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<br /> ~ <br /> Problem Areas: <br /> . 1. Problem 1. <br /> On October l5, 1995, the City closed the by-pass valves at the three metering stations <br /> where Roseville water enters Arden Hills. Immediately on closing the valves the City <br /> was unable to fill the south tower again, for several days. Staff then opened the by-pass <br /> valves for scveral days. Again, the south tower filled and held to within two (2) feet of <br /> top (38' levcl). This matches the Roseville tank elevation when it is full. Staff then <br /> closed by-passed valves and they remain closed. Now again, the City is only able to <br /> maintain 32 feet of water in the south tower. <br /> a. Conclusion <br /> The two 12" lines and the 16" line reduced down to 8" meters provide a <br /> restriction, so that pressure builds up too high on the Roseville sidc shutting off <br /> their pumps before the south tank is full. This restriction amounts to a 2 to 3 <br /> pound pressure drop on the Arden Hills side. By overriding safety shut offs on <br /> thcir side of the meters, Roseville has actually blown water lines, trying to fill the <br /> Arden Hills tower. Also due to the prcssure difference, the Roseville tower is <br /> fillcd to capacity before Arden Hills, causing pumps to turn off. <br /> b. Recommendation <br />- Arden Hills should replace the 8" disc type meter with a less restrictive 16" <br /> turbine meter on our 16" main to increase capacity and flow rate to our south <br /> . watcr tower. This should bring tower back to a higher, ifnot full level. <br />- <br /> c. Problem 1 Costs <br />- A preliminary cost estimate for the 16" turbine meter plus necessary valves and <br /> accessories is $21,000. The cost for the 5' x 12' pre-cast concrete metering vault <br /> is estimated to be $5,800. Labor and equipment estimates for 16 hours at $250.00 <br />- per hour to be $4,000. This brings the total cost of the 16" metering pit installed <br /> with metcr and fittings to be $30,800. <br />- 2. Problem 2. <br />- The electrical sensor which transmits a signal from our south tOwer to Roseville's pumps <br /> is mounted within a few feet of the booster pumps, which fill the north tower. <br />- <br /> a. Consequcnces <br /> When booster pump starts filling the north tower it creates a suction on the south <br />~ tower sensor, This in turn instructs Roseville pumps that the south tower level has <br />- dropped approximately 8 to 12 feet and immediately kicks their variable speed <br />~ pumps into a higher speed unnecessarily. This causes, once again, unnecessary <br /> high pressure on the Roseville side of the metering stations as water is forced <br />- through the restricted meters. <br />~- <br />- . <br />-- <br />- <br />~ <br />