MATERIALS AND PRECEDENTS

Porous Asphalt

An alternative to conventional asphalt, porous asphalt shows great promise as a surface for multi-use paths. The combination of increased drainage ability with a firm and stable surface means that porous asphalt is both more environmentally friendly and still suitable for ADA paths. A study done by the USGS in 2018 showed that porous asphalt may help filter pollutants and sediments out of stormwater (Selbig, 52). In addition, porous asphalt retains heat longer in the winter than conventional asphalt; this, combined with the require less ice and snow removal (51).

This trail, located in Hadley, MA, is a fully accessible 1.2-mile trail that passes through a variety of natural systems including forest, grasslands, and river lands. The main part of the trail ability of water to flow into the surface, means that porous asphalt is likely to

is surfaced with crushed stone, but extensive portions of the trail cross through wetlands via boardwalks. This trail was built with the aid of a youth conservation corps, providing valuable education and volunteer opportunities for local teens. The process of building the trail took four summers and was completed in the fall of 2014. Now, six years later, the trail is a favorite with locals for birdwatching and wildlife sitings, and a place for children, the elderly, and the mobility-impaired to experience a beautiful natural trail.

For further information: www.gazettenet.com/Archives/2014/07/ trailswork-hg-073014

www.kestreltrust.org/places/fort-river-trail $10-15 more per ton than regular asphalt, the removal and winter maintenance costs • Less cracking. After two years of daily use and enjoying both the fully accessible firm and compared to regular asphalt, leading to less maintenance was required. In 2001 the City of Woodinville developed a master plan for a city park that contained several wetlands and a creek used by endangered salmon. Part of the design was a trail system that included 1,470 feet of trail within the wetland buffers, with viewing platforms. This was intended to be used as both a recreational trail and an outdoor classroom. After much research, the city decided to use recycled plastic lumber instead of treated lumber, to reduce harmful impacts to the wetlands and stream. This lumber is 100% recycled and reinforced with fiberglass rebar, making it stronger than wood. This allowed the joists to span greater lengths than traditional wood, which reduced the cost of installation, and will last longer than wood, further reducing overall costs. The boardwalk itself was installed with the help of volunteers, and was completed in 2008. The local Rotary Club promised to manage and maintain the park and trail system.

For further information: www.americantrails.org/resources/a

Case Study: Pheasant Branch Creek Corridor Trail, Middleton, Wisconsin

What: A project to improve an existing 1.2-mile community trail system that connects two major roads as well as two schools.

Why: The existing crushed rock surface suffered from flooding, erosion, washouts, steep grades, blind corners, and three stream crossings that made it impassable in the winter.

How: The trail was regraded and widened to 10’ with a 4’ crushed limestone shoulder, and the entire trail surface was paved with porous asphalt.

Benefits reported by the city:

The trail used recycled materials, which were sourced locally. Faster snow and ice melting and less winter • Protection of wetlands and soil health, both by slowing runoff and by filtering pollutants. • Competitive price: while the porous asphalt cost porous material spread 10-12% farther, making the overall difference in price negligible. • Easier to maintain: the reduction in snow amounted to $3,500 per year compared to regular asphalt trails. The trail is cleaned twice a year with blowers or sweepers to remove leaves and dirt. cold winters, the trail had no cracks and still looked brand new. • Trail users have given positive feedback, stable surface and the 20% reduction in density tale-of-a-trail-boardwalks-for-woodinville

stress on runners’ joints. For further information: www.americantrails.org/ resources/porous-asphalt-shows-advantages-fortrail-surfacing

Boardwalk with Helical Piles

Of the alternative footing options available for boardwalks, helical piles make the most sense in terms of low environmental impact. Because they are narrow metal rods, screwed directly into the ground, they disturb a minimal amount of ground and do not impact wildlife. They also don’t require grout or other potentially polluting additives, and are quick to install. They are stable even in soft soils and can be installed in areas with limited maneuvering space.

The boardwalk itself should be elevated high enough to ensure adequate sunlight reaches the vegetation beneath. The gaps between the planks should not exceed 1/2 inch. Narrower boards will leave more gaps, which increases the amount of sunlight that shines through.

For more information about helical piles: contecompany.com/wetland-boardwalkconstruction-in-a-fragile-eco-system