Where engineers are called upon to design and analyze man-made earth structures, and 

 where such structures can be constructed to closely approximate the models of analysis, 

 then the methods of analysis employed can be considered reasonably reliable. However, 

 when dealing with the vagaries of nature or with complex and uncontrolled man-made 

 structures, the confidence one places in most methods of investigation and analysis 

 must necessarily be reduced. 



It is important, however, that some measure of soil strengths and depths, and their 

 degree of variability within an area for which development is planned, be obtained be- 

 fore development proceeds. Such parameters may be determined by intensive exploratory 

 and laboratory techniques, by correlations between topography and movement, or simply 

 through experience gained in other similar areas; but without this knowledge the loca- 

 tion and design of roads cannot proceed on a completely rational basis. 



Similarly, knowledge of surface and subsurface water conditions must precede road 

 location and design if erosion and landslides are to be avoided or controlled. Beyond 

 these areas of information, the designers must exercise their professional judgments 

 regarding the appropriate specifications, methods of analysis, and intensity of inspec- 

 tion and control during construction. 



As a consequence of this investigation, the following tentative criteria are 

 recommended : 



1. Fill slopes should be specified by the design engineer and based upon suitable 

 stability analyses. In no cases should unretained fill slopes exceed 70 

 percent . 



2. Cut-bank slopes should generally be as steep as possible consistent with sub- 

 surface conditions. Slope rounding should be practiced when overburden depths 

 require it. 



3. In general, alignment should be sacrificed whenever possible to avoid deep 

 fills and/or cuts. 



4. All fill slopes should be compacted to a degree consistent with design 

 standards and material properties. 



5. Drainage facilities should be provided to prevent damaging concentrations of 

 surface runoff and to avoid high pore pressures in cuts and fills. 



6. All fill sections should be insloped with an adequate berm on the outside, 

 unless adequate means for protecting the fill slopes against erosion can be 

 provided. Benched sections can be outsloped providing adequate vegetative 

 cover or other erosion protection remains after construction. 



7. Specifications requiring log and debris removal from fill slope sections must 

 be rigidly enforced. 



8. All fill surfaces should be revegetated with suitable species as soon as 

 possible after construction. In addition , rip-rap or other suitable debris 

 should be placed at or near the toes of fill slopes to halt the downhill 

 movement of sediment from the fill surfaces. 



9. Roadbeds should be stabilized to prevent erosion and rapid deterioration. 



10. Provisions should be made to prevent raveled cut-slope materials from reach- 

 ing live streams. 



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