Surrey Waste Disposal Authority and domestic waste collected by Spelthorne Borough Council. Locally produced inert waste for disposal is sent to landfill in Alfold and Shefford, and a proportion to energy from waste plants in Slough and Kent to lower landfill tax. Plans have been approved to permit gasification in Charlton in the north of the Shepperton post town as part of the county's Eco Park to take up to half of the county's residual waste. Shepperton's distribution network operator for electricity is UK Power Networks; aside from renewables there are no power stations in the area. Thames Water manages Shepperton's drinking and waste water; water supplies being sourced from the London sources including several reservoirs fed by the River Thames locally. There are water treatment works at Ashford, Hampton and sewage treatment works at Isleworth. Topography Shepperton has a long boundary with the River Thames in its southernmost salient, which almost surrounds Spelthorne. Old Shepperton is almost surrounded by the extreme southern meander within this. Prehistoric glacial retreat north of this has made the north bank almost flat for a considerable distance and as such, elevation never exceeds 14 m above mean sea level (on the border of Laleham). The river never exceeds 11.5 m, (beside Dumsey Meadow and under Chertsey Bridge). The lowest elevation is 9 m in flood meadows at the confluence of the Ash with the Thames. The Ash is the border with Littleton and Sunbury-on-Thames (mostly, to the northeast, with its technical hamlet, Upper Halliford). Dumsey Meadow SSSI is the only piece of undeveloped, unfenced water meadow by the river remaining on the River Thames below Caversham, and is home to a variety of rare plants and insects. The Swan Sanctuary moved to an old gravel extraction site by Fordbridge Road in 2005 from its former base in Egham. On the opposite bank are in downstream order are Chertsey Bridge and Chertsey Meads, the now residential Hamm Court riverside neighbourhood, three islands, (the first two of which have multiple properties) (Lock, Hamhaugh and D'Oyly Carte, one large man-made island, (Desborough), and the riverside parts of Walton on Thames, the upstream part of which is also open land, Cowey Sale Park. The towpath is the official route of three passing through the Shepperton reaches (of the Thames Path) as heading upstream from Hampton Court Palace another marked version takes Walton Bridge, the official version takes the