revised final closure plan - Salinas Valley Solid Waste Authority

Revised Final Closure Plan July 2010
Crazy Horse Sanitary Landfill -13- 103-97133
2.11 Construction Documents and CQA
Construction plans and specifications previously had been prepared based on the RFCP (2009).
These plans will be revised and submitted for regulatory review in late July 2010. The construction
documents will include final construction drawings, specifications, and a construction quality
assurance plan, which will be prepared under the supervision of a Registered Civil Engineer or
Certified Engineering Geologist in the State of California. Appendix G includes a CQA Plan that
addresses placement of the geosynthetic material closure design as described in this document.
CQA will be implemented during closure to verify that the construction complies with approved
construction drawings, specifications, and the CQA Plan. The CQA activities will be completed
under the supervision of a Registered Civil Engineer or Certified Engineering Geologist in the State
of California as required by Title 27 CCR.
2.12 Final Grading
27 CCR 21090(b), 21790(b)(8)(B), 21142, and 21769(b)(2)
Background and Existing Conditions. The final landfill grades were configured to maximize refuse
fill while addressing existing topographic restrictions, drainage requirements, and aesthetics. The
existing sideslopes of the landfill have been constructed with a nominal slope of approximately
3H:1V. However, as discussed previously and presented on Figure 3, there are five basic areas where
final slopes at the CHLF will exceed 3H:1V. These slopes are specifically discussed in Section 2.13
for overall drainage, static and seismic stability.
Regulatory Requirements. According to 27 CCR 21090(b), the final elevations of the landfill must
be designed to prevent ponding, accommodate anticipated future settlement, and reduce runoff
velocities in order to protect the final cover from soil erosion. Additionally, 27 CCR 21142 requires
that final grades be designed and maintained to reduce impacts to health and safety and take into
consideration any postclosure land use.
Final Grades. The final grades are consistent with 27 CCR requirements. The final grades on the
topdeck will be constructed with slopes no flatter than 5 percent to provide sufficient slope for
continued stormwater runoff after refuse consolidation and settlement, and to prevent the potential for
ponding in the event of differential settlement. Sideslopes will be nominally 3H:1V, or flatter.
However, some sideslope areas are steeper approaching 2H:1V under current conditions. The highest
peak elevation of the closed facility will be on the topdeck area at about 635 feet amsl. The proposed
final grades for the Crazy Horse Sanitary Landfill are shown in Figure 4.
The final grades are controlled by surrounding topography, existing waste fill, anticipated refuse
settlement, and minimum gradients for adequate drainage of the completed fill. Final landfill grades
are designed to prevent ponding, to accommodate anticipated future settlement, and to reduce runoff
velocities to minimize erosive conditions. The final landfill grades, shown in Figure 4, represent presettlement
grades. Refuse settlement after closure is estimated to be up to approximately 25 feet on
the southern slope (settlement calculations are presented in Appendix B). This estimate is based on
the method of landfill operation, effects of surcharging over the deepest parts of the fill, estimated
settlement during the active life of the landfill, refuse decomposition and landfill settlement
experienced at other sites with similar characteristics.
Final Cover Surveys. To monitor settlement of the site during the postclosure maintenance period,
measuring techniques, such as aerial photographic surveys, will be used. The entire landfill will be
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