Citizen Water Quality Monitoring

The Test Sites

Samples are collected from 11 locations along the main stem of the Arroyo Seco. These sites were established by the Los Angeles County Department of Public Works as being important for determining the condition of the stream in general. You can view a map of them here.

  • Confluence — The site where the Arroyo Seco joins the Los Angeles River, near Downtown Los Angeles.
  • North Branch — A major tributary that flows through Sycamore Grove Park in Northeast Los Angeles.
  • Arroyo Seco Golf Course — The base of the northern end of the Arroyo Seco bike trail.
  • San Rafael Creek — The creek coming from Johnson Lake in Pasadena that enters the Arroyo just north of the South Pasadena city line.
  • BFI Lower Arroyo Park — The low flow streams in Pasadena's Lower Arroyo.
  • Slime Slide — The area under the Colorado Street Bridge where the concrete channel meet the natural soft bottom.
  • Seco Street — The storm drain system that drains much of Northwest Pasadena and enters the Arroyo near Brookside Park, just south of the Rose Bowl.
  • Flint Canyon — The Arroyo tributary that drains La Cañada Flintridge and meets the Arroyo northwest of Devil's Gate Dam in Hahamongna Watershed Park.
  • Altadena Drain — The storm drain outlet from Altadena near the top of the Hahamongna Basin.
  • Millard Canyon — The first major interface between natural and urbanized parts of the watershed.
  • El Prieto — The canyon near the Forest Service's homes above the Hahamongna Basin. This is the most natural site we test at.