Tuesday, October 4, 2011

Bear Creek Bank Stabilization Project

In an effort to protect existing sanitary sewer infrastructure, Public Works is stabilizing portions of the streambank on Bear Creek along the Bear Creek Trail.  When sewer lines are undermined by eroding banks, joints can sag causing waste to leak into the creek.  By maintaining and protecting the sewer lines, the City can prevent waste from entering our creeks and waterways.

The existing banks were six to ten feet tall, near vertical, continuing to erode and beginning to expose vital sanitary sewer infrastructure.  The City contracted with Plan B Development to construct a bank stabilization project. A product called A-Jacks was used to stabilize the toe (or bottom) of the slope.  These armour units are available in many sizes.  A smaller size was chosen for this project so that it could be installed by a person reducing the need for large machinery.  Most alternative solutions would require multiple concrete trucks or dump trucks full of rock to travel up and down the trail.  By using A-Jacks, the contractor could minimize the use of large construction equipment and minimize damage to the Bear Creek Trail.

A-Jacks fit together and interlock.
The A-Jacks interlock, creating a solid foundation for the streambank.  The streambank is then sloped away from the creek and will be re-vegetated.  The roots of vegetation will help to keep the soil from eroding.  A special fabric is installed as an interim erosion control measure until the vegetation is established.

Sloping banks with A-Jacks at the bottom. 
Erosion control fabric and vegetation will stablize the upper portion of the slope.
Extra A-Jacks were used at this pipe outlet.  They are easy to install and will slow the water and prevent erosion. 
A-Jacks at pipe outlet with erosion control fabric on the adjacent bank.
Not only will this bank stabilization project protect our sanitary sewer infrastructure, but it will stablize a portion of Bear Creek and prevent continued erosion.  All these measures keep our creeks and waterways clean.