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Annual Report 2023

Annual Report 2023

Water Quality

Administration

Water
Quality

Achievements

Zone 7 continued to provide safe, clean water to over a quarter-million people in the Tri-Valley, in partnership with our retailers. All water provided not only met, but often performed better than state and federal health standards.

36,000+

water samples collected and tested

in 2022-2023 fiscal year

174

different contaminants monitored

in order to provide high quality treated drinking water

29

different analytical methods used

PFAS Update

Zone 7 is committed to proactively and swiftly addressing Per and Polyfluoroalkyl substances (PFAS) detected in the Tri-Valley’s local groundwater basin in recent years.

PFAS Sources

Regulatory Progress

In March 2023, the US Environmental Protection Agency (EPA) released its proposed PFAS regulations which include maximum contaminant levels (MCLs) for six different PFAS. The regulations are expected to be finalized in the spring of 2024 and water systems would then have three years to be in compliance with the MCLs.

EPA Proposed PFAS MCLs

PFOS
PFOA
PFHxS
GenX Chemicals
PFNA
PFBS
4 parts per trillion (4.0 ppt)
4 parts per trillion (4.0 ppt)
Hazard Index = 1.0 (unities)*
Hazard Index = 1.0 (unities)*
Hazard Index = 1.0 (unities)*
Hazard Index = 1.0 (unities)*

* Hazard Index = ([GenX]/[10 ppt]) + ([PFBS]/[2000 ppt]) + ([PFNA]/[10 ppt]) + ([PFHxS]/[9.0 ppt])

CA Advisory Levels for PFAS

PFAS
PFOS
PFOA
PFBS
PFHxS
Notification Level (ppt)
6.5
5.1
500
3
Response Level (ppt)
40
10
5,000
20
Issued Date/Status
February 6, 2020
February 6, 2020
March 5, 2021
October 31, 2022

Common Names for Types of PFAS

PFOS

https://zone7water.report/2023/wp-content/uploads/sites/2/2023/12/PFOS.png

Perfluorooctane Sulfonic Acid

PFBS

https://zone7water.report/2023/wp-content/uploads/sites/2/2023/12/PFBS.png

Perfluorobutane Sulfonic Acid and its potassium salt - developed as replacements for PFOS

PFOA

https://zone7water.report/2023/wp-content/uploads/sites/2/2023/12/PFOA.png

Perfluorooctanoic Acid

PFHxS

https://zone7water.report/2023/wp-content/uploads/sites/2/2023/12/PFHXS.png

Perfluorohexane Sulfonic Acid

PFNA

https://zone7water.report/2023/wp-content/uploads/sites/2/2023/12/PFNA.png

Perfluorononanoic Acid

GenX

https://zone7water.report/2023/wp-content/uploads/sites/2/2023/12/GenX.png

Hexafluoropropylene Oxide Dimer Acid

Zone 7 Response

Zone 7 has completed design of two new PFAS treatment facilities, both of which made major progress during the 2022-23 fiscal year.  

  • The PFAS treatment facility for the Stoneridge Well came online in September 2023.
  • The treatment facility for the Chain-of-Lakes (COL) wellfield is anticipated to come online in late summer of 2024.  

The safety of our community’s water supply is our number one priority. Our community can be assured that all water delivered to our customers meets regulatory standards and advisory levels.

Water Quality Capital Project Updates

Stoneridge Well
Ion Exchange PFAS Treatment Facility Upgrade

Vessel installation was completed in May of 2023, a major milestone for the overall completion of the Ion Exchange (IX) PFAS Treatment Facility at Stoneridge Well. The new facility removes PFAS from groundwater pumped into the facility to ensure the Tri-Valley community has a safe, reliable water supply.

Stoneridge Well Upgrade Timeline

E

August 17, 2022

Ion exchange vessels purchased
E

October 19, 2022

Zone 7 Board of Directors approves project
E

February 2, 2023

Construction begins
E

May 23, 2023

Ion exchange vessels and equipment are installed at Stoneridge

E

September 2023

Facility goes back online delivering clean, safe drinking water

E

September 13, 2023

Ion exchange grand opening ceremony commemorates new treatment facility

E

Spring 2024

Final construction expected to be complete

Watershed Protection Activities

Living Arroyos

Living Arroyos, the Tri-Valley’s collaborative partnership working to realize a community vision on a healthy watershed worked with partners and community volunteers to:

Remove 3,025 gallons of trash to keep our watershed clean

Plant 100 trees to provide shade, oxygen, soil stability and other benefits

Plant 369 acorns to replenish our oak woodlands which protect soil from erosion

Remove over 1,364 gallons of invasive weeds to keep local habitat thriving

Counting Our Valuable Trees

This year we initiated a new systemwide tree inventory project to assess and inventory individual trees along Zone 7-owned channel maintenance roads and right-of-ways.

Benefits of new tree inventory system
will serve as an asset management tool
help plan for long term sustainability
ensure healthy riparian trees
support a healthy ecosystem including water quality

Sycamore Trees & Water Quality

Zone 7 is nearing completion of a multi-year EPA Water Quality Improvement Fund grant, in collaboration with San Francisco Estuary Institute and H.T. Harvey Ecological Consultants.

Goals
Improve San Francisco Bay water quality and the health and resilience of Alameda Creek watershed
Enhance aquatic and riparian habitat
Advance stormwater planning
Support coarse sediment reuse

Progress in 2022-23 fiscal year

  • Prepared Sycamore Alluvial Woodland Restoration and Enhancement Suitability Study report
  • Completed guidelines for implementing, maintaining, and monitoring a study to restore sycamore alluvial woodland at two locations in Livermore 
  • Collected and installed sycamore cuttings at the study sites
  • Collected and began propagating approximately 700 additional California sycamore cuttings as container plantings

Zone 7 Water Agency – Annual Report 2023

Zone 7 Water Agency – Annual Report 2023