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ANDREW SMITH, PE, CFM LAURIE BROWN

MCCLAY VALLEY DETENTION BASIN RETROFITS

AGENDA

Project Background

Water Quality in Detention Basins

Improvement Features

Proposed Project Improvements

Questions

2

PROJECT BACKGROUND

3

PR

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BA

CK

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PROJECT BACKGROUND

4

2012 Stormwater Masterplan •Basins Identified for Water Quality Retrofits •Black & Veatch team selected for improvement design

Meeting with trustees on May 20th Hydrologic and Hydraulic Investigations

WATER QUALITY IN DETENTION BASINS

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WA

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WATER QUALITY

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Methods of WQ Improvement

• Removal of Sediment

• Nutrient Uptake

• Detention of Small Events

• Filtering Overland Flow

IMPROVEMENT FEATURES

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IMP

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• Improved McClay Valley Outlet

• Debris screen to prevent clogging of the outlet

• Low flow outlet for small events

• Improved Francis Howell Outlet will provide Water Quality Improvement

• Debris Screen

• Plate with holes drains small events

• Overflow outlet for larger storms

MODIFIED OUTLET

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IMP

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• Provides Water Quality Improvement

• Prevents Sediment Accumulation in Basin

• Assists with Flood Control

• Prevents debris from clogging outlet

SEDIMENT FOREBAYS

9

Sediment Forebay Locations

IMP

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NT

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• Native Plantings

• Provides Water Quality Improvement

• Habitat for Fish and Aquatic Species

SHORELINE TREATMENT

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PROPOSED PROJECT IMPROVEMENTS

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PR

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• Rebuild Spillway and Outlet

• Replace existing apron

• Provides WQ Storage

• Reduces downstream flows

• Re-shape/Revegetate Basin

• Replace Downstream Pipe with Open Channel

• Sediment Forebay

• Remains a Dry Detention Basin

FRANCIS HOWELL BASIN IMPROVEMENTS

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• Modified Outlet

• Permanent Pool lowered to original 554 elevation

• Provides WQ Storage

• Reduces downstream flows

• Eliminate Overtopping

• Dredge Sediment

• Shoreline Treatments

• South Bank Stabilization

• Sediment Forebay

MCCLAY VALLEY BASIN IMPROVEMENTS

13

PR

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MC

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BASIN IMPROVEMENTS

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EXISTING CONDITIONS

10/28/2013

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PROPOSED ENHANCEMENTS

EXISTING CONDITIONS

26 December 2012 PowerPoint Sample

18

PROPOSED ENHANCEMENTS

QU

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TIO

NS

19

QUESTIONS

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