Field Dispatch #3 - Like Frosting on a Cake

Field Dispatch is a blog series from the Santa Cruz Mountains Trail Stewardship (SCMTS) that gives you a behind-the-scenes view into the world of professional trail building from right here in the Santa Cruz Mountains. Through this monthly series, you’ll learn about in-depth trail building techniques from our expert SCMTS Trail Crew and project managers who specialize in environmentally-minded trail construction and maintenance. We’ll cover many unique skill sets, including everything from building retaining walls with rock, designing new trails with geographic information systems, to crafting the perfect berm. We hope you enjoy it!

Suggestions for techniques or skills you’d like to learn about? Submit a request to Emma Ussat ([email protected]).

Typical trails, jumps, and bike features all share a common weakness - given enough time, tire traffic, weather, and general use, dirt features will erode back into the earth. While artfully sculpted dirt jumps, or sweeping tacky dirt trails are amazing to enjoy on a bike, the SCMTS Trail Crew knew that with the constant erosion and wet weather issues we experience here in Santa Cruz, paved pumptracks were the natural choice for a fun, future-proofed pumptrack experience. The Ramsay Park Pumptrack was the first project where we dove into the world of asphalt - and we learned quite a bit in the process. Read on for a peek at how our team implemented forward-thinking and innovative design solutions into our work at the Ramsay Park Pumptrack, and how we plan to give the loved-to-death Westside Pumptrack in the City of Santa Cruz the same treatment.

Asphalt is a proven surfacing solution for top-of-the-line pumptracks built around the world. Unlike dirt, pavement requires minimal maintenance, has less rolling resistance, and provides exceptional grip. This creates a better riding experience, and enables users to connect lines and features that would have been impossible on a dirt track. An asphalt surface also opens up pumptracks to a variety of user groups - skateboards, scooters and rollerblades can all enjoy the benefits of a smooth-as-butter asphalt track. Now, you may be asking yourself the same question that many engineers and professional contractors did, “How do you take a material like asphalt, designed to be laid flat on roads, and pave it vertically?”

Sore backs and toughened hands was the answer. There’s no way around it - an intense amount of manual labor is needed to pave a pumptrack like the one in Ramsay Park. The Trail Crew hauled over five hundred thousand pounds of hot asphalt day after day, one wheel barrow at a time, all while meticulously hand sculpting the track features. But before we dive too deep into placement, let's talk a little bit about the preparation and building blocks needed to construct a pumptrack like this.

Phase I of the Ramsay Park project consisted of demolition and exploration of the subsurface. Just like building a paved road or highway, we wanted to make certain that the jobsite was supported by competent subsurface soil. Parts of Ramsay Park had previously been part of the greater slough wetlands and adjacent areas, so the native soil we encountered ranged from marshy clay or sand-clay mixtures. Unconsolidated areas that were over saturated from old broken irrigation required over excavation and placement of geotextile fabric. This is done to mitigate uneven settlement across the entire track sub-base.

One of the hardest things about designing a track of this magnitude is planning out the “guts” of the project before we start building it up. With the help of volunteer crews alongside our Trail Crew, we installed a underground drainage system consisting of 13 islands where water would shed off the track and drain into the local stormwater system.

Once the foundation of the track was prepared, we began the major work of building up the jumps, rollers, and berms. To make sure the asphalt surfacing was prepared to the same standard as a roadway, we imported nearly three thousand tons of granular base rock. Each section of the track was compacted in eight-inch layers with a five-ton single-drum vibratory roller. The track was then built up vertically (think layers of a cake), then each feature was carved out to maintain the structural integrity of the engineered fill. To make sure our features would withstand the test of time, the compacted berms, rollers and jumps were then tested with a nuclear density gauge and signed off by a geotechnical engineer. Of course, beyond the technical side of things, each feature was rigorously tested by the SCMTS staff to ensure flow and perfect alignment before the track was set in stone.

The rest of the process is best told through pictures - take a peek at the paving process, which spanned a full week for this extra-large track, through the photos below. This was one of the hardest weeks of work that our Trail Crew ever experienced, and we couldn’t be more proud of the results.

Once asphalt reaches the jobsite, the clock is ticking to get the material on the ground and compacted at high temperatures. As asphalt cools, it becomes unworkable and will “unravel” or spoil. We used infrared thermometers and propane torches to make certain the asphalt stayed at temperature prior to compaction. We also used rakes to maintain a minimum of 2.5-inches of thickness blanketed across the entire track surface.

Each berm received a thickened edge at the bottom and an apron of asphalt over the top. Asphalt is a “live” material, meaning that with age it will be shaped by gravity, extreme temperature, and use. By building up the edges of each berm, we will help mitigate wear and tear in the future. We also made sure to apply a fog seal and slurry coat to seal to help bind together the asphalt while it matures.

Once the seal coats dried, there was really only one thing that everyone on the Trail Crew wanted to do - get in a few laps! Along with the rest of the Trail Crew, I hoped on my bike and gave the track a whirl. It’s fast, fun, and oh-so smooth. If you haven’t yet visited the Ramsay Park Pumptrack, we highly recommend a visit to Watsonville to check it out! Check out the video below for a peek at how the project came together.

Want to see a paved pumptrack in the City of Santa Cruz? Support our rebuild of the Westside Pumptrack to help us redesign, rebuild, and yes, pave, this beloved neighborhood hotspot. With 28 new features suitable for cyclists, skateboarders, scooterers and roller skaters, the new Westside Pumptrack will bring fun to wheel enthusiasts of all types, ages and skill levels. We’re slated to begin this work in the months ahead, and are so close to our fundraising goal! Help us bring a new community resource to life by supporting the Westside Pumptrack today.

Thanks to the following sponsors for making our Ramsay Park Pumptrack work possible!

• Bell Helmets

• Shelton Pipe

• Sierra Azul Nursery

• Delta Bluegrass, Co.