San Mateo County, CA
The federal environmental record for San Mateo County (population 726,353): what is on file, where it is, and what remains open. Sources and retrieval dates are on the methodology page.
0
Superfund NPL sites
9
federal cleanup sites
1
PFAS-detecting water systems
6
TRI facilities
70
open tank releases
Drinking water: PFAS testing
Public water systems serving San Mateo with at least one PFAS detection under UCMR5. The federal limit for PFOA and PFOS is 4 ng/L; EPA proposed in May 2026 to rescind the limits for the other compounds, which are shown for information.
| System | Highest results | Reading |
|---|---|---|
| GUADALUPE VALLEY MID CA4110005 | PFOA: 9.6 ng/L PFOS: 8.3 ng/L PFHpA: 4.3 ng/L | above final limit |
On a system with detections? Testing and treatment options
Facilities reporting toxic releases (2024)
6 facilities in San Mateo filed TRI reports for 2024, totalling 437 lb released.
| Facility | City | Top chemicals | Total released |
|---|---|---|---|
| CHEMELEX LLC | REDWOOD CITY | Zinc compounds, Decabromodiphenyl oxide | 420 lb |
| US DOE SLAC NATIONAL ACCELERATOR LABORATORY | MENLO PARK | Lead | 9 lb |
| GRANITE ROCK CO REDWOOD CITY | REDWOOD CITY | Barium, Lead | 5 lb |
| UNIVAR SOLUTIONS USA | REDWOOD CITY | Nitric acid | 2 lb |
| CSBIO | MENLO PARK | Acetonitrile, N,N-Dimethylformamide | 1 lb |
| TE CONNECTIVY INC. | REDWOOD CITY | - | 0 lb |
Underground fuel tanks
EPA's UST Finder records 254 tank facilities in San Mateo: 687 tanks in service and 0 closed. 1,338 fuel releases are on record, of which 70 remain open. Open releases are cleanups that have not reached "no further action".
Radon
EPA maps San Mateo as Zone 2, moderate predicted indoor radon (2 to 4 pCi/L average). Radon and air quality are covered in depth on lung.com.
The record for one specific address
County figures blur what matters: distance. The Address Environmental Report runs these same federal datasets against one address and reports every site, tank, polluter and water result around it, with distances, in about a minute.
Get the report - $39All federal cleanup sites on file
The wider Superfund enterprise inventory (SEMS) for San Mateo, including sites assessed but never listed. Presence here records that EPA had reason to look, not a finding of danger.
- DUOLITE INTERNATIONALREDWOOD CITY
- MENLO TECH INC.MENLO PARK
- NAVAL FAC ENGINEERING COMMAND WEST DIVSAN BRUNO
- PALO ALTO HEALTH CARE SYSTEM - MENLO PARKMENLO PARK
- PROTO METALSBELMONT
- RHONE-POULENC, INC./ZOECON CORP.EAST PALO ALTO
- ROMIC ENVIRONMENTAL TECHNOLOGIES CORPPALO ALTO
- SLAC NATIONAL ACCELERATOR LABORATORYMENLO PARK
- USGSMENLO PARK