The All-Out Spring Fever Half Marathon, 10k, and 5k is a multicourse event entering its 12th year, proudly supporting the National Kidney Foundation. Challenging Course. Running alongside Arvada’s Blunn Reservoir using the Ralston Creek Trail, this half-marathon course is known to be a challenge for both beginners and elite runners alike. Nestled in the foothills of Colorado’s Rocky Mountains, Golden is a scenic region of the state, so expect incredible National Park-like views and common sitings of wildlife throughout.