoons so the watertable is high, and the characteristic soil is fine sand. The strong infiltration and the washed in fine sand mean serious problem for the sewer system in the waterside districts of the City. The larger cavities created in the bedding around the defects migh lead to major subsidence, and makes the bedding structures statically weak. Repair with traditional excavation is expensive in these districts due to the high costs of well pointing. On the other hand the application of relining systems is sometimes impossible because during jet washing the volume of the inflowing' sand might by even greater due to the vacuum created by the jet, so the correct position and adhesion of the liner can not be ensured.
The Sanipor chemical flood grouting sewer rehabilitation system offered an advantageous opportunity to solve the problem of infiltration accompanied by quick sand outlined above.
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FLOOD SYSTEM
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Sanipor was developed in Hungary in the eighties, to seal exfiltration and infiltration of sewers. There were hundreds of kilometers of sewer system sealed succesfully with flood grouting in East Europe. The system is used with predilection in many countries including Australia, the U.K., Germany and the U.S.A.
The Sanipor process seals the sewer with two consecutively applied chemical solutions called S1, and S2. Both are made of different silicates. The solutions react with each other and the soil creating a watertight soil grout around the defects, thus making the sewer sealed. The system was developed to work under watertable as well. It is a unique feature of Sanipor system that it can seal both the main, the laterals, and the manholes. In other words removing all infiltration and exfiltration of the system in one step.
The application of the system under normal circumstandes is rather syple. The sewer section is first cleaned by flushing with a high pressure water jet. The section and the adjoining house connections are closed off by pneumatic stoppers, then the sewer is filled with the viscous solution S1 up to to the street level to attain sufficient hydrostatic head to force the solution through the defects into the material surrounding the sewer pipe. After about one hour the S1 solution is removed and the same section is filled with the less viscous S2. This reacts chemically with the S1 and the surround material, creating a solidified watertight conglomerate aruond the defects and to a certain extent improving the soundness of the bedding. The effectiveness of repair is confirmed when the level of the S2 solution as measured in the manhole remains constant.
The sanipor System, with a slight modification in the steps, can be an effective and also very simple way to seal infiltrating sewers which are in part filled with quick sand. The essence of the modification is that if after jet cleaning there is still sand flowing into the pipe through the defects, it should be left there, and the first half cycle i.e. the applications of S1 is to be managed in the presence of sand in the pipe. The removal of sand by the jet will take place after the pump out of the S1 solution.
The highly viscous (100 centiPoise) S1 is pumped into the sewer. Due to the hydrostatic head the solution filters through the capillaries between sand particles of 'sand hills' in the pipe and finds ist way through the defects to impregnate the surrounding (sandy) soil outside the defect. By allowing adequate time and pressure head for penetration, the S1 will saturate the capillaries of the sand outside of the defect same way it would happen in case of normal (not accompanied with quick sand) infiltration. S1, due to the high specific gravity, replaces water in the capillaries of the sand particles of the bedding material and due to ist high viscosity increases the friction of them practically gluing them together.
Then, S1 can be pumped out of the manhole section, followed by the jet cleaning of the sediment. Owing to the gluing effect the rate of infiltration will be provisionally reduced and as a consequence of the adhesion ensured by the viscous S1 solution.
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 - The infiltration of sand is therefore suspended, so after a quick jet cleaning the section can be filled in the traditional way with S2. This reacts with S1 in the impregnated material surrounding the sewer pipe creating the solidified watertight grout around the defects.
- The Berlin Wasserbetriebe tested the Sanipor method for the first time to seal leaky sewers on Linderoder weg in Grünau district in 1994 for a total of 8 manhole to manhole sections (384 m, DN 300) and 9 shafts. Proximity to the Lagersee results in a high groundwater table in Grünau and as a result there is infiltration as well as an influx of sand into the leaky sewer system. Sand barriers up to half the height of the pipe were found. In spite of the sand influx the sewer was successfully sealed with Sanipor using the method outlined above preventing further subsidence of the road surface. Both the number of working days and the chemical consumption were within the values originally planned for traditional Sanipor system application.
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- FURTHER PROJECTS
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- Following the succesful solving of the problem posed by sand and water infiltration, the Wasserbetriebe decided to apply the method again in Grünau in 1996.
- One year later in 1997 another contract was awarded to seal a 550 mm diameter sewer beneath the famous Regattastrasse using the Sanipor system.
- In 1998 the next exercise was to seal the sewer suffering from strong infiltration of Wilhelminenhof strasse in Köpenick district which struggles with the same problem as Grünau. The repair of a total of seven manhole sections (372 m long and 700 mm diameter, together with 8 shafts and associated laterals) needed only 12 days. The S1 consumption was 32 m³, that of S2 was 14 m³.
- The contracts listed above were done by Malchin Liefke GmbH of Berlin in cooperation with the engeneers of Sanipor Deutschland GmbH.
- Another major Sanipor contract was performed in Tegel district of Berlin in 1998 under similar conditions by Starline GmbH. The sealing of 12 manhole sections (561 m long and with diameters between 300-600 mm, together with 13 manholes) needed only 11 days. Consumption of S1 and S2 were respectively 20,8 m³ and 13,4 m³.
- The experience collected in the past five years convinced the profession in Berlin that Sanipor is an economical and durable solution for their problems so further projects are expected.
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