Three Options

Cost & Time to Implement

$40 to $60 million

4-5 years

$95 to $140 million

5-6 years

$1.3 to $2.2 billion

30-50 years

DESCRIPTION

All three options require:

• continued sewer separation of a 187-hectare area at an ADDITIONAL cost of $200-$250 million
• completion of the Real Time Control project.

Storage capacity would be added to the combined sewer system to temporarily hold surplus flows during wet weather events, preventing them from overflowing to the Ottawa River.

The amount of storage constructed would ensure compliance with current provincial requirements for combined sewer overflows, (i.e., no more than two overflows during an average year.)

Storage facilities would likely consist of underground storage tanks sited at key locations downtown.

Even more storage capacity than proposed under Option A would be added to the combined sewer system to temporarily hold surplus flows during wet weather events, preventing them from overflowing to the Ottawa River.

The amount of storage constructed would ensure compliance with current provincial requirements (i.e., no more than two overflows during an average year) and due to the greater storage capacity this option would achieve fewer overflows during wet years as well.

Storage would likely be linear, for example a deep tunnel running west to east through the downtown or near the shoreline, possibly extending as far as the Robert O. Pickard Environmental Centre treatment plant.

Alternatively, underground storage tanks could be sited at key locations in the city’s downtown (more numerous and/or larger than those required by Option A)

Ottawa’s 675 hectares of Ultimate Combined Sewer Area would undergo full sewer separation over the next 30+ years.

• City’s Partially Separated Area, roughly 2000 hectares, comprising 80,000 households would undergo the following:
  
• Disconnection of roof downspouts and foundation drains from the sanitary sewer
• Installation of new sewer laterals leading from homes to the storm sewer in the street.
• Installation of sump pumps in basements where sewer laterals cannot be installed.

Separation work would be carried out on a priority basis, addressing first those areas requiring rehabilitation and replacement of infrastructure or flood relief.

Three or more stormwater centrifuges and several storm outfalls to the Ottawa River would be constructed.

ADVANTAGES

All options achieve full regulatory compliance
(i.e., a max. of two overflows in the average year.)

This option will significantly reduce the number of beach closures at Petrie Island and is the most affordable and least disruptive option.

This option will further reduce the frequency and volume of CSOs particularly in wet years, and further reduce the number of beach closures at Petrie Island. It also may provide several opportunities for improving system resiliency and operations.

This option would eliminate combined sewer overflows to the Ottawa River under all except extreme wet weather events.

DISADVANTAGES

This option will have localized impacts during construction, and provides minimal opportunities for achieving ancillary operational improvements.

This option will have greater impacts during construction.

This option will take years to complete, be disruptive to the communities affected, and would result in increased pollution of the Ottawa River from urban stormwater run-off.