⏵ Course guide · Onion Creek loop, Austin
Tejas Trails runs everything from a 5K to a 50K on the same well-marked 6.5-mile loop at Southeast Metro Park, winding through mesquite and oak woods above Onion Creek, right in Austin's backyard. I will walk you through the loop first, then give you a pacing and fueling plan built for repeatable Hill Country climbing. There are free calculators along the way to dial in your own numbers.
These facts come from the official Tejas Trails event page. Check the current year details, cutoffs, and aid stations before you commit. Race logistics change year to year.
Every distance here runs the same marked 6.5-mile loop, just a different number of times: 5K runs it once, 10K and 13.1 mile twice, and the 50K five times.
Each loop opens with a half-mile of rocky downhill jeep road, then a short two-way traffic section perfect for high-fiving fellow runners heading the other direction. From there the course delivers a steep, punchy climb immediately followed by an equally steep descent, before settling into winding singletrack through mesquite trees and tall oaks along Onion Creek.
The loop rolls through the aid station and the start/finish area every few miles, which means frequent crowd energy, easy crew access, and a chance to reset your fueling and gear on every single lap, a real advantage over a point-to-point course.
This race is a partnership with the Great Springs Project, a nonprofit working to conserve land and build a contiguous hike-and-bike trail across Central Texas by 2036, protecting the water resources beneath these very trails. The Travis County Parks Foundation also supports the event with trail-building volunteers and the finish line party.
With about 640 feet of gain per loop and a 2:30 PM final-lap cutoff, the 50K rewards even effort across all five laps over an aggressive early pace.
Because every loop is identical, a grade-adjusted pace target set on loop one gives you an honest read for loops two through five, minus accumulated fatigue. The steep punchy climb-and-descent section is the same test every time; treat it with the same respect on lap five that you do on lap one.
A finish prediction built off your actual loop splits, checked against the 2:30 PM cutoff for starting your final lap, tells you early whether you have room to relax or need to pick up the pace before the aid station cuts you off from another loop.
⏵ Free tools to pace this course
A 6:30 AM start for the 50K means cool early loops that can warm up by the later laps, so plan your intake to scale with the day rather than stay fixed.
Aim for roughly 60 to 90 grams of carbohydrate per hour, and since you pass the aid station every 6.5 miles, use that predictable rhythm to stay on your numbers rather than carrying excess between loops.
Sodium in the 300 to 500 mg per liter range often covers the cooler early loops, moving toward 500 to 700 mg per liter for the later laps if the Central Texas day warms up as expected.
⏵ Build your fueling plan
Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and an early-March Austin loop course with the free ultra fueling calculator. Browse the rest of the free running tools at the tools hub.
⏵ Train for it with Summit Line
Get a race-day plan built around YOUR fitness, this exact loop climbing profile, and your projected splits. Summit Line reads your real training, builds a plan for repeated loop racing, and rehearses your fueling so race day is something you execute, not guess at.
Each 6.5-mile loop carries about 640 feet of gain, so the 50K, which runs that loop five times, totals roughly 3,200 feet over 32.5 miles, a real but not extreme climbing test for Central Texas. The loop opens with a rocky downhill jeep road, adds a steep punchy climb and descent, then settles into wooded singletrack along Onion Creek, so the terrain varies more than the modest elevation numbers suggest.
Each 6.5-mile loop carries about 640 feet of total gain. The 5K runs one loop (about 640 ft), the 10K and 13.1 mile both run two loops (about 1,280 ft), and the 50K runs five loops (roughly 3,200 ft). The 26.2 mile distance sits between the 13.1 mile and 50K on the same loop structure.
A 6:30 AM start for the 50K means cool early loops that likely warm into a typical early-March Central Texas afternoon by the later laps. Aim for roughly 60 to 90 grams of carbohydrate per hour, and sodium in the 300 to 700 mg per liter range. Because the loop passes the aid station and start/finish every lap, roughly every 6.5 miles, you have frequent, predictable chances to reset your intake rather than carrying large reserves. Build your numbers with the free ultra fueling calculator before race day.
You must be on your final lap by 2:30 PM, and the course closes entirely at 4:30 PM. With the 50K starting at 6:30 AM, that gives roughly 10 hours to reach your last lap and 10 hours to finish overall, a workable window for five 6.5-mile loops if you pace evenly.
The loop starts on a rough jeep road with a rocky half-mile downhill, passes through a short two-way traffic section, then hits a steep punchy climb immediately followed by an equally steep descent. From there it settles into wooded singletrack winding through mesquite trees and tall oaks along Onion Creek before returning to the aid station and start/finish. Early March in the Austin area typically brings mild temperatures, though Texas Hill Country weather can swing warm by afternoon.
Yes, the loop format makes this a reasonable first-ultra choice. You pass the start/finish and aid station every 6.5 miles, so crew access, gear changes, and the mental math of counting down laps are simpler than a point-to-point course. About 3,200 feet of gain over the full 50K is real but manageable climbing, and the roughly 10 hour window gives a well-prepared first-timer genuine room to finish.
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<a href="https://runsummitline.com/guides/great-springs-austin">The Great Springs Trail Race - Austin course guide</a>This guide is independent and for planning only. The course details, dates, cutoffs, and aid stations come from public sources and can change year to year, so confirm the current specifics with the official race before you register or run. The fueling and pacing advice is general and not medical advice.