Wednesday, August 24, 2011

Construction Progress: What a Difference a Year Makes!

Construction for the Sunol Valley Water Treatment Plant Expansion Project is moving forward rapidly and is now 44 percent complete. This summer the contractor has made significant progress. The contractor has finished all preparations and started micro-tunneling underneath Alameda Creek to build a new pipeline that will connect to the treatment plant. Also crews have made significant progress with the new 17.5 million-gallon circular treated water reservoir, including completing the installation of the concrete floor slab. Inside the treatment plant, a new treatment train is beginning to take shape. All of these elements together will help boost the overall efficiency of the treatment process at the facility, improving reliability and water quality.

See the photos below that show progress on the treated water reservoir that will act as a balancing reservoir for water as it leaves the plant:

September 2010

The early stages of excavation for the treated water reservoir

August 2011

The treated water reservoir takes its circular shape

Treated Water Reservoir Construction By the Numbers:
• 400,000 cubic yards of soil removed to construct it
• 40,000 cubic yards of concrete to build it
• 1,482 soil nails to secure it
• 1,160 piers drilled underneath it for seismic safety
• 2-3 feet thick floor slab installed

Friday, August 12, 2011

Sustaining the Environment at the New Irvington Tunnel

The seismic upgrade and expedited delivery of the New Irvington Tunnel is crucial to maintaining a consistently reliable, high-quality water supply for 2.5 million Bay Area residents. Engineers and construction and mining professionals work daily to achieve this goal. The San Francisco Public Utilities Commission (SFPUC) is equally committed to remaining environmentally responsible, and is working in collaboration with environmental scientists to ensure the work is done in a timely manner and environmentally sustainable manner.

Before construction could begin at any of the three tunneling sites, the SFPUC took numerous measures to ensure that environmental impacts are kept to a minimum on the project sites. One measure used to protect wildlife is to install wildlife exclusion fencing around each of the work sites. The black 4-foot high fabric fencing deters wildlife from entering the construction sites and is monitored for its integrity on a weekly basis.

The fence won’t discourage all wildlife. For our winged neighbors, an environmental monitor scours work sites for any signs of nesting birds. Initially, monitors try to discourage birds from establishing nests on site. However, if they encounter a completed nest, construction zones are altered or activities are postponed in that area until all the nesting birds have fledged or left the nest.

Protections against erosion and storm water run-off are also required. On the exposed slopes at all three tunneling sites, workers laid down wattles ( which are woven netted tubes filled with straw) to help prevent soil erosion. Wattles are laid down perpendicular to the slope, and when combined with other practices (such as mulching), prevent or slow down the effects of stormwater runoff.

Mulch is also applied to the hillsides to prevent erosion, through both a process called hydro-mulching and by manual methods. Hydro-mulch, which consists of recycled natural fibers combined with a tackifying agent, is sprayed onto the hillside and coats the soil. Straw is also manually laid down onto the slope. To help the vegetation grow, seed is added to the mulch mixture and applied to the slope through a process called hydro-seeding. As the vegetation grows, the mulch decomposes into the soil and the vegetation itself stabilizes the slope and prevents rain from directly falling on the soil and producing erosion.

Finally, all three of the tunneling sites are monitored daily by SFPUC environmental inspectors and specialty monitors. They verify that workers are in compliance with the environmental standards set by the SFPUC and environmental permitting agencies to maintain a healthy environment!