2016/2017 Water Main Flushing

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Water Main Flushing Schedule Update

Through weekly monitoring of the City’s water distribution system, manganese levels above the source water secondary maximum contaminant level (MCL) of 50 parts per billion (ppb) have been detected at the sampling station located on Rockwell Drive in East Davis (SS-037).  

The secondary regulatory standard for manganese in source water (50 ppb) is established to address issues of aesthetics (discoloration), not human health concerns.  Manganese in our source water is below the secondary MCL.  It is suspected that the discolored water and high level of manganese is due to legacy manganese sediment and scale existing in and on the distribution piping system.  The City will be modifying the current flushing schedule to address the area, North of Covell Blvd and East of Pole Line, beginning on January 31 (See Area 5 of the Water Distribution System Flushing Plan Map below).

If you experience discolored water, please flush your service line from a hose bib for a short period to see if the water clears up. If the water does not clear up, please contact the Public Works Office at (530) 757-5686 during regular business hours.  After business hours, contact the non-emergency police number at (530) 757-5400 for assistance.

For more information on manganese you may visit: http://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/Manganese.shtml

Water Distribution System Flushing Plan Map

Water Main Flushing Schedule

Phases 1-7:  Completed

Phase 8: Will be flushed in early 2017

Phases 9 & 10: Completed

(Dates will be updated if the schedule changes - time required for flushing is highly variable depending upon pipe conditions).

Water Main Flushing to Prepare for the Davis Woodland Water Supply Project

The City of Davis Public Works Department began performing water man flushing in Spring 2016 to prepare the water system to receive treated water from the Davis Woodland Water Supply Project. This flushing program follows industry best practices to minimize the potential for red water (typically iron rust from galvanized iron, steel or cast iron pipes) that can occur when a new water supply scours the existing water lines. Red water is not a human health concern, but has the potential to stain laundry. It is anticipated that this water main flushing, while not completely removing the potential for red water as the new water supply is introduced, will reduce the likelihood and severity of red water occurrences.  Find out more information in the Source Water Integration Study (Trussell Technologies Report) commissioned by the Woodland Davis Clean Water Agency.

As a result of the current drought and restrictions on water use, the city’s water main flushing program has been on hold since 2013. Cleaning of water mains has historically been done by flushing water at high velocities through fire hydrants and required large volumes of water. To reduce water loss, the City of Davis will be using a NO-DES process (learn more here http://www.no-des.com) where two fire hydrants are connected through a dual filtering system. Once this loop is created, an onboard pump is used to reverse the normal direction of flow while ensuring the flow rate reaches a minimum of 5 feet per second. The high velocity reached by the onboard pump scours the main, removing any collected sediment. Flushing averages about 15 minutes for each hydrant. The filtered water is then pumped back into the water distribution system instead of draining to a storm drain minimizing the loss of potable water to the storm drain. A chemical metering pump is provided to maintain the distribution system’s target chlorine residual and periodic samples are taken to confirm that bacteriological safety is maintained.

Customers may notice some short term effects during this period, including slight pressure drops, air in the lines or discolored water during the flushing process.  The discoloration is temporary and typically clears within a few hours. It is recommended that residents check their water before use, especially prior to doing laundry, as laundry may become stained. If customers notice these effects, we recommend running cold water for a short time afterward to remove any loosened sediment in the pipeline, possibly saving the water for plants or other landscape needs.

If you have any additional questions, please e-mail PWWeb@CityofDavis.org or call (530) 757-5686.