Laserfiche WebLink
7~hreeRivers <br />PARK DISTRICT <br />Coon Rapids Dam Operational Update <br />February 16, 2010 <br />During a routine inspection in the fall of 2009, dam engineers working for Three <br />Rivers Park District uncovered some significant maintenance issues that will need to <br />be addressed. There is no immediate danger to the dam associated with the <br />problems. Since the repair needs were discovered Three Rivers Parks officials have <br />been communicating with local and state leaders about the future of the Coon Rapids <br />Dam. <br />Questions and Answers <br />What is the current status of the Coon Rapids Dam? <br />A scour hole was found in November 2009. "Scour hole" is the term used to describe <br />the hole caused by the breaking up of a section of concrete below the water level. A <br />section of concrete has broken up on the underwater sloping downstream apron. <br />Is this an emergency, or is the dam in immediate danger of failure? <br />No. This is not an emergency. The hole is approximately 12,000 square feet, and <br />when investigated, it was not found to have extended upstream to a point that has <br />undermined the dam's support pilings. The Department of Natural Resources Dam <br />Safety Office, which is responsible for the safety of all darns in Minnesota, concurs <br />that the scour hole is not currently compromising dam safety. <br />How long before the scour hole creates an emergency? <br />There is no predictable answer. The river is dynamic, and flow rates as well as the <br />methods used in lowering the pool may influence the growth of the scour hole. <br />Protecting the scour area by leaving one of the bags inflated, if possible, depending <br />on flow rates, may slow the expansion of the hole. <br />Will the recreational pool be raised for 2010? <br />Yes, Three Rivers Park District intends to raise the pool this year. However, the DNR <br />makes final decisions in consideration of dam safety. <br />Wasn't a scour hole fixed a few years ago? <br />Yes. The first scour hole was discovered in 2004 and repaired in 2005. This scour <br />hole was also on the downstream apron, but closer to the dam than the current <br />scour hole. <br />How much would it cost to make the recommended current repairs to <br />address the scour hole? <br />A similar repair strategy to what was done in 2005 is estimated to cost <br />approximately $2 million. However, this is not recommended since there may be <br />