Elora Gorge Low Level Bridge Rehabilitation, Canada

Introduction & Problem Statement

A low level bridge at the Elora Gorge Conservation Area was in need of repair above and below the water level. Repair included bridge structure rehabilitation as well as the filling and stabilization of the eroded river bed.

The solution

A flexible, site-fit armouring solution was required to fill the scour pools.
Traditional rock armour was determined to be unsuitable for the application with a 100 year design storm greater than 5 m/s velocity.

The intent was to fill the scour pool and bring the top of the AquaRockBag® elevation to the top of the concrete base slab / top of watercourse bottom adjacent to the scour pool.
AquaRockBag® confined rock, stable to < 5 m/s when used in multi-form, was deemed an acceptable risk when placed to not protrude above the water level. A larger AquaRockBag® format was originally specified to meet the design velocity, but the 2T AquaRockBag® format was installed to better to conform to scour undulations and remain submerged below the water level.
AquaRockBag® manufacturer support assisted with application suitability evaluation and recommendations informing design and risk assessment.
AquaRockBag® met all necessary technical and environmental requirements for in-river use.

2T AquaRockBag® were deployed by crane and guided into place by divers.
Individual bag dimensions are approximately 2.1m diameter x 0.4 high, utilizing approximately 1.25m3 rock. AquaRockBag® were stacked as required to fill the scour pools.
Considering the small laydown area the site, AquaRockBag® were filled at a quarry and transported to site.

Secondary Temporary Site Armouring

Toward the completion of project, post AquaRockBag® scour pool armouring, an intense rain storm inundated the watershed and the Conservation Authority needed to open the upstream dam gates to release excessive impounded stormwater.
Surplus AquaRockBag® still at site were quickly deployed by a hydraulic excavator to temporarily armour two areas of the site that could have potentially erode in the flood event.

Moving Forward

AquaRockBag® was successfully deployed to stabilize an eroded riverbed scour pool.
Periodic inspection will show the extent to which the flexible system conforms to new scour erosion resulting from the intervention. Future system adjustments and / or augmentations are easily executed if required.