THE NEW LAKE TOWNSEND DAM - DESIGN CONSTRAINTS AND CONSTRUCTION CHALLENGES

摘要

Challenges on the Lake Townsend Dam Replacement Project were primarily related to the need to maintain a fully operational reservoir during construction while constructing a new dam immediately downstream, passing up to 10,000 cfs of flood flows through the dam site throughout construction, dewatering and ensuring stability of the excavation, and identification of suitable backfill for the labyrinth spillway. The use of cement-modified soil as foundation backfill resolved issues with borrow materials being too wet to compact effectively. The use of CMS had a number of benefits, including reducing schedule and construction risks by becoming more independent of the weather. Ancillary benefits included providing an excellent, weather resistant foundation surface from which to work, and the ability to carve vertical walls for concrete forming that required no shoring. Figure 21 shows the completed new dam following impoundment and demolition of the old spillway section.