Sunday, May 3, 2026 Update #2: Cuesta Water Main Incident

9:15 p.m. Sunday, May 3, Update #2

"Super Chlorination" for Drucilla Drive and Carla Court
As reported in the Sunday, May 3, 3:55 p.m. Update, test results continue to show coliform bacteria in the water line serving homes on Drucilla Drive and Carla Court.

Through Emergency Declaration procurement procedures, the City of Mountain View has engaged West Valley Construction Co., Inc., to begin the process for a "super chlorination" of the pipeline serving the Drucilla Drive/Carla Court area (Drucilla Drive between Leona Lane and Montalto Drive and all of Carla Court). This section of the pipeline serves 23 households.

The "super chlorination" process will involve the following steps:

1. Establish temporary water lines so that each house on Drucilla Drive and Carla Court has access to water during the chlorination period. Note: the "Boil Water" notice will still be in effect.
2. Excavate a hole to physically disconnect and isolate the water pipe at both ends of Drucilla Drive (at Leona Lane and Montalto Drive).
3. Inject a high concentration of chlorine into this closed section of water pipe.
4. Let the chlorine remain in this section for 24 hours.
5. Check whether the residual amount of chlorine in the pipe remains within standard levels.
6. Discharge the chlorinated water in the pipe to the sanitary sewer system.
7. Flush out the pipe section to rid excess chlorine above drinking water standards.
8. Take two rounds of water samples for bacteria, 12 hours apart, with results available in approximately 24 hours from sample time.
9. Once bacteria sampling results reflect that the pipe has been properly disinfected, reconnect the pipe ends at Druscilla Drive/Leona Lane and Druscilla Drive/Montalto Drive.

This work will only be done in the Drucilla Drive/Carla Court area, which is the location of recent positive tests for bacteria.

The work will begin Monday, May 4, in the morning. The duration of the work will depend on the results of the test of chlorine residual levels at Step 5 AND the test for the presence of bacteria at Step 8. The City will keep affected residents updated on the schedule as more information is available.

During the chlorination and testing process, water service will be maintained to the Drucilla Drive/Carla Court households through a temporary connection from a hydrant and above-ground lines. The "Boil Water" notice will remain in effect, and tap water must be boiled for at least 1 minute before drinking, food and drink preparation, making ice, brushing teeth and other consumptive uses. Bathing, showering, hand washing, and running a dishwasher and clothes washer are approved directly from the tap.

For more information, view the State Water Resources Control Board's Fact Sheet on What to Do During a Boil Water Advisory and the 3:55 p.m. Sunday, May 3, Update.

There will be a brief water shutoff to households on Druscilla Drive and Carla Court to make the transition from piped water to the temporary water system. City crews will go door-to-door to notify affected households in advance of this brief water shutoff. When the treated pipe segment is cleared to return to service, the Drucilla Drive/Carla Court households will be removed from the temporary above-ground water service and reconnected to the street main.

Druscilla Drive and Carla Court will remain open to through-traffic.

Other homes in the impacted area, north of Cuesta Park, will not be impacted by this work. The existing water service and existing "Boil Water" notice remain in place.

Latest Timeline for Boil Water Notice for Affected Homes
The City still does not anticipate fully lifting the "Boil Water" restrictions for the affected homes before the weekend of May 9 and 10.

The City will continue to provide resources to the affected residents, which include temporary lodging if needed; temporary shower access at the El Camino YMCA, Rengstorff Park Aquatics Center, and Eagle Park Pool; drinking water delivery service; and meal and incidental expenses reimbursement ($92 per day per resident; receipts are not needed for meals and incidentals).

About the Water Main Incident
The water main breach involved a private contractor that was hired by the City. The Friday, April 24, incident concerned a contamination breach with some cement slurry mix coming into contact with a live water main near the intersection of Bonita Avenue and Cuesta Drive.

Questions or Assistance
For residents in the affected area who have questions, please call 650-903-6081 or email [email protected].

For questions specifically about the temporary lodging program, call 650-903-6081 and press 2.

Stay Informed
To receive updates via email on the Cuesta Water Main Incident, subscribe to "City News" at MountainView.gov/eNotify.

For more information, including resources for residents, visit MountainView.gov/CuestaWaterMain.

Next Update
The City will issue the next incident update when new information is available.

Media Inquiries
For media inquiries, email [email protected] or call Lenka Wright, Chief Communications Officer, at 650-903-6615.