Water & Wastewater Treatment

www.wwtonline.co.uk | WWT | APRIL 2016 | 21 Project focus Pumps Pump engineering skills help resolve sink hole drama Project focus ● Sink hole opened overnight outside supermarket ● Collapse of underground drain caused destroyed pumping station ● Replacement pump solution delivered in just three weeks By Bryan Orchard W hen storms and torrential rain hit Granbury, Texas back in May 2015, residents were alarmed to find as the rain subsided the following morning a large sink hole in the lakeside car park outside Brookshire's supermarket. Measuring over 90 feet wide and 30€ deep, the hole was caused by the ground becoming saturated, a€er an old 7€ diameter storm drain had collapsed following several inches of heavy rain. This was accompanied by a landslip as the ground was washed away down the adjacent hillside. The water build-up and leak had literally washed away the earth supporting the City's No.4 effluent li€ station, creating the large crater. Such was the damage that Granbury City Council declared it a local disaster; they sealed off the area and brought in specialist engineering crews to stop wastewater flowing from the broken pipes into the nearby Lake Granbury. The pressing concern then was to formulate a programme to replace the damaged li€ station. With this being a highly specialised area of environmental engineering, Granbury City Council called on the resources of Abilene- based Enprotec/Hibbs & Todd (eHT), and Pump Solutions of Dallas/Fort Worth. Scott D. Hay, eHT Vice-President, says: "The City took the lead in stopping up all the water and sewage lines and bringing in a by-pass pump at the start of the emergency. It was a rapid and successful response on behalf of the City. Our Granbury City office was then called to the site to get a handle on the environmental issues and stabilize the situation for the long term." Rebuilding the pump station It was only when eHT commenced working on the site that more information about the original li€ station was forthcoming. A major issue was that the installation was pumping into a 12" force main and that the pumps did not come even close to providing adequate velocity to maintain a flow that would scour and clean the main to prevent it from being plugged by waste and solids. The prime concern related to the integrity of the force main, particularly in respect as to whether it would it be compromised in its ability to perform a full 12-inch flow. As a result a decision was made to address The 90 wide and 30 deep hole opened up overnight following heavy rain

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