Currently Washington’s distribution system does not meet pressure standards developed to ensure that groundwater and contaminated water intrusion does not affect an entire distribution system. The existing State standard for pressurized water systems is 40 psi . Intrusion of contaminated water into the pipe system would be a particular problem for Washington because of the extensive length of many of the residential lateral service lines and the expense involved in decontaminating the system.
The project will balance pressure between the Maybert Road, Washington, and Relief Hill system components and will increase overall pressure throughout the system. These improvements will result in an increase in water pressure sufficient to meet the current State pressure mandate, reduce the likelihood of system contamination from groundwater intrusion, provide the capacity for the district to install water meters to allow for leak detection and drought water management, and improve the standard of water delivery throughout the community.
Current Status (September 2016)
The installation of all pressure pumps, as well as improvements to associated lateral connections and installation of water meters, was completed in April of 2016. The design was completed by the end of November 2015, with component identification and purchase completed in December 2015. Installation and testing of the pressure pumps took place in the third quarter of 2016.
The original design solution for the low pressure problems in this area of the District called for the installation of two pressure pumps, new distribution lines, and new electrical connections to be constructed. Following preparation of a detailed hydraulic model of the area, an evaluation of the existing distribution line characteristics, calculation of the results of improvements to the holding tank (Project #11- Level Control Altitude Valve Improvements) and the integrity of the lateral connections, it has been determined that a more appropriate solution will be the installation of individual pressure assist pumps at six residences along Relief Hill Road (those on the ‘uphill’ side) with a larger-sized pump to be installed to serve a mobile home park which is also on the uphill side of the road.
Further, it was determined that installation of a complex system would require ongoing maintenance and could increase pressure levels to the point where both individual service laterals and the main distribution line would suffer from service failures and /or pressure-induced rupture and would likely require the installation of pressure reducing valves at each connection. Use of individual pressure pumps and replacement of segments of line associated with these improvements (pressure points) appear to be the best solution for addressing both pressure issues along Relief Hill Road and system integrity in this zone.
City of Nevada City
Bryan McAlister, City Engineer, (530) 265-2496 x126, firstname.lastname@example.org
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