GRACIE ROAD INTERTIE
During most years and primarily in the dry-season months, Nevada City’s 1.5 mgd water treatment plant encounters operational problems due to low flow volumes. Both the distribution system and individual structural elements frequently cannot deliver water to maintain system pressure or volume, which causes recharge problems with the storage tanks. Even under normal circumstances, the system often maintains inadequate pressure and does not provide the capacity for peak demand periods. If the water treatment plant suffers even a small failure or temporary closure for repair, particularly during the summer months, the City is unable to provide minimum domestic flows, or adequate flow for firefighting requirements. This can occur within any given 24-hour period, but it most often occurs during dry-season months.
The original project proposal called for the construction of an 8-inch distribution line at the Gracie Road/Gold Flat intersection to intertie the City system directly with NID’s system. This intertie would ensure a backup water supply to the City when treatment plant production is reduced or curtailed. NID and the City initially identified the Gracie Road/Gold Flat intersection as the most appropriate and feasible location to create an intertie.
However, in January 2014, NID and the City identified an alternative solution to the Gracie Road Intertie. NID approached the City with an opportunity to install a tie-in with the Cascade Canal, as part of NID’s program to increase the flexibility of water delivery in low-flow or emergency situations. The City authorized the connection and a 6” outlet meter was installed on the canal in May 2014.
Prior to installation of the tie-in, the City engaged in a formal evaluation of the functionality of this alternative to the Gracie Road intertie project. This analysis determined that the alternative project would meet the objectives of the Gracie Road project, as articulated in the grant agreement, while having the following additional beneficial impact to the City:
- Creates a full tie-in with an alternative water source that would build flexibility and sustainability into the system (i.e., the existing canal service is from the District South (DS) canal which provides water from the Bear River watershed, while the Cascade Canal provides water from the Bowman/Spaulding system in the upper reaches of the Yuba River. Thus, this tie in provides water both from a different canal system and from a different watershed).
- Creates redundancy of source water in case of water shortages in one watershed, or an emergency canal failure/blockage, or interrupted flows in the DS canal
The Cascade Canal tie-in will enable NID to provide the City with up to 2 mgd, which will provide a back-up water supply source during periods of peak demand, system failure, or closure of the City water treatment plant for any reason, and which will supplement firefighting flows in the event of a catastrophic fire.
Current Status (Sept 2016)
The Cascade Canal tie-in was competed in May 2014.
Since the tie-in became operational, it has been used extensively by the City. During the periods of December 2014 through April 2015 and December 2015 through April 2016, the Cascade Canal tie-in supplied water to the City following the seasonal closure of the DS canal. Using the tie-in, the City was able to augment its own water treatment plant supply without having to purchase more expensive treated water from NID (as the Cascade Canal supplies raw water). Additionally, the ability to use water coming from a year-round source protects the City from shortages/outages that may occur on the seasonally operated District South Canal.
City of Nevada City
Catrina Olson, Assistant City Manager, (530) 265-2496 x134, firstname.lastname@example.org
Measurable Physical Benefits
Water Supply , Water Quality