Tainter Gate Cable Replacement (and Drawdown) Lake Red Rock Marion County, Iowa
Environmental Assessment Decision
On February 8, 2005, a Finding of No Significant Impact (FONSI) was signed by the Corps of Engineers for the project, as proposed in the Environmental Assessment, and summarized below. The Statement of Findings (SOF) summarizes the public involvement, public review comments, the preferred alternative, and includes the FONSI. This package is available below. One comment letter did prompt a further review of the effect of the drawdown on local area shallow wells. The examination of the existing data concluded that municipal wells upstream of the dam should not be significantly affected by the 10-foot drawdown. Of the public municipal wells where the installation date is known, none are expected to be reduced to an inadequate pumping level, although there may be minor reductions in some well capacities.
This information and analysis has been compiled into a report entitled, “ Lake Red Rock Groundwater Well Analysis for Tainter Gate Repair Drawdown”, dated January 2005. This report is an attachment to this SOF package. As a result of the EA and subsequent groundwater well investigation, no significant impacts resulting from the implementation of the project have been identified.
Statement of Finding Package:
| Title | Size | Posted On |
|---|---|---|
| Statement of Finding | 170 KB | 02-09-2005 |
| FONSI | 62 KB | 02-09-2005 |
| Ground Water Well Analysis | 1 MB | 02-09-2005 |
| US Fish and Wildlife Conversation Record | 22 KB | 02-09-2005 |
| Letter from Carlisle Water Department | 62 KB | 02-09-2005 |
| Corps Response to Letter | 54 KB | 02-09-2005 |
Environmental Assessment
Summary:
The Rock Island District of the U.S. Army Corps of Engineers (District) has prepared the Environmental Assessment (EA) and draft Finding of No Significant Impact (FONSI) addressing the tainter gate cable replacement at Lake Red Rock, Marion County, Iowa. The purpose of this EA was to assess the impacts associated with the dewatering the tainter gate bays, replacement of the tainter gate lifting cables, as well as touch-up painting of the gates, and periodic inspection and maintenance of the dam.
The District originally scheduled the work to begin in September 2007, yet high water in 2007 and 2008 has delayed the project.
At the current elevation of the conservation pool, the tainter gate cables and brackets are permanently submerged, making performance of scheduled repair and maintenance on the tainter gates and lifting cables virtually impossible without dewatering the tainter gate bays. The District proposes a one time 10-foot drawdown and performance of the scheduled repair and maintenance to the tainter gates and cables during the fall of 2007, with future installation of a traveling bulkhead system.
The District will lower the lake at a rate of 0.5 feet per day, completing the drawdown in 20 days. The estimated time for cable replacement and touch-up painting is 4 to 7 weeks. When the District completes the work it will raise the pool as quickly as possible, while still maintaining outflows of at least 300 cubic feet per second. The District anticipates the lake will resume its conservation pool elevation in approximately 54 days. The project will take approximately 3.4 to 4 months to complete under ideal conditions; however, the time to raise the pool is entirely weather dependent.
The primary purpose of the drawdown is to replace the cables on the dam tainter gates. During the flood of 2008, the existing cables performed well and will remain in service until other 2008 flood recovery work is accomplished.
This EA evaluated the alternatives and assessed the impacts of the preferred alternative. This tainter gate maintenance will ensures the long-term project purpose of flood control is maintained at the current levels, without any reduction in the life, health, and safety to local and regional human populations.
Copies of the Environmental Assessment are available at the following locations:
Area Post Offices:
Melcher, Harvey, Eddyville, Hamilton, Lacona, Dallas Center, Pella, Pershing, Knoxville, Cumming, Ottumwa, Bussey, Columbia, Swan
Area Libraries:
Pella (public and Central College), Ottumwa (public and Indian Hills Community College), Knoxville (public)
Public Review and Comment Period:
The 30-day public review and comment period ended on September 25, 2004.
Report Files:
| Title | Size | Posted On |
|---|---|---|
| Report Cover Letter | 85 KB | 08-24-2004 |
| Executive Summary | 30 KB | 08-24-2004 |
| Table of Contents | 22 KB | 08-24-2004 |
| Environmental Assessment | 353 KB | 08-24-2004 |
| Draft FONSI | 18 KB | 08-24-2004 |
| Figure 1. Location and plan view of Red Rock Dam | 53 KB | 08-24-2004 |
| Figure 2. Red Rock Reservoir depth at elevation 732 NGVD | 238 KB | 08-24-2004 |
| Figure 3. Lake Red Rock project area with conservation pool, proposed drawdown pool, and areas exposed by drawdown | 201 KB | 08-24-2004 |
| Figure 4. Lake Red Rock pool elevation average based on data from 1994-2003 | 24 KB | 08-24-2004 |
| Appendix A - Coordination | 4218 KB | 08-24-2004 |
| Appendix B - Distribution List | 93 KB | 08-24-2004 |
| Appendix C - Construction procedures for tainter gate cable replacement | 105 KB | 08-24-2004 |
| Appendix D - Construction procedures for tainter gate painting | 136 KB | 08-24-2004 |
| Appendix E - Construction procedures for installation of the bulkhead system | 31 KB | 08-24-2004 |