Clearing excess water from a flooded tunnel

Torrential rain waterlogged building works at a road in Prague, causing a deep crater to appear. A pump solution was needed which could deal with the emergency situation. Two vacuum assisted self-priming pumps were deployed to clear the excess water, and deal with the slurry created during the drainage process.

The 17 m deep tunnel was drained using two SPP Autoprime Q1200 vacuum assisted self-priming pump units.
The 17 m deep tunnel was drained using two SPP Autoprime Q1200 vacuum assisted self-priming pump units.

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The Blanka city ring is a complex new highway designed to alleviate traffic in the centre of the picturesque but crowded city. In 2006, construction began on the road which leads through Bubenec and then descends into a tunnel under the Stromovka Park. Construction of the tunnel ground to a halt earlier this year, when a 20 metre wide and 10 metre deep crater appeared in the park after very heavy rainfall which had waterlogged the earth.

The tunnel itself is 17 m deep at this point. It is carved into the indigenous slate that lies beneath the park, which is a difficult material to deal with. The huge cavity filled with water very quickly, which severely hampered rescue work - but fortunately there were no casualties.

To help with clearing the excess water, two SPP Auto prime QI200 vacuum assisted self-priming pump units were installed to pump the water to a drain canal approximately 250 metres from the site. These pumps were ideally suited to the job, due to their ability to automatically and rapidly self-prime to depths up to 9 metres, a key requirement in this sink hole dewatering application. In addition, the solids handling capabilities of the Q series, the result of an improved impeller design, proved essential to deal with the slurry created as the water was drained.

The SPP Q series range of pumps are all fitted with the same robust and efficient oil lubricated 65 cam vacuum priming system which allows the pump to be located away from the edge of a sump or, in this case, unsafe ground that could collapse further. Positioning the pumps some distance from the sump edge ensures the operators are completely safe.

Manufactured in sizes from 4 to 8 in, each pump is supplied complete with a full set of suction and discharge hoses including the suction strainer. These kits, along with the compact and mobile Q design, allow the pumps to be quickly deployed on applications such as this emergency situation.

Other benefits making the Q Series pump the perfect choice for use on difficult terrain are its overall lightweight construction, mobility and manoeuvrability, combined with the robust, hard wearing and reliable pump-end.

The large fuel tanks allow up to 24 hours continuous running, which provided another advantage when dealing with an emergency situation that could become dangerous if the pumping was stopped for a lengthy period of time.

The units deployed at Stromovka Park are part of a fleet of sixteen QI200 and XF250 Autoprime pump sets which were co-financed by the EU and the Prague Magistrature following the disastrous flood in Prague in 2002, and they are kept on standby for just such an emergency.

A representative of the main contractor, Metrostav, announced that the landslide won’t influence the work schedule or the planned 2011 opening deadline for the tunnel.