Clearflow Group Inc.

Municipal/Stormwater

INNISFIL SEDIMENT EROSION CONTROL PILOT

FCM-funded Lake Simcoe pilot at Sleeping Lion: Gel Flocculant in storm mains cut pond sediment discharge ~74% in an extreme event and phosphorus ~90% across three SWMFs-about $2M in offsetting savings.

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INNISFIL SEDIMENT EROSION CONTROL PILOT

Location: Sleeping Lion subdivision, Town of Innisfil, Ontario, Canada

The Challenge

Innisfil, Ontario, on the southwestern shore of Lake Simcoe, needed to protect the lake from silt pollution and associated phosphorus in stormwater. The Lake Simcoe Protection Plan and LSRCA Phosphorus Offsetting Policy push new developments such as Sleeping Lion toward Zero Phosphorus release-or substantial offsetting fees (offset ratio 2.5:1; offset value about $35,770/kg/yr). Ontario SWMF guidelines target sediment ≥40 microns, but during extreme events most mass can be finer, including dissolved fractions under 2 microns that will not settle without Advanced Sedimentation Technology.

The Solution

A $500,000 FCM Municipal Green Fund grant supported an ~$2M, 18-month pilot. Greenland Engineering selected Clearflow Gel Flocculants as the AST. After Clearflow lab matching, Gel Floc types 494 and 360 were installed in stormwater mains upstream of three SWMFs under construction. Blocks were strung in manholes so gravity flow doses the chemistry passively-leveraging existing infrastructure with almost no CAPEX.

Results

During a near 50-year rain event (~95 mm in 19 hours), about 36,000 kg of fine sediment washed from ~20 hectares of stripped subdivision-only ~9% >40 microns. With Gel Flocculant installed, particles <2 microns fell from ~44% to ~3% of mass, and that pond saw about a 74% reduction in sediments leaving the facility. Phosphorus was reduced by an average of about 90% across the three ponds-representing roughly $2 million in developer offsetting savings under LSRCA policy. Innisfil plans to add ASTs to development engineering specifications. Historical results are examples, not guarantees.

Field record

Proof from the field

Site photography, lab results and drawings recorded as the work was carried out.

The rocky shoreline of Lake Simcoe at Innisfil, Ontario
Fig. 01
Lake Simcoe at Innisfil — the receiving water the pilot was built to protect.
Crew laying out strings of Gel Floc blocks around an open manhole on Farrow Crescent, Innisfil
Fig. 02
Installation at 1452 Farrow Crescent. Strings of blocks were secured to the bottom ladder rung, then floated downstream into the storm main.
Yellow Gel Floc blocks strung together with polyethylene rope and carabiners on pavement
Fig. 03
Blocks strung on polyethylene rope with carabiners, ready to go into the manhole.
Green Gel Floc blocks in mesh sleeves beside a Clearflow shipping box
Fig. 04
Gel Floc blocks arrive ready to install — passive treatment driven by the flow itself.
Packaged WLB 494 and WLB 360 Gel Floc blocks side by side
Fig. 05
The two chemistries chosen for the pilot after lab testing: WLB 494 and WLB 360.

Measured results

Fig. 06Lab testing prescribed the chemistry: turbidity fell from 802 NTU to 11.28 NTU with GFB 494 followed by GFB 360.
Fig. 07The Sleeping Lion subdivision study area on the southwestern shore of Lake Simcoe.
Fig. 08Prescribed block counts and placements at the storm-main manholes upstream of the ponds.
Fig. 09SWMF 4, 2–3 August 2020: 95.4 mm of rain over 19.25 hours, and a 74% total particle-mass reduction.
Fig. 10Average phosphorus removal across the three ponds — 94%, 80% and 98%.

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