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              Section 319
              NONPOINT SOURCE PROGRAM SUCCESS STORY
 Nine Eagles Lake Overcomes Siltation and Turbidity Problems


WatPrbndv Imnrnvpd   ^ven t'10u9'1 tne Nine Eagles Lake watershed lies within Nine
                  !      "     Eagles State Park and is almost entirely forested,  erosion has
 created siltation and turbidity problems in the lake. Sediment basins were constructed to
 slow sediment delivery to the lake, and trails were reworked to reduce erosion.  Post-proj-
 ect monitoring data reveal an 85 percent reduction in sediment delivery, exceeding the 50
 percent reduction goal set by the total maximum daily load (TMDL).


 Problem
 In 1998 Iowa included Nine Eagles Lake on
 the state's 303(d) list due to high turbidity.
 The main cause of turbidity in the lake is
 colloidal clays, which remain suspended for
 long periods. The Iowa Department of Natural
 Resources (IDNR) completed a forestry
 management plan for the state park area in
 February 2001. A detailed assessment of the
 area identified  improperly maintained trails and
 failing sediment ponds as two of the leading
 causes of erosion.

 Project Highlights
 In 2001 EPA approved a TMDL for turbidity in
 the Nine Eagles Lake watershed. The TMDL
 established water clarity targets (as measured
 by a Secchi disk depth) of 1.25 meters and a 50
 percent reduction in sediment delivery.

 To accomplish  these goals, IDNR developed
 an implementation plan for Nine Eagles Lake
 focusing on  reducing sediment delivery in the
 watershed. Section 319 grant funds were used
 to construct 17 sediment basins. In 2003 the
 IDNR Parks Bureau rerouted and reworked some
 of the trails to reduce impacts. Throughout the
 project, care was taken to protect the forested
 areas, home to the endangered Indiana bat.
                                        Nine Eagles Lake is a popular recreation area where visitors enjoy
                                        swimming, boating, and fishing.
                                        Results
                                        To evaluate the impact of the project, bathy-
                                        metric mapping was used to map the original
                                        lake bottom and the depth of sediment depos-
                                        its. Further monitoring of Nine Eagles Lake
                                        took place in 2000-2004 as part of the Iowa
                                        Lakes Survey.

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