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i 40 Contaminated Clay Renlacemem The construction of the Indian River County Landfill Infill Cell required the placement of a liner system to act as a barrier to leachate infiltration to the groundwater. The bottom liner system consists of a high density polyethylene primary liner on top and a clay secondary liner underneath. The construction of the clay liner requires the clay to be placed in four-six inch layers. Each clay layer, called a lift, is well mixed, compacted, and tested before the next layer is placed. A rain event in May 194$ washed sand into the clay liner system along the south western edge of Segment II. The clay liner system was two lifts thick at the time of the sand contamination. Alger the rain event, leachate also seeped from the open cut along Segment 11. The open cut was required to reveal the edge of the existing cell for the synthetic liner tie-in. The leachate seepage contaminated the clay further. The tainted clay was removed from the Infill area and replaced with new clean clay. Waste Management Inc. of Florida (WMIF) submitted a claim for tate costs of removing tate contaminated clay and installing replacement clay. WMIF did not feel it was their responsibility to control the unexpected leachate seepage. After determining the total amount of impacted clay with WMIF, CDM recommends Indian River County SWDD pay only half of the amount of the claim. The rationale being the contractor should pay for the removal of the sand contamination because of their obligation to control stormwater runoff. However, because the presence of the leachate seepage, which is not considered stormwater, CRM believes it is fair to reimburse the contractor for half of the remediation cost. CDM feels that the contractor successfully removed the contaminated clay and the liner system should perform as designed. While the clay was determined to be compatible with the leachate, CDM believes the clay liner should be constructed free of any contamination to achieve the maximum barrier to leakage. The seepage of leachate onto the clay arises from a unique aspect of this project. Tile edge of liner of Segment II had to be revealed in order to tie the new liner system to the existing liner system. When the cover material was removed from the existing trash, a pathway was created which allowed leachate to escape in the area of the excavation. Leachate movement is somewhat unpredictable and moves vertically or laterally along the path of least resistance. This occurs for several reasons. The presence of film plastics in the waste hinders vertical flow. The older material near the bottom of the cell has had longer to degrade and is more dense than the upper levels. The leachate seepage is also directly attributed to the rain event. Please note that the quantity of clay material purchased is greater than the amount removed. The amount of clay removed had been compacted in place. The amount of clay purchased accounts for the loose material as it arrives by truck. A compaction factor of 1.35 was determined from the overall quantity of clay required for the job compared to the amount or compacted clay that was placed. Please find pictures attached showing the area of contamination