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Slurry Wall Repair Concepts The slurrywall repair methods will depend on the construction technique used to penetrate the slung wall. The construction method presented in the project manual and drawings have assumed that the pipeline will be installed using cut and cover construction. The contractor has proposed to bore through the slurry wall on the north side of the South Dahlia Pit and open cut the slurry wall on the south side of the North Dahlia Pit. The repair concept for a cut and cover penetration is shown in plan and profile on Sheets 3 and 4 with details on Slteet 7, Section B and L in Appendix I of Amendment No. 2 and is described briefly below: 1. Install sheet piles across the slurry wall to bedrock. 2. Excavate between the sheet piles. Brace tl\e excavation as needed. 3. Install pipe with welded collars as shown on the drawings. 4. Place cement bentonite around pipe as shown on the drawings. 5. Backfill the excavation with common fill to the top of the slurry wall. 6. Reconstntct the disturbed portion of the slurzy wall using slurry wall construction techniques to reconstruct a soil bentonite slurry wall, as shown on the drawings. The concept to seal the slurry wall around the bored casing pipe is shown on the following page and described below. 1. Dewater the alignment to be bored. 2. Compaction grout along the alignment to densify the soils along the pipeline alignment and above the pipeline crown. 3. Bore the soils and jack the casing pipe into place. 4. Install grout nipples through the casing pipe at the location of the slurry wall. 5. Inject cement grout around [he casing pipe. 6. Install the carrier pipe within the casing pipe. 7. Install two brick and mortar seals between the carrier and casing pipes at each end and grout the space between the brick and mortar seals with anon-shrink grout. 1:\PROJECTS\98017 Corley Gravel Pn\98017 00~ 12-20 Lv AM: Add inio.wpd