Greenway Features that Impact Cost
Several greenway features may not be identifiable at the planning level but can have a significant impact on the overall cost, particularly if they are higher than average or higher than anticipated. These features have been incorporated into the cost estimates at a high level, but in practice they can vary and influence different aspects of the project. Below are some ex- amples based on current practices: • Stormwater drainage. Drainage considerations are always an important aspect of trail design; trails should be designed so that runoff does not alter surrounding drainage patterns. While drain- age systems are not typically a significant cost fac- tor, there are situations in which drainage design may be more complex, and therefore costly. • Accessibility. Addressing handicap accessibility, terrain, and adjacent land use can change dramat- ically along a single trail. • Pavement materials. A typical paved cross sec- tion includes a two - inch thick surface layer of hot mix asphalt above a six - inch thick layer of aggre- gate base course. As an alternative, a four - inch - thick layer of concrete may be used. Concrete is generally more expensive yet more durable. Varia- bles that could increase the cost include any need- ed subgrade stabilization or whether the depths need to be increased to accommodate regular motorized traffic from maintenance vehicles. • Retaining walls. Steep banks in some locations may mandate the use of retaining walls. Typical areas where this may be common are areas where a roadway is close to a stream or river, narrow shelves built for existing utility easements, and areas close to existing structures. • Amenities may be desirable along a greenway, and the types and locations of these would not be known until an alignment is finalized. For example, fishing piers and observation platforms generally consist of wooden structures with an appearance similar to a residential deck and built adjacent to a water body. Other features may include benches, garbage cans, playgrounds, fitness stations, way- finding, and interpretative signage. • Trailheads. The number and types of amenities needed for trailheads can vary significantly de- pending on the intended users. For example, blue- way - specific trailhead amenities include boat
ramps, piers, kayak launch equipment, access pathways, informational and interpretive signage, restrooms, and parking for cars and bicycles. In contrast, a trail tailored for cyclists could have a bike repair station at the trailhead. • Boardwalks and bridges. Wooden boardwalks or premanufactured bridges can be used to minimize disturbances to environmentally sensitive areas without significantly affecting an alignment.
Trail bridge on pipeline greenway in King County, WA.
Pavement material on a greenway
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HILLSBOROUGH COUNTY GREENWAYS AND TRAILS MASTER PLAN
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