Stormwater bypass and treatment project protects sensitive cold water stream


Source: Aquatech Dewatering Company

Aquatech Dewatering was recently retained to intercept, bypass and filter exceedingly turbid stormwater passing through a large drainage ditch, which ran through an area under construction before entering a natural water course, located in the Greater Toronto Area.

The main challenge was to design, install and commission a system that would handle flows raining from 76 litres to 7,600 litres per minute, (depending on whether conditions). Aquatech also had to design the filtration system to handle varying flows and water quality to ensure that discharges always met the stringent water quality guidelines of a natural creek deemed a 'cold water fisheries' habitat. Another major challenge was to install this large system quickly on a site with very limited footprint.

The system was designed quickly by Aquatech, but it was discovered that there was insufficient space to install the needed equipment, without accessing the privately owned adjacent property. The private landowner granted access permission after being contacted by Aquatech's staff. Then the general contractor immediately constructed an access road and a staging area. Once this work was completed, Aquatech started installing the pumping and filtration equipment. Working round the clock enabled startup of the pumping and treatment systems within a few days. Once started, the system was able to convey stormwater through the bypass pumping and filtration system as planned. After startup, numerous adjustments were made to accommodate the higher rain event flows. Fine tuning the filtration system has continued to significantly improve water quality results to levels that now far exceed expectations and the stringent guidelines.

This bypass and filtration system employs numerous fully automated electric and diesel powered pumps, generates, light towers, integrated organic flocculent, weir tanks and micron filtration (sand media and pressurized micron filtration filters).

It has been very successful and effective, lowering nephelometric turbidity units levels from 800 NTU to 2 NTU. These results were thought by many as being unattainable on this project, without the use of non-organic methods.

Auatech equipment used on-site included:

  • three 2' (gsp 10) submersible pumps
  • one 3' (gsp 25) submersible pump
  • one 4' (gsp 80) submerisble pump
  • four cd150 6' diesel silenced pumps
  • one cd103 4' diesel pump
  • five automative float panels (a91)
  • one 26kw generator (ghp26kw-rc)
  • two 20kw generators (ghp20kw-rc)
  • two light towers (glt416)
  • two 18,000 gallon weir tanks
  • two 4-pod sand media filters
  • four pressurized micron filter canisters

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