2 6o PARKS 



previously outlined (under 30) should be applied to the construction of 

 tanbark walks with the following exceptions: Tanbark surfaces are much 

 more susceptible to injury from any surface flow of water and therefore 

 such walks should not be constructed on steep grades (6% or greater) nor 

 on slopes where it is not possible to remove entirely the danger of damage 

 from surface wash. On such walks the problem of subsurface drainage is 

 exceedingly important and provision for this should be very adequate and 

 complete. 



(c) Turf walks and woodland trails (drainage}. The principles above 

 outlined (under 30) apply to the drainage of turf walks and woodland 

 trails with the following exceptions: Woodland trails do not require, because 

 of their natural characteristics and the firm texture of the soil on which 

 they are made, the provision for drainage normally installed for tanbark 

 walks. Subsurface drainage for woodland trails is seldom desirable, not 

 only because of the expense but also because of the great variation in sur- 

 face profile and the danger to surrounding trees. 



Turf walks not only require adequate surface drainage as discussed 

 under 3*3, but they also require adequate subsurface drainage, especially 

 if such walks are constructed on a clay foundation and are frequently used. 

 Turf walks constructed on a light sandy loam require little or no drainage 

 other than surface drainage. The presence of excessive ground water under 

 the area of turf walks does not cause the same injury to turf surfaces that 

 it causes to walks with hard surfaces as listed under ^a. It causes the 

 greatest difficulty through the development of soft surface conditions after 

 a rain, or during early spring and fall. 



(d) Stepping-stone walks (drainage}. Stepping-stone walks present the 

 same problems of drainage as outlined under 3*2 and 30 with the exception 

 that unless stepping-stones require a continuous excavated area the problem 

 of subsurface drainage is usually ignored. Such subsurface drainage as is 

 necessary for the turf surrounding the stepping-stones is provided for by 

 the general solution of the drainage problem on the surrounding lawn or 

 garden area. 



(e) Board walks (drainage). Board walks are usually constructed with 

 a surface at least two inches above the surrounding grade and therefore 

 the problem of surface drainage is a negligible factor. 



4. Foundation Course and Wearing Surface (General Considerations). 



The types of foundations required for various kinds of walks are so 

 varied that a detailed discussion of each is included in these notes. In 

 locations where frost action is slight (with freezing conditions occurring 

 only occasionally and the depth of frost action seldom being more than 



