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Ground Water
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Sole Source Aquifer
The EPA's Sole Source Aquifer (SSA) Program was established under Section 1424(e) of the Safe Drinking Water Act (SDWA.) Since 1977, it has been used by communities to help prevent contamination of groundwater from federally-funded projects. It has increased public awareness of the vulnerability of groundwater resources. The SSA program allows for EPA environmental review of any project which is financially assisted by federal grants or federal loan guarantees. These projects are evaluated to determine whether they have the potential to contaminate a sole source aquifer.
In Region 9, nine sole source aquifers have been designated:
| State | Sole Source Aquifer Name | Federal Reg. Cit | Publ. Date | GIS map |
| AZ | Upper Santa Cruz & Avra Basin Aquifer | 49 FR 2948 | 01/24/84 | (PDF) (1pg, 263K) |
| AZ | Bisbee-Naco Aquifer | 53 FR 38337 | 09/30/88 | (PDF) (1 pg, 113K) |
| CA | Fresno County Aquifer | 44 FR 52751 | 09/10/79 | (PDF) (1 pg, 618K) |
| CA | Santa Margarita Aquifer, Scotts Valley | 50 FR 2023 | 01/14/85 | (PDF) (1 pg, 89K) |
| CA | Campo/Cottonwood Creek | 58 FR 31024 | 05/28/93 | (PDF) (1 pg, 112K) |
| CA | Ocotillo-Coyote Wells Aquifer | 61 FR 47752 | 09/10/96 | (PDF) (1 pg, 74K) |
| GU | Northern Guam Aquifer System | 43 FR 17867 | 04/26/78 | (PDF) (1 pg, 170K) |
| HI | Southern Oahu Basal Aquifer | 52 FR 45496 | 11/30/87 | (PDF) (1 pg, 170K) |
| HI | Molokai Aquifer | 59 FR 23063 | 04/20/93 | (PDF) (1 pg, 146K) |
A map of all nationally designated SSAs is also available.
For more information, please contact the Ground Water Office at
415-972-3542 or visit the national EPA Sole Source Aquifer Program site.
Outreach documents
Sole Source Aquifer Fact Sheet (PDF) (1pg, 34K)
Contact information
See the Sole Source Aquifer section of the Ground Water contacts page.