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Plan of Study for City of North Olmsted Phase I by Floyd Browne Group January 4, 2006 addition, the exact volume of the wet well was difficult to determine as the fillets and concrete slab making up the influent channel were not exactly constructed as the station was designed so some error was evident in volume calculations. Still, much was learned during the test. The meter seemed to be accurate and the draw down was smooth. The pumps appeared to be in good condition and operating within range. The middle pump is pumping less than the other two at the 100% range and should be scheduled for some maintenance during a low flow period to prepare for the spring storm season. The test also gave the Floyd Browne Group staff a chance to look for vortexes that could impact the pumping rate. No surface vortexes were observed. From the test it appears that the three pump performance problems are not a result of mechanical failure or inconsistent pump performance. There was no way of testing three (3) pumps simultaneously as the draw down would be too rapid and airlock the pumps. Conclusions It appears that the station design is adequate for two (2) pumps and that the performance curve is accurate for the actual performance of the station. The fact that the poor pumping performance can be terminated with the by-pass pump recirculating the water in the wet well at the critical wet well depth is evidence that the wet well geometry may be the issue. Internal vortexing may be setting up when the head is at the 8-foot level affecting pump performance. Another possibility is that low pressure areas may be setting up close to the pump intakes as a result of the three pumps simultaneously in service. This could "starve" at least one of the pumps preventing proper operation. The bypass pump would shift the low pressure area(s) allowing proper operation at the critical wet well height. The Floyd Browne Group recommends the following: As the pump station flow is critical when three (3) pumps are required during periods of high sanitary flow, a study should be performed using at least one larger capacity pump so that only two (2) pumps are required to take care of emergency situations. 2. More research on some of the causes of low pumping capacity at this wet well level. a. Vortex internal to the bell of the intake? b. Stream lines setting up low pressure zones making suction difficult until the bypass pump disturbs those stream lines and allows normal operation. 1) Cones or angle iron on fillets disturbing the flow lines to avoid using the bypass pump. 3. A cost analysis should be performed by studying the increase of pump capacity vs. removal of I/I from the system by a foundation drain sump pump program or by EQ basins to store, pump and treat. Theoretically, with an EQ tank installed, no pump station improvements should be required. 4. Other economic analysis studies should be used to compare the following: 25