Mossbrae Springs Improvements Project

The proposed project addresses priority improvements identified in the City’s 2015 Master Water Plan. The City’s water supply is provided through the diversion of a few of the 16 springs that are collectively known as Mossbrae Springs. The remaining springs form Mossbrae Falls, which is directly tributary to the Sacramento River. Water from the springs is of excellent quality and requires no long-term treatment or chlorination at this time; however, emergency chlorination facilities are available adjacent to the spring headworks. The original project included miscellaneous improvements to the City’s water collection system at Mossbrae Springs. In addition, the original project included a new permanent emergency chlorination system located at the Castle Rock Water Bottling facility (APN 059-010-190). The revised project includes the following proposed improvements at the Springs under a two phases. The chlorination system at the Castle Rock Water Bottling facility would not be installed. Phase 1 – Mossbrae Springs Emergency Chlorination • Installation of new emergency chlorination equipment within the existing building and construction of a new chlorination vault on an existing steel water main located at the Springs site. SCADA system improvements would be completed on the existing North Dunsmuir Tank and within the existing emergency chlorination building. • Addition of 4-inch thick gravel fill along the access pathway. In addition to the improvements at the Springs, the project includes updates to the existing SCADA system at the North Dunsmuir Tank, including replacement of the existing antenna and modifications to the existing control panel. Phase 2 – Mossbrae Springs Improvements • Removal and replacement of the existing parallel 12-inch steel water pipes with a single 18-inch steel pipe in the same alignment; • Installation of isolation valves, sample taps, and overflow lines to the existing drainage for each spring; • Replacement of the steel doors on Tunnel 1 and 2 of Spring 2; • Demolition and replacement of the weir building with a concrete retaining wall and a vault containing flowmeters and piping to maintain the existing hydraulics. Existing culverts would be replaced and a new drain box would be installed adjacent to the vault. • Construction of a new concrete box around each of the five existing spring boxes. Holes would be cut through the existing stream boxes to connect the steel pipe replacements. • Addition of 4-inch thick gravel fill along the access pathway.