It was an unseasonably warm autumn day when I pulled into French Regional Park in Plymouth, Minnesota. The fall colors were near peak–a perfect day for a hike–but instead I was there to meet with friend and fellow cyclist, Jay Thompson. Jay is a project manager for Three Rivers Park District, a 21-park, 27,000-acre system in the Minneapolis/St. Paul western suburbs. French Regional Park is home to the Three Rivers’ Field Operations Center, which is where I was headed.
Jay had agreed to sit down with me to discuss one of Three Rivers’ most recent success stories; 12.7 miles of single-track mountain bike trails at its Elm Creek Park Reserve, and more specifically, the technology and sustainability techniques that went into their development.
Here at Three Rivers, we are in the business of recreation, but we’re also in the business of conservation, and because of that, we needed to focus on sustainable design.
Located just north of Maple Grove, Elm Creek is the crown jewel of the park district with its 5,500 acres and endless list of amenitites. Because it covers more than 1,000 acres, Elm Creek is considered a park reserve, a designation that protects 80% of its land as wildlife or nature preserves. Only 20% of a park reserve can ever be developed.
Guided by satellites
When I arrived at the field operations center, Jay was just returning from conducting an erosion audit of the trails at Lake Rebecca Park Reserve. I commented that I though the GPS unit he was carrying would have looked more, well…impressive.
“The GPS we used in the past looked something like this”, Jay replied as he opened a desk drawer and pulled out a large yellow bag. “This backpack housed the GPS receiver and had a mast with a big Frisbee antenna on top. Now the same accuracy is built into this handheld unit.”
Three Rivers uses two different grades of GPS receivers: map-quality and survey-quality. “The more expensive, survey-quality units used by the development department for laying out property lines and such has to be ‘gnats ass’; it has to be right on,” Jay explained, “while the map-quality units we use for laying out or recording trails has sub-meter accuracy which is plenty accurate for our purposes.”
Jay stood up and pointed to a map of the new Elm Creek mountain bike trails hanging on his wall. “This line is close enough for what we need to know about this trail on this map. We could spend a lot of money on survey-quality equipment and the map you’d see wouldn’t look altogether different. This line represents a single-track trail about 18” wide. If drawn to actual scale, it would be hair-thin, so there is already some error introduced because of its width on the map just to be visible.”
Working hand in hand with the GPS is the Geographical Information System (GIS) software that Jay uses to create both public and internal development maps used by the park district. “We create our own custom contour maps from data collected by aerial flights over these areas in the 80s and 90s. We’re able to do anything from 10’ contours to what I used here; 2’ contours. The reason I like to use 2’ for the development of trails is that the map almost becomes 3D as the contours gets steeper. Another reason is that Elm Creek only has 60’ of elevation from its lowest point to its highest point, so if I used 5’ or 10’ contours, you’d see very few lines.”
Mapping it out
These contour maps were the first step in the single-track trail design process at Elm Creek. Jay explained, “I started by drawing my lines–which represented the trail–on the contour map. We then downloaded these lines to the GPS unit, headed out into the field, and followed the lines on the GPS. We used ribbon tied high in trees to flag the trail, creating a corridor that we were going to work within, say 20-30’ on each side.”
“This was our first pass, because on the map you don’t see trees and small features on the ground like rocks. Once you get out on the trail you’d say, ‘well there’s an interesting tree or landform we’d like to go around,’ and basically tweak the trail within this corridor. Once the trail was completed, we went back out and remapped the trail with the GPS.”
“With the old-school way of doing it, we’d go out there with a clinometer–a device for measuring grades. We’d then just start going through the woods saying, ‘let’s try this way or let’s try that way.’ The advantage of doing it with GPS is that we lay out our entire trail system before we even hit the ground.”
Design, planning and funding of the Elm Creek trail started in the fall of 2009. Three Rivers chose the sustainable recreational trail building company, Trail Source, of Rosemount, Minnesota for a majority of the actual trail construction. A grant received to help in the construction cost of the trail required the involvement of a nonprofit organization, so the Minnesota Off Road Cyclists (MORC) stepped up to the plate. They constructed what is considered to be an advanced, 2.4-mile section of the trail with in-kind labor. Trail construction began in the fall of 2010, halting over the winter, and then finishing up spring of 2011. The trail opened to cyclists that June.
The path to sustainability
When designing the new mountain bike trails, Three Rivers wanted the system to be environmentally sustainable. “Up to this point with all our trails, no thought was given to sustainability when they were designed. It was just, ‘let’s plow a trail through here and up that hill and over there,’ and because of this, every park has areas with sections of wash-out.”
“Here at Three Rivers, we are in the business of recreation, but we’re also in the business of conservation, and because of that, we needed to focus on sustainable design.” To accomplish this, they enlisted the help of the International Mountain Bicycling Association (IMBA), a member of the Professional Trail Builders Association (PTBA). Three Rivers followed trail-building guidelines developed by these two organizations to ensure there would be very little impact on the surrounding environment.
The ability to see detailed elevation plots on a map is the foundation for developing a sustainable trail system. “A fall line is the way water runs down an embankment. We’re trying to avoid fall lines because then the water finds and follows the trail, causing erosion. Our sustainability guidelines state that no trail will traverse up or down a slope at greater than half its grade. This ‘half rule’ is designed to get the water to run across the trail, not down the trail. You also want to build in grade reversal–a lot of ups and downs–so that if water does get on the trail, it’s not going to run along that section for long.”
Besides water runoff, mountain bikes themselves can be a source of trail erosion. The Elm Creek single-track trails close when conditions are too wet, minimizing ruts caused by the bike tires cutting into the soft ground. Sharp corners and hillsides can also be victims of erosion from the bikes. “Over time, a trail can increase in width on its downhill side and in corners as cyclists creep off the trail.” Sustainability guidelines call for the use of natural boundaries such as trees, large rocks and logs to ‘pin’ the trail in place and keep it from expanding. “I explain to people when they look at a trail map that it may look very random–the way the trail goes–but there is quite a bit of engineering that goes into it–where a trail goes and why it goes there.” states Jay.
One of the most unique features of the trail system is a 2.2-mile section of the trail designed to be accessible by 3 and 4-wheel adaptive mountain bikes used by those with disabilities. This section of trail averages 4 feet in width and narrowing in section to 36”. The trail base is relatively firm and smooth, but bikes with at least a 20” diameter wheel are suggested for softer, rougher sections.
As our conversation came to a close, Jay paused, “To come by the trailhead parking lot in the evening and see it packed with cars and people is very satisfying. It’s the most satisfying project I’ve ever done. To see the cross-section of people…I’ll stop to talk to someone I know, and at the same time I’ll be watching people, and I’ll say to myself, ‘you know, you’re a 70 year-old woman and you’re just out on a mountain bike riding the trail alone. What prompted you to do that?’ Or, I’ll see a mom and dad coming off the trail on their comfort bikes and I’ll think, ‘Really…you just rode that whole trail?’ I mean, I expected to see typical mountain bikers out there, but never thought I’d see such a wide variety of people enjoying the trail. It’s very satisfying.”
If you would like to check out the Elm Creek single-track trails for yourself or find information on any of the other Three Rivers Park District locations, visit www.threeriversparks.org.