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News Centre > Thursday 22 December 2016

Tonnes of rubble and artefacts found during La Piette CSO excavations

Artefacts found during excavations of La Piette CSO

Old coins, cutlery and bullet shells were some of the more interesting finds amongst the tonnes of rubble excavated from the La Piette combined sewer outfall (CSO) pipe during last week's work.

Guernsey Water engineers have already managed to remove around three tonnes of rubble the bulk of which is sand, silt, blocks and bricks as well as a road cone and some gully gratings.

Mark Walker, capital delivery manager of Guernsey Water said: "When we began sieving through the debris we discovered some pre-decimalisation coins, some old cutlery (mainly spoons) and several bullet shells which shows how old the pipe is and how long this debris has been there."

"As anticipated the pipe's condition is very poor making it difficult to survey and clear.  This will naturally impact on what rehabilitation options we may have available to use.

"We believe that the relatively newer downstream section of cast iron pipe can be saved and its life extended, however the options are limited with the upper 150m of brick pipe where we may need to fully replace the worst condition sections.

"As you can imagine a great deal of care needs to be taken in tackling this delicate work."

The La Piette CSO is almost 350m long and extends from the sea wall opposite Piette Road on St George's Esplanade to the low water mark in Belle Greve Bay.  It serves as a CSO discharge outfall, which activates to prevent localised flooding when the foul water sewer on land reaches unacceptably high levels and becomes overloaded.  This CSO is only activated when there has been a lot of rain.

 

The pipe, some 600mm in diameter, is over 166 years old, its original section built with an inner brick lining surrounded by granite masonry.  Originally only 150m in length, it was extended by approximately 200m with a cast iron pipe in around 1890 but since then has not undergone any significant maintenance.

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