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26. Paragraph 8.4.0.0.3, page 8-4 <br /> This paragraph recommends abandoning, in place, portions of the Industrial Waste <br /> Pipeline (IWPL) which were determined not to contain any defects. However, the <br /> trench backfill can act as a preferential flow path. As a result, leaks at defective <br /> locations can travel along the trench backfill and contaminate non-defective sections of <br /> the pipeline. This also applies to other buried utility line trenches that could have <br /> intercepted prior leaks from pipelines, ponds, etc. <br /> • Abandonment of non-defective pipe sections should be allowed only if the <br /> Phase II work and remediation work at defective locations confidently <br /> delineates the extent of the contaminants not just within the natural soil, but <br /> also within the original backfill soil. Phase II native soil sampling (alone) at <br /> 50-ft intervals (Paragraph 8.4.0.0.3) would not accomplish this. Thus, Phase II <br /> sampling should also include sampling of the original backfill material <br /> extending from known leaks to determine the extent, if any, liquid may have <br /> preferentially moved along the backfill material. <br /> EPA 14FEB94 10/10 <br />