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Project Mirfield questions regarding the £1.2 million project to reduce the risk of internal sewer flooding

By pmadmin
Aug 13th, 2014

I would like to thank Yorkshire Water for their response to the Questions which we put to them on the 17-7-2014

Q, How long has Yorkshire Water known about the problem of flooding on Old Bank Road? A, Initial report of flooding from property No.87 was 10/08/04 and the return period was 1 in 20. YW have only started resolving 1 in 20 year flooders in Amp 5. Further investigation identified this as a 2 in 10 year risk with an additional 13 internal flooders. This allowed sufficient funding on a cost benefit ration per property to gain funding for a scheme.

Q, What is the life time expectancy of the tank? A, Expected 100 years asset life.

Q,  How many pumps to be installed to the wet-well and what happens if they fail?

A, There are two pumps to be installed in a duty/standby arrangement. A generator socket in the kiosk will also be installed in the event of a prolonged power failure.

Q, How many houses will the new tank service for foul discharge? Please name all roads in full answer.

A, The scheme will service 11 properties on Old Bank Road and 3 Properties on Sunny Bank Road. Protection is from internal flooding from the sewer however only the cellars of these properties are directly connected to the tank.

Q, How many square meters of storm water area will discharge in to the tank? Roads, paths, drives, house roofs, garage roofs please name all roads in full answer. If the highways gullies and drainage system connect in to the tank indirectly via Yorkshire water drains please state number of gullies and road names

A, Only cellars of the 14 properties drain directly into the tank. The routing of other drainage is unchanged. The weirs provide relief of excess flows from the sewer system to the tank at times of high rainfall.

 Q, How many litres per second will the pumps, discharge back in to the existing drain in old bank road?

A, The proposed pump will have a variable pump rate to work with the changing head of effluent in the tank. The current designed pump return flow rate will be 17l/s. The pumps will be controlled so that they cannot activate until sufficient capacity is available in this return sewer

 Q, What is the diameter of the pipe and what is its total capacity before the drains hydraulically fail, and the current fall of the drain from man hole to man hole start from upstream and end at downstream?

A, The sewer in Old Bank Road is a 300mm pipe with a capacity of 53 l/s with a fall of 220mm over 81.5m of sewer where the pump is proposed to return.

Q, Is the tank designed for a 1-100 years worst storm plus 30%.?

A,The tank is designed to 1 in 30 years as per water industry guidelines from Defra, Ofwat and the Water Research Council

 Q, Please state what would happen if the tank was near full to capacity with one storm then a second storm hit within minutes of the first storm of the same magnitude?

A, The fourteen properties we are working to resolve their flooding issues, are likely to be at risk if another storm event occurs when the tank is full. (This is deemed an exceptional circumstance and the weather is beyond YW’s control)

Q, Could the car park ever flood, or be expected to flood directly from this deigned scheme.

A,The car park can flood but it won’t be due to the works we have installed. There would have to be a failure of the duty pump, then the standby pump and the maintenance crew failing to fix the pumps in time before another storm event occurs.

Q, Other than installing the new tank, is there another alternative?

A, A thorough investigation has taken place and we have determined that to provide a solution of a storage and pump arrangement, is the most cost effective solution on a cost benefit ratio per property.

Yorshire Water ,,,,

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