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C from the compactor is 430 lbs, per sq. in. (59,799 lbs. / 139 sq. in.). Applying the compactor's ground pressure over ASTM D4833 specified test area means that in-place geomembrane could experience a direct applied force of 33.5 lbs (0.078 sq. in x 430 psi), less than half the material's rated puncture resistance. Factor of Safety The Factor of Safety (FOS) against puncture of the 60 mil LLDPE Microspike geomembrane is the material puncture resistance strength divide by force applied by the compactor, or in this case, greater than two (2), which is acceptable (70 lbs / 33.5 lbs). This FOS is theoretically attainable even with the compactor used directly on the geomembrane. Additional Considerations The above calculations assume the weight of the compactor is transmitted straight down (vertically) through the soil. This is, however, not how the force is actually transferred through the soil. The soil beneath the compactor will shear along the outside of the perimeter of the compactor's pads along an angle equivalent to the internal shear strength of the soil. That means that the effective ground pressure of 430 psi would be reduced by a function of soil depth and its interface shear friction angle. The soil used for the vegetative soil layer is a fine-grained, silty material. The minimum soil friction angle is 18 degrees for such soil. The vegetative cover was placed with a minimum lift thickness of 12 inches. The geomembrane area in contact with the force of the compactor is increased by 5.8 inches on each side of the compactor pad contact area (12 inches x tangent (18) = 3.9 inches). The contact area of one pad is 13.9 sq. in. Assuming the pads are square, each pad's side length is the square root of 13.9, or 3.73 inches. The additional contact area of 5.8 inches would add to side of all the pads to give us the geomembrane contact area of 520 sq. in. ((3.73 in. x 10 pads + 3.9 in. x 2) x (3.73 in. + 3.9 in. x 2)). Therefore, the actual theoretical ground pressure exerted by the compactor would be only 115 psi (59,799 lbs / 520 sq. in). When applied to the ASTM test area of 0.078 sq. in., the resultant force is 9 lbs (0.078 sq. in. x 115 psi). Therefore, the factor of safety against puncture is estimated to exceed 7.8 (70 lbs. / 9 lbs.). Furthermore, the geomembrane subgrade was inspected prior to placement for objects that would possibly puncture the geomembrane. Then, prior to cover soil placement, the geomembrane was overlain with a geocomposite drainage fabric, which itself was comprised of a geonet and two layers of filter fabric, for a total 6.5 oz/sq yd, adding further protection against puncture. Lastly, the fine-grained soil material used for the vegetative cover did not contain angular particles which could puncture the geomembrane. Conclusion In conclusion, this analysis verifies that the integrity of the geomembrane was not compromised. It is evident that equipment used to compact the vegetative cover soil did not damage the 60 mil LLDPE Microspike geomembrane cover at the Landfill. During the placement of the vegetative cover with a minimum lift thickness of 12 inches, an estimated FOS of 7.8 against puncture to the geomembrane was theoretically achieved.