The Dublin San Ramon Services District Regional Wastewater Treatment Facility passed a recent heavy rainfall simulation test with flying colors, ensuring the site is ready for the rainy season as crew members continue working there on a $19 million primary sedimentation expansion project.
“It is a good opportunity for the operators to test the actual operation of the primary sedimentation tanks under high wastewater flows versus the theoretical hydraulic model,” operations manager Jeff Carson said in a statement.
Since spring, crews have been working to partially demolish and replace one sedimentation tank and install another, which the district says will help reduce energy costs and improve wastewater treatment. As the district’s largest project since 2000, the site’s currently undersized primary treatment capacity will grow by 33% when work is finished, according to DSRSD.
During the early hours of Aug. 7, operators shut down and diverted incoming wastewater into a holding basin for six hours and for the first time in more than 20 years, then drained the settled sewage channel for inspection. This also allowed workers to adhere a steel trench plate to the north wall of the channel where the wastewater will eventually connect with the new primary sedimentation tank currently under construction.
The channel carries wastewater to aeration basins, where “millions of beneficial microscopic organisms break down dissolved organic wastes in a biological process,” according to DSRSD spokeswoman Lea Blevins.
After completing the shutdown, crew members tested plant operations with three of the tanks at high flows instead of the usual four. Next they used the extra flow in the holding basin to pump in both regular and wastewater flows from the basin as a stress test for the four primary sedimentation tanks currently at the site.
Heavy winter rains can make water seep into cracks in sewer pipes and increase wastewater flows; by replicating the same conditions, DSRSD was able to confirm the facility’s preparedness for the upcoming rainy season.
The expansion and upgrades will leave room for future buildout and give the primary treatment capacity needed for both flows. Blevins told the Weekly that “construction crews are moving progress along swiftly, though with a project as large as this, there can be considerable time between milestones.” Work on the facility is scheduled to finish in fall 2021.
DSRSD is also wrapping up rehab work that’s been taking place since April on a 405-foot-long foul air pipe running from the facility and along Interstate 680. All the pipes are finally in place as well as special dirt and other material used in the biofilter beds -- ”the final stop for the foul air,” Blevins said. This week the contractor will pave the road and install curbs; the district is currently testing the biofilter beds, which involves circulating foul air through for a minimum of 2 to 3 weeks and then making sure the foul air is being properly filtered.