October 13, 1999
To: Works Committee
From: Barry H. Gutteridge, Commissioner of Works and Emergency Services
Subject: Costs for Connecting the Remaining Eastern Beaches Storm Sewers to the Maclean Avenue Detention Tank (East
Toronto)
Purpose:
To report on costs for connecting the remaining Eastern Beaches storm sewers to the Maclean Avenue Detention Tank in
conjunction with the construction of a forcemain from the R. C. Harris Filtration Plant along the beach to the Ashbridges
Bay Treatment Plant.
Financial Implications and Impact Statement:
Not applicable.
Recommendations:
It is recommended that this report be received for information.
Background:
On January 13, 1999 the Works and Utilities Committee received a report entitled "Eastern Beaches Water Quality and
Effectiveness of the Kenilworth Avenue and Maclean Avenue Detention Tanks (Ward 26)". The Committee requested that
"the Commissioner of Works and Emergency Services submit a report to the Committee on the costs of completing the
connection of the remaining storm sewers to the Eastern Beaches detention tank(s), in the event that the R. C. Harris
Residue Management EA recommends the construction of a forcemain from the water treatment plant, along the beach, to
the sewage treatment plant".
The R. C. Harris Residue Management Class EA study is now completed and has recommended the forcemain construction
along the beach alignment. This report describes some advantages and disadvantages of constructing the facilities at the
same time and recommends next steps.
Comments:
As part of the implementation of the proposed Sewer System Master Plan for the virtual elimination of combined sewer
overflow (CSO's), two detention tanks have been built in the Eastern Beaches and a number of storm sewers and combined
sewer overflows have been connected to them. These are shown on Attachment No. 1 and are described below:
Elements of the Master Plan built so far
Kenilworth and Maclean Avenue Detention Tanks:
In 1990, the first Eastern Beaches detention tank was completed at the foot of Kenilworth Avenue. This detention tank
intercepts the flows from one combined sewer overflow (CSO) and four storm sewers between Woodbine Avenue and Lee
Avenue. These flows are detained and released later at a controlled rate to the Lakefront Interceptor for conveyance to the
Ashbridges Bay Treatment Plant.
In 1994, the second Eastern Beaches detention tank was installed at the foot of Maclean Avenue. The Maclean Avenue
Detention Tank intercepts the flows from one CSO and two storm sewers between Glen Manor Road and Balsam Avenue.
The detention tank has two compartments, one for the CSO flows and the other for the storm flows. The CSO flows are
detained and released later to the Lakefront Interceptor, which flows to the Ashbridges Bay Treatment Plant. The storm
flows are detained and pumped later 400 metres offshore through a forcemain. The solids that have settled are pumped to
the Lakefront Interceptor for conveyance to the Ashbridges Bay Treatment Plant.
These two detention facilities capture the flows from most of the rainfall events in the Eastern Beaches during the
swimming season. They have been constructed at a cost of $13.5 million. However, there remain four storm sewers to the
east of the Maclean Avenue Detention Tank, between Willow Avenue and Nursewood Road, which still discharge storm
runoff pollutants directly to the Lake.
Elements of the Master Plan remaining to be built
Connection of Storage Pipe Conduit to the Maclean Avenue Detention Tank:
Phase IV of the Sewer System Master Plan proposed that a storage conduit extending along the shoreline from Nursewood
Avenue, intercepting the four remaining storm outfalls and discharging to the Maclean Avenue Detention Tank be
constructed if water quality monitoring indicated that it is needed.
The cost of constructing a storage conduit connection to the Maclean Avenue Detention Tank is an estimated $3.28
million, including design and construction administration fees. This estimate is based on a storm water detention twin
culvert, intercepting the four storm sewer outlets, extending 660m from Nursewood Road and connecting to the Maclean
Avenue Detention Tank.
At its meeting last January, the Works and Utilities Committee requested information on what savings could be achieved
on the $3.28 million by constructing the storage conduit at the same time as a proposed forcemain for residue from the R.
C. Harris Filtration Plant.
Advantages of Building Proposed Forcemain for Residue from the R. C. Harris Filtration Plant and Storage Conduit
Together:
In August, 1999, a Class EA for Schedule "B" projects was completed for the R. C. Harris Residue Management Project.
The preferred solution consists of Off-site Treatment at the Ashbridges Bay Treatment Plant with a 600mm forcemain from
the R. C. Harris Filtration Plant, along the beach shoreline, to the Ashbridges Bay Treatment Plant. This project is expected
to cost $33.1 million including $9.4 million for the forcemain and pumping station.
If the construction of the proposed forcemain for the residue from the R. C. Harris Filtration Plant is undertaken at the
same time as the storage culvert, the forcemain could be put either in the same trench or inside the culvert. This would
realize a savings of approximately $0.2 million.
The main advantage in carrying out the two projects at the same time is that the beach area from the filtration plant to the
Maclean Avenue Detention Tank would be disturbed only once for a construction period of approximately four months.
This is in addition to the benefits each project would be providing.
However, before any design or construction can proceed for the storage conduit, it will be necessary to undertake a
Schedule B Class EA to confirm the benefits of undertaking the project and obtain public comments. The Class EA will
consider alternatives and evaluate the benefits in constructing the storage conduit. Water quality monitoring taken this
summer and over previous summers shows that there is a slight increase in bacteriological loadings at the location of the
four storm outlets when rainfall events are coincident with lake currents from the east. This would indicate that if the four
storm outlets were connected to the Maclean Avenue Detention Tank, there would be a slight reduction in the percentage
of days the provincial guidelines for bacteriological concentration at this location would be exceeded. The purpose of the
Class EA study would be to examine the costs and benefits of the storage conduit and to provide information to assist
Council in making a decision about whether to invest in this project given its effect on water quality.
The Department will request funding of $60,000.00 from the 2000 Capital Budget to undertake a Class EA for Schedule
"B" projects for the connection of the four remaining Eastern Beaches Storm outlets to the Maclean Avenue Detention
Tank. In the event the recommendation of the EA is to intercept these storm sewers and connect them to the detention tank,
this work could proceed together with the proposed construction of the forcemain for the residue from the R. C. Harris
Filtration Plant.
Conclusions:
The estimated cost to construct a storage conduit to intercept the four storm sewers and connect to the Maclean Avenue
Detention Tank is $3.28 million. The Department will request $60,000.00 from the 2000 Capital Budget to undertake a
Class EA for Schedule "B" projects to evaluate the costs and benefits of undertaking such a project. If the Class EA
concludes that the storage conduit is recommended, $0.2 million in savings would be realized and the impact of
construction would be minimized if this work is done together with the proposed forcemain for the residue from the R. C.
Harris Filtration Plant.
Contact:
David Crichton, P.Eng.
Manager of Design and Construction
District 1, Area 1
Tel. (416)392-7674
Fax (416)392-7874
E-mail: dcrichto@toronto.ca
Tom G. Denes, P.Eng.
Executive Director, Technical Services Division
Barry H. Gutteridge
Commissioner, Works and Emergency Services
DC/fh
List of Attachments:
Attachment #1
