Concrete Cloth Erosion Control
Concrete Cloth Erosion Control
Concrete Cloth Erosion Control

Seattle, WA
Concrete Cloth™: Erosion Control

Project Overview

In late 2014, a new gas line lateral installed on a steep 2:1 slope faced severe erosion issues due to the effects of heavy Pacific Northwest rainfall. Within weeks of installing a conventional rip-rap drainage channel, excess runoff water bypassing the faulty channel began eroding the soil near the gas line and potentially destabilizing the bedding material around the pipe.

Along with a regional technical manager from Milliken Infrastructure Solutions (MIS), erosion control distributor ACF West reviewed the situation and developed a comprehensive plan to correct the problem. The design goal was to convey the water down the slope and eliminate the erosion caused by the shear forces from the water flow (more than 14 lbs/ft2). The group provided recommendations to repair the erosion without disturbing the existing pipe, and create a low-maintenance, environmentally friendly channel that could handle runoff water from continuous storms. Per Federal Energy Regulatory Commission (FERC) requirements, the ground surface also had to remain at the same elevation as preconstruction.

Rip-rap typically requires maintenance when used in drainage channels, riverbanks, slopes, etc. While the solution usually creates an acceptable drainage structure, it degrades easily on slopes greater than 3:1. Rip-rap also moves over time – creating instability issues and excessive vegetation growth that can lead to flow restrictions, hydraulic capacity reductions and more. These were the major causes of the problem at this site.

Solution

Milliken Infrastructure Solutions evaluated the channel width, depth and several dynamic external forces on the steep slope – including water movement and other live loads – to determine how to best apply Concrete Cloth GCCM, and what kind of anchoring system would be needed to hold it in place. Less than two weeks after the initial assessment, the owner approved the repair solution, and ACF West supplied approximately 30 portable batch rolls.

The contractor carried the batch rolls to the top of the slope by hand and positioned the Concrete Cloth GCCM in place over a span of two days. The ability to hydrate Concrete Cloth GCCM in the field using an overflow catchment pipe was another advantage that allowed the contractor to reduce time and resources needed for installation. The area was re-vegetated to enhance aesthetics and return the slope to its natural condition, per FERC standards. Throughout the process, MIS made recommendations to the contractor to accelerate construction and meet budget goals, while minimizing disturbances to the area.