More Info: Test your skills at this year's Mayor's Triathlon. The race begins at 7:30am with a 500 meter open water staggered swim. The second leg of the race is a 13 mile bike ride on parts of the hard surface trail and highways around Walnut Creek. Lastly, a 3.1 mile run on the trail will complete the triathlon. Race is open to ages 15 and up.