use of vacuum sewerage, taking advantage of the system's requirement for small bore sewer pipes laid in shallow trenches, dramatically reducing the requirement for pumping stations as would be required by conventional gravity sewer systems. The largest vacuum sewerage scheme in this region serves the villages of Outwell and Upwell; four vacuum collection stations serve some 1500 homes in this agglomeration. On initial costings for a conventional gravity sewer to serve the area, previously served by domestic septic settlement tanks the site would have required the installation of 32 pumping stations. Using a vacuum sewer system, this number of pumping stations was reduced to four vacuum stations. Other companies in the UK such as Southern Water operate vacuum sewer systems, too. In northern Germany, several hundred systems have been operating since the 1970s. More are planned. Hamburg's 770-unit Jenfelder Au development was planned with vacuum sewers. The city of Ocean Shores, Washington makes a good case for vacuum sewer reliability and endurance. The city's vacuum system is one of the largest in the world, and it is also mature; most of its components are more than 20 years old and must function in a challenging operational environment along with gravity sewer and grinder pump systems. The county of Sarasota, Florida and other localities in Florida have adopted vacuum systems, in some cases as an anti-eutrophication measure. The city of Carnation, Washington is developing a collection system that incorporates vacuum sewers. Good examples can be found on the Maldives, the post-tsunami WATSAN project UNICEF - UN, where on several islands vacuum sewer systems have been the best option. Several other project, mainly for resorts, have already been realized on the Maldives. Provincetown, Massachusetts, USA Areas with seasonal freezing The biggest installation in Europe (several vacuum stations) can be found in Gerasdorf (near Vienna), Austria, where many benefits of a vacuum sewer system helped to overcome difficult conditions in this mountainous area. Estonia has vacuum sewers. Poland has vacuum sewers. Ruling technical guidelines and norms EN 16932-3:2018 Drain and sewer systems outside buildings DWA-A 120-3 WEF (Water Environment Federation) Alternative Sewer Systems (Second Edition -2008) WSA 07 (Australian Code) AS 4310 - 2004 (Australian Vacuum Interface Valve Standard) See also Gravity sewer (the more common competing system) Composting toilet (an application for vacuum toilet-and-sewer systems) Pneumatics References Works Cited Sewerage infrastructure