Shake, Rattle and Bypass
July 20, 2011Those of you who don’t live in an area that is prone to earthquakes may have no idea what happens when a large earthquake strikes.
Let me help you understand. First, the ground under your feet seems to slide back and forth or you might experience a sudden drop, like an elevator when it starts to descend. Then you hold your breath and start to look for a place that will protect you from falling objects or, worst case, the roof of the building comes down. Once the shaking stops, the damage starts to be accessed. Stores have aisles full of merchandise, plate glass windows are broken, roofs of buildings collapse, cracks appear in the walls of buildings, and trees are toppled over. Those are all very visible signs of damage that occurs after a big shake, what the public doesn’t think about are the miles of water, gas and sewer lines that run beneath the streets.
Happily, gas lines weren’t ruptured, nor were water mains broken; however, among the damage caused by the April 4, 2010, earthquake — a magnitude 7.3 quake, centered 32 miles from downtown Calexico, Calif. — was a 30-in. pipeline carrying raw sewage into the Calexico Treatment plant. The damage was in several locations, along the section of pipe that crosses the New River. When it was discovered that raw sewage was pouring into the river at a rate of approximately 200 gpm, City and treatment plant officials contacted local contractor Cora Constructors Inc., which was awarded the contract to repair and/or replace the damaged line.
After making attempts at repairing the pipeline and being unsuccessful, the contractor called Griffin’s Ontario, Calif.-facility, requesting help in controlling the raw sewage. The flows were uncertain but were thought to be under 8,000-gpm peak flow. Griffin’s pump experts evaluated the data that was available, and recommended that the contractor use 2-model 10NCRD pumps as primary and 2-model 10NCRD pumps as standby pumps. Griffin then compiled a list of fittings and pipe to complete a bypass of approxwimately 500 ft. Griffin has extensive experience with emergency sewer bypasses and has learned over the years that by maintaining a portion of its rental fleet in a very high state of readiness it is able to respond more quickly in any emergency. The contractor signed the agreement with Griffin on Wednesday, on Thursday morning the pipe was delivered and by Saturday the system was running and handling the total flow.
The contractor also needed to meet the budget of an already overburdened city. In order to keep down the cost of the bypass installation, Griffin agreed to send a supervisor to show the contractor how to complete the bypass installation using its personnel. Griffin Dewatering Corp.’s able and experienced personnel were able to direct, and train the contractor’s workers in the fusion butt welding of the HDPE pipe and were able to show them how to build the manifold and setup the pumps for this rather simple bypass setup.
The bypass took three long days (10 to 12 hours per day) to install, test and start. The installation included fusing 500 ft of pipe, elbows and fittings for tie in points, setting the pumps in place, cutting and fitting the suction pipes, building the discharge manifold and hooking the discharge from each pump into the manifold. The pipe was then pulled into place on pipe supports that were fabricated by the contractor, when the pipe was in place; pipe restraints were installed to complete the installation.
Once the bypass was in operation the contractor began removing the damaged pipe, then replacing it with a new pipeline. The work took three months to complete, during that time the contractor relied on Griffin to provide the weekly service on the diesel engines, and provide repair or replacement for any parts that became worn or unserviceable. Once the new pipe was completed and tested the bypass pumps were turned off, the flow was once again allowed to flow to the treatment plant through the pipeline normally. The temporary bypass system was then removed, loaded on trucks and returned to Griffin’s Ontario, Calif.-facility.
It is often the case that in an emergency situation, we must determine the size of the pumps with little data available. It is helpful to choose pumps that are capable of pumping one half to three quarters of the projected flow, and utilizing two pumps. Thus covering the projected flow and having additional capacity for unforeseen incidents, such as heavy rainfall entering into the sewer system, or a broken water main, broken fire hydrant or any number of catastrophes that might happen. Remember it was a disaster of some kind that caused the need for pumps in the first place. At the same time when the flows fall off, during night time hours and when people are at the workplace, one pump can be shut off and the other idled down, to save fuel and still be ready for increases in flow as they happen.
Training of the pump operators was of the utmost importance, not only did they need to monitor the flow level and increase or decrease the pump speed to compensate for the flow, but they had to clean the intake of the pumps on a regular schedule. They also had to switch pumps when they needed maintenance. The plug had to be checked for proper air pressure and the fittings on the manifold had to be checked for leaks several times each shift.
Griffin’s supervisor on this project was Doug Polsley, who has extensive experience on these types of pumps and has operated and installed many bypasses in the past. His experience and the knowledge of what problems are likely to be encountered, enabled him to provide the invaluable training for the contractor that was necessary to insure a successful project.
Although this was a fairly simple installation, the circumstances surrounding it and the fact that it was built using a crew that was not trained, before starting the project, make it a rather interesting study. It also shows that experience gets the job done right even when that experience is being shared through another contractors workers. In any disaster or emergency situation cooperation is the key to success.