Hydrogen Sulphide Master Plan

REGION OF PEEL

February 2004

The Region of Peel engaged AndrewsInfrastructure to develop a long term strategy to deal with odour and corrosion issues in the trunk sewers in South-Central Mississauga. Work focused on the Cooksville Creek and Little Etobicoke Creek Drainage areas south of Highway 401 and east of Mavis Road. Initial stages of work involved monitoring gas concentrations and air pressures in the trunk sewers.

Monitoring was carried out in two stages; mid-winter monitoring and during mid-summer. Since odour generation and corrosion are temperature dependant these two monitoring periods enabled us to determine variations in conditions on a yearly-cycle. In addition, sewage sampling and monitoring of sewage flow rates was undertaken in order to establish a relationship between odour generation and hydraulic conditions.

Once the data collection was complete, a comprehensive list of feasible options was developed to address the identified issues. Through discussions with the Region, a short list of best options was selected and a suggested overall strategy prepared.

The strategy:

• identified sources of odour and made predictions about future changes in odour generation
• recommended the best methods available to control odours in the South-Central Mississauga area
• listed works required, with a time line and budget, to control odour in the years to come

The strategy also:

• listed areas of concern regarding pipe corrosion with forecasts of potential for on-going corrosion
• identified areas where rehabilitation is now required due to corrosion damage
• identified opportunities and constraints related to optimizing the hydraulic capacity of the trunks and listed potential impacts that hydraulic conditions have on odour control

The damage site was located in the sewer 85 m downstream of a 30 m deep manhole shaft; work was completed under live conditions along this access route. Given the challenging worker safety requirements at this site Andrews Infrastructure developed a detailed Operations Strategy including a Rescue and Emergency Evacuation Plan.