Bad Bass Half Marathon, 10K & 5K

Saturday, July 22, 2023 • Castro Valley, CA • Course Map

Runners follow an out-and-back course for the the “Bad Bass” Half Marathon along a combination of paved and natural-surface trails along the shoreline of California’s Lake Chabot, which doubles both as a drinking water reservoir for the East Bay area and as a recreational park, filled with more than 20 miles of hiking trails as well as the 315-acre lake that draws visitors year-round for fishing and boating.

All three races in the event start and finish at the Lake Chalbot Marina, which lies at the southernmost tip of the lake just off Fairmont Drive.

From there, runners in the half marathon follow a counter-clockwise out-and-back loop route that takes them first northward around the eastern side of the lake, along which runners can expect both paved trails and later natural trails through the woods along the lakeshore.

(Organizers say that over the course of the half marathon, the surface is roughly half paved and half natural trails.)

While the first couple miles of the half marathon course are mostly flat, runners can expect the course to turn hilly between the 2nd and 3rd mile markers as the route heads into the fire trails and hills around the eastern side of the lake.

The hilly stretches continue for roughly the next five to six miles, after which the route descends from the hills around the lake back onto the trails that hug closer to the lake’s shoreline, and bring runners back in to the marina for the finish line.

Like the 10K and 5K races, the half marathon will be open to runners as well as walkers and hikers, who will be permitted to start their race an hour before the official starting time of 8:30 AM (for the half marathon), if they desire to do so in order to complete the race within the event’s 4-hour time limit.

Race Weather & Climate

Located in Northern California’s East Bay, roughly 15 miles southeast of Oakland and about a 25-mile drive from San Francisco across the bay, Castro Valley typically experiences moderately warm and usually dry weather in July, when temperatures range from the mid-50s to the mid-70s.

  • July 22 average low temp: 58ºF
  • July 22 average high temp: 74ºF

Past Results

Course Map

See the race route map for the Bad Bass Half Marathon here.

Starting Time

  • 7:30 AM – half marathon (hikers only)
  • 8:30 AM – half marathon
  • 8:55 AM – 10K
  • 9:10 AM – 5K


  • $90 and up – half marathon
  • $72 and up – 10K
  • $63 and up – 5K


To reserve your spot in the 2023 running of Castro Valley’s Bad Bass Half Marathon, 10K or 5K race, register online at here.

Official Race Website


Ever run in the Bad Bass Half Marathon? Share your impressions here, or post your review in the Comments below.

See more races in: July, California

0 comments… add one

Leave a Comment