The general requirements for side slopes, including the treatment of side slope drainage disposal, are thoroughly detailed in the Los Angeles Grading Ordinance, No. 123,970 . Construction specifications are covered in the Standard Specifications (1970 Edition). It is suggested that the designer become familiar with the design criteria and specifications in these publications.
To summarize the side slope requirements: Side slopes should not be graded more steeply than 2-foot horizontal to 1-foot vertical for cut and fill slopes. Figure E 481A shows a typical cut and fill slope section and the type of bench used. For hillside construction in existing unimproved streets with existing abutting improvements, the street improvement is often limited to the central portion of the dedicated streets. The grading usually extends on a slope to the property line. Fences and other private improvements abutting the property line may be affected. Where possible, grading should not extend to the property line but should provide at least 1 foot clearance from the property line. A greater distance from the property line to the toe of slope or top of fill may be necessary to protect existing improvements. In any case, grading must be consistent with good engineering practice and economy.
The treatment of side slopes where the roadway or sidewalk is constructed on fill is as follows: Where slope easements are required and the sidewalk is constructed abutting the property line, or where no easements are required but there is space for grading between the back of sidewalk and the top of fill, the grading should be extended at a 1-percent slope to form a hinge point 1 foot back of the sidewalk. See Figure E 481B, below.
The amount of water falling on or carried by this additional foot of grading is negligible. In addition, it drains away from the sidewalk. Therefore, the additional grading serves as a safety factor in the event of even moderate slope erosion and thus minimizes the possibility of undermining the sidewalk.
To determine the maximum inclination to assign to the side slopes, the engineer must consider the following factors: The type of soil involved, as shown by soil tests; the geological formations; the geographical location; and whether excess water, springs, etc., are present in the sidehills. For example, some types of solid rock formations may permit a vertical or nearly vertical cut.
Consideration will be given by the City Engineer to modifying slope requirements where the geological formation, as evidenced by existing cuts, by exploration, or by soil tests, is such as to indicate that steeper slopes would be satisfactory.
(When any doubt exists as to the nature, stability, or allowable maximum slopes of the side slopes, it is advisable to confer with staff members of the Geology and Soils Engineering Section of the Street Opening and Widening Division.)1
Footnotes
- The text in parenthesis is from the legacy Street Design Manual text and is no longer in use.
Comments