REMEDIAL ACTION WORK PLAN OPERABLE UNIT 2, LANDFILL ...

geomembrane on 3 horizontal to 1 vertical (3:1) sideslopes around the landfill perimeter.
However, for erosion control and maintenance purposes, a 4:1 sideslope is now proposed.,
California Code of Regulations (CCR) Title 14, Division 7, Article 7.S, Section 17777 requires a
slope stability report for sideslopes less than 3:1, Therefore, stability calculations are not required
for 4:1 vertical sideslopes.
Action:
Change perimeter sideslopes to 4:1.
8. Comment:
The drainage and final grades will also be revised. Since these are important factors in the slope
stability analysis and 14 CCR requirements, CIWMB staff will also need to review these design
modifications.
Response:
The final sideslope soil-geomembrane grades will be reduced from 2 horizontal to 1 vertical (2:1)
to 4:1. The final cover grades will be increased from the regulatory minimum of three percent to
not greaterthan 10 percent. This later grade is less than the sideslope grades, so the cover slopes
should also be stable.
The modification to the drainage pattern and design is minimal. As with the original design,
stormwater drainage is directed off the landfill cover to an intltration trench instead of an
irrilltration basin.
Action:
Constructibility improvements are shown on Figure 2-16. Construction specifications will be
included in Appendix G - Construction Specifications.
SJ/4-23-96/SACTERCiFTORDOU2/CIWM13
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