65B - PROPOSED WATER AND SEWER RATE ADJ

Home Browse Search

City of Santa Ana, CA WATER RATE STUDY • Two critical customers within 300 feet of pipe: Increase CoF by 2. • One critical customer within 300 feet of pipe: Increase CoF by 1. • No critical customers within 300 feet of pipe: CoF is based solely on diameter score. • Total CoF score not to exceed 10. Other CoF Criteria Other CoF criteria have been used in assessments like this: such as proximity to major roads, water intake sources, industry / business; public health and safety concerns; reputational damage; or other financial impacts. Several of these were discussed at a risk workshop with the City. However, due to limited source data available and /or schedule, these additional considerations were outside the scope of this assessment. The City should consider addressing these in future assessments. • Major Customers: The City indicated the desire to give higher consideration to top water consumers. However, a reliable list of top 20 consumers was not available. A partial list was considered for use. However, without hydraulic modeling support, only the closest pipe to each top customer would have received a higher score. In reality, numerous pipes should receive higher risk scores based on the hydraulic impact caused by a possible pipe failure along any given pipe segment. Therefore, this criterion was not used. • Proximity to Pumping Station: The concern here is that a failure along one of the primary network feeder pipelines (i.e., near pumping stations) would cause a major impact to the distribution system's ability to supply adequate water and /or pressure. As in the previous topic, this would also require hydraulic modeling support to correctly identify the most critical pipe segments. However, as a reasonable alternative, pipe diameter could be considered. This assumes that larger pipes are more important (not necessarily the closest to the pump stations) and should receive the higher risk ratings. Since this factor was already considered in the CoF analysis, it was not repeated here. • Customer Impacts: The City suggested that a cumulative count of water services associated to each main segment might identify more "important" facilities. To be accurate, hydraulic modeling support would be needed. The other approach would be to consider only the most immediate pipe segments. However, since service lines are mostly on the smaller diameter pipes, the importance of the larger mains would be lowered —thus canceling out the other criteria. Therefore, this criterion was not used. • Proximity to major roads, railroads, industry / business, easements: This assumes that access will be more difficult in some locations and that potential damage impacts would potentially be greater — thus more costly. Identification of key sites (Central Business District, Mall, Civic Center Plaza, and easements), major roads and railroads was considered. However, other than roads and railroads, this source data was unavailable within the schedule. • Depth of Burial: Do not currently have this data — future capability. Overall CoF Calculation To produce an overall CoF score for individual pipe segments, weighted scores for each of the contributing CoF criteria were added together. The resulting CoF scores are, by design, within the range of 0 to 10. Because the Proximity to Critical Customers criteria was considered to be less important than the other two criteria, it received a lower weighting. Therefore, the Pipe Diameter criteria was weighted at 100% and the Critical Customer count was weighted at 0 %. By adjusting these weights other assessment scenarios could be created. Table B - 10 below provides a summary of the CoF criteria used in this analysis. BLACK & VEATCH I Appendix B: Water CIP Prioritization Prn_es- 65B -129 117