- The Sanipor sewer repair system has been available for several years and a number of licensed operators have been appointed around the U.K.
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SANIPOR
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Sanipor is a two part sealing system which utilises a pressure head to induce exfiltration of ist liquid chemical constituents through pipe defects into the ground surrounding the pipeline. Using the first solution (S1), a length of isolated sewerline is filled via an existing upstream manhole, using the manhole depth to establish the required pressure head wherever possible. After allowing the S1 solution to exfiltrate for about one hour the solution is quickly pumped out and returned to the charging tanker. Before the S1 solution has time to reinfiltrate back into the sewer from the surrounding ground solution (S2) is introduced through the same manhole under the same pressure head. On contacting with solution S1, S2 begins to react and form a gel which solidifies within the pipe defaults and the ground matrix around the pipe. Although relatively solid, once set, the matrix formed in the surrounding ground does afford some flexibility in the pipeline to allow for future ground movements. If complete sealing of the pipe is not achieved on the first pass, a second is normally sufficient to complete the work.
The chemical compounds can be varied slightly to ensure that the reaction is not affected by different ground types, a method that was recently utilised on-site.
Contractor O.C. Summers is one of the licensed companies for the use of the Sanipor system within the U.K. and has recently used the system to solve two different sewer problems in two areas of the country.
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BLACKPOOL
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The first project took place in the northwest of England in Blackpool, one of the country`s busiest tourist resorts. Blackpool Borough Council (BBC), acting as agent for North West Water (NWW), found a problem with a discrete section of surcharging sewer where alternate exfiltration and infiltration occurred. The soil around sewer comprised a mixture of fine sands whith included lenses of peat.
The exfiltartion/infiltration cycle caused migration of the fine sand into the sewer resulting in siltation problems and, more importantly, sewer and highway stability problems through voiding around the pipe. The silting together with complaints from the highways authorities led to the decision to undertake repairs before any catastrophic collapse of the sewer or already - uneven road occurred.
CCTV surveys and cleaning of the silt by BBC highlighted the areas in most need of repair. These centred on a residential area with some light industrial buildings to the south of the town centre and north of the airport.
Despite earlier cleaning efforts by BBC to enable surveying to be done, and attempts at joint sealing which proved prohibitively expensive due to high chemical usage. O.C. Summers still had to complete further cleaning of up to 25% siltation prior to applying the Sanipor system, indicating to some extent the nature of the problem. Sanipor was eventually chosen after NWW engineers visited another operational site in Southport with O.C. Summers where the technique's applicability to Blackpool became apparent.
The Blackpool project comprised the treatment of some 2,300 m of 300 mm diameter clayware sewer over a scheduled 6 week period. The £150,750 project was actually completed within the 6 weeks to the full satisfaction of the client.
On completion of the project, however, one small problem did occur for some of the buildings along the treated route. Due to the now-sealed sewer no longer acting as a land drain for ground water, some of the basements of buildings were required to fit pumping systems to ensure that their below ground level sectios remained dry, a problem that previously had not occurred.
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- PWLLHELI
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- In contrast to the Blackpool work, a project in Pwllheli, North Wales was required to be completed to ensure that sewage flows to a new sewage treatment works were not too high in salinity,a condition which would severely and adversely effect the plant's treatment processes. Due to ist coastal position the town of Pwllheli has ground water and a sewer system which runs under the influence of tides, therefore infiltration into the sewers is normally saline in nature.
- Dwyfor District Council, acting as agent for Welsh Water, identified the areas of the town most affected by this saline infiltration and decided to seal the sewer lines prior to the commissioning of the new treatment facility in 1997.
- Sanipor was chosen as a system practicularly suited to the Pwllheli situation as the method not only treats the mainline but also the laterals up to an elevation equivalent to the top of the liquid chemical level in the manhole used to fill the system. As many of the laterals were difficult to access for anything other than visual inspection due to their position within properties along the pipe routes, the system allowed the contractor to remotely seal them, thereby maximising the reduction in saline infiltration.
- The tidal natur of the ground water meant that the contractor timed the majority of the works to coincide with low tide to make best use of the manhole pressure head which, at this time, would not have to overcome higher ground water pressure. The chemicals chosen were those which would be least affected by the prevailing saline ground conditions.
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- ADVANTAGES
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- In all, the works comprised the treatment of some 900 m of 300 mm diameter clayware sewer, plus numerous laterals, at a cost of £118,000 over 5 weeks. When NO-DIG International visited the Pwllheli site the project was about completed and the client was well satisfied with the sewers treated to that time. CCTV surveys had alredy shown a significant drop in the levels of infiltration into the sewer system.
- Neither of the foregoing projects required any form of separate excavation to allow the operations to be completed, as existing manholes were used for all works. There were no road closures and access to all properties was maintained at all times. A publicity campaign prior to the works informed all residents of the time and date at which their section of the sewer would be treated and all that was asked of them during this time was to reduce waste water production by minimising use of washing machines and toilet flushing so as not to overload sections of the line being used for waste storage during the works. As each section was completed in under one day, this request was of minimal disruption to the majority of residents and businesses.
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