Common questions.
- Is Union Island Drain @ Bonetti Rd safe to swim today?
- Union Island Drain @ Bonetti Rd is currently inconclusive for swimming. Last sample is over 30 days old — too stale to be a reliable swim-safety indicator.
- When was Union Island Drain @ Bonetti Rd last tested?
- The most recent water-quality sample at Union Island Drain @ Bonetti Rd was collected on Sep 24, 2025 (251 days ago). California monitoring agencies test Bay Area beaches weekly during swim season (roughly May through October).
- What is the bacteria level at Union Island Drain @ Bonetti Rd?
- The latest reading at Union Island Drain @ Bonetti Rd shows E. coli at 8 MPN/100mL (EPA single-sample limit: 235).
- Does rain affect water quality at Union Island Drain @ Bonetti Rd?
- Yes. Heavy rainfall washes bacteria and pollutants from land into the water, raising contamination risk for 24–72 hours. The past 48 hours recorded 0.00 in of rain; the past 72 hours recorded 0.00 in. Our advisory threshold is ≥1.00 in over 48h (or ≥0.50 in over 72h) for enclosed or storm-drain beaches.
- Where is Union Island Drain @ Bonetti Rd located?
- Union Island Drain @ Bonetti Rd is located in the East Bay area of the San Francisco Bay region (coordinates: 37.8717°N, 121.5255°W). You can get turn-by-turn directions via Google Maps or Apple Maps directly from this page.
- How is the water quality data for Union Island Drain @ Bonetti Rd collected?
- Bacteria samples are collected by California state and county health agencies under the AB 411 Safe-to-Swim program and reported to the state's Safe-to-Swim database (data.ca.gov). Rainfall figures come from Open-Meteo forecast and archive data. Bay Area Swim aggregates both sources and updates every morning.
Also nearby
Data: California Safe-to-Swim (ODbL 1.0) · Open-Meteo — Precipitation (CC-BY 4.0) · Pipeline status