Pump-less Flow Diversion
The two large interceptor structures at Sand Creek in Colorado Springs, Colo., have been due for a new pipe connection and rehabilitation for some time. Now that time has come.
The interceptors each have a 66-in. influent line and a 66-in. effluent line. The effluent needed to be abandoned, and the flow shifted into the new 66-in. line that will be tied into the interceptors. Also of concern is the environmentally sensitive Sand Creek, which runs parallel to these inceptor structures.
The contractor that was awarded the project, High Country Pipelines, contacted Darald Grimes with Maverick Pumps in Colorado to do a surface pump bypass to dry up the interceptor while work was being done or to determine if another method could be found. Estimates for the surface pumping were in the $300,000 range. The pipes for the surface pump operation would have been close to Sand Creek, increasing the risk of a negative impact to the area during setup and take down. Grimes contacted Plug-It Products to see if one of its pump-less flow diversion systems could be used instead because all the flow would be contained within the existing interceptors walls.
Grimes explained that the entire pump-less flow diversion would have to be lowered into place horizontally, fitting between the existing vertical walls of the structure. He did a full analysis of the flow rates and determined the flow was too great to just have someone push the inflatable diverters up into the influent pipe, even during periods of low flow. Also, in the first installation, the influent and effluent pipes were directly opposite of each other. For the second step, the new effluent pipe was at a 45-degree angle from the influent pipe, so the pump-less flow diverter would have to accommodate that angle. There would also need to be enough room under the bypass tube to form the new channel. Because of the weight of the water in the 48-in. diameter, steel tube support straps hung from above would be required to carry that weight.
What Plug-It Products proposed to construct was a 48-in. diameter steel bypass tube with a 250 series 66-in. high flow diverter at each end. The 250 series flow diverters have inflatable rubber bladders to seal against the inside wall of the 66-in. pipe, diverting the flow into the 48-in. diameter steel tube. The end bladders were telescopic; the ends retracted over the 48-in. steel tube or can be extended outward 24 in. on each end to place the inflatable bladders up inside the 66-in. pipe. This way, the entire flow diverter could be lowered into place between the existing walls of the structure. The end bladders have hydraulic cylinders to extend the telescopic end bladders up into the pipe against flow. The 48-in. diameter bypass tube left enough room to form the new concrete channel junction underneath it. Plug-It Products provided a seal between the outside of the steel tube and the inside of the 250 series flow diverter.
As planned, with the supervision of Grimes, the top half of the pipe was removed between the two end walls of the structure. Then, the pump-less flow diversion was lowered into place during a low flow period. The end bladders were extended up into the 66-in. pipes with the use of the attached hydraulic cylinders, controlled remotely with a hydraulic power pack supplied by Plug-It Products for this application. Once in place, the bladders were inflated, diverting all the flow through the 48-in. steel bypass tube, drying up the structure.
The interceptor structure was then prepared to tie-in the new 66-in. effluent pipe and have the new channel constructed in the bottom to direct the flow at an angle from the existing 66-in. influent pipe. Once the new effluent pipe was completely connected to the structure and the channel formed, the flow diversion end bladders were deflated during low flow and then retracted into place over the steel bypass tube. The entire flow diversion was then removed.
To make the steel bypass tube accommodate the 45-degree angle, one end of the steel tube was flanged, unbolted, rotated and bolted back together. Then the flow diverter was lowered back into the structure and re-installed, directing the flow down the new effluent pipe and leaving the old effluent pipe exposed and the structure dry. Concrete was poured to finish the new shelf or bench and the old line was sealed off. When completed, the flow diverter was again removed and transported to the next structure to repeat the operation.
Even though this was a one-time use, Plug-It Products rented the pump-less flow diversion for $42,000, saving High Country Pipelines and Colorado Springs Utilities an estimated $260,000. Because Plug-It Products gets the flow diversion back, the inventory of these flow diversions builds up so Plug-It Products can keep costs down, as well as reduce fabrication times.
Since there was no setup and tear down of a traditional surface pump operation, 16 to 20 working days were saved, moving the project quicker to completion.
The possible negative impact on environmentally sensitive Sand Creek was minimized, as no pipes were run along the surface. Only one person was required to watch for a surcharge after the work crew left for the day. If a storm caused a surcharge, the first step would be to just deflate the bladders — easily and quickly done by one person.
To view a video of this project, visit www.plugitproducts.com, click on videos, then select: Project Maverick Pump Services.
Jon Smith is senior vice president of sales/marketing with Plug-It Products, which is based in Lodi, Calif.