Groundwater Monitoring Program Update

The New Irvington Tunnel project team is currently monitoring some local groundwater decline. So far, four properties south of the Sheridan Valley project area have been affected. It appears that these declines are related to tunnel construction and dewatering activities. We have initiated mitigation measures at each property and we are maintaining their water supply.

Our commitment to protecting the groundwater in Sheridan Valley has not changed. If tunnel construction causes a decline in groundwater levels that affect an individual’s property, we will initiate the contingency measures defined in each site-specific Groundwater Management Plan. The project team continues to keep a close eye on groundwater levels and will take appropriate actions to maintain water supply.

If you notice any change in your water system, please contact the SFPUC’s 24-hour Answer Line (866.973.1476). Contacting the answer line will ensure the appropriate team members respond to you in a timely manner.

Should you have any questions or concerns, we will host question and answer coffee sessions next week:

Thursday February 9
4:00 PM to 6:00 PM
Sunol Jazz Café
11986 Main Street
Sunol, CA

Friday February 10
7:00 AM to 9:00 AM
Sunol Railroad Café
11882 Main Street
Sunol, CA

If you cannot attend either of those sessions, please contact Francis Zamora at 925.232.4059 or fzamora@sfwater.org. We are always available to answer questions and address your concerns.

Four Steps to Protecting Water

A hydrogeologist collects groundwater data

In the hills between Sunol Valley and Fremont, the water that flows between the cracks and faults underground is worth more than gold. For nearly every property owner, it is their only source of water for drinking, agriculture and fire protection. It goes without saying that residents are very protective of their only water supply.

In the late 1920s, the construction of the existing Irvington Tunnel caused water levels in many wells, ponds and springs to drop. Fast forward to the present day and now you have an aging water system in serious need of a seismic upgrade. How did the New Irvington Tunnel project team come up with plan to protect water supplies? Here are the 4 steps:

1. Understand the problem – “We understand the problem” said the project manager and engineers. Hydrogeologic experts were hired to study the groundwater table, and quantify and forecast the problem with a sophisticated groundwater model. Using the model the project team has identified which residents may be affected and developed measures to offset any possible water supply interruption for each resident. "We are concerned about the loss of groundwater too!”

2. Share your knowledge – “Tunneling techniques have greatly improved over the past 80 years” said mining engineers and tunnel designers. Our team of experts described to the public how probe drills bore ahead of tunnel excavation to find pockets of water. If water is found, these holes are filled with grout keep the water from flowing into the tunnel.

3. Come up with a plan – “What if I still lose water?” asked many property owners. A groundwater management program was developed by the project team. In addition to water monitoring, each property owner received a site specific plan detailing the steps the project team will take to prevent an interruption in water supply.

4. Keep your commitments – No matter how well the first three steps were received this last step is what people will remember. Did we do what we said we were going to do? The jury is still out, however, since we started the program hydrogeologists have monitored water levels and shared the information with property owners. Regardless of the time of day or day of the week the project team responds when a property owner thinks there is an issue with their water supply. This week, construction crews are installing measures designed to prevent an interruption in water supply.

The project team’s work is far from complete, however, the groundwork has be laid to protect local water supplies. As tunneling progresses, groundwater monitoring will intensify and the team will continue to be ready to respond.