55A - SAN LORENZO SEWER LIFT STATION

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February 2, 2012 Page 2 EXHIBIT "B" Existing computer software is old and obsolete compared to existing technology and support is not readily available. Existing lift station does not have any odor control system. The proposed lift station will have an odor control system. A. Age and Replacement Parts Original mechanical equipment was all replaced in 1989 (at age of 29 years). Pumps were rebuilt in 2007 (at age of 18 years). By time proposed lift station is constructed and placed in service, existing mechanical equipment will be about 26 years old and will need to be replaced again. Rebuilt pumps will also have been in service for about 7 years at that same time and would be requiring additional maintenance work. The environment (below -grade manhole with high humidity) reduces the design life of the equipment. Replacement parts for the pumps are not readily available (within day or two of request). For the last pump replacement work, it took about four weeks to get the replacement parts. (The City contacted Mr. Chris Brown of Orange County Pump who confirmed that the minimum lead time for the pump rotating assemblies was 3 to 4 weeks as they are not readily available but need to be assembled from off the shelf parts and shipped). With only two pumps in the existing lift station, this delay in getting replacement parts places the City at a very large risk of a potential spill. To reduce this potential, the City has been storing used spare parts at their yard in case replacement parts are necessary. As the existing lift station equipment gets older, the need for maintenance and repair work increases. Section III The existing dry pit (contains the mechanical piping /valves /pumps /motors) is subject to flooding due to its location within the often flooded Bristol Street. The proposed dry pit is protected by curbs and elevation to minimize any potential flooding. Any flood at the end of San Lorenzo will be relieved to Segestrom prior reaching the elevation of the top of the dry well. The existing electrical panels are located outside and exposed to elements. The proposed electrical facilities will be located within a building. Section VII Retrofitting the existing lift station by installing a submersible pump will not eliminate the issues of the existing lift station being located in Bristol Street. The majority of the project's objectives will not be met by retrofitting the existing lift station. C: \Documents and Settings\nmitre \Local Settings \Temporary Internet Files \Content.Outlook \VDSN8UCB \santa ana memo on silverstream letter - TetraTech (FINAL 2012- 02- 02).DOC 55A -132