McKinney Healthy Lakes

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McKinney Healthy Lakes Streams
Eldorado Lakes (Site 5A) - Sediment Removal
Project
McKinney, Texas June 11, 2008
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Purpose of Meeting

• Discuss the project to remove and dispose of
  sediment from Eldorado Lake (Site 5A). Sediment
  will be removed from the Main Lake, and Lower and
  Middle Lakes located upstream of the Main Lake.

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McKinney Healthy Lakes Streams
Final Master Plan
McKinney, Texas February 2006
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Background

• The Master Plan provides the Citys plan of
  action to restore, maintain or improve the health
  of the 18 floodwater-retarding structures
  (lakes) and about 77 miles of streams within the
  city limits of the City of McKinney and its
  Extraterritorial Jurisdiction (ETJ).

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Background (continued)

• Significant Points
• Most of the dams are in need of upgrade in order
  to extend their useful life.
• Most have significant amounts of sediment.
• Significant erosion in the streams.

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Comegys Creek Erosion
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Background (continued)

• Significant Points
• ? A dedicated City Drainage crew has completed
  improvements on several drainage projects.
• Removal of sediment from Site 5A identified as a
  high priority project.
• Six dams have been upgraded to current design
  criteria. (One is currently under construction by
  TEI Construction Inc.)

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A Lake Full of Sediment
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McKinney Healthy Lakes Streams
Eldorado Lakes (Site 5A) - Sediment Removal
Project
McKinney, Texas June 11, 2008
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Existing Conditions

• Significant Points
• Site 5A was constructed in 1958 as a low hazard
  floodwater retarding structure with a 50 year
  design life.
• The Lower Lake was created as part of the golf
  course.
• The Middle Lake was created as part of the
  development.
• Sediment has previously been removed.

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Section of a Typical Floodwater Retarding
Structure Storage in Pool
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Existing Conditions

• Significant Points
• A recent study indicates there are about 80,500
  cubic yards(50 ac ft) of sediment in the three
  lakes.
• The Lower and Middle Lakes are nearly full of
  sediment. The water is stagnant and provide
  breeding habitat for mosquitoes and creates odor
  problems during hot weather.
• The average depth of the Main Lake is about 4.5
  feet.
• The dam was modified in 2006 to meet current
  design criteria.

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Lake Above Eldorado (Site 5A)
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Description of the Project
? About 80,500 cubic yards of sediment will be
removed from the three lakes and transported to a
disposal site on City-owned property near the
airport. ? A combination of excavation and
hydraulic dredging may be used to remove the
sediment. ? The contractor will discuss their
plan of action.
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Location Map
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Practices to Minimize Adverse Impacts

• Three Tiers of Practices
• Tier 1 Above the 5A Dam
• Tier 2 Below the Site 5A Dam
• Tier 3 Operational

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Practices to Minimize Adverse Impacts

• Tier 1 Above the 5A Dam
• ? The Main Lake will be drained and capture any
  disturbed material.
• ? A safety fence will be installed.
• ? Silt fences will be installed around the two
  principal spillways.

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Practices to Minimize Adverse Impacts

• Tier 1 Above the 5A Dam
• ? Low flows will be diverted away from
  construction activities.
• ? A tire washing rack will be required.
• ? A final grading plan will be required.

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Practices to Minimize Adverse Impacts

• Tier 2 Below the Site 5A Dam
• Silt fences will installed in the three
  reflecting ponds below the dam.

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Practices to Minimize Adverse Impacts

• Tier 3 - Operational
• ? Cease operations if significant stream flow
  increases or significant rainfall is predicted.
• ? Monitor water quality downstream of the filter
  fences in the Main Lake and the reflecting
  ponds.

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Other Significant Points

• ? Project duration - 180 days, excluding bad
  weather days
• ? Monday thru Friday 7 to 7
• ? Saturday 8 until 5
• ? No Holiday Work
• There will be increased noise levels and possibly
  odors
• Arrangements have been made to provide suitable
  irrigation water for the golf course
• The Golf course will remain open

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Other Significant Points

• Fish and Wildlife
• Some unavoidable adverse impacts to fish and
  wildlife.
• Limited fishery at present. Some will move
  downstream when the Lake is drained.
• Restocking of the Lake is being considered.
• Adverse impacts to wildlife minimal and
  temporary.

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End Results

• Health of Three Lakes Improved
• Sediment will be removed
• Depth of water will be increased
• Life of the lakes will be extended significantly
• Breeding ground for mosquitoes reduced
• Stagnant water reduced
• Quality of fish and wildlife improved