Renwick Dam Rehabilitation

TONGUE RIVER DAM #M-4 (RENWICK DAM) WATERSHED REHABILIATION PROJECT

The purpose of the project was to bring Tongue River Dam #M-4, originally constructed in 1962, into compliance with current State and Federal dam design and safety criteria.  Phase I, completed in 2012 raised the height of the existing structure by 5-feet, and installed settlement plates across the new fill material to monitor any settlement prior to Phase II construction activities.  Access improvements were also made to the existing drainage system (12” perforated corrugated metal pipe) located within the downstream face of the dam.  Phase II, completed in 2014, included the excavation of a new 500 foot wide spillway located near the center of the structure (old earthen auxiliary spillway was located north of the main dam structure).  Additional new drain lines were added across the new spillway.  Concrete retaining walls over 20 foot in height were constructed along both sides of the new spillway.  The stepped spillway itself was then constructed with air-entrained roller compacted concrete (AERCC).  Containing much less water than conventional concrete mixes, the over 19,000 cubic yards of AERCC was batched onsite, delivered to the spillway with a conveyor system, spread with bulldozers, and compacted with smooth drum rollers.  The 5-foot thick stilling basin at the bottom of the spillway was constructed first, then a total of (32) 1-foot thick steps, each 500 feet wide were constructed to the top of the spillway.  Upon completion of the spillway construction a new 2,200 foot long AERCC road was constructed along the upstream face of the dam to provide access to Icelandic State Park located along the north side of the reservoir.

Current Status

Complete

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