Oakwood CSO Control Facility and Pump Station (PC-755)

June 24, 2013

Mirza Rabbaig, DWSD

Mark TenBroek, CDM Smith

Project Purpose

• Address capacity issues in original sewer system: – Oakwood District sewers built by Oakwood Village

– DWSD inherited these sewers

– Sewers undersized for combined sewer flows

• Install relief sewers in Oakwood Sewer District: – Mitigate chronic basement and street flooding issue

– Address 140 flooding complaints from 1994-1996

• DWSD design process: – Began to evaluate district in 2000

– Determined street flooding caused drainage system

– DWSD has designed new relief sewer system

Project Purpose

• Provide Combined Sewage Overflow (CSO) control:

– Treat water before discharge to Rouge River

– Improve Rouge River water quality

– Facility required by MDEQ

• Provide increased pumping capacity:

– Additional relief sewers under design for district (PCS-79)

– Current pump station - 650 cfs

– New pump station - 1,660 cfs

Benefits from Project

• Improve Rouge River water quality

• Remain compliant with MDEQ permit

• Reduce street flooding in district

• Reduce basement flooding in district

• Convey sanitary wastewater to wastewater treatment plant

• Remove older obsolete pump station

Ple

as

an

t Stre

et

Liddesdale

Liebold

Deacon Site Plan

Project Work Area

Perspective view looking Northwest Perspective view looking Northeast

Perspective view looking North Perspective view looking Southeast

Design Rendering

CSO Basin Pump Station

Facilities

Scre

ens

Early Foundation Construction (2008)

Unique Features

• Slurry Wall – Deep facility construction

• Pump Hydraulics – Physical model study

• Chemical Mixing – Reduced maintenance compared to mixers

typically used

• Ground Level Basin – Improved dewatering control

• Perforated Plate Screens – Six perforated plate screens

Slurry Wall Construction

• Pump station proposed rectangular trench style wet well

• Wet well base slab slightly above underlying rock

• Artesian aquifer in rock, causing concerns with uplift forces

• Circular caisson construction not deemed feasible

• Slurry wall construction selected, while not commonly used in

Southeast Michigan

Slurry Wall Excavator

Slurry Supporting the Slot Excavation

Reinforcement Dropped into Excavation

Concrete is Tremie Placed and Slurry is Displaced

Pump Station Work Area

Wet Well Support During Construction

Pump Station Hydraulics Required Physical Model

• Wet well relatively small compared to peak pumping capacity

– 1,660 cfs

– 8 vertical turbine pumps

• Concerned with swirl that could cause pump problems

• Commissioned physical model

– Initial during design

– Updated during construction when inlet conditions changed

• Resulted in small modifications to protect pumps

Model Included Both Pump Station Wet Wells and Inlets from the Upstream Junction Chamber

The Model Incorporates All Important Physical Features

Dye Used to Identify Problem Swirl and Determine Corrective Actions

Pump Arrival

Pumps Placed in Wet Well

Pump Station Motor Floor

Completed Motor Floor

Disinfection Solution Added at Pump Discharge

• Most CSO basins add chemical using mixers to properly distribute

disinfectant

• Oakwood places disinfectant in the pump discharge lines

• Simplified chemical application control since each storm pump is

matched with a chemical pump

Pump Station Intermediate Level

Ground Level CSO Basin

• Most DWSD CSO basins are gravity flow through style

• Hydraulics in the Oakwood District required pumping

• Decided to construct basin partially above ground:

– Reduced excavation costs

– Fewer dewatering issues

– Allows mostly gravity dewatering

Basin Pile Foundation Construction

CSO Screening and Basin Area

CSO Basin Effluent Weirs

Basin Flushing Lanes

Influent Screening using Perforated Plate Screens

• Provides removal of small material

• Includes bypass channels should screens become blinded with

excessive material

• Screen discharge includes screening washer and discharge to a

dumpster

Perforated Plate Screen Installation

Project Summary

• Slurry wall construction installed quickly

• Pumping systems have worked well, in spite of small wet well

• Chemical application has worked effectively

• Flushing system has removed solids with single flush

• No problems have been encountered with screen blinding

• Project PPC 1-year sampling period has been completed

• Final PPC report to be submitted this fall

Completed Facility

Acknowledgements

Detroit Water & Sewerage Department (DWSD)

• Sue McCormick DWSD Director

• Mirza Rabbaig CSO Program Manager

CDM Michigan Inc. (CDM Smith) Engineering Partners

Applied Science, Inc. Hamilton Anderson Associates

JE Associates PMA Consultants, LLC

SOMAT Inc. Spalding DeDecker Associates

Sigma Associates Superior Engineering, Inc.

Tucker Young Jackson Tull, Inc.

L D’Agostini & Sons (LDS) Construction Contractor

• Gino L. D’Agostini, Jr. Project Manager