ARCHIVED REPORTS_2014_7 - Laserfiche WebLink

Home Browse Search

5-13 soils will satisfy the regulatory requirements for an alternative final cover as defined in 27 CCR. A traditional barrier layer is not proposed for the alternative final cover design. A cover slope stability analysis was also completed for the Phase I Partial Final Closure (GLA, 2005). This analysis was included in the Stage 1A Partial FCPCMP (BAS, 2005) and Stage 1B Partial FCPCMP (SWT, 2011). 5.3.4 Settlement Analyses 5.3.4.1 Settlement Analyses Settlement analyses were completed to evaluate how the Forward Landfill containment system will respond through time as refuse decomposes and is mechanically compressed. These analyses considered the consolidation potential of native sub grade soils as well as the settlement potential of both existing and future refuse materials. These settlement analyses were prepared by CH2M Hill and R.W. Beck are still adequate for the landfill (see Appendix Q. The results of the settlement analyses indicate that the sub grade soils could consolidate up to 2 feet in response to maximum refuse loads, but that the differential settlement of sub grade soils across the planned refuse footprint would be relatively minor (0.3%). While the potential for existing refuse to settle continues to exist, since the existing landfill configuration mimics the geometry of the proposed expanded landfill, the differential settlement of existing wastes is expected to be negligible. The settlement analyses of new wastes indicate that significant settlement can occur. However, assuming a uniform settlement potential for refuse of 25%, the minimum landfill final cover slope gradient is calculated to drop from 5% to 3.75%. If randomly differential settlement of 22% to 28% occurs, the calculations indicate that the final cover gradient could range from 1% to 6% in areas where a 5% cover gradient is constructed. 5.3.4.2 Survey/Settlement Monumentation In order to monitor the future settlement of the landfill, a settlement and survey monuments will be installed on the landfill in accordance with 27 CCR, Section 20950 (d). These monuments are proposed to consist of galvanized pipe, two inches in diameter and six inches in length placed in blocks of concrete, 24 -inches in diameter by eight inches in depth. A nail and tag will be placed in the center of each monument for identification (see Drawing 5). Permanent perimeter survey monuments have been placed on undisturbed ground as reference points not subject to settlement. These points are the horizontal and vertical control points for the site aerial topographic survey and will be maintained or replaced, as needed, throughout the post -closure maintenance period. An aerial photographic survey of Ol the site with a maximum contour interval of two feet will be performed and provided to the RWQCB, LEA, and CalRecycle upon completion of closure activities. The settlement Forward Landfill SWT Engineering Joint Technical Document - April 2014 z:\projects\allied waste\forward\five year permit rvw 2013\jtd-5 yr pr 2013\text\sec 5_final.doc