Bailey Civil Engineering PO Box 280, Pioneer, CA 95666 –
[email protected] – (209) 256-6510
Executive Summary The Amador Water Agency (Agency) was established in 1959 for the purpose of providing water and wastewater services to Amador County. The Agency has 4 service areas: CAWP (Central Amador Water Project), AWS (Amador Water System), Lake Camanche and LaMel Heights. The CAWP system provides water to over 1/3 of the Agency’s total customer connections. The primary tank in the CAWP system is Tank A, with a 500,000 gallon nominal capacity. Nearly half of the CAWP customers are served from the Tank A distribution system, which consists mostly of severely undersized piping constructed when fewer customers were on the system and the ability for a distribution system to provide fire flow was less of a concern. The pipelines that serve water to customers in the Tank A system are nearing the end of their useful lifetime and flows from fire hydrants in some areas can severely reduce system pressure or even create negative pressure in the pipelines. Very low or negative pressures can result in contaminants entering the drinking water. The recent CDBG Pioneer Water Rehabilitation Project was the first step in addressing these undersized lines and contamination potential, however, the new pipeline for that project was installed nearly 2 miles from Tank A, beginning at Tank C and proceeding downstream. The critical next step will be upsizing the main pipeline from Tank A to Tank C to ensure adequate system pressure and security in all conditions. Without this completed step, the flow available downstream of Tank C is entirely dependent on Tank C’s storage. Due to its age and condition, Tank C is not reliable storage. Phase 2 Design
Water modeling completed in 2014 during the pre-design for phase 1 of the Pioneer Water Distribution System Improvement Project showed based on the best available data that replacement of existing distribution system piping from Tank A downstream with new 12” pipe could provide 1,500 gpm fire flow capacity along most of this new pipeline. This analysis is detailed in the phase 1 technical memorandum. The critical design point for phase 2 is Mt. Misery Lane, at approximate elevation of 3,489’, the highest point between Tank A and Tank C. Previous survey work determined Tank A’s outlet to be 3,532.3’ and overflow to be 3,562’. 1,500 gpm of flow results in 7 psi of friction head loss between Tank A and Mt. Misery Lane. Based on elevation data available, there will be greater than 20 psi residual pressure with 1,500 gpm fire flow and a 12” ductile iron pipeline, depending on Tank A’s operating level. Any smaller pipeline between Tank A and Mt. Misery Lane will result in ultimate capacity less than 1,500 gpm. A larger pipeline will add cost and will not provide significant additional residual pressure due to the minimal elevation differences between Tank A and system high points. An elevated tank at the Tank A location could overcome these elevation issues but is likely cost prohibitive. Elevations should be confirmed after a design survey is completed. 2
Bailey Civil Engineering PO Box 280, Pioneer, CA 95666 –
[email protected] – (209) 256-6510
Until the pipeline is upsized between tanks A and C, any other downstream improvements will provide no benefit. Phase 2 of the Pioneer Water Distribution System Improvements will consist of approximately 9,600 feet of new 12” pipeline from Tank A to the new PRV station in Buckhorn Ridge Road at Deadwood Court and a new PRV station at or near North Cedar Heights. New fire hydrants would be placed along this new distribution main and connections to the existing distribution system branch lines would be made in multiple locations.
Ductile Iron Pipe will be used for the new pipeline due to longevity, ease of tapping and strength. The new pipeline will be located in the roadway with 30”-36” of cover. The pipeline will be constructed in accordance with the Agency’s standard trench detail SW002, shown in Appendix A. Phase 2 Alignment
The Phase 2 pipeline will proceed out of Tank A, approximately 500’ west on Elkhorn Court, approximately 450’ south on Deer Trail, approximately 575’ west on Oxbow Road, approximately 500’ south on Prospect Place and approximately 7575’ west on Buckhorn Ridge Road to the intersection of Deadwood Court and Buckhorn Ridge Road where it will connect to the existing pressure reducing station constructed as part of phase 1 improvements. Tank C’s elevation was established by previous survey as 3192.77’. The elevation difference between Tank A and Tank C provides over 150 psi immediately upstream of Tank C without pressure reduction, unsuitably high for distribution system piping. The project will include replacement of the existing North Cedar Heights PRV station in order to mitigate this. Upon completion of design survey for the project, the exact location of the replacement PRV station can be established. There may be a more suitable location for this PRV station than its current North Cedar Heights location. If North Cedar Heights is determined to be the best location, the new PRV station will likely be located in the roadway of North Cedar Heights Drive.
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